CONNECTING GRBs AND ULIRGs: A SENSITIVE, UNBIASED SURVEY FOR RADIO EMISSION FROM GAMMA-RAY BURST HOST GALAXIES AT 0 < z < 2.5

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Perley, D. A. [Department of Astronomy, California Institute of Technology, MC 249-17, 1200 East California Boulevard, Pasadena, CA 91125 (United States); Perley, R. A. [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States); Hjorth, J.; Malesani, D. [Dark Cosmology Centre, Niels Bohr Institute, DK-2100 Copenhagen (Denmark); Michałowski, M. J. [Scottish Universities Physics Alliance, Institute for Astronomy, University of Edinburgh, Royal Observatory, Edinburgh, EH9 3HJ (United Kingdom); Cenko, S. B. [NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Jakobsson, P. [Centre for Astrophysics and Cosmology, Science Institute, University of Iceland, Dunhagi 5, 107 Reykjavík (Iceland); Krühler, T. [European Southern Observatory, Alonso de Córdova 3107, Vitacura, Casilla 19001, Santiago 19 (Chile); Levan, A. J. [Department of Physics, University of Warwick, Coventry CV4 7AL (United Kingdom); Tanvir, N. R., E-mail: dperley@astro.caltech.edu [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom)

2015-03-10

Luminous infrared galaxies and submillimeter galaxies contribute significantly to stellar mass assembly and provide an important test of the connection between the gamma-ray burst (GRB) rate and that of overall cosmic star formation. We present sensitive 3 GHz radio observations using the Karl G. Jansky Very Large Array of 32 uniformly selected GRB host galaxies spanning a redshift range from 0 < z < 2.5, providing the first fully dust- and sample-unbiased measurement of the fraction of GRBs originating from the universe's most bolometrically luminous galaxies. Four galaxies are detected, with inferred radio star formation rates (SFRs) ranging between 50 and 300 M {sub ☉} yr{sup –1}. Three of the four detections correspond to events consistent with being optically obscured 'dark' bursts. Our overall detection fraction implies that between 9% and 23% of GRBs between 0.5 < z < 2.5 occur in galaxies with S {sub 3GHz} > 10 μJy, corresponding to SFR > 50 M {sub ☉} yr{sup –1} at z ∼ 1 or >250 M {sub ☉} yr{sup –1} at z ∼ 2. Similar galaxies contribute approximately 10%-30% of all cosmic star formation, so our results are consistent with a GRB rate that is not strongly biased with respect to the total SFR of a galaxy. However, all four radio-detected hosts have stellar masses significantly lower than IR/submillimeter-selected field galaxies of similar luminosities. We suggest that the GRB rate may be suppressed in metal-rich environments but independently enhanced in intense starbursts, producing a strong efficiency dependence on mass but little net dependence on bulk galaxy SFR.

TWO BRIGHT SUBMILLIMETER GALAXIES IN A z = 4.05 PROTOCLUSTER IN GOODS-NORTH, AND ACCURATE RADIO-INFRARED PHOTOMETRIC REDSHIFTS

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Daddi, E.; Elbaz, D.; Mancini, C.; Dannerbauer, H.; Stern, D.; Dickinson, M.; Pope, A.; Morrison, G.; Giavalisco, M.; Spinrad, H.

2009-01-01

We present the serendipitous discovery of molecular gas CO emission lines with the IRAM Plateau de Bure interferometer coincident with two luminous submillimeter galaxies (SMGs) in the Great Observatories Origins Deep Survey North (GOODS-N) field. The identification of the millimeter emission lines as CO[4-3] at z = 4.05 is based on the optical and near-IR photometric redshifts, radio-infrared photometric redshifts, and Keck+DEIMOS optical spectroscopy. These two galaxies include the brightest submillimeter source in the field (GN20; S 850μm = 20.3 mJy, z CO = 4.055 ± 0.001) and its companion (GN20.2; S 850μm = 9.9 mJy, z CO = 4.051 ± 0.003). These are among the most distant submillimeter-selected galaxies reliably identified through CO emission and also some of the most luminous known. GN20.2 has a possible additional counterpart and a luminous active galactic nucleus inside its primary counterpart revealed in the radio. Continuum emission of 0.3 mJy at 3.3 mm (0.65 mm in the rest frame) is detected at 5σ for GN20, the first dust continuum detection in an SMG at such long wavelength, unveiling a spectral energy distribution that is similar to local ultra luminous IR galaxies. In terms of CO to bolometric luminosities, stellar mass, and star formation rates (SFRs), these newly discovered z > 4 SMGs are similar to z ∼ 2-3 SMGs studied to date. These z ∼ 4 SMGs have much higher specific star formation rates than those of typical B-band dropout Lyman break galaxies at the same redshift. The stellar mass-SFR correlation for normal galaxies does not seem to evolve much further, between z ∼ 2 and z ∼ 4. A significant z = 4.05 spectroscopic redshift spike is observed in GOODS-N, and a strong spatial overdensity of B-band dropouts and IRAC selected z > 3.5 galaxies appears to be centered on the GN20 and GN20.2 galaxies. This suggests a protocluster structure with total mass ∼10 14 M sun . Using photometry at mid-IR (24 μm), submillimeter (850 μm), and

EXTENDED [C II] EMISSION IN LOCAL LUMINOUS INFRARED GALAXIES

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Díaz-Santos, T.; Armus, L.; Surace, J. A.; Charmandaris, V.; Stacey, G.; Murphy, E. J.; Haan, S.; Stierwalt, S.; Evans, A. S.; Malhotra, S.; Appleton, P.; Inami, H.; Magdis, G. E.; Elbaz, D.; Mazzarella, J. M.; Xu, C. K.; Lu, N.; Howell, J. H.; Van der Werf, P. P.; Meijerink, R.

2014-01-01

We present Herschel/PACS observations of extended [C II] 157.7 μm line emission detected on ∼1-10 kpc scales in 60 local luminous infrared galaxies (LIRGs) from the Great Observatories All-sky LIRG Survey. We find that most of the extra-nuclear emission show [C II]/FIR ratios ≥4 × 10 –3 , larger than the mean ratio seen in the nuclei, and similar to those found in the extended disks of normal star-forming galaxies and the diffuse interstellar medium of our Galaxy. The [C II] ''deficits'' found in the most luminous local LIRGs are therefore restricted to their nuclei. There is a trend for LIRGs with warmer nuclei to show larger differences between their nuclear and extra-nuclear [C II]/FIR ratios. We find an anti-correlation between [C II]/FIR and the luminosity surface density, Σ IR , for the extended emission in the spatially resolved galaxies. However, there is an offset between this trend and that found for the LIRG nuclei. We use this offset to derive a beam filling-factor for the star-forming regions within the LIRG disks of ∼6% relative to their nuclei. We confront the observed trend to photo-dissociation region models and find that the slope of the correlation is much shallower than the model predictions. Finally, we compare the correlation found between [C II]/FIR and Σ IR with measurements of high-redshift starbursting IR-luminous galaxies

New Members in the Galaxy Group Around Giant Radio Galaxy DA 240

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Chen, Ru-Rong; Peng, Bo; Strom, Richard

2018-05-01

With new spectroscopic observations of group candidates around the giant radio galaxy DA 240, we have identified five new group members, increasing the number to twenty-five. While all the new members are located some distance from the host galaxy, two of them lie in one of the radio lobes, and the rest are found at a distance from the radio components. The new group members reinforce our earlier conclusion that the distribution of the DA 240 group with respect to the radio lobes is unusual among giant radio galaxy host environments.

THE SPITZER HIGH-REDSHIFT RADIO GALAXY SURVEY

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De Breuck, Carlos; Galametz, Audrey; Vernet, Joel; Seymour, Nick; Stern, Daniel; Eisenhardt, P. R. M.; Willner, S. P.; Fazio, G. G.; Lacy, Mark; Rettura, Alessandro; Rocca-Volmerange, Brigitte

2010-01-01

We present results from a comprehensive imaging survey of 70 radio galaxies at redshifts 1 3 μ m /S 1.6 μ m versus S 5 μ m /S 3 μ m criterion, we identify 42 sources where the rest-frame 1.6 μm emission from the stellar population can be measured. For these radio galaxies, the median stellar mass is high, 2 x 10 11 M sun , and remarkably constant within the range 1 3, there is tentative evidence for a factor of two decrease in stellar mass. This suggests that radio galaxies have assembled the bulk of their stellar mass by z ∼ 3, but confirmation by more detailed decomposition of stellar and active galactic nucleus (AGN) emission is needed. The rest-frame 500 MHz radio luminosities are only marginally correlated with stellar mass but are strongly correlated with the rest-frame 5 μm hot dust luminosity. This suggests that the radio galaxies have a large range of Eddington ratios. We also present new Very Large Array 4.86 and 8.46 GHz imaging of 14 radio galaxies and find that radio core dominance-an indicator of jet orientation-is strongly correlated with hot dust luminosity. While all of our targets were selected as narrow-lined, type 2 AGNs, this result can be understood in the context of orientation-dependent models if there is a continuous distribution of orientations from obscured type 2 to unobscured type 1 AGNs rather than a clear dichotomy. Finally, four radio galaxies have nearby (<6'') companions whose mid-IR colors are suggestive of their being AGNs. This may indicate an association between radio galaxy activity and major mergers.

Clustering of Star-forming Galaxies Near a Radio Galaxy at z=5.2

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Overzier, Roderik A.; Miley, G. K.; Bouwens, R. J.; Cross, N. J. G.; Zirm, A. W.; Benítez, N.; Blakeslee, J. P.; Clampin, M.; Demarco, R.; Ford, H. C.; Hartig, G. F.; Illingworth, G. D.; Martel, A. R.; Röttgering, H. J. A.; Venemans, B.; Ardila, D. R.; Bartko, F.; Bradley, L. D.; Broadhurst, T. J.; Coe, D.; Feldman, P. D.; Franx, M.; Golimowski, D. A.; Goto, T.; Gronwall, C.; Holden, B.; Homeier, N.; Infante, L.; Kimble, R. A.; Krist, J. E.; Mei, S.; Menanteau, F.; Meurer, G. R.; Motta, V.; Postman, M.; Rosati, P.; Sirianni, M.; Sparks, W. B.; Tran, H. D.; Tsvetanov, Z. I.; White, R. L.; Zheng, W.

2006-01-01

We present HST ACS observations of the most distant radio galaxy known, TN J0924-2201 at z=5.2. This radio galaxy has six spectroscopically confirmed Lyα-emitting companion galaxies and appears to lie within an overdense region. The radio galaxy is marginally resolved in i775 and z850, showing continuum emission aligned with the radio axis, similar to what is observed for lower redshift radio galaxies. Both the half-light radius and the UV star formation rate are comparable to the typical values found for Lyman break galaxies at z~4-5. The Lyα emitters are sub-L* galaxies, with deduced star formation rates of 1-10 Msolar yr-1. One of the Lyα emitters is only detected in Lyα. Based on the star formation rate of ~3 Msolar yr-1 calculated from Lyα, the lack of continuum emission could be explained if the galaxy is younger than ~2 Myr and is producing its first stars. Observations in V606i775z850 were used to identify additional Lyman break galaxies associated with this structure. In addition to the radio galaxy, there are 22 V606 break (z~5) galaxies with z850dropouts extracted from GOODS and the UDF parallel fields. We find evidence for an overdensity to very high confidence (>99%), based on a counts-in-cells analysis applied to the control field. The excess suggests that the V606 break objects are associated with a forming cluster around the radio galaxy. Based on observations made with the NASA/ESA Hubble Space Telescope, 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 9291.

Structure in radio galaxies

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Breugel, W. van.

1980-01-01

It is shown that radio jets are a rather common phenomenon in radio galaxies. Jets can be disguised as trails in head-tail sources, bridges in double sources or simply remain undetected because of lack of resolution and sensitivity. It is natural to associate these jets with the channels which had previously been suggested to supply energy to the extended radio lobes. The observations of optical emission suggest that a continuous non-thermal spectrum extending from 10 9 to 10 15 Hz is a common property of jets. Because significant amounts of interstellar matter are also observed in each of the galaxies surveyed it seems that models for jets which involve an interaction with this medium may be most appropriate. New information about the overall structure of extended radio sources has been obtained from the detailed multifrequency study with the WSRT. (Auth.)

The cluster environments of powerful, high-redshift radio galaxies

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Yates, M.G.

1989-01-01

We present deep imaging of a sample of 25 powerful radio galaxies in the redshift range 0.15 gr ) about each source, a measure of the richness of environment. The powerful radio galaxies in this sample at z>0.3 occupy environments nearly as rich on average as Abell class 0 clusters of galaxies, about three times richer than the environments of the z<0.3 radio galaxies. This trend in cluster environment is consistent with that seen in radio-loud quasars over the same redshift range. Our previous work on the 3CR sample suggested that the fundamental parameter which correlates with the richness of environment might be the radio luminosity of the galaxy, rather than its redshift. Our direct imaging confirms that the most powerful radio galaxies do inhabit rich environments. (author)

A multi-wavelength view of the central kiloparsec region in the luminous infrared galaxy NGC 1614

Energy Technology Data Exchange (ETDEWEB)

Herrero-Illana, Rubén; Pérez-Torres, Miguel Á.; Alberdi, Antxon; Hernández-García, Lorena [Instituto de Astrofísica de Andalucía-CSIC, P.O. Box 3004, E-18008 Granada (Spain); Alonso-Herrero, Almudena [Instituto de Física de Cantabria, CSIC-Universidad de Cantabria, E-39005 Santander (Spain); Colina, Luis [Centro de Astrobiología (INTA-CSIC), Ctra. de Torrejón a Ajalvir, km 4, E-28850 Torrejón de Ardoz, Madrid (Spain); Efstathiou, Andreas [School of Sciencies, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia (Cyprus); Miralles-Caballero, Daniel [Instituto de Física Teórica, Universidad Autónoma de Madrid, E-28049 Madrid (Spain); Väisänen, Petri [South African Astronomical Observatory, P.O. Box 9, Observatory 7935 Cape Town (South Africa); Packham, Christopher C. [Department of Physics and Astronomy, University of Texas at San Antonio, One UTSA Circle, San Antonio, TX 78249 (United States); Rajpaul, Vinesh [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Zijlstra, Albert A. [Jodrell Bank Centre for Astrophysics, University of Manchester, Manchester M13 9PL (United Kingdom)

2014-05-10

The Luminous Infrared Galaxy NGC 1614 hosts a prominent circumnuclear ring of star formation. However, the nature of the dominant emitting mechanism in its central ∼100 pc is still under debate. We present sub-arcsecond angular resolution radio, mid-infrared, Paα, optical, and X-ray observations of NGC 1614, aimed at studying in detail both the circumnuclear ring and the nuclear region. The 8.4 GHz continuum emission traced by the Very Large Array and the Gemini/T-ReCS 8.7 μm emission, as well as the Paα line emission, show remarkable morphological similarities within the star-forming ring, suggesting that the underlying emission mechanisms are tightly related. We used a Hubble Space Telescope/NICMOS Paα map of similar resolution to our radio maps to disentangle the thermal free-free and non-thermal synchrotron radio emission, from which we obtained the intrinsic synchrotron power law for each individual region within the central kiloparsec of NGC 1614. The radio ring surrounds a relatively faint, steep-spectrum source at the very center of the galaxy, suggesting that the central source is not powered by an active galactic nucleus (AGN), but rather by a compact (r ≲ 90 pc) starburst (SB). Chandra X-ray data also show that the central kiloparsec region is dominated by SB activity, without requiring the existence of an AGN. We also used publicly available infrared data to model-fit the spectral energy distribution of both the SB ring and a putative AGN in NGC 1614. In summary, we conclude that there is no need to invoke an AGN to explain the observed bolometric properties of the galaxy.

Radio Observations of Ultra-Luminous X-Ray Sources ---Microblazars or Intermediate-Mass Black Holes?---

Science.gov (United States)

Körding, E.; Colbert, E.; Falcke, H.

In recent years Ultra-Luminous X-Ray sources (ULXs) received wide attention, however, their true nature is not yet understood. Many explanations have been suggested, including intermediate-mass black holes, super-Eddington accretion flows, anisotropic emission, and relativistic beaming of microquasars. We model the logN-logS distribution of ULXs assuming that each neutron star or black hole XRB can be described by an accretion disk plus jet model, where the jet is relativistically beamed. The distribution can be either fit by intermediate-mass black holes or by stellar mass black holes with mildly relativistic jets. Even though the jet is intrinsically weaker than the accretion disk, relativistic beaming can in the latter approach lead to the high fluxes observed. To further explore the possibility of microblazars contributing to the ULX phenomenon, we have embarked on a radio-monitoring study of ULXs in nearby galaxies with the VLA. However, up to now no radio flare has been detected. Using the radio/X-ray correlation the upper limits on the radio flux can be converted into upper limits for the black hole masses of MBH ≲ 10^3 M⊙.

Radio-continuum emission from quasar host galaxies

International Nuclear Information System (INIS)

Condon, J. J.; Gower, A. C.; Hutchings, J. B.; Victoria Univ., Canada; Dominion Astrophysical Observatory, Victoria)

1987-01-01

Seven low-redshift quasars that are likely to be in spiral galaxies have been observed in a search for radio-continuum emission from the host galaxies of quasars. The properties of the individual quasars are listed, and 1.49 GHz contour maps of the seven quasar fields are presented. Map parameters and radio source parameters are given along with optical images of three of the objects. The results indicate that these quasars probably do reside in spiral galaxies. The radio luminosities, sizes, orientations, and u values all indicate that relativistic beaming alone cannot be used to explain the differences between the present sources and the far stronger radio sources seen in blazars or larger optically selected quasar samples. However, an apparent correlation between the radio luminosity and the ratio of the optical nuclear to host-galaxy luminosity is consistent with some beaming of nuclear radiation. 26 references

STAR FORMATION SUPPRESSION DUE TO JET FEEDBACK IN RADIO GALAXIES WITH SHOCKED WARM MOLECULAR GAS

International Nuclear Information System (INIS)

Lanz, Lauranne; Ogle, Patrick M.; Appleton, Philip N.; Alatalo, Katherine

2016-01-01

We present Herschel observations of 22 radio galaxies, selected for the presence of shocked, warm molecular hydrogen emission. We measured and modeled spectral energy distributions in 33 bands from the ultraviolet to the far-infrared to investigate the impact of jet feedback on star formation activity. These galaxies are massive, early-type galaxies with normal gas-to-dust ratios, covering a range of optical and infrared colors. We find that the star formation rate (SFR) is suppressed by a factor of ∼3–6, depending on how molecular gas mass is estimated. We suggest that this suppression is due to the shocks driven by the radio jets injecting turbulence into the interstellar medium (ISM), which also powers the luminous warm H 2 line emission. Approximately 25% of the sample shows suppression by more than a factor of 10. However, the degree of SFR suppression does not correlate with indicators of jet feedback including jet power, diffuse X-ray emission, or intensity of warm molecular H 2 emission, suggesting that while injected turbulence likely impacts star formation, the process is not purely parameterized by the amount of mechanical energy dissipated into the ISM. Radio galaxies with shocked warm molecular gas cover a wide range in SFR–stellar mass space, indicating that these galaxies are in a variety of evolutionary states, from actively star-forming and gas-rich to quiescent and gas-poor. SFR suppression appears to have the largest impact on the evolution of galaxies that are moderately gas-rich.

A multiwavelength and multiscale study of Luminous and Ultraluminous Infrared Galaxies in the local Universe

Science.gov (United States)

Herrero-Illana, Rubén

2014-10-01

This dissertation deals with the multiwavelength study of luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs, respectively) in the local Universe under different spatial scales. The work is focused on the properties of massive starbursts, the contribution of active galactic nuclei (AGN) and the interplay between both phenomena. The study of local (U)LIRGs is the best scenario where to understand the properties of these objects at cosmological distances, where their luminosity contribution dominates the cosmic infrared background. Our first approach to the study of (U)LIRGs consisted of a spectral line study in the millimeter range, obtained with the IRAM 30m radio-telescope in Pico Veleta, Granada of a subsample of 56 (U)LIRGs from the GOALS project sample. We observed and analyzed spectra of several molecular features, focusing in the study of carbon monoxide (CO), a well-known tracer of cold molecular gas. We explored the relation between them as well as the properties of molecular gas. Besides of the sample characterization, we confirmed the increase of the isotopic ratio 12CO/13CO with the dust temperature, explained by the 12CO optical depth decreasing with temperature. We have also studied the kinematics and gas distribution using the spectral profiles of several molecular transitions. In a second part of this thesis, we analyzed the central kiloparsec region of a sample of 12 LIRGs, stressing the importance of the multiwavelength approach, aimed at deriving the star formation processes of these galaxies, as well as to study the contribution of the putative AGN to the bolometric luminosity in our sample. For one of these LIRGs, NGC1614, we performed a deep multiwavelength study, including data from radio, infrared, optical and X-rays. These data allowed us to establish that the the IR emission in the circumnuclear region is completely dominated by a powerful starburst and, in case it hosts an AGN, its contribution is irrelevant. We also performed

Radio halo sources in clusters of galaxies

International Nuclear Information System (INIS)

Hanisch, R.J.

1986-01-01

Radio halo sources remain one of the most enigmatic of all phenomena related to radio emission from galaxies in clusters. The morphology, extent, and spectral structure of these sources are not well known, and the models proposed to explain them suffer from this lack of observational detail. However, recent observations suggest that radio halo sources may be a composite of relic radio galaxies. The validity of this model could be tested using current and planned high resolutions, low-frequency radio telescopes. 31 references

Infrared and radio emission from S0 galaxies

International Nuclear Information System (INIS)

Bally, J.; Thronson, H.A. Jr.

1989-01-01

Far-IR data are presented on 74 early-type S0 galaxies that were selected on the basis of the availability of radio-continuum measurements. Most of the galaxies are detected at IR wavelengths with IRAS, indicating the presence of a cold interstellar medium (ISM) in these galaxies. The mass of gas in these systems is estimated to lie in the range of 10 to the 7th to 10 to the 10th solar. The most massive ISM in some S0s approaches that found in some spirals. The brighter IR-emitting galaxies all lie close to a relationship established for gas-rich spiral galaxies. None of these galaxies have large ratio fluxes, suggesting that strong nuclear radio sources or extended radio lobes and jets are absent or suppressed. Strong radio emission is found among those galaxies that are either faint or not detected at IR wavelengths. The absence of an ISM suggests that these galaxies are of an earlier type that those that have large IR fluxes. 38 references

CONSTRAINING JET PRODUCTION SCENARIOS BY STUDIES OF NARROW-LINE RADIO GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Sikora, Marek [Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw (Poland); Stasinska, Grazyna [LUTH, Observatoire de Paris, CNRS, Universite Paris Diderot, Place Jules Janssen, F-92190 Meudon (France); Koziel-Wierzbowska, Dorota [Astronomical Observatory, Jagiellonian University, ul. Orla 171, 30-244 Krakow (Poland); Madejski, Greg M. [Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305 (United States); Asari, Natalia V., E-mail: sikora@camk.edu.pl [Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA (United Kingdom)

2013-03-01

We study a large sample of narrow-line radio galaxies (NLRGs) with extended radio structures. Using 1.4 GHz radio luminosities L {sub 1.4}, narrow optical emission line luminosities L {sub [OIII]} and L{sub H{sub {alpha}}}, as well as black hole masses M {sub BH} derived from stellar velocity dispersions measured from the optical spectra obtained with the Sloan Digital Sky Survey, we find that (1) NLRGs cover about four decades of the Eddington ratio, {lambda} {identical_to} L {sub bol}/L {sub Edd}{proportional_to}L {sub line}/M {sub BH}; (2) L {sub 1.4}/M {sub BH} strongly correlates with {lambda}; and (3) radio loudness, R{identical_to}L{sub 1.4}/L{sub line}, strongly anti-correlates with {lambda}. A very broad range of the Eddington ratio indicates that the parent population of NLRGs includes both radio-loud quasars (RLQs) and broad-line radio galaxies (BLRGs). The correlations they obey and their high jet production efficiencies favor a jet production model which involves the so-called magnetically choked accretion scenario. In this model, production of the jet is dominated by the Blandford-Znajek mechanism, and the magnetic fields in the vicinity of the central black hole are confined by the ram pressure of the accretion flow. Since large net magnetic flux accumulated in central regions of the accretion flow required by the model can take place only via geometrically thick accretion, we speculate that the massive, 'cold' accretion events associated with luminous emission-line active galactic nucleus can be accompanied by an efficient jet production only if preceded by a hot, very sub-Eddington accretion phase.

Clustering of very luminous infrared galaxies and their environment

Science.gov (United States)

Gao, YU

1993-01-01

The IRAS survey reveals a class of ultraluminous infrared (IR) galaxies (ULIRG's) with IR luminosities comparable to the bolometric luminosities of quasars. The nature, origin, and evolution of ULIRG's are attracting more and more attention recently. Since galaxy morphology is certainly a function of environment, morphological observations show that ULIRG's are interacting/merging galaxies, and some ULIRG's might be the dust-enshrouded quasars (S88) or giant ellipticals, the study of ULIRG's environment and large scale clustering effects should be worthwhile. ULIRG's and very luminous IR galaxies have been selected from the 2Jy IRAS redshift survey. Meanwhile, a catalog of IRAS groups of galaxies has been constructed using a percolation-like algorithm. Therefore, whether ULIRG's and/or VLIRG's have a group environment can be checked immediately. Other aspects of the survey are discussed.

Giant Double Radio Source DA 240: Purveyor of Galaxies

Science.gov (United States)

Chen, Ru-Rong; Strom, Richard; Peng, Bo

2018-05-01

Galaxies of stars are building blocks of the baryonic universe. Their composition, structure, and kinematics have been well studied, but details of their origins remain sketchy. The collapse of gas clouds, induced by external forces whereby gravity overcomes internal pressure to form stars, is the likely starting point. Among the perturbing initiators of galaxy formation, radio source beams (jets) are quite effective. Typically, a beam may spawn one galaxy, though instances of several aligned with the radio axis are known. Recently, we found an impressive 14 companions in the lobes of the giant radio galaxy DA 240, which we argue formed as the result of jet instigation. This conclusion is bolstered by the fact that the galaxy groups display Z-shaped symmetry with respect to the radio axis. There is some evidence for star formation among the aligned companions. We also conclude that galaxy alignments at low redshift may derive from line-emitting gas observed in radio components of high-redshift galaxies.

H I absorption in nearby compact radio galaxies

Science.gov (United States)

Glowacki, M.; Allison, J. R.; Sadler, E. M.; Moss, V. A.; Curran, S. J.; Musaeva, A.; Deng, C.; Parry, R.; Sligo, M. C.

2017-05-01

H I absorption studies yield information on both active galactic nucleus (AGN) feeding and feedback processes. This AGN activity interacts with the neutral gas in compact radio sources, which are believed to represent the young or recently re-triggered AGN population. We present the results of a survey for H I absorption in a sample of 66 compact radio sources at 0.040 100 km s-1) features, indicative of disturbed gas kinematics. Such broad, shallow and offset features are also found within low-excitation radio galaxies which is attributed to disturbed circumnuclear gas, consistent with early-type galaxies typically devoid of a gas-rich disc. Comparing mid-infrared colours of our galaxies with H I detections indicates that narrow and deep absorption features are preferentially found in late-type and high-excitation radio galaxies in our sample. These features are attributed to gas in galactic discs. By combining XMM-Newton archival data with 21-cm data, we find support that absorbed X-ray sources may be good tracers of H I content within the host galaxy. This sample extends previous H I surveys in compact radio galaxies to lower radio luminosities and provides a basis for future work exploring the higher redshift universe.

Flattening and radio emission among elliptical galaxies

International Nuclear Information System (INIS)

Disney, M.J.; Sparks, W.B.; Wall, J.V.

1984-01-01

In a sample of 132 bright elliptical galaxies it is shown that there is a strong correlation between radio activity and flattening in the sense that radio ellipticals are both apparently and inherently rounder than the average elliptical. Both extended and compact sources are subject to the same correlation. No galaxies with axial ratios below 0.65 are found to be radio emitters. (author)

Luminous quasars do not live in the most overdense regions of galaxies at z ˜ 4

Science.gov (United States)

Uchiyama, Hisakazu; Toshikawa, Jun; Kashikawa, Nobunari; Overzier, Roderik; Chiang, Yi-Kuan; Marinello, Murilo; Tanaka, Masayuki; Niino, Yuu; Ishikawa, Shogo; Onoue, Masafusa; Ichikawa, Kohei; Akiyama, Masayuki; Coupon, Jean; Harikane, Yuichi; Imanishi, Masatoshi; Kodama, Tadayuki; Komiyama, Yutaka; Lee, Chien-Hsiu; Lin, Yen-Ting; Miyazaki, Satoshi; Nagao, Tohru; Nishizawa, Atsushi J.; Ono, Yoshiaki; Ouchi, Masami; Wang, Shiang-Yu

2018-01-01

We present the cross-correlation between 151 luminous quasars (MUV 4 σ. The distributions of the distances between quasars and the nearest protoclusters and the significance of the overdensity at the positions of quasars are statistically identical to those found for g-dropout galaxies, suggesting that quasars tend to reside in almost the same environment as star-forming galaxies at this redshift. Using stacking analysis, we find that the average density of g-dropout galaxies around quasars is slightly higher than that around g-dropout galaxies on 1.0-2.5 pMpc scales, while at anti-correlated with overdensity. These findings are consistent with a scenario in which luminous quasars at z ˜ 4 reside in structures that are less massive than those expected for the progenitors of today's rich clusters of galaxies, and possibly that luminous quasars may be suppressing star formation in their close vicinity.

Stellar populations in distant radio galaxies

International Nuclear Information System (INIS)

Lilly, S.J.; Longair, M.S.

1984-01-01

A homogeneous data set of infrared observations of 83 3CR galaxies with redshifts 0< z<1.6, selected from a statistically complete sample of 90 radio sources, is used to study the colours and magnitudes of these galaxies as a function of their redshifts. New infrared observations are presented for 66 radio galaxies, in addition to new optical results obtained from a re-analysis of existing CCD images. It is shown that the infrared colours do not deviate from the predicted relations with redshift for a standard giant elliptical galaxy spectrum. The optical to infrared colours, however, show substantial deviations at high redshift. No galaxies have been found that are significantly redder than a passively evolving galaxy, and there is a significant scatter of colours bluewards from this model. The excess of ultraviolet light responsible for these colours is not concentrated at the nucleus, and is interpreted as resulting from bursts of star formation, throughout the galaxy. (author)

EVOLUTION OF THE MOST LUMINOUS DUSTY GALAXIES

International Nuclear Information System (INIS)

Weedman, Daniel W.; Houck, James R.

2009-01-01

A summary of mid-infrared continuum luminosities arising from dust is given for very luminous galaxies, L IR > 10 12 L sun , with 0.005 0.7 in the 9.7 μm silicate absorption feature (i.e., half of the continuum is absorbed) and having equivalent width of the 6.2 μm polycyclic aromatic hydrocarbon feature ν (8 μm) for the most luminous obscured AGNs is found to scale as (1+z) 2.6 to z = 2.8. For unobscured AGNs, the scaling with redshift is similar, but luminosities νL ν (8 μm) are approximately three times greater for the most luminous sources. Using both obscured and unobscured AGNs having total infrared fluxes from the Infrared Astronomical Satellite, empirical relations are found between νL ν (8 μm) and L IR . Combining these relations with the redshift scaling of luminosity, we conclude that the total infrared luminosities for the most luminous obscured AGNs, L IR (AGN obscured ) in L sun , scale as log L IR (AGN obscured ) = 12.3 ± 0.25 + 2.6(±0.3)log(1+z), and for the most luminous unobscured AGNs, scale as log L IR (AGN1) = 12.6(±0.15) + 2.6(±0.3)log(1+z). We previously determined that the most luminous starbursts scale as log L IR (SB) = 11.8 ± 0.3 + 2.5(±0.3)log(1+z), indicating that the most luminous AGNs are about 10 times more luminous than the most luminous starbursts. Results are consistent with obscured and unobscured AGNs having the same total luminosities with differences arising only from orientation, such that the obscured AGNs are observed through very dusty clouds which extinct about 50% of the intrinsic luminosity at 8 μm. Extrapolations of observable f ν (24 μm) to z = 6 are made using evolution results for these luminous sources. Both obscured and unobscured AGNs should be detected to z ∼ 6 by Spitzer surveys with f ν (24 μm) > 0.3 mJy, even without luminosity evolution for z > 2.5. By contrast, the most luminous starbursts cannot be detected for z > 3, even if luminosity evolution continues beyond z = 2.5.

Radio emission in peculiar galaxies

Science.gov (United States)

Demellorabaca, Dulia F.; Abraham, Zulema

1990-01-01

During the last decades a number of surveys of peculiar galaxies have been carried out and accurate positions become available. Since peculiarities are a possible evidence of radio emission (Wright, 1974; Sulentic, 1976; Stocke et al., 1978), the authors selected a sample of 24 peculiar galaxies with optical jet-like features or extensions in different optical catalogues, mainly the Catalogue of Southern Peculiar Galaxies and Associations (Arp and Madore, 1987) and the ESO/Uppsala Survey of the ESO(B) Atlas (Lauberts, 1982) for observation at the radio continuum frequency of 22 GHz. The sample is listed in a table. Sol (1987) studied this sample and concluded that the majority of the jet-like features seem to admit an explanation in terms of interactive galaxies with bridges and/or tails due to tidal effects. Only in a few cases do the jets seem to be possibly linked to some nuclear activity of the host galaxy. The observations were made with the 13.7m-radome enclosed Itapetinga Radiotelescope (HPBW of 4.3 arcmin), in Brazil. The receiver was a 1 GHz d.s.b. super-heterodine mixer operated in total-power mode, with a system temperature of approximately 800 K. The observational technique consisted in scans in right ascention, centralized in the optical position of the galaxy. The amplitude of one scan was 43 arcmin, and its duration time was 20 seconds. The integration time was at least 2 hours (12 ten-minute observations) and the sensibility limit adopted was an antenna temperature greater than 3 times the r.m.s. error of the baseline determination. Virgo A was used as the calibrator source. Three galaxies were detected for the first time as radio sources and four other known galaxies at low frequencies had their flux densities measured at 22 GHz. The results for these sources are presented.

The Evolution of the Stellar Hosts of Radio Galaxies

International Nuclear Information System (INIS)

Lacy, Mark; Bunker, Andrew J.; Ridgway, Susan E.

2000-01-01

We present new near-infrared images of z>0.8 radio galaxies from the flux-limited 7C-iii sample of radio sources for which we have recently obtained almost complete spectroscopic redshifts. The 7C objects have radio luminosities ≅20 times fainter than 3C radio galaxies at a given redshift. The absolute magnitudes of the underlying host galaxies and their scale sizes are only weakly dependent on radio luminosity. Radio galaxy hosts at z∼2 are significantly brighter than the hosts of radio-quiet quasars at similar redshifts and the recent model AGN hosts of Kauffmann and Haehnelt. There is no evidence for strong evolution in scale size, which shows a large scatter at all redshifts. The hosts brighten significantly with redshift, consistent with the passive evolution of a stellar population that formed at z(greater-or-similar sign)3. This scenario is consistent with studies of host galaxy morphology and submillimeter continuum emission, both of which show strong evolution at z(greater-or-similar sign)2.5. The lack of a strong ''redshift cutoff'' in the radio luminosity function to z>4 suggests that the formation epoch of the radio galaxy host population lasts (greater-or-similar sign)1 Gyr, from z(greater-or-similar sign)5 to z∼3. We suggest these facts are best explained by models in which the most massive galaxies and their associated AGN form early because of high baryon densities in the centers of their dark matter haloes. (c) 2000 The American Astronomical Society

The Host Galaxy and the Extended Emission-Line Region of the Radio Galaxy 3C 79

Science.gov (United States)

Fu, Hai; Stockton, Alan

2008-04-01

We present extensive ground-based spectroscopy and HST imaging of 3C 79, an FR II radio galaxy associated with a luminous extended emission-line region (EELR). Surface brightness modeling of an emission-line-free HST R-band image reveals that the host galaxy is a massive elliptical with a compact companion 0.8'' away and 4 mag fainter. The host galaxy spectrum is best described by an intermediate-age (1.3 Gyr) stellar population (4% by mass), superimposed on a 10 Gyr old population and a power law (αλ = - 1.8); the stellar populations are consistent with supersolar metallicities, with the best fit given by the 2.5 Z⊙ models. We derive a dynamical mass of 4 × 1011 M⊙ within the effective radius from the velocity dispersion. The EELR spectra clearly indicate that the EELR is photoionized by the hidden central engine. Photoionization modeling shows evidence that the gas metallicity in both the EELR and the nuclear narrow-line region is mildly subsolar (0.3-0.7 Z⊙), significantly lower than the supersolar metallicities deduced from typical active galactic nuclei in the Sloan Digital Sky Survey. The more luminous filaments in the EELR exhibit a velocity field consistent with a common disk rotation. Fainter clouds, however, show high approaching velocities that are uncoupled from this apparent disk rotation. The striking similarities between this EELR and the EELRs around steep-spectrum radio-loud quasars provide further evidence for the orientation-dependent unification schemes. The metal-poor gas is almost certainly not native to the massive host galaxy. We suggest that the close companion galaxy could be the tidally stripped bulge of a late-type galaxy that is merging with the host galaxy. The interstellar medium of such a galaxy is probably the source for the low-metallicity gas in 3C 79. Based in part on observations obtained at the Gemini Observatory, which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative

RADIO SOURCE FEEDBACK IN GALAXY EVOLUTION

International Nuclear Information System (INIS)

Shabala, Stanislav; Alexander, Paul

2009-01-01

We present a galaxy evolution model which incorporates a physically motivated implementation of active galactic nucleus feedback. Intermittent jets inflate cocoons of radio plasma which then expand supersonically, shock heating the ambient gas. The model reproduces observed star formation histories to the highest redshifts for which reliable data exist, as well as the observed galaxy color bimodality. Intermittent radio source feedback also naturally provides a way of keeping the black hole and spheroid growth in step. We find possible evidence for a top-heavy initial mass function for z > 2, consistent with observations of element abundances, and submillimeter and Lyman break galaxy counts.

Radio emission in the Virgo cluster and in SO galaxies

International Nuclear Information System (INIS)

Kotanyi, C.

1981-01-01

A survey of the radio continuum emission from the galaxies in the Virgo Cluster is presented. The sample of 274 galaxies in total contains a subsample of 188 galaxies complete down to magntiude msub(p) = 14. The observations consisted mostly of short (10 minutes) observations providing one-dimensional (East-West) strip distributions of the radio brightness at 1.4 GHz, with an East-West resolution of 23'' allowing separation of central sources from extended emission, and an r.m.s. noise level of 2 mJy. The radio emission of SO galaxies is examined. A sample of 145 SO galaxies is obtained by combining the Virgo cluster SO's with the nearby non-cluster SO's. The radio data, mainly from short observations, are used to derive the RLF. The radio emission in SO galaxies is at least three times weaker than that in ellipticals and spirals. Flat-spectrum compact nuclear sources are found in SO galaxies but they are at least 10 times weaker than in elliptical galaxies, which is attributed to the small mass of the bulges in SO's as compared to the mass of elliptical galaxies. The absence of steep-spectrum, extended central sources and of disk radio emission in SO's is attributed to their low neutral hydrogen content. (Auth.)

Millimeter observations of radio-loud active galaxies

NARCIS (Netherlands)

van Bemmel, IM; Bertoldi, F

In order to study the nature of the far-infrared emission observed in radio-loud active galaxies, we have obtained 1.2 mill observations with the IRAM 30 m telescope for a sample of eight radio-loud active galaxies. In all objects we find that the 1.2 mm emission is dominated by non-thermal

The difference between radio-loud and radio-quiet active galaxies

Science.gov (United States)

Wilson, A. S.; Colbert, E. J. M.

1995-01-01

The recent development of unified theories of active galactic nuclei (AGNs) has indicated that there are two physically distinct classes of these objects--radio-loud and radio-quiet. Despite differences, the (probable) thermal emissions from the AGNs (continua and lines from X-ray to infrared wavelengths) are quite similar to the two classes of object. We argue that this last result suggests that the black hole masses and mass accretion rates in the two classes are not greatly different, and that the difference between the classes is associated with the spin of the black hole. We assume that the normal process of accretion through a disk does not lead to rapidly spinning holes and propose that galaxies (e.g., spirals) which have not suffered a recent major merger event contain nonrotating or only slowly rotating black holes. When two such galaxies merge, the two black holes are known to form a binary and we assume that they eventually coalesce. The ratio of the number of radio-loud to radio-quiet AGNs at a given thermal (e.g., optical) luminosity is determined by the galaxy merger rate. Comparisons between the predicted and observed radio luminosity functions constrain the efficiencies with which jet power is extracted from the spinning hole and radio emission is produced by the jet.

A composite plot of far-infrared versus radio luminosity, and the origin of far-infrared luminosity in quasars

International Nuclear Information System (INIS)

Sopp, H.M.; Alexander, P.

1991-01-01

We have constructed a composite plot of far-infrared versus radioluminosity for late-type galaxies, Seyferts, quasars and radio galaxies. The most striking result is that the radio and far-infrared luminosities of radio-quiet quasars are correlated and follow the same correlation as normal star-forming galaxies and ultra-luminous infrared galaxies, whereas the radio-loud quasars have luminosities in both bands similar to those of radio galaxies. We conclude that the far-infrared emission from radio-quiet quasars is from star-forming host galaxies and not from active galactic nuclei. The far-infrared radio plot may be a powerful discriminator between host galaxy type. (author)

Tracking Galaxy Evolution Through Low-Frequency Radio ...

Indian Academy of Sciences (India)

This justify focussing on transitional galaxies to find relic-evidences of the immediate past AGN-feedback which decide the future course of evolution of a galaxy. Relic radio lobes can be best detected in low frequency observations with the GMRT, LOFAR and in future SKA. The age of these relic radio plasma can be as old ...

Classifying Radio Galaxies with the Convolutional Neural Network

Energy Technology Data Exchange (ETDEWEB)

Aniyan, A. K.; Thorat, K. [Department of Physics and Electronics, Rhodes University, Grahamstown (South Africa)

2017-06-01

We present the application of a deep machine learning technique to classify radio images of extended sources on a morphological basis using convolutional neural networks (CNN). In this study, we have taken the case of the Fanaroff–Riley (FR) class of radio galaxies as well as radio galaxies with bent-tailed morphology. We have used archival data from the Very Large Array (VLA)—Faint Images of the Radio Sky at Twenty Centimeters survey and existing visually classified samples available in the literature to train a neural network for morphological classification of these categories of radio sources. Our training sample size for each of these categories is ∼200 sources, which has been augmented by rotated versions of the same. Our study shows that CNNs can classify images of the FRI and FRII and bent-tailed radio galaxies with high accuracy (maximum precision at 95%) using well-defined samples and a “fusion classifier,” which combines the results of binary classifications, while allowing for a mechanism to find sources with unusual morphologies. The individual precision is highest for bent-tailed radio galaxies at 95% and is 91% and 75% for the FRI and FRII classes, respectively, whereas the recall is highest for FRI and FRIIs at 91% each, while the bent-tailed class has a recall of 79%. These results show that our results are comparable to that of manual classification, while being much faster. Finally, we discuss the computational and data-related challenges associated with the morphological classification of radio galaxies with CNNs.

Classifying Radio Galaxies with the Convolutional Neural Network

Science.gov (United States)

Aniyan, A. K.; Thorat, K.

2017-06-01

We present the application of a deep machine learning technique to classify radio images of extended sources on a morphological basis using convolutional neural networks (CNN). In this study, we have taken the case of the Fanaroff-Riley (FR) class of radio galaxies as well as radio galaxies with bent-tailed morphology. We have used archival data from the Very Large Array (VLA)—Faint Images of the Radio Sky at Twenty Centimeters survey and existing visually classified samples available in the literature to train a neural network for morphological classification of these categories of radio sources. Our training sample size for each of these categories is ˜200 sources, which has been augmented by rotated versions of the same. Our study shows that CNNs can classify images of the FRI and FRII and bent-tailed radio galaxies with high accuracy (maximum precision at 95%) using well-defined samples and a “fusion classifier,” which combines the results of binary classifications, while allowing for a mechanism to find sources with unusual morphologies. The individual precision is highest for bent-tailed radio galaxies at 95% and is 91% and 75% for the FRI and FRII classes, respectively, whereas the recall is highest for FRI and FRIIs at 91% each, while the bent-tailed class has a recall of 79%. These results show that our results are comparable to that of manual classification, while being much faster. Finally, we discuss the computational and data-related challenges associated with the morphological classification of radio galaxies with CNNs.

Classifying Radio Galaxies with the Convolutional Neural Network

International Nuclear Information System (INIS)

Aniyan, A. K.; Thorat, K.

2017-01-01

We present the application of a deep machine learning technique to classify radio images of extended sources on a morphological basis using convolutional neural networks (CNN). In this study, we have taken the case of the Fanaroff–Riley (FR) class of radio galaxies as well as radio galaxies with bent-tailed morphology. We have used archival data from the Very Large Array (VLA)—Faint Images of the Radio Sky at Twenty Centimeters survey and existing visually classified samples available in the literature to train a neural network for morphological classification of these categories of radio sources. Our training sample size for each of these categories is ∼200 sources, which has been augmented by rotated versions of the same. Our study shows that CNNs can classify images of the FRI and FRII and bent-tailed radio galaxies with high accuracy (maximum precision at 95%) using well-defined samples and a “fusion classifier,” which combines the results of binary classifications, while allowing for a mechanism to find sources with unusual morphologies. The individual precision is highest for bent-tailed radio galaxies at 95% and is 91% and 75% for the FRI and FRII classes, respectively, whereas the recall is highest for FRI and FRIIs at 91% each, while the bent-tailed class has a recall of 79%. These results show that our results are comparable to that of manual classification, while being much faster. Finally, we discuss the computational and data-related challenges associated with the morphological classification of radio galaxies with CNNs.

Dynamical evolution in clusters of galaxies with low-frequency radio emission

International Nuclear Information System (INIS)

Guthrie, B.N.G.

1977-01-01

Clusters of galaxies in which radio emission at low frequencies ( approximately 10 9 yr). Confinement would probably occur for radio sources associated with bright galaxies in the cores of clusters and cD galaxies in clusters. However, cD galaxies may have recurrent radio outbursts so that steep spectra are not always observed. (Auth.)

Cold Molecular Gas Along the Merger Sequence in Local Luminous Infrared Galaxies

Science.gov (United States)

Yamashita, Takuji; Komugi, Shinya; Matsuhara, Hideo; Armus, Lee; Inami, Hanae; Ueda, Junko; Iono, Daisuke; Kohno, Kotaro; Evans, Aaron S.; Arimatsu, Ko

2017-08-01

We present an initial result from the 12CO (J = 1-0) survey of 79 galaxies in 62 local luminous and ultraluminous infrared galaxy (LIRG and ULIRG) systems obtained using the 45 m telescope at the Nobeyama Radio Observatory. This is a systematic 12CO (J = 1-0) survey of the Great Observatories All-sky LIRGs Survey (GOALS) sample. The molecular gas mass of the sample is in the range 2.2× {10}8{--}7.0× {10}9 {M}⊙ within the central several kiloparsecs subtended by the 15\\prime\\prime beam. A method to estimate the size of a CO gas distribution is introduced, which is combined with the total CO flux in the literature. This method is applied to part of our sample, and we find that the median CO radius is 1-4 kpc. From the early stage to the late stage of mergers, we find that the CO size decreases while the median value of the molecular gas mass in the central several-kiloparsec region is constant. Our results statistically support a scenario where molecular gas inflows toward the central region from the outer disk to replenish gas consumed by starburst, and that such a process is common in merging LIRGs.

Radio and infrared observations of (almost) one hundred non-Seyfert Markarian galaxies

Science.gov (United States)

Dressel, Linda L.

1987-01-01

The 13 cm flux densities of 96 non-Seyfert Markarian galaxies were measured at Arecibo Observatory. Far infrared flux densities have been published for 78 of these galaxies in the IRAS catalog. The radio, infrared, and optical fluxes of these galaxies and of a magnitude limited sample of normal galaxies were compared to clarify the nature of the radio emission in Markarian galaxies. It was found that Markarian galaxies of a given apparent magnitude and Hubble type generally have radio fluxes several times higher that the fluxes typical of normal galaxies of the same magnitude and type. Remarkably, the ratio of radio flux to far infrared flux is nearly the same for most of these starburst galaxies and for normal spiral disks. However, the compact and peculiar Markarian galaxies consistently have about 60% more radio flux per unit infrared flux than the other Markarian galaxies and the normal spirals. It is not clear whether this difference reflects a difference in the evolution of the starbursts in these galaxies or whether there is excess radio emission of nonstellar origin.

The radio galaxy K-z relation to z ~ 4.5

OpenAIRE

Jarvis, Matt J.; Rawlings, Steve; Eales, Steve; Blundell, Katherine M.; Willott, Chris J.

2001-01-01

Using a new radio sample, 6C* designed to find radio galaxies at z > 4 along with the complete 3CRR and 6CE sample we extend the radio galaxy K-z relation to z~4.5. The 6C* K-z data significantly improve delineation of the K-z relation for radio galaxies at high redshift (z > 2). Accounting for non-stellar contamination, and for correlations between radio luminosity and estimates of stellar mass, we find little support for previous claims that the underlying scatter in the stellar luminosity ...

THE MOST LUMINOUS GALAXIES DISCOVERED BY WISE

Energy Technology Data Exchange (ETDEWEB)

Tsai, Chao-Wei; Eisenhardt, Peter R. M.; Stern, Daniel; Moustakas, Leonidas A. [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States); Wu, Jingwen; Wright, Edward L. [Department of Physics and Astronomy, UCLA, Los Angeles, CA 90095-1547 (United States); Assef, Roberto J. [Núcleo de Astronomía de la Facultad deIngeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile); Blain, Andrew W. [Department of Physics and Astronomy, University of Leicester, 1 University Road, Leicester, LE1 7RH (United Kingdom); Bridge, Carrie R.; Sayers, Jack [Division of Physics, Math, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Benford, Dominic J.; Leisawitz, David T. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Cutri, Roc M.; Masci, Frank J.; Yan, Lin [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States); Griffith, Roger L. [Department of Astronomy and Astrophysics, The Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States); Jarrett, Thomas H. [Astronomy Department, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Lonsdale, Carol J. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Petty, Sara M. [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Stanford, S. Adam, E-mail: Chao-Wei.Tsai@jpl.nasa.gov [Department of Physics, University of California Davis, One Shields Avenue, Davis, CA 95616 (United States); and others

2015-06-01

We present 20 Wide-field Infrared Survey Explorer (WISE)-selected galaxies with bolometric luminosities L{sub bol} > 10{sup 14} L{sub ☉}, including five with infrared luminosities L{sub IR} ≡ L{sub (rest} {sub 8–1000} {sub μm)} > 10{sup 14} L{sub ☉}. These “extremely luminous infrared galaxies,” or ELIRGs, were discovered using the “W1W2-dropout” selection criteria which requires marginal or non-detections at 3.4 and 4.6 μm (W1 and W2, respectively) but strong detections at 12 and 22 μm in the WISE survey. Their spectral energy distributions are dominated by emission at rest-frame 4–10 μm, suggesting that hot dust with T{sub d} ∼ 450 K is responsible for the high luminosities. These galaxies are likely powered by highly obscured active galactic nuclei (AGNs), and there is no evidence suggesting these systems are beamed or lensed. We compare this WISE-selected sample with 116 optically selected quasars that reach the same L{sub bol} level, corresponding to the most luminous unobscured quasars in the literature. We find that the rest-frame 5.8 and 7.8 μm luminosities of the WISE-selected ELIRGs can be 30%–80% higher than that of the unobscured quasars. The existence of AGNs with L{sub bol} > 10{sup 14} L{sub ☉} at z > 3 suggests that these supermassive black holes are born with large mass, or have very rapid mass assembly. For black hole seed masses ∼10{sup 3} M{sub ☉}, either sustained super-Eddington accretion is needed, or the radiative efficiency must be <15%, implying a black hole with slow spin, possibly due to chaotic accretion.

Mechanical feedback in the molecular ISM of luminous IR galaxies

NARCIS (Netherlands)

Loenen, A. F.; Spaans, M.; Baan, W. A.; Meijerink, R.

Aims. Molecular emission lines originating in the nuclei of luminous infra-red galaxies are used to determine the physical properties of the nuclear ISM in these systems. Methods. A large observational database of molecular emission lines is compared with model predictions that include heating by UV

Galaxy Evolution in the Radio Band: The Role of Star-forming Galaxies and Active Galactic Nuclei

Energy Technology Data Exchange (ETDEWEB)

Mancuso, C.; Prandoni, I. [INAF-IRA, Via P. Gobetti 101, I-40129 Bologna (Italy); Lapi, A.; Obi, I.; Perrotta, F.; Bressan, A.; Celotti, A.; Danese, L. [SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Gonzalez-Nuevo, J. [Departamento de Fisica, Universidad de Oviedo, C. Calvo Sotelo s/n, E-33007 Oviedo (Spain)

2017-06-20

We investigate the astrophysics of radio-emitting star-forming galaxies and active galactic nuclei (AGNs) and elucidate their statistical properties in the radio band, including luminosity functions, redshift distributions, and number counts at sub-mJy flux levels, which will be crucially probed by next-generation radio continuum surveys. Specifically, we exploit the model-independent approach by Mancuso et al. to compute the star formation rate functions, the AGN duty cycles, and the conditional probability of a star-forming galaxy to host an AGN with given bolometric luminosity. Coupling these ingredients with the radio emission properties associated with star formation and nuclear activity, we compute relevant statistics at different radio frequencies and disentangle the relative contribution of star-forming galaxies and AGNs in different radio luminosity, radio flux, and redshift ranges. Finally, we highlight that radio-emitting star-forming galaxies and AGNs are expected to host supermassive black holes accreting with different Eddington ratio distributions and to occupy different loci in the galaxy main-sequence diagrams. These specific predictions are consistent with current data sets but need to be tested with larger statistics via future radio data with multiband coverage on wide areas, as will become routinely achievable with the advent of the Square Kilometre Array and its precursors.

Radio identifications of UGC galaxies - starbursts and monsters

International Nuclear Information System (INIS)

Condon, J.J.; Broderick, J.J.

1988-01-01

New and previously published observational data on galaxies with declination less than +82 deg from the Uppsala General Catalog (Nilson, 1973) are compiled in extensive tables and characterized in detail. Optical positions are confirmed by measurement of Palomar Sky Survey O prints, and radio identifications for 176 galaxies are made on the basis of 1.4-GHz Green Bank sky maps or 1.49-GHz observations obtained with the C configuration of the VLA in November-December 1986; contour maps based on the latter observations are provided. Radio-selected and IR-selected galaxy populations are found to be similar (and distinct from optically selected populations), and three radio/IR criteria are developed to distinguish galaxies powered by starbursts from those with supermassive black holes or other monster energy sources. 197 references

The Origin of Powerful Radio Sources

Science.gov (United States)

Wilson, A. S.; Colbert, E. J. M.

