WorldWideScience

Sample records for active galaxy centaurus

  1. Centaurus A - The nearest active galaxy

    Science.gov (United States)

    Burns, J. O.; Price, R. M.

    1983-11-01

    Observed features of the active galaxy Centaurus A are described, and attention is given to the physical processes responsible for the two detected radio lobes. Data have been taken in visible, X ray, and radio wavelengths. Most of the radiation emitted has originated from the loss of energy by electrons through thermal processes in the interstellar gas, synchrotron radiation, and by randomly polarized atomic emission. Cen A displays features of both elliptical and spiral galaxies, with a dust lane in the middle of the ellipse holding hot, newly formed blue stars. Spectroscopic studies of the emission lines of hot gas in Cen A indicate that the source of excited gas is in the center of the galaxy. The radio region has a 2,700,000 light year extent, with a plasma jet directed from the center into the north radio lobe. X ray maps of Cen A suggest a black hole with a mass of a billion suns is the source of the jet. Electrons in the beam could be accelerated by shock waves, turbulence, or collisions with protons.

  2. New low surface brightness dwarf galaxies in the Centaurus group

    CERN Document Server

    Müller, Oliver; Binggeli, Bruno

    2016-01-01

    We conducted an extensive CCD search for faint, unresolved dwarf galaxies of very low surface brightness in the whole Centaurus group region encompassing the Cen A and M 83 subgroups lying at a distance of roughly 4 and 5 Mpc, respectively. The aim is to significantly increase the sample of known Centaurus group members down to a fainter level of completeness, serving as a basis for future studies of the 3D structure of the group. Following our previous survey of 60 square degrees covering the M 83 subgroup, we extended and completed our survey of the Centaurus group region by imaging another 500 square degrees area in the g and r bands with the wide-field Dark Energy Survey Camera at the 4m Blanco telescope at CTIO. The limiting central surface brightness reached for suspected Centaurus members is $\\mu_r \\approx 29$ mag arcsec$^{-2}$, corresponding to an absolute magnitude $M_r \\approx -9.5$. The images were enhanced using different filtering techniques. We found 41 new dwarf galaxy candidates, which togethe...

  3. Centaurus

    Science.gov (United States)

    Murdin, P.

    2000-11-01

    (the Centaur; abbrev. Cen, gen. Centauri; area 1060 sq. deg.) A southern constellation which lies between Vela and Lupus, and surrounds Crux on three sides. It culminates at midnight in early April. Its origin dates back at least to ancient Greece, where it was identified with Chiron in Greek mythology. The brightest stars of Centaurus were cataloged by Ptolemy (c. AD 100-175) in the Almagest....

  4. New dwarf galaxy candidates in the Centaurus group

    CERN Document Server

    Müller, Oliver; Binggeli, Bruno

    2015-01-01

    Recent studies of the distribution and kinematics of the Milky Way and Andromeda satellite galaxy systems have confirmed the existence of coplanar, corotating structures of galaxies. In addition to the 'missing satellite problem', these structures pose a major challenge to the standard $\\Lambda$CDM scenario of structure formation. We complement the efforts made by the dwarf galaxy community to extend these studies to other nearby galaxy groups by systematically searching for faint, unresolved dwarf members with a low surface brightness in the Southern Centaurus group of galaxies. The aim is to determine whether these coplanar, corotating structures are a universal phenomenon. We imaged an area of 60 square degrees (0.3 Mpc$^2$) around the M83 subgroup with the wide-field Dark Energy Camera (DECam) at the CTIO 4 m Blanco telescope in $g$ and $r$ down to a limiting surface brightness of $\\mu_r\\approx 30$ mag arcsec$^{-2}$. Various image-filtering techniques were applied to the DECam data to enhance the visibili...

  5. ASCA Temperature Maps of Three Clusters of Galaxies Abell 1060, AWM7, and the Centaurus Cluster

    CERN Document Server

    Furusho, T; Ohashi, T; Shibata, R; Kagei, T; Ishisaki, Y; Kikuchi, K; Ezawa, H; Ikebe, Y

    2001-01-01

    We present two-dimensional temperature maps of three bright clusters of galaxies Abell 1060, AWM7, and the Centaurus cluster, based on multi-pointing observations with the ASCA GIS. The temperatures are derived from hardness ratios by taking into account the XRT response. For the Centaurus cluster, we subtracted the central cool component using the previous ASCA and ROSAT results, and the metallicity gradients observed in AWM7 and the Centaurus cluster were included in deriving the temperatures. The intracluster medium in Abell 1060 and AWM7 is almost isothermal from the center to outer regions with a temperature of 3.3 and 3.9 keV, respectively. The Centaurus cluster exhibits remarkable hot regions within about 30' from the cluster center showing a temperature increase of +0.8 keV from the surrounding level of 3.5 keV, and outer cool regions with lower temperatures by -1.3 keV. These results imply that a strong merger has occurred in the Centaurus in the recent 2-3 Gyr, and the central cool component has sur...

  6. Discovery of Molecular Gas Shells around the Unusual Galaxy Centaurus A

    Science.gov (United States)

    2000-03-01

    - and farther out than most of the stars - would be liberated earlier than the stars. As a consequence, one would also expect to observe a certain displacement between the gaseous and stellar shells. The SEST observations ESO PR Photo 08a/00 ESO PR Photo 08a/00 [Preview - JPEG: 343 x 400 pix - 188k] [Normal - JPEG: 686 x 800 pix - 560k] [High-Res - JPEG: 2571 x 3000 pix - 4.4M] Caption : ESO PR Photo 08a/00 shows an optical image of the galaxy Centaurus A (from the 1-m ESO Schmidt telescope at La Silla), with the surrounding shells outlined as contours. The image has been enhanced to show the full extent of the galaxy; due to this process, the central dust band is less visible. The stellar shells (see the text) are indicated in yellow; they are otherwise only visible on very deep images. The contours of the observed distribution of atomic hydrogen gas are white. The radio jet from the active centre of Centaurus A is shown in blue. The new SEST observations prove the existence of carbon monoxide (CO) in the S1 and S2 shells (indicated in red). The field measures approx. 32 x 32 arcmin 2. North is up and East is left. A detailed photo of Centaurus A was recently obtained with the FORS2 instrument at VLT KUEYEN, cf. ESO PR Photo 05b/00 ESO PR Photo 08b/00 ESO PR Photo 08b/00 [Preview - JPEG: 247 x 400 pix - 60k] [Normal - JPEG: 493 x 800 pix - 128k] [High-Res - JPEG: 3000 x 1847 pix - 756k] Caption : ESO PR Photo 08b/00 shows the observed CO emission spectra in the S1 and S2 shells. In both cases, two lines from different molecular states were observed that stand out clearly from the sky noise. The abscissa indicates the velocity (i.e., the radio frequency) and the ordinate the temperature (i.e., the intensity). These diagrammes represent approx. 20 and 30 hours of observation, respectively. In order to test this hypothesis, the astronomers decided to look for the possible presence in the shells around some nearby elliptical galaxies of specific gases that are typical of

  7. Star Formation in Dwarf Galaxies of the Nearby Centaurus A Group

    CERN Document Server

    Cote, Stephanie; Skillman, Evan D; Miller, Bryan W

    2009-01-01

    We present Halpha narrow-band imaging of 17 dwarf irregular galaxies (dIs) in the nearby Centaurus A Group. Although all large galaxies of the group have a current or recent enhanced star formation episode, the dIs have normal star formation rates and do not contain a larger fraction of dwarf starbursts than other nearby groups. Relative distances between dIs and larger galaxies of the group can be computed in 3D since most of them have now fairly accurately known distances. We find that the dI star formation rates do not depend on local environment, and in particular they do not show any correlation with the distance of the dI to the nearest large galaxy of the group. There is a clear morphology-density relation in the Centaurus A Group, similarly to the Sculptor and Local Groups, in the sense that dEs/dSphs tend to be at small distances from the more massive galaxies of the group, while dIs are on average at larger distances. We find four transition dwarfs in the Group, dwarfs that show characteristics of b...

  8. A very deep Chandra view of metals, sloshing and feedback in the Centaurus cluster of galaxies

    CERN Document Server

    Sanders, J S; Taylor, G B; Russell, H R; Blundell, K M; Canning, R E A; Hlavacek-Larrondo, J; Walker, S A; Grimes, C K

    2016-01-01

    We examine deep Chandra X-ray observations of the Centaurus cluster of galaxies, Abell 3526. Applying a gradient magnitude filter reveals a wealth of structure, from filamentary soft emission on 100pc (0.5 arcsec) scales close to the nucleus to features 10s of kpc in size at larger radii. The cluster contains multiple high-metallicity regions with sharp edges. Relative to an azimuthal average, the deviations of metallicity and surface brightness are correlated, and the temperature is inversely correlated, as expected if the larger scale asymmetries in the cluster are dominated by sloshing motions. Around the western cold front are a series of ~7 kpc 'notches', suggestive of Kelvin-Helmholtz instabilities. The cold front width varies from 4 kpc down to close to the electron mean free path. Inside the front are multiple metallicity blobs on scales of 5-10 kpc, which could have been uplifted by AGN activity, also explaining the central metallicity drop and flat inner metallicity profile. Close to the nucleus are...

  9. A very deep Chandra view of metals, sloshing and feedback in the Centaurus cluster of galaxies

    Science.gov (United States)

    Sanders, J. S.; Fabian, A. C.; Taylor, G. B.; Russell, H. R.; Blundell, K. M.; Canning, R. E. A.; Hlavacek-Larrondo, J.; Walker, S. A.; Grimes, C. K.

    2016-03-01

    We examine deep Chandra X-ray observations of the Centaurus cluster of galaxies, Abell 3526. Applying a gradient magnitude filter reveals a wealth of structure, from filamentary soft emission on 100 pc (0.5 arcsec) scales close to the nucleus to features 10 s of kpc in size at larger radii. The cluster contains multiple high-metallicity regions with sharp edges. Relative to an azimuthal average, the deviations of metallicity and surface brightness are correlated, and the temperature is inversely correlated, as expected if the larger scale asymmetries in the cluster are dominated by sloshing motions. Around the western cold front are a series of ˜7 kpc `notches', suggestive of Kelvin-Helmholtz instabilities. The cold front width varies from 4 kpc down to close to the electron mean free path. Inside the front are multiple metallicity blobs on scales of 5-10 kpc, which could have been uplifted by AGN activity, also explaining the central metallicity drop and flat inner metallicity profile. Close to the nucleus are multiple shocks, including a 1.9-kpc-radius inner shell-like structure and a weak 1.1-1.4 Mach number shock around the central cavities. Within a 10 kpc radius are nine depressions in surface brightness, several of which appear to be associated with radio emission. The shocks and cavities imply that the nucleus has been repeatedly active on 5-10 Myr time-scales, indicating a tight balance between heating and cooling. We confirm the presence of a series of linear quasi-periodic structures. If they are sound waves, the ˜5 kpc spacing implies a period of 6 Myr, similar to the ages of the shocks and cavities. Alternatively, these structures may be Kelvin-Helmholtz instabilities, their associated turbulence or amplified magnetic field layers.

  10. Fermi-LAT and Suzaku Observations of the Radio Galaxy Centaurus B

    Energy Technology Data Exchange (ETDEWEB)

    Katsuta, Junichiro; /Stanford U., HEPL /KIPAC, Menlo Park; Tanaka, Y.T.; /Hiroshima U.; Stawarz, L.; /JAXA, Sagamihara /Jagiellonian U., Astron. Observ.; O' Sullivan, S.P.; /Australia, CSIRO, Epping; Cheung, C.C.; /NAS, Washington, D.C.; Kataoka, J.; /Waseda U., RISE; Funk, S.; /Stanford U., HEPL /KIPAC, Menlo Park; Yuasa, T.; Odaka, H.; Takahashi, T.; /JAXA, Sagamihara; Svoboda, J.; /European Space Agency

    2012-08-17

    CentaurusB is a nearby radio galaxy positioned in the Southern hemisphere close to the Galactic plane. Here we present a detailed analysis of about 43 months accumulation of Fermi-LAT data and of newly acquired Suzaku X-ray data for Centaurus B. The source is detected at GeV photon energies, although we cannot completely exclude the possibility that it is an artifact due to incorrect modeling of the bright Galactic diffuse emission in the region. The LAT image provides a weak hint of a spatial extension of the {gamma} rays along the radio lobes, which is consistent with the lack of source variability in the GeV range. We note that the extension cannot be established statistically due to the low number of the photons. Surprisingly, we do not detect any diffuse emission of the lobes at X-ray frequencies, with the provided upper limit only marginally consistent with the previously claimed ASCA flux. The broad-band modeling shows that the observed {gamma}-ray flux of the source may be produced within the lobes, if the diffuse non-thermal X-ray emission component is not significantly below the derived Suzaku upper limit. This association would imply that efficient in-situ acceleration of the ultrarelativistic particles is occurring and that the lobes are dominated by the pressure from the relativistic particles. However, if the diffuse X-ray emission is much below the Suzaku upper limits, the observed {gamma}-ray flux is not likely to be produced within the lobes, but instead within the unresolved core of Centaurus B. In this case, the extended lobes could be dominated by the pressure of the magnetic field.

  11. Discovery of a close pair of faint dwarf galaxies in the halo of Centaurus A

    CERN Document Server

    Crnojević, D; Caldwell, N; Guhathakurta, P; McLeod, B; Seth, A; Simon, J; Strader, J; Toloba, E

    2014-01-01

    As part of the Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) we report the discovery of a pair of faint dwarf galaxies (CenA-MM-Dw1 and CenA-MM-Dw2) at a projected distance of $\\sim$90 kpc from the nearby elliptical galaxy NGC5128 (CenA). We measure a tip of the red giant branch distance to each dwarf, finding $D=3.63 \\pm 0.41$ Mpc for CenA-MM-Dw1 and $D=3.60 \\pm 0.41$ Mpc for CenA-MM-Dw2, both of which are consistent with the distance to NGC5128. A qualitative analysis of the color magnitude diagrams indicates stellar populations consisting of an old, metal-poor red giant branch ($\\gtrsim 12$ Gyr, [Fe/H]$\\sim-1.7$ to -1.9). In addition, CenA-MM-Dw1 seems to host an intermediate-age population as indicated by its candidate asymptotic giant branch stars. The derived luminosities ($M_V=-10.9\\pm0.3$ for CenA-MM-Dw1 and $-8.4\\pm0.6$ for CenA-MM-Dw2) and half-light radii ($r_{h}=1.4\\pm0.04$ kpc for CenA-MM-Dw1 and $0.36\\pm0.08$ kpc for CenA-MM-Dw2) are consistent with those of Local Group dwarfs. Cen...

  12. CENTAURUS A: THE INSIDE STORY

    Science.gov (United States)

    2002-01-01

    Astronomers have used NASA's Hubble Space Telescope to probe the core of the nearest active galaxy to Earth, Centaurus A. [UPPER LEFT] - A close-up high resolution Wide Field Planetary Camera 2 image of the dramatic dust disk which is thought to be the remnant of a smaller spiral galaxy that merged with the large elliptical galaxy. The shock of the collision compressed interstellar gas, precipitating a flurry of star formation and giving the material a fleecy pattern. Dark filaments of dust mixed with cold hydrogen gas are silhouetted against the incandescent yellow-orange glow from stars behind it. [LOWER RIGHT] - Hubble's Near Infrared Camera and Multi-Object Spectrometer was used to peer past the dust to discover a tilted disk of hot gas at the galaxy's center (white bar running diagonally across image center). This 130 light-year diameter disk encircles a suspected black hole which may be one billion times the mass of our Sun. The disk feeds material to presumably an inner, unresolved accretion disk that is made up of gas entrapped by the black hole. The red blobs near the disk are glowing gas clouds which have been heated up and ionized by the powerful radiation from the active nucleus. The false-color NICMOS image was taken on Aug. 11, 1997 at a wavelength of 1.87 microns ('Paschen alpha'), characteristic of ionized Hydrogen. Centaurus A (NGC 5128) Fast Facts Right Ascension: 13 : 25.5 (hours : minutes) Declination: -43 : 01 (degrees : minutes) Apparent Magnitude: 7.0 Apparent Diameter: 18.2 (arc minutes) Distance: 10 million light-years Constellation: Centaurus (southern sky) Credit: E.J. Schreier, (STScI) and NASA Team members are: Ethan J. Schreier, Alessandro Marconi, David J. Axon, Nicola Caon, Duccio Macchetto ( STScI), Alessandro Capetti - (Osservatorio Astronomico di Torino, Italy), James H. Hough, Stuart Young ( University of Hertfordshire, UK), and Chris Packham (Isaac Newton Group, Islas Canarias, SPAIN)

  13. ISO Images of Starbursts and Active Galaxies

    CERN Document Server

    Mirabel, I F

    1999-01-01

    We present some highlights from the mid-infrared (5-16 micron) images of mergers of massive galaxies obtained with the Infrared Space Observatory (ISO). We have observed: 1) ultraluminous infrared nuclei, 2) luminous dust-enshrouded extranuclear starbursts, and 3) active galaxy nuclei (AGNs). In this contribution we discuss the observations of Arp 299, a prototype for very luminous infrared galaxies, the Antennae which is a prototype of mergers, and Centaurus A which is the closest AGN to Earth. From these observations we conclude the following: 1) the most intense starbursts in colliding systems of galaxies and the most massive stars are dust-enshrouded in regions that appear inconspicuous at optical wavelengths, 2) the most intense nuclear infrared sources are a combination of AGN and starburst activity, 3) the hosts of radio loud AGNs that trigger giant double-lobe structures may be symbiotic galaxies composed of barred spirals inside ellipticals.

  14. A deep spectroscopic study of the filamentary nebulosity in NGC4696, the brightest cluster galaxy in the Centaurus cluster

    CERN Document Server

    Canning, R E A; Johnstone, R M; Sanders, J S; Crawford, C S; Ferland, G J; Hatch, N A

    2011-01-01

    We present results of deep integral field spectroscopy observations using high resolution optical (4150-7200 A) VIMOS VLT spectra, of NGC 4696, the dominant galaxy in the Centaurus cluster (Abell 3526). After the Virgo cluster, this is the second nearest (z=0.0104) example of a cool core cluster. NGC 4696 is surrounded by a vast, luminous H alpha emission line nebula (L = 2.2 \\times 10^40 ergs per second). We explore the origin and excitation of the emission-line filaments and find their origin consistent with being drawn out, under rising radio bubbles, into the intracluster medium as in other similar systems. Contrary to previous observations we do not observe evidence for shock excitation of the outer filaments. Our optical spectra are consistent with the recent particle heating excitation mechanism of Ferland et al.

  15. Centaurus A - NGC 5128

    OpenAIRE

    Israel, F.P.

    1998-01-01

    This review summarizes the state of the knowledge of the nearby (D = 3.4 Mpc) radio source Centaurus A and its host galaxy NGC 5128. The massive elliptical host galaxy appears to be moderately triaxial. It contains a strongly warped thin disk, rich in gas, dust and young stars, and roughly aligned with the minor axis of the elliptical galaxy. This and other evidence suggests that NGC 5128 has experienced a major merger at least once in its past. The subparsec nucleus is variable at radio and ...

  16. Active Galaxies

    DEFF Research Database (Denmark)

    Kilerci Eser, Ece

    is sufficiently powerful, energy feedback from the AGN blows away the gas fuel and shuts off both the star formation and the black hole growth. In this thesis I study local AGN and ULIRGs. I address 2 different studies of AGN: one is related to the potential use of AGN to measure cosmic distances and the other...... one is related to the mass estimates of supermassive black holes (SMBHs). Mass estimates of SMBHs are important to understand the formation and evolution of SMBHs and their host galaxies. Black hole masses in Type 1 AGN are measured with the reverberation mapping (RM) technique. Reverberation mapping...... on a single-epoch spectrum. Recently, it has been shown that the R - L  relationship can also be used to measure cosmic distances beyond redshifts that can be probed by supernovae. The current local (z

  17. Application of a XMM-Newton EPIC Monte Carlo to analysis and interpretation of data for Abell 1689, RXJ0658-55 and the Centaurus clusters of galaxies

    CERN Document Server

    Andersson, K E; Madejski, G M

    2006-01-01

    We propose a new Monte Carlo method to study extended X-ray sources with the European Photon Imaging Camera (EPIC) aboard XMM Newton. The Smoothed Particle Inference (SPI) technique, described in a companion paper, is applied here to the EPIC data for the clusters of galaxies Abell 1689, Centaurus and RXJ 0658-55 (the ``bullet cluster''). We aim to show the advantages of this method of simultaneous spectral-spatial modeling over traditional X-ray spectral analysis. In Abell 1689 we confirm our earlier findings about structure in temperature distribution and produce a high resolution temperature map. We also confirm our findings about velocity structure within the gas. In the bullet cluster, RXJ 0658-55, we produce the highest resolution temperature map yet to be published of this cluster allowing us to trace what looks like the motion of the bullet in the cluster. We even detect a south to north temperature gradient within the bullet itself. In the Centaurus cluster we detect, by dividing up the luminosity of...

  18. Planck revealed bulk motion of Centaurus A lobes

    CERN Document Server

    De Paolis, F; Nucita, A A; Ingrosso, G; Kashin, A L; Khachatryan, H G; Mirzoyan, S; Yegorian, G; Jetzer, Ph; Qadir, A; Vetrugno, D

    2015-01-01

    Planck data towards the active galaxy Centaurus A are analyzed in the 70, 100 and 143 GHz bands. We find a temperature asymmetry of the northern radio lobe with respect to the southern one that clearly extends at least up to 5 degrees from the Cen A center and diminishes towards the outer regions of the lobes. That transparent parameter - the temperature asymmetry - thus has to carry a principal information, i.e. indication on the line-of-sight bulk motion of the lobes, while the increase of that asymmetry at smaller radii reveals the differential dynamics of the lobes as expected at ejections from the center.

  19. The Centaurus A Northern Middle Lobe as a Buoyant Bubble

    CERN Document Server

    Saxton, C J; Bicknell, G V; Saxton, Curtis J.; Sutherland, Ralph S.; Bicknell, Geoffrey V.

    2001-01-01

    We model the northern middle radio lobe of Centaurus A (NGC 5128) as a buoyant bubble of plasma deposited by an intermittently active jet. The extent of the rise of the bubble and its morphology imply that the ratio of its density to that of the surrounding ISM is less than 10^{-2}, consistent with our knowledge of extragalactic jets and minimal entrainment into the precursor radio lobe. Using the morphology of the lobe to date the beginning of its rise through the atmosphere of Centaurus A, we conclude that the bubble has been rising for approximately 140Myr. This time scale is consistent with that proposed by Quillen et al. (1993) for the settling of post-merger gas into the presently observed large scale disk in NGC 5128, suggesting a strong connection between the delayed re-establishment of radio emission and the merger of NGC 5128 with a small gas-rich galaxy. This suggests a connection, for radio galaxies in general, between mergers and the delayed onset of radio emission. In our model, the elongated X-...

  20. A consequence of the asymmetry of jets in quasars and active nuclei of galaxies

    Science.gov (United States)

    Shklovsky, I. S.

    The possibility that radio emission of quasars and radio galaxies is a result of ejections of plasmoids issuing from the supercritical accretion on massive black holes at the center of galaxies is discussed. Evidence from observations of Cygnus A, Centaurus A, and Fornax A are cited to suggest that one-sided and two-sided jets occur near the center of galaxies. The ejection of a jet is shown to be a nonsymetrical event, thus allowing the possibility that all jets are one-sided, with two-sided jets actually being evidence for one remnant jet in the company of another remnant or an active event. The recoil velocity acquired by a black hole because of the ejection of plasmoids is modeled numerically. The black hole is determined to necessarily escape from the parent galaxy, which then ceases being a compact source. Short-lived quasars are therefore extinguished when super-critically accreting regimes end.

  1. Centaurus A : Morphology and kinematics of the atomic hydrogen

    NARCIS (Netherlands)

    Struve, C.; Oosterloo, T. A.; Morganti, R.; Saripalli, L.

    2010-01-01

    We present new ATCA 21-cm line observations of the neutral hydrogen in the nearby radio galaxy Centaurus A. We image in detail (with a resolution down to 7 '', similar to 100 pc) the distribution of HI along the dust lane. Our data have better velocity resolution and better sensitivity than previous

  2. Nuclear activity in nearby galaxies

    NARCIS (Netherlands)

    Filho, Mercedes Esteves

    2003-01-01

    The main focus of this thesis has been the search for and study of low luminosity AGN. We have detected severa low luminosity AGN in nearby galaxies, revealing that this type of activity can occur in a broad range of galaxy types and powers. Furthermore, we have been able to establish importan const

  3. LABOCA observations of nearby, active galaxies

    CERN Document Server

    Weiss, A; Guesten, R; Menten, K M; Schuller, F; Siringo, G; Kreysa, E

    2008-01-01

    We present large scale 870 micron maps of the nearby starburst galaxies NGC253, NGC4945 and the nearest giant elliptical radio galaxy Centaurus A (NGC 5128) obtained with the newly commissioned Large Apex Bolometer Camera (LABOCA) operated at the APEX telescope. Our continuum images reveal for the first time the distribution of cold dust at a angular resolution of 20" across the entire optical disks of NGC253 and NGC4945 out to a radial distance of 10' (7.5 kpc). In NGC5128 our LABOCA image also shows, for the first time at submillimeter wavelengths, the synchrotron emission associated with the radio jet and the inner radio lobes. From an analysis of the 870 micron emission in conjunction with ISO-LWS, IRAS and long wavelengths radio data we find temperatures for the cold dust in the disks of all three galaxies of 17-20 K, comparable to the dust temperatures in the disk of the Milky Way. The total gas mass in the three galaxies is determined to be 2.1, 4.2 and 2.8 x 10^9 solar masses for NGC253, NGC4945 and N...

  4. Nuclear Activity In Isolated Galaxies

    CERN Document Server

    Hernandez-Ibarra, Francisco; Krongold, Yair; Del Olmo, Ascencion; Perea, Jaime; Gonzalez, Jesus

    2012-01-01

    We present a spectroscopic study of the incidence of AGN nuclear activity in two samples of isolated galaxies (Karachentseva, V.E. & Varela, J.). Our results show that the incidence of non-thermal nuclear activity is about 43% and 31% for galaxies with emission lines and for the total sample 40% and 27% respectively. For the first time we have a large number of bona-fide isolated galaxies (513 objects), with statistically significant number of all types. We find a clear relation between bulge mass and the incidence of nuclear activity in the sample with emission lines. This relation becomes flatter when we take into account the complete sample with no emission line galaxies. A large fration ($\\sim$70%) of elliptical galaxies or early type spirals have an active galactic nucleus and $\\sim$70% of them are LINERs. Only 3% of the AGN show the presence of broad lines (a not a single one can be classified as type 1 AGN). This is a remarkable result which is completely at odds with the unified model even if we c...

  5. Sub-parsec scale imaging of Centaurus A

    CERN Document Server

    Müller, Cornelia; Ojhas, R; Böck, M; Fromm, C M; Ros, E; Rothschild, R E; Wilms, J

    2010-01-01

    At a distance of about 3.4 Mpc, the radio galaxy Centaurus A is the closest active galaxy. Therefore it is a key target for studying the innermost regions of active galactic nuclei (AGN). VLBI observations conducted within the framework of the TANAMI program enable us to study the central region of the Cen A jet with some of the highest linear resolutions ever achieved in an AGN. This region is the likely origin of the gamma-ray emission recently detected by the Fermi Large Area Telescope (LAT). TANAMI monitors a sample of radio and gamma-ray selected extragalactic jets south of -30 degrees declination at 8.4 GHz and 22.3 GHz with the Australian Long Baseline Array (LBA) and the transoceanic antennas Hartebeesthoek in South Africa, the 6 m Transportable Integrated Geodetic Observatory (TIGO) in Chile and the 9 m German Antarctic Receiving Station (GARS) in O'Higgins, Antarctica. The highest angular resolution achieved at 8.4 GHz in the case of Cen A is 0.59mas x 0.978mas (natural weighting) corresponding to a...

  6. Star formation efficiency in the outer filaments of Centaurus A

    Science.gov (United States)

    Salomé, Q.; Salomé, P.; Combes, F.; Hamer, S.; Heywood, I.

    2015-12-01

    We present a multi-wavelength study of the northern filaments of Centaurus A (at a distance of ˜ 20 kpc from the galaxy center) based on FUV (GALEX), FIR (Herschel) and CO (SEST and ALMA) emission. We also searched for HCN and HCO^+ (ATCA) and observed optical emission lines (VLT/MUSE) in different places of the filament. An upper limit of the dense gas of L'_{HCN}inhibits star formation.

  7. Two Planes of Satellites in the Centaurus A Group

    Science.gov (United States)

    Tully, R. Brent; Libeskind, Noam I.; Karachentsev, Igor D.; Karachentseva, Valentina E.; Rizzi, Luca; Shaya, Edward J.

    2015-04-01

    Tip of the red giant branch measurements based on Hubble Space Telescope and ground-based imaging have resulted in accurate distances to 29 galaxies in the nearby Centaurus A Group. All but 2 of the 29 galaxies lie in either of two thin planes roughly parallel with the supergalactic equator. The planes are only slightly tilted from the line of sight, leaving little ambiguity regarding the morphology of the structure. The planes have characteristic rms long axis dimensions of ∼300 kpc and short axis dimensions of ∼60 kpc, hence axial ratios ∼0.2, and are separated in the short axis direction by 303 kpc.

  8. Two Planes of Satellites in the Centaurus A Group

    CERN Document Server

    Tully, R Brent; Karachentsev, Igor D; Karachentseva, Valentina E; Rizzi, Luca; Shaya, Edward J

    2015-01-01

    Tip of the red giant branch measurements based on Hubble Space Telescope and ground-based imaging have resulted in accurate distances to 29 galaxies in the nearby Centaurus A Group. All but two of the 29 galaxies lie in either of two thin planes roughly parallel with the supergalactic equator. The planes are only slightly tilted from the line-of-sight, leaving little ambiguity regarding the morphology of the structure. The planes have characteristic r.m.s. long axis dimensions of ~300 kpc and short axis dimensions of ~60 kpc, hence axial ratios ~0.2, and are separated in the short axis direction by 303 kpc.

  9. The Complex North Transition Region of Centaurus A: A Galactic Wind

    CERN Document Server

    Neff, Susan G; Owen, Frazer N

    2015-01-01

    We present deep GALEX images of NGC 5128, the parent galaxy of Centaurus A. We detect a striking "weather ribbon" of Far-UV and H$\\alpha$ emission, which extends more than 35 kpc northeast of the galaxy. The ribbon is associated with a knotty ridge of radio/X-ray emission, and is an extension of the previously known string of optical emission-line filaments. Many phenomena in the region are too short-lived to have survived transit out from the inner galaxy; something must be driving them locally. We also detect Far-UV emission from the galaxy's central dust lane. Combining this with previous radio and Far-IR measurements, we infer an active starburst in the central galaxy, which is currently forming stars at $\\sim 2 M_{sun}$yr$^{-1}$, and has been doing so for 50-100Myr. If the wind from this starburst is enhanced by energy and mass driven out from the AGN, the powerful augmented wind can be the driver needed for the northern weather system. We argue that both the diverse weather system, and the enhanced radi...

  10. Nuclear Activity in Nearby Galaxies

    Directory of Open Access Journals (Sweden)

    Thaisa Bergmann Storchi

    2001-01-01

    Full Text Available I discuss some recent observational results in the research of nearby active galactic nuclei (AGN. These results cover three main topics: (i evidences for the current paradigm for AGN´s, which includes a nuclear supermassive blackhole (SMBH fed via an accretion disk; (ii evidence that this paradigm may also apply to LINER´s, the lowest luminous AGN´s and to normal galaxies; (iii evidences of how the fueling of the SMBH occurs and its relation to recent and intermediate age (106 to 108 yrs old episodes of star formation.

  11. The Complex North Transition Region of Centaurus A: Radio Structure

    CERN Document Server

    Neff, Susan G; Owen, Frazer N

    2015-01-01

    We present deep radio images of the inner 50 kpc of Centaurus A, taken with the Karl G. Jansky Very Large Array (VLA) at 90cm. We focus on the Transition Regions between the inner galaxy - including the active nucleus, inner radio lobes, and star-forming disk - and the outer radio lobes. We detect previously unknown extended emission around the Inner Lobes, including radio emission from the star-forming disk. We find that the radio-loud part of the North Transition Region, known as the North Middle Lobe, is significantly overpressured relative to the surrounding ISM. We see no evidence for a collimated flow from the Active Galactic Nucleus (AGN) through this region. Our images show that the structure identified by Morganti et al. (1999) as a possible large-scale jet appears to be part of a narrow ridge of emission within the broader, diffuse, radio-loud region. This knotty radio ridge is coincident with other striking phenomena: compact X-ray knots, ionized gas filaments, and streams of young stars. Several s...

  12. The extended halo of Centaurus A: uncovering satellites, streams and substructures

    CERN Document Server

    Crnojević, D; Spekkens, K; Caldwell, N; Guhathakurta, P; McLeod, B; Seth, A; Simon, J; Strader, J; Toloba, E

    2015-01-01

    We present the widest-field resolved stellar map to date of the closest ($D\\sim3.8$ Mpc) massive elliptical galaxy NGC 5128 (Centaurus A; Cen A), extending out to a projected galactocentric radius of $\\sim150$ kpc. The dataset is part of our ongoing Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS) utilizing the Magellan/Megacam imager. We resolve a population of old red giant branch stars down to $\\sim1.5$ mag below the tip of the red giant branch, reaching surface brightness limits as low as $\\mu_{V,0}\\sim32$ mag arcsec$^{-2}$. The resulting spatial stellar density map highlights a plethora of previously unknown streams, shells, and satellites, including the first tidally disrupting dwarf around Cen A, which underline its active accretion history. We report 13 previously unknown dwarf satellite candidates, of which 9 are confirmed to be at the distance of Cen A (the remaining 4 are not resolved into stars), with magnitudes in the range $M_V=-7.2$ to $-13.0$, central surface brightness values of $\\...

  13. DISCOVERY OF NUCLEAR WATER MASER EMISSION IN CENTAURUS A

    International Nuclear Information System (INIS)

    We report the detection of a 22 GHz water maser line in the nearest (D ∼ 3.8 Mpc) radio galaxy Centaurus A (Cen A) using the Australia Telescope Compact Array (ATCA). The line is centered at a velocity of ∼960 km s–1, which is redshifted by about 415 km s–1 from the systemic velocity. Such an offset, as well as the width of ∼120 km s–1, could be consistent with either a nuclear maser arising from an accretion disk of the central supermassive black hole (SMBH), or with a jet maser that is emitted from the material that is shocked near the base of the jet in Cen A. The best spatial resolution of our ATCA data constrains the origin of the maser feature within ☉, which classifies it as a kilomaser, and appears to be variable on timescales of months. A kilomaser can also be emitted by shocked gas in star-forming regions. Given the small projected distance from the core, the large offset from systemic velocity, and the smoothness of the line feature, we conclude that a jet maser line emitted by shocked gas around the base of the active galactic nucleus is the most likely explanation. For this scenario we can infer a minimum density of the radio jet of ∼> 10 cm–3, which indicates substantial mass entrainment of surrounding gas into the propagating jet material.

  14. The outer filament of Centaurus A as seen by MUSE

    Science.gov (United States)

    Santoro, F.; Oonk, J. B. R.; Morganti, R.; Oosterloo, T. A.; Tremblay, G.

    2015-03-01

    Context. Radio-loud active galactic nuclei (AGN) are known to inject kinetic energy into the surrounding interstellar medium (ISM) of their host galaxy via plasma jets. Understanding the impact that these flows can have on the host galaxy helps to characterize a crucial phase in their evolution. Because of its proximity, Centaurus A is an excellent laboratory in which the physics of the coupling of jet mechanical energy to the surrounding medium may be investigated. About 15 kpc northeast of this galaxy, a particularly complex region is found: the so-called outer filament, where jet-cloud interactions have been proposed to occur. Aims: We investigate signatures of a jet-ISM interaction using optical integral-field observations of this region, expanding on previous results that were obtained on a more limited area. Methods: Using the Multi Unit Spectroscopic Explorer (MUSE) on the VLT during the science verification period, we observed two regions that together cover a significant fraction of the brighter emitting gas across the outer filament. Emission from a number of lines, among which Hβλ4861 Å, [ O iii ] λλ4959,5007 Å, Hαλ6563 Å, and [ N ii ] λλ6548,6584 Å, is detected in both regions. Results: The ionized gas shows a complex morphology with compact blobs, arc-like structures, and diffuse emission. Based on the kinematics, we identified three main components of ionized gas. Interestingly, their morphology is very different. The more collimated component is oriented along the direction of the radio jet. The other two components exhibit a diffuse morphology together with arc-like structures, which are also oriented along the radio jet direction. Furthermore, the ionization level of the gas, as traced by the [O iii]λ5007/Hβ ratio, is found to decrease from the more collimated component to the more diffuse components. Conclusions: The morphology and velocities of the more collimated component confirm the results of our previous study, which was

  15. Nuclear Activity in Circumnuclear Ring Galaxies

    CERN Document Server

    Aguero, M P; Dottori, H

    2016-01-01

    We have analyzed the frequency and properties of the nuclear activity in a sample of galaxies with circumnuclear rings and spirals (CNRs). This sample was compared with a control sample of galaxies with very similar global properties but without circumnuclear rings. We discuss the relevance of the results in regard to the AGN feeding processes and present the following results: (i) bright companion galaxies seem not to be important for the appearance of CNRs, which appear to be more related to intrinsic properties of the host galaxies or to minor merger processes; (ii) the proportion of strong bars in galaxies with an AGN and a CNR is somewhat higher than the expected ratio of strongly barred AGN galaxies from the results of Ho and co-workers; (iii) the incidence of Seyfert activity coeval with CNRs is clearly larger than the rate expected from the morphological distribution of the host galaxies; (iv) the rate of Sy 2 to Sy 1 type galaxies with CNRs is about three times larger than the expected ratio for gala...

  16. Lithium in the Upper Centaurus Lupus and Lower Centaurus Crux Subgroups of Scorpius-Centaurus

    CERN Document Server

    Bubar, Eric J; King, Jeremy R; Mamajek, Eric E; Stauffer, John R

    2011-01-01

    We utilize spectroscopically derived model atmosphere parameters and the \\ion{Li}{1} $\\lambda6104$ subordinate line and the $\\lambda6708$ doublet to derive lithium abundances for 12 members of the Upper-Centaurus Lupus (UCL) and Lower-Centaurus Crux (LCC) subgroups of the Scorpius Centaurus OB Association. The results indicate any intrinsic Li scatter in our 0.9-1.4 $M_{\\odot}$ stars is limited to ${\\sim}0.15$ dex, consistent with the lack of dispersion in ${\\ge}1.0$ $M_{\\odot}$ stars in the 100 Myr Pleiades and 30-50 Myr IC 2391 and 2602 clusters. Both ab initio uncertainty estimates and the derived abundances themselves indicate that the $\\lambda$6104 line yields abundances with equivalent or less scatter than is found from the $\\lambda$6708 doublet as a result of lower uncertainties for the subordinate feature, a result of low sensitivity to broadening in the subordinate feature. Because NLTE corrections are less susceptible to changes in surface gravity and/or metallicity for the 6104 {\\AA} line, the subo...

  17. AGN Zoo and Classifications of Active Galaxies

    Science.gov (United States)

    Mickaelian, Areg M.

    2015-07-01

    We review the variety of Active Galactic Nuclei (AGN) classes (so-called "AGN zoo") and classification schemes of galaxies by activity types based on their optical emission-line spectrum, as well as other parameters and other than optical wavelength ranges. A historical overview of discoveries of various types of active galaxies is given, including Seyfert galaxies, radio galaxies, QSOs, BL Lacertae objects, Starbursts, LINERs, etc. Various kinds of AGN diagnostics are discussed. All known AGN types and subtypes are presented and described to have a homogeneous classification scheme based on the optical emission-line spectra and in many cases, also other parameters. Problems connected with accurate classifications and open questions related to AGN and their classes are discussed and summarized.

  18. Herschel observations of the Centaurus cluster - the dynamics of cold gas in a cool core

    CERN Document Server

    Mittal, Rupal; Ferland, Gary; Oonk, Raymond; Edge, Alastair C; Canning, Rebecca E A; Russell, Helen; Baum, Stefi A; Böhringer, Hans; Combes, Francoise; Donahue, Megan; Fabian, Andy C; Hatch, Nina A; Hoffer, Aaron; Johnstone, Roderick; McNamara, Brian R; Salomé, Philippe; Tremblay, Grant

    2011-01-01

    Brightest cluster galaxies (BCGs) in the cores of galaxy clusters have distinctly different properties from other low redshift massive ellipticals. The majority of the BCGs in cool-core clusters show signs of active star formation. We present observations of NGC 4696, the BCG of the Centaurus galaxy cluster, at far-infrared (FIR) wavelengths with the Herschel space telescope. Using the PACS spectrometer, we detect the two strongest coolants of the interstellar medium, CII at 157.74 micron and OI at 63.18 micron, and in addition NII at 121.90 micron. The CII emission is extended over a region of 7 kpc with a similar spatial morphology and kinematics to the optical H-alpha emission. This has the profound implication that the optical hydrogen recombination line, H-alpha, the optical forbidden lines, NII 6583 Angstrom, the soft X-ray filaments and the far-infrared CII line all have the same energy source. We also detect dust emission using the PACS and SPIRE photometers at all six wavebands. We perform a detailed...

  19. Infrared Observations of Active Galaxies

    Directory of Open Access Journals (Sweden)

    J. Guichard

    2001-01-01

    Full Text Available We report medium resolution, spectroscopic observations of a selected sample of AGNs and Starburst galaxies, at wavelengths ranging from 1.1 to 2.4 microns . Strong HI, HeI, H2 and [FeII] emission lines have been detected, as well as stellar features, such as the CO bandheads in both H- and K-band, and SiI, NaI, and CaI lines. The excitation mechanisms for the H2 emission are discussed.

  20. LITHIUM IN THE UPPER CENTAURUS LUPUS AND LOWER CENTAURUS CRUX SUBGROUPS OF SCORPIUS-CENTAURUS

    Energy Technology Data Exchange (ETDEWEB)

    Bubar, Eric J. [Department of Biology and Physical Sciences, Marymount University, Arlington, VA 22207 (United States); Schaeuble, Marc; King, Jeremy R. [Department of Physics and Astronomy, Clemson University, Clemson, SC 29630-0978 (United States); Mamajek, Eric E. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627-0171 (United States); Stauffer, John R. [Spitzer Science Center, Caltech, Pasadena, CA 91125 (United States)

    2011-12-15

    We utilize spectroscopically derived model atmosphere parameters and the Li I {lambda}6104 subordinate line and the {lambda}6708 doublet to derive lithium abundances for 12 members of the Upper Centaurus Lupus and Lower Centaurus Crux subgroups of the Scorpius-Centaurus OB Association. The results indicate any intrinsic Li scatter in our 0.9-1.4 M{sub Sun} stars is limited to {approx}0.15 dex, consistent with the lack of dispersion in {>=}1.0 M{sub Sun} stars in the 100 Myr Pleiades and 30-50 Myr IC 2391 and 2602 clusters. Both ab initio uncertainty estimates and the derived abundances themselves indicate that the {lambda}6104 line yields abundances with equivalent or less scatter than is found from the {lambda}6708 doublet as a result of lower uncertainties for the subordinate feature, a result of low sensitivity to broadening in the subordinate feature. Because non-local thermodynamic equilibrium (NLTE) corrections are less susceptible to changes in surface gravity and/or metallicity for the 6104 A line, the subordinate Li feature is preferred for deriving lithium abundances in young Li-rich stellar association stars with T{sub eff} {>=} 5200 K. At these temperatures, we find no difference between the Li abundances derived from the two Li I lines. For cooler stars, having temperatures at which main-sequence dwarfs show abundance patterns indicating overexcitation and overionization, the {lambda}6104-based Li abundances are {approx}0.4 dex lower than those derived from the {lambda}6708 doublet. The trends of the abundances from each feature with T{sub eff} suggest that this difference is due to (near)UV photoionization, which in NLTE preferentially ionizes Li atoms in the subordinate 2p state relative to the 2s resonance line state due to opacity effects. Consequently, this overionization of Li in the 2p state, apparently not adequately accounted for in NLTE corrections, weakens the {lambda}6104 feature in cooler stars. Accordingly, the {lambda}6708-based

  1. A Radio Search for UHE Particles from Centaurus A

    Science.gov (United States)

    Ekers, Ron; Phillips, Chris; Reynolds, John; Protheroe, Ray; McFadden, Rebecca; James, Clancy; Roberts, Paul; Bray, Justin

    2011-04-01

    The origin of ultra-high energy (UHE) cosmic rays is a long-standing unsolved mystery in astrophysics. Recent results from the Pierre Auger Observatory hint that the radio galaxy Centaurus A is a possible source, but are limited by the fact that cosmic rays follow curved paths in magnetic fields. The detection of a UHE neutrino from Centaurus A would be definitive evidence in favour of it being a source, as the processes that accelerate cosmic rays are also expected to produce neutrinos, which travel in straight lines. Our collaboration employs the lunar Cherenkov technique for neutrino detection, in which we search for a nanosecond-scale pulse at ~GHz frequencies from the particle shower induced by a neutrino interacting in the upper layers of the Moon. The greatest difficulty in this technique is distinguishing such pulses from transient RFI. By observing simultaneously with Parkes and the ATCA, as we propose, we should be able to perfectly distinguish between a pulse from an interacting neutrino (visible to both telescopes) and a pulse from local RFI (visible to only one telescope).

  2. Watching a Cannibal Galaxy Dine

    Science.gov (United States)

    2009-11-01

    galaxy a very active one. Centaurus A is in fact one of the brightest radio sources in the sky (hence the "A" in its name). Jets of high energy particles from the centre are also observed in radio and X-ray images. The new image of Centaurus A is a wonderful example of how frontier science can be combined with aesthetic aspects. Fine images of Centaurus A have been obtained in the past with ESO's Very Large Telescope and with the Wide Field Imager on the MPG/ESO 2.2-metre telescope at La Silla. More information This research was presented in a paper in Astronomy and Astrophysics (vol. 502): "Uncovering the kiloparsec-scale stellar ring of NGC5128", by J.T. Kainulainen et al. The team is composed of J. T. Kainulainen (University of Helsinki, Finland, and MPIA, Germany), J. F. Alves (Calar Alto Observatory, Spain and University of Vienna, Austria), Y. Beletsky (ESO), J. Ascenso (Harvard-Smithsonian Center for Astrophysics, USA), J. M. Kainulainen (TKK/Department of Radio Science and Engineering, Finland), A. Amorim, J. Lima, F. D. Santos, and A. Moitinho (SIM-IDL, University of Lisbon, Portugal), R. Marques and J. Pinhão (University of Coimbra, Portugal), and J. Rebordão (INETI, Amadora, Portugal). SOFI (Son of ISAAC) is an infrared spectro-imager attached to ESO's 3.58-metre New Technology Telescope (NTT) and a simplified version of the Short Wavelength arm of ISAAC on the Very Large Telescope. ESO, the European Southern Observatory, is the foremost intergovernmental astronomy organisation in Europe and the world's most productive astronomical observatory. It is supported by 14 countries: Austria, Belgium, the Czech Republic, Denmark, France, Finland, Germany, Italy, the Netherlands, Portugal, Spain, Sweden, Switzerland and the United Kingdom. ESO carries out an ambitious programme focused on the design, construction and operation of powerful ground-based observing facilities enabling astronomers to make important scientific discoveries. ESO also plays a leading role in

  3. Fugitive stars in active galaxies

    CERN Document Server

    Zotos, Euaggelos E

    2016-01-01

    We investigate in detail the escape dynamics in an analytical gravitational model which describes the motion of stars in a quasar galaxy with a disk and a massive nucleus. We conduct a thorough numerical analysis distinguishing between regular and chaotic orbits as well as between trapped and escaping orbits, considering only unbounded motion for several energy levels. In order to distinguish safely and with certainty between ordered and chaotic motion we apply the Smaller ALingment Index (SALI) method. It is of particular interest to locate the escape basins through the openings around the collinear Lagrangian points $L_1$ and $L_2$ and relate them with the corresponding spatial distribution of the escape times of the orbits. Our exploration takes place both in the configuration $(x,y)$ and in the phase $(x,\\dot{x})$ space in order to elucidate the escape process as well as the overall orbital properties of the galactic system. Our numerical analysis reveals the strong dependence of the properties of the con...

  4. The Frequency of Active and Quiescent Galaxies with Companions

    CERN Document Server

    Schmitt, H R

    2002-01-01

    We study the percentage of active, HII and quiescent galaxies with companions in the Palomar survey. We find that when we separate the galaxies by their morphological types (ellipticals or spirals), to avoid morphology-density effects, there is no difference in the percentage of galaxies with companions among the different activity types.

  5. A Supermassive Black Hole in a Nearby Galaxy

    Science.gov (United States)

    2001-03-01

    not know, however, that this beautiful and spectacular appearance is due to an opaque dust lane that covers the central part of the galaxy. This dust is likely the remain of a cosmic merger between a giant elliptical galaxy, and a smaller spiral galaxy full of dust. Centaurus A is even more spectacular when observed with radio telescopes. It is in fact one of the brightest radio sources in the sky (its name indicates that it is the strongest radio source in the southern constellation Centaurus). At a distance of merely 11 million light-years, it is also the nearest radio galaxy. The radio emission from the very compact centre exhibits strong activity. It has for some time been suspected that this powerful energy release is due to accretion of material onto a massive black hole. The details of the centre have remained largely unknown, due to the dense dust lane that completely obscures the central part of the galaxy in optical light, cf. PR Photo 08a/01 . Observations of the dust emission in the mid-infrared spectral region were carried out with the ISOCAM camera onboard the ESA Infrared Space Observatory . They revealed a structure extending over 5 arcmin (16,500 light-years or 5 kpc), centred on the compact radio source, and very similar to that of a small barred galaxy. This bar may serve to funnel gas towards the active nucleus of the galaxy. Peering through the dust To look into the very centre of the galaxy, the observations must be carried out at wavelengths longer than those of visual light, e.g., in the infrared spectral region. This is because the dust absorbs much less the infrared radiation. Infrared observations of the innermost regions (of Centaurus A (on an arcsec scale) were recently done by a team of astronomers from Italy, UK and USA [1], by means of the multi-mode ISAAC instrument on the ESO Very Large Telescope (VLT) at Paranal Observatory. In fact, the team started their infrared studies of this galaxy already in 1997, using the NICMOS camera on

  6. RXTE monitoring of Centaurus A

    CERN Document Server

    Benlloch, S; Wilms, J; Reynolds, C S; Heindl, W A; Staubert, R

    2001-01-01

    We report on the analysis from ~110 ks of X-ray observations of Centaurus A carried out with the Proportional Counter Array (PCA) and the High Energy X-ray Timing Experiment (HEXTE) instruments on Rossi X-ray Timing Explorer (RXTE) during three monitoring campaigns over the last 4 years (10 ks in 1996, 74 ks in 1998, and 25 ks in 2000). The joint PCA/HEXTE X-ray spectrum can be well described by a heavily absorbed power law with photon index 1.8 and a narrow iron line due to fluorescence of cold matter. The measured column depth decreased by about 30% between 1996 and 2000, while the detected 2-10 keV continuum flux remained constant between 1996 and 1998, but increased by 60% in 2000. Since in all three observations the iron line flux did not vary, a corresponding decrease in equivalent width was noted. No appreciable evidence for a reflection continuum in the spectrum was detected. We present the interpretation of the iron line strength through Monte Carlo computations of various geometries. No significant ...

  7. 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...

  8. Analysis of nuclear activity of ten polar ring galaxies

    CERN Document Server

    Freitas-Lemes, P; Dors, O L; Faúndez-Abans, M

    2013-01-01

    The accumulation of mass from the interaction process that forms the polar ring galaxies is a factor that favors the conditions necessary to trigger nonthermal nuclear activities.. This fact encouraged the chemical analysis of ten polar ring galaxies. In order to verify the presence of an active nucleus in these galaxias, we built diagnostic diagrams using lines H{\\beta}, [OIII], [HI], H{\\alpha}, [NII], and [SII] and classified the type of nuclear activity. For galaxies that do not show shock, the parameters N2 and O3N2 were also determined. From this sample, we identified seven galaxies with an active nucleus and three that behave as HII regions. One galaxy with an active nucleus was classified as Seyfert. Although our data do not provide a statistically significant sample, we can speculate that polar ring galaxies are a setting conducive to trigger non-thermal nuclear activities.

  9. Consequences of a possible jet-star interaction in the inner central parsec of Centaurus A

    Science.gov (United States)

    Mueller, C.; Kadler, M.; Mannheim, K.; Perucho, M.; Ojha, R.; Ros, E.; Schulz, R.; Wilms, J.

    The jet-counterjet system of the closest radio-loud active galaxy Centaurus A (Cen A) can be studied with Very Long Baseline Interferometry (VLBI) on unprecedented small linear scales of ~0.018 pc. These high-resolution observations provide essential information on jet emission and propagation within the inner parsec of an AGN jet. We present the results of a kinematic study performed within the framework of the Southern-hemisphere AGN monitoring program TANAMI. Over 3.5 years, the evolution of the central-parsec jet structure of Cen A was monitored with VLBI. These observations reveal complex jet dynamics which are well explained by a spine-sheath structure supported by the downstream acceleration occurring where the jet becomes optically thin. Both moving and stationary jet features are tracked. A persistent local minimum in surface brightness suggests the presence of an obstacle interrupting the jet flow, which can be explained by the interaction of the jet with a star at a distance of ~0.4 pc from the central black hole. We briefly discuss possible implications of such an interaction regarding the expected neutrino and high-energy emission and the effect on a putative planet.

  10. TANAMI monitoring of Centaurus A: The complex dynamics within the inner parsec of an extragalactic jet

    CERN Document Server

    Müller, C; Ojha, R; Perucho, M; Großberger, C; Ros, E; Wilms, J; Blanchard, J; Böck, M; Carpenter, B; Dutka, M; Edwards, P G; Hase, H; Horiuchi, S; Kreikenbohm, A; Lovell, J E J; Markowitz, A; Phillips, C; Plötz, C; Pursimo, T; Quick, J; Rothschild, R; Schulz, R; Steinbring, T; Stevens, J; Trüstedt, J; Tzioumis, A K

    2014-01-01

    Centaurus A is the closest radio-loud active galaxy. Very Long Baseline Interferometry (VLBI) enables us to study the jet-counterjet system on milliarcsecond (mas) scales, providing essential information for jet emission and propagation models. We study the evolution of the central parsec jet structure of Cen A over 3.5 years. The proper motion analysis of individual jet components allows us to constrain jet formation and propagation and to test the proposed correlation of increased high energy flux with jet ejection events. Cen A is an exceptional laboratory for such detailed study as its proximity translates to unrivaled linear resolution, where 1 mas corresponds to 0.018 pc. The first 7 epochs of high-resolution TANAMI VLBI observations at 8 GHz of Cen A are presented, resolving the jet on (sub-)mas scales. They show a differential motion of the sub-pc scale jet with significantly higher component speeds further downstream where the jet becomes optically thin. We determined apparent component speeds within...

  11. Exploring active galaxies with integral field spectroscopy

    Science.gov (United States)

    Turner, James E. H.; Miller, Bryan W.; Gerssen, Joris; Allington-Smith, Jeremy R.

    2004-11-01

    Integral Field Spectroscopy provides a powerful new tool for disentangling the complex structure of Active Galactic Nuclei& -- allowing 2D mapping of the distribution, kinematics and excitation of ionized gas and of stellar velocity profiles and populations. Such comprehensive datasets are likely to reveal important clues about the physics of the narrow line region, interactions with the host galaxy and central dynamical forces. Here we present observations of the central regions of NGC1068, obtained using the visible-wavelength GMOS-IFU at Gemini North and NGC4151, taken with a prototype near-infrared fibre IFU at the UK Infrared Telescope.

  12. The role of active galactic nuclei in galaxy formation

    CERN Document Server

    Thomas, P A

    2009-01-01

    We use Monte-Carlo Markov chain techniques to constrain acceptable parameter regions for the Munich L-Galaxies semi-analytic galaxy formation model. Feedback from active galactic nuclei (AGN) is required to limit star-formation in the most massive galaxies. However, we show that the introduction of tidal stripping of dwarf galaxies as they fall into and merge with their host systems can lead to a reduction in the required degree of AGN feedback. In addition, the new model correctly reproduces both the metallicity of large galaxies and the fraction of intracluster light.

  13. HST imaging of the dusty filaments and nucleus swirl in NGC4696 at the centre of the Centaurus Cluster

    CERN Document Server

    Fabian, A C; Russell, H R; Pinto, C; Canning, R E A; Salome, P; Sanders, J S; Taylor, G B; Zweibel, E G; Conselice, C J; Combes, F; Crawford, C S; Ferland, G J; Gallagher, J S; Hatch, N A; Johnstone, R M; Reynolds, C S

    2016-01-01

    Narrow-band HST imaging has resolved the detailed internal structure of the 10 kpc diameter H alpha+[NII] emission line nebulosity in NGC4696, the central galaxy in the nearby Centaurus cluster, showing that the dusty, molecular, filaments have a width of about 60pc. Optical morphology and velocity measurements indicate that the filaments are dragged out by the bubbling action of the radio source as part of the AGN feedback cycle. Using the drag force we find that the magnetic field in the filaments is in approximate pressure equipartition with the hot gas. The filamentary nature of the cold gas continues inward, swirling around and within the Bondi accretion radius of the central black hole, revealing the magnetic nature of the gas flows in massive elliptical galaxies. HST imaging resolves the magnetic, dusty, molecular filaments at the centre of the Centaurus cluster to a swirl around and within the Bondi radius.

  14. Unveiling multiple AGN activity in galaxy mergers

    CERN Document Server

    De Rosa, A; Bogdanovic, T; Decarli, R; Heidt, J; Herrero-Illana, R; Husemann, B; Komossa, S; Kun, E; Loiseau, N; Guainazzi, M; Paragi, Z; Perez-Torres, M; Piconcelli, E; Schawinski, K; Vignali, C

    2016-01-01

    In this paper we present an overview of the MAGNA (Multiple AGN Activity) project aiming at a comprehensive study of multiple supemassive black hole systems. With the main goal to characterize the sources in merging systems at different stages of evolution, we selected a sample of objects optically classified as multiple systems on the basis of emission line diagnostics and started a massive multiband observational campaign. Here we report on the discovery of the exceptionally high AGN density compact group SDSS~J0959+1259. A multiband study suggests that strong interactions are taking place among its galaxies through tidal forces, therefore this system represents a case study for physical mechanisms that trigger nuclear activity and star formation. We also present a preliminary analysis of the multiple AGN system SDSS~J1038+3921.}

  15. A submillimetre-selected, ultraluminous, active galaxy

    CERN Document Server

    Ivison, R J; Le Borgne, J F; Blain, A W; Kneib, J P; Bézecourt, J; Kerr, T H; Davies, J K; Ivison, Rob; Smail, Ian

    1997-01-01

    We present a detailed study of SMM 02399-0136, an ultraluminous, active galaxy selected from a sub-mm survey of the distant Universe. This object is the brightest source in the fields of 4 rich, lensing clusters that we have mapped with a sensitivity better than 2 mJy/beam at 850um. We identify a compact optical counterpart with B ~ 23 and a LSB companion about 3" away. Our spectroscopy shows that components have the same redshift; z = 2.803 +/- 0.003. The narrow emission lines, FWHM ~ 1000-1500 km/s, and line ratios along with the compact morphology and high luminosity (M_B ~ -24.0) of the galaxy indicate that SMM 02399-0136 contains a rare dust-embedded, narrow-line or type-2 AGN. The source is gravitationally lensed by the foreground cluster, amplifying its apparent luminosity by a factor of 2.5. Taking the amplification into account, we estimate that SMM 02399-0136 is intrinsically 5 times more luminous than F10214+4724. Its far-IR and H-alpha luminosities and LSB radio emission all indicate an extremely ...

  16. Spherical Accretion in Nearby Weakly Active Galaxies

    CERN Document Server

    Moscibrodzka, M A

    2005-01-01

    We consider the sample of weakly active galaxies situated in 'Local Universe' collected in the paper of Pellegrini (2005) with inferred accretion efficiencies from $10^{-2}$ to $10^{-7}$. We apply a model of spherically symmetrical Bondi accretion for given parameters ($M_{BH}$,$T_{\\infty}$,$\\rho_{\\infty}$,) taken from observation. We calculate spectra emitted by the gas accreting onto its central objects using Monte Carlo method including synchrotron and bremsstrahlung photons as seed photons. We compare our results with observed nuclear X-ray luminosities $L_{X,nuc}$ (0.3-10 keV) of the sample. Model is also tested for different external medium parameters ($\\rho_{\\infty}$ and $T_{\\infty}$) and different free parameters of the model. Our model is able to explain most of the observed nuclear luminosities $L_X$ under an assumption that half of the compresion energy is transfered directly to the electrons.

  17. The Role of Host Galaxy for the Environmental Dependence of Active Nuclei in Local Galaxies

    CERN Document Server

    Davies, R I; Erwin, P; Burtscher, L; Contursi, A; Genzel, R; Janssen, A; Koss, M; Lin, M -Y; Lutz, D; Maciejewski, W; Mueller-Sanchez, F; de Xivry, G Orban; Ricci, C; Riffel, R; Riffel, R A; Rosario, D; Schartmann, M; Schnorr-Mueller, A; Shimizu, T; Sternberg, A; Sturm, E; Storchi-Bergmann, T; Tacconi, L; Veilleux, S

    2016-01-01

    We discuss the environment of local hard X-ray selected active galaxies, with reference to two independent group catalogues. We find that the fraction of these AGN in S0 host galaxies decreases strongly as a function of galaxy group size (halo mass) - which contrasts with the increasing fraction of galaxies of S0 type in denser environments. However, there is no evidence for an environmental dependence of AGN in spiral galaxies. Because most AGN are found in spiral galaxies, this dilutes the signature of environmental dependence for the population as a whole. We argue that the differing results for AGN in disk-dominated and bulge-dominated galaxies is related to the source of the gas fuelling the AGN, and so may also impact the luminosity function, duty cycle, and obscuration. We find that there is a significant difference in the luminosity function for AGN in spiral and S0 galaxies, and tentative evidence for some difference in the fraction of obscured AGN.

  18. A dark matter gravitational accretion scenario for E galaxy activity

    NARCIS (Netherlands)

    Valentijn, E. A.

    1988-01-01

    The application of gravitational accretion into massive galaxies is reviewed. A strong correlation between central radio activity, optical and X-ray luminosity over five decades in both the radio and the X-ray bands and ranging from ordinary elliptical to D and cD type galaxies is reported and the i

  19. The Rise and Fall of Galaxy Activity in Dark Matter Haloes

    OpenAIRE

    Pasquali, Anna; Bosch, Frank C. van den; Mo, H. J.; Yang, Xiaohu; Somerville, Rachel

    2008-01-01

    We use a SDSS galaxy group catalogue to study the dependence of galaxy activity on stellar mass, halo mass, and group hierarchy (centrals vs. satellites). We split our galaxy sample in star-forming galaxies, galaxies with optical AGN activity and radio sources. We find a smooth transition in halo mass as the activity of central galaxies changes from star formation to optical AGN activity to radio emission. Star-forming centrals preferentially reside in haloes with M

  20. Star formation efficiency along the radio jet in Centaurus A

    CERN Document Server

    Salomé, Quentin; Combes, Françoise; Hamer, Stephen; Heywood, Ian

    2016-01-01

    Centaurus A is the most nearby powerful AGN, widely studied at all wavelengths. Molecular gas has been found in the halo at a distance of ~20 kpc from the galaxy centre, associated with HI shells. The molecular gas lies inside some IR and UV bright star-forming filaments that have recently been observed in the direction of the radio jets. These archival data show that there is dust and very weak star formation on scales of hundreds of parsecs. On top of analysing combined archival data, we have performed searches of HCN(1-0) and HCO+(1-0) emission with ATCA at the interaction of the northern filaments and the HI shell of Cen A. Measuring the dense gas is another indicator of star formation efficiency inside the filaments. However, we only derived upper limits of 1.6x10^3 K.km/s.pc^2 at 3 sigma in the synthesised beam of 3.1". We also compared the CO masses with the SFR estimates in order to measure a star formation efficiency. Using a standard conversion factor leads to long depletion times (7 Gyr). We then c...

  1. The low-power nucleus of PKS 1246-410 in the Centaurus Cluster

    CERN Document Server

    Taylor, G B; Fabian, A C; Allen, S W

    2006-01-01

    We present Chandra, Very Large Array (VLA), and Very Long Baseline Array (VLBA) observations of the nucleus of NGC 4696, a giant elliptical in the Centaurus cluster of galaxies. Like M87 in the Virgo cluster, PKS 1246-410 in the Centaurus cluster is a nearby example of a radio galaxy in a dense cluster environment. In analyzing the new X-ray data we have found a compact X-ray feature coincident with the optical and radio core. While nuclear emission from the X-ray source is expected, its luminosity is low, <10^{40} erg/s. We estimate the Bondi accretion radius to be 30 pc and the accretion rate to be 0.01 M_sun/yr which under the canonical radiative efficiency of 10% would overproduce by 3.5 orders of magnitude the radiative luminosity. Much of this energy can be directed into the kinetic energy of the jet, which over time inflates the observed cavities seen in the thermal gas. The VLBA observations reveal a weak nucleus and a broad, one-sided jet extending over 25 parsecs in position angle -150 degrees. T...

  2. Star formation efficiency along the radio jet in Centaurus A

    Science.gov (United States)

    Salomé, Q.; Salomé, P.; Combes, F.; Hamer, S.; Heywood, I.

    2016-02-01

    NGC 5128 (also known as Centaurus A) is the most nearby powerful AGN, widely studied at all wavelengths. Molecular gas has been found in the halo at a distance of ~ 20 kpc from the galaxy center, associated with H i shells, through CO line detection at SEST (Charmandaris et al. 2000, A&A, 356, L1). The molecular gas lies inside some IR and UV bright star-forming filaments that have recently been observed in the direction of the radio jets. These archival data from GALEX (FUV) and Herschel (IR) show that there is dust and very weak star formation (a few 10-5-10-4M⊙ yr-1) on scales of hundreds of parsecs. NGC 5128 is thus a perfect target for detailed studies of the star formation processes at the interface of the jet/gas interaction. On top of analysing combined archival data, we have performed searches of HCN(1-0) and HCO+(1-0) emission with ATCA at the interaction of the northern filaments and the northern H i shell of Centaurus A. Measuring the dense gas is another indicator of star formation efficiency inside the filaments. However, we only derived upper limits L'HCN MUSE data, we estimated the metallicity spread (0.4-0.8Z⊙) in an other region of the filament, that corresponds to gas-to-dust ratios of ~200-400. Assuming the same metallicity range in the CO-detected part of the filament, the CO/H2 conversion ratio is corrected for low metallicity by a factor between 1.4 and 3.2. Such a low-metallicity correction leads to even more massive clouds with higher depletion times (16 Gyr). We finally present ALMA observations that detect 3 unresolved CO(2-1) clumps of size < 37 × 21 pc and masses around 104M⊙. The velocity width of the CO emission line is ~ 10 km s-1, leading to a rather high virial parameter. This is a hint of a turbulent gas probably powered by kinetic energy injection from the AGN jet/wind and leading to molecular gas reservoir not forming star efficiently. This work shows the importance of high resolution data analysis to bring a new light on

  3. Large scale environments of z<0.4 active galaxies

    CERN Document Server

    Lietzen, H; Nurmi, P; Liivamägi, L J; Saar, E; Tago, E; Takalo, L O; Einasto, M

    2011-01-01

    Properties of galaxies depend on their large-scale environment. As the influence of active galactic nuclei (AGN) in galaxy evolution is becoming more evident, their large scale environments may help us understand the evolutionary processes leading to activity. The effect of activity can be seen particularly by showing if different types of active galaxies are formed by similar mechanisms. Our aim is to study the supercluster-scale environments of active galaxies up to redshift 0.4. Our data includes quasars, BL Lac objects, Seyfert and radio galaxies. We use a three-dimensional low-resolution luminosity-density field constructed of a sample of luminous red galaxies in the seventh data release of the Sloan Digital Sky Survey. We calculate the average density of this field in a volume of a 3\\,$h^{-1}$Mpc sphere around each AGN for estimating the environmental density levels of different types of AGN. This analysis gives us the distribution of AGN in the global environment of superclusters, filaments, and voids....

