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Sample records for active galactic nucleus

  1. Active galactic nucleus feedback in clusters of galaxies

    CERN Document Server

    Blanton, Elizabeth L; Sarazin, Craig L; Randall, Scott W; McNamara, Brian R; ),

    2010-01-01

    Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves.

  2. An off-centered active galactic nucleus in NGC 3115

    CERN Document Server

    Menezes, R B; Ricci, T V

    2014-01-01

    NGC 3115 is an S0 galaxy that has always been considered to have a pure absorption-line spectrum. Some recent studies have detected a compact radio-emitting nucleus in this object, coinciding with the photometric center and with a candidate for the X-ray nucleus. This is evidence of the existence of a low-luminosity active galactic nucleus (AGN) in the galaxy, although no emission line has ever been observed. We report the detection of an emission-line spectrum of a type 1 AGN in NGC 3115, with an H$\\alpha$ luminosity of $L_{H\\alpha} = (4.2 \\pm 0.4) \\times 10^{37}$ erg s$^{-1}$. Our analysis revealed that this AGN is located at a projected distance of $\\sim 0.29" \\pm 0.05"$ (corresponding to $\\sim 14.3 \\pm 2.5$ pc) from the stellar bulge center, which is coincident with the kinematic center of this object's stellar velocity map. The black hole corresponding to the observed off-centered AGN may form a binary system with a black hole located at the stellar bulge center. However, it is also possible that the dis...

  3. Mid-infrared Spectral Indicators of Star Formation and Active Galactic Nucleus Activity in Normal Galaxies

    NARCIS (Netherlands)

    Treyer, Marie; Schiminovich, David; Johnson, Benjamin D.; O'Dowd, Matt; Martin, Christopher D.; Wyder, Ted; Charlot, Stephane; Heckman, Timothy; Martins, Lucimara; Seibert, Mark; van der Hulst, J. M.

    2010-01-01

    We investigate the use of mid-infrared (MIR) polycyclic aromatic hydrocarbon (PAH) bands, the continuum, and emission lines as probes of star formation (SF) and active galactic nucleus (AGN) activity in a sample of 100 "normal" and local (z similar to 0.1) emission-line galaxies. The MIR spectra wer

  4. Ultrafast Outflows: Galaxy-scale Active Galactic Nucleus Feedback

    Science.gov (United States)

    Wagner, A. Y.; Umemura, M.; Bicknell, G. V.

    2013-01-01

    We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves in the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.

  5. ULTRAFAST OUTFLOWS: GALAXY-SCALE ACTIVE GALACTIC NUCLEUS FEEDBACK

    Energy Technology Data Exchange (ETDEWEB)

    Wagner, A. Y.; Umemura, M. [Center for Computational Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki, 305-8577 (Japan); Bicknell, G. V., E-mail: ayw@ccs.tsukuba.ac.jp [Research School of Astronomy and Astrophysics, Australian National University, ACT 2611 (Australia)

    2013-01-20

    We show, using global three-dimensional grid-based hydrodynamical simulations, that ultrafast outflows (UFOs) from active galactic nuclei (AGNs) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous, hot, hydrostatic medium. The outflow floods through the intercloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves in the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically rather than in a disk. In the latter case, the turbulent backflow of the wind drives mass inflow toward the central black hole. Considering the common occurrence of UFOs in AGNs, they are likely to be important in the cosmological feedback cycles of galaxy formation.

  6. Ultra Fast Outflows: Galaxy-Scale Active Galactic Nucleus Feedback

    CERN Document Server

    Wagner, A Y; Bicknell, G V

    2012-01-01

    We show, using global 3D grid-based hydrodynamical simulations, that Ultra Fast Outflows (UFOs) from Active Galactic Nuclei (AGN) result in considerable feedback of energy and momentum into the interstellar medium (ISM) of the host galaxy. The AGN wind interacts strongly with the inhomogeneous, two-phase ISM consisting of dense clouds embedded in a tenuous hot hydrostatic medium. The outflow floods through the inter-cloud channels, sweeps up the hot ISM, and ablates and disperses the dense clouds. The momentum of the UFO is primarily transferred to the dense clouds via the ram pressure in the channel flow, and the wind-blown bubble evolves in the energy-driven regime. Any dependence on UFO opening angle disappears after the first interaction with obstructing clouds. On kpc scales, therefore, feedback by UFOs operates similarly to feedback by relativistic AGN jets. Negative feedback is significantly stronger if clouds are distributed spherically, rather than in a disc. In the latter case the turbulent backflow...

  7. MODELING THE MOLECULAR COMPOSITION IN AN ACTIVE GALACTIC NUCLEUS DISK

    Energy Technology Data Exchange (ETDEWEB)

    Harada, Nanase [Max Planck Institute for Radio Astronomy, D-53121 Bonn (Germany); Thompson, Todd A. [Department of Astronomy, Ohio State University, Columbus, OH 43210 (United States); Herbst, Eric [Departments of Chemistry, Astronomy, and Physics, University of Virginia, Charlottesville, VA 22904 (United States)

    2013-03-10

    We use a high-temperature chemical network to derive the molecular abundances in axisymmetric accretion disk models around active galactic nuclei (AGNs) within 100 pc using simple radial and vertical density and temperature distributions motivated by more detailed physical models. We explore the effects of X-ray irradiation and cosmic-ray ionization on the spatial distribution of the molecular abundances of CO, CN, CS, HCN, HCO{sup +}, HC{sub 3}N, C{sub 2}H, and c-C{sub 3}H{sub 2} using a variety of plausible disk structures. These simple models have molecular regions with an X-ray-dominated region layer, a midplane without the strong influence of X-rays, and a high-temperature region in the inner portion with moderate X-ray flux where families of polyynes (C{sub n}H{sub 2}) and cyanopolyynes can be enhanced. For the high midplane density disks we explore, we find that cosmic rays produced by supernovae do not significantly affect the regions unless the star formation efficiency significantly exceeds that of the Milky Way. We highlight molecular abundance observations and ratios that may distinguish among theoretical models of the density distribution in AGN disks. Finally, we assess the importance of the shock crossing time and the accretion time relative to the formation time for various chemical species. Vertical column densities are tabulated for a number of molecular species at both the characteristic shock crossing time and steady state. Although we do not attempt to fit any particular system or set of observations, we discuss our models and results in the context of the nearby AGN NGC 1068.

  8. Bar Effects on Central Star Formation and Active Galactic Nucleus Activity

    Science.gov (United States)

    Oh, Seulhee; Oh, Kyuseok; Yi, Sukyoung K.

    2012-01-01

    Galactic bars are often suspected to be channels of gas inflow to the galactic center and to trigger central star formation and active galactic nucleus (AGN) activity. However, the current status on this issue based on empirical studies is unsettling, especially regarding AGNs. We investigate this question based on the Sloan Digital Sky Survey Data Release 7. From the nearby (0.01 inspection. We found 36% of them to have a bar. Bars are found to be more common in galaxies with earlier morphology. This makes sample selection critical. Parameter-based selections would miss a large fraction of barred galaxies of early morphology. Bar effects on star formation or AGNs are difficult to understand properly because multiple factors (bar frequency, stellar mass, black hole mass, gas contents, etc.) seem to contribute to them in intricate manners. In the hope of breaking these degeneracies, we inspect bar effects for fixed galaxy properties. Bar effects on central star formation seem higher in redder galaxies. Bar effects on AGNs on the other hand are higher in bluer and less massive galaxies. These effects seem more pronounced with increasing bar length. We discuss possible implications in terms of gas contents, bar strength, bar evolution, fueling timescale, and the dynamical role of supermassive black hole.

  9. Nuclear Radio Continuum Emission of Low-Luminosity Active Galactic Nucleus NGC 4258

    CERN Document Server

    Doi, Akihiro; Nakanishi, Kouichiro; Kameno, Seiji; Inoue, Makoto; Hada, Kazuhiro; Sorai, Kazuo

    2011-01-01

    The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak radio continuum emission at the galactic center. Quasi-simultaneous multi-frequency observations using the Very Large Array (VLA) from 5 GHz (6 cm) to 22 GHz (1.3 cm) showed inverted spectra in all epochs, which were intra-month variable, as well as complicated spectral features that cannot be represented by a simple power law, indicating multiple blobs in nuclear jets. Using the Nobeyama Millimeter Array (NMA), we discovered a large amplitude variable emission at 100 GHz (3 mm), which had higher flux densities at most epochs than those of the VLA observations. A James Clerk Maxwell Telescope (JCMT) observation at 347 GHz (850 micron) served an upper limit of dust contamination. The inverted radio spectrum of the nucleus NGC 4258 is suggestive of an analogy to our Galactic center Sgr A*, but with three orders of magnitude higher radio luminosity. In addition to the LLAGN M 81, we discuss the nucleus of NGC 4258 as another up-scaled ...

  10. A Heuristic Model for the Active Galactic Nucleus Based on the Planck Vacuum Theory

    Directory of Open Access Journals (Sweden)

    Daywitt W. C.

    2009-07-01

    Full Text Available The standard explanation for an active galactic nucleus (AGN is a "central engine" consisting of a hot accretion disk surrounding a supermassive black hole. Energy is generated by the gravitational infall of material which is heated to high temperatures in this dissipative accretion disk. What follows is an alternative model for the AGN based on the Planck vacuum (PV theory, where both the energy of the AGN and its variable luminosity are explained in terms of a variable photon flux emanating from the PV.

  11. EXPLORING THE CONNECTION BETWEEN STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY IN THE LOCAL UNIVERSE

    Energy Technology Data Exchange (ETDEWEB)

    LaMassa, Stephanie M.; Heckman, T. M. [Johns Hopkins University, Department of Physics and Astronomy, Baltimore, MD 21218 (United States); Ptak, A. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Schiminovich, D.; Bertincourt, B. [Columbia University, Department of Astronomy, New York, NY 10027 (United States); O' Dowd, M. [Lehman College, City University of New York, Bronx, NY 10468 (United States)

    2012-10-10

    We study a combined sample of 264 star-forming, 51 composite, and 73 active galaxies using optical spectra from the Sloan Digital Sky Survey (SDSS) and mid-infrared (mid-IR) spectra from the Spitzer Infrared Spectrograph. We examine optical and mid-IR spectroscopic diagnostics that probe the amount of star formation and relative energetic contributions from star formation and an active galactic nucleus (AGN). Overall we find good agreement between optical and mid-IR diagnostics. Misclassifications of galaxies based on the SDSS spectra are rare despite the presence of dust obscuration. The luminosity of the [Ne II] 12.8 {mu}m emission line is well correlated with the star formation rate measured from the SDSS spectra, and this holds for the star-forming, composite, and AGN-dominated systems. AGNs show a clear excess of [Ne III] 15.6 {mu}m emission relative to star-forming and composite systems. We find good qualitative agreement between various parameters that probe the relative contributions of the AGN and star formation, including the mid-IR spectral slope, the ratio of the [Ne V] 14.3 {mu}m to [Ne II] {mu}m 12.8 fluxes, the equivalent widths of the 7.7 {mu}m, 11.3 {mu}m, and 17 {mu}m polycyclic aromatic hydrocarbon (PAH) features, and the optical 'D' parameter which measures the distance at which a source lies from the locus of star-forming galaxies in the optical BPT emission-line diagnostic diagram. We also consider the behavior of the three individual PAH features by examining how their flux ratios depend upon the degree of AGN dominance. We find that the PAH 11.3 {mu}m feature is significantly suppressed in the most AGN-dominated systems.

  12. Response of circumnuclear water masers to luminosity changes in an active galactic nucleus

    CERN Document Server

    Neufeld, D A

    2000-01-01

    Circumnuclear water masers can respond in two ways to changes in the luminosity of an active galactic nucleus. First, an increase in the X-ray luminosity can lead to an increase in the maser emissivity; and second, an increase in the intrinsic bolometric luminosity may result in a temporary decrease in the difference between the gas and dust temperature and a consequent decrease in the maser output. Whilst the latter effect can occur over a period shorter than the thermal timescale, the former effect cannot. Quantitative estimates of the response of the water maser emissivity to changes in either the X-ray or bolometric luminosity are presented, together with estimates of the relevant timescales. Either mechanism could account for recent observations by Gallimore et al. which suggest that the water maser variability in two widely separated regions of the circumnuclear gas in NGC 1068 have been coordinated by a signal from the active nucleus. For either mechanism, a minimum H2 density ~ 1.E+8 cm-3 is needed to...

  13. A Compton-thick active galactic nucleus powering the hyperluminous infrared galaxy IRAS 00182-7112

    Science.gov (United States)

    Nandra, K.; Iwasawa, K.

    2007-11-01

    We present X-ray observations of the hyperluminous infrared galaxy (HLIRG) IRAS 00182- 7112 obtained using the XMM-Newton EPIC camera. A luminous hard X-ray source coincident with the nucleus is revealed, along with weaker soft X-ray emission which may be extended or offset from the hard emission. The EPIC spectrum is extremely flat and shows Fe Kα emission with very high equivalent width: both are typical characteristics of a buried, Compton-thick active galactic nucleus (AGN) which is seen only in scattered light. Perhaps the most remarkable characteristic of the spectrum is that the Fe Kα line energy is that of He-like iron, making IRAS 00182-7112 the first hidden AGN known to be dominated by ionized, Compton-thick reflection. Taking an appropriate bolometric correction, we find that this AGN could easily dominate the far-infrared (FIR) energetics. The nuclear reflection spectrum is seen through a relatively cold absorber with column density consistent with recent Spitzer observations. The soft X-ray emission, which may be thermal in nature and associated with star-forming activity, is seen unabsorbed. The soft X-rays and weak polycyclic aromatic hydrocarbon features both give estimates of the star formation rate ~300Msolar yr-1, insufficient to power the FIR emission and supportive of the idea that this HLIRG is AGN-dominated.

  14. Nuclear Radio Jet from Low-Luminosity Active Galactic Nucleus in NGC 4258

    CERN Document Server

    Doi, Akihiro; Nakanishi, Kouichiro; Kameno, Seiji; Inoue, Makoto; Hada, Kazuhiro; Sorai, Kazuo

    2013-01-01

    The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak radio continuum component at the galactic center. We investigate its radio spectral properties on the basis of our new observations using the Nobeyama Millimeter Array at 100 GHz and archival data from the Very Large Array (VLA) at 1.7-43 GHz and James Clerk Maxwell Telescope at 347 GHz. The NGC 4258 nuclear component exhibits (1) an intra-month variable and complicated spectral feature at 5-22 GHz and (2) a slightly inverted spectrum at 5-100 GHz (a spectral index of ~0.3) in a time-averaged flux density, which are also apparent in the closest LLAGN M81. These similarities between NGC 4258 and M81 in radio spectral natures in addition to previously known core shift in their AU-scale jet structures produce evidence that the same mechanism drives their nuclei. We interpret the observed spectral property as the superposition of emission spectra originating at different locations with frequency-dependent opacity along the nuclear jet. ...

  15. Serendipitous discovery of the long-sought active galactic nucleus in Arp 299-A

    Science.gov (United States)

    Pérez-Torres, M. A.; Alberdi, A.; Romero-Cañizales, C.; Bondi, M.

    2010-09-01

    Context. The dusty nuclear regions of luminous infra-red galaxies (LIRGs) are heated by either an intense burst of massive star formation, an active galactic nucleus (AGN), or a combination of both. Disentangling the contribution of each of those putative dust-heating agents is a challenging task, and direct imaging of the innermost few pc can only be accomplished at radio wavelengths, using very high-angular resolution observations. Aims: We observed the nucleus A of the interacting starburst galaxy Arp 299, using very long baseline interferometry (VLBI) radio observations at 1.7 and 5.0 GHz. Our aim was to characterize the compact sources in the innermost few pc region of Arp 299-A, as well as to detect recently exploded core-collapse supernovae. Methods: We used the European VLBI Network (EVN) to image the 1.7 and 5.0 GHz compact radio emission of the parsec-scale structure in the nucleus of Arp 299-A with milliarcsecond resolution. Results: Our EVN observations show that one of the compact VLBI sources, A1, previously detected at 5.0 GHz, has a flat spectrum between 1.7 and 5.0 GHz and is the brightest source at both frequencies. Our 1.7 GHz EVN image shows also diffuse, low-surface brightness emission extending westwards from A1 and displays a prominent core-jet structure. Conclusions: The morphology, radio luminosity, spectral index and ratio of radio-to-X-ray emission of the A1-A5 region is consistent with a low-luminosity AGN (LLAGN), and rules out the possibility that it is a chain of young radio supernovae (RSNe) and supernova remnants (SNRs). We therefore conclude that A1-A5 is the long-sought AGN in Arp 299-A. This finding may suggest that both starburst and AGN are frequently associated phenomena in mergers.

  16. The sign of active galactic nucleus quenching in a merger remnant with radio jets

    CERN Document Server

    Ichikawa, Kohei; Shidatsu, Megumi; Kawamuro, Taiki; Matsuoka, Kenta

    2015-01-01

    We investigate optical, infrared, and radio active galactic nucleus (AGN) signs in the merger remnant Arp 187, which hosts luminous jets launched in the order of $10^5$ yr ago but whose present-day AGN activity is still unknown. We find AGN signs from the optical BPT diagram and infrared [OIV]25.89 $\\mu$m line, originating from the narrow line regions of AGN. On the other hand, Spitzer/IRS show the host galaxy dominated spectra, suggesting that the thermal emission from the AGN torus is considerably small or already diminished. Combining the black hole mass, the upper limit of radio luminosity of the core, and the fundamental plane of the black hole enable us to estimate X-ray luminosity, which gives $<10^{40}$ erg s$^{-1}$. Those results suggest that the AGN activity of Arp 187 has already been quenched, but the narrow line region is still alive owing to the time delay of emission from the past AGN activity.

  17. A CANDIDATE DUAL ACTIVE GALACTIC NUCLEUS AT z = 1.175

    Energy Technology Data Exchange (ETDEWEB)

    Scott Barrows, R. [Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701 (United States); Stern, Daniel; Assef, Roberto J.; Cushing, Michael C. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Madsen, Kristin; Harrison, Fiona [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Comerford, Julia M. [Astronomy Department, University of Texas at Austin, Austin, TX 78712 (United States); Fassnacht, Christopher D.; Lagattuta, David J. [Department of Physics, University of California at Davis, One Shields Avenue, Davis, CA 95616 (United States); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Griffith, Roger; Davy Kirkpatrick, J. [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Hickox, Ryan, E-mail: rbarrows@uark.edu [Department of Physics, Durham University, Durham DHI 3LE (United Kingdom)

    2012-01-01

    The X-ray source CXOXBJ142607.6+353351 (CXOJ1426+35), which was identified in a 172 ks Chandra image in the Booetes field, shows double-peaked rest-frame optical/UV emission lines, separated by 0.''69 (5.5 kpc) in the spatial dimension and by 690 km s{sup -1} in the velocity dimension. The high excitation lines and emission line ratios indicate both systems are ionized by an active galactic nucleus (AGN) continuum, and the double-peaked profile resembles that of candidate dual AGNs. At a redshift of z = 1.175, this source is the highest redshift candidate dual AGN yet identified. However, many sources have similar emission line profiles for which other interpretations are favored. We have analyzed the substantial archival data available in this field as well as acquired near-infrared (NIR) adaptive optics (AO) imaging and NIR slit spectroscopy. The X-ray spectrum is hard, implying a column density of several 10{sup 23} cm{sup -2}. Though heavily obscured, the source is also one of the brightest in the field, with an absorption-corrected 2-10 keV luminosity of {approx}10{sup 45} erg s{sup -1}. Outflows driven by an accretion disk may produce the double-peaked lines if the central engine accretes near the Eddington limit. However, we may be seeing the narrow line regions of two AGNs following a galactic merger. While the AO image reveals only a single source, a second AGN would easily be obscured by the significant extinction inferred from the X-ray data. Understanding the physical processes producing the complex emission line profiles seen in CXOJ1426+35 and related sources is important for interpreting the growing population of dual AGN candidates.

  18. A luminous hot accretion flow in the low-luminosity active galactic nucleus NGC 7213

    CERN Document Server

    Xie, Fu-Guo; Ma, Renyi; Yang, Qi-Xiang

    2016-01-01

    The radio luminosity, $L_R$, of the low-luminosity active galactic nucleus (AGN) NGC~7213 weakly correlates with its 2--10 keV X-ray luminosity, $L_X$, when $L_X$ is low, and apparently strongly when $L_X$ is high. Such a hybrid correlation in an individual AGN is unexpected as it deviates from the fundamental plane of AGN activity. On the other hand, a similar correlation pattern is present in the black-hole X-ray binary H1743--322, where it has been modelled as due to switching between different modes of accretion. For NGC~7213, we propose that its $L_R$--$L_X$ correlation is due to the presence of a luminous hot accretion flow, which radiative efficiency is sensitive to the accretion rate. Given the low luminosity of the source, $L_X\\sim 10^{-4}$ of the Eddington luminosity, the viscosity parameter is determined to be small in NGC 7213, $\\alpha\\approx 0.01$. We also examine the broad-band spectrum from radio to X-rays, the time lag between the radio and X-ray light curves, and the implied size and the Lore...

  19. Collimation and scattering of the active galactic nucleus emission in the Sombrero galaxy

    CERN Document Server

    Menezes, R B; Ricci, T V; 10.1088/2041-8205/765/2/L40

    2013-01-01

    We present an analysis of a data cube of the central region of M104, the Sombrero galaxy, obtained with the GMOS-IFU of the Gemini-South telescope, and report the discovery of collimation and scattering of the active galactic nucleus (AGN) emission in the circumnuclear region of this galaxy. Analysis with PCA Tomography and spectral synthesis revealed the existence of collimation and scattering of the AGN featureless continuum and also of a broad component of the H{\\alpha} emission line. The collimation and scattering of this broad H{\\alpha} component was also revealed by fitting the [NII] {\\lambda}{\\lambda}6548,6583 and H{\\alpha} emission lines as a sum of Gaussian functions. The spectral synthesis, together with a V-I image obtained with the Hubble Space Telescope, showed the existence of circumnuclear dust, which may cause the light scattering. We also identify a dusty feature that may be interpreted as a torus/disk structure. The existence of two opposite regions with featureless continuum (P.A. = -18{\\de...

  20. A MULTI-WAVELENGTH ANALYSIS OF NGC 4178: A BULGELESS GALAXY WITH AN ACTIVE GALACTIC NUCLEUS

    Energy Technology Data Exchange (ETDEWEB)

    Secrest, N. J.; Satyapal, S.; Gliozzi, M. [Department of Physics and Astronomy, George Mason University, MS 3F3, 4400 University Drive, Fairfax, VA 22030 (United States); Moran, S. M. [Department of Physics and Astronomy, Johns Hopkins University, 366 Bloomberg Center, 3400 N. Charles Street, Baltimore, MD 21218 (United States); Cheung, C. C. [Space Science Division, Naval Research Laboratory, Washington, DC 20375-5352 (United States); Giroletti, M. [INAF Istituto di Radioastronomia, I-40129 Bologna (Italy); Bergmann, M. P. [NOAO Gemini Science Center, P.O. Box 26732, Tucson, AZ 85726 (United States); Seth, A. C. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States)

    2013-11-10

    We present Gemini longslit optical spectroscopy and Very Large Array radio observations of the nuclear region of NGC 4178, a late-type bulgeless disk galaxy recently confirmed to host an active galactic nucleus (AGN) through infrared and X-ray observations. Our observations reveal that the dynamical center of the galaxy is coincident with the location of the Chandra X-ray point source discovered in a previous work, providing further support for the presence of an AGN. While the X-ray and IR observations provide robust evidence for an AGN, the optical spectrum shows no evidence for the AGN, underscoring the need for the penetrative power of mid-IR and X-ray observations in finding buried or weak AGNs in this class of galaxy. Finally, the upper limit to the radio flux, together with our previous X-ray and IR results, is consistent with the scenario in which NGC 4178 harbors a deeply buried AGN accreting at a high rate.

  1. Active galactic nucleus torus models and the puzzling infrared spectrum of IRAS F10214+4724

    CERN Document Server

    Efstathiou, A; Verma, A; Siebenmorgen, R

    2013-01-01

    We present a revised model for the infrared emission of the hyperluminous infrared galaxy IRAS F10214+4724 which takes into account recent photometric data from Spitzer and Herschel that sample the peak of its spectral energy distribution. We first present and discuss a grid of smooth active galactic nucleus (AGN) torus models computed with the method of Efstathiou & Rowan-Robinson and demonstrate that the combination of these models and the starburst models of Efstathiou and coworkers, while able to give an excellent fit to the average spectrum of Seyfert 2s and spectra of individual type 2 quasars measured by Spitzer, fails to match the spectral energy distribution of IRAS F10214+4724. This is mainly due to the fact that the nuSnu distribution of the galaxy falls very steeply with increasing frequency (a characteristic that is usually indicative of heavy absorption by dust) but shows a silicate feature in emission. Such emission features are not expected in sources with optical/near-infrared type 2 AGN ...

  2. Evidence for widespread active galactic nucleus activity among massive quiescent galaxies at z ~ 2

    DEFF Research Database (Denmark)

    Olsen, K.P.; Rasmussen, J.; Toft, S.;

    2013-01-01

    We quantify the presence of active galactic nuclei (AGNs) in a mass-complete (M > 5 × 10 M ) sample of 123 star-forming and quiescent galaxies at 1.5 = z = 2.5, using X-ray data from the 4 Ms Chandra Deep Field-South (CDF-S) survey. 41% ± 7% of the galaxies are detected directly in X-rays, 22% ± ......%-65%). Our discovery of the ubiquity of AGNs in massive, quiescent z ~ 2 galaxies provides observational support for the importance of AGNs in impeding star formation during galaxy evolution. © 2013. The American Astronomical Society. All rights reserved.....

  3. Probing the active galactic nucleus unified model torus properties in Seyfert galaxies

    Science.gov (United States)

    Audibert, Anelise; Riffel, Rogério; Sales, Dinalva A.; Pastoriza, Miriani G.; Ruschel-Dutra, Daniel

    2017-01-01

    We studied the physical parameters of a sample comprising of all Spitzer/Infrared Spectrograph public spectra of Seyfert galaxies in the mid-infrared (5.2-38 μm range) under the active galactic nucleus (AGN) unified model. We compare the observed spectra with ˜106 CLUMPY model spectral energy distributions, which consider a torus composed of dusty clouds. We find a slight difference in the distribution of line-of-sight inclination angle, i, requiring larger angles for Seyfert 2 (Sy 2) and a broader distribution for Seyfert 1 (Sy 1). We found small differences in the torus angular width, σ, indicating that Sy 1 may host a slightly narrower torus than Sy 2. The torus thickness, together with the bolometric luminosities derived, suggests a very compact torus up to ˜6 pc from the central AGN. The number of clouds along the equatorial plane, N, as well the index of the radial profile, q, is nearly the same for both types. These results imply that the torus cloud distribution is nearly the same for type 1 and type 2 objects. The torus mass is almost the same for both types of activity, with values in the range of Mtor ˜ 104-107 M⊙. The main difference appears to be related to the clouds' intrinsic properties: type 2 sources present higher optical depths τV. The results presented here reinforce the suggestion that the classification of a galaxy may also depend on the intrinsic properties of the torus clouds rather than simply on their inclination. This is in contradiction with the simple geometric idea of the unification model.

  4. COLLIMATION AND SCATTERING OF THE ACTIVE GALACTIC NUCLEUS EMISSION IN THE SOMBRERO GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Menezes, R. B.; Steiner, J. E.; Ricci, T. V., E-mail: robertobm@astro.iag.usp.br [Instituto de Astronomia Geofisica e Ciencias Atmosfericas, Universidade de Sao Paulo, Rua do Matao 1226, Cidade Universitaria, Sao Paulo, SP CEP 05508-090 (Brazil)

    2013-03-10

    We present an analysis of a data cube of the central region of M104, the Sombrero galaxy, obtained with the GMOS-IFU of the Gemini-South telescope, and report the discovery of collimation and scattering of the active galactic nucleus (AGN) emission in the circumnuclear region of this galaxy. Analysis with PCA Tomography and spectral synthesis revealed the existence of collimation and scattering of the AGN featureless continuum and also of a broad component of the H{alpha} emission line. The collimation and scattering of this broad H{alpha} component was also revealed by fitting the [N II] {lambda}{lambda}6548, 6583 and H{alpha} emission lines as a sum of Gaussian functions. The spectral synthesis, together with a V-I image obtained with the Hubble Space Telescope, showed the existence of circumnuclear dust, which may cause the light scattering. We also identify a dusty feature that may be interpreted as a torus/disk structure. The existence of two opposite regions with featureless continuum (P.A. = -18 Degree-Sign {+-} 13 Degree-Sign and P.A. = 162 Degree-Sign {+-} 13 Degree-Sign ) along a direction perpendicular to the torus/disk (P.A. = 72 Degree-Sign {+-} 14 Degree-Sign ) suggests that this structure is approximately edge-on and collimates the AGN emission. The edge-on torus/disk also hides the broad-line region. The proposed scenario is compatible with the unified model and explains why only a weak broad component of the H{alpha} emission line is visible and also why many previous studies detected no broad H{alpha}. The technique used here proved to be an efficient method not only for detecting scattered light, but also for testing the unified model in low-luminosity AGNs.

  5. Active galactic nucleus torus models and the puzzling infrared spectrum of IRAS F10214+4724

    Science.gov (United States)

    Efstathiou, A.; Christopher, N.; Verma, A.; Siebenmorgen, R.

    2013-12-01

    We present a revised model for the infrared emission of the hyperluminous infrared galaxy IRAS F10214+4724 which takes into account recent photometric data from Spitzer and Herschel that sample the peak of its spectral energy distribution. We first present and discuss a grid of smooth active galactic nucleus (AGN) torus models computed with the method of Efstathiou & Rowan-Robinson and demonstrate that the combination of these models and the starburst models of Efstathiou and coworkers, while able to give an excellent fit to the average spectrum of Seyfert 2s and spectra of individual type 2 quasars measured by Spitzer, fails to match the spectral energy distribution of IRAS F10214+4724. This is mainly due to the fact that the νSν distribution of the galaxy falls very steeply with increasing frequency (a characteristic that is usually indicative of heavy absorption by dust) but shows a silicate feature in emission. Such emission features are not expected in sources with optical/near-infrared type 2 AGN spectral signatures. The Herschel data show that there is more power emitted in the rest-frame 20-50 μm wavelength range compared with the model presented by Efstathiou which assumes three components of emission: an edge-on torus, clouds (at a temperature of 610 and 200 K) that are associated with the narrow-line region (NLR) and a highly obscured starburst that dominates in the submillimetre. We present a revised version of that model that assumes an additional component of emission which we associate with NLR clouds at a temperature of 100 K. The 100 K dust component could also be explained by a highly obscured hot starburst. The model suggests that the NLR of IRAS F10214+4724 has an unusually high covering factor (≥17 per cent) or more likely the magnification of the emission from the NLR clouds is significantly higher than that of the emission from the torus.

  6. Variability-based Active Galactic Nucleus Selection Using Image Subtraction in the SDSS and LSST Era

    Science.gov (United States)

    Choi, Yumi; Gibson, Robert R.; Becker, Andrew C.; Ivezić, Željko; Connolly, Andrew J.; MacLeod, Chelsea L.; Ruan, John J.; Anderson, Scott F.

    2014-02-01

    With upcoming all-sky surveys such as LSST poised to generate a deep digital movie of the optical sky, variability-based active galactic nucleus (AGN) selection will enable the construction of highly complete catalogs with minimum contamination. In this study, we generate g-band difference images and construct light curves (LCs) for QSO/AGN candidates listed in Sloan Digital Sky Survey Stripe 82 public catalogs compiled from different methods, including spectroscopy, optical colors, variability, and X-ray detection. Image differencing excels at identifying variable sources embedded in complex or blended emission regions such as Type II AGNs and other low-luminosity AGNs that may be omitted from traditional photometric or spectroscopic catalogs. To separate QSOs/AGNs from other sources using our difference image LCs, we explore several LC statistics and parameterize optical variability by the characteristic damping timescale (τ) and variability amplitude. By virtue of distinguishable variability parameters of AGNs, we are able to select them with high completeness of 93.4% and efficiency (i.e., purity) of 71.3%. Based on optical variability, we also select highly variable blazar candidates, whose infrared colors are consistent with known blazars. One-third of them are also radio detected. With the X-ray selected AGN candidates, we probe the optical variability of X-ray detected optically extended sources using their difference image LCs for the first time. A combination of optical variability and X-ray detection enables us to select various types of host-dominated AGNs. Contrary to the AGN unification model prediction, two Type II AGN candidates (out of six) show detectable variability on long-term timescales like typical Type I AGNs. This study will provide a baseline for future optical variability studies of extended sources.

  7. From starburst to quiescence: testing active galactic nucleus feedback in rapidly quenching post-starburst galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Yesuf, Hassen M.; Faber, S. M.; Trump, Jonathan R.; Koo, David C.; Fang, Jerome J.; Liu, F. S. [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Wild, Vivienne [School of Physics and Astronomy, University of St Andrews, North Haugh, St Andrews, KY16 9SS (United Kingdom); Hayward, Christopher C. [Heidelberger Institut für Theoretische Studien, Schloss-Wolfsbrunnenweg 35, D-69118 Heidelberg (Germany)

    2014-09-10

    Post-starbursts are galaxies in transition from the blue cloud to the red sequence. Although they are rare today, integrated over time they may be an important pathway to the red sequence. This work uses Sloan Digital Sky Survey, the Galaxy Evolution Explorer, and Wide-field Infrared Survey Explorer observations to identify the evolutionary sequence from starbursts to fully quenched post-starbursts (QPSBs) in the narrow mass range log M(M {sub ☉}) = 10.3-10.7, and identifies 'transiting' post-starbursts (TPSBs) which are intermediate between these two populations. In this mass range, ∼0.3% of galaxies are starbursts, ∼0.1% are QPSBs, and ∼0.5% are the transiting types in between. The TPSBs have stellar properties that are predicted for fast-quenching starbursts and morphological characteristics that are already typical of early-type galaxies. The active galactic nucleus (AGN) fraction, as estimated from optical line ratios, of these post-starbursts is about three times higher (≳ 36% ± 8%) than that of normal star forming galaxies of the same mass, but there is a significant delay between the starburst phase and the peak of nuclear optical AGN activity (median age difference of ≳ 200 ± 100 Myr), in agreement with previous studies. The time delay is inferred by comparing the broadband near-NUV-to-optical photometry with stellar population synthesis models. We also find that starbursts and post-starbursts are significantly more dust obscured than normal star forming galaxies in the same mass range. About 20% of the starbursts and 15% of the TPSBs can be classified as 'dust-obscured galaxies' (DOGs), with a near-UV-to-mid-IR flux ratio of ≳ 900, while only 0.8% of normal galaxies are DOGs. The time delay between the starburst phase and AGN activity suggests that AGNs do not play a primary role in the original quenching of starbursts but may be responsible for quenching later low-level star formation by removing gas and dust during

  8. EVIDENCE FOR WIDESPREAD ACTIVE GALACTIC NUCLEUS ACTIVITY AMONG MASSIVE QUIESCENT GALAXIES AT z {approx} 2

    Energy Technology Data Exchange (ETDEWEB)

    Olsen, Karen P.; Rasmussen, Jesper; Toft, Sune; Zirm, Andrew W., E-mail: karen@dark-cosmology.dk [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark)

    2013-02-10

    We quantify the presence of active galactic nuclei (AGNs) in a mass-complete (M {sub *} > 5 Multiplication-Sign 10{sup 10} M {sub Sun }) sample of 123 star-forming and quiescent galaxies at 1.5 {<=} z {<=} 2.5, using X-ray data from the 4 Ms Chandra Deep Field-South (CDF-S) survey. 41% {+-} 7% of the galaxies are detected directly in X-rays, 22% {+-} 5% with rest-frame 0.5-8 keV luminosities consistent with hosting luminous AGNs (L {sub 0.5-8keV} > 3 Multiplication-Sign 10{sup 42} erg s{sup -1}). The latter fraction is similar for star-forming and quiescent galaxies, and does not depend on galaxy stellar mass, suggesting that perhaps luminous AGNs are triggered by external effects such as mergers. We detect significant mean X-ray signals in stacked images for both the individually non-detected star-forming and quiescent galaxies, with spectra consistent with star formation only and/or a low-luminosity AGN in both cases. Comparing star formation rates inferred from the 2-10 keV luminosities to those from rest-frame IR+UV emission, we find evidence for an X-ray excess indicative of low-luminosity AGNs. Among the quiescent galaxies, the excess suggests that as many as 70%-100% of these contain low- or high-luminosity AGNs, while the corresponding fraction is lower among star-forming galaxies (43%-65%). Our discovery of the ubiquity of AGNs in massive, quiescent z {approx} 2 galaxies provides observational support for the importance of AGNs in impeding star formation during galaxy evolution.

  9. UNCOVERING THE DEEPLY EMBEDDED ACTIVE GALACTIC NUCLEUS ACTIVITY IN THE NUCLEAR REGIONS OF THE INTERACTING GALAXY Arp 299

    Energy Technology Data Exchange (ETDEWEB)

    Alonso-Herrero, A. [Instituto de Física de Cantabria, CSIC-UC, E-39005 Santander (Spain); Roche, P. F. [Astrophysics Department, University of Oxford, Oxford OX1 3RH (United Kingdom); Esquej, P.; Colina, L. [Centro de Astrobiología, CSIC-INTA, E-28035 Madrid (Spain); González-Martín, O.; Ramos Almeida, C.; Asensio Ramos, A.; Rodríguez Espinosa, J. M.; Alvarez, C. [Instituto de Astrofísica de Canarias, E-38205 La Laguna (Spain); Pereira-Santaella, M. [Istituto di Astrofisica e Planetologia Spaziali, INAF, I-00133 Rome (Italy); Levenson, N. A. [Gemini Observatory, La Serena (Chile); Packham, C. [University of Texas at San Antonio, San Antonio, TX 78249 (United States); Mason, R. E. [Gemini Observatory, Hilo, HI 96720 (United States); Aretxaga, I. [INAOE, 72000 Puebla (Mexico); Díaz-Santos, T. [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States); Perlman, E. [Florida Institute of Technology, Melbourne, FL 32901 (United States); Telesco, C. M., E-mail: aalonso@ifca.unican.es [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States)

    2013-12-10

    We present mid-infrared (MIR) 8-13 μm spectroscopy of the nuclear regions of the interacting galaxy Arp 299 (IC 694+NGC 3690) obtained with CanariCam (CC) on the 10.4 m Gran Telescopio Canarias (GTC). The high angular resolution (∼0.''3-0.''6) of the data allows us to probe nuclear physical scales between 60 and 120 pc, which is a factor of 10 improvement over previous MIR spectroscopic observations of this system. The GTC/CC spectroscopy displays evidence of deeply embedded active galactic nucleus (AGN) activity in both nuclei. The GTC/CC nuclear spectrum of NGC 3690/Arp 299-B1 can be explained as emission from AGN-heated dust in a clumpy torus with both a high covering factor and high extinction along the line of sight. The estimated bolometric luminosity of the AGN in NGC 3690 is 3.2 ± 0.6 × 10{sup 44} erg s{sup –1}. The nuclear GTC/CC spectrum of IC 694/Arp 299-A shows 11.3 μm polycyclic aromatic hydrocarbon emission stemming from a deeply embedded (A{sub V} ∼ 24 mag) region of less than 120 pc in size. There is also a continuum-emitting dust component. If associated with the putative AGN in IC 694, we estimate that it would be approximately five times less luminous than the AGN in NGC 3690. The presence of dual AGN activity makes Arp 299 a good example to study such phenomena in the early coalescence phase of interacting galaxies.

  10. Galaxy Zoo: the effect of bar-driven fueling on the presence of an active galactic nucleus in disc galaxies

    CERN Document Server

    Galloway, Melanie A; Fortson, Lucy F; Cardamone, Carolin N; Schawinski, Kevin; Cheung, Edmond; Lintott, Chris J; Masters, Karen L; Melvin, Thomas; Simmons, Brooke D

    2015-01-01

    We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky Survey and morphological classifications from the Galaxy Zoo 2 project, we create a volume-limited sample of 19,756 disc galaxies at $0.01galactic bars is strongly correlated with both the stellar mass and integrated colour of the host galaxy. We control for this effect by examining the difference in AGN fraction between barred and unbarred galaxies in fixed bins of mass and colour. Once this effect is accounted for, there remains a small but statistically significant increase that represents 16% of the average barred AGN fraction. Using the $L_{\\rm...

  11. Type 1 Active Galactic Nucleus Fraction in SDSS/FIRST Survey

    CERN Document Server

    Lu, Yu; Dong, Xiao-Bo; Zhou, Hong-Yan

    2010-01-01

    In the unification scheme, narrow-lined (type 2) active galactic nuclei (AGN) are intrinsically similar to broad-lined (type 1) AGN with the exception that the line of sight to the broad emission line region and accretion disk is blocked by a dusty torus. The fraction of type 1 AGN measures the average covering factor of the torus. In this paper, we explore the dependence of this fraction on nuclear properties for a sample of low redshift (z 10^{23}W/Hz) AGN selected by matching the spectroscopic catalog of Sloan Digital Sky Survey and the radio source catalog of Faint Image of Radio Sky at Twenty cm. After correcting for several selection effects, we find that : (1) type 1 fraction $f_1$ keeps at a constant of ~20 per cent in the [O III] 5007 luminosity range of 40.7< log(L_{[O III]}/ erg/s) <43.5 . This result is significantly different from previous studies, and the difference can be explained by extinction correction and different treatment of selection effects. (2) $f_1$ rises with black hole mass ...

  12. Metal enrichment by radiation pressure in active galactic nucleus outflows -- theory and observations

    CERN Document Server

    Baskin, Alexei

    2012-01-01

    Outflows from active galactic nuclei may be produced by absorption of continuum radiation by UV resonance lines of abundant metal ions, as observed in broad absorption line quasars (BALQs). The radiation pressure exerted on the metal ions is coupled to the rest of the gas through Coulomb collisions of the metal ions. We calculate the photon density and gas density which allow decoupling of the metal ions from the rest of the gas. These conditions may lead to an outflow composed mostly of the metal ions. We derive a method to constrain the metals/H ratio of observed UV outflows, based on the Ly {\\alpha} and Si iv {\\lambda}{\\lambda}1394, 1403 absorption profiles. We apply this method to an SDSS sample of BALQs to derive a handful of candidate outflows with a higher than solar metal/H ratio. This mechanism can produce ultra fast UV outflows, if a shield of the continuum source with a strong absorption edge is present.

  13. PKS 0347+05: a radio-loud/radio-quiet double active galactic nucleus system triggered in a major galaxy merger

    NARCIS (Netherlands)

    Tadhunter, C. N.; Ramos Almeida, C.; Morganti, R.; Holt, J.; Rose, M.; Dicken, D.; Inskip, K.

    2012-01-01

    We present optical, infrared (IR) and radio observations of the powerful Fanaroff-Riley type II (FR II) radio source PKS 0347+05 (z = 0.3390), and demonstrate that it is a rare example of a radio-loud/radio-quiet double active galactic nucleus (AGN) system, comprising a weak-line radio galaxy (WLRG)

  14. NuSTAR Observations of the Compton-Thick Active Galactic Nucleus and Ultraluminous X-Ray Source Candidate in NGC 5643

    DEFF Research Database (Denmark)

    Annuar, A.; Gandhi, P.; Alexander, D. M.;

    2015-01-01

    We present two Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the local Seyfert 2 active galactic nucleus (AGN) and an ultraluminous X-ray source (ULX) candidate in NGC 5643. Together with archival data from Chandra, XMM-Newton, and Swift-BAT, we perform a high-quality broadband s...

  15. High-Resolution X-Ray Spectroscopy of a Low-Luminosity Active Galactic Nucleus: The Structure and Dynamics of M81*

    NARCIS (Netherlands)

    Young, A.J.; Nowak, M.A.; Markoff, S.; Marshall, H.L.; Canizares, C.R.

    2007-01-01

    We present Chandra HETGS observations of the low-luminosity active galactic nucleus (LLAGN) of M81. The HETGS is unique in providing high-resolution spectroscopy of the central 1" of M81, including the iron K bandpass. The continuum is a power law of photon index Gamma=1.8, similar to that seen in h

  16. Cosmic Train Wreck by Massive Black Holes: Discovery of a kpc-Scale Triple Active Galactic Nucleus

    CERN Document Server

    Liu, Xin; Strauss, Michael A

    2011-01-01

    Hierarchical galaxy mergers will lead to the formation of binary and, in particular, triple SMBHs, given that most massive galaxies harbor central SMBHs. A triple of SMBHs becomes visible as a triple Active Galactic Nucleus (AGN) when the BHs accrete large amounts of gas at the same time. Here we report the discovery of a kpc-scale triple AGN, SDSSJ1027+1749 at z = 0.066, from our systematic search for hierarchical mergers of AGNs. The galaxy contains three emission-line nuclei, two of which are offset by ~ 450 and 110 km/s in velocity and by 2.4 and 3.0 kpc in projected separation from the central nucleus. All three nuclei are classified as obscured AGNs based on optical diagnostic emission line ratios, with black hole mass estimates M_BH >~ 10^8 M_sun from stellar velocity dispersions measured in the associated stellar components. Based on dynamical friction timescale estimates, the three stellar components in SDSSJ1027+1749 will merge in ~ 40 Myr, and their associated SMBHs may evolve into a gravitationall...

  17. Black Hole Lightning from the Peculiar Gamma-Ray Loud Active Galactic Nucleus IC 310

    CERN Document Server

    Glawion, Dorit Eisenacher; Mannheim, Karl; Colin, Pierre; Kadler, Matthias; Schulz, Robert; Ros, Eduardo; Bach, Uwe; Krauß, Felicia; Wilms, Jörn

    2015-01-01

    The nearby active galaxy IC 310, located in the outskirts of the Perseus cluster of galaxies is a bright and variable multi-wavelength emitter from the radio regime up to very high gamma-ray energies above 100 GeV. Originally, the nucleus of IC 310 has been classified as a radio galaxy. However, studies of the multi-wavelength emission showed several properties similarly to those found from blazars as well as radio galaxies. In late 2012, we have organized the first contemporaneous multi-wavelength campaign including radio, optical, X-ray and gamma-ray instruments. During this campaign an exceptionally bright flare of IC 310 was detected with the MAGIC telescopes in November 2012 reaching an averaged flux level in the night of up to one Crab above 1 TeV with a hard spectrum over two decades in energy. The intra-night light curve showed a series of strong outbursts with flux-doubling time scales as fast as a few minutes. The fast variability constrains the size of the gamma-ray emission regime to be smaller th...

  18. Active galactic nucleus X-ray variability in the XMM-COSMOS survey

    Energy Technology Data Exchange (ETDEWEB)

    Lanzuisi, G.; Ponti, G.; Salvato, M.; Brusa, M.; Nandra, P. K.; Merloni, A.; Rosario, D. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching (Germany); Hasinger, G.; Sanders, D. [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822-1839 (United States); Cappelluti, N.; Comastri, A.; Gilli, R. [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Bongiorno, A. [Istituto Nazionale di Astrofisica-Osservatorio Astronomico di Roma Via Frascati 33, I-00040, Monte Porzio Catone (Italy); Lusso, E.; Steinhardt, C. [Max Planck Institut für Astronomie, Königstuhl 17, D-69117 Heidelberg (Germany); Silverman, J.; Schramm, M. [Kavli Institute for the Physics and Mathematics of the Universe (Kavli IPMU) 5-1-5 Kashiwanoha Kashiwa, Chiba 277-8583 (Japan); Trump, J. [University of California Observatories/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Vignali, C. [Dipartimento di Fisica e Astronomia, Universitá di Bologna, viale Berti Pichat 6/2, I-40127 Bologna (Italy); Kartaltepe, J., E-mail: lanzuisi@noa.gr [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); and others

    2014-02-01

    We used the observations carried out by XMM in the COSMOS field over 3.5 yr to study the long term variability of a large sample of active galactic nuclei (AGNs) (638 sources) in a wide range of redshifts (0.1 < z < 3.5) and X-ray luminosities (10{sup 41} < L {sub 0.5-10} <10{sup 45.5}). Both a simple statistical method to assess the significance of variability and the Normalized Excess Variance (σ{sub rms}{sup 2}) parameter were used to obtain a quantitative measurement of the variability. Variability is found to be prevalent in most AGNs, whenever we have good statistics to measure it, and no significant differences between type 1 and type 2 AGNs were found. A flat (slope –0.23 ± 0.03) anti-correlation between σ{sub rms}{sup 2} and X-ray luminosity is found when all significantly variable sources are considered together. When divided into three redshift bins, the anti-correlation becomes stronger and evolving with z, with higher redshift AGNs being more variable. We prove, however, that this effect is due to the pre-selection of variable sources: when considering all of the sources with an available σ{sub rms}{sup 2} measurement, the evolution in redshift disappears. For the first time, we were also able to study long term X-ray variability as a function of M {sub BH} and Eddington ratio for a large sample of AGNs spanning a wide range of redshifts. An anti-correlation between σ{sub rms}{sup 2} and M {sub BH} is found, with the same slope of anti-correlation between σ{sub rms}{sup 2} and X-ray luminosity, suggesting that the latter may be a by-product of the former. No clear correlation is found between σ{sub rms}{sup 2} and the Eddington ratio in our sample. Finally, no correlation is found between the X-ray σ{sub rms}{sup 2} and optical variability.

  19. Galaxy Zoo: the effect of bar-driven fuelling on the presence of an active galactic nucleus in disc galaxies

    Science.gov (United States)

    Galloway, Melanie A.; Willett, Kyle W.; Fortson, Lucy F.; Cardamone, Carolin N.; Schawinski, Kevin; Cheung, Edmond; Lintott, Chris J.; Masters, Karen L.; Melvin, Thomas; Simmons, Brooke D.

    2015-04-01

    We study the influence of the presence of a strong bar in disc galaxies which host an active galactic nucleus (AGN). Using data from the Sloan Digital Sky Survey and morphological classifications from the Galaxy Zoo 2 project, we create a volume-limited sample of 19 756 disc galaxies at 0.01 < z < 0.05 which have been visually examined for the presence of a bar. Within this sample, AGN host galaxies have a higher overall percentage of bars (51.8 per cent) than inactive galaxies exhibiting central star formation (37.1 per cent). This difference is primarily due to known effects: that the presence of both AGN and galactic bars is strongly correlated with both the stellar mass and integrated colour of the host galaxy. We control for this effect by examining the difference in AGN fraction between barred and unbarred galaxies in fixed bins of mass and colour. Once this effect is accounted for, there remains a small but statistically significant increase that represents 16 per cent of the average barred AGN fraction. Using the L_{[O III]}/MBH ratio as a measure of AGN strength, we show that barred AGNs do not exhibit stronger accretion than unbarred AGNs at a fixed mass and colour. The data are consistent with a model in which bar-driven fuelling does contribute to the probability of an actively growing black hole, but in which other dynamical mechanisms must contribute to the direct AGN fuelling via smaller, non-axisymmetric perturbations.

  20. Peculiar objects towards 3FGL J0133.3+5930: an eclipsing Be star and an active galactic nucleus

    Science.gov (United States)

    Martí, Josep; Luque-Escamilla, Pedro L.; Paredes, Josep M.; Iwasawa, Kazushi; Galindo, Daniel; Ribó, Marc; Marín-Felip, Víctor

    2017-02-01

    Aims: We aim to contribute to the identification of unassociated gamma-ray sources in the galactic plane to enlarge the currently known population of gamma-ray binaries and related systems, such as radio-emitting X-ray binaries and microquasars. These objects are currently regarded as excellent test beds for the understanding of high-energy phenomena in stellar systems. Methods: Potential targets of study are selected based on cross-identification of the third Fermi Large Area Telescope catalogue with historical catalogues of luminous stars that have often been found as optical counterparts in known cases. Follow-up observations and analysis of multi-wavelength archival data are later used to seek further proofs of association beyond the simple positional agreement. Results: Current results enable us to present here the case of the Fermi source 3FGL J0133.3+5930 where two peculiar objects have been discovered inside its region of uncertainty. One of them is the star TYC 3683-985-1 (LS I +59 79) whose eclipsing binary nature is reported in this work. The other is the X-ray source Swift J0132.9+5932, which we found to be a likely low-power active galactic nucleus at z = 0.1143 ± 0.0002. If this second object is of blazar type, it could easily account for the observed gamma-ray photon flux. However, this is not confirmed at present, thus rendering the star system TYC 3683-985-1 as a still possible alternative counterpart candidate to the Fermi source.

  1. Outflowing Diffuse Gas in the Active Galactic Nucleus of NGC 1068

    CERN Document Server

    Geballe, T R; Oka, T

    2015-01-01

    Spectra of the archetypal Type II Seyfert galaxy NGC 1068 in a narrow wavelength interval near 3.7 microns have revealed a weak absorption feature due to two lines of the molecular ion H3+. The observed wavelength of the feature corresponds to velocity of -70 km/s relative to the systemic velocity of the galaxy, implying an outward flow from the nucleus along the line of sight. The absorption by H3+ along with the previously known broad hydrocarbon absorption at 3.4~microns probably are formed in diffuse gas that is in close proximity to the continuum source, i.e. within a few tens of parsecs of the central engine. Based on that conclusion and the measured H3+ absorption velocity and with the assumption of a spherically symmetric wind we estimate a rate of mass outflow from the AGN of ~1 Msun/yr.

  2. The effects of baryon physics, black holes and active galactic nucleus feedback on the mass distribution in clusters of galaxies

    Science.gov (United States)

    Martizzi, Davide; Teyssier, Romain; Moore, Ben; Wentz, Tina

    2012-06-01

    The spatial distribution of matter in clusters of galaxies is mainly determined by the dominant dark matter component; however, physical processes involving baryonic matter are able to modify it significantly. We analyse a set of 500 pc resolution cosmological simulations of a cluster of galaxies with mass comparable to Virgo, performed with the AMR code RAMSES. We compare the mass density profiles of the dark, stellar and gaseous matter components of the cluster that result from different assumptions for the subgrid baryonic physics and galaxy formation processes. First, the prediction of a gravity-only N-body simulation is compared to that of a hydrodynamical simulation with standard galaxy formation recipes, and then all results are compared to a hydrodynamical simulation which includes thermal active galactic nucleus (AGN) feedback from supermassive black holes (SMBHs). We find the usual effects of overcooling and adiabatic contraction in the run with standard galaxy formation physics, but very different results are found when implementing SMBHs and AGN feedback. Star formation is strongly quenched, producing lower stellar densities throughout the cluster, and much less cold gas is available for star formation at low redshifts. At redshift z= 0 we find a flat density core of radius 10 kpc in both the dark and stellar matter density profiles. We speculate on the possible formation mechanisms able to produce such cores and we conclude that they can be produced through the coupling of different processes: (I) dynamical friction from the decay of black hole orbits during galaxy mergers; (II) AGN-driven gas outflows producing fluctuations of the gravitational potential causing the removal of collisionless matter from the central region of the cluster; (III) adiabatic expansion in response to the slow expulsion of gas from the central region of the cluster during the quiescent mode of AGN activity.

  3. PROBING THE EXTREME REALM OF ACTIVE GALACTIC NUCLEUS FEEDBACK IN THE MASSIVE GALAXY CLUSTER, RX J1532.9+3021

    Energy Technology Data Exchange (ETDEWEB)

    Hlavacek-Larrondo, J.; Allen, S. W.; Canning, R. E. A.; Werner, N.; Ehlert, S.; Von der Linden, A. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 452 Lomita Mall, Stanford, CA 94305-4085 (United States); Taylor, G. B.; Grimes, C. K. [Department of Physics and Astronomy, University of New-Mexico, Albuquerque, NM 87131 (United States); Fabian, A. C. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom); Sanders, J. S., E-mail: juliehl@stanford.edu [Max-Planck-Institut fur extraterrestrische Physik (MPE), Giessenbachstrasse, D-85748 Garching (Germany)

    2013-11-10

    We present a detailed Chandra, XMM-Newton, Very Large Array (VLA) and Hubble Space Telescope analysis of one of the strongest cool core clusters known, RX J1532.9+3021 (z = 0.3613). Using new, deep 90 ks Chandra observations, we confirm the presence of a western X-ray cavity or bubble, and report on a newly discovered eastern X-ray cavity. The total mechanical power associated with these active galactic nucleus (AGN) driven outflows is (22 ± 9) × 10{sup 44} erg s{sup –1}, and is sufficient to offset the cooling, indicating that AGN feedback still provides a viable solution to the cooling flow problem even in the strongest cool core clusters. Based on the distribution of the optical filaments, as well as a jet-like structure seen in the 325 MHz VLA radio map, we suggest that the cluster harbors older outflows along the north to south direction. The jet of the central AGN is therefore either precessing or sloshing-induced motions have caused the outflows to change directions. There are also hints of an X-ray depression to the north aligned with the 325 MHz jet-like structure, which might represent the highest redshift ghost cavity discovered to date. We further find evidence of a cold front (r ≈ 65 kpc) that coincides with the outermost edge of the western X-ray cavity and the edge of the radio mini-halo. The common location of the cold front with the edge of the radio mini-halo supports the idea that the latter originates from electrons being reaccelerated due to sloshing-induced turbulence. Alternatively, its coexistence with the edge of the X-ray cavity may be due to cool gas being dragged out by the outburst. We confirm that the central AGN is highly sub-Eddington and conclude that a >10{sup 10} M{sub ☉} or a rapidly spinning black hole is favored to explain both the radiative-inefficiency of the AGN and the powerful X-ray cavities.

  4. ACTIVE GALACTIC NUCLEUS FEEDBACK AT z ∼ 2 AND THE MUTUAL EVOLUTION OF ACTIVE AND INACTIVE GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Cimatti, A.; Brusa, M.; Talia, M. [Dipartimento di Fisica e Astronomia, Università di Bologna, Viale Berti Pichat 6/2, I-30127 Bologna (Italy); Mignoli, M. [INAF, Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Rodighiero, G. [Dipartimento di Fisica e Astronomia, Università di Padova, Vicolo dell' Osservatorio 3, I-35122 Padova (Italy); Kurk, J. [Max-Planck-Institut für Extraterrestrial Physik, Giessenbachstrasse, D-85748 Garching bei München (Germany); Cassata, P. [Aix Marseille Universite, CNRS, Laboratoire d' Astrophysique de Marseille, UMR 7326, F-13388 Marseille (France); Halliday, C. [23 rue d' Yerres, F-91230 Montgeron (France); Renzini, A. [INAF, Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Daddi, E., E-mail: a.cimatti@unibo.it [Laboratoire AIM, CEA/DSM-CNRS-Universite Paris Diderot, Irfu/Service d' Astrophysique, CEA Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France)

    2013-12-10

    The relationship between galaxies of intermediate stellar mass and moderate luminosity active galactic nuclei (AGNs) at 1 < z < 3 is investigated with a Galaxy Mass Assembly ultra-deep Spectroscopic Survey (GMASS) sample complemented with public data in the GOODS-South field. Using X-ray data, hidden AGNs are identified in unsuspected star-forming galaxies with no apparent signs of non-stellar activity. In the color-mass plane, two parallel trends emerge during the ∼2 Gyr between the average redshifts z ∼ 2.2 and z ∼ 1.3: while the red sequence becomes significantly more populated by ellipticals, the majority of AGNs with L(2-10 keV) > 10{sup 42.3} erg s{sup –1} disappear from the blue cloud/green valley where they were hosted predominantly by star-forming systems with disk and irregular morphologies. These results are even clearer when the rest-frame colors are corrected for dust reddening. At z ∼ 2.2, the ultraviolet spectra of active galaxies (including two Type 1 AGNs) show possible gas outflows with velocities up to about –500 km s{sup –1}, which are observed neither in inactive systems at the same redshift, nor at lower redshifts. Such outflows indicate the presence of gas that can move faster than the escape velocities of active galaxies. These results suggest that feedback from moderately luminous AGNs (log L{sub X} < 44.5 erg s{sup –1}) played a key role at z ≳ 2 by contributing to outflows capable of ejecting part of the interstellar medium and leading to a rapid decrease in star formation in host galaxies with stellar masses 10 < log(M/M{sub ⊙})< 11.

  5. KILOPARSEC-SCALE SPATIAL OFFSETS IN DOUBLE-PEAKED NARROW-LINE ACTIVE GALACTIC NUCLEI. I. MARKERS FOR SELECTION OF COMPELLING DUAL ACTIVE GALACTIC NUCLEUS CANDIDATES

    Energy Technology Data Exchange (ETDEWEB)

    Comerford, Julia M. [Astronomy Department, University of Texas at Austin, Austin, TX 78712 (United States); Gerke, Brian F. [Kavli Institute for Particle Astrophysics and Cosmology, M/S 29, Stanford Linear Accelerator Center, 2575 Sand Hill Road, Menlo Park, CA 94725 (United States); Stern, Daniel [Jet Propulsion Laboratory, California Institute of Technology, MS 169-221, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Cooper, Michael C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Weiner, Benjamin J. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Newman, Jeffrey A. [Department of Physics and Astronomy, Pittsburgh Particle Physics, Astrophysics, and Cosmology Center, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Madsen, Kristin [Space Radiation Laboratory, California Institute of Technology, MS 105-24, Pasadena, CA 91125 (United States); Barrows, R. Scott [Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701 (United States)

    2012-07-01

    Merger-remnant galaxies with kiloparsec (kpc) scale separation dual active galactic nuclei (AGNs) should be widespread as a consequence of galaxy mergers and triggered gas accretion onto supermassive black holes, yet very few dual AGNs have been observed. Galaxies with double-peaked narrow AGN emission lines in the Sloan Digital Sky Survey (SDSS) are plausible dual AGN candidates, but their double-peaked profiles could also be the result of gas kinematics or AGN-driven outflows and jets on small or large scales. To help distinguish between these scenarios, we have obtained spatial profiles of the AGN emission via follow-up long-slit spectroscopy of 81 double-peaked narrow-line AGNs in SDSS at 0.03 {<=} z {<=} 0.36 using Lick, Palomar, and MMT Observatories. We find that all 81 systems exhibit double AGN emission components with {approx}kpc projected spatial separations on the sky (0.2 h{sup -1}{sub 70} kpc <{Delta}x < 5.5 h{sup -1}{sub 70} kpc; median {Delta}x = 1.1 h{sup -1}{sub 70} kpc), which suggests that they are produced by kiloparsec-scale dual AGNs or kiloparsec-scale outflows, jets, or rotating gaseous disks. Further, the objects split into two subpopulations based on the spatial extent of the double emission components and the correlation between projected spatial separations and line-of-sight velocity separations. These results suggest that the subsample (58{sup +5}{sub -6}%) of the objects with spatially compact emission components may be preferentially produced by dual AGNs, while the subsample (42{sup +6}{sub -5}%) with spatially extended emission components may be preferentially produced by AGN outflows. We also find that for 32{sup +8}{sub -6}% of the sample the two AGN emission components are preferentially aligned with the host galaxy major axis, as expected for dual AGNs orbiting in the host galaxy potential. Our results both narrow the list of possible physical mechanisms producing the double AGN components, and suggest several observational

  6. The `harder when brighter' X-ray behaviour of the low luminosity active galactic nucleus NGC 7213

    CERN Document Server

    Emmanoulopoulos, D; McHardy, I M; Arevalo, P; Calvelo, D E; Uttley, P

    2012-01-01

    We present the first robust evidence of an anti-correlation between the X-ray photon index, \\Gamma, and the X-ray luminosity in a single low luminosity active galactic nuclei (LLAGN), NGC 7213. Up to now, such anti-correlation trends have been seen only in large samples of LLAGN that span a wide range of X-ray fluxes, although the opposite behaviour (i.e. a positive correlation between \\Gamma and X-ray luminosity) has been extensively studied for individual X-ray bright active galactic nuclei. For NGC 7213, we use the long-term X-ray monitoring data of Rossi X-ray Timing Explorer (RXTE), regularly obtained on average every two days from March 2006 to December 2009. Based on our X-ray data, we derive the \\Gamma versus flux and the hardness ratio versus flux relations, indicating clearly that NGC 7213 follows a `harder when brighter' spectral behaviour. Additionally, by analysing radio and optical data, and combining data from the literature, we form the most complete spectral energy distribution (SED) of the s...

  7. Active Galactic Nucleus Pairs from the Sloan Digital Sky Survey. I. The Frequency on ~ 5-100 kpc Scales

    CERN Document Server

    Liu, Xin; Strauss, Michael A; Hao, Lei

    2011-01-01

    Galaxy-galaxy mergers and close interactions have long been regarded as a viable mechanism for channeling gas towards the central supermassive black holes (SMBHs) of galaxies which are triggered as active galactic nuclei (AGNs). AGN pairs, in which the central SMBHs of a galaxy merger are both active, are expected to be common from such events. We conduct a systematic study of 1286 AGN pairs at z ~ 0.1 with line-of-sight velocity offsets dv 80% for pairs with the brightest nuclei. Our sample increases the number of known AGN pairs on these scales by more than an order of magnitude. We present their AGN and host star formation properties in a companion paper.

  8. NuSTAR Observations of the Compton-thick Active Galactic Nucleus and Ultraluminous X-ray Source Candidate in NGC 5643

    CERN Document Server

    Annuar, A; Alexander, D M; Lansbury, G B; Arévalo, P; Ballantyne, D R; Baloković, M; Bauer, F E; Boggs, S E; Brandt, W N; Brightman, M; Christensen, F E; Craig, W W; Del Moro, A; Hailey, C J; Harrison, F A; Hickox, R C; Matt, G; Puccetti, S; Ricci, C; Rigby, J R; Stern, D; Walton, D J; Zappacosta, L; Zhang, W

    2015-01-01

    We present two NuSTAR observations of the local Seyfert 2 active galactic nucleus (AGN) and an ultraluminous X-ray source (ULX) candidate in NGC 5643. Together with archival data from Chandra, XMM-Newton and Swift-BAT, we perform a high-quality broadband spectral analysis of the AGN over two decades in energy ($\\sim$0.5-100 keV). Previous X-ray observations suggested that the AGN is obscured by a Compton-thick (CT) column of obscuring gas along our line-of-sight. However, the lack of high-quality $\\gtrsim$ 10 keV observations, together with the presence of a nearby X-ray luminous source, NGC 5643 X-1, had left significant uncertainties in the characterization of the nuclear spectrum. NuSTAR now enables the AGN and NGC 5643 X-1 to be separately resolved above 10 keV for the first time and allows a direct measurement of the absorbing column density toward the nucleus. The new data show that the nucleus is indeed obscured by a CT column of $N_{\\rm{H}}$ $\\gtrsim$ 5 $\\times$ 10$^{24}$ cm$^{-2}$. The range of 2-10 ...

  9. Multi-wavelength GOALS Observations of Star Formation and Active Galactic Nucleus Activity in the Luminous Infrared Galaxy IC 883

    CERN Document Server

    Modica, F; Evans, A S; Kim, D C; Mazzarella, J M; Iwasawa, K; Petric, A; Howell, J H; Surace, J A; Armus, L; Spoon, H W W; Sanders, D B; Barnes, J E

    2011-01-01

    New optical HST, Spitzer, GALEX, and Chandra observations of the single-nucleus, luminous infrared galaxy (LIRG) merger IC 883 are presented. The galaxy is a member of the Great Observatories All-sky LIRG Survey (GOALS), and is of particular interest for a detailed examination of a luminous late-stage merger due to the richness of the optically-visible star clusters and the extended nature of the nuclear X-ray, mid-IR, CO and radio emission. In the HST ACS images, the galaxy is shown to contain 156 optically visible star clusters distributed throughout the nuclear regions and tidal tails of the merger, with a majority of visible clusters residing in an arc ~ 3-7 kpc from the position of the mid-infrared core of the galaxy. The luminosity functions of the clusters have an alpha_F435W ~ -2.17+/-0.22 and alpha_F814W ~ -2.01+/-0.21. Further, the colors and absolute magnitudes of the majority of the clusters are consistent with instantaneous burst population synthesis model ages in the range of a few x10^7 - 10^8 ...

  10. X-ray observational signature of a black hole accretion disc in an active galactic nucleus RXJ1633+4718

    CERN Document Server

    Yuan, Weimin; Zhou, Hongyan; Wang, Tinggui

    2010-01-01

    We report the discovery of a luminous ultra-soft X-ray excess in a radio-loud narrow-line Seyfert1 galaxy, RXJ1633+4718, from archival ROSAT observations. The thermal temperature of this emission, when fitted with a blackbody, is as low as 32.5(+8.0,-6.0)eV. This is in remarkable contrast to the canonical temperatures of ~0.1-0.2keV found hitherto for the soft X-ray excess in active galactic nuclei (AGN), and is interestingly close to the maximum temperature predicted for a postulated accretion disc in this object. If this emission is indeed blackbody in nature, the derived luminosity [3.5(+3.3,-1.5)x10^(44)ergs/s] infers a compact emitting area with a size [~5x10^(12)cm or 0.33AU in radius] that is comparable to several times the Schwarzschild radius of a black hole at the mass estimated for this AGN (3x10^6Msun). In fact, this ultra-steep X-ray emission can be well fitted as the (Compton scattered) Wien tail of the multi-temperature blackbody emission from an optically thick accretion disc, whose parameters...

  11. Physical Properties, Star Formation, and Active Galactic Nucleus Activity in Balmer Break Galaxies at 0 < z < 1

    CERN Document Server

    Tello, J Díaz; Padilla, N; Fujishiro, N; Hanami, H; Yoshikawa, T; Hatsukade, 'and' B; .,

    2013-01-01

    We present a spectroscopic study with the derivation of the physical properties of 37 Balmer break galaxies, which have the necessary lines to locate them in star-forming-AGN diagnostic diagrams. These galaxies span a redshift range from 0.045 to 0.93 and are somewhat less massive than similar samples of previous works. The studied sample has multiwavelength photometric data coverage from the ultraviolet to MIR Spitzer bands. We investigate the connection between star formation and AGN activity via optical, mass-excitation (MEx) and MIR diagnostic diagrams. Through optical diagrams, 31 (84%) star-forming galaxies, 2 (5%) composite galaxies and 3 (8%) AGNs were classified, whereas from the MEx diagram only one galaxy was classified as AGN. A total of 19 galaxies have photometry available in all the IRAC/Spitzer bands. Of these, 3 AGN candidates were not classified as AGN in the optical diagrams, suggesting they are dusty/obscured AGNs, or that nuclear star formation has diluted their contributions. Furthermore...

  12. The 60 Month All-Sky Burst Alert Telescope Survey of Active Galactic Nucleus and the Anisotropy of Nearby AGNs

    Science.gov (United States)

    Ajello, M.; Alexander, D. M.; Greiner, J.; Madejeski, G. M.; Gehrels, N.; Burlon, D.

    2014-01-01

    Surveys above 10 keV represent one of the best resources to provide an unbiased census of the population of active galactic nuclei (AGNs). We present the results of 60 months of observation of the hard X-ray sky with Swift/Burst Alert Telescope (BAT). In this time frame, BAT-detected (in the 15-55 keV band) 720 sources in an all-sky survey of which 428 are associated with AGNs, most of which are nearby. Our sample has negligible incompleteness and statistics a factor of approx. 2 larger over similarly complete sets of AGNs. Our sample contains (at least) 15 bona fide Compton-thick AGNs and 3 likely candidates. Compton-thick AGNs represent approx. 5% of AGN samples detected above 15 keV. We use the BAT data set to refine the determination of the log N-log S of AGNs which is extremely important, now that NuSTAR prepares for launch, toward assessing the AGN contribution to the cosmic X-ray background. We show that the log N-log S of AGNs selected above 10 keV is now established to approx. 10% precision. We derive the luminosity function of Compton-thick AGNs and measure a space density of 7.9(+4.1/-2.9)× 10(exp -5)/cubic Mpc for objects with a de-absorbed luminosity larger than 2 × 10(exp 42) erg / s. As the BAT AGNs are all mostly local, they allow us to investigate the spatial distribution of AGNs in the nearby universe regardless of absorption. We find concentrations of AGNs that coincide spatially with the largest congregations of matter in the local (much < 85 Mpc) universe. There is some evidence that the fraction of Seyfert 2 objects is larger than average in the direction of these dense regions..

  13. RESOLVING THE ACTIVE GALACTIC NUCLEUS AND HOST EMISSION IN THE MID-INFRARED USING A MODEL-INDEPENDENT SPECTRAL DECOMPOSITION

    Energy Technology Data Exchange (ETDEWEB)

    Hernán-Caballero, Antonio; Alonso-Herrero, Almudena [Instituto de Física de Cantabria, CSIC-UC, Avenida de los Castros s/n, E-39005, Santander (Spain); Hatziminaoglou, Evanthia [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching bei München (Germany); Spoon, Henrik W. W. [Cornell University, CRSR, Space Sciences Building, Ithaca, NY 14853 (United States); Almeida, Cristina Ramos [Instituto de Astrofísica de Canarias, Vía Láctea s/n, E-38205 La Laguna, Tenerife (Spain); Santos, Tanio Díaz [Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile); Hönig, Sebastian F. [School of Physics and Astronomy, University of Southampton, Southampton SO18 1BJ (United Kingdom); González-Martín, Omaira [Centro de Radioastronomía y Astrofísica (CRyA-UNAM), 3-72 (Xangari), 8701, Morelia (Mexico); Esquej, Pilar, E-mail: ahernan@ifca.unican.es [Departamento de Astrofísica, Facultad de CC. Físicas, Universidad Complutense de Madrid, E-28040 Madrid (Spain)

    2015-04-20

    We present results on the spectral decomposition of 118 Spitzer Infrared Spectrograph (IRS) spectra from local active galactic nuclei (AGNs) using a large set of Spitzer/IRS spectra as templates. The templates are themselves IRS spectra from extreme cases where a single physical component (stellar, interstellar, or AGN) completely dominates the integrated mid-infrared emission. We show that a linear combination of one template for each physical component reproduces the observed IRS spectra of AGN hosts with unprecedented fidelity for a template fitting method with no need to model extinction separately. We use full probability distribution functions to estimate expectation values and uncertainties for observables, and find that the decomposition results are robust against degeneracies. Furthermore, we compare the AGN spectra derived from the spectral decomposition with sub-arcsecond resolution nuclear photometry and spectroscopy from ground-based observations. We find that the AGN component derived from the decomposition closely matches the nuclear spectrum with a 1σ dispersion of 0.12 dex in luminosity and typical uncertainties of ∼0.19 in the spectral index and ∼0.1 in the silicate strength. We conclude that the emission from the host galaxy can be reliably removed from the IRS spectra of AGNs. This allows for unbiased studies of the AGN emission in intermediate- and high-redshift galaxies—currently inaccesible to ground-based observations—with archival Spitzer/IRS data and in the future with the Mid-InfraRed Instrument of the James Webb Space Telescope. The decomposition code and templates are available at http://denebola.org/ahc/deblendIRS.

  14. THERMAL AND RADIATIVE ACTIVE GALACTIC NUCLEUS FEEDBACK HAVE A LIMITED IMPACT ON STAR FORMATION IN HIGH-REDSHIFT GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Roos, Orianne; Juneau, Stéphanie; Bournaud, Frédéric; Gabor, Jared M., E-mail: orianne.roos@cea.fr [CEA-Saclay, F-91190 Gif-sur-Yvette (France)

    2015-02-10

    The effects of active galactic nuclei (AGNs) on their host galaxies depend on the coupling between the injected energy and the interstellar medium (ISM). Here, we model and quantify the impact of long-range AGN ionizing radiation—in addition to the often considered small-scale energy deposition—on the physical state of the multi-phase ISM of the host galaxy and on its total star formation rate (SFR). We formulate an AGN spectral energy distribution matched with observations, which we use with the radiative transfer (RT) code Cloudy to compute AGN ionization in a simulated high-redshift disk galaxy. We use a high-resolution (∼6 pc) simulation including standard thermal AGN feedback and calculate RT in post-processing. Surprisingly, while these models produce significant AGN-driven outflows, we find that AGN ionizing radiation and heating reduce the SFR by a few percent at most for a quasar luminosity (L {sub bol} = 10{sup 46.5} erg s{sup –1}). Although the circumgalactic gaseous halo can be kept almost entirely ionized by the AGN, most star-forming clouds (n ≳ 10{sup 2} {sup –} {sup 3} cm{sup –3}) and even the reservoirs of cool atomic gas (n ∼ 0.3-10 cm{sup –3})—which are the sites of future star formation (SF; 100-200 Myr), are generally too dense to be significantly affected. Our analysis ignores any absorption from a putative torus, making our results upper limits on the effects of ionizing radiation. Therefore, while the AGN-driven outflows can remove substantial amounts of gas in the long term, the impact of AGN feedback on the SF efficiency in the interstellar gas in high-redshift galaxies is marginal, even when long-range radiative effects are accounted for.

  15. WISE J233237.05–505643.5: A double-peaked, broad-lined active galactic nucleus with a spiral-shaped radio morphology

    Energy Technology Data Exchange (ETDEWEB)

    Tsai, Chao-Wei [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Jarrett, T. H. [Astronomy Department, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Stern, Daniel; Assef, Roberto J.; Eisenhardt, Peter R. M.; Wu, Jingwen [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States); Emonts, Bjorn [Centro de Astrobiología (INTA-CSIC), Ctra de Torrejón a Ajalvir, km 4, E-28850 Torrejón de Ardoz, Madrid (Spain); Barrows, R. Scott [Arkansas Center for Space and Planetary Sciences, University of Arkansas, Fayetteville, AR 72701 (United States); Norris, Ray P. [Australia Telescope National Facility, CSIRO Astronomy and Space Science, P.O. Box 76, Epping NSW 1710 (Australia); Lonsdale, Carol [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Blain, Andrew W. [Department of Physics and Astronomy, University of Leicester, 1 University Road, Leicester LE1 7RH (United Kingdom); Benford, Dominic J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Stalder, Brian; Stubbs, Christopher W. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); High, F. William [Kavli Institute for Cosmological Physics, University of Chicago, 5640 South Ellis Avenue, Chicago, IL 60637 (United States); Li, K. L.; Kong, Albert K. H., E-mail: Chao-Wei.Tsai@jpl.nasa.gov [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

    2013-12-10

    We present radio continuum mapping, optical imaging, and spectroscopy of the newly discovered double-peaked, broad-lined active galactic nucleus (AGN) WISE J233237.05–505643.5 at redshift z = 0.3447. This source exhibits an FR-I and FR-II hybrid morphology, characterized by a bright core, jet, and Doppler-boosted lobe structures in Australian Telescope Compact Array continuum maps at 1.5, 5.6, and 9 GHz. Unlike most FR-II objects, W2332–5056 is hosted by a disk-like galaxy. The core has a projected 5'' linear radio feature that is perpendicular to the curved primary jet, hinting at unusual and complex activity within the inner 25 kpc. The multi-epoch, optical-near-IR photometric measurements indicate significant variability over a 3-20 yr baseline from the AGN component. Gemini South optical data show unusual double-peaked emission-line features: the centroids of the broad-lined components of Hα and Hβ are blueshifted with respect to the narrow lines and host galaxy by ∼3800 km s{sup –1}. We examine possible cases that involve single or double supermassive black holes in the system and discuss the required future investigations to disentangle the mysterious nature of this system.

  16. X-ray spectral analysis of the low-luminosity active galactic nucleus NGC 7213 using long XMM-Newton observations

    CERN Document Server

    Emmanoulopoulos, D; Nicastro, F; McHardy, I M

    2012-01-01

    We present the X-ray spectral results from the longest X-ray multi-mirror mission-Newton observation, 133 ks, of the low luminosity active galactic nucleus NGC 7213. The hardness ratio analysis of the X-ray light curves discloses a rather constant X-ray spectral shape, at least for the observed exposure time, enabling us to perform X-ray spectral studies using the total observed spectrum. Apart from a neutral Fe K\\alpha emission line, we also detect narrow emission lines from the ionised iron species, Fe xxv and Fe xxvi. Our analysis suggests that the neutral Fe K\\alpha originates from a Compton-thin reflector, while the gas responsible for the high ionisation lines is collisionally excited. The overall spectrum, in the 0.3-10 keV energy band, registered by the European Photon Imaging Camera, can be modelled by a power-law component (with a slope of \\Gamma\\simeq1.9) plus two thermal components at 0.36 and 8.84 keV. The low-energy thermal component is entirely consistent with the X-ray spectral data obtained b...

  17. Multi-phase Nature of a Radiation-Driven Fountain with Nuclear Starburst in a Low-mass Active Galactic Nucleus

    CERN Document Server

    Wada, Keiichi; Meijerink, Rowin

    2016-01-01

    The structures and dynamics of molecular, atomic, and ionized gases are studied around a low-luminosity active galactic nucleus (AGN) with a small ($2\\times 10^6 M_\\odot$) black hole using 3D radiation hydrodynamic simulations. We studied, for the first time, the non-equilibrium chemistry for the X-ray dominated region in the "radiation-driven fountain" (Wada 2012) with supernova feedback. A double hollow cone structure is naturally formed without postulating a thick "torus" around a central source. The cone is occupied with an inhomogeneous, diffuse ionized gas and surrounded by a geometrically thick ($h/r \\gtrsim 1$) atomic gas. Dense molecular gases are distributed near the equatorial plane, and energy feedback from supernovae enhances their scale height. Molecular hydrogen exists in a hot phase ( > 1000 K) as well as in a cold ( $10^3$ cm$^{-3}$) phase. The velocity dispersion of H$_2$ in the vertical direction is comparable to the rotational velocity, which is consistent with near infrared observations o...

  18. NuSTAR OBSERVATIONS OF THE COMPTON-THICK ACTIVE GALACTIC NUCLEUS AND ULTRALUMINOUS X-RAY SOURCE CANDIDATE IN NGC 5643

    Energy Technology Data Exchange (ETDEWEB)

    Annuar, A.; Gandhi, P.; Alexander, D. M.; Lansbury, G. B.; Moro, A. Del [Centre for Extragalactic Astronomy, Department of Physics, University of Durham, South Road, Durham, DH1 3LE (United Kingdom); Arévalo, P. [Instituto de Física y Astronomía, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretana N 1111, Playa Ancha, Valparaíso (Chile); Ballantyne, D. R. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Baloković, M.; Brightman, M.; Harrison, F. A. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Bauer, F. E. [EMBIGGEN Anillo, Concepción (Chile); Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Brandt, W. N. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Christensen, F. E. [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Matt, G. [Dipartimento di Matematica e Fisica, Universitá degli Studi Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Puccetti, S. [ASI Science Data Center, via Galileo Galilei, I-00044 Frascati (Italy); Ricci, C. [Department of Astronomy, Kyoto University, Kitashirakawa-Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); and others

    2015-12-10

    We present two Nuclear Spectroscopic Telescope Array (NuSTAR) observations of the local Seyfert 2 active galactic nucleus (AGN) and an ultraluminous X-ray source (ULX) candidate in NGC 5643. Together with archival data from Chandra, XMM-Newton, and Swift-BAT, we perform a high-quality broadband spectral analysis of the AGN over two decades in energy (∼0.5–100 keV). Previous X-ray observations suggested that the AGN is obscured by a Compton-thick (CT) column of obscuring gas along our line of sight. However, the lack of high-quality ≳10 keV observations, together with the presence of a nearby X-ray luminous source, NGC 5643 X–1, have left significant uncertainties in the characterization of the nuclear spectrum. NuSTAR now enables the AGN and NGC 5643 X–1 to be separately resolved above 10 keV for the first time and allows a direct measurement of the absorbing column density toward the nucleus. The new data show that the nucleus is indeed obscured by a CT column of N{sub H} ≳ 5 × 10{sup 24} cm{sup −2}. The range of 2–10 keV absorption-corrected luminosity inferred from the best-fitting models is L{sub 2–10,int} = (0.8–1.7) × 10{sup 42} erg s{sup −1}, consistent with that predicted from multiwavelength intrinsic luminosity indicators. In addition, we also study the NuSTAR data for NGC 5643 X–1 and show that it exhibits evidence of a spectral cutoff at energy E ∼ 10 keV, similar to that seen in other ULXs observed by NuSTAR. Along with the evidence for significant X-ray luminosity variations in the 3–8 keV band from 2003 to 2014, our results further strengthen the ULX classification of NGC 5643 X–1.