1995-05-01

Radio-loud active galaxies are associated with elliptical or elliptical-like galaxies, many of which appear to be the result of a recent merger. In contrast, radio-quiet active galaxies prefer spiral hosts. Despite the very large difference in radio luminosities between the two classes, their continua and line spectra from infrared through X-ray frequencies are very similar. In this paper, we describe recent developments of our model (Ap. J. 438, 62 1995) in which the radio-loud phenomenon is the result of a merger of two galaxies, with each galaxy nucleus containing a slowly (or non-) rotating supermassive black hole. It is envisaged that the two black holes eventually coalesce. For the small fraction of mergers in which the two holes are both massive and of comparable mass, a rapidly-spinning, high-mass hole results. The spin energy of a rapidly rotating 10(8-9) solar mass hole suffices to provide the ~ 10(60) ergs in relativistic particles and magnetic fields in the most energetic radio sources. Luminous radio-quiet active galaxies contain high-mass, slowly-rotating holes, with the infrared through X-ray emission of both classes being fuelled by accretion as commonly assumed. We discuss constraints on the model from the luminosity functions of radio-loud and radio-quiet galaxies and from the known cosmological evolution of the radio source population; this evolution is assumed to reflect higher galaxy merger rates in the past.

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

International Nuclear Information System (INIS)

Hunik, Dominika; Jamrozy, Marek

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

Enigmatic sub-luminous accreting neutron stars in our Galaxy

NARCIS (Netherlands)

Wijnands, R.

2008-01-01

During the last few years a class of enigmatic sub-luminous accreting neutron stars has been found in our Galaxy. They have peak X-ray luminosities (2-10 keV) of a few times 10(34) erg s(−1) to a few times 10(35) erg s(−1), and both persistent and transient sources have been found. I present a short

Integrated radio continuum spectra of galaxies

Energy Technology Data Exchange (ETDEWEB)

Marvil, Joshua; Owen, Frazer [National Radio Astronomy Observatory, 1003 Lopezville Rd, Socorro, NM 87801 (United States); Eilek, Jean, E-mail: josh.marvil@csiro.au [New Mexico Tech, Socorro, NM 87801 (United States)

2015-01-01

We investigate the spectral shape of the total continuum radiation, between 74 MHz and 5 GHz (400-6 cm in wavelength), for a large sample of bright galaxies. We take advantage of the overlapping survey coverage of the VLA Low-Frequency Sky Survey, the Westerbork Northern Sky Survey, the NRAO VLA Sky Survey, and the Green Bank 6 cm Survey to achieve significantly better resolution, sensitivity, and sample size compared to prior efforts of this nature. For our sample of 250 bright galaxies we measure a mean spectral index, α, of –0.69 between 1.4 and 4.85 GHz, –0.55 between 325 MHz and 1.4 GHz, and –0.45 between 74 and 325 MHz, which amounts to a detection of curvature in the mean spectrum. The magnitude of this curvature is approximately Δα = –0.2 per logarithmic frequency decade when fit with a generalized function having constant curvature. No trend in low-frequency spectral flattening versus galaxy inclination is evident in our data, suggesting that free-free absorption is not a satisfying explanation for the observed curvature. The ratio of thermal to non-thermal emission is estimated through two independent methods: (1) using the IRAS far-IR fluxes and (2) with the value of the total spectral index. Method (1) results in a distribution of 1.4 GHz thermal fractions of 9% ± 3%, which is consistent with previous studies, while method (2) produces a mean 1.4 GHz thermal fraction of 51% with dispersion 26%. The highly implausible values produced by method (2) indicate that the sum of typical power-law thermal and non-thermal components is not a viable model for the total spectral index between 325 and 1.4 GHz. An investigation into relationships between spectral index, infrared-derived quantities, and additional source properties reveals that galaxies with high radio luminosity in our sample are found to have, on average, a flatter radio spectral index, and early types tend to have excess radio emission when compared to the radio-infrared ratio of later

Radio properties of type 1.8 and 1.9 Seyfert galaxies

International Nuclear Information System (INIS)

Ulvestad, J.S.

1986-01-01

A number of type 1.8 and 1.9 Seyfert galaxies have been observed at the VLA in order to compare their properties with those of the other types of Seyfert galaxy. The observed types have radio luminosities in the range of 10 to the 39th-40.5th args/s, with the median near 10 to the 40th ergs/s. Most of these galaxies have radio sources with diameters of about 500 pc or less. The ratio of radio luminosity to featureless optical continuum luminosity in the Seyfert 1.8/12.9 galaxies and Seyfert 1.2/1.5 galaxies is intermediate between the values for Seyfert 1 and Seyfert 2 galaxies. The infrared-to-radio ratio decreases along the sequence from Seyfert 1 galaxies, through intermediate Seyfert galaxies, to Seyfert 2 galaxies. This systematic statistical difference in the ratio of two aspect-independent quantities implies that the differences among the Seyfert classes cannot be attributed solely to differences in viewing angle. 39 references

DISCOVERY OF A GIANT RADIO HALO IN A NEW PLANCK GALAXY CLUSTER PLCKG171.9-40.7

Energy Technology Data Exchange (ETDEWEB)

Giacintucci, Simona [Department of Astronomy, University of Maryland, College Park, MD 20742 (United States); Kale, Ruta; Venturi, Tiziana [INAF-Istituto di Radioastronomia, via Gobetti 101, I-40129 Bologna (Italy); Wik, Daniel R.; Markevitch, Maxim, E-mail: simona@astro.umd.edu [Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771 (United States)

2013-03-20

We report the discovery of a giant radio halo in a new, hot, X-ray luminous galaxy cluster recently found by Planck, PLCKG171.9-40.7. The radio halo was found using Giant Metrewave Radio Telescope observations at 235 MHz and 610 MHz, and in the 1.4 GHz data from an NRAO Very Large Array Sky Survey pointing that we have reanalyzed. The diffuse radio emission is coincident with the cluster X-ray emission, and has an extent of {approx}1 Mpc and a radio power of {approx}5 Multiplication-Sign 10{sup 24} W Hz{sup -1} at 1.4 GHz. Its integrated radio spectrum has a slope of {alpha} Almost-Equal-To 1.8 between 235 MHz and 1.4 GHz, steeper than that of a typical giant halo. The analysis of the archival XMM-Newton X-ray data shows that the cluster is hot ({approx}10 keV) and disturbed, consistent with X-ray-selected clusters hosting radio halos. This is the first giant radio halo discovered in one of the new clusters found by Planck.

An intrinsically asymmetric radio galaxy: 0500+630?

Science.gov (United States)

Saikia, D. J.; Thomasson, P.; Jackson, N.; Salter, C. J.; Junor, W.

1996-10-01

As part of a search for high-luminosity radio galaxies with one-sided structures, the radio galaxy 0500+630 has been imaged with both the VLA and MERLIN and its optical spectrum determined using the Isaac Newton Telescope on La Palma. The galaxy is found to have a redshift of 0.290+/-0.004. The radio observations show the source to be highly asymmetric, with an overall structure which cannot be understood easily by ascribing it either to orientation and relativistic beaming effects or to an asymmetric distribution of gas in the central region. A comparison of this source with objects of similar luminosity suggests that it is one of the best examples yet of a source with possibly an intrinsic asymmetry in either the collimation of its jets or the supply of energy from the central engine to opposite sides.

Unusual broad-line Mg II emitters among luminous galaxies in the baryon oscillation spectroscopic survey

International Nuclear Information System (INIS)

Roig, Benjamin; Blanton, Michael R.; Ross, Nicholas P.

2014-01-01

Many classes of active galactic nuclei (AGNs) have been observed and recorded since the discovery of Seyfert galaxies. In this paper, we examine the sample of luminous galaxies in the Baryon Oscillation Spectroscopic Survey. We find a potentially new observational class of AGNs, one with strong and broad Mg II λ2799 line emission, but very weak emission in other normal indicators of AGN activity, such as the broad-line Hα, Hβ, and the near-ultraviolet AGN continuum, leading to an extreme ratio of broad Hα/Mg II flux relative to normal quasars. Meanwhile, these objects' narrow-line flux ratios reveal AGN narrow-line regions with levels of activity consistent with the Mg II fluxes and in agreement with that of normal quasars. These AGN may represent an extreme case of the Baldwin effect, with very low continuum and high equivalent width relative to typical quasars, but their ratio of broad Mg II to broad Balmer emission remains very unusual. They may also be representative of a class of AGN where the central engine is observed indirectly with scattered light. These galaxies represent a small fraction of the total population of luminous galaxies (≅ 0.1%), but are more likely (about 3.5 times) to have AGN-like nuclear line emission properties than other luminous galaxies. Because Mg II is usually inaccessible for the population of nearby galaxies, there may exist a related population of broad-line Mg II emitters in the local universe which is currently classified as narrow-line emitters (Seyfert 2 galaxies) or low ionization nuclear emission-line regions.

Radio jets and gamma-ray emission in radio-silent narrow-line Seyfert 1 galaxies

Science.gov (United States)

Lähteenmäki, A.; Järvelä, E.; Ramakrishnan, V.; Tornikoski, M.; Tammi, J.; Vera, R. J. C.; Chamani, W.

2018-06-01

We have detected six narrow-line Seyfert 1 (NLS1) galaxies at 37 GHz that were previously classified as radio silent and two that were classified as radio quiet. These detections reveal the presumption that NLS1 galaxies labelled radio quiet or radio silent and hosted by spiral galaxies are unable to launch jets to be incorrect. The detections are a plausible indicator of the presence of a powerful, most likely relativistic jet because this intensity of emission at 37 GHz cannot be explained by, for example, radiation from supernova remnants. Additionally, one of the detected NLS1 galaxies is a newly discovered source of gamma rays and three others are candidates for future detections. 37 GHz data are only available in electronic form at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/614/L1

The Weak Lensing Masses of Filaments between Luminous Red Galaxies

Science.gov (United States)

Epps, Seth D.; Hudson, Michael J.

2017-07-01

In the standard model of non-linear structure formation, a cosmic web of dark-matter-dominated filaments connects dark matter haloes. In this paper, we stack the weak lensing signal of an ensemble of filaments between groups and clusters of galaxies. Specifically, we detect the weak lensing signal, using CFHTLenS galaxy ellipticities, from stacked filaments between Sloan Digital Sky Survey (SDSS)-III/Baryon Oscillation Spectroscopic Survey luminous red galaxies (LRGs). As a control, we compare the physical LRG pairs with projected LRG pairs that are more widely separated in redshift space. We detect the excess filament mass density in the projected pairs at the 5σ level, finding a mass of (1.6 ± 0.3) × 1013 M⊙ for a stacked filament region 7.1 h-1 Mpc long and 2.5 h-1 Mpc wide. This filament signal is compared with a model based on the three-point galaxy-galaxy-convergence correlation function, as developed in Clampitt et al., yielding reasonable agreement.

STELLAR MASSES OF LYMAN BREAK GALAXIES, Lyα EMITTERS, AND RADIO GALAXIES IN OVERDENSE REGIONS AT z = 4-6

International Nuclear Information System (INIS)

Overzier, Roderik A.; Shu Xinwen; Zheng Wei; Rettura, Alessandro; Zirm, Andrew; Ford, Holland; Bouwens, Rychard J.; Illingworth, Garth D.; Miley, George K.; Venemans, Bram; White, Richard L.

2009-01-01

We present new information on galaxies in the vicinity of luminous radio galaxies (RGs) and quasars at z≅4, 5, and 6. These fields were previously found to contain overdensities of Lyman Break Galaxies (LBGs) or spectroscopic Lyα emitters, which were interpreted as evidence for clusters-in-formation ('protoclusters'). We use Hubble Space Telescope and Spitzer data to infer stellar masses from stellar synthesis models calibrated against the Millennium Run simulations, and contrast our results with large samples of LBGs in more average environments as probed by the Great Observatories Origins Deep Survey (GOODS). The following results were obtained. First, LBGs in both overdense regions and in the field at z = 4-5 lie on a very similar sequence in a z'-[3.6] versus 3.6 μm color-magnitude diagram. This is interpreted as a sequence in stellar mass (M * ∼ 10 9 -10 11 M sun ) in which galaxies become increasingly red due to dust and age as their star formation rate (SFR) increases, while their specific SFR stays constant. Second, the two RGs are among the most massive objects (M * ∼ 10 11 M sun ) known to exist at z ≅ 4-5, and are extremely rare based on the low number density of such objects as estimated from the ∼25x larger area GOODS survey. We suggest that the presence of the massive (radio) galaxies and associated supermassive black holes has been boosted through rapid accretion of gas or merging inside overdense regions. Third, the total stellar mass found in the z = 4 protocluster TN1338 accounts for 4, based on a comparison with the massive X-ray cluster Cl1252 at z = 1.2. Although future near-infrared observations should determine whether any massive galaxies are currently being missed by our UV/Lyα selections, one possible explanation for this mass difference is that TN1338 evolves into a smaller cluster than Cl1252. This raises the interesting question of whether the most massive protocluster regions at z > 4 remain yet to be discovered.

Particle content, radio-galaxy morphology, and jet power: all radio-loud AGN are not equal

Science.gov (United States)

Croston, J. H.; Ineson, J.; Hardcastle, M. J.

2018-05-01

Ongoing and future radio surveys aim to trace the evolution of black hole growth and feedback from active galactic nuclei (AGNs) throughout cosmic time; however, there remain major uncertainties in translating radio luminosity functions into a reliable assessment of the energy input as a function of galaxy and/or dark matter halo mass. A crucial and long-standing problem is the composition of the radio-lobe plasma that traces AGN jet activity. In this paper, we carry out a systematic comparison of the plasma conditions in Fanaroff & Riley class I and II radio galaxies to demonstrate conclusively that their internal composition is systematically different. This difference is best explained by the presence of an energetically dominant proton population in the FRI, but not the FRII radio galaxies. We show that, as expected from this systematic difference in particle content, radio morphology also affects the jet-power/radio-luminosity relationship, with FRII radio galaxies having a significantly lower ratio of jet power to radio luminosity than the FRI cluster radio sources used to derive jet-power scaling relations via X-ray cavity measurements. Finally, we also demonstrate conclusively that lobe composition is unconnected to accretion mode (optical excitation class): the internal conditions of low- and high-excitation FRII radio lobes are indistinguishable. We conclude that inferences of population-wide AGN impact require careful assessment of the contribution of different jet subclasses, particularly given the increased diversity of jet evolutionary states expected to be present in deep, low-frequency radio surveys such as the LOFAR Two-Metre Sky Survey.

Inverse Compton X-Ray Halos Around High-z Radio Galaxies: A Feedback Mechanism Powered by Far-Infrared Starbursts or the Cosmic Microwave Background?

Science.gov (United States)

Small, Ian; Blundell, Katherine M.; Lehmer, B. D.; Alexander, D. M.

2012-01-01

We report the detection of extended X-ray emission around two powerful radio galaxies at z approx. 3.6 (4C 03.24 and 4C 19.71) and use these to investigate the origin of extended, inverse Compton (IC) powered X-ray halos at high redshifts. The halos have X-ray luminosities of L(sub X) approx. 3 x 10(exp 44) erg/s and sizes of approx.60 kpc. Their morphologies are broadly similar to the approx.60 kpc long radio lobes around these galaxies suggesting they are formed from IC scattering by relativistic electrons in the radio lobes, of either cosmic microwave background (CMB) photons or far-infrared photons from the dust-obscured starbursts in these galaxies. These observations double the number of z > 3 radio galaxies with X-ray-detected IC halos. We compare the IC X-ray-to-radio luminosity ratios for the two new detections to the two previously detected z approx. 3.8 radio galaxies. Given the similar redshifts, we would expect comparable X-ray IC luminosities if millimeter photons from the CMB are the dominant seed field for the IC emission (assuming all four galaxies have similar ages and jet powers). Instead we see that the two z approx. 3.6 radio galaxies, which are 4 fainter in the far-infrared than those at z 3.8, also have approx.4x fainter X-ray IC emission. Including data for a further six z > or approx. 2 radio sources with detected IC X-ray halos from the literature, we suggest that in the more compact, majority of radio sources, those with lobe sizes < or approx.100-200 kpc, the bulk of the IC emission may be driven by scattering of locally produced far-infrared photons from luminous, dust-obscured starbursts within these galaxies, rather than millimeter photons from the CMB. The resulting X-ray emission appears sufficient to ionize the gas on approx.100-200 kpc scales around these systems and thus helps form the extended, kinematically quiescent Ly(alpha) emission line halos found around some of these systems. The starburst and active galactic nucleus

INVERSE COMPTON X-RAY HALOS AROUND HIGH-z RADIO GALAXIES: A FEEDBACK MECHANISM POWERED BY FAR-INFRARED STARBURSTS OR THE COSMIC MICROWAVE BACKGROUND?

Energy Technology Data Exchange (ETDEWEB)

Smail, Ian [Institute for Computational Cosmology, Durham University, South Road, Durham DH1 3LE (United Kingdom); Blundell, Katherine M. [Department of Astrophysics, University of Oxford, Keble Road, Oxford OX1 3RH (United Kingdom); Lehmer, B. D. [Department of Physics and Astronomy, The Johns Hopkins University, Homewood Campus, Baltimore, MD 21218 (United States); Alexander, D. M. [Department of Physics, Durham University, South Road, Durham DH1 3LE (United Kingdom)

2012-12-01

We report the detection of extended X-ray emission around two powerful radio galaxies at z {approx} 3.6 (4C 03.24 and 4C 19.71) and use these to investigate the origin of extended, inverse Compton (IC) powered X-ray halos at high redshifts. The halos have X-ray luminosities of L {sub X} {approx} 3 Multiplication-Sign 10{sup 44} erg s{sup -1} and sizes of {approx}60 kpc. Their morphologies are broadly similar to the {approx}60 kpc long radio lobes around these galaxies suggesting they are formed from IC scattering by relativistic electrons in the radio lobes, of either cosmic microwave background (CMB) photons or far-infrared photons from the dust-obscured starbursts in these galaxies. These observations double the number of z > 3 radio galaxies with X-ray-detected IC halos. We compare the IC X-ray-to-radio luminosity ratios for the two new detections to the two previously detected z {approx} 3.8 radio galaxies. Given the similar redshifts, we would expect comparable X-ray IC luminosities if millimeter photons from the CMB are the dominant seed field for the IC emission (assuming all four galaxies have similar ages and jet powers). Instead we see that the two z {approx} 3.6 radio galaxies, which are {approx}4 Multiplication-Sign fainter in the far-infrared than those at z {approx} 3.8, also have {approx}4 Multiplication-Sign fainter X-ray IC emission. Including data for a further six z {approx}> 2 radio sources with detected IC X-ray halos from the literature, we suggest that in the more compact, majority of radio sources, those with lobe sizes {approx}<100-200 kpc, the bulk of the IC emission may be driven by scattering of locally produced far-infrared photons from luminous, dust-obscured starbursts within these galaxies, rather than millimeter photons from the CMB. The resulting X-ray emission appears sufficient to ionize the gas on {approx}100-200 kpc scales around these systems and thus helps form the extended, kinematically quiescent Ly{alpha} emission line

`Zwicky's Nonet': a compact merging ensemble of nine galaxies and 4C 35.06, a peculiar radio galaxy with dancing radio jets

Science.gov (United States)

Biju, K. G.; Bagchi, Joydeep; Ishwara-Chandra, C. H.; Pandey-Pommier, M.; Jacob, Joe; Patil, M. K.; Kumar, P. Sunil; Pandge, Mahadev; Dabhade, Pratik; Gaikwad, Madhuri; Dhurde, Samir; Abraham, Sheelu; Vivek, M.; Mahabal, Ashish A.; Djorgovski, S. G.

2017-10-01

We report the results of our radio, optical and infrared studies of a peculiar radio source 4C 35.06, an extended radio-loud active galactic nucleus (AGN) at the centre of galaxy cluster Abell 407 (z = 0.047). The central region of this cluster hosts a remarkably tight ensemble of nine galaxies, the spectra of which resemble those of passive red ellipticals, embedded within a diffuse stellar halo of ˜1 arcmin size. This system (named 'Zwicky's Nonet') provides unique and compelling evidence for a multiple-nucleus cD galaxy precursor. Multifrequency radio observations of 4C 35.06 with the Giant Meterwave Radio Telescope (GMRT) at 610, 235 and 150 MHz reveal a system of 400-kpc scale helically twisted and kinked radio jets and outer diffuse lobes. The outer extremities of jets contain extremely steep-spectrum (spectral index -1.7 to -2.5) relic/fossil radio plasma with a spectral age of a few ×(107-108) yr. Such ultra-steep spectrum relic radio lobes without definitive hotspots are rare and they provide an opportunity to understand the life cycle of relativistic jets and physics of black hole mergers in dense environments. We interpret our observations of this radio source in the context of growth of its central black hole, triggering of its AGN activity and jet precession, all possibly caused by galaxy mergers in this dense galactic system. A slow conical precession of the jet axis due to gravitational perturbation between interacting black holes is invoked to explain the unusual jet morphology.

A CANDIDATE FOR THE MOST LUMINOUS OB ASSOCIATION IN THE GALAXY

International Nuclear Information System (INIS)

Rahman, Mubdi; Matzner, Christopher; Moon, Dae-Sik

2011-01-01

The Milky Way harbors giant H II regions, which may be powered by star complexes more luminous than any known Galactic OB association. Being across the disk of the Galaxy, however, these brightest associations are severely extinguished and confused. We present a search for one such association toward the most luminous H II region in the recent catalog by Murray and Rahman, which, at ∼9.7 kpc, has a recombination rate of ∼7 x 10 51 s -1 . Prior searches have identified only small-scale clustering around the rim of this shell-like region, but the primary association has not previously been identified. We apply a near-infrared color selection and find an overdensity of point sources toward its southern central part. The colors and magnitudes of these excess sources are consistent with O- and early B-type stars at extinctions 0.96 K < 1.2, and they are sufficiently numerous (406 ± 102 after subtraction of field sources) to ionize the surrounding H II region, making this a candidate for the most luminous OB association in the Galaxy. We reject an alternate theory, in which the apparent excess is caused by localized extinction, as inconsistent with source demographics.

Coma cluster ultradiffuse galaxies are not standard radio galaxies

Science.gov (United States)

Struble, Mitchell F.

2018-02-01

Matching members in the Coma cluster catalogue of ultradiffuse galaxies (UDGs) from SUBARU imaging with a very deep radio continuum survey source catalogue of the cluster using the Karl G. Jansky Very Large Array (VLA) within a rectangular region of ∼1.19 deg2 centred on the cluster core reveals matches consistent with random. An overlapping set of 470 UDGs and 696 VLA radio sources in this rectangular area finds 33 matches within a separation of 25 arcsec; dividing the sample into bins with separations bounded by 5, 10, 20 and 25 arcsec finds 1, 4, 17 and 11 matches. An analytical model estimate, based on the Poisson probability distribution, of the number of randomly expected matches within these same separation bounds is 1.7, 4.9, 19.4 and 14.2, each, respectively, consistent with the 95 per cent Poisson confidence intervals of the observed values. Dividing the data into five clustercentric annuli of 0.1° and into the four separation bins, finds the same result. This random match of UDGs with VLA sources implies that UDGs are not radio galaxies by the standard definition. Those VLA sources having integrated flux >1 mJy at 1.4 GHz in Miller, Hornschemeier and Mobasher without SDSS galaxy matches are consistent with the known surface density of background radio sources. We briefly explore the possibility that some unresolved VLA sources near UDGs could be young, compact, bright, supernova remnants of Type Ia events, possibly in the intracluster volume.

THE UNIFICATION OF POWERFUL QUASARS AND RADIO GALAXIES AND THEIR RELATION TO OTHER MASSIVE GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Podigachoski, Pece; Barthel, Peter [Kapteyn Astronomical Institute, University of Groningen, 9747 AD Groningen (Netherlands); Haas, Martin [Astronomisches Institut, Ruhr Universität, D-44801 Bochum (Germany); Leipski, Christian [Max-Planck Institut für Astronomie (MPIA), D-69117 Heidelberg (Germany); Wilkes, Belinda, E-mail: podigachoski@astro.rug.nl [Harvard-Smithsonian Center for Astrophysics, Cambridge, MA 02138 (United States)

2015-06-10

The unification model for powerful radio galaxies (RGs) and radio-loud quasars postulates that these objects are intrinsically the same but viewed along different angles. Herschel Space Observatory data permit the assessment of that model in the far-infrared spectral window. We analyze photometry from Spitzer and Herschel for the distant 3CR hosts, and find that RGs and quasars have different mid-infrared, but indistinguishable far-infrared colors. Both these properties, the former being orientation dependent and the latter orientation invariant, are in line with expectations from the unification model. Adding powerful radio-quiet active galaxies and typical massive star-forming (SF) galaxies to the analysis, we demonstrate that infrared colors not only provide an orientation indicator, but can also distinguish active from SF galaxies.

THE UNIFICATION OF POWERFUL QUASARS AND RADIO GALAXIES AND THEIR RELATION TO OTHER MASSIVE GALAXIES

International Nuclear Information System (INIS)

Podigachoski, Pece; Barthel, Peter; Haas, Martin; Leipski, Christian; Wilkes, Belinda

2015-01-01

The unification model for powerful radio galaxies (RGs) and radio-loud quasars postulates that these objects are intrinsically the same but viewed along different angles. Herschel Space Observatory data permit the assessment of that model in the far-infrared spectral window. We analyze photometry from Spitzer and Herschel for the distant 3CR hosts, and find that RGs and quasars have different mid-infrared, but indistinguishable far-infrared colors. Both these properties, the former being orientation dependent and the latter orientation invariant, are in line with expectations from the unification model. Adding powerful radio-quiet active galaxies and typical massive star-forming (SF) galaxies to the analysis, we demonstrate that infrared colors not only provide an orientation indicator, but can also distinguish active from SF galaxies

Statistical analysis of the Einstein normal galaxy sample. III. Radio and X-ray properties of elliptical and S0 galaxies

International Nuclear Information System (INIS)

Fabbiano, G.; Klein, U.; Trinchieri, G.; Wielebinski, R.; Bonn Universitaet, West Germany; Arcetri, Osservatorio Astrofisico, Florence, Italy; Max-Planck-Institut fuer Radioastronomie, Bonn, West Germany)

1987-01-01

Radioastronomy, optical and X-ray data were used to probe the cause of high X-ray luminosities of 28 radio-quiet elliptical galaxies (RQE) and S0 galaxies previously scanned by the Einstein Observatory. Comparisons were made with similar data on double-lobed 3CR galaxies. Radio luminosities were highly correlated with the X-ray luminosities, agreeing with models of radio nuclear sources in early-type galaxies as accreting compact objects. Additionally, 3CR galaxies seemed to be large-scale versions of normal RQE. The significance of interstellar medium/intracluster medium interactions for high correlations between the core and total radio power from X-ray emitting galaxies is discussed. 54 references

Model of the electron acceleration in the clouds of radio galaxies

International Nuclear Information System (INIS)

Fedorenko, V.N.

1980-01-01

The mechanism of electron turbulent acceleration in the clouds of radio galaxies is studied. It is suggested that clouds of radio galaxies are continuously filled by relativistic matter. A self-consistent turbulent acceleration regime in the clouds of radio galaxies is shown to be realized. The synchrotron energetic losses of the ultra-relativistic electrons are compensated by the turbulent acceleration due to Langmuir and Alfven waves. The source of Langmuir waves turbulence is the relativistic matter emanating from the galaxy nuclei and relaxating within the ''hot spots'' of the clouds

The host galaxy of a fast radio burst.

Science.gov (United States)

Keane, E F; Johnston, S; Bhandari, S; Barr, E; Bhat, N D R; Burgay, M; Caleb, M; Flynn, C; Jameson, A; Kramer, M; Petroff, E; Possenti, A; van Straten, W; Bailes, M; Burke-Spolaor, S; Eatough, R P; Stappers, B W; Totani, T; Honma, M; Furusawa, H; Hattori, T; Morokuma, T; Niino, Y; Sugai, H; Terai, T; Tominaga, N; Yamasaki, S; Yasuda, N; Allen, R; Cooke, J; Jencson, J; Kasliwal, M M; Kaplan, D L; Tingay, S J; Williams, A; Wayth, R; Chandra, P; Perrodin, D; Berezina, M; Mickaliger, M; Bassa, C

2016-02-25

In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty in pinpointing their celestial coordinates. Here we report the discovery of a fast radio burst and the identification of a fading radio transient lasting ~6 days after the event, which we use to identify the host galaxy; we measure the galaxy's redshift to be z = 0.492 ± 0.008. The dispersion measure and redshift, in combination, provide a direct measurement of the cosmic density of ionized baryons in the intergalactic medium of ΩIGM = 4.9 ± 1.3 per cent, in agreement with the expectation from the Wilkinson Microwave Anisotropy Probe, and including all of the so-called 'missing baryons'. The ~6-day radio transient is largely consistent with the radio afterglow of a short γ-ray burst, and its existence and timescale do not support progenitor models such as giant pulses from pulsars, and supernovae. This contrasts with the interpretation of another recently discovered fast radio burst, suggesting that there are at least two classes of bursts.

3C 220.3: A Radio Galaxy Lensing a Submillimeter Galaxy

NARCIS (Netherlands)

Haas, Martin; Leipski, Christian; Barthel, Peter; Wilkes, Belinda J.; Vegetti, Simona; Bussmann, R. Shane; Willner, S. P.; Westhues, Christian; Ashby, Matthew L. N.; Chini, Rolf; Clements, David L.; Fassnacht, Christopher D.; Horesh, Assaf; Klaas, Ulrich; Koopmans, Léon V. E.; Kuraszkiewicz, Joanna; Lagattuta, David J.; Meisenheimer, Klaus; Stern, Daniel; Wylezalek, Dominika

2014-01-01

Herschel Space Observatory photometry and extensive multiwavelength follow-up have revealed that the powerful radio galaxy (PRG) 3C 220.3 at z = 0.685 acts as a gravitational lens for a background submillimeter galaxy (SMG) at z = 2.221. At an observed wavelength of 1 mm, the SMG is lensed into

THE WHIQII SURVEY: METALLICITIES AND SPECTROSCOPIC PROPERTIES OF LUMINOUS COMPACT BLUE GALAXIES

International Nuclear Information System (INIS)

Tollerud, Erik J.; Barton, Elizabeth J.; Cooke, Jeff; Van Zee, Liese

2010-01-01

As part of the WIYN High Image Quality Indiana-Irvine (WHIQII) survey, we present 123 spectra of faint emission-line galaxies, selected to focus on intermediate redshift (0.4 ∼ 23 -O 32 plane that differs from luminous local galaxies and is more consistent with dwarf irregulars at the present epoch, suggesting that cosmic 'downsizing' is observable in even the most fundamental parameters that describe star formation. These properties for our sample are also generally consistent with lying between local galaxies and those at high redshift, as expected by this scenario. Surprisingly, our sample exhibits no detectable correlation between compactness and metallicity, strongly suggesting that at these epochs of rapid star formation, the morphology of compact star-forming galaxies is largely transient.

A Polarimetric Search for Hidden Quasars in Three Radio-selected Ultraluminous Infrared Galaxies

International Nuclear Information System (INIS)

Tran, H.D.; Brotherton, M.S.; Stanford, S.A.; Breugel, W. van; Dey, A.; Stern, D.; Antonucci, R.

1999-01-01

We have carried out a spectropolarimetric search for hidden broad-line quasars in three ultraluminous infrared galaxies (ULIRGs) discovered in the positional correlations between sources detected in deep radio surveys and the IRAS Faint Source Catalog. Only the high-ionization Seyfert 2 galaxy TF J1736+1122 is highly polarized, displaying a broad-line spectrum visible in polarized light. The other two objects, TF J1020+6436 and FF J1614+3234, display spectra dominated by a population of young (A type) stars similar to those of open-quotes E+Aclose quotes galaxies. They are unpolarized, showing no sign of hidden broad-line regions. The presence of young starburst components in all three galaxies indicates that the ULIRG phenomenon encompasses both active galactic nuclei (AGNs) and starburst activity, but the most energetic ULIRGs do not necessarily harbor open-quotes buried quasars.close quotes We find that a luminous infrared galaxy is most likely to host an obscured quasar if it exhibits a high-ionization ([O iii] λ5007/Hβ approx-gt 5) spectrum typical of a 'classic' Seyfert 2 galaxy with little or no Balmer absorption lines, is 'ultraluminous' (L IR approx-gt 10 12 L circle-dot ), and has a 'warm' IR color (f 25 /f 60 approx-gt 0.25). The detection of hidden quasars in this group but not in the low-ionization, starburst-dominated ULIRGs (classified as LINERs or H ii galaxies) may indicate an evolutionary connection, with the latter being found in younger systems. copyright copyright 1999. The American Astronomical Society

A Fast Radio Burst Host Galaxy

OpenAIRE

Keane, E. F.; Johnston, S.; Bhandari, S.; Barr, E.; Bhat, N. D. R.; Burgay, M.; Caleb, M.; Flynn, C.; Jameson, A.; Kramer, M.; Petroff, E.; Possenti, A.; van Straten, W.; Bailes, M.; Burke-Spolaor, S.

2016-01-01

In recent years, millisecond duration radio signals originating from distant galaxies appear to have been discovered in the so-called Fast Radio Bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity which, in tandem with a redshift measurement, can be used for fundamental physical investigations. While every fast radio burst has a dispersion measurement, none before now have had a redshift measurement, due to the difficulty in...

The Atacama Cosmology Telescope: Detection or Sunyaev-Zel'Dovich Decrement in Groups and Clusters Associated with Luminous Red Galaxies

Science.gov (United States)

Hand, Nick; Appel, John William; Battaglia, Nick; Bond, J. Richard; Das, Sudeep; Devlin, Mark J.; Dunkley, Joanna; Dunner, Rolando; Essinger-Hileman, Thomas; Fowler, Joseph W.;

The First Hyper-Luminous Infrared Galaxy Discovered by WISE

Science.gov (United States)

Eisenhardt, Peter R.; Wu, Jingwen; Tsai, Chao-Wei; Assef, Roberto; Benford, Dominic; Blain, Andrew; Bridge, Carrie; Condon, J. J.; Cushing, Michael C.; Cutri, Roc;

A statistical analysis of the Einstein normal galaxy sample. III - Radio and X-ray properties of elliptical and S0 galaxies

Science.gov (United States)

Fabbiano, G.; Klein, U.; Trinchieri, G.; Wielebinski, R.

1987-01-01

Radioastronomy, optical and X-ray data were used to probe the cause of high X-ray luminosities of 28 radio-quiet elliptical galaxies (RQE) and S0 galaxies previously scanned by the Einstein Observatory. Comparisons were made with similar data on double-lobed 3CR galaxies. Radio luminosities were highly correlated with the X-ray luminosities, agreeing with models of radio nuclear sources in early-type galaxies as accreting compact objects. Additionally, 3CR galaxies seemed to be large-scale versions of normal RQE. The significance of interstellar medium/intracluster medium interactions for high correlations between the core and total radio power from X-ray emitting galaxies is discussed.

The radio halo and active galaxies in the Coma cluster

International Nuclear Information System (INIS)

Cordey, R.A.

1985-01-01

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)

WARM MOLECULAR GAS IN LUMINOUS INFRARED GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Lu, N.; Zhao, Y.; Xu, C. K.; Mazzarella, J. M.; Howell, J.; Appleton, P.; Lord, S.; Schulz, B. [Infrared Processing and Analysis Center, California Institute of Technology, MS 100-22, Pasadena, CA 91125 (United States); Gao, Y. [Purple Mountain Observatory, Chinese Academy of Sciences, Nanjing 210008 (China); Armus, L.; Díaz-Santos, T.; Surace, J. [Spitzer Science Center, California Institute of Technology, MS 220-6, Pasadena, CA 91125 (United States); Isaak, K. G. [ESA Astrophysics Missions Division, ESTEC, P.O. Box 299, 2200-AG Noordwijk (Netherlands); Petric, A. O. [Gemini Observatory, 670 N. A' ohoku Place, Hilo, HI 96720 (United States); Charmandaris, V. [Department of Physics, University of Crete, GR-71003 Heraklion (Greece); Evans, A. S. [Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904 (United States); Inami, H. [National Optical Astronomy Observatory, Tucson, AZ 85719 (United States); Iwasawa, K. [ICREA and Institut de Ciències del Cosmos (ICC), Universitat de Barcelona (IEEC-UB), Martí i Franquès 1, E-08028 Barcelona (Spain); Leech, J. [Department of Physics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom); Sanders, D. B., E-mail: lu@ipac.caltech.edu [Institute for Astronomy, University of Hawaii, 2680 Woodlawn Drive, Honolulu, HI 96822 (United States); and others

2014-06-01

We present our initial results on the CO rotational spectral line energy distribution (SLED) of the J to J–1 transitions from J = 4 up to 13 from Herschel SPIRE spectroscopic observations of 65 luminous infrared galaxies (LIRGs) in the Great Observatories All-Sky LIRG Survey. The observed SLEDs change on average from one peaking at J ≤ 4 to a broad distribution peaking around J ∼ 6 to 7 as the IRAS 60-to-100 μm color, C(60/100), increases. However, the ratios of a CO line luminosity to the total infrared luminosity, L {sub IR}, show the smallest variation for J around 6 or 7. This suggests that, for most LIRGs, ongoing star formation (SF) is also responsible for a warm gas component that emits CO lines primarily in the mid-J regime (5 ≲ J ≲ 10). As a result, the logarithmic ratios of the CO line luminosity summed over CO (5–4), (6–5), (7–6), (8–7) and (10–9) transitions to L {sub IR}, log R {sub midCO}, remain largely independent of C(60/100), and show a mean value of –4.13 (≡log R{sub midCO}{sup SF}) and a sample standard deviation of only 0.10 for the SF-dominated galaxies. Including additional galaxies from the literature, we show, albeit with a small number of cases, the possibility that galaxies, which bear powerful interstellar shocks unrelated to the current SF, and galaxies, in which an energetic active galactic nucleus contributes significantly to the bolometric luminosity, have their R {sub midCO} higher and lower than R{sub midCO}{sup SF}, respectively.

THE HOST GALAXY OF THE SUPER-LUMINOUS SN 2010gx AND LIMITS ON EXPLOSIVE 56Ni PRODUCTION

International Nuclear Information System (INIS)

Chen, Ting-Wan; Smartt, Stephen J.; Kotak, Rubina; McCrum, Matt; Fraser, Morgan; Bresolin, Fabio; Kudritzki, Rolf-Peter; Pastorello, Andrea; Valenti, Stefano

2013-01-01

Super-luminous supernovae have a tendency to occur in faint host galaxies which are likely to have low mass and low metallicity. While these extremely luminous explosions have been observed from z = 0.1 to 1.55, the closest explosions allow more detailed investigations of their host galaxies. We present a detailed analysis of the host galaxy of SN 2010gx (z = 0.23), one of the best studied super-luminous type Ic supernovae. The host is a dwarf galaxy (M g = –17.42 ± 0.17) with a high specific star formation rate. It has a remarkably low metallicity of 12 + log (O/H) = 7.5 ± 0.1 dex as determined from the detection of the [O III] λ4363 line. This is the first reliable metallicity determination of a super-luminous stripped-envelope supernova host. We collected deep multi-epoch imaging with Gemini + GMOS between 240 and 560 days after explosion to search for any sign of radioactive 56 Ni, which might provide further insights on the explosion mechanism and the progenitor's nature. We reach griz magnitudes of m AB ∼ 26, but do not detect SN 2010gx at these epochs. The limit implies that any 56 Ni production was similar to or below that of SN 1998bw (a luminous type Ic SN that produced around 0.4 M ☉ of 56 Ni). The low volumetric rates of these supernovae (∼10 –4 of the core-collapse population) could be qualitatively matched if the explosion mechanism requires a combination of low-metallicity (below 0.2 Z ☉ ), high progenitor mass (>60 M ☉ ) and high rotation rate (fastest 10% of rotators).

GMRT Low Radio Frequency Study of the Wolf Rayet Galaxy NGC ...

Indian Academy of Sciences (India)

In this paper, we present the first low frequency (< 1.4 GHz) radio continuum study of a Wolf Rayet galaxy NGC 4214 using the Giant Meterwave Radio Telescope (GMRT). We detect diffuse extended emission from the galaxy disk at 325 MHz and find that the radio emission closely follows the ultraviolet emission mapped by ...

GMRT Low Radio Frequency Study of the Wolf Rayet Galaxy NGC ...

Indian Academy of Sciences (India)

Abstract. In this paper, we present the first low frequency (< 1.4 GHz) radio continuum study of a Wolf Rayet galaxy NGC 4214 using the. Giant Meterwave Radio Telescope (GMRT). We detect diffuse extended emission from the galaxy disk at 325 MHz and find that the radio emis- sion closely follows the ultraviolet emission ...

Radio Selection of the Most Distant Galaxy Clusters

Science.gov (United States)

Daddi, E.; Jin, S.; Strazzullo, V.; Sargent, M. T.; Wang, T.; Ferrari, C.; Schinnerer, E.; Smolčić, V.; Calabró, A.; Coogan, R.; Delhaize, J.; Delvecchio, I.; Elbaz, D.; Gobat, R.; Gu, Q.; Liu, D.; Novak, M.; Valentino, F.

2017-09-01

We show that the most distant X-ray-detected cluster known to date, Cl J1001 at {z}{spec}=2.506, hosts a strong overdensity of radio sources. Six of them are individually detected (within 10\\prime\\prime ) in deep 0\\buildrel{\\prime\\prime}\\over{.} 75 resolution VLA 3 GHz imaging, with {S}3{GHz}> 8 μ {Jy}. Of the six, an active galactic nucleus (AGN) likely affects the radio emission in two galaxies, while star formation is the dominant source powering the remaining four. We searched for cluster candidates over the full COSMOS 2 deg2 field using radio-detected 3 GHz sources and looking for peaks in {{{Σ }}}5 density maps. Cl J1001 is the strongest overdensity by far with > 10σ , with a simple {z}{phot}> 1.5 preselection. A cruder photometric rejection of zsamples of the first generation of forming galaxy clusters. In these remarkable structures, widespread star formation and AGN activity of massive galaxy cluster members, residing within the inner cluster core, will ultimately lead to radio continuum as one of the most effective means for their identification, with detection rates expected in the ballpark of 0.1-1 per square degree at z≳ 2.5. Samples of hundreds such high-redshift clusters could potentially constrain cosmological parameters and test cluster and galaxy formation models.

Total molecular gas masses of Planck - Herschel selected strongly lensed hyper luminous infrared galaxies

Science.gov (United States)

Harrington, K. C.; Yun, M. S.; Magnelli, B.; Frayer, D. T.; Karim, A.; Weiß, A.; Riechers, D.; Jiménez-Andrade, E. F.; Berman, D.; Lowenthal, J.; Bertoldi, F.

2018-03-01

We report the detection of CO(1-0) line emission from seven Planck and Herschel selected hyper luminous ({L_{IR (8-1000{μ m})} > 10^{13} L_{⊙}) infrared galaxies with the Green Bank Telescope (GBT). CO(1-0) measurements are a vital tool to trace the bulk molecular gas mass across all redshifts. Our results place tight constraints on the total gas content of these most apparently luminous high-z star-forming galaxies (apparent IR luminosities of LIR > 1013 - 14 L⊙), while we confirm their predetermined redshifts measured using the Large Millimeter Telescope, LMT (zCO = 1.33-3.26). The CO(1-0) lines show similar profiles as compared to Jup = 2-4 transitions previously observed with the LMT. We report enhanced infrared to CO line luminosity ratios of = 110 ± 22 L_{⊙} (K km s^{-1} pc^{-2})^{-1} compared to normal star-forming galaxies, yet similar to those of well-studied IR-luminous galaxies at high-z. We find average brightness temperature ratios of 〈 r21〉 = 0.93 (2 sources), 〈 r31〉 = 0.34 (5 sources), and 〈 r41〉 = 0.18 (1 source). The r31 and r41 values are roughly half the average values for SMGs. We estimate the total gas mass content as {μ M_{H2} = (0.9-27.2) × 10^{11} (α _CO/0.8) M_{⊙}, where μ is the magnification factor and αCO is the CO line luminosity to molecular hydrogen gas mass conversion factor. The rapid gas depletion times, = 80} Myr, reveal vigorous starburst activity, and contrast the Gyr depletion time-scales observed in local, normal star-forming galaxies.

The HR diagram for luminous stars in nearby galaxies

International Nuclear Information System (INIS)

Humphreys, R.M.

1978-01-01

Due to the extreme faintness of stars in other galaxies it is only possible to sample the brightest stars in the nearest galaxies. The observations must then be compared with comparable data for the brightest stars, the supergiants and O-type stars, in the Milky Way. The data for the luminous stars are most complete for the Milky Way and the Large Magellanic Cloud. The luminosities for the stars in our Galaxy are based on their membership in associations and clusters, and consequently are representative of Population I within approximately 3kpc of the Sun. The data for the stars in the LMC with spectral types O to G8 come from published observations, and the M supergiants are from the author's recent observations of red stars in the LMC. This is the first time that the M supergiants have been included in an HR diagram of the Large Cloud. The presence of the red stars is important for any discussion of the evolution of the massive stars. (Auth.)

Spectroscopy of 125 QSO candidates and radio galaxies

International Nuclear Information System (INIS)

Wills, B.J.; Wills, D.

1980-01-01

Spectroscopic observations of 125 QSO candidates and radio galaxies are reported, many of which are optical identifications of radio sources in the deep survey in progress at the University of Texas Radio Astronomy Observatory (UTRAO). The remainder include optical identifications of sources in other radio surveys and radio-quiet objects selected by their ultraviolet continua or optical variability. Optical positions are given with O''.5 accuracy for 56 of the objects.Forty objects are confirmed as QSOs; redshifts are given for 38 of them and for 18 galaxies. There are also seven objects with apparently continuous spectra: some of them were already known or suspected to be BL Lacertae objects. Twenty-nine objects were found to be Galactic stars, and the results for the remaining 31 are inconclusive, although 12 of them are probable QSOs and six are probable stars.Our spectroscopy of a sample of 90 blue stellar objects found within 3'' of the UTRAO radio positions (including results from two earlier papers) shows that 81 (90%) are QSOs, with inconclusive results fo the other nine; none of the 90 is known to be a star. Even within 5'' of the UTRAO positions, 111 of 128 blue objects (87%) are QSOs, and only five (4%) are known or suspected to be stars. Among 21 red or neutral-color, apparently stellar objects within 3'' of the UTRAO positions, six are QSOs or compact galaxies, 13 are stars, and the results for two more are inconclusive

Radio properties of central dominant galaxies in cluster cooling flows

International Nuclear Information System (INIS)

O'dea, C.P.; Baum, S.A.

1986-01-01

New VLA observations of central dominant (cd) galaxies currently thought to be in cluster cooling flows are combined with observations from the literature to examine the global properties of a heterogeneous sample of 31 cd galaxies. The radio sources tend to be of low or intermediate radio power and have small sizes (median extent about 25 kpc). The resolved sources tend to have distorted morphologies (e.g., wide-angle tails and S shapes). It is not yet clear whether the radio emission from these cd galaxies is significantly different from those not thought to be in cluster cooling flows. The result of Jones and Forman (1984), that there is a possible correlation between radio power and excess X-ray luminosity in the cluster center (above a King model fit to the X-ray surface brightness), is confirmed. 43 references

The radio properties of infrared-faint radio sources

Science.gov (United States)

Middelberg, E.; Norris, R. P.; Hales, C. A.; Seymour, N.; Johnston-Hollitt, M.; Huynh, M. T.; Lenc, E.; Mao, M. Y.

2011-02-01

Context. Infrared-faint radio sources (IFRS) are objects that have flux densities of several mJy at 1.4 GHz, but that are invisible at 3.6 μm when using sensitive Spitzer observations with μJy sensitivities. Their nature is unclear and difficult to investigate since they are only visible in the radio. Aims: High-resolution radio images and comprehensive spectral coverage can yield constraints on the emission mechanisms of IFRS and can give hints to similarities with known objects. Methods: We imaged a sample of 17 IFRS at 4.8 GHz and 8.6 GHz with the Australia Telescope Compact Array to determine the structures on arcsecond scales. We added radio data from other observing projects and from the literature to obtain broad-band radio spectra. Results: We find that the sources in our sample are either resolved out at the higher frequencies or are compact at resolutions of a few arcsec, which implies that they are smaller than a typical galaxy. The spectra of IFRS are remarkably steep, with a median spectral index of -1.4 and a prominent lack of spectral indices larger than -0.7. We also find that, given the IR non-detections, the ratio of 1.4 GHz flux density to 3.6 μm flux density is very high, and this puts them into the same regime as high-redshift radio galaxies. Conclusions: The evidence that IFRS are predominantly high-redshift sources driven by active galactic nuclei (AGN) is strong, even though not all IFRS may be caused by the same phenomenon. Compared to the rare and painstakingly collected high-redshift radio galaxies, IFRS appear to be much more abundant, but less luminous, AGN-driven galaxies at similar cosmological distances.

AN EXAMINATION OF THE OPTICAL SUBSTRUCTURE OF GALAXY CLUSTERS HOSTING RADIO SOURCES

International Nuclear Information System (INIS)

Wing, Joshua D.; Blanton, Elizabeth L.

2013-01-01

Using radio sources from the Faint Images of the Radio Sky at Twenty-cm survey, and optical counterparts in the Sloan Digital Sky Survey, we have identified a large number of galaxy clusters. The radio sources within these clusters are driven by active galactic nuclei, and our cluster samples include clusters with bent, and straight, double-lobed radio sources. We also included a single-radio-component comparison sample. We examine these galaxy clusters for evidence of optical substructure, testing the possibility that bent double-lobed radio sources are formed as a result of large-scale cluster mergers. We use a suite of substructure analysis tools to determine the location and extent of substructure visible in the optical distribution of cluster galaxies, and compare the rates of substructure in clusters with different types of radio sources. We found no preference for significant substructure in clusters hosting bent double-lobed radio sources compared to those with other types of radio sources.

WISE Discovery of Hyper Luminous Galaxies at z=2-4 and Their Implications for Galaxy and AGN Evolution

Science.gov (United States)

Tsai, Chao Wei; Eisenhardt, Peter; Wu, Jingwen; Bridge, Carrie; Assef, Roberto; Benford, Dominic; Blain, Andrew; Cutri, Roc; Griffith, Robert L.; Jarrett, Thomas;

Cosmological information in the intrinsic alignments of luminous red galaxies

Energy Technology Data Exchange (ETDEWEB)

Chisari, Nora Elisa [Department of Astrophysical Sciences, Princeton University, 4 Ivy Lane, Princeton, NJ 08544 (United States); Dvorkin, Cora, E-mail: nchisari@astro.princeton.edu, E-mail: cdvorkin@ias.edu [Institute for Advanced Study, School of Natural Sciences, Einstein Drive, Princeton, NJ 08540 (United States)

2013-12-01

The intrinsic alignments of galaxies are usually regarded as a contaminant to weak gravitational lensing observables. The alignment of Luminous Red Galaxies, detected unambiguously in observations from the Sloan Digital Sky Survey, can be reproduced by the linear tidal alignment model of Catelan, Kamionkowski and Blandford (2001) on large scales. In this work, we explore the cosmological information encoded in the intrinsic alignments of red galaxies. We make forecasts for the ability of current and future spectroscopic surveys to constrain local primordial non-Gaussianity and Baryon Acoustic Oscillations (BAO) in the cross-correlation function of intrinsic alignments and the galaxy density field. For the Baryon Oscillation Spectroscopic Survey, we find that the BAO signal in the intrinsic alignments is marginally significant with a signal-to-noise ratio of 1.8 and 2.2 with the current LOWZ and CMASS samples of galaxies, respectively, and increasing to 2.3 and 2.7 once the survey is completed. For the Dark Energy Spectroscopic Instrument and for a spectroscopic survey following the EUCLID redshift selection function, we find signal-to-noise ratios of 12 and 15, respectively. Local type primordial non-Gaussianity, parametrized by f{sub NL} = 10, is only marginally significant in the intrinsic alignments signal with signal-to-noise ratios < 2 for the three surveys considered.

Galaxy masses in large surveys: Connecting luminous and dark matter with weak lensing and kinematics

Science.gov (United States)

Reyes, Reinabelle

2011-01-01

Galaxy masses are difficult to determine because light traces stars and gas in a non-trivial way, and does not trace dark matter, which extends well beyond the luminous regions of galaxies. In this thesis, I use the most direct probes of dark matter available---weak gravitational lensing and galaxy kinematics---to trace the total mass in galaxies (and galaxy clusters) in large surveys. In particular, I use the large, homogeneous dataset from the Sloan Digital Sky Survey (SDSS), which provides spectroscopic redshifts for a large sample of galaxies at z ≲ 0.2 and imaging data to a depth of r < 22. By combining complementary probes, I am able to obtain robust observational constraints that cannot be obtained from any single technique alone. First, I use weak lensing of galaxy clusters to derive an optimal optical tracer of cluster mass, which was found to be a combination of cluster richness and the luminosity of the brightest cluster galaxy. Next, I combine weak lensing of luminous red galaxies with redshift distortions and clustering measurements to derive a robust probe of gravity on cosmological scales. Finally, I combine weak lensing with the kinematics of disk galaxies to constrain the total mass profile over several orders of magnitude. I derive a minimal-scatter relation between disk velocity and stellar mass (also known as the Tully-Fisher relation) that can be used, by construction, on a similarly-selected lens sample. Then, I combine this relation with halo mass measurements from weak lensing to place constraints on the ratio of the optical to virial velocities, as well as the ratio of halo to stellar masses, both as a function of stellar mass. These results will serve as inputs to and constraints on disk galaxy formation models, which will be explored in future work.

Galaxy evolution. Black hole feedback in the luminous quasar PDS 456.

Science.gov (United States)

Nardini, E; Reeves, J N; Gofford, J; Harrison, F A; Risaliti, G; Braito, V; Costa, M T; Matzeu, G A; Walton, D J; Behar, E; Boggs, S E; Christensen, F E; Craig, W W; Hailey, C J; Matt, G; Miller, J M; O'Brien, P T; Stern, D; Turner, T J; Ward, M J

2015-02-20

The evolution of galaxies is connected to the growth of supermassive black holes in their centers. During the quasar phase, a huge luminosity is released as matter falls onto the black hole, and radiation-driven winds can transfer most of this energy back to the host galaxy. Over five different epochs, we detected the signatures of a nearly spherical stream of highly ionized gas in the broadband x-ray spectra of the luminous quasar PDS 456. This persistent wind is expelled at relativistic speeds from the inner accretion disk, and its wide aperture suggests an effective coupling with the ambient gas. The outflow's kinetic power larger than 10(46) ergs per second is enough to provide the feedback required by models of black hole and host galaxy coevolution. Copyright © 2015, American Association for the Advancement of Science.

A search for HI in elliptical galaxies with nuclear radio sources

International Nuclear Information System (INIS)

Dressel, L.L.; Bania, T.M.; O'Connell, R.W.

1982-01-01

Two of the galaxies with large HI mass, NGC 1052 and 4278, are known to have powerful nuclear continuum radio sources (P 2380 approximately 10 22 WHz -1 ). Since both of these attributes are fairly rare among elliptical galaxies, their coexistence in these galaxies is not likely to have occurred by chance. The authors have therefore observed twelve other elliptical galaxies with nuclear radio power P 2380 > 10 22 WHz -1 at Arecibo Observatory, to determine whether a large mass of HI is a necessary auxillary to nuclear continuum emission. (Auth.)

Empirical Constraints on the Origin of Fast Radio Bursts: Volumetric Rates and Host Galaxy Demographics as a Test of Millisecond Magnetar Connection

Science.gov (United States)

Nicholl, M.; Williams, P. K. G.; Berger, E.; Villar, V. A.; Alexander, K. D.; Eftekhari, T.; Metzger, B. D.