  4. MUSE discovers perpendicular arcs in the inner filament of Centaurus A

    Science.gov (United States)

    Hamer, S.; Salomé, P.; Combes, F.; Salomé, Q.

    2015-03-01

    Context. Evidence of active galactic nuclei (AGN) interaction with the intergalactic medium is observed in some galaxies and many cool core clusters. Radio jets are suspected to dig large cavities into the surrounding gas. In most cases, very large optical filaments (several kpc) are also seen all around the central galaxy. The origin of these filaments is still not understood. Star-forming regions are sometimes observed inside the filaments and are interpreted as evidence of positive feedback (AGN-triggered star formation). Aims: Centaurus A is a very nearby galaxy with huge optical filaments aligned with the AGN radio-jet direction. Here, we searched for line ratio variations along the filaments, kinematic evidence of shock-broadend line widths, and large-scale dynamical structures. Methods: We observed a 1' × 1' region around the so-called inner filament of Cen A with the Multi Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT) during the Science Verification period. Results: (i) The brightest lines detected are the Hαλ6562.8, [NII]λ6583, [OIII]λ4959+5007 and [SII]λ6716+6731. MUSE shows that the filaments are made of clumpy structures inside a more diffuse medium aligned with the radio-jet axis. We find evidence of shocked shells surrounding the star-forming clumps from the line profiles, suggesting that the star formation is induced by shocks. The clump line ratios are best explained by a composite of shocks and star formation illuminated by a radiation cone from the AGN. (ii) We also report a previously undetected large arc-like structure: three streams running perpendicular to the main filament; they are kinematically, morphologically, and excitationally distinct. The clear difference in the excitation of the arcs and clumps suggests that the arcs are very likely located outside of the radiation cone and match the position of the filament only in projection. The three arcs are thus most consistent with neutral material swept along by a

  5. Chandra Finds Surprising Black Hole Activity In Galaxy Cluster

    Science.gov (United States)

    2002-09-01

    Scientists at the Carnegie Observatories in Pasadena, California, have uncovered six times the expected number of active, supermassive black holes in a single viewing of a cluster of galaxies, a finding that has profound implications for theories as to how old galaxies fuel the growth of their central black holes. The finding suggests that voracious, central black holes might be as common in old, red galaxies as they are in younger, blue galaxies, a surprise to many astronomers. The team made this discovery with NASA'S Chandra X-ray Observatory. They also used Carnegie's 6.5-meter Walter Baade Telescope at the Las Campanas Observatory in Chile for follow-up optical observations. "This changes our view of galaxy clusters as the retirement homes for old and quiet black holes," said Dr. Paul Martini, lead author on a paper describing the results that appears in the September 10 issue of The Astrophysical Journal Letters. "The question now is, how do these black holes produce bright X-ray sources, similar to what we see from much younger galaxies?" Typical of the black hole phenomenon, the cores of these active galaxies are luminous in X-ray radiation. Yet, they are obscured, and thus essentially undetectable in the radio, infrared and optical wavebands. "X rays can penetrate obscuring gas and dust as easily as they penetrate the soft tissue of the human body to look for broken bones," said co-author Dr. Dan Kelson. "So, with Chandra, we can peer through the dust and we have found that even ancient galaxies with 10-billion-year-old stars can have central black holes still actively pulling in copious amounts of interstellar gas. This activity has simply been hidden from us all this time. This means these galaxies aren't over the hill after all and our theories need to be revised." Scientists say that supermassive black holes -- having the mass of millions to billions of suns squeezed into a region about the size of our Solar System -- are the engines in the cores of

  6. Active galaxies can make axionic dark energy

    OpenAIRE

    Dimopoulos, Konstantinos; Cormack, Sam

    2016-01-01

    AGN jets carry helical magnetic fields, which can affect dark matter if the latter is axionic. This preliminary study shows that, in the presence of strong helical magnetic fields, the nature of the axionic condensate may change and become dark energy. Such dark energy may affect galaxy formation and galactic dynamics, so this possibility should not be ignored when considering axionic dark matter.

  7. Nuclear Activity is more prevalent in Star-Forming Galaxies

    CERN Document Server

    Rosario, D J; Lutz, D; Netzer, H; Bauer, F E; Berta, S; Magnelli, B; Popesso, P; Alexander, D; Brandt, W N; Genzel, R; Maiolino, R; Mullaney, J R; Nordon, R; Saintonge, A; Tacconi, L; Wuyts, S

    2013-01-01

    We explore the question of whether low and moderate luminosity Active Galactic Nuclei (AGNs) are preferentially found in galaxies that are undergoing a transition from active star formation to quiescence. This notion has been suggested by studies of the UV-to-optical colors of AGN hosts, which find them to be common among galaxies in the so-called "Green Valley", a region of galaxy color space believed to be composed mostly of galaxies undergoing star-formation quenching. Combining the deepest current X-ray and Herschel. PACS far-infrared (FIR) observations of the two Chandra Deep Fields (CDFs) with redshifts, stellar masses and rest-frame photometry derived from the extensive and uniform multi-wavelength data in these fields, we compare the rest-frame U-V color distributions and SFR distributions of AGNs and carefully constructed samples of inactive control galaxies. The UV-to-optical colors of AGNs are consistent with equally massive inactive galaxies at redshifts out to z~2, but we show that such colors ar...

  8. The Nuclear Activities of Nearby S0 Galaxies

    CERN Document Server

    Xiao, Mengyuan; Chen, Yanmei; Zhou, Luwenjia

    2016-01-01

    We present a study of nuclear activities in nearby S0 galaxies. After cross-matching the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) with the Third Reference Catalog of Bright Galaxies (RC3) and visually checking the SDSS images, we derive a sample of 583 S0 galaxies with the central spectrophotometric information. In order to separate nebular emission lines from the underlying stellar contribution, we fit the stellar population model to the SDSS spectra of these S0 galaxies. According to the BPT diagram, we find that $8\\%$ of S0 galaxies show central star-forming activity, while the fractions of Seyfert, Composite and LINERs are 2\\%, 8\\%, and 21.4\\%, respectively. We also find that star-forming S0s have the lowest stellar masses, over one magnitude lower than the others, and that the active S0s locate mainly in the sparse environment, while the normal S0s in the dense environment, which might suggest that the environment plays an important role in quenching star formation and/or AGN activity in S0 gal...

  9. The Lost Dwarfs of Centaurus A and the Formation of its Dark Globular Clusters

    CERN Document Server

    Bovill, Mia Sauda; Ricotti, Massimo; Taylor, Matthew A

    2016-01-01

    We present theoretical constraints for the formation of the newly discovered dark star clusters (DSCs) with high mass-to-light (M/L) ratios, from Taylor et al (2015). These compact stellar systems photometrically resemble globular clusters (GCs) but have dynamical M/L ratios of ~ 10 - 100, closer to the expectations for dwarf galaxies. The baryonic properties of the dark star clusters (DSCs) suggest their host dark matter halos likely virialized at high redshift with M > 10^8 M_sun. We use a new set of high-resolution N-body simulations of Centaurus A to determine if there is a set of z=0 subhalos whose properties are in line with these observations. While we find such a set of subhalos, when we extrapolate the dark matter density profiles into the inner 20 pc, no dark matter halo associated with Centaurus A in our simulations, at any redshift, can replicate the extremely high central mass densities of the DSCs. Among the most likely options for explaining 10^5 - 10^7 M_sun within 10 pc diameter subhalos is t...

  10. Atomic hydrogen properties of active galactic nuclei host galaxies: H I in 16 nuclei of galaxies (NUGA) sources

    International Nuclear Information System (INIS)

    We present a comprehensive spectroscopic imaging survey of the distribution and kinematics of atomic hydrogen (H I) in 16 nearby spiral galaxies hosting low luminosity active galactic nuclei (AGN), observed with high spectral and spatial resolution (resolution: ∼20'', ∼5 km s–1) using the NRAO Very Large Array (VLA). The sample contains a range of nuclear types ranging from Seyfert to star-forming nuclei, and was originally selected for the NUclei of GAlaxies project (NUGA)—a spectrally and spatially resolved interferometric survey of gas dynamics in nearby galaxies designed to identify the fueling mechanisms of AGN and the relation to host galaxy evolution. Here we investigate the relationship between the H I properties of these galaxies, their environment, their stellar distribution, and their AGN type. The large-scale H I morphology of each galaxy is classified as ringed, spiral, or centrally concentrated; comparison of the resulting morphological classification with the AGN type reveals that ring structures are significantly more common in low-ionization narrow emission-line regions (LINER) than in Seyfert host galaxies, suggesting a time evolution of the AGN activity together with the redistribution of the neutral gas. Dynamically disturbed H I disks are also more prevalent in LINER host galaxies than in Seyfert host galaxies. While several galaxies are surrounded by companions (some with associated H I emission), there is no correlation between the presence of companions and the AGN type (Seyfert/LINER).

  11. 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...... fields spanning the redshift range 0.2 z ..., both of which are also suppressed near cluster centres to a comparable extent. These results strongly support the idea that X-ray AGN activity and strong star formation are linked through their common dependence on available reservoirs of cold gas. © 2013 The Authors. Published by Oxford University...

  12. An imaging and spectroscopic study of the planetary nebulae in NGC 5128 (Centaurus A): Planetary nebulae catalogues

    OpenAIRE

    Walsh, J. R.; Rejkuba, M.; Walton, N. A.

    2015-01-01

    Imaging and spectroscopic observations of planetary nebulae (PNe) in the nearest large elliptical galaxy NGC 5128 (Centaurus A), were obtained to find more PNe and measure their radial velocities. NTT imaging was obtained in 15 fields in NGC 5128 over an area of about 1 square degree with EMMI using [O III] and off-band filters. Newly detected sources, combined with literature PNe, were used as input for VLT FLAMES multi-fibre spectroscopy in MEDUSA mode. Spectra of the 4600-5100A region were...

  13. Active galactic nucleus feedback in clusters of galaxies.

    Science.gov (United States)

    Blanton, Elizabeth L; Clarke, T E; Sarazin, Craig L; Randall, Scott W; McNamara, Brian R

    2010-04-20

    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. PMID:20351250

  14. Active galaxies may harbour wormholes if dark matter is axionic

    CERN Document Server

    Dimopoulos, Konstantinos

    2016-01-01

    AGN jets carry helical magnetic fields, which can affect dark matter if the latter is axionic. This preliminary study shows that the nature of the axionic condensate may change and instead of dark matter may behave more like exotic matter, which violates the null energy condition. If the central supermassive black hole of an active galaxy is laced with exotic matter then it may become a wormhole. In general, the presence of exotic matter may affect galaxy formation and galactic dynamics, so this possibility should not be ignored when considering axionic dark matter.

  15. 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.

  16. Properties of Active Galaxies Deduced from H I Observations

    CERN Document Server

    Ho, Luis C; Greene, Jenny E

    2008-01-01

    We completed a new survey for H I emission for a large, well-defined sample of 154 nearby (z < 0.1) galaxies with type 1 AGNs. We make use of the extensive database presented in a companion paper to perform a comprehensive appraisal of the cold gas content in active galaxies and to seek new strategies to investigate the global properties of the host galaxies and their relationship to their central black holes (BHs). We show that the BH mass obeys a strong, roughly linear relation with the host galaxy's dynamical mass. BH mass follows a looser, though still highly significant, correlation with the maximum rotation velocity of the galaxy, as expected from the known scaling between rotation velocity and central velocity dispersion. Neither of these H I-based correlations is as tight as the more familiar relations between BH mass and bulge luminosity or velocity dispersion, but they offer the advantage of being insensitive to the glare of the nucleus and therefore are promising new tools for probing the host g...

  17. CANGAROO-III Search for Gamma Rays from Centaurus A and the $\\omega$ Centauri Region

    CERN Document Server

    Kabuki, S; Bicknell, G V; Clay, R W; Edwards, P G; Gunji, S; Hara, S; Hattori, T; Hayashi, S; Higashi, Y; Inoue, R; Itoh, C; Kajino, F; Katagiri, H; Kawachi, A; Kawasaki, S; Kifune, T; Kiuchi, R; Konno, K; Kubo, H; Kushida, J; Matsubara, Y; Mizukami, T; Mizuniwa, R; Mori, M; Muraishi, H; Naito, T; Nakamori, T; Nishida, D; Nishijima, K; Ohishi, M; Sakamoto, Y; Stamatescu, V; Suzuki, S; Suzuki, T; Swaby, D L; Tanimori, T; Thornton, G; Tokanai, F; Tsuchiya, K; Watanabe, S; Yamada, Y; Yamazaki, M; Yanagita, S; Yoshida, T; Yoshikoshi, T; Yuasa, M; Yukawa, Y

    2007-01-01

    We have observed the giant radio galaxy Centaurus A and the globular cluster $\\omega$ Centauri in the TeV energy region using the CANGAROO-III stereoscopic system. The system has been in operation since 2004 withan array of four Imaging Atmospheric Cherenkov Telescopes (IACT) with $\\sim$100-m spacings. The observations were carried out in March and April 2004. In total, approximately 10 hours data were obtained for each target.No statistically significant gamma-ray signal has been found above 420 GeV over a wide angular region (a one-degree radius from thepointing center) and we derive flux upper limits using all of the field of view.Implications for the total energy of cosmic rays and the density of the cold dark matter are considered.

  18. Centaurus A: constraints on the nature of the giant lobe filaments from XMM-Newton observations

    CERN Document Server

    Wykes, Sarka; Croston, Judith H

    2015-01-01

    We report on deep XMM-Newton observations of the vertex filament in the southern giant lobe of the Fanaroff-Riley class I radio galaxy Centaurus A. We find no X-ray excess from the filament region and place a 3 sigma upper limit on the 1 keV flux density of the filament of 9.6 nJy. This directly constrains the electron density and magnetic field strength in the filament. For the first time in an individual filament, we show that the excess in synchrotron emissivity cannot be produced purely by excess electrons: the filament magnetic field strength must be higher than in the giant lobes as a whole, and close to or above the equipartition value for the filament. The filaments are not significantly overpressured with respect to the surrounding lobe with a pressure provided by relativistic electrons.

  19. Line and Continuum Variability in Active Galaxies

    CERN Document Server

    Rashed, Y E; Valencia-S., M; García-Marín, M; Busch, G; Zuther, J; Horrobin, M; Zhou, H

    2015-01-01

    We compared optical spectroscopic and photometric data for 18 AGN galaxies over 2 to 3 epochs, with time intervals of typically 5 to 10 years. We used the Multi-Object Double Spectrograph (MODS) at the Large Binocular Telescope (LBT) and compared the spectra to data taken from the SDSS database and the literature. We find variations in the forbidden oxygen lines as well as in the hydrogen recombination lines of these sources. For 4 of the sources we find that, within the calibration uncertainties, the variations in continuum and line spectra of the sources are very small. We argue that it is mainly the difference in black hole mass between the samples that is responsible for the different degree of continuum variability. In addition we find that for an otherwise constant accretion rate the total line variability (dominated by the narrow line contributions) reverberates the continuum variability with a dependency $\\Delta L_{line} \\propto (\\Delta L_{cont.})^{\\frac{3}{2}}$. Since this dependency is prominently e...

  20. QSO Pairs across Active Galaxies: Evidence of Blueshifts?

    Indian Academy of Sciences (India)

    D. Basu

    2006-12-01

    Several QSO pairs have been reported and their redshifts determined, where the two objects in each pair are located across an active galaxy. The usually accepted explanation of such occurrences is that the pair is ejected from the parent galaxy. Currently interpreted redshifted spectra for both the QSOs imply that both the objects are receding from the observer. However, ejection can occur towards and away from the observer with equal probability. We argue that for a system with two QSOs lying across the parent galaxy, ejection should have occurred in opposite directions, whereby one object will be approaching us and the other will be receding from us. The former would exhibit a blueshifted spectrum. We analyse here a sample of four such pairs and show that the observed spectrum of one QSO in each pair can be interpreted as blueshifted. The other exhibits the usual redshifted spectrum. A scenario based on the ‘sling-shot’ mechanism of ejection is presented to explain the occurrences of the pairs in opposite sides of the active galaxies moving in opposite directions.

  1. An atlas of Calcium triplet spectra of active galaxies

    CERN Document Server

    Garcia-Rissmann, A; Asari, N V; Fernandes, R C; Schmitt, H; González-Delgado, R M; Storchi-Bergmann, T

    2005-01-01

    We present a spectroscopic atlas of active galactic nuclei covering the region around the 8498, 8542, 8662 Calcium triplet (CaT) lines. The sample comprises 78 objects, divided into 43 Seyfert 2s, 26 Seyfert 1s, 3 Starburst and 6 normal galaxies. The spectra pertain to the inner ~300 pc in radius, and thus sample the central kinematics and stellar populations of active galaxies. The data are used to measure stellar velocity dispersions (sigma_star) both with cross-correlation and direct fitting methods. These measurements are found to be in good agreement with each-other and with those in previous studies for objects in common. The CaT equivalent width is also measured. We find average values and sample dispersions of W_CaT of 4.6+/-2.0, 7.0 and 7.7+/-1.0 angstrons for Seyfert 1s, Seyfert 2s and normal galaxies, respectively. We further present an atlas of [SIII]\\lambda 9069 emission line profiles for a subset of 40 galaxies. These data are analyzed in a companion paper which addresses the connection between ...

  2. Paired galaxies with different activity levels and their supernovae

    CERN Document Server

    Nazaryan, T A; Hakobyan, A A; Adibekyan, V Zh; Kunth, D; Mamon, G A; Turatto, M; Aramyan, L S

    2013-01-01

    We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The statistical study of SN hosts shows that there is no significant difference between morphologies of hosts in our sample and the larger general sample of SN hosts in the Sloan Digital Sky Survey (SDSS) Data Release 8 (DR8). The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are consistent with previous results compiled with the larger sample. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies. SN types are not correlated with the luminosity ratio of ho...

  3. 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 ...

  4. How old are the stars in the halo of NGC 5128 (Centaurus A)?

    CERN Document Server

    Rejkuba, M; Greggio, L; Harris, G L H

    2010-01-01

    NGC 5128 (Centaurus A) is, at the distance of just 3.8 Mpc, the nearest easily observable giant elliptical galaxy. Therefore it is the best target to investigate the early star formation history of an elliptical galaxy. Our aims are to establish when the oldest stars formed in NGC 5128, and whether this galaxy formed stars over a long period. We compare simulated colour-magnitude diagrams with the deep ACS/HST photometry. We find that that the observed colour-magnitude diagram can be reproduced satisfactorily only by simulations that have the bulk of the stars with ages in excess of ~10 Gyr, and that the alpha-enhanced models fit the data much better than the solar scaled ones. Data are not consistent with extended star formation over more than 3-4 Gyr. Two burst models, with 70-80% of the stars formed 12+/-1 Gyr ago and with 20-30% younger contribution with 2-4 Gyr old stars provide the best agreement with the data. The old component spans the whole metallicity range of the models (Z=0.0001-0.04), while for ...

  5. The broadband spectrum of Centaurus X-3

    Science.gov (United States)

    Gottlieb, Amy; Pottschmidt, Katja; Marcu, Diana; Wolff, Michael Thomas; Kühnel, Matthias; Falkner, Sebastian; Britton Hemphill, Paul; Suchy, Slawomir; Becker, Peter A.; Wood, Kent S.; Wilms, Joern

    2016-04-01

    We present an analysis of a Suzaku observation of the accreting pulsar and high mass X-ray binary Centaurus X-3. The observation was performed in 2008 and covers one 2.1 day binary orbit. Strong flux and hardness variability is present in the energy range from 0.8 to 60 keV. We selected a part of the observation covering ~40% of the first half of the orbit during which the spectral shape was stable and less absorbed than during other parts of the observation. We confirm earlier results that the broadband spectrum can be modeled with acutoff power law modified by a partial absorber, three iron lines -- from near-neutral, helium-like, and hydrogen-like iron --, and a cyclotron resonant scattering line at 30 keV. The pulse profile shows a shift above the cyclotron line energy which is qualitatively consistent with recent theoretical predictions. In addition we findthat the presence of the so-called ``13 keV'' bump is model dependent and that there are indications for further line-like spectral components at 1 keV and 6 keV and a broader residual around 2 keV. We also apply the newly implemented radiation dominated radiative shock model for luminous accretion pulsars by Becker and Wolff (2007, ApJ 654, 435) to model the broadband spectrum. Replacing the cutoff power law with the physical continuum while retaining all other components we obtain a similar goodness of fit as before. From the physical continuum model we determine a mass accretion rate of ~2.17 x 10^17 g/s, an accretion column radius of 65 (+12, -4) m, and a temperature of the accreted plasma of 3.1 (+0.4, -0.1) keV.

  6. A circumnuclear disk of atomic hydrogen in Centaurus A

    NARCIS (Netherlands)

    Morganti, R.; Oosterloo, T.; Struve, C.; Saripalli, L.

    2008-01-01

    We present new observations, performed with the Australia Telescope Compact Array, of the Hi absorption in the central regions of Centaurus A. For the first time, absorption is detected against the radio core at velocities blueshifted with respect to the systemic velocity. Moreover, the data show th

  7. Kinematic Interpretation of the Centaurus A Absorption-Line System

    NARCIS (Netherlands)

    Eckart, A.; Wild, W.; Ageorges, N.

    1999-01-01

    The location of the gas responsible for the absorption-line system toward the nucleus of Centaurus A is a puzzle. It is generally accepted that the line features close to the systemic velocity originate in the disk. The redshifted line features in particular, however, are usually thought to be due t

  8. The quenching of the star formation activity in cluster galaxies

    CERN Document Server

    Boselli, A; Fossati, M; Buat, V; Boissier, S; Boquien, M; Burgarella, D; Ciesla, L; Gavazzi, G; Serra, P

    2016-01-01

    We study the star formation quenching mechanism in cluster galaxies by fitting the SED of the Herschel Reference Survey, a complete volume-limited K-band-selected sample of nearby galaxies including objects in different density regions, from the core of the Virgo cluster to the general field. The SED are fitted using the CIGALE SED modelling code. The truncated activity of cluster galaxies is parametrised using a specific SFH with 2 free parameters, the quenching age QA and the quenching factor QF. These 2 parameters are crucial for the identification of the quenching mechanism which acts on long timescales if starvation while rapid and efficient if ram pressure. To be sensitive to an abrupt and recent variation of the star formation activity, we combine in a new way 20 UV to FIR photometric bands with 3 age-sensitive Balmer line absorption indices extracted from available medium-resolution integrated spectroscopy and with Halpha narrow band imaging data. The use of a truncated SFH significantly increases the...

  9. SAGACE: the Spectroscopic Active Galaxies And Clusters Explorer

    CERN Document Server

    De Bernardis, P; Bardi, A; Battistelli, E; Birkinshaw, M; Calvo, M; Colafrancesco, S; Conte, A; De Gregori, S; De Petris, M; De Zotti, G; Donati, A; Ferrari, L; Franceschini, A; Gatti, F; Gervasi, M; Giommi, P; Giordano, C; Gonzalez-Nuevo, J; Lamagna, L; Lapi, A; Luzzi, G; Maiolino, R; Marchegiani, P; Mariani, A; Masi, S; Massardi, M; Mauskopf, P; Nati, F; Nati, L; Natoli, P; Negrello, M; Piacentini, F; Polenta, G; Salatino, M; Savini, G; Schillaci, A; Spinelli, S; Tartari, A; Tavanti, M; Tortora, A; Vaccari, M; Vaccarone, R; Zannoni, M; Zolesi, V

    2010-01-01

    The SAGACE experiment consists of a mm/sub-mm telescope with a 3-m diameter primary mirror, coupled to a cryogenic multi-beam differential spectrometer. SAGACE explores the sky in the 100-760 GHz frequency range, using four diffraction-limited bolometer arrays. The instrument is designed to perform spectroscopic surveys of the Sunyaev-Zeldovich effects of thousands of galaxy clusters, of the spectral energy distribution of active galactic nuclei, and of the [CII] line of a thousand galaxies in the redshift desert. In 2008 a full phase-A study for a national small mission was completed and delivered to the Italian Space Agency (ASI). We have shown that taking advantage of the differential operation of the Fourier Transform Spectrometer, this ambitious instrument can operate from a Molniya orbit, and can be built and operated within the tight budget of a small mission.

  10. Misaligned Disks as Obscurers in Active Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Lawrence, A.; Elvis, M.; /Edinburgh U., Inst. Astron. /Harvard-Smithsonian Ctr. Astrophys.

    2010-06-02

    We review critically the evidence concerning the fraction of Active Galactic Nuclei (AGN) which appear as Type 2 AGN, carefully distinguishing strict Type 2 AGN from both more lightly reddened Type 1 AGN, and from low excitation narrow line AGN, which may represent a different mode of activity. Low excitation AGN occur predominantly at low luminosities; after removing these, true Type 2 AGN represent 58{-+}5% of all AGN, and lightly reddened Type 1 AGN a further {approx}15%. Radio, IR, and volume-limited samples all agree in showing no change of Type 2 fraction with luminosity. X-ray samples do show a change with luminosity; we discuss possible reasons for this discrepancy. We test a very simple picture which produces this Type 2 fraction with minimal assumptions. In this picture, infall from large scales occurs in random directions, but must eventually align with the inner accretion flow, producing a severely warped disk on parsec scales. If the re-alignment is dominated by tilt, with minimal twist, a wide range of covering factors is predicted in individual objects, but with an expected mean fraction of Type 2 AGN of exactly 50%. This 'tilted disc' picture predicts reasonable alignment of observed nuclear structures on average, but with distinct misalignments in individual cases. Initial case studies of the few well resolved objects show that such misalignments are indeed present.

  11. 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 $0.01galaxies have a higher overall percentage of bars (51.8%) than inactive galaxies exhibiting central star formation (37.1%). 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% of the average barred AGN fraction. Using the $L_{\\rm...

  12. High-resolution molecular line observations of active galaxies

    CERN Document Server

    García-Burillo, S; Usero, A; Gracia-Carpio, J

    2008-01-01

    The study of the content, distribution and kinematics of interstellar gas is a key to understand the origin and maintenance of both starburst and nuclear (AGN) activity in galaxies. The processes involved in AGN fueling encompass a wide range of scales, both spatial and temporal, which have to be studied. Probing the gas flow from the outer disk down to the central engine of an AGN host, requires the use of specific tracers of the interstellar medium adapted to follow the change of phase of the gas as a function of radius. Current mm-interferometers can provide a sharp view of the distribution and kinematics of molecular gas in the circumnuclear disks of galaxies through extensive CO line mapping. As such, CO maps are an essential tool to study AGN feeding mechanisms in the local universe. This is the scientific driver of the NUclei of GAlaxies (NUGA) survey, whose latest results are here reviewed. On the other hand, the use of specific molecular tracers of the dense gas phase can probe the feedback influence...

  13. 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.

  14. Actively Star Forming Elliptical Galaxies at Low Redshifts in the Sloan Digital Sky Survey

    CERN Document Server

    Fukugita, M; Turner, E L; Helmboldt, J; Nichol, R C; Fukugita, Masataka; Nakamura, Osamu; Turner, Edwin L.; Helmboldt, Joe

    2004-01-01

    We report discovery of actively star forming elliptical galaxies in a morphologically classified sample of bright galaxies at a low redshift obtained from the Sloan Digital Sky Survey. The emission lines of these galaxies do not show the characteristics of active galactic nuclei, and thus their strong H$\\alpha$ emission is ascribed to star formation with a rate nearly as high as that is seen in typical late spiral galaxies. This is taken as evidence against the traditional view that all elliptical galaxies formed early and now evolve only passively. The frequency of such star forming elliptical galaxies is a few tenths of a percent in the sample, but increases to 3% if we include active S0 galaxies. We may identify these galaxies as probable progenitors of so-called E+A galaxies that show the strong Balmer absorption feature of A stars superimposed on an old star population. The approximate match of the abundance of active elliptical plus S0 galaxies with that of E+A galaxies indicates that the duration of su...

  15. 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.

  16. STAR FORMATION ACTIVITY IN CLASH BRIGHTEST CLUSTER GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Fogarty, Kevin [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Postman, Marc [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Connor, Thomas; Donahue, Megan [Physics and Astronomy Dept., Michigan State University, East Lansing, MI 48824 (United States); Moustakas, John [Department of Physics and Astronomy, Siena College, 515 Loudon Road, Loudonville, NY 12211 (United States)

    2015-11-10

    The CLASH X-ray selected sample of 20 galaxy clusters contains 10 brightest cluster galaxies (BCGs) that exhibit significant (>5σ) extinction-corrected star formation rates (SFRs). Star formation activity is inferred from photometric estimates of UV and Hα+[N ii] emission in knots and filaments detected in CLASH Hubble Space Telescope ACS and WFC3 observations. UV-derived SFRs in these BCGs span two orders of magnitude, including two with a SFR ≳ 100 M{sub ⊙} yr{sup −1}. These measurements are supplemented with [O ii], [O iii], and Hβ fluxes measured from spectra obtained with the SOAR telescope. We confirm that photoionization from ongoing star formation powers the line emission nebulae in these BCGs, although in many BCGs there is also evidence of a LINER-like contribution to the line emission. Coupling these data with Chandra X-ray measurements, we infer that the star formation occurs exclusively in low-entropy cluster cores and exhibits a correlation with gas properties related to cooling. We also perform an in-depth study of the starburst history of the BCG in the cluster RXJ1532.9+3021, and create 2D maps of stellar properties on scales down to ∼350 pc. These maps reveal evidence for an ongoing burst occurring in elongated filaments, generally on ∼0.5–1.0 Gyr timescales, although some filaments are consistent with much younger (≲100 Myr) burst timescales and may be correlated with recent activity from the active galactic nucleus. The relationship between BCG SFRs and the surrounding intracluster medium gas properties provide new support for the process of feedback-regulated cooling in galaxy clusters and is consistent with recent theoretical predictions.

  17. The colour-magnitude relation of Globular Clusters in Centaurus and Hydra - Constraints on star cluster self-enrichment with a link to massive Milky Way GCs

    CERN Document Server

    Fensch, J; Mueller-Seidlitz, J; Hilker, M

    2014-01-01

    We investigate the colour-magnitude relation of metal-poor globular clusters, the 'blue tilt', in the Hydra and Centaurus galaxy clusters and constrain the primordial conditions for star cluster self-enrichment. We analyse U,I photometry for about 2500 globular clusters in the central regions of Hydra and Centaurus, based on FORS1@VLT data. We convert the measured colour-magnitude relations into mass-metallicity space and obtain a scaling of Z \\propto M^{0.27 \\pm 0.05} for Centaurus GCs and Z \\propto M^{0.40 \\pm 0.06} for Hydra GCs, consistent with results in other environments. We find that the GC mass-metallicity relation already sets in at present-day masses of a few 10^5 solar masses and is well established in the luminosity range of massive MW clusters like omega Centauri. We compare the mass-metallicity relation with predictions from the star cluster self-enrichment model by Bailin & Harris (2009). For this we include effects of dynamical and stellar evolution and a physically well motivated primord...

  18. Is the cluster environment quenching the Seyfert activity in elliptical and spiral galaxies?

    Science.gov (United States)

    de Souza, R. S.; Dantas, M. L. L.; Krone-Martins, A.; Cameron, E.; Coelho, P.; Hattab, M. W.; de Val-Borro, M.; Hilbe, J. M.; Elliott, J.; Hagen, A.; COIN Collaboration

    2016-09-01

    We developed a hierarchical Bayesian model (HBM) to investigate how the presence of Seyfert activity relates to their environment, herein represented by the galaxy cluster mass, M200, and the normalized cluster centric distance, r/r200. We achieved this by constructing an unbiased sample of galaxies from the Sloan Digital Sky Survey, with morphological classifications provided by the Galaxy Zoo Project. A propensity score matching approach is introduced to control the effects of confounding variables: stellar mass, galaxy colour, and star formation rate. The connection between Seyfert-activity and environmental properties in the de-biased sample is modelled within an HBM framework using the so-called logistic regression technique, suitable for the analysis of binary data (e.g. whether or not a galaxy hosts an AGN). Unlike standard ordinary least square fitting methods, our methodology naturally allows modelling the probability of Seyfert-AGN activity in galaxies on their natural scale, i.e. as a binary variable. Furthermore, we demonstrate how an HBM can incorporate information of each particular galaxy morphological type in an unified framework. In elliptical galaxies our analysis indicates a strong correlation of Seyfert-AGN activity with r/r200, and a weaker correlation with the mass of the host cluster. In spiral galaxies these trends do not appear, suggesting that the link between Seyfert activity and the properties of spiral galaxies are independent of the environment.

  19. Atomic-to-molecular gas phase transition triggered by the radio jet in Centaurus A

    CERN Document Server

    Salomé, Quentin; Combes, Françoise; Hamer, Stephen

    2016-01-01

    NGC 5128 (Centaurus A) is one of the best example to study AGN-feedback in the local Universe. At 13.5 kpc from the galaxy, optical filaments with recent star formation are lying along the radio-jet direction. We used the Atacama Pathfinder EXperiment (APEX) to map the CO(2-1) emission all along the filament structure. Molecular gas mass of 8.2x10^7 Msun was found over the 4.2 kpc-structure which represents about 3% of the total gas mass of the NGC 5128 cold gas content. Two dusty mostly molecular structure are identified, following the optical filaments. The region corresponds to the crossing of the radio jet with the Northern HI shell, coming from a past galaxy merger. One filament is located at the border of the HI shell, while the other is entirely molecular, and devoid of HI gas. The molecular mass is comparable to the HI mass in the shell, suggesting a scenario where the atomic gas was shocked and transformed in molecular clouds by the radio jet. Comparison with combined FIR Herschel and UV GALEX estima...

  20. The gas-to-dust mass ratio of Centaurus A as seen by Herschel

    CERN Document Server

    Parkin, T J; Foyle, K; Baes, M; Bendo, G J; Boselli, A; Boquien, M; Cooray, A; Cormier, D; Davies, J I; Eales, S A; Galametz, M; Gomez, H L; Lebouteiller, V; Madden, S; Mentuch, E; Page, M J; Pohlen, M; Remy, A; Roussel, H; Sauvage, M; Smith, M W L; Spinoglio, L

    2012-01-01

    We present photometry of the nearby galaxy NGC 5128 (Centaurus A) observed with the PACS and SPIRE instruments on board the Herschel Space Observatory, at 70, 160, 250, 350 and 500 {\\mu}m, as well as new CO J = 3-2 observations taken with the HARP-B instrument on the JCMT. Using a single component modified blackbody, we model the dust spectral energy distribution within the disk of the galaxy using all five Herschel wavebands, and find dust temperatures of ~30 K towards the centre of the disk and a smoothly decreasing trend to ~20 K with increasing radius. We find a total dust mass of (1.59 \\pm 0.05) \\times 10^7 M\\odot, and a total gas mass of (2.7 \\pm 0.2) \\times 10^9 M\\odot. The average gas-to-dust mass ratio is 103 \\pm 8 but we find an interesting increase in this ratio to approximately 275 toward the centre of Cen A. We discuss several possible physical processes that may be causing this effect, including dust sputtering, jet entrainment and systematic variables such as the XCO factor. Dust sputtering by ...

  1. The physical characteristics of the gas in the disk of Centaurus a using the Herschel space observatory

    Energy Technology Data Exchange (ETDEWEB)

    Parkin, T. J.; Wilson, C. D.; Schirm, M. R. P. [Department of Physics and Astronomy, McMaster University, Hamilton, Ontario, L8S 4M1 (Canada); Baes, M.; De Looze, I. [Sterrenkundig Observatorium, Universiteit Gent, Krijgslaan 281 S9, B-9000 Gent (Belgium); Boquien, M.; Boselli, A. [Laboratoire d' Astrophysique de Marseille, Université d' Aix-Marseille and CNRS, UMR7326, F-13388 Marseille Cedex 13 (France); Cormier, D. [Institut für theoretische Astrophysik, Zentrum für Astronomie der Universität Heidelberg, Albert-Ueberle Str. 2, D-69120 Heidelberg (Germany); Galametz, M. [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge, CB3 0HA (United Kingdom); Karczewski, O. Ł. [Department of Physics and Astronomy, University of Sussex, Brighton, BN1 9QH (United Kingdom); Lebouteiller, V.; Madden, S. C. [CEA, Laboratoire AIM, Université Paris VII, IRFU/Service d' Astrophysique, Bat. 709, Orme des Merisiers, F-91191 Gif-sur-Yvette (France); Roussel, H. [Institut d' Astrophysique de Paris, UMR7095 CNRS, Université Pierre and Marie Curie, 98 bis Boulevard Arago, F-75014 Paris (France); Smith, M. W. L. [School of Physics and Astronomy, Cardiff University, The Parade, Cardiff CF24 3AA (United Kingdom); Spinoglio, L., E-mail: parkintj@mcmaster.ca [Istituto di Astrofisica e Planetologia Spaziali, INAF-IAPS, Via Fosso del Cavaliere 100, I-00133 Roma (Italy)

    2014-05-20

    We search for variations in the disk of Centaurus A of the emission from atomic fine structure lines using Herschel PACS and SPIRE spectroscopy. In particular, we observe the [C II](158 μm), [N II](122 and 205 μm), [O I](63 and 145 μm), and [O III](88 μm) lines, which all play an important role in cooling the gas in photo-ionized and photodissociation regions (PDRs). We determine that the ([C II]+[O I]{sub 63})/F {sub TIR} line ratio, a proxy for the heating efficiency of the gas, shows no significant radial trend across the observed region, in contrast to observations of other nearby galaxies. We determine that 10%-20% of the observed [C II] emission originates in ionized gas. Comparison between our observations and a PDR model shows that the strength of the far-ultraviolet radiation field, G {sub 0}, varies between 10{sup 1.75} and 10{sup 2.75} and the hydrogen nucleus density varies between 10{sup 2.75} and 10{sup 3.75} cm{sup –3}, with no significant radial trend in either property. In the context of the emission line properties of the grand-design spiral galaxy M51 and the elliptical galaxy NGC 4125, the gas in Cen A appears more characteristic of that in typical disk galaxies rather than elliptical galaxies.

  2. Properties of hot gas in halos of active galaxies and clusters of galaxies

    International Nuclear Information System (INIS)

    The importance of the inverse Compton effect in the X-ray emission of cluster galaxies is discussed; the X-ray origin problem from galaxy clusters (spectra and emission mechanisms) is studied. The insufficiency of the X-ray bremsstrahlung emission model in an isothermal gas is proved. The ionized halos in narrow-line galaxies (NLG) are studied; after some general points on NLG, one NLG is described and a brief view an emission mechanism models is given; a detailed study of the galaxy IC 5063 and its nebulosity is given: the ionized gas density is calculated together with the evaporation rate for such clouds

  3. Mass entrainment and turbulence-driven acceleration of ultra-high energy cosmic rays in Centaurus A

    CERN Document Server

    Wykes, Sarka; Hardcastle, Martin J; Eilek, Jean A; Biermann, Peter L; Achterberg, Abraham; Bray, Justin D; Bicknell, Geoffrey V; Lazarian, Alex; Haverkorn, Marijke; Protheroe, Ray J; Bromberg, Omer

    2013-01-01

    Observations of the FR I radio galaxy Centaurus A in radio, X-ray and gamma-ray bands provide evidence for lepton acceleration up to several TeV and clues about hadron acceleration to tens of EeV. Synthesising the available observational constraints on the physical conditions and particle content in the jets, inner lobes and giant lobes of Centaurus A, we aim to evaluate its feasibility as an ultra-high-energy cosmic-ray source. We apply several methods of determining jet power and affirm the consistency of various power estimates of ~ 1 x 10^43 erg s^-1. Employing scaling relations based on the results of Laing & Bridle (2002), we estimate particle number densities in the jets, encompassing available radio through X-ray observations. Our model is compatible with the jets ingesting ~ 3 x 10^21 g s^-1 of matter via external entrainment from hot gas and ~ 7 x 10^22 g s^-1 via internal entrainment from jet-contained stars. This leads to an imbalance between the internal lobe pressure securable from radiating...

  4. Ultraviolet Diagnostics for the Emission Line Gas in Active Galaxies

    CERN Document Server

    Allen, M G; Tsvetanov, Z I

    1998-01-01

    Optical diagnostic diagrams are frequently ambiguous as a test of the photoionization or fast shock models of the narrow line regions of active galaxies. Here, we present a set of UV line ratio diagrams which can discriminate between pure shock and photoionization modes of excitation, and to some extent, also discriminate shocks with ionized precursors from photoionization. These diagrams use relatively bright emission lines and reddening insensitive ratios and provide a practical observational test for separating the excitation mechanisms of the narrow line regions of active galaxies. The most useful diagrams are those involving the various ionization stages of Carbon, [OIII]5007/H-beta vs. CIV 1550/ HeII 1640 and the purely UV ratio pair CII] 2326 / CIII] 1909 vs. CIV 1550 / CIII]909. Temperature sensitive FUV lines CIII 977 and NIII 991 also provide good discriminants. The models are compared to observations of nearby AGN, and also to high redshift objects where the UV lines are shifted into the optical.

  5. 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

  6. Formation, Evolution, and Revolution of Galaxies by SKA: Activities of SKA-Japan Galaxy Evolution Sub-SWG

    CERN Document Server

    Takeuchi, Tsutomu T; Iono, Daisuke; Hirashita, Hiroyuki; Tee, Wei Leong; Wang, Wei-Hao; Momose, Rieko

    2016-01-01

    Formation and evolution of galaxies have been a central driving force in the studies of galaxies and cosmology. Recent studies provided a global picture of cosmic star formation history. However, what drives the evolution of star formation activities in galaxies has long been a matter of debate. The key factor of the star formation is the transition of hydrogen from atomic to molecular state, since the star formation is associated with the molecular phase. This transition is also strongly coupled with chemical evolution, because dust grains, i.e., tiny solid particles of heavy elements, play a critical role in molecular formation. Therefore, a comprehensive understanding of neutral-molecular gas transition, star formation and chemical enrichment is necessary to clarify the galaxy formation and evolution. Here we present the activity of SKA-JP galaxy evolution sub-science working group (subSWG) Our activity is focused on three epochs: z \\sim 0, 1, and z > 3. At z \\sim 0, we try to construct a unified picture o...

  7. Is the cluster environment quenching the Seyfert activity in elliptical and spiral galaxies?

    CERN Document Server

    de Souza, R S; Krone-Martins, A; Cameron, E; Coelho, P; Hattab, M W; de Val-Borro, M; Hilbe, J M; Elliott, J; Hagen, A

    2016-01-01

    We developed a hierarchical Bayesian model (HBM) to investigate how the presence of Seyfert activity relates to their environment, herein represented by the galaxy cluster mass, $M_{200}$, and the normalized cluster centric distance, $r/r_{200}$. We achieved this by constructing an unbiased sample of galaxies from the Sloan Digital Sky Survey, with morphological classifications provided by the Galaxy Zoo Project. A propensity score matching approach is introduced to control for the effects of confounding variables: stellar mass, galaxy colour, and star formation rate. The connection between Seyfert-activity and environmental properties in the de-biased sample is modelled within a HBM framework using the so-called logistic regression technique, suitable for the analysis of binary data (e.g., whether or not a galaxy hosts an AGN). Unlike standard ordinary least square fitting methods, our methodology naturally allows modelling the probability of Seyfert-AGN activity in galaxies on their natural scale, i.e. as a...

  8. 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.

  9. The Nearest OB Association: Scorpius-Centaurus (Sco OB2)

    CERN Document Server

    Preibisch, Thomas

    2008-01-01

    We summarize observational results on the stellar population and star formation history of the Scorpius-Centaurus OB Association (Sco OB2), the nearest region of recent massive star formation. It consists of three subgroups, Upper Scorpius (US), Upper Centaurus-Lupus (UCL), and Lower Centaurus-Crux (LCC) which have ages of about 5, 17, and 16 Myr. In Upper Scorpius, numerous studies have recently revealed hundreds of low-mass association members, including dozens of brown dwarfs. The empirical mass function could be established over the full stellar mass range from 0.1 M_sun up to 20 M_sun, and was found to be consistent with recent determinations of the field initial mass function. A narrow range of ages around 5 Myr was found for the low-mass stars, the same age as had previously (and independently) been derived for the high-mass members. This supports earlier indications that the star formation process in US was triggered, and agrees with previous conjectures that the triggering event was a supernova- and ...

  10. 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.

  11. 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.

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

    International Nuclear Information System (INIS)

    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.

  13. The detailed nature of active central cluster galaxies

    CERN Document Server

    Loubser, S I

    2013-01-01

    We present detailed integral field unit (IFU) observations of the central few kiloparsecs of the ionised nebulae surrounding four active central cluster galaxies (CCGs) in cooling flow clusters (Abell 0496, 0780, 1644 and 2052). Our sample consists of CCGs with H{\\alpha} filaments, and have existing data from the X-ray regime available. Here, we present the detailed optical emission-line (and simultaneous absorption line) data over a broad wavelength range to probe the dominant ionisation processes, excitation sources, morphology and kinematics of the hot gas (as well as the morphology and kinematics of the stars). This, combined with the other multiwavelength data, will form a complete view of the different phases (hot and cold gas and stars) and how they interact in the processes of star formation and feedback detected in central galaxies in cooling flow clusters, as well as the influence of the host cluster. We derive the optical dust extinction maps of the four nebulae. We also derive a range of different...

  14. Star Formation Activity in CLASH Brightest Cluster Galaxies

    CERN Document Server

    Fogarty, Kevin; Connor, Thomas; Donahue, Megan; Moustakas, John

    2015-01-01

    The CLASH X-ray selected sample of 20 galaxy clusters contains ten brightest cluster galaxies (BCGs) that exhibit significant ($>$5 $\\sigma$) extinction-corrected star formation rates (SFRs). Star formation activity is inferred from photometric estimates of UV and H$\\alpha$+[NII] emission in knots and filaments detected in CLASH HST observations. These measurements are supplemented with [OII], [OIII], and H$\\beta$ fluxes measured from spectra obtained with the SOAR telescope. Reddening-corrected UV-derived SFRs in these BCGs are broadly consistent with H$\\alpha$-derived SFRs. Five BCGs exhibit SFRs $>$10 M$_{\\odot}$ yr$^{-1}$ and an additional two have a SFR $>$ 100 M$_{\\odot}$ yr$^{-1}$. We confirm that photoionization from ongoing star formation powers the line emission nebulae in these BCGs, although in many BCGs there is also evidence for a LINER-like contribution. Using Chandra X-ray measurements, we infer that the star formation occurs exclusively in low-entropy cluster cores and exhibits a correlation ...

  15. Hunting for Infrared Signatures of Supermassive Black Hole Activity in Dwarf Galaxies

    Science.gov (United States)

    Hainline, Kevin; Reines, Amy; Greene, Jenny; Stern, Daniel

    2016-08-01

    In order to explore the origin of the relationship between the growth of a galaxy and its central supermassive black hole, evidence must be found for black holes in galaxies at a wide range in masses. Searching for supermassive black holes in dwarf galaxies is especially important as these objects have less complicated merger histories, and they may host black holes that are similar to early proposed ``seed'' black holes. However, this selection is complicated by the fact that star formation in these dwarf galaxies can often mask the optical signatures of supermassive black hole growth and active galactic nucleus (AGN) activity in these objects. The all-sky infrared coverage offered by the Wide-field Infrared Survey Explorer (WISE) has been used to great success to select AGNs in more massive galaxies, but great care must be used when using infrared selection techniques on samples of dwarf galaxies. In particular, compact, highly star-forming dwarf galaxies can have infrared colors that may lead them to be erroneously selected as AGNs. In this talk, I will discuss recent work exploring infrared selection of AGN candidates in dwarf galaxies, and present a set of potential IR dwarf-galaxy AGN candidates. I will also outline the importance in these results with respect to future selection of AGNs in low-metallicity galaxies at high-redshift.

  16. The Ghosts of Galaxies: Tidal Debris in Clusters

    CERN Document Server

    Gregg, M D; Gregg, Michael D.; West, Michael J.

    2003-01-01

    Gravitational interactions in rich clusters can strip material from the outer parts of galaxies or even completely disrupt entire systems, giving rise to large scale, low surface brightness ghostly features stretching across intergalactic space. The nearby Coma and Centaurus clusters both have striking examples of galaxy ghosts, in the form of 100 kpc-long plumes of intergalactic debris. By searching HST archival images, we have found numerous other examples of galaxy ghosts in rich clusters at low redshift, evidence that galaxy destruction and recycling are ubiquitous, important in cluster formation and evolution, and continue to mold clusters at the present epoch. Many ghosts appear in X-ray bright clusters, perhaps signaling a connection with energetic subcluster mergers. The fate of such material has important ramifications for cluster evolution. Our new HST WFPC2 V & I images of a portion of the Centaurus plume reveal that it contains an excess of discrete objects with -12 < M_v < -6, consisten...

  17. Star Formation Activity in CLASH Brightest Cluster Galaxies

    Science.gov (United States)

    Fogarty, Kevin; Postman, Marc; Connor, Thomas; Donahue, Megan; Moustakas, John

    2015-11-01

    The CLASH X-ray selected sample of 20 galaxy clusters contains 10 brightest cluster galaxies (BCGs) that exhibit significant (>5σ) extinction-corrected star formation rates (SFRs). Star formation activity is inferred from photometric estimates of UV and Hα+[N ii] emission in knots and filaments detected in CLASH Hubble Space Telescope ACS and WFC3 observations. UV-derived SFRs in these BCGs span two orders of magnitude, including two with a SFR ≳ 100 M⊙ yr-1. These measurements are supplemented with [O ii], [O iii], and Hβ fluxes measured from spectra obtained with the SOAR telescope. We confirm that photoionization from ongoing star formation powers the line emission nebulae in these BCGs, although in many BCGs there is also evidence of a LINER-like contribution to the line emission. Coupling these data with Chandra X-ray measurements, we infer that the star formation occurs exclusively in low-entropy cluster cores and exhibits a correlation with gas properties related to cooling. We also perform an in-depth study of the starburst history of the BCG in the cluster RXJ1532.9+3021, and create 2D maps of stellar properties on scales down to ˜350 pc. These maps reveal evidence for an ongoing burst occurring in elongated filaments, generally on ˜0.5-1.0 Gyr timescales, although some filaments are consistent with much younger (≲100 Myr) burst timescales and may be correlated with recent activity from the active galactic nucleus. The relationship between BCG SFRs and the surrounding intracluster medium gas properties provide new support for the process of feedback-regulated cooling in galaxy clusters and is consistent with recent theoretical predictions. Based on observations obtained at the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação (MCTI) da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory (NOAO), the University of North Carolina at Chapel

  18. The Rise and Fall of Galaxy Activity in Dark Matter Haloes

    CERN Document Server

    Pasquali, Anna; Mo, H J; Yang, Xiaohu; Somerville, Rachel

    2008-01-01

    We use a SDSS galaxy group catalogue to study the dependence of galaxy activity on stellar mass, halo mass, and group hierarchy (centrals vs. satellites). We split our galaxy sample in star-forming galaxies, galaxies with optical AGN activity and radio sources. We find a smooth transition in halo mass as the activity of central galaxies changes from star formation to optical AGN activity to radio emission. Star-forming centrals preferentially reside in haloes with M<10^{12} Msun, central galaxies with optical-AGN activity typically inhabit haloes with M \\sim 10^{13} Msun, and centrals emitting in the radio mainly reside in haloes more massive than 10^{14} Msun. Although this seems to suggest that the environment (halo mass) determines the type of activity of its central galaxy, we find a similar trend with stellar mass: central star formers typically have stellar masses below 10^{10} Msun, while optical-AGN hosts and central radio sources have characteristic stellar masses of 10^{10.8} Msun and 10^{11.6} M...

  19. Reverberation Mapping of Optical Emission Lines in Five Active Galaxies

    CERN Document Server

    Fausnaugh, M M; Bentz, M C; Denney, K D; De Rosa, G; Peterson, B M; Kochanek, C S; Pogge, R W; Adams, S M; Barth, A J; Beatty, Thomas G; Bhattacharjee, A; Borman, G A; Boroson, T A; Bottorff, M C; Brown, Jacob E; Brown, Jonathan S; Brotherton, M S; Coker, C T; Crawford, S M; Croxall, K V; Eftekharzadeh, Sarah; Eracleous, Michael; Joner, M D; Henderson, C B; Holoien, T W -S; Horne, Keith; Hutchison, T; Kaspi, Shai; Kim, S; King, Anthea L; Li, Miao; Lochhaas, Cassandra; Ma, Zhiyuan; MacInnis, F; Manne-Nicholas, E R; Mason, M; Montuori, Carmen; Mosquera, Ana; Mudd, Dale; Musso, R; Nazarov, S V; Nguyen, M L; Okhmat, D N; Onken, Christopher A; Ou-Yang, B; Pancoast, A; Pei, L; Penny, Matthew T; Poleski, Radoslaw; Rafter, Stephen; Romero-Colmenero, E; Runnoe, Jessie; Sand, David J; Schimoia, Jaderson S; Sergeev, S G; Shappee, B J; Simonian, Gregory V; Somers, Garrett; Spencer, M; Starkey, D; Stevens, Daniel J; Tayar, Jamie; Treu, T; Valenti, Stefano; Van Saders, J; Villanueva, S; Villforth, C; Weiss, Yaniv; Winkler, H; Zhu, W

    2016-01-01

    We present the first results from an optical reverberation mapping campaign executed in 2014, targeting the active galactic nuclei (AGN) MCG+08-11-011, NGC 2617, NGC 4051, 3C 382, and Mrk 374. Our targets have diverse and interesting observational properties, including a "changing look" AGN and a broad-line radio galaxy. Based on continuum-H$\\beta$ lags, we measure black hole masses for all five targets. We also obtain H$\\gamma$ and He{\\sc ii}\\,$\\lambda 4686$ lags for all objects except 3C 382. The He{\\sc ii}\\,$\\lambda 4686$ lags indicate radial stratification of the BLR, and the masses derived from different emission lines are in general agreement. The relative responsivities of these lines are also in qualitative agreement with photoionization models. These spectra have extremely high signal-to-noise ratios (100--300 per pixel) and there are excellent prospects for obtaining velocity-resolved reverberation signatures.

  20. The Evolution of Galaxies (via SF activity and gas content) versus Environment

    Science.gov (United States)

    Cybulski, Ryan; Yun, Min Su

    2016-01-01

    My dissertation work concerns the accurate mapping of the large-scale structure (LSS), traced by galaxies, and the assessment of the dependence of fundamental galaxy properties (e.g. star-formation activity, color, and gas content) on their environment. Mapping of the LSS is done with two complementary techniques, and together they provide both a local measure of the density field and a more global characterization of the environment of a galaxy, thereby allowing for a more complete measure of a galaxy's environment. I have applied this LSS mapping technique to the entire Sloan Digital Sky Survey (SDSS) spectroscopic galaxy sample at zdivided into multiple redshift bins, to explore the environmental dependence on galaxy evolution over a significant volume and a large dynamic range of environments. I will also present a more focused study looking at the molecular gas content of galaxies in two clusters at z~0.2, based on a program I am leading with the Large Millimeter Telescope that has obtained CO spectroscopy for ~70 galaxies with a range of stellar masses, atomic gas masses, and different parts of projected phase space around the two clusters. This molecular gas study provides a detailed statistical look at how the molecular and atomic gas contents of galaxies are affected by the environmental processes in their host clusters. I will summarize all of my results in these various aspects of my dissertation, with the overall theme of how galaxies are affected by their environment.

  1. Comparative Studies of Clustering Properties Between Active Galactic Nucleus (AGN) Host Galaxies and Star-Forming Ones

    International Nuclear Information System (INIS)

    Using the volume-limited Main galaxy sample of the Sloan Digital Sky Survey Data Release 6 (SDSS DR6), we have explored the difference of clustering properties between Active Galactic Nucleus (AGN) host galaxies and star-forming galaxies. Our results preferentially show that AGN host galaxies have a lower fraction in isolated, close double and multiple systems than star-forming galaxies. (authors)

  2. Class I methanol megamasers: a potential probe of starburst activity and feedback in active galaxies

    Science.gov (United States)

    Chen, X.; Ellingsen, S. P.; Zhang, J.-S.; Wang, J.-Z.; Shen, Z.-Q.; Wu, Q.-W.; Wu, Z.-Z.

    2016-06-01

    Previous observations have shown that the distribution of 36.2-GHz class I methanol megamaser (MM) emission in Arp 220 is highly correlated with the diffuse X-rays. On this basis it was suggested that methanol MM may be produced either by the effects of galactic-outflow-driven shocks and/or cosmic rays. Here we report the results of a single-dish survey undertaken with the Greenbank Telescope (GBT) to improve our understanding of the pumping conditions of extragalactic class I methanol masers and their relationship to starburst and feedback processes within the host galaxies, towards a sample which includes 16 galaxies which show both extended soft X-ray emission, and either OH or H2O MM emission. Large baseline ripples in the GBT spectra limited our results to tentative detections towards 11 of the target galaxies. Analysis of these tentative detections shows that there are significant correlations between the methanol intensity and the host-galaxy infrared, radio and OH MM emission, but no correlation with the X-ray and H2O MM emission. Some sources show methanol emission significantly offset from the systemic velocity of the galaxy (by up to 1000 km s-1) and we propose that these are associated with galactic-scale outflows from active galactic nuclei (AGNs) feedback. The combined observational properties suggest that class I methanol MMs are related to significant starburst and molecular outflow activity and hence may provide a potential probe of AGN feedback and starburst processes in the host galaxies.

  3. Nuclear activity in galaxy pairs: a spectroscopic analysis of 48 UZC-BGPs

    CERN Document Server

    Focardi, Paola; Marinoni, Silvia

    2008-01-01

    Galaxy pairs are ideal sites in which to investigate the role of interaction on nuclear activity. For this reason we have undertaken a spectroscopic survey of a large homogeneous sample of galaxy pairs (UZC-BGP) and we present the results of the nuclear spectral classification of 48 pairs (more than half of the whole sample). The fraction of emission line galaxies is extremely large, especially among spirals (84 % and 95 %, for early and late spirals respectively). SB is the most frequent type of nuclear activity encountered (30 % of galaxies) while AGNs are only 19%. The fractions raise to 45 % and 22 % when considering only spirals. Late spirals are characterized by both an unusual increase (35 %) of AGN activity and high luminosity (44 % have M_B <-20.0 + 5log h). LLAGNs are only 8% of the total number of galaxies, but this activity could be present in another 10 % of the galaxies (LLAGN candidates). Absorption line galaxies reside mostly (61 %) in S0 galaxies and display the lowest B luminosity in the ...

  4. The Northern Middle Lobe of Centaurus A: Circumgalactic Gas in a Starburst Wind

    Science.gov (United States)

    Neff, S. G.; Eilek, J. A.; Owen, F. N.; Schiminovich, D.; Seibert, M.; Thilker, D.

    2012-01-01

    We present deep ultraviolet (GALEX), radio continuum (VLA) and H-alpha (Magellan) images of the circumgalactic medium around Centaurus A (NGC5128). We focus on the Northern Middle Lobe (NML), a region extending more than 50kpc beyond the galaxy and known to host a collection of striking phenomena: emission line filaments, recent star formation, disrupted HI/molecular gas streams, and short-lived X-ray clouds. Far UV emission is tightly correlated with H-alpha emission for more than 50kpc, and loosely associated with a filament of X-ray clouds and with the radio continuum emission. The radio emission in the NML region does not appear to be an extension of the inner radio jet (10kpc) or a typical radio lobe. We speculate that the "weather" seen in the NML region is a short-lived phenomenon, caused by an outflow encountering cool gas deposited by one of the recent merger/encounter events which have characterized the history of NGC5128.

  5. The Survey of Centaurus A's Baryonic Structures (SCABS). I. Survey Description and Initial Source Catalogues

    CERN Document Server

    Taylor, Matthew A; Puzia, Thomas H; Mieske, Steffen; Eigenthaler, Paul; Bovill, Mia Sauda

    2016-01-01

    We present new, wide-field, optical ($u'g'r'i'z'$) Dark Energy Camera observations covering $\\sim21\\,{\\rm deg}^2$ centred on the nearby giant elliptical galaxy NGC5128 called "The Survey of Centaurus A's Baryonic Structures" (SCABS). The data reduction and analysis procedures are described including initial source detection, photometric and astrometric calibration, image stacking, and point-spread function modelling. We estimate 50 and 90 percent, field-dependent, point-source completeness limits of at least $u'=24.08$ and $23.62$ mag (AB), $g'=22.67$ and $22.27$ mag, $r'=22.46$ and $22.00$ mag, $i'=22.05$ and $21.63$ mag, and $z'=21.71$ and $21.34$ mag. Deeper imaging in the $u'$-, $i'$- and $z'$-bands provide the fainter limits for the inner $\\sim3\\,{\\rm deg}^2$ of the survey, and we find very stable photometric sensitivity across the entire field of view. Source catalogues are released in all filters including spatial, photometric, and morphological information for a total of $\\sim5\\times10^5-1.5\\times10^6...

  6. Discovery of a sub-parsec radio counterjet in the nucleus of Centaurus A

    CERN Document Server

    Jones, D L; Murphy, D W; Meier, D L; Jauncey, D L; Reynolds, J E; Tzioumis, A K; Preston, R A; McCulloch, P M; Costa, M E; Kemball, A J; Nicolson, G D; Quick, J F H; King, E A; Lovell, J E J; Clay, R W; Ferris, R H; Gough, R G; Sinclair, M W; Ellingsen, S P; Edwards, P G; Jones, P A; Van Ommen, T D; Harbison, P; Migenes, V

    1996-01-01

    A sub-parsec scale radio counterjet has been detected in the nucleus of the closest radio galaxy, Centaurus A (NGC 5128), with VLBI imaging at 2.3 and 8.4 GHz. This is one of the first detections of a VLBI counterjet and provides new constraints on the kinematics of the radio jets emerging from the nucleus of Cen A. A bright, compact core is seen at 8.4 GHz, along with a jet extending along P.A. 51 degrees. The core is completely absorbed at 2.3 GHz. Our images show a much wider gap between the base of the main jet and the counterjet at 2.3 GHz than at 8.4 GHz and also that the core has an extraordinarily inverted spectrum. These observations provide evidence that the innermost 0.4-0.8 pc of the source is seen through a disk or torus of ionized gas which is opaque at low frequencies due to free-free absorption.

  7. Disentangling the circumnuclear environs of Centaurus A: II. On the nature of the broad absorption line

    CERN Document Server

    Espada, D; Matsushita, S; Sakamoto, K; Henkel, C; Iono, D; Israel, F P; Muller, S; Petitpas, G; Pihlstroem, Y; Taylor, G B; Trung, D V

    2010-01-01

    We report on atomic gas (HI) and molecular gas (as traced by CO(2-1)) redshifted absorption features toward the nuclear regions of the closest powerful radio galaxy, Centaurus A (NGC 5128). Our HI observations using the Very Long Baseline Array allow us to discern with unprecedented sub-parsec resolution HI absorption profiles toward different positions along the 21 cm continuum jet emission in the inner 0."3 (or 5.4 pc). In addition, our CO(2-1) data obtained with the Submillimeter Array probe the bulk of the absorbing molecular gas with little contamination by emission, not possible with previous CO single-dish observations. We shed light with these data on the physical properties of the gas in the line of sight, emphasizing the still open debate about the nature of the gas that produces the broad absorption line (~55 km/s). First, the broad H I line is more prominent toward the central and brightest 21 cm continuum component than toward a region along the jet at a distance ~ 20 mas (or 0.4 pc) further from...

  8. Hα and [SII] Emission from Warm Ionized Gas in the Scutum-Centaurus Arm

    Science.gov (United States)

    Hill, Alex S.; Benjamin, Robert A.; Haffner, L. Matthew; Gostisha, Martin C.; Barger, Kathleen A.

    2014-06-01

    We present Wisconsin H-Alpha Mapper [SII] λ6716 and Hα spectroscopic maps of the warm ionized medium (WIM) in the Scutum-Centaurus Arm at Galactic longitudes 310° extinction-corrected Hα intensities (I_{{H} \\alpha }^c), we measure an exponential scale height of electron density squared in the arm of H_{n_e^2}= 0.30 \\, {kpc} (assuming a distance of 3.5 kpc), intermediate between that observed in the inner Galaxy and in the Perseus Arm. The [S II]/Hα line ratio is enhanced at large |z| and in sightlines with faint I_{{H} \\alpha }^c. We find that the [S II]/Hα line ratio has a power-law relationship with I_{{H} \\alpha }^c from a value of ≈1.0 at I_{{H} \\alpha }^creinforce the well-established picture in which the diffuse Hα emission is due primarily to emission from in situ photoionized gas, with scattered light only a minor contributor.

  9. Twelve and a Half Years of Observations of Centaurus A with RXTE

    CERN Document Server

    Rothschild, Richard E; Rivers, Elizabeth; Suchy, Slawomir; Pottschmidt, Katja; Kadler, Matthias; Mueller, Cornelia; Wilms, Joern

    2011-01-01

    The Rossi X-ray Timing Explorer has observed the nearest radio galaxy, Centaurus A, in 13 intervals from 1966 August to 2009 February over the 3--200 keV band. Spectra accumulated over the 13 intervals were well described with an absorbed power law and iron line. Cut-off power laws and Compton reflection from cold matter did not provide a better description. For the 2009 January observation, we set a lower limit on the cut-off energy at over 2 MeV. The power spectral density function was generated from RXTE/ASM and PCA data, as well as an XMM-Newton long look, and clear evidence for a break at 18+10-7 days (68% conf.) was seen. Given Cen A's high black hole mass and very low value of Lx/LEdd, the break was a factor of 17+/-9 times higher than the break frequency predicted by the McHardy and co-workers' relation, which was empirically derived for a sample of objects, which are radio-quiet and accreting at relatively high values of Lbol/LEdd. We have interpreted our observations in the context of a clumpy molec...

  10. X-ray emission from spiral galaxies with normal and low-activity nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Giuricin, G. (Trieste Univ. (Italy). Dip. di Astronomia); Bertotti, G. (Centre for Advanced Research in Space Optics, Trieste (Italy)); Mardirossian, F.; Mezzetti, M. (Trieste Univ. (Italy). Dip. di Astronomia Centro Interuniversitario Regionale per l' Astrofisica e la Cosmologia (CIRAC), Trieste (Italy))

    1991-05-15

    A statistical analysis of the soft X-ray emission from spiral galaxies with normal and low-luminosity active nuclei (LINERs and Seyfert 2) - derived from published observations obtained with the Einstein Observatory - has revealed a number of previously unrecognised characteristics of the X-ray emission. Seyfert 2 galaxies (the least powerful X-ray sources of the Seyfert class) turn out to be, on average, stronger X-ray emitters (per unit light) than non-Seyfert galaxies, whereas galaxies with LINER nuclei and H II-region-like nuclei exhibit X-ray emissions of comparable strength. We have verified that the X-ray luminosity (per unit light) is linked to the total H {alpha} emission-line strength. Remarkably, more enhanced X-ray emission (per unit light) has been found in Arp atlas galaxies, in galaxies included in the Atlas and Catalogue of Interacting Galaxies of Vorontsov-Vel'yaminov, and in interacting galaxies compared to normal galaxies. (Author).

  11. Metallicity evolution in mergers of disk galaxies with black holes

    Science.gov (United States)

    Rantala, Antti; Johansson, Peter H.