  19. Peculiar objects towards 3FGL J0133.3+5930: an eclipsing Be star and an active galactic nucleus

    CERN Document Server

    Martí, Josep; Paredes, Josep M; Iwasawa, Kazushi; Galindo, Daniel; Ribó, Marc; Marín-Felip, Víctor

    2016-01-01

    Aims. We aim to contribute to the identification of unassociated gamma-ray sources in the galactic plane in order to enlarge the currently known population of gamma-ray binaries and related systems, such as radio emitting X-ray binaries and microquasars. These objects are currently regarded as excellent test beds for the understanding of high energy phenomena in stellar systems. Methods. Potential targets of study are selected based on cross-identification of the 3rd Fermi Large Area Telescope catalogue with historical catalogues of luminous stars often found as optical counterparts in known cases. Follow-up observations and analysis of multi-wavelength archival data are later used to seek further proofs of association beyond the simple positional agreement. Results. Current results enable us to present here the case of the Fermi source 3FGL J0133.3+5930 where two peculiar objects have been discovered inside its region of uncertainty. One of them is the star TYC 3683-985-1 (LS I +59 79) whose eclipsing binary...

  20. The Fingerprint of a Galactic Nucleus

    Science.gov (United States)

    Nogueras-Lara, Francisco; Schödel, Rainer

    2017-01-01

    Because of the unique observational challenges -extreme crowding and extinction- any existing large-scale near-infrared (NIR) imaging data on the Galactic Center (GC) are limited by either one, or a combination, of the following: saturation, lack of sensitivity, too low angular resolution, or lack of multi-wavelength coverage. To overcome this situation, we are currently carrying out a sensitive, 0.2'' resolution JHK imaging survey of the Galactic Centre with HAWK-I/VLT. Thanks to holographic imaging, we achieve a similar resolution than with HST/WFC, but can cover also the long NIR, beyond 2 micrometers, which is essential to deal with extinction. Our survey is supported by an ESO Large Programme and will provide photometrically accurate (few percent uncertainty for H < 18 stars), high-angular resolution, NIR data for an area of several 1000 pc2, a more than ten-fold increase compared to the current state of affairs. Here we present an overview and first results.

  1. The New Numerical Galaxy Catalog (ν2GC): An updated semi-analytic model of galaxy and active galactic nucleus formation with large cosmological N-body simulations

    Science.gov (United States)

    Makiya, Ryu; Enoki, Motohiro; Ishiyama, Tomoaki; Kobayashi, Masakazu A. R.; Nagashima, Masahiro; Okamoto, Takashi; Okoshi, Katsuya; Oogi, Taira; Shirakata, Hikari

    2016-04-01

    We present a new cosmological galaxy formation model, ν2GC, as an updated version of our previous model νGC. We adopt the so-called "semi-analytic" approach, in which the formation history of dark matter halos is computed by N-body simulations, while the baryon physics such as gas cooling, star formation, and supernova feedback are simply modeled by phenomenological equations. Major updates of the model are as follows: (1) the merger trees of dark matter halos are constructed in state-of-the-art N-body simulations, (2) we introduce the formation and evolution process of supermassive black holes and the suppression of gas cooling due to active galactic nucleus (AGN) activity, (3) we include heating of the intergalactic gas by the cosmic UV background, and (4) we tune some free parameters related to the astrophysical processes using a Markov chain Monte Carlo method. Our N-body simulations of dark matter halos have unprecedented box size and mass resolution (the largest simulation contains 550 billion particles in a 1.12 Gpc h-1 box), enabling the study of much smaller and rarer objects. The model was tuned to fit the luminosity functions of local galaxies and mass function of neutral hydrogen. Local observations, such as the Tully-Fisher relation, the size-magnitude relation of spiral galaxies, and the scaling relation between the bulge mass and black hole mass were well reproduced by the model. Moreover, the model also reproduced well the cosmic star formation history and redshift evolution of rest-frame K-band luminosity functions. The numerical catalog of the simulated galaxies and AGNs is publicly available on the web.

  2. Elusive active galactic nuclei

    NARCIS (Netherlands)

    Maiolino, R; Comastri, A; Gilli, R; Nagar, NM; Bianchi, S; Boker, T; Colbert, E; Krabbe, A; Marconi, A; Matt, G; Salvati, M

    2003-01-01

    A fraction of active galactic nuclei do not show the classical Seyfert-type signatures in their optical spectra, i.e. they are optically 'elusive'. X-ray observations are an optimal tool to identify this class of objects. We combine new Chandra observations with archival X-ray data in order to obtai

  3. Probing quantum gravity using photons from a flare of the active galactic nucleus Markarian 501 observed by the MAGIC telescope

    CERN Document Server

    Albert, J; Anderhub, H; Antonelli, L A; Antoranz, P; Backes, M; Baixeras, C; Barrio, J A; Bartko, H; Bastieri, D; Becker, J K; Bednarek, W; Berger, K; Bernardini, E; Bigongiari, C; Biland, A; Bock, R K; Bordas, P; Bosch-Ramon, V; Bretz, T; Britvitch, I; Camara, M; Carmona, E; Chilingarian, A; Commichau, S; Contreras, J L; Cortina, J; Costado, M T; Covino, S; Dazzi, F; De Angelis, A; De Cea del Pozo, E; Delgado Mendez, C; de los Reyes, R; De Lotto, B; De Maria, M; De Sabata, F; Dominguez, A; Dorner, D; Doro, M; Errando, M; Fagiolini, M; Ferenc, D; Fernández, E; Firpo, R; Fonseca, M V; Font, L; Galante, N; García-López, R J; Garczarczyk, M; Gaug, M; Göbel, F; Hayashida, M; Herrero, A; Höhne, D; Hose, J; Hsu, C C; Huber, S; Jogler, T; Kranich, D; La Barbera, A; Laille, A; Leonardo, E; Lindfors, E; Lombardi, S; Longo, F; López, M; Lorenz, E; Majumdar, P; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Mariotti, M; Martínez, M; Mazin, D; Meucci, M; Meyer, M; Miranda, J M; Mirzoyan, R; Moles, M; Moralejo, A; Nieto, D; Nilsson, K; Ninkovic, J; Otte, N; Oya, I; Panniello, M; Paoletti, R; Paredes, J M; Pasanen, M; Pascoli, D; Pauss, F; Pegna, R; Pérez-Torres, M A; Persic, M; Peruzzo, L; Piccioli, A; Prada, F; Puchades, N; Raymers, A; Ribó, M; Rico, J; Rissi, M; Robert, A; Rügamer, S; Saggion, A; Saitô, T; Salvati, M; Sanchez-Conde, M; Sartori, P; Satalecka, K; Scalzotto, V; Scapin, V; Schmitt, R; Schweizer, T; Shayduk, M; Shinozaki, K; Sidro, N; Sierpowska-Bartosik, A; Sillanpää, A; Spanier, F; Stamerra, A; Stark, L S; Takalo, L; Tavecchio, F; Temnikov, P; Tescaro, D; Teshima, M; Tluczykont, M; Torres, D F; Turini, N; Vankov, H; Venturini, A; Vitale, V; Wagner, R M; Wittek, W; Zabalza, M; Zandanel, F; Zanin, R; Ellis, Jonathan Richard; Mavromatos, N E; Nanopoulos, D V; Sakharov, Alexander S; Sarkisyan-Grinbaum, E

    2008-01-01

    We use the timing of photons observed by the MAGIC gamma-ray telescope during a flare of the active galaxy Markarian 501 to probe a vacuum refractive index ~ 1-(E/M_QGn)^n, n = 1,2, that might be induced by quantum gravity. The peaking of the flare is found to maximize for quantum-gravity mass scales M_QG1 ~ 0.4x10^18 GeV or M_QG2 ~ 0.6x10^11 GeV, and we establish lower limits M_QG1 > 0.26x10^18 GeV or M_QG2 > 0.39x10^11 GeV at the 95% C.L. Monte Carlo studies confirm the MAGIC sensitivity to propagation effects at these levels. Thermal plasma effects in the source are negligible, but we cannot exclude the importance of some other source effect.

  4. Galactic outflow driven by the active nucleus and the origin of the gamma-ray emission in NGC 1068

    CERN Document Server

    Lamastra, A; Guetta, D; Antonelli, L A; Colafrancesco, S; Menci, N; Puccetti, S; Stamerra, A; Zappacosta, L

    2016-01-01

    We compute the non-thermal emissions produced by relativistic particles accelerated by the AGN-driven shocks in NGC 1068, and we compare the model predictions with the observed gamma-ray and radio spectra . The former is contributed by pion decay, inverse Compton scattering, and bremsstrahlung, while the latter is produced by synchrotron radiation. We derive the gamma-ray and radio emissions by assuming the standard acceleration theory, and we discuss how our results compare with those corresponding to other commonly assumed sources of gamma-ray and radio emissions, like Supernova remnants (SNR) or AGN jets. We find that the AGN-driven shocks observed in the circumnuclear molecular disk of such a galaxy provide a contribution to the gamma-ray emission comparable to that provided by the starburst activity when standard particle acceleration efficiencies are assumed, while they can yield the whole gamma-ray emission only when the parameters describing the acceleration efficiency and the proton coupling with the...

  5. Self-regulated growth of supermassive black holes by a dual jet-heating active galactic nucleus feedback mechanism: methods, tests and implications for cosmological simulations

    Science.gov (United States)

    Dubois, Yohan; Devriendt, Julien; Slyz, Adrianne; Teyssier, Romain

    2012-03-01

    We develop a subgrid model for the growth of supermassive black holes (BHs) and their associated active galactic nucleus (AGN) feedback in hydrodynamical cosmological simulations. This model transposes previous attempts to describe BH accretion and AGN feedback with the smoothed particle hydrodynamics (SPH) technique to the adaptive mesh refinement framework. It also furthers their development by implementing a new jet-like outflow treatment of the AGN feedback which we combine with the heating mode traditionally used in the SPH approach. Thus, our approach allows one to test the robustness of the conclusions derived from simulating the impact of self-regulated AGN feedback on galaxy formation vis-à-vis the numerical method. Assuming that BHs are created in the early stages of galaxy formation, they grow by mergers and accretion of gas at a Eddington-limited Bondi accretion rate. However this growth is regulated by AGN feedback which we model using two different modes: a quasar-heating mode when accretion rates on to the BHs are comparable to the Eddington rate, and a radio-jet mode at lower accretion rates which not only deposits energy, but also deposits mass and momentum on the grid. In other words, our feedback model deposits energy as a succession of thermal bursts and jet outflows depending on the properties of the gas surrounding the BHs. We assess the plausibility of such a model by comparing our results to observational measurements of the co-evolution of BHs and their host galaxy properties, and check their robustness with respect to numerical resolution. We show that AGN feedback must be a crucial physical ingredient for the formation of massive galaxies as it appears to be able to efficiently prevent the accumulation of and/or expel cold gas out of haloes/galaxies and significantly suppress star formation. Our model predicts that the relationship between BHs and their host galaxy mass evolves as a function of redshift, because of the vigorous accretion

  6. The Structure and Dynamics of An Active Galactic Nucleus Torus : CO Line Predictions for ALMA from Three-dimensional Hydrodynamical Simulations with X-ray-driven Chemistry

    NARCIS (Netherlands)

    Perez Beaupuits, J.P.; Wada, K.; Spaans, M.

    2011-01-01

    Several attempts have been made to model the mass distribution and dynamical evolution of the circumnuclear gas in active galactic nuclei (AGNs). However, chemical evolution is not included in detail in three-dimensional (3D) hydrodynamic simulations. The X-ray radiation from the AGN can drive the g

  7. The Structure and Dynamics of An Active Galactic Nucleus Torus: CO Line Predictions for ALMA from Three-dimensional Hydrodynamical Simulations with X-ray-driven Chemistry

    NARCIS (Netherlands)

    Pérez-Beaupuits, J. P.; Wada, K.; Spaans, M.

    2011-01-01

    Several attempts have been made to model the mass distribution and dynamical evolution of the circumnuclear gas in active galactic nuclei (AGNs). However, chemical evolution is not included in detail in three-dimensional (3D) hydrodynamic simulations. The X-ray radiation from the AGN can drive the g

  8. Shedding Light on the Compton-thick Active Galactic Nucleus in the Ultraluminous Infrared Galaxy UGC 5101 with Broadband X-Ray Spectroscopy

    Science.gov (United States)

    Oda, Saeko; Tanimoto, Atsushi; Ueda, Yoshihiro; Imanishi, Masatoshi; Terashima, Yuichi; Ricci, Claudio

    2017-02-01

    We report the broadband X-ray spectra of the ultraluminous infrared galaxy (ULIRG) UGC 5101 in the 0.25–100 keV band observed with the Swift/Burst Alert Telescope (BAT), Nuclear Spectroscopic Telescope Array (NuSTAR), Suzaku, XMM-Newton, and Chandra. A Compton-thick active galactic nucleus (AGN) obscured with a hydrogen column density of ≈ 1.3× {10}24 cm‑2 is detected above 10 keV. A spectral fit with a numerical torus model favors a large half-opening angle of the torus, > 41°, suggesting that the covering fraction of material heavily obscuring the X-ray source is moderate. The intrinsic 2–10 keV luminosity is determined to be ≈ 1.4× {10}43 erg s‑1, which is ≈ 2.5 times larger than the previous estimate using only data below 10 keV with a simple spectral model. We find that UGC 5101 shows the ratio between the [O iv] 26 μm line and 2–10 keV luminosities similar to those of normal Seyfert galaxies, along with other ULIRGs observed with NuSTAR, indicating that a significant portion of local ULIRGs are not really “X-ray faint” with respect to the flux of forbidden lines originating from the narrow-line region. We propose a possible scenario that (1) the AGN in UGC 5101 is surrounded not only by Compton-thick matter located close to the equatorial plane but also by Compton-thin ({N}{{H}}∼ {10}21 cm‑2) matter in the torus-hole region and (2) it is accreting at a high Eddington rate with a steep UV to X-ray spectral energy distribution. Nevertheless, we argue that AGNs in many ULIRGs do not look extraordinary (i.e., extremely X-ray faint), as suggested by recent works, compared with normal Seyferts.

  9. Understanding active galactic nuclei: peeling the onion.

    Science.gov (United States)

    Krolik, J. H.

    A brief review is presented of selected current problems in understanding active galactic nuclei, with special emphasis on the contributions that X-ray observations can make. Questions having to do with: how the character of the host galaxy influences nuclear activity; emission line regions; the border between the nucleus and the stellar portion of the active galaxy; radiation of the nonthermal continuum; and the possible existence of an accretion disk are touched upon.

  10. Active Galactic Nuclei Feedback and Galactic Outflows

    Science.gov (United States)

    Sun, Ai-Lei

    Feedback from active galactic nuclei (AGN) is thought to regulate the growth of supermassive black holes (SMBHs) and galaxies. The most direct evidence of AGN feedback is probably galactic outflows. This thesis addresses the link between SMBHs and their host galaxies from four different observational perspectives. First, I study the local correlation between black hole mass and the galactic halo potential (the MBH - Vc relation) based on Very Large Array (VLA) HI observations of galaxy rotation curves. Although there is a correlation, it is no tighter than the well-studied MBH - sigma* relation between the black hole mass and the potential of the galactic bulge, indicating that physical processes, such as feedback, could link the evolution of the black hole to the baryons in the bulge. In what follows, I thus search for galactic outflows as direct evidence of AGN feedback. Second, I use the Atacama Large Millimeter Array (ALMA) to observe a luminous obscured AGN that hosts an ionized galactic outflow and find a compact but massive molecular outflow that can potentially quench the star formation in 10. 6 years.The third study extends the sample of known ionized outflows with new Magellan long-slit observations of 12 luminous obscured AGN. I find that most luminous obscured AGN (Lbol > 1046 ergs s-1) host ionized outflows on 10 kpc scales, and the size of the outflow correlates strongly with the luminosity of the AGN. Lastly, to capitalize on the power of modern photometric surveys, I experiment with a new broadband imaging technique to study the morphology of AGN emission line regions and outflows. With images from the Sloan Digital Sky Survey (SDSS), this method successfully constructs images of the [OIII]lambda5007 emission line and reveals hundreds of extended emission-line systems. When applied to current and future surveys, such as the Large Synoptic Survey Telescope (LSST), this technique could open a new parameter space for the study of AGN outflows. In

  11. Active galactic nuclei

    CERN Document Server

    Blandford, RD; Woltjer, L

    1990-01-01

    Starting with this volume, the Lecture Notes of the renowned Advanced Courses of the Swiss Society for Astrophysics and Astronomy will be published annually. In each course, three extensive lectures given by leading experts in their respective fields cover different and essential aspects of the subject. The 20th course, held at Les Diablerets in April 1990, dealt with current research on active galactic nuclei; it represents the most up-to-date views on the subject, presented with particular regard for clarity. The previous courses considered a wide variety of subjects, beginning with ""Theory

  12. A Chandra Observation of the Ultraluminous Infrared Galaxy IRAS 19254-7245 (The Superantennae): X-Ray Emission from the Compton-Thick Active Galactic Nucleus and the Diffuse Starburst

    Science.gov (United States)

    Jia, Jianjun; Ptak, Andrew; Heckman, Timothy M.; Braito, Valentina; Reeves, James

    2012-01-01

    We present a Chandra observation of IRAS 19254-7245, a nearby ultraluminous infrared galaxy also known as the Superantennae. The high spatial resolution of Chandra allows us to disentangle for the first time the diffuse starburst (SB) emission from the embedded Compton-thick active galactic nucleus (AGN) in the southern nucleus. No AGN activity is detected in the northern nucleus. The 2-10 keV spectrum of the AGN emission is fitted by a flat power law (TAU = 1.3) and an He-like Fe Kalpha line with equivalent width 1.5 keV, consistent with previous observations. The Fe K line profile could be resolved as a blend of a neutral 6.4 keV line and an ionized 6.7 keV (He-like) or 6.9 keV (H-like) line. Variability of the neutral line is detected compared with the previous XMM-Newton and Suzaku observations, demonstrating the compact size of the iron line emission. The spectrum of the galaxy-scale extended emission excluding the AGN and other bright point sources is fitted with a thermal component with a best-fit kT of approximately 0.8 keV. The 2-10 keV luminosity of the extended emission is about one order of magnitude lower than that of the AGN. The basic physical and structural properties of the extended emission are fully consistent with a galactic wind being driven by the SB. A candidate ultraluminous X-ray source is detected 8 south of the southern nucleus. The 0.3 - 10 keV luminosity of this off-nuclear point source is approximately 6 x 10(exp 40) erg per second if the emission is isotropic and the source is associated with the Superantennae.

  13. THE SPITZER MID-INFRARED ACTIVE GALACTIC NUCLEUS SURVEY. I. OPTICAL AND NEAR-INFRARED SPECTROSCOPY OF OBSCURED CANDIDATES AND NORMAL ACTIVE GALACTIC NUCLEI SELECTED IN THE MID-INFRARED

    Energy Technology Data Exchange (ETDEWEB)

    Lacy, M. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Ridgway, S. E. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Gates, E. L. [UCO/Lick Observatory, P.O. Box 85, Mount Hamilton, CA 95140 (United States); Nielsen, D. M. [Department of Astronomy, University of Wisconsin, 475 N. Charter Street, Madison, WI 53706 (United States); Petric, A. O. [Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Sajina, A. [Department of Physics and Astronomy, Tuffs University, 212 College Avenue, Medford, MA 02155 (United States); Urrutia, T. [Leibniz-Institut für Astrophysik Potsdam, An der Sternwarte 16, D-14482 Potsdam (Germany); Cox Drews, S. [946 Mangrove Avenue 102, Sunnyvale, CA 94086 (United States); Harrison, C. [Department of Astronomy, University of Michigan, Ann Arbor, MI 48109 (United States); Seymour, N. [CSIRO, P.O. Box 76, Epping, NSW 1710 (Australia); Storrie-Lombardi, L. J. [Spitzer Science Center, California Institute of Technology, Pasadena, CA 91125 (United States)

    2013-10-01

    We present the results of a program of optical and near-infrared spectroscopic follow-up of candidate active galactic nuclei (AGNs) selected in the mid-infrared. This survey selects both normal and obscured AGNs closely matched in luminosity across a wide range, from Seyfert galaxies with bolometric luminosities L {sub bol} ∼ 10{sup 10} L {sub ☉} to highly luminous quasars (L {sub bol} ∼ 10{sup 14} L {sub ☉}), all with redshifts ranging from 0 to 4.3. Samples of candidate AGNs were selected with mid-infrared color cuts at several different 24 μm flux density limits to ensure a range of luminosities at a given redshift. The survey consists of 786 candidate AGNs and quasars, of which 672 have spectroscopic redshifts and classifications. Of these, 137 (20%) are type 1 AGNs with blue continua, 294 (44%) are type 2 objects with extinctions A{sub V} ∼> 5 toward their AGNs, 96 (14%) are AGNs with lower extinctions (A{sub V} ∼ 1), and 145 (22%) have redshifts, but no clear signs of AGN activity in their spectra. Of the survey objects 50% have L {sub bol} > 10{sup 12} L {sub ☉}, in the quasar regime. We present composite spectra for type 2 quasars and objects with no signs of AGN activity in their spectra. We also discuss the mid-infrared—emission-line luminosity correlation and present the results of cross correlations with serendipitous X-ray and radio sources. The results show that: (1) obscured objects dominate the overall AGN population, (2) mid-infrared selected AGN candidates exist which lack AGN signatures in their optical spectra but have AGN-like X-ray or radio counterparts, and (3) X-ray and optical classifications of obscured and unobscured AGNs often differ.

  14. Detection of a possible X-ray Quasi-periodic Oscillation in the Active Galactic Nucleus 1H~0707-495

    CERN Document Server

    Pan, Hai-Wu; Yao, Su; Zhou, Xin-Lin; Liu, Bifang; Zhou, Hongyan; Zhang, Shuang-Nan

    2016-01-01

    Quasi-periodic oscillation (QPO) detected in the X-ray radiation of black hole X-ray binaries (BHXBs) is thought to originate from dynamical processes in the close vicinity of the black holes (BHs), and thus carries important physical information therein. Such a feature is extremely rare in active galactic nuclei (AGNs) with supermassive BHs. Here we report on the detection of a possible X-ray QPO signal with a period of 3800\\,s at a confidence level $>99.99\\%$ in the narrow-line Seyfert 1 galaxy (NLS1) 1H~0707-495 in one data set in 0.2-10\\,keV taken with {\\it XMM-Newton}. The statistical significance is higher than that of most previously reported QPOs in AGNs. The QPO is highly coherent (quality factor $Q=\

  15. Elusive Active Galactic Nuclei

    CERN Document Server

    Maiolino, R; Gilli, R; Nagar, N M; Bianchi, S; Böker, T; Colbert, E; Krabbe, A; Marconi, A; Matt, G; Salvati, M

    2003-01-01

    A fraction of active galactic nuclei do not show the classical Seyfert-type signatures in their optical spectra, i.e. they are optically "elusive". X-ray observations are an optimal tool to identify this class of objects. We combine new Chandra observations with archival X-ray data in order to obtain a first estimate of the fraction of elusive AGN in local galaxies and to constrain their nature. Our results suggest that elusive AGN have a local density comparable to or even higher than optically classified Seyfert nuclei. Most elusive AGN are heavily absorbed in the X-rays, with gas column densities exceeding 10^24 cm^-2, suggesting that their peculiar nature is associated with obscuration. It is likely that in elusive AGN, the nuclear UV source is completely embedded and the ionizing photons cannot escape, which prevents the formation of a classical Narrow Line Region. Elusive AGN may contribute significantly to the 30 keV bump of the X-ray background.

  16. Evidence for wide-spread active galactic nucleus-driven outflows in the most massive z ∼ 1-2 star-forming galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Genzel, R.; Förster Schreiber, N. M.; Rosario, D.; Lang, P.; Lutz, D.; Wisnioski, E.; Wuyts, E.; Wuyts, S.; Bandara, K.; Bender, R.; Berta, S.; Kurk, J.; Mendel, J. T.; Tacconi, L. J.; Wilman, D.; Beifiori, A.; Burkert, A.; Buschkamp, P.; Chan, J. [Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstr.1, D-85748 Garching (Germany); Brammer, G., E-mail: forster@mpe.mpg.de, E-mail: genzel@mpe.mpg.de [Space Telescope Science Institute, Baltimore, MD 21218 (United States); and others

    2014-11-20

    In this paper, we follow up on our previous detection of nuclear ionized outflows in the most massive (log(M {sub *}/M {sub ☉}) ≥ 10.9) z ∼ 1-3 star-forming galaxies by increasing the sample size by a factor of six (to 44 galaxies above log(M {sub *}/M {sub ☉}) ≥ 10.9) from a combination of the SINS/zC-SINF, LUCI, GNIRS, and KMOS{sup 3D}spectroscopic surveys. We find a fairly sharp onset of the incidence of broad nuclear emission (FWHM in the Hα, [N II], and [S II] lines ∼450-5300 km s{sup –1}), with large [N II]/Hα ratios, above log(M {sub *}/M {sub ☉}) ∼ 10.9, with about two-thirds of the galaxies in this mass range exhibiting this component. Broad nuclear components near and above the Schechter mass are similarly prevalent above and below the main sequence of star-forming galaxies, and at z ∼ 1 and ∼2. The line ratios of the nuclear component are fit by excitation from active galactic nuclei (AGNs), or by a combination of shocks and photoionization. The incidence of the most massive galaxies with broad nuclear components is at least as large as that of AGNs identified by X-ray, optical, infrared, or radio indicators. The mass loading of the nuclear outflows is near unity. Our findings provide compelling evidence for powerful, high-duty cycle, AGN-driven outflows near the Schechter mass, and acting across the peak of cosmic galaxy formation.

  17. The man behind the curtain: X-rays drive the UV through NIR variability in the 2013 active galactic nucleus outburst in NGC 2617

    Energy Technology Data Exchange (ETDEWEB)

    Shappee, B. J.; Kochanek, C. S.; Stanek, K. Z.; De Rosa, G.; Mathur, S.; Zu, Y.; Peterson, B. M.; Pogge, R. W.; Jencson, J.; Holoien, T.W-S.; Basu, U.; Beacom, J. F.; Adams, S. [Department of Astronomy, The Ohio State University, Columbus, OH 43210 (United States); Prieto, J. L. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Grupe, D. [Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Komossa, S. [Max-Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Im, M. [CEOU/Department of Physics and Astronomy, Seoul National University, Seoul 151-742 (Korea, Republic of); Szczygieł, D. M. [Warsaw University Astronomical Observatory, Al. Ujazdowskie 4, 00-478 Warsaw (Poland); Brimacombe, J. [Coral Towers Observatory, Cairns, Queensland A-4870 (Australia); Campillay, A., E-mail: shappee@astronomy.ohio-state.edu [Carnegie Observatories, Las Campanas Observatory, Colina El Pino, Casilla 601 (Chile); and others

    2014-06-10

    After the All-Sky Automated Survey for SuperNovae discovered a significant brightening of the inner region of NGC 2617, we began a ∼70 day photometric and spectroscopic monitoring campaign from the X-ray through near-infrared (NIR) wavelengths. We report that NGC 2617 went through a dramatic outburst, during which its X-ray flux increased by over an order of magnitude followed by an increase of its optical/ultraviolet (UV) continuum flux by almost an order of magnitude. NGC 2617, classified as a Seyfert 1.8 galaxy in 2003, is now a Seyfert 1 due to the appearance of broad optical emission lines and a continuum blue bump. Such 'changing look active galactic nuclei (AGNs)' are rare and provide us with important insights about AGN physics. Based on the Hβ line width and the radius-luminosity relation, we estimate the mass of central black hole (BH) to be (4 ± 1) × 10{sup 7} M {sub ☉}. When we cross-correlate the light curves, we find that the disk emission lags the X-rays, with the lag becoming longer as we move from the UV (2-3 days) to the NIR (6-9 days). Also, the NIR is more heavily temporally smoothed than the UV. This can largely be explained by a simple model of a thermally emitting thin disk around a BH of the estimated mass that is illuminated by the observed, variable X-ray fluxes.

  18. Detection of a Possible X-Ray Quasi-periodic Oscillation in the Active Galactic Nucleus 1H 0707-495

    Science.gov (United States)

    Pan, Hai-Wu; Yuan, Weimin; Yao, Su; Zhou, Xin-Lin; Liu, Bifang; Zhou, Hongyan; Zhang, Shuang-Nan

    2016-03-01

    The quasi-periodic oscillation (QPO) detected in the X-ray radiation of black hole X-ray binaries (BHXBs) is thought to originate from dynamical processes in close vicinity of black holes (BHs), and thus carries important physical information therein. Such a feature is extremely rare in active galactic nuclei (AGNs) with supermassive BHs. Here we report on the detection of a possible X-ray QPO signal with a period of 3800 s at a confidence level >99.99% in the narrow-line Seyfert 1 galaxy (NLS1) 1H 0707-495 in one data set in 0.2-10 keV taken with XMM-Newton. The statistical significance is higher than that of most previously reported QPOs in AGNs. The QPO is highly coherent (quality factor Q=ν /{{Δ }}ν ≥slant 15) with a high rms fractional variability (˜15%). A comprehensive analysis of the optical spectra of this AGN is also performed, yielding a central BH mass of 5.2 × 106 M⊙ from the broad emission lines based on the scaling relation. The QPO follows the known frequency-BH mass relation closely, which spans from stellar-mass to supermassive BHs. The absence of QPOs in other observations of the object suggests that it is a transient phenomenon. We suggest that the (high-frequency) QPOs tend to occur in highly accreting BH systems, from BHXBs to supermassive BHs. Future precise estimation of the BH mass may be used to infer the BH spin from the QPO frequency.

  19. THE CLUSTER AND FIELD GALAXY ACTIVE GALACTIC NUCLEUS FRACTION AT z = 1-1.5: EVIDENCE FOR A REVERSAL OF THE LOCAL ANTICORRELATION BETWEEN ENVIRONMENT AND AGN FRACTION

    Energy Technology Data Exchange (ETDEWEB)

    Martini, Paul [Department of Astronomy and Center for Cosmology and Astroparticle Physics, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Miller, E. D.; Bautz, M. [Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Brodwin, M. [Department of Physics and Astronomy, University of Missouri, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Stanford, S. A. [Department of Physics, University of California, One Shields Avenue, Davis, CA 95616 (United States); Gonzalez, Anthony H. [Department of Astronomy, University of Florida, Gainesville, FL 32611 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Stern, D.; Eisenhardt, P. R. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Galametz, A. [INAF-Osservatorio di Roma, Via Frascati 33, I-00040 Monteporzio (Italy); Norman, D.; Dey, A. [NOAO, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Jannuzi, B. T. [Department of Astronomy and Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Murray, S.; Jones, C. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Brown, M. J. I., E-mail: martini@astronomy.ohio-state.edu [School of Physics, Monash University, Clayton, Victoria 3800 (Australia)

    2013-05-01

    The fraction of cluster galaxies that host luminous active galactic nuclei (AGNs) is an important probe of AGN fueling processes, the cold interstellar medium at the centers of galaxies, and how tightly black holes and galaxies co-evolve. We present a new measurement of the AGN fraction in a sample of 13 clusters of galaxies (M {>=} 10{sup 14} M{sub Sun }) at 1 < z < 1.5 selected from the Spitzer/IRAC Shallow Cluster Survey, as well as the field fraction in the immediate vicinity of these clusters, and combine these data with measurements from the literature to quantify the relative evolution of cluster and field AGN from the present to z {approx} 3. We estimate that the cluster AGN fraction at 1 < z < 1.5 is f{sub A} = 3.0{sup +2.4}{sub -1.4}% for AGNs with a rest-frame, hard X-ray luminosity greater than L{sub X,{sub H}} {>=} 10{sup 44} erg s{sup -1}. This fraction is measured relative to all cluster galaxies more luminous than M{sup *}{sub 3.6}(z) + 1, where M{sup *}{sub 3.6}(z) is the absolute magnitude of the break in the galaxy luminosity function at the cluster redshift in the IRAC 3.6 {mu}m bandpass. The cluster AGN fraction is 30 times greater than the 3{sigma} upper limit on the value for AGNs of similar luminosity at z {approx} 0.25, as well as more than an order of magnitude greater than the AGN fraction at z {approx} 0.75. AGNs with L{sub X,{sub H}} {>=} 10{sup 43} erg s{sup -1} exhibit similarly pronounced evolution with redshift. In contrast to the local universe, where the luminous AGN fraction is higher in the field than in clusters, the X-ray and MIR-selected AGN fractions in the field and clusters are consistent at 1 < z < 1.5. This is evidence that the cluster AGN population has evolved more rapidly than the field population from z {approx} 1.5 to the present. This environment-dependent AGN evolution mimics the more rapid evolution of star-forming galaxies in clusters relative to the field.

  20. Active galactic nuclei

    CERN Document Server

    Beckmann, Volker

    2012-01-01

    This AGN textbook includes phenomena based on new results in the X-Ray domain from new telescopes such as Chandra and XMM Newton not mentioned in any other book. Furthermore, it considers also the Fermi Gamma Ray Space Telescope with its revolutionary advances of unprecedented sensitivity, field of view and all-sky monitoring. Those and other new developments as well as simulations of AGN merging events and formations, enabled through latest super-computing capabilities. The book gives an overview on the current knowledge of the Active Galacitc Nuclei phenomenon. The spectral energy d

  1. Active galactic nuclei as scaled-up Galactic black holes.

    Science.gov (United States)

    McHardy, I M; Koerding, E; Knigge, C; Uttley, P; Fender, R P

    2006-12-07

    A long-standing question is whether active galactic nuclei (AGN) vary like Galactic black hole systems when appropriately scaled up by mass. If so, we can then determine how AGN should behave on cosmological timescales by studying the brighter and much faster varying Galactic systems. As X-ray emission is produced very close to the black holes, it provides one of the best diagnostics of their behaviour. A characteristic timescale--which potentially could tell us about the mass of the black hole--is found in the X-ray variations from both AGN and Galactic black holes, but whether it is physically meaningful to compare the two has been questioned. Here we report that, after correcting for variations in the accretion rate, the timescales can be physically linked, revealing that the accretion process is exactly the same for small and large black holes. Strong support for this linkage comes, perhaps surprisingly, from the permitted optical emission lines in AGN whose widths (in both broad-line AGN and narrow-emission-line Seyfert 1 galaxies) correlate strongly with the characteristic X-ray timescale, exactly as expected from the AGN black hole masses and accretion rates. So AGN really are just scaled-up Galactic black holes.

  2. Evolution of active galactic nuclei

    CERN Document Server

    Merloni, Andrea

    2012-01-01

    [Abriged] Supermassive black holes (SMBH) lurk in the nuclei of most massive galaxies, perhaps in all of them. The tight observed scaling relations between SMBH masses and structural properties of their host spheroids likely indicate that the processes fostering the growth of both components are physically linked, despite the many orders of magnitude difference in their physical size. This chapter discusses how we constrain the evolution of SMBH, probed by their actively growing phases, when they shine as active galactic nuclei (AGN) with luminosities often in excess of that of the entire stellar population of their host galaxies. Following loosely the chronological developments of the field, we begin by discussing early evolutionary studies, when AGN represented beacons of light probing the most distant reaches of the universe and were used as tracers of the large scale structure. This early study turned into AGN "Demography", once it was realized that the strong evolution (in luminosity, number density) of ...

  3. The 2-79 keV X-ray spectrum of the circinus galaxy with NuSTAR, XMM-Newton, and Chandra: a fully compton-thick active galactic nucleus

    DEFF Research Database (Denmark)

    Arévalo, P.; Bauer, F. E.; Puccetti, S.;

    2014-01-01

    The Circinus galaxy is one of the closest obscured active galactic nuclei (AGNs), making it an ideal target for detailed study. Combining archival Chandra and XMM-Newton data with new NuSTAR observations, we model the 2-79 keV spectrum to constrain the primary AGN continuum and to derive physical...

  4. Energy Radiation of the Active Galactic Nuclei

    Institute of Scientific and Technical Information of China (English)

    TANG Zhi-Ming; WANG Yong-Jiu

    2004-01-01

    In the Hellings-Nordtvedt theory, we obtain some expressions of energy radiation and mass defect effect for a kind of the active galactic nuclei, which is meaningful to calculating the energy radiation in the procession of forming this kind of celestial bodies. This calculation can give some interpretation for energy source of the jet from the active galactic nuclei.

  5. Observational Signatures of Galactic Winds Powered by Active Galactic Nuclei

    CERN Document Server

    Nims, Jesse; Faucher-Giguere, Claude-Andre

    2014-01-01

    We predict the observational signatures of galaxy scale outflows powered by active galactic nuclei (AGN). Most of the emission is produced by the forward shock driven into the ambient interstellar medium (ISM) rather than by the reverse shock. AGN powered galactic winds with energetics suggested by phenomenological feedback arguments should produce spatially extended 1-10 keV X-ray emission of 10^(41-44) erg/s, significantly in excess of the spatially extended X-ray emission associated with normal star forming galaxies. The presence of such emission is a direct test of whether AGN outflows significantly interact with the ISM of their host galaxy. We further show that even radio quiet quasars should have a radio luminosity comparable to or in excess of the far infrared-radio correlation of normal star forming galaxies. This radio emission directly constrains the total kinetic energy flux in AGN-powered galactic winds. Radio emission from AGN wind shocks can also explain the recently highlighted correlations be...

  6. The Environments of Active Galactic Nuclei within the zCOSMOS Density Field

    NARCIS (Netherlands)

    Silverman, J. D.; Kovac, K.; Knobel, C.; Lilly, S.; Bolzonella, M.; Lamareille, F.; Mainieri, V.; Brusa, M.; Cappelluti, N.; Peng, Y.; Hasinger, G.; Zamorani, G.; Scodeggio, M.; Contini, T.; Carollo, C. M.; Jahnke, K.; Kneib, J. -P.; Le Fevre, O.; Bardelli, S.; Bongiorno, A.; Brunner, H.; Caputi, K.; Civano, F.; Comastri, A.; Coppa, G.; Cucciati, O.; de la Torre, S.; de Ravel, L.; Elvis, M.; Finoguenov, A.; Fiore, F.; Franzetti, P.; Garilli, B.; Gilli, R.; Griffiths, R.; Iovino, A.; Kampczyk, P.; Koekemoer, A.; Le Borgne, J. -F.; Le Brun, V.; Maier, C.; Mignoli, M.; Pello, R.; Montero, E. Perez; Ricciardelli, E.; Tanaka, M.; Tasca, L.; Tresse, L.; Vergani, D.; Vignali, C.; Zucca, E.; Bottini, D.; Cappi, A.; Cassata, P.; Marinoni, C.; McCracken, H. J.; Memeo, P.; Meneux, B.; Oesch, P.; Porciani, C.; Salvato, M.

    2009-01-01

    The impact of environment on active galactic nucleus (AGN) activity up to z ~ 1 is assessed by utilizing a mass-selected sample of galaxies from the 10k catalog of the zCOSMOS spectroscopic redshift survey. We identify 147 AGN by their X-ray emission as detected by XMM-Newton from a parent sample of

  7. The 2-79 keV X-ray spectrum of the Circinus galaxy with NuSTAR, XMM-Newton, and Chandra: a fully Compton-thick active galactic nucleus

    Energy Technology Data Exchange (ETDEWEB)

    Arévalo, P.; Bauer, F. E. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 306, Santiago 22 (Chile); Puccetti, S. [ASDC-ASI, Via del Politecnico, I-00133 Roma (Italy); Walton, D. J.; Fuerst, F.; Grefenstette, B. W.; Harrison, F. A.; Madsen, K. K. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Koss, M. [Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Brandt, W. N.; Luo, B. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Brightman, M. [Max-Planck-Institut für extraterrestrische Physik, Giessenbachstrasse 1, D-85748, Garching bei München (Germany); Christensen, F. E. [Danish Technical University, Lyngby (Denmark); Comastri, A. [INAF-Osservatorio Astronomico di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Gandhi, P. [Department of Physics, Durham University, South Road, Durham, DH1 3LE (United Kingdom); Hailey, C. J. [Columbia Astrophysics Laboratory and Department of Physics, Columbia University, 550 West 120th Street, New York, NY 10027 (United States); Madejski, G. [Kavli Institute for Particle Astrophysics and Cosmology, SLAC National Accelerator Laboratory, Stanford University, 2575 Sand Hill Road M/S 29, Menlo Park, CA 94025 (United States); Marinucci, A. [Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); and others

    2014-08-20

    The Circinus galaxy is one of the closest obscured active galactic nuclei (AGNs), making it an ideal target for detailed study. Combining archival Chandra and XMM-Newton data with new NuSTAR observations, we model the 2-79 keV spectrum to constrain the primary AGN continuum and to derive physical parameters for the obscuring material. Chandra's high angular resolution allows a separation of nuclear and off-nuclear galactic emission. In the off-nuclear diffuse emission, we find signatures of strong cold reflection, including high equivalent-width neutral Fe lines. This Compton-scattered off-nuclear emission amounts to 18% of the nuclear flux in the Fe line region, but becomes comparable to the nuclear emission above 30 keV. The new analysis no longer supports a prominent transmitted AGN component in the observed band. We find that the nuclear spectrum is consistent with Compton scattering by an optically thick torus, where the intrinsic spectrum is a power law of photon index Γ = 2.2-2.4, the torus has an equatorial column density of N {sub H} = (6-10) × 10{sup 24} cm{sup –2}, and the intrinsic AGN 2-10 keV luminosity is (2.3-5.1) × 10{sup 42} erg s{sup –1}. These values place Circinus along the same relations as unobscured AGNs in accretion rate versus Γ and L{sub X} versus L {sub IR} phase space. NuSTAR's high sensitivity and low background allow us to study the short timescale variability of Circinus at X-ray energies above 10 keV for the first time. The lack of detected variability favors a Compton-thick absorber, in line with the spectral fitting results.

  8. Cosmic rays from active galactic nuclei

    CERN Document Server

    Berezhko, E G

    2008-01-01

    Cosmic ray (CR) acceleration at the shock created by the expanding cocoons around active galactic nuclei (AGNs) is studied. It is shown that above the energy $10^{18}$ eV the overall energy spectrum of CRs, produced during the AGN evolution and released in the intergalactic space, has the form $N\\propto \\epsilon^{-\\gamma}$, with $\\gamma\\approx 2.6$, which extends up to $\\epsilon_{max}\\sim 10^{20}$ eV. It is concluded that cocoons shocks have to be considered as a main source of extragalactic CRs, which together with Galactic supernova remnants provide the observed CR spectrum.

  9. Power spectra of active galactic nuclei

    Institute of Scientific and Technical Information of China (English)

    WANG TaiShan; WU YuXiang; LIU Yuan

    2009-01-01

    The power spectral densities (PSDs) for a sample of active galactic nuclei (AGNs) are analyzed in both the frequency domain and the time domain. We find for each object that for broadband noise a character timescale-bifurcation timescale of Fourier and time-domain PSD exists in the 103-106 s range,below which the time-domain power spectrum is systematically higher than the corresponding Fourier spectrum. The relationship between bifurcation timescale, AGN mass and luminosity is studied. Compared with the fact that similar phenomena have been found for Galactic black hole candidates (GBHs)with bifurcation timescale ~0.1 s but not for accreting neutron stars, our finding indicates that AGNs and GBHs have common intrinsic nature in rapid X-ray variability with a character time parameter scaled with their masses.

  10. Power spectra of active galactic nuclei

    Institute of Scientific and Technical Information of China (English)

    2009-01-01

    The power spectral densities(PSDs)for a sample of active galactic nuclei(AGNs)are analyzed in both the frequency domain and the time domain.We find for each object that for broadband noise a character timescale-bifurcation timescale of Fourier and time-domain PSD exists in the 10 3 -10 6 s range, below which the time-domain power spectrum is systematically higher than the corresponding Fourier spectrum.The relationship between bifurcation timescale,AGN mass and luminosity is studied.Compared with the fact that similar phenomena have been found for Galactic black hole candidates(GBHs) with bifurcation timescale~0.1 s but not for accreting neutron stars,our finding indicates that AGNs and GBHs have common intrinsic nature in rapid X-ray variability with a character time parameter scaled with their masses.

  11. The Evolution of the Globular Cluster System in a Triaxial Galaxy Can a Galactic Nucleus Form by Globular Cluster Capture?

    CERN Document Server

    Capuzzo-Dolcetta, R

    1993-01-01

    Dynamical friction due to field stars and tidal disruption caused by a central nucleus are crucial in determining the evolution of the globular cluster system in an elliptical galaxy. In this paper I examine the possibility that some of galactic nuclei have been formed by frictionally decayied globular clusters moving in a triaxial potential. The initial rapid growth of the nucleus, due mainly to massive clusters on box orbits falling in a short time scale into the galactic centre, is found to be later slowed by tidal disruption induced by the nucleus itself on less massive clusters in the way described by Ostriker, Binney & Saha. The efficiency of dynamical friction is such to carry to the centre of the galaxy enough globular cluster mass available to form a compact nucleus, but the actual modes of its collisionless formation remains to be investigated. The mass of the resulting nucleus is determined by the mutual feedback of the two mentioned processes, together with the knowlegde of the initial spatial...

  12. Active galactic nuclei activity: self-regulation from backflow

    Science.gov (United States)

    Antonuccio-Delogu, V.; Silk, Joseph

    2010-06-01

    We study the internal circulation within the cocoon carved out by the relativistic jet emanating from an active galactic nucleus (AGN) within the interstellar medium (ISM) of its host galaxy. First, we develop a model for the origin of the internal flow, noticing that a significant increase of large-scale velocity circulation within the cocoon arises as significant gradients in the density and entropy are created near the hotspot (a consequence of Crocco's vorticity generation theorem). We find simple and accurate approximate solutions for the large-scale flow, showing that a backflow towards the few inner parsec region develops. We solve the appropriate fluid dynamic equations, and we use these solutions to predict the mass inflow rates towards the central regions. We then perform a series of 2D simulations of the propagation of jets using FLASH 2.5, in order to validate the predictions of our model. In these simulations, we vary the mechanical input power between 1043 and 1045 ergs-1, and assume a Navarro-Frenk-White (NFW) density profile for the dark matter halo, within which an isothermal diffuse ISM is embedded. The backflows which arise supply the central AGN region with very low angular-momentum gas, at average rates of the order of , the exact value seen to be strongly dependent on the central ISM density (for fixed input jet power). The time-scales of these inflows are apparently weakly dependent on the jet/ISM parameters, and are of the order of . We then argue that these backflows could (at least partially) feed the AGN, and provide a self-regulatory mechanism of AGN activity, that is not directly controlled by, but instead controls, the star formation rate within the central circumnuclear disc.

  13. Spatially Offset Active Galactic Nuclei. I. Selection and Spectroscopic Properties

    Science.gov (United States)

    Barrows, R. Scott; Comerford, Julia M.; Greene, Jenny E.; Pooley, David

    2016-09-01

    We present a sample of 18 optically selected and X-ray-detected spatially offset active galactic nuclei (AGNs) from the Sloan Digital Sky Survey (SDSS). In nine systems, the X-ray active galactic nucleus (AGN) is spatially offset from the galactic stellar core that is located within the 3″ diameter SDSS spectroscopic fiber. In 11 systems, the X-ray AGN is spatially offset from a stellar core that is located outside the fiber, with an overlap of two. To build the sample, we cross-matched Type II AGNs selected from the SDSS galaxy catalog with archival Chandra imaging and employed our custom astrometric and registration procedure. The projected angular (physical) offsets span a range of 0.″6 (0.8 kpc) to 17.″4 (19.4 kpc), with a median value of 2.″7 (4.6 kpc). The offset nature of an AGN is an unambiguous signature of a galaxy merger, and these systems can be used to study the properties of AGNs in galaxy mergers without the biases introduced by morphological merger selection techniques. In this paper (Paper I), we use our sample to assess the kinematics of AGN photoionized gas in galaxy mergers. We find that spectroscopic offset AGN selection may be up to {89}-16+7% incomplete due to small projected velocity offsets. We also find that the magnitude of the velocity offsets are generally larger than expected if our spatial selection introduces a bias toward face-on orbits, suggesting the presence of complex kinematics in the emission line gas of AGNs in galaxy mergers.

  14. Obscuration of Active Galactic Nuclei by Circumnuclear Starbursts

    CERN Document Server

    Watabe, Y; Watabe, Yasuyuki; Umemura, Masayuki

    2004-01-01

    We examine the possibility of the active galactic nucleus (AGN) obscuration by dusty gas clouds that spurt out from circumnuclear starburst regions. For the purpose, the dynamical evolution of gas clouds is pursued, including the effects of radiation forces by an AGN as well as a starburst. Here, we solve the radiative transfer equations for clouds, taking into consideration the growth of clouds by inelastic cloud-cloud collisions and the resultant change in optical depth. As a result, it is shown that if the starburst is more luminous than the AGN, gas clouds are distributed extensively above a galactic disk with the assistance of radiation pressure from the starburst. The total covering factor of gas clouds reaches a maximum of around 20%. After several $10^{7}$yr, gas clouds with larger optical depth form by cloud-cloud collisions and thereafter the clouds fall back due to weakened radiation pressure. The larger clouds undergo runaway growth and are eventually distributed around the equatorial plane on the...

  15. The Radius-Luminosity Relationship for Active Galactic Nuclei: The Effect of Host-Galaxy Starlight on Luminosity Measurements. II. The Full Sample of Reverberation-Mapped AGNs

    DEFF Research Database (Denmark)

    Bentz, Misty C.; Peterson, Bradley M.; Netzer, Hagai

    2009-01-01

    We present high-resolution Hubble Space Telescope images of all 35 active galactic nuclei (AGNs) with optical reverberation-mapping results, which we have modeled to create a nucleus-free image of each AGN host galaxy. From the nucleus-free images, we determine the host-galaxy contribution to gro...

  16. Dielectronic Recombination In Active Galactic Nuclei

    Science.gov (United States)

    Lukić, D.; Savin, D. W.; Schnell, M.; Brandau, C.; Schmidt, E.; Schippers, S.; Müller, A.; Lestinsky, M.; Sprenger, F.; Wolf, A.; Altun, Z.; Badnell, N. R.

    2006-05-01

    Recent X-ray satelitte observations of active galactic nuclei point out shortcomings in our understanding of low temperature dielectronic recombination (DR) for iron M- shell ions. In order to resolve this issue and to provide reliable iron M-shell DR data for modeling astrophysical plasmas, we are carrying out a series of laboratory measurements using the heavy-ion Test Storage Ring at the Max- Plank-Institute for Nuclear Physics in Heidelberg, Germany. Storage rings are currently the only laboratory method capable of studying low temperature DR. We use our results to produce experimentally- derived DR rate coefficients. We are also providing our data to atomic theorist to benchmark their DR calculations. Here we will report our recent DR results for selected Fe M-shell ions. At temperatures where these ions are predicted to form in photoionized gas, we find a significant discrepancy between our experimental results and previously recommended DR rate coefficients.

  17. Active Galactic Nuclei Feedback and Clusters

    Indian Academy of Sciences (India)

    Biman B. Nath

    2011-12-01

    The Intracluster Medium (ICM) is believed to have been affected by feedback from Active Galactic Nuclei (AGN) and/or supernovae-driven winds. These sources are supposed to have injected entropy into the ICM gas. The recently determined universal pressure profile of the ICM gas has been used and after comparing with the entropy profile of the gas from gravitational effects of the dark matter halo, the additional entropy injected by non-gravitational sources, as a function of the total cluster mass is determined. The current observational data of red-shift evolution of cluster scaling relation is shown that allow models in which the entropy injection decreases at high red-shift.

  18. Correlations of Active Galactic Nuclei with Microquasars

    Institute of Scientific and Technical Information of China (English)

    YE Yong-Chun; ZUO Xue-Qin; WANG Ding-Xiong

    2006-01-01

    Correlations of active galactic nuclei (AGNs) with microquasars are discussed based on the coexistence of the Blandford-Znajek (BZ) and magnetic coupling (MC) processes (CEBZMC) in black hole (BH) accretion disk.The proportions of several quantities of BH systems for both AGNs and microquasars are derived by combining the observational data with CEBZMC. It is shown that the square of the magnetic field at the BH horizon is inversely proportional to the BH mass, while the accretion rate of the disk is proportional to the BH mass. In addition, the very steep emissivity indexes from the recent XMM-Newton observations of the nearby bright Seyfert 1 galaxy MCG-6-30-15 and the microquasars XTE J1650-500 are well fitted by considering the MC effects on the disk radiation. These results suggest strongly the correlations of A GNs with microquasars.

  19. Recurrent radio activity in active galactic nuclei

    Directory of Open Access Journals (Sweden)

    Jamrozy M.

    2012-12-01

    Full Text Available There has been a growing body of persuasive evidence to indicate that AGN activity, powered by mass accretion onto a supermassive black hole, can involve multiple episodes. Thus thinking of jet activity as occurring within a unique brief period in the life of a galaxy is no longer valid. The most striking examples of AGNs with recurrent jet activity are the double-double radio sources, which contain two or more pairs of distinct lobes on the opposite sides of a parent optical object. On the other hand, we have now conclusive arguments that galaxy mergers and interactions are principal triggers for AGNs. Quite a number of examples of powerful radio sources hosted by galaxies with peculiar optical morphologies (tails, shells, dust-lanes, etc. can be cited to support such a scenario. The structure and spectra of extended radio emission from radio galaxies, with sizes ranging up to a few Mpc, can provide a lot of information on the history of the central AGN activity, while the spectral and dynamical ages of these extended radio lobes could be used to constrain the time scales of recurrent AGN activity.

  20. On the Evolution of High-Redshift Active Galactic Nuclei

    CERN Document Server

    Mao, Jirong

    2016-01-01

    We build a simple physical model to study the high-redshift active galactic Nucleus (AGN) evolution within the co-evolution framework of central black holes (BHs) and their host galaxies. The correlation between the circular velocity of a dark halo $V_c$ and the velocity dispersion of a galaxy $\\sigma$ is used to link the dark matter halo mass and BH mass. The dark matter halo mass function is converted to the BH mass function for any given redshift. The high-redshift optical AGN luminosity functions (LFs) are constructed. At $z\\sim 4$, the flattening feature is not shown at the faint end of the optical AGN LF. This is consistent with observational results. If the optical AGN LF at $z\\sim 6$ can be reproduced in the case in which central BHs have the Eddington-limited accretion, it is possible for the AGN lifetime to have a small value of $2\\times 10^5$ yrs. The X-ray AGN LFs and X-ray AGN number counts are also calculated at $2.03$, respectively, using the same parameters adopted in the calculation for the o...

  1. Hypoxia activates nucleus tractus solitarii neurons projecting to the paraventricular nucleus of the hypothalamus

    OpenAIRE

    King, T. Luise; Heesch, Cheryl M.; Clark, Catharine G.; Kline, David D.; Hasser, Eileen M.

    2012-01-01

    Peripheral chemoreceptor afferent information is sent to the nucleus tractus solitarii (nTS), integrated, and relayed to other brain regions to alter cardiorespiratory function. The nTS projects to the hypothalamic paraventricular nucleus (PVN), but activation and phenotype of these projections during chemoreflex stimulation is unknown. We hypothesized that activation of PVN-projecting nTS neurons occurs primarily at high intensities of hypoxia. We assessed ventilation and cardiovascular para...

  2. GT2_rguesten_5: Spectral mapping of the closest galactic nucleus

    Science.gov (United States)

    Guesten, R.

    2011-05-01

    Due to its proximity, our Galactic Center provides a unique opportunity to study the physical processes that occur within (extra)galactic nuclei with unprecedented sensitivity and spatial resolution. Herschel provides the only opportunity to probe the detailed physical conditions of the circumnuclear neutral material and the feedback processes with the central energy source(s) in our own Galaxy, and by extension in other galactic nuclei. We propose to acquire wide range (51 to 670 micron) spectral maps towards the atomic and molecular gas surrounding SgrA. Combining data from the PACS and SPIRE instruments, we will establish a complete inventory of the FIR spectrum accessible to Herschel across the central 5 arcmin (12 pc) of the Galaxy. Our immediate goal is to characterize the physical and chemical conditions of the gas in both the central (ionized) cavity and in the surrounding neutral gas (often referred to as circumnuclear disk, or CND) that is presumably the reservoir of material that can flow to the central black hole. Our supporting ground-based and first targeted HIFI observations show a high-excitation state of the molecular gas in the CND, with a strong radial excitation gradient across the disk and a very sharp inner transition zone to the central cavity. These early data resemble the hard XDR-type CO line SED observed towards e.g. Mrk231.Herschel data cover lines from energy levels needed to constrain the conditions within, and energetics of the CND. We will use state-of-the-art XDR/PDR models that include multiple heating processes (a.o., shock, dissipation of turbulence) to interpret the data. The data product will be one of Herschel's legacies in the detailed study of galactic nuclei. This data set, with high sensitivity, high spatial resolution, and broad wavelength coverage, will be an essential resource for many studies of the Galactic Center. No comparable study of this region will be possible for many years to come.

  3. Active galactic nuclei at gamma-ray energies

    Science.gov (United States)

    Dermer, Charles Dennison; Giebels, Berrie

    2016-06-01

    Active Galactic Nuclei can be copious extragalactic emitters of MeV-GeV-TeV γ rays, a phenomenon linked to the presence of relativistic jets powered by a super-massive black hole in the center of the host galaxy. Most of γ-ray emitting active galactic nuclei, with more than 1500 known at GeV energies, and more than 60 at TeV energies, are called "blazars". The standard blazar paradigm features a jet of relativistic magnetized plasma ejected from the neighborhood of a spinning and accreting super-massive black hole, close to the observer direction. Two classes of blazars are distinguished from observations: the flat-spectrum radio-quasar class (FSRQ) is characterized by strong external radiation fields, emission of broad optical lines, and dust tori. The BL Lac class (from the name of one of its members, BL Lacertae) corresponds to weaker advection-dominated flows with γ-ray spectra dominated by the inverse Compton effect on synchrotron photons. This paradigm has been very successful for modeling the broadband spectral energy distributions of blazars. However, many fundamental issues remain, including the role of hadronic processes and the rapid variability of a few FSRQs and several BL Lac objects whose synchrotron spectrum peaks at UV or X-ray frequencies. A class of γ-ray-emitting radio galaxies, which are thought to be the misaligned counterparts of blazars, has emerged from the results of the Fermi-Large Area Telescope and of ground-based Cherenkov telescopes. Soft γ-ray emission has been detected from a few nearby Seyfert galaxies, though it is not clear whether those γ rays originate from the nucleus. Blazars and their misaligned counterparts make up most of the ≳100 MeV extragalactic γ-ray background (EGB), and are suspected of being the sources of ultra-high energy cosmic rays. The future "Cherenkov Telescope Array", in synergy with the Fermi-Large Area Telescope and a wide range of telescopes in space and on the ground, will write the next chapter

  4. Age determination of the nuclear stellar population of Active Galactic Nuclei using Locally Weighted Regression

    CERN Document Server

    Estrada-Piedra, T; Terlevich, R J; Fuentes, O; Terlevich, E; Estrada-Piedra, Trilce; Torres-Papaqui, Juan Pablo; Terlevich, Roberto; Fuentes, Olac; Terlevich, Elena

    2003-01-01

    We present a new technique to segregate old and young stellar populations in galactic spectra using machine learning methods. We used an ensemble of classifiers, each classifier in the ensemble specializes in young or old populations and was trained with locally weighted regression and tested using ten-fold cross-validation. Since the relevant information concentrates in certain regions of the spectra we used the method of sequential floating backward selection offline for feature selection. The application to Seyfert galaxies proved that this technique is very insensitive to the dilution by the Active Galactic Nucleus (AGN) continuum. Comparing with exhaustive search we concluded that both methods are similar in terms of accuracy but the machine learning method is faster by about two orders of magnitude.

  5. The low-luminosity end of the radius-luminosity relationship for active galactic nuclei

    DEFF Research Database (Denmark)

    Bentz, M.C.; Denney, K.D.; Vestergaard, Marianne

    2013-01-01

    We present an updated and revised analysis of the relationship between the Hß broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of nine new AGNs imaged...... reverberation-mapping measurements of the Hß time lag, which is assumed to yield the average Hß BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R BLR-L relationship. The best...

  6. Observing—and Imaging—Active Galactic Nuclei with the Event Horizon Telescope

    Directory of Open Access Journals (Sweden)

    Vincent L. Fish

    2016-10-01

    Full Text Available Originally developed to image the shadow region of the central black hole in Sagittarius A* and in the nearby galaxy M87, the Event Horizon Telescope (EHT provides deep, very high angular resolution data on other active galactic nucleus (AGN sources too. The challenges of working with EHT data have spurred the development of new image reconstruction algorithms. This work briefly reviews the status of the EHT and its utility for observing AGN sources, with emphasis on novel imaging techniques that offer the promise of better reconstructions at 1.3 mm and other wavelengths.

  7. Nonthermal Fluctuations and Mechanics of the Active Cell Nucleus

    CERN Document Server

    Smith, K; Byrd, H; MacKintosh, F C; Kilfoil, M L

    2013-01-01

    We present direct measurements of fluctuations in the nucleus of yeast cells. While prior work has shown these fluctuations to be active and non-thermal in character, their origin and time dependence are not understood. We show that nuclear fluctuations can be quantitatively understood by uncorrelated, active force fluctuations driving a nuclear medium that is dominated by an uncondensed DNA solution, for which we perform rheological measurements on an in vitro model system under similar conditions to what is expected in the nucleus. We conclude that the eukaryotic nucleus of living cells is a nonequilibrium soft material whose fluctuations are actively driven, and are far from thermal in their time dependence.

  8. STEPS TOWARD UNVEILING THE TRUE POPULATION OF ACTIVE GALACTIC NUCLEI: PHOTOMETRIC CHARACTERIZATION OF ACTIVE GALACTIC NUCLEI IN COSMOS

    Energy Technology Data Exchange (ETDEWEB)

    Schneider, Evan E.; Impey, Christopher D. [Steward Observatory, University of Arizona, Tucson, AZ 85719 (United States); Trump, Jonathan R. [University of California Observatories/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Salvato, Mara, E-mail: eschneider@as.arizona.edu [Max Planck Institute for Extraterrestrial Physics and Excellence Cluster, D-85748 Garching (Germany)

    2013-04-01

    Using a physically motivated, model-based active galactic nucleus (AGN) characterization technique, we fit a large sample of X-ray-selected AGNs with known spectroscopic redshifts from the Cosmic Evolution Survey field. We identify accretion disks in the spectral energy distributions of broad- and narrow-line AGNs, and infer the presence or absence of host galaxy light in the SEDs. Based on infrared and UV excess AGN selection techniques, our method involves fitting a given SED with a model consisting of three components: infrared power-law emission, optical-UV accretion disk emission, and host galaxy emission. Each component can be varied in relative contribution, and a reduced chi-square minimization routine is used to determine the optimum parameters for each object. Using this technique, both broad- and narrow-line AGNs fall within well-defined and plausible bounds on the physical parameters of the model, allowing trends with luminosity and redshift to be determined. In particular, based on our sample of spectroscopically confirmed AGNs, we find that approximately 95% of the broad-line AGNs and 50% of the narrow-line AGNs in our sample show evidence of an accretion disk, with maximum disk temperatures ranging from 1 to 10 eV. Because this fitting technique relies only on photometry, we hope to apply it in future work to the characterization and eventually the selection of fainter AGNs than are accessible in wide-field spectroscopic surveys, and thus probe a population of less luminous and/or higher redshift objects without prior redshift or X-ray data. With the abundant availability of photometric data from large surveys, the ultimate goal is to use this technique to create large samples that will complement and complete AGN catalogs selected by X-ray emission alone.

  9. Galactic Center gamma-ray ``excess'' from an active past of the Galactic Centre?

    Science.gov (United States)

    Petrović, Jovana; Dario Serpico, Pasquale; Zaharijaš, Gabrijela

    2014-10-01

    Several groups have recently claimed evidence for an unaccounted gamma-ray excess over the diffuse backgrounds at few GeV in the Fermi-LAT data in a region around the Galactic Center, consistent with a dark matter annihilation origin. We demonstrate that the main spectral and angular features of this excess can be reproduced if they are mostly due to inverse Compton emission from high-energy electrons injected in a burst event of ~ 1052÷1053 erg roughly Script O(106) years ago. We consider this example as a proof of principle that time-dependent phenomena need to be understood and accounted for—together with detailed diffuse foregrounds and unaccounted ``steady state'' astrophysical sources—before any robust inference can be made about dark matter signals at the Galactic Center. In addition, we point out that the timescale suggested by our study, which controls both the energy cutoff and the angular extension of the signal, intriguingly matches (together with the energy budget) what is indirectly inferred by other evidences suggesting a very active Galactic Center in the past, for instance related to intense star formation and accretion phenomena.

  10. Studies of relativistic jets in active galactic nuclei with SKA

    NARCIS (Netherlands)

    Agudo, I.; Bottcher, M.; Falcke, H.; Georganopoulos, M.; Ghisellini, G.; Giovannini, G.; Giroletti, M.; Gomez, J.L.; Gurvits, L.; Laing, R.; Lister, M.; Marti, J.M.; Meyer, E.T.; Mizuno, Y.; O'Sullivan, S.; Padovani, P.; Paragi, Z.; Perucho, M.; Schleicher, D.; Stawarz, L.; Vlahakis, N.; Wardle, J.

    2014-01-01

    Relativistic jets in active galactic nuclei (AGN) are among the most powerful astrophysical objects discovered to date. Indeed, jetted AGN studies have been considered a prominent science case for SKA, and were included in several different chapters of the previous SKA Science Book (Carilli & Rawlin

  11. On the Evolution of High-redshift Active Galactic Nuclei

    Science.gov (United States)

    Mao, Jirong; Kim, Minsun

    2016-09-01

    We build a simple physical model to study the high-redshift active galactic nucleus (AGN) evolution within the co-evolution framework of central black holes (BHs) and their host galaxies. The correlation between the circular velocity of a dark halo V c and the velocity dispersion of a galaxy σ is used to link the dark matter halo mass and BH mass. The dark matter halo mass function is converted to the BH mass function for any given redshift. The high-redshift optical AGN luminosity functions (LFs) are constructed. At z˜ 4, the flattening feature is not shown at the faint end of the optical AGN LF. This is consistent with observational results. If the optical AGN LF at z˜ 6 can be reproduced in the case in which central BHs have the Eddington-limited accretion, it is possible for the AGN lifetime to have a small value of 2× {10}5 {{years}}. The X-ray AGN LFs and X-ray AGN number counts are also calculated at 2.0\\lt z\\lt 5.0 and z\\gt 3, respectively, using the same parameters adopted in the calculation for the optical AGN LF at z˜ 4. It is estimated that about 30 AGNs per {{{\\deg }}}2 at z\\gt 6 can be detected with a flux limit of 3× {10}-17 {erg} {{cm}}-2 {{{s}}}-1 in the 0.5-2 keV band. Additionally, the cosmic reionization is also investigated. The ultraviolet photons emitted from the high-redshift AGNs mainly contribute to the cosmic reionization, and the central BHs of the high-redshift AGNs have a mass range of {10}6{--}{10}8{M}⊙ . We also discuss some uncertainties in both the AGN LFs and AGN number counts originating from the {M}{{BH}}{--}σ relation, Eddington ratio, AGN lifetime, and X-ray attenuation in our model.

  12. A Statistical Method to Search for Recoiling Supermassive Black Holes in Active Galactic Nuclei

    CERN Document Server

    Raffai, Peter; Frei, Zsolt

    2015-01-01

    We propose an observational test for gravitationally recoiling supermassive black holes (BHs) in active galactic nuclei, based on a correlation between the velocities of BHs relative to their host galaxies, |\\Delta v|, and their obscuring dust column densities, \\Sigma_{dust} (both measured along the line of sight). Proxies for both quantities can be derived from spectral features of individual quasars. We use toy models for the distribution of recoil velocities, BH trajectories, and the geometry of obscuring dust tori in galactic centres, to simulate 2.5x10^5 random observations of recoiling quasars. BHs with recoil velocities comparable to the escape velocity from the galactic centre remain bound to the nucleus, and do not fully settle back to the centre of the torus due to dynamical friction in a typical quasar lifetime. We find that |\\Delta v| and \\Sigma_ {dust} for these BHs are positively correlated. For obscured (\\Sigma_{dust}>0) and for partially obscured (0=45 km/s, the sample correlation coefficient ...

  13. Changing ionization conditions in SDSS galaxies with active galactic nuclei as a function of environment from pairs to clusters

    Energy Technology Data Exchange (ETDEWEB)

    Khabiboulline, Emil T.; Steinhardt, Charles L. [California Institute of Technology, 1200 East-California Boulevard, Pasadena, CA 91125 (United States); Silverman, John D. [Kavli Institute for the Physics and Mathematics of the Universe, University of Tokyo, Kashiwanoha 5-1-5, Kashiwa-Shi, Chiba 277-8583 (Japan); Ellison, Sara L. [Department of Physics and Astronomy, University of Victoria, Finnerty Road, Victoria, British Columbia, V8P 1A1 (Canada); Mendel, J. Trevor [Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse, D-85748 Garching (Germany); Patton, David R., E-mail: ekhabibo@caltech.edu [Department of Physics and Astronomy, Trent University, 1600 West Bank Drive, Peterborough, Ontario, K9J 7B8 (Canada)

    2014-11-01

    We study how active galactic nucleus (AGN) activity changes across environments from galaxy pairs to clusters using 143,843 galaxies with z < 0.2 from the Sloan Digital Sky Survey. Using a refined technique, we apply a continuous measure of AGN activity, characteristic of the ionization state of the narrow-line emitting gas. Changes in key emission-line ratios ([N II] λ6548/Hα, [O III] λ5007/Hβ) between different samples allow us to disentangle different environmental effects while removing contamination. We confirm that galaxy interactions enhance AGN activity. However, conditions in the central regions of clusters are inhospitable for AGN activity even if galaxies are in pairs. These results can be explained through models of gas dynamics in which pair interactions stimulate the transfer of gas to the nucleus and clusters suppress gas availability for accretion onto the central black hole.

  14. Nuclear 11.3$\\mu$m PAH emission in local active galactic nuclei

    CERN Document Server

    Alonso-Herrero, A; Esquej, P; Roche, P F; Hernan-Caballero, A; Hoenig, S F; Gonzalez-Martin, O; Aretxaga, I; Mason, R E; Packham, C; Levenson, N A; Espinosa, J M Rodriguez; Siebenmorgen, R; Pereira-Santaella, M; Diaz-Santos, T; Colina, L; Alvarez, C; Telesco, C M

    2014-01-01

    We present Gran Telescopio CANARIAS CanariCam 8.7$\\mu$m imaging and 7.5-13$\\mu$m spectroscopy of six local systems known to host an active galactic nucleus (AGN) and have nuclear star formation. Our main goal is to investigate whether the molecules responsible for the 11.3$\\mu$m polyclyclic aromatic hydrocarbon (PAH) feature are destroyed in the close vicinity of an AGN. We detect 11.3$\\mu$m PAH feature emission in the nuclear regions of the galaxies as well as extended PAH emission over a few hundred parsecs. The equivalent width (EW) of the feature shows a minimum at the nucleus but increases with increasing radial distances, reaching typical star-forming values a few hundred parsecs away from the nucleus. The reduced nuclear EW are interpreted as due to increased dilution from the AGN continuum rather than destruction of the PAH molecules. We conclude that at least those molecules responsible for the 11.3$\\mu$m PAH feature survive in the nuclear environments as close as 10pc from the AGN and for Seyfert-li...

  15. NGC5252: a pair of radio-emitting active galactic nuclei?

    CERN Document Server

    Yang, Xiaolong; Paragi, Zsolt; Liu, Xiang; An, Tao; Bianchi, Stefano; Ho, Luis C; Cui, Lang; Zhao, Wei; Wu, Xiaocong

    2016-01-01

    The X-ray source CXO J133815.6+043255 has counterparts in the UV, optical, and radio bands. Based on the multi-band investigations, it has been recently proposed by Kim et al. (2015) as a rarely-seen off-nucleus ultraluminous X-ray (ULX) source with a black hole mass of >= 10^4 solar mass in the nearby Seyfert galaxy NGC 5252. To explore its radio properties at very high angular resolution, we performed very long-baseline interferometry (VLBI) observations with the European VLBI Network (EVN) at 1.7 GHz. We find that the radio counterpart is remarkably compact among the known ULXs. It does not show a resolved structure with a resolution of a few milliarcsecond (mas), and the total recovered flux density is comparable to that measured in earlier sub-arcsecond-resolution images. The compact radio structure, the relatively flat spectrum, and the high radio luminosity are consistent with a weakly accreting supermassive black hole in a low-luminosity active galactic nucleus. The nucleus of NGC 5252 itself has simi...

  16. Infrared-ultraviolet spectra of active galactic nuclei

    Science.gov (United States)

    Malkan, M. A.; These corrected SEDs are shown.

    1987-01-01

    Data from IRAS and IUE were combined with ground based optical and infrared spectrophotometry to derive emission line free spectral energy distributions (SEDs) for 29 active galactic nuclei (AGNs) between 0.1 and 100 microns. The IRAS data were scaled down to account for extended emission. These correction factors, determined by comparing small aperture ground based 10.6 micron data with large aperture IRAS 12 micron fluxes, were usually less than 25%. These corrected SEDs are shown.

  17. From local active galactic nuclei to early quasars

    Energy Technology Data Exchange (ETDEWEB)

    Cavaliere, A.; Giallongo, E.; Vagnetti, F.

    1985-09-15

    To close the gap between the local luminosity function of the optically selected active galactic nuclei and the population properties of distant (z< or approx. =2) quasars, we propose a model of differential luminosity evolution which is astrophysically based and contains a minimal number of free parameters. We discuss the advantages of the model and its predictions, and indicate how to extend it for z > 2 to cover the beginning of the quasar era.

  18. A Search For Neutrinos From Active Galactic Nuclei

    CERN Document Server

    Demuth, D M

    1999-01-01

    Several authors have presented astrophysical mechanisms that would lead to measureable sources of high energy neutrinos. These include binary pulsars, early supernova remnants, and active galactic nuclei (AGN). In the case of AGN, a portion of the gravitational energy released by plasma accreting onto a central black hole is converted into non-thermal luminosity which produce high energy protons. Neutrinos (ν ) and gamma-rays (γ ) are among the particles produced in inelastic collisions of protons with thermal matter or radiation...

  19. Galactic Center gamma-ray "excess" from an active past of the Galactic Centre?

    CERN Document Server

    Petrovic, Jovana; Zaharijas, Gabrijela

    2014-01-01

    Several groups have recently claimed evidence for unaccounted gamma-ray excesses over diffuse backgrounds at few GeV in Fermi-LAT data in a region around the Galactic Center, consistent with a dark matter annihilation origin. We demonstrate that the main spectral and angular features of this "excess" can be reproduced if they are mostly due to inverse Compton emission from high-energy electrons injected in a burst event of ~ 10^{52}-10^{53} erg roughly O(10^6) years ago. We consider this example as a proof of principle that time-dependent phenomena need to be understood and accounted for---together with detailed diffuse foregrounds and unaccounted "steady state" astrophysical sources---before any robust inference can be made about dark matter signals at the Galactic Center. In addition, we point out that the timescale suggested by our study, which controls both the energy cutoff and the angular extension of the signal, intriguingly matches what is inferred by other forensic evidences suggesting a very active ...

  20. Active galactic nuclei and their panchromatic beauty.

    Science.gov (United States)

    Lusso, Elisabeta

    2016-08-01

    The rapid development of new observational capabilities provides the ability to detect both the obscured (Type 2) and the unobscured (Type 1) flavours of active galaxies. In particular, the combination of sensitive observations from mid-IR to X-rays allows us to pierce through large columns of gas and dust hiding the Type 2 obscured AGN nuclear region. The study of the relative AGN/host-galaxy contribution over different portions of the broad-band Spectral Energy Distribution (SED) is fundamental to constrain the physical evolution of AGN and how to place them into the context of galaxy evolution.I will discuss a study of the multi-wavelength properties of an X-ray selected sample of both obscured and unobscured AGN using the XMM-Newton wide field survey in the COSMOS field. I will focus on their SEDs, the morphology of the host-galaxies, the stellar masses, the bolometric luminosities and bolometric corrections. Finally, I will briefly discuss what are the perspectives of AGN in the context of observational cosmology.

  1. PeV neutrinos from intergalactic interactions of cosmic rays emitted by active galactic nuclei

    CERN Document Server

    Kalashev, Oleg E; Essey, Warren

    2013-01-01

    The observed spectra of distant blazars are well described by secondary gamma rays produced in line-of-sight interactions of cosmic rays with background photons. In the absence of the cosmic-ray contribution, these spectra would appear surprisingly hard, but the cosmic ray interactions generate very high energy gamma rays relatively close to the observer, and the spectra agree with the data. The same interactions of cosmic rays are expected to produce a flux of neutrinos with energies peaked around 1 PeV. We show that the predicted diffuse isotropic neutrino background from many distant sources can explain the neutrino events recently detected by the IceCube experiment. We also find that the flux from any individual nearby source is insufficient to account for these events. The narrow spectrum around 1 PeV implies that a typical active galactic nucleus can accelerate protons to EeV energies.

  2. Parsec-scale Faraday Rotation Measures from General Relativistic MHD Simulations of Active Galactic Nuclei Jets

    CERN Document Server

    Broderick, Avery E

    2010-01-01

    For the first time it has become possible to compare global 3D general relativistic magnetohydrodynamic (GRMHD) jet formation simulations directly to very-long baseline interferometric multi-frequency polarization observations of the pc-scale structure of active galactic nucleus (AGN) jets. Unlike the jet emission, which requires post hoc modeling of the non-thermal electrons, the Faraday rotation measures (RMs) depend primarily upon simulated quantities and thus provide a robust way in which to confront simulations with observations. We compute RM distributions of 3D global GRMHD jet formation simulations, with which we explore the dependence upon model and observational parameters, emphasizing the signatures of structures generic to the theory of MHD jets. With typical parameters, we find that it is possible to reproduce the observed magnitudes and many of the structures found in AGN jet RMs, including the presence of transverse RM gradients. In our simulations the RMs are generated within a smooth extensio...

  3. Feedback from Active Galactic Nuclei: Energy- versus momentum-driving

    CERN Document Server

    Costa, Tiago; Haehnelt, Martin G

    2014-01-01

    We employ hydrodynamical simulations using the moving-mesh code AREPO to investigate the role of energy and momentum input from Active Galactic Nuclei (AGN) in driving large-scale galactic outflows. We start by reproducing analytic solutions for both energy- and momentum-driven outflowing shells in simulations of a spherical isolated dark matter potential with gas in hydrostatic equilibrium and with no radiative cooling. We confirm that for this simplified setup, galactic outflows driven by a momentum input rate of order L_Edd/c can establish an M_BH - sigma relation with slope and normalisation similar to that observed. We show that momentum input at a rate of L_Edd/c is however insufficient to drive efficient outflows once cooling and gas inflows as predicted by cosmological simulations at resolved scales are taken into account. We argue that observed large-scale AGN-driven outflows are instead likely to be energy-driven and show that such outflows can reach momentum fluxes exceeding 10 L_Edd/c within the i...

  4. Composition of cosmic rays accelerated in active galactic nuclei

    CERN Document Server

    Berezhko, E G

    2009-01-01

    The composition of the overall spectrum of cosmic rays (CRs) is studied under the assumption that ultra high energy CRs above the energy 10^{17} eV are produced at the shock created by the expanding cocoons around active galactic nuclei (AGNs). It is shown that the expected CR composition is characterised by two peaks in the energy dependence of the mean CR atomic number . The first one at the energy \\epsilon \\approx 10^{17} eV corresponds to the very end of the Galactic CR component, produced in supernova remnants (SNRs). It is followed by a sharp decrease of within the energy interval from 10^{17} to 10^{18} eV. This is a signature of the transition from Galactic to extragalactic CRs. The second peak, with \\approx 2, at energy \\epsilon\\approx 10^{19} eV, expected at the beginning of the GZK cutoff, is the signature of the CR production by the nonrelativistic cocoon shocks. The calculated CR composition is consistent with the existing data. The alternative scenario, which suggests reacceleration increasing...

  5. Jet precession in the active nucleus of M81. Ongoing VLBI monitoring

    CERN Document Server

    Marti-Vidal, I; Alberdi, A; Brunthaler, A

    2013-01-01

    In a recent publication, we reported results of a multi-frequency VLBI campaign of observations of the Active Galactic Nucleus (AGN) in galaxy M\\,81, phase-referenced to the supernova SN\\,1993J. We were able to extract precise information on the relative astrometry of the AGN radio emission at different epochs and frequencies. We found strong evidence of precession in the AGN jet (i.e., a systematic evolution in the jet inclination at each frequency) coupled to changes in the overall flux density at the different frequencies. In these proceedings, we summarise the main contents of our previous publication and we report on (preliminary) new results from our follow-up VLBI observations, now phase-referenced to the young supernova SN2008iz. We also briefly discuss how these results match the picture of our previously-reported precession model.

  6. X-ray and infrared diagnostics of nearby active galactic nuclei with MAXI and AKARI

    CERN Document Server

    Isobe, Naoki; Oyabu, Shinki; Nakagawa, Takao; Baba, Shunsuke; Yano, Kenichi; Ueda, Yoshihiro; Toba, Yoshiki

    2016-01-01

    Nearby active galactic nuclei were diagnosed in the X-ray and mid-to-far infrared wavelengths, with Monitor of All-sky X-ray Image (MAXI) and the Japanese infrared observatory AKARI, respectively. Among the X-ray sources listed in the second release of the MAXI all-sky X-ray source catalog, 100 ones are currently identified as a non-blazar-type active galactic nucleus. These include 95 Seyfert galaxies and 5 quasars, and they are composed of 73 type-1 and 27 type-2 objects. The AKARI all-sky survey point source catalog was searched for their mid- and far-infrared counterparts at 9, 18, and 90 $\\mu$m. As a result, 69 Seyfert galaxies in the MAXI catalog (48 type-1 and 21 type-2 ones) were found to be detected with AKARI. The X-ray (3-4 keV and 4-10 keV) and infrared luminosities of these objects were investigated, together with their color information. Adopting the canonical photon index, $\\Gamma = 1.9$, of the intrinsic X-ray spectrum of the Seyfert galaxies, the X-ray hardness ratio between the 3-4 and 4-10 ...

  7. Statistics of Superluminal Motion in Active Galactic Nuclei

    Institute of Scientific and Technical Information of China (English)

    Yong-Wei Zhang; Jun-Hui Fan

    2008-01-01

    We have collected an up-to-date sample of 123 superluminal sources (84 quasars, 27 BL Lac objects and 12 galaxies) and calculated the apparent velocities (βapp) for 224 components in the sources with the A-CDM model. We checked the relationships between their proper motions, redshifts,βapp and 5 GHz flux densities. Our analysis shows that the radio emission is strongly boosted by the Doppler effect. The superluminal motion and the relativistic beaming boosting effect are, to some extent, the same in active galactic nuclei.

  8. Kepler Observations of Rapid Optical Variability in Active Galactic Nuclei

    CERN Document Server

    Mushotzky, Richard F; Baumgartner, Wayne H; Gandhi, Poshak

    2011-01-01

    Over three quarters in 2010-2011, Kepler monitored optical emission from four active galactic nuclei (AGN) with ~30 min sampling, >90% duty cycle, and <~0.1% repeatability. These data determined the AGN optical fluctuation power spectral density functions (PSDs) over a wide range in temporal frequency. Fits to these PSDs yielded power law slopes of -2.6 to -3.3, much steeper than typically seen in the X-rays. We find evidence that individual AGN exhibit intrinsically different PSD slopes. The steep PSD fits are a challenge to recent AGN variability models but seem consistent with first order MRI theoretical calculations of accretion disk fluctuations.

  9. Active galactic nuclei, neutrinos, and interacting cosmic rays in NGC 253 and NGC 1068

    Energy Technology Data Exchange (ETDEWEB)

    Yoast-Hull, Tova M.; Zweibel, Ellen G. [Department of Physics, University of Wisconsin-Madison, WI 53706 (United States); Gallagher III, J. S. [Department of Astronomy, University of Wisconsin-Madison, WI 53706 (United States); Everett, John E., E-mail: yoasthull@wisc.edu [Center for Interdisciplinary Exploration and Research in Astrophysics, Northwestern University, IL 60208 (United States)

    2014-01-10

    The galaxies M82, NGC 253, NGC 1068, and NGC 4945 have been detected in γ-rays by Fermi. Previously, we developed and tested a model for cosmic-ray interactions in the starburst galaxy M82. Now, we aim to explore the differences between starburst and active galactic nucleus (AGN) environments by applying our self-consistent model to the starburst galaxy NGC 253 and the Seyfert galaxy NGC 1068. Assuming a constant cosmic-ray acceleration efficiency by supernova remnants with Milky Way parameters, we calculate the cosmic-ray proton and primary and secondary electron/positron populations, predict the radio and γ-ray spectra, and compare with published measurements. We find that our models easily fit the observed γ-ray spectrum for NGC 253 while constraining the cosmic-ray source spectral index and acceleration efficiency. However, we encountered difficultly modeling the observed radio data and constraining the speed of the galactic wind and the magnetic field strength, unless the gas mass is less than currently preferred values. Additionally, our starburst model consistently underestimates the observed γ-ray flux and overestimates the radio flux for NGC 1068; these issues would be resolved if the AGN is the primary source of γ-rays. We discuss the implications of these results and make predictions for the neutrino fluxes for both galaxies.