2017-07-01

The localization of the repeating fast radio burst (FRB) 121102 to a low-metallicity dwarf galaxy at z = 0.193, and its association with a luminous quiescent radio source, suggests the possibility that FRBs originate from magnetars, formed by the unusual supernovae that occur in such galaxies. We investigate this possibility via a comparison of magnetar birth rates, the FRB volumetric rate, and host galaxy demographics. We calculate average volumetric rates of possible millisecond magnetar production channels, such as superluminous supernovae (SLSNe), long and short gamma-ray bursts (GRBs), and general magnetar production via core-collapse supernovae (CCSNe). For each channel, we also explore the expected host galaxy demographics using their known properties. We determine for the first time the number density of FRB emitters (the product of their volumetric birth rate and lifetime), {R}{FRB}τ ≈ {10}4 Gpc-3, assuming that FRBs are predominantly emitted from repetitive sources similar to FRB 121102 and adopting a beaming factor of 0.1. By comparing rates, we find that production via rare channels (SLSNe, GRBs) implies a typical FRB lifetime of ˜30-300 years, in good agreement with other lines of argument. The total energy emitted over this time is consistent with the available energy stored in the magnetic field. On the other hand, any relation to magnetars produced via normal CCSNe leads to a very short lifetime of ˜0.5 years, in conflict with both theory and observation. We demonstrate that due to the diverse host galaxy distributions of the different progenitor channels, many possible sources of FRB birth can be ruled out with ≲ 10 host galaxy identifications. Conversely, targeted searches of galaxies that have previously hosted decades-old SLSNe and GRBs may be a fruitful strategy for discovering new FRBs and related quiescent radio sources, and determining the nature of their progenitors.

Evolution of Extragalactic Radio Sources and Quasar/Galaxy Unification

Science.gov (United States)

Onah, C. I.; Ubachukwu, A. A.; Odo, F. C.; Onuchukwu, C. C.

2018-04-01

We use a large sample of radio sources to investigate the effects of evolution, luminosity selection and radio source orientation in explaining the apparent deviation of observed angular size - redshift (θ - z) relation of extragalactic radio sources (EGRSs) from the standard model. We have fitted the observed θ - z data with standard cosmological models based on a flat universe (Ω0 = 1). The size evolution of EGRSs has been described as luminosity, temporal and orientation-dependent in the form DP,z,Φ ≍ P±q(1 + z)-m sinΦ, with q=0.3, Φ=59°, m=-0.26 for radio galaxies and q=-0.5, Φ=33°, m=3.1 for radio quasars respectively. Critical points of luminosity, logPcrit=26.33 WHz-1 and logDc=2.51 kpc (316.23 kpc) of the present sample of radio sources were also observed. All the results were found to be consistent with the popular quasar/galaxy unification scheme.

New radio observations of the Circinus Galaxy

International Nuclear Information System (INIS)

Harnett, J.I.; Reynolds, J.E.

1990-01-01

We present new radio continuum and OH observations of the Circinus Galaxy which confirm the active nature of the nucleus. The continuum structure is dominated by two spurs of emission, which probably originate in the core and extend roughly along the minor axis of the galaxy. In addition, the OH absorption profiles clearly indicate a rapidly rotating cloud surrounding the nucleus or several independent clouds in the vicinity with inflowing and outflowing motions. The Circinus Galaxy is most probably a Seyfert with underlying nuclear starburst activity. (author)

The gas content in starburst galaxies

International Nuclear Information System (INIS)

Mirabel, I.F.; Sanders, D.B.

1987-01-01

The results from two large and homogeneous surveys, one in HI, the other in CO, are used for a statistical review of the gaseous properties of bright infrared galaxies. A constant ratio between the thermal far-infrared radiation and non-thermal radio emission is a universal property of star formation in spiral galaxies. The current rate of star formation in starburst galaxies is found to be 3-20 times larger than in the Milky Way. Galaxies with the higher far-infrared luminosities and warmer dust, have the larger mass fractions of molecular to atomic interstellar gas, and in some instances, striking deficiencies of neutral hydrogen are found. A statistical blueshift of the optical systemic velocities relative to the radio systemic velocities, may be due to an outward motion of the optical line-emitting gas. From the high rates of star formation, and from the short times required for the depletion of the interstellar gas, we conclude that the most luminous infrared galaxies represent a brief but important phase in the evolution of some galaxies, when two galaxies merge changing substantially their overall properties

High-energy neutrinos from FR0 radio galaxies?

Science.gov (United States)

Tavecchio, F.; Righi, C.; Capetti, A.; Grandi, P.; Ghisellini, G.

2018-04-01

The sources responsible for the emission of high-energy (≳100 TeV) neutrinos detected by IceCube are still unknown. Among the possible candidates, active galactic nuclei with relativistic jets are often examined, since the outflowing plasma seems to offer the ideal environment to accelerate the required parent high-energy cosmic rays. The non-detection of single-point sources or - almost equivalently - the absence, in the IceCube events, of multiplets originating from the same sky position - constrains the cosmic density and the neutrino output of these sources, pointing to a numerous population of faint sources. Here we explore the possibility that FR0 radio galaxies, the population of compact sources recently identified in large radio and optical surveys and representing the bulk of radio-loud AGN population, can represent suitable candidates for neutrino emission. Modelling the spectral energy distribution of an FR0 radio galaxy recently associated with a γ-ray source detected by the Large Area Telescope onboard Fermi, we derive the physical parameters of its jet, in particular the power carried by it. We consider the possible mechanisms of neutrino production, concluding that pγ reactions in the jet between protons and ambient radiation is too inefficient to sustain the required output. We propose an alternative scenario, in which protons, accelerated in the jet, escape from it and diffuse in the host galaxy, producing neutrinos as a result of pp scattering with the interstellar gas, in strict analogy with the processes taking place in star-forming galaxies.

4C radio sources in clusters of galaxies

International Nuclear Information System (INIS)

McHardy, I.M.

1979-01-01

Observations of a complete sample of 4C and 4CT radio sources in Abell clusters with the Cambridge One-Mile telescope are analysed. It is concluded that radio sources are strongly concentrated towards the cluster centres and are equally likely to be found in clusters of any richness. The probability of a galaxy of a given absolute magnitude producing a source above a given luminosity does not depend on cluster membership. 4C and 4CT radio sources in clusters, selected at 178 MHz, occur preferentially in Bautz-Morgan (BM) class 1 clusters, whereas those selected at 1.4 GHz do not. The most powerful radio source in the cluster is almost always associated with the optically brightest galaxy. The average spectrum of 4C sources in the range 408 to 1407 MHz is steeper in BM class 1 than in other classes. Spectra also steepen with cluster richness. the morphology of 4C sources in clusters depends strongly on BM class and, in particular, radio-trail sources occur only in BM classes II, II-III and III. (author)

GREEN PEA GALAXIES AND COHORTS: LUMINOUS COMPACT EMISSION-LINE GALAXIES IN THE SLOAN DIGITAL SKY SURVEY

International Nuclear Information System (INIS)

Izotov, Yuri I.; Guseva, Natalia G.; Thuan, Trinh X.

2011-01-01

We present a large sample of 803 star-forming luminous compact galaxies (LCGs) in the redshift range z = 0.02-0.63, selected from Data Release 7 of the Sloan Digital Sky Survey (SDSS). The global properties of these galaxies are similar to those of the so-called green pea star-forming galaxies in the redshift range z = 0.112-0.360 and selected from the SDSS on the basis of their green color and compact structure. In contrast to green pea galaxies, our LCGs are selected on the basis of both their spectroscopic and photometric properties, resulting in a ∼10 times larger sample, with galaxies spanning a redshift range ∼>2 times larger. We find that the oxygen abundances and the heavy element abundance ratios in LCGs do not differ from those of nearby low-metallicity blue compact dwarf galaxies. The median stellar mass of LCGs is ∼10 9 M sun . However, for galaxies with high EW(Hβ), ≥ 100 A, it is only ∼7 x 10 8 M sun . The star formation rate in LCGs varies in the large range of 0.7-60 M sun yr -1 , with a median value of ∼4 M sun yr -1 , a factor of ∼3 lower than in high-redshift star-forming galaxies at z ∼> 3. The specific star formation rates in LCGs are extremely high and vary in the range ∼10 -9 -10 -7 yr -1 , comparable to those derived in high-redshift galaxies.

Powerful Radio Galaxies with Simbol-X: the Nuclear Environment

Science.gov (United States)

Torresi, E.; Grandi, P.; Malaguti, G.; Palumbo, G. G. C.; Bianchin, V.

2009-05-01

Fanaroff & Riley type II radio galaxies (FRII) are complex objects. In particular FRII Narrow Line Radio Galaxies (NLRG), optically classified as High Excitation Galaxies (HEG) show X-ray spectra very similar to their radio-quiet counterparts, the Seyfert 2 galaxies. They show 2-10 keV continua heavily obscured (NH~1023-24 cm-2) and intense FeKα lines, typical cold matter reprocessing features. Moreover recent Chandra and XMM-Newton observations suggest that the soft X-ray emission of HEG and Seyfert 2 have a common origin from photoionized gas, reinforcing the idea that not only their nuclear engine but also the circumnuclear gas (at least the warm phase) are similar. On the contrary, our knowledge of NLRG HEG above 10 keV is very poor when compared to brighter Seyfert 2. As a consequence, the physical properties of the cold phase of the circumnuclear gas (possibly linked to a dusty torus) are largely unknown. Thanks to its high sensitivity up to 80 keV, Simbol-X will provide very accurate spectra and will allow a direct comparison between the NLRG and Seyfert 2 cold environments.

Stellar Dynamics and Star Formation Histories of z ∼ 1 Radio-loud Galaxies

Energy Technology Data Exchange (ETDEWEB)

Barišić, Ivana; Van der Wel, Arjen; Chauké, Priscilla; Van Houdt, Josha; Straatman, Caroline [Max-Planck Institut für Astronomie, Königstuhl 17, D-69117, Heidelberg (Germany); Bezanson, Rachel [Department of Astrophysics, Princeton University, Princeton, NJ 08544 (United States); Pacifici, Camilla [Astrophysics Science Division, Goddard Space Flight Center, Code 665, Greenbelt, MD 20771 (United States); Noeske, Kai [experimenta gGmbH, Kranenstraße 14, 74072 Heilbronn (Germany); Muñoz-Mateos, Juan C. [European Southern Observatory, Alonso de Córdova 3107, Casilla 19001, Vitacura, Santiago (Chile); Franx, Marijn; Labbé, Ivo; Maseda, Michael V.; Sobral, David [Leiden Observatory, Leiden University, P.O. Box 9513, NL-2300 AA Leiden (Netherlands); Smolčić, Vernesa [Department of Physics, Faculty of Science, University of Zagreb, Bijenicka cesta 32, 10000 Zagreb (Croatia); Bell, Eric F. [Department of Astronomy, University of Michigan, 1085 S. University Avenue, Ann Arbor, MI 48109 (United States); Brammer, Gabriel [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Calhau, João [Department of Physics, Lancaster University, Lancaster LA1 4 YB (United Kingdom); Van Dokkum, Pieter G. [Department of Astronomy, Yale University, New Haven, CT 06511 (United States); Gallazzi, Anna [INAF-Osservatorio Astrofsico di Arcetri, Largo Enrico Fermi 5, I-50125 Firenze (Italy); Muzzin, Adam, E-mail: barisic@mpia.de [Department of Physics and Astronomy, York University, 4700 Keele Street, Toronto, Ontario, ON MJ3 1P3 (Canada); and others

2017-09-20

We investigate the stellar kinematics and stellar populations of 58 radio-loud galaxies of intermediate luminosities ( L {sub 3} {sub GHz} > 10{sup 23} W Hz{sup −1}) at 0.6 < z < 1. This sample is constructed by cross-matching galaxies from the deep VLT/VIMOS LEGA-C spectroscopic survey with the VLA 3 GHz data set. The LEGA-C continuum spectra reveal for the first time stellar velocity dispersions and age indicators of z ∼ 1 radio galaxies. We find that z ∼ 1 radio-loud active galactic nucleus (AGN) occur exclusively in predominantly old galaxies with high velocity dispersions: σ {sub *} > 175 km s{sup −1}, corresponding to black hole masses in excess of 10{sup 8} M {sub ⊙}. Furthermore, we confirm that at a fixed stellar mass the fraction of radio-loud AGN at z ∼ 1 is five to 10 times higher than in the local universe, suggesting that quiescent, massive galaxies at z ∼ 1 switch on as radio AGN on average once every Gyr. Our results strengthen the existing evidence for a link between high black hole masses, radio loudness, and quiescence at z ∼ 1.

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

Energy Technology Data Exchange (ETDEWEB)

Ma, C.-J.; McNamara, B. R. [Department of Physics and Astronomy, University of Waterloo, 200 University Ave. W., Waterloo, Ontario N2L 3G1 (Canada); Nulsen, P. E. J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138-1516 (United States)

2013-01-20

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 < z < 0.6 that overlap the area covered by the NRAO VLA Sky Survey (NVSS). The radio-AGN mechanical power was estimated from the radio luminosity of central NVSS sources, using the relation of Cavagnolo et al. that is based on mechanical powers determined from the enthalpies of X-ray cavities. We find only a weak correlation between radio luminosity and cluster X-ray luminosity, although the most powerful radio sources reside in luminous clusters. The average AGN mechanical power of 3 Multiplication-Sign 10{sup 44} erg s{sup -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 {eta} = 0.1, our result implies that the supermassive black holes that released this energy did so by accreting an average of {approx}10{sup 9} M {sub Sun} over time, which is comparable to the level of growth expected during the quasar era.

A radio monitoring survey of ultra-luminous X-ray sources

Science.gov (United States)

Körding, E.; Colbert, E.; Falcke, H.

2005-06-01

We present the results of a radio monitoring campaign to search for radio emission from nearby ultra-luminous X-ray sources (ULXs). These sources are bright off-nuclear X-ray point sources with luminosities exceeding LX > 1039 erg s-1. A well-defined sample of the 9 nearest ULXs has been monitored eight times over 5 months with the Very Large Array in A and B configuration. Our limiting sensitivity is ≈0.15 mJy (4σ) for radio flares and ≈60 μJy for continuous emission. In M 82 two ULXs seem to have coincident compact radio sources, which are probably supernova remnants. No continuous or flaring radio emission has been detected from any other ULX. Thus, ULXs do not generally emit steady-state radio emission above radio powers of 1.5 × 1017 W/Hz. The non-detections of the continuous emission are consistent with beamed or unbeamed radio emission from accreting black holes of ≤ 103 M⊙ based on the radio/X-ray correlation. Other published radio detections (M 82, NGC 5408) are also discussed in this context. Both detections are significantly above our detection limit. If ULXs have flaring radio emission above 4 × 1017 W/Hz we can give an upper limit on the duty cycle of the flares of 6%. This upper limit is in agreement with the observed number of flares in Galactic radio transients. Additionally we present a yet unreported radio double structure in the nearby low-luminosity AGN NGC 4736.

THE ROLE OF STARBURST-ACTIVE GALACTIC NUCLEUS COMPOSITES IN LUMINOUS INFRARED GALAXY MERGERS: INSIGHTS FROM THE NEW OPTICAL CLASSIFICATION SCHEME

International Nuclear Information System (INIS)

Yuan, T.-T.; Kewley, L. J.; Sanders, D. B.

2010-01-01

We investigate the fraction of starbursts, starburst-active galactic nucleus (AGN) composites, Seyferts, and low-ionization narrow emission-line region galaxies (LINERs) as a function of infrared luminosity (L IR ) and merger progress for ∼500 infrared (IR)-selected galaxies. Using the new optical classifications afforded by the extremely large data set of the Sloan Digital Sky Survey, we find that the fraction of LINERs in IR-selected samples is rare ( IR > 10 12 L sun ), starburst-AGN composite galaxies dominate at early-intermediate stages of the merger, and AGN galaxies dominate during the final merger stages. Our results are consistent with models for IR-luminous galaxies where mergers of gas-rich spirals fuel both starburst and AGN, and where the AGN becomes increasingly dominant during the final merger stages of the most luminous IR objects.

Radio Jets Clearing the Way Through a Galaxy: Watching Feedback in Action in the Seyfert Galaxy IC 5063

NARCIS (Netherlands)

Morganti, R.; Oosterloo, T. A.; Oonk, J. B. R.; Frieswijk, W.; Tadhunter, C. N.

2015-01-01

High-resolution (0.5 arcsec) CO(2-1) observations performed with the Atacama Large Millimetre/submillimetre Array have been used to trace the kinematics of the molecular gas in the Seyfert 2 galaxy{IC 5063}. Although one of the most radio-loud Seyfert galaxy, IC 5063 is a relatively weak radio

Revealing the Heart of the Galaxy : The Milky Way and its Black Hole

NARCIS (Netherlands)

Sanders, Robert H.

2014-01-01

1. Introduction: the luminous pathway; 2. The discovery of the Milky Way Galaxy; 3. The new physics; 4. Parting the veil with radio astronomy; 5. The violent Universe; 6. New windows on the Galactic Center; 7. The Milky Way as a barred spiral galaxy; 8. The evolving view of active galactic nuclei;

GROUND-BASED Paα NARROW-BAND IMAGING OF LOCAL LUMINOUS INFRARED GALAXIES. I. STAR FORMATION RATES AND SURFACE DENSITIES

Energy Technology Data Exchange (ETDEWEB)

Tateuchi, Ken; Konishi, Masahiro; Motohara, Kentaro; Takahashi, Hidenori; Kato, Natsuko Mitani; Kitagawa, Yutaro; Todo, Soya; Toshikawa, Koji; Sako, Shigeyuki; Uchimoto, Yuka K.; Ohsawa, Ryou; Asano, Kentaro; Kamizuka, Takafumi; Nakamura, Tomohiko; Okada, Kazushi [Institute of Astronomy, Graduate School of Science, The University of Tokyo, 2-21-1 Osawa, Mitaka, Tokyo 181-0015 (Japan); Ita, Yoshifusa [Astronomical Institute, Tohoku University, 6-3 Aoba, Aramaki, Aoba-ku, Sendai, Miyagi 980-8578 (Japan); Komugi, Shinya [Division of Liberal Arts, Kogakuin University, 2665-1, Hachioji, Tokyo 192-0015 (Japan); Koshida, Shintaro [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States); Manabe, Sho [Department of Earth and Planetary Sciences, Kobe University, Kobe 657-8501 (Japan); Nakashima, Asami, E-mail: tateuchi@ioa.s.u-tokyo.ac.jp [Department of Astronomy, Graduate School of Science, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-0033 (Japan); and others

2015-03-15

Luminous infrared galaxies (LIRGs) are enshrouded by a large amount of dust produced by their active star formation, and it is difficult to measure their activity in optical wavelengths. We have carried out Paα narrow-band imaging observations of 38 nearby star forming galaxies including 33 LIRGs listed in the IRAS Revised Bright Galaxy Sample catalog with the Atacama Near InfraRed camera on the University of Tokyo Atacama Observatory (TAO) 1.0 m telescope (miniTAO). Star formation rates (SFRs) estimated from the Paα fluxes, corrected for dust extinction using the Balmer decrement method (typically A{sub V} ∼ 4.3 mag), show a good correlation with those from the bolometric infrared luminosity of the IRAS data within a scatter of 0.27 dex. This suggests that the correction of dust extinction for the Paα flux is sufficient in our sample. We measure the physical sizes and surface densities of infrared luminosities (Σ{sub L(IR)}) and the SFR (Σ{sub SFR}) of star forming regions for individual galaxies, and we find that most of the galaxies follow a sequence of local ultra-luminous or luminous infrared galaxies (U/LIRGs) on the L(IR)-Σ{sub L(IR)} and SFR-Σ{sub SFR} plane. We confirm that a transition of the sequence from normal galaxies to U/LIRGs is seen at L(IR) = 8 × 10{sup 10} L {sub ☉}. Also, we find that there is a large scatter in physical size, different from normal galaxies or ULIRGs. Considering the fact that most U/LIRGs are merging or interacting galaxies, this scatter may be caused by strong external factors or differences in their merging stages.

Giant Metrewave Radio Telescope Observations of Head–Tail Radio Galaxies

Energy Technology Data Exchange (ETDEWEB)

Sebastian, Biny; Lal, Dharam V.; Rao, A. Pramesh, E-mail: biny@ncra.tifr.res.in [National Center for Radio Astrophysics—Tata Institute of Fundamental Research Post Box 3, Ganeshkhind P.O., Pune 41007 (India)

2017-10-01

We present results from a study of seven large known head–tail radio galaxies based on observations using the Giant Metrewave Radio Telescope at 240 and 610 MHz. These observations are used to study the radio morphologies and distribution of the spectral indices across the sources. The overall morphology of the radio tails of these sources is suggestive of random motions of the optical host around the cluster potential. The presence of multiple bends and wiggles in several head–tail sources is possibly due to the precessing radio jets. We find steepening of the spectral index along the radio tails. The prevailing equipartition magnetic field also decreases along the radio tails of these sources. These steepening trends are attributed to the synchrotron aging of plasma toward the ends of the tails. The dynamical ages of these sample sources have been estimated to be ∼10{sup 8} yr, which is a factor of six more than the age estimates from the radiative losses due to synchrotron cooling.

Revealing the Faraday depth structure of radio galaxy NGC 612 with broad-band radio polarimetric observations

Science.gov (United States)

Kaczmarek, J. F.; Purcell, C. R.; Gaensler, B. M.; Sun, X.; O'Sullivan, S. P.; McClure-Griffiths, N. M.

2018-05-01

We present full-polarization, broad-band observations of the radio galaxy NGC 612 (PKS B0131-637) from 1.3 to 3.1 GHz using the Australia Telescope Compact Array. The relatively large angular scale of the radio galaxy makes it a good candidate with which to investigate the polarization mechanisms responsible for the observed Faraday depth structure. By fitting complex polarization models to the polarized spectrum of each pixel, we find that a single polarization component can adequately describe the observed signal for the majority of the radio galaxy. While we cannot definitively rule out internal Faraday rotation, we argue that the bulk of the Faraday rotation is taking place in a thin skin that girts the polarized emission. Using minimum energy estimates, we find an implied total magnetic field strength of 4.2 μG.

Observations of neutral hydrogen in radio-loud and interacting galaxies

Science.gov (United States)

Heckman, T. M.; Balick, B.; Van Breugel, W. J. W.; Miley, G. K.

1983-01-01

The results of a survey of H I in radio-loud and interacting galaxies is presented. Four cases of H I absorption and five of emission are reported. The interesting features found for individual galaxies are described, and the systematic properties are discussed. Column densities of absorbing gas generally exceed those expected for a 'Milky Way' H I disk by more than an order of magnitude. The absorbing gas must have a flattened, disklike morphology oriented roughly parallel to the optical disk of the galaxy. Turbulent noncircular gas motions are evidently present, which are shown to be almost certainly induced by galaxy-galaxy interactions. The set of galaxies in which H I absorption has been detected is dominated by morphologically peculiar objects. It is concluded that the detection of H I seen in absorption against a nuclear radio source permits direct determination of the sense of radial flow of extranuclear material, and is direct evidence that potential 'food' for a compact object in the nucleus exists in the galaxy.

Redshifts of radio galaxies in Abell clusters of galaxies

International Nuclear Information System (INIS)

Owen, F.N.; White, R.A.; Thronson, H.A. Jr.

1988-01-01

The paper presents redshifts for 51 radio galaxies and companion systems which were obtained with the Steward 2.3-m and multiple mirror telescopes. The observations were performed over the course of six runs during 1980-1983. The sample includes eight multiple systems (or multiple nuclei) having internal velocity differences ranging from 150 to 2400 km/s. 17 references

KILOPARSEC-SCALE RADIO STRUCTURES IN NARROW-LINE SEYFERT 1 GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Doi, Akihiro; Kino, Motoki [Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuou-ku, Sagamihara, Kanagawa 252-5210 (Japan); Nagira, Hiroshi [Graduate School of Science and Engineering, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Yamaguchi 753-8512 (Japan); Kawakatu, Nozomu [Graduate School of Pure and Applied Sciences, University of Tsukuba, 1-1-1 Tennodai, Tsukuba, Ibaraki 305-8571 (Japan); Nagai, Hiroshi [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Asada, Keiichi, E-mail: akihiro.doi@vsop.isas.jaxa.jp [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China)

2012-11-20

We report the finding of kiloparsec (kpc)-scale radio structures in three radio-loud narrow-line Seyfert 1 (NLS1) galaxies from the Faint Images of the Radio Sky at Twenty-centimeters of the Very Large Array, which increases the number of known radio-loud NLS1s with kpc-scale structures to six, including two {gamma}-ray-emitting NLS1s (PMN J0948+0022 and 1H 0323+342) detected by the Fermi Gamma-ray Space Telescope. The detection rate of extended radio emissions in NLS1s is lower than that in broad-line active galactic nuclei (AGNs) with a statistical significance. We found both core-dominated (blazar-like) and lobe-dominated (radio-galaxy-like) radio structures in these six NLS1s, which can be understood in the framework of the unified scheme of radio-loud AGNs that considers radio galaxies as non-beamed parent populations of blazars. Five of the six NLS1s have (1) extended radio luminosities suggesting jet kinetic powers of {approx}> 10{sup 44} erg s{sup -1}, which is sufficient to make jets escape from hosts' dense environments; (2) black holes of {approx}> 10{sup 7} M {sub Sun }, which can generate the necessary jet powers from near-Eddington mass accretion; and (3) two-sided radio structures at kpc scales, requiring expansion rates of {approx}0.01c-0.3c and kinematic ages of {approx}> 10{sup 7} years. On the other hand, most typical NLS1s would be driven by black holes of {approx}< 10{sup 7} M {sub Sun} in a limited lifetime of {approx}10{sup 7} years. Hence, the kpc-scale radio structures may originate in a small window of opportunity during the final stage of the NLS1 phase just before growing into broad-line AGNs.

An Analysis Framework for Understanding the Origin of Nuclear Activity in Low-power Radio Galaxies

Science.gov (United States)

Lin, Yen-Ting; Huang, Hung-Jin; Chen, Yen-Chi

2018-05-01

Using large samples containing nearly 2300 active galaxies of low radio luminosity (1.4 GHz luminosity between 2 × 1023 and 3 × 1025 W Hz‑1, essentially low-excitation radio galaxies) at z ≲ 0.3, we present a self-contained analysis of the dependence of the nuclear radio activity on both intrinsic and extrinsic properties of galaxies, with the goal of identifying the best predictors of the nuclear radio activity. While confirming the established result that stellar mass must play a key role on the triggering of radio activities, we point out that for the central, most massive galaxies, the radio activity also shows a strong dependence on halo mass, which is not likely due to enhanced interaction rates in denser regions in massive, cluster-scale halos. We thus further investigate the effects of various properties of the intracluster medium (ICM) in massive clusters on the radio activities, employing two standard statistical tools, principle component analysis and logistic regression. It is found that ICM entropy, local cooling time, and pressure are the most effective in predicting the radio activity, pointing to the accretion of gas cooling out of a hot atmosphere to be the likely origin in triggering such activities in galaxies residing in massive dark matter halos. Our analysis framework enables us to logically discern the mechanisms responsible for the radio activity separately for central and satellite galaxies.

GHASP: an Hα kinematical survey of spiral galaxies - XI. Distribution of luminous and dark matter in spiral and irregular nearby galaxies using WISE photometry.

Science.gov (United States)

Korsaga, M.; Carignan, C.; Amram, P.; Epinat, B.; Jarrett, T. H.

2018-04-01

We present the mass distribution of a sample of 121 nearby galaxies with high quality optical velocity fields and available infra-red WISE 3.4 μm data. Contrary to previous studies, this sample covers all morphological types and is not biased toward late-type galaxies. These galaxies are part of the Fabry-Perot kinematical GHASP survey of spirals and irregular nearby galaxies. Combining the kinematical data to the WISE surface brightness data probing the emission from the old stellar population, we derive mass models allowing us to compare the luminous to the dark matter halo mass distribution in the optical regions of those galaxies. Dark matter (DM) models are constructed using the isothermal core profile and the Navarro-Frenk-White cuspy profile. We allow the M/L of the baryonic disc to vary or we keep it fixed, constrained by stellar evolutionary models (WISE W1-W2 color) and we carry out best fit (BFM) and pseudo-isothermal maximum disc (MDM) models. We found that the MDM provides M/L values four times higher than the BFM, suggesting that disc components, on average, tend to be maximal. The main results are: (i) the rotation curves of most galaxies are better fitted with core rather than cuspy profiles; (ii) the relation between the parameters of the DM and of the luminous matter components mostly depends on morphological types. More precisely, the distribution of the DM inside galaxies depends on whether or not the galaxy has a bulge.

FAR-UV EMISSION PROPERTIES OF FR1 RADIO GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Danforth, Charles W.; Stocke, John T.; France, Kevin; Begelman, Mitchell C. [Department of Astrophysical and Planetary Sciences, University of Colorado, 391-UCB, Boulder, CO 80309 (United States); Perlman, Eric, E-mail: danforth@colorado.edu [Department of Physics and Space Sciences, Florida Institute of Technology, 150 W. University Boulevard, Melbourne, FL 32901 (United States)

2016-11-20

The power mechanism and accretion geometry for low-power FR 1 radio galaxies are poorly understood in comparison to those for Seyfert galaxies and QSOs. In this paper, we use the diagnostic power of the Ly α recombination line observed using the Cosmic Origins Spectrograph (COS) aboard the Hubble Space Telescope ( HST ) to investigate the accretion flows in three well-known, nearby FR 1s: M87, NGC 4696, and Hydra A. The Ly α emission line’s luminosity, velocity structure, and the limited knowledge of its spatial extent provided by COS are used to assess conditions within a few parsecs of the supermassive black hole in these radio-mode active galactic nuclei. We observe strong Ly α emission in all three objects with total luminosity similar to that seen in BL Lacertae objects. M87 shows a complicated emission-line profile in Ly α , which varies spatially across the COS aperture and possibly temporally over several epochs of observation. In both NGC 4696 and M87, the Ly α luminosities ∼10{sup 40} erg s{sup -1} are closely consistent with the observed strength of the ionizing continuum in Case B recombination theory and with the assumption of a near-unity covering factor. It is possible that the Ly α -emitting clouds are ionized largely by beamed radiation associated with the jets. Long-slit UV spectroscopy can be used to test this hypothesis. Hydra A and the several BL Lac objects studied in this and previous papers have Ly α luminosities larger than M87 but their extrapolated, nonthermal continua are so luminous that they overpredict the observed strength of Ly α , a clear indicator of relativistic beaming in our direction. Given their substantial space density (∼4 × 10{sup -3} Mpc{sup -3}), the unbeamed Lyman continuum radiation of FR 1s may make a substantial minority contribution (∼10%) to the local UV background if all FR 1s are similar to M87 in ionizing flux level.

The Role of the Most Luminous Obscured AGNs in Galaxy Assembly at z ∼ 2

Energy Technology Data Exchange (ETDEWEB)

Farrah, Duncan [Department of Physics, Virginia Tech, Blacksburg, VA 24061 (United States); Petty, Sara [Green Science Policy Institute, Berkeley, CA 94709 (United States); Connolly, Brian [Cincinnati Children’s Hospital Medical Center, 3333 Burnet Avenue, Cincinnati, OH 45229 (United States); Blain, Andrew [Department of Physics and Astronomy, University of Leicester, Leicester LE1 7RH (United Kingdom); Efstathiou, Andreas [School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia (Cyprus); Lacy, Mark [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Stern, Daniel; Bridge, Carrie; Eisenhardt, Peter; Moustakas, Leonidas [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive, Pasadena, CA 91109 (United States); Lake, Sean; Tsai, Chao-Wei [Physics and Astronomy Department, University of California, Los Angeles, CA 90095 (United States); Jarrett, Tom [Department of Astronomy, University of Cape Town, 7700 Rondebosch, Capetown 7700 (South Africa); Benford, Dominic [Observational Cosmology Lab., Code 665, NASA at Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Jones, Suzy [Department of Space, Earth, and Environment, Chalmers University of Technology, Onsala Space Observatory, SE-43992 Onsala (Sweden); Assef, Roberto [Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av. Ejército Libertador 441, Santiago (Chile); Wu, Jingwen [National Astronomical Observatories, Chinese Academy of Sciences, 20A Datun Road, Chaoyang District, Beijing, 100012 (China)

2017-08-01

We present Hubble Space Telescope WFC3 F160W imaging and infrared spectral energy distributions for 12 extremely luminous, obscured active galactic nuclei (AGNs) at 1.8 < z < 2.7 selected via “hot, dust-obscured” mid-infrared colors. Their infrared luminosities span (2–15) × 10{sup 13} L {sub ⊙}, making them among the most luminous objects in the universe at z ∼ 2. In all cases, the infrared emission is consistent with arising at least for the most part from AGN activity. The AGN fractional luminosities are higher than those in either submillimeter galaxies or AGNs selected via other mid-infrared criteria. Adopting the G , M {sub 20}, and A morphological parameters, together with traditional classification boundaries, infers that three-quarters of the sample are mergers. Our sample does not, however, show any correlation between the considered morphological parameters and either infrared luminosity or AGN fractional luminosity. Moreover, the asymmetries and effective radii of our sample are distributed identically to those of massive galaxies at z ∼ 2. We conclude that our sample is not preferentially associated with mergers, though a significant merger fraction is still plausible. Instead, we propose that our sample includes examples of the massive galaxy population at z ∼ 2 that harbor a briefly luminous, “flickering” AGN and in which the G and M {sub 20} values have been perturbed due to either the AGN and/or the earliest formation stages of a bulge in an inside-out manner. Furthermore, we find that the mass assembly of the central black holes in our sample leads the mass assembly of any bulge component. Finally, we speculate that our sample represents a small fraction of the immediate antecedents of compact star-forming galaxies at z ∼ 2.

The host galaxy of a fast radio burst

OpenAIRE

Keane, E. F.; Jencson, J.; Kasliwal, Mansi M.

2016-01-01

In recent years, millisecond-duration radio signals originating in distant galaxies appear to have been discovered in the so-called fast radio bursts. These signals are dispersed according to a precise physical law and this dispersion is a key observable quantity, which, in tandem with a redshift measurement, can be used for fundamental physical investigations. Every fast radio burst has a dispersion measurement, but none before now have had a redshift measurement, because of the difficulty i...

Spectro-polarimetric study of the early evolutionary phases of the most massive galaxies

International Nuclear Information System (INIS)

Vernet, Joel

2001-01-01

This research thesis addresses the study of the early phases of evolution of the most massive galaxies (giant elliptic), a fundamental process which is a matter of study for various reasons exposed by the author in his introduction. While presented results are based on spectro-polarimetric observations, the author first presents specific instruments and methods used by spectropolarimetry which provides access to variations of all vectorial properties of light, without loss of information. Then, he reports the study of a near powerful radio-galaxy, Cygnus A, the study of nine radio-galaxies with a high redshift, and the study of a far ultra-luminous infrared galaxy (SMM J02399-0136). Results are then discussed and perspectives of research are proposed. Appendices present the theoretical study of the contribution of massive stars to the diffuse extragalactic ionizing background, and observations made on a near radio-galaxy (NGC 6251)

THE UBIQUITOUS RADIO CONTINUUM EMISSION FROM THE MOST MASSIVE EARLY-TYPE GALAXIES

International Nuclear Information System (INIS)

Brown, Michael J. I.; Jannuzi, Buell T.; Floyd, David J. E.; Mould, Jeremy R.

2011-01-01

We have measured the radio continuum emission of 396 early-type galaxies brighter than K = 9, using 1.4 GHz imagery from the NRAO Very Large Array Sky Survey, Green Bank 300 ft Telescope, and 64 m Parkes Radio Telescope. For M K K < -25.5 early-type galaxies are greater than zero in all cases. It is thus highly likely that the most massive galaxies always host an active galactic nucleus or have recently undergone star formation.

Giant Radio Jet Coming From Wrong Kind of Galaxy

Science.gov (United States)

2003-01-01

Giant jets of subatomic particles moving at nearly the speed of light have been found coming from thousands of galaxies across the Universe, but always from elliptical galaxies or galaxies in the process of merging -- until now. Using the combined power of the Hubble Space Telescope, the Very Large Array (VLA) and the 8-meter Gemini-South Telescope, astronomers have discovered a huge jet coming from a spiral galaxy similar to our own Milky Way. Radio-optical view of galaxy Combined HST and VLA image of the galaxy 0313-192. Optical HST image shows the galaxy edge-on; VLA image, shown in red, reveals giant jet of speeding particles. For more images, see this link below. CREDIT: Keel, Ledlow & Owen; STScI,NRAO/AUI/NSF, NASA "We've always thought spirals were the wrong kind of galaxy to generate these huge jets, but now we're going to have to re-think some of our ideas on what produces these jets," said William Keel, a University of Alabama astronomer who led the research team. Keel worked with Michael Ledlow of Gemini Observatory and Frazer Owen of the National Radio Astronomy Observatory. The scientists reported their findings at the American Astronomical Society's meeting in Seattle, Washington. "Further study of this galaxy may provide unique insights on just what needs to happen in a galaxy to produce these powerful jets of particles," Keel said. In addition, Owen said, "The loose-knit nature of the cluster of galaxies in which this galaxy resides may play a part in allowing this particular spiral to produce jets." Astronomers believe such jets originate at the cores of galaxies, where supermassive black holes provide the tremendous gravitational energy to accelerate particles to nearly the speed of light. Magnetic fields twisted tightly by spinning disks of material being sucked into the black hole are presumed to narrow the speeding particles into thin jets, like a nozzle on a garden hose. Both elliptical and spiral galaxies are believed to harbor supermassive

A young source of optical emission from distant radio galaxies.

Science.gov (United States)

Hammer, F; Fèvre, O Le; Angonin, M C

1993-03-25

DISTANT radio galaxies provide valuable insights into the properties of the young Universe-they are the only known extended optical sources at high redshift and might represent an early stage in the formation and evolution of galaxies in general. This extended optical emission often has very complex morphologies, but the origin of the light is still unclear. Here we report spectroscopic observations for several distant radio galaxies (0.75≤ z ≤ 1.1) in which the rest-frame spectra exhibit featureless continua between 2,500 Å and 5,000 Å. We see no evidence for the break in the spectrum at 4,000 Å expected for an old stellar population 1-3 , and suggest that young stars or scattered emissions from the active nuclei are responsible for most of the observed light. In either case, this implies that the source of the optical emission is com-parable in age to the associated radio source, namely 10 7 years or less.

Direct HST Dust Lane Detection in Powerful Narrow-Line Radio Galaxies

Energy Technology Data Exchange (ETDEWEB)

Ramírez, Edgar A.; Aretxaga, Itziar [Instituto Nacional de Astrofísica, Óptica y Electrónica, Puebla (Mexico); Tadhunter, Clive N. [Department of Physics and Astronomy, University of Sheffield, Sheffield (United Kingdom); Lopez-Rodriguez, Enrique [NASA Ames Research Center, SOFIA Science Center, SOFIA/USRA, Mountain View, CA (United States); Department of Astronomy, University of Texas at Austin, Austin, TX (United States); McDonald Observatory, University of Texas at Austin, Austin, TX (United States); Packham, Chris, E-mail: e.ramirez@inaoep.mx [Department of Physics and Astronomy, University of Texas at San Antonio, San Antonio, TX (United States); National Astronomical Observatory of Japan, Tokyo (Japan)

2017-11-22

We present the analysis of near-infrared Hubble Space Telescope imaging of 10 Fanaroff Riley II powerful radio galaxies at low redshift (0.03 < z < 0.11) optically classified as narrow-line radio galaxies. The photometric properties of the host galaxy are measured using galfit, and compared with those from the literature. Our high resolution near-infrared observations provide new and direct information on the central kpc-scale dust lanes in our sample that could be connected to the pc-scale torus structure. Moreover, analyzing the infrared spectrograph Spitzer spectra of our sample, we suggest properties of the dust size of the torus.

In situ particle acceleration and physical conditions in radio tail galaxies

International Nuclear Information System (INIS)

Pacholczyk, A.G.; Scott, J.S.

1976-01-01

A model for the objects known as radio tail galaxies is presented. Independent plasmons emerging from an active radio galaxy into an intracluster medium become turbulent due to Rayleigh-Taylor and Kelvin-Helmholtz instabilities. The turbulence produces both in situ betatron and second order Fermi acceleration. Predictions of the dependence of spectral index and flux on distance along the tail match observations well. Fitting provides values of physical parameters in the tail. The relevance of this method of particle acceleration for the problem of the origin of X-ray emission in clusters of galaxies is discussed

High-Redshift Radio Galaxies from Deep Fields

Indian Academy of Sciences (India)

2016-01-27

Jan 27, 2016 ... High-Redshift Radio Galaxies from Deep Fields ... Here we present results from the deep 150 MHz observations of LBDS-Lynx field, which has been imaged at 327, ... Articles are also visible in Web of Science immediately.

Blue optical continuum associated with a radio knot in 3C346

Science.gov (United States)

Dey, Arjun; van Breugel, Wil J. M.

1994-06-01

We report the discovery of extremely luminous near-UV continuum emission associated with a bright radio knot in the radio galaxy 3C346 (zeta = 0.162). Photometric measurements from U and r' band images and longslit spectra show a spectral energy distribution that steepens at higher frequencies, with radio and optical spectral indices alphar = -0.37 +/- 0.02 and alphao = -1.8 +/- 0.2, respectively. Based on a comparison of the optical properties of this knot with other known cases of optical emission associated with radio structures, we conclude that the continuum emission is optical synchrotron radiation. Our observations are consistent with the suggestion that 3C346 is a foreshortened FR-II radio galaxy with its radio axis oriented close to the line of sight. The optical and radio emission from the knot appear to be associated with a hotspot (at the end of a jet) on the near side. Finally, our U and r' images of 3C346 provide a striking illustration that the optical morphologies of nearby radio galaxies also depend upon wavelength and that studies of these objects are relevant to the interpretation of the alignment effect seen in the high redshift radio galaxies.

THE SCALING RELATIONS AND THE FUNDAMENTAL PLANE FOR RADIO HALOS AND RELICS OF GALAXY CLUSTERS

International Nuclear Information System (INIS)

Yuan, Z. S.; Han, J. L.; Wen, Z. L.

2015-01-01

Diffuse radio emission in galaxy clusters is known to be related to cluster mass and cluster dynamical state. We collect the observed fluxes of radio halos, relics, and mini-halos for a sample of galaxy clusters from the literature, and calculate their radio powers. We then obtain the values of cluster mass or mass proxies from previous observations, and also obtain the various dynamical parameters of these galaxy clusters from optical and X-ray data. The radio powers of relics, halos, and mini-halos are correlated with the cluster masses or mass proxies, as found by previous authors, while the correlations concerning giant radio halos are in general the strongest. We found that the inclusion of dynamical parameters as the third dimension can significantly reduce the data scatter for the scaling relations, especially for radio halos. We therefore conclude that the substructures in X-ray images of galaxy clusters and the irregular distributions of optical brightness of member galaxies can be used to quantitatively characterize the shock waves and turbulence in the intracluster medium responsible for re-accelerating particles to generate the observed diffuse radio emission. The power of radio halos and relics is correlated with cluster mass proxies and dynamical parameters in the form of a fundamental plane

On the origin of X-shaped radio galaxies

International Nuclear Information System (INIS)

Gopal-Krishna; Biermann, Peter L.; Gergely, László Á.; Wiita, Paul J.

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 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.

INFRARED SPECTROGRAPH SPECTROSCOPY AND MULTI-WAVELENGTH STUDY OF LUMINOUS STAR-FORMING GALAXIES AT z ≅ 1.9

International Nuclear Information System (INIS)

Huang, J.-S.; Lai, K.; Younger, J. D.; Fazio, G. G.; Faber, S. M.; Koo, D.; Daddi, E.; Laird, E. S.; Omont, A.; Wu, Y.; Bundy, K.; Cattaneo, A.; Chapman, S. C.; Conselice, C. J.; Dickinson, M.; Egami, E.; Im, M.; Le Floc'h, E.; Papovich, C.; Rigopoulou, D.

2009-01-01

We analyze a sample of galaxies chosen to have F 24μm > 0.5 mJy and satisfy a certain IRAC color criterion. Infrared Spectrograph (IRS) spectra yield redshifts, spectral types, and polycyclic aromatic hydrocarbons (PAH) luminosities, to which we add broadband photometry from optical through IRAC wavelengths, MIPS from 24-160 μm, 1.1 mm, and radio at 1.4 GHz. Stellar population modeling and IRS spectra together demonstrate that the double criteria used to select this sample have efficiently isolated massive star-forming galaxies at z ∼ 1.9. This is the first starburst (SB)-dominated ultraluminous infrared galaxies (ULIRG) sample at high redshift with total infrared luminosity measured directly from FIR and millimeter photometry, and as such gives us the first accurate view of broadband spectral energy distributions for SB galaxies at extremely high luminosity and at all wavelengths. Similar broadband data are assembled for three other galaxy samples-local SB galaxies, local active galactic nucleus (AGN)/ULIRGs, and a second 24 μm-luminous z ∼ 2 sample dominated by AGN. L PAH /L IR for the new z ∼ 2 SB sample is the highest ever seen, some three times higher than in local SBs, whereas in AGNs this ratio is depressed below the SB trend, often severely. Several pieces of evidence imply that AGNs exist in this SB-dominated sample, except two of which even host very strong AGN, while they still have very strong PAH emission. The Advanced Camera for Surveys images show that most objects have very extended morphologies in the rest-frame ultraviolet band, thus extended distribution of PAH molecules. Such an extended distribution prevents further destruction PAH molecules by central AGNs. We conclude that objects in this sample are ULIRGs powered mainly by SB; and the total infrared luminosity density contributed by this type of objects is 0.9-2.6 x 10 7 L sun Mpc -3 .

On the relationship between optical and radio emission from active galaxy nuclei

International Nuclear Information System (INIS)

Zentsova, A.S.; Fedorenko, V.N.

1991-01-01

Model in which the radio emission of nuclei of Seyfert galaxies emerges in the regions of formation of their narrow emission lines, R∼100 pc is developed. Gaseous clouds, producing this emission, are moving in the surrounding hot gas and induce shock waves. The shock waves accelerate electrons, which produce radio emission via synchrotron mechanism. The model explains an observational correlation between the radio and optical properties of Seyfert galaxies and makes some predictions on the parameters of the region R∼100 pc

VLBA Observations of Low Luminosity Flat Spectrum Radio Galaxies and BL Lac Objects: Polarisation Properties

Science.gov (United States)

Bondi, M.; Dallacasa, D.; Stanghellini, C.; Marchã, M. J. M.

We obtained two-epoch VLBA observations at 5 GHz of a list of radio galaxies drawn from the 200 mJy sample (Marcha et al. 1996). The objects selected for milli-arcsecond scale observations are classified, on the basis of their optical spectroscopic and polarimetric properties, as BL Lac objects, normal weak line radio galaxies, broad line radio galaxies, and transition objects (those with intermediate properties). We present preliminary results on the radio polarization properties, on the milli-arcsecond scale, of objects with different optical properties and discuss structural variations detected from the two epochs.

RADIO GALAXY FEEDBACK IN X-RAY-SELECTED GROUPS FROM COSMOS: THE EFFECT ON THE INTRACLUSTER MEDIUM

International Nuclear Information System (INIS)

Giodini, S.; Finoguenov, A.; Boehringer, H.; Pierini, D.; Smolcic, V.; Massey, R.; BIrzan, L.; Zamorani, G.; Oklopcic, A.; Pratt, G. W.; Schinnerer, E.; Koekemoer, A. M.; Salvato, M.; Sanders, D. B.; Kartaltepe, J. S.; Thompson, D.

2010-01-01

We quantify the importance of the mechanical energy released by radio galaxies inside galaxy groups. We use scaling relations to estimate the mechanical energy released by 16 radio-active galactic nuclei located inside X-ray-detected galaxy groups in the COSMOS field. By comparing this energy output to the host groups' gravitational binding energy, we find that radio galaxies produce sufficient energy to unbind a significant fraction of the intragroup medium. This unbinding effect is negligible in massive galaxy clusters with deeper potential wells. Our results correctly reproduce the breaking of self-similarity observed in the scaling relation between entropy and temperature for galaxy groups.

Hot-spots of radio sources in clusters of galaxies

International Nuclear Information System (INIS)

Saikia, D.J.

1979-01-01

A sample of extragalactic double radio sources is examined to test for a correlation between the prominence of compact hot-spots located at their outer edges and membership of clusters of galaxies. To minimize the effects of incompleteness in published catalogues of clusters, cluster classification is based on the number of galaxies in the neighbourhood of each source. After eliminating possible selection effects, it is found that sources in regions of high galactic density tend to have less prominent hot-spots. It is argued that the result is consistent with the 'continuous-flow' models of radio sources, but poses problems for the gravitational slingshot model. (author)

Optical images of quasars and radio galaxies

Science.gov (United States)

Hutchings, J. B.; Johnson, I.; Pyke, R.

1988-04-01

Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions.

Discovery of large-scale diffuse radio emission in low-mass galaxy cluster Abell 1931

Science.gov (United States)

Brüggen, M.; Rafferty, D.; Bonafede, A.; van Weeren, R. J.; Shimwell, T.; Intema, H.; Röttgering, H.; Brunetti, G.; Di Gennaro, G.; Savini, F.; Wilber, A.; O'Sullivan, S.; Ensslin, T. A.; De Gasperin, F.; Hoeft, M.

2018-04-01

Extended, steep-spectrum radio synchrotron sources are pre-dominantly found in massive galaxy clusters as opposed to groups. LOFAR Two-Metre Sky Survey images have revealed a diffuse, ultra-steep spectrum radio source in the low-mass cluster Abell 1931. The source has a fairly irregular morphology with a largest linear size of about 550 kpc. The source is only seen in LOFAR observations at 143 MHz and GMRT observations at 325 MHz. The spectral index of the total source between 143 MHz and 325 MHz is α _{143}^{325} = -2.86 ± 0.36. The source remains invisible in Very Large Array (1-2 GHz) observations as expected given the spectral index. Chandra X-ray observations of the cluster revealed a bolometric luminosity of LX = (1.65 ± 0.39) × 1043 erg s-1 and a temperature of 2.92_{-0.87}^{+1.89} keV which implies a mass of around ˜1014M⊙. We conclude that the source is a remnant radio galaxy that has shut off around 200 Myr ago. The brightest cluster galaxy, a radio-loud elliptical galaxy, could be the source for this extinct source. Unlike remnant sources studied in the literature, our source has a steep spectrum at low radio frequencies. Studying such remnant radio galaxies at low radio frequencies is important for understanding the scarcity of such sources and their role in feedback processes.

Low frequency radio observations of five rich clusters of galaxies

International Nuclear Information System (INIS)

Hanisch, R.J.; Erickson, W.C.

1980-01-01

Observations have been made at 43.0 and 73.8 MHz of five rich x-ray emitting clusters of galaxies: Abell 399/401, Abell 426 (the Perseus cluster), Abell 1367, Abell 1656 (the Coma cluster), and the Virgo cluster. A fan beam synthesis system has been used to search for extended radio emission, i.e., radio halos, in these clusters. Radio halos were detected in the Coma and Virgo clusters. No evidence was found for the existence of 3C84B, the halo source previously thought to exist in the Perseus cluster. If halo sources exist in Abell 399/401 or Abell 1367, they must be quite weak at frequencies less than 100 MHz. The observed sizes of the extended sources in Coma and Virgo imply that the rate of particle propagation away from strong radio galaxies greatly exceeds the Alfven velocity and is probably independent of particle energy

The Multiwavelength Study of Two Unique Radio Galaxies Nectaria ...

Indian Academy of Sciences (India)

R. Narasimhan (Krishtel eMaging) 1461 1996 Oct 15 13:05:22

They have no compact hotspots and consist of sharply-bounded lobes. They are probably the only two radio galaxies that show large multiple circular radio features (ring-like structures) that are interior to the lobes and not just phenomena of the boundaries. A few of these rings are the largest material circles known ...

Galactic interaction as the trigger for the young radio galaxy MRC B1221-423

OpenAIRE

Anderson, Craig; Johnston, Helen; Hunstead, Richard

2013-01-01

Mergers between a massive galaxy and a small gas-rich companion (minor mergers) have been proposed as a viable mechanism for triggering radio emission in an active galaxy. Until now the problem has been catching this sequence of events as they occur. With MRC B1221$-$423 we have an active radio galaxy that has only recently been triggered, and a companion galaxy that provides the "smoking gun". Using spectroscopic data taken with the VIMOS Integral Field Unit detector on the European Southern...

Search and modelling of remnant radio galaxies in the LOFAR Lockman Hole field

NARCIS (Netherlands)

Brienza, M.; Godfrey, L.; Morganti, R.; Prandoni, I.; Harwood, J.; Mahony, E. K.; Hardcastle, M. J.; Murgia, M.; Röttgering, H. J. A.; Shimwell, T. W.; Shulevski, A.

2017-01-01

Context. The phase of radio galaxy evolution after the jets have switched off, often referred to as the remnant phase, is poorly understood and very few sources in this phase are known. Aims: In this work we present an extensive search for remnant radio galaxies in the Lockman Hole, a well-studied

The Type Ia Supernova Rate in Radio and Infrared Galaxies from the CFHT Supernova Legacy Survey

OpenAIRE

Graham, M. L.; Pritchet, C. J.; Sullivan, M.; Howell, D. A.; Gwyn, S. D. J.; Astier, P.; Balland, C.; Basa, S.; Carlberg, R. G.; Conley, A.; Fouchez, D.; Guy, J.; Hardin, D.; Hook, I. M.; Pain, R.

2009-01-01

We have combined the large SN Ia database of the Canada-France-Hawaii Telescope Supernova Legacy Survey and catalogs of galaxies with photometric redshifts, VLA 1.4 GHz radio sources, and Spitzer infrared sources. We present eight SNe Ia in early-type host galaxies which have counterparts in the radio and infrared source catalogs. We find the SN Ia rate in subsets of radio and infrared early-type galaxies is ~1-5 times the rate in all early-type galaxies, and that any enhancement is always

A far-infrared spectroscopic survey of intermediate redshift (ultra) luminous infrared galaxies

International Nuclear Information System (INIS)

Magdis, Georgios E.; Rigopoulou, D.; Hopwood, R.; Clements, D.; Huang, J.-S.; Farrah, D.; Pearson, C.; Alonso-Herrero, Almudena; Bock, J. J.; Cooray, A.; Griffin, M. J.; Oliver, S.; Perez Fournon, I.; Riechers, D.; Swinyard, B. M.; Thatte, N.; Scott, D.; Valtchanov, I.; Vaccari, M.

2014-01-01

We present Herschel far-IR photometry and spectroscopy as well as ground-based CO observations of an intermediate redshift (0.21 ≤ z ≤ 0.88) sample of Herschel-selected (ultra)-luminous infrared galaxies (L IR > 10 11.5 L ☉ ). With these measurements, we trace the dust continuum, far-IR atomic line emission, in particular [C II] 157.7 μm, as well as the molecular gas of z ∼ 0.3 luminous and ultraluminous infrared galaxies (LIRGs and ULIRGs) and perform a detailed investigation of the interstellar medium of the population. We find that the majority of Herschel-selected intermediate redshift (U)LIRGs have L C II /L FIR ratios that are a factor of about 10 higher than that of local ULIRGs and comparable to that of local normal and high-z star-forming galaxies. Using our sample to bridge local and high-z [C II] observations, we find that the majority of galaxies at all redshifts and all luminosities follow an L C II –L FIR relation with a slope of unity, from which local ULIRGs and high- z active-galactic-nucleus-dominated sources are clear outliers. We also confirm that the strong anti-correlation between the L C II /L FIR ratio and the far-IR color L 60 /L 100 observed in the local universe holds over a broad range of redshifts and luminosities, in the sense that warmer sources exhibit lower L C II /L FIR at any epoch. Intermediate redshift ULIRGs are also characterized by large molecular gas reservoirs and by lower star formation efficiencies compared to that of local ULIRGs. The high L C II /L FIR ratios, the moderate star formation efficiencies (L IR /L CO ′ or L IR /M H 2 ), and the relatively low dust temperatures of our sample (which are also common characteristics of high-z star-forming galaxies with ULIRG-like luminosities) indicate that the evolution of the physical properties of (U)LIRGs between the present day and z > 1 is already significant by z ∼ 0.3.