    2016-10-01

    We use the TreeSPH simulation code Gadget-3 including a recently improved smoothed particle hydrodynamics (SPH) module, a detailed metallicity evolution model and sophisticated subresolution feedback models for supernovae and supermassive black holes in order to study the metallicity evolution in disk galaxy mergers. In addition, we examine the simulated morphology, star formation histories, metallicity gradients and kinematic properties of merging galaxies and merger remnants. We will compare our simulation results with observations of the early-type Centaurus A galaxy and the currently colliding Antennae galaxies.

  12. First detection of cold dust in the northern shell of NGC 5128 (Centaurus A)

    Science.gov (United States)

    Stickel, M.; van der Hulst, J. M.; van Gorkom, J. H.; Schiminovich, D.; Carilli, C. L.

    2004-02-01

    Deep far-infrared (FIR) imaging data obtained with ISOPHOT at 90 μm, 150 μm, and 200 μm detected the thermal emission from cold dust in the northern shell region of NGC 5128 (Centaurus A), where previously neutral hydrogen and molecular gas has been found. A somewhat extended FIR emission region is present in both the 150 μm and 200 μm map, while only an upper flux limit could be derived from the 90 μm data. The FIR spectral energy distribution can be reconciled with a modified blackbody spectrum with very cold dust color temperatures and emissivity indices in the range 13 K β > 1, respectively, where the data favor the low temperature end. A representative value for the associated dust mass is MDust ≈ 7×104 M⊙, which together with the HI gas mass gives a gas-to-dust ratio of ≈300, close the average values of normal inactive spiral galaxies. This value, in conjunction with the atomic to molecular gas mass ratio typical for a spiral galaxy, indicates that the interstellar medium (ISM) from the inner part of a captured disk galaxy is likely the origin of the outlying gas and dust. These observations are in agreement with recent theoretical considerations that in galaxy interactions leading to stellar shell structures the less dissipative clumpy component of the ISM from the captured galaxy can lead to gaseous shells. Alternatively, the outlying gas and dust could be a rotating ring structure resulting from an interaction or even late infall of tidal material of a merger in the distant past. With all three components (atomic gas, molecular gas, dust) of the ISM present in the northern shell region, local star formation may account for the chains of young blue stars surrounding the region to the east and north. The dust cloud may also be involved in the disruption of the large scale radio jet before entering the brighter region of the northern radio lobe. Based on observations with ISO, an ESA project with instruments funded by ESA Member States

  13. Galaxy gas as obscurer: II. Separating the galaxy-scale and nuclear obscurers of Active Galactic Nuclei

    CERN Document Server

    Buchner, Johannes

    2016-01-01

    The "torus" obscurer of Active Galactic Nuclei (AGN) is poorly understood in terms of its density, substructure and physical mechanisms. Large X-ray surveys provide model boundary constraints, for both Compton-thin and Compton-thick levels of obscuration, as obscured fractions are mean covering factors $f_{\\text{cov}}$. However, a major remaining uncertainty is host galaxy obscuration. In Paper I we discovered a relation of $N_H \\propto M_{\\star}^{1/3}$ for the obscuration of galaxy-scale gas. Here we apply this observational relation to the AGN population, and find that galaxy-scale gas is responsible for a luminosity-independent fraction of Compton-thin AGN, but does not produce Compton-thick columns. With the host galaxy obscuration understood, we present a model of the remaining, nuclear obscurer which is consistent with a range of observations. Our radiation-lifted torus model consists of a Compton-thick component ($f_{\\text{cov}}\\sim35\\%$) and a Compton-thin component ($f_{\\text{cov}}\\sim40\\%$), which d...

  14. Embedded star formation in the extended narrow line region of Centaurus A: Extreme mixing observed by MUSE

    Science.gov (United States)

    Santoro, F.; Oonk, J. B. R.; Morganti, R.; Oosterloo, T. A.; Tadhunter, C.

    2016-05-01

    We present a detailed study of the complex ionization structure in a small (~250 pc) extended narrow line region (ENLR) cloud near Centaurus A using the Multi Unit Spectroscopic Explorer. This cloud is located in the so-called outer filament of ionized gas (about 15 kpc from the nucleus) where jet-induced star formation has been suggested to occur by different studies. We find that, despite the small size, a mixture of ionization mechanisms is operating, resulting in considerable complexity in the spatial ionization structure. The area includes two H ii regions where star formation is occurring and another location where star formation must have ceased very recently. Interestingly, the extreme Balmer decrement of one of the star forming regions (Hα/Hβobs ~ 6) indicates that it is still heavily embedded in its natal cocoon of gas and dust. At all three locations a continuum counterpart is found with spectra matching those of O/B stars local to Centaurus A. The H ii regions are embedded in a larger gas complex which is photoionized by the radiation of the central active galactic nucleus (AGN), but the O/B stars affect the spatial ionization pattern in the ENLR cloud very locally. In particular, in the surroundings of the youngest star forming region, we can isolate a tight mixing sequence in the diagnostic diagram going from gas with ionization due to a pure stellar continuum to gas only photoionized by the AGN. These results emphasize the complexity and the mixture of processes occurring in star forming regions under the influence of an AGN radiation. This is relevant for our understanding of AGN-induced star formation suggested to occur in a number of objects, including this region of Centaurus A. They also illustrate that these young stars influence the gas over only a limited region.

  15. The Search for signals of technological activities in the galaxy

    CERN Document Server

    Lemarchand, Guillermo A

    2010-01-01

    In this article an analysis of the fundamentals used to search for extraterrestrial artificial signals in the galaxy, which have been developing for more than five decades, is presented. It is shown that the key factor for the success of these research projects is given by the technological civilizations lifetimes. Assuming the Principle of Mediocrity, estimations are made to determine the minimum number of civilizations that may co-exist in the galaxy and the probability of detecting a signal from them.

  16. The Search for signals of technological activities in the galaxy

    OpenAIRE

    Lemarchand, Guillermo A.

    2010-01-01

    In this article an analysis of the fundamentals used to search for extraterrestrial artificial signals in the galaxy, which have been developing for more than five decades, is presented. It is shown that the key factor for the success of these research projects is given by the technological civilizations lifetimes. Assuming the Principle of Mediocrity, estimations are made to determine the minimum number of civilizations that may co-exist in the galaxy and the probability of detecting a signa...

  17. 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...

  18. MAXI and GLAST Studies of Jets in Active Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Madejski, Greg; Kataoka, Jun; Sikora, Marek

    2008-10-13

    The recent launch of GLAST--coinciding with the MAXI workshop--opens a new era for studies of jet-dominated active galaxies, known as blazars. While the emission processes operating in various spectral bands in blazars are reasonably well understood, the knowledge of the details of the structure of the jet, location of the dissipation region with respect to the accreting black hole, and coupling of the jet to the accretion process are known only at a rudimentary level. Blazars are variable, and this provides an opportunity to use the variability in various bands--and in particular, the relationship of respective time series to each other--to explore the relative location of regions responsible for emission in the respective bands. Observationally, this requires well-sampled time series in as many spectral bands as possible. To this end, with its all-sky, sensitive monitoring capability, the recently launched GLAST, and MAXI, to be deployed in 2009, are the most promising instruments bound to provide good sampling in respectively the energetic gamma-ray, and the soft X-ray band. This paper highlights the inferences regarding blazar jets that can be gleaned from such joint observations.

  19. On the behaviour of the IR Ca II triplet in normal and active galaxies

    International Nuclear Information System (INIS)

    Ca II triplet in absorption at λλ8498,8542,8662 A is the strongest feature in the infrared spectrum of late-type stars and normal galaxies. Its strength has been found to be a good luminosity indicator for metal-rich stellar populations. We present high signal-to-noise near-IR spectroscopic data for the nuclear region of 42 normal and active galaxies. We have explored the behaviour of the Ca II triplet strength and found that it shows a small spread around a mean value of 7 A for our sample of normal galaxies. We also found that, in all the Seyfert type 2 galaxies measured and even in some Seyfert type 1, while the optical stellar features show substantial dilution, the strength of the IR Ca II triplet is equal to and in some cases larger than that in normal elliptical galaxies. (author)

  20. An Infrared Examination of Young Stars in Upper Centaurus Lupus

    Science.gov (United States)

    Johnson, Chelen H.; Linahan, M.; Barge, J.; Rebull, L. M.; Aranda, D.; Canlas, N. G.; Donahoe, K. E.; Ernst, M. K.; Ford, S.; Fox, M. E.; Gutierrez, E.; Haecker, L. W.; Hibbs, C. A.; Maddaus, M. R.; Martin, T. A.; Ng, E.; Niedbalec, A. P.; O'Bryan, S. E.; Searls, E. F.; Zeidner, A. B.; Zegeye, D.

    2014-01-01

    Optical studies of the Upper Centaurus Lupus (UCL) region of the Scorpius-Centaurus (Sco-Cen) complex have found many young stellar objects. The nearby G/K/M Sco-Cen members have been estimated to be much younger 10 Myr) than similar star associations (Song, et al 2012). We have assembled infrared data for the objects thought to be members of UCL by mining various archives including the 2-Micron All-Sky Survey (2MASS), the Spitzer Heritage Archive (SHA), specifically the Spitzer Enhanced Imaging Products Source List, and the Wide-field Infrared Survey Explorer (WISE) all-sky source catalog. We created spectral energy distributions (SEDs) and color-magnitude diagrams (CMDs) with multiple wavelengths to identify infrared excesses and determine what fraction of these stars have circumstellar disks. Students from three high schools collaborated on this project, which is a follow-up project made possible through the NASA/IPAC Teacher Archive Research Project (NITARP; http://nitarp.ipac.caltech.edu).

  1. Centaurus X-3 A Source of High Energy $\\gamma$ Rays

    CERN Document Server

    Chadwick, P M; Dipper, N A; Kendall, T R; McComb, T J L; Orford, K J; Osborne, J L; Rayner, S M; Roberts, I D; Shaw, S E; Turver, K E

    1998-01-01

    Centaurus X-3 is a well-studied high-mass accreting X-ray binary and a variable source of high energy gamma rays with energies from 100 MeV to 1 TeV. Previous results have suggested that the origin of the gamma rays is not the immediate vicinity of the neutron star but is sited in the accretion disc, perhaps in an accretion wake. The Durham Mark 6 gamma ray telescope has been used to measure the gamma ray flux from Centaurus X-3 with much higher sensitivity than previous ground-based measurements. The flux above ~ 400 GeV was measured to be (2 +/- 0.3) x 10^-11 cm^-2 s^-1 and appears constant over a period of 2 - 3 months. In 10 hours of observations there is no evidence for periodicity in the detected gamma rays at the X-ray spin period either from a site in the region of the neutron star, or from any other potential site in the orbit.

  2. An actively accreting massive black hole in the dwarf starburst galaxy Henize 2-10.

    Science.gov (United States)

    Reines, Amy E; Sivakoff, Gregory R; Johnson, Kelsey E; Brogan, Crystal L

    2011-02-01

    Supermassive black holes are now thought to lie at the heart of every giant galaxy with a spheroidal component, including our own Milky Way. The birth and growth of the first 'seed' black holes in the earlier Universe, however, is observationally unconstrained and we are only beginning to piece together a scenario for their subsequent evolution. Here we report that the nearby dwarf starburst galaxy Henize 2-10 (refs 5 and 6) contains a compact radio source at the dynamical centre of the galaxy that is spatially coincident with a hard X-ray source. From these observations, we conclude that Henize 2-10 harbours an actively accreting central black hole with a mass of approximately one million solar masses. This nearby dwarf galaxy, simultaneously hosting a massive black hole and an extreme burst of star formation, is analogous in many ways to galaxies in the infant Universe during the early stages of black-hole growth and galaxy mass assembly. Our results confirm that nearby star-forming dwarf galaxies can indeed form massive black holes, and that by implication so can their primordial counterparts. Moreover, the lack of a substantial spheroidal component in Henize 2-10 indicates that supermassive black-hole growth may precede the build-up of galaxy spheroids. PMID:21217688

  3. An actively accreting massive black hole in the dwarf starburst galaxy Henize 2-10.

    Science.gov (United States)

    Reines, Amy E; Sivakoff, Gregory R; Johnson, Kelsey E; Brogan, Crystal L

    2011-02-01

    Supermassive black holes are now thought to lie at the heart of every giant galaxy with a spheroidal component, including our own Milky Way. The birth and growth of the first 'seed' black holes in the earlier Universe, however, is observationally unconstrained and we are only beginning to piece together a scenario for their subsequent evolution. Here we report that the nearby dwarf starburst galaxy Henize 2-10 (refs 5 and 6) contains a compact radio source at the dynamical centre of the galaxy that is spatially coincident with a hard X-ray source. From these observations, we conclude that Henize 2-10 harbours an actively accreting central black hole with a mass of approximately one million solar masses. This nearby dwarf galaxy, simultaneously hosting a massive black hole and an extreme burst of star formation, is analogous in many ways to galaxies in the infant Universe during the early stages of black-hole growth and galaxy mass assembly. Our results confirm that nearby star-forming dwarf galaxies can indeed form massive black holes, and that by implication so can their primordial counterparts. Moreover, the lack of a substantial spheroidal component in Henize 2-10 indicates that supermassive black-hole growth may precede the build-up of galaxy spheroids.

  4. Galaxy Formation

    DEFF Research Database (Denmark)

    Sparre, Martin

    Galaxy formation is an enormously complex discipline due to the many physical processes that play a role in shaping galaxies. The objective of this thesis is to study galaxy formation with two different approaches: First, numerical simulations are used to study the structure of dark matter and how...... galaxies form stars throughout the history of the Universe, and secondly it is shown that observations of gamma-ray bursts (GRBs) can be used to probe galaxies with active star formation in the early Universe. A conclusion from the hydrodynamical simulations is that the galaxies from the stateof-the-art...

  5. VizieR Online Data Catalog: Star formation in active and normal galaxies (Tsai+, 2015)

    Science.gov (United States)

    Tsai, M.; Hwang, C.-Y.

    2015-11-01

    We selected 104 active galaxies from the lists of Melendez et al. (2010MNRAS.406..493M), Condon et al. 1991 (cat. J/ApJ/378/65), and Ho & Ulvestad 2001 (cat. J/ApJS/133/77). Most of the sources are identified as Active Galactic Nuclei (AGNs), and a few of them are classified as Luminous InfraRed Galaxies (LIRGs). We obtained 3.6 and 8μm infrared images of these galaxies from the Spitzer Archive (http://sha.ipac.caltech.edu/applications/Spitzer/SHA/) and 8GHz images from the VLA archive (http://archive.nrao.edu/archive/archiveimage.html). We also selected a nearby AGN sub-sample containing 21 radio-selected AGNs for further spatial analysis. We selected 25 nearby AGNs exhibiting no detected radio emission in order to compare with the results of the radio-selected sources. For comparison, we also selected normal galaxies with distances less than 15Mpc from the catalog of Tully 1994 (see cat. VII/145). We only selected the galaxies that have Spitzer archive data and are not identified as AGNs in either the Veron-Cetty & Veron 2006 (see cat. VII/258) AGN catalog or in the NED database (http://ned.ipac.caltech.edu/). Our results for the radio-selected and the non-radio-selected active galaxies are listed in Table1, and those for the normal galaxies are listed in Table2. (2 data files).

  6. PHYSICAL PROPERTIES, STAR FORMATION, AND ACTIVE GALACTIC NUCLEUS ACTIVITY IN BALMER BREAK GALAXIES AT 0 < z < 1

    Energy Technology Data Exchange (ETDEWEB)

    Diaz Tello, J.; Donzelli, C. [IATE, Observatorio Astronomico de Cordoba, Universidad Nacional de Cordoba (Argentina); Padilla, N. [Departamento de Astronomia y Astrofisica, Pontificia Universidad Catolica de Chile (Chile); Fujishiro, N.; Yoshikawa, T. [Koyama Astronomical Observatory, Kyoto Sangyo University (Japan); Hanami, H. [Physics Section, Iwate University (Japan); Hatsukade, B., E-mail: jdiazt@oac.uncor.edu [Department of Astronomy, Kyoto University (Japan)

    2013-07-01

    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-active galactic nuclei (AGNs) 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 mid-infrared (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, two (5%) composite galaxies, and three (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, three 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. By fitting the spectral energy distribution of the galaxies, we derived the stellar masses, dust reddening E(B - V), ages, and UV star formation rates (SFRs). Furthermore, the relationship between SFR surface density ({Sigma}{sub SFR}) and stellar mass surface density per time unit ({Sigma}{sub M{sub */{tau}}}) as a function of redshift was investigated using the [O II] {lambda}3727, 3729, H{alpha} {lambda}6563 luminosities, which revealed that both quantities are larger for higher redshift galaxies. We also studied the SFR and specific SFR (SSFR) versus stellar mass and color relations, with the more massive galaxies having higher SFR values but lower SSFR values than less massive galaxies. These results are consistent with previous ones showing that, at a given mass, high-redshift galaxies have on average larger SFR and SSFR values than low-redshift galaxies. Finally, bluer galaxies have larger SSFR values than redder

  7. Resolving the extended stellar halos of nearby galaxies: the wide-field PISCeS survey

    CERN Document Server

    Crnojević, D; Caldwell, N; Guhathakurta, P; McLeod, B; Seth, A; Simon, J D; Strader, J; Toloba, E

    2015-01-01

    In the wide-field Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS), we investigate the resolved stellar halos of two nearby galaxies (the elliptical Centaurus A and the spiral Sculptor, D $\\sim3.7$ Mpc) out to a projected galactocentric radius of 150 kpc with Magellan/Megacam. The survey has led to the discovery of $\\sim$20 faint satellites to date, plus prominent streams and substructures in two environments that are substantially different from the Local Group, i.e. the Centaurus A group dominated by an elliptical and the loose Sculptor group of galaxies. These discoveries clearly attest to the importance of past and ongoing accretion processes in shaping the halos of these nearby galaxies, and provide the first census of their satellite systems down to an unprecedented $M_V<-8$. The detailed characterization of the stellar content, shape and gradients in the extended halos of Sculptor, Centaurus A, and their dwarf satellites provides key constraints on theoretical models of galaxy formation a...

  8. Resolving the extended stellar halos of nearby galaxies: the wide-field PISCeS survey†

    Science.gov (United States)

    Crnojević, D.; Sand, D. J.; Caldwell, N.; Guhathakurta, P.; McLeod, B.; Seth, A.; Simon, J. D.; Strader, J.; Toloba, E.

    2016-08-01

    In the wide-field Panoramic Imaging Survey of Centaurus and Sculptor (PISCeS), we investigate the resolved stellar halos of two nearby galaxies (the elliptical Centaurus A and the spiral Sculptor, D ~ 3.7 Mpc) out to a projected galactocentric radius of 150 kpc with Magellan/Megacam. The survey has led to the discovery of ~20 faint satellites to date, plus prominent streams and substructures in two environments that are substantially different from the Local Group, i.e. the Centaurus A group dominated by an elliptical and the loose Sculptor group of galaxies. These discoveries clearly attest to the importance of past and ongoing accretion processes in shaping the halos of these nearby galaxies, and provide the first census of their satellite systems down to an unprecedented MV < -8. The detailed characterization of the stellar content, shape and gradients in the extended halos of Sculptor, Centaurus A, and their dwarf satellites provides key constraints on theoretical models of galaxy formation and evolution.

  9. Accretion/jet activity and narrow [O III] kinematics in young radio galaxies

    Institute of Scientific and Technical Information of China (English)

    Andrew; HUMPHREY

    2010-01-01

    We estimate black hole masses and Edenton ratios for a sample of 81 young radio galaxies,which includes 42 compact steep-spectrum(CSS) and 39 gigahertz-peaked spectrum(GPS) sources.We find that the average black hole(BH) mass of these young radio galaxies is〈log Mbh〉-8.3,which is less than that of radio loud QSOs and low redshift radio galaxies(〈 log Mbh〉-9.0).The CSS/GPS sources have relatively high Eddington ratios,with an average value of〈log Lbol/LEdd〉=-0.75,which are similar to those of narrow line Seyfert 1 galaxies(NLS1s).This suggests that young radio galaxies may not only be in the early stages of their radio activity,but also in the early stage of their accretion activity.We find that the young radio galaxies,as a class,systematically deviate from the Mbh-σ relation defined by nearby inactive galaxies,when using σ[O III] as a surrogate for stellar velocity dispersion σ.We also find that the deviation of the [O III] line width,Δσ =σ[O III]-σ[pred],is correlated with the Eddington ratio;sources with Lbol/LEdd-1 have the largest deviations,which are similar to those of radio quiet QSOs/NLS1s(i.e.,sources in which the radio jets are absent or weak),and where σ[pred] is calculated from the Tremaine et al.relation using our estimated BH masses.A similar result has been obtained for 9 linear radio Seyfert galaxies.On the basis of these results,we suggest that,in addition to the possible jet-gas interactions,accretion activities may also play an important role in shaping the kinematics of the narrow [O III] line in young radio galaxies.

  10. On the Host Galaxy of GRB 150101B and the Associated Active Galactic Nucleus

    CERN Document Server

    Xie, Chen; Wang, Junfeng; Liu, Tong; Jiang, Xiaochuan

    2016-01-01

    We present a multi-wavelength analysis of the host galaxy of short-duration gamma-ray burst (GRB) 150101B. Follow-up optical and X-ray observations suggested that the host galaxy, 2MASX J12320498-1056010, likely harbors a low-luminosity active galactic nuclei (AGN). Our modeling of the spectral energy distribution (SED) has confirmed the nature of the AGN, making it the first reported GRB host that contains an AGN. We have also found the host galaxy is a massive elliptical galaxy with stellar population of $\\sim 5.7\\ Gyr$, one of the oldest among the short-duration GRB hosts. Our analysis suggests that the host galaxy can be classified as an X-ray bright, optically normal galaxy (XBONG), and the central AGN is likely dominated by a radiatively inefficient accretion flow (RIAF). Our work explores interesting connection that may exist between GRB and AGN activities of the host galaxy, which can help understand the host environment of the GRB events and the roles of AGN feedback.

  11. Accretion/Jet Activity and Narrow [O III] Kinematics in Young Radio Galaxies

    CERN Document Server

    Wu, Qingwen; Humphrey, Andrew

    2009-01-01

    We estimate black hole masses and Eddington ratios for a sample of 81 young radio galaxies (42 CSS +39 GPS). We find that the average black hole (BH) mass of these young radio galaxies is ~8.3, which is less than that of radio loud QSOs and low redshift radio galaxies. The CSS/GPS sources have relatively high Eddington ratios, with an average value of =-0.75, which are similar to those of narrow line Seyfert 1 galaxies (NLS1s). This suggests that young radio galaxies may not only be in the early stages of their radio activity, but also in the early stage of their accretion activity. We find that the young radio galaxies as a class deviate systematically from M_bh-\\sigma relation defined by nearby inactive galaxies, when using [O III] as a surrogate for stellar velocity dispersion, \\sigma_* . We also find that the deviation of the [O III] line width is correlated with the Eddington ratio and sources with Lbol/LEdd~1 have the largest deviations, which are similar to those of radio quiet QSOs/NLS1s (radio jets i...

  12. The nature and origin of Narrow Line AGN activity in a sample of isolated SDSS galaxies

    CERN Document Server

    Coziol, R; Plauchu-Frayn, I; Islas-Islas, J M; Ortega-Minakata, R A; Larios, D M Neri; Andernach, H

    2011-01-01

    We discuss the nature and origin of the nuclear activity observed in a sample of 292 SDSS narrow-emission-line galaxies, considered to have formed and evolved in isolation. All these galaxies are spiral like and show some kind of nuclear activity. The fraction of Narrow Line AGNs (NLAGNs) and Transition type Objects (TOs; a NLAGN with circumnuclear star formation) is relatively high, amounting to 64% of the galaxies. There is a definite trend for the NLAGNs to appear in early-type spirals, while the star forming galaxies and TOs are found in later-type spirals. We verify that the probability for a galaxy to show an AGN characteristic increases with the bulge mass of the galaxy (Torre-Papaqui et al. 2011), and find evidence that this trend is really a by-product of the morphology, suggesting that the AGN phenomenon is intimately connected with the formation process of the galaxies. Consistent with this interpretation, we establish a strong connection between the astration rate--the efficiency with which the ga...

  13. 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...

  14. The radio halo and active galaxies in the Coma cluster

    International Nuclear Information System (INIS)

    The Cambridge Low-Frequency Synthesis Telescope has been used to map the Coma cluster at 151 MHz. Two new extended sources are found, associated with the cluster galaxies NGC4839 and NGC4849. The central halo radio source is shown not to have a simple symmetrical structure but to be distorted, with separate centres of brightening near the radio galaxies NGC4874 and IC4040. The structure cannot be accounted for by cluster-wide acceleration processes but implies a close connection with current radio galaxies and, in particular, models requiring diffusion of electrons out of radio sources seem to be favoured. The other large source, near Coma A, is detected and higher resolution data at 1407 MHz are used to clarify its structure. (author)

  15. Shock heating in the group atmosphere of the radio galaxy B2 0838+32A

    CERN Document Server

    Jetha, Nazirah N; Ponman, Trevor J; Sakelliou, Irini

    2008-01-01

    We present Chandra and radio observations, and analysis of Sloan Digital Sky Survey data, of the radio galaxy B2 0838+32A (4C 32.26) and its environment. The radio galaxy is at the centre of a nearby group that has often been identified with the cluster Abell 695, but we argue that the original Abell cluster is likely to be an unrelated and considerably more distant system. The radio source is a restarting radio galaxy and, using our Chandra data, we argue that the currently active lobes are expanding supersonically, driving a shock with Mach number $2.4^{+1.0}_{-0.5}$ into the inter-stellar medium. This would be only the third strong shock round a young radio source to be discovered, after Centaurus A and NGC 3801. However, in contrast to both these systems, the host galaxy of B2 0838+32A shows no evidence for a recent merger, while the AGN spectrum shows no evidence for the dusty torus that would imply a large reservoir of cold gas close to the central black hole. On the contrary, the AGN spectrum is of a t...

  16. The Incidence of Active Galactic Nuclei in Pure Disk Galaxies: The Spitzer View

    CERN Document Server

    Satyapal, S; Mcalpine, W; Gliozzi, M; Abel, N P; Heckman, T

    2009-01-01

    We have conducted a high-resolution spectroscopic study using Spitzer of 18 bulgeless (Sd/Sdm) galaxies that show no definitive signatures of nuclear activity in their optical spectra. This is the first systematic mid-IR search for weak or hidden AGNs in a statistically significant sample of bulgeless disk galaxies. Based on the detection of the high-ionization [NeV] line, we report the discovery of an AGN in one out of the 18 galaxies in the sample. This galaxy, NGC 4178, is a nearby edge-on Sd galaxy, which likely hosts a prominent nuclear star cluster (NSC). The bolometric luminosity of the AGN inferred from the [NeV] luminosity is ~ 8e41 ergs/s. This is almost two orders of magnitude greater than the luminosity of the AGN in NGC 4395, the best studied AGN in a bulgeless disk galaxy. Assuming that the AGN in NGC 4178 is radiating below the Eddington limit, the lower mass limit for the black hole is ~ 6e3M_sun. The fact that none of the other galaxies in the sample shows any evidence for an AGN demonstrates...

  17. Investigating the AGN activity and black hole masses in Low Surface brightness galaxies

    CERN Document Server

    Subramanian., Smitha; Das., Mousumi; George., Koshy; Sivarani, T; Prabhu, T P

    2015-01-01

    We present an analysis of the optical nuclear spectra from the active galactic nuclei (AGN) in a sample of giant low surface brightness (GLSB) galaxies. GLSB galaxies are extreme late type spirals that are large, isolated and poorly evolved compared to regular spiral galaxies. Earlier studies have indicated that their nuclei have relatively low mass black holes. Using data from the Sloan Digital Sky Survey (SDSS), we selected a sample of 30 GLSB galaxies that showed broad H$\\alpha$ emission lines in their AGN spectra. In some galaxies such as UGC 6284, the broad component of H$\\alpha$ is more related to outflows rather than the black hole. One galaxy (UGC 6614) showed two broad components in H$\\alpha$, one associated with the black hole and the other associated with an outflow event. We derived the nuclear black hole (BH) masses of 29 galaxies from their broad H$\\alpha$ parameters. We find that the nuclear BH masses lie in the range $10^{5}-10^{7} M_{\\odot}$. The bulge stellar velocity dispersion $\\sigma_{e}$...

  18. Star Formation and AGN Activity in Interacting Galaxies: A Near-UV Perspective

    CERN Document Server

    Scott, Caroline

    2013-01-01

    We study nearby galaxies in close pairs to study the key factors affecting star formation and AGN activity triggered during galaxy interactions. Close pairs are selected from the Sloan Digital Sky Survey assuming a projected separation of $<$30kpc and recessional velocity difference $<$500km s$^{-1}$. Near-ultraviolet (NUV) fluxes from GALEX are used to estimate specific star formation rates (SSFRs). We find a factor of $\\sim$5.3 increase in SSFR for low mass (10$^{8}-10^{11}$M$_{\\odot}$) close pair galaxies and a factor of $\\sim$2.1 increase in SSFR for high mass mass (10$^{11}-10^{13}$M$_{\\odot}$) close pairs compared to the general galaxy population. Considering galaxies of all masses, we find a factor of $\\sim$1.8 enhancement in SSFR for close pairs in field environments compared to non-pairs, with no significant increase for pairs in group and cluster environments. A modest decrease of a factor of $\\sim$1.4 is found in the Seyfert fraction in close pair galaxies when compared to isolated galaxies, ...

  19. 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...

  20. Backwards Spiral Galaxy

    Science.gov (United States)

    1999-01-01

    Astronomers using NASA's Hubble Space Telescope have found a spiral galaxy that may rotate in the opposite direction from what was expected. A picture of the oddball galaxy is available at http://heritage.stsci.edu or http://oposite.stsci.edu/pubinfo/pr/2002/03 or http://www.jpl.nasa.gov/images/wfpc . It was taken in May 2001 by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The picture showed which side of galaxy NGC 4622 is closer to Earth; that information helped astronomers determine that the galaxy may be spinning clockwise. The image shows NGC 4622 and its outer pair of winding arms full of new stars, shown in blue. Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise. NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. Astronomers suspect this oddity was caused by the interaction of NGC 4622 with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a smaller companion galaxy. Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 lies 111 million light-years away in the direction of the constellation Centaurus. The science team, consisting of Drs. Ron Buta and Gene Byrd from the University of Alabama, Tuscaloosa, and Tarsh Freeman of Bevill State Community College in Alabama

  1. The outer filament of Centaurus A as seen by MUSE

    CERN Document Server

    Santoro, F; Morganti, R; Oosterloo, T A; Tremblay, G

    2015-01-01

    We investigate signatures of a jet-interstellar medium (ISM) interaction using optical integral-field observations of the so-called outer filament near Centaurus A, expanding on previous results obtained on a more limited area. Using the Multi Unit Spectroscopic Explorer (MUSE) on the VLT during science verification, we observed a significant fraction of the brighter emitting gas across the outer filament. The ionized gas shows complex morphology with compact blobs, arc-like structures and diffuse emission. Based on the kinematics, we identified three main components. The more collimated component is oriented along the direction of the radio jet. The other two components exhibit diffuse morphology together with arc-like structures also oriented along the radio jet direction. Furthermore, the ionization level of the gas is found to decrease from the more collimated component to the more diffuse components. The morphology and velocities of the more collimated component confirm our earlier results that the outer...

  2. The Far-Infrared Energy Distributions of Seyfert and Starburst Galaxies in the Local Universe: Infrared Space Observatory Photometry of the 12 Micron Active Galaxy Sample

    Science.gov (United States)

    Spinoglio, Luigi; Andreani, Paola; Malkan, Matthew A.

    2002-06-01

    New far-infrared photometry with ISOPHOT aboard the Infrared Space Observatory (ISO) is presented for 58 galaxies with homogeneous published data for another 32 galaxies, all belonging to the 12 μm galaxy sample-in total, 29 Seyfert 1 galaxies, 35 Seyfert 2 galaxies, and 12 starburst galaxies, or about half of the 12 μm active galaxy sample, plus 14 normal galaxies for comparison. ISO and Infrared Astronomical Satellite (IRAS) data are used to define color-color diagrams and spectral energy distributions (SEDs). Thermal dust emission at two temperatures (one cold at 15-30 K and one warm at 50-70 K) can fit the 60-200 μm SED, with a dust emissivity law proportional to the inverse square of the wavelength. Seyfert 1 galaxies and Seyfert 2 galaxies are indistinguishable longward of 100 μm, while, as already seen by IRAS, the former have flatter SEDs shortward of 60 μm. A mild anticorrelation is found between the [200-100] color and the ``60 μm excess.'' We infer that this is due to the fact that galaxies with a strong starburst component and thus a strong 60 μm flux have a steeper far-infrared turnover. In non-Seyfert galaxies, increasing the luminosity corresponds to increasing the star formation rate, which enhances the 25 and 60 μm emission. This shifts the peak emission from around 150 μm in the most quiescent spirals to shorter than 60 μm in the strongest starburst galaxies. To quantify these trends further, we identified with the IRAS colors three idealized infrared SEDs: pure quiescent disk emission, pure starburst emission, and pure Seyfert nucleus emission. Even between 100 and 200 μm, the quiescent disk emission remains much cooler than the starburst component. Seyfert galaxies have 100-200 μm SEDs ranging from pure disks to pure starbursts, with no apparent contribution from their active nuclei at those wavelengths. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France

  3. Bulges and disks in the local Universe. Linking the galaxy structure to star formation activity

    CERN Document Server

    Morselli, L; Erfanianfar, G; Concas, A

    2016-01-01

    Galaxy morphology and star formation activity are strictly linked, in the way that bulge-dominated galaxies are in general quiescent, while disk dominated galaxies are actively star-forming. In this paper, we study the properties of bulges and disks as a function of the position of galaxies in the star formation rate (SFR) - stellar mass ($M_{\\star}$) plane. Our sample is built on the SDSS DR7 catalogue, and the bulge-disk decomposition is the one of Simard et al. (2011). We find that at a given stellar mass the Main Sequence (MS) is populated by galaxies with the lowest B/T ratios. The B/T on the MS increases with increasing stellar mass, thus confirming previous results in literature. In the upper envelop of the MS, the average B/T is higher than that of MS counterparts at fixed stellar mass. This indicates that starburst galaxies have a significant bulge component. In addition, bulges above the MS are characterised by blue colours, whereas, if on the MS or below it, they are mostly red and dead. The disks ...

  4. The rotation of the Galaxy within the solar circle

    Energy Technology Data Exchange (ETDEWEB)

    Alvarez, H.; May, J.; Bronfman, L. (Universidad de Chile, Santiago (Chile))

    1990-01-01

    A rotation curve for the Galaxy within the solar circle is found using data from the fourth Galactic quadrant. The observations are consistent with a picture in which the Galaxy rotates with a circular velocity of 209 + or - 2 km/s between Galactocentric distances of 0.24 and 1.0 solar radius. Clouds associated with a part of the Carina spiral arm exhibit an average rotation velocity 12 km/s higher than expected, implying an apparent anomalous motion. An excess in velocity of about the same magnitude observed at the tangent direction of the Centaurus arm is attributed to streaming and internal motions of large molecular complexes. Similar phenomena found in the Sagittarius and Scutum arms by northern observers strongly support the hypothesis that Carina is the continuation of the Sagittarius arm and Centaurus is that of the Scutum arm. 30 refs.

  5. Infrared Signature of Active Massive Black Holes in Nearby Dwarf Galaxies

    CERN Document Server

    Marleau, Francine R; Bianconi, Matteo; Habas, Rebecca

    2014-01-01

    We have identified 314 nearby galaxies that display the infrared signature of black hole activity. Of these, twelve lie within a distance of 11 Mpc, the nearest being EW Eri located only 50 kpc away. Using the Wide-field Infrared Survey Explorer (WISE) All-Sky Release Source Catalog, we examine the IR colors of a sample of known nearby dwarf galaxies in order to identify both unobscured (type 1) and obscured (type 2) active galactic nuclei in these low-mass systems. We estimate the stellar and black hole masses for our nearby dwarf galaxy sample and find that activity is detected in galaxies with stellar masses from 10^5 to 10^9 M_sun and that this activity is due to black holes with masses in the range 10^2-10^6 M_sun. The black hole masses probed here are several orders of magnitude smaller than previously reported for centrally located massive black holes. We examine the stellar mass versus black hole mass relationship in this low galaxy mass regime, and find that the existing relation extends to these low...

  6. Cosmic web and star formation activity in galaxies at z ∼ 1

    International Nuclear Information System (INIS)

    We investigate the role of the delineated cosmic web/filaments on star formation activity by exploring a sample of 425 narrow-band selected Hα emitters, as well as 2846 color-color selected underlying star-forming galaxies for a large-scale structure at z = 0.84 in the COSMOS field from the HiZELS survey. Using the scale-independent Multi-scale Morphology Filter algorithm, we are able to quantitatively describe the density field and disentangle it into its major components: fields, filaments, and clusters. We show that the observed median star formation rate (SFR), stellar mass, specific SFR, the mean SFR-mass relation, and its scatter for both Hα emitters and underlying star-forming galaxies do not strongly depend on different classes of environment, in agreement with previous studies. However, the fraction of Hα emitters varies with environment and is enhanced in filamentary structures at z ∼ 1. We propose mild galaxy-galaxy interactions as the possible physical agent for the elevation of the fraction of Hα star-forming galaxies in filaments. Our results show that filaments are the likely physical environments that are often classed as the 'intermediate' densities and that the cosmic web likely plays a major role in galaxy formation and evolution which has so far been poorly investigated.

  7. THE CLUSTERING OF GALAXIES AROUND RADIO-LOUD ACTIVE GALACTIC NUCLEI

    Energy Technology Data Exchange (ETDEWEB)

    Worpel, Hauke [Monash Centre for Astrophysics, School of Mathematical Sciences, Monash University, Clayton, Victoria 3800 (Australia); Brown, Michael J. I.; Jones, D. Heath; Floyd, David J. E. [Monash Centre for Astrophysics, School of Physics, Monash University, Clayton, Victoria 3800 (Australia); Beutler, Florian [ICRAR, University of Western Australia, 35 Stirling Highway, Perth, WA 6009 (Australia)

    2013-07-20

    We examine the hypothesis that mergers and close encounters between galaxies can fuel active galactic nuclei (AGNs) by increasing the rate at which gas accretes toward the central black hole. We compare the clustering of galaxies around radio-loud AGNs with the clustering around a population of radio-quiet galaxies with similar masses, colors, and luminosities. Our catalog contains 2178 elliptical radio galaxies with flux densities greater than 2.8 mJy at 1.4 GHz from the Six Degree Field Galaxy Survey. We find tentative evidence that radio AGNs with more than 200 times the median radio power have, on average, more close (r < 160 kpc) companions than their radio-quiet counterparts, suggesting that mergers play a role in forming the most powerful radio galaxies. For ellipticals of fixed stellar mass, the radio power is neither a function of large-scale environment nor halo mass, consistent with the radio powers of ellipticals varying by orders of magnitude over billions of years.

  8. Evidence for Widespread AGN Activity among Massive Quiescent Galaxies at z ~ 2

    CERN Document Server

    Olsen, Karen Pardos; Toft, Sune; Zirm, Andrew W

    2012-01-01

    We quantify the presence of Active Galactic nuclei (AGN) in a mass-complete (M_* >5e10 M_sun) sample of 123 star-forming and quiescent galaxies at 1.5 3e42 ergs/s). The latter fraction is similar for star-forming and quiescent galaxies, and does not depend on galaxy stellar mass, suggesting that perhaps luminous AGN 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 AGN. Among the quiescent galaxies, the excess suggests that as many as 70-100% of these contain low- or high-luminosity AGN, while the corresponding fraction is lower among star-forming galaxies (43-65%). The ubiquitous presence of AGN in massive, q...

  9. Disentangling star formation and AGN activity in powerful infrared luminous radio galaxies at 1 < z < 4

    Science.gov (United States)

    Drouart, G.; Rocca-Volmerange, B.; De Breuck, C.; Fioc, M.; Lehnert, M.; Seymour, N.; Stern, D.; Vernet, J.

    2016-09-01

    High-redshift radio galaxies present signs of both star formation and AGN activity, making them ideal candidates to investigate the connection and coevolution of AGN and star formation in the progenitors of present-day massive galaxies. We make use of a sample of 11 powerful radio galaxies spanning 1 relative contribution of the AGN and star formation by combining the galaxy evolution code PÉGASE.3 with an AGN torus model. We find that three components are necessary to reproduce the observed SEDs: an evolved and massive stellar component, a submm bright young starburst, and an AGN torus. We find that powerful radio galaxies form at very high-redshift, but experience episodic and important growth at 1 mass of the associated starburst varies from 5 to 50% of the total mass of the system. The properties of star formation differ from source to source, indicating no general trend of the star formation properties in the most infrared luminous high-redshift radio galaxies and no correlation with the AGN bolometric luminosity. Moreover, we find that AGN scattered light have a very limited impact on broad-band SED fitting on our sample. Finally, our analysis also suggests a wide range in origins for the observed star formation,which we partially constrain for some sources.

  10. Star Formation and AGN Activity in Luminous and Ultraluminous Infrared Galaxies

    Science.gov (United States)

    Kartaltepe, Jeyhan

    2015-08-01

    In the local universe, Ultraluminous Infrared Galaxies (ULIRGs, L_IR > 10^12 L⊙) are all interacting and merging systems. We explore the evolution of the morphological and nuclear properties of (U)LIRGs over cosmic time using a large sample of galaxies from Her- schel observations of the CANDELS fields (including GOODS, COSMOS, and UDS). In particular, we investigate whether the role of galaxy mergers has changed between z ˜ 2 and now using the extensive visual classification catalogs produced by the CANDELS team. The combination of a selection from Herschel, near the peak of IR emission, and rest-frame optical morphologies from CANDELS, provides the ideal comparison to nearby (U)LIRGs. We also use rest-frame optical emission line diagnostics, X-ray luminosity, and MIR colors to separate AGN from star-formation dominated galaxies. We then study the how role of galaxy mergers and the presence of AGN activity correspond to the galaxy’s position in the star formation rate - stellar mass plane. Are galaxies that have specific star formation rates elevated above the main sequence more likely to be mergers? We investigate how AGN identified with different methods correspond to different morphologies and merger stages as well as position on the star formation rate - stellar mass plane.

  11. 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...

  12. High levels of absorption in orientation-unbiased, radio-selected 3CR Active Galaxies

    NARCIS (Netherlands)

    Wilkes, Belinda J.; Haas, Martin; Barthel, Peter; Leipski, Christian; Kuraszkiewicz, Joanna; Worrall, Diana; Birkinshaw, Mark; Willner, Steven P.

    2014-01-01

    A critical problem in understanding active galaxies (AGN) is the separation of intrinsic physical differences from observed differences that are due to orientation. Obscuration of the active nucleus is anisotropic and strongly frequency dependent leading to complex selection effects for observations

  13. HUBBLE REVEALS 'BACKWARDS' SPIRAL GALAXY

    Science.gov (United States)

    2002-01-01

    Astronomers have found a spiral galaxy that may be spinning to the beat of a different cosmic drummer. To the surprise of astronomers, the galaxy, called NGC 4622, appears to be rotating in the opposite direction to what they expected. Pictures by NASA's Hubble Space Telescope helped astronomers determine that the galaxy may be spinning clockwise by showing which side of the galaxy is closer to Earth. A Hubble telescope photo of the oddball galaxy is this month's Hubble Heritage offering. The image shows NGC 4622 and its outer pair of winding arms full of new stars [shown in blue]. Astronomers are puzzled by the clockwise rotation because of the direction the outer spiral arms are pointing. Most spiral galaxies have arms of gas and stars that trail behind as they turn. But this galaxy has two 'leading' outer arms that point toward the direction of the galaxy's clockwise rotation. To add to the conundrum, NGC 4622 also has a 'trailing' inner arm that is wrapped around the galaxy in the opposite direction it is rotating. Based on galaxy simulations, a team of astronomers had expected that the galaxy was turning counterclockwise. NGC 4622 is a rare example of a spiral galaxy with arms pointing in opposite directions. What caused this galaxy to behave differently from most galaxies? Astronomers suspect that NGC 4622 interacted with another galaxy. Its two outer arms are lopsided, meaning that something disturbed it. The new Hubble image suggests that NGC 4622 consumed a small companion galaxy. The galaxy's core provides new evidence for a merger between NGC 4622 and a smaller galaxy. This information could be the key to understanding the unusual leading arms. Galaxies, which consist of stars, gas, and dust, rotate very slowly. Our Sun, one of many stars in our Milky Way Galaxy, completes a circuit around the Milky Way every 250 million years. NGC 4622 resides 111 million light-years away in the constellation Centaurus. The pictures were taken in May 2001 with Hubble

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

    International Nuclear Information System (INIS)

    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.

  15. 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.

  16. Dual-frequency VLBI study of Centaurus A on sub-parsec scales

    CERN Document Server

    Müller, Cornelia; Ojha, R; Wilms, J; Böck, M; Edwards, P G; Fromm, C M; Hase, H; Horiuchi, S; Katz, U; Lovell, J E J; Plötz, C; Pursimo, T; Richers, S; Ros, E; Rothschild, R E; Taylor, G B; Tingay, S J; Zensus, J A

    2011-01-01

    Centaurus A is the closest active galactic nucleus. High resolution imaging using Very Long Baseline Interferometry (VLBI) enables us to study the spectral and kinematic behavior of the radio jet-counterjet system on sub-parsec scales, providing essential information for jet emission and formation models. Our aim is to study the structure and spectral shape of the emission from the central-parsec region of Cen A. As a target of the Southern Hemisphere VLBI monitoring program TANAMI (Tracking Active Galactic Nuclei with Milliarcsecond Interferometry), VLBI observations of Cen A are made regularly at 8.4 and 22.3 GHz with the Australian Long Baseline Array (LBA) and associated telescopes in Antarctica, Chile, and South Africa. The first dual-frequency images of this source are presented along with the resulting spectral index map. An angular resolution of 0.4 mas x 0.7 mas is achieved at 8.4 GHz, corresponding to a linear scale of less than 0.013 pc. Hence, we obtain the highest resolution VLBI image of Cen A, ...

  17. 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...

  18. The Relationship of Active Galactic Nuclei & Quasars With Their Local Galaxy Environment

    CERN Document Server

    Strand, Natalie Erin

    2009-01-01

    We explore how the local environment is related to properties of active galactic nuclei (AGNs) of various luminosities. Recent simulations and observations are converging on the view that the extreme luminosity of quasars, the brightest of AGNs, is fueled in major mergers of gas-rich galaxies. In such a picture, quasars, the highest luminosity AGNs, are expected to be located in regions with a higher density of galaxies on small scales where mergers are more likely to take place. However, in this picture, the activity observed in low-luminosity AGNs is due to secular processes that are less dependent on the local galaxy density. To test this hypothesis, we compare the local photometric galaxy density on kiloparsec scales around spectroscopic type I and type II quasars to the local density around lower-luminosity spectroscopic type I and type II AGNs. To minimize projection effects and evolution in the photometric galaxy sample we use to characterize AGN environments, we place our random control sample at the ...

  19. Multiple tidal disruption flares in the active galaxy IC 3599

    CERN Document Server

    Campana, S; Colpi, M; Lodato, G; D'Avanzo, P; Evans, P A; Moretti, A

    2015-01-01

    Tidal disruption events occur when a star passes too close to a massive black hole and it is totally ripped apart by tidal forces. Alternatively, if the star does not get close enough to the black hole to be totally disrupted, a less dramatic event might happen with the star surviving the encounter and loosing only a small fraction of its mass. In this situation if the stellar orbit is bound and highly eccentric, just like some stars in the centre of our own Galaxy, repeated flares should occur. When the star approaches the black hole tidal radius at periastron, matter might be stripped resulting in lower intensity outbursts recurring once every orbital period. We report on Swift observations of a recent bright flare from the galaxy IC 3599 hosting a middle-weight black hole, where a possible tidal disruption event was observed in the early 1990s. By light curve modelling and spectral fitting we can consistently account for the events as the non-disruptive tidal stripping of a star into a highly eccentric orb...

  20. Star formation activities in early-type brightest cluster galaxies

    CERN Document Server

    Liu, F S; Meng, X M

    2012-01-01

    We identify a total of 120 early-type Brightest Cluster Galaxies (BCGs) at 0.1galaxy stellar mass). We also compare their statistical properties with a control sample selected from X-ray luminous c...

  1. Wind from the black-hole accretion disk driving a molecular outflow in an active galaxy.

    Science.gov (United States)

    Tombesi, F; Meléndez, M; Veilleux, S; Reeves, J N; González-Alfonso, E; Reynolds, C S

    2015-03-26

    Powerful winds driven by active galactic nuclei are often thought to affect the evolution of both supermassive black holes and their host galaxies, quenching star formation and explaining the close relationship between black holes and galaxies. Recent observations of large-scale molecular outflows in ultraluminous infrared galaxies support this quasar-feedback idea, because they directly trace the gas from which stars form. Theoretical models suggest that these outflows originate as energy-conserving flows driven by fast accretion-disk winds. Proposed connections between large-scale molecular outflows and accretion-disk activity in ultraluminous galaxies were incomplete because no accretion-disk wind had been detected. Conversely, studies of powerful accretion-disk winds have until now focused only on X-ray observations of local Seyfert galaxies and a few higher-redshift quasars. Here we report observations of a powerful accretion-disk wind with a mildly relativistic velocity (a quarter that of light) in the X-ray spectrum of IRAS F11119+3257, a nearby (redshift 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow. The active galactic nucleus is responsible for about 80 per cent of the emission, with a quasar-like luminosity of 1.5 × 10(46) ergs per second. The energetics of these two types of wide-angle outflows is consistent with the energy-conserving mechanism that is the basis of the quasar feedback in active galactic nuclei that lack powerful radio jets (such jets are an alternative way to drive molecular outflows). PMID:25810204

  2. The structure of host galaxies of radio-loud quasars and possible triggering mechanisms for quasar activity

    Energy Technology Data Exchange (ETDEWEB)

    Romanishin, W.; Hintzen, P. (Arizona State Univ., Tempe (USA); NASA, Goddard Space Flight Center, Greenbelt, MD (USA))

    1989-06-01

    An image modeling program is used to analyze optical imaging data for a sample of radio-loud quasars with redshifts between 0.2 and 0.7. It is found that the host galaxies of these quasars tend to be more compact than normal ellipticals. The cooling flow cluster elliptical galaxies near these host galaxies are studied. It is suggested that these cooling flow galaxies are also compact due to star formation in their central regions. Two populations of quasars are identified. One, in which activity is triggered by galaxy mergers of interactions has predominately spiral galaxies and are radio quiet. The other, in which activity is triggered by star formation bursts induced by cooling flows, has predominately elliptical hosts and may be radio loud. 28 refs.

  3. The structure of host galaxies of radio-loud quasars and possible triggering mechanisms for quasar activity

    International Nuclear Information System (INIS)

    An image modeling program is used to analyze optical imaging data for a sample of radio-loud quasars with redshifts between 0.2 and 0.7. It is found that the host galaxies of these quasars tend to be more compact than normal ellipticals. The cooling flow cluster elliptical galaxies near these host galaxies are studied. It is suggested that these cooling flow galaxies are also compact due to star formation in their central regions. Two populations of quasars are identified. One, in which activity is triggered by galaxy mergers of interactions has predominately spiral galaxies and are radio quiet. The other, in which activity is triggered by star formation bursts induced by cooling flows, has predominately elliptical hosts and may be radio loud. 28 refs

  4. The structure of host galaxies of radio-loud quasars and possible triggering mechanisms for quasar activity

    Science.gov (United States)

    Romanishin, W.; Hintzen, Paul

    1989-01-01

    An image modeling program is used to analyze optical imaging data for a sample of radio-loud quasars with redshifts between 0.2 and 0.7. It is found that the host galaxies of these quasars tend to be more compact than normal ellipticals. The cooling flow cluster elliptical galaxies near these host galaxies are studied. It is suggested that these cooling flow galaxies are also compact due to star formation in their central regions. Two populations of quasars are identified. One, in which activity is triggered by galaxy mergers of interactions has predominately spiral galaxies and are radio quiet. The other, in which activity is triggered by star formation bursts induced by cooling flows, has predominately elliptical hosts and may be radio loud.

  5. Where the active galaxies live: a panchromatic view of radio-AGN in the AKARI-NEP field

    CERN Document Server

    Karouzos, Marios; Trichas, Markos

    2013-01-01

    We study the host galaxy properties of radio sources in the AKARI-North Ecliptic Pole (NEP) field, using an ensemble of multi-wavelength datasets. We identify both radio-loud and radio-quiet AGN and study their host galaxy properties by means of SED fitting. We investigate the relative importance of nuclear and star-formation activity in radio-AGN and assess the role of radio-AGN as efficient quenchers of star-formation in their host galaxies.

  6. J1216+0709: A Radio Galaxy with Three Episodes of AGN Jet Activity

    Science.gov (United States)

    Singh, Veeresh; Ishwara-Chandra, C. H.; Kharb, Preeti; Srivastava, Shweta; Janardhan, P.

    2016-08-01

    We report the discovery of a “triple-double radio galaxy,” J1216+0709, detected in deep low-frequency Giant Metrewave Radio Telescope (GMRT) observations. J1216+0709 is only the third radio galaxy, after B0925+420 and Speca, with three pairs of lobes resulting from three different episodes of active galactic nucleus (AGN) jet activity. The 610 MHz GMRT image clearly displays an inner pair of lobes, a nearly coaxial middle pair of lobes, and a pair of outer lobes that is bent with respect to the axis of the inner pair of lobes. The total end-to-end projected sizes of the inner, middle, and outer lobes are 40″ (∼95 kpc), 1.‧65 (∼235 kpc), and 5.‧7 (∼814 kpc), respectively. Unlike the outer pair of lobes, both the inner and middle pairs of lobes exhibit asymmetries in arm lengths and flux densities, but in the opposite sense, i.e., the eastern sides are farther and also brighter than the western sides, thus, suggesting the possibility of the jet being intrinsically asymmetric rather than due to a relativistic beaming effect. The host galaxy is a bright elliptical (m r ∼ 16.56) with M SMBH ∼ 3.9 × 109 M ⊙ and a star formation rate of ∼{4.66}-1.61{{+4.65}} M ⊙ yr‑1. The host galaxy resides in a small group of three galaxies (m r ≤ 17.77) and is possibly going through an interaction with faint dwarf galaxies in the neighborhood, which may have triggered the recent episodes of AGN activity.

  7. A formation scenario of young stellar groups in the region of the Scorpio Centaurus OB association

    CERN Document Server

    Ortega, V G; De la Reza, R; Bazzanella, B

    2009-01-01

    The main objective of this work is to investigate the role played by Lower Centaurus Crux (LCC) and Upper Centaurus Lupus (UCL), both subcomponents of the Scorpio Centaurus OB association (Sco-Cen), in the formation of the groups beta Pictoris, TW Hydrae and the eta Chamaeleontis cluster. The dynamical evolution of all the stellar groups involved and of the bubbles and shells blown by LCC and UCL are calculated and followed from the past to the present. This leads to a formation scenario in which (1) the groups beta Pictoris, TW Hydrae were formed in the wake of the shells created by LCC and UCL, (2) the young cluster eta Chamaeleontis was born as a consequence of the collision of the shells of LCC and UCL, and (3) the formation of Upper Scorpius (US), the other main subcomponent of the Sco-Cen association, may have been started by the same process that created eta Chamaeleontis.

  8. NEW MEMBERS OF THE SCORPIUS-CENTAURUS COMPLEX AND AGES OF ITS SUB-REGIONS

    Energy Technology Data Exchange (ETDEWEB)

    Song, Inseok [Department of Physics and Astronomy, The University of Georgia, Athens, GA 30602-2451 (United States); Zuckerman, B. [Department of Physics and Astronomy, University of California, Los Angeles, 475 Portola Plaza, Los Angeles, CA 90095-1547 (United States); Bessell, M. S. [Research School of Astronomy and Astrophysics, Institute of Advanced Studies, The Australian National University, ACT 2611 (Australia)

    2012-07-15

    We have spectroscopically identified {approx}100 G-, K-, and M-type members of the Scorpius-Centaurus complex. To deduce the age of these young stars we compare their Li {lambda}6708 absorption line strengths against those of stars in the TW Hydrae association and {beta} Pictoris moving group. These line strengths indicate that Sco-Cen stars are younger than {beta} Pic stars whose ages of {approx}12 Myr have previously been derived from a kinematic traceback analysis. Our derived age, {approx}10 Myr, for stars in the Lower Centaurus Crux and Upper Centaurus Lupus subgroups of ScoCen is younger than previously published ages based on the moving cluster method and upper main-sequence fitting. The discrepant ages are likely due to an incorrect (or lack of) cross-calibration between model-dependent and model-independent age-dating methods.

  9. The giant lobes of Centaurus A observed at 118 MHz with the Murchison Widefield Array

    CERN Document Server

    McKinley, B; Gaensler, B M; Feain, I J; Bernardi, G; Wayth, R B; Johnston-Hollitt, M; Offringa, A R; Arcus, W; Barnes, D G; Bowman, J D; Bunton, J D; Cappallo, R J; Corey, B E; Deshpande, A; deSouza, L; Emrich, D; Goeke, R; Greenhill, L J; Hazelton, B J; Herne, D; Hewitt, J N; Kaplan, D L; Kasper, J C; Kincaid, B B; Koenig, R; Kratzenberg, E; Lonsdale, C J; Lynch, M J; McWhirter, S R; Mitchell, D A; Morales, M F; Morgan, E; Oberoi, D; Ord, S M; Pathikulangara, J; Prabu, T; Remillard, R A; Rogers, A E E; Roshi, A; Salah, J E; Sault, R J; Shankar, N Udaya; Srivani, K S; Stevens, J; Subrahmanyan, R; Tingay, S J; Waterson, M; Webster, R L; Whitney, A R; Williams, A; Williams, C L; Wyithe, J S B

    2013-01-01

    We present new wide-field observations of Centaurus A (Cen A) and the surrounding region at 118 MHz with the Murchison Widefield Array (MWA) 32-tile prototype, with which we investigate the spectral-index distribution of Cen A's giant radio lobes. We compare our images to 1.4 GHz maps of Cen A and compute spectral indices using temperature-temperature plots and spectral tomography. We find that the morphologies at 118 MHz and 1.4 GHz match very closely apart from an extra peak in the southern lobe at 118 MHz, which provides tentative evidence for the existence of a southern counterpart to the northern middle lobe of Cen A. Our spatially-averaged spectral indices for both the northern and southern lobes are consistent with previous analyses, however we find significant spatial variation of the spectra across the extent of each lobe. Both the spectral-index distribution and the morphology at low radio frequencies support a scenario of multiple outbursts of activity from the central engine. Our results are consi...

  10. Simulations of spiral galaxies with an active potential: molecular cloud formation and gas dynamics

    OpenAIRE

    Dobbs, Clare; Bonnell, Ian

    2008-01-01

    We describe simulations of the response of a gaseous disc to an active spiral potential. The potential is derived from an N-body calculation and leads to a multi-armed time-evolving pattern. The gas forms long spiral arms typical of grand design galaxies, although the spiral pattern is asymmetric. The primary difference from a grand-design spiral galaxy, which has a consistent 2/4-armed pattern, is that instead of passing through the spiral arms, gas generally falls into a developing potentia...

  11. A Soft X-Ray Lag Detected in Centaurus A

    CERN Document Server

    Tachibana, Yutaro; Ueda, Yoshihiro; Shidatsu, Megumi; Arimoto, Makoto; Yoshii, Taketoshi; Yatsu, Yoichi; Saito, Yoshihiko; Pike, Sean; Kawai, Nobuyuki

    2015-01-01

    We performed time lag analysis on the X-ray light curves of Centaurus A (Cen A) obtained by the Gas Slit Camera (GSC) aboard the Monitor of All-sky X-ray Image (MAXI) in three energy bands (2--4 keV, 4--10 keV, and 10--20 keV). We discovered a soft X-ray lag relative to higher energies (soft lag) on a time scale of days by employing the discrete correlation function (DCF) and the z-transformed discrete correlation function (ZDCF) method in a flare episode. A peak in the DCF and the ZDCF was observed at a soft lag of $\\sim 5$ days in 2--4 keV versus 4--10 keV and in 4--10 keV versus 10--20 keV, and $\\sim 10$ days in 2--4 keV versus 10--20 keV. We found it difficult to explain the observed X-ray variation with the one-zone synchrotron self-Compton (SSC) model, in which the soft lags reflect the different cooling times of the relativistic electrons in these three energy bands. Alternatively, if the X-ray variation was produced in a corona surrounding or along the inner part of the accretion disk, we can explain ...

  12. Imaging on PAPER: Centaurus A at 148 MHz

    CERN Document Server

    Stefan, Irina I; Green, David A; Ali, Zaki; Aguirre, James E; Bradley, Richard F; DeBoer, Dave; Dexter, Matthew; Gugliucci, Nicole E; Harris, D E; Jacobs, Daniel C; MacMahon, Dave; Manley, Jason; Moore, David F; Parsons, Aaron R; Pober, Jonathan C; Walbrugh, William P

    2012-01-01

    We present observations taken with the Donald C. Backer Precision Array for Probing the Epoch of Reionization (PAPER) of the Centaurus A field in the frequency range 120 to 180 MHz. The resulting image has a dynamic range of 3000 and an r.m.s. of 0.5 Jy/beam. A spectral index map of Cen A is produced across the full band. The spectral index distribution is qualitatively consistent with electron reacceleration in regions of excess turbulence in the radio lobes, as previously identified morphologically. Hence, there appears to be an association of `severe weather' in radio lobes with energy input into the relativistic electron population. We perform a detailed comparison of the large scale radio and X-ray emission from the ROSAT All Sky Survey. While the ROSAT field has significant gradients and structures on 10 deg scales possibly unrelated to Cen A, two interesting correlations are seen between the radio and X-ray emission. First is an apparent `cavity' generated by the northern radio lobe on a scale of 5 deg...

  13. On the behaviour of the IR Ca II triplet in normal and active galaxies

    OpenAIRE

    Terlevich, Elena; Angeles I. Díaz; Terlevich, Roberto

    1990-01-01

    This is an electronic version of an article published in Monthly Notices of the Royal Astronomical Society. Terlevich, E., Díaz, A.I., Terlevich, R. On the behaviour of the IR Ca II triplet in normal and active galaxies. Monthly Notices of the Royal Astronomical Society 242 (1990): 271-284

  14. 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

  15. Mid- to far infrared properties of star-forming galaxies and active galactic nuclei

    CERN Document Server

    Magdis, G E; Helou, G; Farrah, D; Hurley, P; Alonso-Herrero, A; Bock, J; Burgarella, D; Chapman, S; Charmandaris, V; Cooray, A; Dai, Y S; Dale, D; Elbaz, D; Feltre, A; Hatziminaoglou, E; Huang, J-S; Morrison, G; Oliver, S; Page, M; Scott, D; Shi, Y

    2013-01-01

    We study the mid- to far-IR properties of a 24um-selected flux-limited sample (S24 > 5mJy) of 154 intermediate redshift (~0.15), infrared luminous galaxies, drawn from the 5MUSES survey. By combining existing mid-IR spectroscopy and new Herschel SPIRE submm photometry from the HerMES program, we derived robust total infrared luminosity (LIR) and dust mass (Md) estimates and infered the relative contribution of the AGN to the infrared energy budget of the sources. We found that the total infrared emission of galaxies with weak 6.2um PAH emission (EW0.2um more than 50% of the LIR arises from star formation. We also found that for galaxies detected in the 250-500um Herschel bands an AGN has a statistically insignificant effect on the temperature of the cold dust and the far-IR colours of the host galaxy, which are primarily shaped by star formation activity. For star-forming galaxies we reveal an anti-correlation between the LIR-to-rest-frame 8um luminosity ratio, IR8 = LIR\\L8, and the strength of PAH features. ...

  16. The host galaxies of active galactic nuclei with powerful relativistic jets

    Science.gov (United States)

    Olguín-Iglesias, A.; León-Tavares, J.; Kotilainen, J. K.; Chavushyan, V.; Tornikoski, M.; Valtaoja, E.; Añorve, C.; Valdés, J.; Carrasco, L.

    2016-08-01

    We present deep near-infrared (NIR) images of a sample of 19 intermediate-redshift (0.3 1027 W Hz-1), previously classified as flat-spectrum radio quasars. We also compile host galaxy and nuclear magnitudes for blazars from literature. The combined sample (this work and compilation) contains 100 radio-loud AGN with host galaxy detections and a broad range of radio luminosities L1.4 GHz ˜ 1023.7-1028.3 W Hz-1, allowing us to divide our sample into high-luminosity blazars (HLBs) and low-luminosity blazars (LLBs). The host galaxies of our sample are bright and seem to follow the μe-Reff relation for ellipticals and bulges. The two populations of blazars show different behaviours in the MK,nuclear -MK,bulge plane, where a statistically significant correlation is observed for HLBs. Although it may be affected by selection effects, this correlation suggests a close coupling between the accretion mode of the central supermassive black hole and its host galaxy, which could be interpreted in terms of AGN feedback. Our findings are consistent with semi-analytical models where low-luminosity AGN emit the bulk of their energy in the form of radio jets, producing a strong feedback mechanism, and high-luminosity AGN are affected by galaxy mergers and interactions, which provide a common supply of cold gas to feed both nuclear activity and star formation episodes.

  17. 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...

  18. Tracing the evolution of active galactic nuclei host galaxies over the last 9 Gyr of cosmic time

    Energy Technology Data Exchange (ETDEWEB)

    Goulding, A. D.; Forman, W. R.; Jones, C.; Murray, S. S.; Paggi, A.; Ashby, M. L. N.; Huang, J.-S.; Kraft, R.; Willner, S. P. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Hickox, R. C. [Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755 (United States); Coil, A. L. [Department of Physics, Center for Astrophysics and Space Sciences, University of California at San Diego, 9500 Gilman Drive, La Jolla, San Diego, CA 92093 (United States); Cooper, M. C. [Center for Galaxy Evolution, Department of Physics and Astronomy, University of California, Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697 (United States); Newman, J. A. [Department of Physics and Astronomy, University of Pittsburgh, 3941 O' Hara Street, Pittsburgh, PA 15260 (United States); Weiner, B. J., E-mail: agoulding@cfa.harvard.edu [Steward Observatory, 933 North Cherry Street, University of Arizona, Tucson, AZ 85721 (United States)

    2014-03-01

    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 Sloan Digital Sky Survey, Boötes, 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 remained as separate galaxy populations throughout the last 9 Gyr. Furthermore, it appears that galaxies hosting AGN have evolved along the same path as galaxies that are not hosting AGN with little evidence for distinctly separate evolution.

  19. 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...

  20. Active Galactic Nuclei and their Role in Galaxy Evolution: The Infrared Perspective

    CERN Document Server

    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 IR observations provide a wealth of complementary information that cannot be derived from data in other wavelength regimes. In this review, I summarize the unique contribution that IR astronomy has recently made to our understanding of AGN and their role in galaxy evolution, including both physical studies of AGN at IR wavelengths, and the search for AGN among IR galaxies in general. Finally, I identify and discuss key open issues that it should be possible to address with forthcoming IR telescopes.

  1. 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.

  2. Galaxy Zoo: The properties of merging galaxies in the nearby Universe - local environments, colours, masses, star-formation rates and AGN activity

    CERN Document Server

    Darg, D W; Lintott, C J; Schawinski, K; Sarzi, M; Bamford, S; Silk, J; Andreescu, D; Murray, P; Nichol, R C; Raddick, M J; Slosar, A; Szalay, A S; Thomas, D; Vandenberg, J

    2009-01-01

    Following the study of Darg et al. (2009; hereafter D09a) we explore the environments, optical colours, stellar masses, star-formation and AGN activity in a sample of 3003 merging galaxies drawn from the SDSS using the Galaxy Zoo project. While D09a found that the spiral-to-elliptical ratio in (major) mergers appeared higher than that of the global galaxy population, no significant differences are found between the environmental distributions of mergers and a randomly selected control sample. This makes the high occurrence of spirals in mergers unlikely to be an environmental effect and must, therefore, arise from differing time-scales of detectability for spirals and ellipticals. We find that merging galaxies have a wider spread in colour than the global galaxy population, with a significant blue tail resulting from intense star-formation in spiral mergers. Galaxies classed as star-forming using their emission-line properties have average star-formation rates approximately doubled by the merger process thoug...