  10. Serotonergic modulation of astrocytic activity in the hamster suprachiasmatic nucleus.

    Science.gov (United States)

    Glass, J D; Chen, L

    1999-01-01

    The present study was undertaken to explore the effects of central serotonin receptor activation on the expression of glial fibrillary acidic protein in the suprachiasmatic nucleus of Syrian hamsters. Immunoblot and immunohistochemical procedures were used to examine the effects of systemic application of the serotonin-1A and serotonin-7 receptor agonist, (+/-)-2-dipropyl-amino-8-hydroxyl-1,2,3,4-tetrahydronaphthalene hydrobromide (8-OH-DPAT; 3.75 mg/kg) on the contents and distribution of glial fibrillary acidic protein in the suprachiasmatic nucleus. Administration of 8-OH-DPAT at midday caused a significant reduction in immunoreactive glial fibrillary acidic protein content within 1 h of injection, compared to vehicle controls. This effect was not evident 3 h after drug injection. Treatment with 8-OH-DPAT during the late dark phase had little effect on glial fibrillary acidic protein content. The 8-OH-DPAT-induced reduction in glial fibrillary acidic protein content seen at midday was blocked partially by pretreatment with the serotonin-2 and serotonin-7 receptor antagonist, ritanserin, and more substantially by pretreatment with the serotonin-1A receptor antagonist, NAN-190. Treatment with 8-OH-DPAT also caused a significant redistribution of immunoreactive glial fibrillary acidic protein, such that the dense mesh-like appearance seen in vehicle controls was significantly reduced. The 8-OH-DPAT treatment also significantly decreased expression of polysialic acid, a cell-surface molecule associated with neural plasticity. Immunoblot assessments of glial fibrillary acidic protein contents 2 h before and 1 h after lights off revealed a significant time-of-day difference in glial fibrillary acidic protein expression, with lowest levels occurring at the latter time-point, associated with maximal endogenous serotonin release in the suprachiasmatic nucleus. Collectively, these results indicate that acute plastic changes in glial fibrillary acidic protein

  11. Close stars and accretion in Low Luminosity Active Galactic Nuclei

    CERN Document Server

    Nayakshin, S

    2004-01-01

    Quasar accretion disks are believed to form stars by self-gravity. Low Luminosity Active Galactic Nuclei (LLAGN) are much dimmer galactic centers, and are often believed to be quasars that ran out of gaseous fuel. LLAGN accretion disks should thus co-exist with thousands to millions of stars or proto-stars left from the previous stronger accretion activity. In principle, these stars may produce several important effects: (i) contribute to the optical/UV spectra of some LLAGN; (ii) reprocessing of the stellar radiation in the dusty disks could dominate the LLAGN infra-red spectra; (iii) deplete the (accretion) gas disk much faster than it can accrete onto the supper-massive black hole (SMBH); (iv) stars, individually or in groups, may slow down and modulate the accretion flow significantly due to their inertia. In this way they may produce the LLAGN cut-off disks; (v) alternatively, frequent enough stellar collisions and resulting stellar disruptions could keep the inner disk empty. Here we explore these ideas...

  12. Active galactic nuclei at gamma-ray energies

    CERN Document Server

    Dermer, Charles Dennison

    2016-01-01

    Active Galactic Nuclei can be copious extragalactic emitters of MeV-GeV-TeV gamma rays, a phenomenon linked to the presence of relativistic jets powered by a super-massive black hole in the center of the host galaxy. Most of gamma-ray emitting active galactic nuclei, with more than 1500 known at GeV energies, and more than 60 at TeV energies, are called "blazars". The standard blazar paradigm features a jet of relativistic magnetized plasma ejected from the neighborhood of a spinning and accreting super-massive black hole, close to the observer direction. Two classes of blazars are distinguished from observations: the flat-spectrum radio-quasar class (FSRQ) is characterized by strong external radiation fields, emission of broad optical lines, and dust tori. The BL Lac class (from the name of one of its members, BL Lacertae) corresponds to weaker advection-dominated flows with gamma-ray spectra dominated by the inverse Compton effect on synchrotron photons. This paradigm has been very successful for modeling t...

  13. Traces of past activity in the Galactic Centre

    CERN Document Server

    Ponti, Gabriele; Terrier, Regis; Goldwurm, Andrea

    2012-01-01

    The Milky Way centre hosts a supermassive Black Hole (BH) with a mass of ~4*10^6 M_Sun. Sgr A*, its electromagnetic counterpart, currently appears as an extremely weak source with a luminosity L~10^-9 L_Edd. The lowest known Eddington ratio BH. However, it was not always so; traces of "glorious" active periods can be found in the surrounding medium. We review here our current view of the X-ray emission from the Galactic Center (GC) and its environment, and the expected signatures (e.g. X-ray reflection) of a past flare. We discuss the history of Sgr A*'s past activity and its impact on the surrounding medium. The structure of the Central Molecular Zone (CMZ) has not changed significantly since the last active phase of Sgr A*. This relic torus provides us with the opportunity to image the structure of an AGN torus in exquisite detail.

  14. Spatially Offset Active Galactic Nuclei I: Selection and Spectroscopic Properties

    CERN Document Server

    Barrows, R Scott; Greene, Jenny E; Pooley, David

    2016-01-01

    We present a sample of 18 optically-selected and X-ray detected spatially offset active galactic nuclei (AGN) from the Sloan Digital Sky Survey (SDSS). In 9 systems, the X-ray AGN is spatially offset from the galactic stellar core that is located within the 3'' diameter SDSS spectroscopic fiber. In 11 systems, the X-ray AGN is spatially offset from a stellar core that is located outside the fiber, with an overlap of 2. To build the sample, we cross-matched Type II AGN selected from the SDSS galaxy catalogue with archival Chandra imaging and employed our custom astrometric and registration procedure. The projected angular (physical) offsets span a range of 0."6 (0.8 kpc) to 17."4 (19.4 kpc), with a median value of 2."7 (4.6 kpc). The offset nature of an AGN is an unambiguous signature of a galaxy merger, and these systems can be used to study the properties of AGN in galaxy mergers without the biases introduced by morphological merger selection techniques. In this paper (Paper I), we use our sample to assess t...

  15. Two-temperature coronae in active galactic nuclei

    CERN Document Server

    Matteo, T D; Fabian, A C

    1997-01-01

    We show that coronal magnetic dissipation in thin active sheets that sandwich standard thin accretion disks in active galactic nuclei may account for canonical electron temperatures of a few $\\times 10^9$K if protons acquire most of the dissipated energy. Coulomb collisions transfer energy from the ions to the electrons, which subsequently cool rapidly by inverse-Compton scattering. In equilibrium, the proton energy density likely exceeds that of the magnetic field and both well exceed the electron and photon energy densities. The Coulomb energy transfer from protons to electrons is slow enough to maintain a high proton temperature, but fast enough to explain observed rapid X-ray variabilities in Seyferts. The $\\sim 10^9$K electron temperature is insensitive to the proton temperature when the latter is $\\ge 10^{12}$K.

  16. The Halo Occupation Distribution of Active Galactic Nuclei

    CERN Document Server

    Chatterjee, Suchetana; Richardson, Jonathan; Zheng, Zheng; Nagai, Daisuke; Di Matteo, Tiziana

    2011-01-01

    Using a fully cosmological hydrodynamic simulation that self-consistently incorporates the growth and feedback of supermassive black holes and the physics of galaxy formation, we examine the effects of environmental factors (e.g., local gas density, black hole feedback) on the halo occupation distribution of low luminosity active galactic nuclei (AGN). We decompose the mean occupation function into central and satellite contribution and compute the conditional luminosity functions (CLF). The CLF of the central AGN follows a log-normal distribution with the mean increasing and scatter decreasing with increasing redshifts. We analyze the light curves of individual AGN and show that the peak luminosity of the AGN has a tighter correlation with halo mass compared to instantaneous luminosity. We also compute the CLF of satellite AGN at a given central AGN luminosity. We do not see any significant correlation between the number of satellites with the luminosity of the central AGN at a fixed halo mass. We also show ...

  17. Active Galactic Nuclei Discovered in the Kepler Mission

    CERN Document Server

    Shaya, Edward J; Mushotzky, Richard

    2015-01-01

    We report on candidate active galactic nuclei (AGN) discovered during the monitoring of $\\sim$500 bright (r < 18 mag) galaxies over several years with the Kepler Mission. Most of the targets were sampled every 30 minutes nearly continuously for a year or more. Variations of 0.001 mag and often less could be detected reliably. About 4.0% (19) of our random sample continuously fluctuated with amplitudes increasing with longer timescales, but the majority are close to the limits of detectability with Kepler. We discuss our techniques to mitigate the long term instrumental trends in Kepler light curves and our resulting structure function curves. The amplitudes of variability over four month periods, as seen in the structure functions and PSDs, can dramatically change for many of these AGN candidates. Four of the candidates have features in their Structure Functions that may indicate quasi-periodic behavior, although other possibilities are discussed.

  18. KEPLER OBSERVATIONS OF RAPID OPTICAL VARIABILITY IN ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Mushotzky, R. F.; Edelson, R. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Baumgartner, W. [Laboratory for High Energy Astrophysics, NASA/GSFC, Code 662, Greenbelt, MD 20771 (United States); Gandhi, P., E-mail: richard@astro.umd.edu [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

    2011-12-10

    Over three quarters in 2010-2011, Kepler monitored optical emission from four active galactic nuclei (AGNs) with {approx}30 minute sampling, >90% duty cycle, and {approx}<0.1% repeatability. These data determined the AGN optical fluctuation power spectral density (PSD) functions over a wide range in temporal frequency. Fits to these PSDs yielded power-law slopes of -2.6 to -3.3, much steeper than typically seen in the X-rays. We find evidence that individual AGNs exhibit intrinsically different PSD slopes. The steep PSD fits are a challenge to recent AGN variability models but seem consistent with first-order magnetorotational instability theoretical calculations of accretion disk fluctuations.

  19. Studies of Relativistic Jets in Active Galactic Nuclei with SKA

    CERN Document Server

    Agudo, Ivan; Falcke, Heino; Georganopoulos, Markos; Ghisellini, Gabriele; Giovannini, Gabriele; Giroletti, Marcello; Gomez, Jose L; Gurvits, Leonid; Laing, Robert; Lister, Matthew; Marti, Jose-Maria; Meyer, Eileen T; Mizuno, Yosuke; O'Sullivan, Shane; Padovani, Paolo; Paragi, Zsolt; Perucho, Manel; Schleicher, Dominik; Stawarz, Lukasz; Vlahakis, Nektarios; Wardle, John

    2015-01-01

    Relativistic jets in active galactic nuclei (AGN) are among the most powerful astrophysical objects discovered to date. Indeed, jetted AGN studies have been considered a prominent science case for SKA, and were included in several different chapters of the previous SKA Science Book (Carilli & Rawlings 2004). Most of the fundamental questions about the physics of relativistic jets still remain unanswered, and await high-sensitivity radio instruments such as SKA to solve them. These questions will be addressed specially through analysis of the massive data sets arising from the deep, all-sky surveys (both total and polarimetric flux) from SKA1. Wide-field very-long-baseline-interferometric survey observations involving SKA1 will serve as a unique tool for distinguishing between extragalactic relativistic jets and star forming galaxies via brightness temperature measurements. Subsequent SKA1 studies of relativistic jets at different resolutions will allow for unprecedented cosmological studies of AGN jets up...

  20. The interaction between feedback from active galactic nuclei and supernovae

    CERN Document Server

    Booth, C M

    2012-01-01

    Energetic feedback from supernovae (SNe) and from active galactic nuclei (AGN) are both important processes that are thought to control how much gas is able to condense into galaxies and form stars. We show that although both AGN and SNe suppress star formation, they mutually weaken one another's effect by up to an order of magnitude in haloes in the mass range for which both feedback processes are efficient (10^11.25 M_sun < m_200 < 10^12.5 M_sun). These results demonstrate the importance of the simultaneous, non-independent inclusion of these two processes in models of galaxy formation to estimate the total feedback strength. These results are of particular relevance to semi-analytic models, which implicitly assume the effects of the two feedback processes to be independent, and also to hydrodynamical simulations that model only one of the feedback processes.

  1. Evolution of Broad-line Emission from Active Galactic Nuclei

    CERN Document Server

    Elitzur, Moshe; Trump, Jonathan R

    2013-01-01

    Apart from viewing-dependent obscuration, intrinsic broad-line emission from active galactic nuclei (AGNs) follows an evolutionary sequence: Type $1 \\to 1.2/1.5 \\to 1.8/1.9 \\to 2$ as the accretion rate onto the central black hole is decreasing. This spectral evolution is controlled, at least in part, by the parameter $L_{\\rm bol}/M^{2/3}$, where $L_{\\rm bol}$ is the AGN bolometric luminosity and $M$ is the black hole mass. Both this dependence and the double-peaked profiles that emerge along the sequence arise naturally in the disk-wind scenario for the AGN broad-line region.

  2. Time Delay Evolution of Five Active Galactic Nuclei

    Indian Academy of Sciences (India)

    A. Kovačević; L. Č. Popović; A. I. Shapovalova; D. Ilić; A. N. Burenkov; V. H. Chavushyan

    2015-12-01

    Here we investigate light curves of the continuum and emission lines of five type 1 active galactic nuclei (AGN) from our monitoring campaign, to test time-evolution of their time delays. Using both modeled and observed AGN light curves, we apply Gaussian kernel-based estimator to capture variation of local patterns of their time evolving delays. The largest variations of time delays of all objects occur in the period when continuum or emission lines luminosity is the highest. However, Gaussian kernel-based method shows instability in the case of NGC 5548, 3C 390.3, E1821+643 and NGC 4051 possibly due to numerical discrepancies between damped random walk (DRW) time scale of light curves and sliding time windows of the method. The temporal variations of time lags of Arp 102B can correspond to the real nature of the time lag evolution.

  3. On the time delay evolution of five Active Galactic Nuclei

    CERN Document Server

    Kovacevic, Andjelka; Shapovalova, Alla I; Ilic, Dragana; Burenkov, Aleksandr N; Chavushyan, Vahram H

    2015-01-01

    Here we investigate light curves of the continuum and emission lines of five type 1 active galactic nuclei (AGN) from our monitoring campaign, to test time-evolution of their time delays.Using both modeled and observed AGN light curves we apply Gaussian-kernel based estimator to capture variation of local patterns of their time evolving delays. The largest variations of time delays of all objects occur in the period when continuum or emission lines luminosity is the highest. However, Gaussian kernel based method shows instability in the case of NGC 5548, 3C 390.3, E1821+643 and NGC 4051 possible due to numerical discrepancies between Damped Random Walk (DRW) time scale of light curves and sliding time windows of the method. The temporal variations of time lags of Arp 102B can correspond to the real nature of the time lag evolution.

  4. Active Galactic Nuclei: The TeV Challenge

    CERN Document Server

    Blandford, R; Nalewajko, K; Yuan, Y; Zrake, J

    2015-01-01

    Jets associated with Active Galactic Nuclei (AGN) have been observed for almost a century, initially at optical and radio wavelengths. They are now widely accepted as "exhausts" produced electromagnetically by the central, spinning, massive black hole and its orbiting, accreting gas. Observations at X-ray and, especially, gamma-ray energies have transformed our understanding of how these jets evolve dynamically, accelerate electrons (and positrons) and radiate throughout the entire electromagnetic spectrum. Some new approaches to modeling the powerful and rapidly variable TeV emission observed from many blazars are sketched. Observations at the highest TeV energies, to which the High Altitude Water Cherenkov Gamma-Ray Observatory (HAWC) will contribute, promise crucial discrimination between rival models of AGN jets.

  5. Neutrinos in IceCube from active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Kalashev, O., E-mail: kalashev@inr.ac.ru [Russian Academy of Sciences, Institute for Nuclear Research (Russian Federation); Semikoz, D. [Laboratory of AstroParticle and Cosmology (APC) (France); Tkachev, I. [Russian Academy of Sciences, Institute for Nuclear Research (Russian Federation)

    2015-03-15

    Recently, the IceCube collaboration reported first evidence for the astrophysical neutrinos. Observation corresponds to the total astrophysical neutrino flux of the order of 3 × 10{sup −8} GeV cm{sup −2} s{sup −1} sr{sup −1} in a PeV energy range [1]. Active galactic nuclei (AGN) are natural candidate sources for such neutrinos. To model the neutrino creation in AGNs, we study photopion production processes on the radiation field of the Shakura-Sunyaev accretion discs in the black hole vicinity. We show that this model can explain the detected neutrino flux and at the same time avoids the existing constraints from the gamma-ray and cosmic-ray observations.

  6. Emission Line Galaxies and Active Galactic Nuclei in WINGS clusters

    CERN Document Server

    Marziani, P; Bettoni, D; Poggianti, B M; Moretti, A; Fasano, G; Fritz, J; Cava, A; Varela, J; Omizzolo, A

    2016-01-01

    We present the analysis of the emission line galaxies members of 46 low redshift (0.04 < z < 0.07) clusters observed by WINGS (WIde-field Nearby Galaxy cluster Survey, Fasano et al. 2006). Emission line galaxies were identified following criteria that are meant to minimize biases against non-star forming galaxies and classified employing diagnostic diagrams. We have examined the emission line properties and frequencies of star forming galaxies, transition objects and active galactic nuclei (AGNs: LINERs and Seyferts), unclassified galaxies with emission lines, and quiescent galaxies with no detectable line emission. A deficit of emission line galaxies in the cluster environment is indicated by both a lower frequency with respect to control samples, and by a systematically lower Balmer emission line equivalent width and luminosity (up to one order of magnitude in equivalent width with respect to control samples for transition objects) that implies a lower amount of ionised gas per unit mass and a lower s...

  7. Powerful Outflows and Feedback from Active Galactic Nuclei

    CERN Document Server

    King, Andrew

    2015-01-01

    Active Galactic Nuclei (AGN) represent the growth phases of the supermassive black holes in the center of almost every galaxy. Powerful, highly ionized winds, with velocities $\\sim 0.1- 0.2c$ are a common feature in X--ray spectra of luminous AGN, offering a plausible physical origin for the well known connections between the hole and properties of its host. Observability constraints suggest that the winds must be episodic, and detectable only for a few percent of their lifetimes. The most powerful wind feedback, establishing the $M -\\sigma$ relation, is probably not directly observable at all. The $M - \\sigma$ relation signals a global change in the nature of AGN feedback. At black hole masses below $M-\\sigma$ feedback is confined to the immediate vicinity of the hole. At the $M-\\sigma$ mass it becomes much more energetic and widespread, and can drive away much of the bulge gas as a fast molecular outflow.

  8. Galactic Winds in Galaxies with Active Black Holes

    Science.gov (United States)

    Lee, Lin; Yesuf, Hassen Mohammed

    2017-01-01

    Post-starbursts galaxies are in a rapid transition from star-forming to quiescent, and are excellent candidates to test Active galactic nuclei (AGN) feedback models. A key physical manifestation of AGN feedback is predicted to be galactic-scale powerful winds. We study winds in stacked spectra of 375 post-starburst AGN and of a control sample of star-forming (non-AGN) galaxies, both taken from the Sloan Digital Sky Survey (SDSS). Using a two component (ISM+wind) absorption line model of the Na I 5890,5896 A doublet, after accounting for the stellar photospheric absorption, we find that the post-starburst AGN have a centroid wind velocity shift of -174 +/- 24 km/s and a wind velocity dispersion of 148 +/- 10 km/s. In comparison, the control sample, matched in redshift, stellar mass, axis-ratio, and the 4000 angstrom break index, has a centroid wind velocity shift of -132 +/- 7 km/s and a wind velocity dispersion of 86 +/- 5 km/s. The equivalent widths due to the winds are slightly higher in post-starburst AGN (0.25 +/- 0.03 A) than in the control sample (0.14 +/- 0.01 A) while the ISM contribution to the total equivalent widths is much higher in the AGN (0.62 +/- 0.05 A) than in the control sample (0.15 +/- 0.01 A). The observed winds in the post-starburst AGN are not powerful enough to sweep significant amount gas out of the halos of the host galaxies, thereby cause rapid and permanent quenching of star-formation.

  9. STACEE Observations of Active Galactic Nuclei and Other Sources

    Science.gov (United States)

    Ong, R. A.; Boone, L. M.; Bramel, D.; Chae, E.; Covault, C. E.; Fortin, P.; Gingrich, D.; Hanna, D. S.; Hinton, J. A.; Meuller, C.; Mukherjee, R.; Ragan, K.; Scalzo, R. A.; Schuette, D. R.; Theoret, C. G.; Williams, D. A.

    2001-08-01

    We describe recent observations and future plans for the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE) located at Sandia National Laboratories in Albuquerque, New Mexico. STACEE is a ground-based experiment for detecting atmospheric Cherenkov light from γrays in the energy range 50 to 500 GeV. We describe recent observations of active galactic nuclei such as Mrk 501, and also outline plans for the observations of other AGN, including Flat Spectrum Radio Quasars (FSRQs) detected by EGRET above 1 GeV and other BL-Lac objects. We summarize plans for observing other sources, including the Crab Nebula, other pulsars, supernova remnants, and unidentified EGRET objects. The up-to-date results from recent source observations by STACEE will be presented at the conference. 1 Intergalactic absorption and the γ-ray horizon The energy range from 50 to 250 GeV is important for understanding many high energy astrophysical objects, especially active galactic nuclei. Great progress has been made during the last decade, but many problems remain. For example, while dozens of AGN at a variety of redshifts were detected by EGRET, only a few of the closest AGN have been detected by ground-based experiments above 250 GeV. These results imply that the power-law spectra of many AGN cut off at energies between 20 and 250 GeV, and the fact that only nearby AGN are seen at very high energies argues that the γrays are attenuated on their long journey to Earth. High energy γ-rays interact with photons at infrared/optical/UV energies via the pair-production process (Stecker and de Jager, 1993; Biller, 1995). The level of such extragalactic background light (EBL) from galaxies is not well known, but measurements of absorption features of AGN should provide constraints on its flux and spectral shape. These constraints in turn could give us valuable information about the epoch of galaxy formation and the composition of dark mat-

  10. The Radius-Luminosity Relationship for Active Galactic Nuclei

    DEFF Research Database (Denmark)

    Bentz, Misty C.; Peterson, Bradley M.; Netzer, Hagai

    2009-01-01

    We present high-resolution HST images of all 35 AGNs with optical reverberation-mapping results, which we have modeled to create a nucleus-free image of each AGN host galaxy. From the nucleus-free images, we determine the host-galaxy contribution to ground-based spectroscopic luminosity measureme...

  11. Variability in Active Galactic Nuclei from Propagating Turbulent Relativistic Jets

    CERN Document Server

    Pollack, Maxwell; Wiita, Paul J

    2016-01-01

    We use the Athena hydrodynamics code to model propagating two-dimensional relativistic jets as approximations to the growth of radio-loud active galactic nuclei for various input jet velocities and jet-to-ambient matter density ratios. Using results from these simulations we estimate the changing synchrotron emission by summing the fluxes from a vertical strip of zones behind the reconfinement shock, which is nearly stationary, and from which a substantial portion of the flux variability should arise. We explore a wide range of time scales by considering two light curves from each simulation; one uses a relativistic turbulence code with bulk velocities taken from our simulations as input, while the other uses the bulk velocity data to compute fluctuations caused by variations in the Doppler boosting due to changes in the direction and the speed of the flow through all zones in the strip. We then calculate power spectral densities (PSDs) from the light curves for both turbulent and bulk velocity origins for va...

  12. VARIABILITY IN ACTIVE GALACTIC NUCLEI FROM PROPAGATING TURBULENT RELATIVISTIC JETS

    Energy Technology Data Exchange (ETDEWEB)

    Pollack, Maxwell; Pauls, David; Wiita, Paul J., E-mail: wiitap@tcnj.edu [Department of Physics, The College of New Jersey P.O. Box 7718, Ewing, NJ 08628-0718 (United States)

    2016-03-20

    We use the Athena hydrodynamics code to model propagating two-dimensional relativistic jets as approximations to the growth of radio-loud active galactic nuclei for various input jet velocities and jet-to-ambient matter density ratios. Using results from these simulations we estimate the changing synchrotron emission by summing the fluxes from a vertical strip of zones behind the reconfinement shock, which is nearly stationary, and from which a substantial portion of the flux variability should arise. We explore a wide range of timescales by considering two light curves from each simulation; one uses a relativistic turbulence code with bulk velocities taken from our simulations as input, while the other uses the bulk velocity data to compute fluctuations caused by variations in the Doppler boosting due to changes in the direction and the speed of the flow through all zones in the strip. We then calculate power spectral densities (PSDs) from the light curves for both turbulent and bulk velocity origins for variability. The range of the power-law slopes of the PSDs for the turbulence induced variations is −1.8 to −2.3, while for the bulk velocity produced variations this range is −2.1 to −2.9; these are in agreement with most observations. When superimposed, these power spectra span a very large range in frequency (about five decades), with the turbulent fluctuations yielding most of the shorter timescale variations and the bulk flow changes dominating the longer periods.

  13. Optical-radio positional offsets for active galactic nuclei

    CERN Document Server

    Orosz, G

    2013-01-01

    Context. It will soon become possible to directly link the most accurate radio reference frame with the Gaia optical reference frame using many common extragalactic objects. It is important to know the level of coincidence between the radio and optical positions of compact active galactic nuclei (AGN). Aims. Using the best catalogues available at present, we investigate how many AGN with significantly large optical-radio positional offsets exist as well as the possible causes of these offsets. Methods. We performed a case study by finding optical counterparts to the International Celestial Reference Frame (ICRF2) radio sources in the Sloan Digital Sky Survey (SDSS) Data Release 9 (DR9). The ICRF2 catalogue was used as a reference because the radio positions determined by Very Long Baseline Interferometry (VLBI) observations are about two orders of magnitude more accurate than the optical positions. Results. We find 1297 objects in common for ICRF2 and SDSS DR9. Statistical analysis of the optical-radio differ...

  14. On the radio dichotomy of active galactic nuclei

    CERN Document Server

    Cao, Xinwu

    2016-01-01

    It is still a mystery why only a small fraction of active galactic nuclei (AGNs) contain relativistic jets. Strong magnetic field is a necessary ingredient for jet formation, however, the advection of the external field in a geometrically thin disk is inefficient. The gas with a small angular velocity may fall from the Bondi radius $R_{\\rm B}$ nearly freely to the circularization radius $R_{\\rm c}$, and a thin accretion disk is formed within $R_{\\rm c}$. We suggest that the external magnetic field is substantially enhanced in this region, and the magnetic field at $R_{\\rm c}$ can be sufficiently strong to drive outflows from the disk if the angular velocity of the gas is low at $R_{\\rm B}$. The magnetic field is efficiently dragged in the disk, because most angular momentum of the disk is removed by the outflows that leads to a significantly high radial velocity. The strong magnetic field formed in this way may accelerate jets in the region near the black hole either by the Blandford-Payne or/and Blandford-Zn...

  15. The suppression of star formation by powerful active galactic nuclei

    CERN Document Server

    Page, M J; Vieira, J D; Altieri, B; Amblard, A; Arumugam, V; Aussel, H; Babbedge, T; Blain, A; Bock, J; Boselli, A; Buat, V; Castro-Rodr'iguez, N; Cava, A; Chanial, P; Clements, D L; Conley, A; Conversi, L; Cooray, A; Dowell, C D; Dubois, E N; Dunlop, J S; Dwek, E; Dye, S; Eales, S; Elbaz, D; Farrah, D; Fox, M; Franceschini, A; Gear, W; Glenn, J; Griffin, M; Halpern, M; Hatziminaoglou, E; Ibar, E; Isaak, K; Ivison, R J; Lagache, G; Levenson, L; Lu, N; Madden, S; Maffei, B; Mainetti, G; Marchetti, L; Nguyen, H T; O'Halloran, B; Oliver, S J; Omont, A; Panuzzo, P; Papageorgiou, A; Pearson, C P; Perez-Fournon, I; Pohlen, M; Rawlings, J I; Rigopoulou, D; Riguccini, L; Rizzo, D; Rodighiero, G; Roseboom, I G; Rowan-Robinson, M; Portal, M Sanchez; Schulz, B; Scott, Douglas; Seymour, N; Shupe, D L; Smith, A J; Stevens, J A; Trichas, M; Tugwell, K E; Vaccari, M; Valtchanov, I; Viero, M; Vigroux, L; Wang, L; Ward, R; Wright, G; Xu, C K; Zemcov, M

    2013-01-01

    The old, red stars which constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly from accretion onto black holes. It is widely suspected, but unproven, that the tight correlation in mass of the black hole and stellar components results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, while powerful star-forming galaxies are usually dust-obscured and are brightest at infrared to submillimetre wavelengths. Here we report observations in the submillimetre and X-ray which show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 Gyrs old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10^44 erg/s. This suppression of star formation in the host galaxies of powerful AGN ...

  16. The star formation rates of active galactic nuclei host galaxies

    CERN Document Server

    Ellison, Sara L; Rosario, David J; Mendel, J Trevor

    2016-01-01

    Using artificial neural network (ANN) predictions of total infra-red luminosities (LIR), we compare the host galaxy star formation rates (SFRs) of ~21,000 optically selected active galactic nuclei (AGN), 466 low excitation radio galaxies (LERGs) and 721 mid-IR selected AGN. SFR offsets (Delta SFR) relative to a sample of star-forming `main sequence' galaxies (matched in M*, z and local environment) are computed for the AGN hosts. Optically selected AGN exhibit a wide range of Delta SFR, with a distribution skewed to low SFRs and a median Delta SFR = -0.06 dex. The LERGs have SFRs that are shifted to even lower values with a median Delta SFR = -0.5 dex. In contrast, mid-IR selected AGN have, on average, SFRs enhanced by a factor ~1.5. We interpret the different distributions of Delta SFR amongst the different AGN classes in the context of the relative contribution of triggering by galaxy mergers. Whereas the LERGs are predominantly fuelled through low accretion rate secular processes which are not accompanied ...

  17. The dust covering factor in active galactic nuclei

    CERN Document Server

    Stalevski, Marko; Ueda, Yoshihiro; Lira, Paulina; Fritz, Jacopo; Baes, Maarten

    2016-01-01

    The primary source of emission of active galactic nuclei (AGN), the accretion disk, is surrounded by an optically and geometrically thick dusty structure ("the so-called dusty torus"). The infrared radiation emitted by the dust is nothing but a reprocessed fraction of the accretion disk emission, so the ratio of the torus to the AGN luminosity ($L_{\\text{torus}}/L_{\\text{AGN}}$) should correspond to the fraction of the sky obscured by dust, i.e. the covering factor. We undertook a critical investigation of the $L_{\\text{torus}}/L_{\\text{AGN}}$ as the dust covering factor proxy. Using state-of-the-art 3D Monte Carlo radiative transfer code, we calculated a grid of SEDs emitted by the clumpy two-phase dusty structure. With this grid of SEDs, we studied the relation between $L_{\\text{torus}}/L_{\\text{AGN}}$ and the dust covering factor for different parameters of the torus. We found that in case of type 1 AGNs the torus anisotropy makes $L_{\\text{torus}}/L_{\\text{AGN}}$ underestimate low covering factors and ove...

  18. Feedback of Active Galactic Nuclei in Seyfert 2 Galaxies

    Institute of Scientific and Technical Information of China (English)

    En-Peng Zhang; Wei-Hao Bian; Chen Hu; Wei-Ming Mao; ALi Luo; Yong-Heng Zhao

    2008-01-01

    It is well accepted that feedback from active galactic nuclei (AGNs) plays an important role in the coevolution of the supermassive black hole (SMBH) and its host galaxy,but the concrete mechanism of feedback remains unclear.A considerable body of evidence suggests that AGN feedback suppresses star formation in the host galaxy.We assemble a sample of Seyfert 2 galaxies with recent observational data of compact nuclear starbursts and estimate the gas surface density as a function of column density to illuminate the relation between feedback and AGN properties.Although there are some uncertainties,our data still imply the deviation from the star formation law (Kennicutt-Schmidt law).Further,they indicate that:(1) Feedback correlates with the Eddington ratio,rather than with the mass of SMBH,as a result of decreasing star formation efficiency.(2) The SMBH and the torus are probably undergoing coevolution.Conclusions presented here can be refined through future high resolution CO or HCN observations.

  19. Active Galactic Nuclei under the scrutiny of CTA

    CERN Document Server

    Sol, H; Boisson, C; de Almeida, U Barres; Biteau, J; Contreras, J -L; Giebels, B; Hassan, T; Inoue, Y; Katarzynski, K; Krawczynski, H; Mirabal, N; Poutanen, J; Rieger, F; Totani, T; Benbow, W; Cerruti, M; Errando, M; Fallon, L; Pino, E de Gouveia Dal; Hinton, J -A; Inoue, S; Lenain, J -P; Neronov, A; Takahashi, K; Takami, H; White, R

    2013-01-01

    Active Galactic Nuclei (hereafter AGN) produce powerful outflows which offer excellent conditions for efficient particle acceleration in internal and external shocks, turbulence, and magnetic reconnection events. The jets as well as particle accelerating regions close to the supermassive black holes (hereafter SMBH) at the intersection of plasma inflows and outflows, can produce readily detectable very high energy gamma-ray emission. As of now, more than 45 AGN including 41 blazars and 4 radiogalaxies have been detected by the present ground-based gamma-ray telescopes, which represents more than one third of the cosmic sources detected so far in the VHE gamma-ray regime. The future Cherenkov Telescope Array (CTA) should boost the sample of AGN detected in the VHE range by about one order of magnitude, shedding new light on AGN population studies, and AGN classification and unification schemes. CTA will be a unique tool to scrutinize the extreme high-energy tail of accelerated particles in SMBH environments, t...

  20. The Suppression of Star Formation by Powerful Active Galactic Nuclei

    Science.gov (United States)

    Dwek, E.

    2012-01-01

    The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight corre1ation between the mass of the black hole and the mas. of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming ga1axies are usually dust-obscured and are brightest at infrared and submillimeter wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(exp 44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expe11ing the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time.

  1. Hot Bubbles from Active Galactic Nuclei as a Heat Source in Cooling Flow Clusters

    CERN Document Server

    Brüggen, M; Brueggen, Marcus; Kaiser, Christian R.

    2002-01-01

    The hot plasma permeating clusters of galaxies often shows a central peak in the X-ray surface brightness that is coincident with a drop in entropy. This is taken as evidence for a cooling flow where the radiative cooling in the central regions of a cluster causes a slow subsonic inflow. Searches in all wavebands have revealed significantly less cool gas than predicted indicating that the mass deposition rate of cooling flows is much lower than expected. However, most cooling flow clusters host an Active Galactic Nucleus (AGN) at their centres. AGN can inflate large bubbles of hot plasma that subsequently rise through the cluster atmosphere, thus stirring this gas. Here we report on the results from highly resolved hydrodynamic simulations which for the first time show that buoyant bubbles increase the cooling time in the inner cluster regions and thereby significantly reduce the deposition of cold gas. This work demonstrates that the action of AGN in the centres of cooling flow clusters can explain the obser...

  2. The Low-Luminosity End of the Radius-Luminosity Relationship for Active Galactic Nuclei

    CERN Document Server

    Bentz, Misty C; Grier, Catherine J; Barth, Aaron J; Peterson, Bradley M; Vestergaard, Marianne; Bennert, Vardha N; Canalizo, Gabriela; De Rosa, Gisella; Filippenko, Alexei V; Gates, Elinor L; Greene, Jenny E; Li, Weidong; Malkan, Matthew A; Pogge, Richard W; Stern, Daniel; Treu, Tommaso; Woo, Jong-Hak

    2013-01-01

    We present an updated and revised analysis of the relationship between the Hbeta broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of 9 new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create "AGN-free" images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the Hbeta time lag, which is assumed to yield the average Hbeta BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of alpha = 0.533 (+0.035/-0.033), consistent ...

  3. On the Scatter in the Radius - Luminosity Relationship for Active Galactic Nuclei

    CERN Document Server

    Eser, E Kilerci; Peterson, B M; Denney, K D; Bentz, M C

    2014-01-01

    We investigate and quantify the observed scatter in the empirical relationship between the broad line region size R and the luminosity of the active galactic nucleus (AGN), in order to better understand its origin. This study is motivated by the indispensable role of this relationship in the mass estimation of cosmologically distant black holes, but may also be relevant to the recently proposed application of this relationship for measuring cosmic distances. We study six nearby reverberation-mapped AGN for which simultaneous UV and optical monitoring data exist. We also examine the long-term optical luminosity variations of Seyfert 1 galaxy NGC 5548 and employ Monte Carlo simulations to study the effects of the intrinsic variability of individual objects on the scatter in the global relationship for a sample of ~40 AGN. We find the scatter in this relationship has a correctable dependence on color. For individual AGN, the size of the Hbeta emitting region has a steeper dependence on the nuclear optical lumino...

  4. An X-ray spectral model for clumpy tori in active galactic nuclei

    CERN Document Server

    Liu, Yuan

    2014-01-01

    We construct an X-ray spectral model for the clumpy torus in an active galactic nucleus (AGN) using Geant4, which includes the physical processes of the photoelectric effect, Compton scattering, Rayleigh scattering, $\\gamma$ conversion, fluorescence line, and Auger process. Since the electrons in the torus are expected to be bounded instead of free, the deviation of the scattering cross section from the Klein-Nishina cross section has also been included, which changes the X-ray spectra by up to 25% below $10$ keV. We have investigated the effect of the clumpiness parameters on the reflection spectra and the strength of the fluorescent line Fe K$\\alpha$. The volume filling factor of the clouds in the clumpy torus only slightly influences the reflection spectra, however, the total column density and the number of clouds along the line of sight significantly change the shapes and amplitudes of the reflection spectra. The effect of column density is similar to the case of a smooth torus, while a small number of c...

  5. The radio-loud active nucleus in the "dark lens" galaxy J1218+2953

    CERN Document Server

    Frey, S; Campbell, R M; Moor, A

    2010-01-01

    Context: There is a possibility that the optically unidentified radio source J1218+2953 may act as a gravitational lens, producing an optical arc ~4" away from the radio position. Until now, the nature of the lensing object has been uncertain since it is not detected in any waveband other than the radio. The estimated high mass-to-light ratio could even allow the total mass of this galaxy to be primarily in the form of dark matter. In this case, J1218+2953 could be the first known example of a "dark lens". Aims: We investigate the nature of J1218+2953 by means of high-resolution radio imaging observations to determine whether there is a radio-loud active galactic nucleus (AGN) in the position of the lensing object. Methods: We report on Very Long Baseline Interferometry (VLBI) observations with the European VLBI Network (EVN) at 1.6 and 5 GHz. Results: Our images, having angular resolutions of ~1 to ~10 milli-arcseconds (mas), reveal a rich and complex radio structure extending to almost 1". Based on its radi...

  6. The Magnetospheric Eternally Collapsing Object (MECO) Model of Galactic Black Hole Candidates and Active Galactic Nuclei

    CERN Document Server

    Robertson, S L; Robertson, Stanley L.; Leiter, Darryl J.

    2006-01-01

    The spectral, timing, and jet formation properties of neutron stars in low mass x-ray binary systems are influenced by the presence of central magnetic moments. Similar features shown by the galactic black hole candidates (GBHC) strongly suggest that their compact cores might be intrinsically magnetic as well. We show that the existence of intrinsically magnetic GBHC is consistent with a new class of solutions of the Einstein field equations of General Relativity. These solutions are based on a strict adherence to the Strong Principle of Equivalence (SPOE) requirement that the world lines of physical matter must remain timelike in all regions of spacetime. The new solutions emerge when the structure and radiation transfer properties of the energy momentum tensor on the right hand side of the Einstein field equations are appropriately chosen to dynamically enforce this SPOE requirement of timelike world line completeness. In this context, we find that the Einstein field equations allow the existence of highly ...

  7. Report on the ESO Workshop ''Active Galactic Nuclei: what's in a name?''

    Science.gov (United States)

    Padovani, P.

    2016-09-01

    The workshop was aimed at presenting a multi-wavelength picture of active galactic nuclei. The contents of the workshop are here briefly summarised; a review article synthesising the invited reviews, presentations and discussions is in preparation.

  8. On the deceleration of relativistic jets in active galactic nuclei- I. Radiation drag

    Science.gov (United States)

    Beskin, V. S.; Chernoglazov, A. V.

    2016-12-01

    Deceleration of relativistic jets from active galactic nuclei (AGNs) detected recently by the Monitoring Of Jets in Active galactic nuclei with Very Long Baseline Array Experiments (MOJAVE) team is discussed in connection with the interaction of the jet material with an external photon field. The appropriate energy density of the isotropic photon field necessary to decelerate jets is determined. It is shown that disturbances of the electric potential and magnetic surfaces play an important role in the general dynamics of particle deceleration.

  9. Nucleus of the active Centaur C/2011 P2 (PANSTARRS)

    Science.gov (United States)

    Mazzotta Epifani, E.; Perna, D.; Dotto, E.; Palumbo, P.; Dall'Ora, M.; Micheli, M.; Ieva, S.; Perozzi, E.

    2017-01-01

    Aims: In this paper we present observations of the active Centaur C/2011 P2 (PANSTARRS), showing a compact comet-like coma at the heliocentric distance of rh = 9 au. The observations were obtained in the framework of a wider program on Centaurs aimed at searching for comet-like activity in several targets outside Jupiter's aphelion. Methods: We analysed visible images of the Centaur taken at the TNG telescope in the R filter to investigate the level of coma contributing to the target brightness and to derive information on its nucleus size. Results: Centaur C/2011 P2 (PANSTARRS) shows a faint but still detectable comet-like activity, which accounts for more than 50% to the observed brightness. The coma contribution has been subtracted in order to derive an estimate for the Centaur's diameter of D 16 km, assuming an albedo of A = 0.07 (average of albedo measured within the Centaur group). The results for Centaur C/2011 P2 (PANSTARRS) fit in the general picture of the group: Centaurs with smaller perihelion distance q and semi-major axis a are smaller than those remaining farther from the Sun during their orbital path, thus reinforcing the idea that active Centaurs are "comets in fieri". Based on observations collected at the Telescopio Nazionale Galileo (TNG), operated on the island of La Palma by the Centro Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofísica de Canarias.

  10. Ultrafast outflows in radio-loud active galactic nuclei

    Science.gov (United States)

    Tombesi, F.; Tazaki, F.; Mushotzky, R. F.; Ueda, Y.; Cappi, M.; Gofford, J.; Reeves, J. N.; Guainazzi, M.

    2014-09-01

    Recent X-ray observations show absorbing winds with velocities up to mildly relativistic values of the order of ˜0.1c in a limited sample of six broad-line radio galaxies. They are observed as blueshifted Fe XXV-XXVI K-shell absorption lines, similarly to the ultrafast outflows (UFOs) reported in Seyferts and quasars. In this work we extend the search for such Fe K absorption lines to a larger sample of 26 radio-loud active galactic nuclei (AGN) observed with XMM-Newton and Suzaku. The sample is drawn from the Swift Burst Alert Telescope 58-month catalogue and blazars are excluded. X-ray bright Fanaroff-Riley Class II radio galaxies constitute the majority of the sources. Combining the results of this analysis with those in the literature we find that UFOs are detected in >27 per cent of the sources. However, correcting for the number of spectra with insufficient signal-to-noise ratio, we can estimate that the incidence of UFOs is this sample of radio-loud AGN is likely in the range f ≃ (50 ± 20) per cent. A photoionization modelling of the absorption lines with XSTAR allows us to estimate the distribution of their main parameters. The observed outflow velocities are broadly distributed between vout ≲ 1000 km s-1 and vout ≃ 0.4c, with mean and median values of vout ≃ 0.133c and vout ≃ 0.117c, respectively. The material is highly ionized, with an average ionization parameter of logξ ≃ 4.5 erg s-1 cm, and the column densities are larger than NH > 1022 cm-2. Overall, these characteristics are consistent with the presence of complex accretion disc winds in a significant fraction of radio-loud AGN and demonstrate that the presence of relativistic jets does not preclude the existence of winds, in accordance with several theoretical models.

  11. Chemistry in the Molecular Disks of Active Galactic Nuclei

    Science.gov (United States)

    Harada, Nanase; Herbst, Eric

    2010-06-01

    Active galactic nuclei (AGNs) are the centers of galaxies with supermassive blackholes whose accretion of mass causes very high luminosities of L˜1044-46erg s-1. An accretion disk has a molecular component that extends to hundreds of pc from the central AGN core. The question of how much central illumination affects the disk and how much star formation is present near the core have been astrophysical interests. Rotational lines from these disks at a sub-kpc scale have been observed for molecules such as CO, HCO+, HCN, and HNC. When ALMA becomes fully operational, it will be able to resolve these disks at much higher resolution than currently. Molecular observations at higher resolution may give some hints on the physics in the molecular disk. We modeled the chemical composition of a molecular disk in an AGN on a scale of tens of pc. To do this, we extended our standard gas-phase OSU network to include important processes at much higher temperatures, approaching 1000 K. We used the density model of Thompson et al., and determined the temperature by the blackbody approximation from the luminosity of the AGN core. The ionization by X-rays from the AGN core, by cosmic-rays from the AGN core, supernovae and stellar winds, and by UV-photons from OB stars are considered. We will briefly mention the effects from other factors that may change the molecular abundances such as shock waves and inhomogeneity of the density of the disk. T. Thompson, E. Quataert, and N. Murray, Astrophysical J. 630, 167 (2005)

  12. On the Radio Dichotomy of Active Galactic Nuclei

    Science.gov (United States)

    Cao, Xinwu

    2016-12-01

    It is still a mystery why only a small fraction of active galactic nuclei (AGNs) contain relativistic jets. A strong magnetic field is a necessary ingredient for jet formation, however, the advection of the external field in a geometrically thin disk is inefficient. Gas with a small angular velocity may fall from the Bondi radius {R}{{B}} nearly freely to the circularization radius {R}{{c}}, and a thin accretion disk is formed within {R}{{c}}. We suggest that the external magnetic field is substantially enhanced in this region, and the magnetic field at {R}{{c}} can be sufficiently strong to drive outflows from the disk if the angular velocity of the gas is low at {R}{{B}}. The magnetic field is efficiently dragged in the disk, because most angular momentum of the disk is removed by the outflows that lead to a significantly high radial velocity. The strong magnetic field formed in this way may accelerate jets in the region near the black hole, either by the Blandford-Payne or/and Blandford-Znajek mechanisms. We suggest that the radio dichotomy of AGNs predominantly originates from the angular velocity of the circumnuclear gas. An AGN will appear as a radio-loud (RL) one if the angular velocity of the circumnuclear gas is lower than a critical value at the Bondi radius, otherwise, it will appear as a radio-quiet (RQ) AGN. This is supported by the observations that RL nuclei are invariably hosted by core galaxies. Our model suggests that the mass growth of the black holes in RL quasars is much faster than that in RQ quasars with the same luminosity, which is consistent with the fact that the massive black holes in RL quasars are systematically a few times heavier than those in their RQ counterparts.

  13. The Evolution of Active Galactic Nuclei and their Spins

    Science.gov (United States)

    Volonteri, M.; Sikora, M.; Lasota, J.-P.; Merloni, A.

    2013-10-01

    Massive black holes (MBHs), in contrast to stellar mass black holes, are expected to substantially change their properties over their lifetime. MBH masses increase by several orders of magnitude over a Hubble time, as illustrated by Sołtan's argument. MBH spins also must evolve through the series of accretion and mergers events that increase the masses of MBHs. We present a simple model that traces the joint evolution of MBH masses and spins across cosmic time. Our model includes MBH-MBH mergers, merger-driven gas accretion, stochastic fueling of MBHs through molecular cloud capture, and a basic implementation of accretion of recycled gas. This approach aims at improving the modeling of low-redshift MBHs and active galactic nuclei (AGNs), whose properties can be more easily estimated observationally. Despite the simplicity of the model, it does a good job capturing the global evolution of the MBH population from z ~ 6 to today. Under our assumptions, we find that the typical spin and radiative efficiency of MBHs decrease with cosmic time because of the increased incidence of stochastic processes in gas-rich galaxies and MBH-MBH mergers in gas-poor galaxies. At z = 0, the spin distribution in gas-poor galaxies peaks at spins 0.4-0.8 and is not strongly mass dependent. MBHs in gas-rich galaxies have a more complex evolution, with low-mass MBHs at low redshift having low spins and spins increasing at larger masses and redshifts. We also find that at z > 1 MBH spins are on average the highest in high luminosity AGNs, while at lower redshifts these differences disappear.

  14. Galaxy interactions and active galactic nuclei in the local universe

    Science.gov (United States)

    Ryan, Christopher J.

    2009-06-01

    It has been suggested that galaxy interactions may be the principal mechanism responsible for triggering non-thermal activity in galactic nuclei. This thesis investigates the possible role of interactions in the local Universe by searching for evidence of a causal relationship between major interactions and the initiation of activity in Seyfert galaxies using high-quality, multiwavelength imaging data. The connection between interacting galaxies and Seyferts is explored by comparing the clustering properties of their environments, as quantified by the spatial cross-correlation function amplitude. If a direct evolutionary relationship exists, the objects should be located in environments that are statistically similar. It was previously demonstrated that Seyferts are found in fields comparable to isolated galaxies. The analysis presented in this work reveals that interacting galaxies are preferentially situated in regions consistent with Abell Richness Classes of 0 to 1. The apparent dissimilarity of their environments provides a strong argument against a link between major interactions and Seyfert galaxies. An examination of the photometric and morphological properties of the interacting systems does not uncover any trends that could be associated with the initiation of nuclear activity. The role of major interactions in triggering low-redshift AGNs is then assessed using near-infrared imagery of a sample of Narrow-Line Seyfert 1 galaxies. It has been postulated that these objects are evolutionarily young AGNs, powered by accretion onto supermassive black holes that are considerably lower in mass than those found in typical broad-line Seyferts. By employing the correlation between black hole mass and host galaxy bulge luminosity, the mean black hole mass, [Special characters omitted.] BH , in solar units for the sample is found to be [left angle bracket]log [Special characters omitted.] ( BH )[right angle bracket] = 7.7 ± 0.1, consistent with typical broad

  15. The suprachiasmatic nucleus changes the daily activity of the arcuate nucleus α-MSH neurons in male rats.

    Science.gov (United States)

    Guzmán-Ruiz, M; Saderi, N; Cazarez-Márquez, F; Guerrero-Vargas, N N; Basualdo, M C; Acosta-Galván, G; Buijs, R M

    2014-02-01

    Timing of metabolic processes is crucial for balanced physiology; many studies have shown the deleterious effects of untimely food intake. The basis for this might be an interaction between the arcuate nucleus (ARC) as the main integration site for metabolic information and the suprachiasmatic nucleus (SCN) as the master clock. Here we show in male rats that the SCN influences ARC daily neuronal activity by imposing a daily rhythm on the α-MSH neurons with a peak in neuronal activity at the end of the dark phase. Bilateral SCN lesions showed a complete disappearance of ARC neuronal rhythms and unilateral SCN lesions showed a decreased activation in the ARC at the lesioned side. Moreover light exposure during the dark phase inhibited ARC and α-MSH neuronal activity. The daily inhibition of ARC neuronal activity occurred in light-dark conditions as well as in dark-dark conditions, demonstrating the inhibitory effect to be mediated by increased SCN (subjective) day neuronal activity. Injections into the SCN with the neuronal tracer cholera toxin B showed that α-MSH neurons receive direct projections from the SCN. The present study demonstrates that the SCN activates and possibly also inhibits depending on the moment of the circadian cycle ARC α-MSH neurons via direct neuronal input. The persistence of these activity patterns in fasted animals demonstrates that this SCN-ARC interaction is not necessarily satiety associated but may support physiological functions associated with changes in the sleep-wake cycle.

  16. The angular clustering of WISE-selected active galactic nuclei: Different halos for obscured and unobscured active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Donoso, E. [Instituto de Ciencias Astronómicas, de la Tierra, y del Espacio (ICATE), 5400 San Juan (Argentina); Yan, Lin [Infrared Processing and Analysis Center, Department of Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Stern, D.; Assef, R. J. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

    2014-07-01

    We calculate the angular correlation function for a sample of ∼170,000 active galactic nuclei (AGNs) extracted from the Wide-field Infrared Survey Explorer (WISE) catalog, selected to have red mid-IR colors (W1 – W2 > 0.8) and 4.6 μm flux densities brighter than 0.14 mJy). The sample is expected to be >90% reliable at identifying AGNs and to have a mean redshift of (z) = 1.1. In total, the angular clustering of WISE AGNs is roughly similar to that of optical AGNs. We cross-match these objects with the photometric Sloan Digital Sky Survey catalog and distinguish obscured sources with r – W2 > 6 from bluer, unobscured AGNs. Obscured sources present a higher clustering signal than unobscured sources. Since the host galaxy morphologies of obscured AGNs are not typical red sequence elliptical galaxies and show disks in many cases, it is unlikely that the increased clustering strength of the obscured population is driven by a host galaxy segregation bias. By using relatively complete redshift distributions from the COSMOS survey, we find that obscured sources at (z) ∼ 0.9 have a bias of b = 2.9 ± 0.6 and are hosted in dark matter halos with a typical mass of log (M/M {sub ☉} h {sup –1}) ∼ 13.5. In contrast, unobscured AGNs at (z) ∼ 1.1 have a bias of b = 1.6 ± 0.6 and inhabit halos of log (M/M {sub ☉} h {sup –1}) ∼ 12.4. These findings suggest that obscured AGNs inhabit denser environments than unobscured AGNs, and they are difficult to reconcile with the simplest AGN unification models, where obscuration is driven solely by orientation.

  17. Detection of jet precession in the active nucleus of M 81

    Science.gov (United States)

    Martí-Vidal, I.; Marcaide, J. M.; Alberdi, A.; Pérez-Torres, M. A.; Ros, E.; Guirado, J. C.

    2011-09-01

    We report on very-long-baseline-interferometry (VLBI) monitoring observations of the low-luminosity active galactic nucleus (LLAGN) in the galaxy M 81 at the frequencies of 1.7, 2.3, 5.0, and 8.4 GHz. The observations reported here are phase-referenced to the supernova SN 1993J (located in the same galaxy) and cover from late 1993 to late 2005. The large amount of available observations allows us to study the stability of the AGN position in the frame of its host galaxy at different frequencies and chromatic effects in the jet morphology, together with their time evolution. The source consists at all frequencies of a slightly resolved core and a small jet extension towards the northeast direction (position angle of ~65 degrees) in agreement with previous publications. We find that the position of the intensity peak in the images at 8.4 GHz is very stable in the galactic frame of M 81 (proper motion upper limit about 10 μas per year). We confirm previous reports that the peaks at all frequencies are systematically shifted among them, possibly due to opacity effects in the jet as predicted by the standard relativistic jet model. We use this model, under plausible assumptions, to estimate the magnetic field in the jet close to the jet base and the mass of the central black hole. We obtain a black-hole mass of ~2 × 107 M⊙, comparable to estimates previously reported using different approaches, but the magnetic fields obtained are 103-104 times lower than previous estimates. We find that the positions of the cores at 1.7, 2.3, and 5.0 GHz are less stable than that at 8.4 GHz and evolve systematically, shifting southward at a rate of several tens of μas per year. The evolution in the jet orientation seems to be related to changes in the inclination of the cores at all frequencies. These results can be interpreted as due to a precessing jet. The evolving jet orientation also seems to be related to a flare in the peak flux densities at 5.0 and 8.4 GHz, which lasts ~4

  18. A New Perspective on the Radio Active Zone at The Galactic Center - Feedback from Nuclear Activities

    CERN Document Server

    Zhao, Jun-Hui; Goss, W M

    2013-01-01

    Based on our deep image of Sgr A using broadband data observed with the Jansky VLA at 6 cm, we present a new perspective of the radio bright zone at the Galactic center. We further show the radio detection of the X-ray Cannonball, a candidate neutron star associated with the Galactic center SNR Sgr A East. The radio image is compared with the Chandra X-ray image to show the detailed structure of the radio counterparts of the bipolar X-ray lobes. The bipolar lobes are likely produced by the winds from the activities within Sgr A West, which could be collimated by the inertia of gas in the CND, or by the momentum driving of Sgr A*; and the poloidal magnetic fields likely play an important role in the collimation. The less-collimated SE lobe, in comparison to the NW one, is perhaps due to the fact that the Sgr A East SN might have locally reconfigured the magnetic field toward negative galactic latitudes. In agreement with the X-ray observations, the time-scale of ~ $1\\times10^4$ yr estimated for the outermost r...

  19. NUCLEAR INFRARED SPECTRAL ENERGY DISTRIBUTION OF TYPE II ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Videla, Liza; Lira, Paulina [Departamento de Astronomia, Universidad de Chile (Chile); Andrews, Heather [Leiden Observatory, Leiden University, NL-2300 RA Leiden (Netherlands); Alonso-Herrero, Almudena [Instituto de Fisica de Catabria, CSIC-UC, E-39005 Santander (Spain); Alexander, David M.; Ward, Martin [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)

    2013-02-15

    We present near- and mid-IR observations of a sample of Seyfert II galaxies drawn from the 12 {mu}m Galaxy sample. The sample was observed in the J, H, K, L, M and N bands. Galaxy surface brightness profiles are modeled using nuclear, bulge, bar (when necessary), and disk components. To check the reliability of our findings, the procedure was tested using Spitzer observations of M 31. Nuclear spectral energy distributions (SEDs) are determined for 34 objects, and optical spectra are presented for 38, including analysis of their stellar populations using the STARLIGHT spectral synthesis code. Emission line diagnostic diagrams are used to discriminate between genuine active galactic nuclei (AGNs) and H II nuclei. Combining our observations with those found in the literature, we have a total of 40 SEDs. It is found that about 40% of the SEDs are characterized by an upturn in the near-IR, which we have quantified as a NIR slope {alpha} < 1 for an SED characterized as {lambda}f {sub {lambda}}{proportional_to}{lambda}{sup {alpha}}. The three objects with an H II nucleus and two Seyfert nuclei with strong contamination from a circumnuclear also show an upturn. For genuine AGNs, this component could be explained as emission from the accretion disk, a jet, or from a very hot dust component leaking from the central region through a clumpy obscuring structure. The presence of a very compact nuclear starburst as the origin for this NIR excess emission is not favored by our spectroscopic data for these objects.

  20. Analysing the transverse structure of the relativistic jets of active galactic nuclei

    Science.gov (United States)

    Murphy, E.; Cawthorne, T. V.; Gabuzda, D. C.

    2013-04-01

    This paper describes a method of fitting total intensity and polarization profiles in very long baseline interferometry (VLBI) images of astrophysical jets to profiles predicted by a theoretical model. As an example, the method is used to fit profiles of the jet in the active galactic nucleus (AGN) Mrk 501 with profiles predicted by a model in which a cylindrical jet of synchrotron plasma is threaded by a magnetic field with helical and disordered components. This fitting yields model Stokes Q profiles that agree with the observed profiles to within the 1-2σ uncertainties; the I model and observed profiles are overall not in such good agreement, with the model I profiles being generally more symmetrical than the observed profiles. Consistent fitting results are obtained for profiles derived from 6-cm VLBI images at two distances from the core, and also for profiles obtained for different wavelengths at a single location in the VLBI jet. The most striking success of the model is its ability to reproduce the spine-sheath polarization structure observed across the jet. Using the derived viewing angle in the jet rest frame, δ' ≃ 83°, together with a superluminal speed reported in the literature, βapp = 3.3, yields a solution for the viewing angle and velocity of the jet in the observer's frame, δ ≃ 15° and β ≃ 0.96. Although these results for Mrk 501 must be considered tentative, the combined analysis of polarization profiles and apparent component speeds holds promise as a means of further elucidating the magnetic field structures and other parameters of parsec-scale AGN jets.

  1. Tissue plasminogen activator in the bed nucleus of stria terminalis regulates acoustic startle.

    Science.gov (United States)

    Matys, T; Pawlak, R; Strickland, S

    2005-01-01

    The bed nucleus of stria terminalis is a basal forebrain region involved in regulation of hormonal and behavioral responses to stress. In this report we demonstrate that bed nucleus of stria terminalis has a high and localized expression of tissue plasminogen activator, a serine protease with neuromodulatory properties and implicated in neuronal plasticity. Tissue plasminogen activator activity in the bed nucleus of stria terminalis is transiently increased in response to acute restraint stress or i.c.v. administration of a major stress mediator, corticotropin-releasing factor. We show that tissue plasminogen activator is important in bed nucleus of stria terminalis function using two criteria: 1, Neuronal activation in this region as measured by c-fos induction is reduced in tissue plasminogen activator-deficient mice; and 2, a bed nucleus of stria terminalis-dependent behavior, potentiation of acoustic startle by corticotropin-releasing factor, is attenuated in tissue plasminogen activator-deficient mice. These studies identify a novel site of tissue plasminogen activator expression in the mouse brain and demonstrate a functional role for this protease in the bed nucleus of stria terminalis.

  2. Can a Satellite Galaxy Merger Explain the Active Past of the Galactic Center?

    CERN Document Server

    Lang, Meagan; Bogdanovic, Tamara; Amaro-Seoane, Pau; Sesana, Alberto

    2011-01-01

    Observations of the Galactic Center (GC) have accumulated a multitude of "forensic" evidence indicating that several million years ago the center of the Milky Way galaxy was teaming with starforming and accretion-powered activity -- this paints a rather different picture from the GC as we understand it today. We examine a possibility that this epoch of activity could have been triggered by the infall of a satellite galaxy into the Milky Way which began at the redshift of 10 and ended few million years ago with a merger of the Galactic supermassive black hole with an intermediate mass black hole brought in by the inspiralling satellite.

  3. Timing Analysis of Light Curves in the Tartarus Active Galactic Nuclei Database

    CERN Document Server

    O'Neill, P M; Papadakis, I E; Turner, T J; Neill, Paul M. O'; Nandra, Kirpal; Papadakis, Iossif E.

    2004-01-01

    The Tartarus database contains products for 529 ASCA observations of active galactic nuclei. We have been updating Tartarus to include observing sequences conducted after 1999 January. The revised database will contain products for 375 objects, with a total of 614 observing sequences. We have begun a systematic timing analysis of the Tartarus light curves. We present here some preliminary results of an investigation into the relation between excess variance and black-hole mass. Having optimised our analysis to minimize the scatter in the variance measurements, we find that the narrow-line active galactic nuclei follow roughly the same relation as the broad-line objects.

  4. DISCOVERY OF THE RECOMBINING PLASMA IN THE SOUTH OF THE GALACTIC CENTER: A RELIC OF THE PAST GALACTIC CENTER ACTIVITY?

    Energy Technology Data Exchange (ETDEWEB)

    Nakashima, S.; Nobukawa, M.; Uchida, H.; Tanaka, T.; Tsuru, T. G.; Koyama, K. [Department of Physics, Graduate School of Science, Kyoto University, Kitashirakawa Oiwake-cho, Sakyo-ku, Kyoto 606-8502 (Japan); Murakami, H. [Department of Information Science, Faculty of Liberal Arts, Tohoku Gakuin University 2-1-1 Tenjinzawa, Izumi-ku, Sendai, Miyagi 981-3193 (Japan); Uchiyama, H., E-mail: shinya@cr.scphys.kyoto-u.ac.jp [Science Education, Faculty of Education, Shizuoka University, 836 Ohya, Suruga-ku, Shizuoka 422-8529 (Japan)

    2013-08-10

    We report Suzaku results for soft X-ray emission to the south of the Galactic center (GC). The emission (hereafter {sup G}C South{sup )} has an angular size of {approx}42' Multiplication-Sign 16' centered at (l, b) {approx} (0. Degree-Sign 0, - 1. Degree-Sign 4) and is located in the largely extended Galactic ridge X-ray emission (GRXE). The X-ray spectrum of GC South exhibits emission lines from highly ionized atoms. Although the X-ray spectrum of the GRXE can be well fitted with a plasma in collisional ionization equilibrium (CIE), that of GC South cannot be fitted with a plasma in CIE, leaving hump-like residuals at {approx}2.5 and 3.5 keV, which are attributable to the radiative recombination continua of the K-shells of Si and S, respectively. In fact, GC South spectrum is well fitted with a recombination-dominant plasma model; the electron temperature is 0.46 keV while atoms are highly ionized (kT = 1.6 keV) in the initial epoch, and the plasma is now in a recombining phase at a relaxation scale (plasma density Multiplication-Sign elapsed time) of 5.3 Multiplication-Sign 10{sup 11} s cm{sup -3}. The absorption column density of GC South is consistent with that toward the GC region. Thus, GC South is likely to be located in the GC region ({approx}8 kpc distance). The size of the plasma, the mean density, and the thermal energy are estimated to be {approx}97 pc Multiplication-Sign 37 pc, 0.16 cm{sup -3}, and 1.6 Multiplication-Sign 10{sup 51} erg, respectively. We discuss possible origins of the recombination-dominant plasma as a relic of past activity in the GC region.

  5. Active Galactic Nuclei: Sources for ultra high energy cosmic rays?

    Energy Technology Data Exchange (ETDEWEB)

    Biermann, Peter L. [MPI for Radioastronomy, Bonn (Germany); Dept. of Phys. and Astron., Univ. of Bonn (Germany); Dept. of Phys. and Astr., Univ. of Alabama, Tuscaloosa, AL (United States); Dept. of Phys., Univ. of Alabama at Huntsville, AL (United States); Inst. Nucl. Phys. FZ, Karlsruhe Inst. of Techn. (KIT) (Germany); Becker, Julia K. [Institution foer Fysik, Goeteborgs Univ. (Sweden); Dept. of Phys., Univ. Dortmund, Dortmund (Germany); Caramete, Laurentiu [MPI for Radioastronomy, Bonn (Germany); Institute for Space Studies, Bucharest (Romania); Curutiu, Alex [MPI for Radioastronomy, Bonn (Germany); Engel, Ralph [Inst. Nucl. Phys. FZ, Karlsruhe Inst. of Techn. (KIT) (Germany); Falcke, Heino [Dept. of Astrophys., IMAP, Radboud Univ., Nijmegen (Netherlands); ASTRON, Dwingeloo (Netherlands); Gergely, Laszlo A. [Dept. Appl. Sci., London South Bank University (United Kingdom); Dept. of Theoret. and Exp. Phys., Univ. of Szeged, Szeged (Hungary); Isar, P. Gina [Inst. Nucl. Phys. FZ, Karlsruhe Inst. of Techn. (KIT) (Germany); Institute for Space Studies, Bucharest (Romania); Maris, Ioana C. [Inst. Nucl. Phys. FZ, Karlsruhe Inst. of Techn. (KIT) (Germany); Meli, Athina [Physik. Inst. Univ. Erlangen-Nuernberg (Germany); Kampert, Karl-Heinz [Phys. Dept., Univ. Wuppertal (Germany); Stanev, Todor [Bartol Research Inst., Univ. of Delaware, Newark, DE (United States); Tascau, Oana [Phys. Dept., Univ. Wuppertal (Germany); Zier, Christian [MPI for Radioastronomy, Bonn (Germany); Raman Res. Inst., Bangalore (India)

    2009-05-15

    The origin of ultra high energy cosmic rays promises to lead us to a deeper understanding of the structure of matter. This is possible through the study of particle collisions at center-of-mass energies in interactions far larger than anything possible with the Large Hadron Collider, albeit at the substantial cost of no control over the sources and interaction sites. For the extreme energies we have to identify and understand the sources first, before trying to use them as physics laboratories. Here we describe the current stage of this exploration. The most promising contenders as sources are radio galaxies and gamma ray bursts. The sky distribution of observed events yields a hint favoring radio galaxies. Key in this quest are the intergalactic and galactic magnetic fields, whose strength and structure are not yet fully understood. Current data and statistics do not yet allow a final judgement. We outline how we may progress in the near future.

  6. Fermi Bubbles and Periodic Past Activity of the Central Galactic Black Hole

    Science.gov (United States)

    Chernyshov, Dmitry; Cheng, K.; Dogiel, V.; Ko, C.

    2013-04-01

    We investigate the consequences of the past quasi-periodic activity of the supermassive black hole in the Galactic center due to capture and tidal disruption of stars. This activity will result in plasma outflow towards Galactic halo with velocity of order of 10^8 cm/s. This quasi-periodic injection of hot plasma can produce a series of shocks, where electrons and protons are accelerated to relativistic energies. The shock accelerated electrons can emit gamma-rays by inverse Compton scattering with the relic photons and the Galactic background soft photons whereas the radio to microwave result from synchrotron radiation producing so called Fermi bubbles and WMAP haze. Acceleration of protons on these shocks may be responsible for the formation of cosmic ray spectum above 10^15 eV observed near the Earth.

  7. Sexual activity increases dopamine transmission in the nucleus accumbens and striatum of female rats.

    Science.gov (United States)

    Pfaus, J G; Damsma, G; Wenkstern, D; Fibiger, H C

    1995-09-25

    In vivo microdialysis was used to monitor extracellular concentrations of dopamine (DA), and its metabolites dihydroxyphenylacetic acid (DOPAC) and homovanillic acid (HVA) in the nucleus accumbens and dorsal striatum of sexually active female rats during tests of locomotor activity, exposure to a novel chamber, exposure to sex odors, the presentation of a sexually active male rat, and copulation. DA increased slightly but significantly in the nucleus accumbens when a sexually active male was placed behind a wire-mesh screen, and further during copulation. DA also increased significantly in the dorsal striatum during copulation; however, the magnitude of this effect was significantly lower than that observed in the nucleus accumbens. The metabolites DOPAC and HVA generally followed DA with a delay, and increased significantly during copulation in both regions. In contrast, forced locomotion on a rotating drum, exposure to a novel testing chamber, and exposure to sex odors did not increase DA significantly in either region, although forced locomotion increased DOPAC significantly in both regions, and HVA significantly in the nucleus accumbens. The magnitude of DA release in the nucleus accumbens was significantly greater during copulation than running, whereas no significant difference was detected for striatal DA release between these two behavioral conditions. These results indicate that novelty or locomotor activity alone do not account for the increase in DA observed in the nucleus accumbens of female rats during copulation, and suggest that DA transmission in the nucleus accumbens is associated with anticipatory and consummatory aspects of sexual activity, as it is in male rats. In the dorsal striatum, however, DA release during copulation may reflect an increase in locomotor activity associated with active pacing of the male.

  8. Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei

    NARCIS (Netherlands)

    Abraham, J.; Abreu, P.; Aglietta, M.; Aguirre, C.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Alvarez-Muniz, J.; Ambrosio, M.; Anchordoqui, L.; Andringa, S.; Anzalone, A.; Aramo, C.; Argiro, S.; Arisaka, K.; Armengaud, E.; Arneodo, F.; Arqueros, F.; Asch, T.; Asorey, H.; Assis, P.; Atulugama, B. S.; Aublin, J.; Ave, M.; Avila, G.; Baecker, T.; Badagnani, D.; Barbosa, A. F.; Barnhill, D.; Barroso, S. L. C.; Bauleo, P.; Beatty, J. J.; Beau, T.; Becker, B. R.; Becker, K. H.; Bellido, J. A.; BenZvi, S.; Berat, C.; Bergmann, T.; Bernardini, P.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanch-Bigas, O.; Blanco, F.; Blasi, P.; Bleve, C.; Bluemer, H.; Bohacova, M.; Bonifazi, C.; Bonino, R.; Brack, J.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Burton, R. E.; Busca, N. G.; Caballero-Mora, K. S.; Cai, B.; Camin, D. V.; Caramete, L.; Caruso, R.; Carvalho, W.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Chiavassa, A.; Chinellato, J. A.; Chou, A.; Chye, J.; Clay, R. W.; Colombo, E.; Conceicao, R.; Connolly, B.; Contreras, F.; Coppens, J.; Cordier, A.; Cotti, U.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; De Donato, C.; Bg, S. J. de Jong; De La Vega, G.; de Mello, W. J. M.; de Mello Neto, J. R. T.; De Mitri, I.; de Souza, V.; del Peral, L.; Deligny, O.; Della Selva, A.; Delle Fratte, C.; Dembinski, H.; Di Giulio, C.; Diaz, J. C.; Diep, P. N.; Dobrigkeit, C.; D'Olivo, J. C.; Dong, P. N.; Dornic, D.; Dorofeev, A.; dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; DuVernois, M. A.; Engel, R.; Epele, L.; Escobar, C. O.; Etchegoyen, A.; Luis, P. Facal San; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferrer, F.; Ferry, S.; Fick, B.; Filevich, A.; Filipcic, A.; Fleck, I.; Fracchiolla, C. E.; Fulgione, W.; Garcia, B.; Gaimez, D. Garcia; Garcia-Pinto, D.; Garrido, X.; Geenen, H.; Gelmini, G.; Gemmeke, H.; Ghia, P. L.; Giller, M.; Glass, H.; Gold, M. S.; Golup, G.; Albarracin, F. Gomez; Berisso, M. Gomez; Herrero, R. Gomez; Goncalves, P.; do Amaral, M. Goncalves; Gonzalez, D.; Gonzalezc, J. G.; Gonzalez, M.; Gora, D.; Gorgi, A.; Gouffon, P.; Grassi, V.; Grillo, A. F.; Grunfeld, C.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Gutierrez, J.; Hague, J. D.; Hamilton, J. C.; Hansen, P.; Harari, D.; Harmsma, S.; Harton, J. L.; Haungs, A.; Hauschildt, T.; Healy, M. D.; Hebbeker, T.; Hebrero, G.; Heck, D.; Hojvat, C.; Holmes, V. C.; Homola, P.; Hoerandel, J.; Horneffer, A.; Horvat, M.; Hrabovsky, M.; Huege, T.; Hussain, M.; Larlori, M.; Insolia, A.; Ionita, F.; Italiano, A.; Kaducak, M.; Kampert, K. H.; Karova, T.; Kegl, B.; Keilhauer, B.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapik, R.; Knapp, J.; Koanga, V. -H.; Krieger, A.; Kroemer, O.; Kuempel, D.; Kunka, N.; Kusenko, A.; La Rosa, G.; Lachaud, C.; Lago, B. L.; Lebrun, D.; LeBrun, P.; Lee, J.; de Oliveira, M. A. Leigui; Lopez, R.; Letessier-Selvon, A.; Leuthold, M.; Lhenry-Yvon, I.; Aguera, A. Lopez; Bahilo, J. Lozano; Garcia, R. Luna; Maccarone, M. C.; Macolino, C.; Maldera, S.; Mancarella, G.; Mancenido, M. E.; Mandatat, D.; Mantsch, P.; Mariazzi, A. G.; Maris, I. C.; Falcon, H. R. Marquez; Martello, D.; Martinez, J.; Bravo, O. Martinez; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurizio, D.; Mazur, P. O.; McCauley, T.; McEwen, M.; McNeil, R. R.; Medina, M. C.; Medina-Tanco, G.; Meli, A.; Melo, D.; Menichetti, E.; Menschikov, A.; Meurer, Chr.; Meyhandan, R.; Micheletti, M. I.; Miele, G.; Miller, W.; Mollerach, S.; Monasor, M.; Ragaigne, D. Monnier; Montanet, F.; Morales, B.; Morello, C.; Moreno, J. C.; Morris, C.; Mostafa, M.; Muller, M. A.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Newman-Holmes, C.; Newton, D.; Nhung, P. T.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nozka, L.; Oehlschlaeger, J.; Ohnuki, T.; Olinto, A.; Olmos-Gilbaja, V. M.; Ortiz, M.; Ortolani, F.; Ostapchenko, S.; Otero, L.; Pacheco, N.; Selmi-Dei, D. Pakk; Palatka, M.; Pallotta, J.; Parente, G.; Parizot, E.; Parlati, S.; Pastor, S.; Patel, M.; Paul, T.; Pavlidou, V.; Payet, K.; Pech, M.; Pekala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Petrera, S.; Petrinca, P.; Petrov, Y.; Pichel, A.; Piegaia, R.; Pierog, T.; Pimenta, M.; Pinto, T.; Pirronello, V.; Pisanti, O.; Platino, M.; Pochon, J.; Privitera, P.; Prouza, M.; Quel, E. J.; Rautenberg, J.; Redondo, A.; Reucroft, S.; Revenu, B.; Rezende, F. A. S.; Ridky, J.; Riggi, S.; Risse, M.; Riviere, C.; Rizi, V.; Roberts, M.; Robledo, C.; Rodriguez, G.; Martino, J. Rodriguez; Rojo, J. Rodriguez; Rodriguez-Cabo, I.; Rodriguez-Frias, M. D.; Ros, G.; Rosado, J.; Roth, M.; Rouille-d'Orfeuil, B.; Roulet, E.; Roverok, A. C.; Salamida, F.; Salazar, H.; Salina, G.; Sanchez, F.; Santander, M.; Santo, C. E.; Santos, E. M.; Sarazin, F.; Sarkar, S.; Sato, R.; Scherini, V.; Schieler, H.; Schmidt, A.; Schmidt, F.; Schmidt, T.; Scholten, O.; Schovanek, P.; Schuessler, F.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Semikoz, D.; Settimo, M.; Shellard, R. C.; Sidelnik, I.; Siffert, B. B.; Sigl, G.; De Grande, N. Smetniansky; Smialkowski, A.; Smida, R.; Smith, A. G. K.; Smith, B. E.; Snow, G. R.; Sokolsky, P.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Strazzeri, E.; Stutz, A.; Suarez, F.; Suomijarvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Takahashi, J.; Tamashiro, A.; Tamburro, A.; Tascau, O.; Tcaciuc, R.; Thao, N. T.; Thomas, D.; Ticona, R.; Tiffenberg, J.; Timmermans, C.; Tkaczyk, W.; Peixoto, C. J. Todero; Tome, B.; Tonachini, A.; Torres, I.; Travnicek, P.; Tripathi, A.; Tristram, G.; Tscherniakhovski, D.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Galicia, J. F. Valdes; Valino, I.; Valore, L.; van den Berg, A. M.; van Elewyck, V.; Vazquez, R. A.; Veberic, D.; Veiga, A.; Velarde, A.; Venters, T.; Verzi, V.; Videla, M.; Villasenor, L.; Vorobiov, S.; Voyvodic, L.; Wahlberg, H.; Wainberg, O.; Warner, D.; Watson, A. A.; Westerhoff, S.; Wieczorek, G.; Wiencke, L.; Wilczynska, B.; Wilczynski, H.; Wileman, C.; Winnick, M. G.; Wu, H.; Wundheiler, B.; Yamamoto, T.; Younk, P.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zech, A.; Zepeda, A.; Ziolkowski, M.

    2008-01-01

    Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest-energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [Pierre Auger Collaboration, Science 318 (2007) 938]. The c

  9. EVN observations of low-luminosity flat-spectrum active galactic nuclei

    NARCIS (Netherlands)

    Caccianiga, A; Marcha, MJM; Thean, A; Dennett-Thorpe, J

    2001-01-01

    We present and discuss the results of very-long baseline interferometry (VLBI, EVN) observations of three low-luminosity (P-5GHz <10(25) W Hz(-1)) broad emission line active galactic nuclei (AGNs) carefully selected from a sample of flat-spectrum radio sources (CLASS). Based on the total and the ext

  10. Active galactic nuclei and their role in galaxy evolution : The infrared perspective

    NARCIS (Netherlands)

    Caputi, K. I.

    2014-01-01

    The remarkable progress made in infrared (IR) astronomical instruments over the last 10-15 years has radically changed our vision of the extragalactic IR sky, and overall understanding of galaxy evolution. In particular, this has been the case for the study of active galactic nuclei (AGN), for which

  11. The X-ray Power Spectral Density Function of the Seyfert Active Galactic Nucleus NGC 7469

    CERN Document Server

    Markowitz, Alex

    2010-01-01

    We present the broadband X-ray power spectral density function (PSD) of the X-ray-luminous Seyfert 1.2 NGC 7469, measured from Rossi X-ray Timing Explorer monitoring data and two XMM-Newton observations. We find significant evidence for a turnover in the 2-10 keV PSD at a temporal frequency of 2.0(+3.0,-0.8)e-6 Hz or 1.0(+3.0,-0.6)e-6 Hz, depending on the exact form of the break (sharply-broken or slowly-bending power-law, respectively). The ``surrogate'' Monte Carlo method of Press et al. (1992) was used to map out the probability distributions of PSD model parameters and obtain reliable uncertainties (68 per cent confidence limits quoted here). The corresponding break time scale of 5.8 (+/- 3.5) days or 11.6(+17.5,-8.7) days, respectively, is consistent with the empirical relation between PSD break time scale, black hole mass and bolometric luminosity of McHardy et al. Compared to the 2-10 keV PSD, the 10-20 keV PSD has a much flatter shape at high temporal frequencies, and no PSD break is significantly det...

  12. 3C 273 with NuSTAR: Unveiling the Active Galactic Nucleus

    DEFF Research Database (Denmark)

    Madsen, Kristin K.; Fürst, Felix; Walton, Dominic J.

    2015-01-01

    We present results from a 244 ks NuSTAR observation of 3C 273 obtained during a cross-calibration campaign with the Chandra, INTEGRAL, Suzaku, Swift, and XMM-Newton observatories. We show that the spectrum, when fit with a power-law model using data from all observatories except INTEGRAL over the...

  13. The Ionization Fraction in the Obscuring "Torus" of an Active Galactic Nucleus

    CERN Document Server

    Wilson, A S; Ulvestad, J S; Colbert, E J M; Weaver, K A; Braatz, J A; Henkel, C; Matsuoka, M; Xue, S; Iyomoto, N; Okada, K

    1998-01-01

    In this paper, we report VLBA radio maps at three frequencies and an ASCA X-ray spectrum of the water megamaser galaxy NGC 2639, which is believed to contain an edge-on viewed accretion disk. The radio observations reveal a compact ($<$ 0.2 pc) nuclear source with a spectrum that turns over sharply near 5 GHz. The X-ray spectrum shows emission in excess of a power-law model at energies greater than 4 keV; we interpret this excess as compact, nuclear, hard X-ray emission with the lower energies photoelectrically absorbed by an equivalent hydrogen column of $\\simeq$ 5 $\\times$ 10$^{23}$ cm$^{-2}$. If we assume that the turnover in the radio spectrum is caused by free-free absorption and that both the free-free and photoelectric absorptions are produced by the same gaseous component, the ratio $\\int n_{e}^{2} dl/\\int n_{H} dl$ may be determined. If the masing molecular gas is responsible for both absorptions, the required ionization fraction is $\\gtrsim 1.3 \\times 10^{-5}$, which is comparable to the theoreti...

  14. Revealing a strongly reddened, faint active galactic nucleus population by stacking deep co-added images

    CERN Document Server

    Varga, József; Dobos, László; 10.1111/j.1365-2966.2012.21560.x

    2012-01-01

    More than half of the sources identified by recent radio sky surveys have not been detected by wide-field optical surveys. We present a study based on our co-added image stacking technique, in which our aim is to detect the optical emission from unresolved, isolated radio sources of the Very Large Array (VLA) Faint Images of the Radio Sky at Twenty-cm (FIRST) survey that have no identified optical counterparts in the Sloan Digital Sky Survey (SDSS) Stripe 82 co-added data set. From the FIRST catalogue, 2116 such radio point sources were selected, and cut-out images, centred on the FIRST coordinates, were generated from the Stripe 82 images. The already co-added cut-outs were stacked once again to obtain images of high signal-to-noise ratio, in the hope that optical emission from the radio sources would become detectable. Multiple stacks were generated, based on the radio luminosity of the point sources. The resulting stacked images show central peaks similar to point sources. The peaks have very red colours w...