Optical images of quasars and radio galaxies

Energy Technology Data Exchange (ETDEWEB)

Hutchings, J.B.; Johnson, I.; Pyke, R.

1988-04-01

Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions. 12 references.

Optical images of quasars and radio galaxies

International Nuclear Information System (INIS)

Hutchings, J.B.; Johnson, I.; Pyke, R.

1988-01-01

Matched contour plots and gray-scale diagrams are presented for 54 radio quasars or radio galaxies of redshift 0.1-0.6, observed with the Canada-France-Hawaii Telescope. All except four were recorded on the RCA1 CCD chip; four were summed from several photographic exposures behind an image tube. All except nine of the objects form the principal data base used by Hutchings (1987). Detailed comments are given on all objects, and some further measures of the objects and their companions. 12 references

THE RADIO PROPERTIES OF RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES ON PARSEC SCALES

Energy Technology Data Exchange (ETDEWEB)

Gu, Minfeng; Chen, Yongjun; Shen, Zhiqiang [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China); Komossa, S.; Zensus, J. A. [Max-Planck-Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Yuan, Weimin [Key Lab for Space Astronomy and Technology, National Astronomical Observatories, Chinese Academy of Sciences, Beijing 100012 (China); Wajima, Kiyoaki [Korea Astronomy and Space Science Institute, 776 Daedeokdae-ro, Yuseong, Daejeon 305-348 (Korea, Republic of); Zhou, Hongyan, E-mail: gumf@shao.ac.cn [Polar Research Institute of China, 451 Jinqiao Road, Shanghai 200136 (China)

2015-11-15

We present the detection of the compact radio structures of 14 radio-loud narrow-line Seyfert 1 (NLS1) galaxies from Very Long Baseline Array (VLBA) observations at 5 GHz performed in 2013. While 50% of the sources of our sample show a compact core only, the remaining 50% exhibit a core-jet structure. The measured brightness temperatures of the cores range from 10{sup 8.4} to 10{sup 11.4} K with a median value of 10{sup 10.1} K, indicating that the radio emission is from non-thermal jets, and that, likely, most sources are not strongly beamed, thus implying a low jet speed in these radio-loud NLS1 galaxies. In combination with archival data taken at multiple frequencies, we find that seven sources show flat or even inverted radio spectra, while steep spectra are revealed in the remaining seven objects. Although all of these sources are very radio-loud with R > 100, their jet properties are diverse in terms of their milliarcsecond (mas) scale (parsec scale) morphology and their overall radio spectral shape. The evidence for slow jet speeds (i.e., less relativistic jets), in combination with the low kinetic/radio power, may offer an explanation for the compact VLBA radio structure in most sources. The mildly relativistic jets in these high accretion rate systems are consistent with a scenario where jets are accelerated from the hot corona above the disk by the magnetic field and the radiation force of the accretion disk. Alternatively, a low jet bulk velocity can be explained by low spin in the Blandford–Znajek mechanism.

Radio Astronomy at the Centre for High Performance Computing in South Africa

Science.gov (United States)

Catherine Cress; UWC Simulation Team

2014-04-01

I will present results on galaxy evolution and cosmology which we obtained using the supercomputing facilities at the CHPC. These include cosmological-scale N-body simulations modelling neutral hydrogen as well as the study of the clustering of radio galaxies to probe the relationship between dark and luminous matter in the universe. I will also discuss the various roles that the CHPC is playing in Astronomy in SA, including the provision of HPC for a variety of Astronomical applications, the provision of storage for radio data, our educational programs and our participation in planning for the SKA.

Testing the dark matter origin of the WMAP-Planck haze with radio observations of spiral galaxies

Energy Technology Data Exchange (ETDEWEB)

Carlson, Eric; Linden, Tim; Profumo, Stefano [Department of Physics, University of California, Santa Cruz, 1156 High Street, Santa Cruz, CA, 95064 (United States); Hooper, Dan, E-mail: erccarls@ucsc.edu, E-mail: dhooper@fnal.gov, E-mail: tlinden@ucsc.edu, E-mail: profumo@ucsc.edu [Center for Particle Astrophysics, Fermi National Accelerator Laboratory, Batavia, IL 60510 (United States)

2013-07-01

If the Galactic WMAP radio haze, as recently confirmed by Planck, is produced by dark matter annihilation or decay, similar diffuse radio halos should exist around other galaxies with physical properties comparable to the Milky Way. If instead the haze is due to an astrophysical mechanism peculiar to the Milky Way or to a transient event, a similar halo need not exist around all Milky Way ''twins''. We use radio observations of 66 spiral galaxies to test the dark matter origin of the haze. We select galaxies based on morphological type and maximal rotational velocity, and obtain their luminosities from a 1.49 GHz catalog and additional radio observations at other frequencies. We find many instances of galaxies with radio emission that is less than 5% as bright as naively expected from dark matter models that could produce the Milky Way haze, and at least 3 galaxies that are less than 1% as bright as expected, assuming dark matter distributions, magnetic fields, and cosmic ray propagation parameters equal to those of the Milky Way. For reasonable ranges for the variation of these parameters, we estimate the fraction of galaxies that should be expected to be significantly less bright in radio, and argue that this is marginally compatible with the observed distribution. While our findings therefore cannot rule out a dark matter origin for the radio haze at this time, we find numerous examples (including the Andromeda Galaxy) where, if dark matter is indeed the origin of the Milky Way haze, some mechanism must be in place to suppress the corresponding haze of the external galaxy. We point out that Planck data will offer opportunities to improve this type of constraint in a highly relevant frequency range and for a potentially larger set of candidate galaxies.

Powerful Radio Galaxies with Simbol-X: Lobes and Hot Spots

Science.gov (United States)

Migliori, G.; Grandi, P.; Angelini, L.; Raimondi, L.; Torresi, E.; Palumbo, G. G. C.

2009-05-01

We present here the first Simbol-X simulations of the extended components, lobes and hot spots, of the radio galaxies. We use the paradigmatic case of Pictor A to test the capabilities of Simbol-X in this field of studies. Simulations demonstrate that Simbol-X will be able not only to perform spatially resolved studies on the lobes of radio galaxies below 10 keV but also to observe, for the first time, hard X-ray emission from the hot spots. These extremely promising results show the considerable potentiality of Simbol-X in studying interaction phenomena between relativistic plasma and surrounding environment.

Powerful Radio Galaxies with Simbol-X: Lobes and Hot Spots

International Nuclear Information System (INIS)

Migliori, G.; Grandi, P.; Raimondi, L.; Torresi, E.; Angelini, L.; Palumbo, G. G. C.

2009-01-01

We present here the first Simbol-X simulations of the extended components, lobes and hot spots, of the radio galaxies. We use the paradigmatic case of Pictor A to test the capabilities of Simbol-X in this field of studies. Simulations demonstrate that Simbol-X will be able not only to perform spatially resolved studies on the lobes of radio galaxies below 10 keV but also to observe, for the first time, hard X-ray emission from the hot spots. These extremely promising results show the considerable potentiality of Simbol-X in studying interaction phenomena between relativistic plasma and surrounding environment.

The hard X–ray emission of the luminous infrared galaxy NGC 6240 as observed by NuSTAR

DEFF Research Database (Denmark)

Puccetti, S.; Comastri, A.; Bauer, F. E.

2016-01-01

We present a broad–band (∼0.3–70 keV) spectral and temporal analysis of NuSTAR observations of the luminous infrared galaxy NGC6240, combined with archival Chandra, XMM–Newton and BeppoSAX data. NGC 6240 is a galaxy in a relatively early merger statewith two distinct nuclei separated by ∼1′.′5. P...

Observations of a nearby filament of galaxy clusters with the Sardinia Radio Telescope

Science.gov (United States)

Vacca, Valentina; Murgia, M.; Loi, F. Govoni F.; Vazza, F.; Finoguenov, A.; Carretti, E.; Feretti, L.; Giovannini, G.; Concu, R.; Melis, A.; Gheller, C.; Paladino, R.; Poppi, S.; Valente, G.; Bernardi, G.; Boschin, W.; Brienza, M.; Clarke, T. E.; Colafrancesco, S.; Enßlin, T.; Ferrari, C.; de Gasperin, F.; Gastaldello, F.; Girardi, M.; Gregorini, L.; Johnston-Hollitt, M.; Junklewitz, H.; Orrù, E.; Parma, P.; Perley, R.; Taylor, G. B.

2018-05-01

We report the detection of diffuse radio emission which might be connected to a large-scale filament of the cosmic web covering a 8° × 8° area in the sky, likely associated with a z≈0.1 over-density traced by nine massive galaxy clusters. In this work, we present radio observations of this region taken with the Sardinia Radio Telescope. Two of the clusters in the field host a powerful radio halo sustained by violent ongoing mergers and provide direct proof of intra-cluster magnetic fields. In order to investigate the presence of large-scale diffuse radio synchrotron emission in and beyond the galaxy clusters in this complex system, we combined the data taken at 1.4 GHz with the Sardinia Radio Telescope with higher resolution data taken with the NRAO VLA Sky Survey. We found 28 candidate new sources with a size larger and X-ray emission fainter than known diffuse large-scale synchrotron cluster sources for a given radio power. This new population is potentially the tip of the iceberg of a class of diffuse large-scale synchrotron sources associated with the filaments of the cosmic web. In addition, we found in the field a candidate new giant radio galaxy.

Giant Radio Halos in Galaxy Clusters as Probes of Particle ...

Indian Academy of Sciences (India)

2016-01-27

Jan 27, 2016 ... Giant radio halos in galaxy clusters probe mechanisms of particle acceleration connected with cluster merger events. Shocks and turbulence are driven in the inter-galactic medium (IGM) during clusters mergers and may have a deep impact on the non-thermal properties of galaxy clusters. Models of ...

Flat radio-spectrum galaxies and BL Lacs I. Core properties

NARCIS (Netherlands)

Dennett-Thorpe, J; Marcha, MJ

This paper concerns the relationship of BL Lacs and flat-spectrum weak emission-line galaxies. We compare the weak emission-line galaxies and the BL Lacs in a sample of 57 flat-spectrum objects (Marcha et al. 1996), using high-frequency radio and non-thermal optical flux densities, spectral indices

Fast radio burst tied to distant dwarf galaxy (Image 2)

National Science Foundation

2017-06-07

Full Text Available Radio telescope at Arecibo only localized the fast radio burst to the area inside the two circles in this image, but the Very Large Array was able to pinpoint it as a dwarf galaxy within the square (shown at intersection of cross hairs in enlarged box)

Optical polarization position angle versus radio structure axis in Seyfert galaxies

Energy Technology Data Exchange (ETDEWEB)

Antonucci, R R.J. [National Radio Astronomy Observatory, Charlottesville, VA (USA)

1983-05-12

The hypothesis that there are two polarization classes of Seyfert galaxies, analogous to the perpendicular and parallel radio galaxy groups, is investigated by examining optical polarimetry data. In the sample considered it is shown that all the Seyfert 1 galaxies have roughly parallel polarization while all the Seyfert 2 galaxies have roughly perpendicular polarizations. These alignment effects can be interpreted as being due to thin and thick scattering disks, respectively, surrounding the continuum sources. This would represent a fundamental difference between the two types of Seyfert galaxies.

Measuring size evolution of distant, faint galaxies in the radio regime

Science.gov (United States)

Lindroos, L.; Knudsen, K. K.; Stanley, F.; Muxlow, T. W. B.; Beswick, R. J.; Conway, J.; Radcliffe, J. F.; Wrigley, N.

2018-05-01

We measure the evolution of sizes for star-forming galaxies as seen in 1.4 GHz continuum radio for z = 0-3. The measurements are based on combined VLA+MERLIN data of the Hubble Deep Field, and using a uv-stacking algorithm combined with model fitting to estimate the average sizes of galaxies. A sample of ˜1000 star-forming galaxies is selected from optical and near-infrared catalogues, with stellar masses M⊙ ≈ 1010-1011 M⊙ and photometric redshifts 0-3. The median sizes are parametrized for stellar mass M* = 5 × 1010 M⊙ as R_e = A× {}(H(z)/H(1.5))^{α _z}. We find that the median radio sizes evolve towards larger sizes at later times with αz = -1.1 ± 0.6, and A (the median size at z ≈ 1.5) is found to be 0.26^'' ± 0.07^'' or 2.3±0.6 kpc. The measured radio sizes are typically a factor of 2 smaller than those measure in the optical, and are also smaller than the typical H α sizes in the literature. This indicates that star formation, as traced by the radio continuum, is typically concentrated towards the centre of galaxies, for the sampled redshift range. Furthermore, the discrepancy of measured sizes from different tracers of star formation, indicates the need for models of size evolution to adopt a multiwavelength approach in the measurement of the sizes star-forming regions.

Quark nugget dark matter: Comparison with radio observations of nearby galaxies

Energy Technology Data Exchange (ETDEWEB)

Lawson, K., E-mail: klawson@phas.ubc.ca; Zhitnitsky, A.R.

2016-06-10

It has been recently claimed that radio observations of nearby spiral galaxies essentially rule out a dark matter source for the galactic haze [1]. Here we consider the low energy thermal emission from a quark nugget dark matter model in the context of microwave emission from the galactic centre and radio observations of nearby Milky Way like galaxies. We demonstrate that observed emission levels do not strongly constrain this specific dark matter candidate across a broad range of the allowed parameter space in drastic contrast with conventional dark matter models based on the WIMP paradigm.

Recent star formation in interacting galaxies

International Nuclear Information System (INIS)

Joseph, R.D.; Wright, G.S.

1985-01-01

The subset of galaxy-galaxy interactions which have resulted in a merger are, as a class, ultraluminous IR galaxies. Their IR luminosities span a narrow range which overlaps with the most luminous Seyfert galaxies. However, in contrast with Seyfert galaxies, the available optical, IR, and radio properties of mergers show no evidence for a compact non-thermal central source, and are easily understood in terms of a burst of star formation of extraordinary intensity and spatial extent; they are 'super starbursts'. We argue that super starbursts occur in the evolution of most mergers, and discuss the implications of super starbursts for the suggestion that mergers evolve into elliptical galaxies. Finally, we note that merger-induced shocks are likely to leave the gas from both galaxies in dense molecular form which will rapidly cool, collapse, and fragment. Thus a merger might in fact be expected to result in a burst of star formation of exceptional intensity and spatial extent, i.e. a super starburst. (author)

DISCOVERY OF TWO SUPERNOVAE IN THE NUCLEAR REGIONS OF THE LUMINOUS INFRARED GALAXY IC 883

Energy Technology Data Exchange (ETDEWEB)

Kankare, E.; Mattila, S.; Takalo, A. [Tuorla Observatory, Department of Physics and Astronomy, University of Turku, Vaeisaelaentie 20, FI-21500 Piikkioe (Finland); Ryder, S. [Australian Astronomical Observatory, P.O. Box 296, Epping, NSW 1710 (Australia); Vaeisaenen, P. [South African Astronomical Observatory, P.O. Box 9, Observatory 7935 (South Africa); Alberdi, A.; Perez-Torres, M.-A.; Romero-Canizales, C. [Instituto de Astrofsica de Andalucia, IAA-CSIC, Apartado 3004, 18080 Granada (Spain); Alonso-Herrero, A.; Colina, L. [Departamento de Astrofisica, Centro de Astrobiologia, CSIC/INTA, Carretera de Torrejon a Ajalvir, km 4, 28850, Torrejon de Ardoz, Madrid (Spain); Efstathiou, A. [School of Sciences, European University Cyprus, Diogenes Street, Engomi, 1516 Nicosia (Cyprus); Kotilainen, J. [Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Vaeisaelaentie 20, FI-21500 Piikkioe (Finland); Melinder, J., E-mail: erkki.kankare@utu.fi [Department of Astronomy, Oskar Klein Centre, Stockholm University, AlbaNova University Centre, 106 91 Stockholm (Sweden)

2012-01-10

We report the discovery of two consecutive supernovae (SNe), 2010cu and 2011hi, located at 0.''37 (180 pc) and 0.''79 (380 pc) projected distance, respectively, from the center of the K-band nucleus of the luminous infrared galaxy (LIRG) IC 883. The SNe were discovered in an ongoing near-infrared K-band search for core-collapse SNe in such galaxies using the ALTAIR/NIRI adaptive optics system with laser guide star at the Gemini-North Telescope. These are thus the closest SNe yet discovered to an LIRG nucleus in optical or near-infrared wavelengths. The near-infrared light curves and colors of both SNe are consistent with core-collapse events. Both SNe seem to suffer from relatively low host galaxy extinction suggesting that regardless of their low projected galactocentric distances, they are not deeply buried in the nuclear regions of the host galaxy.

Submillimeter H2O and H2O+emission in lensed ultra- and hyper-luminous infrared galaxies at z 2-4

NARCIS (Netherlands)

Yang, C.; Omont, A.; Beelen, A.; González-Alfonso, E.; Neri, R.; Gao, Y.; van der Werf, P.; Weiß, A.; Gavazzi, R.; Falstad, N.; Baker, A. J.; Bussmann, R. S.; Cooray, A.; Cox, P.; Dannerbauer, H.; Dye, S.; Guélin, M.; Ivison, R.; Krips, M.; Lehnert, M.; Michałowski, M. J.; Riechers, D. A.; Spaans, M.; Valiante, E.

2016-01-01

We report rest-frame submillimeter H2O emission line observations of 11 ultra- or hyper-luminous infrared galaxies (ULIRGs or HyLIRGs) at z 2-4 selected among the brightest lensed galaxies discovered in the Herschel-Astrophysical Terahertz Large Area Survey (H-ATLAS). Using the IRAM NOrthern

A LUMINOUS GAMMA-RAY BINARY IN THE LARGE MAGELLANIC CLOUD

Energy Technology Data Exchange (ETDEWEB)

Corbet, R. H. D. [University of Maryland, Baltimore County, and X-ray Astrophysics Laboratory, Code 662 NASA Goddard Space Flight Center, Greenbelt Rd., MD 20771 (United States); Chomiuk, L.; Strader, J. [Department of Physics and Astronomy, Michigan State University, East Lansing, MI 48824 (United States); Coe, M. J. [University of Southampton, School of Physics and Astronomy, Southampton SO17 1BJ (United Kingdom); Coley, J. B. [NASA Postdoctoral Program, and Astroparticle Physics Laboratory, Code 661 NASA Goddard Space Flight Center, Greenbelt Rd., MD 20771 (United States); Dubus, G. [Institut de Planétologie et d’Astrophysique de Grenoble, Univ. Grenoble Alpes, CNRS, F-38000 Grenoble (France); Edwards, P. G.; Stevens, J. [Commonwealth Scientific and Industrial Research Organisation Astronomy and Space Science, P.O. Box 76, Epping, New South Wales 1710 (Australia); Martin, P. [Institut de Recherche en Astrophysique et Planétologie, Université de Toulouse, CNRS, F-31028 Toulouse cedex 4 (France); McBride, V. A.; Townsend, L. J. [Department of Astronomy, University of Cape Town, Private Bag X3, Rondebosch 7701 (South Africa); Udalski, A. [Warsaw University Observatory, Al. Ujazdowskie 4, 00-478 Warszawa (Poland)

2016-10-01

Gamma-ray binaries consist of a neutron star or a black hole interacting with a normal star to produce gamma-ray emission that dominates the radiative output of the system. Only a handful of such systems have been previously discovered, all within our Galaxy. Here, we report the discovery of a luminous gamma-ray binary in the Large Magellanic Cloud, found with the Fermi Large Area Telescope (LAT), from a search for periodic modulation in all sources in the third Fermi LAT catalog. This is the first such system to be found outside the Milky Way. The system has an orbital period of 10.3 days, and is associated with a massive O5III star located in the supernova remnant DEM L241, previously identified as the candidate high-mass X-ray binary (HMXB) CXOU J053600.0–673507. X-ray and radio emission are also modulated on the 10.3 day period, but are in anti-phase with the gamma-ray modulation. Optical radial velocity measurements suggest that the system contains a neutron star. The source is significantly more luminous than similar sources in the Milky Way, at radio, optical, X-ray, and gamma-ray wavelengths. The detection of this extra-galactic system, but no new Galactic systems, raises the possibility that the predicted number of gamma-ray binaries in our Galaxy has been overestimated, and that HMXBs may be born containing relatively slowly rotating neutron stars.

The Hyperluminous Infrared Quasar 3C 318 and Its Implications for Interpreting Sub-MM Detections of High-Redshift Radio Galaxies

Science.gov (United States)

Willott, Chris J.; Rawlings, Steve; Jarvis, Matt J.

1999-01-01

We present near-infrared spectroscopy and imaging of the compact steep-spectrum radio source 3C 318 which shows it to be a quasar at redshift z = 1.574 (the z = 0.752 value previously reported is incorrect). 3C 318 is an IRAS, ISO and SCUBA source so its new redshift makes it the most intrinsically luminous far-infrared (FIR) source in the 3C catalogue (there is no evidence of strong gravitational lensing effects). Its bolometric luminosity greatly exceeds the 10(exp 13) solar luminosity level above which an object is said to be hyperluminous. Its spectral energy distribution (SED) requires that the quasar heats the dust responsible for the FIR flux, as is believed to be the case in other hyperluminous galaxies, and contributes (at the greater than 10% level) to the heating of the CIA dust responsible for the sub-mm emission. We cannot determine whether a starburst makes an important contribution to the heating of the coolest dust, so evidence for a high star-formation rate is circumstantial being based on the high dust, and hence gas, C-1 mass required by its sub-mm detection. We show that the current sub-mm and FIR data available for the highest-redshift radio galaxies are consistent with SEDs similar to that of 3C 318. This indicates that at least some of this population may be detected in the sub-mm because of dust heated by the quasar nucleus, and that interpreting sub-mm detection as evidence for very high (approx. less than 1000 solar mass/yr) star-formation rates may not always be valid. We show that the 3C318 quasar is slightly reddened (A(sub v) approx. = 0.5), the most likely cause of which is SMC-type dust in the host galaxy. If very distant radio galaxies are reddened in a similar way then we show that only slightly greater amounts of dust could obscure the quasars in these sources. We speculate that the low fraction of quasars amongst the very high redshift (z approx. greater than 3) objects in low-frequency radio-selected samples is the result of

The polarization of radio galaxies

International Nuclear Information System (INIS)

Jaegers, W.J.

1986-01-01

In this thesis radio observations at 0.6 GHz together with matched (convolved) observations at 1.4 GHz of 30 radiosources are described and interpreted. Sources of great interest which are individually discussed are the complex nearby source 3C66B, the source 4C73.48, the narrow edge-darkened double source 3C130 (together with two newly observed narrow-edge-darkened doubles), the galaxies 3C129 and 3C390.3 and the giant quasar 4C34.47. (Auth.)

LeMMINGs - I. The eMERLIN legacy survey of nearby galaxies. 1.5-GHz parsec-scale radio structures and cores

Science.gov (United States)

Baldi, R. D.; Williams, D. R. A.; McHardy, I. M.; Beswick, R. J.; Argo, M. K.; Dullo, B. T.; Knapen, J. H.; Brinks, E.; Muxlow, T. W. B.; Aalto, S.; Alberdi, A.; Bendo, G. J.; Corbel, S.; Evans, R.; Fenech, D. M.; Green, D. A.; Klöckner, H.-R.; Körding, E.; Kharb, P.; Maccarone, T. J.; Martí-Vidal, I.; Mundell, C. G.; Panessa, F.; Peck, A. B.; Pérez-Torres, M. A.; Saikia, D. J.; Saikia, P.; Shankar, F.; Spencer, R. E.; Stevens, I. R.; Uttley, P.; Westcott, J.

2018-05-01

We present the first data release of high-resolution (≤0.2 arcsec) 1.5-GHz radio images of 103 nearby galaxies from the Palomar sample, observed with the eMERLIN array, as part of the LeMMINGs survey. This sample includes galaxies which are active (low-ionization nuclear emission-line regions [LINER] and Seyfert) and quiescent (H II galaxies and absorption line galaxies, ALGs), which are reclassified based upon revised emission-line diagrams. We detect radio emission ≳0.2 mJy for 47/103 galaxies (22/34 for LINERS, 4/4 for Seyferts, 16/51 for H II galaxies, and 5/14 for ALGs) with radio sizes typically of ≲100 pc. We identify the radio core position within the radio structures for 41 sources. Half of the sample shows jetted morphologies. The remaining half shows single radio cores or complex morphologies. LINERs show radio structures more core-brightened than Seyferts. Radio luminosities of the sample range from 1032 to 1040 erg s-1: LINERs and H II galaxies show the highest and lowest radio powers, respectively, while ALGs and Seyferts have intermediate luminosities. We find that radio core luminosities correlate with black hole (BH) mass down to ˜107 M⊙, but a break emerges at lower masses. Using [O III] line luminosity as a proxy for the accretion luminosity, active nuclei and jetted H II galaxies follow an optical Fundamental Plane of BH activity, suggesting a common disc-jet relationship. In conclusion, LINER nuclei are the scaled-down version of FR I radio galaxies; Seyferts show less collimated jets; H II galaxies may host weak active BHs and/or nuclear star-forming cores; and recurrent BH activity may account for ALG properties.

A tale of two feedbacks: Star formation in the host galaxies of radio AGNs

Energy Technology Data Exchange (ETDEWEB)

Karouzos, Marios; Im, Myungshin; Jeon, Yiseul; Kim, Ji Hoon [CEOU-Astronomy Program, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul (Korea, Republic of); Trichas, Markos [Airbus Defence and Space, Gunnels Wood Road, Stevenage SG1 2AS (United Kingdom); Goto, Tomo [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries Vej 30, DK-2100 Copenhagen (Denmark); Malkan, Matt [Division of Astronomy and Astrophysics, 3-714 UCLA, CA 90095-1547 (United States); Ruiz, Angel [Inter-University Centre for Astronomy and Astrophysics (IUCAA), Post Bag 4, Ganeshkhind, 411 007 Pune (India); Lee, Hyung Mok; Kim, Seong Jin [Astronomy Program, Department of Physics and Astronomy, Seoul National University, Gwanak-gu, Seoul (Korea, Republic of); Oi, Nagisa; Matsuhara, Hideo; Takagi, Toshinobu; Murata, K.; Wada, Takehiko; Wada, Kensuke [Institute of Space and Astronautical Science, JAXA, Yoshino-dai 3-1-1, Sagamihara, Kanagawa 229-8510 (Japan); Shim, Hyunjin [Department of Earth Science Education, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Hanami, Hitoshi [Physics Section, Faculty of Humanities, Iwate University, Ueda 3 chome, 18-34 Morioka, Morioka, Iwate 020-8550 (Japan); Serjeant, Stephen; White, Glenn J., E-mail: mkarouzos@astro.snu.ac.kr [Department of Physics and Astronomy, The Open University, Walton Hall, Milton Keynes (United Kingdom); and others

2014-04-01

Several lines of argument support the existence of a link between activity at the nuclei of galaxies, in the form of an accreting supermassive black hole, and star formation activity in these galaxies. Radio jets have long been argued to be an ideal mechanism that allows active galactic nuclei (AGNs) to interact with their host galaxies and affect star formation. We use a sample of radio sources in the North Ecliptic Pole (NEP) field to study the nature of this putative link, by means of spectral energy distribution (SED) fitting. We employ the excellent spectral coverage of the AKARI infrared space telescope and the rich ancillary data available in the NEP to build SEDs extending from UV to far-IR wavelengths. We find a significant AGN component in our sample of relatively faint radio sources (galaxy, independent of the radio luminosity. In contrast, for narrow redshift and AGN luminosity ranges, we find that increasing radio luminosity leads to a decrease in the specific star formation rate. The most radio-loud AGNs are found to lie on the main sequence of star formation for their respective redshifts. For the first time, we potentially see such a two-sided feedback process in the same sample. We discuss the possible suppression of star formation, but not total quenching, in systems with strong radio jets, that supports the maintenance nature of feedback from radio AGN jets.

Star Formation Rates in Lyman Break Galaxies: Radio Stacking of LBGs in the COSMOS Field and the Sub-μJy Radio Source Population

Science.gov (United States)

Carilli, C. L.; Lee, Nicholas; Capak, P.; Schinnerer, E.; Lee, K.-S.; McCraken, H.; Yun, M. S.; Scoville, N.; Smolčić, V.; Giavalisco, M.; Datta, A.; Taniguchi, Y.; Urry, C. Megan

2008-12-01

We present an analysis of the radio properties of large samples of Lyman break galaxies (LBGs) at z ~ 3, 4, and 5 from the COSMOS field. The median stacking analysis yields a statistical detection of the z ~ 3 LBGs (U-band dropouts), with a 1.4 GHz flux density of 0.90 +/- 0.21 μJy. The stacked emission is unresolved, with a size = 3 is smaller than at lower redshifts. Conversely, the radio luminosity for a given star formation rate may be systematically lower at very high redshift. Two possible causes for a suppressed radio luminosity are (1) increased inverse Compton cooling of the relativistic electron population due to scattering off the increasing CMB at high redshift or (2) cosmic-ray diffusion from systematically smaller galaxies. The radio detections of individual sources are consistent with a radio-loud AGN fraction of 0.3%. One source is identified as a very dusty, extreme starburst galaxy (a "submillimeter galaxy"). Based on observations in the COSMOS Legacy Survey including those taken on the HST, Keck, NRAO-VLA, Subaru, KPNO 4 m, CTIO 4 m, and CFHT 3.6 m. The Very Large Array of the National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc.

Radio continuum processes in clusters of galaxies; Proceedings of the Workshop, Green Bank, WV, Aug. 4-8, 1986

International Nuclear Information System (INIS)

O'dea, C.P.; Uson, J.M.

1986-01-01

Recent observational and theoretical investigations of clusters of galaxies are examined in reviews and reports. Topics addressed include radio surveys of clusters, accretion flows, wide-angle-tail radio sources, the interaction of radio sources with the intracluster medium, diffuse emission in clusters, cluster dynamics, and the environment of powerful radio sources. Particular attention is given to a local perspective on galaxies in rich clusters, X-ray observations of clusters, VLA observations of distant clusters, the halo of Vir A at 327 MHz, Exosat observations of the Vir Cluster, accretion flows in elliptical galaxies, jet disruption in wide-angle-tail radio galaxies, beam trajectories in the intracluster medium, the Suniaev-Zel'dovich effect, dark matter in clusters, and the H I environment of high-redshift quasars

POLARIZED EXTENDED Ly{alpha} EMISSION FROM A z = 2.3 RADIO GALAXY

Energy Technology Data Exchange (ETDEWEB)

Humphrey, A. [Centro de Astrofisica da Universidade do Porto, Rua das Estrelas, 4150-762 Porto (Portugal); Vernet, J.; Fosbury, R. A. E. [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Villar-Martin, M. [Centro de Astrobiologia (INTA-CSIC), Carretera de Ajalvir, km 4, E-28850 Torrejon de Ardoz, Madrid (Spain); Di Serego Alighieri, S. [INAF-Osservatorio Astrofisico di Arcetri, L.go E. Fermi 5, I-50125 Firenze (Italy); Cimatti, A., E-mail: andrew.humphrey@astro.up.pt [Dipartimento di Astronomia, Universita di Bologna, Via Ranzani 1, I-40127 Bologna (Italy)

2013-05-01

We present spatially resolved spectropolarimetric measurements of the 100 kpc scale gaseous environment of the z = 2.34 radio galaxy TXS 0211-122. The polarization level of the narrow Ly{alpha} emission is low centrally (P < 5%), but rises to P = 16.4% {+-} 4.6% in the eastern part of the nebula, indicating that the nebula is at least partly powered by the scattering of Ly{alpha} photons by H I. Not only is this the first detection of polarized Ly{alpha} around a radio-loud active galaxy, it is also the second detection to date for any kind of Ly{alpha} nebula. We also detect a pair of diametrically opposed UV continuum sources along the slit, at the outer edges of the Ly{alpha} nebula, which we suggest may be the limb of a dusty shell, related to the large-scale H I absorbers often associated with high-z radio galaxies.

LLAMA: normal star formation efficiencies of molecular gas in the centres of luminous Seyfert galaxies

Science.gov (United States)

Rosario, D. J.; Burtscher, L.; Davies, R. I.; Koss, M.; Ricci, C.; Lutz, D.; Riffel, R.; Alexander, D. M.; Genzel, R.; Hicks, E. H.; Lin, M.-Y.; Maciejewski, W.; Müller-Sánchez, F.; Orban de Xivry, G.; Riffel, R. A.; Schartmann, M.; Schawinski, K.; Schnorr-Müller, A.; Saintonge, A.; Shimizu, T.; Sternberg, A.; Storchi-Bergmann, T.; Sturm, E.; Tacconi, L.; Treister, E.; Veilleux, S.

2018-02-01

Using new Atacama Pathfinder Experiment and James Clerk Maxwell Telescope spectroscopy of the CO 2→1 line, we undertake a controlled study of cold molecular gas in moderately luminous (Lbol = 1043-44.5 erg s-1) active galactic nuclei (AGN) and inactive galaxies from the Luminous Local AGN with Matched Analogs (LLAMA) survey. We use spatially resolved infrared photometry of the LLAMA galaxies from 2MASS, the Wide-field Infrared Survey Explorer the Infrared Astronomical Satellite and the Herschel Space Observatory (Herschel), corrected for nuclear emission using multicomponent spectral energy distribution fits, to examine the dust-reprocessed star formation rates, molecular gas fractions and star formation efficiencies (SFEs) over their central 1-3 kpc. We find that the gas fractions and central SFEs of both active and inactive galaxies are similar when controlling for host stellar mass and morphology (Hubble type). The equivalent central molecular gas depletion times are consistent with the discs of normal spiral galaxies in the local Universe. Despite energetic arguments that the AGN in LLAMA should be capable of disrupting the observable cold molecular gas in their central environments, our results indicate that nuclear radiation only couples weakly with this phase. We find a mild preference for obscured AGN to contain higher amounts of central molecular gas, which suggests connection between AGN obscuration and the gaseous environment of the nucleus. Systems with depressed SFEs are not found among the LLAMA AGN. We speculate that the processes that sustain the collapse of molecular gas into dense pre-stellar cores may also be a prerequisite for the inflow of material on to AGN accretion discs.

The Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS): survey design, data catalogue and GAMA/WiggleZ spectroscopy

Science.gov (United States)

Ching, John H. Y.; Sadler, Elaine M.; Croom, Scott M.; Johnston, Helen M.; Pracy, Michael B.; Couch, Warrick J.; Hopkins, A. M.; Jurek, Russell J.; Pimbblet, K. A.

2017-01-01

We present the Large Area Radio Galaxy Evolution Spectroscopic Survey (LARGESS), a spectroscopic catalogue of radio sources designed to include the full range of radio AGN populations out to redshift z ˜ 0.8. The catalogue covers ˜800 deg2 of sky, and provides optical identifications for 19 179 radio sources from the 1.4 GHz Faint Images of the Radio Sky at Twenty-cm (FIRST) survey down to an optical magnitude limit of Imod point-like objects are included, and no colour cuts are applied. In collaboration with the WiggleZ and Galaxy And Mass Assembly (GAMA) spectroscopic survey teams, we have obtained new spectra for over 5000 objects in the LARGESS sample. Combining these new spectra with data from earlier surveys provides spectroscopic data for 12 329 radio sources in the survey area, of which 10 856 have reliable redshifts. 85 per cent of the LARGESS spectroscopic sample are radio AGN (median redshift z = 0.44), and 15 per cent are nearby star-forming galaxies (median z = 0.08). Low-excitation radio galaxies (LERGs) comprise the majority (83 per cent) of LARGESS radio AGN at z < 0.8, with 12 per cent being high-excitation radio galaxies (HERGs) and 5 per cent radio-loud QSOs. Unlike the more homogeneous LERG and QSO sub-populations, HERGs are a heterogeneous class of objects with relatively blue optical colours and a wide dispersion in mid-infrared colours. This is consistent with a picture in which most HERGs are hosted by galaxies with recent or ongoing star formation as well as a classical accretion disc.

AXIAL RATIO OF EDGE-ON SPIRAL GALAXIES AS A TEST FOR BRIGHT RADIO HALOS

International Nuclear Information System (INIS)

Singal, J.; Jones, E.; Dunlap, H.; Kogut, A.

2015-01-01

We use surface brightness contour maps of nearby edge-on spiral galaxies to determine whether extended bright radio halos are common. In particular, we test a recent model of the spatial structure of the diffuse radio continuum by Subrahmanyan and Cowsik which posits that a substantial fraction of the observed high-latitude surface brightness originates from an extended Galactic halo of uniform emissivity. Measurements of the axial ratio of emission contours within a sample of normal spiral galaxies at 1500 MHz and below show no evidence for such a bright, extended radio halo. Either the Galaxy is atypical compared to nearby quiescent spirals or the bulk of the observed high-latitude emission does not originate from this type of extended halo. (letters)

LOFAR-Boötes: properties of high- and low-excitation radio galaxies at 0.5 < z < 2.0

Science.gov (United States)

Williams, W. L.; Calistro Rivera, G.; Best, P. N.; Hardcastle, M. J.; Röttgering, H. J. A.; Duncan, K. J.; de Gasperin, F.; Jarvis, M. J.; Miley, G. K.; Mahony, E. K.; Morabito, L. K.; Nisbet, D. M.; Prandoni, I.; Smith, D. J. B.; Tasse, C.; White, G. J.

2018-04-01

This paper presents a study of the redshift evolution of radio-loud active galactic nuclei (AGN) as a function of the properties of their galaxy hosts in the Boötes field. To achieve this we match low-frequency radio sources from deep 150-MHz LOFAR (LOw Frequency ARray) observations to an I-band-selected catalogue of galaxies, for which we have derived photometric redshifts, stellar masses, and rest-frame colours. We present spectral energy distribution (SED) fitting to determine the mid-infrared AGN contribution for the radio sources and use this information to classify them as high- versus low-excitation radio galaxies (HERGs and LERGs) or star-forming galaxies. Based on these classifications, we construct luminosity functions for the separate redshift ranges going out to z = 2. From the matched radio-optical catalogues, we select a sub-sample of 624 high power (P150 MHz > 1025 W Hz-1) radio sources between 0.5 ≤ z negative evolution of the LERG luminosity functions over this redshift range, is consistent with LERGs being fuelled by hot gas in quiescent galaxies.

Classifying bent radio galaxies from a mixture of point-like/extended images with Machine Learning.

Science.gov (United States)

Bastien, David; Oozeer, Nadeem; Somanah, Radhakrishna

2017-05-01

The hypothesis that bent radio sources are supposed to be found in rich, massive galaxy clusters and the avalibility of huge amount of data from radio surveys have fueled our motivation to use Machine Learning (ML) to identify bent radio sources and as such use them as tracers for galaxy clusters. The shapelet analysis allowed us to decompose radio images into 256 features that could be fed into the ML algorithm. Additionally, ideas from the field of neuro-psychology helped us to consider training the machine to identify bent galaxies at different orientations. From our analysis, we found that the Random Forest algorithm was the most effective with an accuracy rate of 92% for a classification of point and extended sources as well as an accuracy of 80% for bent and unbent classification.

A search for X-ray bright distant clusters of galaxies

Science.gov (United States)

Nichol, R. C.; Ulmer, M. P.; Kron, R. G.; Wirth, G. D.; Koo, D. C.

1994-01-01

We present the results of a search for X-ray luminous distant clusters of galaxies. We found extended X-ray emission characteristic of a cluster toward two of our candidate clusters of galaxies. They both have a luminosity in the ROSAT bandpass of approximately equals 10(exp 44) ergs/s and a redshift greater than 0.5; thus making them two of the most distant X-ray clusters ever observed. Furthermore, we show that both clusters are optically rich and have a known radio source associated with them. We compare our result with other recent searches for distant X-ray luminous clusters and present a lower limit of 1.2 x 10(exp -7)/cu Mpc for the number density of such high-redshift clusters. This limit is consistent with the expected abundance of such clusters in a standard (b = 2) cold dark matter universe. Finally, our clusters provide important high-redshift targets for further study into the origin and evolution of massive clusters of galaxies.

The X-Ray Core of the Low-Luminosity Radio Galaxy 3C346 and ASCA Spectroscopy to Test BL LAC/Radio Galaxy Unification

Science.gov (United States)

Worrall, Diana

2000-01-01

Radio galaxies are relatively faint sources for Advanced Spacecraft for Cosmology Astrophysics (ASCA), and so in order to get the best possible results from the observations two things have been necessary, both of which delayed the fast preparation of papers. Firstly, the best possible data screening and background subtraction were necessary to improve the signal-to-noise, and all our several initial analysis trials were discarded in favor of using FTOOLS versions 4.1 and above. Secondly, we found that the ASCA spectra were statistically too poor to discriminate well between non-thermal and thermal models, never mind the mixture of the two which we expected on the basis of our ROSAT spatial separation of components in radio galaxies. This means that in each case we have needed to combine the ASCA spectroscopy with analysis of data from other X-ray or radio observations in order to exploit the ASCA data to the full. Our analysis for 3C 346 has yielded the cleanest final result. This powerful radio galaxy at a redshift of 0.161, lies in a poor cluster, which we have separated well from the dominant X-ray component of unresolved emission using a spatial analysis of archival ROSAT data. We were then able to fix the thermal component in our ASCA spectral analysis, and have found evidence that the unresolved emission varied by 32 +/- 13% over the 18 months between the ROSAT and ASCA observations. The unresolved X-ray emission does not suffer from intrinsic absorption, and we have related it to radio structures on both milliarcsecond scales and the arcsecond scales which Chandra can resolve. The source is a target of a Chandra AO2 proposal which we have recently submitted to follow up on our ASCA (and ROSAT) work. 3C 346's orientation to the line of sight is uncertain. However, the absence of X-ray absorption, and the radio/optical/X-ray colors, when combined with with previous radio evidence that the source is a foreshortened radio galaxy of the FRII class, suggest that

The x-ray luminous galaxy cluster population at 0.9 < z ≲ 1.6 as revealed by the XMM-Newton Distant Cluster Project

International Nuclear Information System (INIS)

Fassbender, R; Böhringer, H; Nastasi, A; Šuhada, R; Mühlegger, M; Mohr, J J; Pierini, D; De Hoon, A; Kohnert, J; Lamer, G; Schwope, A D; Pratt, G W; Quintana, H; Rosati, P; Santos, J S

2011-01-01

local clusters, the z > 0.9 systems mostly do not harbor central dominant galaxies coincident with the x-ray centroid position, but rather exhibit significant brightest cluster galaxy (BCG) offsets from the x-ray center with a median value of about 50 kpc in projection and a smaller median luminosity gap to the second-ranked galaxy of Δm 12 ≃ 0.3 mag. We estimate a fraction of cluster-associated NVSS 1.4 GHz radio sources of about 30%, preferentially located within 1′ from the x-ray center. This value suggests an increase of the fraction of very luminous cluster-associated radio sources by about a factor of 2.5-5 relative to low-z systems. The galaxy populations in z ≳ 1.5 cluster environments show first evidence for drastic changes on the high-mass end of galaxies and signs of a gradual disappearance of a well-defined cluster red-sequence as strong star formation activity is observed in an increasing fraction of massive galaxies down to the densest core regions. The presented XDCP high-z sample will allow first detailed studies of the cluster population during the critical cosmic epoch at lookback times of 7.3-9.5 Gyr on the aggregation and evolution of baryons in the cold and hot phases as a function of redshift and system mass. (paper)

Radio haloes in nearby galaxies modelled with 1D cosmic ray transport using SPINNAKER

Science.gov (United States)

Heesen, V.; Krause, M.; Beck, R.; Adebahr, B.; Bomans, D. J.; Carretti, E.; Dumke, M.; Heald, G.; Irwin, J.; Koribalski, B. S.; Mulcahy, D. D.; Westmeier, T.; Dettmar, R.-J.

2018-05-01

We present radio continuum maps of 12 nearby (D ≤ 27 Mpc), edge-on (i ≥ 76°), late-type spiral galaxies mostly at 1.4 and 5 GHz, observed with the Australia Telescope Compact Array, Very Large Array, Westerbork Synthesis Radio Telescope, Effelsberg 100-m, and Parkes 64-m telescopes. All galaxies show clear evidence of radio haloes, including the first detection in the Magellanic-type galaxy NGC 55. In 11 galaxies, we find a thin and a thick disc that can be better fitted by exponential rather than Gaussian functions. We fit our SPINNAKER (SPectral INdex Numerical Analysis of K(c)osmic-ray Electron Radio-emission) 1D cosmic ray transport models to the vertical model profiles of the non-thermal intensity and to the non-thermal radio spectral index in the halo. We simultaneously fit for the advection speed (or diffusion coefficient) and magnetic field scale height. In the thick disc, the magnetic field scale heights range from 2 to 8 kpc with an average across the sample of 3.0 ± 1.7 kpc; they show no correlation with either star formation rate (SFR), SFR surface density (ΣSFR), or rotation speed (Vrot). The advection speeds range from 100 to 700 km s - 1 and display correlations of V∝SFR0.36 ± 0.06 and V∝ Σ _SFR^{0.39± 0.09}; they agree remarkably well with the escape velocities (0.5 ≤ V/Vesc ≤ 2), which can be explained by cosmic ray-driven winds. Radio haloes show the presence of disc winds in galaxies with ΣSFR > 10 - 3 M⊙ yr - 1 kpc - 2 that extend over several kpc and are driven by processes related to the distributed star formation in the disc.

Identification and spectrophotometry of faint southern radio galaxies

International Nuclear Information System (INIS)

Spinrad, H.; Kron, R.G.; Hunstead, R.W.

1980-01-01

We have observed a mixed sample of southern radio sources, identified on the Palomar sky survey or on previous direct plates taken with medium-aperture reflectors. At CIO we obtained a few deep 4m photographs and SIT spectrophotometry for redshift and continuum-color measurement. Almost all our sources were faint galaxies; the largest redshift measured was for 3C 275, with z=0.480. The ultraviolet continuum of PKS 0400--643, a ''thermal'' galaxy with z=0.476, closely resembles that of 3C 295 and shows some color evolution in U--B compared to nearby giant ellipticals

2.2 micron image of 3C 368 at z = 1.13, a galaxy with aligned radio and stellar axes

International Nuclear Information System (INIS)

Chambers, K.C.; Miley, G.K.; Joyce, R.R.

1988-01-01

A K-band IR image of the z = 1.13 radio galaxy 3C 368, one of the brightest examples of the recently discovered phenomenon of alignment between the optical and radio axes of powerful distant radio galaxies, is presented. The observations show that the IR morphology is also elongated and aligned along the optical and radio axes, but is not coincident with the radio emission. Various mechanisms for producing the IR and optical flux and the resultant constraints on the origin of the alignment effect in high-redshift radio galaxies are discussed. The most likely explanation is that the emission is produced mainly by young stars formed by interaction of the radio source with the ISM. The IR flux is then interpreted as dominated by a population of red supergiants. Independent of the origin of the emission, the observed alignment implies that powerful radio galaxies at high redshifts are distant from giant ellipticals, even in the IR. Hence, attempts to derive a cosmological standard candle using studies which combine these two types of galaxies are likely to be invalid. 32 references

Infrared photometry of the nuclei of early-type radio galaxies

International Nuclear Information System (INIS)

Sparks, W.B.; Bailey, J.

1986-01-01

J,H,K,L' two-aperture photometry and single-aperture 10-μm(N) photometry of the nuclei of 44 nearby radio elliptical and SO galaxies are presented. Clear infrared excesses are found from the galaxies with broad emission-lines, the BL Lac objects, and two other galaxies, one of which appears to have an extended infrared excess. In addition, the sample as a whole appears to have positive 10-μm emission which is believed to be largely due to starlight. The near-infrared colours in general are characteristic of normal starlight, with only the strongest 10-μm emitters showing a significant near-infrared excess. These latter galaxies have blue optical colours. (author)

KILOPARSEC-SCALE JETS IN THREE RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Richards, Joseph L.; Lister, Matthew L., E-mail: jlr@purdue.edu [Department of Physics and Astronomy, Purdue University, 525 Northwestern Avenue, West Lafayette, IN 47907 (United States)

2015-02-10

We have discovered kiloparsec-scale extended radio emission in three narrow-line Seyfert 1 galaxies (NLS1s) in sub-arcsecond resolution 9 GHz images from the Karl G. Jansky Very Large Array. We find all sources show two-sided, mildly core-dominated jet structures with diffuse lobes dominated by termination hotspots. These span 20–70 kpc with morphologies reminiscent of FR II radio galaxies, while the extended radio luminosities are intermediate between FR I and FR II sources. In two cases the structure is linear, while a 45° bend is apparent in the third. Very Long Baseline Array images at 7.6 GHz reveal parsec-scale jet structures, in two cases with extended structure aligned with the inner regions of the kiloparsec-scale jets. Based on this alignment, the ratio of the radio core–luminosity to the optical luminosity, the jet/counter-jet intensity and extension length ratios, and moderate core brightness temperatures (≲10{sup 10} K), we conclude these jets are mildly relativistic (β≲0.3, δ∼1−1.5) and aligned at moderately small angles to the line of sight (10–15°). The derived kinematic ages of ∼10{sup 6}–10{sup 7} yr are much younger than radio galaxies but comparable to other NLS1s. Our results increase the number of radio-loud NLS1s with known kiloparsec-scale extensions from 7 to 10 and suggest that such extended emission may be common, at least among the brightest of these sources.

A multiwavelength view of the galaxy cluster Abell 523 and its peculiar diffuse radio source

Science.gov (United States)

Girardi, M.; Boschin, W.; Gastaldello, F.; Giovannini, G.; Govoni, F.; Murgia, M.; Barrena, R.; Ettori, S.; Trasatti, M.; Vacca, V.

2016-03-01

We study the structure of the galaxy cluster Abell 523 (A523) at z = 0.104 using new spectroscopic data for 132 galaxies acquired at the Telescopio Nazionale Galileo, new photometric data from the Isaac Newton Telescope, and X-ray and radio data from the Chandra and Very Large Array archives. We estimate the velocity dispersion of the galaxy population, σ _V=949_{-60}^{+80} km s-1, and the X-ray temperature of the hot intracluster medium, kT = 5.3 ± 0.3 keV. We infer that A523 is a massive system: M200 ˜ 7-9 × 1014 M⊙. The analysis of the optical data confirms the presence of two subclusters, 0.75 Mpc apart, tracing the SSW-NNE direction and dominated by the two brightest cluster galaxies (BCG1 and BCG2). The X-ray surface brightness is strongly elongated towards the NNE direction, and its peak is clearly offset from both the brightest cluster galaxies (BCGs). We confirm the presence of a 1.3 Mpc large radio halo, elongated in the ESE-WNW direction and perpendicular to the optical/X-ray elongation. We detect a significant radio/X-ray offset and radio polarization, two features which might be the result of a magnetic field energy spread on large spatial scales. A523 is found consistent with most scaling relations followed by clusters hosting radio haloes, but quite peculiar in the Pradio-LX relation: it is underluminous in the X-rays or overluminous in radio. A523 can be described as a binary head-on merger caught after a collision along the SSW-NNE direction. However, minor optical and radio features suggest a more complex cluster structure, with A523 forming at the crossing of two filaments along the SSW-NNE and ESE-WNW directions.

Discovery of GeV emission from the direction of the luminous infrared galaxy NGC 2146

Energy Technology Data Exchange (ETDEWEB)

Tang, Qing-Wen; Wang, Xiang-Yu [School of Astronomy and Space Science, Nanjing University, Nanjing, 210093 (China); Thomas Tam, Pak-Hin, E-mail: xywang@nju.edu.cn, E-mail: phtam@phys.nthu.edu.tw [Institute of Astronomy and Department of Physics, National Tsing Hua University, Hsinchu 30013, Taiwan (China)

2014-10-10

Recent detections of high-energy gamma-ray emission from starburst galaxies M82 and NGC 253 suggest that starburst galaxies are huge reservoirs of cosmic rays and these cosmic rays convert a significant fraction of their energy into gamma-rays by colliding with the dense interstellar medium. In this paper, we report the search for high-energy gamma-ray emission from several nearby star-forming and starburst galaxies using the 68 month data obtained with the Fermi Large Area Telescope. We found a ∼5.5σ detection of gamma-ray emission above 200 MeV from a source spatially coincident with the location of the luminous infrared galaxy NGC 2146. Also taking into account the temporal and spectral properties of the gamma-ray emission, we suggest that the gamma-ray source is likely to be the counterpart of NGC 2146. The gamma-ray luminosity suggests that cosmic rays in NGC 2146 convert most of their energy into secondary pions, so NGC 2146 is a 'proton calorimeter'. It is also found that NGC 2146 obeys the quasi-linear scaling relation between gamma-ray luminosity and total infrared luminosity for star-forming galaxies, strengthening the connection between massive star formation and gamma-ray emission of star-forming galaxies. Possible TeV emission from NGC 2146 is predicted and the implications for high-energy neutrino emission from starburst galaxies are discussed.

Calibrating photometric redshifts of luminous red galaxies

International Nuclear Information System (INIS)

Padmanabhan, Nikhil; Budavari, Tamas; Schlegel, David J.; Bridges, Terry; Brinkmann, Jonathan

2005-01-01

We discuss the construction of a photometric redshift catalogue of luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS), emphasizing the principal steps necessary for constructing such a catalogue: (i) photometrically selecting the sample, (ii) measuring photometric redshifts and their error distributions, and (iii) estimating the true redshift distribution. We compare two photometric redshift algorithms for these data and find that they give comparable results. Calibrating against the SDSS and SDSS–2dF (Two Degree Field) spectroscopic surveys, we find that the photometric redshift accuracy is σ~ 0.03 for redshifts less than 0.55 and worsens at higher redshift (~ 0.06 for z < 0.7). These errors are caused by photometric scatter, as well as systematic errors in the templates, filter curves and photometric zero-points. We also parametrize the photometric redshift error distribution with a sum of Gaussians and use this model to deconvolve the errors from the measured photometric redshift distribution to estimate the true redshift distribution. We pay special attention to the stability of this deconvolution, regularizing the method with a prior on the smoothness of the true redshift distribution. The methods that we develop are applicable to general photometric redshift surveys.

Neutrino Bursts from Fanaroff-Riley I Radio Galaxies

CERN Document Server

Anchordoqui, Luis A.; Halzen, Francis; Weiler, Thomas J.; Anchordoqui, Luis A.; Goldberg, Haim; Halzen, Francis; Weiler, Thomas J.

2004-01-01

On the basis of existing observations (at the 4.5 \\sigma level) of TeV gamma-ray outbursts from the Fanaroff-Riley I (FRI) radio galaxy Centaurus A, we estimate the accompanying neutrino flux in a scenario where both photons and neutrinos emerge from pion decay. We find a neutrino flux on Earth dF_{\

X-ray study of a sample of FR0 radio galaxies: unveiling the nature of the central engine

Science.gov (United States)

Torresi, E.; Grandi, P.; Capetti, A.; Baldi, R. D.; Giovannini, G.