  3. 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

  4. Detection of optical coronal emission from 10^6 K gas in the core of the Centaurus cluster

    CERN Document Server

    Canning, R E A; Johnstone, R M; Sanders, J S; Crawford, C S; Hatch, N A; Ferland, G J

    2010-01-01

    We report a detection (3.5x10^37 \\pm 5.6x10^36 ergps) of the optical coronal emission line [Fe X]6374 and upper limits of four other coronal lines using high resolution VIMOS spectra centred on NGC 4696, the brightest cluster galaxy in the Centaurus cluster. Emission from these lines is indicative of gas at temperatures between 1 and 5 million K so traces the interstellar gas in NGC 4696. The rate of cooling derived from the upper limits is consistent with the cooling rate from X-ray observations (~10 solar masses per year) however we detect twice the luminosity expected for [Fe X]6374 emission, at 1 million K, our lowest temperature probe. We suggest this emission is due to the gas being heated rather than cooling out of the intracluster medium. We detect no coronal lines from [Ca XV], which are expected from the 5 million K gas seen near the centre in X-rays with Chandra. Calcium is however likely to be depleted from the gas phase onto dust grains in the central regions of NGC 4696.

  5. NuSTAR and XMM-Newton Observations of the Hard X-Ray Spectrum of Centaurus A

    CERN Document Server

    Fuerst, F; Madsen, K K; Lanz, L; Rivers, E; Brightman, M; Arevalo, P; Balokovic, M; Beuchert, T; Boggs, S E; Christensen, F E; Craig, W W; Dauser, T; Farrah, D; Graefe, C; Hailey, C J; Harrison, F A; Kadler, M; King, A; Krauss, F; Madejski, G; Matt, G; Marinucci, A; Markowitz, A; Ogle, P; Ojha, R; Rothschild, R; Stern, D; Walton, D J; Wilms, J; Zhang, W

    2015-01-01

    We present simultaneous XMM-Newton and NuSTAR observations spanning 3-78 keV of the nearest radio galaxy, Centaurus A (Cen A), performed during a very high flux state. The accretion geometry around the central engine in Cen A is still debated, and we investigate possible configurations using detailed X-ray spectral modeling. NuSTAR imaged the central region of Cen A with subarcminute resolution at X-ray energies above 10 keV for the first time, but finds no evidence for an extended source or other off-nuclear point-sources. The XMM-Newton and NuSTAR spectra agree well and can be described with an absorbed power-law with a photon index {\\Gamma} = 1.815 +/- 0.005 and a fluorescent Fe K{\\alpha} line in good agreement with literature values. The spectrum does not require a high-energy exponential rollover, with a constraint of E_fold > 1MeV. A thermal Comptonization continuum describes the data well, with parameters that agree with values measured by INTEGRAL, in particular an electron temperature of kT_e ~ 220 k...

  6. Filaments in the southern giant lobe of Centaurus A: constraints on nature and origin from modelling and GMRT observations

    CERN Document Server

    Wykes, Sarka; Hardcastle, Martin J; Achterberg, Abraham; Jones, Thomas W; Jerjen, Helmut; Orru, Emanuela; Lazarian, Alex; Shimwell, Timothy W; Wise, Michael W; Kronberg, Philipp P

    2014-01-01

    We present results from imaging of the radio filaments in the southern giant lobe of Centaurus A using data from GMRT observations at 325 and 235 MHz, and outcomes from filament modelling. The observations reveal a rich filamentary structure, largely matching the morphology at 1.4 GHz. We find no clear connection of the filaments to the jet. We seek to constrain the nature and origin of the vertex and vortex filaments associated with the lobe and their role in high-energy particle acceleration. We deduce that these filaments are at most mildly overpressured with respect to the global lobe plasma showing no evidence of large-scale efficient Fermi I-type particle acceleration, and persist for ~ 2-3 Myr. We demonstrate that the dwarf galaxy KK 196 (AM 1318-444) cannot account for the features, and that surface plasma instabilities, the internal sausage mode and radiative instabilities are highly unlikely. An internal tearing instability and the kink mode are allowed within the observational and growth time const...

  7. The physical characteristics of the gas in the disk of Centaurus A using the Herschel Space Observatory

    CERN Document Server

    Parkin, T J; Schirm, M R P; Baes, M; Boquien, M; Boselli, A; Cormier, D; Galametz, M; Karczewski, O Ł; Lebouteiller, V; De Looze, I; Madden, S C; Roussel, H; Smith, M W L; Spinoglio, L

    2014-01-01

    We search for variations in the disk of Centaurus A of the emission from atomic fine structure lines using Herschel PACS and SPIRE spectroscopy. In particular we observe the [C II](158 $\\mu$m), [N II](122 and 205 $\\mu$m), [O I](63 and 145 $\\mu$m) and [O III](88 $\\mu$m) lines, which all play an important role in cooling the gas in photo-ionized and photodissociation regions. We determine that the ([C II]+[O I]$_{63}$)/$F_{TIR}$ line ratio, a proxy for the heating efficiency of the gas, shows no significant radial trend across the observed region, in contrast to observations of other nearby galaxies. We determine that 10 - 20% of the observed [C II] emission originates in ionized gas. Comparison between our observations and a PDR model shows that the strength of the far-ultraviolet radiation field, $G_0$, varies between $10^{1.75}$ and $10^{2.75}$ and the hydrogen nucleus density varies between $10^{2.75}$ and $10^{3.75}$ cm$^{-3}$, with no significant radial trend in either property. In the context of the emis...

  8. 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

    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...

  9. A GMRT Study of Seyfert Galaxies NGC4235 & NGC4594: Evidence of Episodic Activity ?

    CERN Document Server

    Kharb, P; Singh, V; Gallimore, J F; Ishwara-Chandra, C H; Hota, Ananda

    2016-01-01

    Low frequency observations at 325 and 610 MHz have been carried out for two "radio-loud" Seyfert galaxies, NGC4235 and NGC4594 (Sombrero galaxy), using the Giant Meterwave Radio Telescope (GMRT). The 610 MHz total intensity and 325-610 MHz spectral index images of NGC4235 tentatively suggest the presence of a "relic" radio lobe, most likely from a previous episode of AGN activity. This makes NGC4235 only the second known Seyfert galaxy after Mrk6 to show signatures of episodic activity. Spitzer and Herschel infrared spectral energy distribution (SED) modelling using the clumpyDREAM code predicts star formation rates (SFR) that are an order of magnitude lower than those required to power the radio lobes in these Seyferts (~0.13-0.23 M_sun/yr compared to the required SFR of ~2.0-2.7 M_sun/yr in NGC4594 and NGC4235, respectively). This finding along with the detection of parsec and sub-kpc radio jets in both Seyfert galaxies, that are roughly along the same position angles as the radio lobes, strongly support th...

  10. A soft X-ray lag detected in Centaurus A

    Science.gov (United States)

    Tachibana, Yutaro; Kawamuro, Taiki; Ueda, Yoshihiro; Shidatsu, Megumi; Arimoto, Makoto; Yoshii, Taketoshi; Yatsu, Yoichi; Saito, Yoshihiko; Pike, Sean; Kawai, Nobuyuki

    2016-06-01

    We performed time-lag analysis on the X-ray light curves of Centaurus A (Cen A) obtained by the Gas Slit Camera (GSC) aboard the Monitor of All-sky X-ray Image (MAXI) in three energy bands (2-4 keV, 4-10 keV, and 10-20 keV). We discovered a soft X-ray lag relative to higher energies (soft lag) on a timescale of days in a flaring episode by employing the discrete correlation function (DCF) and the z-transformed discrete correlation function (ZDCF) method. In the episode, a peak and a centroid in the DCF and the ZDCF was observed at a soft lag of ˜ 5 d in 2-4 keV versus 4-10 keV and in 4-10 keV versus 10-20 keV, and ˜ 10 d in 2-4 keV versus 10-20 keV. We found it difficult to explain the observed X-ray variation by a single energy injection with the one-zone synchrotron self-Compton (SSC) model, in which the soft lags in these three energy bands reflect the different cooling times of the relativistic electrons, by assuming the magnetic field and minimum Lorentz factor estimated from a broad-band spectral energy distribution. Alternatively, if the phenomenon is interpreted as cooling of Comptonizing electrons in a corona covering the accretion disk, the temperature of the corona producing the variable X-rays should be ˜ 10 keV for reconciliation with the soft lag in the energy range of 2-20 keV.

  11. The connection between radio loudness and central surface brightness profiles in optically selected low-luminosity active galaxies

    Science.gov (United States)

    Richings, A. J.; Uttley, P.; Körding, E.

    2011-08-01

    Recent results indicate a correlation between nuclear radio loudness of active galaxies and their central stellar surface-brightness profiles, in that 'core' galaxies (with inner logarithmic slope γ≤ 0.3) are significantly more radio loud than 'power-law' galaxies (γ≥ 0.5). This connection, which indicates possible links between radio loudness and galaxy formation history (e.g. through black hole spin), has so far only been confirmed for a radio-selected sample of galaxies. Furthermore, it has since been shown that the Nuker law, which was used to parametrize the brightness profiles in these studies, gives a poor description of the brightness profile, with its parameters varying systematically with the radial fitted extent of the profile. Here, we present an analysis of the central surface brightness profiles of the active galaxies of Hubble type T≤ 3, that were identified by the optically selected Palomar spectroscopic survey of nearby galaxies. We fit the brightness profiles using Sérsic, Core-Sérsic and, where necessary, Double-Sérsic models, which we fit to the semimajor axis brightness profiles extracted from high-resolution images of the galaxies from the Hubble Space Telescope. We use these fits to classify the galaxies as 'Core', 'Sérsic' or 'Double-Sérsic'. We compare the properties of the active galactic nuclei (AGN) and their host galaxies with this classification, and we recover the already established trend for Core galaxies to be more luminous and contain a higher mass supermassive black hole. Defining the radio loudness of an AGN as the ratio of the nuclear radio luminosity to [O III] line luminosity, which allows us to include most of the AGN in our sample and prevents a bias against dim nuclei that are harder to extract from the brightness profiles, we find that AGN hosted in Core galaxies are generally more radio loud than those hosted in Sérsic galaxies, although there is a large overlap between the two subsamples. The correlation

  12. The Hidden Lives of Galaxies: An Information & Activity Booklet, Grades 9-12, 2000-2001. Imagine the Universe! Probing the Structure & Evolution of the Cosmos.

    Science.gov (United States)

    Lochner, James C.; Williamson, Lisa; Fitzhugh, Ethel

    This National Aeronautics and Space Administration (NASA) document presents activities on the properties of galaxies for additional curriculum support. The activities presented in this document include: (1) "How Big Is the Universe"; (2) "Identifying Galaxies"; (3) "Classifying Galaxies Using Hubble's Fork Diagram"; (4) "Identifying Unusual…

  13. High resolution 12CO(2-1) observations of the molecular gas in Centaurus A

    NARCIS (Netherlands)

    Rydbeck, G.; Wiklind, T.; Cameron, M.; Wild, W.; Eckart, A.; Genzel, R.; Rothermel, H.

    1993-01-01

    Observations of (C-12)O(2-1) emission in the dust lane of Centaurus A show that, except for the center region, the overall distribution and kinematics of the molecular gas is consistent with that of ionized gas. Deconvolution of the observed emission reveals (i) a structure agreeing with what would

  14. VizieR Online Data Catalog: Centaurus Cluster catalog (Chiboucas+, 2007)

    Science.gov (United States)

    Chiboucas, K.; Mateo, M.

    2007-09-01

    Observations of A3526 (Centaurus, 12:48:51.8, -41:18:21, J2000.0) were acquired with the LCO 1m and a TEK 2K Camera having a field of view of 20.48' and scale size 0.6"/pix on 1993 13-20 May and 1997 1-8 May. (1 data file).

  15. Simulating the formation of disk galaxies: The impact of Jets from Active Galactic Nuclei

    CERN Document Server

    Okamoto, Takashi; Bower, Richard G

    2007-01-01

    Recent semi-analytic models have highlighted the role of AGN jets in regulating the formation of galaxies. In this paper, we present a new implementation of feedback due to active galactic nuclei (AGN) in cosmological hydrodynamic simulations of galaxy formation in which AGN feedback is assumed to heat the halo gas through the production of jets. Combining a theoretical model of mass accretion onto black holes with a multiphase description of star-forming gas, we self-consistently follow evolution of both galaxies and their central black holes. The novelty in our model is that we consider the two distinct accretion modes: standard radiatively efficient thin accretion disks and radiatively inefficient accretion flows which we will generically refer to as RIAFs; motivated by the theoretical modelsfor jet production in accretion disks, we assume that only the RIAF is responsible for the production of powerful jets. The focus of this paper is to investigate the interplay between galaxies and their central black h...

  16. AGN Activity and Black Hole Masses in Low Surface Brightness Galaxies

    CERN Document Server

    Ramya, S; Das, M

    2011-01-01

    We present medium resolution optical spectroscopy of a sample of nine Low Surface Brightness (LSB) galaxies. For those that show clear signatures of AGN emission, we have disentangled the AGN component from stellar light and any Fe I and Fe II contribution. We have decomposed the H_alpha line into narrow and broad components and determined the velocities of the broad components; typical values lie between 900--2500 km/s. Of the galaxies in our study, UGC 6614, UGC 1922, UGC 6968 and LSBC F568-6 (Malin~2) show clear signatures of AGN activity. We have calculated the approximate black hole masses for these galaxies from the H_alpha line emission using the virial approximation. The black hole masses are ~3x10^{5} M_sun for three galaxies and lie in the intermediate mass black holes domain rather than the supermassive range. UGC 6614 harbors a BH of mass 3.8x10^{6} M_sun; it also shows an interesting feature blueward of H_alpha and H_beta implying outflow of gas or a one-sided jet streaming towards us. We have al...

  17. Disentangling star formation and AGN activity in powerful infrared luminous radio galaxies at 1

    CERN Document Server

    Drouart, Guillaume; De Breuck, Carlos; Fioc, Michel; Lehnert, Matthew; Seymour, Nick; Stern, Dan; Vernet, Joel

    2016-01-01

    High-redshift radio galaxies present signs of both star formation and AGN activity, making them ideal candidates to investigate the connection and coevolution of AGN and star formation in the progenitors of present-day massive galaxies. We make use of a sample of 11 powerful radio galaxies spanning 1galaxies form at very high-redshift, but experience episodic and important growth at 1

  18. Testing Diagnostics of Nuclear Activity and Star Formation in Galaxies at z>1

    CERN Document Server

    Trump, Jonathan R; Barro, Guillermo; Koo, David C; Kocevski, Dale D; Juneau, Stephanie; Weiner, Benjamin J; Faber, S M; McLean, Ian S; Yan, Renbin; Perez-Gonzalez, Pablo G; Villar, Victor

    2012-01-01

    We present some of the first science data with the new Keck/MOSFIRE instrument to test the effectiveness of different AGN/SF diagnostics at z~1.5. MOSFIRE spectra were obtained in three H-band multi-slit masks in the GOODS-S field, resulting in two hour exposures of 36 emission-line galaxies. We compare X-ray data with the traditional "BPT" line ratio diagnostics and the alternative mass-excitation and color-excitation diagrams, combining new MOSFIRE infrared data with previous HST/WFC3 infrared spectra (from the 3D-HST survey) and multiwavelength photometry. We demonstrate that a high [OIII]/\\Hb ratio is insufficient as an AGN indicator at z>1. For the four X-ray detected galaxies, the classic BPT diagnostic ([OIII]/Hb vs. [NII]/Ha and [SII]/Ha) remains consistent with X-ray AGN/SF classification. The X-ray data also suggest that "composite" galaxies (with intermediate AGN/SF classification) host bona-fide AGNs. Nearly 2/3 of the z~1.5 emission-line galaxies have nuclear activity detected by either X-rays or...

  19. BROAD Hβ EMISSION-LINE VARIABILITY IN A SAMPLE OF 102 LOCAL ACTIVE GALAXIES

    Energy Technology Data Exchange (ETDEWEB)

    Runco, Jordan N.; Cosens, Maren; Bennert, Vardha N.; Scott, Bryan [Physics Department, California Polytechnic State University, San Luis Obispo CA 93407 (United States); Komossa, S. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121, Bonn (Germany); Malkan, Matthew A.; Treu, Tommaso [Department of Physics, University of California, Los Angeles, CA 90095 (United States); Lazarova, Mariana S. [Department of Physics and Physical Science, University of Nebraska Kearney, Kearney, NE 68849 (United States); Auger, Matthew W. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Park, Daeseong, E-mail: jrunco@calpoly.edu, E-mail: mcosens@calpoly.edu, E-mail: vbennert@calpoly.edu, E-mail: malkan@astro.ucla.edu, E-mail: tt@physics.ucsb.edu, E-mail: lazarovam2@unk.edu, E-mail: mauger@ast.cam.ac.uk, E-mail: daeseongpark@kasi.re.kr [Korea Astronomy and Space Science Institute, Daejeon, 34055 (Korea, Republic of)

    2016-04-10

    A sample of 102 local (0.02 ≤ z ≤ 0.1) Seyfert galaxies with black hole masses M{sub BH} > 10{sup 7}M{sub ⊙} was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between M{sub BH} and host galaxy properties. We study profile changes of the broad Hβ emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad Hβ emission line is of particular interest, not only because it is used to estimate M{sub BH}, but also because its strength and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (∼66%) of the objects, resulting in a Seyfert-type change for ∼38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hβ line virtually disappears in 3/102 (∼3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of Hβ line variability in a sample of low-redshift Seyfert galaxies.

  20. The discovery of five new H2O megamasers in active galaxies

    Science.gov (United States)

    Braatz, J. A.; Wilson, A. S.; Henkel, C.

    1994-01-01

    H2O megamasers with (isotropic) luminosities between 60 and 200 solar luminosity (H(sub 0) = 75 km/s/Mpc) have been detected in the Seyfert 2 galaxies Mrk 1, Mrk 1210, and NGC 5506 and in the LINERs NGC 1052 and NGC 2639. No megamasers have been found in Seyfert 1's. The galaxies have redshifts between 1500 and 4800 km/s and are the most distant H2O sources reported to date. NGC 1052 is also the first elliptical galaxy known to contain an H2O maser. The intensity distribution of an H2O five-point map obtained toward NGC 5506 shows that the H2O emission is pointlike compared to the 40 sec telescope beam. The lack of CO emission in NGC 1052 implies a conservative lower limit to the H2O brightness temperature of 1000 K, thus ruling out a thermal origin for the H2O emission. The success of this survey relative to other recent searches makes it evident that H2O megamasers are preferentially found in galaxies with active nuclei.

  1. 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.

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

    International Nuclear Information System (INIS)

    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.

  3. Testing the two planes of satellites in the Centaurus Group

    CERN Document Server

    Müller, Oliver; Pawlowski, Marcel S; Binggeli, Bruno

    2016-01-01

    The existence of satellite galaxy planes poses a major challenge for the standard picture of structure formation with non-baryonic dark matter. Recently Tully et al. (2015) reported the discovery of two almost parallel planes in the nearby Cen A group using mostly high-mass galaxies (M$_B$ $<$ -10 mag) in their analysis. Our team detected a large number of new group member candidates in the Cen A group (M\\"uller et al. 2016). This dwarf galaxy sample combined with other recent results from the literature enables us to test the galaxy distribution in the direction of the Cen A group and to determine the statistical significance of the geometric alignment. Taking advantage of the fact that the two galaxy planes lie almost edge-on along the line of sight, the newly found 13 group members by Crnojevic et al. (2014, 2016) and our 16 new Cen A group candidates (M\\"uller et al. 2016) can be assigned relative to the two planes. We use various statistical methods to test whether the distribution of galaxies follows...

  4. CHANDRA OBSERVATIONS OF GALAXY ZOO MERGERS: FREQUENCY OF BINARY ACTIVE NUCLEI IN MASSIVE MERGERS

    Energy Technology Data Exchange (ETDEWEB)

    Teng, Stacy H. [Observational Cosmology Laboratory, NASA/GSFC, Greenbelt, MD 20771 (United States); Schawinski, Kevin; Urry, C. Megan; Bonning, Erin W. [Department of Physics, Yale University, New Haven, CT 06511 (United States); Darg, Dan W.; Kaviraj, Sugata; Lintott, Chris J. [Department of Physics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom); Oh, Kyuseok [Department of Astronomy, Yonsei University, Seoul 120-749 (Korea, Republic of); Cardamone, Carolin N. [Harriet W. Sheridan Center for Teaching and Learning, Brown University, P.O. Box 1912, Providence, RI 02912 (United States); Keel, William C. [Department of Physics and Astronomy, 206 Gallalee Hall, 514 University Boulevard, University of Alabama, Tuscaloosa, AL 35487-034 (United States); Simmons, Brooke D. [Yale Center for Astronomy and Astrophysics, Yale University, P.O. Box 208121, New Haven, CT 06520 (United States); Treister, Ezequiel, E-mail: stacy.h.teng@nasa.gov [Departamento de Astronomia, Universidad de Concepcion, Casilla 160-C, Concepcion (Chile)

    2012-07-10

    We present the results from a Chandra pilot study of 12 massive galaxy mergers selected from Galaxy Zoo. The sample includes major mergers down to a host galaxy mass of 10{sup 11} M{sub Sun} that already have optical active galactic nucleus (AGN) signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured (N{sub H} {approx}< 1.1 Multiplication-Sign 10{sup 22} cm{sup -2}) X-ray nuclei are relatively common (8/12), but the detections are too faint (<40 counts per nucleus; f{sub 2-10keV} {approx}< 1.2 Multiplication-Sign 10{sup -13} erg s{sup -1} cm{sup -2}) to reliably separate starburst and nuclear activity as the origin of the X-ray emission. Only one merger is found to have confirmed binary X-ray nuclei, though the X-ray emission from its southern nucleus could be due solely to star formation. Thus, the occurrences of binary AGNs in these mergers are rare (0%-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.

  5. Dissecting Galaxies: Spatial and Spectral Separation of Emission Excited by Star Formation and AGN Activity

    CERN Document Server

    Davies, Rebecca L; Kewley, Lisa J; Dopita, Michael A; Hampton, Elise J; Shastri, Prajval; Scharwachter, Julia; Sutherland, Ralph; Kharb, Preeti; Bhatt, Harish; Jin, Chichuan; Banfield, Julie; Zaw, Ingyin; James, Bethan; Juneau, Stephanie; Srivastava, Shweta

    2016-01-01

    The optical spectra of Seyfert galaxies are often dominated by emission lines excited by both star formation and AGN activity. Standard calibrations (such as for the star formation rate) are not applicable to such composite (mixed) spectra. In this paper, we describe how integral field data can be used to spectrally and spatially separate emission associated with star formation from emission associated with accretion onto an active galactic nucleus (AGN). We demonstrate our method using integral field data for two AGN host galaxies (NGC 5728 and NGC 7679) from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). The spectra of NGC 5728 and NGC 7679 form clear sequences of AGN fraction on standard emission line ratio diagnostic diagrams. We show that the emission line luminosities of the majority (> 85 per cent) of spectra along each AGN fraction sequence can be reproduced by linear superpositions of the emission line luminosities of one AGN dominated spectrum and one star formation dominated...

  6. RADIO ACTIVE GALAXY NUCLEI IN GALAXY CLUSTERS: HEATING HOT ATMOSPHERES AND DRIVING SUPERMASSIVE BLACK HOLE GROWTH OVER COSMIC TIME

    International Nuclear Information System (INIS)

    We estimate the average radio active galactic nucleus (AGN, mechanical) power deposited into the hot atmospheres of galaxy clusters over more than three quarters of the age of the Universe. Our sample was drawn from eight major X-ray cluster surveys and includes 685 clusters in the redshift range 0.1 44 erg s–1 exceeds the X-ray luminosity of 44% of the clusters, indicating that the accumulation of radio-AGN energy is significant in these clusters. Integrating the AGN mechanical power to redshift z = 2.0, using simple models for its evolution and disregarding the hierarchical growth of clusters, we find that the AGN energy accumulated per particle in low luminosity X-ray clusters exceeds 1 keV per particle. This result represents a conservative lower limit to the accumulated thermal energy. The estimate is comparable to the level of energy needed to 'preheat' clusters, indicating that continual outbursts from radio-AGN are a significant source of gas energy in hot atmospheres. Assuming an average mass conversion efficiency of η = 0.1, our result implies that the supermassive black holes that released this energy did so by accreting an average of ∼109 M ☉ over time, which is comparable to the level of growth expected during the quasar era.

  7. Herschel observed Stripe 82 quasars and their host galaxies: connections between the AGN activity and the host galaxy star formation

    CERN Document Server

    Dong, Xiaoyi

    2016-01-01

    In this work, we present a study of 207 quasars selected from the Sloan Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars within this sample are high luminosity quasars with a mean bolometric luminosity of $10^{46.4}$ erg s$^{-1}$. The redshift range of this sample is within $z<4$, with a mean value of $1.5\\pm0.78$. Because we only selected quasars that have been detected in all three Herschel-SPIRE bands, the quasar sample is complete yet highly biased. Based on the multi-wavelength photometric observation data, we conducted a spectral energy distribution (SED) fitting through UV to FIR. Parameters such as active galactic nucleus (AGN) luminosity, FIR luminosity, stellar mass, as well as many other AGN and galaxy properties are deduced from the SED fitting results. The mean star formation rate (SFR) of the sample is 419 $M_{\\odot}$ yr$^{-1}$ and the mean gas mass is $\\sim 10^{11.3}$ $M_{\\odot}$. All these results point to an IR luminous quasar system. Comparing with star format...

  8. Starburst or Seyfert? Adding a radio and far-infrared perspective to the investigation of activity in composite galaxies

    CERN Document Server

    Hill, T L; Norris, R P; Reynolds, J E; Hunstead, R W; Hill, Tanya L.; Heisler, Charlene A.; Norris, Ray P.; Reynolds, John E.; Hunstead, Richard W.

    2001-01-01

    It was once common to regard Seyfert and starburst galaxies as completely different types of object, but there is growing recognition that these classifications refer to the extremes of a continuous spectrum of galaxy types. In a previous study we investigated a sample of galaxies with ambiguous optical emission-line ratios and concluded from near-infrared spectroscopic observations that the sample consisted of composite galaxies, containing both a starburst and an active galactic nucleus (AGN). We now extend our study using radio synthesis and long-baseline interferometer observations made with the Australia Telescope, together with far-infrared IRAS observations, to discuss the relative contribution of starburst and AGN components to the overall luminosity of the composite galaxies. We find that only a small fraction of the radio emission (90%) is probably due to the starburst component. We also show that an AGN contribution to the optical emission of as little as 10% is sufficient to account for the ambigu...

  9. Chandra Observations of Galaxy Zoo Mergers: Frequency of Binary Active Nuclei in Massive Mergers

    Science.gov (United States)

    Teng, Stacy H.; Schawinski, Kevin; Urry, C. Megan; Darg, Dan W.; Kaviraj, Sugata; Oh, Kyuseok; Bonning, Erin W.; Cardamone, Carolin N.; Keel, William C.; Lintott, Chris J.; Simmons, Brooke D.; Treister, Ezequiel

    2012-01-01

    We present the results from a Chandra pilot study of 12 massive galaxy mergers selected from Galaxy Zoo. The sample includes major mergers down to a host galaxy mass of 1011 M that already have optical AGN signatures in at least one of the progenitors. We find that the coincidences of optically selected active nuclei with mildly obscured (N(sub H) approx < 1.1 10(exp 22)/sq cm) X-ray nuclei are relatively common (8/12), but the detections are too faint (< 40 counts per nucleus; (sub -10) keV approx < 1.2 10(exp -13) erg/s/sq cm) to reliably separate starburst and nuclear activity as the origin of the X-ray emission. Only one merger is found to have confirmed binary X-ray nuclei, though the X-ray emission from its southern nucleus could be due solely to star formation. Thus, the occurrences of binary AGN in these mergers are rare (0-8%), unless most merger-induced active nuclei are very heavily obscured or Compton thick.

  10. The Fermi Bubbles. I. Possible Evidence for Recent AGN Jet Activity in the Galaxy

    OpenAIRE

    Guo, Fulai; Mathews, William G.

    2011-01-01

    The Fermi Gamma-ray Space Telescope reveals two large gamma-ray bubbles in the Galaxy, which extend about 50 degrees (~ 10 kpc) above and below the Galactic center (GC) and are symmetric about the Galactic plane. Using axisymmetric hydrodynamic simulations with a self-consistent treatment of the dynamical cosmic ray (CR) - gas interaction, we show that the bubbles can be created with a recent active galactic nucleus (AGN) jet activity about 1 - 3 Myr ago, which was active for a duration of ~ ...

  11. LOCAL LUMINOUS INFRARED GALAXIES. III. CO-EVOLUTION OF BLACK HOLE GROWTH AND STAR FORMATION ACTIVITY?

    International Nuclear Information System (INIS)

    Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of 7 M☉ using [Ne III] 15.56 μm and optical [O III] λ5007 gas velocity dispersions and literature stellar velocity dispersions. We find that in a large fraction of local LIRGs, the current SFR is taking place not only in the inner nuclear ∼1.5 kpc region, as estimated from the nuclear 11.3 μm PAH luminosities, but also in the host galaxy. We next use the ratios between the SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to BHAR ratios higher than those of optically selected Seyferts of similar active galactic nucleus (AGN) luminosities. However, the majority of the IR-bright galaxies in the revised-Shapley-Ames Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be higher in local LIRGs with the lowest SFRs. All of this suggests that in local LIRGs there is a distinct IR-bright star-forming phase taking place prior to the bulk of the current BH growth (i.e., AGN phase). The latter is reflected first as a composite and then as a Seyfert, and later as a non-LIRG optically identified Seyfert nucleus with moderate SF in its host galaxy.

  12. Investigating the Nuclear Activity of Barred Spiral Galaxies: The Case of NGC 1672

    Science.gov (United States)

    Jenkins, L. P.; Brandt, W. N.; Colbert, E. J.; Koribalski, B.; Kuntz, K. D.; Levan, A. J.; Ojha, R.; Roberts, T. P.; Ward, M. J.; Zezas, A.

    2011-01-01

    We have performed an X-ray study of the nearby barred spiral galaxy NGC 1672, primarily to ascertain the effect of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST) infrared imaging from the Spitzer Space Telescope, and Australia Telescope Compact Array ground-based radio data. We detect 28 X-ray sources within the D25 area of the galaxy; many are spatially correlated with star formation in the bar and spiral arms, and two are identified as background galaxies in the HST images. Nine of the X-ray sources are ultraluminous X-ray sources, with the three brightest (LX 5 * 10(exp 39) erg s(exp -1)) located at the ends of the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC 1672 possesses a hard (1.5) nuclear X-ray source with a 2-10 keV luminosity of 4 * 10(exp 38) erg s(exp -1). This is surrounded by an X-ray-bright circumnuclear star-forming ring, comprised of point sources and hot gas, which dominates the 2-10 keV emission in the central region of the galaxy. The spatially resolved multiwavelength photometry indicates that the nuclear source is a low-luminosity active galactic nucleus (LLAGN), but with star formation activity close to the central black hole. A high-resolution multiwavelength survey is required to fully assess the impact of both large-scale bars and smaller-scale phenomena such as nuclear bars, rings, and nuclear spirals on the fueling of LLAGN.

  13. Local Luminous Infrared Galaxies. III. Co-evolution of Black Hole Growth and Star Formation Activity?

    Science.gov (United States)

    Alonso-Herrero, Almudena; Pereira-Santaella, Miguel; Rieke, George H.; Diamond-Stanic, Aleksandar M.; Wang, Yiping; Hernán-Caballero, Antonio; Rigopoulou, Dimitra

    2013-03-01

    Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of nuclear ~1.5 kpc region, as estimated from the nuclear 11.3 μm PAH luminosities, but also in the host galaxy. We next use the ratios between the SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to BHAR ratios higher than those of optically selected Seyferts of similar active galactic nucleus (AGN) luminosities. However, the majority of the IR-bright galaxies in the revised-Shapley-Ames Seyfert sample behave like local LIRGs. Moreover, the AGN incidence tends to be higher in local LIRGs with the lowest SFRs. All of this suggests that in local LIRGs there is a distinct IR-bright star-forming phase taking place prior to the bulk of the current BH growth (i.e., AGN phase). The latter is reflected first as a composite and then as a Seyfert, and later as a non-LIRG optically identified Seyfert nucleus with moderate SF in its host galaxy. This work is based on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under NASA contract 1407.

  14. Relativistic jet production and propagation in active galaxies

    International Nuclear Information System (INIS)

    Recent studies of the phenomena of active galactic nuclei are beginning to identify the most likely physical processes involved in the galactic nuclei cores which give rise to a fast moving plasma that emerges in directed beams and energizes radio sources. In particular, the formation of the beams appears to be a generic property of the flow pattern around collapsed objects, where there is a relativistically deep potential well. These beams are relevant to extended radio sources, superluminal variations in compact sources, and the injection of high-energy plasma into the intergalactic medium. There is a physical similarity, and not merely a superficial analogy, between the physical mechanisms of such objects as SS 433 and Sco X-1 and the processes in active galactic nuclei. The exploration of fluid dynamic and electrodynamic effects around black holes is envisaged as a fruitful line of inquiry in the present field of study

  15. A Search for "Dwarf" Seyfert Nuclei; 5, Demographics of Nuclear Activity in Nearby Galaxies

    CERN Document Server

    Ho, L C; Sargent, W L W; Ho, Luis C.; Filippenko, Alexei V.; Sargent, Wallace L. W.

    1997-01-01

    We use the sample of emission-line nuclei derived from a recently completed optical spectroscopic survey of nearby galaxies to quantify the incidence of local (z = 0) nuclear activity. Consistent with previous studies, we find detectable amounts of ionized gas in the central few hundred parsecs of most (86%) galaxies. Half of the objects can be classified as H II or star-forming nuclei and the other half as some form of AGN, of which we distinguish three classes --- Seyfert nuclei, LINERs, and transition objects. The population of AGNs consequently is very large; approximately 43% of the galaxies in our survey can be regarded as "active." Most of the objects have much lower luminosities than AGNs commonly studied; the median luminosity of the narrow H-alpha line, after correcting for extinction, is only 2 x 10^39 erg/s. Our sample therefore occupies the extreme faint end of the AGN luminosity function. We detect signatures of a broad-line region, as revealed by visible broad H-alpha emission, in $\\sim$ 20% of...

  16. COLA. III. RADIO DETECTION OF ACTIVE GALACTIC NUCLEUS IN COMPACT MODERATE LUMINOSITY INFRARED GALAXIES

    International Nuclear Information System (INIS)

    We present results from 4.8 GHz Very Large Array (VLA) and global very long baseline interferometry (VLBI) observations of the northern half of the moderate FIR luminosity (median LIR = 1011.01 Lsun) COLA sample of star-forming galaxies. VLBI sources are detected in a high fraction (20/90) of the galaxies observed. The radio luminosities of these cores (∼1021 W Hz-1) are too large to be explained by radio supernovae or supernova remnants and we argue that they are instead powered by active galactic nuclei (AGNs). These sub-parsec scale radio cores are preferentially detected toward galaxies whose VLA maps show bright 100-500 parsec scale nuclear radio components. Since these latter structures tightly follow the FIR to radio-continuum correlation for star formation, we conclude that the AGN-powered VLBI sources are associated with compact nuclear starburst environments. The implications for possible starburst-AGN connections are discussed. The detected VLBI sources have a relatively narrow range of radio luminosity consistent with models in which intense compact Eddington-limited starbursts regulate the gas supply onto a central supermassive black hole. The high incidence of AGN radio cores in compact starbursts suggests little or no delay between the starburst phase and the onset of AGN activity.

  17. The Lick AGN Monitoring Project: The MBH - sigma* Relation For Reverberation-Mapped Active Galaxies

    CERN Document Server

    Woo, Jong-Hak; Barth, Aaron J; Wright, Shelley A; Walsh, Jonelle L; Bentz, Misty C; Martiny, Paul; Bennert, Vardha N; Canalizo, Gabriela; FIlippenko, Alex V; Gate, Ellinor; Li, Weidong; Malkan, Mattew A; Stern, Daniel; Minezaki, Takeo

    2010-01-01

    To investigate the black hole mass vs. stellar velocity dispersion (\\msigma) relation of active galaxies, we measured the velocity dispersions of a sample of local Seyfert 1 galaxies, for which we have recently determined black hole masses using reverberation mapping. For most objects, stellar velocity dispersions were measured from high signal-to-noise ratio optical spectra centered on the \\ion{Ca}{2} triplet region ($\\sim 8500$ \\AA), obtained at the Keck, Palomar, and Lick Observatories. For two objects, in which the \\ion{Ca}{2} triplet region was contaminated by nuclear emission, the measurement was based on high-quality $H$-band spectra obtained with the OH-Suppressing Infrared Imaging Spectrograph at the Keck-II Telescope. Combining our new measurements with data from the literature, we assemble a sample of 24 active galaxies with stellar velocity dispersions {\\it and} reverberation-based black hole mass measurements in the range of black hole mass $10^{6}< \\mbh/\\msun < 10^{9}$. We use this sample ...

  18. Herschel/SPIRE Sub-millimeter Spectra of Local Active Galaxies

    CERN Document Server

    Pereira-Santaella, Miguel; Busquet, Gemma; Wilson, Christine D; Glenn, Jason; Isaak, Kate G; Kamenetzky, Julia; Rangwala, Naseem; Schirm, Maximilien R P; Baes, Maarten; Barlow, Michael J; Boselli, Alessandro; Cooray, Asantha; Cormier, Diane

    2013-01-01

    We present the sub-millimeter spectra from 450 GHz to 1550 GHz of eleven nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) onboard Herschel. We detect CO transitions from J_up = 4 to 12, as well as the two [CI] fine structure lines at 492 and 809 GHz and the [NII] 461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions (SLEDs). The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (n_H2 ~ 10^3.2 - 10^3.9 cm^-3 and T_kin ~ 300 - 800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H2 emission. We could not determine the specific heating mechanism of the warm gas, however it is possibly related to the star-formation activity in these galaxies. Our modeling of the [CI] emission suggests that it is produced in cold (T_kin 1...

  19. Nuclear star formation activity and black hole accretion in nearby Seyfert galaxies

    International Nuclear Information System (INIS)

    Recent theoretical and observational works indicate the presence of a correlation between the star-formation rate (SFR) and active galactic nucleus (AGN) luminosity (and, therefore, the black hole accretion rate, M-dot BH) of Seyfert galaxies. This suggests a physical connection between the gas-forming stars on kpc scales and the gas on sub-pc scales that is feeding the black hole. We compiled the largest sample of Seyfert galaxies to date with high angular resolution (∼0.''4-0.''8) mid-infrared (8-13 μm) spectroscopy. The sample includes 29 Seyfert galaxies drawn from the AGN Revised Shapley-Ames catalog. At a median distance of 33 Mpc, our data allow us to probe nuclear regions on scales of ∼65 pc (median value). We found no general evidence of suppression of the 11.3 μm polycyclic aromatic hydrocarbon (PAH) emission in the vicinity of these AGN, and we used this feature as a proxy for the SFR. We detected the 11.3 μm PAH feature in the nuclear spectra of 45% of our sample. The derived nuclear SFRs are, on average, five times lower than those measured in circumnuclear regions of 600 pc in size (median value). However, the projected nuclear SFR densities (median value of 22 M ☉ yr–1 kpc–2) are a factor of 20 higher than those measured on circumnuclear scales. This indicates that the SF activity per unit area in the central ∼65 pc region of Seyfert galaxies is much higher than at larger distances from their nuclei. We studied the connection between the nuclear SFR and M-dot BH and showed that numerical simulations reproduce our observed relation fairly well.

  20. Determining Central Black Hole Masses in Distant Active Galaxies

    DEFF Research Database (Denmark)

    Vestergaard, Marianne

    2002-01-01

    An empirical relationship, of particular interest for studies of high redshift active galactic nuclei (AGNs) and quasars, between the masses of their central black-holes and rest-frame ultraviolet (UV) parameters measured in single-epoch AGN spectra is presented. This relationship is calibrated...... black-hole demographics at high redshift as well as to statistically study the fundamental properties of AGNs. The broad line region size - luminosity relationship is key to the calibrations presented here. The fact that its intrinsic scatter is also the main source of uncertainty in the calibrations...

  1. Detecting edges in the X-ray surface brightness of galaxy clusters

    Science.gov (United States)

    Sanders, J. S.; Fabian, A. C.; Russell, H. R.; Walker, S. A.; Blundell, K. M.

    2016-08-01

    The effects of many physical processes in the intracluster medium of galaxy clusters imprint themselves in X-ray surface brightness images. It is therefore important to choose optimal methods for extracting information from and enhancing the interpretability of such images. We describe in detail a gradient filtering edge detection method that we previously applied to images of the Centaurus cluster of galaxies. The Gaussian gradient filter measures the gradient in the surface brightness distribution on particular spatial scales. We apply this filter on different scales to Chandra X-ray observatory images of two clusters with active galactic nucleus feedback, the Perseus cluster and M 87, and a merging system, A 3667. By combining filtered images on different scales using radial filters spectacular images of the edges in a cluster are produced. We describe how to assess the significance of features in filtered images. We find the gradient filtering technique to have significant advantages for detecting many kinds of features compared to other analysis techniques, such as unsharp masking. Filtering cluster images in this way in a hard energy band allows shocks to be detected.

  2. Photometric properties of Local Volume dwarf galaxies

    CERN Document Server

    Sharina, M E; Dolphin, A E; Karachentseva, V E; Tully, R Brent; Karataeva, G M; Makarov, D I; Makarova, L N; Sakai, S; Shaya, E J; Nikolaev, E Yu; Kuznetsov, A N

    2007-01-01

    We present surface photometry and metallicity measurements for 104 nearby dwarf galaxies imaged with the Advanced Camera for Surveys and Wide Field and Planetary Camera 2 aboard the Hubble Space Telescope. In addition, we carried out photometry for 26 galaxies of the sample and for Sextans~B on images of the Sloan Digital Sky Survey. Our sample comprises dwarf spheroidal, irregular and transition type galaxies located within ~10 Mpc in the field and in nearby groups: M81, Centaurus A, Sculptor, and Canes Venatici I cloud. It is found that the early-type galaxies have on average higher metallicity at a given luminosity in comparison to the late-type objects. Dwarf galaxies with M_B > -12 -- -13 mag deviate toward larger scale lengths from the scale length -- luminosity relation common for spiral galaxies, h \\propto L^{0.5}_B. The following correlations between fundamental parameters of the galaxies are consistent with expectations if there is pronounced gas-loss through galactic winds: 1) between the luminosit...

  3. Determining Central Black Hole Masses in Distant Active Galaxies

    CERN Document Server

    Vestergaard, M

    2002-01-01

    An empirical relationship, of particular interest for studies of high redshift active galactic nuclei (AGNs) and quasars, between the masses of their central black-holes and rest-frame ultraviolet (UV) parameters measured in single-epoch AGN spectra is presented. This relationship is calibrated to recently measured reverberation masses of low-redshift AGNs and quasars. An empirical relationship between single-epoch rest-frame optical spectrophotometric measurements and the central masses is also presented. The UV relationship allows reasonable estimates of the central masses to be made of high-redshift AGNs and quasars for which these masses cannot be directly or easily measured by the techniques applicable to the lower luminosity, nearby AGNs. The central mass obtained by this method can be estimated to within a factor of ~3 for most objects. This is reasonable given the intrinsic uncertainty of a factor less than 2 in the primary methods used to measure the central masses of nearby inactive and active galax...

  4. CO SPECTRAL LINE ENERGY DISTRIBUTIONS OF INFRARED-LUMINOUS GALAXIES AND ACTIVE GALACTIC NUCLEI

    International Nuclear Information System (INIS)

    We report on new sensitive CO J = 6-5 line observations of several luminous infrared galaxies (LIRGs; L IR(8-1000 μm) ∼> 1011 L sun), 36% (8/22) of them ultraluminous infrared galaxies (ULIRGs) (L IR>1012 L sun), and two powerful local active galactic nuclei (AGNs)-the optically luminous QSO PG 1119+120 and the powerful radio galaxy 3C 293-using the James Clerk Maxwell Telescope on Mauna Kea in Hawaii. We combine these observations with existing low-J CO data and dust emission spectral energy distributions in the far-infrared-submillimeter from the literature to constrain the properties of the star-forming interstellar medium (ISM) in these systems. We then build the first local CO spectral line energy distributions (SLEDs) for the global molecular gas reservoirs that reach up to high J-levels. These CO SLEDs are neither biased by strong lensing (which affects many of those constructed for high-redshift galaxies), nor suffer from undersampling of CO-bright regions (as most current high-J CO observations of nearby extended systems do). We find: (1) a significant influence of dust optical depths on the high-J CO lines, suppressing the J = 6-5 line emission in some of the most IR-luminous LIRGs, (2) low global CO line excitation possible even in vigorously star-forming systems, (3) the first case of a shock-powered high-excitation CO SLED in the radio galaxy 3C 293 where a powerful jet-ISM interaction occurs, and (4) unusually highly excitated gas in the optically powerful QSO PG 1119+120. In Arp 220 and possibly other (U)LIRGs very faint CO J = 6-5 lines can be attributed to significant dust optical depths at short submillimeter wavelengths immersing those lines in a strong dust continuum, and also causing the C+ line luminosity deficit often observed in such extreme starbursts. Re-analysis of the CO line ratios available for submillimeter galaxies suggests that similar dust opacities also may be present in these high-redshift starbursts, with genuinely low

  5. Les galaxies

    Science.gov (United States)

    Combes, Francoise

    2016-08-01

    Considerable progress has been made on galaxy formation and evolution in recent years, and new issues. The old Hubble classification according to the tuning fork of spirals, lenticulars and ellipticals, is still useful but has given place to the red sequence, the blue cloud and the green valley, showing a real bimodality of types between star forming galaxies (blue) and quenched ones (red). Large surveys have shown that stellar mass and environment density are the two main factors of the evolution from blue to red sequences. Evolution is followed directly with redshift through a look-back time of more than 12 billion years. The most distant galaxy at z=11. has already a stellar mass of a billion suns. In an apparent anti-hierarchical scenario, the most massive galaxies form stars early on, while essentially dwarf galaxies are actively star-formers now. This downsizing feature also applies to the growth of super-massive black holes at the heart of each bulgy galaxy. The feedback from active nuclei is essential to explain the distribution of mass in galaxies, and in particular to explain why the fraction of baryonic matter is so low, lower by more than a factor 5 than the baryonic fraction of the Universe. New instruments just entering in operation, like MUSE and ALMA, provide a new and rich data flow, which is developed in this series of articles.

  6. The Survey of Centaurus A's Baryonic Structures (SCABS). II. The Extended Globular Cluster System of NGC5128 and its Nearby Environment

    CERN Document Server

    Taylor, Matthew A; Muñoz, Roberto P; Mieske, Steffen; Zhang, Hongxin; Eigenthaler, Paul; Bovill, Mia Sauda

    2016-01-01

    We present new, wide-field Dark Energy Camera observations covering $\\sim21\\,{\\rm deg}^2$ centred on the nearby giant elliptical galaxy NGC5128 in the five optical $u'g'r'i'z'$ filters. With filter-dependent 90 percent point-source completeness depths of $21.4 < m < 23.9$ mag (AB), we combine optical colours with source morphologies to compile a new catalogue of 2676 globular cluster (GC) candidates, of which 2404 are newly identified, and that includes the vast majority of globular clusters within $\\sim140$ kpc of NGC5128. Evidence is presented for a transition from GCs "intrinsic" to NGC5128 to those likely to be part of the intra-group medium of the Centaurus A galaxy group at a galactocentric radius of $R_{\\rm gc}\\approx55$ kpc. Inside this transition radius, we find that the red GC subpopulation is more centrally concentrated than the blue, with surface number density profiles of the form $\\Sigma_{N,red}\\sim R_{\\rm gc}^{-1.88}$ and $\\Sigma_{N,blue}\\sim R_{\\rm gc}^{-1.50}$. The median $(g'\\!-\\!z')_0...

  7. Dynamical Delays Between Starburst and AGN Activity in Galaxy Nuclei

    CERN Document Server

    Hopkins, Philip F

    2011-01-01

    Observations of AGN have suggested a possible delay between the peak of star formation (on some scale) and AGN activity. Feedback from fast stellar winds has been invoked to explain this, but this is not likely to be viable in bright systems accreting primarily cold dense gas. We show that such a delay can arise even in bright quasars for purely dynamical reasons. If some large-scale process produces rapid inflow, smaller scales will quickly become gas-dominated. As the gas density peaks, so does the SFR. However, gravitational torques which govern further inflow are relatively inefficient in gas-dominated systems; as more gas is turned into stars, the stars provide an efficient angular momentum sink allowing more rapid inflow. Moreover, the gas provided to the central regions in mergers or strong disk instabilities will typically be ~100 times larger than that needed to fuel the BH; the system is effectively in the 'infinite gas supply' limit. BH growth can therefore continue for some time while the gas supp...

  8. First-Ever Census of Variable Mira-Type Stars in Galaxy Outside the Local Group

    Science.gov (United States)

    2003-05-01

    First-Ever Census of Variable Mira-Type Stars in Galaxy Outsidethe Local Group Summary An international team led by ESO astronomer Marina Rejkuba [1] has discovered more than 1000 luminous red variable stars in the nearby elliptical galaxy Centaurus A (NGC 5128) . Brightness changes and periods of these stars were measured accurately and reveal that they are mostly cool long-period variable stars of the so-called "Mira-type" . The observed variability is caused by stellar pulsation. This is the first time a detailed census of variable stars has been accomplished for a galaxy outside the Local Group of Galaxies (of which the Milky Way galaxy in which we live is a member). It also opens an entirely new window towards the detailed study of stellar content and evolution of giant elliptical galaxies . These massive objects are presumed to play a major role in the gravitational assembly of galaxy clusters in the Universe (especially during the early phases). This unprecedented research project is based on near-infrared observations obtained over more than three years with the ISAAC multi-mode instrument at the 8.2-m VLT ANTU telescope at the ESO Paranal Observatory . PR Photo 14a/03 : Colour image of the peculiar galaxy Centaurus A . PR Photo 14b/03 : Location of the fields in Centaurus A, now studied. PR Photo 14c/03 : "Field 1" in Centaurus A (visual light; FORS1). PR Photo 14d/03 : "Field 2" in Centaurus A (visual light; FORS1). PR Photo 14e/03 : "Field 1" in Centaurus A (near-infrared; ISAAC). PR Photo 14f/03 : "Field 2" in Centaurus A (near-infrared; ISAAC). PR Photo 14g/03 : Light variation of six variable stars in Centaurus A PR Photo 14h/03 : Light variation of stars in Centaurus A (Animated GIF) PR Photo 14i/03 : Light curves of four variable stars in Centaurus A. Mira-type variable stars Among the stars that are visible in the sky to the unaided eye, roughly one out of three hundred (0.3%) displays brightness variations and is referred to by astronomers as a

  9. Investigating the nuclear activity of barred spiral galaxies: the case of NGC 1672

    CERN Document Server

    Jenkins, L P; Colbert, E J M; Koribalski, B; Kuntz, K D; Levan, A J; Ojha, R; Roberts, T P; Ward, M J; Zezas, A

    2011-01-01

    We have performed an X-ray study of the nearby barred spiral galaxy NGC1672, primarily to ascertain the effect of the bar on its nuclear activity. We use both Chandra and XMM-Newton observations to investigate its X-ray properties, together with supporting high-resolution optical imaging data from the Hubble Space Telescope (HST), infrared imaging from the Spitzer Space Telescope, and ATCA ground-based radio data. We detect 28 X-ray sources within the D25 area of the galaxy, many of which correlate spatially with star-formation in the bar and spiral arms, while two are identified as background galaxies in the HST images. Nine of the X-ray sources are ULXs, with the three brightest (LX > 5E39 erg/s) located at the ends of the bar. With the spatial resolution of Chandra, we are able to show for the first time that NGC1672 possesses a hard (Gamma~1.5) nuclear X-ray source with a 2-10 keV luminosity of 4E38 erg/s. This is surrounded by an X-ray bright circumnuclear star-forming ring, comprised of point sources an...

  10. Submillimetre observations of galaxy clusters with BLAST: the star-formation activity in Abell 3112

    CERN Document Server

    Braglia, Filiberto G; Bock, James J; Chapin, Edward L; Devlin, Mark J; Edge, Alastair; Griffin, Matthew; Gundersen, Joshua O; Halpern, Mark; Hargrave, Peter C; Hughes, David H; Klein, Jeff; Marsden, Gaelen; Mauskopf, Philip; Moncelsi, Lorenzo; Netterfield, Calvin B; Ngo, Henry; Olmi, Luca; Pascale, Enzo; Patanchon, Guillaume; Pimbblet, Kevin A; Rex, Marie; Scott, Douglas; Semisch, Christopher; Thomas, Nicholas; Truch, Matthew D P; Tucker, Carole; Tucker, Gregory S; Valiante, Elisabetta; Viero, Marco P; Wiebe, Donald V

    2010-01-01

    We present observations at 250, 350, and 500 um of the nearby galaxy cluster Abell 3112 (z=0.075) carried out with BLAST, the Balloon-borne Large Aperture Submillimeter Telescope. Five cluster members are individually detected as bright submillimetre sources. Their far-infrared SEDs and optical colours identify them as normal star-forming galaxies of high mass, with globally evolved stellar populations. They all have B-R colours of 1.38+/-0.08, transitional between the blue, active population and the red, evolved galaxies that dominate the cluster core. We stack to determine the mean submillimetre emission from all cluster members, which is determined to be 16.6+/-2.5, 6.1+/-1.9, and 1.5+/-1.3 mJy at 250, 350, and 500 um, respectively. Stacking analyses of the submillimetre emission of cluster members reveal trends in the mean far-infrared luminosity with respect to cluster-centric radius and Ks-band magnitude. We find that a large fraction of submillimetre emission comes from the boundary of the inner, viria...

  11. High resolution ALMA observations of dense molecular medium in the central regions of active galaxies

    CERN Document Server

    Kohno, Kotaro; Taniguchi, Akio; Izumi, Takuma; Tosaki, Tomoka

    2016-01-01

    In the central regions of active galaxies, dense molecular medium are exposed to various types of radiation and energy injections, such as UV, X-ray, cosmic ray, and shock dissipation. With the rapid progress of chemical models and implementation of new-generation mm/submm interferometry, we are now able to use molecules as powerful diagnostics of the physical and chemical processes in galaxies. Here we give a brief overview on the recent ALMA results to demonstrate how molecules can reveal underlying physical and chemical processes in galaxies. First, new detections of Galactic molecular absorption systems with elevated HCO/H$^{13}$CO$^+$ column density ratios are reported, indicating that these molecular media are irradiated by intense UV fields. Second, we discuss the spatial distributions of various types of shock tracers including HNCO, CH$_3$OH and SiO in NGC 253 and NGC 1068. Lastly, we provide an overview of proposed diagnostic methods of nuclear energy sources using ALMA, with an emphasis on the syne...

  12. 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.

  13. The formation of the brightest cluster galaxies in cosmological simulations: the case for active galactic nucleus feedback

    OpenAIRE

    Martizzi, Davide; Teyssier, Romain; Moore, Ben

    2012-01-01

    We use 500 pc resolution cosmological simulations of a Virgo-like galaxy cluster to study the properties of the brightest cluster galaxy (BCG) that forms at the centre of the halo. We compared two simulations; one incorporating only supernova feedback and a second that also includes prescriptions for black hole growth and the resulting active galactic nucleus (AGN) feedback from gas accretion. As previous work has shown, with supernova feedback alone we are unable to reproduce any of the obse...

  14. Planes of satellite galaxies and the cosmic web

    Science.gov (United States)

    Libeskind, Noam I.; Hoffman, Yehuda; Tully, R. Brent; Courtois, Helene M.; Pomarède, Daniel; Gottlöber, Stefan; Steinmetz, Matthias

    2015-09-01

    Recent observational studies have demonstrated that the majority of satellite galaxies tend to orbit their hosts on highly flattened, vast, possibly corotating planes. Two nearly parallel planes of satellites have been confirmed around the M31 galaxy and around the Centaurus A galaxy, while the Milky Way also sports a plane of satellites. It has been argued that such an alignment of satellites on vast planes is unexpected in the standard Λ cold dark matter (ΛCDM) model of cosmology if not even in contradiction to its generic predictions. Guided by ΛCDM numerical simulations, which suggest that satellites are channelled towards hosts along the axis of the slowest collapse as dictated by the ambient velocity shear tensor, we re-examine the planes of local satellites systems within the framework of the local shear tensor derived from the Cosmicflows-2 data set. The analysis reveals that the Local Group and Centaurus A reside in a filament stretched by the Virgo cluster and compressed by the expansion of the Local Void. Four out of five thin planes of satellite galaxies are indeed closely aligned with the axis of compression induced by the Local Void. Being the less massive system, the moderate misalignment of the Milky Way's satellite plane can likely be ascribed to its greater susceptibility to tidal torques, as suggested by numerical simulations. The alignment of satellite systems in the local Universe with the ambient shear field is thus in general agreement with predictions of the ΛCDM model.

  15. Contribution of Augosoma centaurus beetle to rural livelihoods in the East region of Cameroon : study report

    OpenAIRE

    F. J. Muafor; Le Gall, Philippe; Levang, Patrice

    2012-01-01

    This report describes the level to which forest dependent people in the East region of Cameroon rely on the consumption of Augosoma centaurus beetle (Dynastidae) for food security and rural livelihood. In total, 14 villages and 2 small towns, comprising of 9 ethnic groups in 10 sub-divisions were surveyed using quantitative and qualitative socioeconomic approaches. From the results of this study, both the larvae and adult individuals of the Augosoma beetle are traditional delic...

  16. X-ray Detected Active Galactic Nuclei in Dwarf Galaxies at $0

    CERN Document Server

    Pardo, Kristina; Greene, Jenny E; Somerville, Rachel S; Gallo, Elena; Hickox, Ryan C; Miller, Brendan P; Reines, Amy E; Silverman, John D

    2016-01-01

    We present a sample of accreting supermassive black holes (SMBHs) in low-mass galaxies at $z200$ ks) archival \\textit{Chandra} X-ray data. From our sample of $\\sim 600$ low-mass galaxies, $10$ exhibit X-ray emission consistent with that arising from AGN activity. If black hole mass scales roughly with stellar mass, then we expect that these AGN are powered by SMBHs with masses of $\\sim 10^5-10^6 \\ M_{\\odot}$ and typical Eddington ratios $\\sim 5\\%$. Furthermore, we find an active fraction consistent with extrapolations of other searches of $\\sim 0.006-3\\%$ for $10^9 \\ M_{\\odot} \\leq M_{\\star} \\leq 3\\times 10^{9} \\ M_{\\odot}$ and $0.1active fraction has been directly measured outside of the local universe for these SMBH mass ranges. We find good agreement with semi-analytic models, suggesting that as we search larger volumes we may use comparisons between observed active fractions and models to understand seeding mechanisms in the early universe.

  17. Dissecting galaxies: spatial and spectral separation of emission excited by star formation and AGN activity

    Science.gov (United States)

    Davies, Rebecca L.; Groves, Brent; Kewley, Lisa J.; Dopita, Michael A.; Hampton, Elise J.; Shastri, Prajval; Scharwächter, Julia; Sutherland, Ralph; Kharb, Preeti; Bhatt, Harish; Jin, Chichuan; Banfield, Julie; Zaw, Ingyin; James, Bethan; Juneau, Stéphanie; Srivastava, Shweta

    2016-10-01

    The optical spectra of Seyfert galaxies are often dominated by emission lines excited by both star formation and active galactic nucleus (AGN) activity. Standard calibrations (such as for the star formation rate) are not applicable to such composite (mixed) spectra. In this paper, we describe how integral field data can be used to spectrally and spatially separate emission associated with star formation from emission associated with accretion on to an AGN. We demonstrate our method using integral field data for two AGN host galaxies (NGC 5728 and NGC 7679) from the Siding Spring Southern Seyfert Spectroscopic Snapshot Survey (S7). The spectra of NGC 5728 and NGC 7679 form clear sequences of AGN fraction on standard emission line ratio diagnostic diagrams. We show that the emission line luminosities of the majority (>85 per cent) of spectra along each AGN fraction sequence can be reproduced by linear superpositions of the emission line luminosities of one AGN dominated spectrum and one star formation dominated spectrum. We separate the Hα, Hβ, [N II]λ6583, [S II]λλ6716, 6731, [O III]λ5007 and [O II]λλ3726, 3729 luminosities of every spaxel into contributions from star formation and AGN activity. The decomposed emission line images are used to derive the star formation rates and AGN bolometric luminosities for NGC 5728 and NGC 7679. Our calculated values are mostly consistent with independent estimates from data at other wavelengths. The recovered star-forming and AGN components also have distinct spatial distributions which trace structures seen in high-resolution imaging of the galaxies, providing independent confirmation that our decomposition has been successful.

  18. Combined X-Ray and mm-Wave Observations of Radio Quiet Active Galaxies

    Science.gov (United States)

    Behar, E.

    2016-06-01

    A connection between the X-ray and radio sources in radio quiet active galaxies (AGNs) will be demonstrated. High radio frequency, i.e., mm-wave observations are promising probes of the X-ray emitting inner regions of the accretion disks in radio quiet AGNs. An argument for simultaneous observations in X-rays and in mm waves will be made, in order to promote these as one of the future science goals of X-ray and AGN astronomy in the next decade. Preliminary results from an exploratory campaign with several space and ground based telescopes will be presented.

  19. Limits to Quantum Gravity Effects from Observations of TeV Flares in Active Galaxies

    OpenAIRE

    Biller, S. D.; Breslin, A. C.; Buckley, J.; Catanese, M.; Carson, M.; Carter-Lewis, D. A.; Cawley, M. F.; Fegan, D. J.; Finley, J.; Gaidos, J. A.; Hillas, A.M.; Krennrich, F.; Lamb, R. C.; Lessard, R.; Masterson, C.

    1998-01-01

    We have used data from the TeV gamma-ray flare associated with the active galaxy Markarian 421 observed on 15 May 1996 to place bounds on the possible energy-dependence of the speed of light in the context of an effective quantum gravitational energy scale. The possibility of an observable time dispersion in high energy radiation has recently received attention in the literature, with some suggestions that the relevant energy scale could be less than the Planck mass and perhaps as low as 10^1...

  20. Herschel Observed Stripe 82 Quasars and Their Host Galaxies: Connections between AGN Activity and host Galaxy Star Formation

    Science.gov (United States)

    Dong, X. Y.; Wu, Xue-Bing

    2016-06-01

    In this work, we present a study of 207 quasars selected from the Sloan Digital Sky Survey quasar catalogs and the Herschel Stripe 82 survey. Quasars within this sample are high-luminosity quasars with a mean bolometric luminosity of 1046.4 erg s-1. The redshift range of this sample is within z luminosity, far-IR (FIR) luminosity, stellar mass, as well as many other AGN and galaxy properties are deduced from the SED fitting results. The mean star formation rate (SFR) of the sample is 419 M ⊙ yr-1 and the mean gas mass is ˜1011.3 M ⊙. All of these results point to an IR luminous quasar system. Compared with star formation main sequence (MS) galaxies, at least 80 out of 207 quasars are hosted by starburst galaxies. This supports the statement that luminous AGNs are more likely to be associated with major mergers. The SFR increases with the redshift up to z = 2. It is correlated with the AGN bolometric luminosity, where {L}{{FIR}}\\propto {L}{{Bol}}0.46+/- 0.03. The AGN bolometric luminosity is also correlated with the host galaxy mass and gas mass. Yet the correlation between L FIR and L Bol has higher significant level, implies that the link between AGN accretion and the SFR is more primal. The M BH/M * ratio of our sample is 0.02, higher than the value 0.005 in the local universe. It might indicate an evolutionary trend of the M BH-M * scaling relation.

  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. The gas metallicity gradient and the star formation activity of disc galaxies

    CERN Document Server

    Tissera, Patricia B; Sillero, Emanuel; Vilchez, Jose M

    2015-01-01

    We study oxygen abundance profiles of the gaseous disc components in simulated galaxies in a hierarchical universe. We analyse the disc metallicity gradients in relation to the stellar masses and star formation rates of the simulated galaxies. We find a trend for galaxies with low stellar masses to have steeper metallicity gradients than galaxies with high stellar masses at z ~0. We also detect that the gas-phase metallicity slopes and the specific star formation rate (sSFR) of our simulated disc galaxies are consistent with recently reported observations at z ~0. Simulated galaxies with high stellar masses reproduce the observed relationship at all analysed redshifts and have an increasing contribution of discs with positive metallicity slopes with increasing redshift. Simulated galaxies with low stellar masses a have larger fraction of negative metallicity gradients with increasing redshift. Simulated galaxies with positive or very negative metallicity slopes exhibit disturbed morphologies and/or have a clo...

  3. The Intrinsic Eddington Ratio Distribution of Active Galactic Nuclei in Star-forming Galaxies from the Sloan Digital Sky Survey

    Science.gov (United States)

    Jones, Mackenzie L.; Hickox, Ryan C.; Black, Christine S.; Hainline, Kevin N.; DiPompeo, Michael A.; Goulding, Andy D.

    2016-07-01

    An important question in extragalactic astronomy concerns the distribution of black hole accretion rates of active galactic nuclei (AGNs). 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 whether or not an intrinsic Eddington ratio distribution that takes the form of a Schechter function is consistent with previous work suggesting 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 AGNs using a broad, instantaneous luminosity distribution described by a Schechter function near the Eddington limit. This simulated AGN population is then compared to observed galaxies via their positions on an emission line excitation diagram and Eddington ratio distributions. 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 for optically selected AGNs in young galaxies, the intrinsic Eddington ratio distribution is consistent with a possibly universal, broad power law with an exponential cutoff, as this distribution is observed in old, optically selected galaxies and X-rays.

  4. The search for active black holes in nearby low-mass galaxies using optical and mid-IR data

    CERN Document Server

    Sartori, Lia F; Treister, Ezequiel; Trakhtenbrot, Benny; Koss, Michael; Shirazi, Maryam; Oh, Kyuseok

    2015-01-01

    We investigated AGN activity in low-mass galaxies, an important regime that can shed light onto BH formation and evolution, and their interaction with their host galaxies. We identified 336 AGN candidates from a parent sample of $\\sim 48,000$ nearby low-mass galaxies ($M_{\\rm \\star} \\leq 10^{9.5}M_\\odot$, $z < 0.1$) in the SDSS. We selected the AGN using the classical BPT diagram, a similar optical emission line diagnostic based on the HeII$\\lambda$4686 line, and mid-IR color cuts. Different criteria select host galaxies with different physical properties such as stellar mass and optical color, and only 3 out of 336 sources fulfill all three criteria. This could be in part due to selection biases. The resulting AGN fraction of $\\sim 0.7 \\%$ is at least one order of magnitude below the one estimated for more massive galaxies. At optical wavelengths, the HeII-based AGN selection appears to be more sensitive to AGN hosted in star-forming galaxies than the classical BPT diagram, at least in the low-mass regime...

  5. X-Ray Properties Expected from Active Galactic Nucleus Feedback in Elliptical Galaxies

    Science.gov (United States)

    Pellegrini, Silvia; Ciotti, Luca; Ostriker, Jeremiah P.