  15. Dissecting Photometric Redshift for Active Galactic Nucleus Using XMM- and Chandra-COSMOS Samples

    NARCIS (Netherlands)

    Salvato, M.; Ilbert, O.; Hasinger, G.; Rau, A.; Civano, F.; Zamorani, G.; Brusa, M.; Elvis, M.; Vignali, C.; Aussel, H.; Comastri, A.; Fiore, F.; Le Floc'h, E.; Mainieri, V.; Bardelli, S.; Bolzonella, M.; Bongiorno, A.; Capak, P.; Caputi, K.; Cappelluti, N.; Carollo, C. M.; Contini, T.; Garilli, B.; Iovino, A.; Fotopoulou, S.; Fruscione, A.; Gilli, R.; Halliday, C.; Kneib, J. -P.; Kakazu, Y.; Kartaltepe, J. S.; Koekemoer, A. M.; Kovac, K.; Ideue, Y.; Ikeda, H.; Impey, C. D.; Le Fevre, O.; Lamareille, F.; Lanzuisi, G.; Le Borgne, J. -F.; Le Brun, V.; Lilly, S.; Maier, C.; Manohar, S.; Masters, D.; McCracken, H.; Messias, H.; Mignoli, M.; Mobasher, B.; Nagao, T.; Pello, R.; Puccetti, S.; Perez-Montero, E.; Renzini, A.; Sargent, M.; Sanders, D. B.; Scodeggio, M.; Scoville, N.; Shopbell, P.; Silvermann, J.; Taniguchi, Y.; Tasca, L.; Tresse, L.; Trump, J. R.; Zucca, E.

    2011-01-01

    In this paper, we release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the Cosmic Evolution Survey (COSMOS) field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redsh

  16. A Census of Broad-Line Active Galactic Nuclei in Nearby Galaxies: Coeval Star Formation and Rapid Black Hole Growth

    CERN Document Server

    Trump, Jonathan R; Fang, Jerome J; Faber, S M; Koo, David C; Kocevski, Dale D

    2012-01-01

    We present the first quantified, statistical map of broad-line active galactic nucleus (AGN) frequency with host galaxy color and stellar mass in nearby (0.01 < z < 0.11) galaxies. Aperture photometry and z-band concentration measurements from the Sloan Digital Sky Survey (SDSS) are used to dis- entangle AGN and galaxy emission, resulting in estimates of uncontaminated galaxy rest-frame color, luminosity, and stellar mass. Broad-line AGNs are distributed throughout the blue cloud and green valley at a given stellar mass, and are much rarer in quiescent (red sequence) galaxies. This is in contrast to the published host galaxy properties of weaker narrow-line AGNs, indicating that broad-line AGNs occur during a different phase in galaxy evolution. More luminous broad-line AGNs have bluer host galaxies, even at fixed mass, suggesting that the same processes that fuel nuclear activity also efficiently form stars. The data favor processes that simultaneously fuel both star formation activity and rapid superm...

  17. A CENSUS OF BROAD-LINE ACTIVE GALACTIC NUCLEI IN NEARBY GALAXIES: COEVAL STAR FORMATION AND RAPID BLACK HOLE GROWTH

    Energy Technology Data Exchange (ETDEWEB)

    Trump, Jonathan R.; Fang, Jerome J.; Faber, S. M.; Koo, David C.; Kocevski, Dale D. [University of California Observatories/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Hsu, Alexander D. [The Harker School, 500 Saratoga Avenue, San Jose, CA 95129 (United States)

    2013-02-15

    We present the first quantified, statistical map of broad-line active galactic nucleus (AGN) frequency with host galaxy color and stellar mass in nearby (0.01 < z < 0.11) galaxies. Aperture photometry and z-band concentration measurements from the Sloan Digital Sky Survey are used to disentangle AGN and galaxy emission, resulting in estimates of uncontaminated galaxy rest-frame color, luminosity, and stellar mass. Broad-line AGNs are distributed throughout the blue cloud and green valley at a given stellar mass, and are much rarer in quiescent (red sequence) galaxies. This is in contrast to the published host galaxy properties of weaker narrow-line AGNs, indicating that broad-line AGNs occur during a different phase in galaxy evolution. More luminous broad-line AGNs have bluer host galaxies, even at fixed mass, suggesting that the same processes that fuel nuclear activity also efficiently form stars. The data favor processes that simultaneously fuel both star formation activity and rapid supermassive black hole accretion. If AGNs cause feedback on their host galaxies in the nearby universe, the evidence of galaxy-wide quenching must be delayed until after the broad-line AGN phase.

  18. Angiotensin converting enzyme in Alzheimer's disease increased activity in caudate nucleus and cortical areas.

    Science.gov (United States)

    Arregui, A; Perry, E K; Rossor, M; Tomlinson, B E

    1982-05-01

    The activity of the dipeptidyl carboxypeptidase, angiotensin converting enzyme, was assayed in several brain regions of patients dying with Alzheimer's disease and compared to that of appropriately age-matched controls. Enzyme activity was found to be elevated by 44% and 41% in the medial hippocampus and parahippocampal gyrus, respectively, and by 27% and 29% in the frontal cortex (area 10 of Brodman) and caudate nucleus, respectively, in Alzheimer's disease patients. Converting enzyme activity did not differ from controls in the nucleus accumbens, substantia nigra, temporal cortex, anterior or posterior hippocampus, amydgala, and septal nuclei.

  19. Host galaxies and environment of active galactic nuclei : a study of the XMM large scale structure survey

    NARCIS (Netherlands)

    Tasse, Cyril

    2008-01-01

    Active galactic nuclei (AGN) result from the infall of matter onto the super-massive black holes that are situated at the centres of galaxies. This process releases an enormous amount of energy into the inter-stellar and inter-galactic medium. Hence, the study of AGN becomes essential in the context

  20. Supermassive Black Holes in Active Galactic Nuclei. II. Calibration of the Black Hole Mass-Velocity Dispersion Relationship for Active Galactic Nuclei

    DEFF Research Database (Denmark)

    Onken, Christopher A.; Ferrarese, Laura; Merritt, David

    2004-01-01

    We calibrate reverberation-based black hole masses in active galactic nuclei (AGNs) by using the correlation between black hole mass, M, and bulge/spheroid stellar velocity dispersion, sigma. We use new measurements of sigma for 6 AGNs and published velocity dispersions for 10 others......, in conjunction with improved reverberation mapping results, to determine the scaling factor required to bring reverberation-based black hole masses into agreement with the quiescent galaxy M-sigma relationship. The scatter in the AGN black hole masses is found to be less than a factor of 3. The current...

  1. Delayed triggering of radio Active Galactic Nuclei in gas-rich minor mergers in the local Universe

    CERN Document Server

    Shabala, Stanislav; Kaviraj, Sugata; Middelberg, Enno; Turner, Ross; Ting, Yuan-Sen; Allison, James; Davis, Tim

    2016-01-01

    We examine the processes triggering star formation and Active Galactic Nucleus (AGN) activity in a sample of 25 low redshift ($z10^7$ K) brightness temperature required for an mJIVE-20 detection allows us to unambiguously identify the radio AGN in our sample. We find three such objects. Our VLBI AGN identifications are classified as Seyferts or LINERs in narrow line optical diagnostic plots; mid-infrared colours of our targets and the comparison of H$\\alpha$ star formation rates with integrated radio luminosity are also consistent with the VLBI identifications. We reconstruct star formation histories in our galaxies using optical and UV photometry, and find that these radio AGN are not triggered promptly in the merger process, consistent with previous findings for non-VLBI samples of radio AGN. This delay can significantly limit the efficiency of feedback by radio AGN triggered in galaxy mergers. We find that radio AGN hosts have lower star formation rates than non-AGN radio-selected galaxies at the same star...

  2. Luminosity and redshift dependence of the covering factor of active galactic nuclei viewed with WISE and Sloan digital sky survey

    Energy Technology Data Exchange (ETDEWEB)

    Toba, Y.; Matsuhara, H. [Department of Space and Astronautical Science, the Graduate University for Advanced Studies (Sokendai), 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Oyabu, S. [Graduate School of Science, Nagoya University, Furo-cho, Chikusa-ku, Nagoya, Aichi 464-8602 (Japan); Malkan, M. A. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Gandhi, P. [Department of Physics, Durham University, Durham DH1-3LE (United Kingdom); Nakagawa, T.; Isobe, N.; Shirahata, M.; Oi, N.; Takita, S.; Yano, K. [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Ohyama, Y. [Institute of Astronomy and Astrophysics, Academia Sinica, P.O. Box 23-141, Taipei 10617 Taiwan (China); Yamauchi, C., E-mail: toba@ir.isas.jaxa.jp [Misato Observatory, 180 Matsugamine, Misato-cho, Kaiso-gun, Wakayama 640-1366 (Japan)

    2014-06-10

    In this work, we investigate the dependence of the covering factor (CF) of active galactic nuclei (AGNs) on the mid-infrared (MIR) luminosity and the redshift. We constructed 12 and 22 μm luminosity functions (LFs) at 0.006 ≤z ≤ 0.3 using Wide-field Infrared Survey Explorer (WISE) data. Combining the WISE catalog with Sloan Digital Sky Survey (SDSS) spectroscopic data, we selected 223,982 galaxies at 12 μm and 25,721 galaxies at 22 μm for spectroscopic classification. We then identified 16,355 AGNs at 12 μm and 4683 AGNs at 22 μm by their optical emission lines and cataloged classifications in the SDSS. Following that, we estimated the CF as the fraction of Type 2 AGN in all AGNs whose MIR emissions are dominated by the active nucleus (not their host galaxies) based on their MIR colors. We found that the CF decreased with increasing MIR luminosity, regardless of the choice of Type 2 AGN classification criteria, and the CF did not change significantly with redshift for z ≤ 0.2. Furthermore, we carried out various tests to determine the influence of selection bias and confirmed that similar dependences exist, even when taking these uncertainties into account. The luminosity dependence of the CF can be explained by the receding torus model, but the 'modified' receding torus model gives a slightly better fit, as suggested by Simpson.

  3. CREB activity in the nucleus accumbens shell controls gating of behavioral responses to emotional stimuli

    NARCIS (Netherlands)

    Barrot, Michel; Olivier, Jocelien D A; Perrotti, Linda I; DiLeone, Ralph J; Berton, Olivier; Eisch, Amelia J; Impey, Soren; Storm, Daniel R; Neve, Rachael L; Yin, Jerry C; Zachariou, Venetia; Nestler, Eric J

    2002-01-01

    The transcription factor cAMP response element (CRE)-binding protein (CREB) has been shown to regulate neural plasticity. Drugs of abuse activate CREB in the nucleus accumbens, an important part of the brain's reward pathways, and local manipulations of CREB activity have been shown to affect cocain

  4. The hadronic origin of multi-TeV gamma rays from low-luminosity active galactic nuclei: implications of past activities of the Galactic center

    CERN Document Server

    Fujita, Yutaka; Murase, Kohta

    2015-01-01

    Radiatively inefficient accretion flows (RIAFs) in low-luminosity active galactic nuclei (LLAGNs) have been suggested as cosmic-ray and neutrino sources, which may largely contribute to the observed diffuse neutrino intensity. We show that this scenario naturally predicts hadronic multi-TeV gamma-ray excesses around galactic centers. The protons accelerated in the RIAF in Sagittarius A* (Sgr A*) escape and interact with dense molecular gas surrounding Sgr A*, which is known as the Central Molecular Zone (CMZ), and produce gamma rays as well as neutrinos. Based on a theoretical model that is compatible with the IceCube data, we calculate gamma-ray spectra of the CMZ and find that the gamma rays with $\\gtrsim 1$~TeV may have already been detected with the High Energy Stereoscopic System (HESS), if Sgr A* was more active in the past than it is today as indicated by various observations. Our model predicts that neutrinos should come from the CMZ with a spectrum similar to the gamma-ray spectrum. We also show that...

  5. MODELING THE Fe K LINE PROFILES IN TYPE I ACTIVE GALACTIC NUCLEI WITH A COMPTON-THICK DISK WIND

    Energy Technology Data Exchange (ETDEWEB)

    Tatum, M. M.; Turner, T. J. [Department of Physics, University of Maryland, Baltimore County, Baltimore, MD 21250 (United States); Sim, S. A. [Research School of Astronomy and Astrophysics, Mount Stromlo Observatory, Cotter Road, Weston Creek, ACT 2611 (Australia); Miller, L. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Reeves, J. N.; Patrick, A. R. [Astrophysics Group, School of Physical and Geographical Sciences, Keele University, Keele, Staffordshire ST5 5BG (United Kingdom); Long, K. S. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States)

    2012-06-20

    We have modeled a small sample of Seyfert galaxies that were previously identified as having simple X-ray spectra with little intrinsic absorption. The sources in this sample all contain moderately broad components of Fe K-shell emission and are ideal candidates for testing the applicability of a Compton-thick accretion disk wind model to active galactic nucleus (AGN) emission components. Viewing angles through the wind allow the observer to see the absorption signature of the gas, whereas face-on viewing angles allow the observer to see the scattered light from the wind. We find that the Fe K emission line profiles are well described with a model of a Compton-thick accretion disk wind of solar abundances, arising tens to hundreds of gravitational radii from the central black hole. Further, the fits require a neutral component of Fe K{alpha} emission that is too narrow to arise from the inner part of the wind, and likely comes from a more distant reprocessing region. Our study demonstrates that a Compton-thick wind can have a profound effect on the observed X-ray spectrum of an AGN, even when the system is not viewed through the flow.

  6. X-Ray bright active galactic nuclei in massive galaxy clusters - II. The fraction of galaxies hosting active nuclei

    DEFF Research Database (Denmark)

    Ehlert, S.; von der Linden, A.; Allen, S. W.

    2013-01-01

    We present a measurement of the fraction of cluster galaxies hosting X-ray bright active galactic nuclei (AGN) as a function of clustercentric distance scaled in units of r500. Our analysis employs high-quality Chandra X-ray and Subaru optical imaging for 42 massive X-ray-selected galaxy cluster...

  7. The Covering Factor of Warm Dust in Weak Emission-Line Active Galactic Nuclei

    CERN Document Server

    Zhang, Xudong

    2016-01-01

    Weak emission-line active galactic nuclei (WLAGNs) are radio-quiet active galactic nuclei (AGNs) that have nearly featureless optical spectra. We investigate the ultraviolet to mid-infrared spectral energy distributions of 73 WLAGNs (0.4

  8. ALMA observations of the submillimetre hydrogen recombination line from the type 2 active nucleus of NGC 1068

    CERN Document Server

    Izumi, Takuma; Imanishi, Masatoshi; Kohno, Kotaro

    2016-01-01

    Hydrogen recombination lines at the submillimetre band (submm-RLs) can serve as probes of ionized gas without dust extinction. One therefore expects to probe the broad line region (BLR) of an obscured (type 2) active galactic nucleus (AGN) with those lines. However, admitting the large uncertainty in the continuum level, here we report on the non-detection of both broad and narrow H26$\\alpha$ emission line (rest frequency = 353.62 GHz) towards the prototypical type 2 AGN of NGC 1068 with the Atacama Large Millimeter/submillimeter Array (ALMA). We also investigate the nature of BLR clouds that can emit submm-RLs with model calculations. As a result, we suggest that clouds with an electron density ($N_e$) of $\\sim$ 10$^9$ cm$^{-3}$ can mainly contribute to broad submm-RLs in terms of the line flux. On the other hand, line flux from other density clouds would be insignificant considering their too large or too small line optical depths. Since $N_e$ $\\sim$ 10$^9$ cm$^{-3}$ is typical in BLRs, insufficient sensiti...

  9. On the deceleration of relativistic jets in active galactic nuclei I: Radiation drag

    CERN Document Server

    Beskin, V S

    2016-01-01

    Deceleration of relativistic jets from active galactic nuclei (AGNs) detected recently by MOJAVE team is discussed in connection with the interaction of the jet material with the external photon field. Appropriate energy density of the isotropic photon field which is necessary to decelerate jets is determined. It is shown that the disturbances of the electric potential and magnetic surfaces play important role in general dynamics of particle deceleration.

  10. Active Galactic Nuclei and Quasars: Why Still a Puzzle after 50 years?

    CERN Document Server

    Antonucci, Robert

    2015-01-01

    The first part of this article is a historical and physical introduction to quasars and their close cousins, called Active Galactic Nuclei (AGN). In the second part, I argue that our progress in understanding them has been unsatisfactory and in fact somewhat illusory since their discovery fifty years ago, and that much of the reason is a pervasive lack of critical thinking in the research community. It would be very surprising if other fields do not suffer similar failings.

  11. Modelling the cloud condensation nucleus activity of organic acids

    Directory of Open Access Journals (Sweden)

    Z. Varga

    2007-04-01

    Full Text Available In this study vapour pressure osmometry was used to determine water activity in solutions of organic acids. The surface tension of the solutions was also monitored in parallel and then Köhler curves were calculated for nine organic acids (oxalic, malonic, succinic, glutaric, adipic acid, maleic acid, malic acid, citric acid and pinonic acid. Surface tension depression is negligible for most of the organic acids in dilute (≤1 w/w% solutions. Therefore, these compounds affect the supersaturation only in the beginning phase of droplet formation but not necessarily at the critical size. An exception is cis-pinonic acid which remarkably depress surface tension also in dilute (0.1 w/w% solution and hence at the critical point. The surface tension of organic acid solutions is influenced by the solubility of the compound, the length of the carbon chain and also by the polar functional groups present in the molecule. Similarly to surface tension solubility plays an important role also in water activity: compounds with higher solubility (e.g. malonic, maleic, and glutaric acid reduce water activity significantly in the early phase of droplet formation while less soluble acids (e.g. succinic and adipic acid are saturated in small droplets and the solution starts diluting only in bigger droplets. As a consequence, compounds with lower solubility have a minor effect on water activity in the early phase of droplet formation. To deduce the total effect Köhler curves were calculated and critical supersaturations were determined for the organic acids using measured surface tension and water activity. It was found that critical supersaturation grew with growing carbon number. Oxalic acid had the lowest critical supersaturation in the size range studied and it was comparable to the activation of ammonium sulfate. The Sc values obtained in this study were compared to data from CCNC measurements. In most cases good agreement was found.

  12. A Mid-Infrared Census of Star Formation Activity in Bolocam Galactic Plane Survey Sources

    CERN Document Server

    Dunham, Miranda K; Evans, Neal J; Schlingman, Wayne M; Cyganowski, Claudia J; Urquhart, James

    2011-01-01

    We present the results of a search for mid-infrared signs of star formation activity in the 1.1 mm sources in the Bolocam Galactic Plane Survey (BGPS). We have correlated the BGPS catalog with available mid-IR Galactic plane catalogs based on the Spitzer Space Telescope GLIMPSE legacy survey and the Midcourse Space Experiment (MSX) Galactic plane survey. We find that 44% (3,713 of 8,358) of the BGPS sources contain at least one mid-IR source, including 2,458 of 5,067 (49%) within the area where all surveys overlap (10 deg < l < 65 deg). Accounting for chance alignments between the BGPS and mid-IR sources, we conservatively estimate that 20% of the BPGS sources within the area where all surveys overlap show signs of active star formation. We separate the BGPS sources into four groups based on their probability of star formation activity. Extended Green Objects (EGOs) and Red MSX Sources (RMS) make up the highest probability group, while the lowest probability group is comprised of "starless" BGPS sources...

  13. The Energetics and Lifetimes of Local Radio Active Galactic Nuclei

    CERN Document Server

    Turner, Ross J

    2015-01-01

    We present a model describing the evolution of Fanaroff-Riley type I and II radio AGN, and the transition between these classes. We quantify galaxy environments using a semi-analytic galaxy formation model, and apply our model to a volume-limited low redshift ($0.03 \\leqslant z \\leqslant 0.1$) sample of observed AGN to determine the distribution of jet powers and active lifetimes at the present epoch. Radio sources in massive galaxies are found to remain active for longer, spend less time in the quiescent phase, and inject more energy into their hosts than their less massive counterparts. The jet power is independent of the host stellar mass within uncertainties, consistent with maintenance-mode AGN feedback paradigm. The environments of these AGN are in or close to long-term heating-cooling balance. We also examine the properties of high- and low-excitation radio galaxy sub-populations. The HERGs are younger than LERGs by an order of magnitude, whilst their jet powers are greater by a factor of four. The Edd...

  14. Active star formation at intermediate Galactic latitude: the case of IRAS 06345-3023

    CERN Document Server

    Yun, J L

    2015-01-01

    We report the discovery of a small aggregate of young stars seen in high-resolution, deep near-infrared ($JHK_S$) images towards IRAS 06345-3023 in the outer Galaxy and well below the mid-plane of the Galactic disc. The group of young stars is likely to be composed of low-mass stars, mostly Class I young stellar objects. The stars are seen towards a molecular cloud whose CO map peaks at the location of the IRAS source. The near-infrared images reveal, additionally, the presence of nebular emission with rich morphological features, including arcs in the vicinity of embedded stars, wisps and bright rims of a butterfly-shaped dark cloud. The location of this molecular cloud as a new star formation site well below the Galactic plane in the outer Galaxy indicates that active star formation is taking place at vertical distances larger than those typical of the (thin) disc.

  15. Gamma-Ray Observations of Active Galactic Nuclei

    Science.gov (United States)

    Madejski, Grzegorz (Greg); Sikora, Marek

    2016-09-01

    This article reviews the recent observational results regarding γ-ray emission from active galaxies. The most numerous discrete extragalactic γ-ray sources are AGNs dominated by relativistic jets pointing in our direction (commonly known as blazars), and they are the main subject of the review. They are detected in all observable energy bands and are highly variable. The advent of the sensitive γ-ray observations, afforded by the launch and continuing operation of the Fermi Gamma-ray Space Telescope and the AGILE Gamma-ray Imaging Detector, as well as by the deployment of current-generation Air Cerenkov Telescope arrays such as VERITAS, MAGIC, and HESS-II, continually provides sensitive γ-ray data over the energy range of ˜100 MeV to multi-TeV. Importantly, it has motivated simultaneous, monitoring observations in other bands, resulting in unprecedented time-resolved broadband spectral coverage. After an introduction, in Sections 3, 4, and 5, we cover the current status and highlights of γ-ray observations with (mainly) Fermi but also AGILE and put those in the context of broadband spectra in Section 6. We discuss the radiation processes operating in blazars in Section 7, and we discuss the content of their jets and the constraints on the location of the energy dissipation regions in, respectively, Sections 8 and 9. Section 10 covers the current ideas for particle acceleration processes in jets, and Section 11 discusses the coupling of the jet to the accretion disk in the host galaxy. Finally, Sections 12, 13, and 14 cover, respectively, the contribution of blazars to the diffuse γ-ray background, the utility of blazars to study the extragalactic background light, and the insight they provide for study of populations of supermassive black holes early in the history of the Universe.

  16. Hypoglycemia-activated GLUT2 neurons of the nucleus tractus solitarius stimulate vagal activity and glucagon secretion.

    Science.gov (United States)

    Lamy, Christophe M; Sanno, Hitomi; Labouèbe, Gwenaël; Picard, Alexandre; Magnan, Christophe; Chatton, Jean-Yves; Thorens, Bernard

    2014-03-04

    Glucose-sensing neurons in the brainstem participate in the regulation of energy homeostasis but have been poorly characterized because of the lack of specific markers to identify them. Here we show that GLUT2-expressing neurons of the nucleus of the tractus solitarius form a distinct population of hypoglycemia-activated neurons. Their response to low glucose is mediated by reduced intracellular glucose metabolism, increased AMP-activated protein kinase activity, and closure of leak K(+) channels. These are GABAergic neurons that send projections to the vagal motor nucleus. Light-induced stimulation of channelrhodospin-expressing GLUT2 neurons in vivo led to increased parasympathetic nerve firing and glucagon secretion. Thus GLUT2 neurons of the nucleus tractus solitarius link hypoglycemia detection to counterregulatory response. These results may help identify the cause of hypoglycemia-associated autonomic failure, a major threat in the insulin treatment of diabetes.

  17. UNCOVERING THE NUCLEUS CANDIDATE FOR NGC 253

    Energy Technology Data Exchange (ETDEWEB)

    Günthardt, G. I.; Camperi, J. A. [Observatorio Astronómico, Universidad Nacional de Córdoba (Argentina); Agüero, M. P. [Observatorio Astronómico, Universidad Nacional de Córdoba, and CONICET (Argentina); Díaz, R. J.; Gomez, P. L.; Schirmer, M. [Gemini Observatory, AURA (United States); Bosch, G., E-mail: gunth@oac.uncor.edu, E-mail: camperi@oac.uncor.edu, E-mail: mpaguero@oac.uncor.edu, E-mail: rdiaz@gemini.edu, E-mail: pgomez@gemini.edu, E-mail: mschirmer@gemini.edu, E-mail: guille@fcaglp.unlp.edu.ar [Instituto de Astrofísica de La Plata (CONICET-UNLP) (Argentina)

    2015-11-15

    NGC 253 is the nearest spiral galaxy with a nuclear starburst that becomes the best candidate for studying the relationship between starburst and active galactic nucleus activity. However, this central region is veiled by large amounts of dust, and it has been so far unclear which is the true dynamical nucleus to the point that there is no strong evidence that the galaxy harbors a supermassive black hole co-evolving with the starburst as was supposed earlier. Near-infrared (NIR) spectroscopy, especially NIR emission line analysis, could be advantageous in shedding light on the true nucleus identity. Using Flamingos-2 at Gemini South we have taken deep K-band spectra along the major axis of the central structure and through the brightest infrared source. In this work, we present evidence showing that the brightest NIR and mid-infrared source in the central region, already known as radio source TH7 and so far considered just a large stellar supercluster, in fact presents various symptoms of a genuine galactic nucleus. Therefore, it should be considered a valid nucleus candidate. Mentioning some distinctive aspects, it is the most massive compact infrared object in the central region, located at 2.″0 of the symmetry center of the galactic bar, as measured in the K-band emission. Moreover, our data indicate that this object is surrounded by a large circumnuclear stellar disk and it is also located at the rotation center of the large molecular gas disk of NGC 253. Furthermore, a kinematic residual appears in the H{sub 2} rotation curve with a sinusoidal shape consistent with an outflow centered in the candidate nucleus position. The maximum outflow velocity is located about 14 pc from TH7, which is consistent with the radius of a shell detected around the nucleus candidate, observed at 18.3 μm (Qa) and 12.8 μm ([Ne ii]) with T-ReCS. Also, the Brγ emission line profile shows a pronounced blueshift and this emission line also has the highest equivalent width at this

  18. X-ray Spectral Model of Reprocessing by Smooth and Clumpy Molecular Tori in Active Galactic Nuclei with the MONACO framework

    CERN Document Server

    Furui, Shun'ya; Odaka, Hirokazu; Kawaguchi, Toshihiro; Ohno, Masanori; Hayashi, Kazuma

    2016-01-01

    We construct an X-ray spectral model of reprocessing by a torus in an active galactic nucleus (AGN) with a Monte Carlo simulation framework MONACO. Two torus geometries of smooth and clumpy cases are considered and compared. In order to reproduce a Compton shoulder accurately, MONACO includes not only free electron scattering but also bound electron scattering. Raman and Reyleigh scattering are also treated, and scattering cross sections dependent on chemical states of hydrogen and helium are included. Doppler broadening by turbulence velocity can be implemented. Our model gives consistent results with other available models, such as MYTorus, except for differences due to different physical parameters and assumptions. We studied the dependence on torus parameters for Compton shoulder, and found that a intensity ratio of Compton shoulder to line core mainly depends on the column density, inclination angle, and metal abundance. For instance, an increase of metal abundance makes the Compton shoulder relatively w...

  19. A High Fraction of Double-peaked Narrow Emission Lines in Powerful Active Galactic Nuclei

    CERN Document Server

    Lyu, Yang

    2016-01-01

    One percent of redshift z~0.1 Active Galactic Nuclei (AGNs) show velocity splitting of a few hundred km/s in the narrow emission lines in spatially integrated spectra. Such line profiles have been found to arise from the bulk motion of ionized gas clouds associated with galactic-scale outflows, merging pairs of galaxies each harboring a supermassive black hole (SMBH), and/or galactic-scale disk rotation. It remains unclear, however, how the frequency of narrow-line velocity splitting may depend on AGN luminosity. Here we study the correlation between the fraction of Type 2 AGNs with double-peaked narrow emission lines and AGN luminosity as indicated by [O III]5007 emission-line luminosity L_[O III]. We combine the sample of Liu et al. (2010) at z~0.1 with a new sample of 178 Type 2 AGNs with double-peaked [O III] emission lines at z~0.5. We select the new sample from a parent sample of 2089 Type 2 AGNs from the SDSS-III/Baryon Oscillation Spectroscopic Survey. We find a statistically significant (~4.2\\sigma) ...

  20. Diffuse gamma-ray emission from the Galactic center and implications of its past activities

    CERN Document Server

    Fujita, Yutaka; Murase, Kohta

    2016-01-01

    It has been indicated that low-luminosity active galactic nuclei (LLAGNs) are accelerating high-energy cosmic-ray (CR) protons in their radiatively inefficient accretion flows (RIAFs). If this is the case, Sagittarius A* (Sgr A*) should also be generating CR protons, because Sgr A* is a LLAGN. Based on this scenario, we calculate a production rate of CR protons in Sgr A* and their diffusion in the central molecular zone (CMZ) around Sgr A*. The CR protons diffusing in the CMZ create gamma-rays through pp interaction. We show that the gamma-ray luminosity and spectrum are consistent with observations if Sgr A* was active in the past.

  1. Spectral components at visual and infrared wavelengths in active galactic nuclei

    Science.gov (United States)

    Stein, W. A.; Tokunaga, A. T.; Rudy, R. J.

    1984-01-01

    Aperture-dependent infrared photometry of active galactic nuclei are presented which illustrate the importance of eliminating starlight of the galaxy in order to obtain the intrinsic spectral distribution of the active nuclei. Separate components of emission are required to explain the infrared emission with a spectral index of alpha approx = 2 and the typical visual-ultraviolet continuum with alpha approx = 0.3 (where F(nu) varies as nu(sup-alpha). Present evidence does not allow unique determination of the appropriate mechanisms, but the characteristics of each are discussed.

  2. Star formation rates from [C II] 158 μm and mid-infrared emission lines for starbursts and active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Sargsyan, L.; Lebouteiller, V.; Weedman, D.; Barry, D.; Spoon, H. [Center for Radiophysics and Space Research, Cornell University, Ithaca, NY 14853 (United States); Samsonyan, A. [Byurakan Astrophysical Observatory, Byurakan 0213 (Armenia); Bernard-Salas, J. [Department of Physical Sciences, Open University, Milton Keynes MK7 6AA (United Kingdom); Houck, J., E-mail: sargsyan@isc.astro.cornell.edu, E-mail: dweedman@isc.astro.cornell.edu [Astronomy Department, Cornell University, Ithaca, NY 14853 (United States)

    2014-07-20

    A summary is presented for 130 galaxies observed with the Herschel Photodetector Array Camera and Spectrometer instrument to measure fluxes for the [C II] 158 μm emission line. Sources cover a wide range of active galactic nucleus to starburst classifications, as derived from polycyclic aromatic hydrocarbon strength measured with the Spitzer Infrared Spectrograph. Redshifts from [C II] and line to continuum strengths (equivalent width (EW) of [C II]) are given for the full sample, which includes 18 new [C II] flux measures. Calibration of L([C II)]) as a star formation rate (SFR) indicator is determined by comparing [C II] luminosities with mid-infrared [Ne II] and [Ne III] emission line luminosities; this gives the same result as determining SFR using bolometric luminosities of reradiating dust from starbursts: log SFR = log L([C II)]) – 7.0, for SFR in M{sub ☉} yr{sup –1} and L([C II]) in L{sub ☉}. We conclude that L([C II]) can be used to measure SFR in any source to a precision of ∼50%, even if total source luminosities are dominated by an active galactic nucleus (AGN) component. The line to continuum ratio at 158 μm, EW([C II]), is not significantly greater for starbursts (median EW([C II]) = 1.0 μm) compared to composites and AGNs (median EW([C II]) = 0.7 μm), showing that the far-infrared continuum at 158 μm scales with [C II] regardless of classification. This indicates that the continuum at 158 μm also arises primarily from the starburst component within any source, giving log SFR = log νL{sub ν}(158 μm) – 42.8 for SFR in M{sub ☉} yr{sup –1} and νL{sub ν}(158 μm) in erg s{sup –1}.

  3. Activity-dependent transport of the transcriptional coactivator CRTC1 from synapse to nucleus.

    Science.gov (United States)

    Ch'ng, Toh Hean; Uzgil, Besim; Lin, Peter; Avliyakulov, Nuraly K; O'Dell, Thomas J; Martin, Kelsey C

    2012-07-01

    Long-lasting changes in synaptic efficacy, such as those underlying long-term memory, require transcription. Activity-dependent transport of synaptically localized transcriptional regulators provides a direct means of coupling synaptic stimulation with changes in transcription. The CREB-regulated transcriptional coactivator (CRTC1), which is required for long-term hippocampal plasticity, binds CREB to potently promote transcription. We show that CRTC1 localizes to synapses in silenced hippocampal neurons but translocates to the nucleus in response to localized synaptic stimulation. Regulated nuclear translocation occurs only in excitatory neurons and requires calcium influx and calcineurin activation. CRTC1 is controlled in a dual fashion with activity regulating CRTC1 nuclear translocation and cAMP modulating its persistence in the nucleus. Neuronal activity triggers a complex change in CRTC1 phosphorylation, suggesting that CRTC1 may link specific types of stimuli to specific changes in gene expression. Together, our results indicate that synapse-to-nuclear transport of CRTC1 dynamically informs the nucleus about synaptic activity.

  4. Delayed triggering of radio Active Galactic Nuclei in gas-rich minor mergers in the local Universe

    Science.gov (United States)

    Shabala, S. S.; Deller, A.; Kaviraj, S.; Middelberg, E.; Turner, R. J.; Ting, Y. S.; Allison, J. R.; Davis, T. A.

    2016-10-01

    We examine the processes triggering star formation and Active Galactic Nucleus (AGN) activity in a sample of 25 low redshift (z 107 K) brightness temperature required for an mJIVE-20 detection allows us to unambiguously identify the radio AGN in our sample. We find three such objects. Our VLBI AGN identifications are classified as Seyferts or LINERs in narrow line optical diagnostic plots; mid-infrared colours of our targets and the comparison of Hα star formation rates with integrated radio luminosity are also consistent with the VLBI identifications. We reconstruct star formation histories in our galaxies using optical and UV photometry, and find that these radio AGN are not triggered promptly in the merger process, consistent with previous findings for non-VLBI samples of radio AGN. This delay can significantly limit the efficiency of feedback by radio AGN triggered in galaxy mergers. We find that radio AGN hosts have lower star formation rates than non-AGN radio-selected galaxies at the same starburst age. Conventional and VLBI radio imaging shows these AGN to be compact on arcsecond scales. Our modeling suggests that the actual sizes of AGN-inflated radio lobes may be much larger than this, but these are too faint to be detected in existing observations. Deep radio imaging is required to map out the true extent of the AGN, and to determine whether the low star formation rates in radio AGN hosts are a result of the special conditions required for radio jet triggering, or the effect of AGN feedback.

  5. Delayed triggering of radio active galactic nuclei in gas-rich minor mergers in the local Universe

    Science.gov (United States)

    Shabala, S. S.; Deller, A.; Kaviraj, S.; Middelberg, E.; Turner, R. J.; Ting, Y. S.; Allison, J. R.; Davis, T. A.

    2017-02-01

    We examine the processes triggering star formation and active galactic nucleus (AGN) activity in a sample of 25 low-redshift (z 107 K) brightness temperature required for an mJIVE-20 detection allows us to unambiguously identify the radio AGN in our sample. We find three such objects. Our VLBI AGN identifications are classified as Seyferts or low-ionization nuclear emission-line regions (LINERs) in narrow line optical diagnostic plots; mid-infrared colours of our targets and the comparison of Hα star formation rates with integrated radio luminosity are also consistent with the VLBI identifications. We reconstruct star formation histories in our galaxies using optical and UV photometry, and find that these radio AGN are not triggered promptly in the merger process, consistent with previous findings for non-VLBI samples of radio AGN. This delay can significantly limit the efficiency of feedback by radio AGN triggered in galaxy mergers. We find that radio AGN hosts have lower star formation rates than non-AGN radio-selected galaxies at the same starburst age. Conventional and VLBI radio imaging shows these AGN to be compact on arcsecond scales. Our modelling suggests that the actual sizes of AGN-inflated radio lobes may be much larger than this, but these are too faint to be detected in existing observations. Deep radio imaging is required to map out the true extent of the AGN, and to determine whether the low star formation rates in radio AGN hosts are a result of the special conditions required for radio jet triggering, or the effect of AGN feedback.

  6. The supramammillary nucleus and the claustrum activate the cortex during REM sleep.

    Science.gov (United States)

    Renouard, Leslie; Billwiller, Francesca; Ogawa, Keiko; Clément, Olivier; Camargo, Nutabi; Abdelkarim, Mouaadh; Gay, Nadine; Scoté-Blachon, Céline; Touré, Rouguy; Libourel, Paul-Antoine; Ravassard, Pascal; Salvert, Denise; Peyron, Christelle; Claustrat, Bruno; Léger, Lucienne; Salin, Paul; Malleret, Gael; Fort, Patrice; Luppi, Pierre-Hervé

    2015-04-01

    Evidence in humans suggests that limbic cortices are more active during rapid eye movement (REM or paradoxical) sleep than during waking, a phenomenon fitting with the presence of vivid dreaming during this state. In that context, it seemed essential to determine which populations of cortical neurons are activated during REM sleep. Our aim in the present study is to fill this gap by combining gene expression analysis, functional neuroanatomy, and neurochemical lesions in rats. We find in rats that, during REM sleep hypersomnia compared to control and REM sleep deprivation, the dentate gyrus, claustrum, cortical amygdaloid nucleus, and medial entorhinal and retrosplenial cortices are the only cortical structures containing neurons with an increased expression of Bdnf, FOS, and ARC, known markers of activation and/or synaptic plasticity. Further, the dentate gyrus is the only cortical structure containing more FOS-labeled neurons during REM sleep hypersomnia than during waking. Combining FOS staining, retrograde labeling, and neurochemical lesion, we then provide evidence that FOS overexpression occurring in the cortex during REM sleep hypersomnia is due to projections from the supramammillary nucleus and the claustrum. Our results strongly suggest that only a subset of cortical and hippocampal neurons are activated and display plasticity during REM sleep by means of ascending projections from the claustrum and the supramammillary nucleus. Our results pave the way for future studies to identify the function of REM sleep with regard to dreaming and emotional memory processing.

  7. Discovery of the recombining plasma in the south of the Galactic center; a relic of the past Galactic center activity?

    CERN Document Server

    Nakashima, S; Uchida, H; Tanaka, T; Tsuru, T G; Koyama, K; Murakami, H; Uchiyama, H

    2013-01-01

    We report Suzaku results for soft X-ray emission to the south of the Galactic center (GC). The emission (hereafter "GC South") has an angular size of ~42' x 16' centered at (l, b) ~ (0.0, -1.4), and is located in the largely extended Galactic ridge X-ray emission (GRXE). The X-ray spectrum of GC South exhibits emission lines from highly ionized atoms. Although the X-ray spectrum of the GRXE can be well fitted with a plasma in collisional ionization equilibrium (CIE), that of GC South cannot be fitted with a plasma in CIE, leaving hump-like residuals at ~2.5 and 3.5 keV, which are attributable to the radiative recombination continua of the K-shells of Si and S, respectively. In fact, GC South spectrum is well fitted with a recombination-dominant plasma model; the electron temperature is 0.46 keV while atoms are highly ionized (kT = 1.6 keV) in the initial epoch, and the plasma is now in a recombining phase at a relaxation scale (plasma density x elapsed time) of 5.3 x 10^11 s cm^-3. The absorption column densi...

  8. Optogenetic Activation of the Sublaterodorsal (SLD) Nucleus Induces Rapid Muscle Inhibition

    Science.gov (United States)

    2015-09-01

    Optogenetic Activation of the Sublaterodorsal (SLD) Nucleus Induces Rapid Muscle Inhibition 5a. CONTRACT NUMBER 1120-1120-99 5b. GRANT NUMBER 5c...eye movement (NREM/REM) sleep, involves rapid state changes that are physiologically distinct in their impact on sensory perception, muscle tone... Muscle Inhibition prepared by Cameron H Good ORISE 4502 Darlington St, Aberdeen Proving Ground, Maryland Thomas Jhou and Nathan Burnham

  9. Evidence for Infrared-faint Radio Sources as z > 1 Radio-loud Active Galactic Nuclei

    Science.gov (United States)

    Huynh, Minh T.; Norris, Ray P.; Siana, Brian; Middelberg, Enno

    2010-02-01

    Infrared-Faint Radio Sources (IFRSs) are a class of radio objects found in the Australia Telescope Large Area Survey which have no observable mid-infrared counterpart in the Spitzer Wide-area Infrared Extragalactic (SWIRE) survey. The extended Chandra Deep Field South now has even deeper Spitzer imaging (3.6-70 μm) from a number of Legacy surveys. We report the detections of two IFRS sources in IRAC images. The non-detection of two other IFRSs allows us to constrain the source type. Detailed modeling of the spectral energy distribution of these objects shows that they are consistent with high-redshift (z >~ 1) active galactic nuclei.

  10. The quenching of star formation in accretion-driven clumpy turbulent tori of active galactic nuclei

    OpenAIRE

    Vollmer, B; Davies, R. I.

    2013-01-01

    Galactic gas-gas collisions involving a turbulent multiphase ISM share common ISM properties: dense extraplanar gas visible in CO, large linewidths (>= 50 km/s), strong mid-infrared H_2 line emission, low star formation activity, and strong radio continuum emission. Gas-gas collisions can occur in the form of ICM ram pressure stripping, galaxy head-on collisions, compression of the intragroup gas and/or galaxy ISM by an intruder galaxy which flies through the galaxy group at a high velocity, ...

  11. Photometric Monitoring of Active Galactic Nuclei in the Center for Automated Space Science: Preliminary Results

    Science.gov (United States)

    Culler, Ryan; Deckard, Monica; Guilaran, Fonsie; Watson, Casey; Carini, Michael; Gelderman, Richard; Neely, William

    1997-02-01

    In this paper, we will present preliminary results of our program to photometrically monitor a set of Active Galactic Nuclei (AGN) known as Blazars. Using CCDs as N-star photometers and a technique known as aperture photometry, we can achieve close to 0.02 magnitude precision with small to midsize telescopes. Blazars are highly luminous and highly variable; studying these variations provides insight into the central engines producing the high luminosities. we report on our reduction and analysis of CCD data obtained at one of our collaborating institutions, the NF Observatory at Western New Mexico University. CCD data obtained at the Western Kentucky University 24 inch telescope will also be discussed.

  12. Studying the spectral properties of Active Galactic Nuclei in the JWST era

    CERN Document Server

    Nakos, Th; Alonso-Herrero, A; Labiano, A

    2009-01-01

    The James Webb Space Telescope (JWST), due to launch in 2014, shall provide an unprecedented wealth of information in the near and mid-infrared wavelengths, thanks to its high-sensitivity instruments and its 6.5 m primary mirror, the largest ever launched into space. NIRSpec and MIRI, the two spectrographs onboard JWST, will play a key role in the study of the spectral features of Active Galactic Nuclei in the 0.6-28 micron wavelength range. This talk aims at presenting an overview of the possibilities provided by these two instruments, in order to prepare the astronomical community for the JWST era.

  13. Study of solar activity modulation of galactic cosmic rays using the Pierre Auger Observatory

    Energy Technology Data Exchange (ETDEWEB)

    Anjos, J.C. dos [Centro Brasileiro de Pesquisas Fisicas (CBPF), Rio de Janeiro, RJ (Brazil)

    2011-07-01

    Full text: We show that the count rates of low energy secondary cosmic ray particles used for self-calibration of the water- Cherenkov detectors of the surface detector array of the Pierre Auger Observatory are highly sensitive, after correcting for atmospheric effects, to modulations of galactic cosmic rays due to solar activity and to transient events. The technique consists in recording low threshold rates - scalers - with all the surface detectors of the array. Transient events such as Gamma Ray Bursts and solar flares are expected to be seen as a significant change of the counting rates from the expected value. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. We will present the available data collected since March 2005 together with an analysis focused on the observation of Forbush decreases, transient events characterized by short-term periods of strong depression of the cosmic ray flux observed at earth caused by the transit of a solar ejecta from a Coronal Mass Ejection from the Sun. A strong correlation with neutron monitor data from the close-by Observatory Los Cerrilos is observed, showing that water-Cherenkov detectors operating in scaler mode are highly sensitive to Forbush decreases and other transient events related to solar activity modulation of galactic cosmic rays. (author)

  14. On the virialization of disk winds: Implications for the black hole mass estimates in active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Kashi, Amit; Proga, Daniel; Nagamine, Kentaro [Department of Physics and Astronomy, University of Nevada, Las Vegas, 4505 South Maryland Parkway, Las Vegas, NV 89154-4002 (United States); Greene, Jenny [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Barth, Aaron J., E-mail: kashia@physics.unlv.edu [Department of Physics and Astronomy, University of California, Irvine, Irvine, CA 92697 (United States)

    2013-11-20

    Estimating the mass of a supermassive black hole in an active galactic nucleus usually relies on the assumption that the broad line region (BLR) is virialized. However, this assumption seems to be invalid in BLR models that consist of an accretion disk and its wind. The disk is likely Keplerian and therefore virialized. However, beyond a certain point, the wind material must be dominated by an outward force that is stronger than gravity. Here, we analyze hydrodynamic simulations of four different disk winds: an isothermal wind, a thermal wind from an X-ray-heated disk, and two line-driven winds, one with and the other without X-ray heating and cooling. For each model, we determine whether gravity governs the flow properties by computing and analyzing the volume-integrated quantities that appear in the virial theorem: internal, kinetic, and gravitational energies. We find that in the first two models, the winds are non-virialized, whereas the two line-driven disk winds are virialized up to a relatively large distance. The line-driven winds are virialized because they accelerate slowly so that the rotational velocity is dominant and the wind base is very dense. For the two virialized winds, the so-called projected virial factor scales with inclination angle as 1/sin {sup 2} i. Finally, we demonstrate that an outflow from a Keplerian disk becomes unvirialized more slowly when it conserves the gas specific angular momentum, as in the models considered here, than when it conserves the angular velocity, as in the so-called magneto-centrifugal winds.

  15. [Local GABA-ergic modulation of serotonergic neuron activity in the nucleus raphe magnus].

    Science.gov (United States)

    Iniushkin, A N; Merkulova, N A; Orlova, A O; Iniushkina, E M

    2009-07-01

    In voltage-clamp experimental on slices of the rat brainstem the effects of 5-HT and GABA on serotonergic neurons of nucleus raphe magnus were investigated. Local applications of 5-HT induced an increase in IPCSs frequency and amplitude in 45% of serotonergic cells. The effect suppressed by the blocker of fast sodium channels tetradotoxin. Antagonist of GABA receptor gabazine blocked IPSCs in neurons both sensitive and non-sensitive to 5-HT action. Applications of GABA induced a membrane current (I(GABA)), which was completely blocked by gabazine. The data suggest self-control of the activity of serotonergic neurons in nucleus raphe magnus by negative feedback loop via local GABAergic interneurons.

  16. The Complete Infrared View of Active Galactic Nuclei from the 70-month Swift/BAT Catalog

    CERN Document Server

    Ichikawa, Kohei; Ueda, Yoshihiro; Matsuoka, Kenta; Toba, Yoshiki; Kawamuro, Taiki; Trakhtenbrot, Benny; Koss, Michael J

    2016-01-01

    We systematically investigate the near- (NIR) to far-infrared (FIR) photometric properties of a nearly complete sample of local active galactic nuclei (AGN) detected in the Swift/Burst Alert Telescope (BAT) all-sky ultra hard X-ray (14-195 keV) survey. Out of 606 non-blazar AGN in the Swift/BAT 70-month catalog at high galactic latitude of $|b|>10^{\\circ}$, we obtain IR photometric data of 604 objects by cross-matching the AGN positions with catalogs from the WISE, AKARI, IRAS, and Herschel infrared observatories. We find a good correlation between the ultra-hard X-ray and mid-IR (MIR) luminosities over five orders of magnitude ($41 < \\log (L_{14-195}/{\\rm erg}~{\\rm s}^{-1})< 46$). Informed by previous measures of the intrinsic spectral energy distribution of AGN, we find FIR pure-AGN candidates whose FIR emission is thought to be AGN-dominated with low starformation activity. We demonstrate that the dust covering factor decreases with the bolometric AGN luminosity, confirming the luminosity-dependent u...

  17. Ensemble spectral variability study of Active Galactic Nuclei from the XMM-Newton serendipitous source catalogue

    CERN Document Server

    Serafinelli, Roberto; Middei, Riccardo

    2016-01-01

    The variability of the X-ray spectra of active galactic nuclei (AGN) usually includes a change of the spectral slope. This has been investigated for a small sample of local AGNs by Sobolewska and Papadakis, who found that slope variations are well correlated with flux variations, and that spectra are typically steeper in the bright phase (softer when brighter behaviour). Not much information is available for the spectral variability of high-luminosity AGNs and quasars. In order to investigate this phenomenon, we use data from the XMM-Newton Serendipitous Source Catalogue, Data Release 5, which contains X-ray observations for a large number of active galactic nuclei in a wide luminosity and redshift range, for several different epochs. This allows to perform an ensemble analysis of the spectral variability for a large sample of quasars. We quantify the spectral variability through the spectral variability parameter $\\beta$, defined as the ratio between the change in spectral slope and the corresponding logarit...

  18. CAN WE REPRODUCE THE X-RAY BACKGROUND SPECTRAL SHAPE USING LOCAL ACTIVE GALACTIC NUCLEI?

    Energy Technology Data Exchange (ETDEWEB)

    Vasudevan, Ranjan V.; Mushotzky, Richard F. [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Gandhi, Poshak, E-mail: ranjan@astro.umd.edu [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan)

    2013-06-20

    The X-ray background (XRB) is due to the aggregate of active galactic nuclei (AGNs), which peak in activity at z {approx} 1 and is often modeled as the sum of different proportions of unabsorbed, moderately, and heavily absorbed AGN. We present the summed spectrum of a complete sample of local AGN (the Northern Galactic Cap of the 58 month Swift/BAT catalog, z < 0.2) using 0.4-200 keV data and directly determine the different proportions of unabsorbed, moderately and heavily absorbed AGN that make up the summed spectrum. This stacked low redshift AGN spectrum is remarkably similar in shape to the XRB spectrum (when shifted to z {approx} 1), but the observed proportions of different absorption populations differ from most XRB synthesis models. AGN with Compton-thick absorption account for only {approx}12% of the sample, but produce a significant contribution to the overall spectrum. We confirm that Compton reflection is more prominent in moderately absorbed AGN and that the photon index differs intrinsically between unabsorbed and absorbed AGN. The AGN in our sample account for only {approx}1% of the XRB intensity. The reproduction of the XRB spectral shape suggests that strong evolution in individual AGN properties is not required between z {approx} 0 and 1.

  19. Active Galactic Videos: A YouTube Channel for Astronomy Education and Outreach

    Science.gov (United States)

    Austin, Carmen; Calahan, Jenny; Resi Baucco, Alexandria; Bullivant, Christopher William; Eckley, Ross; Ekstrom, W. Haydon; Fitzpatrick, M. Ryleigh; Genovese, Taylor Fay; Impey, Chris David; Libby, Kaitlin; McCaw, Galen; Olmedo, Alexander N.; Ritter, Joshua; Wenger, Matthew; Williams, Stephanie

    2017-01-01

    Active Galactic Videos is an astronomy-focused YouTube channel run by a team at the University of Arizona. The channel has two main purposes: to produce educational content for public audiences, and to learn about astronomy and to open a window into the world of professional astronomy by showcasing the work done at Steward Observatory and in Southern Arizona. Our team consists of faculty, staff, and students from a variety of backgrounds including: astronomy, education, film, music, english, and writing. In addition to providing educational content for public audiences, this project provides opportunities for undergraduate students to learn about astronomy content, educational practice, and science communication while developing the practical skills needed to write, film, score, direct, and edit videos that effectively engage and teach viewers about topics in astronomy. The team has produced various styles of video: presentational, interviews, musical/poetic, and documentaries. In addition to YouTube, the Active Galactic Videos team maintains a social media presence on Facebook, Twitter, and Instagram. These help to widely distribute the content as well as to publicize the main Youtube channel. In addition to providing an overview of our educational work, this poster will present a year's worth of online analytics that we are using to better understand our audience, to examine what videos have been popular and successful and how people are accessing our content. We will present our experience in order to help others learn about improving astronomy education online, and astronomy communication and outreach in general.

  20. The Evolution of Radio Loud Active Galactic Nuclei as a Function of Black Hole Spin

    CERN Document Server

    Garofalo, David; Sambruna, Rita M

    2010-01-01

    Recent work on the engines of active galactic nuclei jets suggests their power depends strongly and perhaps counter-intuitively on black hole spin. We explore the consequences of this on the radio-loud population of active galactic nuclei and find that the time evolution of the most powerful radio galaxies and radio-loud quasars fits into a picture in which black hole spin varies from retrograde to prograde with respect to the accreting material. Unlike the current view, according to which jet powers decrease in tandem with a global downsizing effect, we argue for a drop in jet power resulting directly from the paucity of retrograde accretion systems at lower redshift $z$ caused by a continuous history of accretion dating back to higher $z$. In addition, the model provides simple interpretations for the basic spectral features differentiating radio-loud and radio-quiet objects, such as the presence or absence of disk reflection, broadened iron lines and signatures of disk winds. We also briefly describe our m...

  1. Mechanical Feedback from Active Galactic Nuclei in Galaxies, Groups, and Clusters

    CERN Document Server

    McNamara, B R

    2012-01-01

    The radiative cooling timescales at the centers of hot atmospheres surrounding elliptical galaxies, groups, and clusters are much shorter than their ages. Therefore, hot atmospheres are expected to cool and to form stars. Cold gas and star formation are observed in central cluster galaxies but at levels below those expected from an unimpeded cooling flow. X-ray observations have shown that wholesale cooling is being offset by mechanical heating from radio active galactic nuclei. Feedback is widely considered to be an important and perhaps unavoidable consequence of the evolution of galaxies and supermassive black holes. We show that cooling X-ray atmospheres and the ensuing star formation and nuclear activity are probably coupled to a self-regulated feedback loop. While the energetics are now reasonably well understood, other aspects of feedback are not. We highlight the problems of atmospheric heating and transport processes, accretion, and nuclear activity, and we discuss the potential role of black hole sp...

  2. Merger-driven Fueling of Active Galactic Nuclei: Six Dual and Offset Active Galactic Nuclei Discovered with Chandra and Hubble Space Telescope Observations

    CERN Document Server

    Comerford, Julia M; Barrows, R Scott; Greene, Jenny E; Zakamska, Nadia L; Madejski, Greg M; Cooper, Michael C

    2015-01-01

    Dual active galactic nuclei (AGNs) and offset AGNs are kpc-scale separation supermassive black holes pairs created during galaxy mergers, where both or one of the black holes are AGNs, respectively. These dual and offset AGNs are valuable probes of the link between mergers and AGNs but are challenging to identify. Here we present Chandra/ACIS observations of 12 optically-selected dual AGN candidates at z < 0.34, where we use the X-rays to identify AGNs. We also present HST/WFC3 observations of 10 of these candidates, which reveal any stellar bulges accompanying the AGNs. We discover a dual AGN system with separation of 2.2 kpc, where the two stellar bulges have coincident [O III] and X-ray sources. This system is an extremely minor merger (460:1) that may include a dwarf galaxy hosting an intermediate mass black hole. We also find six single AGNs, and five systems that are either dual or offset AGNs with separations < 10 kpc. Four of the six dual AGNs and dual/offset AGNs are in ongoing major mergers, a...

  3. Uncovering the nucleus candidate for NGC 253

    CERN Document Server

    Günthardt, G I; Camperi, J A; Díaz, R J; Gomez, P L; Bosch, G; Schirmer, M

    2015-01-01

    NGC253 is the nearest spiral galaxy with a nuclear starburst which becomes the best candidate to study the relationship between starburst and AGN activity. However, this central region is veiled by large amounts of dust, and it has been so far unclear which is the true dynamical nucleus. The near infrared spectroscopy could be advantageous in order to shed light on the true nucleus identity. Using Flamingos-2 at Gemini South we have taken deep K-band spectra along the major axis and through the brightest infrared source. We present evidence showing that the brightest near infrared and mid infrared source in the central region, already known as radio source TH7 and so far considered just a stellar supercluster, in fact, presents various symptoms of a genuine galactic nucleus. Therefore, it should be considered a valid nucleus candidate. It is the most massive compact infrared object in the central region, located at 2.0" of the symmetry center of the galactic bar. Moreover, our data indicate that this object i...

  4. Inhibitory short-term plasticity modulates neuronal activity in the rat entopeduncular nucleus in vitro.

    Science.gov (United States)

    Lavian, Hagar; Korngreen, Alon

    2016-04-01

    The entopeduncular nucleus (EP) is one of the basal ganglia output nuclei integrating synaptic information from several pathways within the basal ganglia. The firing of EP neurons is modulated by two streams of inhibitory synaptic transmission, the direct pathway from the striatum and the indirect pathway from the globus pallidus. These two inhibitory pathways continuously modulate the firing of EP neurons. However, the link between these synaptic inputs to neuronal firing in the EP is unclear. To investigate this input-output transformation we performed whole-cell and perforated-patch recordings from single neurons in the entopeduncular nucleus in rat brain slices during repetitive stimulation of the striatum and the globus pallidus at frequencies within the in vivo activity range of these neurons. These recordings, supplemented by compartmental modelling, showed that GABAergic synapses from the striatum, converging on EP dendrites, display short-term facilitation and that somatic or proximal GABAergic synapses from the globus pallidus show short-term depression. Activation of striatal synapses during low presynaptic activity decreased postsynaptic firing rate by continuously increasing the inter-spike interval. Conversely, activation of pallidal synapses significantly affected postsynaptic firing during high presynaptic activity. Our data thus suggest that low-frequency striatal output may be encoded as progressive phase shifts in downstream nuclei of the basal ganglia while high-frequency pallidal output may continuously modulate EP firing.

  5. The Third Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope

    CERN Document Server

    Ackermann, M; Atwood, W; Baldini, L; Ballet, J; Barbiellini, G; Bastieri, D; Gonzalez, J; Bellazzini, R; Bissaldi, E; Blandford, R; Bloom, E; Bonino, R; Bottacini, E; Brandt, T; Bregeon, J; Britto, R; Bruel, P; Buehler, R; Buson, S; Caliandro, G; Cameron, R; Caragiulo, M; Caraveo, P; Casandjian, J; Cavazzuti, E; Cecchi, C; Charles, E; Chekhtman, A; Cheung, C; Chiang, J; Chiaro, G; Ciprini, S; Claus, R; Cohen-Tanugi, J; Cominsky, L; Conrad, J; Cutini, S; D'Abrusco, R; D'Ammando, F; Angelis, A; Desiante, R; Digel, S; Venere, L; Drell, P; Favuzzi, C; Fegan, S; Ferrara, E; Finke, J; Focke, W; Franckowiak, A; Fuhrmann, L; Furniss, A; Fusco, P; Gargano, F; Gasparrini, D; Giglietto, N; Giommi, P; Giordano, F; Giroletti, M; Glanzman, T; Godfrey, G; Grenier, I; Grove, J; Guiriec, S; Hewitt, J W; Hill, A; Horan, D; J'ohannesson, G; Johnson, A; Johnson, W; Kataoka, J; Kuss, M; Mura, G; Larsson, S; Latronico, L; Leto, C; Li, J; Li, L; Longo, F; Loparco, F; Lott, B; Lovellette, M; Lubrano, P; Madejski, G; Mayer, M; Mazziotta, M; McEnery, J; Michelson, P; Mizuno, T; Moiseev, A; Monzani, M; Morselli, A; Moskalenko, I; Murgia, S; Nuss, E; Ohno, M; Ohsugi, T; Ojha, R; Omodei, N; Orienti, M; Orlando, E; Paggi, A; Paneque, D; Perkins, J; Pesce-Rollins, M; Piron, F; Pivato, G; Porter, T; Rain`o, S; Rando, R; Razzano, M; Razzaque, S; Reimer, A; Reimer, O; Romani, R; Salvetti, D; Schaal, M; Schinzel, F; Schulz, A; Sgr`o, C; Siskind, E; Sokolovsky, K; Spada, F; Spandre, G; Spinelli, P; Stawarz, L; Suson, D; Takahashi, H; Takahashi, T; Tanaka, Y; Thayer, J; Tibaldo, L; Torres, D; Torresi, E; Tosti, G; Troja, E; Uchiyama, Y; Vianello, G; Winer, B; Wood, K; Zimmer, S

    2015-01-01

    The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected with a test statistic (TS) greater than 25, using the first 4 years of data. The 3LAC includes 1591 AGNs located at high Galactic latitudes (|b|>10{\\deg}), which is a 71% increase over the second catalog that was based on 2 years of data. There are 28 duplicate associations (two counterparts to the same gamma-ray source), thus 1563 of the 2192 high-latitude gamma-ray sources of the 3FGL catalog are AGNs. A very large majority of these AGNs (98%) are blazars. About half of the newly detected blazars are of unknown type, i.e., they lack spectroscopic information of sufficient quality to determine the strength of their emission lines. Based on their spectral properties, these sources are evenly split between FSRQs and BL~Lacs. The general properties of the 3LAC sample confirm previous findings from earlier catalogs, but some new subclasses (e.g., ...

  6. Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei

    Science.gov (United States)

    Pierre Auger Collaboration; Abraham, J.; Abreu, P.; Aglietta, M.; Aguirre, C.; Allard, D.; Allekotte, I.; Allen, J.; Allison, P.; Alvarez-Muñiz, J.; Ambrosio, M.; Anchordoqui, L.; Andringa, S.; Anzalone, A.; Aramo, C.; Argirò, S.; Arisaka, K.; Armengaud, E.; Arneodo, F.; Arqueros, F.; Asch, T.; Asorey, H.; Assis, P.; Atulugama, B. S.; Aublin, J.; Ave, M.; Avila, G.; Bäcker, T.; Badagnani, D.; Barbosa, A. F.; Barnhill, D.; Barroso, S. L. C.; Bauleo, P.; Beatty, J. J.; Beau, T.; Becker, B. R.; Becker, K. H.; Bellido, J. A.; Benzvi, S.; Berat, C.; Bergmann, T.; Bernardini, P.; Bertou, X.; Biermann, P. L.; Billoir, P.; Blanch-Bigas, O.; Blanco, F.; Blasi, P.; Bleve, C.; Blümer, H.; Boháčová, M.; Bonifazi, C.; Bonino, R.; Brack, J.; Brogueira, P.; Brown, W. C.; Buchholz, P.; Bueno, A.; Burton, R. E.; Busca, N. G.; Caballero-Mora, K. S.; Cai, B.; Camin, D. V.; Caramete, L.; Caruso, R.; Carvalho, W.; Castellina, A.; Catalano, O.; Cataldi, G.; Cazon, L.; Cester, R.; Chauvin, J.; Chiavassa, A.; Chinellato, J. A.; Chou, A.; Chye, J.; Clay, R. W.; Colombo, E.; Conceição, R.; Connolly, B.; Contreras, F.; Coppens, J.; Cordier, A.; Cotti, U.; Coutu, S.; Covault, C. E.; Creusot, A.; Criss, A.; Cronin, J.; Curutiu, A.; Dagoret-Campagne, S.; Daumiller, K.; Dawson, B. R.; de Almeida, R. M.; de Donato, C.; de Jong, S. J.; de La Vega, G.; de Mello, W. J. M.; de Mello Neto, J. R. T.; de Mitri, I.; de Souza, V.; Del Peral, L.; Deligny, O.; Della Selva, A.; Delle Fratte, C.; Dembinski, H.; di Giulio, C.; Diaz, J. C.; Diep, P. N.; Dobrigkeit, C.; D'Olivo, J. C.; Dong, P. N.; Dornic, D.; Dorofeev, A.; Dos Anjos, J. C.; Dova, M. T.; D'Urso, D.; Dutan, I.; Duvernois, M. A.; Engel, R.; Epele, L.; Erdmann, M.; Escobar, C. O.; Etchegoyen, A.; San Luis, P. Facal; Falcke, H.; Farrar, G.; Fauth, A. C.; Fazzini, N.; Ferrer, F.; Ferry, S.; Fick, B.; Filevich, A.; Filipčič, A.; Fleck, I.; Fracchiolla, C. E.; Fulgione, W.; García, B.; García Gámez, D.; Garcia-Pinto, D.; Garrido, X.; Geenen, H.; Gelmini, G.; Gemmeke, H.; Ghia, P. L.; Giller, M.; Glass, H.; Gold, M. S.; Golup, G.; Gomez Albarracin, F.; Gómez Berisso, M.; Gómez Herrero, R.; Gonçalves, P.; Gonçalves Do Amaral, M.; Gonzalez, D.; Gonzalez, J. G.; González, M.; Góra, D.; Gorgi, A.; Gouffon, P.; Grassi, V.; Grillo, A. F.; Grunfeld, C.; Guardincerri, Y.; Guarino, F.; Guedes, G. P.; Gutiérrez, J.; Hague, J. D.; Hamilton, J. C.; Hansen, P.; Harari, D.; Harmsma, S.; Harton, J. L.; Haungs, A.; Hauschildt, T.; Healy, M. D.; Hebbeker, T.; Hebrero, G.; Heck, D.; Hojvat, C.; Holmes, V. C.; Homola, P.; Hörandel, J.; Horneffer, A.; Horvat, M.; Hrabovský, M.; Huege, T.; Hussain, M.; Iarlori, M.; Insolia, A.; Ionita, F.; Italiano, A.; Kaducak, M.; Kampert, K. H.; Karova, T.; Kégl, B.; Keilhauer, B.; Kemp, E.; Kieckhafer, R. M.; Klages, H. O.; Kleifges, M.; Kleinfeller, J.; Knapik, R.; Knapp, J.; Koang, D.-H.; Krieger, A.; Krömer, O.; Kuempel, D.; Kunka, N.; Kusenko, A.; La Rosa, G.; Lachaud, C.; Lago, B. L.; Lebrun, D.; Lebrun, P.; Lee, J.; de Oliveira, M. A. Leigui; Letessier-Selvon, A.; Leuthold, M.; Lhenry-Yvon, I.; López, R.; Lopez Agüera, A.; Lozano Bahilo, J.; García, R. Luna; Maccarone, M. C.; Macolino, C.; Maldera, S.; Mancarella, G.; Manceñido, M. E.; Mandat, D.; Mantsch, P.; Mariazzi, A. G.; Maris, I. C.; Falcon, H. R. Marquez; Martello, D.; Martínez, J.; Martínez Bravo, O.; Mathes, H. J.; Matthews, J.; Matthews, J. A. J.; Matthiae, G.; Maurizio, D.; Mazur, P. O.; McCauley, T.; McEwen, M.; McNeil, R. R.; Medina, M. C.; Medina-Tanco, G.; Meli, A.; Melo, D.; Menichetti, E.; Menschikov, A.; Meurer, Chr.; Meyhandan, R.; Micheletti, M. I.; Miele, G.; Miller, W.; Mollerach, S.; Monasor, M.; Ragaigne, D. Monnier; Montanet, F.; Morales, B.; Morello, C.; Moreno, J. C.; Morris, C.; Mostafá, M.; Muller, M. A.; Mussa, R.; Navarra, G.; Navarro, J. L.; Navas, S.; Necesal, P.; Nellen, L.; Newman-Holmes, C.; Newton, D.; Nhung, P. T.; Nierstenhoefer, N.; Nitz, D.; Nosek, D.; Nožka, L.; Oehlschläger, J.; Ohnuki, T.; Olinto, A.; Olmos-Gilbaja, V. M.; Ortiz, M.; Ortolani, F.; Ostapchenko, S.; Otero, L.; Pacheco, N.; Selmi-Dei, D. Pakk; Palatka, M.; Pallotta, J.; Parente, G.; Parizot, E.; Parlati, S.; Pastor, S.; Patel, M.; Paul, T.; Pavlidou, V.; Payet, K.; Pech, M.; PȩKala, J.; Pelayo, R.; Pepe, I. M.; Perrone, L.; Petrera, S.; Petrinca, P.; Petrov, Y.; Pichel, A.; Piegaia, R.; Pierog, T.; Pimenta, M.; Pinto, T.; Pirronello, V.; Pisanti, O.; Platino, M.; Pochon, J.; Privitera, P.; Prouza, M.; Quel, E. J.; Rautenberg, J.; Redondo, A.; Reucroft, S.; Revenu, B.; Rezende, F. A. S.; Ridky, J.; Riggi, S.; Risse, M.; Rivière, C.; Rizi, V.; Roberts, M.; Robledo, C.; Rodriguez, G.; Rodriguez Martino, J.; Rodriguez Rojo, J.; Rodriguez-Cabo, I.; Rodríguez-Frías, M. D.; Ros, G.; Rosado, J.; Roth, M.; Rouillé-D'Orfeuil, B.; Roulet, E.; Rovero, A. C.; Salamida, F.; Salazar, H.; Salina, G.; Sánchez, F.; Santander, M.; Santo, C. E.; Santos, E. M.; Sarazin, F.; Sarkar, S.; Sato, R.; Scherini, V.; Schieler, H.; Schmidt, A.; Schmidt, F.; Schmidt, T.; Scholten, O.; Schovánek, P.; Schüssler, F.; Sciutto, S. J.; Scuderi, M.; Segreto, A.; Semikoz, D.; Settimo, M.; Shellard, R. C.; Sidelnik, I.; Siffert, B. B.; Sigl, G.; de Grande, N. Smetniansky; Smiałkowski, A.; Šmída, R.; Smith, A. G. K.; Smith, B. E.; Snow, G. R.; Sokolsky, P.; Sommers, P.; Sorokin, J.; Spinka, H.; Squartini, R.; Strazzeri, E.; Stutz, A.; Suarez, F.; Suomijärvi, T.; Supanitsky, A. D.; Sutherland, M. S.; Swain, J.; Szadkowski, Z.; Takahashi, J.; Tamashiro, A.; Tamburro, A.; Taşcău, O.; Tcaciuc, R.; Thao, N. T.; Thomas, D.; Ticona, R.; Tiffenberg, J.; Timmermans, C.; Tkaczyk, W.; Peixoto, C. J. Todero; Tomé, B.; Tonachini, A.; Torres, I.; Travnicek, P.; Tripathi, A.; Tristram, G.; Tscherniakhovski, D.; Tueros, M.; Ulrich, R.; Unger, M.; Urban, M.; Galicia, J. F. Valdés; Valiño, I.; Valore, L.; van den Berg, A. M.; van Elewyck, V.; Vázquez, R. A.; Veberič, D.; Veiga, A.; Velarde, A.; Venters, T.; Verzi, V.; Videla, M.; Villaseñor, L.; Vorobiov, S.; Voyvodic, L.; Wahlberg, H.; Wainberg, O.; Warner, D.; Watson, A. A.; Westerhoff, S.; Wieczorek, G.; Wiencke, L.; Wilczyńska, B.; Wilczyński, H.; Wileman, C.; Winnick, M. G.; Wu, H.; Wundheiler, B.; Yamamoto, T.; Younk, P.; Zas, E.; Zavrtanik, D.; Zavrtanik, M.; Zech, A.; Zepeda, A.; Ziolkowski, M.

    2008-04-01

    Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest-energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [Pierre Auger Collaboration, Science 318 (2007) 938]. The correlation has maximum significance for cosmic rays with energy greater than ˜6 × 1019 eV and AGN at a distance less than ˜75 Mpc. We have confirmed the anisotropy at a confidence level of more than 99% through a test with parameters specified a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest-energies originate from extra-galactic sources close enough so that their flux is not significantly attenuated by interaction with the cosmic background radiation (the Greisen Zatsepin Kuz’min effect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic fields are very weak outside the thin disk of our galaxy. Our present data do not identify AGN as the sources of cosmic rays unambiguously, and other candidate sources which are distributed as nearby AGN are not ruled out. We discuss the prospect of unequivocal identification of individual sources of the highest-energy cosmic rays within a few years of continued operation of the Pierre Auger Observatory.

  7. Magnetically elevated accretion disks in active galactic nuclei: broad emission line regions and associated star formation

    Science.gov (United States)

    Begelman, Mitchell C.; Silk, Joseph

    2016-10-01

    We propose that the accretion disks fueling active galactic nuclei are supported vertically against gravity by a strong toroidal (φ -direction) magnetic field that develops naturally as the result of an accretion disk dynamo. The magnetic pressure elevates most of the gas carrying the accretion flow at R to large heights z ˜ 0.1 R and low densities, while leaving a thin dense layer containing most of the mass - but contributing very little accretion - around the equator. We show that such a disk model leads naturally to the formation of a broad emission line region through thermal instability. Extrapolating to larger radii, we demonstrate that local gravitational instability and associated star formation are strongly suppressed compared to standard disk models for AGN, although star formation in the equatorial zone is predicted for sufficiently high mass supply rates. This new class of accretion disk models thus appears capable of resolving two longstanding puzzles in the theory of AGN fueling: the formation of broad emission line regions and the suppression of fragmentation thought to inhibit accretion at the required rates. We show that the disk of stars that formed in the Galactic Center a few million years ago could have resulted from an episode of magnetically elevated accretion at ˜0.1 of the Eddington limit.

  8. Rapid and Bright Stellar-mass Binary Black Hole Mergers in Active Galactic Nuclei

    Science.gov (United States)

    Bartos, Imre; Kocsis, Bence; Haiman, Zoltán; Márka, Szabolcs

    2017-02-01

    The Laser Interferometer Gravitational-wave Observatory (LIGO) found direct evidence for double black hole binaries emitting gravitational waves. Galactic nuclei are expected to harbor the densest population of stellar-mass black holes. A significant fraction (∼ 30 % ) of these black holes can reside in binaries. We examine the fate of the black hole binaries in active galactic nuclei, which get trapped in the inner region of the accretion disk around the central supermassive black hole. We show that binary black holes can migrate into and then rapidly merge within the disk well within a Salpeter time. The binaries may also accrete a significant amount of gas from the disk, well above the Eddington rate. This could lead to detectable X-ray or gamma-ray emission, but would require hyper-Eddington accretion with a few percent radiative efficiency, comparable to thin disks. We discuss implications for gravitational-wave observations and black hole population studies. We estimate that Advanced LIGO may detect ∼20 such gas-induced binary mergers per year.

  9. Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei

    CERN Document Server

    Abraham, J; Aglietta, M; Aguirre, C; Allard, D; Allekotte, I; Allen, J; Allison, P; Alvarez, C; Alvarez-Muñiz, J; Ambrosio, M; Anchordoqui, L; Andringa, S; Anzalone, A; Aramo, C; Argiro, S; Arisaka, K; Armengaud, E; Arneodo, F; Arqueros, F; Asch, T; Asorey, H; Assis, P; Atulugama, B S; Aublin, J; Ave, M; Avila, G; Backer, T; Badagnani, D; Barbosa-Ademarlaudo, F; Barnhill, D; Barroso, S L C; Bauleo, P; Beatty, J J; Beau, T; Becker, B R; Becker, K H; Bellido, J A; Ben Zvi, S; Bérat, C; Bergmann, T; Bernardini, P; Bertou, X; Biermann, P L; Billoir, P; Blanch-Bigas, O; Blanco, F; Blasi, P; Bleve, C; Blümer, H; Bohaov, M; Bonifazi, C; Bonino, R; Boratav, M; Brack, J; Brogueira, P; Brown, W C; Buchholz, P; Bueno, A; Burton, R E; Busca, N G; Caballero-Mora, K S; Cai, B; Camin, D V; Caramete, L; Caruso, R; Carvalho, W; Castellina, A; Catalano, O; Cataldi, G; Cazon, L; Cester, R; Chauvin, J; Chiavassa, A; Chinellato, J A; Chou, A; Chye, J; Clark, P D J; Clay, R W; Colombo, E; Conceico, R; Connolly, B; Contreras, F; Coppens, J; Cordier, A; Cotti, U; Coutu, S; Covault, C E; Creusot, A; Criss, A; Cronin, J; Curutiu, A; Dagoret-Campagne, S; Daumiller, K; Dawson, B R; de Almeida, R M; De Donato, C; De Jong, S J; De La Vega, G; de Mello Junior, W J M; De Mello-Neto, J R T; De Mitri, I; De Souza, V; Del Peral, L; Deligny, O; Della Selva, A; Delle Fratte, C; Dembinski, H; Di Giulio, C; Diaz, J C; Dobrigkeit, C; D'Olivo, J C; Dornic, D; Dorofeev, A; dos Anjos, J C; Dova, M T; D'Urso, D; Dutan, I; Duvernois, M A; Engel, R; Epele, L; Erdmann, M; Escobar, C O; Etchegoyen, A; Facal San Luis, P; Falcke, H; Farrar, G; Fauth, A C; Fazzini, N; Fernández, A; Ferrer, F; Ferry, S; Fick, B; Filevich, A; Filipi, A; Fleck, ccI; Fonte, R; Fracchiolla, C E; Fulgione, W; Garca, B; Garca Gamez, D; Garcia-Pinto, D; Garrido, X; Geenen, H; Gelmini, i G; Gemmeke, H; Ghia, P L; Giller, M; Glass, H; Gold, M S; Golup, G; Gomez Albarracin, F; Gomez Berisso, M; Gmez Herrero, R; Gonalves, P; Goncalvesdo Amaral, M; González, D; Gonzalez, J G; González, M; Gora, D; Gorgi, A; Gouffon, P; Grassi, V; Grillo, A F; Grunfeld, C; Guardincerri, Y; Guarino, F; Guedes, G P; Gutirrez, J; Hague, J D; Hamilton, J C; Hansen, P; Harari, D; Harmsma, S; Harton, J L; Haungs, A; Hauschildt, T; Healy, M D; Hebbeker, T; Hebrero, G; Heck, D; Hojvat, C; Holmes, V C; Homola, P; Horandel, J; Horneffer, A; Horvat, M; Hrabovsky, M; Huege, T; Hussain, M; Iarlori, M; Insolia, A; Ionita, F; Italiano, A; Kaducak, M; Kampert, K H; Karova, T; Kgl, B; Keilhauer, B; Kemp, E; Kieckhafer, R M; Klages, H O; Kleifges, M; Kleinfeller, J; Knapik, R; Knapp, J; Koang, D H; Krieger, A; Krömer, O; Kuempel, D; Kunka, N; Kusenko, A; La Rosa, G; Lachaud, C; Lago, B L; Lebrun, D; Le Brun, P; Lee, J; Leiguide Oliveira, M A; Letessier-Selvon, A A; Leuthold, M; Lhenry-Yvon, I; López, R; López-Aguera, A; LozanoBahilo, J; Luna Garca, R; Maccarone, M C; Macolino, C; Maldera, S; Mancarella, G; Mancenido, M E; Mandat, D; Mantsch, P; Mariazzi, A G; Maris, I C; Marquez Falcon, H R; Martello, D; Martínez, J; Martinez Bravo, O; Mathes, H J; Matthews, J; Matthews, ii J A J; Matthiae, Giorgio; Maurizio, D; Mazur, P O; McCauley, T; McEwen, M; McNeil, R R; Medina, M C; Medina-Tanco, G; Meli, A; Melo, D; Menichetti, E; Menschikov, A; Meurer, Chr; Meyhandan, R; Micheletti, M I; Miele, G; Miller, W; Mollerach, S; Monasor, M; Monnier Ragaigne, D; Montanet, F; Morales, B; Morello, C; Moreno, E; Moreno, J C; Morris, C; Mostaf, M; Muller, M A; Mussa, R; Navarra, G; Navarro, J L; Navas, a S; Necesal, P; Nellen, L; Newman-Holmes, C; Newton, D; Nguyen Thi, T; Nierstenhoefer, N; Nitz, D; Nosek, D; Noka, L; Oehlschläger, J; Ohnuki, T; Olinto, A; Olmos-Gilbaja, V M; Ortiz, M; Ortolani, F; Ostapchenko, S; Otero, L; Pacheco, N; Pakk Selmi-Dei, D; Palatka, M; Pallotta, J; Parente, G; Parizot, E; Parlati, S; Pastor, S; Patel, M; Paul, T; Pavlidou, V; Payet, K; Pech, M; Pkala, J; Pelayo, R; Pepe, I M; Perrone, L; Petrera, S; Petrinca, P; Petrov, Y; Diep Pham Ngoc Dong Pham Ngoc; Pham Thi, T N; Pichel, A; Piegaia, R; Pierog, T; Pimenta, M; Pinto, T; Pirronello, V; Pisanti, O; Platino, M; Pochon, J; Porter, T A; Privitera, P; Prouza, M; Quel, E J; Rautenberg, J; Redondo, A; Reucroft, S; Revenu, B; Rezende, F A S; Rídky, J; Riggi, S; Risse, M; Rivi`re, C; Rizi, V; Roberts, M; Robledo, C; Rodríguez, G; Rodrguez Fras, D; Rodríguez-Martino, J; RodrigueziiRojo, J; Rodriguez-Cabo, I; Ros, G; Rosado, J; Roth, M; Rouill-d'Orfeuil, B; Roulet, E; Rovero, A C; Salamida, F; Salazar, H; Salina, G; Sánchez, F; Santander, M; Santo, C E; Santos, E M; Sarazin, F; Sarkar, S; Sato, R; Scherini, V; Schieler, H; Schmidt, A; Schmidt, F; Schmidt, T; Scholten, O; Schovnek, P; Schussler, F; Sciutto, S J; Scuderi, M; Segreto, A; Semikoz, D; Settimo, M; Shellard, R C; Sidelnik, I; Siffert, B B; Sigl, i G; Smetniansky De Grande, N; Smialkowski, A; Smda, R; Smith, A G K; Smith, B E; Snow, G R; Sokolsky, P; Sommers, P; Sorokin, J; Spinka, H; Squartini, R; Strazzeri, E; Stutz, A; Suárez, F; Suomijärvi, T; Supanitsky, A D; Sutherland, M S; Swain, J; Szadkowski, Z; Takahashi, J; Tamashiro, A; Tamburro, A; Tacu, O; Tcaciuc, R; Thomas, D; Ticona, R; Tiffenberg, J; Timmermans, C; Tkaczyk, W; Todero Peixoto, C J; Tom, B; Tonachini, A; Torres, I; Torresi, D; Travnicek, P; Tripathi, A; Tristram, G; Tscherniakhovski, D; Tueros, M; Tunnicliffe, V; Ulrich, R; Unger, M; Urban, M; Valds Galicia, J F; Valino, I; Valore, e L; vanden Berg, A M; van Elewyck, V; Vázquez, R A; Veberi, D; Veiga, A; Velarde, A; Venters, T; Verzi, V; Videla, cM; Villaseñor, L; Vorobiov, S; Voyvodic, L; Wahlberg, H; Wainberg, O; Walker, P; Warner, D; Watson, A A; Westerhoff, S; Wieczorek, G; Wiencke, L; Wilczynska, B; Wilczynski, H; Wileman, C; Winnick, M G; Wu, H; Wundheiler, B; Yamamoto, T; Younk, P; Zas, E; Zavrtanik, D; Zavrtanik, M; Zech, A; Zepeda, A; Ziolkowski, M

    2007-01-01

    Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) \\cite{science}. The correlation has maximum significance for cosmic rays with energy greater than ~ 6x10^{19}$ eV and AGN at a distance less than ~ 75 Mpc. We have confirmed the anisotropy at a confidence level of more than 99% through a test with parameters specified {\\em a priori}, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest energies originate from extra-galactic sources close enough so that their flux is not significantly attenuated by interaction with the cosmic background radiation (the Greisen-Zatsepin-Kuz'min effect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic fields are very weak outside the thin d...

  10. The First Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope

    CERN Document Server

    Abdo, A A

    2010-01-01

    We present the first catalog of active galactic nuclei (AGN) detected by the LAT, corresponding to 11 months of data collected in scientific operation mode. The First LAT AGN Catalog (1LAC) includes 671 gamma-ray sources located at high Galactic latitudes (|b| > 10 deg) that are detected with a test statistic (TS) greater than 25 and associated statistically with AGNs. Some LAT sources are associated with multiple AGNs, and consequently, the catalog includes 709 AGNs, comprising 300 BL Lacertae objects (BL Lacs), 296 flat-spectrum radio quasars (FSRQs), 41 AGNs of other types, and 72 AGNs of unknown type. We also classify the blazars based on their spectral energy distributions (SEDs) as archival radio, optical, and X-ray data permit. In addition to the format 1LAC sample, we provide AGN associations for 51 low-latitude LAT sources and AGN "affiliations" (unquantified counterpart candidates) for 104 high-latitude LAT sources without AGN associations. The overlap of the 1LAC with existing gamma-ray AGN catalog...