2018-06-01

Fanaroff-Riley type 0 radio galaxies (FR0s) are compact radio sources that represent the bulk of the radio-loud active galactic nuclei (AGN) population, but they are still poorly understood. Pilot studies on these sources have been already performed at radio and optical wavelengths: here we present the first X-ray study of a sample of 19 FR0 radio galaxies selected from the Sloan Digital Sky Survey/NRAO VLA Sky Survey/Faint Images of the Radio Sky at Twenty-cm sample of Best & Heckman, with redshift ≤0.15, radio size ≤10 kpc, and optically classified as low-excitation galaxies. The X-ray spectra are modelled with a power-law component absorbed by Galactic column density with, in some cases, a contribution from thermal extended gas. The X-ray photons are likely produced by the jet as attested by the observed correlation between X-ray (2-10 keV) and radio (5 GHz) luminosities, similar to Fanaroff-Riley type I radio galaxies (FRIs). The estimated Eddington-scaled luminosities indicate a low accretion rate. Overall, we find that the X-ray properties of FR0s are indistinguishable from those of FRIs, thus adding another similarity between AGN associated with compact and extended radio sources. A comparison between FR0s and low-luminosity BL Lacs rules out important beaming effects in the X-ray emission of the compact radio galaxies. FR0s have different X-ray properties with respect to young radio sources (e.g. gigahertz-peaked spectrum/compact steep spectrum sources), generally characterized by higher X-ray luminosities and more complex spectra. In conclusion, the paucity of extended radio emission in FR0s is probably related to the intrinsic properties of their jets that prevent the formation of extended structures, and/or to intermittent activity of their engines.

A combined optical, infrared and radio study of the megamaser galaxy III Zw 35

International Nuclear Information System (INIS)

Chapman, J.M.; Axon, D.J.; Cohen, R.J.; Pedlar, A.; Davies, R.D.; Unger, S.W.

1990-01-01

III Zw 35 is a pair of galaxies characterized by powerful radio continuum, far-infrared and OH maser radiation. We have made a multi-frequency study of the galaxy pair based on optical, infrared and radio observations. The brighter northern component is identified as an early-type LINER or Seyfert galaxy containing an active nuclear region from which radio continuum, OH maser and thermal dust emission are detected. We propose that the northern component has a compact active nucleus deeply embedded in a highly obscured region of diameter ∼ 210 pc, within which enhanced star-formation occurs. The lower luminosity southern component is of low mass and is undergoing starburst activity over an extended region of diameter ∼ 5.5 kpc. The origin of the starburst and non-thermal activity appears to be an interaction between the two components. (author)

The 60 micron to 20 centimeter infrared-to-radio ratio within spiral galaxies

Science.gov (United States)

Bicay, M. D.; Helou, G.

1990-01-01

A detailed comparison is presented of the distribution of 60 micron IR and 20 cm radio continuum emission within 25 galaxies, mostly disk spirals. Local maxima in the thermal IR and nonthermal radio emission are found to be spatially coincident on scales of less than about 0.4 kpc in the nearest sample galaxies. The IR-red disk in normal spirals appears to be characterized by a shorter scale length than that of the radio continuum disk, suggesting that the IR-to-radio ratio should decrease as a function of radius. A model that successfully accounts for the observations is introduced which is based on the assumptions of steady-state star formation activity within the disk on kpc scales and a tight coupling between the origins of the dust-heating radiation and the radio-emitting cosmic-ray electrons. The underlying source is described as an exponential disk. The results also suggest that a random walk process cannot by itself describe the temporal evolution of cosmic rays.

Giant Radio Halos in Galaxy Clusters as Probes of Particle ...

Indian Academy of Sciences (India)

scenario still remain poorly understood. ... to test models with future observations. ... A popular scenario for the origin of radio halos assumes that relativis- ..... based on particle acceleration by merger-driven turbulence in galaxy clusters shows.

GALAXY CLUSTER RADIO RELICS IN ADAPTIVE MESH REFINEMENT COSMOLOGICAL SIMULATIONS: RELIC PROPERTIES AND SCALING RELATIONSHIPS

International Nuclear Information System (INIS)

Skillman, Samuel W.; Hallman, Eric J.; Burns, Jack O.; Smith, Britton D.; O'Shea, Brian W.; Turk, Matthew J.

2011-01-01

Cosmological shocks are a critical part of large-scale structure formation, and are responsible for heating the intracluster medium in galaxy clusters. In addition, they are capable of accelerating non-thermal electrons and protons. In this work, we focus on the acceleration of electrons at shock fronts, which is thought to be responsible for radio relics-extended radio features in the vicinity of merging galaxy clusters. By combining high-resolution adaptive mesh refinement/N-body cosmological simulations with an accurate shock-finding algorithm and a model for electron acceleration, we calculate the expected synchrotron emission resulting from cosmological structure formation. We produce synthetic radio maps of a large sample of galaxy clusters and present luminosity functions and scaling relationships. With upcoming long-wavelength radio telescopes, we expect to see an abundance of radio emission associated with merger shocks in the intracluster medium. By producing observationally motivated statistics, we provide predictions that can be compared with observations to further improve our understanding of magnetic fields and electron shock acceleration.

What drives the evolution of Luminous Compact Blue Galaxies in Clusters vs. the Field?

Science.gov (United States)

Wirth, Gregory D.; Bershady, Matthew A.; Crawford, Steven M.; Hunt, Lucas; Pisano, Daniel J.; Randriamampandry, Solohery M.

2018-06-01

Low-mass dwarf ellipticals are the most numerous members of present-day galaxy clusters, but the progenitors of this dominant population remain unclear. A prime candidate is the class of objects known as Luminous Compact Blue Galaxies (LCBGs), common in intermediate-redshift clusters but virtually extinct today. Recent cosmological simulations suggest that present-day dwarf galaxies begin as irregular field galaxies, undergo an environmentally-driven starburst phase as they enter the cluster, and stop forming stars earlier than their counterparts in the field. This model predicts that cluster dwarfs should have lower stellar mass per unit dynamical mass than their counterparts in the field. We are undertaking a two-pronged archival research program to test this key prediction using the combination of precision photometry from space and high-quality spectroscopy. First, we are combining optical HST/ACS imaging of five z=0.55 clusters (including two HST Frontier Fields) with Spitzer IR imaging and publicly-released Keck/DEIMOS spectroscopy to measure stellar-to-dynamical-mass ratios for a large sample of cluster LCBGs. Second, we are exploiting a new catalog of LCBGs in the COSMOS field to gather corresponding data for a significant sample of field LCBGs. By comparing mass ratios from these datasets, we aim to test theoretical predictions and determine the primary physical driver of cluster dwarf-galaxy evolution.

ON THE NATURE OF THE FIRST GALAXIES SELECTED AT 350 μm

International Nuclear Information System (INIS)

Khan, Sophia A.; Chanial, Pierre F.; Clements, David L.; Sumner, Timothy J.; Willner, S. P.; Ashby, M. L. N.; Fazio, G. G.; Huang, J.-S.; Pearson, Chris P.; Benford, Dominic J.; Moseley, S. Harvey; Shafer, Richard A.; Staguhn, Johannes; Dye, Simon; Farrah, Duncan; Lebouteiller, V.; Le Floc'h, Emeric; Mainetti, Gabriele; Negrello, Mattia; Serjeant, Stephen

2009-01-01

We present constraints on the nature of the first galaxies selected at 350 μm. The sample includes galaxies discovered in the deepest blank-field survey at 350 μm (in the Booetes Deep Field) and also later serendipitous detections in the Lockman Hole. In determining multiwavelength identifications, the 350 μm position and map resolution of the second generation Submillimeter High Angular Resolution Camera are critical, especially in the cases where multiple radio sources exist and the 24 μm counterparts are unresolved. Spectral energy distribution templates are fitted to identified counterparts, and the sample is found to comprise IR-luminous galaxies at 1 350 < 40 mJy) place these objects near the Herschel/SPIRE 350 μm confusion threshold, with the lower limit on the star formation rate density suggesting the bulk of the 350 μm contribution will come from less luminous infrared sources and normal galaxies. Therefore, the nature of the dominant source of the 350 μm background-star-forming galaxies in the epoch of peak star formation in the universe-could be more effectively probed using ground-based instruments with their angular resolution and sensitivity offering significant advantages over space-based imaging.

Heavy X-ray obscuration in the most luminous galaxies discovered by WISE

Science.gov (United States)

Vito, F.; Brandt, W. N.; Stern, D.; Assef, R. J.; Chen, C.-T. J.; Brightman, M.; Comastri, A.; Eisenhardt, P.; Garmire, G. P.; Hickox, R.; Lansbury, G.; Tsai, C.-W.; Walton, D. J.; Wu, J. W.

2018-03-01

Hot dust-obscured galaxies (DOGs) are hyperluminous (L8-1000 μm > 1013 L⊙) infrared galaxies with extremely high (up to hundreds of K) dust temperatures. The sources powering both their extremely high luminosities and dust temperatures are thought to be deeply buried and rapidly accreting supermassive black holes (SMBHs). Hot DOGs could therefore represent a key evolutionary phase in which the SMBH growth peaks. X-ray observations can be used to study their obscuration levels and luminosities. In this work, we present the X-ray properties of the 20 most luminous (Lbol ≳ 1014 L⊙) known hot DOGs at z = 2-4.6. Five of them are covered by long-exposure (10-70 ks) Chandra and XMM-Newton observations, with three being X-ray detected, and we study their individual properties. One of these sources (W0116-0505) is a Compton-thick candidate, with column density NH = (1.0-1.5) × 1024 cm-2 derived from X-ray spectral fitting. The remaining 15 hot DOGs have been targeted by a Chandra snapshot (3.1 ks) survey. None of these 15 are individually detected; therefore, we applied a stacking analysis to investigate their average emission. From hardness ratio analysis, we constrained the average obscuring column density and intrinsic luminosity to be log NH (cm-2) > 23.5 and LX ≳ 1044 erg s-1, which are consistent with results for individually detected sources. We also investigated the LX-L6 μm and LX-Lbol relations, finding hints that hot DOGs are typically X-ray weaker than expected, although larger samples of luminous obscured quasi-stellar objects are needed to derive solid conclusions.

Relics in galaxy clusters at high radio frequencies

Science.gov (United States)

Kierdorf, M.; Beck, R.; Hoeft, M.; Klein, U.; van Weeren, R. J.; Forman, W. R.; Jones, C.

2017-04-01

Aims: We investigated the magnetic properties of radio relics located at the peripheries of galaxy clusters at high radio frequencies, where the emission is expected to be free of Faraday depolarization. The degree of polarization is a measure of the magnetic field compression and, hence, the Mach number. Polarization observations can also be used to confirm relic candidates. Methods: We observed three radio relics in galaxy clusters and one radio relic candidate at 4.85 and 8.35 GHz in total emission and linearly polarized emission with the Effelsberg 100-m telescope. In addition, we observed one radio relic candidate in X-rays with the Chandra telescope. We derived maps of polarization angle, polarization degree, and Faraday rotation measures. Results: The radio spectra of the integrated emission below 8.35 GHz can be well fitted by single power laws for all four relics. The flat spectra (spectral indices of 0.9 and 1.0) for the so-called Sausage relic in cluster CIZA J2242+53 and the so-called Toothbrush relic in cluster 1RXS 06+42 indicate that models describing the origin of relics have to include effects beyond the assumptions of diffuse shock acceleration. The spectra of the radio relics in ZwCl 0008+52 and in Abell 1612 are steep, as expected from weak shocks (Mach number ≈2.4). Polarization observations of radio relics offer a method of measuring the strength and geometry of the shock front. We find polarization degrees of more than 50% in the two prominent Mpc-sized radio relics, the Sausage and the Toothbrush, which are among the highest percentages of linear polarization detected in any extragalactic radio source to date. This is remarkable because the large beam size of the Effelsberg single-dish telescope corresponds to linear extensions of about 300 kpc at 8.35 GHz at the distances of the relics. The high degree of polarization indicates that the magnetic field vectors are almost perfectly aligned along the relic structure, as expected for shock

A Massive, Cooling-Flow-Induced Starburst in the Core of a Highly Luminous Galaxy Cluster

Science.gov (United States)

McDonald, M.; Bayliss, M.; Benson, B. A.; Foley, R. J.; Ruel, J.; Sullivan, P.; Veilleux, S.; Aird, K. A.; Ashby, M. L. N.; Bautz, M.;

(WAT) Radio Source Associated with the Galaxy PGC 1519010 NG

Indian Academy of Sciences (India)

2009-03-13

Mar 13, 2009 ... 2Raman Research Institute, Sadashivnagar, Bangalore 560 080, India. ∗ e-mail: ... Radio galaxies—cluster of galaxies—ram pressure—intra- ... In this paper, we report the GMRT detection of a WAT associated with the galaxy.

THE TYPE Ia SUPERNOVA RATE IN RADIO AND INFRARED GALAXIES FROM THE CANADA-FRANCE-HAWAII TELESCOPE SUPERNOVA LEGACY SURVEY

International Nuclear Information System (INIS)

Graham, M. L.; Pritchet, C. J.; Balam, D.; Fabbro, S.; Sullivan, M.; Hook, I. M.; Howell, D. A.; Gwyn, S. D. J.; Astier, P.; Balland, C.; Guy, J.; Hardin, D.; Pain, R.; Regnault, N.; Basa, S.; Carlberg, R. G.; Perrett, K.; Conley, A.; Fouchez, D.; Rich, J.

2010-01-01

We have combined the large SN Ia database of the Canada-France-Hawaii Telescope Supernova Legacy Survey and catalogs of galaxies with photometric redshifts, Very Large Array 1.4 GHz radio sources, and Spitzer infrared sources. We present eight SNe Ia in early-type host galaxies which have counterparts in the radio and infrared source catalogs. We find the SN Ia rate in subsets of radio and infrared early-type galaxies is ∼1-5 times the rate in all early-type galaxies, and that any enhancement is always ∼<2σ. Rates in these subsets are consistent with predictions of the two-component 'A+B' SN Ia rate model. Since infrared properties of radio SN Ia hosts indicate dust-obscured star formation, we incorporate infrared star formation rates into the 'A+B' model. We also show the properties of SNe Ia in radio and infrared galaxies suggest the hosts contain dust and support a continuum of delay time distributions (DTDs) for SNe Ia, although other DTDs cannot be ruled out based on our data.

SPITZER OBSERVATIONS OF PASSIVE AND STAR-FORMING EARLY-TYPE GALAXIES: AN INFRARED COLOR-COLOR SEQUENCE

International Nuclear Information System (INIS)

Temi, Pasquale; Brighenti, Fabrizio; Mathews, William G.

2009-01-01

We describe the infrared properties of a large sample of early-type galaxies, comparing data from the Spitzer archive with Ks-band emission from the Two Micron All Sky Survey. While most representations of this data result in correlations with large scatter, we find a remarkably tight relation among colors formed by ratios of luminosities in Spitzer-Multiband Imaging Photometer bands (24, 70, and 160 μm) and the Ks band. Remarkably, this correlation among E and S0 galaxies follows that of nearby normal galaxies of all morphological types. In particular, the tight infrared color-color correlation for S0 galaxies alone follows that of the entire Hubble sequence of normal galaxies, roughly in order of galaxy type from ellipticals to spirals to irregulars. The specific star formation rate (SFR) of S0 galaxies estimated from the 24 μm luminosity increases with decreasing K-band luminosity (or stellar mass) from essentially zero, as with most massive ellipticals, to rates typical of irregular galaxies. Moreover, the luminosities of the many infrared-luminous S0 galaxies can significantly exceed those of the most luminous (presumably post-merger) E galaxies. SFRs in the most infrared-luminous S0 galaxies approach 1-10 solar masses per year. Consistently, with this picture we find that while most early-type galaxies populate an infrared red sequence, about 24% of the objects (mostly S0s) are in an infrared blue cloud together with late-type galaxies. For those early-type galaxies also observed at radio frequencies, we find that the far-infrared luminosities correlate with the mass of neutral and molecular hydrogen, but the scatter is large. This scatter suggests that the star formation may be intermittent or that similar S0 galaxies with cold gaseous disks of nearly equal mass can have varying radial column density distributions that alter the local and global SFRs.

Ultrahigh-energy Cosmic Rays from Fanaroff Riley class II radio galaxies

Science.gov (United States)

Rachen, Joerg; Biermann, Peter L.

1992-08-01

The hot spots of very powerful radio galaxies (Fanaroff Riley class II) are argued to be the sources of the ultrahigh energy component in Cosmic Rays. We present calculations of Cosmic Ray transport in an evolving universe, taking the losses against the microwave background properly into account. As input we use the models for the cosmological radio source evolution derived by radioastronomers (mainly Peacock 1985). The model we adopt for the acceleration in the radio hot spots has been introduced by Biermann and Strittmatter (1987), and Meisenheimer et al. (1989) and is based on first order Fermi theory of particle acceleration at shocks (see, e.g., Drury 1983). As an unknown the actual proportion of energy density in protons enters, which together with structural uncertainties in the hot spots should introduce no more than one order of magnitude in uncertainty: We easily reproduce the observed spectra of high energy cosmic rays. It follows that scattering of charged energetic particles in intergalactic space must be sufficiently small in order to obtain contributions from sources as far away as even the nearest Fanaroff Riley class II radio galaxies. This implies a strong constraint on the turbulent magnetic field in intergalactic space.

Alma observations of nearby luminous infrared galaxies with various agn energetic contributions using dense gas tracers

Energy Technology Data Exchange (ETDEWEB)

Imanishi, Masatoshi [Subaru Telescope, 650 North A' ohoku Place, Hilo, HI 96720 (United States); Nakanishi, Kouichiro, E-mail: masa.imanishi@nao.ac.jp [National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan)

2014-07-01

We present the results of our ALMA Cycle 0 observations, using HCN/HCO{sup +}/HNC J = 4-3 lines, of six nearby luminous infrared galaxies with various energetic contributions from active galactic nuclei (AGNs) estimated from previous infrared spectroscopy. These lines are very effective for probing the physical properties of high-density molecular gas around the hidden energy sources in the nuclear regions of these galaxies. We find that HCN to HCO{sup +} J = 4-3 flux ratios tend to be higher in AGN-important galaxies than in starburst-dominated regions, as was seen at the J = 1-0 transition, while there is no clear difference in the HCN-to-HNC J = 4-3 flux ratios among observed sources. A galaxy with a starburst-type infrared spectral shape and very large molecular line widths shows a high HCN-to-HCO{sup +} J = 4-3 flux ratio, which could be due to turbulence-induced heating. We propose that enhanced HCN J = 4-3 emission relative to HCO{sup +} J = 4-3 could be used to detect more energetic activity than normal starbursts, including deeply buried AGNs, in dusty galaxy populations.

PREDICTIONS FOR ULTRA-DEEP RADIO COUNTS OF STAR-FORMING GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Mancuso, Claudia; Lapi, Andrea; De Zotti, Gianfranco; Bressan, Alessandro; Perrotta, Francesca; Danese, Luigi [Astrophysics Sector, SISSA, Via Bonomea 265, I-34136 Trieste (Italy); Cai, Zhen-Yi [CAS Key Laboratory for Research in Galaxies and Cosmology, Department of Astronomy, University of Science and Technology of China, Hefei, Anhui 230026 (China); Negrello, Mattia; Bonato, Matteo, E-mail: cmancuso@sissa.it [INAF—Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, I-35122 Padova (Italy)

2015-09-01

We have worked outty predictions for the radio counts of star-forming galaxies down to nJy levels, along with redshift distributions down to the detection limits of the phase 1 Square Kilometer Array MID telescope (SKA1-MID) and of its precursors. Such predictions were obtained by coupling epoch-dependent star formation rate (SFR) functions with relations between SFR and radio (synchrotron and free–free) emission. The SFR functions were derived taking into account both the dust-obscured and the unobscured star formation, by combining far-infrared, ultraviolet, and Hα luminosity functions up to high redshifts. We have also revisited the South Pole Telescope counts of dusty galaxies at 95 GHz, performing a detailed analysis of the Spectral Energy Distributions. Our results show that the deepest SKA1-MID surveys will detect high-z galaxies with SFRs two orders of magnitude lower compared to Herschel surveys. The highest redshift tails of the distributions at the detection limits of planned SKA1-MID surveys comprise a substantial fraction of strongly lensed galaxies. We predict that a survey down to 0.25 μJy at 1.4 GHz will detect about 1200 strongly lensed galaxies per square degree, at redshifts of up to 10. For about 30% of them the SKA1-MID will detect at least 2 images. The SKA1-MID will thus provide a comprehensive view of the star formation history throughout the re-ionization epoch, unaffected by dust extinction. We have also provided specific predictions for the EMU/ASKAP and MIGHTEE/MeerKAT surveys.

Star formation in the inner galaxy: a far-infrared and radio study of two H2 regions

International Nuclear Information System (INIS)

Lester, D.F.; Dinerstein, H.L.; Werner, M.W.; Harvey, P.M.; Evans, N.J.II; Brown, R.L.

1985-12-01

Far-infrared and radio continuum maps have been made of the central 6' of the inner-galaxy H II regions G30.8-0.0 (in the W43 complex) and G25.4-02., along with radio and molecular line measurements at selected positions. An effort is made to understand far infrared wavelingths allow the dust temperature structures and total far infrared fluxes to be determined. Comparison of the radio and infrared maps shows a close relationship between the ionized gas and the infrared-emitting material. There is evidence that parts of G30.8 are substantially affected by extinction, even at far-infrared wavelengths. For G25.4-0.2, the radio recombination line and CO line data permit resolution of the distance ambiguity for this source. The confusion in distance determination is found to result from an extraordinary near-superposition of two bright H II regions. Using revised distances of 4.3 kpc for G26.4SE and 12 kpc for G25.4NW, that the latter, which is apparently the fainter of the two sources, is actually the more luminous. Though it is not seen on the Palomar Sky Survey, G25.4SE is easily visible in the 9532A line of S III and is mapped in this line. The ratio of total luminosity to ionizing luminosity is very similar to that of H II regions in the solar circle. Assuming a coeval population of ionizing stars, a normal initial mass function is indicated

Star formation in the inner galaxy: a far-infrared and radio study of two H2 regions

International Nuclear Information System (INIS)

Lester, D.F.; Dinerstein, H.L.; Werner, M.W.; Harvey, P.M.; Evans, N.J.; Brown, R.L.

1985-09-01

Far-infrared and radio continuum maps have been made of the central 6' of the inner-galaxy HII regions G30.8-0.0 (in the W43 complex) and G25.4-0.2, along with radio and molecular line measurements at selected positions. The purpose of this study is an effort to understand star formation in the molecular ring at 5 kpc in galactic radius. Measurements at several far infrared wavelengths allow the dust temperature structures and total far infrared fluxes to be determined. Comparison of the radio and infrared maps shows a close relationship between the ionized gas and the infrared-emitting material. There is evidence that parts of G30.8 are substantially affected by extinction, even at far-infrared wavelengths. Using radio recombination line and CO line data for G25.4-0.2, the distance ambiguity for this source is resolved. The large distance previously ascribed to the entire complex is found to apply to only one of the two main components. The confusion in distance determination is found to result from an extraordinary near-superposition of two bright HII regions. Using the revised distances of 4.3 kpc for G25.4SE and 12 kpc for G25.4NW, it is found that the latter, which is apparently the fainter of the two sources, is actually the more luminous. The ratio of total luminosity to ionizing luminosity is very similar to that of HII regions in the solar circle. Assuming a coeval population of ionizing stars, a normal initial mass function is indicated

On the interaction of the PKS B1358–113 radio galaxy with the A1836 cluster

Energy Technology Data Exchange (ETDEWEB)

Stawarz, Ł.; Simionescu, A.; Hagino, K. [Institute of Space and Astronautical Science, JAXA, 3-1-1 Yoshinodai, Chuo-ku, Sagamihara, Kanagawa 252-5210 (Japan); Szostek, A.; Kozieł-Wierzbowska, D.; Ostrowski, M. [Astronomical Observatory, Jagiellonian University, ulica Orla 171, 30-244 Kraków (Poland); Cheung, C. C. [Space Science Division, Naval Research Laboratory, Washington, DC 20375 (United States); Siemiginowska, A.; Harris, D. E. [Harvard Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Werner, N. [KIPAC, Stanford University, 452 Lomita Mall, Stanford, CA 94305 (United States); Madejski, G. [W. W. Hansen Experimental Physics Laboratory, Kavli Institute for Particle Astrophysics and Cosmology, Department of Physics and SLAC National Accelerator Laboratory, Stanford University, Stanford, CA 94305 (United States); Begelman, M. C., E-mail: stawarz@astro.isas.jaxa.jp [JILA, University of Colorado and National Institute of Standards and Technology, 440 UCB, Boulder, CO 80309-0440 (United States)

2014-10-20

Here we present the analysis of multifrequency data gathered for the Fanaroff-Riley type-II (FR II) radio galaxy PKS B1358-113, hosted in the brightest cluster galaxy in the center of A1836. The galaxy harbors one of the most massive black holes known to date, and our analysis of the acquired optical data reveals that this black hole is only weakly active, with a mass accretion rate M-dot {sub acc}∼2×10{sup −4} M-dot {sub Edd}∼0.02 M{sub ⊙} yr{sup –1}. Based on analysis of new Chandra and XMM-Newton X-ray observations and archival radio data, and assuming the well-established model for the evolution of FR II radio galaxies, we derive the preferred range for the jet kinetic luminosity L {sub j} ∼ (1-6) × 10{sup –3} L {sub Edd} ∼ (0.5-3) × 10{sup 45} erg s{sup –1}. This is above the values implied by various scaling relations proposed for radio sources in galaxy clusters, being instead very close to the maximum jet power allowed for the given accretion rate. We also constrain the radio source lifetime as τ{sub j} ∼ 40-70 Myr, meaning the total amount of deposited jet energy E {sub tot} ∼ (2-8) × 10{sup 60} erg. We argue that approximately half of this energy goes into shock heating of the surrounding thermal gas, and the remaining 50% is deposited into the internal energy of the jet cavity. The detailed analysis of the X-ray data provides indication for the presence of a bow shock driven by the expanding radio lobes into the A1836 cluster environment. We derive the corresponding shock Mach number in the range M{sub sh}∼2--4, which is one of the highest claimed for clusters or groups of galaxies. This, together with the recently growing evidence that powerful FR II radio galaxies may not be uncommon in the centers of clusters at higher redshifts, supports the idea that jet-induced shock heating may indeed play an important role in shaping the properties of clusters, galaxy groups, and galaxies in formation. In this context, we speculate on

LUMINOUS RED GALAXY HALO DENSITY FIELD RECONSTRUCTION AND APPLICATION TO LARGE-SCALE STRUCTURE MEASUREMENTS

International Nuclear Information System (INIS)

Reid, Beth A.; Spergel, David N.; Bode, Paul

2009-01-01

The nontrivial relationship between observations of galaxy positions in redshift space and the underlying matter field complicates our ability to determine the linear theory power spectrum and extract cosmological information from galaxy surveys. The Sloan Digital Sky Survey (SDSS) luminous red galaxy (LRG) catalog has the potential to place powerful constraints on cosmological parameters. LRGs are bright, highly biased tracers of large-scale structure. However, because they are highly biased, the nonlinear contribution of satellite galaxies to the galaxy power spectrum is large and fingers-of-God (FOGs) are significant. The combination of these effects leads to a ∼10% correction in the underlying power spectrum at k = 0.1 h Mpc -1 and ∼40% correction at k = 0.2 h Mpc -1 in the LRG P(k) analysis of Tegmark et al., thereby compromising the cosmological constraints when this potentially large correction is left as a free parameter. We propose an alternative approach to recovering the matter field from galaxy observations. Our approach is to use halos rather than galaxies to trace the underlying mass distribution. We identify FOGs and replace each FOG with a single halo object. This removes the nonlinear contribution of satellite galaxies, the one-halo term. We test our method on a large set of high-fidelity mock SDSS LRG catalogs and find that the power spectrum of the reconstructed halo density field deviates from the underlying matter power spectrum at the ≤1% level for k ≤ 0.1 h Mpc -1 and ≤4% at k = 0.2 h Mpc -1 . The reconstructed halo density field also removes the bias in the measurement of the redshift space distortion parameter β induced by the FOG smearing of the linear redshift space distortions.

VizieR Online Data Catalog: Radio image of Luminous Infrared Galaxies (Vardoulaki+, 2015)

Science.gov (United States)

Vardoulaki, E.; Charmandaris, V.; Murphy, E. J.; Diaz-Santos, T.; Armus, L.; Evans, A.; Mazzarella, J. M.; Privon, G. C.; Stierwalt, S.; Barcos-Munoz, L.

2014-09-01

VLA images at 1.49GHz (name_A2000.fits) and at 8.44GHz (name_X2000.fits). All images are in J2000 coordinates. Some maps contain both interacting galaxies of the system, while others are separated and marked accordingly. (2 data files).

Radio Jets Clearing the Way Through a Galaxy: Watching Feedback in Action in the Seyfert Galaxy IC 5063

Science.gov (United States)

Morganti, R.; Oosterloo, T. A.; Oonk, J. B. R.; Frieswijk, W.; Tadhunter, C. N.

2015-12-01

High-resolution (0.5 arcsec) CO(2-1) observations performed with the Atacama Large Millimetre/submillimetre Array have been used to trace the kinematics of the molecular gas in the Seyfert 2 galaxy{IC 5063}. Although one of the most radio-loud Seyfert galaxy, IC 5063 is a relatively weak radio source (P1.4GHz=3 ×1023 W Hz-1). The data reveal that the kinematics of the gas is very complex. A fast outflow of molecular gas extends along the entire radio jet (˜ 1 kpc), with the highest outflow velocities about 0.5 kpc from the nucleus, at the location of the brighter hot-spot in the W lobe. All the observed characteristics can be described by a scenario of a radio plasma jet expanding into a clumpy medium, interacting directly with the clouds and inflating a cocoon that drives a lateral outflow into the interstellar medium. This suggests that most of the observed cold molecular outflow is due to fast cooling of the gas after the passage of a shock and that it is the end product of the cooling process.

The gaseous haloes of evolving galaxies: a probe using the linear sizes of radio sources

International Nuclear Information System (INIS)

Subramanian, K.; Swarup, G.

1990-01-01

As galaxies form and evolve, their gaseous haloes are expected to undergo corresponding evolution. We examine here whether observations of the linear sizes of radio sources can be used to probe such evolution. For this purpose we first represent the gas density at various stages of galaxy formation and evolution by means of simple model density profiles, and then work out the expected linear sizes (l) of radio sources in these models. (author)

The Infrared-Radio Correlation of Dusty Star Forming Galaxies at High Redshift

Science.gov (United States)

Lower, Sidney; Vieira, Joaquin Daniel; Jarugula, Sreevani

2018-01-01

Far-infrared (FIR) and radio continuum emission in galaxies are related by a common origin: massive stars and the processes triggered during their birth, lifetime, and death. FIR emission is produced by cool dust, heated by the absorption of UV emission from massive stars, which is then re-emitted in the FIR. Thermal free-free radiation emitted from HII regions dominates the spectral energy density (SED) of galaxies at roughly 30 GHz, while non-thermal synchrotron radiation dominates at lower frequencies. At low redshift, the infrared radio correlation (IRC, or qIR) holds as a tight empirical relation for many star forming galaxy types, but until recently, there has not been sensitive enough radio observations to extend this relation to higher redshifts. Many selection biases cloud the results of these analyses, leaving the evolution of the IRC with redshift ambiguous. In this poster, I present CIGALE fitted spectral energy distributions (SEDs) for 24 gravitationally-lensed sources selected in the mm-wave from the South Pole Telescope (SPT) survey. I fit the IRC from infrared and submillimeter fluxes obtained with Herschel, Atacama Pathfinder Experiment (APEX), and SPT and radio fluxes obtained with ATCA at 2.1, 5.5, 9, and 30 GHz. This sample of SPT sources has a spectroscopic redshift range of 2.1poster, I will present the results of this study and compare our results to various results in the literature.

On the origin of the dust lane in the active radio galaxies

International Nuclear Information System (INIS)

Morita, Kazuhiko; Sakashita, Shiro

1979-01-01

A simple explosion model leading to the extragalactic extended radio sources is developed to understand the origin of the dust lane seen in the active radio galaxies. The point explosion in a spheroid with inhomogeneous density distribution is investigated by taking account of the cooling effect induced by radiative energy loss. It is suggested that the morphological relation between the dust lane and double radio sources is well explained on the basis of explosion model. (author)

Tracking Galaxy Evolution Through Low-Frequency Radio Continuum Observations using SKA and Citizen-Science Research using Multi-Wavelength Data

Science.gov (United States)

Hota, Ananda; Konar, C.; Stalin, C. S.; Vaddi, Sravani; Mohanty, Pradeepta K.; Dabhade, Pratik; Dharmik Bhoga, Sai Arun; Rajoria, Megha; Sethi, Sagar

2016-12-01

We present a brief review of progress in the understanding of general spiral and elliptical galaxies, through merger, star formation and AGN activities. With reference to case studies performed with the GMRT, we highlight the unique aspects of studying galaxies in the radio wavelengths where powerful quasars and bright radio galaxies are traditionally the dominating subjects. Though AGN or quasar activity is extremely energetic, it is extremely short-lived. This justify focussing on transitional galaxies to find relic-evidences of the immediate past AGN-feedback which decide the future course of evolution of a galaxy. Relic radio lobes can be best detected in low frequency observations with the GMRT, LOFAR and in future SKA. The age of these relic radio plasma can be as old as a few hundred Myr. There is a huge gap between this and what is found in optical bands. The very first relic-evidences of a past quasar activity (Hanny's Voorwerp) was discovered in 2007 by a Galaxy Zoo citizen-scientist, a school teacher, in the optical bands. This relic is around a few tens of thousand years old. More discoveries needed to match these time-scales with star formation time-scales in AGN host galaxies to better understand black hole galaxy co-evolution process via feedback-driven quenching of star formation. It is now well-accepted that discovery and characterization of such faint fuzzy relic features can be more efficiently done by human eye than a machine. Radio interferometry images are more complicated than optical and need the citizen-scientists to be trained. RAD@home, the only Indian citizen-science research project in astronomy, analysing TIFR GMRT Sky Survey (TGSS) 150 MHz data and observing from the Giant Meterwave Radio Telescope (GMRT), was launched in April 2013. Unique, zero-infrastructure zero-funded design of RAD@home as a collaboratory of 69 trained e-astronomers is briefly described. Some of the new-found objects like episodic radio galaxies, radio-jet and

Associating Fast Radio Bursts with Their Host Galaxies

Science.gov (United States)

Eftekhari, T.; Berger, E.

2017-11-01

The first precise localization of a fast radio burst (FRB) sheds light on the nature of these mysterious bursts and the physical mechanisms that power them. Increasing the sample of FRBs with robust host galaxy associations is the key impetus behind ongoing and upcoming searches and facilities. Here, we quantify the robustness of FRB host galaxy associations as a function of localization area and galaxy apparent magnitude. We also explore the use of FRB dispersion measures to constrain the source redshift, thereby reducing the number of candidate hosts. We use these results to demonstrate that even in the absence of a unique association, a constraint can be placed on the maximum luminosity of a host galaxy as a function of localization and dispersion measure (DM). We find that localizations of ≲ 0.5\\text{'}\\text{'} are required for a chance coincidence probability of ≲ 1 % for dwarf galaxies at z≳ 0.1; if some hosts have luminosities of ˜ {L}\\ast , then localizations of up to ≈ 5\\prime\\prime may suffice at z˜ 0.1. Constraints on the redshift from the DM only marginally improve the association probability unless the DM is low, ≲ 400 pc cm-3. This approach also relies on the determination of galaxy redshifts, which is challenging at z≳ 0.5 if the hosts are dwarf galaxies. Finally, interesting limits on the maximum host luminosity require localizations of ≲ 5\\prime\\prime at z≳ 0.1. Even a few such localizations will explain the nature of FRB progenitors, their possible diversity, and their use as cosmological tools.

LOW-POWER RADIO GALAXIES IN THE DISTANT UNIVERSE: A SEARCH FOR FR I AT 1 < z < 2 IN THE COSMOS FIELD

International Nuclear Information System (INIS)

Chiaberge, Marco; Tremblay, Grant; Macchetto, F. Duccio; Sparks, W. B.; Capetti, Alessandro; Tozzi, Paolo

2009-01-01

We present a search for FR I radio galaxies between 1 < z < 2 in the COSMOS field. In absence of spectroscopic redshift measurements, the selection method is based on multiple steps which make use of both radio and optical constraints. The basic assumptions are that (1) the break in radio power between low-power FR Is and the more powerful FR IIs does not change with redshift, and (2) that the photometric properties of the host galaxies of low-power radio galaxies in the distant universe are similar to those of FR IIs in the same redshift bin, as is the case for nearby radio galaxies. We describe the results of our search, which yields 37 low-power radio galaxy candidates that are possibly FR Is. We show that a large fraction of these low-luminosity radio galaxies display a compact radio morphology that does not correspond to the FR I morphological classification. Furthermore, our objects are apparently associated with galaxies that show clear signs of interactions, at odds with the typical behavior observed in low-z FR I hosts. The compact radio morphology might imply that we are observing intrinsically small and possibly young objects that will eventually evolve into the giant FR Is we observe in the local universe. One of the objects appears as pointlike in Hubble Space Telescope (HST) images. This might belong to a population of FR I-QSOs, which however would represent a tiny minority of the overall population of high-z FR Is. As for the local FR Is, a large fraction of our objects are likely to be associated with groups or clusters, making them 'beacons' for high-redshift clusters of galaxies. Our search for candidate high-z FR Is we present in this paper constitutes a pilot study for objects to be observed with future high-resolution and high-sensitivity instruments such as the EVLA and ALMA in the radio band, HST/WFC3 in the optical and IR, James Webb Space Telescope in the IR, as well as future generation X-ray satellites.

The Gamma-Ray Emitting Radio-Loud Narrow-Line Seyfert 1 Galaxy PKS 2004-447 II. The Radio View

Science.gov (United States)

Schulz, R.; Kreikenbohm, A.; Kadler, M.; Ojha, R.; Ros, E.; Stevens, J.; Edwards, P. G.; Carpenter, B.; Elsaesser, D.; Gehrels, N.;

Interferometric follow-up of WISE hyper-luminous hot, dust-obscured galaxies

Energy Technology Data Exchange (ETDEWEB)

Wu, Jingwen; Wright, Edward L. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095 (United States); Bussmann, R. Shane [Harvard-Smithsonian Center for Astrophysics, 60 Garden St., MS78, Cambridge, MA 02138 (United States); Tsai, Chao-Wei; Eisenhardt, Peter R. M.; Stern, Daniel; Moustakas, Leonidas [Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Dr., Pasadena, CA 91109 (United States); Petric, Andreea [Institute for Astronomy, 2680 Woodlawn Drive, Honolulu, HI 96822-1839 (United States); Blain, Andrew [Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH (United Kingdom); Bridge, Carrie R. [Division of Physics, Math, and Astronomy, California Institute of Technology, Pasadena, CA 91125 (United States); Benford, Dominic J. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Assef, Roberto J. [Núcleo de Astronomía de la Facultad de Ingeniería, Universidad Diego Portales, Av., Santiago, Ejército Libertador 441 (Chile); Gelino, Christopher R., E-mail: jingwen@astro.ucla.edu [Infrared Processing and Analysis Center, California Institute of Technology, Pasadena, CA 91125 (United States)

2014-09-20

The Wide-field Infrared Survey Explorer (WISE) has discovered an extraordinary population of hyper-luminous dusty galaxies that are faint in the two bluer passbands (3.4 μm and 4.6 μm) but are bright in the two redder passbands of WISE (12 μm and 22 μm). We report on initial follow-up observations of three of these hot, dust-obscured galaxies, or Hot DOGs, using the Combined Array for Research in Millimeter-wave Astronomy and the Submillimeter Array interferometer arrays at submillimeter/millimeter wavelengths. We report continuum detections at ∼1.3 mm of two sources (WISE J014946.17+235014.5 and WISE J223810.20+265319.7, hereafter W0149+2350 and W2238+2653, respectively), and upper limits to CO line emission at 3 mm in the observed frame for two sources (W0149+2350 and WISE J181417.29+341224.8, hereafter W1814+3412). The 1.3 mm continuum images have a resolution of 1''-2'' and are consistent with single point sources. We estimate the masses of cold dust are 2.0 × 10{sup 8} M {sub ☉} for W0149+2350 and 3.9 × 10{sup 8} M {sub ☉} for W2238+2653, comparable to cold dust masses of luminous quasars. We obtain 2σ upper limits to the molecular gas masses traced by CO, which are 3.3 × 10{sup 10} M {sub ☉} and 2.3 × 10{sup 10} M {sub ☉} for W0149+2350 and W1814+3412, respectively. We also present high-resolution, near-IR imaging with the WFC3 on the Hubble Space Telescope for W0149+2653 and with NIRC2 on Keck for W2238+2653. The near-IR images show morphological structure dominated by a single, centrally condensed source with effective radius less than 4 kpc. No signs of gravitational lensing are evident.

Suzaku View of the Swift/BAT Active Galactic Nuclei. V. Torus Structure of Two Luminous Radio-Loud Active Galactic Nuclei (3C 206 and PKS 0707-35)

Science.gov (United States)

Tazaki, Fumie; Ueda, Yoshihiro; Terashima, Yuichi; Mushotzky, Richard F.; Tombesi, Francesco

2013-01-01

We present the results from broadband X-ray spectral analysis of 3C 206 and PKS 0707-35 with Suzaku and Swift/BAT, two of the most luminous unobscured and obscured radio-loud active galactic nuclei (AGNs) with hard X-ray luminosities of 10(sup 45.5) erg per second and 10(sup 44.9) erg per second (14-195 keV), respectively. Based on the radio core luminosity, we estimate that the X-ray spectrum of 3C 206 contains a significant (60% in the 14-195 keV band) contribution from the jet, while it is negligible in PKS 0707-35.We can successfully model the spectra with the jet component (for 3C 206), the transmitted emission, and two reflection components from the torus and the accretion disk. The reflection strengths from the torus are found to be R(sub torus)(=Omega/2pi) = 0.29 +/- 0.18 and 0.41 +/- 0.18 for 3C 206 and PKS 0707-35, respectively, which are smaller than those in typical Seyfert galaxies. Utilizing the torus model by Ikeda et al., we quantify the relation between the half-opening angle of a torus (theta(sub oa)) and the equivalent width of an iron-K line. The observed equivalent width of 3C 206, less than 71 eV, constrains the column density in the equatorial plane to N(sup eq)(sub H) lesst han 10(sup 23) per square centimeter, or the half-opening angle to theta(sub oa) greater than 80 deg. if N(sup eq)(sub H) = 10(sup 24) per square centimeter is assumed. That of PKS 0707-35, 72 +/- 36 eV, is consistent with N(sup eq)(sub H) 10(sup 23) per square centimeter. Our results suggest that the tori in luminous radio-loud AGNs are only poorly developed. The trend is similar to that seen in radio-quiet AGNs, implying that the torus structure is not different between AGNs with jets and without jets.

From Radio with Love: An Overview of the Role of Radio Observations in Understanding High-Energy Emission from Active Galaxies

Science.gov (United States)

Ojha, Roopesh

2012-01-01

The gamma-ray satellite Fermi and the ground based TeV facilities MAGIC, VERITAS and HESS have ushered in a new era in the observation of high-energy emission from active galaxies. The energy budgets of these objects have a major contribution from gamma-rays and it is simply not possible to understand their physics without high-energy observations. Though the exact mechanisms for high-energy production in galaxies remains an open question, gamma-rays typically result from interactions between high-energy particles. Via different interactions these same particles can produce radio emission. Thus the non-thermal nature of gamma-ray emission practically guarantees that high-energy emitters are also radio loud. Aside from their obvious role as a component of multiwavelength analysis, radio observations provide two crucial elements essential to understanding the source structure and physical processes of high-energy emitters: very high timing resolution and very high spatial resolution. A brief overview of the unique role played by radio observations in unraveling the mysteries of the high energy Universe as presented here.

Extreme Gaseous Outflows in Radio-Loud Narrow-Line Seyfert 1 Galaxies

Science.gov (United States)

Komossa, S.; Xu, D. W.; Wagner, A. Y.

2018-04-01

We present four radio-loud NLS1 galaxies with extreme emission-line shifts, indicating radial outflow velocities of the ionized gas of up to 2450 km/s, above the escape velocity of the host galaxies. The forbidden lines show strong broadening, up to 2270 km/s. An ionization stratification (higher line shift at higher ionization potential) implies that we see a large-scale outflow rather than single, localized jet-cloud interactions. Similarly, the paucity of zero-velocity [OIII]λ5007 emitting gas implies the absence of a second narrow-line region (NLR) component at rest, and therefore a large part of the high-ionization NLR is affected by the outflow. Given the radio loudness of these NLS1 galaxies, the observations are consistent with a pole on view onto their central engines, so that the effects of polar outflows are maximized. In addition, a very efficient driving mechanism is required, to reach the high observed velocities. We explore implications from recent hydrodynamic simulations of the interaction between fast winds or jets with the large-scale NLR. Overall, the best agreement with observations (and especially the high outflow speeds of the [NeV] emitting gas) can be reached if the NLS1 galaxies are relatively young sources with lifetimes not much exceeding 1 Myr. These systems represent sites of strong feedback at NLR scales at work, well below redshift one.

Close entrainment of massive molecular gas flows by radio bubbles in the central galaxy of Abell 1795

Science.gov (United States)

Russell, H. R.; McNamara, B. R.; Fabian, A. C.; Nulsen, P. E. J.; Combes, F.; Edge, A. C.; Hogan, M. T.; McDonald, M.; Salomé, P.; Tremblay, G.; Vantyghem, A. N.

2017-12-01

We present new ALMA observations tracing the morphology and velocity structure of the molecular gas in the central galaxy of the cluster Abell 1795. The molecular gas lies in two filaments that extend 5-7 kpc to the N and S from the nucleus and project exclusively around the outer edges of two inner radio bubbles. Radio jets launched by the central active galactic nucleus have inflated bubbles filled with relativistic plasma into the hot atmosphere surrounding the central galaxy. The N filament has a smoothly increasing velocity gradient along its length from the central galaxy's systemic velocity at the nucleus to -370 km s^{-1}, the average velocity of the surrounding galaxies, at the furthest extent. The S filament has a similarly smooth but shallower velocity gradient and appears to have partially collapsed in a burst of star formation. The close spatial association with the radio lobes, together with the ordered velocity gradients and narrow velocity dispersions, shows that the molecular filaments are gas flows entrained by the expanding radio bubbles. Assuming a Galactic XCO factor, the total molecular gas mass is 3.2 ± 0.2 × 109 M⊙. More than half lies above the N radio bubble. Lifting the molecular clouds appears to require an infeasibly efficient coupling between the molecular gas and the radio bubble. The energy required also exceeds the mechanical power of the N radio bubble by a factor of 2. Stimulated feedback, where the radio bubbles lift low-entropy X-ray gas that becomes thermally unstable and rapidly cools in situ, provides a plausible model. Multiple generations of radio bubbles are required to lift this substantial gas mass. The close morphological association then indicates that the cold gas either moulds the newly expanding bubbles or is itself pushed aside and shaped as they inflate.

A redshift survey of very faint (B <= 22.5) field galaxies, radio sources, and quasars

International Nuclear Information System (INIS)

Koo, D.C.

1983-01-01

As part of a three year program to study the evolution of quasars, radio sources and galaxies, a 10 night redshift survey has been carried out. A few preliminary results are presented (a magnitude-redshift plot of 54 galaxies). (Auth.)

Radio Observations of Ultra-Luminous X-Ray Sources and their Implication for Models

Science.gov (United States)

Koerding, E. G.; Colbert, E. J. M.; Falcke, H.

2004-05-01

We present the results of a radio monitoring campaign to search for radio emission from nearby ultra-luminous X-ray sources (ULXs). These intriguing sources are bright off-nuclear X-ray point sources with luminosities exceeding LX > 1039 erg/sec. Assuming isotropic emission the Eddington Limit suggests that they harbor intermediate mass black holes. Due to the problems of this explanation also other possibilities are currently discussed, among them are anisotropic emission, super-Eddington accretion flows or relativistically beamed emission from microquasars. Detections of compact radio cores at the positions of ULXs would be a direct hint to jet-emission. However, as the ULX phenomenom is connected to star formation we have to assume that they are strongly accreting objects. Thus, similar to their nearest Galactic cousins, the very high state X-ray binaries (see e.g., GRS 1915), ULXs may show radio flares. A well-defined sample of the 9 nearest ULXs has been monitored eight times during 5 months with the Very Large Array in A and B configuration. Our limiting sensitivity is 0.15 mJy (4 σ ) for flares and 68 μ Jy for continuous emission. In M82 some ULXs seem to be connected to radio supernova remnants. Besides that no flare or continuous emission has been detected. As the timescales of radio flares in ULXs are highly uncertain, it could well be that we have undersampled the lightcurve. However, upper bounds for the probability to detect a flare can be given. The upper limits for the continuous emission are compared with the emission found in NGC 5408 X-1 and with quasars and microquasars. We show that these limits are well in agreement with the microblazar model using the Radio/X-ray correlation of XRBs and AGN. Thus, it could well be that ULXs are microblazers which may be radio loud.

RADIO AND MID-INFRARED PROPERTIES OF COMPACT STARBURSTS: DISTANCING THEMSELVES FROM THE MAIN SEQUENCE

Energy Technology Data Exchange (ETDEWEB)

Murphy, E. J. [Observatories of the Carnegie Institution for Science, 813 Santa Barbara Street, Pasadena, CA 91101 (United States); Stierwalt, S.; Armus, L. [Spitzer Science Center, California Institute of Technology, MC 314-6, Pasadena, CA 91125 (United States); Condon, J. J. [National Radio Astronomy Observatory, 520 Edgemont Road, Charlottesville, VA 22903 (United States); Evans, A. S., E-mail: emurphy@obs.carnegiescience.edu [Department of Astronomy, University of Virginia, 530 McCormick Road, Charlottesville, VA 22904 (United States)

2013-05-01

We investigate the relationship between 8.44 GHz brightness temperatures and 1.4 to 8.44 GHz radio spectral indices with 6.2 {mu}m polycyclic aromatic hydrocarbon (PAH) emission and 9.7 {mu}m silicate absorption features for a sample of 36 local luminous and ultraluminous infrared galaxies. We find that galaxies having small 6.2 {mu}m PAH equivalent widths (EQWs), which signal the presence of weak PAH emission and/or an excess of very hot dust, also have flat spectral indices. The three active galactic nuclei (AGN) identified through their excessively large 8.44 GHz brightness temperatures are also identified as AGN via their small 6.2 {mu}m PAH EQWs. We also find that the flattening of the radio spectrum increases with increasing silicate optical depth, 8.44 GHz brightness temperature, and decreasing size of the radio source even after removing potential AGN, supporting the idea that compact starbursts show spectral flattening as the result of increased free-free absorption. These correlations additionally suggest that the dust obscuration in these galaxies must largely be coming from the vicinity of the compact starburst itself, and is not distributed throughout the (foreground) disk of the galaxy. Finally, we investigate the location of these infrared-bright systems relative to the main sequence (star formation rate versus stellar mass) of star-forming galaxies in the local universe. We find that the radio spectral indices of galaxies flatten with increasing distance above the main sequence, or in other words, with increasing specific star formation rate. This indicates that galaxies located above the main sequence, having high specific star formation rates, are typically compact starbursts hosting deeply embedded star formation that becomes more optically thick in the radio and infrared with increased distance above the main sequence.

A Hidden Radio Halo in the Galaxy Cluster A 1682? T. Venturi1 ...

Indian Academy of Sciences (India)

Abstract. High sensitivity observations of radio halos in galaxy clus- ters at frequencies ν ≤ 330 MHz are still relatively rare, and very little is known compared to the classical 1.4 GHz images. The few radio halos imaged down to 150–240 MHz show a considerable spread in size, mor- phology and spectral properties.

ROTATION MEASURES ACROSS PARSEC-SCALE JETS OF FANAROFF-RILEY TYPE I RADIO GALAXIES

International Nuclear Information System (INIS)

Kharb, P.; Gabuzda, D. C.; O'Dea, C. P.; Shastri, P.; Baum, S. A.

2009-01-01

We present the results of a parsec-scale polarization study of three FRI radio galaxies-3C66B, 3C78, and 3C264-obtained with Very Long Baseline Interferometry at 5, 8, and 15 GHz. Parsec-scale polarization has been detected in a large number of beamed radio-loud active galactic nuclei, but in only a handful of the relatively unbeamed radio galaxies. We report here the detection of parsec-scale polarization at one or more frequencies in all three FRI galaxies studied. We detect Faraday rotation measures (RMs) of the order of a few hundred rad m -2 in the nuclear jet regions of 3C78 and 3C264. In 3C66B, polarization was detected at 8 GHz only. A transverse RM gradient is observed across the jet of 3C78. The inner-jet magnetic field, corrected for Faraday rotation, is found to be aligned along the jet in both 3C78 and 3C264, although the field becomes orthogonal further from the core in 3C78. The RM values in 3C78 and 3C264 are similar to those previously observed in nearby radio galaxies. The transverse RM gradient in 3C78, the increase in the degree of polarization at the jet edge, the large rotation in the polarization angles due to Faraday rotation, and the low depolarization between frequencies suggest that a layer surrounding the jet with a sufficient number of thermal electrons and threaded by a toroidal or helical magnetic field is a good candidate for the Faraday rotating medium. This suggestion is tentatively supported by Hubble Space Telescope optical polarimetry but needs to be examined in a greater number of sources.

Stellar Photometric Structures of the Host Galaxies of Nearby Type 1 Active Galactic Nuclei

Energy Technology Data Exchange (ETDEWEB)

Kim, Minjin [Korea Astronomy and Space Science Institute, Daejeon 305-348 (Korea, Republic of); Ho, Luis C. [Kavli Institute for Astronomy and Astrophysics, Peking University, Beijing 100871 (China); Peng, Chien Y. [Giant Magellan Telescope Corporation, 251 S. Lake Ave., Suite 300, Pasadena, CA 91101 (United States); Barth, Aaron J. [Department of Physics and Astronomy, University of California at Irvine, 4129 Frederick Reines Hall, Irvine, CA 92697-4575 (United States); Im, Myungshin, E-mail: mkim@kasi.re.kr, E-mail: lho.pku@gmail.com, E-mail: peng@gmto.org, E-mail: barth@uci.edu, E-mail: mim@astro.snu.ac.kr [Department of Physics and Astronomy, Frontier Physics Research Division (FPRD), Seoul National University, Seoul (Korea, Republic of)

2017-10-01

We present detailed image analysis of rest-frame optical images of 235 low-redshift ( z ≲ 0.35) Type 1 active galactic nuclei (AGNs) observed with the Hubble Space Telescope . The high-resolution images enable us to perform rigorous two-dimensional image modeling to decouple the luminous central point source from the host galaxy, which, when warranted, is further decomposed into its principal structural components (bulge, bar, and disk). In many cases, care must be taken to account for structural complexities such as spiral arms, tidal features, and overlapping or interacting companion galaxies. We employ Fourier modes to characterize the degree of asymmetry of the light distribution of the stars as a quantitative measure of morphological distortion due to interactions or mergers. We examine the dependence of the physical parameters of the host galaxies on the properties of the AGNs, namely, radio-loudness and the width of the broad emission lines. In accordance with previous studies, narrow-line (H β FWHM ≤ 2000 km s{sup −1}) Type 1 AGNs, in contrast to their broad-line (H β FWHM > 2000 km s{sup −1}) counterparts, are preferentially hosted in later-type, lower-luminosity galaxies, which have a higher incidence of pseudo-bulges, are more frequently barred, and are less morphologically disturbed. This suggests that narrow-line Type 1 AGNs experienced a more quiescent evolutionary history driven primarily by internal secular evolution instead of external dynamical perturbations. The fraction of AGN hosts showing merger signatures is larger for more luminous sources. Radio-loud AGNs generally preferentially live in earlier-type (bulge-dominated), more massive hosts, although a minority of them appear to contain a significant disk component. We do not find convincing evidence for enhanced merger signatures in the radio-loud population.