    2012-01-01

    Detailed hydrodynamic simulations of active galactic nucleus feedback have been performed including the effects of radiative and mechanical momentum and energy input on the interstellar medium (ISM) of typical elliptical galaxies. We focus on the observational properties of the models in the soft and hard X-ray bands: nuclear X-ray luminosity; global X-ray luminosity and temperature of the hot ISM; and temperature and X-ray brightness profiles before, during, and after outbursts. After ~10 Gyr, the bolometric nuclear emission L BH is very sub-Eddington (l = L BH/L Edd ~ 10-4), and within the range observed, though larger than typical values. Outbursts last for ≈107 yr, and the duty cycle of nuclear activity is a few × (10-3 to 10-2), over the last 6 Gyr. The ISM thermal luminosity L X oscillates in phase with the nuclear luminosity, with broader peaks. This behavior helps statistically reproduce the observed large L X variation. The average gas temperature is within the observed range, in the upper half of those observed. In quiescence, the temperature profile has a negative gradient; thanks to past outbursts, the brightness profile lacks the steep shape of cooling flow models. After outbursts, disturbances are predicted in the temperature and brightness profiles (analyzed by unsharp masking). Most significantly, during major accretion episodes, a hot bubble of shocked gas is inflated at the galaxy center (within ≈100 pc) the bubble would be conical in shape in real galaxies and would be radio-loud. Its detection in X-rays is within current capabilities, though it would likely remain unresolved. The ISM resumes its smooth appearance on a timescale of ≈200 Myr the duty cycle of perturbations in the ISM is of the order of 5%-10%. While showing general agreement between the models and real galaxies, this analysis indicates that additional physical input may still be required including moving to two-dimensional or three-dimensional simulations, input of

  6. Non-thermal radiation from collisions of compact objects with intermediate scale jets in active galaxies

    CERN Document Server

    Bednarek, W

    2015-01-01

    Massive black holes in active galaxies are immersed in huge concentrations of late type stars in the galactic bulges and also early type massive stars in the nuclear stellar clusters which are additionally surrounded by quasi-spherical several kpc scale halos containing from a few hundred up to several thousand globular clusters (GCs). It is expected that significant numbers of red giant stars, massive stars and also GCs can move through the jet expelled from the central engine of active galaxy. We consider collisions of stars from the galactic bulge, nuclear cluster and globular clusters with the jet plasma. As a result of such collisions, multiple shocks are expected to appear in the jet around these compact objects. Therefore, the plasma in the kpc scale jet can be significantly disturbed. We show that particles can be accelerated on these shocks up to the multi-TeV energies. TeV leptons emit synchrotron radiation, extending up to the X-ray energies, and also comptonize radiation produced in a stellar clus...

  7. Local Luminous Infrared Galaxies. III. Co-evolution of Black Hole Growth and Star Formation Activity?

    CERN Document Server

    Alonso-Herrero, Almudena; Rieke, George H; Diamond-Stanic, Aleksandar M; Wang, Yiping; Hernan-Caballero, Antonio; Rigopoulou, Dimitra

    2013-01-01

    Local luminous infrared (IR) galaxies (LIRGs) have both high star formation rates (SFR) and a high AGN (Seyfert and AGN/starburst composite) incidence. Therefore, they are ideal candidates to explore the co-evolution of black hole (BH) growth and star formation (SF) activity, not necessarily associated with major mergers. Here, we use Spitzer/IRS spectroscopy of a complete volume-limited sample of local LIRGs (distances of <78Mpc). We estimate typical BH masses of 3x10^7 M_sun using [NeIII]15.56micron and optical [OIII]5007A gas velocity dispersions and literature stellar velocity dispersions. We find that in a large fraction of local LIRGs the current SFR is taking place not only in the inner nuclear ~1.5kpc region, as estimated from the nuclear 11.3micron PAH luminosities, but also in the host galaxy. We next use the ratios between the SFRs and BH accretion rates (BHAR) to study whether the SF activity and BH growth are contemporaneous in local LIRGs. On average, local LIRGs have SFR to BHAR ratios highe...

  8. Uncovering the Spectral Energy Distribution in Active Galaxies Using High Ionization Mid-Infrared Emission Lines

    Science.gov (United States)

    Melendez, M.; Kraemer, S. B.; Weaver, K. A.; Mushotzky, R. F.

    2011-01-01

    The shape of the spectral energy distribution of active galaxies in the EUV soft X-ray band (13.6 eV to 1 keV) is uncertain because obscuration by dust and gas can hamper our view of the continuum. To investigate the shape of the spectral energy distribution in this energy band, we have generated a set of photoionization models which reproduce the small dispersion found in correlations between high-ionization mid-infrared emission lines in a sample of hard X-ray selected AGN. Our calculations show that a broken power-law continuum model is sufficient to reproduce the [Ne V]14.32 microns/[Ne III], [Ne V]24.32 microns/[O IV]25.89 micron and [O IV] 25.89 microns/[Ne III] ratios, and does not require the addition of a "big bump" EUV model component. We constrain the EUV-soft X-ray slope, alpha(sub i), to be between 1.5 - 2.0 and derive a best fit of alpha(sub i) approx. 1.9 for Seyfert 1 galaxies, consistent with previous studies of intermediate redshift quasars. If we assume a blue bump model, most sources in our sample have derived temperatures between T(sub BB) = 10(exp 5.18) K to 10(exp 5.7) K, suggesting that the peak of this component spans a large range of energies extending from approx. (Lambda)600 A to > (Lambda)1900 A. In this case, the best fitting peak energy that matches the mid-infrared line ratios of Seyfert 1 galaxies occurs between approx. (Lambda)700-(Lambda)1000 A. Despite the fact that our results do not rule out the presence of an EUV bump, we conclude that our power-law model produces enough photons with energies > 4 Ry to generate the observed amount of mid-infrared emission in our sample of BAT AGN.

  9. Role of active galactic nuclei in the luminous infrared galaxy phase at z ≤ 3

    Science.gov (United States)

    Lin, Ming-Yi; Hashimoto, Yasuhiro; Foucaud, Sébastien

    2016-03-01

    To understand the interactions between active galactic nuclei (AGNs) and star formation during the evolution of galaxies, we investigate 142 galaxies detected in both X-ray and 70 μm observations in the COSMOS (Cosmic Evolution Survey) field. All of our data are obtained from the archive X-ray point-source catalogues from Chandra and XMM-Newton observations, and the far-infrared 70 μm point-source catalogue from Spitzer-MIPS observations. Although the IRAC [3.6 μm]-[4.5 μm] versus [5.8 μm]-[8.0 μm] colours of our sample indicate that only ˜63 per cent of our sources would be classified as AGNs, the ratio of the rest-frame 2-10 keV luminosity to the total infrared luminosity (8-1000 μm) shows that the entire sample has comparatively higher X-ray luminosity than that expected from pure star-forming galaxies, suggesting the presence of an AGN in all of our sources. From an analysis of the X-ray hardness ratio, we find that sources with both 70 μm and X-ray detection tend to have a higher hardness ratio relative to the whole X-ray-selected source population, suggesting the presence of more X-ray absorption in the 70 μm detected sources. In addition, we find that the observed far-infrared colours of 70 μm detected sources with and without X-ray emission are similar, suggesting the far-infrared emission could be mainly powered by star formation.

  10. Discovery of ultra-steep spectrum giant radio galaxy with recurrent radio jet activity in Abell 449

    CERN Document Server

    Hunik, D

    2016-01-01

    We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and their synchrotron age is about 160 Myr. The parent galaxy of the extended relic structure, which is the dominant galaxy within the cluster, is starting a new jet activity. There are three weak X-rays sources in the vicinity of the cluster as found in the ROSAT survey, however it is not known if they are connected with this cluster of galaxies. Just a few radio galaxy relics are currently known in the literature, as finding them requires sensitive and high angular resolution low-frequency radio observations. Objects of this kind, which also are starting a new jet activity, are important for understanding the life cycle and evolution of active galactic nuclei. A new 613 MHz map as well as the archival radio data pertaining to this object are presented and analyzed.

  11. DISCOVERY OF ULTRA-STEEP SPECTRUM GIANT RADIO GALAXY WITH RECURRENT RADIO JET ACTIVITY IN ABELL 449

    Energy Technology Data Exchange (ETDEWEB)

    Hunik, Dominika; Jamrozy, Marek, E-mail: dominika.hunik@uj.edu.pl [Obserwatorium Astronomiczne, Uniwersytet Jagielloński, ul. Orla 171, 30-244 Kraków (Poland)

    2016-01-20

    We report a discovery of a 1.3 Mpc diffuse radio source with extremely steep spectrum fading radio structures in the vicinity of the Abell 449 cluster of galaxies. Its extended diffuse lobes are bright only at low radio frequencies and their synchrotron age is about 160 Myr. The parent galaxy of the extended relic structure, which is the dominant galaxy within the cluster, is starting a new jet activity. There are three weak X-rays sources in the vicinity of the cluster as found in the ROSAT survey, however it is not known if they are connected with this cluster of galaxies. Just a few radio galaxy relics are currently known in the literature, as finding them requires sensitive and high angular resolution low-frequency radio observations. Objects of this kind, which also are starting a new jet activity, are important for understanding the life cycle and evolution of active galactic nuclei. A new 613 MHz map as well as the archival radio data pertaining to this object are presented and analyzed.

  12. No more active galactic nuclei in clumpy disks than in smooth galaxies at z ∼ 2 in CANDELS/3D-HST

    Energy Technology Data Exchange (ETDEWEB)

    Trump, Jonathan R.; Luo, Bin; Brandt, W. N. [Department of Astronomy and Astrophysics, 525 Davey Lab, The Pennsylvania State University, University Park, PA 16802 (United States); Barro, Guillermo; Guo, Yicheng; Koo, David C.; Faber, S. M. [University of California Observatories/Lick Observatory and Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Juneau, Stéphanie [Irfu/Service d' Astrophysique, CEA-Saclay, Orme des Merisiers, F-91191 Gif-sur-Yvette Cedex (France); Weiner, Benjamin J. [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Brammer, Gabriel B.; Ferguson, Henry C.; Grogin, Norman A.; Kartaltepe, Jeyhan; Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Bell, Eric F. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Dekel, Avishai [Center for Astrophysics and Planetary Science, Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Hopkins, Philip F. [California Institute of Technology, MC 105-24, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Kocevski, Dale D. [Department of Physics and Astronomy, University of Kentucky, Lexington, KY 40506 (United States); McIntosh, Daniel H. [Department of Physics and Astronomy, University of Missouri-Kansas City, 5110 Rockhill Road, Kansas City, MO 64110 (United States); Momcheva, Ivelina [Department of Astronomy, Yale University, New Haven, CT 06520 (United States); and others

    2014-10-01

    We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3 < z < 2.4. We select galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxies. The CANDELS visual classification system is used to identify 44 clumpy disk galaxies, along with mass-matched comparison samples of smooth and intermediate morphology galaxies. We note that despite being mass-matched and having similar star formation rates, the smoother galaxies tend to be smaller disks with more prominent bulges compared to the clumpy galaxies. The lack of smooth extended disks is probably a general feature of the z ∼ 2 galaxy population, and means we cannot directly compare with the clumpy and smooth extended disks observed at lower redshift. We find that z ∼ 2 clumpy galaxies have slightly enhanced AGN fractions selected by integrated line ratios (in the mass-excitation method), but the spatially resolved line ratios indicate this is likely due to extended phenomena rather than nuclear AGNs. Meanwhile, the X-ray data show that clumpy, smooth, and intermediate galaxies have nearly indistinguishable AGN fractions derived from both individual detections and stacked non-detections. The data demonstrate that AGN fueling modes at z ∼ 1.85—whether violent disk instabilities or secular processes—are as efficient in smooth galaxies as they are in clumpy galaxies.

  13. Planes of satellite galaxies and the cosmic web

    CERN Document Server

    Libeskind, Noam I; Tully, R Brent; Courtois, Helene M; Pomarede, Daniel; Gottloeber, Stefan; Steinmetz, Matthias

    2015-01-01

    Recent observational studies have demonstrated that most satellite galaxies tend to orbit their hosts on highly flattened, vast, possibly co-rotating planes. Two nearly parallel planes of satellites have been confirmed around the M31 galaxy and around the Centaurus A galaxy, while the Milky Way also sports a plane of satellites. It has been argued that such an alignment of satellites on vast planes is unexpected in the standard ($\\Lambda$CDM) model of cosmology if not even in contradiction to its generic predictions. Guided by $\\Lambda$CDM numerical simulations, which suggest that satellites are channeled towards hosts along the axis of the slowest collapse as dictated by the ambient velocity shear tensor, we re-examine the planes of local satellites systems within the framework of the local shear tensor derived from the Cosmicflows-2 dataset. The analysis reveals that the Local Group and Centaurus A reside in a filament stretched by the Virgo cluster and compressed by the expansion of the Local Void. Four ou...

  14. The Megamaser Cosmology Project. III. Accurate Masses of Seven Supermassive Black Holes in Active Galaxies with Circumnuclear Megamaser Disks

    Science.gov (United States)

    Kuo, C. Y.; Braatz, J. A.; Condon, J. J.; Impellizzeri, C. M. V.; Lo, K. Y.; Zaw, I.; Schenker, M.; Henkel, C.; Reid, M. J.; Greene, J. E.

    2011-01-01

    Observations of H2O masers from circumnuclear disks in active galaxies for the Megamaser Cosmology Project (MCP) allow accurate measurement of the mass of supermassive black holes (BH) in these galaxies. We present the Very Long Baseline Interferometry images and kinematics of water maser emission in six active galaxies: NGC 1194, NGC 2273, NGC 2960 (Mrk 1419), NGC 4388, NGC 6264 and NGC 6323. We use the Keplerian rotation curves of these six megamaser galaxies, plus a seventh previously published, to determine accurate enclosed masses within the central ~0.3 pc of these galaxies, smaller than the radius of the sphere of influence of the central mass in all cases. We also set lower limits to the central mass densities of between 0.12 × 1010 and 61 × 1010 M sun pc-3. For six of the seven disks, the high central densities rule out clusters of stars or stellar remnants as the central objects, and this result further supports our assumption that the enclosed mass can be attributed predominantly to a supermassive BH. The seven BHs have masses ranging between 0.75 × 107 and 6.5 × 107 M sun, with the mass errors dominated by the uncertainty of the Hubble constant. We compare the megamaser BH mass determination with BH mass measured from the virial estimation method. The virial estimation BH mass in four galaxies is consistent with the megamaser BH mass, but the virial mass uncertainty is much greater. Circumnuclear megamaser disks allow the best mass determination of the central BH mass in external galaxies and significantly improve the observational basis at the low-mass end of the M-σsstarf relation. The M-σsstarf relation may not be a single, low-scatter power law as originally proposed. MCP observations continue and we expect to obtain more maser BH masses in the future.

  15. J1216+0709 : A radio galaxy with three episodes of AGN jet activity

    CERN Document Server

    Singh, Veeresh; Kharb, Preeti; Srivastava, Shweta; Janardhan, P

    2016-01-01

    We report the discovery of a `Triple-Double Radio Galaxy (TDRG)' J1216+0709 detected in deep low-frequency Giant Metrewave Radio Telescope (GMRT) observations. J1216+0709 is only the third radio galaxy, after B0925+420 and Speca, with three pairs of lobes resulting from three different episodes of AGN jet activity. The 610 MHz GMRT image clearly displays an inner pair of lobes, a nearly co-axial middle pair of lobes and a pair of outer lobes that is bent w.r.t. the axis of inner pair of lobes. The total end-to-end projected sizes of the inner, middle, and outer lobes are 40$^{{\\prime}{\\prime}}$ ($\\sim$ 95 kpc), 1$^{\\prime}$.65 ($\\sim$ 235 kpc) and 5$^{\\prime}$.7 ($\\sim$ 814 kpc), respectively. Unlike the outer pair of lobes both the inner and middle pairs of lobes exhibit asymmetries in arm-lengths and flux densities, but in opposite sense, i.e., the eastern sides are farther and also brighter that the western sides, thus suggesting the possibility of jet being intrinsically asymmetric rather than due to rela...

  16. Mid-Infrared Spectral Measures of Star-Formation and AGN Activity in Normal Galaxies

    CERN Document Server

    Treyer, Marie; Johnson, B D; O'Dowd, M; Martin, C D; Wyder, T; Charlot, S; Heckman, T; Martins, L; Seibert, M; van der Hulst, J M

    2010-01-01

    We investigate the use of MIR PAH bands, continuum and emission lines as probes of star-formation and AGN activity in a sample of 100 'normal' and local (z~0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer Space Telescope Infrared Spectrograph (IRS) as part of the Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS) which includes multi-wavelength photometry from the UV to the FIR and optical spectroscopy. The continuum and features were extracted using PAHFIT (Smith et al. 2007), a decomposition code which we find to yield PAH equivalent widths up to ~30 times larger than the commonly used spline methods. Despite the lack of extreme objects in our sample (such as strong AGNs, low metallicity galaxies or ULIRGs), we find significant variations in PAH, continuum and emission line properties and systematic trends between these MIR properties and optically derived physical properties such as age, metallicity and radiation field hardness. We revisit the diagnostic diagram relating PAH equival...

  17. 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.

  18. Mid-Infrared Spectral Indicators of Star-Formation and AGN Activity in Normal Galaxies

    CERN Document Server

    Treyer, Marie; Schiminovich, David; O'Dowd, Matt

    2010-01-01

    We investigate the use of mid-infrared PAH bands, continuum and emission lines as probes of star-formation and AGN activity in a sample of 100 `normal' and local (z~0.1) galaxies. The MIR spectra were obtained with the Spitzer IRS as part of the Spitzer-SDSS-GALEX Spectroscopic Survey (SSGSS) which includes multi-wavelength photometry from the UV to the FIR and optical spectroscopy. The spectra were decomposed using PAHFIT (Smith et al. 2007), which we find to yield PAH equivalent widths (EW) up to ~30 times larger than the commonly used spline methods. Based on correlations between PAH, continuum and emission line properties and optically derived physical properties (gas phase metallicity, radiation field hardness), we revisit the diagnostic diagram relating PAH EWs and [NeII]/[OIV] and find it more efficient as distinguishing weak AGNs from star-forming galaxies than when spline decompositions are used. The luminosity of individual MIR component (PAH, continuum, Ne and molecular hydrogen lines) are found to...

  19. Offset Active Galactic Nuclei as Tracers of Galaxy Mergers and Supermassive Black Hole Growth

    CERN Document Server

    Comerford, Julia M

    2014-01-01

    Offset active galactic nuclei (AGNs) are AGNs that are in ongoing galaxy mergers, which produce kinematic offsets in the AGNs relative to their host galaxies. Offset AGNs are also close relatives of dual AGNs. We conduct a systematic search for offset AGNs in the Sloan Digital Sky Survey, by selecting AGN emission lines that exhibit statistically significant line-of-sight velocity offsets relative to systemic. From a parent sample of 18314 Type 2 AGNs at z<0.21, we identify 351 offset AGN candidates with velocity offsets of 50 km/s < |v| < 410 km/s. When we account for projection effects in the observed velocities, we estimate that 4% - 8% of AGNs are offset AGNs. We designed our selection criteria to bypass velocity offsets produced by rotating gas disks, AGN outflows, and gravitational recoil of supermassive black holes, but follow-up observations are still required to confirm our candidates as offset AGNs. We find that the fraction of AGNs that are offset candidates increases with AGN bolometric l...

  20. Intermittent Jet Activity in the Radio Galaxy 4C29.30?

    Energy Technology Data Exchange (ETDEWEB)

    Jamrozy, M.; /Jagiellonian U., Astron. Observ.; Konar, C.; Saikia, D.J.; /NCRA, Ganeshkhind; Stawarz, L.; /Jagiellonian U., Astron. Observ. /KIPAC, Menlo Park /SLAC; Mack,; /Bologna, Ist. Radioastronomia; Siemiginowska, A.; /Harvard-Smithsonian Ctr. Astrophys.

    2007-04-02

    We present radio observations at frequencies ranging from 240 to 8460 MHz of the radio galaxy 4C29.30 (J0840+2949) using the Giant Metrewave Radio Telescope (GMRT), the Very Large Array (VLA) and the Effelsberg telescope. We report the existence of weak extended emission with an angular size of {approx} 520 arcsec (639 kpc) within which a compact edge-brightened double-lobed source with a size of 29 arcsec (36 kpc) is embedded. We determine the spectrum of the inner double from 240 to 8460 MHz and show that it has a single power-law spectrum with a spectral index is {approx} 0.8. Its spectral age is estimated to be 33 Myr. The extended diffuse emission has a steep spectrum with a spectral index of {approx} 1.3 and a break frequency 240 MHz. The spectral age is {approx}>200 Myr, suggesting that the extended diffuse emission is due to an earlier cycle of activity. We reanalyze archival x-ray data from Chandra and suggest that the x-ray emission from the hotspots consists of a mixture of nonthermal and thermal components, the latter being possibly due to gas which is shock heated by the jets from the host galaxy.

  1. A complete census of silicate features in the mid-infrared spectra of active galaxies

    CERN Document Server

    Hatziminaoglou, Evanthia; Feltre, Anna; Piñol-Ferrer, Nuria

    2015-01-01

    We present a comprehensive study of the silicate features at 9.7 and 18 micron of a sample of almost 800 active galactic nuclei (AGN) with available spectra from the Spitzer InfraRed Spectrograph (IRS). We measure the strength of the silicate feature at 9.7 micron, S9.7, before and after subtracting the host galaxy emission from the IRS spectra. The numbers of type 1 and 2 AGN with the feature in emission increase by 20 and 50%, respectively, once the host galaxy is removed, while 35% of objects with the feature originally in absorption exhibit it in even deeper absorption. The peak of S9.7, lambda_peak, has a bimodal distribution when the feature is in emission, with about 65% of the cases showing lambda_peak > 10.2 micron. Silicates can appear in emission in objects with mid-infrared (MIR) luminosity spanning over six orders of magnitude. The derived distributions of the strength of the silicate features at 9.7 and 18 micron provide a solid test bed for modeling the dust distribution in AGN. Clumpiness is n...

  2. Uncovering the Spectral Energy Distribution in Active Galaxies Using High Ionization Mid-infrared Emission Lines

    CERN Document Server

    Meléndez, M; Weaver, K A; Mushotzky, R F

    2011-01-01

    The shape of the spectral energy distribution of active galaxies in the EUV--soft X-ray band (13.6 eV to 1 keV) is uncertain because obscuration by dust and gas can hamper our view of the continuum. To investigate the shape of the spectral energy distribution in this energy band, we have generated a set of photoionization models which reproduce the small dispersion found in correlations between high-ionization mid-infrared emission lines in a sample of hard X-ray selected AGN. Our calculations show that a broken power-law continuum model is sufficient to reproduce the [Ne V]14.32 mm/[NeIII], [Ne V]24.32mm/[O IV]25.89mm and [O IV] 25.89mm/[Ne III] ratios, and does not require the addition of a "big bump" EUV model component. We constrain the EUV--soft X-ray slope, alpha_i, to be between 1.5 -- 2.0 and derive a best fit of alpha_i ~ 1.9 for Seyfert 1 galaxies, consistent with previous studies of intermediate redshift quasars. If we assume a blue bump model, most sources in our sample have derived temperatures b...

  3. A Distant Echo of Milky Way Central Activity closes the Galaxy's Baryon Census

    CERN Document Server

    Nicastro, F; Krongold, Y; Mathur, S; Elvis, M

    2016-01-01

    We report on the presence of large amounts of million-degree gas in the Milky Way's interstellar and circum-galactic medium. This gas (1) permeates both the Galactic plane and the halo, (2) extends to distances larger than 60-200 kpc from the center, and (3) its mass is sufficient to close the Galaxy's baryon census. Moreover, we show that a vast, $\\sim 6$ kpc radius, spherically-symmetric central region of the Milky Way above and below the 0.16 kpc thick plane, has either been emptied of hot gas or the density of this gas within the cavity has a peculiar profile, increasing from the center up to a radius of $\\sim 6$ kpc, and then decreasing with a typical halo density profile. This, and several other converging pieces of evidence, suggest that the current surface of the cavity, at 6 kpc from the Galaxy's center, traces the distant echo of a period of strong nuclear activity of our super-massive black-hole, occurred about 6 Myrs ago.

  4. LUMINOUS X-RAY ACTIVE GALACTIC NUCLEI IN CLUSTERS OF GALAXIES

    International Nuclear Information System (INIS)

    We present a study of X-ray active galactic nucleus (AGN) overdensities in 16 Abell clusters, within the redshift range 0.073 x ≥ 1042 erg s-1 (at the redshift of the clusters) and within an area of 1 h -172 Mpc radius (excluding the core). To investigate the presence or absence of a true enhancement of luminous X-ray AGNs in the cluster area, we also derived the corresponding optical galaxy overdensities, using a suitable range of r-band magnitudes. We always find the latter to be significantly higher (and only in two cases roughly equal) with respect to the corresponding X-ray overdensities. Over the whole cluster sample, the mean X-ray point-source overdensity is a factor of ∼4 less than that corresponding to bright optical galaxies, a difference which is significant at a >0.995 level, as indicated by an appropriate student's t-test. We conclude that the triggering of luminous X-ray AGNs in rich clusters is strongly suppressed. Furthermore, searching for optical Sloan Digital Sky Survey counterparts of all the X-ray sources, associated with our clusters, we found that about half appear to be background QSOs, while others are background and foreground AGNs or stars. The true overdensity of X-ray point sources, associated with the clusters, is therefore even smaller than what our statistical approach revealed.

  5. The peculiar radio galaxy 4C 35.06: a case for recurrent AGN activity?

    CERN Document Server

    Shulevski, A; Barthel, P D; Murgia, M; van Weeren, R J; White, G J; Brüggen, M; Kunert-Bajraszewska, M; Jamrozy, M; Best, P N; Röttgering, H J A; Chyzy, K T; de Gasperin, F; Bîrzan, L; Brunetti, G; Brienza, M; Rafferty, D A; Anderson, J; Beck, R; Deller, A; Zarka, P; Schwarz, D; Mahony, E; Orrú, E; Bell, M E; Bentum, M J; Bernardi, G; Bonafede, A; Breitling, F; Broderick, J W; Butcher, H R; Carbone, D; Ciardi, B; de Geus, E; Duscha, S; Eislöffel, J; Engels, D; Falcke, H; Fallows, R A; Fender, R; Ferrari, C; Frieswijk, W; Garrett, M A; Grießmeier, J; Gunst, A W; Heald, G; Hoeft, M; Hörandel, J; Horneffer, A; van der Horst, A J; Intema, H; Juette, E; Karastergiou, A; Kondratiev, V I; Kramer, M; Kuniyoshi, M; Kuper, G; Maat, P; Mann, G; McFadden, R; McKay-Bukowski, D; McKean, J P; Meulman, H; Mulcahy, D D; Munk, H; Norden, M J; Paas, H; Pandey-Pommier, M; Pizzo, R; Polatidis, A G; Reich, W; Rowlinson, A; Scaife, A M M; Serylak, M; Sluman, J; Smirnov, O; Steinmetz, M; Swinbank, J; Tagger, M; Tang, Y; Tasse, C; Thoudam, S; Toribio, M C; Vermeulen, R; Vocks, C; Wijers, R A M J; Wise, M W; Wucknitz, O

    2015-01-01

    Using observations obtained with the LOw Fequency ARray (LOFAR), the Westerbork Synthesis Radio Telescope (WSRT) and archival Very Large Array (VLA) data, we have traced the radio emission to large scales in the complex source 4C 35.06 located in the core of the galaxy cluster Abell 407. At higher spatial resolution (~4"), the source was known to have two inner radio lobes spanning 31 kpc and a diffuse, low-brightness extension running parallel to them, offset by about 11 kpc (in projection). At 62 MHz, we detect the radio emission of this structure extending out to 210 kpc. At 1.4 GHz and intermediate spatial resolution (~30"), the structure appears to have a helical morphology. We have derived the characteristics of the radio spectral index across the source. We show that the source morphology is most likely the result of at least two episodes of AGN activity separated by a dormant period of around 35 Myr. The AGN is hosted by one of the galaxies located in the cluster core of Abell 407. We propose that it ...

  6. The Megamaser Cosmology Project. III. Accurate Masses of Seven Supermassive Black Holes in Active Galaxies with Circumnuclear Megamaser Disks

    CERN Document Server

    Kuo, C Y; Condon, J J; Impellizzeri, C M V; Lo, K Y; Zaw, I; Schenker, M; Henkel, C; Reid, M J; Greene, J E

    2010-01-01

    Observations of H$_2$O masers from circumnuclear disks in active galaxies for the Megamaser Cosmology Project allow accurate measurement of the mass of supermassive black holes (BH) in these galaxies. We present the Very Long Baseline Interferometry (VLBI) images and kinematics of water maser emission in six active galaxies: NGC~1194, NGC~2273, NGC~2960 (Mrk~1419), NGC~4388, NGC~6264 and NGC~6323. We use the Keplerian rotation curves of these six megamaser galaxies, plus a seventh previously published, to determine accurate enclosed masses within the central $\\sim0.3$ pc of these galaxies, smaller than the radius of the sphere of influence of the central mass in all cases. We also set lower limits to the central mass densities of between 0.12 and 60 $\\times 10^{10} M_{\\odot}$~pc$^{-3}$. For six of the seven disks, the high central densities rule out clusters of stars or stellar remnants as the central objects, and this result further supports our assumption that the enclosed mass can be attributed predominant...

  7. Studying the evolution of galaxies in compact groups over the past 3 Gyr. I. The nuclear activity

    CERN Document Server

    Bitsakis, T; Ciesla, L; Krongold, Y; Charmandaris, V; Zezas, A

    2015-01-01

    We present the first -- of a series -- study of the evolution of galaxies in compact groups over the past 3 Gyr. This paper focuses on the evolution of the nuclear activity and how it has been affected by the dense environment of the groups. Our analysis is based on the largest multiwavelength compact group sample to-date, containing complete ultraviolet-to-infrared (UV-to-IR) photometry for 1,770 isolated groups (7,417 galaxies). We classified the nuclear activity of the galaxies based on optical emission line and mid-infrared diagnostic methods, as well as using spectral energy distribution fitting. We observe a 15% increase on the number of the AGN-hosting late-type galaxies found in dynamically old groups, over the past 3 Gyr, accompanied by the corresponding decrease of their circumnuclear star formation. Comparing our compact group results with those of local isolated field and interacting pair galaxies, we find no differences in the AGN at the same redshift range. Based on both optical and mid-IR colou...

  8. Shaping galaxy evolution with galaxy structure

    Science.gov (United States)

    Cheung, Edmond

    A fundamental pursuit of astronomy is to understand galaxy evolution. The enormous scales and complex physics involved in this endeavor guarantees a never-ending journey that has enamored both astronomers and laymen alike. But despite the difficulty of this task, astronomers have still attempted to further this goal. Among of these astronomers is Edwin Hubble. His work, which includes the famous Hubble sequence, has immeasurably influenced our understanding of galaxy evolution. In this thesis, we present three works that continues Hubble's line of study by using galaxy structure to learn about galaxy evolution. First, we examine the dependence of galaxy quiescence on inner galactic structure with the AEGIS/ DEEP2 survey at 0.5In this thesis, we present three works that continues Hubble's line of study by using galaxy structure to learn about galaxy evolution. First, we examine the dependence of galaxy quiescence on inner galactic structure with the AEGIS/ DEEP2 survey at 0.5Hubble at 0.2active galaxies to a matched sample of inactive, control galaxies shows that there is no statistically significant excess of bars in active hosts. Our result shows that bars are not the primary fueling mechanism of supermassive black hole growth.

  9. Galaxy Zoo: Are bars responsible for the feeding of active galactic nuclei at 0.2 < z < 1.0?

    Science.gov (United States)

    Cheung, Edmond; Trump, Jonathan R.; 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.

    2015-02-01

    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 (All-wavelength Extended Groth strip International Survey), COSMOS (Cosmological Evolution Survey), and (Great Observatories Origins Deep Survey-South) 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 fuelling mechanism for supermassive black hole growth.

  10. High energy neutrinos from primary cosmic rays accelerated in the cores of active galaxies

    Science.gov (United States)

    Stecker, F. W.; Done, C.; Salamon, M. H.; Sommers, P.

    1991-01-01

    The spectra and high-energy neutrino fluxes are calculated from photomeson production in active galactic nuclei (AGN) such as quasars and Seyfert galaxies using recent UV and X-ray observations to define the photon fields and an accretion-disk shock-acceleration model for producing ultrahigh-energy cosmic rays in the AGN. Collectively AGN should produce the dominant isotropic neutrino background between 10 exp 4 and 10 exp 10 GeV. Measurement of this background could be critical in determining the energy-generation mechanism, evolution, and distribution of AGN. High-energy background spectra and spectra from bright AGN such as NGC4151 and 3C273 are predicted which should be observable with present detectors. High energy AGN nus should produce a sphere of stellar disruption around their cores which could explain their observed broad-line emission regions.

  11. 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

  12. The Need for Plasma Astrophysics in Understanding Life Cycles of Active Galaxies

    CERN Document Server

    Li, H; Bellan, P; Colgate, S; Forest, C; Fowler, K; Goodman, J; Intrator, T; Kronberg, P; Lyutikov, M; Zweibel, E

    2009-01-01

    In this White Paper, we emphasize the need for and the important role of plasma astrophysics in the studies of formation, evolution of, and feedback by Active Galaxies. We make three specific recommendations: 1) We need to significantly increase the resolution of VLA, perhaps by building an EVLA-II at a modest cost. This will provide the angular resolution to study jets at kpc scales, where, for example, detailed Faraday rotation diagnosis can be done at 1GHz transverse to jets; 2) We need to build coordinated programs among NSF, NASA, and DOE to support laboratory plasma experiments (including liquid metal) that are designed to study key astrophysical processes, such as magneto-rotational instability (origin of angular momentum transport), dynamo (origin of magnetic fields), jet launching and stability. Experiments allowing access to relativistic plasma regime (perhaps by intense lasers and magnetic fields) will be very helpful for understanding the stability and dissipation physics of jets from Supermassive...

  13. The EVN view of the highly variable TeV active galaxy IC 310

    CERN Document Server

    Schulz, R; Ros, E; Glawion, D Eisenacher; Bach, U; Elsässer, D; Grossberger, C; Kreykenbohm, I; Mannheim, K; Müller, C; Trüstedt, J; Wilms, J

    2015-01-01

    Very-high-energy $\\gamma$-ray observations of the active galaxy IC 310 with the MAGIC telescopes have revealed fast variability with doubling time scales of less than 4.8min. This implies that the emission region in IC 310 is smaller than 20% of the gravitational radius of the central supermassive black hole with a mass of $3\\times 10^8 M_\\odot$, which poses serious questions on the emission mechanism and classification of this enigmatic object. We report on the first quasi-simultaneous multi-frequency VLBI observations of IC 310 conducted with the EVN. We find a blazar-like one-sided core-jet structure on parsec scales, constraining the inclination angle to be less than $\\sim 20^\\circ$ but very small angles are excluded to limit the de-projected length of the large-scale radio jet.

  14. 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

  15. Far-infrared line spectra of active galaxies from the Herschel/PACS Spectrometer: the complete database

    CERN Document Server

    Fernández-Ontiveros, J A; Pereira-Santaella, M; Malkan, M A; Andreani, P; Dasyra, K M

    2016-01-01

    We present a coherent database of spectroscopic observations of far-IR fine-structure lines from the Herschel/PACS archive for a sample of 170 local AGN, plus a comparison sample of 20 starburst galaxies and 43 dwarf galaxies. Published Spitzer/IRS and Herschel/SPIRE line fluxes are included to extend our database to the full 10-600 $\\mu m$ spectral range. The observations are compared to a set of CLOUDY photoionisation models to estimate the above physical quantities through different diagnostic diagrams. We confirm the presence of a stratification of gas density in the emission regions of the galaxies, which increases with the ionisation potential of the emission lines. The new [OIV]25.9$\\mu m$/[OIII]88$\\mu m$ vs [NeIII]15.6$\\mu m$/[NeII]12.8$\\mu m$ diagram is proposed as the best diagnostic to separate: $i)$ AGN activity from any kind of star formation; and $ii)$ low-metallicity dwarf galaxies from starburst galaxies. Current stellar atmosphere models fail to reproduce the observed [OIV]25.9$\\mu m$/[OIII]8...

  16. The Black Hole-Bulge Relationship in Luminous Broad-Line Active Galactic Nuclei and Host Galaxies

    CERN Document Server

    Shen, J; Schneider, D P; Hall, P B

    2007-01-01

    We have measured the stellar velocity dispersions (\\sigma_*) and estimated the central black hole (BH) masses for over 900 broad-line active galactic nuclei (AGNs) observed with the Sloan Digital Sky Survey. The sample includes objects which have redshifts up to z=0.452, high quality spectra, and host galaxy spectra dominated by an early-type (bulge) component. The AGN and host galaxy spectral components were decomposed using an eigenspectrum technique. The BH masses (M_BH) were estimated from the AGN broad-line widths, and the velocity dispersions were measured from the stellar absorption spectra of the host galaxies. The range of black hole masses covered by the sample is approximately 10^6 < M_BH < 10^9 M_Sun. The host galaxy luminosity-velocity dispersion relationship follows the well-known Faber-Jackson relation for early-type galaxies, with a power-law slope 4.33+-0.21. The estimated BH masses are correlated with both the host luminosities (L_{H}) and the stellar velocity dispersions (\\sigma_*), s...

  17. A study of active galactic nuclei in low surface brightness galaxies with Sloan Digital Sky Survey spectroscopy

    Institute of Scientific and Technical Information of China (English)

    Lin Mei; Wei-Min Yuan; Xiao-Bo Dong

    2009-01-01

    Active galactic nuclei (AGNs) in low surface brightness galaxies (LSBGs) have received little attention in previous studies. We present a detailed spectral analysis of 194 LSBGs from the Impey et al. (1996) APM LSBG sample which has been observed spec-troscopically by the Sloan Digital Sky Survey Data Release 5 (SDSS DR5). Our elaborate spectral analysis enables us to carry out, for the first time, reliable spectral classification of nuclear processes in LSBGs based on the standard emission line diagnostic diagrams in a rigorous way. Star-forming galaxies are common, as found in about 52% of LSBGs. We find that, contrary to some previous claims, the fraction of galaxies that contain AGNs is significantly lower than that found in nearby normal galaxies of high surface brightness. This is qualitatively in line with the finding of Impey et al. This result holds true even within each morphological type from Sa to Sc. LSBGs that have larger central stellar ve-locity dispersions or larger physical sizes tend to have a higher chance of harboring an AGN. For three AGNs with broad emission lines, the black hole masses estimated from the emission lines are broadly consistent with the well known M-σ* relation established for normal galaxies and AGNs.

  18. 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...

  19. Star Dust Formation Activities in AzTEC-3: A Starburst Galaxy at z=5.3

    Science.gov (United States)

    Dwek, Eliahu

    2011-01-01

    Analyses of of high-redshift ultraluminous infrared OR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. In this lecture we add this constraint to the analysis of AzTEC-3, a starburst galaxy at z=5.3. We construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multi wavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

  20. Star and Dust Formation Activities in AzTEC-3: A Starburst Galaxy at z=5.3

    Science.gov (United States)

    Dwek, Eliahu

    2011-01-01

    Analyses of of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. In this lecture we add this constraint to the analysis of AzTEC-3, a starburst galaxy at z=5.3. We construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multiwavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

  1. Star and Dust Formation Activities in AzTEC-3: A Starburst Galaxy at z equals 5.3

    Science.gov (United States)

    Dwek, Eliahu

    2011-01-01

    Analyses of of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. In this lecture we add this constraint to the analysis of AzTEC-3, a starburst galaxy at z=5.3. We construct different stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. A robust result of our models is that all scenarios require most of the radiating dust mass to have been accreted in molecular clouds. Our new procedure highlights the importance of a multi wavelength approach, and of the use of dust evolution models in constraining the age and the star formation activity and history in galaxies.

  2. Kim 3: an Ultra-faint Star Cluster in the Constellation of Centaurus

    OpenAIRE

    Kim, Dongwon; Jerjen, Helmut; Mackey, Dougal; Da Costa, Gary S.; Milone, Antonino P.

    2015-01-01

    We report the discovery of an ultra-faint star cluster in the constellation of Centaurus. This new stellar system, Kim 3, features a half light radius of $r_{h}=2.29^{+1.28}_{-0.52}$ pc and a total luminosity of $M_{V}=+0.7\\pm0.3$. Approximately 26 stars are identified as candidate member stars down to four magnitudes below the main-sequence turn-off, which makes Kim 3 the least luminous star cluster known to date. The compact physical size and extreme low luminosity place it close to faint s...

  3. Low-Mass X-ray Binaries and Globular Clusters in Centaurus A

    OpenAIRE

    Jordan, Andres; Sivakoff, Gregory R.; McLaughlin, Dean E.; Blakeslee, John P; Evans, Daniel A.; Kraft, Ralph P.; Hardcastle, Martin J.; Peng, Eric W.; Cote, Patrick; Croston, Judith H.; Juett, Adrienne M.; Minniti, Dante; Raychaudhury, Somak; Sarazin, Craig L.; Worrall, Diana M.

    2007-01-01

    We present results of Hubble Space Telescope and Chandra X-ray Observatory observations of globular clusters (GCs) and low-mass X-ray binaries (LMXBs) in the central regions of Centaurus A. Out of 440 GC candidates we find that 41 host X-ray point sources that are most likely LMXBs. We fit King models to our GC candidates in order to measure their structural parameters. We find that GCs that host LMXBs are denser and more compact, and have higher encounter rates and concentrations than the GC...

  4. Induced nuclear activity in galaxy pairs with different morphologies (E+E), (E+S) and (S+S)

    CERN Document Server

    Hernández-Ibarra, Francisco J; Dultzin, Deborah; del Olmo, Ascensión; Perea, Jaime; González, Jesús; Mendoza-Castrejón, Sandro; Bitsakis, Theodoros

    2015-01-01

    We analysed 385 galactic spectra from the Sloan Digital Sky Survey Data Release 7 (SDSS-DR7) that belong to the catalog of isolated pairs of galaxies by Karachentsev. The spectra corresponds to physical pairs of galaxies as defined by V $\\leq$ 1200 Km/s and a pair separation $\\leq$ 100 kpc. We search for the incidence of nuclear activity, both thermal (star-forming) and non-thermal -Active Galactic Nuclei (AGN). After a careful extraction of the nuclear spectra, we use diagnostic diagrams and find that the incidence of AGN activity is 48 \\% in the paired galaxies with emission lines and 40\\% for the total sample (as compared to $\\sim$ 43 \\% and 41\\% respectively in a sample of isolated galaxies). These results remain after dissecting the effects of morphological type and galactic stellar mass (with only a small, non significant, enhancement of the AGN fraction in pairs of objects). These results suggest that weak interactions are not necessary or sufficient to trigger low-luminosity AGN. Since the fraction of...

  5. The peculiar radio galaxy 4C 35.06: a case for recurrent AGN activity?

    Science.gov (United States)

    Shulevski, A.; Morganti, R.; Barthel, P. D.; Murgia, M.; van Weeren, R. J.; White, G. J.; Brüggen, M.; Kunert-Bajraszewska, M.; Jamrozy, M.; Best, P. N.; Röttgering, H. J. A.; Chyzy, K. T.; de Gasperin, F.; Bîrzan, L.; Brunetti, G.; Brienza, M.; Rafferty, D. A.; Anderson, J.; Beck, R.; Deller, A.; Zarka, P.; Schwarz, D.; Mahony, E.; Orrú, E.; Bell, M. E.; Bentum, M. J.; Bernardi, G.; Bonafede, A.; Breitling, F.; Broderick, J. W.; Butcher, H. R.; Carbone, D.; Ciardi, B.; de Geus, E.; Duscha, S.; Eislöffel, J.; Engels, D.; Falcke, H.; Fallows, R. A.; Fender, R.; Ferrari, C.; Frieswijk, W.; Garrett, M. A.; Grießmeier, J.; Gunst, A. W.; Heald, G.; Hoeft, M.; Hörandel, J.; Horneffer, A.; van der Horst, A. J.; Intema, H.; Juette, E.; Karastergiou, A.; Kondratiev, V. I.; Kramer, M.; Kuniyoshi, M.; Kuper, G.; Maat, P.; Mann, G.; McFadden, R.; McKay-Bukowski, D.; McKean, J. P.; Meulman, H.; Mulcahy, D. D.; Munk, H.; Norden, M. J.; Paas, H.; Pandey-Pommier, M.; Pizzo, R.; Polatidis, A. G.; Reich, W.; Rowlinson, A.; Scaife, A. M. M.; Serylak, M.; Sluman, J.; Smirnov, O.; Steinmetz, M.; Swinbank, J.; Tagger, M.; Tang, Y.; Tasse, C.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; Vocks, C.; Wijers, R. A. M. J.; Wise, M. W.; Wucknitz, O.

    2015-07-01

    Using observations obtained with the LOw Fequency ARray (LOFAR), the Westerbork Synthesis Radio Telescope (WSRT) and archival Very Large Array (VLA) data, we have traced the radio emission to large scales in the complex source 4C 35.06 located in the core of the galaxy cluster Abell 407. At higher spatial resolution (~ 4″), the source was known to have two inner radio lobes spanning 31 kpc and a diffuse, low-brightness extension running parallel to them, offset by about 11 kpc (in projection). At 62 MHz, we detect the radio emission of this structure extending out to 210 kpc. At 1.4 GHz and intermediate spatial resolution (~ 30″), the structure appears to have a helical morphology. We have derived the characteristics of the radio spectral index across the source. We show that the source morphology is most likely the result of at least two episodes of AGN activity separated by a dormant period of around 35 Myr. The outermost regions of radio emission have a steep spectral index (α< - 1), indicative of old plasma. We connect the spectral index properties of the resolved source structure with the integrated fluxdensity spectral index of 4C 35.06 and suggest an explanation for its unusual integrated flux density spectral shape (a moderately steep power law with no discernible spectral break), possibly providing a proxy for future studies of more distant radio sources through inferring their detailed spectral index properties and activity history from their integrated spectral indices. The AGN is hosted by one of the galaxies located in the cluster core of Abell 407. We propose that it is intermittently active as it moves in the dense environment in the cluster core. In this scenario, the AGN turned on sometime in the past, and has produced the helical pattern of emission, possibly a sign of jet precession/merger during that episode of activity. Using LOFAR, we can trace the relic plasma from that episode of activity out to greater distances from the core than ever

  6. 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.

  7. Energy input from quasars regulates the growth and activity of black holes and their host galaxies.

    Science.gov (United States)

    Di Matteo, Tiziana; Springel, Volker; Hernquist, Lars

    2005-02-10

    In the early Universe, while galaxies were still forming, black holes as massive as a billion solar masses powered quasars. Supermassive black holes are found at the centres of most galaxies today, where their masses are related to the velocity dispersions of stars in their host galaxies and hence to the mass of the central bulge of the galaxy. This suggests a link between the growth of the black holes and their host galaxies, which has indeed been assumed for a number of years. But the origin of the observed relation between black hole mass and stellar velocity dispersion, and its connection with the evolution of galaxies, have remained unclear. Here we report simulations that simultaneously follow star formation and the growth of black holes during galaxy-galaxy collisions. We find that, in addition to generating a burst of star formation, a merger leads to strong inflows that feed gas to the supermassive black hole and thereby power the quasar. The energy released by the quasar expels enough gas to quench both star formation and further black hole growth. This determines the lifetime of the quasar phase (approaching 100 million years) and explains the relationship between the black hole mass and the stellar velocity dispersion. PMID:15703739

  8. The Luminous Polycyclic Aromatic Hydrocarbon Emission Features: Applications to High Redshift Galaxies and Active Galactic Nuclei

    Science.gov (United States)

    Shipley, Heath V.

    2016-01-01

    For decades, significant work has been applied to calibrating emission from the ultra-violet, nebular emission lines, far-infrared, X-ray and radio as tracers of the star-formation rate (SFR) in distant galaxies. Understanding the exact rate of star-formation and how it evolves with time and galaxy mass has deep implications for how galaxies form. The co-evolution of star-formation and supermassive black hole (SMBH) accretion is one of the key problems in galaxy formation theory. But, many of these SFR indicators are influenced by SMBH accretion in galaxies and result in unreliable SFRs. Utilizing the luminous polycyclic aromatic hydrocarbon (PAH) emission features, I provide a new robust SFR calibration using the luminosity emitted from the PAHs at 6.2μm, 7.7μm and 11.3μm to solve this. The PAH features emit strongly in the mid-infrared (mid-IR; 5-25μm) mitigating dust extinction, containing on average 5-10% of the total IR luminosity in galaxies. I use a sample of 105 star-forming galaxies covering a range of total IR luminosity, LIR = L(8-1000μm) = 109 - 1012 L⊙ and redshift 0 blackhole accretion contemporaneously in a galaxy.

  9. The Dust Content and Opacity of Actively Star-Forming Galaxies

    NARCIS (Netherlands)

    Calzetti, D.; Armus, L.; Bohlin, R. C.; Kinney, A. L.; Koornneef, J.; Storchi-Bergmann, T.

    1999-01-01

    Submitted to: Astrophys. J. Abstract: (Abridged) We present far-infrared (FIR) photometry at 150 micron and 205 micron of eight low-redshift starburst galaxies obtained with the ISO Photometer. Five of the eight galaxies are detected in both wavebands and these data are used, in conjunction with IRA

  10. X-ray Analysis of Filaments in Galaxy Clusters

    CERN Document Server

    Walker, S A; Fabian, A C; Sanders, J S

    2015-01-01

    We perform a detailed X-ray study of the filaments surrounding the brightest cluster galaxies in a sample of nearby galaxy clusters using deep Chandra observations, namely the Perseus, Centaurus and Virgo clusters, and Abell 1795. We compare the X-ray properties and spectra of the filaments in all of these systems, and find that their Chandra X-ray spectra are all broadly consistent with an absorbed two temperature thermal model, with temperature components at 0.75 and 1.7 keV. We find that it is also possible to model the Chandra ACIS filament spectra with a charge exchange model provided a thermal component is also present, and the abundance of oxygen is suppressed relative to the abundance of Fe. In this model, charge exchange provides the dominant contribution to the spectrum in the 0.5-1.0 keV band. However, when we study the high spectral resolution RGS spectrum of the filamentary plume seen in X-rays in Centaurus, the opposite appears to be the case. The properties of the filaments in our sample of clu...

  11. The formation of bulges and black holes: lessons from a census of active galaxies in the SDSS.

    Science.gov (United States)

    Kauffmann, Guinevere; Heckman, Timothy M

    2005-03-15

    We examine the relationship between galaxies, supermassive black holes and AGN using a sample of 23,000 narrow-emission-line ('type 2') active galactic nuclei (AGN) drawn from a sample of 123,000 galaxies from the Sloan Digital Sky Survey. We have studied how AGN host properties compare with those of normal galaxies and how they depend on the luminosity of the active nucleus. We find that AGN reside in massive galaxies and have distributions of sizes and concentrations that are similar to those of the early-type galaxies in our sample. The host galaxies of low-luminosity AGN have stellar populations similar to normal early types. The hosts of high- luminosity AGN have much younger mean stellar ages, and a significant fraction have experienced recent starbursts. High-luminosity AGN are also found in lower-density environments. We then use the stellar velocity dispersions of the AGN hosts to estimate black hole masses and their [OIII]lambda5007 emission-line luminosities to estimate black hole accretion rates. We find that the volume averaged ratio of star formation to black hole accretion is approximately 1000 for the bulge-dominated galaxies in our sample. This is remarkably similar to the observed ratio of stellar mass to black hole mass in nearby bulges. Most of the present-day black hole growth is occurring in black holes with masses less than 3 x 10(7)M(3). Our estimated accretion rates imply that low-mass black holes are growing on a time-scale that is comparable with the age of the Universe. Around 50% this growth takes place in AGN that are radiating within a factor of five of the Eddington luminosity. Such systems are rare, making up only 0.2% of the low-mass black hole population at the present day. The remaining growth occurs in lower luminosity AGN. The growth time-scale increases by more than an order of magnitude for the most massive black holes in our sample. We conclude that the evolution of the AGN luminosity function documented in recent optical

  12. New water and remote galaxies complete ISO's observations

    Science.gov (United States)

    clear. It is at right angles to the axis of the radio-emitting regions, which are powered by jets of electrons driven by a black hole in the centre of the galaxy. Excited emissions detected by ISO's Short Wavelength Spectrometer also indicate the presence of an active black hole. "Centaurus A is an example of ISO's magic," says Catherine Cesarsky of CEA Saclay in France, leader of the ISOCAM instrument team. "It transforms opaque clouds seen by visible light into glowing scenes in the infrared. The same thing happens in dust clouds hiding newborn stars, and on a huge scale in dusty starburst galaxies -- which become infrared beacons lighting our way deep into the Universe." Distant galaxies seen through the holes in the sky When ISO was launched, one of the hopes for the space observatory was that it would detect galaxies made luminous by starburst events, or by black-hole activity, very far away in space and therefore far back in time. Dust in our own Milky Way Galaxy usually obscures the remotest and faintest galaxies. But when they look northwards and southwards, at right-angles to the disk of the Milky Way, astronomers find holes in the dust clouds through which distant galaxies are discernible. Both for ISO and the Hubble Space Telescope these holes have been special targets for observations with long exposures, to reveal faint galaxies. ISOCAM results through the northern hole, by a Japanese-led team, were reported last year in an ESA Information Note (25.97) and a picture release (ESA/ISO 97:8/1). They revealed many infrared-luminous galaxies billions of light- years away, from an era corresponding with about half the present age of the Universe. Even more distant and earlier galaxies may be present in ISO's observations, including some objects not yet seen by visible light. Results released at the London press briefing on ISO include "deep field" examinations by groups of astronomers led by Catherine Cesarsky of CEA Saclay and Michael Rowan Robinson of Imperial

  13. Supernovae in paired galaxies

    CERN Document Server

    Nazaryan, T A; Hakobyan, A A; Adibekyan, V Zh; Kunth, D; Mamon, G A; Turatto, M; Aramyan, L S

    2013-01-01

    We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies. SN types are not correlated with the luminosity ratio of host and neighbor galaxies in pairs. The orientation of SNe with respect to the preferred direction toward neighbor galaxy is found to be isotropic and independent of kinematical properties of the galaxy pair.

  14. Occultation Mapping of the Central Engine in the Active Galaxy MCG -6-30-15

    CERN Document Server

    McKernan, B

    1998-01-01

    The colossal power output of active galactic nuclei (AGN) is believed to be fueled by the accretion of matter onto a supermassive black hole. This central accreting region of AGN has hitherto been spatially unresolved and its structure therefore unknown. Here we propose that a previously reported `deep minimum' in the X-ray intensity of the AGN MCG-6-30-15, was due to a unique X-ray occultation event and that it probes structure of the central engine on scales < 1e14 cm, or 1.4e-7 arcseconds. The data are consistent with a bright central source surrounded by a less intense ring, which we identify with the inner edge of an accretion disk. These may be the first direct measurements of the spatial structure and geometry of the accreting black-hole system in an active galaxy.If the ring of X-ray emission is identified with the inner edge of an accretion disk, upper limits on the BH mass can be derived. Our occultation interpretation is controversial in the sense that X-ray variability in AGNs is normally attri...

  15. New active galactic nuclei detected in ROSAT All Sky Survey galaxies - The complete dataset

    CERN Document Server

    Kollatschny, W; Pietsch, W; Bischoff, K; Zetzl, M

    2008-01-01

    The ROSAT ALL Sky Survey Bright Source Catalogue (RASS-BSC) has been correlated with the Catalogue of Principal Galaxies (PGC) to identify new extragalactic counterparts. 550 reliable optical counterparts have been detected. We took optical spectra of 176 X-ray candidates and companions at ESO, Calar Alto observatory and McDonald observatory. We discuss the redshift-, linewidth-, as well as optical and X-ray luminosity distribution of our ROSAT selected sample. 139 galaxies of our 166 X-ray counterparts have been identified as AGN with 93 being Seyfert 1 galaxies (61%). Eighteen of them (20%) are Narrow Line Seyfert 1 galaxies. 34 X-ray candidates (21%) are LINERs and only eight candidates (5%) are Seyfert 2. The ratio of the number of Seyfert 1 galaxies to Seyfert 2 galaxies is about 11/1. Optical surveys result in ratios of 1/1.4. The high fraction of detected Seyfert 1 galaxies is explained by the sensitivity of the ROSAT to soft X-rays which are heavily absorbed in type 2 AGN. Two X-ray candidates are HII...

  16. Are luminous radio-loud active galactic nuclei triggered by galaxy interactions?

    CERN Document Server

    Almeida, C Ramos; Tadhunter, C; Pérez-González, P G; Barro, G; Inskip, K J; Morganti, R; Holt, J; Dicken, D

    2011-01-01

    We present the results of a comparison between the optical morphologies of a complete sample of 46 southern 2Jy radio galaxies at intermediate redshifts (0.05galaxies: 55 ellipticals at redshifts z<0.01 from the Observations of Bright Ellipticals at Yale (OBEY) survey, and 107 early-type galaxies at redshifts 0.2galaxy interactions in the triggering of powerful radio galaxies (PRGs). We find that a significant fraction of quiescent ellipticals at low and intermediate redshifts show evidence for disturbed morphologies at relatively high surface brightness levels, which are likely the result of past or on-going galaxy interactions. However, the morphological features detected in the galaxy hosts of the PRGs (e.g. tidal tails, shells, bridges, etc.) are up to 2 magnitudes brighter than those present in their quiescent counterparts. Indeed, if...

  17. The complex radio and X-ray structure in the nuclear regions of the active galaxy NGC1365

    CERN Document Server

    Stevens, I R; Norris, R P; Stevens, Ian R.; Forbes, Duncan A.; Norris, Ray P.

    1999-01-01

    We present a multiwavelength analysis of the prominent active galaxy NGC1365, in particular looking at the radio and X-ray properties of the central regions of the galaxy. We analyse ROSAT observations of NGC1365, and discuss recent ASCA results. In addition to a number of point sources in the vicinity of NGC1365, we find a region of X-ray emission extending along the central bar of the galaxy, combined with an emission peak near the centre of the galaxy. This X-ray emission is centred on the optical/radio nucleus, but is spatially extended. The X-ray spectrum can be well fitted by a thermal plasma model, with kT=0.6-0.8keV and a low local absorbing column. The thermal spectrum is suggestive of starburst emission rather than emission from a central black-hole. The ATCA radio observations show a number of hotspots, located in a ring around a weak radio nucleus. Synchrotron emission from electrons accelerated by supernovae and supernova remnants (SNRs) is the likely origin of these hotspots. The radio nucleus h...

  18. A Local Baseline of the Black Hole Mass Scaling Relations for Active Galaxies. III. The BH mass - $\\sigma$ relation

    CERN Document Server

    Bennert, Vardha N; Auger, Matthew W; Rosen, Rebecca; Harris, Chelsea E; Malkan, Matthew A; Woo, Jong-Hak

    2014-01-01

    We create a baseline of the black hole (BH) mass ($M_{\\rm BH}$) - stellar-velocity dispersion ($\\sigma$) relation for active galaxies, using a homogeneous sample of 66 Seyfert-1 galaxies in the local Universe (0.02 $< z <$ 0.09) selected from the Sloan Digital Sky Survey (SDSS). A multi-filter analysis of SDSS images yields AGN luminosities free of host-galaxy contamination. High signal-to-noise ratio Keck spectra provide the width of the broad H$\\beta$ emission line free of FeII emission and stellar absorption. $M_{\\rm BH}$ is estimated following the virial method. The Keck long-slit spectra provide spatially-resolved kinematics that is used to determine the rotation-free stellar-velocity dispersion within the spheroid effective radius ($\\sigma_{\\rm reff}$). To probe the effect of the kinematically-cold but rotationally-supported disk component, present in the majority of host galaxies, on aperture sigma measurements, we determine the stellar-velocity dispersion within an aperture of the size of the SD...

  19. The Evolution of Star Formation Activity in Cluster Galaxies Over $0.15

    CERN Document Server

    Wagner, Cory R; Brodwin, Mark; Stanford, S A; Snyder, Gregory F; Stern, Daniel

    2016-01-01

    We explore 7.5 billion years of evolution in the star formation activity of massive ($M_{\\star}>10^{10.1}\\,M_{\\odot}$) cluster galaxies using a sample of 25 clusters over $0.15Galaxy morphologies are determined visually using high-resolution Hubble Space Telescope images. Using the spectral energy distribution fitting code CIGALE, we measure star formation rates, stellar masses, and 4000 \\AA\\ break strengths. The latter are used to separate quiescent and star-forming galaxies (SFGs). From $z\\sim1.3$ to $z\\sim0.2$, the specific star formation rate (sSFR) of cluster SFGs and quiescent galaxies decreases by factors of three and four, respectively. Over the same redshift range, the sSFR of the entire cluster population declines by a factor of 11, from $0.48\\pm0.06\\;\\mathrm{Gyr}^{-1}$ to $0.043\\pm0.009\\;\\mathrm{Gyr}^{-1}$. This strong overall sSFR evolution is driven by t...

  20. Galaxies et trous noirs supermassifs

    Science.gov (United States)

    Collin-Zahn, Suzy

    2016-08-01

    A few percents of galaxies are classified as « active ». An active galaxy is a galaxy whose nucleus emits more energy than the whole galaxy in the form of electromagnetic radiation, relativistic particles, or mechanical energy. It is activated by a supermassive black hole fueled by matter falling on it, whose characteristics (Eddington luminosity, spin) are recalled. The class includes quasars and Seyfert galaxies. All massive "non active" galaxies contain a supermassive black hole, but there is not enough matter in its environment so as the nucleus becomes luminous. Different items are considered in the paper : how supermassive black holes are fueled, the accretion disc, the jets and the winds, the unified model of active galaxies, how are determined the masses of supermassive black holes, and what is the relation between the evolution of galaxies and supermassive black holes.

  1. Active galaxies. A fast and long-lived outflow from the supermassive black hole in NGC 5548.

    Science.gov (United States)

    Kaastra, J S; Kriss, G A; Cappi, M; Mehdipour, M; Petrucci, P-O; Steenbrugge, K C; Arav, N; Behar, E; Bianchi, S; Boissay, R; Branduardi-Raymont, G; Chamberlain, C; Costantini, E; Ely, J C; Ebrero, J; Di Gesu, L; Harrison, F A; Kaspi, S; Malzac, J; De Marco, B; Matt, G; Nandra, K; Paltani, S; Person, R; Peterson, B M; Pinto, C; Ponti, G; Pozo Nuñez, F; De Rosa, A; Seta, H; Ursini, F; de Vries, C P; Walton, D J; Whewell, M

    2014-07-01

    Supermassive black holes in the nuclei of active galaxies expel large amounts of matter through powerful winds of ionized gas. The archetypal active galaxy NGC 5548 has been studied for decades, and high-resolution x-ray and ultraviolet (UV) observations have previously shown a persistent ionized outflow. An observing campaign in 2013 with six space observatories shows the nucleus to be obscured by a long-lasting, clumpy stream of ionized gas not seen before. It blocks 90% of the soft x-ray emission and causes simultaneous deep, broad UV absorption troughs. The outflow velocities of this gas are up to five times faster than those in the persistent outflow, and, at a distance of only a few light days from the nucleus, it may likely originate from the accretion disk.

  2. X-ray Detections of Sub-millimetre Galaxies: Active Galactic Nuclei Versus Starburst Contribution

    CERN Document Server

    Johnson, Seth P; Wang, Danial Q; Williams, Christina C; Scott, Kim S; Yun, Min S; Pope, Alexandra; Lowenthal, James; Aretxaga, Itziar; Hughes, David; Kim, M J; Kim, Sungeun; Tamura, Yoichi; Kohno, Kotaro; Ezawa, Hajime; Kawabe, Ryohei; Oshima, Tai; 10.1093/mnras/stt197

    2013-01-01

    We present a large-scale study of the X-ray properties and near-IR-to-radio SEDs of submillimetre galaxies (SMGs) detected at 1.1mm with the AzTEC instrument across a ~1.2 square degree area of the sky. Combining deep 2-4 Ms Chandra data with Spitzer IRAC/MIPS and VLA data within the GOODS-N/S and COSMOS fields, we find evidence for AGN activity in ~14 percent of 271 AzTEC SMGs, ~28 percent considering only the two GOODS fields. Through X-ray spectral modeling and SED fitting using Monte Carlo Markov Chain techniques to Siebenmorgen et al. (2004) (AGN) and Efstathiou et al. (2000) (starburst) templates, we find that while star formation dominates the IR emission, with SFRs ~100-1000 M_sun/yr, the X-ray emission for most sources is almost exclusively from obscured AGNs, with column densities in excess of 10^23 cm^-2. Only for ~6 percent of our sources do we find an X-ray-derived SFR consistent with NIR-to-radio SED derived SFRs. Inclusion of the X-ray luminosities as a prior to the NIR-to-radio SED effectively...

  3. 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...

  4. 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...

  5. Active galaxy unification in the era of X-ray polarimetry

    CERN Document Server

    Dorodnitsyn, A

    2010-01-01

    Active Galactic Nuclei (AGN), Seyfert galaxies and quasars, are powered by luminous accretion and often accompanied by winds which are powerful enough to affect the AGN mass budget, and whose observational appearance bears an imprint of processes which are happening within the central parsec around the black hole (BH). One example of such a wind is the partially ionized gas responsible for X-ray and UV absorption ('warm absorbers'). Here we show that such gas will have a distinct signature when viewed in polarized X-rays. Observations of such polarization can test models for the geometry of the flow, and the gas responsible for launching and collimating it. We present calculations which show that the polarization depends on the hydrodynamics of the flow, the quantum mechanics of resonance line scattering and the transfer of polarized X-ray light in the highly ionized moving gas. The results emphasize the three dimensional nature of the wind for modeling spectra. We show that the polarization in the 0.1-10 keV...

  6. ASSOCIATIONS OF HIGH-REDSHIFT QUASI-STELLAR OBJECTS WITH ACTIVE, LOW-REDSHIFT SPIRAL GALAXIES

    International Nuclear Information System (INIS)

    Following the discovery in the 1960s of radio and optical QSOs it was found that some of them lie very close to low-redshift (z ≤ 0.01) spiral galaxies with separations of ∼<2 arcmin. These were discovered both serendipitously by many observers, and systematically by Arp. They are some of the brightest QSOs in radio and optical wavelengths and are very rare. We have carried out a new statistical analysis of most of those galaxy-QSO pairs and find that the configurations have high statistical significance. We show that gravitational microlensing due to stars or other dark objects in the halos of the galaxies apparently cannot account for the excess. Sampling or identification bias likewise seems unable to explain it. Following this up we selected all ∼4000 QSOs with g ≤ 18 from a catalog of confirmed QSOs in the Sloan Digital Sky Survey, and compared them with various subsets of galaxies from the RC 3 galaxy catalog. In contrast to the earlier results, no significant excess of such QSOs was found around these galaxies. Possible reasons for the discrepancy are discussed.

  7. The merger fraction of active and inactive galaxies in the local Universe through an improved non-parametric classification

    CERN Document Server

    Cotini, Stefano; Caccianiga, Alessandro; Colpi, Monica; Della Ceca, Roberto; Mapelli, Michela; Severgnini, Paola; Segreto, Alberto; 10.1093/mnras/stt358

    2013-01-01

    We investigate the possible link between mergers and the enhanced activity of supermassive black holes (SMBHs) at the centre of galaxies, by comparing the merger fraction of a local sample (0.003 =< z < 0.03) of active galaxies - 59 active galactic nuclei (AGN) host galaxies selected from the all-sky Swift BAT (Burst Alert Telescope) survey - with an appropriate control sample (247 sources extracted from the Hyperleda catalogue) that has the same redshift distribution as the BAT sample. We detect the interacting systems in the two samples on the basis of non-parametric structural indexes of concentration (C), asymmetry (A), clumpiness (S), Gini coefficient (G) and second order momentum of light (M20). In particular, we propose a new morphological criterion, based on a combination of all these indexes, that improves the identification of interacting systems. We also present a new software - PyCASSo (Python CAS Software) - for the automatic computation of the structural indexes. After correcting for the c...