  11. The First Catalog of Active Galactic Nuclei Detected by the Fermi Large Area Telescope

    Science.gov (United States)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Allafort, A.; Antolini, E.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Bogart, J. R.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Burnett, T. H.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Cannon, A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Celotti, A.; Charles, E.; Chekhtman, A.; Chen, A. W.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Costamante, L.; Cotter, G.; Cutini, S.; D'Elia, V.; Dermer, C. D.; de Angelis, A.; de Palma, F.; De Rosa, A.; Digel, S. W.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Escande, L.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giebels, B.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grandi, P.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guiriec, S.; Hadasch, D.; Harding, A. K.; Hayashida, M.; Hays, E.; Healey, S. E.; Hill, A. B.; Horan, D.; Hughes, R. E.; Iafrate, G.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Johnson, R. P.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lavalley, C.; Lemoine-Goumard, M.; Llena Garde, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Malaguti, G.; Massaro, E.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; McGlynn, S.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohno, M.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piranomonte, S.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Ripken, J.; Ritz, S.; Rodriguez, A. Y.; Romani, R. W.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sgrò, C.; Shaw, M. S.; Siskind, E. J.; Smith, P. D.; Spandre, G.; Spinelli, P.; Starck, J.-L.; Stawarz, Ł.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Taylor, G. B.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Ubertini, P.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Villata, M.; Vitale, V.; Waite, A. P.; Wallace, E.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ylinen, T.; Ziegler, M.

    2010-05-01

    We present the first catalog of active galactic nuclei (AGNs) detected by the Large Area Telescope (LAT), corresponding to 11 months of data collected in scientific operation mode. The First LAT AGN Catalog (1LAC) includes 671 γ-ray sources located at high Galactic latitudes (|b|>10°) that are detected with a test statistic greater than 25 and associated statistically with AGNs. Some LAT sources are associated with multiple AGNs, and consequently, the catalog includes 709 AGNs, comprising 300 BL Lacertae objects, 296 flat-spectrum radio quasars, 41 AGNs of other types, and 72 AGNs of unknown type. We also classify the blazars based on their spectral energy distributions as archival radio, optical, and X-ray data permit. In addition to the formal 1LAC sample, we provide AGN associations for 51 low-latitude LAT sources and AGN "affiliations" (unquantified counterpart candidates) for 104 high-latitude LAT sources without AGN associations. The overlap of the 1LAC with existing γ-ray AGN catalogs (LBAS, EGRET, AGILE, Swift, INTEGRAL, TeVCat) is briefly discussed. Various properties—such as γ-ray fluxes and photon power-law spectral indices, redshifts, γ-ray luminosities, variability, and archival radio luminosities—and their correlations are presented and discussed for the different blazar classes. We compare the 1LAC results with predictions regarding the γ-ray AGN populations, and we comment on the power of the sample to address the question of the blazar sequence.

  12. Active Galactic Nuclei, Neutrinos, and Interacting Cosmic Rays in NGC 253 & NGC 1068

    CERN Document Server

    Yoast-Hull, Tova M; Zweibel, Ellen G; Everett, John E

    2013-01-01

    The galaxies M82, NGC 253, NGC 1068, and NGC 4945 have been detected in gamma-rays by Fermi. Previously, we developed and tested a model for cosmic ray interactions in the starburst galaxy M82. Now, we aim to explore the differences between starburst and active galactic nuclei (AGN) environments by applying our self-consistent model to the starburst galaxy NGC 253 and the Seyfert galaxy NGC 1068. Assuming constant cosmic-ray acceleration efficiency by supernova remnants with Milky-Way parameters, we calculate the cosmic-ray proton and primary and secondary electron/positron populations, predict the radio and gamma-ray spectra, and compare with published measurements. We find that our models easily fits the observed gamma-ray spectrum for NGC 253 while constraining the cosmic ray source spectral index and acceleration efficiency. However, we encountered difficultly modeling the observed radio data and constraining the speed of the galactic wind and the magnetic field strength, unless the gas mass is less than ...

  13. Correlation of the highest-energy cosmic rays with the positions of nearby active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Collaboration, The Pierre auger

    2007-12-01

    Data collected by the Pierre Auger Observatory provide evidence for anisotropy in the arrival directions of the cosmic rays with the highest energies, which are correlated with the positions of relatively nearby active galactic nuclei (AGN) [1]. The correlation has maximum significance for cosmic rays with energy greater than {approx} 6 x 10{sup 19} eV and AGN at a distance less than {approx} 75 Mpc. We have confirmed the anisotropy at a confidence level of more than 99% through a test with parameters specified a priori, using an independent data set. The observed correlation is compatible with the hypothesis that cosmic rays with the highest energies originate from extra-galactic sources close enough so that their flux is not significantly attenuated by interaction with the cosmic background radiation (the Greisen-Zatsepin-Kuzmin effect). The angular scale of the correlation observed is a few degrees, which suggests a predominantly light composition unless the magnetic fields are very weak outside the thin disk of our galaxy. Our present data do not identify AGN as the sources of cosmic rays unambiguously, and other candidate sources which are distributed as nearby AGN are not ruled out. We discuss the prospect of unequivocal identification of individual sources of the highest-energy cosmic rays within a few years of continued operation of the Pierre Auger Observatory.

  14. The quenching of star formation in accretion-driven clumpy turbulent tori of active galactic nuclei

    CERN Document Server

    Vollmer, B

    2013-01-01

    Galactic gas-gas collisions involving a turbulent multiphase ISM share common ISM properties: dense extraplanar gas visible in CO, large linewidths (>= 50 km/s), strong mid-infrared H_2 line emission, low star formation activity, and strong radio continuum emission. Gas-gas collisions can occur in the form of ICM ram pressure stripping, galaxy head-on collisions, compression of the intragroup gas and/or galaxy ISM by an intruder galaxy which flies through the galaxy group at a high velocity, or external gas accretion on an existing gas torus in a galactic center. We suggest that the common theme of all these gas-gas interactions is adiabatic compression of the ISM leading to an increase of the turbulent velocity dispersion of the gas. The turbulent gas clouds are then overpressured and star formation is quenched. Within this scenario we developed a model for turbulent clumpy gas disks where the energy to drive turbulence is supplied by external infall or the gain of potential energy by radial gas accretion wi...

  15. Peripherally injected CCK-8S activates CART positive neurons of the paraventricular nucleus in rats

    Science.gov (United States)

    Noetzel, Steffen; Inhoff, Tobias; Goebel, Miriam; Taché, Yvette; Veh, Rüdiger W.; Bannert, Norbert; Grötzinger, Carsten; Wiedenmann, Bertram; Klapp, Burghard F.; Mönnikes, Hubert; Kobelt, Peter

    2014-01-01

    Cholecystokinin (CCK) plays a role in the short-term inhibition of food intake. Cocaine- and amphetamine-regulated transcript (CART) peptide has been observed in neurons of the paraventricular nucleus (PVN). It has been reported that intracerebroventricular injection of CART peptide inhibits food intake in rodents. The aim of the study was to determine whether intraperitoneally (ip) injected CCK-8S affects neuronal activity of PVN-CART neurons. Ad libitum fed male Sprague-Dawley rats received 6 or 10 μg/kg CCK-8S or 0.15 M NaCl ip (n = 4/group). The number of c-Fos-immunoreactive neurons was determined in the PVN, arcuate nucleus (ARC), and the nucleus of the solitary tract (NTS). CCK-8S dose-dependently increased the number of c-Fos-immunoreactive neurons in the PVN (mean ± SEM: 102 ± 6 vs. 150 ± 5 neurons/section, p < 0.05) and compared to vehicle treated rats (18 ± 7, p < 0.05 vs. 6 and 10 μg/kg CCK-8S). CCK-8S at both doses induced an increase in the number of c-Fos-immunoreactive neurons in the NTS (65 ± 13, p < 0.05, and 182 ± 16, p < 0.05). No effect on the number of c-Fos neurons was observed in the ARC. Immunostaining for CART and c-Fos revealed a dose-dependent increase of activated CART neurons (19 ± 3 vs. 29 ± 7; p < 0.05), only few activated CART neuron were observed in the vehicle group (1 ± 0). The present observation shows that CCK-8S injected ip induces an increase in neuronal activity in PVN-CART neurons and suggests that CART neurons in the PVN may play a role in the mediation of peripheral CCK-8S's anorexigenic effects. PMID:20307613

  16. Neuropeptide Y activity in the nucleus accumbens modulates feeding behavior and neuronal activity

    NARCIS (Netherlands)

    van den Heuvel, José K; Furman, Kara; Gumbs, Myrtille C R; Eggels, Leslie; Opland, Darren M; Land, Benjamin B; Kolk, Sharon M; S Narayanan, Nandakumar; Fliers, Eric; Kalsbeek, A.; DiLeone, Ralph J; la Fleur, Susanne E

    2015-01-01

    BACKGROUND: Neuropeptide Y (NPY) is a hypothalamic neuropeptide that plays a prominent role in feeding and energy homeostasis. Expression of the NPY Y1 receptor (Y1R) is highly concentrated in the nucleus accumbens (Acb), a region important in the regulation of palatable feeding. In this study, we p

  17. Refeeding-activated glutamatergic neurons in the hypothalamic paraventricular nucleus (PVN) mediate effects of melanocortin signaling in the nucleus tractus solitarius (NTS).

    Science.gov (United States)

    Singru, Praful S; Wittmann, Gábor; Farkas, Erzsébet; Zséli, Györgyi; Fekete, Csaba; Lechan, Ronald M

    2012-08-01

    We previously demonstrated that refeeding after a prolonged fast activates a subset of neurons in the ventral parvocellular subdivision of the paraventricular nucleus (PVNv) as a result of increased melanocortin signaling. To determine whether these neurons contribute to satiety by projecting to the nucleus tractus solitarius (NTS), the retrogradely transported marker substance, cholera toxin-β (CTB), was injected into the dorsal vagal complex of rats that were subsequently fasted and refed for 2 h. By double-labeling immunohistochemistry, CTB accumulation was found in the cytoplasm of the majority of refeeding-activated c-Fos neurons in the ventral parvocellular subdivision of the hypothalamic paraventricular nucleus (PVNv). In addition, a large number of refeeding-activated c-Fos-expressing neurons were observed in the lateral parvocellular subdivision (PVNl) that also contained CTB and were innervated by axon terminals of proopiomelanocortin neurons. To visualize the location of neuronal activation within the NTS by melanocortin-activated PVN neurons, α-MSH was focally injected into the PVN, resulting in an increased number of c-Fos-containing neurons in the PVN and in the NTS, primarily in the medial and commissural parts. All refeeding-activated neurons in the PVNv and PVNl expressed the mRNA of the glutamatergic marker, type 2 vesicular glutamate transporter (VGLUT2), indicating their glutamatergic phenotype, but only rare neurons contained oxytocin. These data suggest that melanocortin-activated neurons in the PVNv and PVNl may contribute to refeeding-induced satiety through effects on the NTS and may alter the sensitivity of NTS neurons to vagal satiety inputs via glutamate excitation.

  18. Outflow and metallicity in the broad-line region of low-redshift active galactic nuclei

    CERN Document Server

    Shin, Jaejin; Woo, Jong-Hak

    2016-01-01

    Outflows in active galactic nuclei (AGNs) are crucial to understand in investigating the co-evolution of supermassive black holes (SMBHs) and their host galaxies since outflows may play an important role as an AGN feedback mechanism. Based on the archival UV spectra obtained with HST and IUE, we investigate outflows in the broad-line region (BLR) in low-redshift AGNs (z < 0.4) through the detailed analysis of the velocity profile of the CIV emission line. We find a dependence of the outflow strength on the Eddington ratio and the BLR metallicity in our low-redshift AGN sample, which is consistent with the earlier results obtained for high-redshift quasars. These results suggest that the BLR outflows, gas accretion onto SMBH, and past star-formation activity in the host galaxies are physically related in low-redshift AGNs as in powerful high-redshift quasars.

  19. Mid-infrared Colors of Dwarf Galaxies: Young Starbursts Mimicking Active Galactic Nuclei

    Science.gov (United States)

    Hainline, Kevin N.; Reines, Amy E.; Greene, Jenny E.; Stern, Daniel

    2016-12-01

    Searching for active galactic nuclei (AGNs) in dwarf galaxies is important for our understanding of the seed black holes that formed in the early universe. Here, we test infrared selection methods for AGN activity at low galaxy masses. Our parent sample consists of ˜18,000 nearby dwarf galaxies (M * great care must be taken when selecting AGNs in dwarf galaxies using infrared colors, as star-forming dwarf galaxies are capable of heating dust in such a way that mimics the infrared colors of more luminous AGNs. In particular, a simple W1-W2 color cut alone should not be used to select AGNs in dwarf galaxies. With these complications in mind, we present a sample of 41 dwarf galaxies that fall in the WISE infrared color space typically occupied by more luminous AGNs and that are worthy of follow-up observations.

  20. Spontaneous cluster activity in the inferior olivary nucleus in brainstem slices from postnatal mice

    DEFF Research Database (Denmark)

    Rekling, Jens C; Reveles Jensen, Kristian; Jahnsen, Henrik

    2012-01-01

    largely unknown. Here we show that the IO in in vitro slices from postnatal mice spontaneously generates clusters of neurons with synchronous Ca2+ transients. Neurons in the principal olive (PO), and the vestibular-related dorsomedial cell column (dmcc), showed an age-dependent increase in spontaneous......A distinctive property of the cerebellar system is olivocerebellar modules, where synchronized electrical activity in neurons in the inferior olivary nucleus (IO) evokes organized activity in the cerebellar cortex. However, the exact function of these modules, and how they are developed, is still...... calcium transients. The spatiotemporal activity pattern was occasionally organized in clusters of co-active neighbouring neurons, with regular (16/min) and irregular (2-3/min) repeating cluster activity in the dmcc and PO, respectively. IO clusters had a diameter of 100-170 µm, lasted ~1 s, and increased...

  1. Reactive oxygen species in the paraventricular nucleus of the hypothalamus alter sympathetic activity during metabolic syndrome.

    Directory of Open Access Journals (Sweden)

    JOSIANE CAMPOS CRUZ

    2015-12-01

    Full Text Available The paraventricular nucleus of the hypothalamus (PVN contains heterogeneous populations of neurons involved in autonomic and neuroendocrine regulation. The PVN plays an important role in the sympathoexcitatory response to increasing circulating levels of angiotensin II (Ang-II, which activates AT1 receptors in the circumventricular organs (OCVs, mainly in the subfornical organ (SFO. Circulating Ang-II induces a de novo synthesis of Ang-II in SFO neurons projecting to pre-autonomic PVN neurons. Activation of AT1 receptors induces intracellular increases in reactive oxygen species (ROS, leading to increases in sympathetic nerve activity (SNA. Chronic sympathetic nerve activation promotes a series of metabolic disorders that characterizes the metabolic syndrome (MetS: dyslipidemia, hyperinsulinemia, glucose intolerance, hyperleptinemia and elevated plasma hormone levels, such as noradrenaline, glucocorticoids, leptin, insulin and Ang-II. This review will discuss the contribution of our laboratory and others regarding the sympathoexcitation caused by peripheral Ang-II-induced reactive oxygen species along the subfornical organ and paraventricular nucleus of the hypothalamus. We hypothesize that this mechanism could be involved in metabolic disorders underlying MetS.

  2. X-ray and infrared diagnostics of nearby active galactic nuclei with MAXI and AKARI

    Science.gov (United States)

    Isobe, Naoki; Kawamuro, Taiki; Oyabu, Shinki; Nakagawa, Takao; Baba, Shunsuke; Yano, Kenichi; Ueda, Yoshihiro; Toba, Yoshiki

    2016-10-01

    Nearby active galactic nuclei were diagnosed in the X-ray and mid-to-far infrared wavelengths with Monitor of All-sky X-ray Image (MAXI) and the Japanese infrared observatory AKARI, respectively. One hundred of the X-ray sources listed in the second release of the MAXI all-sky X-ray source catalog are currently identified as non-blazar-type active galactic nuclei. These include 95 Seyfert galaxies and 5 quasars, and they are composed of 73 type-1 and 27 type-2 objects. The AKARI all-sky survey point source catalog was searched for their mid- and far-infrared counterparts at 9, 18, and 90 μm. As a result, 69 Seyfert galaxies in the MAXI catalog (48 type-1 and 21 type-2) were found to be detected with AKARI. The X-ray (3-4 keV and 4-10 keV) and infrared luminosities of these objects were investigated, together with their color information. Adopting the canonical photon index, Γ = 1.9, of the intrinsic X-ray spectrum of the Seyfert galaxies, the X-ray hardness ratio between the 3-4 and 4-10 keV ranges derived with MAXI was roughly converted into the absorption column density. After the X-ray luminosity was corrected for absorption from the estimated column density, the well-known X-ray-to-infrared luminosity correlation was confirmed, at least in the Compton-thin regime. In contrast, NGC 1365, the only Compton-thick object in the MAXI catalog, was found to deviate from the correlation toward a significantly lower X-ray luminosity by nearly an order of magnitude. It was verified that the relation between the X-ray hardness below 10 keV and X-ray-to-infrared color acts as an effective tool to pick up Compton-thick objects. The difference in the infrared colors between the type-1 and type-2 Seyfert galaxies and its physical implication on the classification and unification of active galactic nuclei are briefly discussed.

  3. X-ray and infrared diagnostics of nearby active galactic nuclei with MAXI and AKARI

    Science.gov (United States)

    Isobe, Naoki; Kawamuro, Taiki; Oyabu, Shinki; Nakagawa, Takao; Baba, Shunsuke; Yano, Kenichi; Ueda, Yoshihiro; Toba, Yoshiki

    2016-12-01

    Nearby active galactic nuclei were diagnosed in the X-ray and mid-to-far infrared wavelengths with Monitor of All-sky X-ray Image (MAXI) and the Japanese infrared observatory AKARI, respectively. One hundred of the X-ray sources listed in the second release of the MAXI all-sky X-ray source catalog are currently identified as non-blazar-type active galactic nuclei. These include 95 Seyfert galaxies and 5 quasars, and they are composed of 73 type-1 and 27 type-2 objects. The AKARI all-sky survey point source catalog was searched for their mid- and far-infrared counterparts at 9, 18, and 90 μm. As a result, 69 Seyfert galaxies in the MAXI catalog (48 type-1 and 21 type-2) were found to be detected with AKARI. The X-ray (3-4 keV and 4-10 keV) and infrared luminosities of these objects were investigated, together with their color information. Adopting the canonical photon index, Γ = 1.9, of the intrinsic X-ray spectrum of the Seyfert galaxies, the X-ray hardness ratio between the 3-4 and 4-10 keV ranges derived with MAXI was roughly converted into the absorption column density. After the X-ray luminosity was corrected for absorption from the estimated column density, the well-known X-ray-to-infrared luminosity correlation was confirmed, at least in the Compton-thin regime. In contrast, NGC 1365, the only Compton-thick object in the MAXI catalog, was found to deviate from the correlation toward a significantly lower X-ray luminosity by nearly an order of magnitude. It was verified that the relation between the X-ray hardness below 10 keV and X-ray-to-infrared color acts as an effective tool to pick up Compton-thick objects. The difference in the infrared colors between the type-1 and type-2 Seyfert galaxies and its physical implication on the classification and unification of active galactic nuclei are briefly discussed.

  4. Reward prediction-related increases and decreases in tonic neuronal activity of the pedunculopontine tegmental nucleus

    Directory of Open Access Journals (Sweden)

    Ken-Ichi eOkada

    2013-05-01

    Full Text Available The neuromodulators serotonin, acetylcholine, and dopamine have been proposed to play important roles in the execution of movement, control of several forms of attentional behavior, and reinforcement learning. While the response pattern of midbrain dopaminergic neurons and its specific role in reinforcement learning have been revealed, the roles of the other neuromodulators remain elusive. Reportedly, neurons in the dorsal raphe nucleus, one major source of serotonin, continually track the state of expectation of future rewards by showing a correlated response to the start of a behavioral task, reward cue presentation, and reward delivery. Here, we show that neurons in the pedunculopontine tegmental nucleus (PPTN, one major source of acetylcholine, showed similar encoding of the expectation of future rewards by a systematic increase or decrease in tonic activity. We recorded and analyzed PPTN neuronal activity in monkeys during a reward conditioned visually guided saccade task. The firing patterns of many PPTN neurons were tonically increased or decreased throughout the task period. The tonic activity pattern of neurons was correlated with their encoding of the predicted reward value; neurons exhibiting an increase or decrease in tonic activity showed higher or lower activity in the large reward-predicted trials, respectively. Tonic activity and reward-related modulation ended around the time of reward delivery. Additionally, some tonic changes in activity started prior to the appearance of the initial stimulus, and were related to the anticipatory fixational behavior. A partially overlapping population of neurons showed both the initial anticipatory response and subsequent predicted reward value-dependent activity modulation by their systematic increase or decrease of tonic activity. These bi-directional reward- and anticipatory behavior-related modulation patterns are suitable for the presumed role of the PPTN in reward processing and

  5. Does incentive-elicited nucleus accumbens activation differ by substance of abuse? An examination with adolescents.

    Science.gov (United States)

    Karoly, Hollis C; Bryan, Angela D; Weiland, Barbara J; Mayer, Andrew; Dodd, Andrew; Feldstein Ewing, Sarah W

    2015-12-01

    Numerous questions surround the nature of reward processing in the developing adolescent brain, particularly in regard to polysubstance use. We therefore sought to examine incentive-elicited brain activation in the context of three common substances of abuse (cannabis, tobacco, and alcohol). Due to the role of the nucleus accumbens (NAcc) in incentive processing, we compared activation in this region during anticipation of reward and loss using a monetary incentive delay (MID) task. Adolescents (ages 14-18; 66% male) were matched on age, gender, and frequency of use of any common substances within six distinct groups: cannabis-only (n=14), tobacco-only (n=34), alcohol-only (n=12), cannabis+tobacco (n=17), cannabis+tobacco+alcohol (n=17), and non-using controls (n=38). All groups showed comparable behavioral performance on the MID task. The tobacco-only group showed decreased bilateral nucleus accumbens (NAcc) activation during reward anticipation as compared to the alcohol-only group, the control group, and both polysubstance groups. Interestingly, no differences emerged between the cannabis-only group and any of the other groups. Results from this study suggest that youth who tend toward single-substance tobacco use may possess behavioral and/or neurobiological characteristics that differentiate them from both their substance-using and non-substance-using peers.

  6. Repetitive and retinotopically restricted activation of the dorsal lateral geniculate nucleus with optogenetics.

    Directory of Open Access Journals (Sweden)

    Alexandre Castonguay

    Full Text Available Optogenetics allows the control of cellular activity using focused delivery of light pulses. In neuroscience, optogenetic protocols have been shown to efficiently inhibit or stimulate neuronal activity with a high temporal resolution. Among the technical challenges associated with the use of optogenetics, one is the ability to target a spatially specific population of neurons in a given brain structure. To address this issue, we developed a side-illuminating optical fiber capable of delivering light to specific sites in a target nucleus with added flexibility through rotation and translation of the fiber and by varying the output light power. The designed optical fiber was tested in vivo in visual structures of ChR2-expressing transgenic mice. To assess the spatial extent of neuronal activity modulation, we took advantage of the hallmark of the visual system: its retinotopic organization. Indeed, the relative position of ganglion cells in the retina is transposed in the cellular topography of both the dorsal lateral geniculate nucleus (LGN in the thalamus and the primary visual cortex (V1. The optical fiber was inserted in the LGN and by rotating it with a motor, it was possible to sequentially activate different neuronal populations within this structure. The activation of V1 neurons by LGN projections was recorded using intrinsic optical imaging. Increasing light intensity (from 1.4 to 8.9 mW/mm² led to increasing activation surfaces in V1. Optogenetic stimulation of the LGN at different translational and rotational positions was associated with different activation maps in V1. The position and/or orientation of the fiber inevitably varied across experiments, thus limiting the capacity to pool data. With the optogenetic design presented here, we demonstrate for the first time a transitory and spatially-concise activation of a deep neuronal structure. The optogenetic design presented here thus opens a promising avenue for studying the function

  7. Repetitive and retinotopically restricted activation of the dorsal lateral geniculate nucleus with optogenetics.

    Science.gov (United States)

    Castonguay, Alexandre; Thomas, Sébastien; Lesage, Frédéric; Casanova, Christian

    2014-01-01

    Optogenetics allows the control of cellular activity using focused delivery of light pulses. In neuroscience, optogenetic protocols have been shown to efficiently inhibit or stimulate neuronal activity with a high temporal resolution. Among the technical challenges associated with the use of optogenetics, one is the ability to target a spatially specific population of neurons in a given brain structure. To address this issue, we developed a side-illuminating optical fiber capable of delivering light to specific sites in a target nucleus with added flexibility through rotation and translation of the fiber and by varying the output light power. The designed optical fiber was tested in vivo in visual structures of ChR2-expressing transgenic mice. To assess the spatial extent of neuronal activity modulation, we took advantage of the hallmark of the visual system: its retinotopic organization. Indeed, the relative position of ganglion cells in the retina is transposed in the cellular topography of both the dorsal lateral geniculate nucleus (LGN) in the thalamus and the primary visual cortex (V1). The optical fiber was inserted in the LGN and by rotating it with a motor, it was possible to sequentially activate different neuronal populations within this structure. The activation of V1 neurons by LGN projections was recorded using intrinsic optical imaging. Increasing light intensity (from 1.4 to 8.9 mW/mm²) led to increasing activation surfaces in V1. Optogenetic stimulation of the LGN at different translational and rotational positions was associated with different activation maps in V1. The position and/or orientation of the fiber inevitably varied across experiments, thus limiting the capacity to pool data. With the optogenetic design presented here, we demonstrate for the first time a transitory and spatially-concise activation of a deep neuronal structure. The optogenetic design presented here thus opens a promising avenue for studying the function of deep brain

  8. Higher landing accuracy in expert pilots is associated with lower activity in the caudate nucleus.

    Directory of Open Access Journals (Sweden)

    Maheen M Adamson

    Full Text Available The most common lethal accidents in General Aviation are caused by improperly executed landing approaches in which a pilot descends below the minimum safe altitude without proper visual references. To understand how expertise might reduce such erroneous decision-making, we examined relevant neural processes in pilots performing a simulated landing approach inside a functional MRI scanner. Pilots (aged 20-66 were asked to "fly" a series of simulated "cockpit view" instrument landing scenarios in an MRI scanner. The scenarios were either high risk (heavy fog-legally unsafe to land or low risk (medium fog-legally safe to land. Pilots with one of two levels of expertise participated: Moderate Expertise (Instrument Flight Rules pilots, n = 8 or High Expertise (Certified Instrument Flight Instructors or Air-Transport Pilots, n = 12. High Expertise pilots were more accurate than Moderate Expertise pilots in making a "land" versus "do not land" decision (CFII: d' = 3.62 ± 2.52; IFR: d' = 0.98 ± 1.04; p<.01. Brain activity in bilateral caudate nucleus was examined for main effects of expertise during a "land" versus "do not land" decision with the no-decision control condition modeled as baseline. In making landing decisions, High Expertise pilots showed lower activation in the bilateral caudate nucleus (0.97 ± 0.80 compared to Moderate Expertise pilots (1.91 ± 1.16 (p<.05. These findings provide evidence for increased "neural efficiency" in High Expertise pilots relative to Moderate Expertise pilots. During an instrument approach the pilot is engaged in detailed examination of flight instruments while monitoring certain visual references for making landing decisions. The caudate nucleus regulates saccade eye control of gaze, the brain area where the "expertise" effect was observed. These data provide evidence that performing "real world" aviation tasks in an fMRI provide objective data regarding the relative expertise of pilots and brain regions

  9. Active Galactic Nuclei in Groups and Clusters of Galaxies: Detection and Host Morphology

    CERN Document Server

    Arnold, Timothy J; Mulchaey, John S; Berti, Angela; Jeltema, Tesla E

    2009-01-01

    The incidence and properties of Active Galactic Nuclei (AGN) in the field, groups, and clusters can provide new information about how these objects are triggered and fueled, similar to how these environments have been employed to study galaxy evolution. We have obtained new XMM-Newton observations of seven X-ray selected groups and poor clusters with 0.02 10^{41}; M_R2.5}(L_X>10^{41}; M_R

  10. Linking the fate of massive black hole binaries to the active galactic nuclei luminosity function

    CERN Document Server

    Dotti, Massimo; Montuori, Carmen

    2015-01-01

    Massive black hole binaries are naturally predicted in the context of the hierarchical model of structure formation. The binaries that manage to lose most of their angular momentum can coalesce to form a single remnant. In the last stages of this process, the holes undergo an extremely loud phase of gravitational wave emission, possibly detectable by current and future probes. The theoretical effort towards obtaining a coherent physical picture of the binary path down to coalescence is still underway. In this paper, for the first time, we take advantage of observational studies of active galactic nuclei evolution to constrain the efficiency of gas-driven binary decay. Under conservative assumptions we find that gas accretion toward the nuclear black holes can efficiently lead binaries of any mass forming at high redshift (> 2) to coalescence within the current time. The observed "downsizing" trend of the accreting black hole luminosity function further implies that the gas inflow is sufficient to drive light ...

  11. Accretion disk winds in active galactic nuclei: X-ray observations, models, and feedback

    CERN Document Server

    Tombesi, Francesco

    2016-01-01

    Powerful winds driven by active galactic nuclei (AGN) are often invoked to play a fundamental role in the evolution of both supermassive black holes (SMBHs) and their host galaxies, quenching star formation and explaining the tight SMBH-galaxy relations. A strong support of this "quasar mode" feedback came from the recent X-ray observation of a mildly relativistic accretion disk wind in a ultraluminous infrared galaxy (ULIRG) and its connection with a large-scale molecular outflow, providing a direct link between the SMBH and the gas out of which stars form. Spectroscopic observations, especially in the X-ray band, show that such accretion disk winds may be common in local AGN and quasars. However, their origin and characteristics are still not fully understood. Detailed theoretical models and simulations focused on radiation, magnetohydrodynamic (MHD) or a combination of these two processes to investigate the possible acceleration mechanisms and the dynamics of these winds. Some of these models have been dir...

  12. Optimal strategies for observation of active galactic nuclei variability with Imaging Atmospheric Cherenkov Telescopes

    CERN Document Server

    Giomi, Matteo; Maier, Gernot

    2016-01-01

    Variable emission is one of the defining characteristic of active galactic nuclei (AGN). While providing precious information on the nature and physics of the sources, variability is often challenging to observe with time- and field-of-view-limited astronomical observatories such as Imaging Atmospheric Cherenkov Telescopes (IACTs). In this work, we address two questions relevant for the observation of sources characterized by AGN-like variability: what is the most time-efficient way to detect such sources, and what is the observational bias that can be introduced by the choice of the observing strategy when conducting blind surveys of the sky. Different observing strategies are evaluated using simulated light curves and realistic instrument response functions of the Cherenkov Telescope Array (CTA), a future gamma-ray observatory. We show that strategies that makes use of very small observing windows, spread over large periods of time, allows for a faster detection of the source, and are less influenced by the...

  13. A note on periodicity of long-term variations of optical continuum in active galactic nuclei

    CERN Document Server

    Lu, Kai-Xing; Bi, Shao-Lan; Wang, Jian-Min

    2016-01-01

    Graham et al. found a sample of active galactic nuclei (AGNs) and quasars from the Catalina Real-time Transient Survey (CRTS) that have long-term periodic variations in optical continuum, the nature of the periodicity remains uncertain. We investigate the periodic variability characteristics of the sample by testing the relations of the observed variability periods with AGN optical luminosity, black hole mass and accretion rates, and find no significant correlations. We also test the observed periods in several different aspects related to accretion disks surrounding single black holes, such as the Keplerian rotational periods of 5100~\\AA\\ photon-emission regions and self-gravity dominated regions and the precessing period of warped disks. These tests shed new lights on understanding AGN variability in general. Under the assumption that the periodic behavior is associated with SMBHB systems in particular, we compare the separations ($\\mathscr{D}_{\\bullet}$) against characteristic radii of broad-line regions (...

  14. Search of high energy neutrino flares from active galactic nuclei with the IceCube detector

    Energy Technology Data Exchange (ETDEWEB)

    Cruz Silva, Angel Humberto; Bernardini, Elisa [DESY, Platanenallee 6, D 15738 Zeuthen (Germany); Gora, Dariusz [DESY, Platanenallee 6, D 15738 Zeuthen (Germany); Institute of Nuclear Physics PAN, ul. Radzikowskiego 152,31-342 Cracow, Krakow (Poland); Collaboration: IceCube-Collaboration

    2013-07-01

    Active Galactic Nuclei (AGN) are among the best candidates for sources of high energy cosmic rays. One of their properties is the extreme variability in their electromagnetic emission at different wavelengths with flare durations ranging from minutes, in some cases, to several weeks. This photon flares may be correlated with neutrinos emitted from the same source if protons are also accelerated in the AGN relativistic jet. Here we present a new statistical test method to look for neutrino flares from selected AGNs. The method takes into account a list of possible neutrino sources from different categories (FSRQs and BL-Lacs) in a so called stacking approach. The performance and results of the method using IceCube data in its 79 string configuration are presented.

  15. Understanding Active Galactic Nuclei using near-infrared high angular resolution polarimetry II: Preliminary results

    Science.gov (United States)

    Marin, F.; Grosset, L.; Goosmann, R.; Gratadour, D.; Rouan, D.; Clénet, Y.; Pelat, D.; Rojas Lobos, P. A.

    2016-12-01

    In this second research note of a series of two, we present the first near-infrared results we obtained when modeling Active Galactic Nuclei (AGN). Our first proceedings showed the comparison between the MontAGN and STOKES Monte Carlo codes. Now we use our radiative transfer codes to simulate the polarization maps of a prototypical, NGC 1068-like, type-2 radio-quiet AGN. We produced high angular resolution infrared (1 μm) polarization images to be compared with recent observations in this wavelength range. Our preliminary results already show a good agreement between the models and observations but cannot account for the peculiar linear polarization angle of the torus such as observed. tet{Gratadour2015} found a polarization position angle being perpendicular to the bipolar outflows axis. Further work is needed to improve the models by adding physical phenomena such as dichroism and clumpiness.

  16. Magnetically elevated accretion disks in active galactic nuclei: broad emission line regions and associated star formation

    CERN Document Server

    Begelman, Mitchell C

    2016-01-01

    We propose that the accretion disks fueling active galactic nuclei are supported vertically against gravity by a strong toroidal ($\\phi-$direction) magnetic field that develops naturally as the result of an accretion disk dynamo. The magnetic pressure elevates most of the gas carrying the accretion flow at $R$ to large heights $z > 0.1 R$ and low densities, while leaving a thin dense layer containing most of the mass --- but contributing very little accretion --- around the equator. We show that such a disk model leads naturally to the formation of a broad emission line region through thermal instability. Extrapolating to larger radii, we demonstrate that local gravitational instability and associated star formation are strongly suppressed compared to standard disk models for AGN, although star formation in the equatorial zone is predicted for sufficiently high mass supply rates. This new class of accretion disk models thus appears capable of resolving two longstanding puzzles in the theory of AGN fueling: th...

  17. Understanding Active Galactic Nuclei using near-infrared high angular resolution polarimetry II: Preliminary results

    CERN Document Server

    Marin, F; Goosmann, R; Gratadour, D; Rouan, D; Clénet, Y; Pelat, D; Lobos, P Andrea Rojas

    2016-01-01

    In this second research note of a series of two, we present the first near-infrared results we obtained when modeling Active Galactic Nuclei (AGN). Our first proceedings showed the comparison between the MontAGN and STOKES Monte Carlo codes. Now we use our radiative transfer codes to simulate the polarization maps of a prototypical, NGC 1068-like, type-2 radio-quiet AGN. We produced high angular resolution infrared (1 micron) polarization images to be compared with recent observations in this wavelength range. Our preliminary results already show a good agreement between the models and observations but cannot account for the peculiar linear polarization angle of the torus such as observed. Gratadour et al. 2015 found a polarization position angle being perpendicular to the bipolar outflows axis. Further work is needed to improve the models by adding physical phenomena such as dichroism and clumpiness.

  18. The Relationship Between Luminosity and Broad-Line Region Size in Active Galactic Nuclei

    DEFF Research Database (Denmark)

    Kaspi, Shai; Maoz, Dan; Netzer, Hagai;

    2005-01-01

    We reinvestigate the relationship between the characteristic broad-line region size (R_blr) and the Balmer emission-line, X-ray, UV, and optical continuum luminosities. Our study makes use of the best available determinations of R_blr for a large number of active galactic nuclei (AGNs) from...... of analysis, our results are generally consistent. Assuming a power-law relation R_blr \\propto L^\\alpha, we find the mean best-fitting \\alpha is about 0.67+/-0.05 for the optical continuum and the broad H\\beta luminosity, about 0.56+/-0.05 for the UV continuum luminosity, and about 0.70+/-0.14 for the X...

  19. A Polarimetric Method for Measuring Black Hole Masses in Active Galactic Nuclei

    CERN Document Server

    Piotrovich, M Yu; Silant'ev, N A; Natsvlishvili, T M; Buliga, S D

    2015-01-01

    The structure of the broad emission line region (BLR) in active galactic nuclei (AGN) remains unclear. We test in this paper a flattened configuration model for BLR. The virial theorem, by taking into account the disc shape of BLR, allows us to get a direct connection between the mass of a supermassive black hole (SMBH) and the inclination angle of the accretion flow. The inclination angle itself is derived from the spectropolarimetric data on broad emission lines using the theory for the generation of polarized radiation developed by Sobolev and Chandrasekhar. As the result, the new estimates of SMBH masses in AGN with measured polarization of BLR are presented. It is crucial that the polarimetric data allow also to determine the value of the virial coefficient that is essential for determining SMBH masses.

  20. Active Galactic Nuclei - the Physics of Individual Sources and the Cosmic History of Formation and Evolution

    CERN Document Server

    Treister, Ezequiel

    2013-01-01

    In this paper we give a brief review of the astrophysics of active galactic nuclei (AGN). After a general introduction motivating the study of AGNs, we discuss our present understanding of the inner workings of the central engines, most likely accreting black holes with masses between a million and ten billion solar masses. We highlight recent results concerning the jets (collimated outflows) of AGNs derived from X-ray observations (Chandra) of kpc-scale jets and gamma-ray observations of AGNs (Fermi, Cherenkov telescopes) with jets closely aligned with the lines of sight (blazars), and discuss the interpretation of these observations. Subsequently, we summarize our knowledge about the cosmic history of AGN formation and evolution. We conclude with a description of upcoming observational opportunities.

  1. Probing the circumgalactic medium of active galactic nuclei with background quasars

    CERN Document Server

    Kacprzak, Glenn G; Murphy, Michael T; Cooke, Jeff

    2014-01-01

    We performed a detailed study of the extended cool gas, traced by MgII absorption [$W_r(2796)\\geq0.3$~{\\AA}], surrounding 14 narrow-line active galactic nuclei (AGNs) at 0.1250$ km/s, indicating outflowing gas. The 2/2 intrinsic MgII systems have outflow velocities a factor of $\\sim4$ higher than the NaID outflow velocities. Our results are consistent with AGN-driven outflows destroying the cool gas within their halos, which dramatically decreases their cool gas covering fraction, while star-burst driven winds are expelling cool gas into their circumgalactic media (CGM). This picture appears contrary to quasar--quasar pair studies which show that the quasar CGM contains significant amounts of cool gas whereas intrinsic gas found `down-the-barrel' of quasars reveals no cool gas. We discuss how these results are complementary and provide support for the AGN unified model.

  2. $Ly \\alpha$ Fluorescent Excitation of FeII in Active Galactic Nuclei

    CERN Document Server

    Sigut, T A A; Pradhan, Anil K.

    1998-01-01

    We have calculated FeII emission line strengths for Active Galactic Nuclei Broad-Line Regions using precise radiative transfer and Iron Project atomic data. We improve the treatment of all previously considered excitation mechanisms for the FeII emission, continuum fluorescence, collisional excitation, fluorescence by self-overlap among the iron lines, and fluorescent excitation by Lyman-alpha. We demonstrate that Lyman-alpha fluorescence is of fundamental importance in determining the strength of the FeII emission. In addition to enhancing the ultraviolet and optical FeII flux, Lyman-alpha fluorescence also results in significant near-infrared FeII emission in the 8500-9500 Angstrom wavelength range. New observations are suggested to probe this effect in strong FeII emitting quasars.

  3. Determination of magnetic fields in broad line region of active galactic nuclei from polarimetric observations

    Science.gov (United States)

    Piotrovich, Mikhail; Silant'ev, Nikolai; Gnedin, Yuri; Natsvlishvili, Tinatin; Buliga, Stanislava

    2017-02-01

    Magnetic fields play an important role in confining gas clouds in the broad line region (BLR) of active galactic nuclei (AGN) and in maintaining the stability of these clouds. Without magnetic fields the clouds would not be stable, and soon after their formation they would expand and disperse. We show that the strength of the magnetic field can be derived from the polarimetric observations. Estimates of magnetic fields for a number of AGNs are based on the observed polarization degrees of broad Hα lines and nearby continuum. The difference between their values allows us to estimate the magnetic field strength in the BLR using the method developed by Silant'ev et al. (2013). Values of magnetic fields in BLR for a number of AGNs have been derived.

  4. Disk-Corona Model in Active Galactic Nuclei:an Observational Test

    Institute of Scientific and Technical Information of China (English)

    Fang Yang; Chen Hu; Yan-Mei Chen; Jian-Min Wang

    2007-01-01

    We compiled a sample of 98 radio-quiet active galactic nuclei observed by ASCA,Chandra.XMM-Newton,INTEGRAL and Swift with the aim of testing the formation of hot corona and the magnetic shear stress operating in a disk-corona system.We found a strong correlation between the hard X-ray luminosity,bolometric luminosity LBol and Eddington luminosity LEdd.in the sense that the fraction f of hard X-ray to the bolometric luminosity is inversely proportional to the Eddington ratio.This correlation favors the shear stress tensor being of the form of trφ∝ Pgas,with which the disk-corona structure is stable.

  5. Radiation-driven outflows from and radiative support in dusty tori of active galactic nuclei

    CERN Document Server

    Chan, Chi-Ho

    2015-01-01

    Substantial evidence points to dusty, geometrically thick tori obscuring the central engines of active galactic nuclei, but so far no mechanism satisfactorily explains why cool dust in the torus remains in a puffy geometry. Infrared (IR) radiation pressure on dust can play a significant role in shaping the torus, yet the separation of hydrodynamic evolution from radiative transfer (RT) in previous work on radiation-supported tori precluded a self-consistent picture. Here we present radiative hydrodynamics simulations of an initially smooth torus; we solve the hydrodynamics equations, the time-dependent multi-angle group IR RT equation, and the time-independent ultraviolet (UV) RT equation. IR radiation is highly anisotropic, leaving primarily through the central hole of the torus. The inner edge of the torus exhibits a break in axisymmetry under the influence of radiation and differential rotation. In addition, UV radiation pressure on dust launches a strong wind along the inner edge of the torus with speed $...

  6. The Main Sequences of Starforming Galaxies and Active Galactic Nuclei at High Redshift

    CERN Document Server

    Mancuso, Claudia; Shi, J; Gonzàlez-Nuevo, J; Bèthermin, M; Danese, L

    2016-01-01

    We provide a novel, unifying physical interpretation on the origin, the average shape, the scatter, and the cosmic evolution for the main sequences of starforming galaxies and active galactic nuclei at high redshift z $\\gtrsim$ 1. We achieve this goal in a model-independent way by exploiting: (i) the redshift-dependent SFR functions based on the latest UV/far-IR data from HST/Herschel, and re- lated statistics of strong gravitationally lensed sources; (ii) deterministic evolutionary tracks for the history of star formation and black hole accretion, gauged on a wealth of multiwavelength observations including the observed Eddington ratio distribution. We further validate these ingredients by showing their consistency with the observed galaxy stellar mass functions and AGN bolometric luminosity functions at different redshifts via the continuity equation approach. Our analysis of the main sequence for high-redshift galaxies and AGNs highlights that the present data are consistently interpreted in terms of an in...

  7. Activation of D2 dopamine receptor-expressing neurons in the nucleus accumbens increases motivation.

    Science.gov (United States)

    Soares-Cunha, Carina; Coimbra, Barbara; David-Pereira, Ana; Borges, Sonia; Pinto, Luisa; Costa, Patricio; Sousa, Nuno; Rodrigues, Ana J

    2016-06-23

    Striatal dopamine receptor D1-expressing neurons have been classically associated with positive reinforcement and reward, whereas D2 neurons are associated with negative reinforcement and aversion. Here we demonstrate that the pattern of activation of D1 and D2 neurons in the nucleus accumbens (NAc) predicts motivational drive, and that optogenetic activation of either neuronal population enhances motivation in mice. Using a different approach in rats, we further show that activating NAc D2 neurons increases cue-induced motivational drive in control animals and in a model that presents anhedonia and motivational deficits; conversely, optogenetic inhibition of D2 neurons decreases motivation. Our results suggest that the classic view of D1-D2 functional antagonism does not hold true for all dimensions of reward-related behaviours, and that D2 neurons may play a more prominent pro-motivation role than originally anticipated.

  8. The innermost regions of relativistic jets and their magnetic fields in radio-loud Active Galactic Nuclei

    CERN Document Server

    Donnarumma, I; Costamante, L; D'Ammando, F; Giovannini, G; Giommi, P; Giroletti, M; Grandi, P; Jorstad, S G; Marscher, A P; Orienti, M; Pacciani, L; Savolainen, T; Stamerra, A; Tavecchio, F; Torresi, E; Tramacere, A; Turriziani, S; Vercellone, S; Zech, A

    2015-01-01

    This is a White Paper in support of the mission concept of the Large Observatory for X-ray Timing (LOFT), proposed as a medium-sized ESA mission. We discuss the potential of LOFT for the study of radio-loud Active Galactic Nuclei. For a summary, we refer to the paper.

  9. Line and continuum emission from the outer regions of accretion discs in active galactic nuclei. V. Detailed computational results

    Energy Technology Data Exchange (ETDEWEB)

    Dumont, A.M. (Observatoire de Paris, Section de Meudon, 92 (FR)); Collin-Souffrin, S. (Centre National de la Recherche Scientifique, 75 - Paris (FR). Inst. d' Astrophysique)

    1990-04-01

    This paper completes the results concerning the structure of the outer regions of accretion discs in Active Galactic Nuclei, and of their line emission spectra (profiles and line intensities). The computational method has been described in a series of previous papers.

  10. The structure of the broad-line region in active galactic nuclei. I. Reconstructed velocity-delay maps

    DEFF Research Database (Denmark)

    Grier, C.J.; Peterson, B.M.; Pogge, R.W.;

    2013-01-01

    We present velocity-resolved reverberation results for five active galactic nuclei. We recovered velocity-delay maps using the maximum entropy method for four objects: Mrk 335, Mrk 1501, 3C 120, and PG 2130+099. For the fifth, Mrk 6, we were only able to measure mean time delays in different...

  11. Characterization of ryanodine receptor type 1 single channel activity using "on-nucleus" patch clamp.

    Science.gov (United States)

    Wagner, Larry E; Groom, Linda A; Dirksen, Robert T; Yule, David I

    2014-08-01

    In this study, we provide the first description of the biophysical and pharmacological properties of ryanodine receptor type 1 (RyR1) expressed in a native membrane using the on-nucleus configuration of the patch clamp technique. A stable cell line expressing rabbit RyR1 was established (HEK-RyR1) using the FLP-in 293 cell system. In contrast to untransfected cells, RyR1 expression was readily demonstrated by immunoblotting and immunocytochemistry in HEK-RyR1 cells. In addition, the RyR1 agonists 4-CMC and caffeine activated Ca(2+) release that was inhibited by high concentrations of ryanodine. On nucleus patch clamp was performed in nuclei prepared from HEK-RyR1 cells. Raising the [Ca(2+)] in the patch pipette resulted in the appearance of a large conductance cation channel with well resolved kinetics and the absence of prominent subconductance states. Current versus voltage relationships were ohmic and revealed a chord conductance of ∼750pS or 450pS in symmetrical 250mM KCl or CsCl, respectively. The channel activity was markedly enhanced by caffeine and exposure to ryanodine resulted in the appearance of a subconductance state with a conductance ∼40% of the full channel opening with a Po near unity. In total, these properties are entirely consistent with RyR1 channel activity. Exposure of RyR1 channels to cyclic ADP ribose (cADPr), nicotinic acid adenine dinucleotide phosphate (NAADP) or dantrolene did not alter the single channel activity stimulated by Ca(2+), and thus, it is unlikely these molecules directly modulate RyR1 channel activity. In summary, we describe an experimental platform to monitor the single channel properties of RyR channels. We envision that this system will be influential in characterizing disease-associated RyR mutations and the molecular determinants of RyR channel modulation.

  12. Optogenetic stimulation of the cochlear nucleus using channelrhodopsin-2 evokes activity in the central auditory pathway

    Science.gov (United States)

    Darrow, Keith N.; Slama, Michaël C. C.; Owoc, Maryanna; Kozin, Elliott; Hancock, Kenneth; Kempfle, Judith; Edge, Albert; Lacour, Stephanie; Boyden, Edward; Polley, Daniel; Brown, M. Christian; Lee, Daniel J.

    2016-01-01

    Optogenetics has become an important research tool and is being considered as the basis for several neural prostheses. However, few studies have applied optogenetics to the auditory brainstem. This study explored whether optical activation of the cochlear nucleus (CN) elicited responses in neurons in higher centers of the auditory pathway, and it measured the evoked response to optical stimulation. Viral-mediated gene transfer was used to express channelrhodopsin-2 (ChR2) in the mouse CN. Blue light was delivered via an optical fiber placed near the surface of the infected CN and recordings were made in higher-level centers. Optical stimulation evoked excitatory multiunit spiking activity throughout the tonotopic axis of central nucleus of the inferior colliculus (IC) and the auditory cortex (Actx). The pattern and magnitude of IC activity elicited by optical stimulation was comparable to that obtained with a 50 dB SPL acoustic click stimulus. This broad pattern of activity was consistent with histological confirmation of GFP label of cell bodies and axons throughout the CN. Increasing pulse rates up to 320 Hz did not significantly affect threshold or bandwidth of the IC responses, but rates higher than 50 Hz resulted in desynchronized activity. Optical stimulation also evoked an auditory brainstem response, which had a simpler waveform than the response to acoustic stimulation. Control cases showed no responses to optical stimulation. These data suggest that optogenetic control of central auditory neurons is feasible, but opsins with faster channel kinetics will be necessary to convey information in rates typical of many auditory signals. PMID:25481416

  13. Optogenetic stimulation of the cochlear nucleus using channelrhodopsin-2 evokes activity in the central auditory pathways.

    Science.gov (United States)

    Darrow, Keith N; Slama, Michaël C C; Kozin, Elliott D; Owoc, Maryanna; Hancock, Kenneth; Kempfle, Judith; Edge, Albert; Lacour, Stephanie; Boyden, Edward; Polley, Daniel; Brown, M Christian; Lee, Daniel J

    2015-03-02

    Optogenetics has become an important research tool and is being considered as the basis for several neural prostheses. However, few studies have applied optogenetics to the auditory brainstem. This study explored whether optical activation of the cochlear nucleus (CN) elicited responses in neurons in higher centers of the auditory pathway and whether it elicited an evoked response. Viral-mediated gene transfer was used to express channelrhodopsin-2 (ChR2) in the mouse CN. Blue light was delivered via an optical fiber placed near the surface of the infected CN and recordings were made in higher-level centers. Optical stimulation evoked excitatory multiunit spiking activity throughout the tonotopic axis of the central nucleus of the inferior colliculus (IC) and the auditory cortex (Actx). The pattern and magnitude of IC activity elicited by optical stimulation was comparable to that obtained with a 50dB SPL acoustic click. This broad pattern of activity was consistent with histological confirmation of green fluorescent protein (GFP) label of cell bodies and axons throughout the CN. Increasing pulse rates up to 320Hz did not significantly affect threshold or bandwidth of the IC responses, but rates higher than 50Hz resulted in desynchronized activity. Optical stimulation also evoked an auditory brainstem response, which had a simpler waveform than the response to acoustic stimulation. Control cases showed no responses to optical stimulation. These data suggest that optogenetic control of central auditory neurons is feasible, but opsins with faster channel kinetics may be necessary to convey information at rates typical of many auditory signals.

  14. Sulfated cholecystokinin-8 activates phospho-mTOR immunoreactive neurons of the paraventricular nucleus in rats

    Science.gov (United States)

    Frommelt, Lisa; Inhoff, Tobias; Lommel, Reinhardt; Stengel, Andreas; Taché, Yvette; Grötzinger, Carsten; Bannert, Norbert; Wiedenmann, Bertram; Klapp, Burghard F.; Kobelt, Peter

    2014-01-01

    The serin/threonin-kinase, mammalian target of rapamycin (mTOR) was detected in the arcuate nucleus (ARC) and paraventricular nucleus of the hypothalamus (PVN) and suggested to play a role in the integration of satiety signals. Since cholecystokinin (CCK) plays a role in the short-term inhibition of food intake and induces c-Fos in PVN neurons, the aim was to determine whether intraperitoneally injected CCK-8S affects the neuronal activity in cells immunoreactive for phospho-mTOR in the PVN. Ad libitum fed male Sprague-Dawley rats received 6 or 10 μg/kg CCK-8S or 0.15 M NaCl ip (n=4/group). The number of c-Fosimmunoreactive (ir) neurons was assessed in the PVN, ARC and in the nucleus of the solitary tract (NTS). CCK-8S increased the number of c-Fos-ir neurons in the PVN (6 μg: 103 ± 13 vs. 10 μg: 165 ± 14 neurons/section; p<0.05) compared to vehicle treated rats (4 ± 1, p<0.05), but not in the ARC. CCK-8S also dose-dependently increased the number of c-Fos neurons in the NTS. Staining for phospho-mTOR and c-Fos in the PVN showed a dose-dependent increase of activated phospho-mTOR neurons (17 ± 3 vs. 38 ± 2 neurons/section; p<0.05), while no activated phospho-mTOR neurons were observed in the vehicle group. Triple staining in the PVN showed activation of phospho-mTOR neurons co-localized with oxytocin, corresponding to 9.8 ± 3.6% and 19.5 ± 3.3% of oxytocin neurons respectively. Our observations indicate that peripheral CCK-8S activates phospho-mTOR neurons in the PVN and suggest that phospho-mTOR plays a role in the mediation of CCK-8S's anorexigenic effects. PMID:20933028

  15. Optical Counterparts of Undetermined Type -Ray Active Galactic Nuclei with Blazar-Like Spectral Energy Distributions

    Indian Academy of Sciences (India)

    Giovanni La Mura; Graziano Chiaro; Stefano Ciroi; Piero Rafanelli; David Salvetti; Marco Berton; Valentina Cracco; Fermi-LAT collaboration

    2015-12-01

    During its first four years of scientific observations, the Fermi Large Area Telescope (Fermi-LAT) detected 3033 -ray sources above a 4 significance level. Although most of the extra-galactic sources are active galactic nuclei (AGN) of the blazar class, other families of AGNs are observed too, while a still high fraction of detections (∼30%) remains with uncertain association or classification. According to the currently accepted interpretation, the AGN -ray emission arises from inverse Compton (IC) scattering of low energy photons by relativistic particles confined in a jet, which, in the case of blazars, is oriented very close to our line-of-sight. Taking advantage of data from radio and X-ray wavelengths, which we expect to be produced together with -rays, providing a much better source localization potential, we focused our attention on a sample of -ray Blazar Candidates of Undetermined type (BCUs), starting a campaign of optical spectroscopic observations. The main aims of our investigation include a census of the AGN families that contribute to -ray emission and a study of their redshift distribution, with the subsequent implications on the intrinsic source power. We furthermore analyze which -ray properties can better constrain the nature of the source, thus helping in the study of objects not yet associated with a reliable low frequency counterpart. Here we report on the instruments and techniques used to identify the optical counterparts of -ray sources, we give an overview on the status of our work, and we discuss the implications of a large scale study of -ray emitting AGNs.

  16. Ionized Absorbers in Active Galactic Nuclei and Very Steap Soft X-Ray Quasars

    Science.gov (United States)

    Fiore, Fabrizio; White, Nicholas (Technical Monitor)

    2000-01-01

    Steep soft X-ray (0.1-2 keV) quasars share several unusual properties: narrow Balmer lines, strong Fe II emission, large and fast X-ray variability, and a rather steep 2-10 keV spectrum. These intriguing objects have been suggested to be the analogues of Galactic black hole candidates in the high, soft state. We present here results from ASCA observations for two of these quasars: NAB 0205 + 024 and PG 1244 + 026. Both objects show similar variations (factor of approximately 2 in 10 ks), despite a factor of approximately 10 difference in the 0.5-10 keV luminosity (7.3 x 10(exp 43) erg/s for PG 1244 + 026 and 6.4 x 10(exp 44) erg/s for NAB 0205 + 024, assuming isotropic emission, H(sub 0) = 50.0 and q(sub 0) = 0.0). The X-ray continuum of the two quasars flattens by 0.5-1 going from the 0.1-2 keV band towards higher energies, strengthening recent results on another half-dozen steep soft X-ray active galactic nuclei. PG 1244 + 026 shows a significant feature in the '1-keV' region, which can be described either as a broad emission line centered at 0.95 keV (quasar frame) or as edge or line absorption at 1.17 (1.22) keV. The line emission could be a result of reflection from a highly ionized accretion disc, in line with the view that steep soft X-ray quasars are emitting close to the Eddington luminosity. Photoelectric edge absorption or resonant line absorption could be produced by gas outflowing at a large velocity (0.3-0.6 c).

  17. Leptin signaling in the nucleus tractus solitarii increases sympathetic nerve activity to the kidney.

    Science.gov (United States)

    Mark, Allyn L; Agassandian, Khristofor; Morgan, Donald A; Liu, Xuebo; Cassell, Martin D; Rahmouni, Kamal

    2009-02-01

    The hypothalamic arcuate nucleus was initially regarded as the principal site of leptin action, but there is increasing evidence for functional leptin receptors in extrahypothalamic sites, including the nucleus tractus solitarii (NTS). We demonstrated previously that arcuate injection of leptin increases sympathetic nerve activity (SNA) to brown adipose tissue and kidney. In this study, we tested the hypothesis that leptin signaling in the NTS affects sympathetic neural outflow. Using a stereotaxic device in anesthetized rats, we microinjected leptin (0.25 to 1.00 microg) or saline into the NTS while recording SNA to kidney and brown adipose tissue. Microinjection of leptin into the commissural and medial subnuclei of the caudal NTS at the level of the area postrema in Sprague-Dawley rats produced a dose-related increase in renal SNA (+112+/-15% with leptin 1 microg; n=7; Pleptin receptors, because it was not observed in Zucker obese rats that have a missense mutation in the leptin receptor. Rostral NTS injection of leptin failed to increase SNA, indicating that leptin signaling in the NTS is probably confined to the caudal NTS at the level of the area postrema. In summary, this study demonstrates that leptin signaling in the caudal NTS increases SNA to the kidney but not to the brown adipose tissue. The study strengthens the concept of a distributed brain network of leptin action and demonstrates that these distributed brain sites can mediate contrasting sympathetic responses to leptin.

  18. Constraining the size of the dusty torus in Active Galactic Nuclei: An Optical/Infrared Reverberation Lag Study

    Science.gov (United States)

    Vazquez, Billy

    The dusty torus is the key component in the Active Galactic Nuclei (AGN) Unification Scheme that explains the spectroscopic differences between Seyfert galaxies of types 1 and 2. The torus dust is heated by the nuclear source and emits the absorbed energy in the infrared (IR); but because of light travel times, the torus IR emission responds to variations of the nuclear ultraviolet/optical continuum with a delay that corresponds to the size of the emitting region. The results from a mid-infrared (MIR) monitoring campaign using the Spitzer Space Telescope and optical ground-based telescopes (B and V band imaging), which spanned over 2 years and covered a sample of 12 Seyfert galaxies, are presented. The aim was to constrain the distances from the nucleus to the regions in the torus emitting at wavelengths of 3.6 microm and 4.5 microm. MIR light curves showing the variability characteristics of these AGN are presented and the effects of photometric uncertainties on the time-series analysis of the light curves are discussed. Significant variability was observed in the IR light curves of 10 of 12 objects, with relative amplitudes ranging from ˜10% to ˜100% from their mean flux. The "reverberation lags" between the 3.6 microm and 4.5 microm IR bands were determined for the entire sample and between the optical and MIR bands for NGC6418. In NGC6418, the 3.6 microm and 4.5 microm fluxes lagged behind those of the optical continuum by 47.5+2.0-1.9) days and 62.5+2.5-2.9 days, respectively. This is consistent with the inferred lower limit to the sublimation radius for pure graphite grains at T=1800 K but smaller by a factor of 2 than the lower limit for dust grains with a "standard" interstellar medium (ISM) composition. There is evidence that the lags increased following approximately by a factor of 2 increase in luminosity, consistent with an increase in the sublimation radius.

  19. The role of galactic cold gas in low-level supermassive black hole activity

    CERN Document Server

    Alfvin, Erik D; Haynes, Martha P; Gallo, Elena; Giovanelli, Riccardo; Koopmann, Rebecca A; Hodges-Kluck, Edmund; Cannon, John M

    2016-01-01

    The nature of the relationship between low-level supermassive black hole (SMBH) activity and galactic cold gas, if any, is currently unclear. Here, we test whether central black holes may feed at higher rates in gas-rich galaxies, probing SMBH activity well below the active regime down to Eddington ratios of ~1e-7. We use a combination of radio data from the ALFALFA survey and from the literature, along with archival X-ray flux measurements from the Chandra X-ray observatory, to investigate this potential relationship. We construct a sample of 129 late-type galaxies, with MB<-18 out to 50 Mpc, that have both HI masses and sensitive X-ray coverage. Of these, 75 host a nuclear X-ray source, a 58% detection fraction. There is a highly significant correlation between nuclear X-ray luminosity LX and galaxy stellar mass Mstar with a slope of 1.7+/-0.3, and a tentative correlation (significant at the 2.8 sigma level) between LX and HI gas mass MHI. However, a joint fit to LX as a function of both Mstar and MHI fi...

  20. A survey of dual active galactic nuclei in simulations of galaxy mergers: frequency and properties

    CERN Document Server

    Capelo, Pedro R; Volonteri, Marta; Mayer, Lucio; Bellovary, Jillian M; Shen, Sijing

    2016-01-01

    We investigate the simultaneous triggering of active galactic nuclei (AGN) in merging galaxies, using a large suite of high-resolution hydrodynamical simulations. We compute dual-AGN observability time-scales using bolometric, X-ray, and Eddington-ratio thresholds, confirming that dual activity from supermassive black holes (BHs) is generally higher at late pericentric passages, before a merger remnant has formed, especially at high luminosities. For typical minor and major mergers, dual activity lasts ~20-70 and ~100-160 Myr, respectively. We also explore the effects of X-ray obscuration from gas, finding that the dual-AGN time decreases at most by a factor of ~2, and of contamination from star formation. Using projected separations and velocity differences rather than three-dimensional quantities can decrease the dual-AGN time-scales by up to ~4, and we apply filters which mimic current observational-resolution limitations. In agreement with observations, we find that, for a sample of major mergers hosting ...

  1. Encoding of social state information by neuronal activities in the macaque caudate nucleus.

    Science.gov (United States)

    Santos, Gustavo S; Nagasaka, Yasuo; Fujii, Naotaka; Nakahara, Hiroyuki

    2012-01-01

    Social animals adjust their behavior according to social relationships and momentary circumstances. Dominant-submissive relationships modulate, but do not completely determine, their competitive behaviors. For example, a submissive monkey's decision to retrieve food depends not only on the presence of dominant partners but also on their observed behavior. Thus, behavioral expression requires a dynamic evaluation of reward outcome and momentary social states. The neural mechanisms underlying this evaluation remain elusive. The caudate nucleus (CN) plays a pivotal role in representing reward expectation and translating it into action selection. To investigate whether their activities encode social state information, we recorded from CN neurons in monkeys while they performed a competitive food-grab task against a dominant competitor. We found two groups of CN neurons: one primarily responded to reward outcome, while the other primarily tracked the monkey's social state. These social state-dependent neurons showed greater activity when the monkeys freely retrieved food without active challenges from the competitor and reduced activity when the monkeys were in a submissive state due to the competitor's active behavior. These results indicate that different neuronal activities in the CN encode social state information and reward-related information, which may contribute to adjusting competitive behavior in dynamic social contexts.

  2. Fractal patterns of neural activity exist within the suprachiasmatic nucleus and require extrinsic network interactions.

    Science.gov (United States)

    Hu, Kun; Meijer, Johanna H; Shea, Steven A; vanderLeest, Henk Tjebbe; Pittman-Polletta, Benjamin; Houben, Thijs; van Oosterhout, Floor; Deboer, Tom; Scheer, Frank A J L

    2012-01-01

    The mammalian central circadian pacemaker (the suprachiasmatic nucleus, SCN) contains thousands of neurons that are coupled through a complex network of interactions. In addition to the established role of the SCN in generating rhythms of ~24 hours in many physiological functions, the SCN was recently shown to be necessary for normal self-similar/fractal organization of motor activity and heart rate over a wide range of time scales--from minutes to 24 hours. To test whether the neural network within the SCN is sufficient to generate such fractal patterns, we studied multi-unit neural activity of in vivo and in vitro SCNs in rodents. In vivo SCN-neural activity exhibited fractal patterns that are virtually identical in mice and rats and are similar to those in motor activity at time scales from minutes up to 10 hours. In addition, these patterns remained unchanged when the main afferent signal to the SCN, namely light, was removed. However, the fractal patterns of SCN-neural activity are not autonomous within the SCN as these patterns completely broke down in the isolated in vitro SCN despite persistence of circadian rhythmicity. Thus, SCN-neural activity is fractal in the intact organism and these fractal patterns require network interactions between the SCN and extra-SCN nodes. Such a fractal control network could underlie the fractal regulation observed in many physiological functions that involve the SCN, including motor control and heart rate regulation.

  3. The Effects of Disc Winds on the Spectrum and Black Hole Growth Rate of Active Galactic Nuclei

    OpenAIRE

    Slone, Oren; Netzer, Hagai

    2012-01-01

    Several properties of the standard alpha-disc model for active galactic nuclei (AGN) are not entirely consistent with AGN observations. As well as such discrepencies, observations show evidence for the existence of high mass outflow winds originating from the vicinity of the active black hole (BH). Such winds may originate from various parts of the disc and could change the local accretion rate which should alter the emitted spectral energy distribution (SED) and affect the global disc lumino...

  4. The Near-Infrared Coronal Line Spectrum of 54 Nearby Active Galactic Nuclei

    CERN Document Server

    Rodríguez-Ardila, A; Portilla, J G; Tejeiro, J M

    2011-01-01

    (Abridge) The relationship between coronal line (CL) emission and nuclear activity in active galactic nuclei (AGNs) is analyzed, for the first time, based on NIR spectra. The 8 CLs studied, of Si, S, Fe, Al and Ca elements and corresponding to ionization potentials (IP) in the range 125-450 eV, are detected in 67% (36 AGNs) of the sample. The four most frequent CLs - [SiVI] 19630\\AA, [SVIII] 9913\\AA, [SIX] 12520\\AA\\ and [SiX] 14320\\AA, - display a narrow range in luminosity, with most lines located in the interval logL 39-40 erg/s. We found that the non-detection is largely associated with either a lost of spatial resolution or increasing object distance. Yet, there are AGNs where the lack of CLs may be genuine and reflect an AGN ionising continuum lacking photons below a few keV. The FWHM of the lines profiles increases with increasing IP up to energies around 300 eV, where a maximum in the FWHM is reached. For higher IP lines, the FWHM remains nearly constant or decreases with increasing IP. We ascribe this...

  5. The Evolution of Active Galactic Nuclei in Clusters of Galaxies from the Dark Energy Survey

    CERN Document Server

    Bufanda, E; Jeltema, T E; Rykoff, E S; Rozo, E; Martini, P; Abbott, T M C; Abdalla, F B; Allam, S; Banerji, M; Benoit-Levy, A; Bertin, E; Brooks, D; Rosell, A Carnero; Kind, M Carrasco; Carretero, J; Cunha, C E; da Costa, L N; Desai, S; Diehl, H T; Dietrich, J P; Evrard, A E; Neto, A Fausti; Flaugher, B; Frieman, J; Gerdes, D W; Goldstein, D A; Gruen, D; Gruendl, R A; Gutierrez, G; Honscheid, K; James, D J; Kuehn, K; Kuropatkin, N; Lima, M; Maia, M A G; Marshall, J L; Melchior, P; Miquel, R; Mohr, J J; Ogando, R; Plazas, A A; Romer, A K; Rooney, P; Sanchez, E; Santiago, B; Scarpine, V; Sevilla-Noarbe, I; Smith, R C; Soares-Santos, M; Sobreira, F; Suchyta, E; Tarle, G; Thomas, D; Tucker, D L; Walker, A R

    2016-01-01

    The correlation between active galactic nuclei (AGN) and environment provides important clues to AGN fueling and the relationship of black hole growth to galaxy evolution. In this paper, we analyze the fraction of galaxies in clusters hosting AGN as a function of redshift and cluster richness for X-ray detected AGN associated with clusters of galaxies in Dark Energy Survey (DES) Science Verification data. The present sample includes 33 AGN with L_X > 10^43 ergs s^-1 in non-central, host galaxies with luminosity greater than 0.5 L* from a total sample of 432 clusters in the redshift range of 0.10.7. This result is in good agreement with previous work and parallels the increase in star formation in cluster galaxies over the same redshift range. However, the AGN fraction in clusters is observed to have no significant correlation with cluster mass. Future analyses with DES Year 1 and 2 data will be able to clarify whether AGN activity is correlated to cluster mass and will tightly constrain the relationship betwe...

  6. Binary Active Galactic Nuclei in Stripe 82: Constraints on Synchronized Black Hole Accretion in Major Mergers

    CERN Document Server

    Fu, Hai; Myers, A D; Djorgovski, S G; Yan, Lin

    2015-01-01

    Representing simultaneous black hole accretion during a merger, binary active galactic nuclei (AGNs) could provide valuable observational constraints to models of galaxy mergers and AGN triggering. High-resolution radio interferometer imaging offers a promising method to identify a large and uniform sample of binary AGNs, because it probes a generic feature of nuclear activity and is free from dust obscuration. Our previous search yielded 52 strong candidates of kpc-scale binaries over the 92 deg^2 of the Sloan Digital Sky Survey (SDSS) Stripe 82 area with 2"-resolution Very Large Array (VLA) images. Here we present 0.3"-resolution VLA 6 GHz observations for six candidates that have complete optical spectroscopy. The new data confirm the binary nature of four candidates and identify the other two as line-of-sight projections of radio structures from single AGNs. The four binary AGNs at z ~ 0.1 reside in major mergers with projected separations of 4.2-12 kpc. Optical spectral modeling shows that their hosts ha...

  7. The optical emission lines of type 1 X-ray bright Active Galactic Nuclei

    CERN Document Server

    La Mura, G; Ciroi, S; Cracco, V; Di Mille, F; Rafanelli, P

    2013-01-01

    A strong X-ray emission is one of the defining signatures of nuclear activity in galaxies. According to the Unified Model for Active Galactic Nuclei (AGN), both the X-ray radiation and the prominent broad emission lines, characterizing the optical and UV spectra of Type 1 AGNs, are originated in the innermost regions of the sources, close to the Super Massive Black Holes (SMBH), which power the central engine. Since the emission is concentrated in a very compact region (with typical size $r 2000 km/s) and narrow line (1000 km/s < FWHMH$_{\\rm H\\beta}\\, \\leq$ 2000 km/s) emitting objects, it has been observed that the kinematic and ionization properties of matter close to the SMBHs are related together, and, in particular, that ionization is higher in narrow line sources. Here we report on the study of the optical and X-ray spectra of a sample of Type 1 AGNs, selected from the Sloan Digital Sky Survey (SDSS) database, within an upper redshift limit of z = 0.35, and detected at X-ray energies. We present anal...

  8. Mid-Infrared Colors of Dwarf Galaxies: Young Starbursts Mimicking Active Galactic Nuclei

    CERN Document Server

    Hainline, Kevin N; Greene, Jenny E; Stern, Daniel

    2016-01-01

    Searching for active galactic nuclei (AGN) in dwarf galaxies is important for our understanding of the seed black holes that formed in the early Universe. Here, we test infrared selection methods for AGN activity at low galaxy masses. Our parent sample consists of ~18,000 nearby dwarf galaxies (M*< 3 x 10^9 Msun, $z<0.055$) in the Sloan Digital Sky Survey with significant detections in the first three bands of the AllWISE data release from the Wide-field Infrared Survey Explorer (WISE). First, we demonstrate that the majority of optically-selected AGNs in dwarf galaxies are not selected as AGNs using WISE infrared color diagnostics and that the infrared emission is dominated by the host galaxies. We then investigate the infrared properties of optically-selected star-forming dwarf galaxies, finding that the galaxies with the reddest infrared colors are the most compact, with blue optical colors, young stellar ages and large specific star formation rates. These results indicate that great care must be tak...

  9. The evolution of active galactic nuclei in clusters of galaxies from the Dark Energy Survey

    Science.gov (United States)

    Bufanda, E.; Hollowood, D.; Jeltema, T. E.; Rykoff, E. S.; Rozo, E.; Martini, P.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Banerji, M.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Evrard, A. E.; Fausti Neto, A.; Flaugher, B.; Frieman, J.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Melchior, P.; Miquel, R.; Mohr, J. J.; Ogando, R.; Plazas, A. A.; Romer, A. K.; Rooney, P.; Sanchez, E.; Santiago, B.; Scarpine, V.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Tarle, G.; Thomas, D.; Tucker, D. L.; Walker, A. R.; DES Collaboration

    2017-03-01

    The correlation between active galactic nuclei (AGNs) and environment provides important clues to AGN fuelling and the relationship of black hole growth to galaxy evolution. In this paper, we analyse the fraction of galaxies in clusters hosting AGN as a function of redshift and cluster richness for X-ray-detected AGN associated with clusters of galaxies in Dark Energy Survey (DES) Science Verification data. The present sample includes 33 AGNs with LX > 1043 erg s-1 in non-central, host galaxies with luminosity greater than 0.5L* from a total sample of 432 clusters in the redshift range of 0.1 0.7. This result is in good agreement with previous work and parallels the increase in star formation in cluster galaxies over the same redshift range. However, the AGN fraction in clusters is observed to have no significant correlation with cluster mass. Future analyses with DES Year 1 through Year 3 data will be able to clarify whether AGN activity is correlated to cluster mass and will tightly constrain the relationship between cluster AGN populations and redshift.

  10. A mid-infrared exploration of the dusty environments of active galactic nuclei

    CERN Document Server

    Alonso-Herrero, Almudena

    2013-01-01

    We present the first results from a mid-infrared survey of local Active Galactic Nuclei (AGN) using the CanariCam (CC) instrument on the 10.4m Gran Telescopio Canarias (GTC). We are obtaining sub-arcsecond angular resolution (0.3-0.6 arcsec) mid-IR imaging and spectroscopic observations of a sample of 100 local AGN, which are complemented with data taken with T-ReCS, VISIR, and Michelle. The full sample contains approximately 140 AGN, covers nearly six orders of magnitude in AGN luminosity, and includes low-luminosity AGN (LLAGN), Seyfert 1s and 2s, QSO, radio galaxies, and (U)LIRGs. The main goals of this project are: (1) to test whether the properties of the dusty tori of the AGN Unified Model depend on the AGN type, (2) to study the nuclear star formation activity and obscuration of local AGN, and (3) to explore the role of the dusty torus in LLAGN.

  11. Widespread and Hidden Active Galactic Nuclei in Star-Forming Galaxies at Redshift > 0.3

    CERN Document Server

    Juneau, Stéphanie; Bournaud, Frédéric; Alexander, David M; Daddi, Emanuele; Mullaney, James R; Magnelli, Benjamin; Kartaltepe, Jeyhan S; Hwang, Ho Seong; Willner, S P; Coil, Alison L; Rosario, David J; Trump, Jonathan R; Weiner, Benjamin J; Willmer, Christopher N A; Cooper, Michael C; Elbaz, David; Faber, S M; Frayer, David T; Kocevski, Dale D; Laird, Elise S; Monkiewicz, Jacqueline A; Nandra, Kirpal; Newman, Jeffrey; Salim, Samir; Symeonidis, Myrto

    2012-01-01

    We characterize the incidence of active galactic nuclei (AGNs) is 0.3 < z < 1 star-forming galaxies by applying multi-wavelength AGN diagnostics (X-ray, optical, mid-infrared, radio) to a sample of galaxies selected at 70-micron from the Far-Infrared Deep Extragalactic Legacy survey (FIDEL). Given the depth of FIDEL, we detect "normal" galaxies on the specific star formation rate (sSFR) sequence as well as starbursting systems with elevated sSFR. We find an overall high occurrence of AGN of 37+/-3%, more than twice as high as in previous studies of galaxies with comparable infrared luminosities and redshifts but in good agreement with the AGN fraction of nearby (0.05 < z < 0.1) galaxies of similar infrared luminosities. The more complete census of AGNs comes from using the recently developed Mass-Excitation (MEx) diagnostic diagram. This optical diagnostic is also sensitive to X-ray weak AGNs and X-ray absorbed AGNs, and reveals that absorbed active nuclei reside almost exclusively in infrared-lum...

  12. WIDESPREAD AND HIDDEN ACTIVE GALACTIC NUCLEI IN STAR-FORMING GALAXIES AT REDSHIFT >0.3

    Energy Technology Data Exchange (ETDEWEB)

    Juneau, Stephanie; Bournaud, Frederic; Daddi, Emanuele; Elbaz, David [CEA-Saclay, DSM/IRFU/SAp, F-91191 Gif-sur-Yvette (France); Dickinson, Mark; Kartaltepe, Jeyhan S. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Alexander, David M.; Mullaney, James R. [Department of Physics, Durham University, Durham DH1 3LE (United Kingdom); Magnelli, Benjamin [Max-Planck-Instituet fuer extraterrestrische Physik, Postfach 1312, D-85741 Garching bei Muenchen (Germany); Hwang, Ho Seong; Willner, S. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Coil, Alison L. [Department of Physics, Center for Astrophysics and Space Sciences, University of California, 9500 Gilman Dr., La Jolla, San Diego, CA 92093 (United States); Rosario, David J. [Max-Planck-Instituet fuer extraterrestrische Physik, Giessenbachstrasse, D-85748 Garching bei Muenchen (Germany); Trump, Jonathan R.; Faber, S. M.; Kocevski, Dale D. [University of California Observatories/Lick Observatory, University of California, Santa Cruz, CA 95064 (United States); Weiner, Benjamin J.; Willmer, Christopher N. A. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Cooper, Michael C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California-Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Frayer, David T., E-mail: stephanie.juneau@cea.fr [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); and others

    2013-02-20

    We characterize the incidence of active galactic nuclei (AGNs) in 0.3 < z < 1 star-forming galaxies by applying multi-wavelength AGN diagnostics (X-ray, optical, mid-infrared, radio) to a sample of galaxies selected at 70 {mu}m from the Far-Infrared Deep Extragalactic Legacy survey (FIDEL). Given the depth of FIDEL, we detect 'normal' galaxies on the specific star formation rate (sSFR) sequence as well as starbursting systems with elevated sSFR. We find an overall high occurrence of AGN of 37% {+-} 3%, more than twice as high as in previous studies of galaxies with comparable infrared luminosities and redshifts but in good agreement with the AGN fraction of nearby (0.05 < z < 0.1) galaxies of similar infrared luminosities. The more complete census of AGNs comes from using the recently developed Mass-Excitation (MEx) diagnostic diagram. This optical diagnostic is also sensitive to X-ray weak AGNs and X-ray absorbed AGNs, and reveals that absorbed active nuclei reside almost exclusively in infrared-luminous hosts. The fraction of galaxies hosting an AGN appears to be independent of sSFR and remains elevated both on the sSFR sequence and above. In contrast, the fraction of AGNs that are X-ray absorbed increases substantially with increasing sSFR, possibly due to an increased gas fraction and/or gas density in the host galaxies.

  13. Active galactic nuclei at z ~ 1.5: I. Spectral energy distribution and accretion discs

    CERN Document Server

    Capellupo, Daniel M; Lira, Paulina; Trakhtenbrot, Benny; Mejía-Restrepo, Julían

    2014-01-01

    The physics of active super massive black holes (BHs) is governed by their mass (M_BH), spin (a*) and accretion rate ($\\dot{M}$). This work is the first in a series of papers with the aim of testing how these parameters determine the observable attributes of active galactic nuclei (AGN). We have selected a sample in a narrow redshift range, centered on z~1.55, that covers a wide range in M_BH and $\\dot{M}$, and are observing them with X-shooter, covering rest wavelengths ~1200-9800 \\AA. The current work covers 30 such objects and focuses on the origin of the AGN spectral energy distribution (SED). After estimating M_BH and $\\dot{M}$ based on each observed SED, we use thin AD models and a Bayesian analysis to fit the observed SEDs in our sample. We are able to fit 22/30 of the SEDs. Out of the remaining 8 SEDs, 3 can be fit by the thin AD model by correcting the observed SED for reddening within the host galaxy and 4 can be fit by adding a disc wind to the model. In four of these 8 sources, Milky Way-type exti...

  14. Dietary grape seed polyphenols repress neuron and glia activation in trigeminal ganglion and trigeminal nucleus caudalis

    Directory of Open Access Journals (Sweden)

    Durham Paul L

    2010-12-01

    Full Text Available Abstract Background Inflammation and pain associated with temporomandibular joint disorder, a chronic disease that affects 15% of the adult population, involves activation of trigeminal ganglion nerves and development of peripheral and central sensitization. Natural products represent an underutilized resource in the pursuit of safe and effective ways to treat chronic inflammatory diseases. The goal of this study was to investigate effects of grape seed extract on neurons and glia in trigeminal ganglia and trigeminal nucleus caudalis in response to persistent temporomandibular joint inflammation. Sprague Dawley rats were pretreated with 200 mg/kg/d MegaNatural-BP grape seed extract for 14 days prior to bilateral injections of complete Freund's adjuvant into the temporomandibular joint capsule. Results In response to grape seed extract, basal expression of mitogen-activated protein kinase phosphatase 1 was elevated in neurons and glia in trigeminal ganglia and trigeminal nucleus caudalis, and expression of the glutamate aspartate transporter was increased in spinal glia. Rats on a normal diet injected with adjuvant exhibited greater basal levels of phosphorylated-p38 in trigeminal ganglia neurons and spinal neurons and microglia. Similarly, immunoreactive levels of OX-42 in microglia and glial fibrillary acidic protein in astrocytes were greatly increased in response to adjuvant. However, adjuvant-stimulated levels of phosphorylated-p38, OX-42, and glial fibrillary acidic protein were significantly repressed in extract treated animals. Furthermore, grape seed extract suppressed basal expression of the neuropeptide calcitonin gene-related peptide in spinal neurons. Conclusions Results from our study provide evidence that grape seed extract may be beneficial as a natural therapeutic option for temporomandibular joint disorders by suppressing development of peripheral and central sensitization.

  15. Active Galactic Nuclei In Cosmological Simulations - I. Formation of black holes and spheroids through mergers

    Science.gov (United States)

    Cattaneo, A.; Blaizot, J.; Devriendt, J.; Guiderdoni, B.