POST-STARBURST TIDAL TAILS IN THE ARCHETYPICAL ULTRA LUMINOUS INFRARED GALAXY Arp 220

International Nuclear Information System (INIS)

Taniguchi, Y.; Matsubayashi, K.; Kajisawa, M.; Shioya, Y.; Ideue, Y.; Ohyama, Y.; Nagao, T.; Murayama, T.; Koda, J.

2012-01-01

We present our new deep optical imaging and long-slit spectroscopy for Arp 220, the archetypical ultra luminous infrared galaxy in the local universe. Our sensitive Hα imaging has newly revealed large-scale Hα absorption, i.e., post-starburst regions in this merger. One is found in the eastern superbubble and the other is in the two tidal tails that are clearly revealed in our deep optical imaging. The size of the Hα absorption region in the eastern bubble is 5 kpc × 7.5 kpc, and the observed Hα equivalent widths are ∼2 Å ± 0.2 Å. The sizes of the northern and southern Hα-absorption tidal tails are ∼5 kpc × 10 kpc and ∼6 kpc × 20 kpc, respectively. The observed Hα equivalent widths range from 4 Å to 7 Å. In order to explain the presence of the two post-starburst tails, we suggest a possible multiple-merger scenario for Arp 220 in which two post-starburst disk-like structures merged into one, causing the two tails. This favors Arp 220 as a multiple merging system composed of four or more galaxies arising from a compact group of galaxies. Taking our new results into account, we discuss a star formation history in the last 1 Gyr in Arp 220.

Polarimetry and Unification of Low-Redshift Radio Galaxies

International Nuclear Information System (INIS)

Cohen, Marshall H.; Ogle, Patrick M.; Tran, Hien D.; Goodrich, Robert W.; Miller, Joseph S.

1999-01-01

We have made high-quality measurements of the polarization spectra of 13 FR II radio galaxies and taken polarization images for 11 of these with the Keck telescopes. Seven of the eight narrow-line radio galaxies (NLRGs) are polarized, and six of the seven show prominent broad Balmer lines in polarized light. The broad lines are also weakly visible in total flux. Some of the NLRGs show bipolar regions with roughly circumferential polarization vectors, revealing a large reflection nebula illuminated by a central source. Our observations powerfully support the hidden quasar hypothesis for some NLRGs. According to this hypothesis, the continuum and broad lines are blocked by a dusty molecular torus, but can be seen by reflected, hence polarized, light. Classification as a NLRG, a broad-line radio galaxy (BLRG), or a quasar therefore depends on orientation. However, not all objects fit into this unification scheme. Our sample is biased toward objects known in advance to be polarized, but the combination of our results with the 1996 findings of Hill, Goodrich, and DePoy show that at least six out of a complete, volume and flux-limited sample of nine FR II NLRGs have broad lines, seen either in polarization or Pα.The BLRGs in our sample range from 3C 382, which has a quasar-like spectrum, to the highly reddened IRAS source FSC 2217+259. This reddening sequence suggests a continuous transition from unobscured quasar to reddened BLRG to NLRG. Apparently the obscuring torus does not have a distinct edge. The BLRGs have polarization images that are consistent with a point source broadened by seeing and diluted by starlight. We do not detect extended nebular or scattered emission, perhaps because it is swamped by the nuclear source. Our starlight-corrected BLRG spectra can be explained with a two-component model: a quasar viewed through dust and quasar light scattered by dust. The direct flux is more reddened than the scattered flux, causing the polarization to rise steeply

Polarimetry and Unification of Low-Redshift Radio Galaxies

Energy Technology Data Exchange (ETDEWEB)

Cohen, Marshall H.; Ogle, Patrick M.; Tran, Hien D.; Goodrich, Robert W.; Miller, Joseph S.

1999-11-01

We have made high-quality measurements of the polarization spectra of 13 FR II radio galaxies and taken polarization images for 11 of these with the Keck telescopes. Seven of the eight narrow-line radio galaxies (NLRGs) are polarized, and six of the seven show prominent broad Balmer lines in polarized light. The broad lines are also weakly visible in total flux. Some of the NLRGs show bipolar regions with roughly circumferential polarization vectors, revealing a large reflection nebula illuminated by a central source. Our observations powerfully support the hidden quasar hypothesis for some NLRGs. According to this hypothesis, the continuum and broad lines are blocked by a dusty molecular torus, but can be seen by reflected, hence polarized, light. Classification as a NLRG, a broad-line radio galaxy (BLRG), or a quasar therefore depends on orientation. However, not all objects fit into this unification scheme. Our sample is biased toward objects known in advance to be polarized, but the combination of our results with the 1996 findings of Hill, Goodrich, and DePoy show that at least six out of a complete, volume and flux-limited sample of nine FR II NLRGs have broad lines, seen either in polarization or P{alpha}.The BLRGs in our sample range from 3C 382, which has a quasar-like spectrum, to the highly reddened IRAS source FSC 2217+259. This reddening sequence suggests a continuous transition from unobscured quasar to reddened BLRG to NLRG. Apparently the obscuring torus does not have a distinct edge. The BLRGs have polarization images that are consistent with a point source broadened by seeing and diluted by starlight. We do not detect extended nebular or scattered emission, perhaps because it is swamped by the nuclear source. Our starlight-corrected BLRG spectra can be explained with a two-component model: a quasar viewed through dust and quasar light scattered by dust. The direct flux is more reddened than the scattered flux, causing the polarization to rise

Metal enriched gaseous halos around distant radio galaxies: Clues to feedback in galaxy formation

Energy Technology Data Exchange (ETDEWEB)

Reuland, M; van Breugel, W; de Vries, W; Dopita, A; Dey, A; Miley, G; Rottgering, H; Venemans, B; Stanford, S A; Lacy, M; Spinrad, H; Dawson, S; Stern, D; Bunker, A

2006-08-01

We present the results of an optical and near-IR spectroscopic study of giant nebular emission line halos associated with three z > 3 radio galaxies, 4C 41.17, 4C 60.07 and B2 0902+34. Previous deep narrow band Ly{alpha} imaging had revealed complex morphologies with sizes up to 100 kpc, possibly connected to outflows and AGN feedback from the central regions. The outer regions of these halos show quiet kinematics with typical velocity dispersions of a few hundred km s{sup -1}, and velocity shears that can mostly be interpreted as being due to rotation. The inner regions show shocked cocoons of gas closely associated with the radio lobes. These display disturbed kinematics and have expansion velocities and/or velocity dispersions >1000 km s{sup -1}. The core region is chemically evolved, and we also find spectroscopic evidence for the ejection of enriched material in 4C 41.17 up to a distance of {approx} 60 kpc along the radio-axis. The dynamical structures traced in the Ly{alpha} line are, in most cases, closely echoed in the Carbon and Oxygen lines. This shows that the Ly{alpha} line is produced in a highly clumped medium of small filling factor, and can therefore be used as a tracer of the dynamics of HzRGs. We conclude that these HzRGs are undergoing a final jet-induced phase of star formation with ejection of most of their interstellar medium before becoming 'red and dead' Elliptical galaxies.

The Host Galaxy and Redshift of the Repeating Fast Radio Burst FRB 121102

International Nuclear Information System (INIS)

Tendulkar, S. P.; Kaspi, V. M.; Bassa, C. G.; Adams, E. A. K.; Hessels, J. W. T.; Maddox, N.; Cordes, J. M.; Chatterjee, S.; Bower, G. C.; Law, C. J.; Bogdanov, S.; Burke-Spolaor, S.; Butler, B. J.; Demorest, P.; Lazio, T. J. W.; Marcote, B.; Paragi, Z.; McLaughlin, M. A.; Ransom, S. M.; Scholz, P.

2017-01-01

The precise localization of the repeating fast radio burst (FRB 121102) has provided the first unambiguous association (chance coincidence probability p ≲ 3 × 10"−"4) of an FRB with an optical and persistent radio counterpart. We report on optical imaging and spectroscopy of the counterpart and find that it is an extended (0.″6–0.″8) object displaying prominent Balmer and [O iii] emission lines. Based on the spectrum and emission line ratios, we classify the counterpart as a low-metallicity, star-forming, m_r_′ = 25.1 AB mag dwarf galaxy at a redshift of z = 0.19273(8), corresponding to a luminosity distance of 972 Mpc. From the angular size, the redshift, and luminosity, we estimate the host galaxy to have a diameter ≲4 kpc and a stellar mass of M _* ∼ (4–7) × 10"7 M _⊙, assuming a mass-to-light ratio between 2 to 3 M _⊙ L _⊙ "−"1. Based on the H α flux, we estimate the star formation rate of the host to be 0.4 M _⊙ yr"−"1 and a substantial host dispersion measure (DM) depth ≲324 pc cm"−"3. The net DM contribution of the host galaxy to FRB 121102 is likely to be lower than this value depending on geometrical factors. We show that the persistent radio source at FRB 121102’s location reported by Marcote et al. is offset from the galaxy’s center of light by ∼200 mas and the host galaxy does not show optical signatures for AGN activity. If FRB 121102 is typical of the wider FRB population and if future interferometric localizations preferentially find them in dwarf galaxies with low metallicities and prominent emission lines, they would share such a preference with long gamma-ray bursts and superluminous supernovae.

VizieR Online Data Catalog: Radio haloes in nearby galaxies (Heesen+, 2018)

Science.gov (United States)

Heesen, V.; Krause, M.; Beck, R.; Adebahr, B.; Bomans, D. J.; Carretti, E.; Dumke, M.; Heald, G.; Irwin, J.; Koribalski, B. S.; Mulcahy, D. D.; Westmeier, T.; Dettmar, R.-J.

2018-02-01

We present radio continuum observations of 12 nearby (D=2-27Mpc) edge-on galaxies at two different frequencies, namely at 1.4 and 5GHz (one galaxy at 8.5GHz instead of 5GHz). Our sample includes 11 late-type spiral (Sb or Sc) galaxies and one Magellanic-type barred galaxy (SBm), which are all highly inclined (i>=76°). As part of our study we have obtained several additional radio continuum maps. We make these maps publicly available (as well as all the other radio continuum maps in the paper). For 4 galaxies (NGC 55, 253, 891 and 4631) we have used single-dish maps, to correct for the missing zero-spacing flux where necessary. The Effelsberg maps of NGC 253 and 4631 were already presented in Heesen et al. (2009A&A...494..563H) and Mora & Krause (2013A&A...560A..42M), respectively, and the Effelsberg map of NGC 891 was already presented in Dumke (1997, PhD thesis, University of Bonn). We present these maps for completeness. The 4.80-GHz map of NGC 55 obtained with the 64-m Parkes telescope is so far unpublished. Furthermore, we show two maps of NGC 4631 at 1.35 and 1.65GHz observed with the VLA in D- configuration (R. Beck 2016, priv. comm.). The data were observed in August 1996, with 12 h on-source (ID: AG486) and reduced in standard fashion with AIPS. The maps have an angular resolution of 52 arcsec, so that we did not use them in the analysis, but they also show the halo of this galaxy very well. Lastly, we obtained maps of three further edge-on galaxies observed with the VLA (NGC 4157, 4217 and 4634). We reduced the data as described in Section 2, but since we had only one frequency available and no spectral index map, we did not use them in the analysis. The maps of NGC 4157 and 4217 were created by re-reducing archive data (IDs AI23, AF85, AH457 and AS392 for NGC 4157 and ID AM573 for NGC 4217). The map of NGC 4634 was created by using so far unpublished data from the VLA (ID: AD538). (3 data files).

ON THE ORIGIN OF FANAROFF-RILEY CLASSIFICATION OF RADIO GALAXIES: DECELERATION OF SUPERSONIC RADIO LOBES

International Nuclear Information System (INIS)

Kawakatu, Nozomu; Kino, Motoki; Nagai, Hiroshi

2009-01-01

We argue that the origin of 'FRI/FRII dichotomy' - the division between Fanaroff-Riley class I (FRI) with subsonic lobes and class II (FRII) radio sources with supersonic lobes is sharp in the radio-optical luminosity plane (Owen-White diagram) - can be explained by the deceleration of advancing radio lobes. The deceleration is caused by the growth of the effective cross-sectional area of radio lobes. We derive the condition in which an initially supersonic lobe turns into a subsonic lobe, combining the ram pressure equilibrium between the hot spots and the ambient medium with the relation between 'the hot spot radius' and 'the linear size of radio sources' obtained from the radio observations. We find that the dividing line between the supersonic lobes and subsonic ones is determined by the ratio of the jet power L j to the number density of the ambient matter at the core radius of the host galaxy n-bar a . It is also found that the maximal ratio of (L j ,n-bar a ) exists and its value resides in (L j ,n-bar a ) max ∼10 44-47 er s -1 cm 3 , taking into account considerable uncertainties. This suggests that the maximal value (L j ,n-bar a ) max separates between FRIs and FRIIs.

Superwind Outflows in Seyfert Galaxies? : Large-Scale Radio Maps of an Edge-On Sample

Science.gov (United States)

Colbert, E.; Gallimore, J.; Baum, S.; O'Dea, C.

1995-03-01

Large-scale galactic winds (superwinds) are commonly found flowing out of the nuclear region of ultraluminous infrared and powerful starburst galaxies. Stellar winds and supernovae from the nuclear starburst provide the energy to drive these superwinds. The outflowing gas escapes along the rotation axis, sweeping up and shock-heating clouds in the halo, which produces optical line emission, radio synchrotron emission, and X-rays. These features can most easily be studied in edge-on systems, so that the wind emission is not confused by that from the disk. We have begun a systematic search for superwind outflows in Seyfert galaxies. In an earlier optical emission-line survey, we found extended minor axis emission and/or double-peaked emission line profiles in >~30% of the sample objects. We present here large-scale (6cm VLA C-config) radio maps of 11 edge-on Seyfert galaxies, selected (without bias) from a distance-limited sample of 23 edge-on Seyferts. These data have been used to estimate the frequency of occurrence of superwinds. Preliminary results indicate that four (36%) of the 11 objects observed and six (26%) of the 23 objects in the distance-limited sample have extended radio emission oriented perpendicular to the galaxy disk. This emission may be produced by a galactic wind blowing out of the disk. Two (NGC 2992 and NGC 5506) of the nine objects for which we have both radio and optical data show good evidence for a galactic wind in both datasets. We suggest that galactic winds occur in >~30% of all Seyferts. A goal of this work is to find a diagnostic that can be used to distinguish between large-scale outflows that are driven by starbursts and those that are driven by an AGN. The presence of starburst-driven superwinds in Seyferts, if established, would have important implications for the connection between starburst galaxies and AGN.

Radio synchrotron spectra of star-forming galaxies

Science.gov (United States)

Klein, U.; Lisenfeld, U.; Verley, S.

2018-03-01

We investigated the radio continuum spectra of 14 star-forming galaxies by fitting nonthermal (synchrotron) and thermal (free-free) radiation laws. The underlying radio continuum measurements cover a frequency range of 325 MHz to 24.5 GHz (32 GHz in case of M 82). It turns out that most of these synchrotron spectra are not simple power-laws, but are best represented by a low-frequency spectrum with a mean slope αnth = 0.59 ± 0.20 (Sν ∝ ν-α), and by a break or an exponential decline in the frequency range of 1-12 GHz. Simple power-laws or mildly curved synchrotron spectra lead to unrealistically low thermal flux densities, and/or to strong deviations from the expected optically thin free-free spectra with slope αth = 0.10 in the fits. The break or cutoff energies are in the range of 1.5-7 GeV. We briefly discuss the possible origin of such a cutoff or break. If the low-frequency spectra obtained here reflect the injection spectrum of cosmic-ray electrons, they comply with the mean spectral index of Galactic supernova remnants. A comparison of the fitted thermal flux densities with the (foreground-corrected) Hα fluxes yields the extinction, which increases with metallicity. The fraction of thermal emission is higher than believed hitherto, especially at high frequencies, and is highest in the dwarf galaxies of our sample, which we interpret in terms of a lack of containment in these low-mass systems, or a time effect caused by a very young starburst.

Broad Paschen-alpha emission in two extremely infrared luminous Seyfert 2 galaxies

International Nuclear Information System (INIS)

Hines, D.C.

1991-01-01

The Paschen-alpha emission line in the extremely luminous IRAS-selected galaxies IRAS 20460 + 1925 and IRAS 23060 + 0505 is observed. The observed width of H-α of Pa-α in IRAS 20460 + 1925 is 3300 km/s, with a possible broader component of about 3860 km/s, while the observed width of H-α of Pa-α in IRAS 23060 + 0505 is 3270 km/s, with a possible broader component of about 4780 km/s. Considering these results as well as their bolometric luminosities, IRAS 20460 + 1925 and IRAS 23060 + 0505 are proposed to be classified as QSO's. It is suggested that there is a population of obscured QSO's, and that they can be selected by their warmth infrared energy distributions and QSO-like luminosities. 17 refs

CHANG-ES. IX. Radio scale heights and scale lengths of a consistent sample of 13 spiral galaxies seen edge-on and their correlations

Science.gov (United States)

Krause, Marita; Irwin, Judith; Wiegert, Theresa; Miskolczi, Arpad; Damas-Segovia, Ancor; Beck, Rainer; Li, Jiang-Tao; Heald, George; Müller, Peter; Stein, Yelena; Rand, Richard J.; Heesen, Volker; Walterbos, Rene A. M.; Dettmar, Ralf-Jürgen; Vargas, Carlos J.; English, Jayanne; Murphy, Eric J.

2018-03-01

Aim. The vertical halo scale height is a crucial parameter to understand the transport of cosmic-ray electrons (CRE) and their energy loss mechanisms in spiral galaxies. Until now, the radio scale height could only be determined for a few edge-on galaxies because of missing sensitivity at high resolution. Methods: We developed a sophisticated method for the scale height determination of edge-on galaxies. With this we determined the scale heights and radial scale lengths for a sample of 13 galaxies from the CHANG-ES radio continuum survey in two frequency bands. Results: The sample average values for the radio scale heights of the halo are 1.1 ± 0.3 kpc in C-band and 1.4 ± 0.7 kpc in L-band. From the frequency dependence analysis of the halo scale heights we found that the wind velocities (estimated using the adiabatic loss time) are above the escape velocity. We found that the halo scale heights increase linearly with the radio diameters. In order to exclude the diameter dependence, we defined a normalized scale height h˜ which is quite similar for all sample galaxies at both frequency bands and does not depend on the star formation rate or the magnetic field strength. However, h˜ shows a tight anticorrelation with the mass surface density. Conclusions: The sample galaxies with smaller scale lengths are more spherical in the radio emission, while those with larger scale lengths are flatter. The radio scale height depends mainly on the radio diameter of the galaxy. The sample galaxies are consistent with an escape-dominated radio halo with convective cosmic ray propagation, indicating that galactic winds are a widespread phenomenon in spiral galaxies. While a higher star formation rate or star formation surface density does not lead to a higher wind velocity, we found for the first time observational evidence of a gravitational deceleration of CRE outflow, e.g. a lowering of the wind velocity from the galactic disk.

Peculiar morphology of the high-redshift radio galaxies 3C 13 and 3C 256 in subarcsecond seeing

International Nuclear Information System (INIS)

Le Fevre, O.; Hammer, F.; Nottale, L.; Mazure, A.; Christian, C.

1988-01-01

High-spatial-resolution imaging is presented for two radio galaxies from the 3C catalog, 3C 13 and 3C 256 with redshifts of 1.351 and 1.819, respectively. The excellent image quality obtained at CFHT, 0.6-arcsec FWHM for 3C 13 and 0.7-arcsec FWHM for 3C 256 in the R band, over long integration times, made it possible to resolve these distant galaxies into complex structures. As suggested by Le Fevre et al. (1987) for another source (the gravitational lens candidate 3C 324) an interpretation in terms of gravitational amplification by foreground galaxies or clusters of galaxies is proposed. 3C 13 appears to be the most serious candidate, since a foreground galaxy, with an absolute luminosity M(R) = 23.3 and a redshift z = 0.477, is only 3.9 in from the extended radio galaxy. 18 references

TOPOLOGY OF LUMINOUS RED GALAXIES FROM THE SLOAN DIGITAL SKY SURVEY

International Nuclear Information System (INIS)

Choi, Yun-Young; Kim, Juhan; Rossi, Graziano; Kim, Sungsoo S.; Lee, Jeong-Eun

2013-01-01

We present measurements of the genus topology of luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS) Data Release 7 catalog, with unprecedented statistical significance. To estimate the uncertainties in the measured genus, we construct 81 mock SDSS LRG surveys along the past light cone from Horizon Run 3, one of the largest N-body simulations to date, which evolved 7210 3 particles in a 10,815 h –1  Mpc box. After carefully modeling and removing all known systematic effects due to finite pixel size, survey boundary, radial and angular selection functions, shot noise, and galaxy biasing, we find that the observed genus amplitude reaches 272 at a 22 h –1  Mpc smoothing scale, with an uncertainty of 4.2%; the estimated error fully incorporates cosmic variance. This is the most accurate constraint on the genus amplitude to date and significantly improves on our previous results. In particular, the shape of the genus curve agrees very well with the mean topology of the SDSS LRG mock surveys in a Λ cold dark matter universe. However, comparison with simulations also shows small deviations of the observed genus curve from the theoretical expectation for Gaussian initial conditions. While these discrepancies are mainly driven by known systematic effects such as shot noise and redshift-space distortions, they do contain important cosmological information on the physical effects connected with galaxy formation, gravitational evolution, and primordial non-Gaussianity. We address the key role played by systematics on the genus curve and show how to accurately correct for their effects to recover the topology of the underlying matter. A future work will provide an interpretation of these deviations in the context of the local model of non-Gaussianity

Lensing of Fast Radio Bursts by Plasma Structures in Host Galaxies

NARCIS (Netherlands)

Cordes, J.M.; Wasserman, I.; Hessels, J.W.T.; Lazio, T.J.W.; Chatterjee, S.; Wharton, R.S.

2017-01-01

The amplitudes of fast radio bursts (FRBs) can be strongly modulated by plasma lenses in their host galaxies, including that of the repeating FRB 121102 at ∼1 Gpc luminosity distance. Caustics require the lens’ dispersion measure depth ({{DM}}{\\ell }), scale size (a), and distance from the source

X-Rays from NGC 3256: High-Energy Emission in Starburst Galaxies and Their Contribution to the Cosmic X-Ray Background

International Nuclear Information System (INIS)

Moran, Edward C.; Lehnert, Matthew D.; Helfand, David J.

1999-01-01

The infrared-luminous galaxy NGC 3256 is a classic example of a merger-induced nuclear starburst system. We find here that it is the most X-ray-luminous star-forming galaxy yet detected (L 0.5-10keV =1.6x10 42 ergs s-1). Long-slit optical spectroscopy and a deep, high-resolution ROSAT X-ray image show that the starburst is driving a ''superwind'' which accounts for ∼20% of the observed soft X-ray emission. Analysis of X-ray spectral data from ASCA indicates this gas has a characteristic temperature of kT≅0.3 keV. Our model for the broadband X-ray emission of NGC 3256 contains two additional components: a warm thermal plasma (kT≅0.8 keV) associated with the central starburst, and a hard power-law component with an energy index of α X ≅0.7. We discuss the energy budget for the two thermal plasmas and find that the input of mechanical energy from the starburst is more than sufficient to sustain the observed level of emission. We also examine possible origins for the power-law component, concluding that neither a buried AGN nor the expected population of high-mass X-ray binaries can account for this emission. Inverse Compton scattering, involving the galaxy's copious flux of infrared photons and the relativistic electrons produced by supernovae, is likely to make a substantial contribution to the hard X-ray flux. Such a model is consistent with the observed radio and IR fluxes and the radio and X-ray spectral indices. We explore the role of X-ray-luminous starbursts in the production of the cosmic X-ray background radiation. The number counts and spectral index distribution of the faint radio source population, thought to be dominated by star-forming galaxies, suggest that a significant fraction of the hard X-ray background could arise from starbursts at moderate redshift. (c) (c) 1999. The American Astronomical Society

The radio continuum-star formation rate relation in WSRT sings galaxies

International Nuclear Information System (INIS)

Heesen, Volker; Brinks, Elias; Leroy, Adam K.; Heald, George; Braun, Robert; Bigiel, Frank; Beck, Rainer

2014-01-01

We present a study of the spatially resolved radio continuum-star formation rate (RC-SFR) relation using state-of-the-art star formation tracers in a sample of 17 THINGS galaxies. We use SFR surface density (Σ SFR ) maps created by a linear combination of GALEX far-UV (FUV) and Spitzer 24 μm maps. We use RC maps at λλ22 and 18 cm from the WSRT SINGS survey and Hα emission maps to correct for thermal RC emission. We compare azimuthally averaged radial profiles of the RC and FUV/mid-IR (MIR) based Σ SFR maps and study pixel-by-pixel correlations at fixed linear scales of 1.2 and 0.7 kpc. The ratio of the integrated SFRs from the RC emission to that of the FUV/MIR-based SF tracers is R int =0.78±0.38, consistent with the relation by Condon. We find a tight correlation between the radial profiles of the radio and FUV/MIR-based Σ SFR for the entire extent of the disk. The ratio R of the azimuthally averaged radio to FUV/MIR-based Σ SFR agrees with the integrated ratio and has only quasi-random fluctuations with galactocentric radius that are relatively small (25%). Pixel-by-pixel plots show a tight correlation in log-log diagrams of radio to FUV/MIR-based Σ SFR , with a typical standard deviation of a factor of two. Averaged over our sample we find (Σ SFR ) RC ∝(Σ SFR ) hyb 0.63±0.25 , implying that data points with high Σ SFR are relatively radio dim, whereas the reverse is true for low Σ SFR . We interpret this as a result of spectral aging of cosmic-ray electrons (CREs), which are diffusing away from the star formation sites where they are injected into the interstellar medium. This is supported by our finding that the radio spectral index is a second parameter in pixel-by-pixel plots: those data points dominated by young CREs are relatively radio dim, while those dominated by old CREs are slightly more RC bright than what would be expected from a linear extrapolation. We studied the ratio R of radio to FUV/MIR-based integrated SFR as a function of

Radio Galaxy Zoo: compact and extended radio source classification with deep learning

Science.gov (United States)

Lukic, V.; Brüggen, M.; Banfield, J. K.; Wong, O. I.; Rudnick, L.; Norris, R. P.; Simmons, B.

2018-05-01

Machine learning techniques have been increasingly useful in astronomical applications over the last few years, for example in the morphological classification of galaxies. Convolutional neural networks have proven to be highly effective in classifying objects in image data. In the context of radio-interferometric imaging in astronomy, we looked for ways to identify multiple components of individual sources. To this effect, we design a convolutional neural network to differentiate between different morphology classes using sources from the Radio Galaxy Zoo (RGZ) citizen science project. In this first step, we focus on exploring the factors that affect the performance of such neural networks, such as the amount of training data, number and nature of layers, and the hyperparameters. We begin with a simple experiment in which we only differentiate between two extreme morphologies, using compact and multiple-component extended sources. We found that a three-convolutional layer architecture yielded very good results, achieving a classification accuracy of 97.4 per cent on a test data set. The same architecture was then tested on a four-class problem where we let the network classify sources into compact and three classes of extended sources, achieving a test accuracy of 93.5 per cent. The best-performing convolutional neural network set-up has been verified against RGZ Data Release 1 where a final test accuracy of 94.8 per cent was obtained, using both original and augmented images. The use of sigma clipping does not offer a significant benefit overall, except in cases with a small number of training images.

Unification in the low radio luminosity regime: evidence from optical line emission

Science.gov (United States)

Marchã, M. J. M.; Browne, I. W. A.; Jethava, N.; Antón, S.

2005-08-01

We address the question of whether or not the properties of all low-luminosity flat spectrum radio sources, not just the obvious BL Lac objects, are consistent with them being the relativistically beamed counterparts of the low radio luminosity radio galaxies (the Fanaroff-Riley type 1, FR I). We have accumulated data on a well-defined sample of low redshift, core-dominated, radio sources all of which have one-sided core-jet structures seen with very long baseline interferometry, just like most BL Lac objects. We first compare the emission-line luminosities of the sample of core-dominated radio sources with a matched sample of FR I radio galaxies. The emission lines in the core-dominated objects are on average significantly more luminous than those in the comparison sample, inconsistent with the simplest unified models in which there is no orientation dependence of the line emission. We then compare the properties of our core-dominated sample with those of a sample of radio-emitting UGC galaxies selected without bias to core strength. The core-dominated objects fit well on the UGC correlation between line emission and radio core strength found by Verdoes Kleijn et al. The results are not consistent with all the objects participating in a simple unified model in which the observed line emission is orientation independent, though they could fit a single, unified model provided that some FR I radio galaxies have emission line regions that become more visible when viewed along the jet axis. However, they are equally consistent with a scenario in which, for the majority of objects, beaming has minimal effect on the observed core luminosities of a large fraction of the FR I population and that intrinsically stronger cores simply give rise to stronger emission lines. We conclude that FR I unification is much more complex than usually portrayed, and models combining beaming with an intrinsic relationship between core and emission line strengths need to be explored.

Problem of spiral galaxies and satellite radio sources

International Nuclear Information System (INIS)

Arp, H.; Carpenter, R.; Gulkis, S.; Klein, M.

1976-01-01

A detailed comparison is made between the results of this program and the results of previous investigators. In particular, attention is called to the potentially important implications of an investigation by Tovmasyan, who searched a large number of spirals and found evidence that a small percentage of them apparently have radio satellites located up to 20' from the central galaxy. 15 sources were measured selected from Tovmasyan's list of 43 satellite sources. Results confirm his positions and relative flux densities for each of the sources

Motion and properties of nuclear radio components in Seyfert galaxies seen with VLBI

Science.gov (United States)

Middelberg, E.; Roy, A. L.; Nagar, N. M.; Krichbaum, T. P.; Norris, R. P.; Wilson, A. S.; Falcke, H.; Colbert, E. J. M.; Witzel, A.; Fricke, K. J.

2004-04-01

We report EVN, MERLIN and VLBA observations at 18 cm, 6 cm and 3.6 cm of the Seyfert galaxies NGC 7674, NGC 5506, NGC 2110 and Mrk 1210 to study their structure and proper motions on pc scales and to add some constraints on the many possible causes of the radio-quietness of Seyferts. The component configurations in NGC 7674 and NGC 2110 are simple, linear structures, whereas the configurations in NGC 5506 and Mrk 1210 have multiple components with no clear axis of symmetry. We suggest that NGC 7674 is a low-luminosity compact symmetric object. Comparing the images at different epochs, we find a proper motion in NGC 7674 of (0.92±0.07) c between the two central components separated by 282 pc and, in NGC 5506, we find a 3 σ upper limit of 0.50 c for the components separated by 3.8 pc. Our results confirm and extend earlier work showing that the outward motion of radio components in Seyfert galaxies is non-relativistic on pc scales. We briefly discuss whether this non-relativistic motion is intrinsic to the jet-formation process or results from deceleration of an initially relativistic jet by interaction with the pc or sub-pc scale interstellar medium. We combined our sample with a list compiled from the literature of VLBI observations made of Seyfert galaxies, and found that most Seyfert nuclei have at least one flat-spectrum component on the VLBI scale, which was not seen in the spectral indices measured at arcsec resolution. We found also that the bimodal alignment of pc and kpc radio structures displayed by radio galaxies and quasars is not displayed by this sample of Seyferts, which shows a uniform distribution of misalignment between 0° and 90°. The frequent misalignment could result from jet precession or from deflection of the jet by interaction with gas in the interstellar medium.

Broad Line Radio Galaxies Observed with Fermi-LAT: The Origin of the GeV Gamma-Ray Emission

Energy Technology Data Exchange (ETDEWEB)

Kataoka, J.; /Waseda U., RISE; Stawarz, L.; /JAXA, Sagamihara /Jagiellonian U., Astron. Observ.; Takahashi, Y.; /Waseda U., RISE; Cheung, C.C.; /Natl. Acad. Sci. /Naval Research Lab, Wash., D.C.; Hayashida, M.; /SLAC /Stanford U., HEPL /KIPAC, Menlo Park; Grandi, P.; /Bologna Observ.; Burnett, T.H.; /Washington U., Seattle; Celotti, A.; /SISSA, Trieste; Fegan, S.J.; Fortin, P.; /Ecole Polytechnique; Maeda, K.; Nakamori, T.; /Waseda U., RISE; Taylor, G.B.; /New Mexico U.; Tosti, G.; /INFN, Perugia /Perugia U.; Digel, S.W.; /SLAC /Stanford U., HEPL /KIPAC, Menlo Park; McConville, W.; /NASA, Goddard /Maryland U.; Finke, J.; /Naval Research Lab, Wash., D.C.; D' Ammando, F.; /IASF, Palermo /INAF, Rome

2012-06-07

We report on a detailed investigation of the {gamma}-ray emission from 18 broad line radio galaxies (BLRGs) based on two years of Fermi Large Area Telescope (LAT) data. We confirm the previously reported detections of 3C 120 and 3C 111 in the GeV photon energy range; a detailed look at the temporal characteristics of the observed {gamma}-ray emission reveals in addition possible flux variability in both sources. No statistically significant {gamma}-ray detection of the other BLRGs was however found in the considered dataset. Though the sample size studied is small, what appears to differentiate 3C 111 and 3C 120 from the BLRGs not yet detected in {gamma}-rays is the particularly strong nuclear radio flux. This finding, together with the indications of the {gamma}-ray flux variability and a number of other arguments presented, indicate that the GeV emission of BLRGs is most likely dominated by the beamed radiation of relativistic jets observed at intermediate viewing angles. In this paper we also analyzed a comparison sample of high accretion-rate Seyfert 1 galaxies, which can be considered radio-quiet counterparts of BLRGs, and found none were detected in {gamma}-rays. A simple phenomenological hybrid model applied for the broad-band emission of the discussed radio-loud and radio-quiet type 1 active galaxies suggests that the relative contribution of the nuclear jets to the accreting matter is {ge} 1% on average for BLRGs, while {le} 0.1% for Seyfert 1 galaxies.

Fornax A, Centaurus A other radio galaxies as sources of ultra-high energy cosmic rays

Science.gov (United States)

Matthews, J. H.; Bell, A. R.; Blundell, K. M.; Araudo, A. T.

2018-06-01

The origin of ultra-high energy cosmic rays (UHECRs) is still unknown. It has recently been proposed that UHECR anisotropies can be attributed to starburst galaxies or active galactic nuclei. We suggest that the latter is more likely and that giant-lobed radio galaxies such as Centaurus A and Fornax A can explain the data.

A Radio Study of the Seyfert Galaxy Markarian 6: Implications for Seyfert Life Cycles

Science.gov (United States)

Kharb, P.; O'Dea, C. P.; Baum, S. A.; Colbert, E. J. M.; Xu, C.

2006-11-01

We have carried out an extensive radio study with the Very Large Array on the Seyfert 1.5 galaxy Mrk 6 and imaged a spectacular radio structure in the source. The radio emission occurs on three different spatial scales: ~7.5 kpc bubbles, ~1.5 kpc bubbles lying nearly orthogonal to them, and a ~1 kpc radio jet lying orthogonal to the kiloparsec-scale bubble. To explain the complex morphology, we first consider a scenario in which the radio structures are the result of superwinds ejected by a nuclear starburst. However, recent Spitzer observations of Mrk 6 provide an upper limit to the star formation rate (SFR) of ~5.5 Msolar yr-1, an estimate much lower than the SFR of ~33 Msolar yr-1 derived assuming that the bubbles are a result of starburst winds energized by supernova explosions. Thus, a starburst alone cannot meet the energy requirements for the creation of the bubbles in Mrk 6. We then present an energetically plausible model wherein the bubbles are a result of energy deposited by the kiloparsec-scale jet as it plows into the interstellar medium. Finally, we consider a model in which the complex radio structure is a result of an episodically powered precessing jet that changes its orientation. This model is the most attractive as it can naturally explain the complex radio morphology and is consistent with the energetics, the spectral index, and the polarization structure. Radio emission in this scenario is a short-lived phenomenon in the lifetime of a Seyfert galaxy, which results from an accretion event.

A FAST RADIO BURST IN THE DIRECTION OF THE CARINA DWARF SPHEROIDAL GALAXY

International Nuclear Information System (INIS)

Ravi, V.; Shannon, R. M.; Jameson, A.

2015-01-01

We report the real-time discovery of a fast radio burst (FRB 131104) with the Parkes radio telescope in a targeted observation of the Carina dwarf spheroidal galaxy. The dispersion measure of the burst is 779 cm –3  pc, exceeding predictions for the maximum line-of-sight Galactic contribution by a factor of 11. The temporal structure of the burst is characterized by an exponential scattering tail with a timescale of 2.0 −0.5 +0.8  ms at 1582 MHz that scales as frequency to the power –4.4 −1.8 +1.6 (all uncertainties represent 95% confidence intervals). We bound the intrinsic pulse width to be <0.64 ms due to dispersion smearing across a single spectrometer channel. Searches in 78 hr of follow-up observations with the Parkes telescope reveal no additional sporadic emission and no evidence for associated periodic radio emission. We hypothesize that the burst is associated with the Carina dwarf galaxy. Follow-up observations at other wavelengths are necessary to test this hypothesis

Eight luminous early-type galaxies in nearby pairs and sparse groups. I. Stellar populations spatially analysed

Science.gov (United States)

Rosa, D. A.; Milone, A. C.; Krabbe, A. C.; Rodrigues, I.

2018-06-01

We present a detailed spatial analysis of stellar populations based on long-slit optical spectra in a sample of eight luminous early-type galaxies selected from nearby sparse groups and pairs, three of them may have interaction with another galaxy of similar mass. We have spatially measured luminosity-weighted averages of age, [M/H], [Fe/H], and [α /Fe] in the sample galaxies to add empirical data relative to the influence of galaxy mass, environment, interaction, and AGN feedback in their formation and evolution. The stellar population of the individual galaxies were determined through the well-established stellar population synthesis code starlight using semi-empirical simple stellar population models. Radial variations of luminosity- weighted means of age, [M/H], [Fe/H], and [α /Fe] were quantified up to half of the effective radius of each galaxy. We found trends between representative values of age, [M/H], [α /Fe], and the nuclear stellar velocity dispersion. There are also relations between the metallicity/age gradients and the velocity dispersion. Contributions of 1-4 Gyr old stellar populations were quantified in IC 5328 and NGC 6758 as well as 4-8 Gyr old ones in NGC 5812. Extended gas is present in IC 5328, NGC 1052, NGC 1209, and NGC 6758, and the presence of a LINER is identified in all these galaxies. The regions up to one effective radius of all galaxies are basically dominated by α -enhanced metal-rich old stellar populations likely due to rapid star formation episodes that induced efficient chemical enrichment. On average, the age and [α /Fe] gradients are null and the [M/H] gradients are negative, although discordant cases were found. We found no correlation between the stellar population properties and the LINER presence as well as between the stellar properties and environment or gravitational interaction, suggesting that the influence of progenitor mass cannot be discarded in the formation and evolution of early-type galaxies.

The Origin of the Infrared Emission in Radio Galaxies : III. Analysis of 3CRR Objects

NARCIS (Netherlands)

Dicken, D.; Tadhunter, C.; Axon, D.; Robinson, A.; Morganti, R.; Kharb, P.

2010-01-01

We present Spitzer photometric data for a complete sample of 19 low-redshift (z <0.1) 3CRR radio galaxies as part of our efforts to understand the origin of the prodigious mid-to far-infrared (MFIR) emission from radio-loud active galactic nuclei (AGNs). Our results show a correlation between AGN

The Host Galaxy and Redshift of the Repeating Fast Radio Burst FRB 121102

Energy Technology Data Exchange (ETDEWEB)

Tendulkar, S. P.; Kaspi, V. M. [Department of Physics and McGill Space Institute, McGill University, 3600 University Street, Montreal, QC H3A 2T8 (Canada); Bassa, C. G.; Adams, E. A. K.; Hessels, J. W. T.; Maddox, N. [ASTRON, the Netherlands Institute for Radio Astronomy, Postbus 2, NL-7990 AA Dwingeloo (Netherlands); Cordes, J. M.; Chatterjee, S. [Cornell Center for Astrophysics and Planetary Science and Department of Astronomy, Cornell University, Ithaca, NY 14853 (United States); Bower, G. C. [Academia Sinica Institute of Astronomy and Astrophysics, 645 N. A’ohoku Place, Hilo, HI 96720 (United States); Law, C. J. [Department of Astronomy and Radio Astronomy Lab, University of California, Berkeley, CA 94720 (United States); Bogdanov, S. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Burke-Spolaor, S.; Butler, B. J.; Demorest, P. [National Radio Astronomy Observatory, Socorro, NM 87801 (United States); Lazio, T. J. W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States); Marcote, B.; Paragi, Z. [Joint Institute for VLBI ERIC, Postbus 2, NL-7990 AA Dwingeloo (Netherlands); McLaughlin, M. A. [Department of Physics and Astronomy, West Virginia University, Morgantown, WV 26506 (United States); Ransom, S. M. [National Radio Astronomy Observatory, Charlottesville, VA 22903 (United States); Scholz, P., E-mail: shriharsh@physics.mcgill.ca, E-mail: bassa@astron.nl [National Research Council of Canada, Herzberg Astronomy and Astrophysics, Dominion Radio Astrophysical Observatory, P.O. Box 248, Penticton, BC V2A 6J9 (Canada); and others

2017-01-10

The precise localization of the repeating fast radio burst (FRB 121102) has provided the first unambiguous association (chance coincidence probability p ≲ 3 × 10{sup −4}) of an FRB with an optical and persistent radio counterpart. We report on optical imaging and spectroscopy of the counterpart and find that it is an extended (0.″6–0.″8) object displaying prominent Balmer and [O iii] emission lines. Based on the spectrum and emission line ratios, we classify the counterpart as a low-metallicity, star-forming, m{sub r′} = 25.1 AB mag dwarf galaxy at a redshift of z = 0.19273(8), corresponding to a luminosity distance of 972 Mpc. From the angular size, the redshift, and luminosity, we estimate the host galaxy to have a diameter ≲4 kpc and a stellar mass of M {sub *} ∼ (4–7) × 10{sup 7} M {sub ⊙}, assuming a mass-to-light ratio between 2 to 3 M {sub ⊙} L {sub ⊙} {sup −1}. Based on the H α flux, we estimate the star formation rate of the host to be 0.4 M {sub ⊙} yr{sup −1} and a substantial host dispersion measure (DM) depth ≲324 pc cm{sup −3}. The net DM contribution of the host galaxy to FRB 121102 is likely to be lower than this value depending on geometrical factors. We show that the persistent radio source at FRB 121102’s location reported by Marcote et al. is offset from the galaxy’s center of light by ∼200 mas and the host galaxy does not show optical signatures for AGN activity. If FRB 121102 is typical of the wider FRB population and if future interferometric localizations preferentially find them in dwarf galaxies with low metallicities and prominent emission lines, they would share such a preference with long gamma-ray bursts and superluminous supernovae.

Radio ejection and broad forbidden emission lines in the Seyfert galaxy NGC 7674

International Nuclear Information System (INIS)

Unger, S.W.; Pedlar, A.; Axon, D.J.

1988-01-01

The Seyfert nucleus in NGC7674 (Mkn533) is remarkable for its broad asymmetric forbidden line profiles, which extend 2000 kms -1 blueward of the systemic velocity. The galaxy also has a compact nuclear radio source. We have obtained new high-resolution radio observations of NGC7674, using the European VLBI network and the VLA, and optical spectroscopic observations using the Isaac Newton Telescope. The radio maps reveal a triple radio source with a total angular extent of about 0.7 arcsec, and provide evidence that the radio emission is powered by collimated ejection. In the plane of the sky, the ejection axis appears roughly perpendicular to the galactic rotation axis. Although the dominant radio components are separated by 0.5 arcsec, the broad [OIII]λ5007 line emission is confined to within about 0.25 arcsec of the continuum nucleus. (author)

Suzaku Diagnostics of the Energetics in the Lobes of the Giant Radio Galaxy 3C 35

Science.gov (United States)

Isobe, Naoki; Seta, Hiromi; Gandhi, Poshak; Tashiro, Makoto S.

2011-02-01

The Suzaku observation of a giant radio galaxy 3C 35 revealed faint extended X-ray emission, associated with its radio lobes and/or host galaxy. After careful subtraction of the X-ray and non-X-ray background and contaminating X-ray sources, the X-ray spectrum of the faint emission was reproduced by a sum of the power-law (PL) and soft thermal components. The soft component was attributed to the thermal plasma emission from the host galaxy. The photon index of the PL component, Γ = 1.35+0.56 -0.86 +0.11 -0.10, where the first and second errors represent the statistical and systematic ones, was found to agree with the synchrotron radio index from the lobes, ΓR = 1.7. Thus, the PL component was attributed to the inverse Compton (IC) X-rays from the synchrotron electrons in the lobes. The X-ray flux density at 1 keV was derived as 13.6 ± 5.4+4.0 -3.6 nJy with the photon index fixed at the radio value. The X-ray surface brightness from these lobes (~0.2 nJy arcmin-2) is lowest among the lobes studied through the IC X-ray emission. In combination with the synchrotron radio flux density, 7.5 ± 0.2 Jy at 327.4 MHz, the electron energy density spatially averaged over the lobes was evaluated to be the lowest among those radio galaxies, as u e = (5.8 ± 2.3+1.9 -1.7) × 10-14 erg cm-3 over the electron Lorentz factor of 103-105. The magnetic energy density was calculated as u m = (3.1+2.5 -1.0 +1.4 -0.9) × 10-14 erg cm-3, corresponding to the magnetic field strength of 0.88+0.31 -0.16 +0.19 -0.14 μG. These results suggest that the energetics in the 3C 35 lobes are nearly consistent with equipartition between the electrons and magnetic fields.

Astronomy. ASASSN-15lh: A highly super-luminous supernova.

Science.gov (United States)

Dong, Subo; Shappee, B J; Prieto, J L; Jha, S W; Stanek, K Z; Holoien, T W-S; Kochanek, C S; Thompson, T A; Morrell, N; Thompson, I B; Basu, U; Beacom, J F; Bersier, D; Brimacombe, J; Brown, J S; Bufano, F; Chen, Ping; Conseil, E; Danilet, A B; Falco, E; Grupe, D; Kiyota, S; Masi, G; Nicholls, B; Olivares E, F; Pignata, G; Pojmanski, G; Simonian, G V; Szczygiel, D M; Woźniak, P R

2016-01-15

We report the discovery of ASASSN-15lh (SN 2015L), which we interpret as the most luminous supernova yet found. At redshift z = 0.2326, ASASSN-15lh reached an absolute magnitude of Mu ,AB = -23.5 ± 0.1 and bolometric luminosity Lbol = (2.2 ± 0.2) × 10(45) ergs s(-1), which is more than twice as luminous as any previously known supernova. It has several major features characteristic of the hydrogen-poor super-luminous supernovae (SLSNe-I), whose energy sources and progenitors are currently poorly understood. In contrast to most previously known SLSNe-I that reside in star-forming dwarf galaxies, ASASSN-15lh appears to be hosted by a luminous galaxy (MK ≈ -25.5) with little star formation. In the 4 months since first detection, ASASSN-15lh radiated (1.1 ± 0.2) × 10(52) ergs, challenging the magnetar model for its engine. Copyright © 2016, American Association for the Advancement of Science.

The Seyfert galaxy population

International Nuclear Information System (INIS)

Meurs, E.

1982-01-01

A large sample of Seyfert galaxies, many of which are Markarian galaxies, has been observed with the WSRT in lambda 21 cm continuum radiation. The results are presented, and the number of radio detected Seyferts has now increased considerably. A number of accurate optical positions are given that were needed to identify radio sources with the Seyfert galaxies observed. Optical and radio luminosity functions of Seyfert galaxies are derived. The results are compared with such functions for other categories of objects that may be related to these galaxies. The discussions focus on the possible connections between normal galaxies, Seyferts, and optically selected quasars. Three investigations are reported on individual objects that are related to Seyfert galaxies. WSRT observations of four bright, optically selected quasars are presented. The identification of an X-ray discovered BL Lacertae object is discussed. Its radio emission is on a much lower level than for other BL Lacs. Perhaps it is a radio-quiet object in this class, suggesting a comparable difference in radio emission for BL Lacs as is known for quasars. Photo-electric photometry for the Seyfert galaxy NGC 1566 is reported. Besides a monitoring programme, multi-aperture photometry is described. (Auth.)

Extended radio emission and the nature of blazars

International Nuclear Information System (INIS)

Antonucci, R.R.J.; Ulvestad, J.S.

1985-01-01

The VLA has been used at 20 cm to map all 23 of the 54 confirmed blazars listed in the Angel and Stockman review paper that had not been mapped before at high resolution. (Blazars include BL Lac objects and optically violently variable quasars.) In addition, data on most of the previously mapped blazars have been reprocessed in order to achieve higher dynamic range. Extended emission has been detected associated with 49 of the 54 objects. The extended radio emission has been used to test the hypothesis that blazars are normal radio galaxies and radio quasars viewed along the jet axes. We find that blazars have substantial extended power, consistent with this hypothesis. Many have extended powers as high as the luminous Fanaroff-Riley class 2 radio doubles. The projected linear sizes are small, as expected from foreshortening of the extended sources, and many blazars have the expected core-halo morphology. There are also several small doubles, a head-tail source, and some one-sided sources, and these could be in cases where the line of sight is slightly off the jet axis, or projections of asymmetrical radio galaxies and quasars. The ratio of core to extended radio emission has been studied as a possible indicator of viewing aspect or beaming intensity. It is found to correlate with optical polarization, optical and radio core variability, and one-sided radio morphology. We can go beyond these consistency checks and work toward a proof of the hypothesis under discussion. The flux from the extended emission alone is sufficient in some blazars to qualify them for inclusion in the 3C and 4C catalogs. Suppose that the radio core emission is anisotropic, but the extended emission is predominantly isotropic. The isotropy of the extended emission implies that these blazars would be in the catalogs even if viewed from the side

Gas-rich dwarfs and accretion phenomena in early-type galaxies

International Nuclear Information System (INIS)

Silk, J.; Norman, C.

1979-01-01

Recent constraints on intergalactic H I clouds suggest that allowable accretion rates by several luminous early-type galaxies are too low to account for their observed H I content. We have therefore developed an alternative model, wherein gas-rich dwarf galaxies are accreted into galactic halos. This process is significant in groups of galaxies only when a sufficiently high density of gas-rich dwarfs (approx.30 Mpc -3 ) is present. The dwarf galaxy gas content plays a crucial role in enabling the galaxy to be trapped in the halo by interaction with a galactic wind or extensive gaseous corona. Gas stripping occurs, resulting in the formation of dwarf spheroidal systems that populate the outer halos of massive galaxies and in the injection of a system of clouds into the halo. If the clouds are initially confined by the pressure of the ambient halo medium, dissipation and continuing infall enable the clouds to accrete into the central regions of galaxies before becoming gravitationally unstable and presumably forming stars. Consequences of this scenario include the production of a radial abundance gradient and infall of adequate amounts of neutral gas to account for the observations of H I in early-type galaxies. This gas accretion rate is also sufficient to feed active nuclei and radio sources. An important cosmological implication of our model is that, because the characteristic time scale of a gas-rich dwarf galaxy to be accreted and lose its gas is comparable to a Hubble time, there many have been a far more extensive primordial distribution of such systems at earlier epochs. This implies that accretion rates were greatly enhanced at relatively recent epochs (z> or approx. =0.5) and could account both for the rapid cosmological evolution inferred for radio galaxies and quasars, and for the observed frequency of occurrence of quasar absorption-line systems

Giant Low Surface Brightness Galaxies

Science.gov (United States)

Mishra, Alka; Kantharia, Nimisha G.; Das, Mousumi

2018-04-01

In this paper, we present radio observations of the giant low surface brightness (LSB) galaxies made using the Giant Metrewave Radio Telescope (GMRT). LSB galaxies are generally large, dark matter dominated spirals that have low star formation efficiencies and large HI gas disks. Their properties suggest that they are less evolved compared to high surface brightness galaxies. We present GMRT emission maps of LSB galaxies with an optically-identified active nucleus. Using our radio data and archival near-infrared (2MASS) and near-ultraviolet (GALEX) data, we studied morphology and star formation efficiencies in these galaxies. All the galaxies show radio continuum emission mostly associated with the centre of the galaxy.

MULTI-FREQUENCY STUDIES OF RADIO RELICS IN THE GALAXY CLUSTERS A4038, A1664, AND A786

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Kale, Ruta; Dwarakanath, K. S., E-mail: ruta@iucaa.ernet.in [Raman Research Institute, C. V. Raman Avenue, Sadashivanagar, Bangalore 560 080 (India)

2012-01-01

We present a multi-frequency study of radio relics associated with the galaxy clusters A4038, A1664, and A786. Radio images, integrated spectra, spectral index maps, and fits to the integrated spectra in the framework of the adiabatic compression model are presented. Images of the relic in A4038 at 150, 240, and 606 MHz with the Giant Meterwave Radio Telescope have revealed extended ultra-steep spectrum ({alpha} {approx} -1.8 to -2.7) emission of extent 210 Multiplication-Sign 80 kpc{sup 2}. The model of passively evolving radio lobes compressed by a shock fits the integrated spectrum best. The relic with a circular morphology at the outskirts of the cluster A1664 has an integrated spectral index of {approx} - 1.10 {+-} 0.06 and is best fit by the model of radio lobes lurking for {approx}4 Multiplication-Sign 10{sup 7} yr. The relic near A786 has a curved spectrum and is best fit by a model of radio lobes lurking for {approx}3 Multiplication-Sign 10{sup 7} yr. At 4.7 GHz, a compact radio source, possibly the progenitor of the A786 relic, is detected near the center of the radio relic. The A786 radio relic is thus likely a lurking radio galaxy rather than a site of cosmological shock as has been considered in earlier studies.

Radio observations of some clusters of galaxies at lambda=3.5 and 4 mm

International Nuclear Information System (INIS)

Efanov, V.A.; Zinchenko, I.I.; Kislyakov, A.G.; Krasil'nikov, A.A.; Kukina, E.P.; Moiseev, I.G.