  8. No More Active Galactic Nuclei in Clumpy Disks Than in Smooth Galaxies at z~2 in CANDELS / 3D-HST

    CERN Document Server

    Trump, Jonathan R; Juneau, Stephanie; Weiner, Benjamin J; Luo, Bin; Brammer, Gabriel B; Bell, Eric F; Brandt, W Niel; Dekel, Avishai; Guo, Yicheng; Hopkins, Philip F; Koo, David C; Kocevski, Dale D; McIntosh, Daniel H; Momcheva, Ivelina; Faber, S M; Ferguson, Henry C; Grogin, Norman A; Kartaltepe, Jeyhan; Koekemoer, Anton M; Lotz, Jennifer; Maseda, Michael; Mozena, Mark; Nandra, Kirpal; Rosario, David J; Zeimann, Gregory R

    2014-01-01

    We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxies. The CANDELS visual classification system is used to identify 44 clumpy disk galaxies, along with mass-matched comparison samples of smooth and intermediate morphology galaxies. We note that, despite being being mass-matched and having similar star formation rates, the smoother galaxies tend to be smaller disks with more prominent bulges compared to the clumpy galaxies. The lack of smooth extended disks is probably a general feature of the z~2 galaxy population, and means we cannot directly compare with the clumpy and smooth extended disks observed at lower redshift. We find that z~2 clumpy galaxies have slightly enhanced AGN fractions selected by integrated line ratio...

  9. A CANDELS WFC3 Grism Study of Emission-Line Galaxies at Z approximates 2: A mix of Nuclear Activity and Low-Metallicity Star Formation

    Science.gov (United States)

    Trump, Jonathan R.; Weiner, Benjamin J.; Scarlata, Claudia; Kocevski, Dale D.; Bell, Eric F.; McGrath, Elizabeth J.; Koo, David C.; Faber, S. M.; Laird, Elise S.; Mozena, Mark; Rangel, Cyprian; Yan, Renbin; Yesuf, Hassen; Atek, Hakim; Dickinson, Mark; Donley, Jennifer L.; Dunlop, James S.; Ferguson, Henry C.; Finkelstein, Steven L.; Grogin, Norman A.; Hathi, Nimish P.; Juneau, Stephanie; Kartaltepe, Jeyhan S.; Koekemoer, Anton M.; Nandra, Kirpal

    2011-01-01

    We present Hubble Space Telescope Wide Field Camera 3 slitless grism spectroscopy of 28 emission-line galaxies at z approximates 2, in the GOODS-S region of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS). The high sensitivity of these grism observations, with > 5-sigma detections of emission lines to f > 2.5 X 10(exp -18( erg/s/ square cm, means that the galaxies in the sample are typically approximately 7 times less massive (median M(star). = 10(exp 9.5)M(solar)) than previously studied z approximates 2 emission-line galaxies. Despite their lower mass, the galaxies have [O-III]/H-Beta ratios which are very similar to previously studied z approximates 2 galaxies and much higher than the typical emission-line ratios of local galaxies. The WFC3 grism allows for unique studies of spatial gradients in emission lines, and we stack the two-dimensional spectra of the galaxies for this purpose. In the stacked data the [O-III] emission line is more spatially concentrated than the H-Beta emission line with 98.1% confidence. We additionally stack the X-ray data (all sources are individually undetected), and find that the average L(sub [O-III])/L(sub 0.5.10keV) ratio is intermediate between typical z approximates 0 obscured active galaxies and star-forming galaxies. Together the compactness of the stacked [O-III] spatial profile and the stacked X-ray data suggest that at least some of these low-mass, low-metallicity galaxies harbor weak active galactic nuclei.

  10. The optical redshift survey sample selection and the galaxy distribution

    CERN Document Server

    Santiago, B X; Lahav, O; Davis, M; Dressler, A; Huchra, J P

    1994-01-01

    This is the first in a series of papers describing the {\\it Optical Redshift Survey} (ORS), a redshift survey of optically selected galaxies covering 98\\% of the sky above |b| = 20^\\circ (8.09 ster). The survey is drawn from the UGC, ESO, and ESGC galaxy catalogues, and contains two sub-samples, one complete to a B magnitude of 14.5, the other complete to a B major axis diameter of 1.9^\\prime. The entire sample consists of 8457 objects, of which redshifts are now available for 8286; 171 objects remain without measured redshifts. The ORS provides the most detailed and homogeneous sampling of the large-scale galaxy distribution to date in these areas. The density field of bright optical galaxies is well-defined to 8000 \\kms, and is dominated by the Virgo, Telescopium-Pavo-Indus, Hydra-Centaurus, Pisces-Perseus, and Coma-A1367 Superclusters. The dense sampling provided by ORS allows a detailed analysis of the galaxy density field, and will be used to test its dependence on morphology and other galaxy parameters.

  11. A POSSIBLE EXTENSION OF THE SCUTUM-CENTAURUS ARM INTO THE OUTER SECOND QUADRANT

    Energy Technology Data Exchange (ETDEWEB)

    Sun, Yan; Xu, Ye; Yang, Ji; Li, Fa-Cheng; Du, Xin-Yu; Zhang, Shao-Bo; Zhou, Xin, E-mail: yansun@pmo.ac.cn [Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, Nanjing 210008 (China)

    2015-01-10

    Combining H I data from the Canadian Galactic Plane Survey and CO data from the Milky Way Imaging Scroll Painting project, we have identified a new segment of a spiral arm between Galactocentric radii of 15 and 19 kpc that apparently lies beyond the Outer Arm in the second Galactic quadrant. Over most of its length, the arm is 400-600 pc thick in z. The new arm appears to be the extension of the distant arm recently discovered by Dame and Thaddeus as well as the Scutum-Centaurus Arm into the outer second quadrant. Our current survey identified a total of 72 molecular clouds with masses on the order of 10{sup 2}-10{sup 4} M {sub ☉} that probably lie in the new arm. When all of the available data from the CO molecular clouds are fit, the best-fitting spiral model gives a pitch angle of 9.°3 ± 0.°7.

  12. Halpha and [S II] emission from warm ionized gas in the Scutum-Centaurus Arm

    CERN Document Server

    Hill, Alex S; Haffner, L Matthew; Gostisha, Martin; Barger, Kathleen A

    2014-01-01

    We present Wisconsin H-Alpha Mapper [S II] {\\lambda}6716 and H{\\alpha} spectroscopic maps of the warm ionized medium (WIM) in the Scutum-Centaurus Arm at Galactic longitudes 310{\\deg} = 100 R. The line ratio is better correlated with H{\\alpha} intensity than with height above the plane, indicating that the physical conditions within the WIM vary systematically with electron density. We argue that the variation of the line ratio with height is a consequence of the decrease of electron density with height. Our results reinforce the well-established picture in which the diffuse H{\\alpha} emission is due primarily to emission from in situ photoionized gas, with scattered light only a minor contributor.

  13. Star formation activity in a young galaxy cluster at z=0.866

    CERN Document Server

    Laganá, T F; Martins, L P; da Cunha, E

    2016-01-01

    The galaxy cluster RXJ1257$+$4738 at $z=0.866$ is one of the highest redshift clusters with a richness of multi-wavelength data, and thus a good target to study the star formation-density relation at early epochs. Using a sample of spectroscopically-confirmed cluster members, we derive the star formation rates of our galaxies using two methods, (I) the relation between SFR and total infrared luminosity extrapolated from the observed \\textit{Spitzer} MIPS 24$\\mu$m imaging data, and (II) spectral energy distribution (SED) fitting using the MAGPHYS code, including eight different bands. We show that, for this cluster, the SFR-density relation is very weak and seems to be dominated by the two central galaxies and the SFR presents a mild dependence on stellar mass, with more massive galaxies having higher SFR. However, the specific SFR (SSFR) decreases with stellar mass, meaning that more massive galaxies are forming less stars per unit of mass, and thus suggesting that the increase in star-forming members is driv...

  14. Nebular excitation in z ∼ 2 star-forming galaxies from the SINS and LUCI surveys: The influence of shocks and active galactic nuclei

    Energy Technology Data Exchange (ETDEWEB)

    Newman, Sarah F.; Genzel, Reinhard [Department of Astronomy, Campbell Hall, University of California, Berkeley, CA 94720 (United States); Buschkamp, Peter; Förster Schreiber, Natascha M.; Kurk, Jaron; Rosario, David; Davies, Ric; Eisenhauer, Frank; Lutz, Dieter [Max-Planck-Institut für extraterrestrische Physik (MPE), Giessenbachstr. 1, D-85748 Garching (Germany); Sternberg, Amiel [School of Physics and Astronomy, Tel Aviv University, Tel Aviv 69978 (Israel); Gnat, Orly [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Mancini, Chiara; Renzini, Alvio [Osservatorio Astronomico di Padova, Vicolo dell' Osservatorio 5, I-35122 Padova (Italy); Lilly, Simon J.; Carollo, C. Marcella [Institute of Astronomy, Department of Physics, Eidgenössische Technische Hochschule, ETH, CH-8093 Zürich (Switzerland); Burkert, Andreas [Universitäts-Sternwarte Ludwig-Maximilians-Universität (USM), Scheinerstr. 1, D-81679 München (Germany); Cresci, Giovanni [Istituto Nazionale di Astrofisica Osservatorio di Bologna, Via Ranzani 1, I-40127 Bologna (Italy); Genel, Shy [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Shapiro Griffin, Kristen [Space Sciences Research Group, Northrop Grumman Aerospace Systems, Redondo Beach, CA 90278 (United States); Hicks, Erin K. S., E-mail: sfnewman@berkeley.edu [Department of Astronomy, University of Washington, Box 351580, U.W., Seattle, WA 98195-1580 (United States); and others

    2014-01-20

    Based on high-resolution, spatially resolved data of 10 z ∼ 2 star-forming galaxies from the SINS/zC-SINF survey and LUCI data for 12 additional galaxies, we probe the excitation properties of high-z galaxies and the impact of active galactic nuclei (AGNs), shocks, and photoionization. We explore how these spatially resolved line ratios can inform our interpretation of integrated emission line ratios obtained at high redshift. Many of our galaxies fall in the 'composite' region of the z ∼ 0 [N II]/Hα versus [O III]/Hβ diagnostic (BPT) diagram, between star-forming galaxies and those with AGNs. Based on our resolved measurements, we find that some of these galaxies likely host an AGN, while others appear to be affected by the presence of shocks possibly caused by an outflow or from an enhanced ionization parameter as compared with H II regions in normal, local star-forming galaxies. We find that the Mass-Excitation (MEx) diagnostic, which separates purely star-forming and AGN hosting local galaxies in the [O III]/Hβ versus stellar mass plane, does not properly separate z ∼ 2 galaxies classified according to the BPT diagram. However, if we shift the galaxies based on the offset between the local and z ∼ 2 mass-metallicity relation (i.e., to the mass they would have at z ∼ 0 with the same metallicity), we find better agreement between the MEx and BPT diagnostics. Finally, we find that metallicity calibrations based on [N II]/Hα are more biased by shocks and AGNs at high-z than the [O III]/Hβ/[N II]/Hα calibration.

  15. Molecular excitation in Centaurus A: the ^13^CO J=1-0 map and CO line ratios.

    NARCIS (Netherlands)

    Wild, W.; Eckart, A.; Wiklind, T.

    1997-01-01

    We present a fully sampled map of the ^13^CO J=1-0 emission in the dust lane of Centaurus A as well as ^13^CO 2-1 and for the first time C^18^O 1-0 spectra at selected positions. The morphology of the ^13^CO map is similar to the ^12^CO 1-0 and 2-1 maps. Maps of the ^12^CO 2-1/1-0 and ^12^CO/^13^CO

  16. The host of GRB/XRF 030528 - an actively star forming galaxy at z=0.782

    CERN Document Server

    Rau, A

    2005-01-01

    An important parameter for the distinction of X-ray flashes, X-ray rich bursts and Gamma-ray bursts in the rest frame is the distance to the explosion site. Here we report on the spectroscopic redshift determination of the host galaxy of XRF/GRB 030528 using the ESO VLT FORS2 instrument. From the strong oxygen and hydrogen emission lines the redshift was measured to be z=0.782+-0.001. Obtaining the line luminosities and ratios we find that the host is consistent with being an actively star forming galaxy with sub-solar metallicity. With a stellar mass of ~10E10 Msun the host is placed among the most massive GRB host galaxies at a similar redshift. Estimating the redshifted properties of the prompt emission, we find that XRF/GRB 030528 would be classified as an X-ray rich bursts in the rest frame rather than an X-ray flash in the typically used observer frame.

  17. SPT0346-52: Negligible AGN Activity in a Compact, Hyper-starburst Galaxy at z = 5.7

    CERN Document Server

    Ma, Jingzhe; Vieira, J D; Aravena, M; Ashby, M L N; Bethermin, M; Bothwell, M S; Brandt, W N; de Breuck, C; Carlstrom, J E; Chapman, S C; Gullberg, B; Hezaveh, Y; Litke, K; Malkan, M; Marrone, D P; McDonald, M; Murphy, E J; Spilker, J S; Sreevani, J; Stark, A A; Strandet, M; Wang, S X

    2016-01-01

    We present Chandra ACIS-S and ATCA radio continuum observations of the strongly lensed dusty, star-forming galaxy SPT-S J034640-5204.9 (hereafter SPT0346-52) at $z$ = 5.656. This galaxy has also been observed with ALMA, HST, Spitzer, Herschel, APEX, and the VLT. Previous observations indicate that if the infrared (IR) emission is driven by star formation, then the inferred lensing-corrected star formation rate ($\\sim$ 4500 $M_{\\sun}$ yr$^{-1}$) and star formation rate surface density $\\Sigma_{\\rm SFR}$ ($\\sim$ 2000 $M_{\\sun} {yr^{-1}} {kpc^{-2}}$) are both exceptionally high. It remained unclear from the previous data, however, whether a central active galactic nucleus (AGN) contributes appreciably to the IR luminosity. The {\\it Chandra} upper limit shows that SPT0346-52 is consistent with being star-formation dominated in the X-ray, and any AGN contribution to the IR emission is negligible. The ATCA radio continuum upper limits are also consistent with the FIR-to-radio correlation for star-forming galaxies w...

  18. The Atacama Cosmology Telescope: Dusty Star-Forming Galaxies and Active Galactic Nuclei in the Southern Survey

    CERN Document Server

    Marsden, Danica; Marriage, Tobias A; Switzer, Eric R; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark; Dunner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, Erik D; Schmitt, Benjamin; Sehgal, Neelima; Sievers, Jonathan; Staggs, Suzanne; Swetz, Daniel; Thornton, Robert; Wollack, Edward

    2013-01-01

    We present a catalog of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 GHz and/or 218 GHz in the 2008 Southern survey. Flux densities span 14-1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two sub-populations: 167 radio galaxies powered by central active galactic nuclei (AGN), and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97% of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogs. When combined with flux densities from the Australian Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index of 3.7+0.62-0.86, and includes both local galaxies and sources with redshifts as great as 5.6. Dusty ...

  19. MAGIC observation of an exceptional TeV gamma-ray flare in the active galaxy IC 310

    Energy Technology Data Exchange (ETDEWEB)

    Glawion, Dorit; Mannheim, Karl; Elsaesser, Dominik; Kadler, Matthias; Schulz, Robert [ITPA Wuerzburg (Germany); Sitarek, Julian [IFAE Barcelona (Spain); Ros, Eduardo; Bach, Uwe [Max-Planck-Institut fuer Radioastronomie, Bonn (Germany); Krauss, Felicia; Wilms, Joern [ECAP Erlangen, Dr. Karl Remeis-Sternwarte, Bamberg (Germany); Collaboration: MAGIC-Collaboration

    2015-07-01

    The AGN IC 310 has been identified as a gamma-ray emitter based on observations at very high energies (VHE,E>100 GeV) with the MAGIC telescopes. Despite IC 310 having been classified as a radio galaxy with the jet observed at an angle>10 degrees, it exhibits a mixture of multiwavelength properties of a radio galaxy and a blazar, possibly making it a transitional object. On the night of 12/13th of November 2012 the MAGIC telescopes observed a series of strong outbursts from the direction of IC 310 with flux-doubling time scales faster than 5 min and a peculiar spectrum spreading over two orders of magnitude. Such fast variability constrains the size of the emission region to be smaller than 20% of the gravitational radius of its central black hole. In fact, the measurement challenges the shock acceleration models, commonly used in explanation of gamma-ray radiation from active galaxies. We show that this emission can be associated with pulsar-like particle acceleration by the electric field across a magnetospheric gap at the base of the jet.

  20. Upholding the Unified Model for Active Galactic Nuclei: VLT/FORS2 Spectropolarimetry of Seyfert 2 galaxies

    CERN Document Server

    Almeida, Cristina Ramos; Ramos, A Asensio; Acosta-Pulido, J A; Hönig, S F; Alonso-Herrero, A; Tadhunter, C N; González-Martín, O

    2016-01-01

    The origin of the unification model for Active Galactic Nuclei (AGN) was the detection of broad hydrogen recombination lines in the optical polarized spectrum of the Seyfert 2 galaxy (Sy2) NGC 1068. Since then, a search for the hidden broad-line region (HBLR) of nearby Sy2s started, but polarized broad lines have only been detected in 30-40% of the nearby Sy2s observed to date. Here we present new VLT/FORS2 optical spectropolarimetry of a sample of 15 Sy2s, including Compton-thin and Compton-thick sources. The sample includes six galaxies without previously published spectropolarimetry, some of them normally treated as non-hidden BLR (NHBLR) objects in the literature, four classified as NHBLR, and five as HBLR based on previous data. We report >=4{\\sigma} detections of a HBLR in 11 of these galaxies (73% of the sample) and a tentative detection in NGC 5793, which is Compton-thick according to the analysis of X-ray data performed here. Our results confirm that at least some NHBLRs are misclassified, bringing p...

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

    International Nuclear Information System (INIS)

    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 bol = 1046.5 erg s–1). Although the circumgalactic gaseous halo can be kept almost entirely ionized by the AGN, most star-forming clouds (n ≳ 102 – 3 cm–3) and even the reservoirs of cool atomic gas (n ∼ 0.3-10 cm–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

  2. 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.

  3. Star Formation and AGN Activity in Galaxy Clusters from $z=1-2$: a Multi-wavelength Analysis Featuring $Herschel$/PACS

    CERN Document Server

    Alberts, Stacey; Brodwin, Mark; Chung, Sun Mi; Cybulski, Ryan; Dey, Arjun; Eisenhardt, Peter; Galametz, Audrey; Gonzalez, Anthony; Jannuzi, Buell; Stanford, S Adam; Snyder, Gregory; Stern, Daniel; Zeimann, Gregory

    2016-01-01

    We present a detailed, multi-wavelength study of star formation (SF) and AGN activity in 11 near-infrared (IR) selected, spectroscopically confirmed, massive ($\\gtrsim10^{14}\\,\\rm{M_{\\odot}}$) galaxy clusters at $1galaxies, finding that they can, on average, be well described by field galaxy templates. Identification and decomposition of AGN through SED fittings allows us to include the contribution to cluster SF from AGN host galaxies. We quantify the star-forming fraction, dust-obscured SF rates (SFRs), and specific-SFRs for cluster galaxies as a function of cluster-centric radius and redshift. In good agreement with previous studies, we find that SF in cluster galaxies at $z\\gtrsim1.4$ is largely consistent with field galaxies at similar epochs, indicating an era before significant quenching in the cluster cores ($r<0.5\\,$Mpc). This is followed by a ...

  4. A Spitzer MIPS Study of 2.5-2.0 M\\odot Stars in Scorpius-Centaurus

    CERN Document Server

    Chen, Christine H; Mamajek, Eric E; Su, Kate Y L; Bitner, Martin

    2012-01-01

    We have obtained Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) 24 {\\mu}m and 70 {\\mu}m observations of 215 nearby, Hipparcos B- and A-type common proper motion single and binary systems in the nearest OB association, Scorpius-Centaurus. Combining our MIPS observations with those of other ScoCen stars in the literature, we estimate 24 {\\mu}m B+A-type disk fractions of 17/67 (25+6%), 36/131 (27+4%), and 23/95 (24+5%) for Upper Scorpius (\\sim11 Myr), Upper Centaurus Lupus (\\sim15 Myr), and Lower Centaurus Crux (\\sim17 Myr), respectively, somewhat smaller disk fractions than previously obtained for F- and G-type members. We confirm previous IRAS excess detections and present new discoveries of 51 protoplanetary and debris disk systems, with fractional infrared luminosities ranging from LIR/L\\ast = 1e-6 to 1e-2 and grain temperatures ranging from Tgr = 40 - 300 K. In addition, we confirm that the 24 {\\mu}m and 70 {\\mu}m excesses (or fractional infrared luminosities) around B+A type stars ...

  5. Rotation Curves of Spiral Galaxies

    OpenAIRE

    Sofue, Yoshiaki; Rubin, Vera

    2000-01-01

    Rotation curves of spiral galaxies are the major tool for determining the distribution of mass in spiral galaxies. They provide fundamental information for understanding the dynamics, evolution and formation of spiral galaxies. We describe various methods to derive rotation curves, and review the results obtained. We discuss the basic characteristics of observed rotation curves in relation to various galaxy properties, such as Hubble type, structure, activity, and environment.

  6. Star formation activity in Balmer break galaxies at $z$ < 1.5

    CERN Document Server

    Tello, J Díaz; Padilla, N; Akiyama, M; Fujishiro, N; Yoshikawa, T; Hanami, H

    2016-01-01

    Aims. We present a spectroscopic study of the properties of 64 Balmer break galaxies that show signs of star formation. The studied sample of star-forming galaxies spans a redshift range from 0.094 to 1.475 with stellar masses in the range 10$^{8}-$10$^{12}$ $M_{\\odot}$. The sample also includes eight broad emission line galaxies with redshifts between 1.5 $galaxies with lower SFR values (i.e., decreasing star formation). We also note an anticorrelation for the SSFR with the stellar mass. Again in this case, our data is also consis...

  7. The host galaxies of active galactic nuclei with powerful relativistic jets

    CERN Document Server

    Olguín-Iglesias, A; Kotilainen, J K; Chavushyan, V; Tornikoski, M; Valtaoja, E; Añorve, C; Valdes, J; Carrasco, L

    2016-01-01

    We present deep Near-infrared (NIR) images of a sample of 19 intermediate-redshift ($0.310^{27}$ WHz$^{-1}$), previously classified as flat-spectrum radio quasars. We also compile host galaxy and nuclear magnitudes for blazars from literature. The combined sample (this work and compilation) contains 100 radio-loud AGN with host galaxy detections and a broad range of radio luminosities $L_{1.4GHz} \\sim 10^{23.7} - 10^{28.3}$~WHz$^{-1}$, allowing us to divide our sample into high-luminosity blazars (HLBs) and low-luminosity blazars (LLBs). The host galaxies of our sample are bright and seem to follow the $\\mu_{e}$-$R_{eff}$ relation for ellipticals and bulges. The two populations of blazars show different behaviours in the \\mnuc - \\mbulge plane, where a statistically significant correlation is observed for HLBs. Although it may be affected by selection effects, this correlation suggests a close coupling between the accretion mode of the central supermassive black hole and its host galaxy, that could be interpre...

  8. Hubble Space Telescope Observations of the CFA Seyfert 2 Galaxies: The Fueling of Active Galactic Nuclei

    Science.gov (United States)

    Martini, Paul; Pogge, Richard W.

    1999-12-01

    We present an investigation of possible fueling mechanisms operating in the inner kiloparsec of Seyfert galaxies. We analyze visible and near-infrared Hubble Space Telescope images of 24 Seyfert 2 galaxies from the CfA Redshift Survey sample. In particular, we are searching for the morphological signatures of dynamical processes responsible for transporting gas from kiloparsec scales into the nucleus. The circumnuclear regions are very rich in gas and dust, often taking the form of nuclear spiral dust lanes on scales of a few hundred parsecs. While these nuclear spirals are found in 20 of our 24 Seyfert galaxies, we find only five nuclear bars among the entire sample, strongly reinforcing the conclusions of other investigators that nuclear bars are not the primary means of transporting this material into the nucleus. An estimate of the gas density in the nuclear spirals, based on extinction measurements, suggests that the nuclear spiral dust lanes are probably shocks in nuclear gas disks that are not strongly self-gravitating. Since shocks can dissipate energy and angular momentum, these spiral dust lanes may be the channels by which gas from the host galaxy disks is being fed into the central engines.

  9. Discovery of a population of bulgeless galaxies with extremely red MID-IR colors: Obscured AGN activity in the low-mass regime?

    Energy Technology Data Exchange (ETDEWEB)

    Satyapal, S.; Secrest, N. J.; McAlpine, W.; Rosenberg, J. L. [School of Physics, Astronomy, and Computational Sciences, George Mason University, MS 3F3, 4400 University Drive, Fairfax, VA 22030 (United States); Ellison, S. L. [Department of Physics and Astronomy, University of Victoria, Victoria, BC V8P 1A1 (Canada); Fischer, J., E-mail: satyapal@physics.gmu.edu [Naval Research Laboratory, Remote Sensing Division, 4555 Overlook Avenue SW, Washington, DC 20375 (United States)

    2014-04-01

    In contrast to massive, bulge hosting galaxies, very few supermassive black holes (SMBHs) are known in either low-mass or bulgeless galaxies. Such a population could provide clues to the origins of SMBHs and to secular pathways for their growth. Using the all-sky Wide-field Infrared Survey Explorer (WISE ) survey, and bulge-to-disk decompositions from the Sloan Digital Sky Survey (SDSS) Data Release 7, we report the discovery of a population of local (z < 0.3) bulgeless disk galaxies with extremely red mid-infrared colors which are highly suggestive of a dominant active galactic nucleus (AGN), despite having no optical AGN signatures in their SDSS spectra. Using various mid-infrared selection criteria from the literature, there are between 30 and over 300 bulgeless galaxies with possible AGNs. Other known scenarios that can heat the dust to high temperatures do not appear to explain the observed colors of this sample. If these galaxies are confirmed to host AGNs, this study will provide a breakthrough in characterizing the properties of SMBHs in the low bulge mass regime and in understanding their relation with their host galaxies. Mid-infrared selection identifies AGNs that dominate their host galaxy's emission and therefore reveal a different AGN population than that uncovered by optical studies. We find that the fraction of all galaxies identified as candidate AGNs by WISE is highest at lower stellar masses and drops dramatically in higher mass galaxies, in striking contrast to the findings from optical studies.

  10. How environment drives galaxy evolution: lessons learnt from satellite galaxies

    CERN Document Server

    Pasquali, A

    2015-01-01

    It is by now well established that galaxy evolution is driven by intrinsic and environmental processes, both contributing to shape the observed properties of galaxies. A number of early studies, both observational and theoretical, have shown that the star formation activity of galaxies depends on their environmental local density and also on galaxy hierarchy, i.e. centrals vs. satellites. In fact, contrary to their central (most massive) galaxy of a group/cluster, satellite galaxies are stripped of their gas and stars, and have their star formation quenched by their environment. Large galaxy surveys like SDSS now permit us to investigate in detail environment-driven transformation processes by comparing centrals and satellites. In this paper I summarize what we have so far learnt about environmental effects by analysing the observed properties of local central and satellite galaxies in SDSS, as a function of their stellar mass and the dark matter mass of their host group/cluster.

  11. Black hole variability and the star formation-active galactic nucleus connection: Do all star-forming galaxies host an active galactic nucleus?

    International Nuclear Information System (INIS)

    We investigate the effect of active galactic nucleus (AGN) variability on the observed connection between star formation and black hole accretion in extragalactic surveys. Recent studies have reported relatively weak correlations between observed AGN luminosities and the properties of AGN hosts, which has been interpreted to imply that there is no direct connection between AGN activity and star formation. However, AGNs may be expected to vary significantly on a wide range of timescales (from hours to Myr) that are far shorter than the typical timescale for star formation (≳100 Myr). This variability can have important consequences for observed correlations. We present a simple model in which all star-forming galaxies host an AGN when averaged over ∼100 Myr timescales, with long-term average AGN accretion rates that are perfectly correlated with the star formation rate (SFR). We show that reasonable prescriptions for AGN variability reproduce the observed weak correlations between SFR and L AGN in typical AGN host galaxies, as well as the general trends in the observed AGN luminosity functions, merger fractions, and measurements of the average AGN luminosity as a function of SFR. These results imply that there may be a tight connection between AGN activity and SFR over galaxy evolution timescales, and that the apparent similarities in rest-frame colors, merger rates, and clustering of AGNs compared to 'inactive' galaxies may be due primarily to AGN variability. The results provide motivation for future deep, wide extragalactic surveys that can measure the distribution of AGN accretion rates as a function of SFR.

  12. AN EMBEDDED ACTIVE NUCLEUS IN THE OH MEGAMASER GALAXY IRAS16399–0937

    Energy Technology Data Exchange (ETDEWEB)

    Sales, Dinalva A. [Departamento de Astronomia, Universidade Federal do Rio Grande do Sul. 9500 Bento Gonçalves, Porto Alegre, 91501-970 (Brazil); Robinson, A.; Axon, D. J.; Curran, R. L.; O' Dea, C.; Mittal, R. [School of Physics and Astronomy, Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States); Gallimore, J. [Department of Physics, Bucknell University, Lewisburg, PA 17837 (United States); Kharb, P. [Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560034 (India); Baum, S. [Chester F. Carlson Center for Imaging Science, Rochester Institute of Technology, 54 Lomb Memorial Drive, Rochester, NY 14623 (United States); Elitzur, M. [Physics and Astronomy Department, University of Kentucky, Lexington, KY 40506-0055 (United States)

    2015-01-20

    We present a multiwavelength study of the OH megamaser galaxy IRAS16399–0937, based on new Hubble Space Telescope (HST)/Advanced Camera for Surveys F814W and Hα+[N II] images and archive data from HST, Two Micron All Sky Survey, Spitzer, Herschel and the Very Large Array. This system has a double nucleus, whose northern (IRAS16399N) and southern (IRAS16399S) components have a projected separation of ∼6'' (3.4 kpc) and have previously been identified based on optical spectra as a low ionization nuclear emission line region (LINER) and starburst nucleus, respectively. The nuclei are embedded in a tidally distorted common envelope, in which star formation is mostly heavily obscured. The infrared spectrum is dominated by strong polycyclic aromatic hydrocarbon, but deep silicate and molecular absorption features are also present, and are strongest in the IRAS16399N nucleus. The 0.435-500 μm spectral energy distribution was fitted with a model including stellar, interstellar medium and active galactic nucleus (AGN) torus components using our new Markov Chain Monte Carlo code, CLUMPYDREAM. The results indicate that the IRAS16399N contains an AGN (L {sub bol} ∼ 10{sup 44} erg s{sup –1}) deeply embedded in a quasi-spherical distribution of optically thick clumps with a covering fraction ≈1. We suggest that these clumps are the source of the OHM emission in IRAS16399–0937. The high torus covering fraction precludes AGN photoionization as the origin of the LINER spectrum, however, the spectrum is consistent with shocks (v ∼ 100-200 km s{sup –1}). We infer that the ∼10{sup 8} M {sub ☉} black hole in IRAS16399N is accreting at a small fraction (∼1%) of its Eddington rate. The low accretion rate and modest nuclear star formation rates suggest that while the gas-rich major merger forming the IRAS16399–0937 system has triggered widespread star formation, the massive gas inflows expected from merger simulations have not yet fully developed.

  13. Spectral Characteristics of Radiation from the Nucleus of the Seyfert Galaxy NGC 1275 After an Epoch of its Maximum Activity

    Science.gov (United States)

    Bikmaev, I. F.; Sharipova, L. M.; Galeev, A. I.; Akhmetkhanova, A. É.

    2016-03-01

    The spectral characteristics of radiation from the nucleus of the Seyfert galaxy NGC 1275 are studied on a long time scale. Changes in the profiles of some emission lines and changes in the relative intensities of hydrogen and forbidden lines and their equivalent widths (EWλ ) are demonstrated on a time scale of decades. These studies employed spectral data obtained with the 1.5-m Russian-Turkish telescope (RTT-150) during January 2012 and drew on spectral data published earlier in the literature. These results made it possible to trace the state of the nucleus of NGC 1275 after an activity maximum that occurred during the 1960's.

  14. The X-ray Zurich environmental study (X-zens). I. Chandra and XMM-Newton observations of active galactic nuclei in galaxies in nearby groups

    Energy Technology Data Exchange (ETDEWEB)

    Silverman, J. D. [Kavli Institute for the Physics and Mathematics of the Universe, Todai Institutes for Advanced Study, the University of Tokyo (Kavli IPMU, WPI), Kashiwa 277-8583 (Japan); Miniati, F.; Carollo, C. M.; Cibinel, A.; Lilly, S. J.; Schawinski, K. [Institute for Astronomy, ETH Zürich, CH-8093, Zürich (Switzerland); Finoguenov, A., E-mail: john.silverman@ipmu.jp [Department of Physics, University of Helsinki, Gustaf Hällströmin katu 2a, FI-00014 Helsinki (Finland)

    2014-01-01

    We describe X-ray observations with Chandra and XMM-Newton of 18 M {sub group} ∼ 1-6 × 10{sup 13} M {sub ☉}, z ∼ 0.05 galaxy groups from the Zurich ENvironmental Study. The X-ray data aim at establishing the frequency and properties, unaffected by host galaxy dilution and obscuration, of active galactic nuclei (AGNs) in central and satellite galaxies, also as a function of halo-centric distance. X-ray point-source detections are reported for 22 of the 177 galaxies, down to a sensitivity level of f {sub 0.5} {sub –} {sub 8} {sub keV} ∼ 5 × 10{sup –15} erg cm{sup –2} s{sup –1}, corresponding to a limiting luminosity of L {sub 0.5} {sub –} {sub 8} {sub keV} ∼ 3 × 10{sup 40} erg s{sup –1}. With the majority of the X-ray sources attributed to AGNs of low-to-moderate levels (L/L {sub Edd} ≳ 10{sup –4}), we discuss the detection rate in the context of the occupation of AGNs to halos of this mass scale and redshift and compare the structural and morphological properties between AGN-active and non-active galaxies. At galaxy mass scales <10{sup 11} M {sub ☉}, central galaxies appear to be a factor of ∼4 more likely to host AGNs than satellite galaxies of similar mass. This effect, coupled with the tendency for AGNs to be hosted by massive galaxies, explains the (weak) trend for AGNs to be preferentially found in the inner parts of group halos, with no detectable trend with halo-centric distance in the frequency of AGNs within the satellite population. Finally, our data indicate that the rate of decline with redshift of AGN activity in galaxy groups matches that of the global AGN population, indicating that either AGN activity occurs preferentially in group halos or that the evolution rate is independent of halo mass.

  15. Triggering Active Galactic Nuclei in Hierarchical Galaxy Formation: Disk instability vs. Interactions

    CERN Document Server

    Menci, N; Fiore, F; Lamastra, A

    2014-01-01

    Using a semi analytic model for galaxy formation we investigate the effects of Black Hole accretion triggered by disk instabilities (DI) in isolated galaxies on the evolution of AGN. Specifically, we took on, developed and expanded the Hopkins & Quataert (2011) model for the mass inflow following disk perturbations, and compare the corresponding evolution of the AGN population with that arising in a scenario where galaxy interactions trigger AGN (IT mode). We extended and developed the DI model by including different disk surface density profiles, to study the maximal contribution of DI to the evolution of the AGN population. We obtained the following results: i) for luminosities corresponding to $M_{1450}\\gtrsim -26$ the DI mode can provide the BH accretion needed to match the observed AGN luminosity functions up to $z \\approx 4.5$; in such a luminosity range and redshift, it can compete with the IT scenario as the main driver of cosmological evolution of AGN; ii) The DI scenario cannot provide the obser...

  16. Multi-wavelength study of X-ray luminous clusters at z ~ 0.3 I. Star formation activity of cluster galaxies

    CERN Document Server

    Braglia, F G; Biviano, A; Böhringer, H

    2009-01-01

    The current paradigm of cosmic formation and evolution of galaxy clusters foresees growth mostly through merging. Galaxies in the infall region or in the core of a cluster undergo transformations owing to different environmental stresses. For two X-ray luminous clusters at redshift z ~ 0.3 with opposite X-ray morphologies, RXCJ0014.3-3022 and RXCJ2308.3-0211, we assess differences in galaxy populations as a function of cluster topography. Cluster large-scale structure and substructure are determined from the combined photometry in the B, V, and R bands, and from multi-object optical spectroscopy at low resolution. A spectral index analysis is performed, based on the [OII] and Hdelta features, and the D4000 break, available for more than 100 member galaxies per cluster. Combination of spectral indices and FUV-optical colours provides a picture of the star formation history in galaxies. In spite of the potential presence of a small fraction of galaxies with obscured star formation activity, the average star-for...

  17. The Star Formation History of NGC 1705: a Post-Starburst Galaxy on the Verge of Activity

    CERN Document Server

    Annibali, F; Tosi, M P; Aloisi, A; Leitherer, C

    2003-01-01

    We infer the star formation history in different regions of the blue compact dwarf NGC 1705 by comparing synthetic color-magnitude diagrams with HST optical and near-infrared photometry. We find that NGC 1705 is not a young galaxy because its star formation commenced at least 5 Gyr ago. On the other hand, we confirm the existence of a recent burst of star formation between 15 and 10 Myr ago. We also find evidence for new strong activity, which started 3 Myr ago and is still continuing. The old population is spread across the entire galaxy, while the young and intermediate stars are more concentrated in the central regions. We derive an almost continuous star formation with variable rate, and exclude the presence of long quiescent phases between the episodes during the last ~1 Gyr. The central regions experienced an episode of star formation of \\~0.07 Msun/yr (for a Salpeter initial mass function [IMF]) 15 to 10 Myr ago. This coincides with the strong activity in the central super star cluster. We find a rate ...

  18. The Center of Our Galaxy Activity and High-Energy Emission of the Closest Massive Black Hole

    CERN Document Server

    Goldwurm, A

    2001-01-01

    The Center of our Galaxy is a peculiar region where a number of crucial astrophysical phenomena take place, from star formation to SN explosions and accretion onto a massive black hole. The quest for a massive black hole in the Galactic Nucleus is of course of particular relevance because, it would be the closest of such extreme objects, which are now believed to reside in most of the galactic nuclei of the universe. I will review here the main observational characteristics of the Galactic Center with particular attention to the the problem of existence, physical condition and activity of the 3 10E6 Mo black hole coincident with the compact radio source Sgr A*. I will report historical and recent results of high energy observations of the central degree of our Galaxy, along with the specific accretion models proposed to account for the apparent lack of high energy activity from Sgr A*. The scientific perspectives of the next X and gamma-ray missions in the domain of the Galactic Center physics are also mentio...

  19. Chandra X-ray and Hubble Space Telescope Imaging of Optically Selected Kiloparsec-Scale Binary Active Galactic Nuclei II: Host Galaxy Morphology and AGN Activity

    CERN Document Server

    Shangguan, Jinyi; Ho, Luis C; Shen, Yue; Peng, Chien Y; Greene, Jenny E; Strauss, Michael A

    2016-01-01

    Binary active galactic nuclei (AGNs) provide clues to how gas-rich mergers trigger and fuel AGNs and how supermassive black hole (SMBH) pairs evolve in a gas-rich environment. While significant effort has been invested in their identification, the detailed properties of binary AGNs and their host galaxies are still poorly constrained. In a companion paper, we examined the nature of ionizing sources in the double nuclei of four kpc-scale binary AGNs with redshifts between 0.1~0.2. Here, we present their host galaxy morphology based on F336W (U-band) and F105W (Y-band) images taken by the Wide Field Camera 3 (WFC3) onboard the Hubble Space Telescope. Our targets have double-peaked narrow emission lines and were confirmed to host binary AGNs with follow up observations. We find that kpc-scale binary AGNs occur in galaxy mergers with diverse morphological types. There are three major mergers with intermediate morphologies and a minor merger with a dominant disk component. We estimate the masses of the SMBHs from ...

  20. Upholding the unified model for active galactic nuclei: VLT/FORS2 spectropolarimetry of Seyfert 2 galaxies

    Science.gov (United States)

    Ramos Almeida, C.; Martínez González, M. J.; Asensio Ramos, A.; Acosta-Pulido, J. A.; Hönig, S. F.; Alonso-Herrero, A.; Tadhunter, C. N.; González-Martín, O.

    2016-09-01

    The origin of the unification model for active galactic nuclei (AGN) was the detection of broad hydrogen recombination lines in the optical polarized spectrum of the Seyfert 2 galaxy (Sy2) NGC 1068. Since then, a search for the hidden broad-line region (HBLR) of nearby Sy2s started, but polarized broad lines have only been detected in ˜30-40 per cent of the nearby Sy2s observed to date. Here we present new VLT/FORS2 optical spectropolarimetry of a sample of 15 Sy2s, including Compton-thin and Compton-thick sources. The sample includes six galaxies without previously published spectropolarimetry, some of them normally treated as non-hidden BLR (NHBLR) objects in the literature, four classified as NHBLR, and five as HBLR based on previous data. We report ≥4σ detections of a HBLR in 11 of these galaxies (73 per cent of the sample) and a tentative detection in NGC 5793, which is Compton-thick according to the analysis of X-ray data performed here. Our results confirm that at least some NHBLRs are misclassified, bringing previous publications reporting differences between HBLR and NHBLR objects into question. We detect broad Hα and Hβ components in polarized light for 10 targets, and just broad Hα for NGC 5793 and NGC 6300, with line widths ranging between 2100 and 9600 km s-1. High bolometric luminosities and low column densities are associated with higher polarization degrees, but not necessarily with the detection of the scattered broad components.

  1. Chandra and MMT observations of low-mass black hole active galactic nuclei accreting at low rates in dwarf galaxies

    International Nuclear Information System (INIS)

    We report on Chandra X-ray observations of four candidate low-mass black hole (M bh ≲ 106 M ☉) active galactic nuclei (AGNs) that have the estimated Eddington ratios among the lowest (∼10–2) found for this class. The aims are to validate the nature of their AGNs and to confirm the low Eddington ratios that are derived from the broad Hα line, and to explore this poorly studied regime in the AGN parameter space. Among them, two objects with the lowest significance of the broad lines are also observed with the Multi-Mirror Telescope, and the high-quality optical spectra taken confirm them as Seyfert 1 AGNs and as having small black hole masses. X-ray emission is detected from the nuclei of two of the galaxies, which is variable on timescales of ∼103 s, whereas no significant (or only marginal at best) detection is found for the remaining two. The X-ray luminosities are on the order of 1041 erg s–1 or even lower, on the order of 1040 erg s–1 for non-detections, which are among the lowest regimes ever probed for Seyfert galaxies. The low X-ray luminosities, compared to their black hole masses derived from Hα, confirm their low accretion rates assuming typical bolometric corrections. Our results hint at the existence of a possibly large population of under-luminous low-mass black holes in the local universe. An off-nucleus ultra-luminous X-ray source in one of the dwarf galaxies is detected serendipitously, with a luminosity (6-9)× 1039 erg s–1 in 2-10 keV.

  2. Numerical Simulation of Star Formation by the Bow Shock of the Centaurus A Jet

    CERN Document Server

    Gardner, Carl L; Scannapieco, Evan; Windhorst, Rogier A

    2016-01-01

    Recent Hubble Space Telescope (HST) observations of the extragalactic radio source Centaurus A (Cen A) display a young stellar population around the southwest tip of the inner filament 8.5 kpc from the Cen A galactic center, with ages in the range of 1-3 Myr. Crockett et al. (2012) argue that the transverse bow shock of the Cen A jet triggered this star formation as it impacted dense molecular cores of clouds in the filament. To test this hypothesis, we perform three-dimensional numerical simulations of induced star formation by the jet bow shock in the inner filament of Cen A, using a positivity preserving WENO method to solve the equations of gas dynamics with radiative cooling. We find that star clusters form inside a bow-shocked molecular cloud when the maximum initial density of the cloud is > 40 H2 molecules/cm^3. In a typical molecular cloud of mass 10^6 M_sun and diameter 200 pc, approximately 20 star clusters of mass 10^3 M_sun are formed, matching the HST images.

  3. Kim 3: an Ultra-faint Star Cluster in the Constellation of Centaurus

    CERN Document Server

    Kim, Dongwon; Mackey, Dougal; Da Costa, Gary S; Milone, Antonino P

    2015-01-01

    We report the discovery of an ultra-faint star cluster in the constellation of Centaurus. This new stellar system, Kim 3, features a half light radius of $r_{h}=2.29^{+1.28}_{-0.52}$ pc and a total luminosity of $M_{V}=+0.7\\pm0.3$. Approximately 26 stars are identified as candidate member stars down to four magnitudes below the main-sequence turn-off, which makes Kim 3 the least luminous star cluster known to date. The compact physical size and extreme low luminosity place it close to faint star clusters in the size-luminosity plane. The stellar population of Kim 3 appears to be relatively young ($9.5^{+3.0}_{-1.7}$ Gyr) and metal-poor ([Fe/H]$=-1.6^{+0.45}_{-0.30}$) at a heliocentric distance of $15.14^{+1.00}_{-0.28}$ kpc. The cluster lacks a well-defined center and a small but prominent group of stars consistent with the Kim 3 isochrone is present approximately 9.7 pc in projection south of the cluster center. Both are signs of the cluster being in the final stage of tidal disruption.

  4. The missing link: tracing molecular gas in the outer filament of Centaurus A

    CERN Document Server

    Morganti, Raffaella; Oonk, J B Raymond; Santoro, Francesco; Tadhunter, Clive

    2016-01-01

    We report the detection, using observations of the CO(2-1) line performed with the Atacama Pathfinder EXperiment, of molecular gas in the region of the outer filament of Centaurus A, a complex region known to show various signatures of an interaction between the radio jet, an HI cloud and ionised gas filaments. We detect CO(2-1) at all observed locations, which were selected to represent regions with very different physical conditions. The H_2 masses of the detections range between 0.2 x 10^6 and 1.1 x 10^6 msun, for conservative choices of the CO-to-H_2 conversion factor. Surprisingly, the stronger detections are not coincident with the HI cloud, but instead are in the region of the ionised filaments. We also find variations in the widths of the CO(2-1) lines throughout the region, with broader lines in the region of the ionised gas, i.e. where the jet-cloud interaction is strongest, and narrow profiles in the HI cloud. This may indicate that the molecular gas in the region of the ionised gas has the momentu...

  5. Magnetic Deflections of Ultra-High Energy Cosmic Rays from Centaurus A

    CERN Document Server

    Keivani, Azadeh; Sutherland, Michael

    2014-01-01

    We present the results of a study that simulates trajectories of ultra-high energy cosmic rays from Centaurus A to Earth, for particle rigidities from $E/Z = 2$ EV to 100 EV, i.e., covering the possibility of primary particles as heavy as Fe nuclei with energies exceeding 50 EeV. The Galactic magnetic field is modeled using the recent work of Jansson and Farrar (JF12) which fitted its parameters to match extragalactic Faraday rotation measures and WMAP7 synchrotron emission maps. We include the random component of the GMF using the JF12 3D model for $B_{\\rm rand}(\\vec{r})$ and explore the impact of different random realizations, coherence length and other features on cosmic ray deflections. Gross aspects of the arrival direction distribution such as mean deflection and the RMS dispersion depend mainly on rigidity and differ relatively little from one realization to another. However different realizations exhibit non-trivial substructure whose specific features vary considerably from one realization to another...

  6. IRS Spectra of Debris Disks in the Scorpius-Centaurus OB Association

    CERN Document Server

    Jang-Condell, Hannah; Manoj, P; Watson, Dan; Lisse, Carey M; Nesvold, Erika; Kuchner, Marc

    2015-01-01

    We analyze Spitzer/IRS spectra of 110 B-, A-, F-, and G-type stars with optically thin infrared excess in the Scorpius-Centaurus (ScoCen) OB association. The age of these stars ranges from 11-17 Myr. We fit the infrared excesses observed in these sources by Spitzer/IRS and Spitzer/MIPS to simple dust models according to Mie theory. We find that nearly all the objects in our study can be fit by one or two belts of dust. Dust around lower mass stars appears to be closer in than around higher mass stars, particularly for the warm dust component in the two-belt systems, suggesting mass-dependent evolution of debris disks around young stars. For those objects with stellar companions, all dust distances are consistent with trunction of the debris disk by the binary companion. The gaps between several of the two-belt systems can place limits on the planets that might lie between the belts, potentially constraining the mass and locations of planets that may be forming around these stars.

  7. The Cosmic History of Hot Gas Cooling and Radio AGN Activity in Massive Early-Type Galaxies

    Science.gov (United States)

    Danielson, A. L. R.; Lehmer, B. D.; Alexander, D. M.; Brandt, W. M.; Luo, B.; Miller, N.; Xue, Y. Q.; Stott, J. P.

    2012-01-01

    We study the X-ray properties of 393 optically selected early-type galaxies (ETGs) over the redshift range of z approx equals 0.0-1.2 in the Chandra Deep Fields. To measure the average X-ray properties of the ETG population, we use X-ray stacking analyses with a subset of 158 passive ETGs (148 of which were individually undetected in X-ray). This ETG subset was constructed to span the redshift ranges of z = 0.1-1.2 in the approx equals 4 Ms CDF-S and approx equals 2 Ms CDF-N and z = 0.1-0.6 in the approx equals 250 ks E-CDF-S where the contribution from individually undetected AGNs is expected to be negligible in our stacking. We find that 55 of the ETGs are detected individually in the X-rays, and 12 of these galaxies have properties consistent with being passive hot-gas dominated systems (i.e., systems not dominated by an X-ray bright Active Galactic Nucleus; AGN). On the basis of our analyses, we find little evolution in the mean 0.5-2 keY to B-band luminosity ratio (L(sub x) /L(sub Beta) varies as [1 +z]) since z approx equals 1.2, implying that some heating mechanism prevents the gas from cooling in these systems. We consider that feedback from radio-mode AGN activity could be responsible for heating the gas. We select radio AGNs in the ETG population using their far-infrared/radio flux ratio. Our radio observations allow us to constrain the duty cycle history of radio AGN activity in our ETG sample. We estimate that if scaling relations between radio and mechanical power hold out to z approx equals 1.2 for the ETG population being studied here, the average mechanical power from AGN activity is a factor of approx equals1.4 -- 2.6 times larger than the average radiative cooling power from hot gas over the redshift range z approx equals 0-1.2. The excess of inferred AGN mechanical power from these ETGs is consistent with that found in the local Universe for similar types of galaxies.

  8. NuSTAR unveils a heavily obscured low-luminosity Active Galactic Nucleus in the Luminous Infrared Galaxy NGC 6286

    CERN Document Server

    Ricci, C; Treister, E; Romero-Canizales, C; Arevalo, P; Iwasawa, K; Privon, G C; Sanders, D B; Schawinski, K; Stern, D; Imanishi, M

    2016-01-01

    We report the detection of a heavily obscured Active Galactic Nucleus (AGN) in the luminous infrared galaxy (LIRG) NGC 6286, identified in a 17.5 ks NuSTAR observation. The source is in an early merging stage, and was targeted as part of our ongoing NuSTAR campaign observing local luminous and ultra-luminous infrared galaxies in different merger stages. NGC 6286 is clearly detected above 10 keV and, by including the quasi-simultaneous Swift/XRT and archival XMM-Newton and Chandra data, we find that the source is heavily obscured [$N_{\\rm\\,H}\\simeq (0.95-1.32)\\times 10^{24}\\rm\\,cm^{-2}$], with a column density consistent with being Compton-thick [CT, $\\log (N_{\\rm\\,H}/\\rm cm^{-2})\\geq 24$]. The AGN in NGC 6286 has a low absorption-corrected luminosity ($L_{2-10\\rm\\,keV}\\sim 3-20\\times 10^{41}\\rm\\,erg\\,s^{-1}$) and contributes $\\lesssim$1\\% to the energetics of the system. Because of its low-luminosity, previous observations carried out in the soft X-ray band ($<10$ keV) and in the infrared did not notice th...

  9. Search for gas bulk motions in eight nearby clusters of galaxies with Suzaku

    CERN Document Server

    Ota, Naomi

    2015-01-01

    To search for bulk motions of the intracluster medium, we analyzed the X-ray spectra taken with the Suzaku satellite and measured the Doppler shift of Fe-K line emission from eight nearby clusters of galaxies with various X-ray morphologies. In the cores of the Centaurus and Perseus clusters, the gas bulk velocity does not exceed the sound velocity, which confirms the results of previous research. For the Cen45 subcluster, we found that the radial velocity relative to the Centaurus core, <780 km s^-1, is significantly smaller than that reported in the optical band at the 3.9 sigma level, which suggests an offset between the gas and galaxy distributions along the line of sight due to the subcluster merger. In A2199, A2142, A3667, and A133, no significant bulk motion was detected, indicating an upper limit on the radial velocity of 3000-4000 km s^-1. A sign of large bulk velocity in excess of the instrumental calibration uncertainty was found near the center of cool-core cluster A2029 and in the subcluster o...

  10. Mass-Models of Five Nearby Dwarf Irregular Galaxies

    CERN Document Server

    Côté, S; Carignan, C; Cote, Stephanie; Freeman, Ken; Carignan, Claude

    1997-01-01

    Five nearby dwarf irregular galaxies, amongst the recently surveyed dwarf members of the Sculptor and Centaurus A groups (at 2.5 Mpc and 3.5 Mpc), have been imaged in neutral hydrogen (HI) with the Australia Telescope and the Very Large Array. These objects have absolute magnitudes M_B in the range -14.9 to -12.7, yet they are clearly rotationally supported, with maximum rotation velocities ranging from 43 km/s to 67 km/s. Multi-component mass-models have been fitted to the rotation curves. We investigate the properties of their dark matter halos, and the scaling laws of the dark matter halos parameters.

  11. Cosmological simulations of galaxy clusters with feedback from active galactic nuclei: profiles and scaling relations

    CERN Document Server

    Pike, Simon R; Newton, Richard D A; Thomas, Peter A; Jenkins, Adrian

    2014-01-01

    We present results from a new set of 30 cosmological simulations of galaxy clusters, including the effects of radiative cooling, star formation, supernova feedback, black hole growth and AGN feedback. We first demonstrate that our AGN model is capable of reproducing the observed cluster pressure profile at redshift, z~0, once the AGN heating temperature of the targeted particles is made to scale with the final virial temperature of the halo. This allows the ejected gas to reach larger radii in higher-mass clusters than would be possible had a fixed heating temperature been used. Such a model also successfully reduces the star formation rate in brightest cluster galaxies and broadly reproduces a number of other observational properties at low redshift, including baryon, gas and star fractions; entropy profiles outside the core; and the X-ray luminosity-mass relation. Our results are consistent with the notion that the excess entropy is generated via selective removal of the densest material through radiative c...

  12. Shocks and sonic booms in the intracluster medium X-ray shells and radio galaxy activity

    CERN Document Server

    Reynolds, C S; Begelman, M C

    2001-01-01

    Motivated by hydrodynamic simulations, we discuss the X-ray appearance of radio galaxies embedded in the intracluster medium (ICM) of a galaxy cluster. We distinguish three regimes. In the early life of a powerful source, the entire radio cocoon is expanding supersonically and hence drives a strong shock into the ICM. Eventually, the sides of the cocoon become subsonic and the ICM is disturbed by the sonic booms of the jet's working surface. In both of these regimes, X-ray observations would find an X-ray shell. In the strong shock regime, this shell will be hot and relatively thin. However, in the weak shock (sonic-boom) regime, the shell will be approximately the same temperature as the undisturbed ICM. If a cooling flow is present, the observed shell may even be cooler than the undisturbed ICM due to the lifting of cooler material into the shell from the inner (cooler) regions of the cluster. In the third and final regime, the cocoon has collapsed and no well-defined X-ray shell will be seen. We discuss wa...

  13. Star formation and accretion in the circumnuclear disks of active galaxies

    CERN Document Server

    Wutschik, Stephanie; Palmer, Thomas S

    2013-01-01

    We explore the evolution of supermassive black holes (SMBH) centered in a circumnuclear disk (CND) as a function of the mass supply from the host galaxy and considering different star formation laws, which may give rise to a self-regulation via the injection of supernova-driven turbulence. A system of equations describing star formation, black hole accretion and angular momentum transport was solved for an axisymmetric disk in which the gravitational potential includes contributions from the black hole, the disk and the hosting galaxy. Our model extends the framework provided by Kawakatu et al. (2008) by separately considering the inner and outer part of the disk, and by introducing a potentially non-linear dependence of the star formation rate on the gas surface density and the turbulent velocity. The star formation recipes are calibrated using observational data for NGC 1097, while the accretion model is based on turbulent viscosity as a source of angular momentum transport in a thin viscous accretion disk....

  14. The "shook up" galaxy NGC 3079: the complex interplay between HI, activity and environment

    CERN Document Server

    Shafi, N; Morganti, R; Colafrancesco, S; Booth, R

    2015-01-01

    We present deep neutral hydrogen (HI) observations of the starburst/Seyfert galaxy NGC 3079 and its environment, obtained with the Westerbork Synthesis Radio Telescope. Our observations reveal previously unknown components, both in HI emission and in absorption, that show that NGC 3079 is going through a hectic phase in its evolution. The HI disk appears much more extended than previously observed and is morphologically and kinematically lopsided on all scales with evidence for strong non-circular motions in the central regions. Our data reveal prominent gas streams encircling the entire galaxy suggesting strong interacting with its neighbours. A 33-kpc long HI bridge is detected between NGC 3079 and MCG 9-17-9, likely caused by ram-pressure stripping of MGC 9-17-9 by the halo of hot gas of NGC 3079. The cometary HI tail of the companion NGC 3073, earlier discovered by Irwin et al., extends about twice as long in our data, while a shorter, second tail is also found. This tail is likely caused by ram-pressure ...

  15. Broad Hbeta Emission-Line Variability in a Sample of 102 Local Active Galaxies

    CERN Document Server

    Runco, Jordan N; Bennert, Vardha N; Scott, Bryan; Komossa, S; Malkan, Matthew A; Lazarova, Mariana S; Auger, Matthew W; Treu, Tommaso; Park, Daeseong

    2016-01-01

    A sample of 102 local (0.02 10^7 M_sun was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10-m telescope to study the scaling relations between MBH and host galaxy properties. We study profile changes of the broad Hbeta emission line within the ~3-9 year time-frame between the two sets of spectra. The variability of the broad Hbeta emission line is of particular interest, not only since it is used to estimate MBH, but also since its strength and width is used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (~66%) of the objects, resulting in a Seyfert-type change for ~38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hbeta line virtually disappears in 3/102 (~3%) extreme cases. We discuss potential causes for these changing-look AGNs. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case ...

  16. A SPITZER MIPS STUDY OF 2.5-2.0 M{sub Sun} STARS IN SCORPIUS-CENTAURUS

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Christine H.; Bitner, Martin [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Pecaut, Mark; Mamajek, Eric E. [Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627 (United States); Su, Kate Y. L., E-mail: cchen@stsci.edu [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States)

    2012-09-10

    We have obtained Spitzer Space Telescope Multiband Imaging Photometer for Spitzer (MIPS) 24 {mu}m and 70 {mu}m observations of 215 nearby, Hipparcos B- and A-type common proper-motion single and binary systems in the nearest OB association, Scorpius-Centaurus. Combining our MIPS observations with those of other ScoCen stars in the literature, we estimate 24 {mu}m B+A-type disk fractions of 17/67 (25{sup +6}{sub -5}%), 36/131 (27{sup +4}{sub -4}%), and 23/95 (24{sup +5}{sub -4}%) for Upper Scorpius ({approx}11 Myr), Upper Centaurus Lupus ({approx}15 Myr), and Lower Centaurus Crux ({approx}17 Myr), respectively, somewhat smaller disk fractions than previously obtained for F- and G-type members. We confirm previous IRAS excess detections and present new discoveries of 51 protoplanetary and debris disk systems, with fractional infrared luminosities ranging from L{sub IR}/L{sub *} = 10{sup -6} to 10{sup -2} and grain temperatures ranging from T{sub gr} = 40 to 300 K. In addition, we confirm that the 24 {mu}m and 70 {mu}m excesses (or fractional infrared luminosities) around B+A-type stars are smaller than those measured toward F+G-type stars and hypothesize that the observed disk property dependence on stellar mass may be the result of a higher stellar companion fraction around B- and A-type stars at 10-200 AU. Finally, we note that the majority of the ScoCen 24 {mu}m excess sources also possess 12 {mu}m excess, indicating that Earth-like planets may be forming via collisions in the terrestrial planet zone at {approx}10-100 Myr.

  17. SPITZER SPECTROSCOPY OF INFRARED-LUMINOUS GALAXIES: DIAGNOSTICS OF ACTIVE GALACTIC NUCLEI AND STAR FORMATION AND CONTRIBUTION TO TOTAL INFRARED LUMINOSITY

    International Nuclear Information System (INIS)

    We use mid-infrared (MIR) spectroscopy from the Spitzer Infrared Spectrograph to study the nature of star-formation and supermassive black hole accretion for a sample of 65 IR-luminous galaxies at 0.02 1.2 mJy. The MIR spectra cover wavelengths 5-38 μm, spanning the polycyclic aromatic hydrocarbon (PAH) features and important atomic diagnostic lines. Our sample of galaxies corresponds to a range of total IR luminosity, LIR = L(8-1000 μm) = 1010-1012 L☉ (median LIR of 3.0 × 1011 L☉). We divide our sample into a subsample of galaxies with Spitzer Infrared Array Camera 3.6-8.0 μm colors indicative of warm dust heated by an active galactic nucleus (AGN; IRAGN) and those galaxies whose colors indicate star-formation processes (non-IRAGN). Compared to the non-IRAGN, the IRAGN show smaller PAH emission equivalent widths, which we attribute to an increase in mid-IR continuum from the AGN. We find that in both the IRAGN and star-forming samples, the luminosity in the PAH features correlates strongly with [Ne II] λ12.8 μm emission line, from which we conclude that the PAH luminosity directly traces the instantaneous star-formation rate (SFR) in both the IRAGN and star-forming galaxies. We compare the ratio of PAH luminosity to the total IR luminosity, and we show that for most IRAGN star-formation accounts for 10%-50% of the total IR luminosity. We also find no measurable difference between the PAH luminosity ratios of L11.3/L7.7 and L6.2/L7.7 for the IRAGN and non-IRAGN, suggesting that AGN do not significantly excite or destroy PAH molecules on galaxy-wide scales. Interestingly, a small subset of galaxies (8 of 65 galaxies) show a strong excess of [O IV] λ25.9 μm emission compared to their PAH emission, which indicates the presence of heavily-obscured AGN, including 3 galaxies that are not otherwise selected as IRAGN. The low PAH emission and low [Ne II] emission of the IRAGN and [O IV]-excess objects imply the IR luminosity of these objects is dominated by

  18. MUSE three-dimensional spectroscopy and kinematics of the gigahertz peaked spectrum radio galaxy PKS 1934-63: interaction, recently triggered active galactic nucleus and star formation

    Science.gov (United States)

    Roche, Nathan; Humphrey, Andrew; Lagos, Patricio; Papaderos, Polychronis; Silva, Marckelson; Cardoso, Leandro S. M.; Gomes, Jean Michel

    2016-07-01

    We observe the radio galaxy PKS 1934-63 (at z = 0.1825) using the Multi-Unit Spectroscopic Explorer (MUSE) on the Very Large Telescope (VLT). The radio source is a gigahertz peaked spectrum source and is compact (0.13 kpc), implying an early stage of evolution (≤104 yr). Our data show an interacting pair of galaxies, with projected separation 9.1 kpc and velocity difference Δ(v) = 216 km s-1. The larger galaxy is a M* ≃ 1011 M⊙ spheroidal with the emission-line spectrum of a high-excitation young radio active galactic nucleus (AGN; e.g. strong [O I]6300 and [O III]5007). Emission-line ratios indicate a large contribution to the line luminosity from high-velocity shocks (≃ 550 km s-1). The companion is a non-AGN disc galaxy, with extended Hα emission from which its star formation rate is estimated as 0.61 M⊙ yr-1. Both galaxies show rotational velocity gradients in Hα and other lines, with the interaction being prograde-prograde. The SE-NW velocity gradient of the AGN host is misaligned from the E-W radio axis, but aligned with a previously discovered central ultraviolet source, and a factor of 2 greater in amplitude in Hα than in other (forbidden) lines (e.g. [O III]5007). This could be produced by a fast rotating (100-150 km s-1) disc with circumnuclear star formation. We also identify a broad component of [O III]5007 emission, blueshifted with a velocity gradient aligned with the radio jets, and associated with outflow. However, the broad component of [O I]6300 is redshifted. In spectral fits, both galaxies have old stellar populations plus ˜0.1 per cent of very young stars, consistent with the galaxies undergoing first perigalacticon, triggering infall and star formation from ˜40 Myr ago followed by the radio outburst.

  19. Optical Continuum Variability of the Active Galaxy Mrk 279 - Implications for Different Accretion Regimes

    CERN Document Server

    Bachev, R; Bachev, Rumen; Strigachev, Anton

    2003-01-01

    We present results from a recent broad-band monitoring in optics of the Seyfert 1 type galaxy Mrk 279. We build and analyse the BVRI light curve covering a period of seven years (1995 - 2002). We also show some evidence for the existence of two different states in brightness and suggest, based on a modelling of the optical continuum, that these states may result from transition between a thin disk and an ADAF accretion modes. We assume that the short-term variability is due to a reprocessing of a variable X-ray emission from an inner ADAF part of the flow, while the long-term one may be a result from a change of the transition radius. Our tests show a good match with the observations for a reasonable set of accretion parameters, rather close to the ones, expected for Mrk 279.

  20. Are the Narrow Line Regions in Active Galaxies Dusty and Radiation Pressure Dominated?

    CERN Document Server

    Dopita, M A; Sutherland, R S; Binette, L; Cecil, G N

    2002-01-01

    The remarkable similarity between emission spectra of narrow line regions (NLR) in Seyfert Galaxies has long presented a mystery. In photoionization models, this similarity implies that the ionization parameter is nearly always the same, about U ~ 0.01. Here we present dusty, radiation-pressure dominated photoionization models that can provide natural physical insight into this problem. In these models, dust and the radiation pressure acting on it provide the controlling factor in moderating the density, excitation and surface brightness of photoionized NLR structures. Additionally, photoelectric heating by the dust is important in determining the temperature structure of the models. These models can also explain the coexistence of the low-, intermediate- and coronal ionization zones within a single self-consistent physical structure. The radiation pressure acting on dust may also be capable of driving the fast (~3000 km/s) outflows such as are seen in the HST observations of NGC 1068.

  1. ZFOURGE catalogue of AGN candidates: an enhancement of 160{\\mu}m-derived star-formation rates in active galaxies to $z$ = 3.2

    CERN Document Server

    Cowley, Michael J; Tran, Kim-Vy H; Rees, Glen A; Labbé, Ivo; Allen, Rebecca J; Brammer, Gabriel B; Glazebrook, Karl; Hopkins, Andrew M; Juneau, Stéphanie; Kacprzak, Glenn G; Mullaney, James R; Nanayakkara, Themiya; Papovich, Casey; Quadri, Ryan F; Straatman, Caroline M S; Tomczak, Adam R; van Dokkum, Pieter G

    2016-01-01

    We investigate active galactic nuclei (AGN) candidates within the FourStar Galaxy Evolution Survey (ZFOURGE) to determine the impact they have on star-formation in their host galaxies. We first identify a population of radio, X-ray, and infrared-selected AGN by cross-matching the deep $K_{s}$-band imaging of ZFOURGE with overlapping multi-wavelength data. From this, we construct a mass-complete (log(M$_{*}$/M$_{\\odot}$) $\\ge$ 9.75), AGN luminosity limited sample of 235 AGN hosts over z = 0.2 - 3.2. We compare the rest-frame U - V versus V - J (UVJ) colours and specific star-formation rates (sSFRs) of the AGN hosts to a mass-matched control sample of inactive (non-AGN) galaxies. UVJ diagnostics reveal AGN tend to be hosted in a lower fraction of quiescent galaxies and a higher fraction of dusty galaxies than the control sample. Using 160{\\mu}m Herschel PACS data, we find the mean specific star-formation rate of AGN hosts to be elevated by 0.34$\\pm$0.07 dex with respect to the control sample across all redshift...