    2005-12-01

    This is the first paper of a series on the methods and results of the Active Galactic Nuclei In Cosmological Simulations (AGNICS) project, which incorporates the physics of active galactic nuclei (AGNs) into Galaxies In Cosmological Simulations (GalICS), a galaxy formation model that combines large cosmological N-body simulations of dark matter hierarchical clustering and a semi-analytic approach to the physics of the baryons. The project explores the quasar-galaxy link in a cosmological perspective, in response to growing observational evidence for a close relation between supermassive black holes (SMBHs) and spheroids. The key problems are the quasar fuelling mechanism, the origin of the black hole (BH)-to-bulge mass relation, the causal and chronological link between BH growth and galaxy formation, the properties of quasar hosts and the role of AGN feedback in galaxy formation. This first paper has two goals. The first is to describe the general structure and assumptions that provide the framework for the AGNICS series. The second is to apply AGNICS to studying the joint formation of SMBHs and spheroids in galaxy mergers. We investigate under what conditions this scenario can reproduce the local distribution of SMBHs in nearby galaxies and the evolution of the quasar population. AGNICS contains two star formation modes: a quiescent mode in discs and a starburst mode in proto-spheroids, the latter triggered by mergers and disc instabilities. Here we assume that BH growth is linked to the starburst mode. The simplest version of this scenario, in which the BH accretion rate and the star formation rate in the starburst component are simply related by a constant of proportionality, does not to reproduce the cosmic evolution of the quasar population. A model in which , where ρburst is the density of the gas in the starburst and ζ~= 0.5, can explain the evolution of the quasar luminosity function in B band and X-rays (taking into account the presence of obscured AGNs

  16. Stronger activation of SREBP-1a by nucleus-localized HBx

    Energy Technology Data Exchange (ETDEWEB)

    Wu, Qi [VIDO-InterVac, Veterinary Microbiology, University of Saskatchewan, Saskatoon (Canada); Qiao, Ling [VIDO-InterVac, University of Saskatchewan, Saskatoon, Saskatchewan (Canada); Yang, Jian [Drug Discovery Group, University of Saskatchewan, Saskatoon, Saskatchewan (Canada); Zhou, Yan [VIDO-InterVac, Veterinary Microbiology, Vaccinology and Immunotherapeutics, University of Saskatchewan, Saskatoon, Saskatchewan (Canada); Liu, Qiang, E-mail: qiang.liu@usask.ca [VIDO-InterVac, Veterinary Microbiology, Vaccinology and Immunotherapeutics, University of Saskatchewan, Saskatoon, Saskatchewan (Canada)

    2015-05-08

    We previously showed that hepatitis B virus (HBV) X protein activates the sterol regulatory element-binding protein-1a (SREBP-1a). Here we examined the role of nuclear localization of HBx in this process. In comparison to the wild-type and cytoplasmic HBx, nuclear HBx had stronger effects on SREBP-1a and fatty acid synthase transcription activation, intracellular lipid accumulation and cell proliferation. Furthermore, nuclear HBx could activate HBV enhancer I/X promoter and was more effective on up-regulating HBV mRNA level in the context of HBV replication than the wild-type HBx, while the cytoplasmic HBx had no effect. Our results demonstrate the functional significance of the nucleus-localized HBx in regulating host lipogenic pathway and HBV replication. - Highlights: • Nuclear HBx is more effective on activating SREBP-1a and FASN transcription. • Nuclear HBx is more effective on enhancing intracellular lipid accumulation. • Nuclear HBx is more effective on enhancing cell proliferation. • Nuclear HBx up-regulates HBV enhancer I/X promoter activity. • Nuclear HBx increases HBV mRNA level in the context of HBV replication.

  17. Endogenous GLP-1 acts on paraventricular nucleus to suppress feeding: projection from nucleus tractus solitarius and activation of corticotropin-releasing hormone, nesfatin-1 and oxytocin neurons.

    Science.gov (United States)

    Katsurada, Kenichi; Maejima, Yuko; Nakata, Masanori; Kodaira, Misato; Suyama, Shigetomo; Iwasaki, Yusaku; Kario, Kazuomi; Yada, Toshihiko

    2014-08-22

    Glucagon-like peptide-1 (GLP-1) receptor agonists have been used to treat type 2 diabetic patients and shown to reduce food intake and body weight. The anorexigenic effects of GLP-1 and GLP-1 receptor agonists are thought to be mediated primarily via the hypothalamic paraventricular nucleus (PVN). GLP-1, an intestinal hormone, is also localized in the nucleus tractus solitarius (NTS) of the brain stem. However, the role of endogenous GLP-1, particularly that in the NTS neurons, in feeding regulation remains to be established. The present study examined whether the NTS GLP-1 neurons project to PVN and whether the endogenous GLP-1 acts on PVN to restrict feeding. Intra-PVN injection of GLP-1 receptor antagonist exendin (9-39) increased food intake. Injection of retrograde tracer into PVN combined with immunohistochemistry for GLP-1 in NTS revealed direct projection of NTS GLP-1 neurons to PVN. Moreover, GLP-1 evoked Ca(2+) signaling in single neurons isolated from PVN. The majority of GLP-1-responsive neurons were immunoreactive predominantly to corticotropin-releasing hormone (CRH) and nesfatin-1, and less frequently to oxytocin. These results indicate that endogenous GLP-1 targets PVN to restrict feeding behavior, in which the projection from NTS GLP-1 neurons and activation of CRH and nesfatin-1 neurons might be implicated. This study reveals a neuronal basis for the anorexigenic effect of endogenous GLP-1 in the brain.

  18. Rosetta/OSIRIS: Nucleus morphology and activity of comet 67P/Churyumov-Gerasimenko

    Science.gov (United States)

    Sierks, Holger

    2015-08-01

    Introduction: The Rosetta mission of the European Space Agency arrived on August 6, 2014, at the target comet 67P/Churyumov-Gerasimenko after 10 years of cruise. OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) is the scientific imaging system onboard Rosetta. It comprises a Narrow Angle Camera (NAC) for broad-band nucleus surface and dust studies and a Wide Angle Camera (WAC) for the wide field coma investigations.OSIRIS images the nucleus and the coma of comet 67P/C-G from the arrival throughout early mapping phase, PHILAE landing, and escort phase with close fly-by beginning of the year 2015.The team paper presents the surface morphology and activity of the nucleus as seen in gas, dust, and local jets and the larger scale coma studied by OSIRIS.Acknowledgements: OSIRIS was built by a consortium led by the Max-Planck-Institut für Sonnensystemforschung, Göttingen, Germany, in collaboration with CISAS, University of Padova, Italy, the Laboratoire d'Astrophysique de Marseille, France, the Instituto de Astrofísica de Andalucia, CSIC, Granada, Spain, the Scientific Support Office of the European Space Agency, Noordwijk, The Netherlands, the Instituto Nacional de Técnica Aeroespacial, Madrid, Spain, the Universidad Politéchnica de Madrid, Spain, the Department of Physics and Astronomy of Uppsala University, Sweden, and the Institut für Datentechnik und Kommunikationsnetze der Technischen Universität Braunschweig, Germany.Additional Information: The OSIRIS team is H. Sierks, C. Barbieri, P. Lamy, R. Rodrigo, D. Koschny, H. Rickman, J. Agarwal, M. A'Hearn, I. Bertini, F. Angrilli, M. A. Barucci, J. L. Bertaux, G. Cremonese, V. Da Deppo, B. Davidsson, S. Debei, M. De Cecco, S. Fornasier, M. Fulle, O. Groussin, C. Güttler, P. Gutierrez, S. Hviid, W. Ip, L. Jorda, H. U. Keller, J. Knollenberg, R. Kramm, E. Kührt, M. Küppers, L. Lara, M. Lazzarin, J. J. Lopez, S. Lowry, S. Marchi, F. Marzari, H. Michalik, S. Mottola, G. Naletto, N. Oklay, L

  19. Fueling active galactic nuclei. II. Spatially resolved molecular inflows and outflows

    Energy Technology Data Exchange (ETDEWEB)

    Davies, R. I.; Erwin, P.; Burtscher, L.; Lin, M.; Orban de Xivry, G.; Rosario, D. J.; Schnorr-Müller, A. [Max-Planck-Institute für Extraterrestrische Physik, Postfach 1312, D-85741 Garching (Germany); Maciejewski, W. [Astrophysics Research Institute, Liverpool John Moores University, IC2 Liverpool Science Park, 146 Brownlow Hill, L3 5RF (United Kingdom); Hicks, E. K. S. [Astronomy Department, University of Alaska, Anchorage, Alaska 99508 (United States); Emsellem, E. [European Southern Observatory, Karl-Schwarzschild Str. 1, D-85748 Garching (Germany); Dumas, G. [Institut de Radio Astronomie Millimétrique (IRAM), 300 Rue de la Piscine, Domaine Universitaire, F-38406 Saint Martin d' Heres (France); Malkan, M. A. [Astronomy Division, University of California, Los Angeles, CA 90095-1562 (United States); Müller-Sánchez, F. [Center for Astrophysics and Space Astronomy, University of Colorado, Boulder, CO 80309-0389 (United States); Tran, A. [Department of Astronomy, University of Washington Seattle, WA 98195 (United States)

    2014-09-10

    We analyze the two-dimensional distribution and kinematics of the stars as well as molecular and ionized gas in the central few hundred parsecs of five active and five matched inactive galaxies. The equivalent widths of the Brγ line indicate that there is no ongoing star formation in their nuclei, although recent (terminated) starbursts are possible in the active galaxies. The stellar velocity fields show no signs of non-circular motions, while the 1-0 S(1) H{sub 2} kinematics exhibit significant deviations from simple circular rotation. In the active galaxies the H{sub 2} kinematics reveal inflow and outflow superimposed on disk rotation. Steady-state circumnuclear inflow is seen in three active galactic nuclei (AGNs), and hydrodynamical models indicate it can be driven by a large-scale bar. In three of the five AGNs, molecular outflows are spatially resolved. The outflows are oriented such that they intersect, or have an edge close to, the disk, which may be the source of molecular gas in the outflow. The relatively low speeds imply the gas will fall back onto the disk, and with moderate outflow rates, they will have only a local impact on the host galaxy. H{sub 2} was detected in two inactive galaxies. These exhibit chaotic circumnuclear dust morphologies and have molecular structures that are counter-rotating with respect to the main gas component, which could lead to gas inflow in the near future. In our sample, all four galaxies with chaotic dust morphology in the circumnuclear region exist in moderately dense groups with 10-15 members where accretion of stripped gas can easily occur.

  20. The level of cholinergic nucleus basalis activation controls the specificity of auditory associative memory.

    Science.gov (United States)

    Weinberger, Norman M; Miasnikov, Alexandre A; Chen, Jemmy C

    2006-11-01

    Learning involves not only the establishment of memory per se, but also the specific details of its contents. In classical conditioning, the former concerns whether an association was learned while the latter discloses what was learned. The neural bases of associativity have been studied extensively while neural mechanisms of memory specificity have been neglected. Stimulation of the cholinergic nucleus basalis (NBs) paired with a preceding tone induces CS-specific associative memory. As different levels of acetylcholine may be released naturally during different learning situations, we asked whether the level of activation of the cholinergic neuromodulatory system can control the degree of detail that is encoded and retrieved. Adult male rats were tested pre- and post-training for behavioral responses (interruption of ongoing respiration) to tones of various frequencies (1-15 kHz, 70 dB, 2 s). Training consisted of 200 trials/day of tone (8.0 kHz, 70 dB, 2 s) either paired or unpaired with NBs (CS-NBs = 1.8 s) at moderate (65.7+/-9.0 microA, one day) or weak (46.7+/-12.1 microA, three training days) levels of stimulation, under conditions of controlled behavioral state (pre-trial stable respiration rate). Post-training (24 h) responses to tones revealed that moderate activation induced both associative and CS-specific behavioral memory, whereas weak activation produced associative memory lacking frequency specificity. The degree of memory specificity 24 h after training was positively correlated with the magnitude of CS-elicited increase in gamma activity within the EEG during training, but only in the moderate NBs group. Thus, a low level of acetylcholine released by the nucleus basalis during learning is sufficient to induce associativity whereas a higher level of release enables the storage of greater experiential detail. gamma waves, which are thought to reflect the coordinated activity of cortical cells, appear to index the encoding of CS detail. The findings

  1. Are All Active Galactic Nuclei Born Equal? The Silicate Dust Mineralogy Perspective

    Science.gov (United States)

    Li, Aigen

    Dust is the cornerstone of the unification theory of active galactic nuclei (AGNs). This theory proposes that all AGNs are essentially the same object or "born equal" but viewed from different lines of sight; much of the observed diversity arises from different viewing angles toward the central engine and a dusty toroidal structure around it. When the dusty torus is viewed face-on, both the central engine and the broad-line regions can be seen directly causing objects to appear as type 1 AGNs; when the dusty torus is viewed edge- on, the anisotropic obscuration created by the torus causes objects to appear as type 2 AGNs. It is this crucial role played by dust in the unified model of AGNs that makes understanding dust properties very important in understanding AGNs. Little is known about the dust in the circumnuclear torus of AGNs. There is evidence suggesting that the size and composition of the dust in AGNs may differ substantially from that of the Galactic interstellar dust, as reflected by the flat or "gray" extinction, and the anomalous silicate emission or absorption features observed respectively in type 1 and type 2 AGNs. The silicate feature profiles of AGNs are rather diverse in peak wavelengths, widths, strengths, and band ratios of the 18 micrometer O--Si--O feature to the 9.7 micrometer Si--O feature, suggesting that the AGN silicate grains are diverse in composition and size (or probably not "born equal"). We propose a two-year project to study the size and composition of the dust in AGNs, with special attention paid to the silicate mineralogy. We will obtain constraints on the silicate composition and size by modeling the Spitzer IRS spectra of >100 AGNs of various types. We will examine whether (and how) the silicate composition and size properties vary with the properties of an AGN (e.g. type, luminosity). This research will improve our understanding of the physical properties of the dust torus and the origin of the observed silicate emission

  2. A HYBRID MODEL FOR THE EVOLUTION OF GALAXIES AND ACTIVE GALACTIC NUCLEI IN THE INFRARED

    Energy Technology Data Exchange (ETDEWEB)

    Cai Zhenyi; Lapi, Andrea; Xia Junqing; De Zotti, Gianfranco; Danese, Luigi [Astrophysics Sector, SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Negrello, Mattia [INAF-Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Gruppioni, Carlotta [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Rigby, Emma [Leiden Observatory, P.O. Box 9513, 2300-RA Leiden (Netherlands); Castex, Guillaume; Delabrouille, Jacques, E-mail: zcai@sissa.it [APC, 10, rue Alice Domon et Leonie Duquet, F-75205 Paris Cedex 13 (France)

    2013-05-01

    We present a comprehensive investigation of the cosmological evolution of the luminosity function of galaxies and active galactic nuclei (AGNs) in the infrared (IR). Based on the observed dichotomy in the ages of stellar populations of early-type galaxies on one side and late-type galaxies on the other, the model interprets the epoch-dependent luminosity functions at z {>=} 1.5 using a physical approach for the evolution of proto-spheroidal galaxies and of the associated AGNs, while IR galaxies at z < 1.5 are interpreted as being mostly late-type ''cold'' (normal) and ''warm'' (starburst) galaxies. As for proto-spheroids, in addition to the epoch-dependent luminosity functions of stellar and AGN components separately, we have worked out, for the first time, the evolving luminosity functions of these objects as a whole (stellar plus AGN component), taking into account in a self-consistent way the variation with galactic age of the global spectral energy distribution. The model provides a physical explanation for the observed positive evolution of both galaxies and AGNs up to z {approx_equal} 2.5 and for the negative evolution at higher redshifts, for the sharp transition from Euclidean to extremely steep counts at (sub-)millimeter wavelengths, as well as the (sub-)millimeter counts of strongly lensed galaxies that are hard to account for by alternative, physical or phenomenological, approaches. The evolution of late-type galaxies and z < 1.5 AGNs is described using a parametric phenomenological approach. The modeled AGN contributions to the counts and to the cosmic infrared background (CIB) are always sub-dominant. They are maximal at mid-IR wavelengths: the contribution to the 15 and 24 {mu}m counts reaches 20% above 10 and 2 mJy, respectively, while the contributions to the CIB are of 8.6% and of 8.1% at 15 {mu}m and 24 {mu}m, respectively. The model provides a good fit to the multi-wavelength (from the mid-IR to millimeter

  3. A Hybrid Model for the Evolution of Galaxies and Active Galactic Nuclei in the Infrared

    Science.gov (United States)

    Cai, Zhen-Yi; Lapi, Andrea; Xia, Jun-Qing; De Zotti, Gianfranco; Negrello, Mattia; Gruppioni, Carlotta; Rigby, Emma; Castex, Guillaume; Delabrouille, Jacques; Danese, Luigi

    2013-05-01

    We present a comprehensive investigation of the cosmological evolution of the luminosity function of galaxies and active galactic nuclei (AGNs) in the infrared (IR). Based on the observed dichotomy in the ages of stellar populations of early-type galaxies on one side and late-type galaxies on the other, the model interprets the epoch-dependent luminosity functions at z >= 1.5 using a physical approach for the evolution of proto-spheroidal galaxies and of the associated AGNs, while IR galaxies at z < 1.5 are interpreted as being mostly late-type "cold" (normal) and "warm" (starburst) galaxies. As for proto-spheroids, in addition to the epoch-dependent luminosity functions of stellar and AGN components separately, we have worked out, for the first time, the evolving luminosity functions of these objects as a whole (stellar plus AGN component), taking into account in a self-consistent way the variation with galactic age of the global spectral energy distribution. The model provides a physical explanation for the observed positive evolution of both galaxies and AGNs up to z ~= 2.5 and for the negative evolution at higher redshifts, for the sharp transition from Euclidean to extremely steep counts at (sub-)millimeter wavelengths, as well as the (sub-)millimeter counts of strongly lensed galaxies that are hard to account for by alternative, physical or phenomenological, approaches. The evolution of late-type galaxies and z < 1.5 AGNs is described using a parametric phenomenological approach. The modeled AGN contributions to the counts and to the cosmic infrared background (CIB) are always sub-dominant. They are maximal at mid-IR wavelengths: the contribution to the 15 and 24 μm counts reaches 20% above 10 and 2 mJy, respectively, while the contributions to the CIB are of 8.6% and of 8.1% at 15 μm and 24 μm, respectively. The model provides a good fit to the multi-wavelength (from the mid-IR to millimeter waves) data on luminosity functions at different redshifts and

  4. Piecing together the X-ray background: bolometric corrections for active galactic nuclei

    Science.gov (United States)

    Vasudevan, R. V.; Fabian, A. C.

    2007-11-01

    The X-ray background can be used to constrain the accretion history of supermassive black holes (SMBHs) in active galactic nuclei (AGN), with the SMBH mass density related to the energy density due to accretion. A knowledge of the hard X-ray bolometric correction, κ2-10keV, is a vital input into these studies, as it allows us to constrain the parameters of the accretion responsible for SMBH growth. Earlier studies assumed a constant bolometric correction for all AGN, and more recent work has suggested accounting for a dependence on AGN luminosity. Until recently, the variations in the disc emission in the ultraviolet (UV) have not been taken into account in this calculation; we show that such variations are important by construction of optical-to-X-ray spectral energy distributions for 54 AGN. In particular, we use Far Ultraviolet Spectroscopic Explorer (FUSE) UV and X-ray data from the literature to constrain the disc emission as well as possible. We find evidence for very significant spread in the bolometric corrections, with no simple dependence on luminosity being evident. Populations of AGN such as narrow-line Seyfert 1 nuclei, radio-loud and X-ray-weak AGN may have bolometric corrections which differ systematically from the rest of the AGN population. We identify other sources of uncertainty including intrinsic extinction in the optical-UV, X-ray and UV variability and uncertainties in SMBH mass estimates. Our results suggest a more well-defined relationship between the bolometric correction and Eddington ratio in AGN, with a transitional region at an Eddington ratio of ~0.1, below which the bolometric correction is typically 15-25, and above which it is typically 40-70. We consider the potential-implied parallels with the low/hard and high/soft states in Galactic black hole (GBH) accretion, and present bolometric corrections for the GBH binary GX 339-4 for comparison. Our findings reinforce previous studies proposing a multistate description of AGN

  5. Detailed Shape and Evolutionary Behavior of the X-ray Luminosity Function of Active Galactic Nuclei

    CERN Document Server

    Miyaji, T; Salvato, M; Brusa, M; Cappelluti, N; Civano, F; Puccetti, S; Elvis, M; Brunner, H; Fotopoulou, S; Ueda, Y; Griffiths, R E; Koekemoer, A M; Akiyama, M; Comastri, A; Gilli, R; Lanzuisi, G; Merloni, A; Vignali, C

    2015-01-01

    We construct the rest-frame 2--10 keV intrinsic X-ray luminosity function of Active Galactic Nuclei (AGNs) from a combination of X-ray surveys from the all-sky Swift BAT survey to the Chandra Deep Field-South. We use ~3200 AGNs in our analysis, which covers six orders of magnitude in flux. The inclusion of the XMM and Chandra COSMOS data has allowed us to investigate the detailed behavior of the XLF and evolution. In deriving our XLF, we take into account realistic AGN spectrum templates, absorption corrections, and probability density distributions in photometric redshift. We present an analytical expression for the overall behavior of the XLF in terms of the luminosity-dependent density evolution, smoothed two power-law expressions in 11 redshift shells, three-segment power-law expression of the number density evolution in four luminosity classes, and binned XLF. We observe a sudden flattening of the low luminosity end slope of the XLF slope at z>~0.6. Detailed structures of the AGN downsizing have been als...

  6. Determining the covering factor of compton-thick active galactic nuclei with NuSTAR

    DEFF Research Database (Denmark)

    Brightman, M.; Balokovic, M.; Stern, D.

    2015-01-01

    opening angle as a free parameter and aim to determine the covering factor of the CT gas in these sources individually. Across the sample we find mild to heavy CT columns, with NH measured from 1024 to 1026 cm-2, and a wide range of covering factors, where individual measurements range from 0.2 to 0.9. We......The covering factor of Compton-thick (CT) obscuring material associated with the torus in active galactic nuclei (AGNs) is at present best understood through the fraction of sources exhibiting CT absorption along the line of sight (NH > 1.5 × 1024 cm-2) in the X-ray band, which reveals the average...... covering factor. Determining this CT fraction is difficult, however, due to the extreme obscuration. With its spectral coverage at hard X-rays (>10 keV), Nuclear Spectroscopic Telescope Array (NuSTAR) is sensitive to the AGNs covering factor since Compton scattering of X-rays off optically thick material...

  7. Long-Term X-ray Variability of Typical Active Galactic Nuclei in the Distant Universe

    CERN Document Server

    Yang, G; Luo, B; Xue, Y; Bauer, F; Sun, M; Kim, S; Schulze, S; Zheng, X; Paolillo, M; Shemmer, O; Liu, T; Schneider, D; Vignali, C; Vito, F; Wang, J -X

    2016-01-01

    We perform long-term ($\\approx 15$ yr, observed-frame) X-ray variability analyses of the 68 brightest radio-quiet active galactic nuclei (AGNs) in the 6 Ms $Chandra$ Deep Field-South (CDF-S) survey; the majority are in the redshift range of $0.6-3.1$, providing access to penetrating rest-frame X-rays up to $\\approx 10-30$ keV. Twenty-four of the 68 sources are optical spectral type I AGNs, and the rest (44) are type II AGNs. The time scales probed in this work are among the longest for X-ray variability studies of distant AGNs. Photometric analyses reveal widespread photon-flux variability: $90\\%$ of AGNs are variable above a 95% confidence level, including many X-ray obscured AGNs and several optically classified type II quasars. We characterize the intrinsic X-ray luminosity ($L_{\\rm{X}}$) and absorption ($N_{\\rm{H}}$) variability via spectral fitting. Most (74%) sources show $L_{\\rm{X}}$ variability; the variability amplitudes are generally smaller for quasars. A Compton-thick candidate AGN shows variabili...

  8. The resolved star-formation relation in nearby active galactic nuclei

    CERN Document Server

    Casasola, Viviana; Combes, Francoise; Garcia-Burillo, Santiago

    2015-01-01

    We present an analysis of the relation between star formation rate (SFR) surface density (sigmasfr) and mass surface density of molecular gas (sigmahtwo), commonly referred to as the Kennicutt-Schmidt (K-S) relation, at its intrinsic spatial scale, i.e. the size of giant molecular clouds (10-150 pc), in the central, high-density regions of four nearby low-luminosity active galactic nuclei (AGN). We used interferometric IRAM CO(1-0) and CO(2-1), and SMA CO(3-2) emission line maps to derive sigmahtwo and HST-Halpha images to estimate sigmasfr. Each galaxy is characterized by a distinct molecular SF relation at spatial scales between 20 to 200 pc. The K-S relations can be sub-linear, but also super-linear, with slopes ranging from 0.5 to 1.3. Depletion times range from 1 and 2Gyr, compatible with results for nearby normal galaxies. These findings are valid independently of which transition, CO(1-0), CO(2-1), or CO(3-2), is used to derive sigmahtwo. Because of star-formation feedback, life-time of clouds, turbule...

  9. Long-Term Optical Continuum Color Variability of Nearby Active Galactic Nuclei

    CERN Document Server

    Sakata, Yu; Yoshii, Yuzuru; Kobayashi, Yukiyasu; Koshida, Shintaro; Aoki, Tsutomu; Enya, Keigo; Tomita, Hiroyuki; Suganuma, Masahiro; Uchimoto, Yuka Katsuno; Sugawara, Shota

    2010-01-01

    We examine whether the spectral energy distribution of optical continuum emission of active galactic nuclei (AGNs) changes during flux variation, based on accurate and frequent monitoring observations of 11 nearby Seyfert galaxies and QSOs carried out in the B, V, and I bands for seven years by the MAGNUM telescope. The multi-epoch flux data in any two different bands obtained on the same night show a very tight linear flux to flux relationship for all target AGNs. The flux of the host galaxy within the photometric aperture is carefully estimated by surface brightness fitting to available high-resolution HST images and MAGNUM images. The flux of narrow emission lines in the photometric bands is also estimated from available spectroscopic data. We find that the non-variable component of the host galaxy plus narrow emission lines for all target AGNs is located on the fainter extension of the linear regression line of multi-epoch flux data in the flux to flux diagram. This result strongly indicates that the spec...

  10. Low-Mass Active Galactic Nuclei with Rapid X-Ray Variability

    CERN Document Server

    Ho, Luis

    2016-01-01

    We present a detailed study of the optical spectroscopic properties of 12 active galactic nuclei (AGNs) with candidate low-mass black holes (BHs) selected by Kamizasa et al. through rapid X-ray variability. The high-quality, echellette Magellan spectra reveal broad H$\\alpha$ emission in all the sources, allowing us to estimate robust viral BH masses and Eddington ratios for this unique sample. We confirm that the sample contains low-mass BHs accreting at high rates: the median $M_{\\rm BH} = 1.2\\times 10^6M_\\odot$ and median $L_{\\rm bol}/L_{\\rm Edd}=0.44$. The sample follows the $M_{\\rm BH}-\\sigma_*$ relation, within the considerable scatter typical of pseudobulges, the probable hosts of these low-mass AGNs. Various lines of evidence suggest that ongoing star formation is prevalent in these systems. We propose a new strategy to estimate star formation rates in AGNs hosted by low-mass, low-metallicity galaxies, based on modification of an existing method using the strength of [O II] $\\lambda 3727$, [O III] $\\la...

  11. A Simple test for the existence of two accretion modes in active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Jester, Sebastian; /Fermilab

    2005-02-01

    By analogy to the different accretion states observed in black-hole X-ray binaries (BHXBs), it appears plausible that accretion disks in active galactic nuclei (AGN) undergo a state transition between a radiatively efficient and inefficient accretion flow. If the radiative efficiency changes at some critical accretion rate, there will be a change in the distribution of black hole masses and bolometric luminosities at the corresponding transition luminosity. To test this prediction, the author considers the joint distribution of AGN black hole masses and bolometric luminosities for a sample taken from the literature. The small number of objects with low Eddington-scaled accretion rates m < 0.01 and black hole masses M{sub BH} < 10{sup 9} M{sub {circle_dot}} constitutes tentative evidence for the existence of such a transition in AGN. Selection effects, in particular those associated with flux-limited samples, systematically exclude objects in particular regions of the (M{sub BH}, L{sub bol}) plane. Therefore, they require particular attention in the analysis of distributions of black hole mass, bolometric luminosity, and derived quantities like the accretion rate. The author suggests further observational tests of the BHXB-AGN unification scheme which are based on the jet domination of the energy output of BHXBs in the hard state, and on the possible equivalence of BHXB in the very high (or steep power-law) state showing ejections and efficiently accreting quasars and radio galaxies with powerful radio jets.

  12. On the Contribution of Active Galactic Nuclei to the High-Redshift Metagalactic Ionizing Background

    CERN Document Server

    D'Aloisio, Anson; McQuinn, Matthew; Trac, Hy; Shapiro, Paul R

    2016-01-01

    Motivated by the claimed detection of a large population of faint active galactic nuclei (AGN) at high redshift, recent studies have proposed models in which AGN contribute significantly to the z > 4 H I ionizing background. In some models, AGN are even the chief sources of reionization. If correct, these models would make necessary a complete revision to the standard view that galaxies dominated the high-redshift ionizing background. It has been suggested that AGN-dominated models can better account for two recent observations that appear to be in conflict with the standard view: (1) large opacity variations in the z ~ 5.5 H I Lyman-alpha forest, and (2) slow evolution in the mean opacity of the He II Lyman-alpha forest. Large spatial fluctuations in the ionizing background from the brightness and rarity of AGN may account for the former, while the earlier onset of He II reionization in these models may account for the latter. Here we show that models in which AGN emissions source >~ 50 % of the ionizing bac...

  13. Study of Swift/BAT Selected Low-luminosity Active Galactic Nuclei Observed with Suzaku

    CERN Document Server

    Kawamuro, Taiki; Tazaki, Fumie; Terashima, Yuichi; Mushotzky, Richard

    2016-01-01

    We systematically analyze the broadband (0.5--200 keV) X-ray spectra of hard X-ray ($>10$ keV) selected local low-luminosity active galactic nuclei (LLAGNs) observed with {\\it Suzaku} and {\\it Swift}/BAT. The sample consists of ten LLAGNs detected with {\\it Swift}/BAT with intrinsic 14--195 keV luminosities smaller than $10^{42}$ erg s$^{-1}$ available in the {\\it Suzaku} archive, covering a wide range of the Eddington ratio from $10^{-5}$ to $10^{-2}$. The overall spectra can be reproduced with an absorbed cut-off power law, often accompanied by reflection components from distant cold matter, and/or optically-thin thermal emission from the host galaxy. In all objects, relativistic reflection components from the innermost disk are not required. Eight objects show a significant narrow iron-K$\\alpha$ emission line. Comparing their observed equivalent widths with the predictions from the Monte-Carlo based torus model by \\cite{Ike09}, we constrain the column density in the equatorial plane to be $\\log N^{\\rm eq}_...

  14. LOW-MASS ACTIVE GALACTIC NUCLEI WITH RAPID X-RAY VARIABILITY

    Energy Technology Data Exchange (ETDEWEB)

    Ho, Luis C. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Kim, Minjin [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of)

    2016-04-10

    We present a detailed study of the optical spectroscopic properties of 12 active galactic nuclei (AGNs) with candidate low-mass black holes (BHs) selected by Kamizasa et al. through rapid X-ray variability. The high-quality, echellette Magellan spectra reveal broad Hα emission in all the sources, allowing us to estimate robust virial BH masses and Eddington ratios for this unique sample. We confirm that the sample contains low-mass BHs accreting at high rates: the median M{sub BH} = 1.2 × 10{sup 6} M{sub ⊙} and median L{sub bol}/L{sub Edd} = 0.44. The sample follows the M{sub BH}–σ{sub *} relation, within the considerable scatter typical of pseudobulges, the probable hosts of these low-mass AGNs. Various lines of evidence suggest that ongoing star formation is prevalent in these systems. We propose a new strategy to estimate star formation rates in AGNs hosted by low-mass, low-metallicity galaxies, based on modification of an existing method using the strength of [O ii] λ3727, [O iii] λ5007, and X-rays.

  15. Continuum and Emission Line Strength Relations for a large Active Galactic Nuclei Sample

    CERN Document Server

    Dietrich, M; Shields, J C; Constantin, A; Junkkarinen, V T; Chaffee, F; Foltz, C B

    2002-01-01

    We report on the analysis of a large sample of 744 type 1 Active Galactic Nuclei, including quasars and Seyfert 1 galaxies across the redshift range from 0 < z < 5 and spanning nearly 6 orders of magnitude in continuum luminosity. We discuss correlations of continuum and emission line properties in the rest-frame ultraviolet and optical spectral ranges. The well established Baldwin Effect is detected for almost all emission lines from OVI1034 to [OIII]5007. Their equivalent widths are significantly anti-correlated with the continuum strength, while they are nearly independent of redshift. This is the well known Baldwin Effect. Its slope beta, measured as log W_lambda ~ beta * log lambda * L_lambda (1450A), shows a tendency to become steeper towards higher luminosity. The slope of the Baldwin Effect also increases with the ionization energy needed to create the individual lines. In contrast to this general trend, the NV1240 equivalent width is nearly independent of continuum luminosity and remains nearly...

  16. New Estimators of Black Hole Mass in Active Galactic Nuclei with Hydrogen Paschen Lines

    CERN Document Server

    Kim, Dohyeong; Kim, Minjin; 10.1088/0004-637X/724/1/386

    2010-01-01

    More than 50% of Active Galactic Nuclei (AGNs) are suspected to be red and affected by dust-obscuration. Meanwhile, popular spectral diagnostics of AGNs are based on optical or ultraviolet light, making the dust obscuration as a primary concern for understanding the general nature of AGNs and supermassive black holes residing in them. To provide with a method of investigating properties of the dusty AGNs, we derive new black hole (BH) mass estimators based on velocity widths and luminosities of Near Infrared (NIR) hydrogen emission lines such as P$\\alpha$ and P$\\beta$, and also investigate the line ratios of these Hydrogen lines. To derive the BH mass ($M_{\\rm BH}$) estimators, we used a sample of 37 unobscured Type-1 AGNs with a $M_{\\rm BH}$ range of $10^{6.8}$-$10^{9.4} M_{\\odot}$, where $M_{\\rm BH}$ come from either reverberation mapping method or single-epoch measurement method using Balmer lines. Our work shows that $M_{\\rm BH}$ can be estimated from the Paschen line luminosities and the velocity widths ...

  17. Optimal strategies for observation of active galactic nuclei variability with Imaging Atmospheric Cherenkov Telescopes

    Science.gov (United States)

    Giomi, Matteo; Gerard, Lucie; Maier, Gernot

    2016-07-01

    Variable emission is one of the defining characteristic of active galactic nuclei (AGN). While providing precious information on the nature and physics of the sources, variability is often challenging to observe with time- and field-of-view-limited astronomical observatories such as Imaging Atmospheric Cherenkov Telescopes (IACTs). In this work, we address two questions relevant for the observation of sources characterized by AGN-like variability: what is the most time-efficient way to detect such sources, and what is the observational bias that can be introduced by the choice of the observing strategy when conducting blind surveys of the sky. Different observing strategies are evaluated using simulated light curves and realistic instrument response functions of the Cherenkov Telescope Array (CTA), a future gamma-ray observatory. We show that strategies that makes use of very small observing windows, spread over large periods of time, allows for a faster detection of the source, and are less influenced by the variability properties of the sources, as compared to strategies that concentrate the observing time in a small number of large observing windows. Although derived using CTA as an example, our conclusions are conceptually valid for any IACTs facility, and in general, to all observatories with small field of view and limited duty cycle.

  18. Probing the Active Galactic Nuclei Unified Model Torus Properties in Seyfert Galaxies

    CERN Document Server

    Audibert, Anelise; Sales, Dinalva A; Pastoriza, Miriani G; Ruschel-Dutra, Daniel

    2016-01-01

    We studied the physical parameters of a sample comprising of all Spitzer/IRS public spectra of Seyfert galaxies in the mid-infrared (5.2-38$\\mu$m range) under the active galactic nuclei (AGN) unified model. We compare the observed spectra with $\\sim10^6$ CLUMPY model spectral energy distributions, which consider a torus composed of dusty clouds. We find a slight difference in the distribution of line-of-sight inclination angle, $i$, requiring larger angles for Seyfert 2 (Sy2) and a broader distribution for Seyfert 1 (Sy1). We found small differences in the torus angular width, $\\sigma$, indicating that Sy1 may host a slightly narrower torus than Sy2. The torus thickness, together with the bolometric luminosities derived, suggest a very compact torus up to $\\sim$6 pc from the central AGN. The number of clouds along the equatorial plane, $N$, as well the index of the radial profile, $q$, are nearly the same for both types. These results imply that the torus cloud distribution is nearly the same for type 1 and t...

  19. Clumpy tori illuminated by the anisotropic radiation of accretion discs in active galactic nuclei

    CERN Document Server

    He, Jian-Jian; Zhang, Shuang-Nan

    2015-01-01

    In this paper, we try to explain the observed correlation between the covering factor (CF) of hot dust and the properties of active galactic nuclei (AGNs), e.g., the bolometric luminosity ($L_{\\rm{bol}}$) and black hole mass ($M_{\\rm{BH}}$). Combining the possible dust distribution in the torus, the angular dependence of the radiation of the accretion disc, and the relation between the critical angle of torus and the Eddington ratio, there are eight possible models investigated in our work. We fit the observed CF with these models to determine the parameters of them. As a result, clumpy torus models can generally explain the observed correlations of tori, while the smooth models fail to produce the required CFs. However, there is still significant scatter even for the best-fitting model, which is the combination of a clumpy torus illuminated by the anisotropic radiation of accretion disc in an AGN. Although some of the observed scatter is due to the uncertainties in measuring $L_{\\rm{bol}}$ and $M_{\\rm{BH}}$,...

  20. A hybrid model for the evolution of galaxies and Active Galactic Nuclei in the infrared

    CERN Document Server

    Cai, Zhen-Yi; Xia, Jun-Qing; De Zotti, Gianfranco; Negrello, Mattia; Gruppioni, Carlotta; Rigby, Emma; Castex, Guillaume; Delabrouille, Jacques; Danese, Luigi

    2013-01-01

    [Abridged] We present a comprehensive investigation of the cosmological evolution of the luminosity function (LF) of galaxies and active galactic nuclei (AGN) in the infrared (IR). Based on the observed dichotomy in the ages of stellar populations of early-type galaxies on one side and late-type galaxies on the other, the model interprets the epoch-dependent LFs at z \\geq 1.5 using a physical model for the evolution of proto-spheroidal galaxies and of the associated AGNs, while IR galaxies at z<1.5 are interpreted as being mostly late-type 'cold' (normal) and 'warm' (starburst) galaxies. As for proto-spheroids, in addition to the epoch-dependent LFs of stellar and AGN components separately, we have worked out the evolving LFs of these objects as a whole (stellar plus AGN component). The model provides a physical explanation for the observed positive evolution of both galaxies and AGNs up to z \\simeq 2.5 and for the negative evolution at higher redshifts, for the sharp transition from Euclidean to extremely...

  1. Full Spectral Survey of Active Galactic Nuclei in the Rossi X-ray Timing Explorer Archive

    CERN Document Server

    Rivers, Elizabeth; Rothschild, Richard

    2013-01-01

    We have analyzed spectra for all active galactic nuclei in the Rossi X-ray Timing Explorer (RXTE) archive. We present long-term average values of absorption, Fe line equivalent width, Compton reflection and photon index, as well as calculating fluxes and luminosities in the 2-10 keV band for 100 AGN with sufficient brightness and overall observation time to yield high quality spectral results. We compare these parameters across the different classifications of Seyferts and blazars. Our distributions of photon indices for Seyfert 1's and 2's are consistent with the idea that Seyferts share a common central engine, however our distributions of Compton reflection hump strengths do not support the classical picture of absorption by a torus and reflection off a Compton-thick disk with type depending only on inclination angle. We conclude that a more complex reflecting geometry such as a combined disk and torus or clumpy torus is likely a more accurate picture of the Compton-thick material. We find that Compton ref...

  2. What governs the bulk velocity of the jet components in active galactic nuclei?

    CERN Document Server

    Chai, Bo; Gu, Minfeng

    2012-01-01

    We use a sample of radio-loud active galactic nuclei (AGNs) with measured black hole masses to explore the jet formation mechanisms in these sources. Based on the K\\"{o}nigl's inhomogeneous jet model, the jet parameters, such as the bulk motion Lorentz factor, magnetic field strength, and electron density in the jet, can be estimated with the very long-baseline interferometry and X-ray data. We find a significant correlation between black hole mass and the bulk Lorentz factor of the jet components for this sample, while no significant correlation is present between the bulk Lorentz factor and the Eddington ratio. The massive black holes will be spun up through accretion, as the black holes acquire mass and angular momentum simultaneously through accretion. Recent investigation indeed suggested that most supermassive black holes in elliptical galaxies have on average higher spins than the black holes in spiral galaxies, where random, small accretion episodes (e.g., tidally disrupted stars, accretion of molecul...

  3. Tracing the Physical Conditions in Active Galactic Nuclei with Time-Dependent Chemistry

    CERN Document Server

    Meijerink, Rowin; Kamp, Inga; Aresu, Giambattista; Thi, Wing-Fai; Woitke, Peter

    2013-01-01

    We present an extension of the code ProDiMo that allows for a modeling of processes pertinent to active galactic nuclei and to an ambient chemistry that is time dependent. We present a proof-of-concept and focus on a few astrophysically relevant species, e.g., H+, H2+ and H3+; C+ and N+; C and O; CO and H2O; OH+, H2O+ and H3O+; HCN and HCO+. We find that the freeze-out of water is strongly suppressed and that this affects the bulk of the oxygen and carbon chemistry occurring in AGN. The commonly used AGN tracer HCN/HCO+ is strongly time-dependent, with ratios that vary over orders of magnitude for times longer than 10^4 years. Through ALMA observations this ratio can be used to probe how the narrow-line region evolves under large fluctuations in the SMBH accretion rate. Strong evolutionary trends, on time scales of 10^4-10^8 years, are also found in species such as H3O+, CO, and H2O. These reflect, respectively, time dependent effects in the ionization balance, the transient nature of the production of molecu...

  4. Radiation pressure force emission line profiles and black hole mass in active galactic nuclei

    CERN Document Server

    Netzer, H

    2010-01-01

    We present a new analysis of the motion of broad line region (BLR) clouds in active galactic nuclei (AGNs) taking into account the combined influence of gravity and radiation pressure force. We calculate cloud orbits under a large range of conditions and include the effect of a changing column density as a function of location. The dependence of radiation pressure force on the level of ionization and the column density are accurately computed. The main results are: a. The mean cloud location r(BLR) and the line widths (FWHMs) are combined in such a way that the simple virial mass estimate, r{BLR} FWHM^2/G, gives a reasonable approximation to the black hole mass M even when radiation pressure force is important. The reason is that L/M rather than L is the main parameter affecting the planar cloud motion. b. Reproducing the observed mean radius, FWHM and intensity of H-beta and CIV 1549 requires at least two different populations of clouds. c. The cloud location is a function of both L^{1/2} and L/M. Given this...

  5. AEGIS: New Evidence Linking Active Galactic Nuclei to the Quenching of Star Formation

    CERN Document Server

    Bundy, Kevin; Nandra, Kirpal; Ellis, Richard S; Conselice, Christopher J; Laird, Elise; Coil, Alison; Cooper, Michael; Faber, Sandra M; Newman, Jeff A; Pierce, Christy M; Primack, Joel R; Yan, Renbin

    2007-01-01

    Utilizing Chandra X-ray observations in the All-wavelength Extended Groth Strip International Survey (AEGIS) we identify 241 X-ray selected Active Galactic Nuclei (AGNs, L > 10^{42} ergs/s) and study the properties of their host galaxies in the range 0.4 < z < 1.4. By making use of infrared photometry from Palomar Observatory and BRI imaging from the Canada-France-Hawaii Telescope, we estimate AGN host galaxy stellar masses and show that both stellar mass and photometric redshift estimates (where necessary) are robust to the possible contamination from AGNs in our X-ray selected sample. Accounting for the photometric and X-ray sensitivity limits of the survey, we construct the stellar mass function of X-ray selected AGN host galaxies and find that their abundance decreases by a factor of ~2 since z~1, but remains roughly flat as a function of stellar mass. We compare the abundance of AGN hosts to the rate of star formation quenching observed in the total galaxy population. If the timescale for X-ray det...

  6. A toy model for X-ray spectral variability of active galactic nuclei

    CERN Document Server

    Cao, Xinwu

    2014-01-01

    The long term X-ray spectral variability of ten active galactic nuclei (AGN) shows a positive spectral index-flux correlation for each object (Sobolewska & Papadakis 2009). An inner advection dominated accretion flow (ADAF) may connect to a thin disc/corona at a certain transition radius, which are responsible for hard X-ray emission in AGN. The ADAF is hot and its X-ray spectrum is hard, while the corona above the disc is relatively cold and its X-ray spectrum is therefore soft. The radiation efficiency of the ADAF is usually much lower than that of the thin disc. The increase of the transition radius may lead to decreases of the spectral index (i.e., a hard spectrum) and the X-ray luminosity even if the accretion rate is fixed, and vice versa. We propose that such X-ray variability is caused by the change of the transition radius. Our model calculations can reproduce the observed index-flux correlations, if the transition radius fluctuates around an equilibrium position, and the radiation efficiency of ...

  7. New mechanism of radiation polarization in type 1 Seyfert active galactic nuclei

    Science.gov (United States)

    Silant'ev, N. A.; Gnedin, Yu. N.; Piotrovich, M. Yu.; Natsvlishvili, T. M.; Buliga, S. D.

    2016-10-01

    In most type 1 Seyfert active galactic nuclei (AGNs), the optical linear continuum polarization degree is usually small (less than 1 per cent) and the polarization position angle is nearly parallel to the AGN radio axis. However, there are many type 1 AGNs with unexplained intermediate values for both positional angles and polarization degrees. Our explanation of polarization degree and positional angle of type 1 Seyfert AGNs focuses on the reflection of non-polarized radiation from sub-parsec jets in optically thick accretion discs. The presence of a magnetic field surrounding the scattering media will induce Faraday rotation of the polarization plane, which may explain the intermediate values of positional angles if there is a magnetic field component normal to the accretion disc. The Faraday rotation depolarization effect in the disc diminishes the competition between polarization of the reflected radiation with the parallel component of polarization and the perpendicular polarization from internal radiation of the disc (the Milne problem) in favour of polarization of the reflected radiation. This effect allows us to explain the observed polarization of type 1 Seyfert AGN radiation even though the jet optical luminosity is much lower than the luminosity of the disc. We present the calculation of polarization degrees for a number of type 1 Seyfert AGNs.

  8. X-ray flux variability of active galactic nuclei observed using NuSTAR

    Science.gov (United States)

    Rani, Priyanka; Stalin, C. S.; Rakshit, Suvendu

    2017-04-01

    We present results of a systematic study of flux variability on hourly time-scales in a large sample of active galactic nuclei (AGN) in the 3-79 keV band using data from Nuclear Spectroscopic Telescope Array. Our sample consists of four BL Lac objects (BL Lacs), three flat spectrum radio quasars (FSRQs) 24 Seyfert 1, 42 Seyfert 2 and eight narrow line Seyfert 1 (NLSy1) galaxies. We find that in the 3-79 keV band, about 65 per cent of the sources in our sample show significant variations on hourly time-scales. Using the Mann-Whitney U-test and the Kolmogorov-Smirnov test, we find no difference in the variability behaviour between Seyfert 1 and 2 galaxies. The blazar sources (FSRQs and BL Lacs) in our sample are more variable than Seyfert galaxies that include Seyfert 1 and Seyfert 2 in the soft (3-10 keV), hard (10-79 keV) and total (3-79 keV) bands. NLSy1 galaxies show the highest duty cycle of variability (87 per cent), followed by BL Lacs (82 per cent), Seyfert galaxies (56 per cent) and FSRQs (23 per cent). We obtained flux doubling/halving time in the hard X-ray band less than 10 min in 11 sources. The flux variations between the hard and soft bands in all the sources in our sample are consistent with zero lag.

  9. Radiation pressure confinement - II. Application to the broad line region in active galactic nuclei

    CERN Document Server

    Baskin, Alexei; Stern, Jonathan

    2014-01-01

    Active galactic nuclei (AGN) are characterized by broad emission lines. The lines show similar properties from the lowest luminosity (10^39 erg/s) to the highest luminosity (10^47 erg/s) AGN. What produces this similarity over such a vast range of 10^8 in luminosity? Photoionization is inevitably associated with momentum transfer to the photoionized gas. Yet, most of the photoionized gas in the Broad Line Region (BLR) follows Keplerian orbits, which suggests that the BLR originates from gas clouds with a large enough column for gravity to dominate. The photoionized surface layer of these clouds must develop a pressure gradient which balances the incident radiation force. We present solutions for the structure of such a hydrostatic photoionized gas layer in the BLR. The gas is stratified, with a low-density highly-ionized surface layer, set by the ambient pressure, a density rise inwards, and a uniform density cooler inner region, where the gas pressure, 2n_ekT, reaches the incident radiation pressure n_gamma,...

  10. The Fundamental Plane of the Broad-line Region in Active Galactic Nuclei

    CERN Document Server

    Du, Pu; Hu, Chen; Ho, Luis C; Li, Yan-Rong; Bai, Jin-Ming

    2016-01-01

    Broad emission lines in active galactic nuclei (AGNs) mainly arise from gas photoionized by continuum radiation from an accretion disk around a central black hole. The shape of the broad-line profile, described by ${\\cal D}_{_{\\rm H\\beta}}={\\rm FWHM}/\\sigma_{_{\\rm H\\beta}}$, the ratio of full width at half maximum to the dispersion of broad H$\\beta$, reflects the dynamics of the broad-line region (BLR) and correlates with the dimensionless accretion rate ($\\dot{\\mathscr{M}}$) or Eddington ratio ($L_{\\rm bol}/L_{\\rm Edd}$). At the same time, $\\dot{\\mathscr{M}}$ and $L_{\\rm bol}/L_{\\rm Edd}$ correlate with ${\\cal R}_{\\rm Fe}$, the ratio of optical Fe II to H$\\beta$ line flux emission. Assembling all AGNs with reverberation mapping measurements of broad H$\\beta$, both from the literature and from new observations reported here, we find a strong bivariate correlation of the form $\\log(\\dot{\\mathscr{M}},L_{\\rm bol}/L_{\\rm Edd})=\\alpha+\\beta{\\cal D}_{_{\\rm H\\beta}}+\\gamma{\\cal R}_{\\rm Fe},$ where $\\alpha=(2.47,0.31...

  11. VLBI-Gaia offsets favour parsec-scale jet direction in Active Galactic Nuclei

    CERN Document Server

    Kovalev, Y Y; Plavin, A V

    2016-01-01

    The data release 1 (DR1) of milliarcsecond-scale accurate optical positions of stars and galaxies was recently published by the space mission Gaia. We analyze the offsets of highly accurate absolute radio (very long baseline interferometry, VLBI) and optical positions of active galactic nuclei (AGN) to check whether a signature of wavelength-dependent parsec-scale structure can be seen. We use in the analysis astrometric positions of thousands of AGNs from the VLBI and Gaia observations as well as reconstructed VLBI images. We have found that there is a statistically significant excess of sources with VLBI-to-Gaia positional offset directions along the jet for a full range of offset values as well as an excess for the direction opposite to the jet if offset values are less than 3 mas. An existence of strong extended parsec-scale optical jet structure in many AGNs is required to explain the observed VLBI-Gaia offsets along the jet direction. The 1-mas offsets in the opposite direction are explained by a non-po...

  12. Iron K$\\alpha$ emission in type-I and type-II Active Galactic Nuclei

    CERN Document Server

    Ricci, Claudio; Paltani, Stephane; Ichikawa, Kohei; Gandhi, Poshak; Awaki, Hisamitsu

    2014-01-01

    The narrow Fe K$\\alpha$ line is one of the main signatures of the reprocessing of X-ray radiation from the material surrounding supermassive black holes, and it has been found to be omnipresent in the X-ray spectra of active galactic nuclei (AGN). In this work we study the characteristics of the narrow Fe K$\\alpha$ line in different types of AGN. Using the results of a large Suzaku study we find that Seyfert 2s have on average lower Fe K$\\alpha$ luminosities than Seyfert 1s for the same 10-50 keV continuum luminosity. Simulating dummy Sy1s and Sy2s populations using physical torus models of X-ray reflected emission, we find that this difference can be explained by means of different average inclination angles with respect to the torus, as predicted by the unified model. Alternative explanations include differences in the intensities of Compton humps or in the photon index distributions. We show that the ratio between the flux of the broad and narrow Fe K$\\alpha$ line in the 6.35-6.45 keV range depends on the ...

  13. The subarcsecond mid-infrared view of local active galactic nuclei: III. Polar dust emission

    CERN Document Server

    Asmus, D; Gandhi, P

    2016-01-01

    Recent mid-infrared (MIR) interferometric observations showed in few active galactic nuclei (AGN) that the bulk of the infrared emission originates from the polar region above the putative torus, where only little dust should be present. Here, we investigate whether such strong polar dust emission is common in AGN. Out of 149 Seyferts in the MIR atlas of local AGN (Asmus et al.), 21 show extended MIR emission on single dish images. In 18 objects, the extended MIR emission aligns with the system axis position angle, established by [OIII], radio, polarisation and maser based position angle measurements. The relative amount of resolved MIR emission is at least 40 per cent and scales with the [OIV] fluxes implying a strong connection between the extended continuum and [OIV] emitters. These results together with the radio-quiet nature of the Seyferts support the scenario that the bulk of MIR emission is emitted by dust in the polar region and not by the torus, which would demand a new paradigm for the infrared emi...

  14. Determining the covering factor of Compton-thick active galactic nuclei with NuSTAR

    CERN Document Server

    Brightman, M; Stern, D; Arevalo, P; Ballantyne, D R; Bauer, F E; Boggs, S E; Craig, W W; Christensen, F E; Comastri, A; Fuerst, F; Gandhi, P; Hailey, C J; Harrison, F A; Hickox, R C; Koss, M; LaMassa, S; Puccetti, S; Rivers, E; Vasudevan, R; Walton, D J; Zhang, W W

    2015-01-01

    The covering factor of Compton-thick obscuring material associated with the torus in active galactic nuclei (AGN) is at present best understood through the fraction of sources exhibiting Compton-thick absorption along the line of sight ($N_{H}>1.5\\times10^{24}$ cm$^{-2}$) in the X-ray band, which reveals the average covering factor. Determining this Compton-thick fraction is difficult however, due to the extreme obscuration. With its spectral coverage at hard X-rays ($>$10 keV), NuSTAR is sensitive to the AGN covering factor since Compton scattering of X-rays off optically thick material dominates at these energies. We present a spectral analysis of 10 AGN observed with NuSTAR where the obscuring medium is optically thick to Compton scattering, so called Compton-thick (CT) AGN. We use the torus models of Brightman & Nandra which predict the X-ray spectrum from reprocessing in a torus and include the torus opening angle as a free parameter and aim to determine the covering factor of the Compton-thick gas i...

  15. Ensemble X-ray variability of Active Galactic Nuclei. II. Excess Variance and updated Structure Function

    CERN Document Server

    Vagnetti, F; Antonucci, M; Paolillo, M; Serafinelli, R

    2016-01-01

    Most investigations of the X-ray variability of active galactic nuclei (AGN) have been concentrated on the detailed analyses of individual, nearby sources. A relatively small number of studies have treated the ensemble behaviour of the more general AGN population in wider regions of the luminosity-redshift plane. We want to determine the ensemble variability properties of a rich AGN sample, called Multi-Epoch XMM Serendipitous AGN Sample (MEXSAS), extracted from the latest release of the XMM-Newton Serendipitous Source Catalogue, with redshift between 0.1 and 5, and X-ray luminosities, in the 0.5-4.5 keV band, between 10^{42} and 10^{47} erg/s. We caution on the use of the normalised excess variance (NXS), noting that it may lead to underestimate variability if used improperly. We use the structure function (SF), updating our previous analysis for a smaller sample. We propose a correction to the NXS variability estimator, taking account of the light-curve duration in the rest-frame, on the basis of the knowle...

  16. Reverberation Measurements for 17 Quasars and the Size-Mass-Luminosity Relations in Active Galactic Nuclei

    CERN Document Server

    Kaspi, S; Netzer, H; Maoz, D; Jannuzi, B T; Giveon, U; Kaspi, Shai; Smith, Paul S.; Netzer, Hagai; Maoz, Dan; Jannuzi, Buell T.; Giveon, Uriel

    1999-01-01

    (abridged) We have spectrophotometrically monitored a well-defined sample of 28 Palomar-Green quasars in order to obtain measurements of their BLRs and to investigate the relationships between quasar luminosity, central black hole mass, and broad emission line region (BLR) size in active galactic nuclei (AGN). Spectrophotometry was obtained every 1-4 months for 7.5 years, yielding 20-70 observing epochs per object. Both the continuum and emission line fluxes of all of the quasars were observed to change during the duration of the observing program. Seventeen of the 28 objects were observed with adequate sampling to search for correlated variations between the Balmer emission lines and the continuum flux. For each of these 17 objects, a significant correlation was observed, with the Balmer line variations lagging those of the continuum by studying the size-mass-luminosity relations in AGN by two orders of magnitude and doubles the number of objects suitable for such studies. Combining our results with comparab...

  17. Reverberation Measurements of Quasars and the Size-Mass-Luminosity Relations in Active Galactic Nuclei

    CERN Document Server

    Kaspi, S

    2000-01-01

    A 7.5 years spectrophotometric monitoring program of 28 Palomar-Green quasars to determine the size of their broad emission line region (BLR) is reviewed. We find both the continuum and the emission line fluxes of all quasars to vary during this period. Seventeen objects has adequate sampling for reverberation mapping and in all of them we find the Balmer line variations to lag those of the continuum by ~100 days. This study increases the available luminosity range for studying the size-mass-luminosity relations in active galactic nuclei (AGNs) by two orders of magnitude and doubles the number of objects suitable for such studies. Combining our results with data available for Seyfert 1 galaxies, we find the BLR size to scale with the rest-frame 5100 A luminosity as L^{0.70 +/- 0.03}. This result is different from previous studies, and suggests that the effective ionization parameter in AGNs may be a decreasing function of luminosity. We are also able to constrain, subject to the assumption that gravity domina...

  18. Ultraviolet and X-ray variability of active galactic nuclei with Swift

    Science.gov (United States)

    Buisson, D. J. K.; Lohfink, A. M.; Alston, W. N.; Fabian, A. C.

    2017-01-01

    We analyse a sample of 21 active galactic nuclei using data from the Swift satellite to study the variability properties of the population in the X-ray, UV and optical band. We find that the variable part of the UV-optical emission has a spectrum consistent with a power law, with an average index of -2.21 ± 0.13, as would be expected from central illumination of a thin disc (index of -7/3). We also calculate the slope of a power law from UV to X-ray variable emission, αOX, Var; the average for this sample is αOX, Var = -1.06 ± 0.04. The anticorrelation of αOX with the UV luminosity, LUV, previously found in the average emission is also present in the variable part: αOX, Var = ( - 0.177 ± 0.083)log (Lν, Var(2500 Å)) + (3.88 ± 2.33). Correlated variability between the emission in X-rays and UV is detected significantly for 9 of the 21 sources. All these cases are consistent with the UV lagging the X-rays, as would be seen if the correlated UV variations were produced by the reprocessing of X-ray emission. The observed UV lags are tentatively longer than expected for a standard thin disc.

  19. Revisiting the Infrared Spectra of Active Galactic Nuclei with a New Torus Emission Model

    CERN Document Server

    Fritz, J; Hatziminaoglou, E

    2006-01-01

    We describe improved modelling of the emission by dust in a toroidal--like structure heated by a central illuminating source within Active Galactic Nuclei (AGN). We chose a simple but realistic torus geometry, a flared disc, and a dust grain distribution function including a full range of grain sizes. The optical depth within the torus is computed in detail taking into account the different sublimation temperatures of the silicate and graphite grains, which solves previously reported inconsistencies in the silicate emission feature in type-1 AGN. We exploit this model to study the spectral energy distributions (SEDs) of 58 extragalactic (both type-1 and type-2) sources using archival optical and infrared (IR) data. We find that both AGN and starburst contributions are often required to reproduce the observed SEDs, although in a few cases they are very well fitted by a pure AGN component. The AGN contribution to the far-IR luminosity is found to be higher in type-1 sources, with all the type-2 requiring a subs...

  20. Constraints on the outer radius of the broad emission line region of active galactic nuclei

    CERN Document Server

    Landt, Hermine; Elvis, Martin; Karovska, Margarita

    2014-01-01

    Here we present observational evidence that the broad emission line region (BELR) of active galactic nuclei (AGN) generally has an outer boundary. This was already clear for sources with an obvious transition between the broad and narrow components of their emission lines. We show that the narrow component of the higher-order Paschen lines is absent in all sources, revealing a broad emission line profile with a broad, flat top. This indicates that the BELR is kinematically separate from the narrow emission line region. We use the virial theorem to estimate the BELR outer radius from the flat top width of the unblended profiles of the strongest Paschen lines, Pa alpha and Pa beta, and find that it scales with the ionising continuum luminosity roughly as expected from photoionisation theory. The value of the incident continuum photon flux resulting from this relationship corresponds to that required for dust sublimation. A flat-topped broad emission line profile is produced by both a spherical gas distribution ...

  1. Are Narrow Line Seyfert 1s a special class of Active Galactic Nuclei?

    CERN Document Server

    Valencia-S., M; Eckart, A; Smajic, S; Iserlohe, C; Garcia-Marin, M; Busch, G; Vitale, M; Bremer, M; Fischer, S; Horrobin, M; Moser, L; Rashed, Y E; Straubmeier, C; .,

    2013-01-01

    No. Due to their apparently extreme optical to X-ray properties, Narrow Line Seyfert 1s (NLSy1s) have been considered a special class of active galactic nuclei (AGN). Here, we summarize observational results from different groups to conclude that none of the characteristics that are typically used to define the NLSy1s as a distinct group - from the, nowadays called, Broad Line Seyfert 1s (BLSy1s) - is unique, nor ubiquitous of these particular sources, but shared by the whole Type 1 AGN. Historically, the NLSy1s have been distinguished from the BLSy1s by the narrow width of the broad Hbeta emission line. The upper limit on the full width at half maximum of this line is 2000 km/s for NLSy1s, while in BLSy1s it can be of several thousands of km/s. However, this border has been arbitrarily set and does not correspond to the change of any physical property. All observed parameters in Type 1 AGN cover continues ranges of values, which does not allow to infer the existence of two different kind of populations with ...

  2. Obscured flat spectrum radio active galactic nuclei as sources of high-energy neutrinos

    Science.gov (United States)

    Maggi, G.; Buitink, S.; Correa, P.; de Vries, K. D.; Gentile, G.; Tavares, J. León; Scholten, O.; van Eijndhoven, N.; Vereecken, M.; Winchen, T.

    2016-11-01

    Active galactic nuclei (AGN) are believed to be one of the main source candidates for the high-energy (TeV-PeV) cosmic neutrino flux recently discovered by the IceCube neutrino observatory. Nevertheless, several correlation studies between AGN and the cosmic neutrinos detected by IceCube show no significance. Therefore, in this article we consider a specific subclass of AGN for which an increased neutrino production is expected. This subclass contains AGN for which their high-energy jet is pointing toward Earth. Furthermore, we impose the condition that the jet is obscured by gas or dust surrounding the AGN. A method is presented to determine the total column density of the obscuring medium, which is probed by determining the relative x-ray attenuation with respect to the radio flux as obtained from the AGN spectrum. The total column density allows us to probe the interaction of the jet with the surrounding matter, which leads to additional neutrino production. Finally, starting from two different source catalogs, this method is applied to specify a sample of low redshift radio galaxies for which an increased neutrino production is expected.

  3. Long Term Optical and Infrared Reverberation Mapping of High and Low Luminosity Active Galactic Nuclei

    Science.gov (United States)

    Gorjian, Varoujan; Barth, Aaron; Brandt, Niel; Dawson, Kyle; Green, Paul; Ho, Luis; Horne, Keith; Jiang, Linhua; Joner, Mike; Kenney, John; McGreer, Ian; Nordgren, Tyler; Schneider, Donald; Shen, Yue; Tao, Charling

    2016-08-01

    Previous Spitzer reverberation monitoring projects looking for UV/optical light absorbed and re-emitted in the IR by dust have been limited to very low luminosity active galactic nuclei (AGN) that could potentially show reverberation within a single cycle (~1 year). Cycle 11-12's two year baseline allowed for the reverberation mapping of 17 high luminosity quasars from the Sloan Digital Sky Survey Reverberation Mapping project. By combining ground based monitoring from Pan-STARRS, CFHT, and Steward Observatory telescopes with Spitzer data we have for the first time detected dust reverberation in quasars. We propose to continue this project to capitalize on the continuing optical motnoring from the ground and to increase the confidence in the detected lags. Additionally, the Call for Proposals asks for up to 1000 hours of observations in the Spitzer CVZ to accommodate battery charging needs. We propose to add to our quasar sample five lower luminosity Seyfert galaxies from the Pan-STARRS ground based optical survey that are in the Spitzer CVZ, which will increase the luminosity range of AGN we are studying and, combined with additional ground based observatories, provide for a continuous monitoring campaign lasting 2 years and thus provide the most detailed study of dust around AGN to date.

  4. The different neighbours around Type-1 and Type-2 active galactic nuclei

    CERN Document Server

    Villarroel, Beatriz

    2014-01-01

    One of the most intriguing open issues in galaxy evolution is the structure and evolution of active galactic nuclei (AGN) that emit intense light believed to come from an accretion disk near a super-massive black hole (Rees 1984, Lynden-Bell 1969). To understand the zoo of different AGN classes, it has been suggested that all AGN are the same type of object viewed from different angles (Antonucci 1993). This model -- called AGN unification -- has been successful in predicting e.g. the existence of hidden broad optical lines in the spectrum of many narrow-line AGN. But this model is not unchallenged (Tran 2001) and it is an open problem whether more than viewing angle separates the so-called Type-1 and Type-2 AGN. Here we report the first large-scale study that finds strong differences in the galaxy neighbours to Type-1 and Type-2 AGN with data from the Sloan Digital Sky Survey (SDSS) (York et al. 2000) Data Release 7 (DR7) (Abazajian et al. 2008) and Galaxy Zoo (Lintott et al, 2008, Lintott et al 2011). We fi...

  5. The standard model and some new directions. [for scientific theory of Active Galactic Nuclei

    Science.gov (United States)

    Blandford, R. D.; Rees, M. J.

    1992-01-01

    A 'standard' model of Active Galactic Nuclei (AGN), based upon a massive black hole surrounded by a thin accretion disk, is defined. It is argued that, although there is good evidence for the presence of black holes and orbiting gas, most of the details of this model are either inadequate or controversial. Magnetic field may be responsible for the confinement of continuum and line-emitting gas, for the dynamical evolution of accretion disks and for the formation of jets. It is further argued that gaseous fuel is supplied in molecular form and that this is responsible for thermal re-radiation, equatorial obscuration and, perhaps, the broad line gas clouds. Stars may also supply gas close to the black hole, especially in low power AGN and they may be observable in discrete orbits as probes of the gravitational field. Recent observations suggest that magnetic field, stars, dusty molecular gas and orientation effects must be essential components of a complete description of AGN. The discovery of quasars with redshifts approaching 5 is an important clue to the mechanism of galaxy formation.

  6. Piecing Together the X-ray Background: Bolometric Corrections for Active Galactic Nuclei

    CERN Document Server

    Vasudevan, R V

    2007-01-01

    (Abridged) The X-ray background can be used to constrain the accretion history of Supermassive Black Holes (SMBHs) in Active Galactic Nuclei (AGN). A knowledge of the hard X-ray bolometric correction, \\kappa_{2-10keV} is a vital input into these studies. Variations in the disk emission in the UV have not previously been taken into account in calculating \\kappa_{2-10keV}; we show that such variations are important by constructing optical--to--X-ray SEDs for 54 AGN. In particular, we use FUSE UV and X-ray data from the literature to constrain the disk emission as well as possible. Previous work has suggested a dependence of \\kappa_{2-10keV} on AGN luminosity, but we find significant spread in \\kappa_{2-10keV} with no simple dependence on luminosity. Populations such as Narrow-Line Seyfert 1 nuclei (NLS1s), Radio Loud and X-ray Weak AGN may have values of \\kappa_{2-10keV} differing systematically from the rest of the AGN population. Other sources of uncertainty include intrinsic extinction in the optical--UV, X-...

  7. Why Do Compact Active Galactic Nuclei at High Redshift Scintillate Less?

    CERN Document Server

    Koay, J Y; Rickett, B J; Bignall, H E; Jauncey, D L; Pursimo, T; Reynolds, C; Lovell, J E J; Kedziora-Chudczer, L; Ojha, R

    2012-01-01

    The fraction of compact active galactic nuclei (AGNs) that exhibit interstellar scintillation (ISS) at radio wavelengths, as well as their scintillation amplitudes, have been found to decrease significantly for sources at redshifts z > 2. This can be attributed to an increase in the angular sizes of the \\muas-scale cores or a decrease in the flux densities of the compact \\muas cores relative to that of the mas-scale components with increasing redshift, possibly arising from (1) the space-time curvature of an expanding Universe, (2) AGN evolution, (3) source selection biases, (4) scatter broadening in the ionized intergalactic medium (IGM) and intervening galaxies, or (5) gravitational lensing. We examine the frequency scaling of this redshift dependence of ISS to determine its origin, using data from a dual-frequency survey of ISS of 128 sources at 0 < z < 4. We present a novel method of analysis which accounts for selection effects in the source sample. We determine that the redshift dependence of ISS ...

  8. The Intrinsic Eddington Ratio Distribution of Active Galactic Nuclei in Young Galaxies from SDSS

    Science.gov (United States)

    Jones, Mackenzie L.; Hickox, Ryan C.; Black, Christine; Hainline, Kevin Nicholas; DiPompeo, Michael A.

    2016-04-01

    An important question in extragalactic astronomy concerns the distribution of black hole accretion rates, i.e. the Eddington ratio distribution, of active galactic nuclei (AGN). Specifically, it is matter of debate whether AGN follow a broad distribution in accretion rates, or if the distribution is more strongly peaked at characteristic Eddington ratios. Using a sample of galaxies from SDSS DR7, we test whether an intrinsic Eddington ratio distribution that takes the form of a broad Schechter function is in fact consistent with previous work that suggests instead that young galaxies in optical surveys have a more strongly peaked lognormal Eddington ratio distribution. Furthermore, we present an improved method for extracting the AGN distribution using BPT diagnostics that allows us to probe over one order of magnitude lower in Eddington ratio, counteracting the effects of dilution by star formation. We conclude that the intrinsic Eddington ratio distribution of optically selected AGN is consistent with a power law with an exponential cutoff, as is observed in the X-rays. This work was supported in part by a NASA Jenkins Fellowship.

  9. The Nature of Active Galactic Nuclei with Velocity Offset Emission Lines

    CERN Document Server

    Müller-Sánchez, Francisco; Stern, Daniel; Harrison, Fiona A

    2016-01-01

    We obtained Keck/OSIRIS near-IR adaptive optics-assisted integral-field spectroscopy to probe the morphology and kinematics of the ionized gas in four velocity-offset active galactic nuclei (AGNs) from the Sloan Digital Sky Survey. These objects possess optical emission lines that are offset in velocity from systemic as measured from stellar absorption features. At a resolution of ~0.18", OSIRIS allows us to distinguish which velocity offset emission lines are produced by the motion of an AGN in a dual supermassive black hole system, and which are produced by outflows or other kinematic structures. In three galaxies, J1018+2941, J1055+1520 and J1346+5228, the spectral offset of the emission lines is caused by AGN-driven outflows. In the remaining galaxy, J1117+6140, a counterrotating nuclear disk is observed that contains the peak of Pa$\\alpha$ emission 0.2" from the center of the galaxy. The most plausible explanation for the origin of this spatially and kinematically offset peak is that it is a region of en...

  10. He-like ions as practical astrophysical plasma diagnostics: From stellar coronae to active galactic nuclei

    CERN Document Server

    Porquet, Delphine; Grosso, Nicolas; 10.1007/s11214-010-9731-2

    2011-01-01

    We review X-ray plasma diagnostics based on the line ratios of He-like ions. Triplet/singlet line intensities can be used to determine electronic temperature and density, and were first developed for the study of the solar corona. Since the launches of the X-ray satellites Chandra and XMM-Newton, these diagnostics have been extended and used (from CV to Si XIII) for a wide variety of astrophysical plasmas such as stellar coronae, supernova remnants, solar system objects, active galactic nuclei, and X-ray binaries. Moreover, the intensities of He-like ions can be used to determine the ionization process(es) at work, as well as the distance between the X-ray plasma and the UV emission source for example in hot stars. In the near future thanks to the next generation of X-ray satellites (e.g., Astro-H and IXO), higher-Z He-like lines (e.g., iron) will be resolved, allowing plasmas with higher temperatures and densities to be probed. Moreover, the so-called satellite lines that are formed closed to parent He-like ...

  11. Phase Retrieval Problem. Application to VLBI Mapping of Active Galactic Nuclei

    CERN Document Server

    Bajkova, A T

    2012-01-01

    The well-known phase problem which means image reconstruction from only spectrum magnitude without using any spectrum phase information is considered basically in application to VLBI mapping of compact extragalactic radio sources (active galactic nuclei). The method proposed for phaseless mapping is based on the reconstruction of the spectrum magnitude on the entire UV plane from the measured visibility magnitude on a limited set of points and the reconstruction of the sought-for image of the source by Fienup's error-reduction iterative algorithm from the spectrum magnitude reconstructed at the first stage. It is shown that the technique used ensures unique solution (within a class of equivalent functions) for AGNs with typical structure morphology "bright core + week jet". The method proposed can be used, for example, for imaging with ultra-high resolution using a space{ground radio interferometer with a space antenna in a very high orbit ("RadioAstron"). In this case, a multi-element interferometer essentia...

  12. Ultraviolet and X-ray variability of active galactic nuclei with Swift

    CERN Document Server

    Buisson, Douglas J K; Alston, William N; Fabian, Andrew C

    2016-01-01

    We analyse a sample of 21 active galactic nuclei (AGN) using data from the Swift satellite to study the variability properties of the population in the X-ray, UV and optical band. We find that the variable part of the UV-optical emission has a spectrum consistent with a powerlaw, with an average index of $-2.21\\pm0.13$, as would be expected from central illumination of a thin disc (index of -7/3). We also calculate the slope of a powerlaw from UV to X-ray variable emission, $\\alpha_{\\rm OX,Var}$; the average for this sample is $\\alpha_{\\rm OX,Var} = -1.06 \\pm 0.04$. The anticorrelation of $\\alpha_{\\rm OX}$ with the UV luminosity, $L_{\\rm UV}$, previously found in the average emission is also present in the variable part: $\\alpha_{\\rm OX,Var} = (-0.177 \\pm 0.083) {\\rm log} (L_{\\rm \

  13. Ultra-High-Energy Cosmic Rays from Low-Luminosity Active Galactic Nuclei

    CERN Document Server

    Dutan, Ioana

    2014-01-01

    We investigate the production of ultra-high-energy cosmic ray (UHECR) in relativistic jets from low-luminosity active galactic nuclei (LLAGN). We start by proposing a model for the UHECR contribution from the black holes (BHs) in LLAGN, which present a jet power $P_{\\mathrm{j}} \\leqslant 10^{46}$ erg s$^{-1}$. This is in contrast to the opinion that only high-luminosity AGN can accelerate particles to energies $ \\geqslant 50$ EeV. We rewrite the equations which describe the synchrotron self-absorbed emission of a non-thermal particle distribution to obtain the observed radio flux density from sources with a flat-spectrum core and its relationship to the jet power. We find that the UHECR flux is dependent on the {\\it observed radio flux density, the distance to the AGN, and the BH mass}, where the particle acceleration regions can be sustained by the magnetic energy extraction from the BH at the center of the AGN. We use a complete sample of 29 radio sources with a total flux density at 5 GHz greater than 0.5 ...

  14. Anisotropic radiation from accretion disc-coronae in active galactic nuclei

    CERN Document Server

    Xu, Ya-Di

    2015-01-01

    In the unification scheme of active galactic nuclei (AGN), Seyfert 1s and Seyfert 2s are intrinsically same, but they are viewed at different angles. However, the Fe K\\alpha emission line luminosity of Seyfert 1s was found in average to be about twice of that of Seyfert 2s at given X-ray continuum luminosity in the previous work (Ricci et al. 2014). We construct an accretion disc-corona model, in which a fraction of energy dissipated in the disc is extracted to heat the corona above the disc. The radiation transfer equation containing Compton scattering processes is an integro-differential equation, which is solved numerically for the corona with a parallel plane geometry. We find that the specific intensity of X-ray radiation from the corona changes little with the viewing angle \\theta when \\theta is small (nearly face-on), and it is sensitive to \\theta if the viewing angle is large (\\theta> 40 degrees). The radiation from the cold disc, mostly in infrared/optical/UV bands, is almost proportional to cos\\thet...

  15. Evolution of the X-ray spectrum in the flare model of Active Galactic Nuclei

    CERN Document Server

    Collin, S; Dumont, A M; Petrucci, P O; Rózanska, A R

    2003-01-01

    Nayakshin & Kazanas (2002) have considered the time-dependent illumination of an accretion disc in Active Galactic Nuclei, in the lamppost model. We extend their study to the flare model, which postulates the release of a large X-ray flux above a small region of the accretion disc. A fundamental difference with the lamppost model is that the region of the disc below the flare is not illuminated before the onset of the flare. A few test models show that the spectrum which follows immediately the increase in continuum flux should display the characteristics of a highly illuminated but dense gas, i.e. very intense X-ray emission lines and ionization edges in the soft X-ray range. The behaviour of the iron line is different in the case of a "moderate" and a ``strong'' flare: for a moderate flare, the spectrum displays a neutral component of the Fe K$\\alpha$ line at 6.4 keV, gradually leading to more highly ionized lines. For a strong flare, the lines are already emitted by FeXXV (around 6.7 keV) after the ons...

  16. Invisible Active Galactic Nuclei. II Radio Morphologies & Five New HI 21 cm Absorption Line Detections

    CERN Document Server

    Yan, Ting; Darling, Jeremy; Momjian, Emmanuel; Sharma, Soniya; Kanekar, Nissim

    2015-01-01

    We have selected a sample of 80 candidates for obscured radio-loud active galactic nuclei and presented their basic optical/near-infrared (NIR) properties in Paper 1. In this paper, we present both high-resolution radio continuum images for all of these sources and HI 21cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz VLA continuum observations find that 52 sources are compact or have substantial compact components with size 0.1 Jy at 4.9 GHz. The most compact 36 sources were then observed with the VLBA at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, a detection rate of CSOs ~3 times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty seven sources were observed for HI 21cm absorption at their photometric or spectroscopic redshifts with only ...

  17. Inflows and outflows in nearby active galactic nuclei from integral field spectroscopy

    CERN Document Server

    Storchi-Bergmann, Thaisa

    2010-01-01

    I report recent results on the kinematics of the inner few hundred parsecs (pc) around nearby active galactic nuclei (AGN) at a sampling of a few pc to a few tens of pc, using optical and near-infrared (near-IR) integral field spectroscopy obtained with the Gemini telescopes. The stellar kinematics of the hosts - comprised mostly of spiral galaxies - are dominated by circular rotation in the plane of the galaxy. Inflows with velocities of ~ 50 km/s have been observed along nuclear spiral arms in (optical) ionized gas emission for low-luminosity AGN and in (near-IR) molecular gas emission for higher-luminosity AGN. We have also observed gas rotating in the galaxy plane, sometimes in compact (few tens of pc) disks which may be fuelling the AGN. Outflows have been observed mostly in ionized gas emission from the narrow-line region, whose flux distributions and kinematics frequently correlate with radio flux distributions. Channel maps along the emission-line profiles reveal velocities as high as ~ 600 km/s. Mass...

  18. The SAMI Galaxy Survey: Unveiling the nature of kinematically offset active galactic nuclei

    CERN Document Server

    Allen, J T; Scott, N; Fogarty, L M R; Ho, I -T; Medling, A M; Leslie, S K; Bland-Hawthorn, J; Bryant, J J; Croom, S M; Goodwin, M; Green, A W; Konstantopoulos, I S; Lawrence, J S; Owers, M S; Richards, S N; Sharp, R

    2015-01-01

    We have observed two kinematically offset active galactic nuclei (AGN), whose ionised gas is at a different line-of-sight velocity to their host galaxies, with the SAMI integral field spectrograph (IFS). One of the galaxies shows gas kinematics very different to the stellar kinematics, indicating a recent merger or accretion event. We demonstrate that the star formation associated with this event was triggered within the last 100 Myr. The other galaxy shows simple disc rotation in both gas and stellar kinematics, aligned with each other, but in the central region has signatures of an outflow driven by the AGN. Other than the outflow, neither galaxy shows any discontinuity in the ionised gas kinematics at the galaxy's centre. We conclude that in these two cases there is no direct evidence of the AGN being in a supermassive black hole binary system. Our study demonstrates that selecting kinematically offset AGN from single-fibre spectroscopy provides, by definition, samples of kinematically peculiar objects, bu...

  19. Measurements of M-Shell Dielectronic Recombination for Active Galactic Nuclei

    Science.gov (United States)

    Lukic, D.; Schnell, M.; Savin, D. W.; Mueller, A.; Schippers, S.; Schmidt, E. W.; Brandau, C.; Lestinsky, M.; Sprenger, F.; Wolf, A.

    2005-05-01

    XMM-Newton and Chandra spectroscopy of active galactic nuclei (AGNs) shows a rich spectrum of X-ray absorption lines. These AGN observations have detected a broad unresolved transition array (UTA) between 15-17 A. This is attributed to inner shell photoexcitation of M-shell iron. Modeling these UTA features is currently limited by uncertainties in the low temperature DR data for M-shell iron. In order to resolve this issue and to provide reliable iron M-shell DR data for plasma modeling, we are carrying out a series of laboratory measurements using the heavy-ion Test Storage Ring (TSR) at the Max-Plank-Institute for Nuclear Physics in Heidelberg, Germany. Other commonly used laboratory methods for studying DR (e.g., electron beam ion traps [EBITs]) are unable to measure the relevant low energy DR resonances. Storage rings are currently the only laboratory method capable of studying low temperature DR. We are also providing our data to atomic theorist to benchmark their modern DR calculations. Our initial results indicate that state-of-the-art theory cannot reliably predict the needed low temperature M-shell DR rate coefficients. Here we will report our recent results for DR of Fe XIV and Fe XIII and plans for future work. This work is supported part by NASA, the German Federal Ministry for Education and Research, and the German Research Council.

  20. A growth-rate indicator for Compton-thick active galactic nuclei

    CERN Document Server

    Brightman, M; Ballantyne, D R; Baloković, M; Brandt, W N; Chen, C -T; Comastri, A; Farrah, D; Gandhi, P; Harrison, F A; Ricci, C; Stern, D; Walton, D J

    2016-01-01

    Due to their heavily obscured central engines, the growth rate of Compton-thick (CT) active galactic nuclei (AGN) is difficult to measure. A statistically significant correlation between the Eddington ratio, {\\lambda}$_{Edd}$, and the X-ray power-law index, {\\Gamma}, observed in unobscured AGN offers an estimate of their growth rate from X-ray spectroscopy (albeit with large scatter). However, since X-rays undergo reprocessing by Compton scattering and photoelectric absorption when the line-of-sight to the central engine is heavily obscured, the recovery of the intrinsic {\\Gamma} is challenging. Here we study a sample of local, predominantly Compton-thick megamaser AGN, where the black hole mass, and thus Eddington luminosity, are well known. We compile results on X-ray spectral fitting of these sources with sensitive high-energy (E> 10 keV) NuSTAR data, where X-ray torus models which take into account the reprocessing effects have been used to recover the intrinsic {\\Gamma} values and X-ray luminosities, L$_...

  1. Relativistic hadrons and the origin of relativistic outflows in active galactic nuclei

    Science.gov (United States)

    Contopoulos, John; Kazanas, D.

    1995-01-01

    We examine the hydrodynamic origin of relativistic outflows in active galactic nuclei (AGN). Specifically, we propose that the presence of a population of relativistic hadrons in the AGN 'central engine' and the associated neutron production suffices to produce outflows which under rather general conditions could be relativistic. The main such condition is that the size of the neutron production region be larger than the neutron flight path tau(sub n) approximately 3 x 10(exp 13) cm. This condition guarantees that the mean energy per particle in the proton fluid, resulting from the decay of the neutrons outside their production region, be greater than the proton rest mass. The expansion of this fluid can then lead naturally to a relativistic outflow by conversion of its internal energy to directed motion. We follow the development of such flows by solving the mass, energy as well as the kinetic equation for the proton gas in steady state, taking into account the source terms due to compute accurately the adiabatic index of the expanding gas, and in conjunction with Bernoulli's equation the detailed evolution of the bulk Lorentz factor. We further examine the role of large-scale magnetic fields in confining these outflows to produce the jets observed at larger scales.