1980-01-01

Millimeter radio observations with the 22-m Crimean antenna are reported for the central regions of the clusters of galaxies in Virgo, Hercules, and Coma Berenices, and from the cluster Abell 2199. In two of these, Coma and A2199, sources with a flux density of several jansky have been detected. The position of the source in A2199 matches that of the radio source 3C 338, but the object in the Coma cluster does not correspond to any known radio source. The nature of the emission from the new sources is discussed

Stellar Photometric Structures of the Host Galaxies of Nearby Type 1 Active Galactic Nuclei

Science.gov (United States)

Kim, Minjin; Ho, Luis C.; Peng, Chien Y.; Barth, Aaron J.; Im, Myungshin

2017-10-01

We present detailed image analysis of rest-frame optical images of 235 low-redshift (z ≲ 0.35) Type 1 active galactic nuclei (AGNs) observed with the Hubble Space Telescope. The high-resolution images enable us to perform rigorous two-dimensional image modeling to decouple the luminous central point source from the host galaxy, which, when warranted, is further decomposed into its principal structural components (bulge, bar, and disk). In many cases, care must be taken to account for structural complexities such as spiral arms, tidal features, and overlapping or interacting companion galaxies. We employ Fourier modes to characterize the degree of asymmetry of the light distribution of the stars as a quantitative measure of morphological distortion due to interactions or mergers. We examine the dependence of the physical parameters of the host galaxies on the properties of the AGNs, namely, radio-loudness and the width of the broad emission lines. In accordance with previous studies, narrow-line (Hβ FWHM ≤ 2000 km s-1) Type 1 AGNs, in contrast to their broad-line (Hβ FWHM > 2000 km s-1) counterparts, are preferentially hosted in later-type, lower-luminosity galaxies, which have a higher incidence of pseudo-bulges, are more frequently barred, and are less morphologically disturbed. This suggests that narrow-line Type 1 AGNs experienced a more quiescent evolutionary history driven primarily by internal secular evolution instead of external dynamical perturbations. The fraction of AGN hosts showing merger signatures is larger for more luminous sources. Radio-loud AGNs generally preferentially live in earlier-type (bulge-dominated), more massive hosts, although a minority of them appear to contain a significant disk component. We do not find convincing evidence for enhanced merger signatures in the radio-loud population. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the Data Archive at the Space Telescope Science Institute

LUMINOUS BURIED ACTIVE GALACTIC NUCLEI AS A FUNCTION OF GALAXY INFRARED LUMINOSITY REVEALED THROUGH SPITZER LOW-RESOLUTION INFRARED SPECTROSCOPY

International Nuclear Information System (INIS)

Imanishi, Masatoshi

2009-01-01

We present the results of Spitzer Infrared Spectrograph 5-35 μm low-resolution spectroscopic energy diagnostics of ultraluminous infrared galaxies (ULIRGs) at z> 0.15, classified optically as non-Seyferts. Based on the equivalent widths of polycyclic aromatic hydrocarbon emission and the optical depths of silicate dust absorption features, we searched for signatures of intrinsically luminous, but optically elusive, buried active galactic nuclei (AGNs) in these optically non-Seyfert ULIRGs. We then combined the results with those of non-Seyfert ULIRGs at z IR 12 L sun . We found that the energetic importance of buried AGNs clearly increases with galaxy infrared luminosity, becoming suddenly discernible in ULIRGs with L IR > 10 12 L sun . For ULIRGs with buried AGN signatures, a significant fraction of infrared luminosities can be accounted for by the detected buried AGN and modestly obscured (A V < 20 mag) starburst activity. The implied masses of spheroidal stellar components in galaxies for which buried AGNs become important roughly correspond to the value separating red massive and blue less-massive galaxies in the local universe. Our results may support the widely proposed AGN-feedback scenario as the origin of galaxy downsizing phenomena, where galaxies with currently larger stellar masses previously had higher AGN energetic contributions and star formation originating infrared luminosities, and have finished their major star formation more quickly, due to stronger AGN feedback.

Test of Gravity on Large Scales with Weak Gravitational Lensing and Clustering Measurements of SDSS Luminous Red Galaxies

Science.gov (United States)

Reyes, Reinabelle; Mandelbaum, R.; Seljak, U.; Gunn, J.; Lombriser, L.

2009-01-01

We perform a test of gravity on large scales (5-50 Mpc/h) using 70,000 luminous red galaxies (LRGs) from the Sloan Digital Sky Survey (SDSS) DR7 with redshifts 0.16galaxy peculiar velocities, and galaxy clustering-- that can discriminate between different theories of gravity and is largely independent of galaxy bias and sigma_8. In particular, E_G is sensitive to the relation between the spatial and temporal scalar perturbations in the space-time metric. While these two potentials are equivalent in concordance cosmology (GR+LCDM) in the absence of anisotropic stress, they are not equivalent in alternative theories of gravity in general, so that different models make different predictions for E_G. We find E_G=0.37±0.05 averaged over scales 5galaxy surveys such as LSST, for which a very high signal-to-noise measurement will be possible.

RECOILING SUPERMASSIVE BLACK HOLES IN SPIN-FLIP RADIO GALAXIES

International Nuclear Information System (INIS)

Liu, F. K.; Wang Dong; Chen Xian

2012-01-01

Numerical relativity simulations predict that coalescence of supermassive black hole (SMBH) binaries leads not only to a spin flip but also to a recoiling of the merger remnant SMBHs. In the literature, X-shaped radio sources are popularly suggested to be candidates for SMBH mergers with spin flip of jet-ejecting SMBHs. Here we investigate the spectral and spatial observational signatures of the recoiling SMBHs in radio sources undergoing black hole spin flip. Our results show that SMBHs in most spin-flip radio sources have mass ratio q ∼> 0.3 with a minimum possible value q min ≅ 0.05. For major mergers, the remnant SMBHs can get a kick velocity as high as 2100 km s –1 in the direction within an angle ∼< 40° relative to the spin axes of remnant SMBHs, implying that recoiling quasars are biased to be with high Doppler-shifted broad emission lines while recoiling radio galaxies are biased to large apparent spatial off-center displacements. We also calculate the distribution functions of line-of-sight velocity and apparent spatial off-center displacements for spin-flip radio sources with different apparent jet reorientation angles. Our results show that the larger the apparent jet reorientation angle is, the larger the Doppler-shifting recoiling velocity and apparent spatial off-center displacement will be. We investigate the effects of recoiling velocity on the dust torus in spin-flip radio sources and suggest that recoiling of SMBHs would lead to 'dust-poor' active galactic nuclei. Finally, we collect a sample of 19 X-shaped radio objects and for each object give the probability of detecting the predicted signatures of recoiling SMBH.

A FAST RADIO BURST IN THE DIRECTION OF THE CARINA DWARF SPHEROIDAL GALAXY

Energy Technology Data Exchange (ETDEWEB)

Ravi, V. [School of Physics, University of Melbourne, Parkville, VIC 3010 (Australia); Shannon, R. M. [CSIRO Astronomy and Space Science, Australia Telescope National Facility, P.O. Box 76, Epping, NSW 1710 (Australia); Jameson, A., E-mail: v.vikram.ravi@gmail.com [Swinburne University of Technology, Centre for Astrophysics and Supercomputing, Mail H39, P.O. Box 218, VIC 3122 (Australia)

2015-01-20

We report the real-time discovery of a fast radio burst (FRB 131104) with the Parkes radio telescope in a targeted observation of the Carina dwarf spheroidal galaxy. The dispersion measure of the burst is 779 cm{sup –3} pc, exceeding predictions for the maximum line-of-sight Galactic contribution by a factor of 11. The temporal structure of the burst is characterized by an exponential scattering tail with a timescale of 2.0{sub −0.5}{sup +0.8} ms at 1582 MHz that scales as frequency to the power –4.4{sub −1.8}{sup +1.6} (all uncertainties represent 95% confidence intervals). We bound the intrinsic pulse width to be <0.64 ms due to dispersion smearing across a single spectrometer channel. Searches in 78 hr of follow-up observations with the Parkes telescope reveal no additional sporadic emission and no evidence for associated periodic radio emission. We hypothesize that the burst is associated with the Carina dwarf galaxy. Follow-up observations at other wavelengths are necessary to test this hypothesis.

Dwarf spheroidal galaxies: Keystones of galaxy evolution

Science.gov (United States)

Gallagher, John S., III; Wyse, Rosemary F. G.

1994-01-01

Dwarf spheroidal galaxies are the most insignificant extragalactic stellar systems in terms of their visibility, but potentially very significant in terms of their role in the formation and evolution of much more luminous galaxies. We discuss the present observational data and their implications for theories of the formation and evolution of both dwarf and giant galaxies. The putative dark-matter content of these low-surface-brightness systems is of particular interest, as is their chemical evolution. Surveys for new dwarf spheroidals hidden behind the stars of our Galaxy and those which are not bound to giant galaxies may give new clues as to the origins of this unique class of galaxy.

HerMES: Spectral energy distributions of submillimeter galaxies at z > 4

International Nuclear Information System (INIS)

Huang, J.-S.; Rigopoulou, D.; Magdis, G.; Rowan-Robinson, M.; Clements, D. L.; Dai, Y.; Fazio, G. G.; Bock, J. J.; Burgarella, D.; Chapman, S.; Cooray, A.; Farrah, D.; Glenn, J.; Oliver, S.; Smith, A. J.; Wang, L.; Page, M.; Symeonidis, M.; Riechers, D.; Roseboom, I.

2014-01-01

We present a study of the infrared properties for a sample of seven spectroscopically confirmed submillimeter galaxies (SMGs) at z > 4.0. By combining ground-based near-infrared, Spitzer IRAC and MIPS, Herschel SPIRE, and ground-based submillimeter/millimeter photometry, we construct their spectral energy distributions (SEDs) and a composite model to fit the SEDs. The model includes a stellar emission component at λ rest < 3.5 μm, a hot dust component peaking at λ rest ∼ 5 μm, and cold dust component which becomes significant for λ rest > 50 μm. Six objects in the sample are detected at 250 and 350 μm. The dust temperatures for the sources in this sample are in the range of 40-80 K, and their L FIR ∼ 10 13 L ☉ qualifies them as hyper-luminous infrared galaxies. The mean FIR-radio index for this sample is around (q) = 2.2 indicating no radio excess in their radio emission. Most sources in the sample have 24 μm detections corresponding to a rest-frame 4.5 μm luminosity of Log 10 (L 4.5 /L ☉ ) = 11 ∼ 11.5. Their L 4.5 /L FIR ratios are very similar to those of starburst-dominated SMGs at z ∼ 2. The L CO – L FIR relation for this sample is consistent with that determined for local ULIRGs and SMGs at z ∼ 2. We conclude that SMGs at z > 4 are hotter and more luminous in the FIR but otherwise very similar to those at z ∼ 2. None of these sources show any sign of the strong QSO phase being triggered.

A GIANT RADIO HALO IN THE MASSIVE AND MERGING CLUSTER ABELL 1351

International Nuclear Information System (INIS)

Giacintucci, S.; Venturi, T.; Cassano, R.; Dallacasa, D.; Brunetti, G.

2009-01-01

We report on the detection of diffuse radio emission in the X-ray luminous and massive galaxy cluster A 1351 (z = 0.322) using archival Very Large Array data at 1.4 GHz. Given its central location, morphology, and Mpc-scale extent, we classify the diffuse source as a giant radio halo. X-ray and weak lensing studies show A 1351 to be a system undergoing a major merger. The halo is associated with the most massive substructure. The presence of this source is explained assuming that merger-driven turbulence may re-accelerate high-energy particles in the intracluster medium and generate diffuse radio emission on the cluster scale. The position of A 1351 in the log P 1.4GHz -log L X plane is consistent with that of all other radio-halo clusters known to date, supporting a causal connection between the unrelaxed dynamical state of massive (>10 15 M sun ) clusters and the presence of giant radio halos.

IRAS 14348-1447, an Ultraluminous Pair of Colliding, Gas-Rich Galaxies: The Birth of a Quasar?

Science.gov (United States)

Sanders, D B; Scoville, N Z; Soifer, B T

1988-02-05

Ground-based observations of the object IRAS 14348-1447, which was discovered with the Infrared Astronomical Satellite, show that it is an extremely luminous colliding galaxy system that emits more than 95 percent of its energy at far-infrared wavelengths. IRAS 14348-1447, which is receeding from the sun at 8 percent of the speed of light, has a bolometric luminosity more than 100 times larger than that of our galaxy, and is therefore as luminous as optical quasars. New optical, infrared, and spectroscopic measurements suggest that the dominant luminosity source is a dustenshrouded quasar. The fuel for the intense activity is an enormous supply of molecular gas. Carbon monoxide emission has been detected at a wavelength of 2.6 millimeters by means of a new, more sensitive receiver recently installed on the 12-meter telescope of the National Radio Astronomy Observatory. IRAS 14348-1447 is the most distant and luminous source of carbon monoxide line emission yet detected. The derived mass of interstellar molecular hydrogen is 6 x 10(10) solar masses. This value is approximately 20 times that of the molecular gas content of the Milky Way and is similar to the largest masses of atomic hydrogen found in galaxies. A large mass of molecular gas may be a prerequisite for the formation of quasars during strong galactic collisions.

Cooking a `Sausage': the impact of merger shocks in cluster gas and galaxy evolution

Science.gov (United States)

Stroe, Andra; Sobral, David; Harwood, Jeremy; Van Weeren, Reinout J.; Rumsey, Clare; Intema, Huib; Röttgering, Huub; Brüggen, Marcus; Saunders, Richard; Hardcastle, Martin; Hoeft, Matthias

2015-01-01

Galaxy clusters mainly grow through mergers with other clusters and groups. Major mergers give rise to important astrophysical phenomena such as the segregation of dark and luminous matter and the formation of cluster-wide traveling shocks and also drive galaxy evolution. The observable effects of shock waves can be seen at radio wavelengths as relics: elongated, diffuse synchrotron emitting areas located at the periphery of merging clusters. Despite the great interest in relics, candidates with simple geometry, undisturbed morphology and high surface brightness are scarce. The `Sausage' cluster hosts an extraordinary Mpc-wide relic, which enables us to study to study particle acceleration and the effects of shocks on cluster galaxies. We use a unique combination of facilities (INT, WHT, Keck, Subaru, CFHT, GMRT, WSRT, AMI) to obtain the first cluster-wide, multi-wavelength, multi-method analysis aimed at giving a complete picture of a merging cluster with relics. Using the radio data, we derive shock properties and the magnetic field structure for the relic. Using spectral modeling, we test acceleration and electron energy-loss mechanisms and resolve the discrepancy between the Mach number calculated from the radio and X-rays. Our results indicate that particles are shock-accelerated, but turbulent re-acceleration or unusually efficient transport of particles in the downstream area and line-of-sight mixing are important effects. We demonstrate the feasibility of high-frequency observations of radio relics, by presenting a 16 GHz detection of the `Sausage' relic. The radio analysis is complemented by Hα mapping of the cluster volume, aimed at providing the first direct test as to whether the shock drives or prohibits star formation. We find numerous Hα emitting galaxies in close proximity to the radio relic which are extremely massive, metal-rich, mostly star-forming with evidence for gas mass loss though outflows. We speculate that the complex interaction

Jet-torus connection in radio galaxies. Relativistic hydrodynamics and synthetic emission

Science.gov (United States)

Fromm, C. M.; Perucho, M.; Porth, O.; Younsi, Z.; Ros, E.; Mizuno, Y.; Zensus, J. A.; Rezzolla, L.

2018-01-01

Context. High resolution very long baseline interferometry observations of active galactic nuclei have revealed asymmetric structures in the jets of radio galaxies. These asymmetric structures may be due to internal asymmetries in the jets or they may be induced by the different conditions in the surrounding ambient medium, including the obscuring torus, or a combination of the two. Aims: In this paper we investigate the influence of the ambient medium, including the obscuring torus, on the observed properties of jets from radio galaxies. Methods: We performed special-relativistic hydrodynamic (SRHD) simulations of over-pressured and pressure-matched jets using the special-relativistic hydrodynamics code Ratpenat, which is based on a second-order accurate finite-volume method and an approximate Riemann solver. Using a newly developed radiative transfer code to compute the electromagnetic radiation, we modelled several jets embedded in various ambient medium and torus configurations and subsequently computed the non-thermal emission produced by the jet and thermal absorption from the torus. To better compare the emission simulations with observations we produced synthetic radio maps, taking into account the properties of the observatory. Results: The detailed analysis of our simulations shows that the observed properties such as core shift could be used to distinguish between over-pressured and pressure matched jets. In addition to the properties of the jets, insights into the extent and density of the obscuring torus can be obtained from analyses of the single-dish spectrum and spectral index maps.

Galaxies

International Nuclear Information System (INIS)

1981-01-01

Normal galaxies, radio galaxies, and Seyfert galaxies are considered. The large magellanic cloud and the great galaxy in Andromedia are highlighted. Quasars and BL lacertae objects are also discussed and a review of the spectral observations of all of these galaxies and celestial objects is presented

Radio-continuum jets around the peculiar galaxy pair ESO 295-IG022

Directory of Open Access Journals (Sweden)

Filipović M.D.

2010-01-01

Full Text Available We report new radio-continuum observations with the Australia Telescope Compact Array (ATCA of the region surrounding the peculiar galaxy pair ESO 295-IG022 at the centre of the poor cluster Abell S0102. We observed this cluster at wavelengths of λ=20/13 and 6/3 cm with the ATCA 6 km array. With these configurations, we achieved a resolution of ~2'' at 3 cm which is sufficient to resolve the jet-like structure of ~3' length detected at 20 cm. From our new high resolution images at 6 and 3 cm we confirm the presence of a double jet structure, most likely originating from the northern galaxy (ESO 295-IG022-N, bent and twisted towards the south. We found the spectral index of the jet to be very steep (α=-1.32. No point source was detected that could be associated with the core of ESO 295-IG022-N. On the other hand, ESO 295-IG022-S does not show any jet structure, but does show a point radio source. This source has variable flux and spectral index, and appears to be superposed on the line-of-sight of the jets (seen at 20-cm originating from the northern galaxy ESO 295-IG022-N. Finally, regions of very high and somewhat well ordered polarization were detected at the level of 70%.

VERITAS UPPER LIMIT ON THE VERY HIGH ENERGY EMISSION FROM THE RADIO GALAXY NGC 1275

International Nuclear Information System (INIS)

Acciari, V. A.; Benbow, W.; Aliu, E.; Boltuch, D.; Arlen, T.; Celik, O.; Aune, T.; Bautista, M.; Cogan, P.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Bradbury, S. M.; Byrum, K.; Cannon, A.; Cesarini, A.; Ciupik, L.; Cui, W.; Duke, C.

2009-01-01

The recent detection by the Fermi γ-ray space telescope of high-energy γ-rays from the radio galaxy NGC 1275 makes the observation of the very high energy (VHE: E>100 GeV) part of its broadband spectrum particularly interesting, especially for the understanding of active galactic nuclei with misaligned multi-structured jets. The radio galaxy NGC 1275 was recently observed by VERITAS at energies above 100 GeV for about 8 hr. No VHE γ-ray emission was detected by VERITAS from NGC 1275. A 99% confidence level upper limit of 2.1% of the Crab Nebula flux level is obtained at the decorrelation energy of approximately 340 GeV, corresponding to 19% of the power-law extrapolation of the Fermi Large Area Telescope result.

In Pursuit of the Least Luminous Galaxies

Directory of Open Access Journals (Sweden)

Beth Willman

2010-01-01

Full Text Available The dwarf galaxy companions to the Milky Way are unique cosmological laboratories. With luminosities as low as 10−7LMW, they inhabit the lowest mass dark matter halos known to host stars and are presently the most direct tracers of the distribution, mass spectrum, and clustering scale of dark matter. Their resolved stellar populations also facilitate detailed studies of their history and mass content. To fully exploit this potential requires a well-defined census of virtually invisible galaxies to the faintest possible limits and to the largest possible distances. I review the past and present impacts of survey astronomy on the census of Milky Way dwarf galaxy companions and discuss the future of finding ultra-faint dwarf galaxies around the Milky Way and beyond in wide-field survey data.

TURBULENCE AND RADIO MINI-HALOS IN THE SLOSHING CORES OF GALAXY CLUSTERS

International Nuclear Information System (INIS)

ZuHone, J. A.; Markevitch, M.; Brunetti, G.; Giacintucci, S.

2013-01-01

A number of relaxed, cool-core galaxy clusters exhibit diffuse, steep-spectrum radio sources in their central regions, known as radio mini-halos. It has been proposed that the relativistic electrons responsible for the emission have been reaccelerated by turbulence generated by the sloshing of the cool core gas. We present a high-resolution MHD simulation of gas sloshing in a galaxy cluster coupled with subgrid simulations of relativistic electron acceleration to test this hypothesis. Our simulation shows that the sloshing motions generate turbulence on the order of δv ∼ 50-200 km s –1 on spatial scales of ∼50-100 kpc and below in the cool core region within the envelope of the sloshing cold fronts, whereas outside the cold fronts, there is negligible turbulence. This turbulence is potentially strong enough to reaccelerate relativistic electron seeds (with initial γ ∼ 100-500) to γ ∼ 10 4 via damping of magnetosonic waves and non-resonant compression. The seed electrons could remain in the cluster from, e.g., past active galactic nucleus activity. In combination with the magnetic field amplification in the core, these electrons then produce diffuse radio synchrotron emission that is coincident with the region bounded by the sloshing cold fronts, as indeed observed in X-rays and the radio. The result holds for different initial spatial distributions of pre-existing relativistic electrons. The power and the steep spectral index (α ≈ 1-2) of the resulting radio emission are consistent with observations of mini-halos, though the theoretical uncertainties of the acceleration mechanisms are high. We also produce simulated maps of inverse-Compton hard X-ray emission from the same population of relativistic electrons.

A peculiar distribution of radial velocities of faint radio-galaxies with 13.0<=msub(corr)<=15.5

International Nuclear Information System (INIS)

Karoji, H.; Nottale, L.; Vigier, J.-P.

1976-01-01

A sample of 41 radio-galaxies with 13.0<=msub(corr)<=15.5 has been analyzed to test the angular redshift anisotropy discovered on Sc I galaxies by Rubin, Rubin and Ford (1973). The sample does not present their anisotropy but contains an even more curious distribution of radial velocities which suggests that the Rubin-Ford effect results from an anomalous redshift of light when it travels through clusters of galaxies. (Auth.)

An optical and near-infrared polarization survey of Seyfert and broad-line radio galaxies. Pt. 2

International Nuclear Information System (INIS)

Brindle, C.; Hough, J.H.; Bailey, J.A.; Axon, D.J.; Ward, M.J.; McLean, I.S.

1990-01-01

We discuss the wavelength dependence (0.44-2.2 μm) of polarization of the sample of 71 Seyfert and three broad-line radio galaxies presented in a previous paper. For four galaxies, 3A 0557-383, Fairall 51, IC 4392A and NGC 3783, we also present spectropolarimetry covering the wavelength range of 0.4-0.6 μm. (author)

Pair-Matching of Radio-Loud and Radio-Quiet AGNs

Energy Technology Data Exchange (ETDEWEB)

Kozieł-Wierzbowska, Dorota [Astronomical Observatory, Jagiellonian University, Krakow (Poland); Stasińska, Grażyna [LUTH, Observatoire de Paris, Centre National de la Recherche Scientifique, Université Paris Diderot, Meudon (France); Vale Asari, Natalia [Departamento de Física–CFM, Universidade Federal de Santa Catarina, Florianópolis (Brazil); Sikora, Marek [Nicolaus Copernicus Astronomical Center, Warsaw (Poland); Goettems, Elisa [Departamento de Física–CFM, Universidade Federal de Santa Catarina, Florianópolis (Brazil); Wójtowicz, Anna, E-mail: dorota.koziel@uj.edu.pl [Astronomical Observatory, Jagiellonian University, Krakow (Poland)

2017-11-07

Active galactic nuclei (AGNs) are known to cover an extremely broad range of radio luminosities and the spread of their radio-loudness is very large at any value of the Eddington ratio. This implies very diverse jet production efficiencies which can result from the spread of the black hole spins and magnetic fluxes. Magnetic fluxes can be developed stochastically in the innermost zones of accretion discs, or can be advected to the central regions prior to the AGN phase. In the latter case there could be systematic differences between the properties of galaxies hosting radio-loud (RL) and radio-quiet (RQ) AGNs. In the former case the differences should be negligible for objects having the same Eddington ratio. To study the problem we decided to conduct a comparison study of host galaxy properties of RL and RQ AGNs. In this study we selected type II AGNs from SDSS spectroscopic catalogs. Our RL AGN sample consists of the AGNs appearing in the Best and Heckman (2012) catalog of radio galaxies. To compare RL and RQ galaxies that have the same AGN parameters we matched the galaxies in black hole mass, Eddington ratio and redshift. We compared several properties of the host galaxies in these two groups of objects like galaxy mass, color, concentration index, line widths, morphological type and interaction signatures. We found that in the studied group RL AGNs are preferentially hosted by elliptical galaxies while RQ ones are hosted by galaxies of later type. We also found that the fraction of interacting galaxies is the same in both groups of AGNs. These results suggest that the magnetic flux in RL AGNs is advected to the nucleus prior to the AGN phase.

THE 1.6 μm NEAR-INFRARED NUCLEI OF 3C RADIO GALAXIES: JETS, THERMAL EMISSION, OR SCATTERED LIGHT?

International Nuclear Information System (INIS)

Baldi, Ranieri D.; Chiaberge, Marco; Sparks, William; Macchetto, F. Duccio; Capetti, Alessandro; O'Dea, Christopher P.; Axon, David J.; Baum, Stefi A.; Quillen, Alice C.

2010-01-01

Using HST NICMOS 2 observations we have measured 1.6 μm near-infrared nuclear luminosities of 100 3CR radio galaxies with z < 0.3, by modeling and subtracting the extended emission from the host galaxy. We performed a multiwavelength statistical analysis (including optical and radio data) of the properties of the nuclei following classification of the objects into FR I and FR II, and low-ionization galaxies (LIGs), high-ionization galaxies (HIGs), and broad-line objects (BLOs) using the radio morphology and optical spectra, respectively. The correlations among near-infrared, optical, and radio nuclear luminosity support the idea that the near-infrared nuclear emission of FR Is has a non-thermal origin. Despite the difference in radio morphology, the multiwavelength properties of FR II LIG nuclei are statistically indistinguishable from those of FR Is, an indication of a common structure of the central engine. All BLOs show an unresolved near-infrared nucleus and a large near-infrared excess with respect to FR II LIGs and FR Is of equal radio core luminosity. This requires the presence of an additional (and dominant) component other than the non-thermal light. Considering the shape of their spectral energy distribution, we ascribe the origin of their near-infrared light to hot circumnuclear dust. A near-infrared excess is also found in HIGs, but their nuclei are substantially fainter than those of BLO. This result indicates that substantial obscuration along the line of sight to the nuclei is still present at 1.6 μm. Nonetheless, HIG nuclei cannot simply be explained in terms of dust obscuration: a significant contribution from light reflected in a circumnuclear scattering region is needed to account for their multiwavelength properties.

A simulation-based analytic model of radio galaxies

Science.gov (United States)

Hardcastle, M. J.

2018-04-01

I derive and discuss a simple semi-analytical model of the evolution of powerful radio galaxies which is not based on assumptions of self-similar growth, but rather implements some insights about the dynamics and energetics of these systems derived from numerical simulations, and can be applied to arbitrary pressure/density profiles of the host environment. The model can qualitatively and quantitatively reproduce the source dynamics and synchrotron light curves derived from numerical modelling. Approximate corrections for radiative and adiabatic losses allow it to predict the evolution of radio spectral index and of inverse-Compton emission both for active and `remnant' sources after the jet has turned off. Code to implement the model is publicly available. Using a standard model with a light relativistic (electron-positron) jet, subequipartition magnetic fields, and a range of realistic group/cluster environments, I simulate populations of sources and show that the model can reproduce the range of properties of powerful radio sources as well as observed trends in the relationship between jet power and radio luminosity, and predicts their dependence on redshift and environment. I show that the distribution of source lifetimes has a significant effect on both the source length distribution and the fraction of remnant sources expected in observations, and so can in principle be constrained by observations. The remnant fraction is expected to be low even at low redshift and low observing frequency due to the rapid luminosity evolution of remnants, and to tend rapidly to zero at high redshift due to inverse-Compton losses.

THE SDSS-IV EXTENDED BARYON OSCILLATION SPECTROSCOPIC SURVEY: LUMINOUS RED GALAXY TARGET SELECTION

Energy Technology Data Exchange (ETDEWEB)

Prakash, Abhishek; Licquia, Timothy C.; Newman, Jeffrey A.; Rao, Sandhya M. [PITT PACC, Department of Physics and Astronomy, University of Pittsburgh, Pittsburgh, PA 15260 (United States); Ross, Ashley J. [Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH 43210 (United States); Myers, Adam D. [Department of Physics and Astronomy, University of Wyoming, Laramie, WY 82071 (United States); Dawson, Kyle S.; Bautista, Julian E.; Brownstein, Joel R. [Department of Physics and Astronomy, University of Utah, Salt Lake City, UT 84112 (United States); Kneib, Jean-Paul [Laboratoire d’Astrophysique, Ecole Polytechnique Fédérale de Lausanne Observatoire de Sauverny, 1290 Versoix (Switzerland); Percival, Will J. [Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Portsmouth, PO1 3FX (United Kingdom); Comparat, Johan [Instituto de Física Teórica, (UAM/CSIC), Universidad Autónoma de Madrid, Cantoblanco, E-28049 Madrid (Spain); Tinker, Jeremy L. [Center for Cosmology and Particle Physics, Department of Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Schlegel, David J. [Lawrence Berkeley National Laboratory, One Cyclotron Road, Berkeley, CA 94720 (United States); Tojeiro, Rita [School of Physics and Astronomy, St Andrews, KY16 9SS (United Kingdom); Ho, Shirley; Lang, Dustin [Bruce and Astrid McWilliams Center for Cosmology, Department of Physics, Carnegie Mellon University, 5000 Forbes Avenue, Pittsburgh, PA 15213 (United States); McBride, Cameron K. [Harvard-Smithsonian Center for Astrophysics, Harvard University, 60 Garden Street, Cambridge, MA 02138 (United States); Zhu, Guangtun Ben, E-mail: abp15@pitt.edu [Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD 21218 (United States); and others

2016-06-01

We describe the algorithm used to select the luminous red galaxy (LRG) sample for the extended Baryon Oscillation Spectroscopic Survey (eBOSS) of the Sloan Digital Sky Survey IV (SDSS-IV) using photometric data from both the SDSS and the Wide-field Infrared Survey Explorer . LRG targets are required to meet a set of color selection criteria and have z -band and i -band MODEL magnitudes z < 19.95 and 19.9 < i < 21.8, respectively. Our algorithm selects roughly 50 LRG targets per square degree, the great majority of which lie in the redshift range 0.6 < z < 1.0 (median redshift 0.71). We demonstrate that our methods are highly effective at eliminating stellar contamination and lower-redshift galaxies. We perform a number of tests using spectroscopic data from SDSS-III/BOSS ancillary programs to determine the redshift reliability of our target selection and its ability to meet the science requirements of eBOSS. The SDSS spectra are of high enough signal-to-noise ratio that at least ∼89% of the target sample yields secure redshift measurements. We also present tests of the uniformity and homogeneity of the sample, demonstrating that it should be clean enough for studies of the large-scale structure of the universe at higher redshifts than SDSS-III/BOSS LRGs reached.

A fast radio burst in the direction of the Carina dwarf spheroidal galaxy

OpenAIRE

Ravi, V.; Shannon, R. M.; Jameson, A.

2014-01-01

We report the real-time discovery of a fast radio burst (FRB 131104) with the Parkes radio telescope in a targeted observation of the Carina dwarf spheroidal galaxy. The dispersion measure of the burst is 779 cm$^{-3}$ pc, exceeding predictions for the maximum line-of-sight Galactic contribution by a factor of 11. The temporal structure of the burst is characterized by an exponential scattering tail with a timescale of 2.0$^{+0.8}_{-0.5}$ ms at 1582 MHz that scales as frequency to the power $...

Radio Source Morphology: 'nature or nuture'?

Science.gov (United States)

Banfield, Julie; Emonts, Bjorn; O'Sullivan, Shane

2012-10-01

Radio sources, emanating from supermassive black-holes in the centres of active galaxies, display a large variety of morphological properties. It is a long-standing debate to what extent the differences between various types of radio sources are due to intrinsic properties of the central engine (`nature') or due to the properties of the interstellar medium that surrounds the central engine and host galaxy (`nurture'). Settling this `nature vs. nurture' debate for nearby radio galaxies, which can be studied in great detail, is vital for understanding the properties and evolution of radio galaxies throughout the Universe. We propose to observe the radio galaxy NGC 612 where previous observations have detected the presence of a large-scale HI bridge between the host galaxy and a nearby galaxy NGC 619. We request a total of 13 hrs in the 750m array-configuration to determine whether or not the 100 kpc-scale radio source morphology is directly related to the intergalactic distribution of neutral hydrogen gas.

Theoretical parameters of powerful radio galaxies. II. Generation of MHD turbulence by collisionless shock waves

International Nuclear Information System (INIS)

Baryshev, Yu.V.; Morozov, V.N.

1988-01-01

It is shown that MHD turbulence can be generated by collisionless shock waves due to anisotropy of the pressure behind the front of the reverse sock at the hot spot of a powerful radio galaxy. The energy density of the MHD turbulence generated behind the shock front is estimated. Analysis of the theoretical studies and experimental data on collisionless shock waves in the solar wind indicates that an important part is played by streams of ions reflected by the shock fronts, the streams generating plasma and MHD turbulence in the region ahead of the front. The extension of these ideas to shock waves in powerful radio galaxies must be made with care because of the great difference between the parameters of the shock waves in the two cases

Exploratory X-ray monitoring of luminous radio-quiet quasars at high redshift: Initial results

Energy Technology Data Exchange (ETDEWEB)

Shemmer, Ohad; Stein, Matthew S. [Department of Physics, University of North Texas, Denton, TX 76203 (United States); Brandt, W. N.; Schneider, Donald P. [Department of Astronomy and Astrophysics, The Pennsylvania State University, University Park, PA 16802 (United States); Paolillo, Maurizio [Dipartimento di Scienze Fisiche, Università Federico II di Napoli, via Cinthia 6, I-80126 Napoli (Italy); Kaspi, Shai [School of Physics and Astronomy and the Wise Observatory, Tel Aviv University, Tel Aviv 69978 (Israel); Vignali, Cristian [Dipartimento di Astronomia, Università degli studi di Bologna, via Ranzani 1, I-40127 Bologna (Italy); Lira, Paulina [Departamento de Astronomia, Universidad de Chile, Camino del Observatorio 1515, Santiago (Chile); Gibson, Robert R., E-mail: ohad@unt.edu [Department of Astronomy, University of Washington, Box 351580, Seattle, WA 98195 (United States)

2014-03-10

We present initial results from an exploratory X-ray monitoring project of two groups of comparably luminous radio-quiet quasars (RQQs). The first consists of four sources at 4.10 ≤ z ≤ 4.35, monitored by Chandra, and the second is a comparison sample of three sources at 1.33 ≤ z ≤ 2.74, monitored by Swift. Together with archival X-ray data, the total rest-frame temporal baseline spans ∼2-4 yr and ∼5-13 yr for the first and second group, respectively. Six of these sources show significant X-ray variability over rest-frame timescales of ∼10{sup 2}-10{sup 3} days; three of these also show significant X-ray variability on rest-frame timescales of ∼1-10 days. The X-ray variability properties of our variable sources are similar to those exhibited by nearby and far less luminous active galactic nuclei (AGNs). While we do not directly detect a trend of increasing X-ray variability with redshift, we do confirm previous reports of luminous AGNs exhibiting X-ray variability above that expected from their luminosities, based on simplistic extrapolation from lower luminosity sources. This result may be attributed to luminous sources at the highest redshifts having relatively high accretion rates. Complementary UV-optical monitoring of our sources shows that variations in their optical-X-ray spectral energy distribution are dominated by the X-ray variations. We confirm previous reports of X-ray spectral variations in one of our sources, HS 1700+6416, but do not detect such variations in any of our other sources in spite of X-ray flux variations of up to a factor of ∼4. This project is designed to provide a basic assessment of the X-ray variability properties of RQQs at the highest accessible redshifts that will serve as a benchmark for more systematic monitoring of such sources with future X-ray missions.

On fitting the full spectrum of luminous red galaxies by using ULySS and STARLIGHT

International Nuclear Information System (INIS)

Liu Gao-Chao; Lu You-Jun; Chen Xue-Lei; Du Wei; Zhao Yong-Heng

2013-01-01

We select a sample of quiescent luminous red galaxies (LRGs) from the Sloan Digital Sky Survey Data Release 7 with a high signal-to-noise ratio (S/N) to study the consistency of fitting the full spectrum by using different packages, mainly, ULySS and STARLIGHT. The spectrum of each galaxy in the sample is fitted by the full spectrum fitting packages ULySS and STARLIGHT. We find: (1) for spectra with higher S/Ns, the ages of stellar populations obtained from ULySS are slightly older than those from STARLIGHT, and metallicities derived from ULySS are slightly richer than those from STARLIGHT. In general, both packages can give roughly consistent fitting results. (2) For low S/N spectra, it is possible that the fitting by ULySS can become trapped at some local minimum in the parameter space during execution and thus may give unreliable results, but STARLIGHT can still give reliable results. Based on the fitting results of LRGs, we further analyze their star formation history and the relation between their age and velocity dispersion, and find that they agree well with conclusions from previous works

Neighbours of our galaxy

International Nuclear Information System (INIS)

Wielebinski, R.

1982-01-01

Large telescope and radio-astronomy bring remote regions of the universe into view. Radio waves are emitted by all celestial objects. Precise examination of our own galaxy, the Milky Way, is useful for investigating more remote objects. Some of the remote galaxies are noteworthy, because they emit up to 1,000 times more radio waves than their neighbours. Centaurus A is an example of such an active galaxy. (orig.)

NEW NEUTRINO MASS BOUNDS FROM SDSS-III DATA RELEASE 8 PHOTOMETRIC LUMINOUS GALAXIES

Energy Technology Data Exchange (ETDEWEB)

De Putter, Roland [ICC, University of Barcelona (IEEC-UB), Marti i Franques 1, E-08028 Barcelona (Spain); Mena, Olga; Giusarma, Elena [Instituto de Fisica Corpuscular, University of Valencia-CSIC (Spain); Ho, Shirley; Seo, Hee-Jong; White, Martin; Ross, Nicholas P. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Cuesta, Antonio [Yale University, New Haven, CT (United States); Ross, Ashley J.; Percival, Will J. [Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom); Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Elena; Malanushenko, Viktor; Oravetz, Daniel; Pan, Kaike; Shelden, Alaina; Simmons, Audrey [Apache Point Observatory, P.O. Box 59, Sunspot, NM 88349-0059 (United States); Kirkby, David [Department of Physics and Astronomy, University of California, Irvine, CA 92697 (United States); Schneider, Donald P. [Department of Astronomy and Astrophysics, Pennsylvania State University, University Park, PA 16802 (United States); and others

2012-12-10

We present neutrino mass bounds using 900,000 luminous galaxies with photometric redshifts measured from Sloan Digital Sky Survey III Data Release 8. The galaxies have photometric redshifts between z = 0.45 and z = 0.65 and cover 10,000 deg{sup 2}, thus probing a volume of 3 h {sup -3} Gpc{sup 3} and enabling tight constraints to be derived on the amount of dark matter in the form of massive neutrinos. A new bound on the sum of neutrino masses {Sigma}m{sub {nu}} < 0.27 eV, at the 95% confidence level (CL), is obtained after combining our sample of galaxies, which we call ''CMASS'', with Wilkinson Microwave Anisotropy Probe (WMAP) seven-year cosmic microwave background data and the most recent measurement of the Hubble parameter from the Hubble Space Telescope (HST). This constraint is obtained with a conservative multipole range of 30 < l < 200 in order to minimize nonlinearities, and a free bias parameter in each of the four redshift bins. We study the impact of assuming this linear galaxy bias model using mock catalogs and find that this model causes a small ({approx}1{sigma}-1.5{sigma}) bias in {Omega}{sub DM} h {sup 2}. For this reason, we also quote neutrino bounds based on a conservative galaxy bias model containing additional, shot-noise-like free parameters. In this conservative case, the bounds are significantly weakened, e.g., {Sigma}m{sub {nu}} < 0.38 eV (95% CL) for WMAP+HST+CMASS (l{sub max} = 200). We also study the dependence of the neutrino bound on the multipole range (l{sub max} = 150 versus l{sub max} = 200) and on which combination of data sets is included as a prior. The addition of supernova and/or baryon acoustic oscillation data does not significantly improve the neutrino mass bound once the HST prior is included. A companion paper describes the construction of the angular power spectra in detail and derives constraints on a general cosmological model, including the dark energy equation of state w and the spatial

H α IMAGING OF NEARBY SEYFERT HOST GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Theios, Rachel L.; Malkan, Matthew A. [Department of Physics and Astronomy, University of California, Los Angeles, 430 Portola Plaza, Los Angeles, CA 90095 (United States); Ross, Nathaniel R., E-mail: rtheios@astro.caltech.edu [Raytheon Space and Airborne Systems, 2000 E El Segundo Boulevard, El Segundo, CA 90245 (United States)

2016-05-01

We used narrowband (Δ λ = 70 Å) interference filters with the CCD imaging camera on the Nickel 1.0 m telescope at Lick Observatory to observe 31 nearby ( z < 0.03) Seyfert galaxies in the 12 μ m active galaxy sample. We obtained pure emission-line images of each galaxy, which reach down to a flux limit of 7.3 × 10{sup −15} erg cm{sup −2} s{sup −1} arcsec{sup −2}, and corrected these images for [N ii] emission and extinction. We separated the H α emission line of the “nucleus” (central 100–1000 pc) from that of the host galaxy. The extended H α emission is expected to be powered by newly formed hot stars, and indeed correlates well with other indicators of current star formation rates (SFRs) in these galaxies: extended 7.7 μ m polycyclic aromatic hydrocarbon, total far-infrared, and radio luminosity. Relative to what would be expected from recent star formation, there is a 0.8 dex excess of radio emission in our Seyfert galaxies. The H α luminosity we measured in the centers of our galaxies is dominated by the active galactic nucleus (AGN), and is linearly correlated with the hard X-ray luminosity. There is, however, an upward offset of 1 dex in this correlation for the Seyfert 1s, because their nuclear H α emission includes a strong additional contribution from the broad-line region. We found a correlation between SFR and AGN luminosity. In spite of selection effects, we concluded that the absence of bright Seyfert nuclei in galaxies with low SFRs is real, albeit only weakly significant. Finally, we used our measured spatial distributions of H α emission to determine what these Seyfert galaxies would look like when observed through fixed apertures (e.g., a spectroscopic fiber) at high redshifts. We found that although all of these Seyfert galaxies would be detectable emission-line galaxies at any redshift, most of them would appear to be dominated by (>67%) their H ii region emission. Only the most luminous AGNs (log( L {sub Hα}/erg s

LOCAL LUMINOUS INFRARED GALAXIES. II. ACTIVE GALACTIC NUCLEUS ACTIVITY FROM SPITZER/INFRARED SPECTROGRAPH SPECTRA

Energy Technology Data Exchange (ETDEWEB)

Alonso-Herrero, Almudena; Pereira-Santaella, Miguel [Centro de Astrobiologia, INTA-CSIC, E-28850 Torrejon de Ardoz, Madrid (Spain); Rieke, George H. [Steward Observatory, University of Arizona, Tucson, AZ 85721 (United States); Rigopoulou, Dimitra [Astrophysics Department, University of Oxford, Oxford OX1 3RH (United Kingdom)

2012-01-01

We quantify the active galactic nucleus (AGN) contribution to the mid-infrared (mid-IR) and the total infrared (IR, 8-1000 {mu}m) emission in a complete volume-limited sample of 53 local luminous infrared galaxies (LIRGs, L{sub IR} = 10{sup 11}-10{sup 12} L{sub Sun }). We decompose the Spitzer Infrared Spectrograph low-resolution 5-38 {mu}m spectra of the LIRGs into AGN and starburst components using clumpy torus models and star-forming galaxy templates, respectively. We find that 50% (25/50) of local LIRGs have an AGN component detected with this method. There is good agreement between these AGN detections through mid-IR spectral decomposition and other AGN indicators, such as the optical spectral class, mid-IR spectral features, and X-ray properties. Taking all the AGN indicators together, the AGN detection rate in the individual nuclei of LIRGs is {approx}62%. The derived AGN bolometric luminosities are in the range L{sub bol}(AGN) = (0.4-50) Multiplication-Sign 10{sup 43} erg s{sup -1}. The AGN bolometric contribution to the IR luminosities of the galaxies is generally small, with 70% of LIRGs having L{sub bol}[AGN]/L{sub IR} {<=} 0.05. Only {approx_equal} 8% of local LIRGs have a significant AGN bolometric contribution L{sub bol}[AGN]/L{sub IR} > 0.25. From the comparison of our results with literature results of ultraluminous infrared galaxies (L{sub IR} = 10{sup 12}-10{sup 13} L{sub Sun }), we confirm that in the local universe the AGN bolometric contribution to the IR luminosity increases with the IR luminosity of the galaxy/system. If we add up the AGN bolometric luminosities we find that AGNs only account for 5%{sub -3%}{sup +8%} of the total IR luminosity produced by local LIRGs (with and without AGN detections). This proves that the bulk of the IR luminosity of local LIRGs is due to star formation activity. Taking the newly determined IR luminosity density of LIRGs in the local universe, we then estimate an AGN IR luminosity density of {Omega}{sup AGN

The most luminous heavily obscured quasars have a high merger fraction: morphological study of wise -selected hot dust-obscured galaxies

Energy Technology Data Exchange (ETDEWEB)

Fan, Lulu; Gao, Ying; Zhang, Dandan; Jiang, Xiaoming; Wu, Qiaoqian; Yang, Jun; Li, Zhao [Shandong Provincial Key Lab of Optical Astronomy and Solar-Terrestrial Environment, Institute of Space Science, Shandong University, Weihai 264209 (China); Han, Yunkun [Yunnan Observatories, Chinese Academy of Sciences, Kunming 650011 (China); Fang, Guanwen, E-mail: llfan@sdu.edu.cn, E-mail: hanyk@ynao.ac.cn [Institute for Astronomy and History of Science and Technology, Dali University, Dali 671003 (China)

2016-05-10

Previous studies have shown that Wide-field Infrared Survey Explorer -selected hyperluminous, hot dust-obscured galaxies (Hot DOGs) are powered by highly dust-obscured, possibly Compton-thick active galactic nuclei (AGNs). High obscuration provides us a good chance to study the host morphology of the most luminous AGNs directly. We analyze the host morphology of 18 Hot DOGs at z ∼ 3 using Hubble Space Telescope /WFC3 imaging. We find that Hot DOGs have a high merger fraction (62 ± 14%). By fitting the surface brightness profiles, we find that the distribution of Sérsic indices in our Hot DOG sample peaks around 2, which suggests that most Hot DOGs have transforming morphologies. We also derive the AGN bolometric luminosity (∼10{sup 14} L {sub ⊙}) of our Hot DOG sample by using IR spectral energy distributions decomposition. The derived merger fraction and AGN bolometric luminosity relation is well consistent with the variability-based model prediction. Both the high merger fraction in an IR-luminous AGN sample and relatively low merger fraction in a UV/optical-selected, unobscured AGN sample can be expected in the merger-driven evolutionary model. Finally, we conclude that Hot DOGs are merger-driven and may represent a transit phase during the evolution of massive galaxies, transforming from the dusty starburst-dominated phase to the unobscured QSO phase.

The properties of radio ellipticals

International Nuclear Information System (INIS)

Sparks, W.B.; Disney, M.J.; Rodgers, A.W.

1984-01-01

Optical and additional radio data are presented for the bright galaxies of the Disney and Wall survey (1977 Mon. Not. R. Astron. Soc. 179, 235). These data form the basis of a statistical comparison of the properties of radio elliptical galaxies to radio-quiet ellipticals. The correlations may be explained by the depth of the gravitational potential well in which the galaxy resides governing the circumstances under which an elliptical galaxy rids itself of internally produced gas. (author)

Radio continuum observations of local star-forming galaxies using the Caltech Continuum Backend on the green bank telescope

International Nuclear Information System (INIS)

Rabidoux, Katie; Pisano, D. J.; Kepley, Amanda A.; Johnson, Kelsey E.; Balser, Dana S.

2014-01-01

We observed radio continuum emission in 27 local (D < 70 Mpc) star-forming galaxies with the Robert C. Byrd Green Bank Telescope between 26 GHz and 40 GHz using the Caltech Continuum Backend. We obtained detections for 22 of these galaxies at all four sub-bands and four more marginal detections by taking the average flux across the entire bandwidth. This is the first detection (full or marginal) at these frequencies for 22 of these galaxies. We fit spectral energy distributions (SEDs) for all of the four sub-band detections. For 14 of the galaxies, SEDs were best fit by a combination of thermal free-free and nonthermal synchrotron components. Eight galaxies with four sub-band detections had steep spectra that were only fit by a single nonthermal component. Using these fits, we calculated supernova rates, total number of equivalent O stars, and star formation rates within each ∼23'' beam. For unresolved galaxies, these physical properties characterize the galaxies' recent star formation on a global scale. We confirm that the radio-far-infrared correlation holds for the unresolved galaxies' total 33 GHz flux regardless of their thermal fractions, though the scatter on this correlation is larger than that at 1.4 GHz. In addition, we found that for the unresolved galaxies, there is an inverse relationship between the ratio of 33 GHz flux to total far-infrared flux and the steepness of the galaxy's spectral index between 1.4 GHz and 33 GHz. This relationship could be an indicator of the timescale of the observed episode of star formation.

Radio continuum observations of the quasar-galaxy pair 3C 232-NGC 3067

International Nuclear Information System (INIS)

Haxthausen, E.; Carilli, C.; Vangorkom, J.H.

1990-01-01

The quasar-galaxy pair 3C 232-NGC 3067 is well known to show absorption by gas associated with the foreground galaxy against the background quasar (see Stocke et al. this volume). Observations by Carilli, van Gorkom, and Stocke (Nature 338, 134, 1989) found that the absorbing gas is located in a long tail of gas which extends from the galaxy toward the quasar and beyond (in projection). Though the HI observations of NGC 3067 indicate that the galaxy has been severely disturbed, there is no obvious candidate in the field which could cause such a disturbance, leading to the conclusion that the system has undergone a recent merger. The radio continuum observations of this system were designed to study the nature of this highly disturbed galaxy. New continuum observations confirm the notion that NGC 3067 is a highly disturbed system, and, in particular, the notion that the western half of the galaxy extends only 1/2 as far in radius as the eastern half. This disturbance must have occurred recently, since the galactic rotation would smooth out the observed asymmetry in about 10(exp 8) years. Researchers are left with the problem that there are no obvious candidates which could have caused such a disturbance

Rise of the Titans: A Dusty, Hyper-luminous “870 μm Riser” Galaxy at z ˜ 6

Science.gov (United States)

Riechers, Dominik A.; Leung, T. K. Daisy; Ivison, Rob J.; Pérez-Fournon, Ismael; Lewis, Alexander J. R.; Marques-Chaves, Rui; Oteo, Iván; Clements, Dave L.; Cooray, Asantha; Greenslade, Josh; Martínez-Navajas, Paloma; Oliver, Seb; Rigopoulou, Dimitra; Scott, Douglas; Weiss, Axel

2017-11-01

We report the detection of ADFS-27, a dusty, starbursting major merger at a redshift of z = 5.655, using the Atacama Large Millimeter/submillimeter Array (ALMA). ADFS-27 was selected from Herschel/Spectral and Photometric Imaging Receiver (SPIRE) and APEX/LABOCA data as an extremely red “870 μm riser” (I.e., {S}250μ {{m}}< {S}350μ {{m}}< {S}500μ {{m}}< {S}870μ {{m}}), demonstrating the utility of this technique to identify some of the highest-redshift dusty galaxies. A scan of the 3 mm atmospheric window with ALMA yields detections of CO(J = 5 → 4) and CO(J = 6 → 5) emission, and a tentative detection of H2O(211 → 202) emission, which provides an unambiguous redshift measurement. The strength of the CO lines implies a large molecular gas reservoir with a mass of M gas = 2.5 × 1011 ({α }{CO}/0.8)(0.39/{r}51) M ⊙, sufficient to maintain its ˜2400 M ⊙ yr-1 starburst for at least ˜100 Myr. The 870 μm dust continuum emission is resolved into two components, 1.8 and 2.1 kpc in diameter, separated by 9.0 kpc, with comparable dust luminosities, suggesting an ongoing major merger. The infrared luminosity of L IR ≃ 2.4 × 1013 L ⊙ implies that this system represents a binary hyper-luminous infrared galaxy, the most distant of its kind presently known. This also implies star formation rate surface densities of {{{Σ }}}{SFR}=730 and 750 M ⊙ yr-1 kpc2, consistent with a binary “maximum starburst.” The discovery of this rare system is consistent with a significantly higher space density than previously thought for the most luminous dusty starbursts within the first billion years of cosmic time, easing tensions regarding the space densities of z ˜ 6 quasars and massive quiescent galaxies at z ≳ 3.

The hot and cold interstellar matter of early type galaxies and their radio emission

International Nuclear Information System (INIS)

Kim, Dongwoo; Fabbiano, G.

1990-01-01

Over the last few years, the knowledge of the interstellar matter (ISM) of early type galaxies has increased dramatically. Many early type galaxies are now known to have ISM in three different phases: cold (neutral hydrogen (HI), dust and molecular material), warm (ionized) and hot (S-ray emitting) gas. Early type galaxies have smaller masses of cold ISM (10 to the 7th power - 10 to the 8th power solar mass; Jura et al. 1987) than later type spiral galaxies, while they have far more hot gas (10 to the 9th power - 10 to the tenth power solar mass; Forman et al. 1985, Canizares et al. 1987). In order to understand the relationship between the different phases of the ISM and the role of the ISM in fueling radio continuum sources and star formation, researchers compared observational data from a wide range of wavelengths

Detection of an apparent, distant cluster of galaxies associated with the radio-tail QSO 3C 275.1

International Nuclear Information System (INIS)

Hintzen, P.; Boeshaar, G.O.; Scott, J.S.

1981-01-01

Based on the suggestion that QSOs with distorted radio structures are likely to be members of clusters of galaxies (Hintzen and Scott), we have obtained deep direct observations of the fields containing 3C 270.1 and 3C 275.1, the most reliably substantiated cases of wide-angle radio tails associated with QSOs. Our 75'' square field centered on 3C 275.1 (z = 0.557) contains over three-dozen objects, many of which are nonstellar, between m/sub R/ = 19.8 and m/sub R/ = 23.5. The quasar itself lies at the center of an illiptical nebulosity. The size of this nebulosity and the magnitude distribution of the surrounding objects are consistent with the interpretation that the QSO is the nucleus of a giant elliptical galaxy which is a member of a cluster of galaxies at zapprox.0.55. Our observations of 3C 270.1 (z = 1.519) show no definitive evidence of an associated cluster of galaxies, which is consistent with the cosmological interpretation of QSO redshifts

LOFAR reveals the giant: a low-frequency radio continuum study of the outflow in the nearby FR I radio galaxy 3C 31

Science.gov (United States)

Heesen, V.; Croston, J. H.; Morganti, R.; Hardcastle, M. J.; Stewart, A. J.; Best, P. N.; Broderick, J. W.; Brüggen, M.; Brunetti, G.; ChyŻy, K. T.; Harwood, J. J.; Haverkorn, M.; Hess, K. M.; Intema, H. T.; Jamrozy, M.; Kunert-Bajraszewska, M.; McKean, J. P.; Orrú, E.; Röttgering, H. J. A.; Shimwell, T. W.; Shulevski, A.; White, G. J.; Wilcots, E. M.; Williams, W. L.