  2. Discovery of a Population of Bulgeless Galaxies with Extremely Red Mid-IR Colors: Obscured AGN Activity in the Low Mass Regime?

    CERN Document Server

    Satyapal, Shobita; McAlpine, William; Ellison, Sara L; Fischer, Jacqueline; Rosenberg, Jessica L

    2014-01-01

    In contrast to massive, bulge hosting galaxies, very few supermassive black holes (SMBHs) are known in either low mass, or bulgeless galaxies. Such a population could provide clues to the origins of SMBHs and to secular pathways for their growth. Using the all-sky Wide-Field Infrared Survey Explorer (WISE) survey, and bulge-to-disk decompositions from the Sloan Digital Sky Survey (SDSS) Data Release 7, we report the discovery of a population of local (z<0.3) bulgeless disk galaxies with extremely red mid-infrared colors highly suggestive of a dominant active galactic nucleus (AGN), despite having no optical AGN signatures in their SDSS spectra. Using various mid-infrared selection criteria from the literature, there are between 30 to over 300 bulgeless galaxies with possible AGNs. Other known scenarios that can heat the dust to high temperatures do not appear to explain the observed colors of this sample. If these galaxies are confirmed to host AGNs, this study will provide a breakthrough in characterizing...

  3. Molecular Gas in Lensed z>2 Quasar Host Galaxies and the Star Formation Law for Galaxies with Luminous Active Galactic Nuclei

    CERN Document Server

    Riechers, Dominik A

    2011-01-01

    We report the detection of luminous CO(2-1), CO(3-2), and CO(4-3) emission in the strongly lensed high-redshift quasars B1938+666 (z=2.059), HE0230-2130 (z=2.166), HE1104-1805 (z=2.322), and B1359+154 (z=3.240), using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). B1938+666 was identified in a `blind' CO redshift search, demonstrating the feasibility of such investigations with millimeter interferometers. These galaxies are lensing-amplified by factors of mu_L~11-170, and thus allow us to probe molecular gas in intrinsically fainter galaxies than currently possible without the aid of gravitational lensing. We report lensing-corrected intrinsic CO line luminosities of L'(CO) = 0.65-21 x 10^9 K km/s pc^2, translating to H2 masses of M(H2) = 0.52-1.7 x 10^9 (alpha_CO/0.8) M_sun. To investigate whether or not the AGN in luminous quasars substantially contribute to L_FIR, we study the L'(CO)-L_FIR relation for quasars relative to galaxies without a luminous AGN as a function of redshift. We ...

  4. DISENTANGLING THE CIRCUMNUCLEAR ENVIRONS OF CENTAURUS A. I. HIGH-RESOLUTION MOLECULAR GAS IMAGING

    International Nuclear Information System (INIS)

    We present high-resolution images of the 12CO(2-1) emission in the central 1' (1 kpc) of NGC 5128 (Centaurus A), observed using the Submillimeter Array. We elucidate for the first time the distribution and kinematics of the molecular gas in this region with a resolution of 6.''0 x 2.''4 (100 pc x 40 pc). We spatially resolve the circumnuclear molecular gas in the inner 24''x 12'' (400 pc x 200 pc), which is elongated along a position angle of P.A. ≅155 deg. and perpendicular to the radio/X-ray jet. The southeast (SE) and northwest (NW) components of the circumnuclear gas are connected to molecular gas found at larger radii. This gas appears as two parallel filaments at P.A. = 120 deg., which are coextensive with the long sides of the 3 kpc parallelogram shape of the previously observed dust continuum, as well as ionized and pure rotational H2 lines. Spatial and kinematical asymmetries are apparent in both the circumnuclear and outer gas, suggesting noncoplanar and/or noncircular motions. We extend to inner radii (r12CO(2 - 1) observations show relevant deviations from this model: namely, the physical connection between the circumnuclear gas and that at larger radii, brighter SE and NW sides on the parallelogram-shaped feature, and an outer curvature of its long sides. Overall, it resembles more closely an S-shaped morphology, a trend that is also found in other molecular species. Hence, we qualitatively explore the possible contribution of a weak bi-symmetric potential which would naturally explain these peculiarities.

  5. 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 ground-based spectroscopic luminosity measurements at 5100 Å. After correcting the luminosities of the AGNs for the contribution from starlight, we re-examine the Hß R BLR-L relationship. Our best fit for the relationship gives a power-law slope of 0.52 with a range of 0.45-0.59 allowed...... by the uncertainties. This is consistent with our previous findings, and thus still consistent with the naive assumption that all AGNs are simply luminosity-scaled versions of each other. We discuss various consistency checks relating to the galaxy modeling and starlight contributions, as well as possible systematic...

  6. Multi-wavelength properties and smbh's masses of the isolated galaxies with active nuclei in the Local Universe

    Science.gov (United States)

    Vavilova, Iryna; Vasylenko, Anatolij; Babyk, Iuri; Pulatova, Nadya

    2016-07-01

    We apply the specially-oriented Astro-Space databases obtained with ground-based telescopes and space observatories to study the multi-wavelength spectral and physical properties of galaxies with active nuclei (AGNs), namely of isolated AGNs that are poorly investigated especially in X-rays. Such a study allowed us 1) to separate the internal evolution mechanisms from the environment influence and consider them as two separate processes related to fueling nuclear activity, 2) to explore absorption features and the X-ray continuum radiation from accretion disks around SMBHs (e.g. to select accretion models). In the case of detecting the Fe K emission line, it was possible to analyze the physical conditions in the AGNs innermost parts in more details. Using the SDSS spectral Hβ-line data we were able to estimate the SMBH masses of several isolated AGNs in the Local Universe, which are systematically lower than the SMBH masses of AGNs located in a dense environment. We present also the results of analysis of the spectral data obtained by XMM-Newton, Swift, Chandra, and INTEGRAL space observatories for several isolated AGNs from 2MIG catalogue, for which the available X-ray data were accessed. Among these objects are CGCG 179-005, NGC 6300, NGC 1050, NGC 2989, WKK 3050, ESO 438-009, ESO 317-038 and others. We determined corresponding spectral models and values of their parameters (spectral index, intrinsic absorption etc.). X-ray spectra for bright galaxies, NGC 6300 and Circinus, were analyzed up to 250 keV and their characteristics of emission features were determined in 6-7 keV range.

  7. AGN feedback in galaxy formation

    CERN Document Server

    Antonuccio-Delogu, Vincenzo

    2010-01-01

    During the past decade, convincing evidence has been accumulated concerning the effect of active galactic nuclei (AGN) activity on the internal and external environment of their host galaxies. Featuring contributions from well-respected researchers in the field, and bringing together work by specialists in both galaxy formation and AGN, this volume addresses a number of key questions about AGN feedback in the context of galaxy formation. The topics covered include downsizing and star-formation time scales in massive elliptical galaxies, the connection between the epochs of supermassive black h

  8. Detecting edges in the X-ray surface brightness of galaxy clusters

    CERN Document Server

    Sanders, J S; Russell, H R; Walker, S A; Blundell, K M

    2016-01-01

    The effects of many physical processes in the intracluster medium of galaxy clusters imprint themselves in X-ray surface brightness images. It is therefore important to choose optimal methods for extracting information from and enhancing the interpretability of such images. We describe in detail a gradient filtering edge detection method that we previously applied to images of the Centaurus cluster of galaxies. The Gaussian gradient filter measures the gradient in the surface brightness distribution on particular spatial scales. We apply this filter on different scales to Chandra X-ray observatory images of two clusters with AGN feedback, the Perseus cluster and M87, and a merging system, A3667. By combining filtered images on different scales using radial filters spectacular images of the edges in a cluster are produced. We describe how to assess the significance of features in filtered images. We find the gradient filtering technique to have significant advantages for detecting many kinds of features compar...

  9. GREEN GALAXIES IN THE COSMOS FIELD

    Energy Technology Data Exchange (ETDEWEB)

    Pan, Zhizheng; Kong, Xu; Fan, Lulu, E-mail: panzz@mail.ustc.edu.cn, E-mail: xkong@ustc.edu.cn [Center of Astrophysics, University of Science and Technology of China, Hefei 230026 (China)

    2013-10-10

    We present research on the morphologies, spectra, and environments of ≈2350 'green valley' galaxies at 0.2 < z < 1.0 in the COSMOS field. The bimodality of dust-corrected NUV–r {sup +} color is used to define 'green valley'; it removes dusty star-forming galaxies from galaxies that are truly transitioning between the blue cloud and the red sequence. Morphological parameters of green galaxies are intermediate between those of blue and red galaxy populations, both on the Gini-asymmetry and the Gini-M{sub 20} planes. Approximately 60%-70% of green disk galaxies have intermediate or big bulges, and only 5%-10% are pure disk systems, based on morphological classification using the Zurich Estimator of Structural Types. The obtained average spectra of green galaxies are intermediate between blue and red ones in terms of [O II], Hα, and Hβ emission lines. Stellar population synthesis on the average spectra shows that green galaxies are on average older than blue galaxies but younger than red galaxies. Green galaxies and blue galaxies have similar projected galaxy density (Σ{sub 10}) distributions at z > 0.7. At z < 0.7, the fractions of M{sub *} < 10{sup 10.0} M{sub ☉} green galaxies located in a dense environment are found to be significantly larger than those of blue galaxies. The morphological and spectral properties of green galaxies are consistent with the transitioning population between the blue cloud and the red sequence. The possible mechanisms for quenching star formation activities in green galaxies are discussed. The importance of active galactic nucleus feedback cannot be well constrained in our study. Finally, our findings suggest that environmental conditions, most likely starvation and harassment, significantly affect the transformation of M{sub *} < 10{sup 10.0} M{sub ☉} blue galaxies into red galaxies, especially at z < 0.5.

  10. Discovery of Seven Companions to Intermediate Mass Stars with Extreme Mass Ratios in the Scorpius-Centaurus Association

    CERN Document Server

    Hinkley, Sasha; Ireland, Michael J; Cheetham, Anthony; Carpenter, John M; Tuthill, Peter; Lacour, Sylvestre; Evans, Thomas M; Haubois, Xavier

    2015-01-01

    We report the detection of seven low mass companions to intermediate-mass stars (SpT B/A/F; $M$$\\approx$1.5-4.5 solar masses) in the Scorpius-Centaurus Association using nonredundant aperture masking interferometry. Our newly detected objects have contrasts $\\Delta L'$$\\approx$4-6, corresponding to masses as low as $\\sim$20 Jupiter masses and mass ratios of $q$$\\approx$0.01-0.08, depending on the assumed age of the target stars. With projected separations $\\rho$$\\approx$10-30 AU, our aperture masking detections sample an orbital region previously unprobed by conventional adaptive optics imaging of intermediate mass Scorpius-Centaurus stars covering much larger orbital radii ($\\approx$30-3000 AU). At such orbital separations, these objects resemble higher mass versions of the directly imaged planetary mass companions to the 10-30 Myr, intermediate-mass stars HR 8799, $\\beta$ Pictoris, and HD95086. These newly discovered companions span the brown dwarf desert, and their masses and orbital radii provide a new co...

  11. Embedded star formation in the extended narrow line region of Centaurus A: extreme mixing observed by MUSE

    CERN Document Server

    Santoro, F; Morganti, R; Oosterloo, T A; Tadhunter, C

    2016-01-01

    We present a detailed study of the complex ionization structure in a small (~250 pc) extended narrow line region (ENLR) cloud near Centaurus A using the Multi Unit Spectroscopic Explorer. This cloud is located in the so-called outer filament of ionized gas (about 15 kpc from the nucleus) where jet-induced star formation has been suggested to occur by different studies. We find that, despite the small size, a mixture of ionization mechanisms is operating, resulting in considerable complexity in the spatial ionization structure. The area includes two H II regions where star formation is occurring and another location where star formation must have ceased very recently. Interestingly, the extreme Balmer decrement of one of the star forming regions (H_alpha/H_beta~6) indicates that it is still heavily embedded in its natal cocoon of gas and dust. At all three locations a continuum counterpart is found with spectra matching those of O/B stars local to Centaurus A. The H II regions are embedded in a larger gas comp...

  12. Supernovae in paired galaxies

    CERN Document Server

    Nazaryan, T A; Hakobyan, A A; Adibekyan, V Zh; Kunth, D; Mamon, G A; Turatto, M; Aramyan, L S

    2013-01-01

    We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are consistent with previous results compiled with the larger sample. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies.

  13. Evolution of galaxies

    International Nuclear Information System (INIS)

    The proceedings contain 87 papers divided into 8 chapters. The chapter Bipolar outflows and star formations contains papers on optical and infrared observations of young bipolar outflow objects and the theory thereof, and on observations of cometary nebulae. The chapter Masers and early stellar evolution discusses molecular masers and star forming regions. The following chapter contains papers on initial mass function and star formation rates in galaxies. The chapter Clusters and star formation contains data on OB associations and open star clusters, their development and observations, CO and H2 in our galaxy, the four vector model of radio emission and an atlas of the wavelength dependence of ultraviolet extinction in the Galaxy. The most voluminous is the chapter Evolution of galaxies. It contains papers on the theories of the physical and chemodynamic development of galaxies of different types, rotation research and rotation velocities of galaxies and their arms, and on mathematical and laboratory models of morphological development. Chapter seven contains papers dealing with active extragalactic objects, quasars and active galactic nuclei. The last chapter discusses cosmological models, the theory of the inflationary universe, and presents an interpretation of the central void and X-ray background. (M.D.). 299 figs., 48 tabs., 1651 refs

  14. Neutrino production from photo-hadronic interactions of the gamma flux from Active Galactic Nuclei with their gas content

    CERN Document Server

    Arteaga-Velazquez, J C

    2013-01-01

    The diffuse neutrino flux from FRI and BL Lac type galaxies generated from interactions of their own gamma radiation with the gas and dust at the sources is reported. This neutrino-production channel has not been studied in detail up to now. The calculations are based on individual estimations of the neutrino flux in two nearby AGN's: Centaurus A and M87, assuming the validity of the AGN unification model. The predictions for Centaurus A and M87 involved the parameterization of the measured gamma-ray luminosities and the modeling of the material of the galaxies both based on observations performed by several detectors. No hadronic origin for the TeV photons is assumed. The results show that, although the corresponding neutrino flux ($E^{2} \\Phi_{\

  15. Absorption variability as a probe of the multiphase interstellar media surrounding active galaxies

    CERN Document Server

    Macquart, Jean-Pierre

    2016-01-01

    We examine a model for the variable free-free and neutral hydrogen absorption inferred towards the cores of some compact radio galaxies in which a spatially fluctuating medium drifts in front of the source. We relate the absorption-induced intensity fluctuations to the statistics of the underlying opacity fluctuations. We investigate models in which the absorbing medium consists of either discrete clouds or a power-law spectrum of opacity fluctuations. We examine the variability characteristics of a medium comprised of Gaussian-shaped clouds in which the neutral and ionized matter are co-located, and in which the clouds comprise spherical constant-density neutral cores enveloped by ionized sheaths. The cross-power spectrum indicates the spatial relationship between neutral and ionized matter, and distinguishes the two models, with power in the Gaussian model declining as a featureless power-law, but that in the ionized sheath model oscillating between positive and negative values. We show how comparison of th...

  16. Molecular Gas in Lensed z >2 Quasar Host Galaxies and the Star Formation Law for Galaxies with Luminous Active Galactic Nuclei

    OpenAIRE

    Riechers, Dominik A.

    2011-01-01

    We report the detection of luminous CO(J = 2→1), CO(J = 3→2), and CO(J = 4→3) emission in the strongly lensed high-redshift quasars B1938+666 (z = 2.059), HE 0230-2130 (z = 2.166), HE 1104-1805 (z = 2.322), and B1359+154 (z = 3.240), using the Combined Array for Research in Millimeter-wave Astronomy. B1938+666 was identified in a "blind" CO redshift search, demonstrating the feasibility of such investigations with millimeter interferometers. These galaxies are lensing-amplified by factors of ...

  17. A MULTI-WAVELENGTH STUDY OF LOW-REDSHIFT CLUSTERS OF GALAXIES. I. COMPARISON OF X-RAY AND MID-INFRARED SELECTED ACTIVE GALACTIC NUCLEI

    International Nuclear Information System (INIS)

    Clusters of galaxies have long been used as laboratories for the study of galaxy evolution, but despite intense, recent interest in feedback between active galactic nuclei (AGNs) and their hosts, the impact of environment on these relationships remains poorly constrained. We present results from a study of AGNs and their host galaxies found in low-redshift galaxy clusters. We fit model spectral energy distributions (SEDs) to the combined visible and mid-infrared (MIR) photometry of cluster members and use these model SEDs to determine stellar masses and star formation rates (SFRs). We identify two populations of AGNs, the first based on their X-ray luminosities (X-ray AGNs) and the second based on the presence of a significant AGN component in their model SEDs (IR AGNs). We find that the two AGN populations are nearly disjoint; only 8 out of 44 AGNs are identified with both techniques. We further find that IR AGNs are hosted by galaxies with similar masses and SFRs but higher specific SFRs (sSFRs) than X-ray AGN hosts. The relationship between AGN accretion and host star formation in cluster AGN hosts shows no significant difference compared to the relationship between field AGNs and their hosts. The projected radial distributions of both AGN populations are consistent with the distribution of other cluster members. We argue that the apparent dichotomy between X-ray and IR AGNs can be understood as a combination of differing extinction due to cold gas in the host galaxies of the two classes of AGNs and the presence of weak star formation in X-ray AGN hosts.

  18. A Search for Submillimeter H2O Masers in Active Galaxies: The Detection of 321 GHZ H2O Maser Emission in NGC 4945

    Science.gov (United States)

    Hagiwara, Yoshiaki; Horiuchi, Shinji; Doi, Akihiro; Miyoshi, Makoto; Edwards, Philip G.

    2016-08-01

    We present further results of a search for extragalactic submillimeter H2O masers using the Atacama Large Millimeter/submillimeter Array (ALMA). The detection of a 321 GHz H2O maser in the nearby type 2 Seyfert galaxy, the Circinus galaxy, has previously been reported, and here the spectral analysis of four other galaxies is described. We have discovered H2O maser emission at 321 GHz toward the center of NGC 4945, a nearby type 2 Seyfert. The maser emission shows Doppler-shifted velocity features with velocity ranges similar to those of the previously reported 22 GHz H2O masers however, the non-contemporaneous observations also show differences in velocity offsets. The subparsec-scale distribution of the 22 GHz H2O masers revealed by earlier very long baseline interferometry observations suggests that the submillimeter masers could arise in an edge-on rotating disk. The maser features remain unresolved by the synthesized beam of ˜0.″54 (˜30 pc) and are located toward the 321 GHz continuum peak within errors. A marginally detected (3σ) high-velocity feature is redshifted by 579 km {{{s}}}-1 with respect to the systemic velocity of the galaxy. Assuming that this feature is real and arises from a Keplerian rotating disk in this galaxy, it is located at a radius of ˜0.020 pc (˜1.5 × 105 Schwarzschild radii), which would enable molecular material closer to the central engine to be probed than the 22 GHz H2O masers. This detection confirms that submillimeter H2O masers are a potential tracer of the circumnuclear regions of active galaxies, which will benefit from higher angular resolution studies with ALMA.

  19. Gas-Rich Companions of Isolated Galaxies

    CERN Document Server

    Pisano, D J; Wilcots, Eric M.

    1999-01-01

    We have used the VLA to search for gaseous remnants of the galaxy formation process around six extremely isolated galaxies. We found two distinct HI clouds around each of two galaxies in our sample (UGC 9762 & UGC 11124). These clouds are rotating and appear to have optical counterparts, strongly implying that they are typical dwarf galaxies. The companions are currently weakly interacting with the primary galaxy, but have short dynamical friction timescales (~1 Gyr) suggesting that these triple galaxy systems will shortly collapse into one massive galaxy. Given that the companions are consistent with being in circular rotation about the primary galaxy, and that they have small relative masses, the resulting merger will be a minor one. The companions do, however, contain enough gas that the merger will represent a significant infusion of fuel to drive future star formation, bar formation, or central activity, while building up the mass of the disk thus making these systems important pieces of the galaxy f...

  20. A Multi-Wavelength Photometric Census of AGN and Star Formation Activity in the Brightest Cluster Galaxies of X-ray Selected Clusters

    Science.gov (United States)

    Green, T. S.; Edge, A. C.; Stott, J. P.; Ebeling, H.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Metcalfe, N.; Kaiser, N.; Wainscoat, R. J.; Waters, C.

    2016-06-01

    Despite their reputation as being "red and dead", the unique environment inhabited by Brightest Cluster Galaxies (BCGs) can often lead to a self-regulated feedback cycle between radiatively cooling intracluster gas and star formation and AGN activity in the BCG. However the prevalence of "active" BCGs, and details of the feedback involved, are still uncertain. We have performed an optical, UV and Mid-IR photometric analysis of the BCGs in 981 clusters at 0.03 medium.

  1. Galaxy formation

    International Nuclear Information System (INIS)

    Galaxy formation is at the forefront of observation and theory in cosmology. An improved understanding is essential for improving our knowledge both of the cosmological parameters, of the contents of the universe, and of our origins. In these lectures intended for graduate students, galaxy formation theory is reviewed and confronted with recent observational issues. In lecture 1, the following topics are presented: star formation considerations, including IMF, star formation efficiency and star formation rate, the origin of the galaxy luminosity function, and feedback in dwarf galaxies. In lecture 2, we describe formation of disks and massive spheroids, including the growth of supermassive black holes, negative feedback in spheroids, the AGN-star formation connection, star formation rates at high redshift and the baryon fraction in galaxies.

  2. Galaxy formation

    CERN Document Server

    Silk, Joseph; Dvorkin, Irina

    2015-01-01

    Galaxy formation is at the forefront of observation and theory in cosmology. An improved understanding is essential for improving our knowledge both of the cosmological parameters, of the contents of the universe, and of our origins. In these lectures intended for graduate students, galaxy formation theory is reviewed and confronted with recent observational issues. In Lecture 1, the following topics are presented: star formation considerations, including IMF, star formation efficiency and star formation rate, the origin of the galaxy luminosity function, and feedback in dwarf galaxies. In Lecture 2, we describe formation of disks and massive spheroids, including the growth of supermassive black holes, negative feedback in spheroids, the AGN-star formation connection, star formation rates at high redshift and the baryon fraction in galaxies.

  3. Galaxy Formation and Evolution

    Science.gov (United States)

    Nagamine, Kentaro; Reddy, Naveen; Daddi, Emanuele; Sargent, Mark T.

    2016-07-01

    In this chapter, we discuss the current status of observational and computational studies on galaxy formation and evolution. In particular, a joint analysis of star-formation rates (SFRs), stellar masses, and metallicities of galaxies throughout cosmic time can shed light on the processes by which galaxies build up their stellar mass and enrich the environment with heavy elements. Comparison of such observations and the results of numerical simulations can give us insights on the physical importance of various feedback effects by supernovae and active galactic nuclei. In Sect. 1, we first discuss the primary methods used to deduce the SFRs, stellar masses, and (primarily) gas-phase metallicities in high-redshift galaxies. Then, we show how these quantities are related to each other and evolve with time. In Sect. 2, we further examine the distribution of SFRs in galaxies following the `Main Sequence' paradigm. We show how the so-called `starbursts' display higher specific SFRs and SF efficiencies by an order of magnitude. We use this to devise a simple description of the evolution of the star-forming galaxy population since z ˜3 that can successfully reproduce some of the observed statistics in the infrared (IR) wavelength. We also discuss the properties of molecular gas. In Sect. 3, we highlight some of the recent studies of high-redshift galaxy formation using cosmological hydrodynamic simulations. We discuss the physical properties of simulated galaxies such as luminosity function and escape fraction of ionizing photons, which are important statistics for reionization of the Universe. In particular the escape fraction of ionizing photons has large uncertainties, and studying gamma-ray bursts (which is the main topic of this conference) can also set observational constraints on this uncertain physical parameter as well as cosmic star formation rate density.

  4. Radio properties of fossil galaxy groups

    Science.gov (United States)

    Miraghaei, H.; Khosroshahi, H. G.

    2016-09-01

    We study 1.4 GHz radio properties of a sample of fossil galaxy groups using GMRT radio observations and the FIRST survey catalog. Fossil galaxy groups, having no recent major mergers in their dominant galaxies and also group scale mergers, give us the opportunity to investigate the effect of galaxy merger on AGN activity. In this work, we compare the radio properties of a rich sample of fossil groups with a sample of normal galaxy groups and clusters and show that the brightest group galaxies in fossil groups are under luminous at 1.4 GHz, relative to the general population of the brightest group galaxies, indicating that the dynamically relaxed nature of fossil groups has influenced the AGN activity in their dominant galaxy.

  5. Fermi Large Area Telescope Detection of Extended Gamma-Ray Emission from the Radio Galaxy Fornax A

    CERN Document Server

    ,

    2016-01-01

    We report the Fermi Large Area Telescope detection of extended gamma-ray emission from the lobes of the radio galaxy Fornax A using 6.1 years of Pass 8 data. After Centaurus A, this is now the second example of an extended gamma-ray source attributed to a radio galaxy. Both an extended flat disk morphology and a morphology following the extended radio lobes were preferred over a point-source description, and the core contribution was constrained to be 100 MeV gamma-ray emission established, we model the source broadband emission considering currently available total lobe radio and millimeter flux measurements, as well as X-ray detections attributed to inverse Compton (IC) emission off the cosmic microwave background (CMB). Unlike the Centaurus A case, we find that a leptonic model involving IC scattering of CMB and extragalactic background light (EBL) photons underpredicts the gamma-ray fluxes by factors of about ~ 2 - 3, depending on the EBL model adopted. An additional gamma-ray spectral component is thus ...

  6. The AGN Population in Nearby Galaxies

    NARCIS (Netherlands)

    Filho, Mercedes; Barthel, Peter; Ho, Luis

    2006-01-01

    In order to determine the incidence of black hole accretion-driven nuclear activity in nearby galaxies, we have compiled radio data for the LINERs, composite LINER,/Hn and Seyfert galaxies from a complete magnitude-limited sample of bright nearby galaxies (Palomar sample). Our results show an overal

  7. A Tale of Two Narrow-Line Regions: Ionization, Kinematics, and Spectral Energy Distributions for a Local Pair of Merging Obscured Active Galaxies

    CERN Document Server

    Hainline, Kevin N; Chen, Chien-Ting; Carroll, Christopher M; Jones, Mackenzie L; Zervos, Alexandros S; Goulding, Andrew D

    2016-01-01

    We explore the gas ionization and kinematics, as well as the optical--IR spectral energy distributions for UGC 11185, a nearby pair of merging galaxies hosting obscured active galactic nuclei (AGNs), also known as SDSS J181611.72+423941.6 and J181609.37+423923.0 (J1816NE and J1816SW, $z \\approx 0.04$). Due to the wide separation between these interacting galaxies ($\\sim 23$ kpc), observations of these objects provide a rare glimpse of the concurrent growth of supermassive black holes at an early merger stage. We use BPT line diagnostics to show that the full extent of the narrow line emission in both galaxies is photoionized by an AGN and confirm the existence of a 10-kpc-scale ionization cone in J1816NE, while in J1816SW the AGN narrow-line region is much more compact (1--2 kpc) and relatively undisturbed. Our observations also reveal the presence of ionized gas that nearly spans the entire distance between the galaxies which is likely in a merger-induced tidal stream. In addition, we carry out a spectral an...

  8. Effects of collisions and interactions on star formation in galaxy pairs in the field

    OpenAIRE

    Perez, Josefa; Tissera, Patricia B.; Lambas, Diego G.

    2005-01-01

    By using cosmological simulations, we studied the effects of galaxy interactionson the star formation activity in the local Universe. We selected galaxy pairs from the 3D galaxy distribution according to a proximity criterion. The 2D galaxy catalog was constructed by projecting the 3D total galaxy distribution and then selecting projected galaxy pairs. The analysis of the 3D galaxy pair catalog showed that an enhancement of the star formation activity can be statistically correlated with prox...

  9. Disk Galaxies and Galaxy Disks

    CERN Document Server

    Funes, J G

    2000-01-01

    The conference Galaxy Disks and Disk Galaxies, sponsored by the Vatican Observatory, was held in June 12-16, 2000 at the Pontifical Gregorian University, in Rome (Italy). The meeting hosted about 230 participants coming from 30 countries. The very full program consisted of 29 review papers, 34 invited talks, and more than 180 posters. The meeting covered topics regarding the structure, formation and evolution of galaxies with disks. Particular attention was dedicated to the stellar and gaseous disk of the Milky Way, the global characteristics of galaxy disks, their structure, morphology and dynamics, the gaseous components, star formation, and chemical evolution, the interactions, accretion, mergers and starbursts, the dark and luminous matter, the establishment of the scaling laws, and the formation and evolution of disk galaxies from a theoretical and observational point of view.

  10. Hubble Space Telescope Imaging of Globular Cluster Candidates in Low Surface Brightness Dwarf Galaxies

    CERN Document Server

    Sharina, M E; Makarov, D I; Sharina, Margarita E.; Puzia, Thomas H.; Makarov, Dmitry I.

    2005-01-01

    Fifty-seven nearby low surface brightness dwarf galaxies were searched for globular cluster candidates (GCCs) using Hubble Space Telescope WFPC2 imaging in V and I. The sample consists of 18 dwarf spheroidal (dSph), 36 irregular (dIrr), and 3 "transition" type (dIrr/dSph) galaxies with angular sizes less than 3.7 kpc situated at distances 2-6 Mpc in the field and in the nearby groups: M81, Centaurus A, Sculptor, Canes Venatici I cloud. We find that ~50% of dSph, dIrr/dSph, and dIrr galaxies contain GCCs. The fraction of GCCs located near the center of dwarf spheroidal galaxies is >2 times higher than that for dIrrs. The mean integral color of GCCs in dSphs, V-I = 1.04+/-0.16 mag, coincides with the corresponding value for Galactic globular clusters and is similar to the blue globular cluster sub-populations in massive early-type galaxies. The color distribution for GCCs in dIrrs shows a clear bimodality with peaks near V-I = 0.5 and 1.0 mag. Blue GCCs are presumably young with ages t -6.5 mag in both dSph an...

  11. Chandra X-Ray and Hubble Space Telescope Imaging of Optically Selected Kiloparsec-scale Binary Active Galactic Nuclei. II. Host Galaxy Morphology and AGN Activity

    Science.gov (United States)

    Shangguan, Jinyi; Liu, Xin; Ho, Luis C.; Shen, Yue; Peng, Chien Y.; Greene, Jenny E.; Strauss, Michael A.

    2016-05-01

    Binary active galactic nuclei (AGNs) provide clues to how gas-rich mergers trigger and fuel AGNs and how supermassive black hole (SMBH) pairs evolve in a gas-rich environment. While significant effort has been invested in their identification, the detailed properties of binary AGNs and their host galaxies are still poorly constrained. In a companion paper, we examined the nature of ionizing sources in the double nuclei of four kiloparsec-scale binary AGNs with redshifts between 0.1 and 0.2. Here, we present their host galaxy morphology based on F336W (U-band) and F105W (Y-band) images taken by the Wide Field Camera 3 on board the Hubble Space Telescope. Our targets have double-peaked narrow emission lines and were confirmed to host binary AGNs with follow-up observations. We find that kiloparsec-scale binary AGNs occur in galaxy mergers with diverse morphological types. There are three major mergers with intermediate morphologies and a minor merger with a dominant disk component. We estimate the masses of the SMBHs from their host bulge stellar masses and obtain Eddington ratios for each AGN. Compared with a representative control sample drawn at the same redshift and stellar mass, the AGN luminosities and Eddington ratios of our binary AGNs are similar to those of single AGNs. The U ‑ Y color maps indicate that clumpy star-forming regions could significantly affect the X-ray detection of binary AGNs, e.g., the hardness ratio. Considering the weak X-ray emission in AGNs triggered in merger systems, we suggest that samples of X-ray-selected AGNs may be biased against gas-rich mergers. Based, in part, on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program number GO 12363.

  12. High redshift radio galaxies

    CERN Document Server

    Fosbury, R A E

    2000-01-01

    There is considerable evidence that powerful radio quasars and radio galaxies are orientation-dependent manifestations of the same parent population: massive spheroids containing correspondingly massive black holes. Following the recognition of this unification, research is directed to the task of elucidating the structure and composition of the active nuclei and their hosts to understand the formation and evolution of what we expect to become the most massive of galaxies. In contrast to the quasars, where the nucleus can outshine the galaxy at optical/near infrared wavelengths by a large factor, the radio galaxies contain a 'built-in coronograph' that obscures our direct view to the nucleus. These objects present our best opportunity to study the host galaxy in detail. Of particular interest are those sources with redshifts greater than about 2 that represent an epoch when nuclear activity was much more common that it is now and when we believe these objects were in the process of assembly. In combination wi...

  13. Chandra and MMT observations of low-mass black hole active galactic nuclei accreting at low rates in dwarf galaxies

    CERN Document Server

    Yuan, W; Dou, L; Dong, X -B; Fan, X; Wang, T -G

    2014-01-01

    We report on Chandra X-ray observations of four candidate low-mass black hole (<10^6Msun) active galactic nuclei (AGNs) that have the estimated Eddington ratios among the lowest (~10^(-2)) found for this class. The aims are to validate the nature of their AGNs and to confirm the low Eddington ratios that are derived from the broad H_alpha line, and to explore this poorly studied regime in the AGN parameter space. Among them, two objects with the lowest significance of the broad lines are also observed with Multi-Mirror Telescope, and the high-quality optical spectra taken confirm them as Seyfert 1 AGNs and as having small black hole masses. X-ray emission is detected from the nuclei of two of the galaxies, which is variable on timescales of 10^3s, whereas no significant (or only marginal at best) detection is found for the remaining two. The X-ray luminosities are on the order of 10^(41) ergs/s or even lower, on the order of 10^(40) ergs/s for non-detections, which are among the lowest regimes ever probed ...

  14. Probing Spectroscopic Variability of Galaxies & Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey

    CERN Document Server

    Yip, Ching-Wa; Berk, Daniel Vanden; Scranton, Ryan; Krughoff, Simon; Szalay, Alex; Dobos, Laszlo; Tremonti, Christy; Taghizadeh-Popp, Manuchehr; Budavari, Tamas; Csabai, Istvan; Wyse, Rosemary; Ivezic, Zeljko

    2008-01-01

    Under the unified model for active galactic nuclei (AGNs), narrow-line (Type 2) AGNs are, in fact, broad-line (Type 1) AGNs but each with a heavily obscured accretion disk. We would therefore expect the optical continuum emission from Type 2 AGN to be composed mainly of stellar light and non-variable on the time-scales of months to years. In this work we probe the spectroscopic variability of galaxies and narrow-line AGNs using the multi-epoch data in the Sloan Digital Sky Survey (SDSS) Data Release 6. The sample contains 18,435 sources for which there exist pairs of spectroscopic observations (with a maximum separation in time of ~700 days) covering a wavelength range of 3900-8900 Angstrom. To obtain a reliable repeatability measurement between each spectral pair, we consider a number of techniques for spectrophotometric calibration resulting in an improved spectrophotometric calibration of a factor of two. From these data we find that on average the spectroscopic variability of the continuum for narrow-line...

  15. Do Radio-loud Active Galactic Nuclei really follow the same MBH-σ* Relation as Normal Galaxies?

    Institute of Scientific and Technical Information of China (English)

    Yi Liu; Dong-Rong Jiang

    2006-01-01

    In an examination of the relationship between the black hole mass MBH and stellar velocity dispersion σ* in radio-loud active galactic nuclei (AGNs), we studied two effects which may cause uncertainties in the black hole mass estimates of radio-loud AGNs: the relativistic beaming effect on the observed optical continuum radiation and the orientation effect on the broad emission line width. After correcting these two effects, we re-examined the MBH-σ[OⅢ] relation for a sample of radio-loud and radio-quiet AGNs, and found the relation for radio-loud AGNs still deviated from that for nearby normal galaxies and radio-quiet AGNs. We also found there is no significant correlation between radio jet power and narrow [OⅢ] line width, indicating absence of strong interaction between radio jet and narrow line region. It may be that the deviation of the MBH- σ* relation of radio-loud AGNs is intrinsic,or that the [OⅢ] line width is not a good indicator of σ* for radio-loud AGNs.

  16. Resonance scattering, absorption and off-centre abundance peaks in clusters of galaxies

    CERN Document Server

    Sanders, J S

    2006-01-01

    A possible explanation for the central abundance dips found from spatially-resolved X-ray spectroscopy of several groups and clusters of galaxies is resonance scattering. A number of the prominent iron emission lines are resonance lines. We construct a unique spectral model which takes account of resonance scattering for several thousand resonance lines, projection effects, photoelectric absorption, and allows direct spectral fitting. We apply our model to Chandra observations of two clusters with pronounced central abundance dips, Centaurus and Abell 2199. The results show that the effect of resonance scattering on emission from the centre of the cluster can be as much as 30 per cent for the Fe-K resonance lines, and 10 per cent for several Fe-L lines, if turbulence is low. The change to the metallicities obtained by fitting low resolution CCD spectra is at most 10 per cent. Accounting for resonance scattering does not remove the central dip. Allowing for internal absorption within the Centaurus significantl...

  17. The nature of the ISM in galaxies during the star-formation activity peak of the Universe

    CERN Document Server

    Popping, G; Spaans, M; Trager, S C; Somerville, R S

    2013-01-01

    We combine a semi-analytic model of galaxy formation, which tracks atomic and molecular phases of cold gas, with a three-dimensional radiative-transfer and line tracing code to study the sub-mm emission from several atomic and molecular species (CO, HCN, C, C+, [OI]) in galaxies. We aim to understand if the physics that drives the formation of stars at the epoch of peak star formation in the Universe is similar to or different from that in local galaxies. We find that normal star-forming galaxies at high redshift have much higher CO-excitation peaks than their local counterparts, higher HCN/CO ratios and that CO cooling predominantly takes place through molecules with higher excitation levels. We find an increase in the ratio between [OI] and [CII] in typical star-forming galaxies at z = 1.2 and z = 2.0 with respect to counterparts at z = 0. All our model results suggest that typical star-forming galaxies at high redshift consist of much denser and warmer star-forming clouds than their local counterparts and ...

  18. HST/ACS Observations of Star Formation Driven Outflows in Nearby Edge-on Spiral Galaxies: Dependence of Halo Morphology on Star Formation Activity

    CERN Document Server

    Rossa, Joern; Dettmar, Ralf-Juergen; van der Marel, Roeland P

    2008-01-01

    (Abridged). We present new high spatial resolution narrowband imaging observations of extraplanar diffuse ionized gas (eDIG) in four late-type, actively star forming edge-on spirals, obtained with ACS on-board HST. Our F658N (H-alpha) observations reveal a multitude of structures on both small and large scales. Whereas all four galaxies have been studied with ground-based telescopes before, here the small scale structure of the extended emission line gas is presented for the first time at a spatial resolution of 0.05", corresponding to 5.0 pc at the mean distance to the target galaxies. The eDIG morphology is very different for all four targets, probably as a result of their different levels of star formation activity. We find that the morphology of the eDIG, in particular the break-up of diffuse emission into filaments in galaxy halos, shows a strong dependence on the level of star formation activity per unit area, and eDIG can be arranged into a morphological sequence. NGC4634 and NGC5775 have the highest S...

  19. Model of a black hole gas submitted to background gravitational field for active galaxy nuclei with application to calculating the continuous emission spectra of massless particles (Photons: neutrinos and gravitons)

    International Nuclear Information System (INIS)

    A new theoretical model for active galaxy nuclei which describes the continuous spectrum of rest massless particles (photons, neutrinos and gravitons) in the frequency range from radiofrequency to gamma ray frequency, is presented. The model consists in a black hole gas interacting with a background gravitacional field. The previously models proposed for active galaxy nuclei are exposured. Whole theoretical fundaments based on Einstein general relativity theory for defining and studying singularity properties (black holes) are also presented. (M.C.K.)

  20. The dusty heart of nearby active galaxies. I. High-spatial resolution mid-IR spectro-photometry of Seyfert galaxies

    CERN Document Server

    Hoenig, S F; Gandhi, P; Smette, A; Asmus, D; Duschl, W; Polletta, M; Weigelt, G

    2010-01-01

    We present 8-13 micron imaging and spectroscopy of 9 type 1 and 10 type 2 AGN obtained with the VLT/VISIR instrument at spatial resolution <100 pc. The emission from the host galaxy sources is resolved out in most cases. The silicate absorption features are moderately deep and emission features are shallow. We compare the mid-IR luminosities to AGN luminosity tracers and found that the mid-IR radiation is emitted quite isotropically. In two cases, IC5063 and MCG-3-34-64, we find evidence for extended dust emission in the narrow-line region. We confirm the correlation between observed silicate feature strength and Hydrogen column density recently found in Spitzer data. In a further step, our 3D clumpy torus model has been used to interpret the data. We show that the strength of the silicate feature and the mid-IR spectral index can be used to get reasonable constraints on the dust distribution in the torus. The mid-IR spectral index, alpha, is almost exclusively determined by the radial dust distribution po...

  1. Galaxies & the universe

    CERN Document Server

    Homer, Charlene

    2007-01-01

    Get the big picture about Galaxies and our Universe. From the smallest particles of matter to the biggest star system, our universe is made up of all things that exist in space. Our resource takes you through the Milky Way Galaxy, Black Holes and Gravity, then on to Nebulae, Sources of Light and the Speed of Light, and finally to Quasars, the most distant objects in the universe. Written using simplified language and vocabulary, our resource presents science concepts in a way that makes them accessible to students and easier to understand. Comprised of reading passages, student activities for

  2. Hidden activity in high-redshift spheroidal galaxies from mid-infrared and X-ray observations in the GOODS-North field

    CERN Document Server

    Rodighiero, G; Civano, F; Comastri, A; Franceschini, A; Mignoli, M; Fritz, J; Vignali, C; Treu, T

    2007-01-01

    We exploit very deep mid-IR (MIR) and X-ray observations by Spitzer and Chandra in the GOODS North to identify signs of hidden (either starburst or AGN) activity in spheroidal galaxies between z~0.3 and 1. Our reference is a complete sample of 168 morphologically classified spheroidal galaxies with z[AB]<22.5 selected from GOODS ACS imaging. Nineteen of these have 24 micron detections in the GOODS catalogue, half of which have an X-ray counterpart in the 2 Ms Chandra catalogue, while about 25% have 1.4 GHz fluxes larger than 40 microJy. Traces of hidden activity in the spheroidal population are also searched for in the deep X-ray images and 14 additional galaxies are detected in X-rays only. The nature of the observed MIR emissions is investigated by modelling their SEDs based on the available multi-wavelength photometry, including X-ray, UV, optical, near-IR, MIR and radio fluxes, and optical spectroscopy. The amount of dust derived from the IR emission observed by Spitzer appears in excess of that expect...

  3. ACTIVE GALACTIC NUCLEI AS MAIN CONTRIBUTORS TO THE ULTRAVIOLET IONIZING EMISSIVITY AT HIGH REDSHIFTS: PREDICTIONS FROM A {Lambda}-CDM MODEL WITH LINKED AGN/GALAXY EVOLUTION

    Energy Technology Data Exchange (ETDEWEB)

    Giallongo, E.; Menci, N.; Fiore, F.; Castellano, M.; Fontana, A.; Grazian, A.; Pentericci, L. [INAF-Osservatorio Astronomico di Roma, via di Frascati 33, I-00040 Monteporzio (Italy)

    2012-08-20

    We have evaluated the contribution of the active galactic nuclei (AGN) population to the ionization history of the universe based on a semi-analytic model of galaxy formation and evolution in the cold dark matter cosmological scenario. The model connects the growth of black holes and of the ensuing AGN activity to galaxy interactions. In the model we have included a self-consistent physical description of the escape of ionizing UV photons; this is based on the blast-wave model for the AGN feedback we developed in a previous paper to explain the distribution of hydrogen column densities in AGNs of various redshifts and luminosities, due to absorption by the host galaxy gas. The model predicts UV luminosity functions for AGNs that are in good agreement with those derived from the observations especially at low and intermediate redshifts (z {approx} 3). At higher redshifts (z > 5), the model tends to overestimate the data at faint luminosities. Critical biases in both the data and in the model are discussed to explain such apparent discrepancies. The predicted hydrogen photoionization rate as a function of redshift is found to be consistent with that derived from the observations. All of the above suggests that we should reconsider the role of the AGNs as the main driver of the ionization history of the universe.

  4. A large population of mid-infrared selected, obscured active galaxies in the Bootes field

    CERN Document Server

    Hickox, R C; Forman, W R; Murray, S S; Brodwin, M; Brown, M J I; Eisenhardt, P R; Stern, D; Kochanek, C S; Eisenstein, D; Cool, R J; Jannuzi, B T; Dey, A; Brand, K; Gorjian, V; Caldwell, N

    2007-01-01

    We identify a population of 640 obscured and 839 unobscured active galactic nuclei (AGNs) at redshifts 0.7~80%. The observed numbers of IRAGNs are comparable to predictions from previous X-ray, optical, and IR luminosity functions, for the given redshifts and IRAC flux limits. We observe a bimodal distribution in R-[4.5] color, suggesting that luminous IR-selected AGNs have either low or significant dust extinction, which may have implications for models of AGN obscuration.

  5. A method for determining AGN accretion phase in field galaxies

    Science.gov (United States)

    Micic, Miroslav; Martinović, Nemanja; Sinha, Manodeep

    2016-09-01

    Recent observations of active galactic nucleus (AGN) activity in massive galaxies (log M*/ M⊙ > 10.4) show the following: (1) at z AGN-hosting galaxies do not show enhanced merger signatures compared with normal galaxies, (2) also at z AGNs are hosted by quiescent galaxies and (3) at z > 1, the percentage of AGNs in star-forming galaxies increases and becomes comparable to the AGN percentage in quiescent galaxies at z ˜ 2. How can major mergers explain AGN activity in massive quiescent galaxies that have no merger features and no star formation to indicate a recent galaxy merger? By matching merger events in a cosmological N-body simulation to the observed AGN incidence probability in the COSMOS survey, we show that major merger-triggered AGN activity is consistent with the observations. By distinguishing between `peak' AGNs (recently merger-triggered and hosted by star-forming galaxies) and `faded' AGNs (merger-triggered a long time ago and now residing in quiescent galaxies), we show that the AGN occupation fraction in star-forming and quiescent galaxies simply follows the evolution of the galaxy merger rate. Since the galaxy merger rate drops dramatically at z AGNs left to be observed are the ones triggered by old mergers that are now in the declining phase of their nuclear activity, hosted by quiescent galaxies. As we go towards higher redshifts, the galaxy merger rate increases and the percentages of `peak' AGNs and `faded' AGNs become comparable.

  6. The star formation history and accretion-disc fraction among the K-type members of the Scorpius-Centaurus OB association

    Science.gov (United States)

    Pecaut, Mark J.; Mamajek, Eric E.

    2016-09-01

    We present results of a spectroscopic survey for new K- and M-type members of Scorpius-Centaurus (Sco-Cen), the nearest OB Association (˜100-200 pc). Using an X-ray, proper motion and colour-magnitude selected sample, we obtained spectra for 361 stars, for which we report spectral classifications and Li and Hα equivalent widths. We identified 156 new members of Sco-Cen, and recovered 51 previously published members. We have combined these with previously known members to form a sample of 493 solar-mass (˜0.7-1.3 M⊙) members of Sco-Cen. We investigated the star formation history of this sample, and re-assessed the ages of the massive main-sequence turn-off and the G-type members in all three subgroups. We performed a census for circumstellar discs in our sample using WISE infrared data and find a protoplanetary disc fraction for K-type stars of 4.4^{+1.6}_{-0.9} per cent for Upper Centaurus-Lupus and Lower Centaurus-Crux at ˜16 Myr and 9.0^{+4.0}_{-2.2} per cent for Upper Scorpius at ˜10 Myr. These data are consistent with a protoplanetary disc e-folding time-scale of ˜4-5 Myr for ˜1 M⊙ stars, twice that previously quoted, but consistent with the Bell et al. revised age scale of young clusters. Finally, we construct an age map of Scorpius-Centaurus which clearly reveals substructure consisting of concentrations of younger and older stars. We find evidence for strong age gradients within all three subgroups. None of the subgroups are consistent with being simple, coeval populations which formed in single bursts, but likely represents a multitude of smaller star formation episodes of hundreds to tens of stars each.

  7. Gaseous Flows in Galaxies

    CERN Document Server

    Combes, F

    2007-01-01

    The gas component plays a major role in the dynamics of spiral galaxies, because of its dissipative character, and its ability to exchange angular momentum with stars in the disk. Due to its small velocity dispersion, it triggers gravitational instabilities, and the corresponding non-axisymmetric patterns produce gravity torques, which mediate these angular momentum exchanges. When a srong bar pattern develops with the same pattern speed all over the disk, only gas inside corotation can flow towards the center. But strong bars are not long lived in presence of gas, and multiple-speed spiral patterns can develop between bar phases, and help the galaxy to accrete external gas flowing from cosmic filaments. The gas is then intermittently driven to the galaxy center, to form nuclear starbursts and fuel an active nucleus. The various time-scales of these gaseous flows are described.

  8. H2 in Galaxies

    CERN Document Server

    Combes, F

    1999-01-01

    The bulk of the molecular gas in spiral galaxies is under the form of cold H2, that does not radiate and is only suspected through tracer molecules, such as CO. All tracers are biased, and in particular H2 could be highly underestimated in low metallicity regions. Our knowledge is reviewed of the H2 content of galaxies, according to their types, environment, or star-forming activities. The HI and CO components are generally well-mixed (spiral arms, vertical distribution), although their radial distributions are radically different, certainly due to radial abundance gradients. The hypothesis of H2 as dark matter is discussed, as well as the implications on galaxy dynamics, or the best perspectives for observational tests.

  9. The SAMI Galaxy Survey: first 1000 galaxies

    OpenAIRE

    Allen, J. T.; Team, the SAMI Galaxy Survey

    2014-01-01

    The Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey is an ongoing project to obtain integral field spectroscopic observations of ~3400 galaxies by mid-2016. Including the pilot survey, a total of ~1000 galaxies have been observed to date, making the SAMI Galaxy Survey the largest of its kind in existence. This unique dataset allows a wide range of investigations into different aspects of galaxy evolution. The first public data from the SAMI Galaxy Survey, consisting o...

  10. Joint evolution of black holes and galaxies

    CERN Document Server

    Colpi, M; Haardt, F

    2006-01-01

    OBSERVATIONAL EVIDENCE FOR SUPERMASSIVE BLACK HOLES Introduction Some Useful Formalism General Considerations Resolved Stellar Dynamics Gas as a Tracer of the Gravitational Potential Tackling the Unresolvable: Reverberation Mapping Scaling Relations for SMBHs Black Hole Demographics The Future JOINT EVOLUTION OF BLACK HOLES AND GALAXIES: OBSERVATIONAL ISSUES Galaxy Activity: Generalities Local Evidence on the Interplay Between the Stellar and Gravitational Origin of AGN Activity The Cosmic History of Galaxy Activity Constraints on the Cosmic Energy Budget Current Observational Programs and Fut

  11. A Revised Age for Upper Scorpius and The Star-Formation History Among the F-Type Members of the Scorpius-Centaurus OB Association

    CERN Document Server

    Pecaut, Mark J; Bubar, Eric J

    2011-01-01

    We present an analysis of the ages and star-formation history of the F-type stars in the Upper Scorpius (US), Upper Centaurus-Lupus (UCL) and Lower Centaurus-Crux (LCC) subgroups of Scorpius-Centaurus (Sco-Cen). We find that 1) our empirical isochrones are consistent with the previously published age-rank of the Sco-Cen subgroups, 2) subgroups LCC and UCL appear to reach the main sequence turn-on at spectral types ~F4 and ~F2, respectively. An analysis of the A-type stars shows US reaching the main sequence at about spectral type ~A3. 3) The median ages for the pre-main sequence members of UCL and LCC are 16 Myr and 17 Myr, respectively, in agreement with previous studies, however we find that 4) Upper Sco is much older than previously thought. The luminosities of the F-type stars in US are typically a factor of ~2.5 less luminous than predicted for a 5 Myr old population for four sets of evolutionary tracks. We re-examine the evolutionary state and isochronal ages for the B-, A-, and G-type Upper Sco members...

  12. The Star-formation History and Accretion-Disk Fraction Among the K-Type Members of the Scorpius-Centaurus OB Association

    CERN Document Server

    Pecaut, Mark J

    2016-01-01

    We present results of a spectroscopic survey for new K- and M-type members of Scorpius-Centaurus (Sco-Cen), the nearest OB Association (~100-200 pc). Using an X-ray, proper motion and color-magnitude selected sample, we obtained spectra for 361 stars, for which we report spectral classifications and Li and Halpha equivalent widths. We identified 156 new members of Sco-Cen, and recovered 51 previously published members. We have combined these with previously known members to form a sample of 493 solar-mass (~0.7-1.3 Msun) members of Sco-Cen. We investigated the star-formation history of this sample, and re-assessed the ages of the massive main-sequence turn-off and the G-type members in all three subgroups. We performed a census for circumstellar disks in our sample using WISE infrared data and find a protoplanetary disk fraction for K-type stars of 4.4$^{+1.6}_{-0.9}$% for Upper Centaurus-Lupus and Lower Centaurus-Crux at ~16 Myr and 9.0$^{+4.0}_{-2.2}$% for Upper Scorpius at ~10 Myr. These data are consisten...

  13. Cosmic Collisions: Galaxy Mergers and Evolution

    Science.gov (United States)

    Trouille, Laura; Willett, Kyle; Masters, Karen; Lintott, Christopher; Whyte, Laura; Lynn, Stuart; Tremonti, Christina A.

    2014-08-01

    Over the years evidence has mounted for a significant mode of galaxy evolution via mergers. This process links gas-rich, spiral galaxies; starbursting galaxies; active galactic nuclei (AGN); post-starburst galaxies; and gas-poor, elliptical galaxies, as objects representing different phases of major galaxy mergers. The post-starburst phase is particularly interesting because nearly every galaxy that evolves from star-forming to quiescent must pass through it. In essence, this phase is a sort of galaxy evolution “bottleneck” that indicates that a galaxy is actively evolving through important physical transitions. In this talk I will present the results from the ‘Galaxy Zoo Quench’ project - using post-starburst galaxies to place observational constraints on the role of mergers and AGN activity in quenching star formation. `Quench’ is the first fully collaborative research project with Zooniverse citizen scientists online; engaging the public in all phases of research, from classification to data analysis and discussion to writing the article and submission to a refereed journal.

  14. Mildly obscured active galaxies and the cosmic X-ray background

    CERN Document Server

    Esposito, Valentino

    2016-01-01

    The diffuse cosmic X-ray background (CXB) is the sum of the emission of discrete sources, mostly massive black-holes accreting matter in active galactic nuclei (AGN). The CXB spectrum differs from the integration of the spectra of individual sources, calling for a large population, undetected so far, of strongly obscured Compton thick AGN. Such objects are predicted by unified models, which attribute most of the AGN diversity to their inclination on the line of sight, and play an important role for the understanding of the growth of black holes in the early Universe. The fraction of obscured AGN at low redshift can be derived from the observed CXB spectrum assuming AGN spectral templates and luminosity functions. We show that high signal-to-noise average hard X-ray spectra, derived from more than a billion seconds of effective exposure time with the Swift/BAT instrument, imply that mildly obscured Compton thin AGN feature a strong reflection and contribute massively to the CXB. A population of Compton thick A...

  15. Active galaxies. A strong magnetic field in the jet base of a supermassive black hole.

    Science.gov (United States)

    Martí-Vidal, Ivan; Muller, Sébastien; Vlemmings, Wouter; Horellou, Cathy; Aalto, Susanne

    2015-04-17

    Active galactic nuclei (AGN) host some of the most energetic phenomena in the universe. AGN are thought to be powered by accretion of matter onto a rotating disk that surrounds a supermassive black hole. Jet streams can be boosted in energy near the event horizon of the black hole and then flow outward along the rotation axis of the disk. The mechanism that forms such a jet and guides it over scales from a few light-days up to millions of light-years remains uncertain, but magnetic fields are thought to play a critical role. Using the Atacama Large Millimeter/submillimeter Array (ALMA), we have detected a polarization signal (Faraday rotation) related to the strong magnetic field at the jet base of a distant AGN, PKS 1830-211. The amount of Faraday rotation (rotation measure) is proportional to the integral of the magnetic field strength along the line of sight times the density of electrons. The high rotation measures derived suggest magnetic fields of at least tens of Gauss (and possibly considerably higher) on scales of the order of light-days (0.01 parsec) from the black hole.

  16. On the origin of X-shaped radio galaxies

    International Nuclear Information System (INIS)

    After a brief, critical review of the leading explanations proposed for the small but important subset of radio galaxies showing an X-shaped morphology (XRGs) we propose a generalized model, based on the jet-shell interaction and spin-flip hypotheses. The most popular scenarios for this intriguing phenomenon invoke either hydrodynamical backflows and over-pressured cocoons or rapid jet reorientations, presumably from the spin-flips of central engines following the mergers of pairs of galaxies, each of which contains a supermassive black hole. We confront these models with a number of key observations, and thus argue that none of the models is capable of explaining the entire range of the salient observational properties of XRGs, although some of the arguments raised in the literature against the spin-flip scenario are probably not tenable. We then propose a new scenario which also involves galactic mergers but would allow the spin of the central engine to maintain its direction. Motivated by detailed multi-band observations of the nearest radio galaxy, Centaurus A, this new model emphasizes the role of the interactions between the jets and the shells of stars and gas that form and rotate around the merged galaxy and can cause temporary deflections of the jets, occasionally giving rise to an X-shaped radio structure. Although each model is likely to be relevant to a subset of XRGs, the bulk of the evidence indicates that most of them are best explained by the jet-shell interaction or spin-flip hypotheses.

  17. On the origin of X-shaped radio galaxies

    Institute of Scientific and Technical Information of China (English)

    Gopal-Krishna; Peter L. Biermann; László (A). Gergely; Paul J. Wiita

    2012-01-01

    After a brief,critical review of the leading explanations proposed for the small but important subset of radio galaxies showing an X-shaped morphology (XRGs) we propose a generalized model,based on the jet-shell interaction and spinflip hypotheses.The most popular scenarios for this intriguing phenomenon invoke either hydrodynamical backflows and over-pressured cocoons or rapid jet reorientations,presumably from the spin-flips of central engines following the mergers of pairs of galaxies,each of which contains a supermassive black hole.We confront these models with a number of key observations,and thus argue that none of the models is capable of explaining the entire range of the salient observational properties of XRGs,although some of the arguments raised in the literature against the spin-flip scenario are probably not tenable.We then propose a new scenario which also involves galactic mergers but would allow the spin of the central engine to maintain its direction.Motivated by detailed multi-band observations of the nearest radio galaxy,Centaurus A,this new model emphasizes the role of the interactions between the jets and the shells of stars and gas that form and rotate around the merged galaxy and can cause temporary deflections of the jets,occasionally giving rise to an X-shaped radio structure.Although each model is likely to be relevant to a subset of XRGs,the bulk of the evidence indicates that most of them are best explained by the jet-shell interaction or spin-flip hypotheses.

  18. 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

    International Nuclear Information System (INIS)

    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 ground-based spectroscopic luminosity measurements at 5100 A. After correcting the luminosities of the AGNs for the contribution from starlight, we re-examine the Hβ R BLR-L relationship. Our best fit for the relationship gives a power-law slope of 0.52 with a range of 0.45-0.59 allowed by the uncertainties. This is consistent with our previous findings, and thus still consistent with the naive assumption that all AGNs are simply luminosity-scaled versions of each other. We discuss various consistency checks relating to the galaxy modeling and starlight contributions, as well as possible systematic errors in the current set of reverberation measurements from which we determine the form of the R BLR-L relationship.

  19. The Biases of Optical Line-Ratio Selection for Active Galactic Nuclei, and the Intrinsic Relationship between Black Hole Accretion and Galaxy Star Formation

    CERN Document Server

    Trump, Jonathan R; Zeimann, Gregory R; Luck, Cuyler; Bridge, Joanna S; Grier, Catherine J; Hagen, Alex; Juneau, Stephanie; Montero-Dorta, Antonio; Rosario, David J; Brandt, W Niel; Ciardullo, Robin; Schneider, Donald P

    2015-01-01

    We use 317,000 emission-line galaxies from the Sloan Digital Sky Survey to investigate line-ratio selection of active galactic nuclei (AGNs). In particular, we demonstrate that "star formation dilution" by HII regions causes a significant bias against AGN selection in low-mass, blue, star-forming, disk-dominated galaxies. This bias is responsible for the observed preference of AGNs among high-mass, green, moderately star-forming, bulge-dominated hosts. We account for the bias and simulate the intrinsic population of emission-line AGNs using a physically-motivated Eddington ratio distribution, intrinsic AGN narrow line region line ratios, a luminosity-dependent Lbol/L[OIII] bolometric correction, and the observed Mbh-sigma relation. These simulations indicate that, in massive (log(M*/Msun) > 10) galaxies, AGN accretion is correlated with specific star formation rate but is otherwise uniform with stellar mass. There is some hint of lower black hole occupation in low-mass (log(M*/Msun) < 10) hosts, although o...

  20. Towards Observational Astronomy of Jets in Active Galaxies from General Relativistic Magnetohydrodynamic Simulations

    Science.gov (United States)

    Anantua, Richard; Roger Blandford, Jonathan McKinney and Alexander Tchekhovskoy

    2016-01-01

    We carry out the process of "observing" simulations of active galactic nuclei (AGN) with relativistic jets (hereafter called jet/accretion disk/black hole (JAB) systems) from ray tracing between image plane and source to convolving the resulting images with a point spread function. Images are generated at arbitrary observer angle relative to the black hole spin axis by implementing spatial and temporal interpolation of conserved magnetohydrodynamic flow quantities from a time series of output datablocks from fully general relativistic 3D simulations. We also describe the evolution of simulations of JAB systems' dynamical and kinematic variables, e.g., velocity shear and momentum density, respectively, and the variation of these variables with respect to observer polar and azimuthal angles. We produce, at frequencies from radio to optical, fixed observer time intensity and polarization maps using various plasma physics motivated prescriptions for the emissivity function of physical quantities from the simulation output, and analyze the corresponding light curves. Our hypothesis is that this approach reproduces observed features of JAB systems such as superluminal bulk flow projections and quasi-periodic oscillations in the light curves more closely than extant stylized analytical models, e.g., cannonball bulk flows. Moreover, our development of user-friendly, versatile C++ routines for processing images of state-of-the-art simulations of JAB systems may afford greater flexibility for observing a wide range of sources from high power BL-Lacs to low power quasars (possibly with the same simulation) without requiring years of observation using multiple telescopes. Advantages of observing simulations instead of observing astrophysical sources directly include: the absence of a diffraction limit, panoramic views of the same object and the ability to freely track features. Light travel time effects become significant for high Lorentz factor and small angles between

  1. Mildly obscured active galaxies and the cosmic X-ray background

    Science.gov (United States)

    Esposito, V.; Walter, R.

    2016-05-01

    Context. The diffuse cosmic X-ray background (CXB) is the sum of the emission of discrete sources, mostly massive black-holes accreting matter in active galactic nuclei (AGN). The CXB spectrum differs from the integration of the spectra of individual sources, calling for a large population, undetected so far, of strongly obscured Compton-thick AGN. Such objects are predicted by unified models, which attribute most of the AGN diversity to their inclination on the line of sight, and play an important role for the understanding of the growth of black holes in the early Universe. Aims: The percentage of strongly obscured Compton-thick AGN at low redshift can be derived from the observed CXB spectrum, if we assume AGN spectral templates and luminosity functions. Methods: We show that high signal-to-noise stacked hard X-ray spectra, derived from more than a billion seconds of effective exposure time with the Swift/BAT instrument, imply that mildly obscured Compton-thin AGN feature a strong reflection and contribute massively to the CXB. Results: A population of Compton-thick AGN larger than that which is effectively detected is not required to reproduce the CXB spectrum, since no more than 6% of the CXB flux can be attributed to them. The stronger reflection observed in mildly obscured AGN suggests that the covering factor of the gas and dust surrounding their central engines is a key factor in shaping their appearance. These mildly obscured AGN are easier to study at high redshift than Compton-thick sources are.

  2. S0 galaxies in Formax

    DEFF Research Database (Denmark)

    Bedregal...[], A. G.; Aragón-Salamanca, A.; Merrifield, M. R.;

    2006-01-01

    Galaxies: elliptical and lenticular, cD: galaxies: kinematics and dynamics Udgivelsesdato: Oct.1......Galaxies: elliptical and lenticular, cD: galaxies: kinematics and dynamics Udgivelsesdato: Oct.1...

  3. Einstein x ray observations of the core of the Shapley Supercluster in northern Centaurus

    Science.gov (United States)

    Breen, Jeffrey; Raychaudhury, Somak; Forman, William; Jones, Christine

    1994-01-01

    We present Einstein x ray observations of the core of the Shapley Supercluster, one of the richest and densest known mass concentrations in the local (z less than 0.1) universe. We used Imaging Proportional Counter (IPC) observations supplemented with data from the Einstein Slew Survey to determine the locations and structure of mass concentrations in the region. An x ray map composed of IPC observations of the central (10 deg x 10 deg) region of the Shapley Supercluster is presented. We present evidence that the X-ray clusters observed within 5 deg of the core of the supercluster are on average brighter than those of corresponding richness class distributed throughout the sky. However, we measure no significant difference in the galaxy formation efficiency of these cluster of galaxies compared to other, more isolated clusters. We also find one previously uncataloged cluster-sized mass concentration in the core of the Shapley Supercluster. This new cluster, 'SC 1327-312', is relatively x ray bright (F(sub x) = 1.1 + or - 0.2 x 10(exp -11) erg sec(exp -1) cm(exp -2)) and L(sub x) = 1.1 + or - 0.2 x 10(exp 44) erg sec(exp -1) within 10 minutes, assuming z = 0.0477, H(sub 0) = 50, q(sub 0) = 0). As SC 1327-312 lies well within an Abell radius of the richness R = 4 cluster Shapley 8 (A3558), we suggest it may contribute to an artificially high galaxy count and richness classification for shapley 8. From slew data, we estimate an x ray luminosity for Shapley 8 which is just half the mean luminosity of the four other R = 4 clusters observed by the IPC, further suggesting the richness classification to be an overestimate.

  4. Probing the extremes of Seyfert activity BeppoSAX observations of Narrow-Line Seyfert 1 galaxies

    CERN Document Server

    Comastri, A; Leighly, K M; Fiore, F; Guainazzi, M; Matt, G; Stirpe, G M

    1997-01-01

    Results are presented for the first year of observations of a selected sample of Narrow-Line Seyfert 1 galaxies (Ton S 180, RE J1034+396, Ark 564) obtained with the imaging instruments onboard BeppoSAX. These are the first simultaneous broad band (0.1--10 keV) spectra so far obtained for this class of objects.

  5. The Relationship Between Star-formation Activity and Galaxy Structural Properties in CANDELS and a Semi-analytic Model

    CERN Document Server

    Brennan, Ryan; Somerville, Rachel S; Barro, Guillermo; Bluck, Asa F L; Taylor, Edward N; Wuyts, Stijn; Bell, Eric F; Dekel, Avishai; Faber, Sandra; Ferguson, Henry C; Koekemoer, Anton M; Kurczynski, Peter; McIntosh, Daniel H; Newman, Jeffrey A; Primack, Joel

    2016-01-01

    We study the correlation of galaxy structural properties with their location relative to the SFR-M* correlation, also known as the star formation "main sequence" (SFMS), in the CANDELS and GAMA surveys and in a semi-analytic model (SAM) of galaxy formation. We first study the distribution of median Sersic index, effective radius, star formation rate (SFR) density and stellar mass density in the SFR-M* plane. We then define a redshift dependent main sequence and examine the medians of these quantities as a function of distance from this main sequence, both above (higher SFRs) and below (lower SFRs). Finally, we examine the distributions of distance from the main sequence in bins of these quantities. We find strong correlations between all of these galaxy structural properties and the distance from the SFMS, such that as we move from galaxies above the SFMS to those below it, we see a nearly monotonic trend towards higher median Sersic index, smaller radius, lower SFR density, and higher stellar density. In the...