  2. Modeling the Emission from Turbulent Relativistic Jets in Active Galactic Nuclei

    Indian Academy of Sciences (India)

    Victoria Calafut; Paul J. Wiita

    2015-06-01

    We present a numerical model developed to calculate observed fluxes of relativistic jets in active galactic nuclei. The observed flux of each turbulent eddy is dependent upon its variable Doppler boosting factor, computed as a function of the relativistic sum of the individual eddy and bulk jet velocities, and our viewing angle to the jet. The total observed flux is found by integrating the radiation from the eddies over the turbulent spectrum. We consider jets that contain turbulent eddies that have either standard Kolmogorov or recently derived relativistic turbulence spectra. We also account for the time delays in receiving the emission of the eddies due to their different simulated positions in the jet, as well as due to the varying beaming directions as they turn over. We examine these theoretical light curves and compute power spectral densities (PSDs) for a range of viewing angles, bulk velocities of the jet, and turbulent velocities. These PSD slopes depend significantly on the turbulent velocity, and are essentially independent of viewing angle and bulk velocity. The flux variations produced in the simulations for realistic values of the parameters tested are consistent with the types of variations observed in radio-loud AGN as, for example, recently measured with the Kepler satellite, as long as the turbulent velocities are not too high.

  3. Direct Measurement of the X-ray Time-Delay Transfer Function in Active Galactic Nuclei

    CERN Document Server

    Legg, E; Turner, T J; Giustini, M; Reeves, J N; Kraemer, S B

    2012-01-01

    The origin of the observed time lags, in nearby active galactic nuclei (AGN), between hard and soft X-ray photons is investigated using new XMM-Newton data for the narrow-line Seyfert I galaxy Ark 564 and existing data for 1H0707-495 and NGC 4051. These AGN have highly variable X-ray light curves that contain frequent, high peaks of emission. The averaged light curve of the peaks is directly measured from the time series, and it is shown that (i) peaks occur at the same time, within the measurement uncertainties, at all X-ray energies, and (ii) there exists a substantial tail of excess emission at hard X-ray energies, which is delayed with respect to the time of the main peak, and is particularly prominent in Ark 564. Observation (i) rules out that the observed lags are caused by Comptonization time delays and disfavors a simple model of propagating fluctuations on the accretion disk. Observation (ii) is consistent with time lags caused by Compton-scattering reverberation from material a few thousand light-se...

  4. A Multi-parameter Model for Radio Dichotomy of Active Galactic Nuclei and Jets

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Based on the coexistence of the Blandford-Znajek and magnetic coupling processes in black hole (BH)accretion disc, a multi-parameter model for jet powers and radio loudness of active galactic nuclei (AGNs) is studied. It turns out that radio-loudness of AGNs could be governed by five parameters: (i) the BH spin, (ii) a power-law index of the variation of the magnetic field on the disc; (iii) a parameter determining the position of the inner edge of the disc, (iv)the ratio of the pressure of the magnetic field on the horizon to the ram pressure of the innermost parts of an accretion flow, and (v) the ratio of the angular velocity of the open field lines to that of the horizon. The observed dichotomy between radio-loud and radio-quiet AGNs is well interpreted by the effects of the above parameters. Furthermore, we discuss the derivative of radio loudness of AGNs with respect to each parameter separately. In addition, the effect of the screw instability on radio loudness of A GNs is discussed.

  5. Evidence of the Link between Broad Emission Line Regions and Accretion Disks in Active Galactic Nuclei

    Institute of Scientific and Technical Information of China (English)

    Yun Xu; Xin-Wu Cao

    2007-01-01

    There is observational evidence that broad-line regions (BLRs) exist in most active galactic nuclei (AGNs), but their origin is still unclear. One scenario is that the BLRs originate from winds accelerated from the hot coronae of the disks, and the winds are suppressed when the black hole is accreting at low rates. This model predicts a relation between (m) ((m) = (M)/(M)Edd) and the FWHM of broad emission lines. We estimate the central black hole masses for a sample of bright AGNs by using their broad Hβ line-widths and optical luminosities. The dimensionless accretion rates (m) = (M)/(M)Edd are derived from the optical continuum luminosities by using two different models: using an empirical relation between the bolometric luminosity Lbol and the optical luminosity ((m) = Lbol/LEdd, a fixed radiative efficiency is adopted); and calculating the optical spectra of accretion disks as a function of (m). We find a significant correlation between the derived (m) and the observed line width of Hβ,FWHM∝ (m)-0.37, which almost overlaps the disk-corona model calculations, if the viscosity α≈ 0.1 - 0.2 is adopted. Our results provide strong evidence for the physical link between the BLRs and accretion disks in AGNs.

  6. The disk evaporation model for the spectral features of low-luminosity active galactic nuclei

    CERN Document Server

    Qiao, Erlin; Panessa, Francesca; Liu, J Y

    2013-01-01

    Observations show that the accretion flows in low-luminosity active galactic nuclei (LLAGNs) probably have a two-component structure with an inner ADAF and an outer truncated accretion disk. As shown by Taam et al. (2012), the truncation radius as a function of mass accretion rate is strongly affected by including the magnetic field within the framework of disk evaporation model, i.e., an increase of the magnetic field results in a smaller truncation radius of the accretion disk. In this work, we calculate the emergent spectrum of an inner ADAF + an outer truncated accretion disk around a supermassive black hole based on the prediction by Taam et al. (2012). It is found that an increase of the magnetic field from $\\beta=0.8$ to $\\beta=0.5$ (with magnetic pressure $p_{\\rm m}=B^2/{8\\pi}=(1-\\beta)p_{\\rm tot}$, $p_{\\rm tot}=p_{\\rm gas}+p_{\\rm m}$) results in an increase of $\\sim 8.7$ times of the luminosity from the truncated accretion disk. We found that the equipartition of gas pressure to magnetic pressure, i....

  7. Active galactic nuclei synapses: X-ray versus optical classifications using artificial neural networks

    CERN Document Server

    Gonzalez-Martin, O; Acosta-Pulido, J A; Masegosa, J; Papadakis, I E; Rodriguez-Espinosa, J M; Marquez, I; Hernandez-Garcia, L

    2014-01-01

    (Abridged) Many classes of active galactic nuclei (AGN) have been defined entirely throughout optical wavelengths while the X-ray spectra have been very useful to investigate their inner regions. However, optical and X-ray results show many discrepancies that have not been fully understood yet. The aim of this paper is to study the "synapses" between the X-ray and optical classifications. For the first time, the new EFLUXER task allowed us to analyse broad band X-ray spectra of emission line nuclei (ELN) without any prior spectral fitting using artificial neural networks (ANNs). Our sample comprises 162 XMM-Newton/pn spectra of 90 local ELN in the Palomar sample. It includes starbursts (SB), transition objects (T2), LINERs (L1.8 and L2), and Seyferts (S1, S1.8, and S2). The ANNs are 90% efficient at classifying the trained classes S1, S1.8, and SB. The S1 and S1.8 classes show a wide range of S1- and S1.8-like components. We suggest that this is related to a large degree of obscuration at X-rays. The S1, S1.8...

  8. Cosmic Evolution of Mass Accretion Rate and Metalicity in Active Galactic Nuclei

    CERN Document Server

    Netzer, H; Netzer, Hagai; Trakhtenbrot, Benny

    2006-01-01

    We present line and continuum measurements for 9818 SDSS type-I active galactic nuclei (AGNs) with z le 0.75. The data are used to study the four dimensional space of black hole mass, normalized accretion rate (Ledd), metalicity and redshift. The main results are: 1. Ledd is smaller for larger mass black holes at all redshifts. 2. For a given black hole mass Ledd propto z^gamma or (1+z)^delta where the slope gamma increases with black hole mass. The mean slope is similar to the star formation rate slope over the same redshift interval. 3. The FeII/Hb line ratio is significantly correlated with Ledd. It also shows a weaker negative dependence on redshift. Combined with the known dependence of metalicity on accretion rate, we suggest that the FeII/Hb line ratio is a metalicity indicator. 4. Given the measured accretion rates, the growth times of most AGNs exceed the age of the universe. This suggests past episodes of faster growth for all those sources. Combined with the FeII/Hb result, we conclude that the bro...

  9. The Nature of Double-Peaked [O III] Active Galactic Nuclei

    CERN Document Server

    Fu, Hai; Myers, Adam D; Stockton, Alan; Djorgovski, S G; Aldering, G; Rich, Jeffrey A

    2011-01-01

    Active galactic nuclei (AGNs) with double-peaked [O III] lines are suspected to be sub-kpc or kpc-scale binary AGNs. However, pure gas kinematics can produce the same double-peaked line profile in spatially integrated spectra. Here we combine integral-field spectroscopy and high-resolution imaging of 42 double-peaked [O III] AGNs from Sloan Digital Sky Survey to investigate the constituents of the population. We find two binary AGNs where the line-splitting is driven by the orbital motion of the merging nuclei. Such objects account for only ~2% of the double-peaked AGNs. Almost all (~98%) of the double-peaked AGNs were selected because of gas kinematics; and half of those show spatially resolved narrow-line regions that extend 4-20 kpc from the nuclei. Serendipitously, we find two spectrally unresolved binary AGNs where gas kinematics produced the double-peaked [O III] lines. The relatively frequent serendipitous discoveries indicate that only ~1% of binary AGNs would appear double-peaked in Sloan spectra and...

  10. Observations of Active Galactic Nuclei by the Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE)

    Science.gov (United States)

    Covault, C. E.; Boone, L.M.; Bramel, D.; Carson, J.; Fortin, P.; Gauthier, G.; Gingrich, D.; Hanna, D.; Jarvis, A.; Kildea, J.; Mueller, C.; Mukherjee, R.; Ong, R.A.; Ragan, K.; Scalzo, R.A.; Williams, D.A.; Zweerink, J.

    2003-07-01

    We present new results from observations of Active Galactic Nuclei (AGN) by the STACEE experiment. STACEE is a detector for 50-500 GeV gamma rays which uses the array of heliostat mirrors at the National Solar Thermal Test Facility (NSTTF) located at Sandia Lab oratories, Albuquerque, New Mexico, USA. STACEE uses 64 of these heliostats at night to collect Cherenkov light from air showers due to high energy gamma rays. With a large collecting area, STACEE has good sensitivity below 100 GeV. This allow us to search for gamma rays from extragalactic sources at larger redshift distances (to z of 0.2 or more) than can be studied by more conventional imaging Cherenkov telescopes operating at higher energy thresholds. We summarize recent STACEE observations of W Comae (also known as ON+231), Markarian 421, and H 1426+428. Analysis of observations on these sources in ongoing, and new results will be presented at the conference. We also briefly describe plans for future STACEE observations of AGN in the context of multiwavelength campaigns.

  11. The case for inflow of the broad-line region of active galactic nuclei

    CERN Document Server

    Gaskell, C Martin

    2015-01-01

    The high-ionization lines of the broad-line region (BLR) of thermal active galactic nuclei (AGNs) show blueshifts of a few hundred km/s to several thousand km/sec with respect to the low-ionization lines. This has long been thought to be due to the high-ionization lines of the BLR arising in a wind of which the far side of the outflow is blocked from our view by the accretion disc. Evidence for and against the disc-wind model is discussed. The biggest problem for the model is that velocity-resolved reverberation mapping repeatedly fails to show the expected kinematic signature of outflow of the BLR. The disc-wind model also cannot readily reproduce the red side of the line profiles of high-ionization lines. The rapidly falling density in an outflow makes it difficult to obtain high equivalent widths. We point out a number of major problems with associating the BLR with the outflows producing broad absorption lines. An explanation which avoids all these problems and satisfies the constraints of both the line p...

  12. HerMES: Disentangling active galactic nuclei and star formation in the radio source population

    CERN Document Server

    Rawlings, J I; Symeonidis, M; Bock, J; Cooray, A; Farrah, D; Guo, K; Hatziminaoglou, E; Ibar, E; Oliver, S J; Roseboom, I G; Scott, Douglas; Seymour, N; Vaccari, M; Wardlow, J L

    2015-01-01

    We separate the extragalactic radio source population above ~50 uJy into active galactic nuclei (AGN) and star-forming sources. The primary method of our approach is to fit the infrared spectral energy distributions (SEDs), constructed using Spitzer/IRAC and MIPS and Herschel/SPIRE photometry, of 380 radio sources in the Extended Chandra Deep Field-South. From the fitted SEDs, we determine the relative AGN and star-forming contributions to their infrared emission. With the inclusion of other AGN diagnostics such as X-ray luminosity, Spitzer/IRAC colours, radio spectral index and the ratio of star-forming total infrared flux to k-corrected 1.4 GHz flux density, qIR, we determine whether the radio emission in these sources is powered by star formation or by an AGN. The majority of these radio sources (60 per cent) show the signature of an AGN at some wavelength. Of the sources with AGN signatures, 58 per cent are hybrid systems for which the radio emission is being powered by star formation. This implies that r...

  13. What controls the FeII strength in active galactic nuclei?

    CERN Document Server

    Dong, Xiaobo; Wang, Tinggui; Wang, Huiyuan; Fan, Xiaohui; Zhou, Hongyan; Yuan, Weimin

    2009-01-01

    We have investigated the correlations of the equivalent widths (EWs) of narrow and broad FeII emission lines and the FeII/MgII intensity ratio with fundamental physical parameters of active galactic nuclei (AGNs), luminosity (L), black hole mass (M_{BH}) and Eddington ratio (L/Ledd), using a homogenous sample of z<0.8 Seyfert 1 galaxies and QSOs in the spectroscopic data set of Sloan Digital Sky Survey Fourth Data Release (SDSS DR4). The sample comprises 4178 spectra that are selected to suffer little from the host-galaxy starlight contamination. We find that the strongest correlations of almost all the emission-line intensity ratios and EWs are with L/Ledd, either positively (e.g. FeII EW) or negatively (e.g. MgII EW), rather than with L or M_{BH}; In particular, the intensity ratios of both the ultraviolet and optical FeII emissions to MgII 2800 correlate quite tightly with L/Ledd (e.g., Spearman r_s = 0.74 for the [narrow FeII]/MgII -- L/Ledd correlation). We have also investigated the FeII emission in ...

  14. Searching for Compton-thick active galactic nuclei at z~0.1

    CERN Document Server

    Goulding, Andy; Mullaney, James; Gelbord, Jonathan; Hickox, Ryan; Ward, Martin; Watson, Mike

    2010-01-01

    Using a suite of X-ray, mid-IR and optical active galactic nuclei (AGN) luminosity indicators, we search for Compton-thick (CT) AGNs with intrinsic L_X>10^42erg/s at z~0.03-0.2, a region of parameter space which is currently poorly constrained by deep narrow-field and high-energy (E>10keV) all-sky X-ray surveys. We have used the widest XMM-Newton survey (the serendipitous source catalogue) to select a representative sub-sample (14; ~10%) of the 147 X-ray undetected candidate CT AGNs in the Sloan Digital Sky Survey (SDSS) with f_X/f_[OIII]43%) of our sample appear to be obscured by CT material with N_H>1.5x10^24cm^-2. Under the reasonable assumption that our 14 AGNs are representative of the overall X-ray undetected AGN population in the SDSS-XMM parent sample, we find that >20% of the optical Type-2 AGN population are likely to be obscured by CT material. This implies a space-density of log(Phi) >-4.9Mpc^-3 for CT AGNs with L_X>1 0^42erg/s at z~0.1, which we suggest may be consistent with that predicted by X-...

  15. Discovery of Millimeter-Wave Excess Emission in Radio-Quiet Active Galactic Nuclei

    CERN Document Server

    Behar, Ehud; Laor, Ari; Horesh, Assaf; Stevens, Jamie; Tzioumis, Tasso

    2015-01-01

    The physical origin of radio emission in Radio Quiet Active Galactic Nuclei (RQ AGN) remains unclear, whether it is a downscaled version of the relativistic jets typical of Radio Loud (RL) AGN, or whether it originates from the accretion disk. The correlation between 5 GHz and X-ray luminosities of RQ AGN, which follows $L_R = 10^{-5}L_X$ observed also in stellar coronae, suggests an association of both X-ray and radio sources with the accretion disk corona. Observing RQ AGN at higher (mm-wave) frequencies, where synchrotron self absorption is diminished, and smaller regions can be probed, is key to exploring this association. Eight RQ AGN, selected based on their high X-ray brightness and variability, were observed at 95 GHz with the CARMA and ATCA telescopes. All targets were detected at the $1-10$ mJy level. Emission excess at 95~GHz of up to $\\times 7$ is found with respect to archival low-frequency steep spectra, suggesting a compact, optically-thick core superimposed on the more extended structures that...

  16. Molecular Hydrogen and [Fe II] in Active Galactic Nuclei III: LINERS and Star Forming Galaxies

    CERN Document Server

    Riffel, R; Aleman, I; Brotherton, M S; Pastoriza, M G; Bonatto, C J; Dors, O L

    2013-01-01

    We study the kinematics and excitation mechanisms of H2 and [Fe II] lines in a sample of 67 emission-line galaxies with Infrared Telescope Facility SpeX near-infrared (NIR, 0.8-2.4 micrometers) spectroscopy together with new photoionisation models. H2 emission lines are systematically narrower than narrow-line region (NLR) lines, suggesting that the two are, very likely, kinematically disconnected. The new models and emission-line ratios show that the thermal excitation plays an important role not only in active galactic nuclei but also in star forming galaxies. The importance of the thermal excitation in star forming galaxies may be associated with the presence of supernova remnants close to the region emitting H2 lines. This hypothesis is further supported by the similarity between the vibrational and rotational temperatures of H2. We confirm that the diagram involving the line ratios H2 2.121/Br_gamma and [Fe II] 1.257/Pa_beta is an efficient tool for separating emission-line objects according to their dom...

  17. Active Galactic Nuclei and the Truncation of Star Formation in K+A Galaxies

    CERN Document Server

    Brown, Michael J I; Caldwell, Nelson; Palamara, David; Cool, Richard J; Dey, Arjun; Hickox, Ryan; Jannuzi, Buell T; Murray, Stephen S; Zaritsky, Dennis

    2009-01-01

    We have searched for active galactic nuclei (AGNs) in K+A galaxies, using multiwavelength imaging and spectroscopy in the Bootes field of the NOAO Deep Wide-Field Survey. The K+A galaxies, which have had their star formation rapidly truncated, are selected via their strong Balmer absorption lines and weak H-alpha emission. Our sample consists of 24 K+A galaxies selected from 6594 0.10

  18. Respiratory activity in the facial nucleus in an in vitro brainstem of tadpole, Rana catesbeiana.

    Science.gov (United States)

    Liao G-S; Kubin, L; Galante, R J; Fishman, A P; Pack, A I

    1996-04-15

    1. In studies of the central neural control of breathing, little advantage has been taken of comparative approaches. We have developed an in vitro brainstem preparation using larval Rana catesbeiana which generates two rhythmic neural activities characteristic of lung and gill ventilation. Based on the pattern of the facial (VII) nerve activity both lung and gill rhythm-related respiratory cycles were divided into three distinct phases. The purpose of this study was to characterize and classify membrane potential trajectories of respiratory motoneurons in the VII nucleus at intermediate stages (XII-XVII) of development. 2. Seventy-five respiratory-modulated neurons were recorded intracellularly within the facial motor nucleus region. Their resting membrane potential was between -40 and -80 mV. Sixty of them were identified as VII motoneurons and fifteen were non-antidromically activated. Membrane potentials of fifty-six of the seventy-five neurons were modulated with both lung (5-27 mV) and gill rhythms (3-15 mV) and the remaining nineteen neurons had only a modulation with lung rhythmicity (6-23 mV). No cells with gill modulation alone were observed. 3. All of the cells modulated with lung rhythmicity had only phase-bound depolarizing or hyperpolarizing membrane potential swings which could be categorized into four distinct patterns. In contrast, of the fifty-six cells modulated with gill rhythmicity, thirty-two were phasically depolarized during distinct phases of the gill cycle (four patterns were distinguished), whereas the remaining twenty-four were phase spanning with two distinct patterns. The magnitudes of lung and gill modulations were proportionally related to each other in the cells modulated with both rhythms. 4. In all sixteen neurons studied, a reduction or a reversal of phasic inhibitory inputs during a portion of the lung or gill respiratory cycle was observed following a negative current or chloride ion (Cl-) injection. The phasic membrane

  19. Discovery of five low-luminosity active galactic nuclei at the centre of the Perseus cluster

    Science.gov (United States)

    Park, Songyoun; Yang, Jun; Oonk, J. B. Raymond; Paragi, Zsolt

    2017-03-01

    According to optical stellar kinematics observations, an overmassive black hole candidate has been reported by van den Bosch et al. in the normal early-type galaxy NGC 1277. This galaxy is located in the central region of the Perseus cluster. Westerbork Synthesis Radio Telescope observations have shown that NGC 1277 and other early-type galaxies in the neighbourhood have radio counterparts. These nuclear radio sources have stable flux densities on a time-scale of years. In order to investigate the origin of the radio emission from these normal galaxies, we selected five sources (NGC 1270, NGC 1272, NGC 1277, NGC 1278 and VZw 339) residing in the central 10-arcmin region of the Perseus cluster and requested to re-correlate the data of an existing very long baseline interferometry (VLBI) experiment at these new positions. With the re-correlation data provided by the European VLBI Network (EVN), we imaged the five sources with a resolution of about 8 mas and detected all of them with a confidence level above 5σ at 1.4 GHz. They show compact structure and brightness temperatures above 107 K, which implies that the radio emission is non-thermal. We rule out ongoing nuclear star formation and conclude that these VLBI-detected radio sources are parsec-scale jet activity associated with the supermassive black holes in low-luminosity active galactic nuclei, although there are no clear signs of nuclear activity observed in the optical and infrared bands. Using the Fundamental Plane relation in black holes, we find no significant evidence for or against an extremely massive black hole hiding in NGC 1277.

  20. AN X-RAY SPECTRAL MODEL OF REPROCESSING BY SMOOTH AND CLUMPY MOLECULAR TORI IN ACTIVE GALACTIC NUCLEI WITH THE MONACO FRAMEWORK

    Energy Technology Data Exchange (ETDEWEB)

    Furui, Shun’ya; Fukazawa, Yasushi; Ohno, Masanori; Hayashi, Kazuma [Department of Physical Science, Hiroshima University, 1-3-1 Kagamiyama, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Odaka, Hirokazu [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 2575 Sand Hill Rd, Menlo Park, CA 94025 (United States); Kawaguchi, Toshihiro, E-mail: fukazawa@hep01.hepl.hiroshima-u.ac.jp [Department of Liberal Arts and Sciences, Sapporo Medical University, S1W17, Chuo-ku, Sapporo 060-8556 (Japan)

    2016-02-20

    We construct an X-ray spectral model of reprocessing by a torus in an active galactic nucleus (AGN) with the Monte Carlo simulation framework MONACO. Two torus geometries of smooth and clumpy cases are considered and compared. In order to reproduce a Compton shoulder accurately, MONACO includes not only free electron scattering but also bound electron scattering. Raman and Rayleigh scattering are also treated, and scattering cross sections dependent on chemical states of hydrogen and helium are included. Doppler broadening by turbulence velocity can be implemented. Our model gives results consistent with other available models, such as MYTorus, except for differences due to different physical parameters and assumptions. We studied the dependence on torus parameters for a Compton shoulder, and found that a intensity ratio of a Compton shoulder to the line core mainly depends on column density, inclination angle, and metal abundance. For instance, an increase of metal abundance makes a Compton shoulder relatively weak. Also, the shape of a Compton shoulder depends on the column density. Furthermore, these dependences become different between smooth and clumpy cases. Then, we discuss the possibility of ASTRO-H/SXS spectroscopy of Compton shoulders in AGN reflection spectra.

  1. pH-activated size reduction of large compound nanoparticles for in vivo nucleus-targeted drug delivery.

    Science.gov (United States)

    Fan, Yanbin; Li, Chunyan; Li, Fuyou; Chen, Daoyong

    2016-04-01

    Nucleus-targeted drug delivery is a promising strategy for anticancer therapy, but in vivo nucleus-targeted drug delivery has been challenging. Limited by the channel size of the nucleopore, vehicles that enter the nucleus via the nucleopore actively should be small and decorated with nuclear localization signal (NLS). However, the small vehicle size may promote leakage of vehicles into normal tissues, and the positively-charged NLS can lead to strong non-specific interactions in vivo. In the present study, we demonstrate an in vivo nucleus-targeted drug delivery using large compound nanoparticles with detachable PEG shell. The nanoparticles are composed of PEG-benzoic imine-oligo-l-lysine/iridium(III) metallodrug complex and formed in a kinetically-controlled fashion. Under physiological conditions (pH 7.4), the nanoparticles are large (ca. 150 nm) and protected by an inert PEG shell. When internalized into intracellular acidic endo/lysosomes of cancer cells, the nanoparticles dissociate into smaller ones (ca. 40 nm) and the PEG chains detach due to the cleavage of the benzoic imine bond at low pH. The small nanoparticles, with exposure of the oligo-l-lysine after the detachment of the PEG shield, then translocate into the nucleus via the nucleopore due to the small size and nuclear localization ability of the oligo-l-lysine. Importantly, the small particles could significantly release the contained drug into the nucleus, leading to ca. 20-fold higher cytotoxicity compared to the native drug in vitro. Further in vivo application of the nucleus-targeting nano-system in a nude-mice model showed significant tumor inhibition and remarkable life-span elongation.

  2. High-energy neutrino production from photo-hadronic interactions of gamma rays from Active Galactic Nuclei at source

    CERN Document Server

    Arteaga-Velazquez, J C

    2013-01-01

    Recent astronomical observations reveal that Active Galactic Nuclei (AGN) are sources of high-energy radiation. For example, the Fermi-LAT and Hess telescopes have detected gamma-ray emissions from the cores of several types of AGN's. Even more, the Pierre Auger observatory has found a correlation of ultra-high energy cosmic ray events with the position of Active Galactic Nuclei, such as Centaurus A. In this way, according to particle physics, a flux of high-energy neutrinos should be expected from the interactions of cosmic and gamma-rays with the ambient matter and radiation at the source. In this work, estimations of the diffuse neutrino flux from AGN's arising from interactions of the gamma radiation with the gas and dust of the sources will be presented.

  3. Galaxy Zoo: Are Bars Responsible for the Feeding of Active Galactic Nuclei at 0.2 < z < 1.0?

    CERN Document Server

    Cheung, Edmond; Athanassoula, E; Bamford, Steven P; Bell, Eric F; Bosma, A; Cardamone, Carolin N; Casteels, Kevin R V; Faber, S M; Fang, Jerome J; Fortson, Lucy F; Kocevski, Dale D; Koo, David C; Laine, Seppo; Lintott, Chris; Masters, Karen L; Melvin, Thomas; Nichol, Robert C; Schawinski, Kevin; Simmons, Brooke; Smethurst, Rebecca; Willett, Kyle W

    2014-01-01

    We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS, COSMOS, and GOODS-S surveys to create samples of face-on, disc galaxies at 0.2 1, our findings suggest that large-scale bars have likely never directly been a dominant fueling mechanism for supermassive black hole growth.

  4. X-ray Polarimetry - a Tool for the Galactic center diagnosis

    CERN Document Server

    Marin, F

    2015-01-01

    Was the Milky Way galaxy a low-luminosity active galactic nucleus (AGN) in the past? Can we find traces of remnant structures supporting this idea? What is the three-dimensional arrangement of matter around our central supermassive black hole? A number of fundamental questions concerning our own Galactic center remain controversial. To reveal the structure of the high-energy sky around our galactic core, a technique more sensitive to the morphology of the emitters than spectroscopy is needed. In this lecture note, I describe how X-ray polarimetry can open a new observational window by precisely measuring the three-dimensional position of the scattering material in the Galactic center. The observed polarization degree and polarization position angle would also determine unambiguously the primary source of emission and trace the centennial history of our supermassive black hole by detecting echoes of its past activity thanks to astrophysical mirrors. Finally, the synergy between X-ray polarimetry and infrared a...

  5. Evidence for active galactic nucleus feedback in the broad absorption lines and reddening of MRK 231 {sup ,}

    Energy Technology Data Exchange (ETDEWEB)

    Leighly, Karen M.; Baron, Eddie; Lucy, Adrian B. [Homer L. Dodge Department of Physics and Astronomy, The University of Oklahoma, 440 West Brooks Street, Norman, OK 73019 (United States); Terndrup, Donald M. [Department of Astronomy, The Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Dietrich, Matthias [Department of Physics and Astronomy, Ohio University, Clippinger Labs 251B, Athens, OH 45701 (United States); Gallagher, Sarah C. [Department of Physics and Astronomy, The University of Western Ontario, London, ON, N6A 3K7 (Canada)

    2014-06-20

    We present the first J-band spectrum of Mrk 231, which reveals a large He I* λ10830 broad absorption line with a profile similar to that of the well-known Na I broad absorption line. Combining this spectrum with optical and UV spectra from the literature, we show that the unusual reddening noted by Veilleux et al. is explained by a reddening curve like those previously used to explain low values of total-to-selective extinction in Type Ia supernovae. The nuclear starburst may be the origin and location of the dust. Spatially resolved emission in the broad absorption line trough suggests nearly full coverage of the continuum emission region. The broad absorption lines reveal higher velocities in the He I* lines (produced in the quasar-photoionized H II region) compared with the Na I and Ca II lines (produced in the corresponding partially ionized zone). Cloudy simulations show that a density increase is required between the H II and partially ionized zones to produce ionic column densities consistent with the optical and IR absorption line measurements and limits, and that the absorber lies ∼100 pc from the central engine. These results suggest that the He I* lines are produced in an ordinary quasar BAL wind that impacts upon, compresses, and accelerates the nuclear starburst's dusty effluent (feedback in action), and the Ca II and Na I lines are produced in this dusty accelerated gas. This unusual circumstance explains the rarity of Na I absorption lines; without the compression along our line of sight, Mrk 231 would appear as an ordinary iron low-ionization, broad absorption line quasar.

  6. Increased expression of stefin B in the nucleus of T98G astrocytoma cells delays caspase activation

    Directory of Open Access Journals (Sweden)

    Tao eSun

    2012-09-01

    Full Text Available Stefin B (cystatin B is an endogenous inhibitor of cysteine proteinases localized in the nucleus and the cytosol. Loss-of-function mutations in the stefin B gene (CSTB gene were reported in patients with Unverricht-Lundborg disease (EPM1. Our previous results showed that thymocytes isolated from stefin B-deficient mice are more sensitive to apoptosis induced by the protein kinase C inhibitor staurosporin (STS than the wild-type control cells. We have also shown that the increased expression of stefin B in the nucleus of T98G astrocytoma cells delayed cell cycle progression through the S phase. In the present study we examined if the nuclear or cytosolic functions of stefin B are responsible for the accelerated induction of apoptosis observed in the cells from stefin B-deficient mice. We have shown that the overexpression of stefin B in the nucleus, but not in the cytosol of astrocytoma T98G cells, delayed caspase-3 and-7 activation. Pretreatment of cells with the pan-caspase inhibitor z-Val-Ala-Asp(OMe-fluoromethylketone completely inhibited caspase activation, while treatment with the inhibitor of calpains- and papain-like cathepsins (2S,3S-trans-epoxysuccinyl-leucylamido-3-methyl-butane ethyl ester did not prevent caspase activation. We concluded that the delay of caspase activation in T98G cells overexpressing stefin B in the nucleus is independent of cathepsin inhibition.

  7. The evolution of active galactic nuclei in clusters of galaxies from the Dark Energy Survey

    Energy Technology Data Exchange (ETDEWEB)

    Bufanda, E.; Hollowood, D.; Jeltema, T. E.; Rykoff, E. S.; Rozo, E.; Martini, P.; Abbott, T. M. C.; Abdalla, F. B.; Allam, S.; Banerji, M.; Benoit-Lévy, A.; Bertin, E.; Brooks, D.; Carnero Rosell, A.; Carrasco Kind, M.; Carretero, J.; Cunha, C. E.; da Costa, L. N.; Desai, S.; Diehl, H. T.; Dietrich, J. P.; Evrard, A. E.; Fausti Neto, A.; Flaugher, B.; Frieman, J.; Gerdes, D. W.; Goldstein, D. A.; Gruen, D.; Gruendl, R. A.; Gutierrez, G.; Honscheid, K.; James, D. J.; Kuehn, K.; Kuropatkin, N.; Lima, M.; Maia, M. A. G.; Marshall, J. L.; Melchior, P.; Miquel, R.; Mohr, J. J.; Ogando, R.; Plazas, A. A.; Romer, A. K.; Rooney, P.; Sanchez, E.; Santiago, B.; Scarpine, V.; Sevilla-Noarbe, I.; Smith, R. C.; Soares-Santos, M.; Sobreira, F.; Suchyta, E.; Tarle, G.; Thomas, D.; Tucker, D. L.; Walker, A. R.

    2016-12-13

    The correlation between active galactic nuclei (AGN) and environment provides important clues to AGN fueling and the relationship of black hole growth to galaxy evolution. In this paper, we analyze the fraction of galaxies in clusters hosting AGN as a function of redshift and cluster richness for X-ray detected AGN associated with clusters of galaxies in Dark Energy Survey (DES) Science Verification data. The present sample includes 33 AGN with L_X > 1043 ergs s-1 in non-central, host galaxies with luminosity greater than 0.5 L* from a total sample of 432 clusters in the redshift range of 0.10.7. This result is in good agreement with previous work and parallels the increase in star formation in cluster galaxies over the same redshift range. However, the AGN fraction in clusters is observed to have no significant correlation with cluster mass. Future analyses with DES Year 1 through Year 3 data will be able to clarify whether AGN activity is correlated to cluster mass and will tightly constrain the relationship between cluster AGN populations and redshift.

  8. Enhancement of oscillatory activity in the endopiriform nucleus of rats raised under abnormal oral conditions.

    Science.gov (United States)

    Yoshimura, Hiroshi; Hasumoto-Honjo, Miho; Sugai, Tokio; Segami, Natsuki; Kato, Nobuo

    2014-02-21

    Endopiriform nucleus (EPN) is located deep to the piriform cortex, and has neural connections with not only neighboring sensory areas but also subcortical areas where emotional and nociceptive information is processed. Well-balanced oral condition might play an important role in stability of brain activities. When the oral condition is impaired, several areas in the brain might be affected. In the present study, we investigated whether abnormal conditions of oral region influence neural activities in the EPN. Orthodontic appliance that generates continuous force and chronic pain-related stress was fixed to maxillary incisors of rats, and raised. Field potential recordings were made from the EPN of brain slices. We previously reported that the EPN has an ability to generate membrane potential oscillation. In the present study, we have applied the same methods to assess activities of neuron clusters in the EPN. In the case of normal rats, stable field potential oscillations were induced in the EPN by application of low-frequency electrical stimulation under the medium with caffeine. In the case of rats with the orthodontic appliance, stable field potential oscillations were also induced, but both duration of oscillatory activities and wavelet number were increased. The enhanced oscillations were depressed by blockade of NMDA receptors. Thus, impairment of oral health under application of continuous orthodontic force and chronic pain-related stress enhanced neural activities in the EPN, in which up-regulation of NMDA receptors may be concerned. These findings suggest that the EPN might be involved in information processing with regard to abnormal conditions of oral region.

  9. Serotonin activates catecholamine neurons in the solitary tract nucleus by increasing spontaneous glutamate inputs.

    Science.gov (United States)

    Cui, Ran Ji; Roberts, Brandon L; Zhao, Huan; Zhu, Mingyan; Appleyard, Suzanne M

    2012-11-14

    Serotonin (5-HT) is a critical neurotransmitter in the control of autonomic functions. 5-HT(3) receptors participate in vagal afferent feedback to decrease food intake and regulate cardiovascular reflexes; however, the phenotype of the solitary tract nucleus (NTS) neurons involved is not known. A(2)/C(2) catecholamine (CA) neurons in the NTS are directly activated by visceral afferents and are important for the control of food intake and cardiovascular function, making them good candidates to respond to and mediate the effects of serotonin at the level of the NTS. This study examines serotonin's effects on NTS-CA neurons using patch-clamp techniques and transgenic mice expressing an enhanced green fluorescent protein driven by the tyrosine hydroxylase (TH) promoter (TH-EGFP) to identify catecholamine neurons. Serotonin increased the frequency of spontaneous glutamate excitatory postsynaptic currents (sEPSCs) in >90% of NTS-TH-EGFP neurons, an effect blocked by the 5-HT(3) receptor antagonist ondansetron and mimicked by the 5-HT(3) receptor agonists SR5227 and mCPBG. In contrast, 5-HT(3) receptor agonists increased sEPSCs on a minority (serotonin activates NTS-TH neurons and suggest a pathway by which it can increase catecholamine release in target regions to modulate food intake, motivation, stress, and cardiovascular function.

  10. Dysfunction of nucleus accumbens-1 activates cellular senescence and inhibits tumor cell proliferation and oncogenesis.

    Science.gov (United States)

    Zhang, Yi; Cheng, Yan; Ren, Xingcong; Hori, Tsukasa; Huber-Keener, Kathryn J; Zhang, Li; Yap, Kai Lee; Liu, David; Shantz, Lisa; Qin, Zheng-Hong; Zhang, Suping; Wang, Jianrong; Wang, Hong-Gang; Shih, Ie-Ming; Yang, Jin-Ming

    2012-08-15

    Nucleus accumbens-1 (NAC1), a nuclear factor belonging to the BTB/POZ gene family, has emerging roles in cancer. We report here that NAC1 acts as a negative regulator of cellular senescence in transformed and nontransformed cells, and dysfunction of NAC1 induces senescence and inhibits its oncogenic potential. We show that NAC1 deficiency markedly activates senescence and inhibits proliferation in tumor cells treated with sublethal doses of γ-irradiation. In mouse embryonic fibroblasts from NAC1 knockout mice, following infection with a Ras virus, NAC1-/- cells undergo significantly more senescence and are either nontransformed or less transformed in vitro and less tumorigenic in vivo when compared with NAC1+/+ cells. Furthermore, we show that the NAC1-caused senescence blunting is mediated by ΔNp63, which exerts its effect on senescence through p21, and that NAC1 activates transcription of ΔNp63 under stressful conditions. Our results not only reveal a previously unrecognized function of NAC1, the molecular pathway involved and its impact on pathogenesis of tumor initiation and development, but also identify a novel senescence regulator that may be exploited as a potential target for cancer prevention and treatment.

  11. Activation of nucleus accumbens NMDA receptors differentially affects appetitive or aversive taste learning and memory

    Directory of Open Access Journals (Sweden)

    Luis eNuñez-Jaramillo

    2012-04-01

    Full Text Available Taste memory depends on motivational and post-ingestional consequences; thus, it can be aversive (e.g., conditioned taste aversion, CTA if a novel, palatable taste is paired with visceral malaise, or it can be appetitive if no intoxication appears after novel taste consumption, and a taste preference is developed. The nucleus accumbens (NAc plays a role in hedonic reactivity to taste stimuli, and recent findings suggest that reward and aversion are differentially encoded by the activity of NAc neurons. The present study examined whether the requirement for NMDA receptors in the NAc core during rewarding appetitive taste learning differs from that during aversive taste conditioning, as well as during retrieval of appetitive versus aversive taste memory, using the taste preference or CTA model, respectively. Bilateral infusions of NMDA (1 μg/μl, 0.5 μl into the NAc core were performed before acquisition or before retrieval of taste preference or CTA. Activation of NMDA receptors before taste preference training or CTA acquisition did not alter memory formation. Furthermore, NMDA injections before aversive taste retrieval had no effect on taste memory; however, 24 h later, CTA extinction was significantly delayed. Also, NMDA injections, made before familiar appetitive memory retrieval, interrupted the development of taste preference and produced a preference delay 24 h later. These results suggest that memory formation for a novel taste produces neurochemical changes in the NAc core that have differential requirements for NMDA receptors during retrieval of appetitive or aversive memory.

  12. Circadian rhythmicity of active GSK3 isoforms modulates molecular clock gene rhythms in the suprachiasmatic nucleus.

    Science.gov (United States)

    Besing, Rachel C; Paul, Jodi R; Hablitz, Lauren M; Rogers, Courtney O; Johnson, Russell L; Young, Martin E; Gamble, Karen L

    2015-04-01

    The suprachiasmatic nucleus (SCN) drives and synchronizes daily rhythms at the cellular level via transcriptional-translational feedback loops comprising clock genes such as Bmal1 and Period (Per). Glycogen synthase kinase 3 (GSK3), a serine/threonine kinase, phosphorylates at least 5 core clock proteins and shows diurnal variation in phosphorylation state (inactivation) of the GSK3β isoform. Whether phosphorylation of the other primary isoform (GSK3α) varies across the subjective day-night cycle is unknown. The purpose of this study was to determine if the endogenous rhythm of GSK3 (α and β) phosphorylation is critical for rhythmic BMAL1 expression and normal amplitude and periodicity of the molecular clock in the SCN. Significant circadian rhythmicity of phosphorylated GSK3 (α and β) was observed in the SCN from wild-type mice housed in constant darkness for 2 weeks. Importantly, chronic activation of both GSK3 isoforms impaired rhythmicity of the GSK3 target BMAL1. Furthermore, chronic pharmacological inhibition of GSK3 with 20 µM CHIR-99021 enhanced the amplitude and shortened the period of PER2::luciferase rhythms in organotypic SCN slice cultures. These results support the model that GSK3 activity status is regulated by the circadian clock and that GSK3 feeds back to regulate the molecular clock amplitude in the SCN.

  13. Population calcium imaging of spontaneous respiratory and novel motor activity in the facial nucleus and ventral brainstem in newborn mice

    DEFF Research Database (Denmark)

    Persson, Karin; Rekling, Jens C

    2011-01-01

    The brainstem contains rhythm and pattern forming circuits, which drive cranial and spinal motor pools to produce respiratory and other motor patterns. Here we used calcium imaging combined with nerve recordings in newborn mice to reveal spontaneous population activity in the ventral brainstem...... and in the facial nucleus. In Fluo-8AM loaded brainstem-spinal cord preparations, respiratory activity on cervical nerves was synchronized with calcium signals at the ventrolateral brainstem surface. Individual ventrolateral neurons at the level of the parafacial respiratory group showed perfect or partial...... synchrony with respiratory nerve bursts. In brainstem-spinal cord preparations, cut at the level of the mid-facial nucleus, calcium signals were recorded in the dorsal, lateral and medial facial subnuclei during respiratory activity. Strong activity initiated in the dorsal subnucleus, followed by activity...

  14. Effects of inhibitor of κB kinase activity in the nucleus accumbens on emotional behavior.

    Science.gov (United States)

    Christoffel, Daniel J; Golden, Sam A; Heshmati, Mitra; Graham, Ami; Birnbaum, Shari; Neve, Rachael L; Hodes, Georgia E; Russo, Scott J

    2012-11-01

    Inhibitor of κB kinase (IκK) has historically been studied in the context of immune response and inflammation, but recent evidence demonstrates that IκK activity is necessary and sufficient for regulation of neuronal function. Chronic social defeat stress of mice increases IκK activity in the nucleus accumbens (NAc) and this increase is strongly correlated to depression-like behaviors. Inhibition of IκK signaling results in a reversal of chronic social defeat stress-induced social avoidance behavior. Here, we more completely define the role of IκK in anxiety and depressive-like behaviors. Mice underwent stereotaxic microinjection of a herpes simplex virus expressing either green fluorescent protein, a constitutively active form of IκK (IκKca), or a dominant negative form of IκK into the NAc. Of all three experimental groups, only mice expressing IκKca show a behavioral phenotype. Expression of IκKca results in a decrease in the time spent in the non-periphery zones of an open field arena and increased time spent immobile during a forced swim test. No baseline differences in sucrose preference were observed, but following the acute swim stress we noted a marked reduction in sucrose preference. To determine whether IκK activity alters responses to other acute stressors, we examined behavior and spine morphology in mice undergoing an acute social defeat stress. We found that IκKca enhanced social avoidance behavior and promoted thin spine formation. These data show that IκK in NAc is a critical regulator of both depressive- and anxiety-like states and may do so by promoting the formation of immature excitatory synapses.

  15. Endogenous Opiates in the Nucleus Tractus Solitarius Mediate Electroacupuncture-Induced Sleep Activities in Rats

    Directory of Open Access Journals (Sweden)

    Chiung-Hsiang Cheng

    2011-01-01

    Full Text Available Electroacupuncture (EA possesses various therapeutic effects, including alleviation of pain, reduction of inflammation and improvement of sleep disturbance. The mechanisms of EA on sleep improvement, however, remain to be determined. It has been stated in ancient Chinese literature that the Anmian (EX17 acupoint is one of the trigger points that alleviates insomnia. We previously demonstrated that EA stimulation of Anmian acupoints in rats during the dark period enhances non-rapid eye movement (NREM sleep, which involves the induction of cholinergic activity in the nucleus tractus solitarius (NTS. In addition to cholinergic activation of the NTS, activation of the endogenous opioidergic system may also be a mechanism by which acupuncture affects sleep. Therefore, this study was designed to investigate the involvement of the NTS opioidergic system in EA-induced alterations in sleep. Our present results indicate that EA of Anmian acupoints increased NREM sleep, but not rapid eye movement sleep, during the dark period in rats. This enhancement in NREM sleep was dose-dependently blocked by microinjection of opioid receptor antagonist, naloxone, and the μ-opioid receptor antagonist, naloxonazine, into the NTS; administrations of δ-receptor antagonist, natrindole, and the κ-receptor antagonist, nor-binaltrophimine, however, did not affect EA-induced alterations in sleep. Furthermore, β-endorphin was significantly increased in both the brainstem and hippocampus after the EA stimuli, an effect blocked by administration of the muscarinic antagonist scopolamine into the NTS. Our findings suggest that mechanisms of EA-induced NREM sleep enhancement may be mediated, in part, by cholinergic activation, stimulation of the opiodergic neurons to increase the concentrations of β-endorphin and the involvement of the μ-opioid receptors.

  16. Application of histamine or serotonin to the hypoglossal nucleus increases genioglossus muscle activity across the wake-sleep cycle.

    Science.gov (United States)

    Neuzeret, Pierre-Charles; Sakai, Kazuya; Gormand, Frédéric; Petitjean, Thierry; Buda, Colette; Sastre, Jean-Pierre; Parrot, Sandrine; Guidon, Gérard; Lin, Jian-Sheng

    2009-03-01

    The decrease in genioglossus (GG) muscle activity during sleep, especially rapid eye movement (REM) or paradoxical sleep, can lead to airway occlusion and obstructive sleep apnoea (OSA). The hypoglossal nucleus innervating the GG muscle is under the control of serotonergic, noradrenergic and histaminergic neurons that cease firing during paradoxical sleep. The objectives of this study were to determine the effect on GG muscle activity during different wake-sleep states of the microdialysis application of serotonin, histamine (HA) or noradrenaline (NE) to the hypoglossal nucleus in freely moving cats. Six adult cats were implanted with electroencephalogram, electro-oculogram and neck electromyogram electrodes to record wake-sleep states and with GG muscle and diaphragm electrodes to record respiratory muscle activity. Microdialysis probes were inserted into the hypoglossal nucleus for monoamine application. Changes in GG muscle activity were assessed by power spectrum analysis. In the baseline conditions, tonic GG muscle activity decreased progressively and significantly from wakefulness to slow-wave sleep and even further during slow-wave sleep with ponto-geniculo-occipital waves and paradoxical sleep. Application of serotonin or HA significantly increased GG muscle activity during the wake-sleep states when compared with controls. By contrast, NE had no excitatory effect. Our results indicate that both serotonin and HA have a potent excitatory action on GG muscle activity, suggesting multiple aminergic control of upper airway muscle activity during the wake-sleep cycle. These data might help in the development of pharmacological approaches for the treatment of OSA.

  17. Interactive Effects of Dorsomedial Hypothalamic Nucleus and Time-Restricted Feeding on Fractal Motor Activity Regulation

    Science.gov (United States)

    Lo, Men-Tzung; Chiang, Wei-Yin; Hsieh, Wan-Hsin; Escobar, Carolina; Buijs, Ruud M.; Hu, Kun

    2016-01-01

    One evolutionary adaptation in motor activity control of animals is the anticipation of food that drives foraging under natural conditions and is mimicked in laboratory with daily scheduled food availability. Food anticipation is characterized by increased activity a few hours before the feeding period. Here we report that 2-h food availability during the normal inactive phase of rats not only increases activity levels before the feeding period but also alters the temporal organization of motor activity fluctuations over a wide range of time scales from minutes up to 24 h. We demonstrate this multiscale alteration by assessing fractal patterns in motor activity fluctuations—similar fluctuation structure at different time scales—that are robust in intact animals with ad libitum food access but are disrupted under food restriction. In addition, we show that fractal activity patterns in rats with ad libitum food access are also perturbed by lesion of the dorsomedial hypothalamic (DMH)—a neural node that is involved in food anticipatory behavior. Instead of further disrupting fractal regulation, food restriction restores the disrupted fractal patterns in these animals after the DMH lesion despite the persistence of the 24-h rhythms. This compensatory effect of food restriction is more clearly pronounced in the same animals after the additional lesion of the suprachiasmatic nucleus (SCN)—the central master clock in the circadian system that generates and orchestrates circadian rhythms in behavior and physiological functions in synchrony with day-night cycles. Moreover, all observed influences of food restriction persist even when data during the food anticipatory and feeding period are excluded. These results indicate that food restriction impacts dynamics of motor activity at different time scales across the entire circadian/daily cycle, which is likely caused by the competition between the food-induced time cue and the light-entrained circadian rhythm of the

  18. Interactive effects of dorsomedial hypothalamic nucleus and time-restricted feeding on fractal motor activity regulation

    Directory of Open Access Journals (Sweden)

    Men-Tzung eLo

    2016-05-01

    Full Text Available One evolutionary adaptation in motor activity control of animals is the anticipation of food that drives foraging under natural conditions and is mimicked in laboratory with daily scheduled food availability. Food anticipation is characterized by increased activity a few hours before the feeding period. Here we report that 2-hour food availability during the normal inactive phase of rats not only increases activity levels before the feeding period but also alters the temporal organization of motor activity fluctuations over a wide range of time scales from minutes up to 24 hours. We demonstrate this multiscale alteration by assessing fractal patterns in motor activity fluctuations – similar fluctuation structure at different time scales — that are robust in intact animals with ad libitum food access but are disrupted under food restriction. In addition, we show that fractal activity patterns in rats with ad libitum food access are also perturbed by lesion of the dorsomedial hypothalamic (DMH — a neural node that is involved in food anticipatory behavior. Instead of further disrupting fractal regulation, food restriction restores the disrupted fractal patterns in these animals after the DMH lesion despite the persistence of the 24-h rhythms. This compensatory effect of food restriction is more clearly pronounced in the same animals after the additional lesion of the suprachiasmatic nucleus (SCN — the central master clock in the circadian system that generates and orchestrates circadian rhythms in behavior and physiological functions in synchrony with day-night cycles. Moreover, all observed influences of food restriction persist even when data during the food anticipatory and feeding period are excluded. These results indicate that food restriction impacts dynamics of motor activity at different time scales across the entire circadian/daily cycle, which is likely caused by the competition between the food-induced time cue and the light

  19. CHARACTERIZING THE OPTICAL VARIABILITY OF BRIGHT BLAZARS: VARIABILITY-BASED SELECTION OF FERMI ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Ruan, John J.; Anderson, Scott F.; MacLeod, Chelsea L.; Becker, Andrew C.; Davenport, James R. A.; Ivezic, Zeljko [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States); Burnett, T. H. [Department of Physics, University of Washington, Seattle, WA 98195-1560 (United States); Kochanek, Christopher S. [Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43210 (United States); Plotkin, Richard M. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Sesar, Branimir [Division of Physics, Mathematics and Astronomy, Caltech, Pasadena, CA 91125 (United States); Stuart, J. Scott, E-mail: jruan@astro.washington.edu [Lincoln Laboratory, Massachusetts Institute of Technology, 244 Wood Street, Lexington, MA 02420-9108 (United States)

    2012-11-20

    We investigate the use of optical photometric variability to select and identify blazars in large-scale time-domain surveys, in part to aid in the identification of blazar counterparts to the {approx}30% of {gamma}-ray sources in the Fermi 2FGL catalog still lacking reliable associations. Using data from the optical LINEAR asteroid survey, we characterize the optical variability of blazars by fitting a damped random walk model to individual light curves with two main model parameters, the characteristic timescales of variability {tau}, and driving amplitudes on short timescales {sigma}-circumflex. Imposing cuts on minimum {tau} and {sigma}-circumflex allows for blazar selection with high efficiency E and completeness C. To test the efficacy of this approach, we apply this method to optically variable LINEAR objects that fall within the several-arcminute error ellipses of {gamma}-ray sources in the Fermi 2FGL catalog. Despite the extreme stellar contamination at the shallow depth of the LINEAR survey, we are able to recover previously associated optical counterparts to Fermi active galactic nuclei with E {>=} 88% and C = 88% in Fermi 95% confidence error ellipses having semimajor axis r < 8'. We find that the suggested radio counterpart to Fermi source 2FGL J1649.6+5238 has optical variability consistent with other {gamma}-ray blazars and is likely to be the {gamma}-ray source. Our results suggest that the variability of the non-thermal jet emission in blazars is stochastic in nature, with unique variability properties due to the effects of relativistic beaming. After correcting for beaming, we estimate that the characteristic timescale of blazar variability is {approx}3 years in the rest frame of the jet, in contrast with the {approx}320 day disk flux timescale observed in quasars. The variability-based selection method presented will be useful for blazar identification in time-domain optical surveys and is also a probe of jet physics.

  20. Parsec-scale Faraday rotation and polarization of 20 active galactic nuclei jets

    Science.gov (United States)

    Kravchenko, E. V.; Kovalev, Y. Y.; Sokolovsky, K. V.

    2017-01-01

    We perform polarimetry analysis of 20 active galactic nuclei (AGN) jets using the Very Long Baseline Array (VLBA) at 1.4, 1.6, 2.2, 2.4, 4.6, 5.0, 8.1, 8.4, and 15.4 GHz. The study allowed us to investigate linearly polarized properties of the jets at parsec-scales: distribution of the Faraday rotation measure (RM) and fractional polarization along the jets, Faraday effects and structure of Faraday-corrected polarization images. Wavelength-dependence of the fractional polarization and polarization angle is consistent with external Faraday rotation, while some sources show internal rotation. The RM changes along the jets, systematically increasing its value towards synchrotron self-absorbed cores at shorter wavelengths. The highest core RM reaches 16,900 rad m-2 in the source rest frame for the quasar 0952+179, suggesting the presence of highly magnetized, dense media in these regions. The typical RM of transparent jet regions has values of an order of a hundred rad m-2 . Significant transverse rotation measure gradients are observed in seven sources. The magnetic field in the Faraday screen has no preferred orientation, and is observed to be random or regular from source to source. Half of the sources show evidence for the helical magnetic fields in their rotating magnetoionic media. At the same time jets themselves contain large-scale, ordered magnetic fields and tend to align its direction with the jet flow. The observed variety of polarized signatures can be explained by a model of spine-sheath jet structure.

  1. MEASURING X-RAY VARIABILITY IN FAINT/SPARSELY SAMPLED ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Allevato, V. [Department of Physics, University of Helsinki, Gustaf Haellstroemin katu 2a, FI-00014 Helsinki (Finland); Paolillo, M. [Department of Physical Sciences, University Federico II, via Cinthia 6, I-80126 Naples (Italy); Papadakis, I. [Department of Physics and Institute of Theoretical and Computational Physics, University of Crete, 71003 Heraklion (Greece); Pinto, C. [SRON Netherlands Institute for Space Research, Sorbonnelaan 2, 3584-CA Utrecht (Netherlands)

    2013-07-01

    We study the statistical properties of the normalized excess variance of variability process characterized by a ''red-noise'' power spectral density (PSD), as in the case of active galactic nuclei (AGNs). We perform Monte Carlo simulations of light curves, assuming both a continuous and a sparse sampling pattern and various signal-to-noise ratios (S/Ns). We show that the normalized excess variance is a biased estimate of the variance even in the case of continuously sampled light curves. The bias depends on the PSD slope and on the sampling pattern, but not on the S/N. We provide a simple formula to account for the bias, which yields unbiased estimates with an accuracy better than 15%. We show that the normalized excess variance estimates based on single light curves (especially for sparse sampling and S/N < 3) are highly uncertain (even if corrected for bias) and we propose instead the use of an ''ensemble estimate'', based on multiple light curves of the same object, or on the use of light curves of many objects. These estimates have symmetric distributions, known errors, and can also be corrected for biases. We use our results to estimate the ability to measure the intrinsic source variability in current data, and show that they could also be useful in the planning of the observing strategy of future surveys such as those provided by X-ray missions studying distant and/or faint AGN populations and, more in general, in the estimation of the variability amplitude of sources that will result from future surveys such as Pan-STARRS and LSST.

  2. Active Galactic Nuclei Selected from GALEX Spectroscopy: The Ionizing Source Spectrum at z ~ 1

    Science.gov (United States)

    Barger, Amy J.; Cowie, Lennox L.

    2010-08-01

    We use a complete sample of Lyα-emission-line-selected active galactic nuclei (AGNs) obtained from nine deep blank fields observed with the grism spectrographs on the Galaxy Evolution Explorer (GALEX) satellite to measure the normalization and the spectral shape of the AGN contribution to the ionizing background (rest-frame wavelengths 700-900 Å) at z ~ 1. Our sample consists of 139 sources selected in the redshift range z = 0.65-1.25 in the near-ultraviolet (NUV; 2371 Å central wavelength) channel. The area covered is 8.2 deg2 to a NUV magnitude of 20.5 (AB) and 0.92 deg2 at the faintest magnitude limit of 21.8. The GALEX AGN luminosity function agrees well with those obtained using optical and X-ray AGN samples, and the measured redshift evolution of the ionizing volume emissivity is similar to that previously obtained by measuring the GALEX far-ultraviolet (FUV; 1528 Å central wavelength) magnitudes of an X-ray-selected sample. For the first time, we are able to construct the shape of the ionizing background at z ~ 1 in a fully self-consistent way. Based in part on data obtained from the Multimission Archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for Multimission Archive at STScI (MAST) for non-HST data is provided by the NASA Office of Space Science via grant NAG5-7584 and by other grants and contracts. Based in part on data obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA, and was made possible by the generous financial support of the W. M. Keck Foundation.

  3. A Growth-rate Indicator for Compton-thick Active Galactic Nuclei

    Science.gov (United States)

    Brightman, M.; Masini, A.; Ballantyne, D. R.; Baloković, M.; Brandt, W. N.; Chen, C.-T.; Comastri, A.; Farrah, D.; Gandhi, P.; Harrison, F. A.; Ricci, C.; Stern, D.; Walton, D. J.

    2016-07-01

    Due to their heavily obscured central engines, the growth rate of Compton-thick (CT) active galactic nuclei (AGNs) is difficult to measure. A statistically significant correlation between the Eddington ratio, λ Edd, and the X-ray power-law index, Γ, observed in unobscured AGNs offers an estimate of their growth rate from X-ray spectroscopy (albeit with large scatter). However, since X-rays undergo reprocessing by Compton scattering and photoelectric absorption when the line of sight to the central engine is heavily obscured, the recovery of the intrinsic Γ is challenging. Here we study a sample of local, predominantly CT megamaser AGNs, where the black hole mass, and thus Eddington luminosity, are well known. We compile results of the X-ray spectral fitting of these sources with sensitive high-energy (E > 10 keV) NuSTAR data, where X-ray torus models, which take into account the reprocessing effects have been used to recover the intrinsic Γ values and X-ray luminosities, L X. With a simple bolometric correction to L X to calculate λ Edd, we find a statistically significant correlation between Γ and λ Edd (p = 0.007). A linear fit to the data yields Γ = (0.41 ± 0.18)log10 λ Edd + (2.38 ± 0.20), which is statistically consistent with results for unobscured AGNs. This result implies that torus modeling successfully recovers the intrinsic AGN parameters. Since the megamasers have low-mass black holes (M BH ≈ 106-107 M ⊙) and are highly inclined, our results extend the Γ-λ Edd relationship to lower masses and argue against strong orientation effects in the corona, in support of AGN unification. Finally this result supports the use of Γ as a growth-rate indicator for accreting black holes, even for CT AGNs.

  4. THE Fe II EMISSION IN ACTIVE GALACTIC NUCLEI: EXCITATION MECHANISMS AND LOCATION OF THE EMITTING REGION

    Energy Technology Data Exchange (ETDEWEB)

    Marinello, M. [Universidade Federal de Itajubá, Rua Doutor Pereira Cabral 1303, 37500-903, Itajubá, MG (Brazil); Rodríguez-Ardila, A.; Garcia-Rissmann, A. [Laboratório Nacional de Astrofísica, Rua Estados Unidos 154, Itajubá, MG, 37504-364 (Brazil); Sigut, T. A. A. [The University of Western Ontario, London, ON N6A 3K7 (Canada); Pradhan, A. K., E-mail: murilo.marinello@gmail.com [McPherson Laboratory, The Ohio State University, 140 W. 18th Ave., Columbus, OH 43210-1173 (United States)

    2016-04-01

    We present a study of Fe ii emission in the near-infrared region (NIR) for 25 active galactic nuclei (AGNs) to obtain information about the excitation mechanisms that power it and the location where it is formed. We employ an NIR Fe ii template derived in the literature and find that it successfully reproduces the observed Fe ii spectrum. The Fe ii bump at 9200 Å detected in all objects studied confirms that Lyα fluorescence is always present in AGNs. The correlation found between the flux of the 9200 Å bump, the 1 μm lines, and the optical Fe ii implies that Lyα fluorescence plays an important role in Fe ii production. We determined that at least 18% of the optical Fe ii is due to this process, while collisional excitation dominates the production of the observed Fe ii. The line profiles of Fe ii λ10502, O i λ11287, Ca ii λ8664, and Paβ were compared to gather information about the most likely location where they are emitted. We found that Fe ii, O i and Ca ii have similar widths and are, on average, 30% narrower than Paβ. Assuming that the clouds emitting the lines are virialized, we show that the Fe ii is emitted in a region twice as far from the central source than Paβ. The distance, though, strongly varies: from 8.5 light-days for NGC 4051 to 198.2 light-days for Mrk 509. Our results reinforce the importance of the Fe ii in the NIR to constrain critical parameters that drive its physics and the underlying AGN kinematics, as well as more accurate models aimed at reproducing this complex emission.

  5. An optical and near-infrared color-magnitude diagram for type I Active Galactic Nuclei

    Science.gov (United States)

    Palmer, Robert J.; Gibbs, John; Gorjian, Varoujan; Pruett, Lee; Young, Diedre; Boyd, Robert; Byrd, Joy; Cheshier, Jaicie; Chung, Stephanie; Clark, Ruby; Fernandez, Joseph; Gonzales, Elyse; Kumar, Anika; McGinnis, Gillian; Palmer, John; Perrine, Luke; Phelps, Brittney; Reginio, Margaret; Richter, Kristi; Sanchez, Elias; Washburn, Claire

    2016-01-01

    This project is seeking another standard candle for measuring cosmic distances by trying to establish a color-magnitude diagram for active galactic nuclei (AGN). Type I AGN selected from the NASA/IPAC Extragalactic Database (NED) were used to establish a correlation between the color and the luminosity of AGN. This work builds on previous NASA/IPAC Teacher Archive Research Program team attempts to establish such a relationship. This is novel in that it uses both optical and 1-2 micron near-infrared (NIR) wavelengths as a better color discriminator of the transition between accretion-dominated and dust/torus-dominated emission.Photometric data from the Sloan Digital Sky Survey (SDSS) and the Two Micron All Sky Survey (2MASS) was extracted and analyzed for type I AGN with redshifts z diagram for the area where the dust vaporizes is analogous to a stellar Hertzsprung-Russell (HR) diagram. Data from SDSS and 2MASS were specifically selected to focus on the sublimation boundary between the coolest part of the accretion disk and the hottest region of the inner edge of the dusty torus surrounding the accretion disk to find the greatest ratio for the color. The more luminous the AGN, the more extended the dust sublimation radius, causing a larger hot dust emitting surface area, which corresponds to a greater NIR luminosity.Our findings suggest that the best correlations correspond to colors associated with the Sloan z band and any of the 2MASS bands with slight variations dependent on redshift. This may result in a tool for using AGN as a standard for cosmic distances. This research was made possible through the NASA/IPAC Teacher Archive Research Program (NITARP) and was funded by NASA Astrophysics Data Program.

  6. RADIO-SELECTED BINARY ACTIVE GALACTIC NUCLEI FROM THE VERY LARGE ARRAY STRIPE 82 SURVEY

    Energy Technology Data Exchange (ETDEWEB)

    Fu, Hai [Department of Physics and Astronomy, University of Iowa, Iowa City, IA 52245 (United States); Myers, A. D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Djorgovski, S. G.; Yan, Lin [California Institute of Technology, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Wrobel, J. M. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Stockton, A. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2015-01-20

    Galaxy mergers play an important role in the growth of galaxies and their supermassive black holes. Simulations suggest that tidal interactions could enhance black hole accretion, which can be tested by the fraction of binary active galactic nuclei (AGNs) among galaxy mergers. However, determining the fraction requires a statistical sample of binaries. We have identified kiloparsec-scale binary AGNs directly from high-resolution radio imaging. Inside the 92 deg{sup 2} covered by the high-resolution Very Large Array survey of the Sloan Digital Sky Survey (SDSS) Stripe 82 field, we identified 22 grade A and 30 grade B candidates of binary radio AGNs with angular separations less than 5'' (10 kpc at z = 0.1). Eight of the candidates have optical spectra for both components from the SDSS spectroscopic surveys and our Keck program. Two grade B candidates are projected pairs, but the remaining six candidates are all compelling cases of binary AGNs based on either emission line ratios or the excess in radio power compared to the Hα-traced star formation rate. Only two of the six binaries were previously discovered by an optical spectroscopic search. Based on these results, we estimate that ∼60% of our binary candidates would be confirmed once we obtain complete spectroscopic information. We conclude that wide-area high-resolution radio surveys offer an efficient method to identify large samples of binary AGNs. These radio-selected binary AGNs complement binaries identified at other wavelengths and are useful for understanding the triggering mechanisms of black hole accretion.

  7. THE INTEGRAL HIGH-ENERGY CUT-OFF DISTRIBUTION OF TYPE 1 ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Malizia, A.; Molina, M.; Bassani, L.; Stephen, J. B. [IASF-Bologna, INAF, Via Gobetti 101, I-40129 Bologna (Italy); Bazzano, A.; Ubertini, P. [IAPS-Roma, INAF, Via Fosso del Cavaliere 100, I-00133 Roma (Italy); Bird, A. J., E-mail: malizia@iasfbo.inaf.it [School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ (United Kingdom)

    2014-02-20

    In this Letter we present the primary continuum parameters, the photon index Γ, and the high-energy cut-off E {sub c} of 41 type-1 Seyfert galaxies extracted from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) complete sample of active galactic nuclei (AGNs). We performed broadband (0.3-100 keV) spectral analysis by simultaneously fitting the soft and hard X-ray spectra obtained by XMM and INTEGRAL/IBIS-Swift/BAT, respectively, in order to investigate the general properties of these parameters, in particular their distribution and mean values. We find a mean photon index of 1.73 with a standard deviation of 0.17 and a mean high-energy cut-off of 128 keV with a standard deviation of 46 keV for the whole sample. This is the first time that the cut-off energy is constrained in such a large number of AGNs. We have 26 measurements of the cut-off, which corresponds to 63% of the entire sample, distributed between 50 and 200 keV. There are a further 11 lower limits mostly below 300 keV. Using the main parameters of the primary continuum, we have been able to obtain the actual physical parameters of the Comptonizing region, i.e., the plasma temperature kT {sub e} from 20 to 100 keV and the optical depth τ < 4. Finally, with the high signal-to-noise ratio spectra starting to come from NuSTAR it will soon be possible to better constrain the cut-off values in many AGNs, allowing the determination of more physical models and thus better understand the continuum emission and geometry of the region surrounding black holes.

  8. GPU-based Monte Carlo Dust Radiative Transfer Scheme Applied to Active Galactic Nuclei

    Science.gov (United States)

    Heymann, Frank; Siebenmorgen, Ralf

    2012-05-01

    A three-dimensional parallel Monte Carlo (MC) dust radiative transfer code is presented. To overcome the huge computing-time requirements of MC treatments, the computational power of vectorized hardware is used, utilizing either multi-core computer power or graphics processing units. The approach is a self-consistent way to solve the radiative transfer equation in arbitrary dust configurations. The code calculates the equilibrium temperatures of two populations of large grains and stochastic heated polycyclic aromatic hydrocarbons. Anisotropic scattering is treated applying the Heney-Greenstein phase function. The spectral energy distribution (SED) of the object is derived at low spatial resolution by a photon counting procedure and at high spatial resolution by a vectorized ray tracer. The latter allows computation of high signal-to-noise images of the objects at any frequencies and arbitrary viewing angles. We test the robustness of our approach against other radiative transfer codes. The SED and dust temperatures of one- and two-dimensional benchmarks are reproduced at high precision. The parallelization capability of various MC algorithms is analyzed and included in our treatment. We utilize the Lucy algorithm for the optical thin case where the Poisson noise is high, the iteration-free Bjorkman & Wood method to reduce the calculation time, and the Fleck & Canfield diffusion approximation for extreme optical thick cells. The code is applied to model the appearance of active galactic nuclei (AGNs) at optical and infrared wavelengths. The AGN torus is clumpy and includes fluffy composite grains of various sizes made up of silicates and carbon. The dependence of the SED on the number of clumps in the torus and the viewing angle is studied. The appearance of the 10 μm silicate features in absorption or emission is discussed. The SED of the radio-loud quasar 3C 249.1 is fit by the AGN model and a cirrus component to account for the far-infrared emission.

  9. Line-driven disc wind model for ultrafast outflows in active galactic nuclei - scaling with luminosity

    Science.gov (United States)

    Nomura, M.; Ohsuga, K.

    2017-03-01

    In order to reveal the origin of the ultrafast outflows (UFOs) that are frequently observed in active galactic nuclei (AGNs), we perform two-dimensional radiation hydrodynamics simulations of the line-driven disc winds, which are accelerated by the radiation force due to the spectral lines. The line-driven winds are successfully launched for the range of MBH = 106-9 M⊙ and ε = 0.1-0.5, and the resulting mass outflow rate (dot{M_w}), momentum flux (dot{p_w}), and kinetic luminosity (dot{E_w}) are in the region containing 90 per cent of the posterior probability distribution in the dot{M}_w-Lbol plane, dot{p}_w-Lbol plane, and dot{E}_w-Lbol plane shown in Gofford et al., where MBH is the black hole mass, ε is the Eddington ratio, and Lbol is the bolometric luminosity. The best-fitting relations in Gofford et al., d log dot{M_w}/d log {L_bol}˜ 0.9, d log dot{p_w}/d log {L_bol}˜ 1.2, and d log dot{E_w}/d log {L_bol}˜ 1.5, are roughly consistent with our results, d log dot{M_w}/d log {L_bol}˜ 9/8, d log dot{p_w}/d log {L_bol}˜ 10/8, and d log dot{E_w}/d log {L_bol}˜ 11/8. In addition, our model predicts that no UFO features are detected for the AGNs with ε ≲ 0.01, since the winds do not appear. Also, only AGNs with MBH ≲ 108 M⊙ exhibit the UFOs when ε ∼ 0.025. These predictions nicely agree with the X-ray observations. These results support that the line-driven disc wind is the origin of the UFOs.

  10. Polarization of Rayleigh scattered Lyα in active galactic nuclei

    Science.gov (United States)

    Chang, Seok-Jun; Lee, Hee-Won; Yang, Yujin

    2017-02-01

    The unification scheme of active galactic nuclei invokes an optically thick molecular torus component hiding the broad emission line region. Assuming the presence of a thick neutral component in the molecular torus characterized by a H I column density >1022 cm-2, we propose that far-UV radiation around Lyα can be significantly polarized through Rayleigh scattering. Adopting a Monte Carlo technique, we compute polarization of Rayleigh scattered radiation near Lyα in a thick neutral region in the shape of a slab and a cylindrical shell. It is found that radiation near Lyα Rayleigh reflected from a very thick slab can be significantly polarized in a fairly large range of wavelength Δλ ˜ 50 Å exhibiting a flux profile similar to the incident one. Rayleigh transmitted radiation in a slab is characterized by the central dip with a complicated polarization behaviour. The optically thick part near Lyα centre is polarized in the direction perpendicular to the slab normal, which is in contrast to weakly polarized wing parts in the direction parallel to the slab normal. A similar polarization flip phenomenon is also found in the case of a tall cylindrical shell, in which the spatial diffusion along the vertical direction near the inner cylinder wall for core photons leads to a tendency of the electric field aligned to the direction perpendicular to the vertical axis. Observational implications are briefly discussed including spectropolarimetry of the quasar PG 1630+377 by Koratkar et al. in 1990 where Lyα is strongly polarized with no other emission lines polarized.

  11. DIRECT MEASUREMENT OF THE X-RAY TIME-DELAY TRANSFER FUNCTION IN ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Legg, E.; Miller, L. [Department of Physics, Oxford University, Keble Road, Oxford OX1 3RH (United Kingdom); Turner, T. J.; Giustini, M.; Reeves, J. N. [Department of Physics, University of Maryland Baltimore County, Baltimore, MD 21250 (United States); Kraemer, S. B. [Institute for Astrophysics and Computational Sciences, Department of Physics, The Catholic University of America, Washington, DC 20064 (United States)

    2012-11-20

    The origin of the observed time lags, in nearby active galactic nuclei (AGNs), between hard and soft X-ray photons is investigated using new XMM-Newton data for the narrow-line Seyfert I galaxy Ark 564 and existing data for 1H 0707-495 and NGC 4051. These AGNs have highly variable X-ray light curves that contain frequent, high peaks of emission. The averaged light curve of the peaks is directly measured from the time series, and it is shown that (1) peaks occur at the same time, within the measurement uncertainties, at all X-ray energies, and (2) there exists a substantial tail of excess emission at hard X-ray energies, which is delayed with respect to the time of the main peak, and is particularly prominent in Ark 564. Observation (1) rules out that the observed lags are caused by Comptonization time delays and disfavors a simple model of propagating fluctuations on the accretion disk. Observation (2) is consistent with time lags caused by Compton-scattering reverberation from material a few thousand light-seconds from the primary X-ray source. The power spectral density and the frequency-dependent phase lags of the peak light curves are consistent with those of the full time series. There is evidence for non-stationarity in the Ark 564 time series in both the Fourier and peaks analyses. A sharp 'negative' lag (variations at hard photon energies lead soft photon energies) observed in Ark 564 appears to be generated by the shape of the hard-band transfer function and does not arise from soft-band reflection of X-rays. These results reinforce the evidence for the existence of X-ray reverberation in type I AGN, which requires that these AGNs are significantly affected by scattering from circumnuclear material a few tens or hundreds of gravitational radii in extent.

  12. IDENTIFYING LUMINOUS ACTIVE GALACTIC NUCLEI IN DEEP SURVEYS: REVISED IRAC SELECTION CRITERIA

    Energy Technology Data Exchange (ETDEWEB)

    Donley, J. L.; Koekemoer, A. M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Brusa, M.; Salvato, M. [Max Planck Institut fuer extraterrestrische Physik, Giessenbachstrasse 1, D-85748 Garching bei Muenchen (Germany); Capak, P. [Spitzer Science Center, California Institute of Technology, MC 220-6, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Cardamone, C. N. [Department of Physics, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA 02139 (United States); Civano, F. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Ilbert, O. [Laboratoire d' Astrophysique de Marseille (UMR 6110), CNRS-Universite de Provence, 38 rue Frederic Joliot-Curie, 13388 Marseille Cedex 13 (France); Impey, C. D. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Kartaltepe, J. S. [National Optical Astronomy Observatory, 950 North Cherry Avenue, Tucson, AZ 85719 (United States); Miyaji, T. [Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Ensenada, Baja California (Mexico); Sanders, D. B. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); Trump, J. R. [UCO/Lick, University of California, Santa Cruz, CA 95064 (United States); Zamorani, G., E-mail: donley@stsci.edu [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy)

    2012-04-01

    Spitzer/IRAC selection is a powerful tool for identifying luminous active galactic nuclei (AGNs). For deep IRAC data, however, the AGN selection wedges currently in use are heavily contaminated by star-forming galaxies, especially at high redshift. Using the large samples of luminous AGNs and high-redshift star-forming galaxies in COSMOS, we redefine the AGN selection criteria for use in deep IRAC surveys. The new IRAC criteria are designed to be both highly complete and reliable, and incorporate the best aspects of the current AGN selection wedges and of infrared power-law selection while excluding high-redshift star-forming galaxies selected via the BzK, distant red galaxy, Lyman-break galaxy, and submillimeter galaxy criteria. At QSO luminosities of log L{sub 2-10keV}(erg s{sup -1}) {>=}44, the new IRAC criteria recover 75% of the hard X-ray and IRAC-detected XMM-COSMOS sample, yet only 38% of the IRAC AGN candidates have X-ray counterparts, a fraction that rises to 52% in regions with Chandra exposures of 50-160 ks. X-ray stacking of the individually X-ray non-detected AGN candidates leads to a hard X-ray signal indicative of heavily obscured to mildly Compton-thick obscuration (log N{sub H} (cm{sup -2}) = 23.5 {+-} 0.4). While IRAC selection recovers a substantial fraction of luminous unobscured and obscured AGNs, it is incomplete to low-luminosity and host-dominated AGNs.

  13. Eyeblink classical conditioning and interpositus nucleus activity are disrupted in adult rats exposed to ethanol as neonates.

    Science.gov (United States)

    Green, John T; Johnson, Timothy B; Goodlett, Charles R; Steinmetz, Joseph E

    2002-01-01

    Neonatal exposure to ethanol in rats, during the period of brain development comparable to that of the human third trimester, produces significant, dose-dependent cell loss in the cerebellum and deficits in coordinated motor performance. These rats are also impaired in eyeblink conditioning as weanlings and as adults. The current study examined single-unit neural activity in the interpositus nucleus of the cerebellum in adults following neonatal binge ethanol exposure. Group Ethanol received alcohol doses of 5.25 g/kg/day on postnatal days 4-9. Group Sham Intubated underwent acute intragastric intubation on postnatal days 4-9 but did not receive any infusions. Group Unintubated Control (from separate litters) did not receive any intubations. When rats were 3-7 mo old, pairs of extracellular microelectrodes were implanted in the region of the interpositus nucleus. Beginning 1 wk later, the rats were given either 100 paired or 190 unpaired trials per day for 10 d followed by 4 d of 100 conditioned stimulus (CS)-alone trials per day. As in our previous study, conditioned response acquisition in Group Ethanol rats was impaired. In addition, by session 5 of paired acquisition, Group Sham Intubated and Group Unintubated Control showed significant increases in interpositus nucleus activity, relative to baseline, in the CS-unconditioned stimulus interval. In contrast, Group Ethanol failed to show significant changes in interpositus nucleus activity until later in training. These results indicate that the disruption in eyeblink conditioning after early exposure to ethanol is reflected in alterations in interpositus nucleus activity.

  14. Eyeblink Classical Conditioning and Interpositus Nucleus Activity Are Disrupted in Adult Rats Exposed to Ethanol as Neonates

    Science.gov (United States)

    Green, John T.; Johnson, Timothy B.; Goodlett, Charles R.; Steinmetz, Joseph E.

    2002-01-01

    Neonatal exposure to ethanol in rats, during the period of brain development comparable to that of the human third trimester, produces significant, dose-dependent cell loss in the cerebellum and deficits in coordinated motor performance. These rats are also impaired in eyeblink conditioning as weanlings and as adults. The current study examined single-unit neural activity in the interpositus nucleus of the cerebellum in adults following neonatal binge ethanol exposure. Group Ethanol received alcohol doses of 5.25 g/kg/day on postnatal days 4–9. Group Sham Intubated underwent acute intragastric intubation on postnatal days 4–9 but did not receive any infusions. Group Unintubated Control (from separate litters) did not receive any intubations. When rats were 3–7 mo old, pairs of extracellular microelectrodes were implanted in the region of the interpositus nucleus. Beginning 1 wk later, the rats were given either 100 paired or 190 unpaired trials per day for 10 d followed by 4 d of 100 conditioned stimulus (CS)-alone trials per day. As in our previous study, conditioned response acquisition in Group Ethanol rats was impaired. In addition, by session 5 of paired acquisition, Group Sham Intubated and Group Unintubated Control showed significant increases in interpositus nucleus activity, relative to baseline, in the CS–unconditioned stimulus interval. In contrast, Group Ethanol failed to show significant changes in interpositus nucleus activity until later in training. These results indicate that the disruption in eyeblink conditioning after early exposure to ethanol is reflected in alterations in interpositus nucleus activity. PMID:12359839

  15. Biological substrates of reward and aversion: a nucleus accumbens activity hypothesis.

    Science.gov (United States)

    Carlezon, William A; Thomas, Mark J

    2009-01-01

    The nucleus accumbens (NAc) is a critical element of the mesocorticolimbic system, a brain circuit implicated in reward and motivation. This basal forebrain structure receives dopamine (DA) input from the ventral tegmental area (VTA) and glutamate (GLU) input from regions including the prefrontal cortex (PFC), amygdala (AMG), and hippocampus (HIP). As such, it integrates inputs from limbic and cortical regions, linking motivation with action. The NAc has a well-established role in mediating the rewarding effects of drugs of abuse and natural rewards such as food and sexual behavior. However, accumulating pharmacological, molecular, and electrophysiological evidence has raised the possibility that it also plays an important (and sometimes underappreciated) role in mediating aversive states. Here we review evidence that rewarding and aversive states are encoded in the activity of NAc medium spiny GABAergic neurons, which account for the vast majority of the neurons in this region. While admittedly simple, this working hypothesis is testable using combinations of available and emerging technologies, including electrophysiology, genetic engineering, and functional brain imaging. A deeper understanding of the basic neurobiology of mood states will facilitate the development of well-tolerated medications that treat and prevent addiction and other conditions (e.g., mood disorders) associated with dysregulation of brain motivation systems.

  16. Activation of gastric afferents increases noradrenaline release in the paraventricular nucleus and plasma oxytocin level.

    Science.gov (United States)

    Ueta, Y; Kannan, H; Higuchi, T; Negoro, H; Yamaguchi, K; Yamashita, H

    2000-01-14

    Effects of electrical stimulation of the gastric vagal nerves on plasma levels of oxytocin (OXT) and arginine vasopressin (AVP) were examined in rats anesthetized with urethane. Electrical stimulation of the gastric vagal nerves increased the plasma levels of OXT, but not AVP. The concentrations of extracellular noradrenaline (NA) in the paraventricular nucleus (PVN) were measured by in vivo microdialysis in rats anesthetized with urethane. Electrical stimulation of the gastric vagal nerves evoked an increase followed by a slight decrease in the concentrations of NA. The responses of spontaneous firing magnocellular neurosecretory neurons in the PVN to both electrical stimulation of the gastric vagal nerves and intravenous (i.v.) administration of CCK-8 were examined. Most of the putative OXT-secreting cells recorded were excited by both electrical stimulation of gastric vagal nerves and i.v. administration of CCK-8. These results suggest that gastric vagal afferents activate the central noradrenergic system from the brainstem to the PVN and secretion of OXT.

  17. Stress activates the nucleus incertus and modulates plasticity in the hippocampo-medial prefrontal cortical pathway.

    Science.gov (United States)

    Rajkumar, Ramamoorthy; Wu, You; Farooq, Usman; Tan, Wei Hao; Dawe, Gavin S

    2016-01-01

    The nucleus incertus (NI) is a small cluster of brainstem neurons presumed to play a role in stress responses. We show that swim stress (normal water: 30 min and cold water: 20 min) and elevation stress robustly induced c-Fos expression in the NI and significantly suppressed long-term potentiation (LTP) in the hippocampo-medial prefrontal cortical (HP-mPFC) pathway. To examine whether activation of CRF1 receptors in the NI plays a role in the suppression of HP-mPFC LTP, antalarmin, a specific CRF1 receptor antagonist, was infused directly into the NI either before presentation of (1) elevation stress or (2) high frequency stimulation. As predicted, the intra-NI infusion of antalarmin reversed the elevation stress-induced suppression of LTP in the HP-mPFC pathway. This report suggests that the CRF1 receptor in the NI contributes to stress-related impairment in plasticity of the HP-mPFC pathway. The findings suggest that the NI-HP-mPFC is a stress responsive circuit in the rodent brain.

  18. Sodium salicylate suppresses GABAergic inhibitory activity in neurons of rodent dorsal raphe nucleus.

    Directory of Open Access Journals (Sweden)

    Yan Jin

    Full Text Available Sodium salicylate (NaSal, a tinnitus inducing agent, can activate serotonergic (5-HTergic neurons in the dorsal raphe nucleus (DRN and can increase serotonin (5-HT level in the inferior colliculus and the auditory cortex in rodents. To explore the underlying neural mechanisms, we first examined effects of NaSal on neuronal intrinsic properties and the inhibitory synaptic transmissions in DRN slices of rats by using whole-cell patch-clamp technique. We found that NaSal hyperpolarized the resting membrane potential, decreased the input resistance, and suppressed spontaneous and current-evoked firing in GABAergic neurons, but not in 5-HTergic neurons. In addition, NaSal reduced GABAergic spontaneous and miniature inhibitory postsynaptic currents in 5-HTergic neurons. We next examined whether the observed depression of GABAergic activity would cause an increase in the excitability of 5-HTergic neurons using optogenetic technique in DRN slices of the transgenic mouse with channelrhodopsin-2 expressed in GABAergic neurons. When the GABAergic inhibition was enhanced by optical stimulation to GABAergic neurons in mouse DRN, NaSal significantly depolarized the resting membrane potential, increased the input resistance and increased current-evoked firing of 5-HTergic neurons. However, NaSal would fail to increase the excitability of 5-HTergic neurons when the GABAergic synaptic transmission was blocked by picrotoxin, a GABA receptor antagonist. Our results indicate that NaSal suppresses the GABAergic activities to raise the excitability of local 5-HTergic neural circuits in the DRN, which may contribute to the elevated 5-HT level by NaSal in the brain.

  19. Activation of dopamine receptors in the nucleus accumbens promotes sucrose-reinforced cued approach behavior

    Directory of Open Access Journals (Sweden)

    Saleem M. Nicola

    2016-07-01

    Full Text Available Dopamine receptor activation in the nucleus accumbens (NAc promotes vigorous environmentally-cued food-seeking in hungry rats. Rats fed ad libitum, however, respond to fewer food-predictive cues, particularly when the value of food reward is low. Here, we investigated whether this difference could be due to differences in the degree of dopamine receptor activation in the NAc. First, we observed that although rats given ad libitum access to chow in their home cages approached a food receptacle in response to reward-predictive cues, the number of such approaches declined as animals accumulated food rewards. Intriguingly, cued approach to food occurred in clusters, with several cued responses followed by successive non-responses. This pattern suggested that behavior was dictated by transitions between two states, responsive and non-responsive. Injection of D1 or D2 dopamine receptor agonists into the NAc dose-dependently increased cue responding by promoting transitions to the responsive state and by preventing transitions to the non-responsive state. In contrast, antagonists of either D1 or D2 receptors promoted long bouts of non-responding by inducing transitions to the non-responsive state and by preventing transitions to the responsive state. Moreover, locomotor behavior during the inter-trial interval was correlated with the responsive state, and was also increased by dopamine receptor agonists. These results suggest that activation of NAc dopamine receptors plays an important role in regulating the probability of approach to food under conditions of normative satiety.

  20. Nucleus accumbens-specific interventions in RGS9-2 activity modulate responses to morphine.

    Science.gov (United States)

    Gaspari, Sevasti; Papachatzaki, Maria M; Koo, Ja Wook; Carr, Fiona B; Tsimpanouli, Maria-Efstratia; Stergiou, Eugenia; Bagot, Rosemary C; Ferguson, Deveroux; Mouzon, Ezekiell; Chakravarty, Sumana; Deisseroth, Karl; Lobo, Mary Kay; Zachariou, Venetia

    2014-07-01

    Regulator of G protein signalling 9-2 (Rgs9-2) modulates the actions of a wide range of CNS-acting drugs by controlling signal transduction of several GPCRs in the striatum. RGS9-2 acts via a complex mechanism that involves interactions with Gα subunits, the Gβ5 protein, and the adaptor protein R7BP. Our recent work identified Rgs9-2 complexes in the striatum associated with acute or chronic exposures to mu opioid receptor (MOR) agonists. In this study we use several new genetic tools that allow manipulations of Rgs9-2 activity in particular brain regions of adult mice in order to better understand the mechanism via which this protein modulates opiate addiction and analgesia. We used adeno-associated viruses (AAVs) to express forms of Rgs9-2 in the dorsal and ventral striatum (nucleus accumbens, NAc) in order to examine the influence of this protein in morphine actions. Consistent with earlier behavioural findings from constitutive Rgs9 knockout mice, we show that Rgs9-2 actions in the NAc modulate morphine reward and dependence. Notably, Rgs9-2 in the NAc affects the analgesic actions of morphine as well as the development of analgesic tolerance. Using optogenetics we demonstrate that activation of Channelrhodopsin2 in Rgs9-2-expressing neurons, or in D1 dopamine receptor (Drd1)-enriched medium spiny neurons, accelerates the development of morphine tolerance, whereas activation of D2 dopamine receptor (Drd2)-enriched neurons does not significantly affect the development of tolerance. Together, these data provide new information on the signal transduction mechanisms underlying opiate actions in the NAc.

  1. Models of the Optical/Ultraviolet Continuum Polarization in Active Galactic Nuclei: Implications for Unification Schemes

    Science.gov (United States)

    Kartje, John F.

    1995-10-01

    I have computed the 1200-8000 A thermal continuum polarization induced by gas and dust arranged in configurations compatible with current active galactic nuclei (AGNs) unification schemes. Both uniform- density tori and stratified-density disk-driven winds were considered. A Monte Carlo radiative transfer code was developed which includes the polarization mechanisms of electron and dust scattering as well as dichroic extinction by aligned grains. A Galactic-type grain population was assumed. Based on these calculations, I propose a new interpretation of many of the observed polarization traits of Seyfert galaxies and QSOs: namely, that the polarization in these sources is induced by the same optically thick material which is assumed to obscure the central engine in unification schemes. In particular, I suggest that stratified-density winds could provide a natural explanation (and one consistent with unification models) of the polarization trends observed in Seyfert galaxies. Such winds can display polarizations (P ≲ 20%) oriented perpendicular to the axis along viewing angles inclined to the axis by θ0 ≳ 45° in well-collimated winds, this polarization shifts to smaller magnitudes (P ≲ 2%) and parallel orientations for more face-on viewing, consistent with the patterns observed in Seyfert 2 and Seyfert 1 sources, respectively. In less-collimated winds, scattering alone tends to produce parallel orientations for all viewing angles; perpendicular polarization at large θ0 can result if there is a high degree of magnetic grain alignment. The simplest torus models (i.e., uniform-density, opaque gas and dust) do not reproduce this flip in polarization position angle. Furthermore, they generally display high polarization magnitudes (P ≳ 10%) along most viewing angles θ0 > θ∞ (where θ is the torus half-opening angle) and negligible polarization along θ0 > θ∞. Unlike previous models for AGN polarization which invoke scattering by optically thin electron

  2. Calcium signals in the nucleus accumbens: Activation of astrocytes by ATP and succinate

    Directory of Open Access Journals (Sweden)

    Emri Zsuzsa

    2011-10-01

    Full Text Available Abstract Background Accumulating evidence suggests that glial signalling is activated by different brain functions. However, knowledge regarding molecular mechanisms of activation or their relation to neuronal activity is limited. The purpose of the present study is to identify the characteristics of ATP-evoked glial signalling in the brain reward area, the nucleus accumbens (NAc, and thereby to explore the action of citric acid cycle intermediate succinate (SUC. Results We described the burst-like propagation of Ca2+ transients evoked by ATP in acute NAc slices from rat brain. Co-localization of the ATP-evoked Ca2+ signalling with immunoreactivities of the astroglia-specific gap junction forming channel protein connexin43 (Cx43 and the glial fibrillary acidic protein (GFAP indicated that the responsive cells were a subpopulation of Cx43 and GFAP immunoreactive astrocytes. The ATP-evoked Ca2+ transients were present under the blockade of neuronal activity, but were inhibited by Ca2+ store depletion and antagonism of the G protein coupled purinergic P2Y1 receptor subtype-specific antagonist MRS2179. Similarly, Ca2+ transients evoked by the P2Y1 receptor subtype-specific agonist 2-(Methylthioadenosine 5'-diphosphate were also blocked by MRS2179. These characteristics implied that intercellular Ca2+ signalling originated from the release of Ca2+ from internal stores, triggered by the activation of P2Y1 receptors. Inhibition by the gap junction blockers carbenoxolone and flufenamic acid and by an antibody raised against the gating-associated segment of Cx43 suggested that intercellular Ca2+ signalling proceeded through gap junctions. We demonstrated for the first time that extracellular SUC also evoked Ca2+ transients (EC50 = 50-60 μM in about 15% of the ATP-responsive NAc astrocytes. By contrast to glial cells, electrophysiologically identified NAc neurons surrounded by ATP-responsive astrocytes were not activated simultaneously. Conclusions We

  3. The Pierre Auger Observatory scaler mode for the study of solar activity modulation of galactic cosmic rays

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2011-01-15

    Since data-taking began in January 2004, the Pierre Auger Observatory has been recording the count rates of low energy secondary cosmic ray particles for the self-calibration of the ground detectors of its surface detector array. After correcting for atmospheric effects, modulations of galactic cosmic rays due to solar activity and transient events are observed. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. In this study, the available data are presented together with an analysis focused on the observation of Forbush decreases, where a strong correlation with neutron monitor data is found.

  4. The Pierre Auger Observatory scaler mode for the study of solar activity modulation of galactic cosmic rays

    Energy Technology Data Exchange (ETDEWEB)

    Abreu, P.; /Lisbon, LIFEP /Lisbon, IST; Aglietta, M.; /Turin Observ. /Turin U. /INFN, Turin; Ahn, E.J.; /Fermilab; Allard, D.; /APC, Paris; Allekotte, I.; /Centro Atomico Bariloche /Balseiro Inst., San Carlos de Bariloche; Allen, J.; /New York U.; Alvarez Castillo, J.; /Mexico U.; Alvarez-Muniz, J.; /Santiago de Compostela U.; Ambrosio, M.; /Naples U. /INFN, Naples; Aminaei, A.; /Nijmegen U., IMAPP; Anchordoqui, L.; /Wisconsin U., Milwaukee /Lisbon, LIFEP /Lisbon, IST

    2011-01-01

    Since data-taking began in January 2004, the Pierre Auger Observatory has been recording the count rates of low energy secondary cosmic ray particles for the self-calibration of the ground detectors of its surface detector array. After correcting for atmospheric effects, modulations of galactic cosmic rays due to solar activity and transient events are observed. Temporal variations related with the activity of the heliosphere can be determined with high accuracy due to the high total count rates. In this study, the available data are presented together with an analysis focused on the observation of Forbush decreases, where a strong correlation with neutron monitor data is found.

  5. Sensitivity of cochlear nucleus neurons to spatio-temporal changes in auditory nerve activity.

    Science.gov (United States)

    Wang, Grace I; Delgutte, Bertrand

    2012-12-01

    The spatio-temporal pattern of auditory nerve (AN) activity, representing the relative timing of spikes across the tonotopic axis, contains cues to perceptual features of sounds such as pitch, loudness, timbre, and spatial location. These spatio-temporal cues may be extracted by neurons in the cochlear nucleus (CN) that are sensitive to relative timing of inputs from AN fibers innervating different cochlear regions. One possible mechanism for this extraction is "cross-frequency" coincidence detection (CD), in which a central neuron converts the degree of coincidence across the tonotopic axis into a rate code by preferentially firing when its AN inputs discharge in synchrony. We used Huffman stimuli (Carney LH. J Neurophysiol 64: 437-456, 1990), which have a flat power spectrum but differ in their phase spectra, to systematically manipulate relative timing of spikes across tonotopically neighboring AN fibers without changing overall firing rates. We compared responses of CN units to Huffman stimuli with responses of model CD cells operating on spatio-temporal patterns of AN activity derived from measured responses of AN fibers with the principle of cochlear scaling invariance. We used the maximum likelihood method to determine the CD model cell parameters most likely to produce the measured CN unit responses, and thereby could distinguish units behaving like cross-frequency CD cells from those consistent with same-frequency CD (in which all inputs would originate from the same tonotopic location). We find that certain CN unit types, especially those associated with globular bushy cells, have responses consistent with cross-frequency CD cells. A possible functional role of a cross-frequency CD mechanism in these CN units is to increase the dynamic range of binaural neurons that process cues for sound localization.

  6. Complementary roles of different oscillatory activities in the subthalamic nucleus in coding motor effort in Parkinsonism.

    Science.gov (United States)

    Tan, Huiling; Pogosyan, Alek; Anzak, Anam; Ashkan, Keyoumars; Bogdanovic, Marko; Green, Alexander L; Aziz, Tipu; Foltynie, Thomas; Limousin, Patricia; Zrinzo, Ludvic; Brown, Peter

    2013-10-01

    The basal ganglia may play an important role in the control of motor scaling or effort. Recently local field potential (LFP) recordings from patients with deep brain stimulation electrodes in the basal ganglia have suggested that local increases in the synchronisation of neurons in the gamma frequency band may correlate with force or effort. Whether this feature uniquely codes for effort and whether such a coding mechanism holds true over a range of efforts is unclear. Here we investigated the relationship between frequency-specific oscillatory activities in the subthalamic nucleus (STN) and manual grips made with different efforts. The latter were self-rated using the 10 level Borg scale ranging from 0 (no effort) to 10 (maximal effort). STN LFP activities were recorded in patients with Parkinson's Disease (PD) who had undergone functional surgery. Patients were studied while motor performance was improved by dopaminergic medication. In line with previous studies we observed power increase in the theta/alpha band (4-12 Hz), power suppression in the beta band (13-30 Hz) and power increase in the gamma band (55-90 Hz) and high frequency band (101-375 Hz) during voluntary grips. Beta suppression deepened, and then reached a floor level as effort increased. Conversely, gamma and high frequency power increases were enhanced during grips made with greater effort. Multiple regression models incorporating the four different spectral changes confirmed that the modulation of power in the beta band was the only independent predictor of effort during grips made with efforts rated coding. The latter function is thought to be impaired in untreated PD where task-related reactivity in these two bands is deficient.

  7. THE NUCLEAR INFRARED EMISSION OF LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Mason, R. E. [Gemini Observatory, Northern Operations Center, 670 N. A' ohoku Place, Hilo, HI 96720 (United States); Lopez-Rodriguez, E.; Packham, C. [Department of Astronomy, University of Florida, 211 Bryant Space Science Center, P.O. Box 112055, Gainesville, FL 32611 (United States); Alonso-Herrero, A. [Instituto de Fisica de Cantabria, CSIC-UC, Avenida de los Castros s/n, 39005 Santander (Spain); Levenson, N. A.; Radomski, J. [Gemini Observatory, Southern Operations Center, c/o AURA, Casilla 603, La Serena (Chile); Ramos Almeida, C. [Instituto de Astrofisica de Canarias, C/Via Lactea, s/n, E-38205, La Laguna, Tenerife (Spain); Colina, L. [Departamento de Astrofisica, Centro de Astrobiologia (CSIC/INTA), Instituto Nacional de Tecnica Aeroespacial, Crta de Torrejon a Ajalvir, km 4, 28850 Torrejon de Ardoz, Madrid (Spain); Elitzur, M. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); Aretxaga, I. [Instituto Nacional de Astrofisica, Optica y Electronica (INAOE), Aptdo. Postal 51 y 216, 72000 Puebla (Mexico); Roche, P. F. [Astrophysics, Department of Physics, University of Oxford, DWB, Keble Road, Oxford OX1 3RH (United Kingdom); Oi, N. [Department of Astronomy, School of Science, Graduate University for Advanced Studies (SOKENDAI), Mitaka, Tokyo 181-8588 (Japan)

    2012-07-15

    We present high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs), and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGNs; L{sub bol} {approx}< 10{sup 42} erg s{sup -1}). Infrared (IR) observations may advance our understanding of the accretion flows in LLAGNs, the fate of the obscuring torus at low accretion rates, and, perhaps, the star formation histories of these objects. However, while comprehensively studied in higher-luminosity Seyferts and quasars, the nuclear IR properties of LLAGNs have not yet been well determined. We separate the present LLAGN sample into three categories depending on their Eddington ratio and radio emission, finding different IR characteristics for each class. (1) At the low-luminosity, low-Eddington-ratio (log L{sub bol}/L{sub Edd} < -4.6) end of the sample, we identify 'host-dominated' galaxies with strong polycyclic aromatic hydrocarbon bands that may indicate active (circum-)nuclear star formation. (2) Some very radio-loud objects are also present at these low Eddington ratios. The IR emission in these nuclei is dominated by synchrotron radiation, and some are likely to be unobscured type 2 AGNs that genuinely lack a broad-line region. (3) At higher Eddington ratios, strong, compact nuclear sources are visible in the MIR images. The nuclear SEDs of these galaxies are diverse; some resemble typical Seyfert nuclei, while others lack a well-defined MIR 'dust bump'. Strong silicate emission is present in many of these objects. We speculate that this, together with high ratios of silicate strength to hydrogen column density, could suggest optically thin dust and low dust-to-gas ratios, in accordance with model predictions that LLAGNs do not host a Seyfert-like obscuring torus. We anticipate that detailed modeling of the new data and SEDs in terms of accretion disk, jet, radiatively inefficient accretion flow, and torus components will provide further

  8. Activity of cells in the lateral vestibular nucleus as a function of head position

    Science.gov (United States)

    Fujita, Y.; Rosenberg, Jay; Segundo, J. P.

    1968-01-01

    1. The spike activity of cells in the lateral vestibular nucleus was recorded in cats anaesthetized with pentobarbital sodium. Natural labyrinthine stimulation was applied by fixing the animal at different positions reached through roations about a longitudinal or transverse axis. 2. The majority of cells responded to rotations only about the longitudinal axis. Two types of response were found. The first was characterized by a transient change in activity which occurred only during the movement. The second type had an initial transient component and a subsequent steady component that persisted as long as the head remained fixed. 3. The interspike interval means, standard deviations, histograms and autocorrelograms of the steady response components of cells sensitive to lateral tilt were calculated. In every cell the relation between the head position with respect to gravity and the mean interspike interval of the steady discharge showed two main features. (a) `Directional sensitivity': the mean interval increased following rotation in one sense, and decreased following rotation in the other. In twenty-two out of thirty-three cells, the mean increased when the recording side was raised. The remaining cells showed the opposite relation. (b) `Multivaluedness': each particular position is associated with several different values of mean interval and these values had a relatively wide scatter. The curve that resulted from joining points in the order in which they occurred during the experiment was either closed, open, or combined closed and open portions. 4. The standard deviations, histograms and autocorrelograms also showed directional sensitivity and multivaluedness with respect to position. Several types of interspike interval histograms and autocorrelograms characterized lateral vestibular activity. The forms of the histogram and the autocorrelogram of the discharge from each cell usually remained unchanged during stimulation. 5. The extensive spread of the

  9. High Frequency Very Long Baseline Interferometry Observations of Active Galactic Nuclei

    Science.gov (United States)

    Bower, Geoffrey Copeland

    Millimeter wavelength very long baseline interferometry (VLBI) provides an excellent tool for the investigation of compact synchrotron sources. The high angular resolution and the decline in synchrotron opacity and lifetime with decreasing wavelength give unprecedented spatial and temporal resolution in active galactic nuclei. We present here a description of the implementation of millimeter VLBI with the 9-element millimeter array at Hat Creek Radio Observatory. We emphasize the technical details of array phasing, calibration and observation. The Hat Creek array was used successfully in 5 VLBI experiments between 1995 and 1997. We tested the technique of total power correction for atmospheric phase fluctuations due to water vapor with two epochs of 3mm λ VLBI observations with the Hat Creek array and with the National Radio Astronomy Observatory (NRAO) Kitt Peak 12m antenna. We reduced the root-mean-square phase by as much as a factor of two and to as low as one radian. The limiting factor was the gain stability of the receivers. We present 7mm λ VLBI observations made with the NRAO Very Long Baseline Array (VLBA) of the compact, nonthermal radio source Sgr A*. We find that the image of Sgr A* is fully consistent with the hypothesis that it is a cyclo-synchrotron source powered by accretion onto a 106Msolar black hole and obscured by a screen of thermal electrons. We find no evidence for any asymmetric structure. We also present a two year study of the gamma-ray blazar 530 with multiple epochs of VLBI imaging at 3 mm, 7 mm, 1.3 cm and 3.6 cm λ. We incorporate flux density monitoring ranging from the radio band to positive correlation over 4 years between the millimeter and gamma-ray flux densities. We also find that a bright millimeter wavelength flare in early 1995 corresponded to the creation of a new parsec-scale jet component. We study the spectra and dynamical evolution of the jet. The jet component appears to decelerate from 7.6 ± 2.2c to 0.95 ± 0.16c

  10. DETERMINING THE COVERING FACTOR OF COMPTON-THICK ACTIVE GALACTIC NUCLEI WITH NuSTAR

    Energy Technology Data Exchange (ETDEWEB)

    Brightman, M.; Baloković, M.; Fuerst, F.; Harrison, F. A. [Cahill Center for Astrophysics, California Institute of Technology, 1216 East California Boulevard, Pasadena, CA 91125 (United States); Stern, D. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Mail Stop 169-221, Pasadena, CA 91109 (United States); Arévalo, P. [Instituto de Física y Astronoma, Facultad de Ciencias, Universidad de Valparaíso, Gran Bretana N 1111, Playa Ancha, Valparaíso (Chile); Ballantyne, D. R. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Bauer, F. E. [Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Catolica de Chile, Casilla 306, Santiago 22 (Chile); Boggs, S. E.; Craig, W. W. [Space Sciences Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, F. E. [DTU Space, National Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Comastri, A. [INAF Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Gandhi, P. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, 6127 Wilder Laboratory, Hanover, NH 03755 (United States); Koss, M. [SNSF Ambizione Fellow, Institute for Astronomy, Department of Physics, ETH Zurich, Wolfgang-Pauli-Strasse 27, CH-8093 Zurich (Switzerland); LaMassa, S. [Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208120, New Haven, CT 06520 (United States); and others

    2015-05-20

    The covering factor of Compton-thick (CT) obscuring material associated with the torus in active galactic nuclei (AGNs) is at present best understood through the fraction of sources exhibiting CT absorption along the line of sight (N{sub H} > 1.5 × 10{sup 24} cm{sup −2}) in the X-ray band, which reveals the average covering factor. Determining this CT fraction is difficult, however, due to the extreme obscuration. With its spectral coverage at hard X-rays (>10 keV), Nuclear Spectroscopic Telescope Array (NuSTAR) is sensitive to the AGNs covering factor since Compton scattering of X-rays off optically thick material dominates at these energies. We present a spectral analysis of 10 AGNs observed with NuSTAR where the obscuring medium is optically thick to Compton scattering, so-called CT AGNs. We use the torus models of Brightman and Nandra that predict the X-ray spectrum from reprocessing in a torus and include the torus opening angle as a free parameter and aim to determine the covering factor of the CT gas in these sources individually. Across the sample we find mild to heavy CT columns, with N{sub H} measured from 10{sup 24} to 10{sup 26} cm{sup −2}, and a wide range of covering factors, where individual measurements range from 0.2 to 0.9. We find that the covering factor, f{sub c}, is a strongly decreasing function of the intrinsic 2–10 keV luminosity, L{sub X}, where f{sub c} = (−0.41 ± 0.13)log{sub 10}(L{sub X}/erg s{sup −1})+18.31 ± 5.33, across more than two orders of magnitude in L{sub X} (10{sup 41.5}–10{sup 44} erg s{sup −1}). The covering factors measured here agree well with the obscured fraction as a function of L{sub X} as determined by studies of local AGNs with L{sub X} > 10{sup 42.5} erg s{sup −1}.

  11. The Nature of Active Galactic Nuclei with Velocity Offset Emission Lines

    Science.gov (United States)

    Müller-Sánchez, F.; Comerford, J.; Stern, D.; Harrison, F. A.

    2016-10-01

    We obtained Keck/OSIRIS near-IR adaptive optics-assisted integral-field spectroscopy to probe the morphology and kinematics of the ionized gas in four velocity-offset active galactic nuclei (AGNs) from the Sloan Digital Sky Survey. These objects possess optical emission lines that are offset in velocity from systemic as measured from stellar absorption features. At a resolution of ˜0.″18, OSIRIS allows us to distinguish which velocity offset emission lines are produced by the motion of an AGN in a dual supermassive black hole system, and which are produced by outflows or other kinematic structures. In three galaxies, J1018+2941, J1055+1520, and J1346+5228, the spectral offset of the emission lines is caused by AGN-driven outflows. In the remaining galaxy, J1117+6140, a counterrotating nuclear disk is observed that contains the peak of Paα emission 0.″2 from the center of the galaxy. The most plausible explanation for the origin of this spatially and kinematically offset peak is that it is a region of enhanced Paα emission located at the intersection zone between the nuclear disk and the bar of the galaxy. In all four objects, the peak of ionized gas emission is not spatially coincident with the center of the galaxy as traced by the peak of the near-IR continuum emission. The peaks of ionized gas emission are spatially offset from the galaxy centers by 0.″1-0.″4 (0.1-0.7 kpc). We find that the velocity offset originates at the location of this peak of emission, and the value of the offset can be directly measured in the velocity maps. The emission-line ratios of these four velocity-offset AGNs can be reproduced only with a mixture of shocks and AGN photoionization. Shocks provide a natural explanation for the origin of the spatially and spectrally offset peaks of ionized gas emission in these galaxies. Based on observations at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the

  12. A new method to measure the virial factors in the reverberation mapping of active galactic nuclei

    Science.gov (United States)

    Liu, H. T.; Feng, H. C.; Bai, J. M.

    2017-04-01

    Based on the gravitational red shift, which is a prediction of Einstein's general relativity theory, of broad optical emission lines in active galactic nuclei (AGNs), a new method is proposed to estimate the virial factors f in measuring black hole masses MRM by the reverberation mapping of AGNs. The factors f can be measured based on two physical quantities, i.e. the gravitational red shifts zg and the full widths at half maxima vFWHM of broad lines. In the past, it has been difficult to determine the factors f for individual AGNs. We apply this new method to several reverberation-mapped type 1 Seyfert galaxies. There is a correlation between f and the radius of the broad-line region (BLR) rBLR, f=5.4 r_{BLR}^{0.3}, for the gravitationally red-shifted broad lines He II, He I, Hβ and Hα in the narrow-line type 1 Seyfert galaxy (NLS1) Mrk 110. This correlation results from the influence of the radiation pressure of the accretion disc on the BLR clouds. This influence seems to be more important than usually thought so in AGNs. Mrk 110 has f ≈ 8-16, distinctly larger than the mean ≈ 1 usually used to estimate MRM for vFWHM. NGC 4593 and NLS1 Mrk 486 have f ≈ 3 and f ≈ 9, respectively. Higher f values of several tens are derived for three other NLS1s. There is a correlation between f and accretion rate dot{M}_{f=1}, f=6.8dot{M}^{0.4}_{f=1} for five objects, where dot{M}_{f=1}=dot{M}_{bullet }/L_{Edd}c^{-2} as f = 1 is assumed when estimating MRM used in the Eddington luminosity LEdd, dot{M}_{bullet } is the mass accretion rate, and c is the speed of light. These larger f values will produce higher MRM values and lower Eddington ratios.

  13. Oscillatory activity in the medial prefrontal cortex and nucleus accumbens correlates with impulsivity and reward outcome.

    Directory of Open Access Journals (Sweden)

    Nicholas A Donnelly

    Full Text Available Actions expressed prematurely without regard for their consequences are considered impulsive. Such behaviour is governed by a network of brain regions including the prefrontal cortex (PFC and nucleus accumbens (NAcb and is prevalent in disorders including attention deficit hyperactivity disorder (ADHD and drug addiction. However, little is known of the relationship between neural activity in these regions and specific forms of impulsive behaviour. In the present study we investigated local field potential (LFP oscillations in distinct sub-regions of the PFC and NAcb on a 5-choice serial reaction time task (5-CSRTT, which measures sustained, spatially-divided visual attention and action restraint. The main findings show that power in gamma frequency (50-60 Hz LFP oscillations transiently increases in the PFC and NAcb during both the anticipation of a cue signalling the spatial location of a nose-poke response and again following correct responses. Gamma oscillations were coupled to low-frequency delta oscillations in both regions; this coupling strengthened specifically when an error response was made. Theta (7-9 Hz LFP power in the PFC and NAcb increased during the waiting period and was also related to response outcome. Additionally, both gamma and theta power were significantly affected by upcoming premature responses as rats waited for the visual cue to respond. In a subgroup of rats showing persistently high levels of impulsivity we found that impulsivity was associated with increased error signals following a nose-poke response, as well as reduced signals of previous trial outcome during the waiting period. Collectively, these in-vivo neurophysiological findings further implicate the PFC and NAcb in anticipatory impulsive responses and provide evidence that abnormalities in the encoding of rewarding outcomes may underlie trait-like impulsive behaviour.

  14. Synchronization of PER1 protein in Parabrachial nucleus in a natural model of food anticipatory activity

    Science.gov (United States)

    Juárez, Claudia; Morgado, Elvira; Waliszewski, Stefan M.; Martínez, Armando J.; Meza, Enrique; Caba, Mario

    2012-01-01

    Rabbit pups represent a natural model of food anticipatory activity (FAA). FAA is the behavioral output of a putative food entrainable oscillator (FEO). It had been suggested that the FEO is comprised of a distributed system of clocks that work in concert in response to gastrointestinal input by food. Scheduled food intake synchronizes several nuclei in the brain, and the hypothalamus has received particular attention. On the contrary, brainstem nuclei, despite being among the brain structures to first receive food cues, have been scarcely studied. Here we analyzed by immunohistochemistry possible oscillation of FOS and PER1 proteins through a complete 24 h cycle in the dorsal vagal complex (DVC) and parabrachial nucleus (PBN) of seven to eight day old rabbit pups scheduled to nurse during the night (02:00) or day (10:00) and also in fasted subjects to explore the possible persistence of oscillations. We found a clear induction of FOS that peaks 1.5 h after nursing in all nuclei studied. PER1 was only synchronized in the PBN, reaching highest values 12 h after nursing. Only PER1 oscillations persisted in fasted subjects. We conclude that the DVC nuclei are probably more related to the transmission of food cues to other brain regions but that the PBN participates in the integration of information essential for FAA. Our results support previous findings suggesting that the DVC nuclei, but not PBN, are not essential for FAA. We suggest that PBN is a key component of the proposed distributed system of clocks involved in FAA. PMID:22471601

  15. Synchronization of PER1 protein in parabrachial nucleus in a natural model of food anticipatory activity.

    Science.gov (United States)

    Juárez, Claudia; Morgado, Elvira; Waliszewski, Stefan M; Martínez, Armando J; Meza, Enrique; Caba, Mario

    2012-05-01

    Rabbit pups represent a natural model of food anticipatory activity (FAA). FAA is the behavioral output of a putative food entrainable oscillator (FEO). It had been suggested that the FEO is comprised of a distributed system of clocks that work in concert in response to gastrointestinal input by food. Scheduled food intake synchronizes several nuclei in the brain, and the hypothalamus has received particular attention. On the contrary, brainstem nuclei, despite being among the brain structures to first receive food cues, have been scarcely studied. Here we analysed by immunohistochemistry possible oscillation of FOS and PER1 proteins through a complete 24-h cycle in the dorsal vagal complex (DVC) and parabrachial nucleus (PBN) of 7-8-day-old rabbit pups scheduled to nurse during the night (02:00 h) or day (10:00 h), and also in fasted subjects to explore the possible persistence of oscillations. We found a clear induction of FOS that peaks 1.5 h after nursing in all nuclei studied. PER1 was only synchronized in the PBN, reaching highest values 12 h after nursing. Only PER1 oscillations persisted, with a shift, in fasted subjects. We conclude that the DVC nuclei are probably more related to the transmission of food cues to other brain regions, but that the PBN participates in the integration of information essential for FAA. Our results support previous findings suggesting that the DVC nuclei, but not PBN, are not essential for FAA. We suggest that PBN is a key component of the proposed distributed system of clocks involved in FAA.

  16. A search of new samples of active galactic nuclei with low-mass black holes from SDSS

    Science.gov (United States)

    Liu, H.; Yuan, W.; Zhou, H.; Dong, X.-B.

    2016-02-01

    We report on the progress of our on-going work to search for low-mass black holes (LMBHs) in active galactic nuclei. The masses of black holes are estimated using the broad line width and luminosity obtained from one-epoch optical spectra. As the first step, we fitted the spectra of 1263 objects in the quasar catalog of the SDSS DR10 and obtained accurate measurement of the emission lines. Two AGNs are found to have M BH ~ 106 M⊙. The next step is to analyze the spectra of the DR10 galaxy sample, from which a much larger sample of low-mass AGNs is expected to be obtained.

  17. The Black Hole Mass-Bulge Luminosity Relationship for Active Galactic Nuclei From Reverberation Mapping and Hubble Space Telescope Imaging

    DEFF Research Database (Denmark)

    Bentz, Misty C.; Peterson, Bradley M.; Pogge, Richard W.

    2009-01-01

    We investigate the relationship between black hole mass and bulge luminosity for active galactic nuclei (AGNs) with reverberation-based black hole mass measurements and bulge luminosities from two-dimensional decompositions of Hubble Space Telescope host galaxy images. We find that the slope...... of the relationship for AGNs is 0.76-0.85 with an uncertainty of ~0.1, somewhat shallower than the M BH vprop L 1.0±0.1 relationship that has been fit to nearby quiescent galaxies with dynamical black hole mass measurements. This difference is somewhat perplexing, as the AGN black hole masses include an overall...

  18. Neuropeptide Y activates urocortin 1 neurons in the nonpreganglionic Edinger-Westphal nucleus

    NARCIS (Netherlands)

    Gaszner, B.; Korosi, A.; Palkovits, M.; Roubos, E.W.; Kozicz, L.T.

    2007-01-01

    Central regulatory pathways promoting stress adaptation utilize various neurotransmitters/neuropeptides, such as urocortin 1 (Ucn1) and neuropeptide Y (NPY). Ucn1 is abundantly expressed in the nonpreganglionic Edinger-Westphal nucleus (npEW), where it is codistributed with NPY-immunoreactive (ir) t

  19. Effects of vagus nerve stimulation on parafascicular nucleus neuronal activities in rats

    Institute of Scientific and Technical Information of China (English)

    Yizhe Meng; Jinju Jiao

    2008-01-01

    BACKGROUND: Vagal nerve fibers have many projections to the central nervous system. The anti-epileptic effects of vagus nerve stimulation (VNS) are associated with the thalamus, insular cortex, and other brain regions.OBJECTIVE: To validate the inhibitory effects of vagus nerve stimulation on firing activities of parafascicular nucleus (Pf) neurons in rats. DESIGN, TIME, AND SETTING: The experiment was performed in the Electrophysiological Laboratory of Department of Neurobiology, Liaoning Medical University between September 2006 and September 2007 with multiple-factor self-controlled design.MATERIALS: Twenty-two healthy adult male Sprague Dawley rats were obtained for this experiment. Main instruments: A320R constant electrical stimulation was made by United States World Precision Instruments, Spike2 Biological Signal Processing Systems was provided by British CED Company.METHODS: Under general anesthesia, the left cervical vagus nerve of rats was separated by approximately 1.0 cm. A stimulation electrode was deployed on the vagus nerve, with various settings for VNS parameters.MAIN OUTCOME MEASURES: ① Firing rates of Pf before and after various VNS parameters were measured according to effect (R) ≥ 20%: excited effect, R ≤ -20%: inhibited effect, -20% < R < 20%: no effect. ② Firing rates of excited Pf neurons after various VNS parameters were measured.RESULTS: ① One rat died prior to recording, another was recorded in the wrong brain location, but the remaining 20 rats were included in the final analysis. ② A total of 221 Pf neurons in healthy rats were recorded. The spontaneous firing rats were (6.70 ± 0.56) Hz and varied between 0.34-52.5 Hz. The spontaneous firing rates were significantly increased in 146 neurons (66.1%), increasing from (5.36 ± 0.59) Hz to (8.22 ± 0.81) Hz (P < 0.01). A total of 40 (18.1%) neurons did not respond, and 35 (15.8%) neurons were inhibited. ③ The excitation rates of Pf neurons did not increase with increasing

  20. A model of calcium-mediated coupling between membrane activity and clock gene expression in neurons of the suprachiasmatic nucleus

    CERN Document Server

    Casado, J M

    2015-01-01

    Rhythms in electrical activity in the membrane of cells in the suprachiasmatic nucleus (SCN) are crucial for the function of the circadian timing system, which is characterized by the expression of the so-called clock genes. Intracellular Ca$^{2+}$ ions seem to connect, at least in part, the electrical activity of SCN neurons with the expression of clock genes. In this paper, we introduce a simple mathematical model describing the linking of membrane activity to the transcription of one gene by means of a feedback mechanism based on the dynamics of intracellular calcium ions.

  1. Cosmological Studies with Galaxy Clusters, Active Galactic Nuclei, and Strongly Lensed Quasars

    Science.gov (United States)

    Rumbaugh, Nicholas Andrew

    The large-scale structure (LSS) of the universe provides scientists with one of the best laboratories for studying Lambda Cold Dark Matter (LambdaCDM) cosmology. Especially at high redshift, we see increased rates of galaxy cluster and galaxy merging in LSS relative to the field, which is useful for studying the hierarchical merging predicted by LambdaCDM. The largest identified bound structures, superclusters, have not yet virialized. Despite the wide range of dynamical states of their constituent galaxies, groups, and clusters, they are all still actively evolving, providing an ideal laboratory in which to study cluster and galaxy evolution. In this dissertation, I present original research on several aspects of LSS and LambdaCDM cosmology. Three separate studies are included, each one focusing on a different aspect. In the first study, we use X-ray and optical observations from nine galaxy clusters at high redshift, some embedded in larger structures and some isolated, to study their evolutionary states. We extract X-ray gas temperatures and luminosities as well as optical velocity dispersions. These cluster properties are compared using low-redshift scaling relations. In addition, we employ several tests of substructure, using velocity histograms, Dressler-Shectman tests, and centroiding offsets. We conclude that two clusters out of our sample are most likely unrelaxed, and find support for deviations from self-similarity in the redshift evolution of the Lx-T relation. Our numerous complementary tests of the evolutionary state of clusters suggest potential under-estimations of systematic error in studies employing only a single such test. In the second study, we use multi-band imaging and spectroscopy to study active galactic nuclei (AGN) in high-redshift LSS. The AGN were identified using X-ray imaging and matched to optical catalogs that contained spectroscopic redshifts to identify members of the structures. AGN host galaxies tended to be associated with the

  2. Vertical flows and structures excited by magnetic activity in the Galactic center region

    CERN Document Server

    Kakiuchi, Kensuke; Fukui, Yasuo; Torii, Kazufumi; Machida, Mami; Matsumoto, Ryoji

    2016-01-01

    The vertical flow structure in the galactic center region remains poorly understood. We analyzed the MHD simulation data by Suzuki et al. (2015) for better understanding. As a result, we found the fast downflows with a speed of ~100 km/s near the foot-points of magnetic loops. These downflows are flowing along a magnetic field line and accelerated by the gravity. The direction of the fast flows is changed by the magnetic loop geometry, as it moves. As a result, not only vertical motions but also azimuthal and radial motions are excited. This feature could be relevant to the observed high velocity dispersion in the position-velocity diagram.

  3. The Ultraviolet Emission Properties of Five Low-Redshift Active Galactic Nuclei at High Signal to Noise and Spectral Resolution

    CERN Document Server

    Laor, A; Jannuzi, B T; Schneider, D P; Green, R F; Hartig, G F; Laor, Ari; Bahcall, John N.; Jannuzi, Buell T.; Schneider, Donald P.; Green, IAS; Richard F.; Hartig, NOAO; George F.; ScI, ST

    1994-01-01

    We analyze the ultraviolet (UV) emission line and continuum properties of five low-redshift active galactic nuclei (four luminous quasars: PKS~0405$-$123, H1821+643, PG~0953+414, and 3C273, and one bright Seyfert 1 galaxy: Mrk~205). The HST spectra have higher signal-to-noise ratios (typically $\\sim 60$ per resolution element) and spectral resolution ($R = 1300$) than all previously- published UV spectra used to study the emission characteristics of active galactic nuclei. We include in the analysis ground-based optical spectra covering \\hb\\ and the narrow [O~III]~$\\lambda\\lambda$4959,5007 doublet. The following new results are obtained: \\lyb/\\lya=0.03$-$0.12 for the four quasars, which is the first accurate measurement of the long-predicted \\lyb\\ intensity in QSOs. The cores of \\lya\\ and C~IV are symmetric to an accuracy of better than 2.5\\% within about 2000~km~s$^{-1}$ of the line peak. This high degree of symmetry of \\lya\\ argues against models in which the broad line cloud velocity field has a significan...

  4. A New Perspective of the Radio Bright Zone at The Galactic Center: Feedback from Nuclear Activities

    CERN Document Server

    Zhao, Jun-Hui; Goss, W M

    2015-01-01

    New observations of Sgr A have been carried out with the VLA using the broadband (2 GHz) continuum mode at 5.5 GHz, covering the central 30 pc region of the RBZ at the Galactic center. Using the MS-MFS algorithms in CASA, we have imaged Sgr A with a resolution of 1", achieving an rms 8 $\\mu$Jy/beam, and a dynamic range 100,000:1.The radio image is compared with X-ray, CN emission-line and Paschen-$\\alpha$ images obtained using Chandra, SMA and HST/NICMOS, respectively. We discuss several prominent radio features. The "Sgr A West Wings" extend 5 pc from the NW and SE tips of the ionized "Mini-spiral" in Sgr A West to positions located 2.9 and 2.4 arc min to the NW and SE of Sgr A*, respectively. The NW wing, along with several other prominent features, including the "NW Streamers", form an elongated radio lobe (NW lobe), oriented nearly perpendicular to the Galactic plane. This radio lobe, with a size of 14.4 pc x 7.3 pc, has a known X-ray counterpart. A row of three thermally emitting rings is observed in the...

  5. Optical counterparts of undetermined type $\\gamma$-ray Active Galactic Nuclei with blazar-like Spectral Energy Distributions

    CERN Document Server

    La Mura, G; Ciroi, S; Rafanelli, P; Salvetti, D; Berton, M; Cracco, V

    2015-01-01

    During its first four years of scientific observations, the Fermi Large Area Telescope (Fermi-LAT) detected 3033 $\\gamma$-ray sources above a 4$\\sigma$ significance level. Although most of the extra-Galactic sources are active galactic nuclei (AGN) of the blazar class, other families of AGNs are observed too, while a still high fraction of detections ($\\sim 30\\%$) remains with uncertain association or classification. According to the currently accepted interpretation, the AGN $\\gamma$-ray emission arises from inverse Compton (IC) scattering of low energy photons by relativistic particles confined in a jet that, in the case of blazars, is oriented very close to our line of sight. Taking advantage of data from radio and X-ray wavelengths, which we expect to be produced together with $\\gamma$-rays, providing a much better source localization potential, we focused our attention on a sample of $\\gamma$-ray Blazar Candidates of Undetermined Type (BCUs), starting a campaign of optical spectroscopic observations. The...

  6. Magnetically elevated accretion discs in active galactic nuclei: broad emission-line regions and associated star formation

    Science.gov (United States)

    Begelman, Mitchell C.; Silk, Joseph

    2017-01-01

    We propose that the accretion discs fueling active galactic nuclei (AGN) are supported vertically against gravity by a strong toroidal (φ-direction) magnetic field that develops naturally as the result of an accretion disc dynamo. The magnetic pressure elevates most of the gas carrying the accretion flow at R to large heights z ≳ 0.1R and low densities, while leaving a thin dense layer containing most of the mass - but contributing very little accretion - around the equator. We show that such a disc model leads naturally to the formation of a broad emission-line region through thermal instability. Extrapolating to larger radii, we demonstrate that local gravitational instability and associated star formation are strongly suppressed compared to standard disc models for AGN, although star formation in the equatorial zone is predicted for sufficiently high mass supply rates. This new class of accretion disc models thus appears capable of resolving two longstanding puzzles in the theory of AGN fueling: the formation of broad emission-line regions and the suppression of fragmentation thought to inhibit accretion at the required rates. We show that the disc of stars that formed in the Galactic Center a few million years ago could have resulted from an episode of magnetically elevated accretion at ≳ 0.1 of the Eddington limit.

  7. SPECTRAL ENERGY DISTRIBUTIONS OF TYPE 1 ACTIVE GALACTIC NUCLEI IN THE COSMOS SURVEY. I. THE XMM-COSMOS SAMPLE

    Energy Technology Data Exchange (ETDEWEB)

    Elvis, M.; Hao, H.; Civano, F. [Harvard Smithsonian Center for astrophysics, 60 Garden St., Cambridge, MA 02138 (United States); Brusa, M.; Salvato, M.; Bongiorno, A.; Cappelluti, N. [Max-Planck-Institut fuer Extraterrestrische Physik, Postfach 1312, D-85741, Garching bei Muenchen (Germany); Capak, P. [California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Zamorani, G.; Comastri, A.; Gilli, R. [INAF-Osservatorio Astronomico di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Jahnke, K.; Lusso, E.; Cisternas, M. [Max-Planck-Institut fuer Astronomie, Koenigstuhl 17, Heidelberg, D-69117 (Germany); Mainieri, V. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching bei Muenchen (Germany); Trump, J. R. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Ho, L. C. [The Observatories of the Carnegie Institute for Science, Santa Barbara Street, Pasadena, CA 91101 (United States); Aussel, H. [AIM Unite Mixte de Recherche CEA CNRS, Universite Paris VII UMR n158, Paris (France); Frayer, D. [National Radio Astronomy Observatory, P.O. Box 2, Green Bank, WV 24944 (United States); Hasinger, G., E-mail: elvis@cfa.harvard.edu, E-mail: hhao@cfa.harvard.edu [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); and others

    2012-11-01

    The 'Cosmic Evolution Survey' (COSMOS) enables the study of the spectral energy distributions (SEDs) of active galactic nuclei (AGNs) because of the deep coverage and rich sampling of frequencies from X-ray to radio. Here we present an SED catalog of 413 X-ray (XMM-Newton)-selected type 1 (emission line FWHM > 2000 km s{sup -1}) AGNs with Magellan, SDSS, or VLT spectrum. The SEDs are corrected for Galactic extinction, broad emission line contributions, constrained variability, and host galaxy contribution. We present the mean SED and the dispersion SEDs after the above corrections in the rest-frame 1.4 GHz to 40 keV, and show examples of the variety of SEDs encountered. In the near-infrared to optical (rest frame {approx}8 {mu}m-4000 A), the photometry is complete for the whole sample and the mean SED is derived from detections only. Reddening and host galaxy contamination could account for a large fraction of the observed SED variety. The SEDs are all available online.

  8. The ultraviolet emission properties of five low-redshift active galactic nuclei at high signal-to-noise ratio and spectral resolution

    Science.gov (United States)

    Laor, Ari; Bahcall, John N.; Jannuzi, Buell T.; Schneider, Donald P.; Green, Richard F.; Hartig, George F.

    1994-01-01

    We analyze the ultraviolet (UV) emission line and continuum properties of five low-redshift active galactic nuclei (four luminous quasars: PKS 0405-123, H1821 + 643, PG 0953 + 414, and 3C 273, and one bright Seyfert 1 galaxy: Mrk 205). The HST spectra have higher signal-to-noise ratios (typically approximately 60 per resolution element) and spectral resolution (R = 1300) than all previously published UV spectra used to study the emission characteristics of active galactic nuclei. We include in the analysis ground-based optical spectra covering H beta and the narrow (O III) lambda lambda 4959, 5007 doublet. New results are obtained and presented.

  9. Stochastic Noncircular Motion and Outflows Driven by Magnetic Activity in the Galactic Bulge Region

    CERN Document Server

    Suzuki, Takeru K; Torii, Kazufumi; Machida, Mami; Matsumoto, Ryoji

    2015-01-01

    By performing a global magneto-hydrodynamical simulation for the Milky Way with an axisymmetric gravitational potential, we propose that spatially dependent amplification of magnetic fields possibly explains the observed noncircular motion of the gas in the Galactic center region. The radial distribution of the rotation frequency in the bulge region is not monotonic in general. The amplification of the magnetic field is enhanced in regions with stronger differential rotation, because magnetorotational instability and field-line stretching are more effective. The strength of the amplified magnetic field reaches >~ 0.5 mG, and radial flows of the gas are excited by the inhomogeneous transport of angular momentum through turbulent magnetic field that is amplified in a spatially dependent manner. In addition, the magnetic pressure-gradient force also drives radial flows in a similar manner. As a result, the simulated position-velocity diagram exhibits a time-dependent asymmetric parallelogram-shape owing to the i...

  10. Investigating Magnetic Activity in the Galactic Centre by Global MHD Simulation

    CERN Document Server

    Suzuki, Takeru K; Torii, Kazufumi; Machida, Mami; Matsumoto, Ryoji; Kakiuchi, Kensuke

    2016-01-01

    By performing a global magnetohydrodynamical (MHD) simulation for the Milky Way with an axisymmetric gravitational potential, we propose that spatially dependent amplification of magnetic fields possibly explains the observed noncircular motion of the gas in the Galactic centre (GC) region. The radial distribution of the rotation frequency in the bulge region is not monotonic in general. The amplification of the magnetic field is enhanced in regions with stronger differential rotation, because magnetorotational instability and field-line stretching are more effective. The strength of the amplified magnetic field reaches >~ 0.5 mG, and radial flows of the gas are excited by the inhomogeneous transport of angular momentum through turbulent magnetic field that is amplified in a spatially dependent manner. As a result, the simulated position-velocity diagram exhibits a time-dependent asymmetric parallelogram-shape owing to the intermittency of the magnetic turbulence; the present model provides a viable alternati...

  11. NPY mediates reward activity of morphine, via NPY Y1 receptors, in the nucleus accumbens shell.

    Science.gov (United States)

    Desai, Sagar J; Upadhya, Manoj A; Subhedar, Nishikant K; Kokare, Dadasaheb M

    2013-06-15

    Although the interaction between endogenous neuropeptide Y (NPY) and opioidergic systems in processing of reward has been speculated, experimental evidence is lacking. We investigated the role of NPY, and its Y1 receptors, in the nucleus accumbens shell (AcbSh) in morphine induced reward and reinforcement behavior. Rats were implanted with cannulae targeted at AcbSh for drug administration, and with stimulating electrode in the medial forebrain bundle (MFB). The rats were then conditioned in an operant conditioning chamber for electrical self-stimulation of the MFB. Increased rate of lever pressings was evaluated against the frequency of the stimulating current. Increase in rate of lever presses was considered as a measure of reward and reinforcement. About 30-70% increase in self-stimulation was observed following bilateral intra-AcbSh treatment with morphine, NPY or [Leu(31), Pro(34)]-NPY (NPY Y1/Y5 receptors agonist), however, BIBP3226 (selective NPY Y1 receptors antagonist) produced opposite effect. The reward effect of morphine was significantly potentiated by NPY or [Leu(31), Pro(34)]-NPY, but antagonized by BIBP3226. NPY-immunoreactivity in the AcbSh, arcuate nucleus (ARC) and lateral part of bed nucleus of stria terminalis (BNSTl) was significantly more in the operant conditioned rats than in naïve control. However, morphine administration to the conditioned rats resulted in significant decrease in the NPY-immunoreactivity in all these anatomical regions. Since the role of morphine in modulation of mesolimbic-dopaminergic pathway is well established, we suggest that NPY system in AcbSh, ARC and BNSTl, perhaps acting via Y1-receptor system, may be an important component of the mesolimbic-AcbSh reward circuitry triggered by endogenous opioids.

  12. Study of the unbound proton-rich nucleus $^{21}$Al with resonance elastic and inelastic scattering using an active target

    CERN Multimedia

    We intend to measure the structure of the unbound nucleus $^{21}$Al via resonance elastic and inelastic scattering with an active target. There are many goals: \\\\ a) to locate the 1/2$^{+}$ level in $^{21}$Al that brings information on the Thomas-Ehrman shift, \\\\ b) to measure the energy spectrum of $^{21}$Al which is a N=8 isotone with the resonance elastic scattering reaction, \\\\ c) to investigate via inelastic scattering the strength of core excitations in the existence of narrow unbound resonances beyond the proton drip-line.

  13. Observation of Weak Low-ionization Winds in Host Galaxies of Low Luminosity Active Galactic Nuclei at z ~1

    Science.gov (United States)

    Yesuf, Hassen; David C. Koo, S. M. Faber, J. Xavier Prochaska, Yicheng Guo, F. S. Liu, Emily C. Cunningham, Alison L. Coil, Puragra Guhathakurta

    2017-01-01

    A key physical manifestation of active galactic nuclei (AGN) feedback is predicted to be powerful galactic winds. However, the relative roles between AGN activity and star formation in driving such winds remain largely unexplored at high redshifts, near the peak of cosmic activity for both. We study winds in 12 X-ray AGN host galaxies at z ~ 1 in the CANDELS fields using deep Keck rest-frame UV spectroscopy. We find, using the low-ionization Fe II 2586 absorption in the stacked spectra, that the AGN show a median centroid velocity shift of -137 km/s and a median velocity dispersion of 103 km/ s. The centroid velocity and the velocity dispersions are obtained from a two component (ISM+wind) absorption line model. For comparison, a star-forming and X-ray undetected galaxies at a similar redshift, matched roughly in stellar mass and galaxy inclination, show the outflows to have a median centroid velocity of -135 km/s and a median velocity dispersion of 140 km/s. Thus, winds in the AGN are similar in velocities to those found in star-formation-driven winds, and are weak to escape and expel substantial cool gas from galaxies. A joint reanalysis of the z ~ 0.5 AGN sample and our sample yields a centroid velocity of -139 (+48, -87) km/s and a velocity dispersion of 82 (+47,-37) km/s. For the combined sample, about half the total equivalent width of the Fe II 2586 absorption is due to the wind. We do not observe winds with bulk velocities greater than 500 km/s predicted by some AGN feedback models.

  14. Feeding and feedback in the active nucleus of Mrk 1157 probed with Gemini NIFS

    CERN Document Server

    Riffel, Rogemar A

    2011-01-01

    We have mapped the stellar and gaseous kinematics, as well as the emission-line flux distributions and ratios, from the inner 450pc radius of Mrk1157, using 2D near-IR spectra obtained with the Gemini NIFS at a spatial resolution of 35pc. The stellar velocity field shows a rotation pattern, with a discrete S-shaped zero velocity curve. The presence of a bar is also supported by the residual map between the observed rotation field and a model of circular orbits in a Plummer potential. The stellar velocity dispersion map presents a partial ring of low-sigma values (50-60km/s) at 250pc from the nucleus surrounded by higher sigma values from the galaxy bulge, originated in kinematically colder regions with recent star formation. The velocity dispersion of the bulge (100km/s) implies in a black hole mass of 8.3x10^6M_Sun. Emission-line flux distributions are most extended along PA=27/153deg, reaching at least 450pc from the nucleus and following the orientation observed in previous optical emission-line [OIII] ima...

  15. Cystatin D locates in the nucleus at sites of active transcription and modulates gene and protein expression.

    Science.gov (United States)

    Ferrer-Mayorga, Gemma; Alvarez-Díaz, Silvia; Valle, Noelia; De Las Rivas, Javier; Mendes, Marta; Barderas, Rodrigo; Canals, Francesc; Tapia, Olga; Casal, J Ignacio; Lafarga, Miguel; Muñoz, Alberto

    2015-10-30

    Cystatin D is an inhibitor of lysosomal and secreted cysteine proteases. Strikingly, cystatin D has been found to inhibit proliferation, migration, and invasion of colon carcinoma cells indicating tumor suppressor activity that is unrelated to protease inhibition. Here, we demonstrate that a proportion of cystatin D locates within the cell nucleus at specific transcriptionally active chromatin sites. Consistently, transcriptomic analysis show that cystatin D alters gene expression, including that of genes encoding transcription factors such as RUNX1, RUNX2, and MEF2C in HCT116 cells. In concordance with transcriptomic data, quantitative proteomic analysis identified 292 proteins differentially expressed in cystatin D-expressing cells involved in cell adhesion, cytoskeleton, and RNA synthesis and processing. Furthermore, using cytokine arrays we found that cystatin D reduces the secretion of several protumor cytokines such as fibroblast growth factor-4, CX3CL1/fractalkine, neurotrophin 4 oncostatin-M, pulmonary and activation-regulated chemokine/CCL18, and transforming growth factor B3. These results support an unanticipated role of cystatin D in the cell nucleus, controlling the transcription of specific genes involved in crucial cellular functions, which may mediate its protective action in colon cancer.

  16. Search for gamma-ray-emitting active galactic nuclei in the Fermi-LAT unassociated sample using machine learning

    Energy Technology Data Exchange (ETDEWEB)

    Doert, M. [Fakultät Physik, Technische Universität Dortmund, D-44221 Dortmund (Germany); Errando, M., E-mail: marlene.doert@tu-dortmund.de, E-mail: errando@astro.columbia.edu [Department of Physics and Astronomy, Barnard College, Columbia University, NY 10027 (United States)

    2014-02-10

    The second Fermi-LAT source catalog (2FGL) is the deepest all-sky survey available in the gamma-ray band. It contains 1873 sources, of which 576 remain unassociated. Machine-learning algorithms can be trained on the gamma-ray properties of known active galactic nuclei (AGNs) to find objects with AGN-like properties in the unassociated sample. This analysis finds 231 high-confidence AGN candidates, with increased robustness provided by intersecting two complementary algorithms. A method to estimate the performance of the classification algorithm is also presented, that takes into account the differences between associated and unassociated gamma-ray sources. Follow-up observations targeting AGN candidates, or studies of multiwavelength archival data, will reduce the number of unassociated gamma-ray sources and contribute to a more complete characterization of the population of gamma-ray emitting AGNs.

  17. Understanding Active Galactic Nuclei using near-infrared high angular resolution polarimetry I : MontAGN - STOKES comparison

    Science.gov (United States)

    Grosset, L.; Marin, F.; Gratadour, D.; Goosmann, R.; Rouan, D.; Clénet, Y.; Pelat, D.; Rojas Lobos, P. A.

    2016-12-01

    In this first research note of a series of two, we present a comparison between two Monte Carlo radiative transfer codes: MontAGN and STOKES. Both were developed in order to better understand the observed polarisation of Active Galactic Nuclei (AGN). Our final aim is to use these radiative transfer codes to simulate the polarisation maps of a prototypical type-2 radio-quiet AGN on a wide range of wavelengths, from the infrared band with MontAGN to the X-ray energies with STOKES. Doing so, we aim to analyse in depth the recent SPHERE/IRDIS polarimetric observations conducted on NGC 1068. In order to validate the codes and obtain preliminary results, we set for both codes a common and simple AGN model, and compared their polaro-imaging results.

  18. Tracing the evolution of Active Galactic Nuclei host galaxies over the last 9 Gyrs of Cosmic time

    CERN Document Server

    Goulding, Andy D; Hickox, Ryan C; Jones, Christine; Murray, Stephen S; Paggi, Alessandro; Ashby, Matthew L N; Coil, Alison L; Cooper, Michael C; Huang, Jiasheng; Kraft, Ralph; Newman, Jeffrey A; Weiner, Benjamin J; Willner, Steven P

    2013-01-01

    We present the results of a combined galaxy population analysis for the host galaxies of active galactic nuclei (AGN) identified at 0 < z < 1.4 within the SDSS, Bootes and DEEP2 surveys. We identified AGN in a uniform and unbiased manner at X-ray, infrared and radio wavelengths. Supermassive black holes undergoing radiatively-efficient accretion (detected as X-ray and/or infrared AGN) appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion (radio AGN). Consistent with some previous studies, radiatively efficient AGN appear to be preferentially hosted in modest star-forming galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically-dominated accretion are almost exclusively observed in massive, passive galaxies. Crucially, we now provide strong evidence that the observed host-galaxy trends are independent of redshift. In particular, these different accretion-mode AGN have remai...

  19. The jet-disc connection: evidence for a reinterpretation in radio loud and radio quiet active galactic nuclei

    CERN Document Server

    Garofalo, David

    2013-01-01

    To constrain models of the jet-disc connection, we explore Eddington ratios reported in Foschini (2011) and interpret them in relation to the values in Sikora et al. across the active galactic nuclei population from radio loud quasars, their flat spectrum radio quasar subclass, the recently discovered gamma-ray loud narrow-line type 1 Seyfert galaxies, Fanaroff-Riley type I (FRI) radio galaxies and radio quiet quasars of the Palomar Green survey. While appeal to disc truncation in radiatively inefficient flow appears to explain the observed inverse relation between radio loudness and Eddington ratio in radio loud and radio quiet quasars, FR I objects, scale invariance and recent data on powerful jets in narrow-line Seyfert 1 galaxies offer compelling arguments in favour of a reinterpretaion of the jet-disc connection.

  20. Line-driven Disk Winds in Active Galactic Nuclei: The Critical Importance of Ionization and Radiative Transfer

    CERN Document Server

    Higginbottom, Nick; Knigge, Christian; Long, Knox S; Matthews, James H; Sim, Stuart A

    2014-01-01

    Accretion disk winds are thought to produce many of the characteristic features seen in the spectra of active galactic nuclei (AGN) and quasi-stellar objects (QSOs). These outflows also represent a natural form of feedback between the central supermassive black hole and its host galaxy. The mechanism for driving this mass loss remains unknown, although radiation pressure mediated by spectral lines is a leading candidate. Here, we calculate the ionization state of, and emergent spectra for, the hydrodynamic simulation of a line-driven disk wind previously presented by Proga & Kallman (2004). To achieve this, we carry out a comprehensive Monte Carlo simulation of the radiative transfer through, and energy exchange within, the predicted outflow. We find that the wind is much more ionized than originally estimated. This is because it is much more difficult to shield any wind regions effectively when the outflow itself is allowed to reprocess and redirect ionizing photons. As a result, the wind no longer produ...

  1. The Intrinsic Eddington Ratio Distribution of Active Galactic Nuclei in Star-forming Galaxies from the Sloan Digital Sky Survey

    CERN Document Server

    Jones, M L; Black, C S; Hainline, K N; DiPompeo, M A; Goulding, A D

    2016-01-01

    An important question in extragalactic astronomy concerns the distribution of black hole accretion rates of active galactic nuclei (AGN). Based on observations at X-ray wavelengths, the observed Eddington ratio distribution appears as a power law, while optical studies have often yielded a lognormal distribution. There is increasing evidence that these observed discrepancies may be due to contamination by star formation and other selection effects. Using a sample of galaxies from the Sloan Digital Sky Survey Data Release 7, we test if an intrinsic Eddington ratio distribution that takes the form of a Schechter function is consistent with previous work that suggests that young galaxies in optical surveys have an observed lognormal Eddington ratio distribution. We simulate the optical emission line properties of a population of galaxies and AGN using a broad instantaneous luminosity distribution described by a Schechter function near the Eddington limit. This simulated AGN population is then compared to observe...

  2. Clustering, Cosmology and a New Era of Black Hole Demographics -- I. The Conditional Luminosity Function of Active Galactic Nuclei

    CERN Document Server

    Ballantyne, D R

    2016-01-01

    Deep X-ray surveys have provided a comprehensive and largely unbiased view of active galactic nuclei (AGN) evolution stretching back to $z \\sim 5$. However, it has been challenging to use the survey results to connect this evolution to the cosmological environment that AGNs inhabit. Exploring this connection will be crucial to understanding the triggering mechanisms of AGNs and how these processes manifest in observations at all wavelengths. In anticipation of upcoming wide-field X-ray surveys that will allow quantitative analysis of AGN environments, this paper presents a method to observationally constrain the Conditional Luminosity Function (CLF) of AGNs at a specific $z$. Once measured, the CLF allows the calculation of the AGN bias, mean dark matter halo mass, AGN lifetime, halo occupation number, and AGN correlation function -- all as a function of luminosity. The CLF can be constrained using a measurement of the X-ray luminosity function and the correlation length at different luminosities. The method ...

  3. Iron Kα Emission Lines in Seyfert(-Like) Active Galactic Nuclei: Revelation of a Rapidly Spinning Central Black Hole

    Institute of Scientific and Technical Information of China (English)

    马振国

    2002-01-01

    Fe Kα lines are superimposed upon the x-ray continuum in most Seyfert(-like) active galactic nuclei (AGNs).By a data-fitting study, previous authors have claimed that the central black hole (BH) is either rotating ornon-rotating according to the thin disc model. We develop the disc model to the torus model to determine thereal spin of the BH. With formulations of the motion of both torus particles and photons near a BH in Kerrmetric, we simulate iron emission linesfrom a thin luminous torus. It is found that only spinning BH galaxiescan radiate observable profiles. The data-fitting to Fe lines of four AGNs observed by ASCA predicts that thecentral BH is spinning rapidly with the dimensionless specific angular momentum approaching the maximalvalueof 1.

  4. Understanding active galactic nuclei using near-infrared high angular resolution polarimetry I : MontAGN - stokes comparison

    CERN Document Server

    Grosset, Lucas; Gratadour, Damien; Goosmann, René; Rouan, Daniel; Clénet, Yann; Pelat, Didier; Lobos, Patricia Andrea Rojas

    2016-01-01

    In this first research note of a series of two, we present a comparison between two Monte Carlo radiative transfer codes: MontAGN and STOKES. Both were developed in order to better understand the observed polarisation of Active Galactic Nuclei (AGN). Our final aim is to use these radiative transfer codes to simulate the polarisation maps of a prototypical type-2 radio-quiet AGN on a wide range of wavelengths, from the infrared band with MontAGN to the X-ray energies with STOKES. Doing so, we aim to analyse in depth the recent SPHERE/IRDIS polarimetric observations conducted on NGC 1068. In order to validate the codes and obtain preliminary results, we set for both codes a common and simple AGN model, and compared their polaro-imaging results.

  5. Virilization of the Broad Line Region in Active Galactic Nuclei - connection between shifts and widths of broad emission lines

    CERN Document Server

    Jonic, Sanja; Ilic, Dragana; Popovic, Luka C

    2016-01-01

    We investigate the virilization of the emission lines Hbeta and Mg II in the sample of 287 Type 1 Active Galactic Nuclei taken from the Sloan Digital Sky Survey database. We explore the connections between the intrinsic line shifts and full widths at different levels of maximal intensity. We found that: (i) Hbeta seems to be a good virial estimator of black hole masses, and an intrinsic redshift of Hbeta is dominantly caused by the gravitational effect, (ii) there is an anti-correlation between the redshift and width of the wings of the Mg II line, (iii) the broad Mg II line can be used as virial estimator only at 50% of the maximal intensity, while the widths and intrinsic shifts of the line wings can not be used for this purpose.

  6. CRF1 receptor activation increases the response of neurons in the basolateral nucleus of the amygdala to afferent stimulation

    Directory of Open Access Journals (Sweden)

    2008-07-01

    Full Text Available The basolateral nucleus (BLA of the amygdala contributes to the consolidation of memories for emotional or stressful events. The nucleus contains a high density of CRF1 receptors that are activated by corticotropin-releasing factor (CRF. Modulation of the excitability of neurons in the BLA by CRF may regulate the immediate response to stressful events and the formation of associated memories. In the present study, CRF was found to increase the amplitude of field potentials recorded in the BLA following excitatory afferent stimulation, in vitro. The increase was mediated by CRF1 receptors, since it could be blocked by the selective, non-peptide antagonists, NBI30775 and NBI35583, but not by the CRF2-selective antagonist, astressin 2B. Furthermore, the CRF2-selective agonist, urocortin II had no effect on field potential amplitude. The increase induced by CRF was long-lasting, could not be reversed by subsequent administration of NBI35583, and required the activation of protein kinase C. This effect of CRF in the BLA may be important for increasing the salience of aversive stimuli under stressful conditions, and for enhancing the consolidation of associated memories. The results provide further justification for studying the efficacy of selective antagonists of the CRF1 receptor to reduce memory formation linked to emotional or traumatic events, and suggest that these compounds might be useful as prophylactic treatment for stress-related illness such as post-traumatic stress disorder.

  7. Excitatory effect of histamine on neuronal activity of rat cerebellar fastigial nucleus in vitro

    Institute of Scientific and Technical Information of China (English)

    TANG Biao; ZHANG Jun; LI HongZhao; ZHU JingNing; WANG JianJun

    2007-01-01

    The cerebellar fastigial nucleus (FN) holds an important role in motor control and body balance. Previous studies have revealed that the nucleus is innervated by direct hypothalamocerebellar histaminergic fibers. However, the functional role of histaminergic projection in cerebellar FN has never been established. In this study, we investigated the effect of histamine on neuronal firing of cerebellar FN by using slice preparations. Sixty-five FN cells were recorded from 47 cerebellar slices, and a vast majority of the cells responded to histamine stimulation with an excitatory response (58/65, 89.2%). Perfusing slices with low-Ca2+/high-Mg2+ medium did not block the histamine-induced excitation (n=10), supporting a direct postsynaptic action of histamine on the cells. Furthermore, the excitatory effect of histamine on FN neurons was not blocked by selective histamine H1 receptor antagonist triprolidine (n=15) or chlorpheniramine (n=10), but was effectively suppressed by ranitidine (n=15), a highly selective histamine H2 receptor antagonist. On the other hand, highly selective histamine H2 receptor agonist dimaprit (n=20) instead of histamine H1 receptor agonist 2-pyridylethylamine (n=16) mimicked the excitatory effect of histamine on FN neurons. The dimaprit-induced FN neuronal excitation was effectively antagonized by selective histamine H2 receptor antagonist ranitidine (n=13) but not influenced by selective histamine H1 receptor antagonist triprolidine (n=15). These results demonstrate that histamine excites cerebellar FN cells via the histamine H2 receptor mechanism and suggest that the hypothalamocerebellar histaminergic fibers may modulate cerebellar FN-mediated sensorimotor integration through their excitatory innervations on FN neurons.

  8. Investigating Magnetic Activity in the Galactic Centre by Global MHD Simulation

    Science.gov (United States)

    Suzuki, Takeru K.; Fukui, Yasuo; Torii, Kazufumi; Machida, Mami; Matsumoto, Ryoji; Kakiuchi, Kensuke

    2017-01-01

    By performing a global magnetohydrodynamical (MHD) simulation for the Milky Way with an axisymmetric gravitational potential, we propose that spatially dependent amplification of magnetic fields possibly explains the observed noncircular motion of the gas in the Galactic centre (GC) region. The radial distribution of the rotation frequency in the bulge region is not monotonic in general. The amplification of the magnetic field is enhanced in regions with stronger differential rotation, because magnetorotational instability and field-line stretching are more effective. The strength of the amplified magnetic field reaches >~ 0.5 mG, and radial flows of the gas are excited by the inhomogeneous transport of angular momentum through turbulent magnetic field that is amplified in a spatially dependent manner. As a result, the simulated position-velocity diagram exhibits a time-dependent asymmetric parallelogram-shape owing to the intermittency of the magnetic turbulence; the present model provides a viable alternative to the bar-potential-driven model for the parallelogram shape of the central molecular zone. In addition, Parker instability (magnetic buoyancy) creates vertical magnetic structure, which would correspond to observed molecular loops, and frequently excited vertical flows. Furthermore, the time-averaged net gas flow is directed outward, whereas the flows are highly time dependent, which would contribute to the outflow from the bulge.

  9. Star formation activity in the Galactic H II region Sh2-297

    CERN Document Server

    Mallick, K K; Samal, M R; Pandey, A K; Bhatt, B C; Ghosh, S K; Dewangan, L K; Tamura, M

    2012-01-01

    We present a multiwavelength study of the Galactic H II region Sh2-297, located in Canis Major OB1 complex. Optical spectroscopic observations are used to constrain the spectral type of ionizing star HD 53623 as B0V. The classical nature of this H II region is affirmed by the low values of electron density and emission measure, which are calculated to be 756 cm^-3 and 9.15 x 10^5 cm^-6 pc using the radio continuum observations at 610 and 1280 MHz, and VLA archival data at 1420 MHz. To understand local star formation, we identified the young stellar object (YSO) candidates in a region of area ~ 7.5' x 7.5' centered on Sh2-297 using grism slitless spectroscopy (to identify the Halpha emission line stars), and near infrared (NIR) observations. NIR YSO candidates are further classified into various evolutionary stages using color-color (CC) and color-magnitude (CM) diagrams, giving 50 red sources (H-K > 0.6) and 26 Class II-like sources. The mass and age range of the YSOs are estimated to be ~ 0.1 - 2 Msolar and ...

  10. The NuSTAR view of nearby compton-thick active galactic nuclei: the cases of NGC 424, NGC 1320, AND IC 2560

    DEFF Research Database (Denmark)

    Balokovic´, M.; Comastri, A.; Harrison, F. A.

    2014-01-01

    We present X-ray spectral analyses for three Seyfert 2 active galactic nuclei (AGNs), NGC 424, NGC 1320, and IC 2560, observed by NuSTAR in the 3-79 keV band. The high quality hard X-ray spectra allow detailed modeling of the Compton reflection component for the first time in these sources. Using...

  11. Central Masses and Broad-Line Region Sizes of Active Galactic Nuclei. II. A Homogeneous Analysis of a Large Reverberation-Mapping Database

    DEFF Research Database (Denmark)

    Peterson, B. M.; Ferrarese, L.; Gilbert, K. M.

    2004-01-01

    We present improved black hole masses for 35 active galactic nuclei (AGNs) based on a complete and consistent reanalysis of broad emission-line reverberation-mapping data. From objects with multiple line measurements, we find that the highest precision measure of the virial product is obtained by...

  12. Detection of jet precession in the active nucleus of M81

    CERN Document Server

    Marti-Vidal, I; Alberdi, A; Perez-Torres, M A; Ros, E; Guirado, J C

    2011-01-01

    (See the complete and formatted abstract in the paper). We report on VLBI monitoring of the low-luminosity AGN (LLAGN) in M81 at 1.7, 2.3, 5, and 8.4GHz. These observations are phase-referenced to the supernova SN1993J (located in the same galaxy) and cover from late 1993 to late 2005. The source consists at all frequencies of a slightly resolved core and a small jet extension towards the north-east direction (position angle of ~65 degrees) in agreement with previous publications. We find that the position of the intensity peak in the images at 8.4GHz is very stable in the galactic frame of M81 (proper motion upper limit about 0.010 mas per year). We confirm previous reports that the peaks at all frequencies are systematically shifted among them, possibly due to opacity effects in the jet as predicted by the standard relativistic jet model. We use this model to estimate the magnetic field in the jet and the mass of the central black hole. We obtain a black-hole mass of ~2.e+7 solar masses, comparable to estim...

  13. A NEW PERSPECTIVE OF THE RADIO BRIGHT ZONE AT THE GALACTIC CENTER: FEEDBACK FROM NUCLEAR ACTIVITIES

    Energy Technology Data Exchange (ETDEWEB)

    Zhao, Jun-Hui [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Morris, Mark R. [Department of Physics and Astronomy, University of California Los Angeles, Los Angeles, CA 90095 (United States); Goss, W. M., E-mail: jzhao@cfa.harvard.edu [NRAO, P.O. Box O, Socorro, NM 87801 (United States)

    2016-02-01

    New observations of Sgr A have been carried out with the Jansky VLA in the B and C arrays using the broadband (2 GHz) continuum mode at 5.5 GHz. The field of view covers the central 13′ (30 pc) region of the radio-bright zone at the Galactic center. Using the multi-scale and multi-frequency-synthesis (MS-MFS) algorithms in CASA, we have imaged Sgr A with a resolution of 1″, achieving an rms noise of 8 μJy beam{sup −1}, and a dynamic range of 100,000:1. Both previously known and newly identified radio features in this region are revealed, including numerous filamentary sources. The radio continuum image is compared with Chandra X-ray images, with a CN emission-line image obtained with the Submillimeter Array and with detailed Paschen-α images obtained with Hubble Space Telescope/NICMOS. We discuss several prominent features in the radio image. The “Sgr A west Wings” extend 2′ (5 pc) from the NW and SE tips of the Sgr A west H ii region (the “Mini-spiral”) to positions located 2.9 and 2.4 arcmin to the northwest and southeast of Sgr A*, respectively. The NW wing, along with several other prominent features, including the previously identified “NW Streamers,” form an elongated radio lobe (NW lobe), oriented nearly perpendicular to the Galactic plane. This radio lobe, with a size of 6.′3 × 3.′2 (14.4 pc × 7.3 pc), has a known X-ray counterpart. In the outer region of the NW lobe, a row of three thermally emitting rings is observed. A field containing numerous amorphous radio blobs extends for a distance of ∼2 arcmin beyond the tip of the SE wing; these newly recognized features coincide with the SE X-ray lobe. Most of the amorphous radio blobs in the NW and SE lobes have Paschen-α counterparts. We propose that they have been produced by shock interaction of ambient gas concentrations with a collimated nuclear wind or an outflow that originated from within the circumnuclear disk (CND). We also discuss the possibility that the ionized

  14. A New Perspective of the Radio Bright Zone at The Galactic Center: Feedback from Nuclear Activities

    Science.gov (United States)

    Zhao, Jun-Hui; Morris, Mark R.; Goss, W. M.

    2016-02-01

    New observations of Sgr A have been carried out with the Jansky VLA in the B and C arrays using the broadband (2 GHz) continuum mode at 5.5 GHz. The field of view covers the central 13‧ (30 pc) region of the radio-bright zone at the Galactic center. Using the multi-scale and multi-frequency-synthesis (MS-MFS) algorithms in CASA, we have imaged Sgr A with a resolution of 1″, achieving an rms noise of 8 μJy beam-1, and a dynamic range of 100,000:1. Both previously known and newly identified radio features in this region are revealed, including numerous filamentary sources. The radio continuum image is compared with Chandra X-ray images, with a CN emission-line image obtained with the Submillimeter Array and with detailed Paschen-α images obtained with Hubble Space Telescope/NICMOS. We discuss several prominent features in the radio image. The “Sgr A west Wings” extend 2‧ (5 pc) from the NW and SE tips of the Sgr A west H ii region (the “Mini-spiral”) to positions located 2.9 and 2.4 arcmin to the northwest and southeast of Sgr A*, respectively. The NW wing, along with several other prominent features, including the previously identified “NW Streamers,” form an elongated radio lobe (NW lobe), oriented nearly perpendicular to the Galactic plane. This radio lobe, with a size of 6.‧3 × 3.‧2 (14.4 pc × 7.3 pc), has a known X-ray counterpart. In the outer region of the NW lobe, a row of three thermally emitting rings is observed. A field containing numerous amorphous radio blobs extends for a distance of ˜2 arcmin beyond the tip of the SE wing; these newly recognized features coincide with the SE X-ray lobe. Most of the amorphous radio blobs in the NW and SE lobes have Paschen-α counterparts. We propose that they have been produced by shock interaction of ambient gas concentrations with a collimated nuclear wind or an outflow that originated from within the circumnuclear disk (CND). We also discuss the possibility that the ionized wind or

  15. Star Formation Activity in the Galactic H II Region Sh2-297

    Science.gov (United States)

    Mallick, K. K.; Ojha, D. K.; Samal, M. R.; Pandey, A. K.; Bhatt, B. C.; Ghosh, S. K.; Dewangan, L. K.; Tamura, M.

    2012-11-01

    We present a multiwavelength study of the Galactic H II region Sh2-297, located in the Canis Major OB1 complex. Optical spectroscopic observations are used to constrain the spectral type of ionizing star HD 53623 as B0V. The classical nature of this H II region is affirmed by the low values of electron density and emission measure, which are calculated to be 756 cm-3 and 9.15 × 105 cm-6 pc using the radio continuum observations at 610 and 1280 MHz, and Very Large Array archival data at 1420 MHz. To understand local star formation, we identified the young stellar object (YSO) candidates in a region of area ~7farcm5 × 7farcm5 centered on Sh2-297 using grism slitless spectroscopy (to identify the Hα emission line stars), and near infrared (NIR) observations. NIR YSO candidates are further classified into various evolutionary stages using color-color and color-magnitude (CM) diagrams, giving 50 red sources (H - K > 0.6) and 26 Class II-like sources. The mass and age range of the YSOs are estimated to be ~0.1-2 M ⊙ and 0.5-2 Myr using optical (V/V-I) and NIR (J/J-H) CM diagrams. The mean age of the YSOs is found to be ~1 Myr, which is of the order of dynamical age of 1.07 Myr of the H II region. Using the estimated range of visual extinction (1.1-25 mag) from literature and NIR data for the region, spectral energy distribution models have been implemented for selected YSOs which show masses and ages to be consistent with estimated values. The spatial distribution of YSOs shows an evolutionary sequence, suggesting triggered star formation in the region. The star formation seems to have propagated from the ionizing star toward the cold dark cloud LDN1657A located west of Sh2-297.

  16. Dynamo dominated accretion and energy flow: The mechanism of active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Colgate, S.A.; Li, H.

    1998-12-31

    An explanation of the magnetic fields of the universe, the central mass concentration of galaxies, the massive black hole of every galaxy, and the AGN phenomena has been an elusive goal. The authors suggest here the outlines of such a theoretical understanding and point out where the physical understanding is missing. They believe there is an imperative to the sequence of mass flow and hence energy flow in the collapse of a galactic mass starting from the first non-linearity appearing in structure formation following decoupling. This first non-linearity of a two to one density fluctuation, the Lyman-{alpha} clouds, ultimately leads to the emission spectra of the phenomenon of AGN, quasars, blazars, etc. The over-arching physical principle is the various mechanisms for the transport of angular momentum. They believe they have now understood the new physics of two of these mechanisms that have previously been illusive and as a consequence they impose strong constraints on the initial conditions of the mechanisms for the subsequent emission of the gravitational binding energy. The new phenomena described are: (1) the Rossby vortex mechanism of the accretion disk {alpha}-viscosity, and (2) the mechanism of the {alpha}-{Omega} dynamo in the accretion disk. The Rossby vortex mechanism leads to a prediction of the black hole mass and rate of energy release and the {alpha}-{Omega} dynamo leads to the generation of the magnetic flux of the galaxy (and the far greater magnetic flux of clusters) and separately explains the primary flux of energy emission as force-free magnetic energy density. This magnetic flux and magnetic energy density separately are the necessary consequence of the saturation of a dynamo created by the accretion disk with a gain greater than unity.

  17. Leptin activates oxytocin neurons of the hypothalamic paraventricular nucleus in both control and diet-induced obese rodents.

    Directory of Open Access Journals (Sweden)

    Mario Perello

    Full Text Available The adipocyte-derived hormone leptin acts in the brain to reduce body weight and fat mass. Recent studies suggest that parvocellular oxytocin (OXT neurons of the hypothalamic paraventricular nucleus (PVN can mediate body weight reduction through inhibition of food intake and increased energy expenditure. However, the role of OXT neurons of the PVN as a primary target of leptin has not been investigated. Here, we studied the potential role of OXT neurons of the PVN in leptin-mediated effects on body weight regulation in fasted rats. We demonstrated that intracerebroventricular (ICV leptin activates STAT3 phosphorylation in OXT neurons of the PVN, showed that this occurs in a subpopulation of OXT neurons that innervate the nucleus of the solitary tract (NTS, and provided further evidence suggesting a role of OXT to mediate leptin's actions on body weight. In addition, our results indicated that OXT neurons are responsive to ICV leptin and mediate leptin effects on body weight in diet induced obese (DIO rats, which are resistant to the anorectic effects of the hormone. Thus, we conclude that leptin targets a specific subpopulation of parvocellular OXT neurons of the PVN, and that this action may be important for leptin's ability to reduce body weight in both control and obese rats.

  18. Demystifying the coronal line region of active galactic nuclei: spatially resolved spectroscopy with HST

    CERN Document Server

    Mazzalay, Ximena; Komossa, S

    2010-01-01

    We present an analysis of STIS/HST optical spectra of a sample of ten Seyfert galaxies aimed at studying the structure and physical properties of the coronal-line region (CLR). The high-spatial resolution provided by STIS allowed us to resolve the CLR and obtain key information about the kinematics of the coronal-line gas, measure directly its spatial scale, and study the mechanisms that drive the high-ionisation l