  6. Green galaxies in the COSMOS field

    CERN Document Server

    Pan, Zhizheng; Fan, Lulu

    2013-01-01

    We present a research of morphologies, spectra and environments of $\\approx$ 2350 "green valley" galaxies at $0.20.7$. At $z<0.7$, the fractions of $M_{\\ast}<10^{10.0}M_{\\sun}$ green galaxies located in dense environment are found to be significantly larger than those of blue galaxies. The morphological and spectral properties of green galaxies are consistent with the transiting population between blue cloud and red sequence. The possible mechanisms for quenching star formation activities in green galaxies are discussed. The importance of AGN feedback cannot be well constrained in our study. Finally, our findings suggest that environment conditions, most likely starvation and harassment, significantly affect the transformation of $M_{\\ast}<10^{10.0}M_{\\sun}$ blue galaxies into red galaxies, especially at $z<0.5$.

  7. Radio Galaxy Zoo: host galaxies and radio morphologies derived from visual inspection

    Science.gov (United States)

    Banfield, J. K.; Wong, O. I.; Willett, K. W.; Norris, R. P.; Rudnick, L.; Shabala, S. S.; Simmons, B. D.; Snyder, C.; Garon, A.; Seymour, N.; Middelberg, E.; Andernach, H.; Lintott, C. J.; Jacob, K.; Kapińska, A. D.; Mao, M. Y.; Masters, K. L.; Jarvis, M. J.; Schawinski, K.; Paget, E.; Simpson, R.; Klöckner, H.-R.; Bamford, S.; Burchell, T.; Chow, K. E.; Cotter, G.; Fortson, L.; Heywood, I.; Jones, T. W.; Kaviraj, S.; López-Sánchez, Á. R.; Maksym, W. P.; Polsterer, K.; Borden, K.; Hollow, R. P.; Whyte, L.

    2015-11-01

    We present results from the first 12 months of operation of Radio Galaxy Zoo, which upon completion will enable visual inspection of over 170 000 radio sources to determine the host galaxy of the radio emission and the radio morphology. Radio Galaxy Zoo uses 1.4 GHz radio images from both the Faint Images of the Radio Sky at Twenty Centimeters (FIRST) and the Australia Telescope Large Area Survey (ATLAS) in combination with mid-infrared images at 3.4 μm from the Wide-field Infrared Survey Explorer (WISE) and at 3.6 μm from the Spitzer Space Telescope. We present the early analysis of the WISE mid-infrared colours of the host galaxies. For images in which there is >75 per cent consensus among the Radio Galaxy Zoo cross-identifications, the project participants are as effective as the science experts at identifying the host galaxies. The majority of the identified host galaxies reside in the mid-infrared colour space dominated by elliptical galaxies, quasi-stellar objects and luminous infrared radio galaxies. We also find a distinct population of Radio Galaxy Zoo host galaxies residing in a redder mid-infrared colour space consisting of star-forming galaxies and/or dust-enhanced non-star-forming galaxies consistent with a scenario of merger-driven active galactic nuclei (AGN) formation. The completion of the full Radio Galaxy Zoo project will measure the relative populations of these hosts as a function of radio morphology and power while providing an avenue for the identification of rare and extreme radio structures. Currently, we are investigating candidates for radio galaxies with extreme morphologies, such as giant radio galaxies, late-type host galaxies with extended radio emission and hybrid morphology radio sources.

  8. Making galaxies passive: Insights from resolved studies of nearby galaxies

    OpenAIRE

    Querejeta, Miguel

    2016-01-01

    The rapid suppression of star formation, or quenching, is thought to be an important process in the evolution of the most massive galaxies, but the mechanisms involved are still hotly debated. Here, we consider two agents that control star formation and can ultimately lead to its suppression: AGN feedback and galaxy mergers. In the first part of the thesis, we study the interplay between stellar structure, nuclear activity, and molecular gas in the context of AGN feeding and feedback. We ...

  9. Keck/ESI Long-slit Spectroscopy of SBS 1421+511: A Recoiling Quasar Nucleus in an Active Galaxy Pair?

    Science.gov (United States)

    Sun, Luming; Zhou, Hongyan; Hao, Lei; Jiang, Peng; Ge, Jian; Ji, Tuo; Ma, Jingzhe; Zhang, Shaohua; Shu, Xinwen

    2016-02-01

    We present Keck/Echellette Spectrograph and Imager long-slit spectroscopy of SBS 1421+511, a system consisting of a quasar at z = 0.276 and an extended source 3″ north of the quasar. The quasar shows a blue-skewed profile of Balmer broad emission lines, which can be well modeled as emissions from a circular disk with a blueshift velocity of ˜1400 km s-1. The blueshift is better interpreted as resulting from a recoiling active black hole than from a super-massive black hole binary, since the line profile almost kept steady for over one decade in the quasar rest frame. Alternative interpretations are possible as well, such as emissions from a bipolar outflow or a circular disk with spiral emissivity perturbations. The extended source shows Seyfert-like narrow-line ratios and a [O iii] luminosity of \\gt 1.4× {10}8{L}⊙ , with almost the same redshift as the quasar and a projected distance of 12.5 kpc at the redshift. SBS 1421+511 is thus likely to be an interacting galaxy pair with a dual active galactic nucleus. Alternatively, the quasar companion only appears to be active but not necessarily so: the gas before/in/behind the companion galaxy is illuminated by the quasar as an extended emission-line region is detected at a similar distance in the opposite direction southern to the quasar, which may be generated either by tidal interactions between the galaxy pair or large-scale outflows from the quasar.

  10. HST/ACS Observations of Star Formation Driven Outflows in Nearby Edge-on Spiral Galaxies: Dependence of Halo Morphology on Star Formation Activity

    OpenAIRE

    Rossa, Joern; Dahlem, Michael; Dettmar, Ralf-Juergen; van der Marel, Roeland P.

    2008-01-01

    (Abridged). We present new high spatial resolution narrowband imaging observations of extraplanar diffuse ionized gas (eDIG) in four late-type, actively star forming edge-on spirals, obtained with ACS on-board HST. Our F658N (H-alpha) observations reveal a multitude of structures on both small and large scales. Whereas all four galaxies have been studied with ground-based telescopes before, here the small scale structure of the extended emission line gas is presented for the first time at a s...

  11. Spectral Decomposition of Broad-Line AGNs and Host Galaxies

    CERN Document Server

    Vanden Berk, Daniel E; Yip, C W; Schneider, D P; Connolly, A J; Burton, R E; Jester, S; Hall, P B; Szalay, A S; Brinkmann, J; Berk, Daniel E. Vanden; Shen, Jiajian; Yip, Ching-Wa; Schneider, Donald P.; Connolly, Andrew J.; Burton, Ross E.; Jester, Sebastian; Hall, Patrick B.; Szalay, Alex S.; Brinkmann, John

    2005-01-01

    Using an eigenspectrum decomposition technique, we separate the host galaxy from the broad line active galactic nucleus (AGN) in a set of 4666 spectra from the Sloan Digital Sky Survey (SDSS), from redshifts near zero up to about 0.75. The decomposition technique uses separate sets of galaxy and quasar eigenspectra to efficiently and reliably separate the AGN and host spectroscopic components. The technique accurately reproduces the host galaxy spectrum, its contributing fraction, and its classification. We show how the accuracy of the decomposition depends upon S/N, host galaxy fraction, and the galaxy class. Based on the eigencoefficients, the sample of SDSS broad-line AGN host galaxies spans a wide range of spectral types, but the distribution differs significantly from inactive galaxies. In particular, post-starburst activity appears to be much more common among AGN host galaxies. The luminosities of the hosts are much higher than expected for normal early-type galaxies, and their colors become increasing...

  12. The distribution of satellites around massive galaxies at 1 < z < 3 in ZFOURGE/CANDELS: Dependence on star formation activity

    Energy Technology Data Exchange (ETDEWEB)

    Kawinwanichakij, Lalitwadee; Papovich, Casey; Quadri, Ryan F.; Tran, Kim-Vy H.; Mehrtens, Nicola [George P. and Cynthia W. Mitchell Institute for Fundamental Physics and Astronomy, Department of Physics and Astronomy, Texas A and M University, College Station, TX 77843 (United States); Spitler, Lee R.; Cowley, Michael [Department of Physics and Astronomy, Faculty of Sciences, Macquarie University, Sydney, NSW 2109 (Australia); Kacprzak, Glenn G.; Glazebrook, Karl; Nanayakkara, Themiya [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Labbé, Ivo; Straatman, Caroline M. S. [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands); Allen, Rebecca [Australian Astronomical Observatories, P.O. Box 915, North Ryde, NSW 1670 (Australia); Davé, Romeel [University of the Western Cape, Bellville, Cape Town 7535 (South Africa); Dekel, Avishai [Center for Astrophysics and Planetary Science, Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Ferguson, Henry C.; Koekemoer, Anton M. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Hartley, W. G. [School of Physics and Astronomy, University of Nottingham, Nottingham NG7 2RD (United Kingdom); Koo, David C. [University of California Observatories/Lick Observatory, Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States); Lu, Yu, E-mail: kawinwanichakij@physics.tamu.edu [Kavli Institute for Particle Astrophysics and Cosmology, 452 Lomita Mall, Stanford, CA 94305 (United States); and others

    2014-09-10

    We study the statistical distribution of satellites around star-forming and quiescent central galaxies at 1 < z < 3 using imaging from the FourStar Galaxy Evolution Survey and the Cosmic Assembly Near-IR Deep Extragalactic Legacy Survey. The deep near-IR data select satellites down to log (M/M {sub ☉}) > 9 at z < 3. The radial satellite distribution around centrals is consistent with a projected Navarro-Frenk-White profile. Massive quiescent centrals, log (M/M {sub ☉}) > 10.78, have ∼2 times the number of satellites compared to star-forming centrals with a significance of 2.7σ even after accounting for differences in the centrals' stellar-mass distributions. We find no statistical difference in the satellite distributions of intermediate-mass quiescent and star-forming centrals, 10.48 < log (M/M {sub ☉}) < 10.78. Compared to the Guo et al. semi-analytic model, the excess number of satellites indicates that quiescent centrals have halo masses 0.3 dex larger than star-forming centrals, even when the stellar-mass distributions are fixed. We use a simple toy model that relates halo mass and quenching, which roughly reproduces the observed quenched fractions and the differences in halo mass between star-forming and quenched galaxies only if galaxies have a quenching probability that increases with halo mass from ∼0 for log (M{sub h} /M {sub ☉}) ∼ 11 to ∼1 for log (M{sub h} /M {sub ☉}) ∼ 13.5. A single halo-mass quenching threshold is unable to reproduce the quiescent fraction and satellite distribution of centrals. Therefore, while halo quenching may be an important mechanism, it is unlikely to be the only factor driving quenching. It remains unclear why a high fraction of centrals remain star-forming even in relatively massive halos.

  13. Predictions for imaging and spectroscopic surveys of galaxies and Active Galactic Nuclei in the mid-/far-Infrared

    OpenAIRE

    Bonato, Matteo

    2015-01-01

    While continuum imaging data at far-infrared to sub-millimeter wavelengths have provided tight constraints on the population properties of dusty star-forming galaxies up to high redshifts, future space missions like the Space Infra-Red Telescope for Cosmology and Astrophysics (SPICA) and ground based facilities like the Atacama Large Millimeter/submillimeter Array (ALMA) and the Cerro Chajnantor Atacama Telescope (CCAT) will allow detailed investigations of their physical properties via the...

  14. The discovery of a new ELL variable star in Centaurus and possibility of detecting new exoplanets using the FRAM telescope

    Science.gov (United States)

    Pintr, Pavel; Vápenka, David; Mašek, Martin

    2015-01-01

    We report on the discovery of a new variable star during the search for new exoplanets in the Centaurus constellation from the archive of the FRAM telescope, operated by the FRAM team at Los Leones, near Malargüe, Argentina. The star is catalogued as GSC 08630-01117 (11h 36m 10s -53° 12' 15.04"). From the light curve, the star should be an ELL-type variable. We computed the period P = 0.6311+/- 0.0002 days. The maximum is 13.07 +/- 0.02 mag and minimum is 13.22 +/-0.02 mag (in the Johnson V filter) with an amplitude of about 0.15 mag. We registered this star in the CzeV catalogue and in the VSX catalogue as new variable star CzeV603. The FRAM telescope observed several transits of known exoplanets. These observations show the ability to detect new exoplanets using the FRAM telescope.

  15. New members of the TW Hydrae Association and two accreting M-dwarfs in Scorpius-Centaurus

    CERN Document Server

    Murphy, Simon J; Bento, Joao

    2015-01-01

    We report the serendipitous discovery of several young mid-M stars found during a search for new members of the 30-40 Myr-old Octans Association. Only one of the stars may be considered a possible Octans(-Near) member. However, two stars have proper motions, kinematic distances, radial velocities, photometry and Li I 6708AA measurements consistent with membership in the 8-10 Myr-old TW Hydrae Association. Another may be an outlying member of TW Hydrae but has a velocity similar to that predicted by membership in Octans. We also identify two new lithium-rich members of the neighbouring Scorpius-Centaurus OB Association (Sco-Cen). Both exhibit large 12 and 22 micron excesses and strong, variable H-alpha emission which we attribute to accretion from circumstellar discs. Such stars are thought to be incredibly rare at the ~16 Myr median age of Sco-Cen and they join only one other confirmed M-type and three higher-mass accretors outside of Upper Scorpius. The serendipitous discovery of two accreting stars hosting ...

  16. X-ray Spectroscopy of the High Mass X-ray Binary Pulsar Centaurus X-3 over its Binary Orbit

    CERN Document Server

    Naik, Sachindra; Ali, Zulfikar

    2011-01-01

    We present a comprehensive spectral analysis of the high mass X-ray binary (HMXB) pulsar Centaurus X-3 with the Suzaku observatory covering nearly one orbital period. The light curve shows the presence of extended dips which are rarely seen in HMXBs. These dips are seen up to as high as ~40 keV. The pulsar spectra during the eclipse, out-of-eclipse, and dips are found to be well described by a partial covering power-law model with high energy cut-off and three Gaussian functions for 6.4 keV, 6.7 keV, and 6.97 keV iron emission lines. The dips in the light curve can be explained by the presence of an additional absorption component with high column density and covering fraction, the values of which are not significant during the rest of the orbital phases. The iron line parameters during the dips and eclipse are significantly different compared to those during the rest of the observation. During the dips, the iron line intensities are found to be lesser by a factor of 2--3 with significant increase in the line...

  17. NuSTAR and XMM-Newton Observations of the Hard X-Ray Spectrum of Centaurus A

    DEFF Research Database (Denmark)

    Fürst, F.; Müller, C.; Madsen, K. K.;

    2016-01-01

    We present simultaneous XMM-Newton and NuSTAR observations spanning 3–78 keV of the nearest radiogalaxy, Centaurus A (Cen A), performed during a very high flux state. The accretion geometry around thecentral engine in Cen A is still debated, and we investigate possible configurations using detailed...... X-ray spectralmodeling. NuSTAR imaged the central region of Cen A with subarcminute resolution at X-ray energies above10 keV for the first time, but finds no evidence for an extended source or other off-nuclear point-sources.The XMM-Newton and NuSTAR spectra agree well and can be described with an...... absorbed power-law witha photon index Γ = 1.815 ± 0.005 and a fluorescent Fe Kα line in good agreement with literature values.The spectrum does not require a high-energy exponential rollover, with a constraint of Efold > 1 MeV. Athermal Comptonization continuum describes the data well, with parameters that...

  18. CO excitation in four IR luminous galaxies

    International Nuclear Information System (INIS)

    The correlation between the CO and far infrared luminosities of spiral galaxies is well established. The luminosity ration, L sub FIR/L sub CO in IR luminous active galaxies is, however, systematically five to ten times higher than in ordinary spirals and molecular clouds in our Galaxy. Furthermore, the masses of molecular hydrogen in luminous galaxies are large, M (H2) approx. equals 10(exp 10) solar magnitude, which indicates the observed luminosity ratios are due to an excess of infrared output, rather than a deficiency of molecular gas. These large amounts of molecular gas may fuel luminous galaxies through either star formation or nuclear activity. This interpretation rests on applying the M (H2)/L sub CO ratio calibrated in our Galaxy to galaxies with strikingly different luminosity ratios. But are the physical conditions of the molecular gas different in galaxies with different luminosity ratios. And, if so, does the proportionality between CO and H2 also vary among galaxies. To investigate these questions researchers observed CO (2 to 1) and (1 to 0) emission from four luminous galaxies with the Institute for Radio Astronomy in the Millimeter range (IRAM) 30 m telescope. Researchers conclude that most of the CO emission from these Arp 193, Arp 220, and Mrk 231 arises in regions with moderate ambient densities similar to the clouds in the Milky Way molecular ring. The emission is neither from dense hot cloud cores nor from the cold low density gas characteristic of the envelopes of dark clouds

  19. Broad line emission from iron K- and L-shell transitions in the active galaxy 1H 0707-495.

    Science.gov (United States)

    Fabian, A C; Zoghbi, A; Ross, R R; Uttley, P; Gallo, L C; Brandt, W N; Blustin, A J; Boller, T; Caballero-Garcia, M D; Larsson, J; Miller, J M; Miniutti, G; Ponti, G; Reis, R C; Reynolds, C S; Tanaka, Y; Young, A J

    2009-05-28

    Since the 1995 discovery of the broad iron K-line emission from the Seyfert galaxy MCG-6-30-15 (ref. 1), broad iron K lines have been found in emission from several other Seyfert galaxies, from accreting stellar-mass black holes and even from accreting neutron stars. The iron K line is prominent in the reflection spectrum created by the hard-X-ray continuum irradiating dense accreting matter. Relativistic distortion of the line makes it sensitive to the strong gravity and spin of the black hole. The accompanying iron L-line emission should be detectable when the iron abundance is high. Here we report the presence of both iron K and iron L emission in the spectrum of the narrow-line Seyfert 1 galaxy 1H 0707-495. The bright iron L emission has enabled us to detect a reverberation lag of about 30 s between the direct X-ray continuum and its reflection from matter falling into the black hole. The observed reverberation timescale is comparable to the light-crossing time of the innermost radii around a supermassive black hole. The combination of spectral and timing data on 1H 0707-495 provides strong evidence that we are witnessing emission from matter within a gravitational radius, or a fraction of a light minute, from the event horizon of a rapidly spinning, massive black hole. PMID:19478778

  20. Near-infrared line imaging of the circumnuclear starburst rings in the active galaxies NGC 1097 and NGC 6574

    CERN Document Server

    Kotilainen, J K; Laine, S; Ryder, S D

    1999-01-01

    We present high spatial resolution near-infrared broad-band JHK and Br_gamma 2.166 micron and H_2 1-0 S(1) 2.121 micron emission line images of the circumnuclear star formation rings in the LINER/Seyfert 1 galaxy NGC 1097 and the Seyfert 2 galaxy NGC 6574. We investigate the morphology, extinction, and the star formation properties and history of the rings, by comparing the observed properties with an evolutionary population synthesis model. The clumpy morphology in both galaxies varies strongly with wavelength, due to a combination of extinction, hot dust and red supergiants, and the age of the stellar populations. The near-infrared and radio morphologies are in general agreement, although there are differences in the detailed morphology. From the comparison of Br_gamma and H_alpha fluxes, we derive average extinctions toward the hot spots A_V = 1.3 for NGC 1097 and A_V = 2.1 for NGC 6574. The observed H_2/Br_gamma ratios indicate that in both rings the main excitation mechanism of the molecular gas is UV ra...

  1. The SAMI Galaxy Survey: first 1000 galaxies

    CERN Document Server

    Allen, J T

    2014-01-01

    The Sydney-AAO Multi-object Integral field spectrograph (SAMI) Galaxy Survey is an ongoing project to obtain integral field spectroscopic observations of ~3400 galaxies by mid-2016. Including the pilot survey, a total of ~1000 galaxies have been observed to date, making the SAMI Galaxy Survey the largest of its kind in existence. This unique dataset allows a wide range of investigations into different aspects of galaxy evolution. The first public data from the SAMI Galaxy Survey, consisting of 107 galaxies drawn from the full sample, has now been released. By giving early access to SAMI data for the entire research community, we aim to stimulate research across a broad range of topics in galaxy evolution. As the sample continues to grow, the survey will open up a new and unique parameter space for galaxy evolution studies.

  2. Galaxy-galaxy(-galaxy) lensing as a sensitive probe of galaxy evolution

    Science.gov (United States)

    Saghiha, H.; Hilbert, S.; Schneider, P.; Simon, P.

    2012-11-01

    Context. The gravitational lensing effect provides various ways to study the mass environment of galaxies. Aims: We investigate how galaxy-galaxy(-galaxy) lensing can be used to test models of galaxy formation and evolution. Methods: We consider two semi-analytic galaxy formation models based on the Millennium Run N-body simulation: the Durham model by Bower et al. (2006, MNRAS, 370, 645) and the Garching model by Guo et al. (2011, MNRAS, 413, 101). We generate mock lensing observations for the two models, and then employ Fast Fourier Transform methods to compute second- and third-order aperture statistics in the simulated fields for various galaxy samples. Results: We find that both models predict qualitatively similar aperture signals, but there are large quantitative differences. The Durham model predicts larger amplitudes in general. In both models, red galaxies exhibit stronger aperture signals than blue galaxies. Using these aperture measurements and assuming a linear deterministic bias model, we measure relative bias ratios of red and blue galaxy samples. We find that a linear deterministic bias is insufficient to describe the relative clustering of model galaxies below ten arcmin angular scales. Dividing galaxies into luminosity bins, the aperture signals decrease with decreasing luminosity for brighter galaxies, but increase again for fainter galaxies. This increase is likely an artifact due to too many faint satellite galaxies in massive group and cluster halos predicted by the models. Conclusions: Our study shows that galaxy-galaxy(-galaxy) lensing is a sensitive probe of galaxy evolution.

  3. Galaxy formation.

    Science.gov (United States)

    Peebles, P J

    1998-01-01

    It is argued that within the standard Big Bang cosmological model the bulk of the mass of the luminous parts of the large galaxies likely had been assembled by redshift z approximately 10. Galaxy assembly this early would be difficult to fit in the widely discussed adiabatic cold dark matter model for structure formation, but it could agree with an isocurvature version in which the cold dark matter is the remnant of a massive scalar field frozen (or squeezed) from quantum fluctuations during inflation. The squeezed field fluctuations would be Gaussian with zero mean, and the distribution of the field mass therefore would be the square of a random Gaussian process. This offers a possibly interesting new direction for the numerical exploration of models for cosmic structure formation.

  4. The Densest Galaxy

    Science.gov (United States)

    Strader, Jay; Seth, Anil C.; Forbes, Duncan A.; Fabbiano, Giuseppina; Romanowsky, Aaron J.; Brodie, Jean P.; Conroy, Charlie; Caldwell, Nelson; Pota, Vincenzo; Usher, Christopher; Arnold, Jacob A.

    2013-09-01

    We report the discovery of a remarkable ultra-compact dwarf galaxy around the massive Virgo elliptical galaxy NGC 4649 (M60), which we call M60-UCD1. With a dynamical mass of 2.0 × 108 M ⊙ but a half-light radius of only ~24 pc, M60-UCD1 is more massive than any ultra-compact dwarfs of comparable size, and is arguably the densest galaxy known in the local universe. It has a two-component structure well fit by a sum of Sérsic functions, with an elliptical, compact (rh = 14 pc n ~ 3.3) inner component and a round, exponential, extended (rh = 49 pc) outer component. Chandra data reveal a variable central X-ray source with LX ~ 1038 erg s-1 that could be an active galactic nucleus associated with a massive black hole or a low-mass X-ray binary. Analysis of optical spectroscopy shows the object to be old (gsim 10 Gyr) and of solar metallicity, with elevated [Mg/Fe] and strongly enhanced [N/Fe] that indicates light-element self-enrichment; such self-enrichment may be generically present in dense stellar systems. The velocity dispersion (σ ~ 70 km s-1) and resulting dynamical mass-to-light ratio (M/LV = 4.9 ± 0.7) are consistent with—but slightly higher than—expectations for an old, metal-rich stellar population with a Kroupa initial mass function. The presence of a massive black hole or a mild increase in low-mass stars or stellar remnants is therefore also consistent with this M/LV . The stellar density of the galaxy is so high that no dynamical signature of dark matter is expected. However, the properties of M60-UCD1 suggest an origin in the tidal stripping of a nucleated galaxy with MB ~ -18 to -19.

  5. On Galaxies with UV Excess from Kazarian Lists

    Science.gov (United States)

    Yeghiazaryan, A. A.

    2016-09-01

    Presented are the results of a statistical study of galaxies with UV excess from six Kazarian lists. Morphology, activity, heliocentric redshift and the magnitude of 502 out of 702 galaxies from Kazarian lists were considered. It is shown that these galaxies have different morphological types, different degrees of activity, and often contain condensations and double nuclei. It is also shown that most of the closely located Kazarian galaxies form physical systems.

  6. Formaldehyde Densitometry of Starburst Galaxies

    CERN Document Server

    Mangum, Jeffrey G; Menten, Karl M; Henkel, Christian

    2007-01-01

    With a goal toward deriving the physical conditions in external galaxies, we present a survey of the formaldehyde emission in a sample of starburst systems. By extending a technique used to derive the spatial density in star formation regions in our own Galaxy, we show how the relative intensity of the 1(10)-1(11) and 2(11)-2(12) K-doublet transitions of H2CO can provide an accurate densitometer for the active star formation environments found in starburst galaxies. Relying upon an assumed kinetic temperature and co-spatial emission and absorption from both H2CO transitions, our technique is applied to a sample of nineteen IR-bright galaxies which exhibit various forms of starburst activity. In the five galaxies of our sample where both H2CO transitions were detected we have derived spatial densities. We also use H2CO to estimate the dense gas mass in our starburst galaxy sample, finding similar mass estimates for the dense gas forming stars in these objects as derived using other dense gas tracers. A related...

  7. Elliptical Galaxy Dynamics

    OpenAIRE

    Merritt, David

    1998-01-01

    A review of elliptical galaxy dynamics, with a focus on nonintegrable models. Topics covered include torus construction; modelling axisymmetric galaxies; triaxiality; collisionless relaxation; and collective instabilities.

  8. Effect of bars on the galaxy properties

    CERN Document Server

    Vera, Matias; Coldwell, Georgina

    2016-01-01

    Aims: With the aim of assessing the effects of bars on disc galaxy properties, we present an analysis of different characteristics of spiral galaxies with strong, weak and without bars. Method: We identified barred galaxies from the Sloan Digital Sky Survey. By visual inspection, we classified the face-on spiral galaxies brighter than g<16.5 mag into strong-bar, weak-bar and unbarred. In order to provide an appropiate quantification of the influence of bars on galaxy properties, we also constructed a suitable control sample of unbarred galaxies with similar redshift, magnitude, morphology, bulge sizes, and local density environment distributions to that of barred galaxies. Results: We found 522 strong-barred and 770 weak-barred galaxies, representing a 25.82% of the full sample of spiral galaxies, in good agreement with previous studies. We also found that strong-barred galaxies show less efficient star formation activity and older stellar populations compared to weak-barred and unbarred spirals from the c...

  9. The metal enrichment of passive galaxies in cosmological simulations of galaxy formation

    CERN Document Server

    Okamoto, Takashi; Lacey, Cedric G; Frenk, Carlos S

    2016-01-01

    Massive early-type galaxies have higher metallicities and higher ratios of $\\alpha$ elements to iron than their less massive counterparts. Reproducing these correlations has long been a problem for hierarchical galaxy formation theory, both in semi-analytic models and cosmological hydrodynamic simulations. We show that a simulation in which gas cooling in massive dark haloes is quenched by radio-mode active galactic nuclei (AGNs) feedback naturally reproduces the observed trend between $\\alpha$/Fe and the velocity dispersion of galaxies, $\\sigma$. The quenching occurs earlier for more massive galaxies. Consequently, these galaxies complete their star formation before $\\alpha$/Fe is diluted by the contribution from type Ia supernovae. For galaxies more massive than $\\sim 10^{11}~M_\\odot$ whose $\\alpha$/Fe correlates positively with stellar mass, we find an inversely correlated mass-metallicity relation. This is a common problem in simulations in which star formation in massive galaxies is quenched either by qu...

  10. The Cepheids of Centaurus A (NGC 5128) and Implications for H0

    CERN Document Server

    Majaess, Daniel J

    2010-01-01

    An analysis based on new OGLE observations reaffirms Ferrarese et al.2007 discovery of 5 Type II Cepheids in NGC 5128. The distance to that comparatively unreddened population is d=3.8+-0.4(se)+-0.8(sd) Mpc. The classical Cepheids in NGC 5128 are the most obscured in the extragalactic sample (n=30) surveyed, whereas groups of Cepheids tied to several SNe host galaxies feature negative reddenings. Adopting an anomalous extinction law for Cepheids in NGC 5128 owing to observations of SN 1986G (Rv~2.4) is not favoured, granted SNe Ia may follow small Rv. The distances to classical Cepheids in NGC 5128 exhibit a dependence on colour and CCD chip, which may arise in part from photometric contamination. The mean for the entire sample is d~3.1 Mpc, while applying a colour cut yields d~3.5 Mpc. The distance was established via the latest VI Galactic Wesenheit functions that include the 10 HST calibrators, and which imply a shorter distance scale than Sandage et al.2004 by 15% at P~25 d. HST monitored classical Cephei...

  11. Molecules in galaxies

    CERN Document Server

    Omont, Alain

    2007-01-01

    The main achievements, current developments and prospects of molecular studies in external galaxies are reviewed. They are put in the context of the results of several decades of studies of molecules in local interstellar medium, their chemistry and their importance for star formation. CO observations have revealed the gross structure of molecular gas in galaxies. Together with other molecules, they are among the best tracers of star formation at galactic scales. Our knowledge about molecular abundances in various local galactic environments is progressing. They trace physical conditions and metallicity, and they are closely related to dust processes and large aromatic molecules. Major recent developments include mega-masers, and molecules in Active Galactic Nuclei; millimetre emission of molecules at very high redshift; and infrared H2 emission as tracer of warm molecular gas, shocks and photodissociation regions. The advent of sensitive giant interferometers from the centimetre to sub-millimetre range, espe...

  12. H I observations of strongly interacting galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Gallagher, J.S.; Knapp, G.R.; Faber, S.M.

    1981-12-01

    H I observations of small systems of galaxies in some cases reveal the presence of anomalous, sloping velocity shoulders on the integrated H I line profiles. These are interpreted as evidence for ongoing tidal interactions, most probably associated with galaxies in slow hyperbolic encounters in which extensive transfers of orbital to internal energy can produce extreme noncircular motions. The kinematics of such systems therefore provide a means to identify actively interacting galaxies and a method to probe the energetics of collisions between nonbinary galaxies.

  13. Powerful Activity in the Bright Ages. I. A Visible/IR Survey of High Redshift 3C Radio Galaxies and Quasars

    CERN Document Server

    Hilbert, Bryan; Kotyla, JohnPaul; Tremblay, Grant R; Stanghellini, Carlo; Sparks, William B; Baum, Stefi A; Capetti, Alessandro; Macchetto, F Duccio; Miley, George K; O'Dea, Christopher P; Perlman, Eric S; Quillen, Alice C

    2016-01-01

    We present new rest frame UV and visible observations of 22 high-redshift (1 < z < 2.5) 3C radio galaxies and QSOs obtained with the Hubble Space Telescope's (HST) Wide Field Camera 3 (WFC3) instrument. Using a custom data reduction strategy in order to assure the removal of cosmic rays, persistence signal, and other data artifacts, we have produced high-quality science-ready images of the targets and their local environments. We observe targets with regions of UV emission suggestive of active star formation. In addition, several targets exhibit highly distorted host galaxy morphologies in the rest frame visible images. Photometric analyses reveals that brighter QSOs tend to be generally redder than their dimmer counterparts. Using emission line fluxes from the literature, we estimate that emission line contamination is relatively small in the rest frame UV images for the QSOs. Using archival VLA data, we have also created radio map overlays for each of our targets, allowing for analysis of the optical ...

  14. X-ray bright active galactic nuclei in massive galaxy clusters III: New insights into the triggering mechanisms of cluster AGN

    CERN Document Server

    Ehlert, S; Brandt, W N; Canning, R E A; Luo, B; Mantz, A; Morris, R G; von der Linden, A; Xue, Y Q

    2014-01-01

    We present the results of a new analysis of the X-ray selected Active Galactic Nuclei (AGN) population in the vicinity of 135 of the most massive galaxy clusters in the redshift range of 0.2 < z < 0.9 observed with Chandra. With a sample of more than 11,000 X-ray point sources, we are able to measure, for the first time, evidence for evolution in the cluster AGN population beyond the expected evolution of field AGN. Our analysis shows that overall number density of cluster AGN scales with the cluster mass as $\\sim M_{500}^{-1.2}$. There is no evidence for the overall number density of cluster member X-ray AGN depending on the cluster redshift in a manner different than field AGN, nor there is any evidence that the spatial distribution of cluster AGN (given in units of the cluster overdensity radius r_500) strongly depends on the cluster mass or redshift. The $M^{-1.2 \\pm 0.7}$ scaling relation we measure is consistent with theoretical predictions of the galaxy merger rate in clusters, which is expected ...

  15. Spectropolarimetric monitoring of active galaxy 3C390.3 with 6m telescope SAO RAS in the period 2009-2014

    CERN Document Server

    Afanasiev, V L; Popovic, L C; Borisov, N V

    2015-01-01

    Here we present the spectropolarimetric observations of the radio loud active galaxy 3C 390.3 in the period 2009-2014 (24 epochs). The galaxy has been observed with the 6-meter telescope of SAO RAS using the SCORPIO spectropolarimeter. We explore the variability and lags in the polarized light of the continuum and broad H$\\alpha$ line. We give the Stokes parameters $Q, U$, degree of linear polarization $P$ and the position angle of the polarization plane, $\\varphi$, for 24 epochs. We find a small lag~(10-40 days) between the unpolarized and polarized continuum that is significantly smaller than the estimated lags for the unpolarized broad emission lines (lag(H$\\alpha$)$\\sim$138-186 and lag(H$\\beta$)$\\sim$60-79 days). This shows that the region of the variable polarized continuum is significantly smaller than the broad line region, indicating that a part of the polarized continuum is coming from the jet. The lag of the polarized light in the H$\\alpha$ line (89-156 days) indicates an additional component to the...

  16. Rapid and multi-band variability of the TeV-bright active nucleus of the galaxy IC 310

    CERN Document Server

    Aleksić, J; Antoranz, P; Babic, A; de Almeida, U Barres; Barrio, J A; González, J Becerra; Bednarek, W; Berger, K; Bernardini, E; Biland, A; Blanch, O; Bock, R K; Boller, A; Bonnefoy, S; Bonnoli, G; Tridon, D Borla; Borracci, F; Bretz, T; Carmona, E; Carosi, A; Fidalgo, D Carreto; Colin, P; Colombo, E; Contreras, J L; Cortina, J; Cossio, L; Covino, S; Da Vela, P; Dazzi, F; De Angelis, A; De Caneva, G; Mendez, C Delgado; De Lotto, B; Doert, M; Domínguez, A; Prester, D Dominis; Dorner, D; Doro, M; Eisenacher, D; Elsaesser, D; Farina, E; Ferenc, D; Fonseca, M V; Font, L; Fruck, C; López, R J García; Garczarczyk, M; Terrats, D Garrido; Gaug, M; Giavitto, G; Godinović, N; Muñoz, A González; Gozzini, S R; Hadamek, A; Hadasch, D; Häfner, D; Herrero, A; Hose, J; Hrupec, D; Idec, W; Kadenius, V; Knoetig, M L; Krähenbühl, T; Krause, J; Kushida, J; La Barbera, A; Lelas, D; Lewandowska, N; Lindfors, E; Lombardi, S; López-Coto, R; López, M; López-Oramas, A; Lorenz, E; Lozano, I; Makariev, M; Mallot, K; Maneva, G; Mankuzhiyil, N; Mannheim, K; Maraschi, L; Marcote, B; Mariotti, M; Martínez, M; Masbou, J; Mazin, D; Meucci, M; Miranda, J M; Mirzoyan, R; Moldón, J; Moralejo, A; Munar-Adrover, P; Nakajima, D; Niedzwiecki, A; Nilsson, K; Nowak, N; Orito, R; Overkemping, A; Paiano, S; Palatiello, M; Paneque, D; Paoletti, R; Paredes, J M; Partini, S; Persic, M; Prada, F; Moroni, P G Prada; Prandini, E; Preziuso, S; Puljak, I; Reichardt, I; Reinthal, R; Rhode, W; Ribó, M; Rico, J; Rügamer, S; Saggion, A; Saito, K; Saito, T Y; Salvati, M; Satalecka, K; Scalzotto, V; Scapin, V; Schultz, C; Schweizer, T; Shore, S N; Sillanpää, A; Sitarek, J; Snidaric, I; Sobczynska, D; Spanier, F; Spiro, S; Stamatescu, V; Stamerra, A; Steinke, B; Storz, J; Sun, S; Surić, T; Takalo, L; Takami, H; Tavecchio, F; Temnikov, P; Terzić, T; Tescaro, D; Teshima, M; Thaele, J; Tibolla, O; Torres, D F; Toyama, T; Treves, A; Uellenbeck, M; Vogler, P; Wagner, R M; Weitzel, Q; Zandanel, F; Zanin, R; Dauser, T; Fortin, P; Kadler, M; Krauß, F; Wilbert, S; Wilms, J; Dr-Karl-Remeis-Observatory,; Physics, Erlangen Centre for Astroparticle; Bamberg, 96049; Germany,; Observatory, Fred Lawrence Whipple; Astrophysics, Harvard-Smithsonian Center for; Amado,; 85645, AZ; USA),

    2013-01-01

    Context. The galaxy IC 310 has recently been identified as a $\\gamma$-ray emitter by the Fermi-LAT and at very high energies by the MAGIC telescopes. Originally classified as a head-tail radio galaxy, the nature of this object is subject of controversy because its nucleus shows blazar-like behavior. Aims. In order to understand the nature of IC 310 and the origin of the VHE emission we studied the spectral and flux variability of IC 310 from the X-ray band to the VHE regime. Methods. The daily light curve of IC 310 above 300 GeV has been measured with MAGIC from 2009 October to 2010 February. Contemporaneous Fermi-LAT data (2008-2011) in the 10-500 GeV energy range were also analyzed. In X-ray, archival observations from 2003 to 2007 with XMM-Newton, Chandra, and Swift-XRT in the 0.5-10 keV band were studied. Results. Several flares with similar amplitude can be seen in the MAGIC light curve. Day to day flux variability is clearly present. The photon index between 120 GeV and 8 TeV is measured to be $\\Gamma=2...

  17. Evolution of Galaxy Clustering

    OpenAIRE

    Bagla, J. S.

    1997-01-01

    We show that the galaxy correlation function does not evolve in proportion with the correlation function of the underlying mass distribution. Earliest galaxies cluster very strongly and the amplitude of the galaxy correlation function decreases from this large value. This continues till the average peaks have collapsed, after which, the galaxy correlation function does not evolve very strongly.

  18. Galaxy Groups

    Science.gov (United States)

    Tully, R. Brent

    2015-02-01

    Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well-studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times {{10}12}{{M}⊙ } are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of groups, the ratio of first to second turnaround depends on the dark matter and dark energy content of the universe and a crude estimate can be made from the current observations of {{Ω}matter}˜ 0.15 in a flat topology, with a 68% probability of being less than 0.44.

  19. Galaxy Groups

    CERN Document Server

    Tully, R Brent

    2014-01-01

    Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times 10^12 Msun are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosi...

  20. Galaxy groups

    Energy Technology Data Exchange (ETDEWEB)

    Brent Tully, R. [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States)

    2015-02-01

    Galaxy groups can be characterized by the radius of decoupling from cosmic expansion, the radius of the caustic of second turnaround, and the velocity dispersion of galaxies within this latter radius. These parameters can be a challenge to measure, especially for small groups with few members. In this study, results are gathered pertaining to particularly well-studied groups over four decades in group mass. Scaling relations anticipated from theory are demonstrated and coefficients of the relationships are specified. There is an update of the relationship between light and mass for groups, confirming that groups with mass of a few times 10{sup 12}M{sub ⊙} are the most lit up while groups with more and less mass are darker. It is demonstrated that there is an interesting one-to-one correlation between the number of dwarf satellites in a group and the group mass. There is the suggestion that small variations in the slope of the luminosity function in groups are caused by the degree of depletion of intermediate luminosity systems rather than variations in the number per unit mass of dwarfs. Finally, returning to the characteristic radii of groups, the ratio of first to second turnaround depends on the dark matter and dark energy content of the universe and a crude estimate can be made from the current observations of Ω{sub matter}∼0.15 in a flat topology, with a 68% probability of being less than 0.44.

  1. Merging Galaxy Cluster A2255 in Mid-infrared

    Science.gov (United States)

    Shim, Hyunjin; Im, Myungshin; Lee, Hyung Mok; Lee, Myung Gyoon; Kim, Seong Jin; Hwang, Ho Seong; Hwang, Narae; Ko, Jongwan; Lee, Jong Chul; Lim, Sungsoon; Matsuhara, Hideo; Seo, Hyunjong; Wada, Takehiko; Goto, Tomotsugu

    2011-01-01

    We present the mid-infrared (MIR) observation of a nearby galaxy cluster, A2255, by the AKARI space telescope. Using AKARI's continuous wavelength coverage between 3 and 24 μm and the wide field of view, we investigate the properties of cluster member galaxies to see how the infall of the galaxies, the cluster substructures, and the cluster-cluster merger influence their evolution. We show that the excess of MIR (~11 μm) flux is a good indicator for discriminating galaxies at different evolutionary stages and for dividing galaxies into three classes accordingly: strong MIR-excess (N3 - S11>0.2) galaxies that include both unobscured and obscured star-forming galaxies; weak MIR-excess (-2.0 S11 5 Gyr) galaxies where the MIR emission arises mainly from the circumstellar dust around AGB stars; and intermediate MIR-excess (-1.2 S11 < 0.2) galaxies in between the two classes that are less than a few Gyr old past the prime star formation activity. With the MIR-excess diagnostics, we investigate how local and cluster-scale environments affect the individual galaxies. We derive the total star formation rate (SFR) and the specific SFR of A2255 using the strong MIR-excess galaxies. The dust-free, total SFR of A2255 is ~130 M sun yr-1, which is consistent with the SFRs of other clusters of galaxies at similar redshifts and with similar masses. We find no strong evidence that supports enhanced star formation either inside the cluster or in the substructure region, suggesting that the infall or the cluster merging activities tend to suppress star formation. The intermediate MIR-excess galaxies, representing galaxies in transition from star-forming galaxies to quiescent galaxies, are located preferentially at the medium density region or cluster substructures with higher surface density of galaxies. Our findings suggest that galaxies are being transformed from star-forming galaxies into red, quiescent galaxies from the infall region through near the core which can be explained

  2. Contemporaneous multi-wavelength observations of the gamma-ray emitting active galaxy IC 310. New clues on particle acceleration in extragalactic jets

    Energy Technology Data Exchange (ETDEWEB)

    Glawion, Dorit

    2015-05-08

    In this thesis, the broad band emission, especially in the gamma-ray and radio band, of the active galaxy IC 310 located in the Perseus cluster of galaxies was investigated. The main experimental methods were Cherenkov astronomy using the MAGIC telescopes and high resolution very long baseline interferometry (VLBI) at radio frequencies (MOJAVE, EVN). Additionally, data of the object in different energy bands were studied and a multi-wavelength campaign has been organized and conducted. During the campaign, an exceptional bright gamma-ray flare at TeV energies was found with the MAGIC telescopes. The results were compared to theoretical acceleration and emission models for explaining the high energy radiation of active galactic nuclei. Many open questions regarding the particle acceleration to very high energies in the jets of active galactic nuclei, the particle content of the jets, or how the jets are launched, were addressed in this thesis by investigating the variability of IC 310 in the very high energy band. It is argued that IC310 was originally mis-classified as a head-tail radio galaxy. Instead, it shows a variability behavior in the radio, X-ray, and gamma-ray band similar to the one found for blazars. These are active galactic nuclei that are characterized by flux variability in all observed energy bands and at all observed time scales. They are viewed at a small angle between the jet axis and the line-of-sight. Thus, strong relativistic beaming influences the variability properties of blazars. Observations of IC 310 with the European VLBI Network helped to find limits for the angle between the jet axis and the line-of-sight, namely 10 - 20 . This places IC 310 at the borderline between radio galaxies (larger angles) and blazars (smaller angles). During the gamma-ray outburst detected at the beginning of the multi-wavelength campaign, flux variability as short as minutes was measured. The spectrum during the flare can be described by a simple power

  3. Contemporaneous multi-wavelength observations of the gamma-ray emitting active galaxy IC 310. New clues on particle acceleration in extragalactic jets

    International Nuclear Information System (INIS)

    In this thesis, the broad band emission, especially in the gamma-ray and radio band, of the active galaxy IC 310 located in the Perseus cluster of galaxies was investigated. The main experimental methods were Cherenkov astronomy using the MAGIC telescopes and high resolution very long baseline interferometry (VLBI) at radio frequencies (MOJAVE, EVN). Additionally, data of the object in different energy bands were studied and a multi-wavelength campaign has been organized and conducted. During the campaign, an exceptional bright gamma-ray flare at TeV energies was found with the MAGIC telescopes. The results were compared to theoretical acceleration and emission models for explaining the high energy radiation of active galactic nuclei. Many open questions regarding the particle acceleration to very high energies in the jets of active galactic nuclei, the particle content of the jets, or how the jets are launched, were addressed in this thesis by investigating the variability of IC 310 in the very high energy band. It is argued that IC310 was originally mis-classified as a head-tail radio galaxy. Instead, it shows a variability behavior in the radio, X-ray, and gamma-ray band similar to the one found for blazars. These are active galactic nuclei that are characterized by flux variability in all observed energy bands and at all observed time scales. They are viewed at a small angle between the jet axis and the line-of-sight. Thus, strong relativistic beaming influences the variability properties of blazars. Observations of IC 310 with the European VLBI Network helped to find limits for the angle between the jet axis and the line-of-sight, namely 10 - 20 . This places IC 310 at the borderline between radio galaxies (larger angles) and blazars (smaller angles). During the gamma-ray outburst detected at the beginning of the multi-wavelength campaign, flux variability as short as minutes was measured. The spectrum during the flare can be described by a simple power

  4. A multiwavelength photometric census of AGN and star formation activity in the brightest cluster galaxies of X-ray selected clusters

    Science.gov (United States)

    Green, T. S.; Edge, A. C.; Stott, J. P.; Ebeling, H.; Burgett, W. S.; Chambers, K. C.; Draper, P. W.; Metcalfe, N.; Kaiser, N.; Wainscoat, R. J.; Waters, C.

    2016-09-01

    Despite their reputation as being `red and dead', the unique environment inhabited by brightest cluster galaxies (BCGs) can often lead to a self-regulated feedback cycle between radiatively cooling intracluster gas and star formation and active galactic nucleus (AGN) activity in the BCG. However the prevalence of `active' BCGs, and details of the feedback involved, are still uncertain. We have performed an optical, UV and mid-IR photometric analysis of the BCGs in 981 clusters at 0.03 AGN and/or star formation activity within the BCG. We find that whilst the majority of BCGs are consistent with being passive, at least 14 per cent of our BCGs show a significant colour offset from passivity in at least one colour index. And, where available, supplementary spectroscopy reveals the majority of these particular BCGs show strong optical emission lines. On comparing BCG `activity' with the X-ray luminosity of the host cluster, we find that BCGs showing a colour offset are preferentially found in the more X-ray luminous clusters, indicative of the connection between BCG `activity' and the intracluster medium.

  5. Galaxy-galaxy(-galaxy) lensing as a sensitive probe of galaxy evolution

    CERN Document Server

    Saghiha, Hananeh; Schneider, Peter; Simon, Patrick

    2012-01-01

    The gravitational lensing effect provides various ways to study the mass environment of galaxies. We investigate how galaxy-galaxy(-galaxy) lensing can be used to test models of galaxy formation and evolution. We consider two semi-analytic galaxy formation models based on the Millennium Run N-body simulation: the Durham model by Bower et al. (2006) and the Garching model by Guo et al. (2011). We generate mock lensing observations for the two models, and then employ Fast Fourier Transform methods to compute second- and third-order aperture statistics in the simulated fields for various galaxy samples. We find that both models predict qualitatively similar aperture signals, but there are large quantitative differences. The Durham model predicts larger amplitudes in general. In both models, red galaxies exhibit stronger aperture signals than blue galaxies. Using these aperture measurements and assuming a linear deterministic bias model, we measure relative bias ratios of red and blue galaxy samples. We find that...

  6. The Densest Galaxy

    CERN Document Server

    Strader, Jay; Forbes, Duncan; Fabbiano, Giuseppina; Romanowsky, Aaron; Brodie, Jean; Conroy, Charlie; Caldwell, Nelson; Pota, Vincenzo; Usher, Christopher; Arnold, Jacob

    2013-01-01

    We report the discovery of a remarkable ultra-compact dwarf galaxy around the massive Virgo elliptical galaxy NGC 4649 (M60), which we term M60-UCD1. With a dynamical mass of 2.0 x 10^8 M_sun but a half-light radius of only ~ 24 pc, M60-UCD1 is more massive than any ultra-compact dwarfs of comparable size, and is arguably the densest galaxy known in the local universe. It has a two-component structure well-fit by a sum of Sersic functions, with an elliptical, compact (r_h=14 pc; n ~ 3.3) inner component and a round, exponential, extended (r_h=49 pc) outer component. Chandra data reveal a variable central X-ray source with L_X ~ 10^38 erg/s that could be an active galactic nucleus associated with a massive black hole or a low-mass X-ray binary. Analysis of optical spectroscopy shows the object to be old (~> 10 Gyr) and of solar metallicity, with elevated [Mg/Fe] and strongly enhanced [N/Fe] that indicates light element self-enrichment; such self-enrichment may be generically present in dense stellar systems. T...

  7. Limits to Quantum Gravity Effects on Energy Dependence of the Speed of Light from Observations of TeV Flares in Active Galaxies

    Energy Technology Data Exchange (ETDEWEB)

    Biller, S.D. [Oxford University, Oxford (United Kingdom); Breslin, A.C.; Carson, M.; Fegan, D.J.; Masterson, C.; McKernan, B. [University College, Dublin (Ireland); Buckley, J. [Washington University, St. Louis, Missouri 63130 (United States); Catanese, M.; Carter-Lewis, D.A.; Krennrich, F.; Samuelson, F. [Iowa State University, Ames, Iowa 50011 (United States); Cawley, M.F. [Maynooth University, Maynooth (Ireland); Finley, J.P.; Gaidos, J.A.; Lessard, R.; Sembroski, G. [Purdue University, West Lafayette, Indiana 47907 (United States); Hillas, A.M.; Rose, H.J.; Skelton, P. [University of Leeds, Leeds (United Kingdom); Lamb, R.C. [California Institute of Technology, California 91125 (United States); McEnery, J.E. [University of Utah, Salt Lake City, Utah 84112 (United States); Moriarty, P. [Galway-Mayo Institute of Technology, Galway (Ireland); Quinn, J.; Weekes, T.C. [Whipple Observatory, Amado, Arizona 85645 (United States)

    1999-09-01

    We have used data from a TeV {gamma} -ray flare associated with the active galaxy Markarian 421 to place bounds on the possible energy dependence of the speed of light in the context of an effective quantum gravitational energy scale. Recent theoretical work suggests that such an energy scale could be less than the Planck mass and perhaps as low as 10{sup 16} thinspthinspGeV. The limits derived here indicate this energy scale to be in excess of 6{times}10{sup 16} thinspthinspGeV for at least one approach to quantum gravity in the context of D-brane string theory. To the best of our knowledge, this constitutes the first convincing limit on such phenomena in this energy regime. {copyright} {ital 1999} {ital The American Physical Society}

  8. The electromagnetic Ram action of the plasma focus as a paradigm for the generation of cosmic rays and the gigantic jets in active galaxies

    Science.gov (United States)

    Bostick, W. H.; Nardi, V.

    1985-08-01

    Recent measurements of the energy spectrum of the plasma-focus-generated deuteron beam yield as spectrum of the form N(E)=(approx.) E to the -2.7 for 1MeV E 13 MeV. Other measurements show that the beta 1 electron beam which is generated simultaneously with the deuteron beam is interrupted into segments of spacing 25ps and duration approximately 4ps. A stuttering-electro-magnetic-ram (ser) model of the plasma focus in proposed which is similar to Raudorf's electronic ram which produces a similar spectrum for an electron beam for 1Mev E 10MeV. It is proposed that the cosmic ray spectrum and the giganic galactic jets are both generated by ser action near the centers of active galaxies.

  9. The host galaxies of X-ray selected Active Galactic Nuclei to z=2.5: Structure, star-formation and their relationships from CANDELS and Herschel/PACS

    CERN Document Server

    Rosario, D J; van der Wel, A; Kartaltepe, J; Lang, P; Santini, P; Wuyts, S; Lutz, D; Rafelski, M; Villforth, C; Alexander, D M; Bauer, F E; Bell, E F; Berta, S; Brandt, W N; Conselice, C J; Dekel, A; Faber, S M; Ferguson, H C; Genzel, R; Grogin, N A; Kocevski, D D; Koekemoer, A M; Koo, D C; Lotz, J M; Magnelli, B; Maiolino, R; Mozena, M; Mullaney, J R; Papovich, C J; Popesso, P; Tacconi, L J; Trump, J R; Avadhuta, S; Bassett, R; Bell, A; Bernyk, M; Bournaud, F; Cassata, P; Cheung, E; Croton, D; Donley, J; DeGroot, L; Guedes, J; Hathi, N; Herrington, J; Hilton, M; Lai, K; Lani, C; Martig, M; McGrath, E; Mutch, S; Mortlock, A; McPartland, C; O'Leary, E; Peth, M; Pillepich, A; Poole, G; Snyder, D; Straughn, A; Telford, O; Tonini, C; Wandro, P

    2014-01-01

    We study the relationship between the structure and star-formation rate (SFR) of X-ray selected low and moderate luminosity active galactic nuclei (AGNs) in the two Chandra Deep Fields, using Hubble Space Telescope imaging from the Cosmic Assembly Near Infrared Extragalactic Legacy Survey (CANDELS) and deep far-infrared maps from the PEP+GOODS-Herschel survey. We derive detailed distributions of structural parameters and FIR luminosities from carefully constructed control samples of galaxies, which we then compare to those of the AGNs. At z~1, AGNs show slightly diskier light profiles than massive inactive (non-AGN) galaxies, as well as modestly higher levels of gross galaxy disturbance (as measured by visual signatures of interactions and clumpy structure). In contrast, at z~2, AGNs show similar levels of galaxy disturbance as inactive galaxies, but display a red central light enhancement, which may arise due to a more pronounced bulge in AGN hosts or due to extinguished nuclear light. We undertake a number ...

  10. 棒对星系核区恒星形成活动的影响%The Effect of Bar on Nuclear Star-forming Activities in Nearby Spiral Galaxies

    Institute of Scientific and Technical Information of China (English)

    汪潋

    2009-01-01

    利用SDSS光谱,研究了IRAS卫星亮红外源星表中的盘状星系中的恒星形成性质,并着重探讨了棒对星系核区恒星形成活动的影响.利用星族合成的方法得到了每个样本星系核区的恒星组成性质、恒星形成活动的强度等信息,并比较了星系整体和核区恒星形成性质的差异.得到的结论:除去相互作用,样本中的棒星系显示出比非棒旋星系更强的核区恒星形成活动和更多的年轻星族成分.%By using SDSS spectra, we have studied nuclear star-forming properties of nearby spiral galaxies selected from Infrared Revised Bright Galaxy Sample, and try to find the effect of bar structure on star-forming activities in the nuclear regions of nearby galaxies. The composition of stellar population and the strength of star formation activities in the sample galaxies are acquired by using stellar population synthesis code ?STARLIGHT, and the star formation properties in nuclear regions are compared with that of the whole galaxies. We find that the star formation in barred spiral galaxies is more intensive than non-barred ones and barred spirals show much younger stellar populations.

  11. The Host Galaxies of X-Ray Selected Active Galactic Nuclei to z - 2.5: Structure, Star-Formation and Their Relationships from CANDELS and Herschel/Pacs

    Science.gov (United States)

    Rosario, D.J.; McIntosh, D. H.; van der Wel, A.; Kartaltepe, J.; Lang, P.; Santini, P.; Wuyts, S.; Lutz, D.; Rafelski, M.; Villforth, C.; Alexander, D. M.; Bauer, F. E.; Bell, E. F.; Berta, S.; Brandt, W. N.; Conselice, C. J.; Dekel, A.; Faber, S. M.; Ferguson, H. C.; Genzel, R.; Grogin, N. A.; Kocevski, D. D.; Koekemoer, A. M.; Koo, D. C.; Straughn, A.

    2014-01-01

    We study the relationship between the structure and star-formation rate (SFR) of X-ray selected low and moderate luminosity active galactic nuclei (AGNs) in the two Chandra Deep Fields, using Hubble Space Telescope imaging from the Cosmic Assembly Near Infrared Extragalactic Legacy Survey (CANDELS) and deep far-infrared maps from the PEP+GOODS-Herschel survey. We derive detailed distributions of structural parameters and FIR luminosities from carefully constructed control samples of galaxies, which we then compare to those of the AGNs. At z is approximately 1, AGNs show slightly diskier light profiles than massive inactive (non-AGN) galaxies, as well as modestly higher levels of gross galaxy disturbance (as measured by visual signatures of interactions and clumpy structure). In contrast, at z 2, AGNs show similar levels of galaxy disturbance as inactive galaxies, but display a red central light enhancement, which may arise due to a more pronounced bulge in AGN hosts or due to extinguished nuclear light. We undertake a number of tests of both these alternatives, but our results do not strongly favour one interpretation over the other. The mean SFR and its distribution among AGNs and inactive galaxies are similar at z greater than 1.5. At z less than 1, however, clear and significant enhancements are seen in the SFRs of AGNs with bulge-dominated light profiles. These trends suggest an evolution in the relation between nuclear activity and host properties with redshift towards a minor role for mergers and interactions at z greater than 15

  12. Galaxies in low density regions of the universe

    International Nuclear Information System (INIS)

    Until recently, no sample of galaxies has been offered for study as being representative of isolated galaxies. However, lately two such samples have been published; one of them is the subject of this study. Both lists of isolated galaxies contain only a few percent of all galaxies considered in the original sources. The study of the isolated galaxies' sample includes optical UBV photometry, infrared photometry, 6-cm radio continuum observations and ultraviolet spectrophotometry. The results provide a database to compare the properties of isolated galaxies to those of nonisolated ones which have probably been modified since their formation by encounters with gas or with other galaxies. A tentative explanation of the detected difference, the apparently enhanced degree of nuclear activity in isolated galaxies is given. (Auth.)

  13. THE DENSEST GALAXY

    Energy Technology Data Exchange (ETDEWEB)

    Strader, Jay [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Seth, Anil C. [University of Utah, Salt Lake City, UT 84112 (United States); Forbes, Duncan A.; Pota, Vincenzo; Usher, Christopher [Centre for Astrophysics and Supercomputing, Swinburne University, Hawthorn, VIC 3122 (Australia); Fabbiano, Giuseppina; Caldwell, Nelson [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States); Romanowsky, Aaron J. [Department of Physics and Astronomy, San José State University, San Jose, CA 95192 (United States); Brodie, Jean P.; Arnold, Jacob A. [University of California Observatories/Lick Observatory, Santa Cruz, CA 95064 (United States); Conroy, Charlie, E-mail: strader@pa.msu.edu [Department of Astronomy and Astrophysics, University of California, Santa Cruz, CA 95064 (United States)

    2013-09-20

    We report the discovery of a remarkable ultra-compact dwarf galaxy around the massive Virgo elliptical galaxy NGC 4649 (M60), which we call M60-UCD1. With a dynamical mass of 2.0 × 10{sup 8} M {sub ☉} but a half-light radius of only ∼24 pc, M60-UCD1 is more massive than any ultra-compact dwarfs of comparable size, and is arguably the densest galaxy known in the local universe. It has a two-component structure well fit by a sum of Sérsic functions, with an elliptical, compact (r{sub h} = 14 pc; n ∼ 3.3) inner component and a round, exponential, extended (r{sub h} = 49 pc) outer component. Chandra data reveal a variable central X-ray source with L{sub X} ∼ 10{sup 38} erg s{sup –1} that could be an active galactic nucleus associated with a massive black hole or a low-mass X-ray binary. Analysis of optical spectroscopy shows the object to be old (∼> 10 Gyr) and of solar metallicity, with elevated [Mg/Fe] and strongly enhanced [N/Fe] that indicates light-element self-enrichment; such self-enrichment may be generically present in dense stellar systems. The velocity dispersion (σ ∼ 70 km s{sup –1}) and resulting dynamical mass-to-light ratio (M/L{sub V} = 4.9 ± 0.7) are consistent with—but slightly higher than—expectations for an old, metal-rich stellar population with a Kroupa initial mass function. The presence of a massive black hole or a mild increase in low-mass stars or stellar remnants is therefore also consistent with this M/L{sub V} . The stellar density of the galaxy is so high that no dynamical signature of dark matter is expected. However, the properties of M60-UCD1 suggest an origin in the tidal stripping of a nucleated galaxy with M{sub B} ∼ –18 to –19.

  14. Star Formation in Irregular Galaxies.

    Science.gov (United States)

    Hunter, Deidre; Wolff, Sidney

    1985-01-01

    Examines mechanisms of how stars are formed in irregular galaxies. Formation in giant irregular galaxies, formation in dwarf irregular galaxies, and comparisons with larger star-forming regions found in spiral galaxies are considered separately. (JN)

  15. Combining Galaxy-Galaxy Lensing and Galaxy Clustering

    Energy Technology Data Exchange (ETDEWEB)

    Park, Youngsoo [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Krause, Elisabeth [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Dodelson, Scott [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Jain, Bhuvnesh [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Amara, Adam [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Becker, Matt [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Bridle, Sarah [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Clampitt, Joseph [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Crocce, Martin [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Honscheid, Klaus [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Gaztanaga, Enrique [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Sanchez, Carles [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States); Wechsler, Risa [Fermi National Accelerator Lab. (FNAL), Batavia, IL (United States)

    2015-01-01

    Combining galaxy-galaxy lensing and galaxy clustering is a promising method for inferring the growth rate of large scale structure, a quantity that will shed light on the mechanism driving the acceleration of the Universe. The Dark Energy Survey (DES) is a prime candidate for such an analysis, with its measurements of both the distribution of galaxies on the sky and the tangential shears of background galaxies induced by these foreground lenses. By constructing an end-to-end analysis that combines large-scale galaxy clustering and small-scale galaxy-galaxy lensing, we also forecast the potential of a combined probes analysis on DES datasets. In particular, we develop a practical approach to a DES combined probes analysis by jointly modeling the assumptions and systematics affecting the different components of the data vector, employing a shared halo model, HOD parametrization, photometric redshift errors, and shear measurement errors. Furthermore, we study the effect of external priors on different subsets of these parameters. We conclude that DES data will provide powerful constraints on the evolution of structure growth in the universe, conservatively/ optimistically constraining the growth function to 8%/4.9% with its first-year data covering 1000 square degrees, and to 4%/2.3% with its full five-year data covering 5000 square degrees.

  16. Galaxy-galaxy(-galaxy) lensing as a sensitive probe of galaxy evolution

    OpenAIRE

    Saghiha, Hananeh; Hilbert, Stefan; Schneider, Peter; Simon, Patrick

    2012-01-01

    The gravitational lensing effect provides various ways to study the mass environment of galaxies. We investigate how galaxy-galaxy(-galaxy) lensing can be used to test models of galaxy formation and evolution. We consider two semi-analytic galaxy formation models based on the Millennium Run N-body simulation: the Durham model by Bower et al. (2006) and the Garching model by Guo et al. (2011). We generate mock lensing observations for the two models, and then employ Fast Fourier Transform meth...

  17. Star and dust formation activities in AzTEC-3: A starburst galaxy at z = 5.3

    CERN Document Server

    Dwek, Eli; Arendt, Richard G; Capak, Peter L; Kovacs, Attila; Benford, Dominic; Fixsen, Dale; Karim, Alexander; Leclercq, Samuel; Maher, Stephen F; Moseley, Samuel H; Schinnerer, Eva; Sharp, Elmer H

    2011-01-01

    Analyses of high-redshift ultraluminous infrared (IR) galaxies traditionally use the observed optical to submillimeter spectral energy distribution (SED) and estimates of the dynamical mass as observational constraints to derive the star formation rate (SFR), the stellar mass, and age of these objects. An important observational constraint neglected in the analysis is the mass of dust giving rise to the IR emission. In this paper we add this constraint to the analysis of AzTEC-3. Adopting an upper limit to the mass of stars and a bolometric luminosity for this object, we construct stellar and chemical evolutionary scenarios, constrained to produce the inferred dust mass and observed luminosity before the associated stellar mass exceeds the observational limit. We find that the model with a Top Heavy IMF provided the most plausible scenario consistent with the observational constraints. In this scenario the dust formed over a period of ~200 Myr, with a SFR of ~500 Msun/yr. These values for the age and SFR in A...

  18. Galaxy And Mass Assembly (GAMA) blended spectra catalogue: strong galaxy-galaxy lens and occulting galaxy pair candidates

    OpenAIRE

    Holwerda, B.W.; Baldry, I. K.; Alpaslan, M.; Bauer, A; Bland-Hawthorn, J.; Brough, S.; Brown, M. J. I.; Cluver, M. E.; Conselice, C; Driver, S. P.; Hopkins, A. M.; Jones, D.H.; López-Sánchez, Á. R.; Loveday, J; Meyer, M J

    2015-01-01

    We present the catalogue of blended galaxy spectra from the Galaxy And Mass Assembly (GAMA) survey. These are cases where light from two galaxies are significantly detected in a single GAMA fibre. Galaxy pairs identified from their blended spectrum fall into two principal classes: they are either strong lenses, a passive galaxy lensing an emission-line galaxy; or occulting galaxies, serendipitous overlaps of two galaxies, of any type. Blended spectra can thus be used to reliably identify stro...

  19. DAGAL: Detailed Anatomy of Galaxies

    CERN Document Server

    Knapen, Johan H

    2016-01-01

    The current IAU Symposium is closely connected to the EU-funded network DAGAL (Detailed Anatomy of Galaxies), with the final annual network meeting of DAGAL being at the core of this international symposium. In this short paper, we give an overview of DAGAL, its training activities, and some of the scientific advances that have been made under its umbrella.

  20. How to quench a galaxy

    CERN Document Server

    Pontzen, Andrew; Roth, Nina; Peiris, Hiranya V; Saintonge, Amélie; Volonteri, Marta; Quinn, Tom; Governato, Fabio

    2016-01-01

    We show how the interplay between active galactic nuclei (AGN) and merger history determines whether a galaxy quenches star formation at high redshift. We first simulate, in a full cosmological context, a galaxy of total dynamical mass $10^{12}\\,M_{\\odot}$ at $z=2$. Then we systematically alter the accretion history of the galaxy by minimally changing the linear overdensity in the initial conditions. This "genetic modification" approach allows the generation of three sets of $\\Lambda$CDM initial conditions leading to maximum merger ratios of 1:10, 1:5 and 2:3 respectively. The changes leave the final halo mass, large scale structure and local environment unchanged, providing a controlled numerical experiment. Interaction between the AGN physics and mergers in the three cases lead respectively to a star-forming, temporarily-quenched and permanently-quenched galaxy. However the differences do not primarily lie in the black hole accretion rates, but in the kinetic effects of the merger: the galaxy is resilient a...