2018-03-01

We present a deep, low-frequency radio continuum study of the nearby Fanaroff-Riley class I (FR I) radio galaxy 3C 31 using a combination of LOw Frequency ARray (LOFAR; 30-85 and 115-178 MHz), Very Large Array (VLA; 290-420 MHz), Westerbork Synthesis Radio Telescope (WSRT; 609 MHz) and Giant Metre Radio Telescope (GMRT; 615 MHz) observations. Our new LOFAR 145-MHz map shows that 3C 31 has a largest physical size of 1.1 Mpc in projection, which means 3C 31 now falls in the class of giant radio galaxies. We model the radio continuum intensities with advective cosmic ray transport, evolving the cosmic ray electron population and magnetic field strength in the tails as functions of distance to the nucleus. We find that if there is no in situ particle acceleration in the tails, then decelerating flows are required that depend on radius r as v∝rβ (β ≈ -1). This then compensates for the strong adiabatic losses due to the lateral expansion of the tails. We are able to find self-consistent solutions in agreement with the entrainment model of Croston & Hardcastle, where the magnetic field provides ≈1/3 of the pressure needed for equilibrium with the surrounding intracluster medium. We obtain an advective time-scale of ≈190 Myr, which, if equated to the source age, would require an average expansion Mach number M ≈ 5 over the source lifetime. Dynamical arguments suggest that instead either the outer tail material does not represent the oldest jet plasma or else the particle ages are underestimated due to the effects of particle acceleration on large scales.

Average Heating Rate of Hot Atmospheres in Distant Galaxy Clusters by Radio AGN: Evidence for Continuous AGN Heating

Science.gov (United States)

Ma, Cheng-Jiun; McNamara, B.; Nulsen, P.; Schaffer, R.

2011-09-01

X-ray observations of nearby clusters and galaxies have shown that energetic feedback from AGN is heating hot atmospheres and is probably the principal agent that is offsetting cooling flows. Here we examine AGN heating in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. The jet power for each radio source was determined using scaling relations between radio power and cavity power determined for nearby clusters, groups, and galaxies with atmospheres containing X-ray cavities. Roughly 30% of the clusters show radio emission above a flux threshold of 3 mJy within the central 250 kpc that is presumably associated with the brightest cluster galaxy. We find no significant correlation between radio power, hence jet power, and the X-ray luminosities of clusters in redshift range 0.1 -- 0.6. The detection frequency of radio AGN is inconsistent with the presence of strong cooling flows in 400SD, but cannot rule out the presence of weak cooling flows. The average jet power of central radio AGN is approximately 2 10^{44} erg/s. The jet power corresponds to an average heating of approximately 0.2 keV/particle for gas within R_500. Assuming the current AGN heating rate remained constant out to redshifts of about 2, these figures would rise by a factor of two. Our results show that the integrated energy injected from radio AGN outbursts in clusters is statistically significant compared to the excess entropy in hot atmospheres that is required for the breaking of self-similarity in cluster scaling relations. It is not clear that central AGN in 400SD clusters are maintained by a self-regulated feedback loop at the base of a cooling flow. However, they may play a significant role in preventing the development of strong cooling flows at early epochs.

Luminous arcs in clusters of galaxies

International Nuclear Information System (INIS)

Lynds, R.; Petrosian, V.

1989-01-01

Observations are reported of what appears to be a new class of spatially coherent extragalactic features having, in the two most compelling known examples, the following joint properties: location in clusters of galaxies, narrow arclike shape, enormous apparent length, and situation of center of curvature toward both a cD galaxy and the apparent center of gravity of the cluster. The principal available facts concerning the arcs are presented and a variety of interpretations are briefly discussed. The weight of evidence seems to favor the interpretation that these features are images of more distant objects produced by the gravitational field of the intervening clusters. 24 references

Very Luminous X-ray Point Sources in Starburst Galaxies

Science.gov (United States)

Colbert, E.; Heckman, T.; Ptak, A.; Weaver, K. A.; Strickland, D.

Extranuclear X-ray point sources in external galaxies with luminosities above 1039.0 erg/s are quite common in elliptical, disk and dwarf galaxies, with an average of ~ 0.5 and dwarf galaxies, with an average of ~0.5 sources per galaxy. These objects may be a new class of object, perhaps accreting intermediate-mass black holes, or beamed stellar mass black hole binaries. Starburst galaxies tend to have a larger number of these intermediate-luminosity X-ray objects (IXOs), as well as a large number of lower-luminosity (1037 - 1039 erg/s) point sources. These point sources dominate the total hard X-ray emission in starburst galaxies. We present a review of both types of objects and discuss possible schemes for their formation.

The AGN Population in Nearby Galaxies

International Nuclear Information System (INIS)

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 overall radio detection rate of 54% (22% of all bright nearby galaxies) and we estimate that at least ∼50% (∼20% of all bright nearby galaxies) are true AGN. By comparing the radio luminosity function of the LINERs, composite LINER/Hll and Seyferts galaxies in the Palomar sample with those of selected moderate-redshift AGN, we fhd that our sources naturally extend the radio luminosity function of powerful AGN down to powers of about 10 times that of Sgr A*

ACOUSTIC SCALE FROM THE ANGULAR POWER SPECTRA OF SDSS-III DR8 PHOTOMETRIC LUMINOUS GALAXIES

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Seo, Hee-Jong [Berkeley Center for Cosmological Physics, LBL and Department of Physics, University of California, Berkeley, CA 94720 (United States); Ho, Shirley; White, Martin; Reid, Beth; Schlegel, David J. [Lawrence Berkeley National Laboratory, 1 Cyclotron Road, Berkeley, CA 94720 (United States); Cuesta, Antonio J.; Padmanabhan, Nikhil [Yale Center for Astronomy and Astrophysics, Yale University, New Haven, CT 06511 (United States); Ross, Ashley J.; Percival, Will J.; Nichol, Robert C. [Institute of Cosmology and Gravitation, Dennis Sciama Building, University of Portsmouth, Portsmouth PO1 3FX (United Kingdom); Saito, Shun [Department of Astronomy, 601 Campbell Hall, University of California at Berkeley, Berkeley, CA 94720 (United States); De Putter, Roland [Instituto de Fisica Corpuscular, Valencia (Spain); Eisenstein, Daniel J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 20, Cambridge, MA 02138 (United States); Xu Xiaoying; Skibba, Ramin [Steward Observatory, University of Arizona, 933 North Cherry Avenue, Tucson, AZ 85721 (United States); Schneider, Donald P. [Institute for Gravitation and the Cosmos, The Pennsylvania State University, University Park, PA 16802 (United States); Verde, Licia [Institucio Catalana de Recerca i Estudis Avancats, Barcelona (Spain); Bizyaev, Dmitry; Brewington, Howard; Brinkmann, J. [Apache Point Observatory, 2001 Apache Point Road, Sunspot, NM 88349 (United States); and others

2012-12-10

We measure the acoustic scale from the angular power spectra of the Sloan Digital Sky Survey III (SDSS-III) Data Release 8 imaging catalog that includes 872, 921 galaxies over {approx}10,000 deg{sup 2} between 0.45 < z < 0.65. The extensive spectroscopic training set of the Baryon Oscillation Spectroscopic Survey luminous galaxies allows precise estimates of the true redshift distributions of galaxies in our imaging catalog. Utilizing the redshift distribution information, we build templates and fit to the power spectra of the data, which are measured in our companion paper, to derive the location of Baryon acoustic oscillations (BAOs) while marginalizing over many free parameters to exclude nearly all of the non-BAO signal. We derive the ratio of the angular diameter distance to the sound horizon scale D{sub A} (z)/r{sub s} = 9.212{sup +0.416}{sub -{sub 0.404}} at z = 0.54, and therefore D{sub A} (z) = 1411 {+-} 65 Mpc at z = 0.54; the result is fairly independent of assumptions on the underlying cosmology. Our measurement of angular diameter distance D{sub A} (z) is 1.4{sigma} higher than what is expected for the concordance {Lambda}CDM, in accordance to the trend of other spectroscopic BAO measurements for z {approx}> 0.35. We report constraints on cosmological parameters from our measurement in combination with the WMAP7 data and the previous spectroscopic BAO measurements of SDSS and WiggleZ. We refer to our companion papers (Ho et al.; de Putter et al.) for investigations on information of the full power spectrum.

A NEW TEST OF THE STATISTICAL NATURE OF THE BRIGHTEST CLUSTER GALAXIES

International Nuclear Information System (INIS)

Lin, Yen-Ting; Ostriker, Jeremiah P.; Miller, Christopher J.

2010-01-01

A novel statistic is proposed to examine the hypothesis that all cluster galaxies are drawn from the same luminosity distribution (LD). In such a 'statistical model' of galaxy LD, the brightest cluster galaxies (BCGs) are simply the statistical extreme of the galaxy population. Using a large sample of nearby clusters, we show that BCGs in high luminosity clusters (e.g., L tot ∼> 4 x 10 11 h -2 70 L sun ) are unlikely (probability ≤3 x 10 -4 ) to be drawn from the LD defined by all red cluster galaxies more luminous than M r = -20. On the other hand, BCGs in less luminous clusters are consistent with being the statistical extreme. Applying our method to the second brightest galaxies, we show that they are consistent with being the statistical extreme, which implies that the BCGs are also distinct from non-BCG luminous, red, cluster galaxies. We point out some issues with the interpretation of the classical tests proposed by Tremaine and Richstone (TR) that are designed to examine the statistical nature of BCGs, investigate the robustness of both our statistical test and those of TR against difficulties in photometry of galaxies of large angular size, and discuss the implication of our findings on surveys that use the luminous red galaxies to measure the baryon acoustic oscillation features in the galaxy power spectrum.

The astrophysical consequences of intervening galaxy gas on fast radio bursts

Science.gov (United States)

Prochaska, J. Xavier; Neeleman, Marcel

2018-02-01

We adopt and analyze results on the incidence and physical properties of damped Ly$\\alpha$ systems (DLAs) to predict the astrophysical impact of gas in galaxies on observations of Fast Radio Bursts (FRBs). Three DLA measures form the basis of this analysis: (i) the HI column density distribution, parameterized as a double power-law; (ii) the incidence of DLAs with redshift (derived here), $\\ell(z)=A+B \\arctan(z-C)$ with $A=0.236_{-0.021}^{+0.016}, B=0.168_{-0.017}^{+0.010}, C=2.87_{-0.13}^{+0.17}$ and (iii) the electron density, parameterized as a log-normal deviate with mean $10^{-2.6} cm^{-3}$ and dispersion 0.3dex. Synthesizing these results, we estimate that the average rest-frame dispersion measure from the neutral medium of a single, intersecting galaxy is DM$^{NM}_{DLA}=0.25$ pc/cm^3. Analysis of AlIII and CII* absorption limits the putative warm ionized medium to contribute DM$^{WIM}_{DLA}<20$pc/cm^3. Given the low incidence of DLAs, we find that a population of FRBs at z=2 will incur DM(z=2)=0.01 pc/cm^3 on average, with a 99% c.l. upper bound of 0.22 pc/cm^3. Assuming that turbulence of the ISM in external galaxies is qualitatively similar to our Galaxy, we estimate that the angular broadening of an FRB by intersecting galaxies is negligible ($\\theta<0.1$mas). The temporal broadening is also predicted to be small, $\\tau \\approx 0.3$ms for a z=1 galaxy intersecting a z=2 FRB for an observing frequency of $\

Discovery of a Luminous Radio Transient 460 pc from the Central Supermassive Black Hole in Cygnus A

Energy Technology Data Exchange (ETDEWEB)

Perley, D. A. [Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom); Perley, R. A.; Dhawan, V.; Carilli, C. L., E-mail: d.a.perley@ljmu.ac.uk [National Radio Astronomy Observatory, P.O. Box O, Socorro, NM 87801 (United States)

2017-06-01

We report the appearance of a new radio source at a projected offset of 460 pc from the nucleus of Cygnus A. The flux density of the source (which we designate Cygnus A-2) rose from an upper limit of <0.5 mJy in 1989 to 4 mJy in 2016 ( ν = 8.5 GHz), but is currently not varying by more than a few percent per year. The radio luminosity of the source is comparable to the most luminous known supernovae, it is compact in Very Long Baseline Array observations down to a scale of 4 pc, and it is coincident with a near-infrared point source seen in pre-existing adaptive optics and HST observations. The most likely interpretation of this source is that it represents a secondary supermassive black hole in a close orbit around the Cygnus A primary, though an exotic supernova model cannot be ruled out. The gravitational influence of a secondary SMBH at this location may have played an important role in triggering the rapid accretion that has powered the Cygnus A radio jet over the past 10{sup 7} years.

Star Formation in the Central Regions of Galaxies

Science.gov (United States)

Tsai, Mengchun

2015-08-01

The galactic central region connects the galactic nucleus to the host galaxy. If the central black hole co-evolved with the host galaxies, there should be some evidence left in the central region. We use the environmental properties in the central regions such as star-forming activity, stellar population and molecular abundance to figure out a possible scenario of the evolution of galaxies. In this thesis at first we investigated the properties of the central regions in the host galaxies of active and normal galaxies. We used radio emission around the nuclei of the host galaxies to represent activity of active galactic nuclei (AGNs), and used infrared ray (IR) emission to represent the star-forming activity and stellar population of the host galaxies. We determined that active galaxies have higher stellar masses (SMs) within the central kiloparsec radius than normal galaxies do independent of the Hubble types of the host galaxies; but both active and normal galaxies exhibit similar specific star formation rates (SSFRs). We also discovered that certain AGNs exhibit substantial inner stellar structures in the IR images; most of the AGNs with inner structures are Seyferts, whereas only a few LINERs exhibit inner structures. We note that the AGNs with inner structures show a positive correlation between the radio activity of the AGNs and the SFRs of the host galaxies, but the sources without inner structures show a negative correlation between the radio power and the SFRs. These results might be explained with a scenario of starburst-AGN evolution. In this scenario, AGN activities are triggered following a nuclear starburst; during the evolution, AGN activities are accompanied by SF activity in the inner regions of the host galaxies; at the final stage of the evolution, the AGNs might transform into LINERs, exhibiting weak SF activity in the central regions of the host galaxies. For further investigation about the inner structure, we choose the most nearby and luminous

Galactic radio astronomy

CERN Document Server

Sofue, Yoshiaki

2017-01-01

This book is a concise primer on galactic radio astronomy for undergraduate and graduate students, and provides wide coverage of galactic astronomy and astrophysics such as the physics of interstellar matter and the dynamics and structure of the Milky Way Galaxy and galaxies. Radio astronomy and its technological development have led to significant progress in galactic astronomy and contributed to understanding interstellar matter and galactic structures. The book begins with the fundamental physics of radio-wave radiation, i.e., black body radiation, thermal emission, synchrotron radiation, and HI and molecular line emissions. The author then gives overviews of ingredients of galactic physics, including interstellar matter such as the neutral (HI), molecular hydrogen, and ionized gases, as well as magnetic fields in galaxies. In addition, more advanced topics relevant to the Galaxy and galaxies are also contained here: star formation, supernova remnants, the Galactic Center and black holes, galactic dynamics...

The statistics of radio emission from quasars

International Nuclear Information System (INIS)

Peacock, J.A.; Miller, L.; Longair, M.S.; Edinburgh Univ.

1986-01-01

The radio properties of quasars have traditionally been discussed in terms of the radio-to-optical flux-density ratio R, implying a correlation between emission in these wavebands. It is here shown that, for bright quasars, this apparent correlation is largely due to an abrupt change in the radio properties of the quasar population near absolute magnitude Msub(B)=-24. It is suggested that this change in due to the existence of two classes of quasar with differing host galaxies: a proportion of quasars brighter than Msub(B)approx.=-24 lie in elliptical galaxies and thus generate powerful radio sources, while elliptical galaxies with weaker nuclear quasar components are classified as N-galaxies rather than quasars; quasars fainter than Msub(B)approx.=-24 lie in spiral galaxies and thus are high-luminosity analogues of radio-quiet Seyfert galaxies. (author)

VERY LONG BASELINE ARRAY IMAGING OF PARSEC-SCALE RADIO EMISSIONS IN NEARBY RADIO-QUIET NARROW-LINE SEYFERT 1 GALAXIES

Energy Technology Data Exchange (ETDEWEB)

Doi, Akihiro [The Institute of Space and Astronautical Science, Japan Aerospace Exploration Agency, 3-1-1 Yoshinodai, Chuou-ku, Sagamihara, Kanagawa 252-5210 (Japan); Asada, Keiichi; Inoue, Makoto [Academia Sinica Institute of Astronomy and Astrophysics, P.O. Box 23-141, Taipei 10617, Taiwan (China); Fujisawa, Kenta [The Research Institute of Time Studies, Yamaguchi University, 1677-1 Yoshida, Yamaguchi, Yamaguchi 753-8511 (Japan); Nagai, Hiroshi; Hagiwara, Yoshiaki [National Astronomical Observatory, 2-21-1 Osawa, Mitaka, Tokyo 181-8588 (Japan); Wajima, Kiyoaki, E-mail: akihiro.doi@vsop.isas.jaxa.jp [Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030 (China)

2013-03-01

We conducted Very Long Baseline Array (VLBA) observations of seven nearby narrow-line Seyfert 1 (NLS1) galaxies at 1.7 GHz ({lambda}18 cm) with milliarcsecond resolution. This is the first systematic very long baseline interferometry study focusing on the central parsec-scale regions of radio-quiet NLS1s. Five of the seven were detected at a brightness temperature of {approx}> 5 Multiplication-Sign 10{sup 6} K and contain radio cores with high brightness temperatures of >6 Multiplication-Sign 10{sup 7} K, indicating a nonthermal process driven by jet-producing central engines as in radio-loud NLS1s and other active galactic nucleus classes. VLBA images of MRK 1239, MRK 705, and MRK 766 exhibit parsec-scale jets with clear linear structures. A large portion of the radio power comes from diffuse emission components that are distributed within the nuclear regions ({approx}< 300 pc), which is a common characteristic throughout the observed NLS1s. Jet kinetic powers limited by the Eddington limit may be insufficient to allow the jets to escape to kiloparsec scales for these radio-quiet NLS1s with low-mass black holes of {approx}< 10{sup 7} M {sub Sun }.

Understanding the nature of luminous red galaxies (LRGs): connecting LRGs to central and satellite subhaloes

Science.gov (United States)

Masaki, Shogo; Hikage, Chiaki; Takada, Masahiro; Spergel, David N.; Sugiyama, Naoshi

2013-08-01

We develop a novel abundance matching method to construct a mock catalogue of luminous red galaxies (LRGs) in the Sloan Digital Sky Survey (SDSS), using catalogues of haloes and subhaloes in N-body simulations for a Λ-dominated cold dark matter model. Motivated by observations suggesting that LRGs are passively evolving, massive early-type galaxies with a typical age ≳5 Gyr, we assume that simulated haloes at z = 2 (z2-halo) are progenitors for LRG-host subhaloes observed today, and we label the most tightly bound particles in each progenitor z2-halo as LRG `stars'. We then identify the subhaloes containing these stars to z = 0.3 (SDSS redshift) in descending order of the masses of z2-haloes until the comoving number density of the matched subhaloes becomes comparable to the measured number density of SDSS LRGs, bar{n}_LRG=10^{-4} h^3 Mpc^{-3}. Once the above prescription is determined, our only free parameter is the number density of haloes identified at z = 2 and this parameter is fixed to match the observed number density at z = 0.3. By tracing subsequent merging and assembly histories of each progenitor z2-halo, we can directly compute, from the mock catalogue, the distributions of central and satellite LRGs and their internal motions in each host halo at z = 0.3. While the SDSS LRGs are galaxies selected by the magnitude and colour cuts from the SDSS images and are not necessarily a stellar-mass-selected sample, our mock catalogue reproduces a host of SDSS measurements: the halo occupation distribution for central and satellite LRGs, the projected autocorrelation function of LRGs, the cross-correlation of LRGs with shapes of background galaxies (LRG-galaxy weak lensing) and the non-linear redshift-space distortion effect, the Finger-of-God effect, in the angle-averaged redshift-space power spectrum. The mock catalogue generated based on our method can be used for removing or calibrating systematic errors in the cosmological interpretation of LRG clustering

Multiwavelength observations of Active Galactic Nuclei from the radio to the hard X-rays

Science.gov (United States)

Beuchert, Tobias

2017-07-01

Active Galaxies form a peculiar type of galaxies. Their cores, the so-called "Active Galactic Nuclei" (AGN), are the most persistent luminous objects in the universe. Accretion of several solar masses per year onto black holes of Millions to Billions of solar masses drive the immense energy output of these systems, which can exceed that of the entire galaxy. The compact energy source, however, only measures about one over a Billion times that of the entire galaxy. Subject of my thesis are observations of the two main channels of energy release of selected AGN systems, both of which are encompassed by profound and yet unanswered questions. These channels are on the one hand the pronounced X-ray emission of the hot and compact accreting environment in close vicinity of the black hole, and on the other hand the radio synchrotron emission of magnetically collimated jets that are fed by portions of the accreted matter. These jets also function as effective accelerators and drive the injected matter deep into the intergalactic medium. As the circumnuclear environment of AGN is too compact to be spatially resolved in the X-rays, I show how X-ray spectroscopy can be used to: (1) understand the effects of strong gravity to trace the geometry and physics of the X-ray source and (2) more consistently quantify matter that surrounds and dynamically absorbs our direct line of sight towards the X-ray source. Second, I unveil the valuable information contained in the polarized radio light being emitted from magnetized jet outflows. In contrast to the X-ray emitting region, I am able to spatially resolve the inner parts of the jet of a prominent galaxy with help of the Very Long Baseline Array, a large network of radio telescopes. The resulting polarization maps turn out to be exceptionally promising in answering fundamental questions related to jet physics.

Simulating nonthermal radiation from cluster radio galaxies.

Energy Technology Data Exchange (ETDEWEB)

Tregillis, I. L. (Ian L.); Jones, T. W. (Thomas Walter); Ryu, Dongsu

2004-01-01

We present results from an extensive synthetic observation analysis of numerically-simulated radio galaxy (RG) jets. This analysis is based on the first three-dimensional simulations to treat cosmic ray acceleration and transport self-consistently within a magnetohydrodynamical calculation. We use standard observational techniques to calculate both minimum-energy and inverse-Compton field values for our simulated objects. The latter technique provides meaningful information about the field. Minimum-energy calculations retrieve reasonable field estimates in regions physically close to the minimum-energy partitioning, though the technique is highly susceptible to deviations from the underlying assumptions. We also study the reliability of published rotation measure analysis techniques. We find that gradient alignment statistics accurately reflect the physical situation, and can uncover otherwise hidden information about the source. Furthermore, correlations between rotation measure (RM) and position angle (PA) can be significant even when the RM is completely dominated by an external cluster medium.

A spatially resolved radio spectral index study of the dwarf irregular galaxy NGC 1569

Science.gov (United States)

Westcott, Jonathan; Brinks, Elias; Hindson, Luke; Beswick, Robert; Heesen, Volker

2018-04-01

We study the resolved radio continuum spectral energy distribution of the dwarf irregular galaxy, NGC 1569, on a beam-by-beam basis to isolate and study its spatially resolved radio emission characteristics. Utilizing high-quality NRAO Karl G. Jansky Very Large Array observations that densely sample the 1-34 GHz frequency range, we adopt a Bayesian fitting procedure, where we use H α emission that has not been corrected for extinction as a prior, to produce maps of how the separated thermal emission, non-thermal emission, and non-thermal spectral index vary across NGC 1569's main disc. We find a higher thermal fraction at 1 GHz than is found in spiral galaxies (26^{+2}_{-3} {per cent}) and find an average non-thermal spectral index α = -0.53 ± 0.02, suggesting that a young population of cosmic ray electrons is responsible for the observed non-thermal emission. By comparing our recovered map of the thermal radio emission with literature H α maps, we estimate the total reddening along the line of sight to NGC 1569 to be E(B - V) = 0.49 ± 0.05, which is in good agreement with other literature measurements. Spatial variations in the reddening indicate that a significant portion of the total reddening is due to internal extinction within NGC 1569.

Spitzer mid-IR spectroscopy of powerful 2Jy and 3CRR radio galaxies. II. AGN power indicators and unification

Energy Technology Data Exchange (ETDEWEB)

Dicken, D. [CEA-Saclay, F-91191 Gif-sur-Yvette (France); Tadhunter, C. [University of Sheffield, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Morganti, R. [ASTRON, P.O. Box 2, 7990 AA Dwingeloo (Netherlands); Axon, D.; Robinson, A.; Magagnoli, M. [Rochester Institute of Technology, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States); Kharb, P. [Indian Institute of Astrophysics, II Block, Koramangala, Bangalore 560034 (India); Ramos Almeida, C. [Instituto de Astrofisica de Canarias (IAC), C/V ia Lactea, s/n, E-38205 La Laguna, Tenerife (Spain); Mingo, B. [Department of Physics and Astronomy, University of Leicester, University Road, Leicester LE1 7RH (United Kingdom); Hardcastle, M. [School of Physics, Astronomy and Mathematics, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom); Nesvadba, N. P. H.; Singh, V. [Institut d' Astrophysique Spatiale, CNRS, Université Paris Sud, F-91405 Orsay (France); Kouwenhoven, M. B. N. [Kavli Institute for Astronomy and Astrophysics, Peking University, Yi He Yuan Lu 5, Haidian Qu, Beijing 100871 (China); Rose, M.; Spoon, H. [224 Space Sciences Building, Cornell University, Ithaca, NY 14853 (United States); Inskip, K. J. [Max Planck Institute for Astronomy, Königstuhl 17, D-69117 Heidelberg (Germany); Holt, J., E-mail: daniel.dicken@cea.fr [Leiden Observatory, Leiden University, P.O. Box 9513, 2300 RA Leiden (Netherlands)

2014-06-20

It remains uncertain which continuum and emission line diagnostics best indicate the bolometric powers of active galactic nuclei (AGNs), especially given the attenuation caused by the circumnuclear material and the possible contamination by components related to star formation. Here we use mid-IR spectra along with multiwavelength data to investigate the merit of various diagnostics of AGN radiative power, including the mid-IR [Ne III] λ25.89 μm and [O IV] λ25.89 μm fine-structure lines, the optical [O III] λ5007 forbidden line, and mid-IR 24 μm, 5 GHz radio, and X-ray continuum emission, for complete samples of 46 2Jy radio galaxies (0.05 < z < 0.7) and 17 3CRR FRII radio galaxies (z < 0.1). We find that the mid-IR [O IV] line is the most reliable indicator of AGN power for powerful radio-loud AGNs. By assuming that the [O IV] is emitted isotropically, and comparing the [O III] and 24 μm luminosities of the broad- and narrow-line AGNs in our samples at fixed [O IV] luminosity, we show that the [O III] and 24 μm emission are both mildly attenuated in the narrow-line compared to the broad-line objects by a factor of ≈2. However, despite this attenuation, the [O III] and 24 μm luminosities are better AGN power indicators for our sample than either the 5 GHz radio or the X-ray continuum luminosities. We also detect the mid-IR 9.7 μm silicate feature in the spectra of many objects but not ubiquitously: at least 40% of the sample shows no clear evidence for these features. We conclude that, for the majority of powerful radio galaxies, the mid-IR lines are powered by AGN photoionization.

Galaxy mergers and active nuclei. II. Cosmological evolution

International Nuclear Information System (INIS)

Roos, N.

1985-01-01

Galaxy mergers may produce active galactic nuclei (AGNs) by repopulating stellar loss-cone orbits around a central black hole. In the companion paper we derived a local bolometric luminosity function of AGNs based on this process. In this paper we interpret the observed cosmological evolution of the luminosity function of AGNs as due to evolution of the merging rate among galaxies after their formation at a redshift of approx.3. An important difference between our model and previous (empirical) models is that the evolution depends on galactic (stellar) luminosity instead of central nonthermal luminosity. The radio counts at 1.4 GHz and optical counts are reproduced by the model if the merging rate of the galaxies at the bright end of the galaxy luminosity function evolves considerably faster than the merging rate of the smaller galaxies. The theoretical and observed luminosity functions at high redshift have similar characteristics: (i) at high luminosity the evolution is best described by luminosity evolution, and (2) the luminosity function has a maximum at approx.10 3 Gpc -3 , which is the space density of the most massive galaxies. A large fraction of these galaxies are presumably formed in the precursors of rich clusters. Their merger rate is high initially and declines rapidly on a time scale of a few billion years. If the initial density fluctuation spectrum for protoclusters of mass M/sub cl/ has the form deltarho/rhoproportionalM/sup( -1+n//3)/2/sub cl/, then the steep evolution of the most luminous galaxies suggests nroughly-equal-1.3 at a redshift of approx.3, which is consistent with the observed clustering of galaxies

The extreme behavior of the radio-loud narrow-line Seyfert 1 galaxy J0849+5108

International Nuclear Information System (INIS)

Maune, Jeremy D.; Eggen, Joseph R.; Miller, H. Richard; Marshall, Kevin; Readhead, Anthony C. S.; Hovatta, Talvikki; King, Oliver

2014-01-01

Simultaneous radio, optical (both photometry and polarimetry), X-ray, and γ-ray observations of the radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxy J0849+5108 are presented. A massive three-magnitude optical flare across five nights in 2013 April is detected, along with associated flux increases in the γ-ray, infrared, and radio regimes; no comparable event was detected in the X-rays, though this may be due to poor coverage. A spectral energy distribution (SED) for the object using quasi-simultaneous data centered on the optical flare is compared to the previously published SEDs for the object by D'Ammando et al. The flare event coincided with a high degree of optical polarization. High amplitude optical microvariability is clearly detected, and is found to be of comparable amplitude when the object is observed in both faint and bright states. The object is also seen to undergo rapid shifts in polarization in both degree and electric vector position angle within a single night. J0849+5108 appears to show even more extreme variability than that previously reported for the similar object J0948+0022. These observations appear to support the growing claim that some RL-NLSy1 galaxies constitute a sub-class of blazar-like active galactic nuclei.

The extreme behavior of the radio-loud narrow-line Seyfert 1 galaxy J0849+5108

Energy Technology Data Exchange (ETDEWEB)

Maune, Jeremy D.; Eggen, Joseph R.; Miller, H. Richard [Department of Physics and Astronomy, Georgia State University, Atlanta, GA 30303-3083 (United States); Marshall, Kevin [Department of Physics and Astronomy, Widener University, Chester, PA 19013 (United States); Readhead, Anthony C. S.; Hovatta, Talvikki; King, Oliver, E-mail: maune@chara.gsu.edu [Cahill Laboratory of Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States)

2014-10-10

Simultaneous radio, optical (both photometry and polarimetry), X-ray, and γ-ray observations of the radio-loud narrow-line Seyfert 1 (RL-NLSy1) galaxy J0849+5108 are presented. A massive three-magnitude optical flare across five nights in 2013 April is detected, along with associated flux increases in the γ-ray, infrared, and radio regimes; no comparable event was detected in the X-rays, though this may be due to poor coverage. A spectral energy distribution (SED) for the object using quasi-simultaneous data centered on the optical flare is compared to the previously published SEDs for the object by D'Ammando et al. The flare event coincided with a high degree of optical polarization. High amplitude optical microvariability is clearly detected, and is found to be of comparable amplitude when the object is observed in both faint and bright states. The object is also seen to undergo rapid shifts in polarization in both degree and electric vector position angle within a single night. J0849+5108 appears to show even more extreme variability than that previously reported for the similar object J0948+0022. These observations appear to support the growing claim that some RL-NLSy1 galaxies constitute a sub-class of blazar-like active galactic nuclei.

Galaxy dynamics and the mass density of the universe.

Science.gov (United States)

Rubin, V C

1993-06-01

Dynamical evidence accumulated over the past 20 years has convinced astronomers that luminous matter in a spiral galaxy constitutes no more than 10% of the mass of a galaxy. An additional 90% is inferred by its gravitational effect on luminous material. Here I review recent observations concerning the distribution of luminous and nonluminous matter in the Milky Way, in galaxies, and in galaxy clusters. Observations of neutral hydrogen disks, some extending in radius several times the optical disk, confirm that a massive dark halo is a major component of virtually every spiral. A recent surprise has been the discovery that stellar and gas motions in ellipticals are enormously complex. To date, only for a few spheroidal galaxies do the velocities extend far enough to probe the outer mass distribution. But the diverse kinematics of inner cores, peripheral to deducing the overall mass distribution, offer additional evidence that ellipticals have acquired gas-rich systems after initial formation. Dynamical results are consistent with a low-density universe, in which the required dark matter could be baryonic. On smallest scales of galaxies [10 kiloparsec (kpc); Ho = 50 km.sec-1.megaparsec-1] the luminous matter constitutes only 1% of the closure density. On scales greater than binary galaxies (i.e., >/=100 kpc) all systems indicate a density approximately 10% of the closure density, a density consistent with the low baryon density in the universe. If large-scale motions in the universe require a higher mass density, these motions would constitute the first dynamical evidence for nonbaryonic matter in a universe of higher density.

Constraints on cold dark matter theories from observations of massive x-ray-luminous clusters of galaxies at high redshift

Science.gov (United States)

Luppino, G. A.; Gioia, I. M.

1995-01-01

During the course of a gravitational lensing survey of distant, X-ray selected Einstein Observatory Extended Medium Sensitivity Survey (EMSS) clusters of galaxies, we have studied six X-ray-luminous (L(sub x) greater than 5 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) clusters at redshifts exceeding z = 0.5. All of these clusters are apparently massive. In addition to their high X-ray luminosity, two of the clusters at z approximately 0.6 exhibit gravitationally lensed arcs. Furthermore, the highest redshift cluster in our sample, MS 1054-0321 at z = 0.826, is both extremely X-ray luminous (L(sub 0.3-3.5keV)=9.3 x 10(exp 44)(h(sub 50)(exp -2))ergs/sec) and exceedingly rich with an optical richness comparable to an Abell Richness Class 4 cluster. In this Letter, we discuss the cosmological implications of the very existence of these clusters for hierarchical structure formation theories such as standard Omega = 1 CDM (cold dark matter), hybrid Omega = 1 C + HDM (hot dark matter), and flat, low-density Lambda + CDM models.

Jet disruption in wide-angle tailed radio galaxies

International Nuclear Information System (INIS)

Burns, J.O.; Norman, M.L.; Clarke, D.A.

1986-01-01

The mechanisms responsible for the bending of the jets and tails of wide-angle tailed (WAT) radio galaxies in clusters are investigated theoretically, with a focus on sharp bends and rapid jet disruption. Large (1 Mpc) and small (200 kpc) WATs are differentiated, and it is suggested that the jet-tail transition in large WATs is due to collisions between the jet and cool clouds of the intracluster medium (ICM). The transition in small WATs is attributed to the passage of the jet through a planar Mach disk perpendicular to the jet flow direction. Such a disk is shown in numerical simulations to form when there is a shocklike jump in ambient pressure at the ISM/ICM interface; the origins of such a jump are explored. 14 references

Galaxy Zoo: dust in spiral galaxies

Science.gov (United States)

Masters, Karen L.; Nichol, Robert; Bamford, Steven; Mosleh, Moein; Lintott, Chris J.; Andreescu, Dan; Edmondson, Edward M.; Keel, William C.; Murray, Phil; Raddick, M. Jordan; Schawinski, Kevin; Slosar, Anže; Szalay, Alexander S.; Thomas, Daniel; Vandenberg, Jan

2010-05-01

We investigate the effect of dust on spiral galaxies by measuring the inclination dependence of optical colours for 24276 well-resolved Sloan Digital Sky Survey (SDSS) galaxies visually classified via the Galaxy Zoo project. We find clear trends of reddening with inclination which imply a total extinction from face-on to edge-on of 0.7, 0.6, 0.5 and 0.4mag for the ugri passbands (estimating 0.3mag of extinction in z band). We split the sample into `bulgy' (early-type) and `discy' (late-type) spirals using the SDSS fracdeV (or fDeV) parameter and show that the average face-on colour of `bulgy' spirals is redder than the average edge-on colour of `discy' spirals. This shows that the observed optical colour of a spiral galaxy is determined almost equally by the spiral type (via the bulge-disc ratio and stellar populations), and reddening due to dust. We find that both luminosity and spiral type affect the total amount of extinction, with discy spirals at Mr ~ -21.5mag having the most reddening - more than twice as much as both the lowest luminosity and most massive, bulge-dominated spirals. An increase in dust content is well known for more luminous galaxies, but the decrease of the trend for the most luminous has not been observed before and may be related to their lower levels of recent star formation. We compare our results with the latest dust attenuation models of Tuffs et al. We find that the model reproduces the observed trends reasonably well but overpredicts the amount of u-band attenuation in edge-on galaxies. This could be an inadequacy in the Milky Way extinction law (when applied to external galaxies), but more likely indicates the need for a wider range of dust-star geometries. We end by discussing the effects of dust on large galaxy surveys and emphasize that these effects will become important as we push to higher precision measurements of galaxy properties and their clustering. This publication has been made possible by the participation of more than

State-of-the-art multi-wavelength observations of nearby brightest group/cluster galaxies

Science.gov (United States)

Gendron-Marsolais, Marie-Lou; Hlavacek-Larrondo, Julie

2018-01-01

Nearby galaxy groups and clusters are crucial to our understanding of the impact of nuclear outbursts on the intracluster medium as their proximity allows us to study in detail the processes of feedback from active galactic nuclei in these systems. In this talk, I will present state-of-the-art multi-wavelength observations signatures of this mechanism.I will first show results on multi-configuration 230-470 MHz observations of the Perseus cluster from the Karl G. Jansky Very Large Array, probing the non-thermal emission from the old particle population of the AGN outflows. These observations reveal a multitude of new structures associated with the “mini-halo” and illustrate the high-quality images that can be obtained with the new JVLA at low radio-frequencies.Second, I will present new observations with the optical imaging Fourier transform spectrometer SITELLE (CFHT) of NGC 1275, the Perseus cluster's brightest galaxy. With its wide field of view, it is the only integral field unit spectroscopy instrument able to cover the large emission-line filamentary nebula in NGC 1275. I will present the first detailed velocity map of this nebula in its entirety and tackle the question of its origin (residual cooling flow or dragged gas).Finally, I will present deep Chandra observations of the nearby early-type massive elliptical galaxy NGC 4472, the most optically luminous galaxy in the local Universe, lying on the outskirts of the Virgo cluster. Enhanced X-ray rims around the radio lobes are detected and interpreted as gas uplifted from the core by the buoyant rise of the radio bubbles. We estimate the energy required to lift the gas to constitute a significant fraction of the total outburst energy.I will thus show how these high-fidelity observations of nearby brightest group/cluster galaxies are improving our understanding of the AGN feedback mechanism taking place in galaxy groups and clusters.

NuSTAR reveals the Comptonizing corona of the broad-line radio galaxy 3C 382

Energy Technology Data Exchange (ETDEWEB)

Ballantyne, D. R.; Bollenbacher, J. M. [Center for Relativistic Astrophysics, School of Physics, Georgia Institute of Technology, Atlanta, GA 30332 (United States); Brenneman, L. W. [Harvard-Smithsonian CfA, 60 Garden Street MS-67, Cambridge, MA 02138 (United States); Madsen, K. K.; Baloković, M.; Harrison, F. A.; Walton, D. J. [Cahill Center for Astronomy and Astrophysics, California Institute of Technology, Pasadena, CA 91125 (United States); Boggs, S. E. [Space Science Laboratory, University of California, Berkeley, CA 94720 (United States); Christensen, F. E.; Craig, W. W. [DTU SpaceNational Space Institute, Technical University of Denmark, Elektrovej 327, DK-2800 Lyngby (Denmark); Gandhi, P. [Department of Physics, University of Durham, South Road, Durham DH1 3LE (United Kingdom); Hailey, C. J. [Columbia Astrophysics Laboratory, Columbia University, New York, NY 10027 (United States); Lohfink, A. M. [Department of Astronomy, University of Maryland, College Park, MD 20742-2421 (United States); Marinucci, A. [Dipartimento di Matematica e Fisica, Università degli Studi Roma Tre, via della Vasca Navale 84, I-00146 Roma (Italy); Markwardt, C. B.; Zhang, W. W. [NASA Goddard Space Flight Center, Greenbelt, MD 20771 (United States); Stern, D., E-mail: david.ballantyne@physics.gatech.edu [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA 91109 (United States)

2014-10-10

Broad-line radio galaxies (BLRGs) are active galactic nuclei that produce powerful, large-scale radio jets, but appear as Seyfert 1 galaxies in their optical spectra. In the X-ray band, BLRGs also appear like Seyfert galaxies, but with flatter spectra and weaker reflection features. One explanation for these properties is that the X-ray continuum is diluted by emission from the jet. Here, we present two NuSTAR observations of the BLRG 3C 382 that show clear evidence that the continuum of this source is dominated by thermal Comptonization, as in Seyfert 1 galaxies. The two observations were separated by over a year and found 3C 382 in different states separated by a factor of 1.7 in flux. The lower flux spectrum has a photon-index of Γ=1.68{sub −0.02}{sup +0.03}, while the photon-index of the higher flux spectrum is Γ=1.78{sub −0.03}{sup +0.02}. Thermal and anisotropic Comptonization models provide an excellent fit to both spectra and show that the coronal plasma cooled from kT{sub e} = 330 ± 30 keV in the low flux data to 231{sub −88}{sup +50} keV in the high flux observation. This cooling behavior is typical of Comptonizing corona in Seyfert galaxies and is distinct from the variations observed in jet-dominated sources. In the high flux observation, simultaneous Swift data are leveraged to obtain a broadband spectral energy distribution and indicates that the corona intercepts ∼10% of the optical and ultraviolet emitting accretion disk. 3C 382 exhibits very weak reflection features, with no detectable relativistic Fe Kα line, that may be best explained by an outflowing corona combined with an ionized inner accretion disk.

Enormous Disc of Cool Gas Surrounding the Nearby Powerful Radio Galaxy NGC 612 (PKS 0131-36)

Science.gov (United States)

2008-05-22

galaxies in clus- ters appear to be much more devoid of H I gas, as sug- gested by a recent H I survey of the VIRGO cluster by di Serego Alighieri et...120th Street, New York, N.Y. 10027, USA 2Netherlands Foundation for Research in Astronomy, Postbus 2, 7990 AA Dwingeloo, the Netherlands 3Kapteyn...NGC 612. This paper is part of an ongoing study to map the large-scale neutral hydrogen properties of nearby radio galaxies and it presents the first

Evolution of the plasma universe: I. Double radio galaxies, quasars, and extragalactic jets

International Nuclear Information System (INIS)

Peratt, A.L.

1986-01-01

Cosmic plasma physics and our concept of the universe is in a state of rapid revision. This change started with in-situ measurements of plasmas in Earth's ionosphere, cometary atmospheres, and planetary magnetospheres; the translation of knowledge from laboratory experiments to astrophysical phenomena; discoveries of helical and filamentary plasma structures in the Galaxy and double radio sources; and the particle simulation of plasmas not accessible to in-situ measurement. Because of these, Birkeland (field-aligned) currents, double layers, and magnetic-field-aligned electric fields are now known to be far more important to the evolution of space plasma, including the acceleration of charged particles to high energies, than previously thought. This paper and its sequel investigate the observational evidence for a plasma universe threaded by Birkeland currents or filaments. This model of the universe was inspired by the advent of three-dimensional fully electromagnetic particle simulations and their application to the study of laboratory z pinches. This study resulted in totally unexpected phenomena in the data post-processed from the simulation particle, field, and history dumps. In particular, when the simulation parameters were scaled to galactic dimensions, the interaction between pinched filaments led to synchrotron radiation whose emission properties were found to share the following characteristics with double radio galaxies and quasars: power magnitude, isophotal morphology, spectra, brightness along source, polarization, and jets. The evolution of these pinched synchrotron emitting plasmas to elliptical, peculiar, and spiral galaxies by continuing the simulation run is addressed in a sequel paper

Milliarcsecond Imaging of the Radio Emission from the Quasar with the Most Massive Black Hole at Reionization

Energy Technology Data Exchange (ETDEWEB)

Wang, Ran; Wu, Xue-Bing; Jiang, Linhua [Kavli Institute of Astronomy and Astrophysics at Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871 (China); Momjian, Emmanuel; Carilli, Chris L. [National Radio Astronomy Observatory, P.O. Box 0, Socorro, NM 87801 (United States); Fan, Xiaohui [Steward Observatory, University of Arizona, 933 N Cherry Avenue, Tucson, AZ 85721 (United States); Walter, Fabian [Max-Planck-Institute for Astronomy, Königsstuhl 17, D-69117 Heidelberg (Germany); Strauss, Michael A. [Department of Astrophysical Sciences, Princeton University, Princeton, NJ 08544 (United States); Wang, Feige [Department of Astronomy, School of Physics, Peking University, No. 5 Yiheyuan Road, Haidian District, Beijing 100871 (China)

2017-02-01

We report Very Long Baseline Array (VLBA) observations of the 1.5 GHz radio continuum emission of the z = 6.326 quasar SDSS J010013.02+280225.8 (hereafter J0100+2802). J0100+2802 is by far the most optically luminous and is a radio-quiet quasar with the most massive black hole known at z > 6. The VLBA observations have a synthesized beam size of 12.10 mas ×5.36 mas (FWHM), and detected the radio continuum emission from this object with a peak surface brightness of 64.6 ± 9.0 μ Jy beam{sup −1} and a total flux density of 88 ± 19 μ Jy. The position of the radio peak is consistent with that from SDSS in the optical and Chandra in the X-ray. The radio source is marginally resolved by the VLBA observations. A 2D Gaussian fit to the image constrains the source size to (7.1 ± 3.5) mas × (3.1 ± 1.7) mas. This corresponds to a physical scale of (40 ± 20) pc × (18 ± 10) pc. We estimate the intrinsic brightness temperature of the VLBA source to be T {sub B} = (1.6 ± 1.2) × 10{sup 7} K. This is significantly higher than the maximum value in normal star-forming galaxies, indicating an active galactic nucleus (AGN) origin for the radio continuum emission. However, it is also significantly lower than the brightness temperatures found in highest-redshift radio-loud quasars. J0100+2802 provides a unique example for studying the radio activity in optically luminous and radio-quiet AGNs in the early universe. Further observations at multiple radio frequencies will accurately measure the spectral index and address the dominant radiation mechanism of the radio emission.

NEAR-INFRARED ADAPTIVE OPTICS IMAGING OF INFRARED LUMINOUS GALAXIES: THE BRIGHTEST CLUSTER MAGNITUDE-STAR FORMATION RATE RELATION

International Nuclear Information System (INIS)

Randriamanakoto, Z.; Väisänen, P.; Escala, A.; Kankare, E.; Kotilainen, J.; Mattila, S.; Ryder, S.

2013-01-01

We have established a relation between the brightest super star cluster (SSC) magnitude in a galaxy and the host star formation rate (SFR) for the first time in the near-infrared (NIR). The data come from a statistical sample of ∼40 luminous IR galaxies (LIRGs) and starbursts utilizing K-band adaptive optics imaging. While expanding the observed relation to longer wavelengths, less affected by extinction effects, it also pushes to higher SFRs. The relation we find, M K ∼ –2.6log SFR, is similar to that derived previously in the optical and at lower SFRs. It does not, however, fit the optical relation with a single optical to NIR color conversion, suggesting systematic extinction and/or age effects. While the relation is broadly consistent with a size-of-sample explanation, we argue physical reasons for the relation are likely as well. In particular, the scatter in the relation is smaller than expected from pure random sampling strongly suggesting physical constraints. We also derive a quantifiable relation tying together cluster-internal effects and host SFR properties to possibly explain the observed brightest SSC magnitude versus SFR dependency

ALMA DETECTION OF THE VIBRATIONALLY EXCITED HCN J = 4-3 EMISSION LINE IN THE AGN-HOSTING LUMINOUS INFRARED GALAXY IRAS 20551–4250

Energy Technology Data Exchange (ETDEWEB)

Imanishi, Masatoshi [Subaru Telescope, 650 North A' ohoku Place, Hilo, Hawaii, 96720 (United States); Nakanishi, Kouichiro, E-mail: masa.imanishi@nao.ac.jp [Joint ALMA Observatory, Alonso de Córdova 3107, Vitacura 763-0355, Santiago de Chile (Chile)

2013-10-01

We present results from our ALMA Cycle 0 observations, at the frequencies around the HCN, HCO{sup +}, and HNC J = 4-3 transition lines, of the luminous infrared galaxy IRAS 20551–4250 at z = 0.043, which is known to host an energetically important obscured active galactic nucleus (AGN). In addition to the targeted HCN, HCO{sup +}, and HNC J = 4-3 emission lines, two additional strong emission lines are seen, which we attribute to H{sub 2}S and CH{sub 3}CN(+CCH). The HCN-to-HCO{sup +} J = 4-3 flux ratio (∼0.7) is higher than in the other starburst-dominated galaxy (∼0.2) observed in our ALMA Cycle 0 program. We tentatively (∼5σ) detected the vibrationally excited (v {sub 2} = 1) HCN J = 4-3 (l = 1f) emission line, which is important for testing an infrared radiative pumping scenario for HCN. This is the second detection of this molecular transition in external galaxies. The most likely reason for this detection is not only the high flux of this emission line, but also the small molecular line widths observed in this galaxy, suggesting that vibrational excitation of HCN may be relatively common in AGN-hosting galaxies.

UGC galaxies stronger than 25 mJy at 4.85 GHz

International Nuclear Information System (INIS)

Condon, J.J.; Frayer, D.T.; Broderick, J.J.

1991-01-01

UGC galaxies in the declination band +5 to +75 deg were identified by position coincidence with radio sources stronger than 25 mJy on the Green Bank 4.85 GHz sky maps. Candidate identifications were confirmed or rejected with the aid of published aperture-synthesis maps and new 4.86 GHz VLA maps having 15 or 18 arcsec resolution, resulting in a sample of 347 nearby radio galaxies plus five new quasar-galaxy pairs. The radio energy sources in UGC galaxies were classified as starbursts or monsters on the basis of their infrared-radio flux ratios, infrared spectral indices, and radio morphologies. The rms scatter in the logarithmic infrared-radio ratio q is not more than 0.16 for starburst galaxies selected at 4.85 GHz. Radio spectral indices were obtained for nearly all of the UGC galaxies, and S0 galaxies account for a disproportionate share of the compact flat-spectrum (alpha less than 0.5) radio sources. The extended radio jets and lobes produced by monsters are preferentially, but not exclusively, aligned within about 30 deg of the optical minor axes of their host galaxies. The tendency toward minor-axis ejection appears to be independent of radio-source size and is strongest for elliptical galaxies. 230 refs

The most luminous z ∼ 9-10 galaxy candidates yet found: The luminosity function, cosmic star-formation rate, and the first mass density estimate at 500 Myr

International Nuclear Information System (INIS)

Oesch, P. A.; Illingworth, G. D.; Magee, D.; Bouwens, R. J.; Labbé, I.; Smit, R.; Franx, M.; Van Dokkum, P. G.; Momcheva, I.; Ashby, M. L. N.; Fazio, G. G.; Huang, J.-S.; Willner, S. P.; Gonzalez, V.; Trenti, M.; Brammer, G. B.; Skelton, R. E.; Spitler, L. R.

2014-01-01

We present the discovery of four surprisingly bright (H 160 ∼ 26-27 mag AB) galaxy candidates at z ∼ 9-10 in the complete HST CANDELS WFC3/IR GOODS-N imaging data, doubling the number of z ∼ 10 galaxy candidates that are known, just ∼500 Myr after the big bang. Two similarly bright sources are also detected in a reanalysis of the GOODS-S data set. Three of the four galaxies in GOODS-N are significantly detected at 4.5σ-6.2σ in the very deep Spitzer/IRAC 4.5 μm data, as is one of the GOODS-S candidates. Furthermore, the brightest of our candidates (at z = 10.2 ± 0.4) is robustly detected also at 3.6 μm (6.9σ), revealing a flat UV spectral energy distribution with a slope β = –2.0 ± 0.2, consistent with demonstrated trends with luminosity at high redshift. Thorough testing and use of grism data excludes known low-redshift contamination at high significance, including single emission-line sources, but as-yet unknown low redshift sources could provide an alternative solution given the surprising luminosity of these candidates. Finding such bright galaxies at z ∼ 9-10 suggests that the luminosity function for luminous galaxies might evolve in a complex way at z > 8. The cosmic star formation rate density still shows, however, an order-of-magnitude increase from z ∼ 10 to z ∼ 8 since the dominant contribution comes from low-luminosity sources. Based on the IRAC detections, we derive galaxy stellar masses at z ∼ 10, finding that these luminous objects are typically 10 9 M ☉ . This allows for a first estimate of the cosmic stellar mass density at z ∼ 10 resulting in log 10  ρ ∗ =4.7 −0.8 +0.5 M ☉ Mpc –3 for galaxies brighter than M UV ∼ –18. The remarkable brightness, and hence luminosity, of these z ∼ 9-10 candidates will enable deep spectroscopy to determine their redshift and nature, and highlights the opportunity for the James Webb Space Telescope to map the buildup of galaxies at redshifts much earlier than z ∼ 10.

THE AVERAGE PHYSICAL PROPERTIES AND STAR FORMATION HISTORIES OF THE UV-BRIGHTEST STAR-FORMING GALAXIES AT z ∼ 3.7

International Nuclear Information System (INIS)

Lee, Kyoung-Soo; Glikman, Eilat; Dey, Arjun; Reddy, Naveen; Jannuzi, Buell T.; Brown, Michael J. I.; Gonzalez, Anthony H.; Cooper, Michael C.; Fan Xiaohui; Bian Fuyan; Stern, Daniel; Brodwin, Mark; Cooray, Asantha

2011-01-01

We investigate the average physical properties and star formation histories (SFHs) of the most UV-luminous star-forming galaxies at z ∼ 3.7. Our results are based on the average spectral energy distributions (SEDs), constructed from stacked optical-to-infrared photometry, of a sample of the 1913 most UV-luminous star-forming galaxies found in 5.3 deg 2 of the NOAO Deep Wide-Field Survey. We find that the shape of the average SED in the rest optical and infrared is fairly constant with UV luminosity, i.e., more UV-luminous galaxies are, on average, also more luminous at longer wavelengths. In the rest UV, however, the spectral slope β (≡ dlogF λ /dlogλ; measured at 0.13 μm rest UV and thus star formation rates (SFRs) scale closely with stellar mass such that more UV-luminous galaxies are also more massive, (2) the median ages indicate that the stellar populations are relatively young (200-400 Myr) and show little correlation with UV luminosity, and (3) more UV-luminous galaxies are dustier than their less-luminous counterparts, such that L ∼ 4-5L* galaxies are extincted up to A(1600) = 2 mag while L ∼ L* galaxies have A(1600) = 0.7-1.5 mag. We argue that the average SFHs of UV-luminous galaxies are better described by models in which SFR increases with time in order to simultaneously reproduce the tight correlation between the UV-derived SFR and stellar mass and their universally young ages. We demonstrate the potential of measurements of the SFR-M * relation at multiple redshifts to discriminate between simple models of SFHs. Finally, we discuss the fate of these UV-brightest galaxies in the next 1-2 Gyr and their possible connection to the most massive galaxies at z ∼ 2.

DISCOVERY OF DRAMATIC OPTICAL VARIABILITY IN SDSS J1100+4421: A PECULIAR RADIO-LOUD NARROW-LINE SEYFERT 1 GALAXY?

Energy Technology Data Exchange (ETDEWEB)

Tanaka, Masaomi [National Astronomical Observatory of Japan, Mitaka, Tokyo 181-8588 (Japan); Morokuma, Tomoki; Doi, Mamoru; Kikuchi, Yuki [Institute of Astronomy, School of Science, University of Tokyo, Mitaka, Tokyo 181-0015 (Japan); Itoh, Ryosuke [Department of Physical Sciences, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Akitaya, Hiroshi; Tanaka, Yasuyuki T.; Kawabata, Koji S. [Hiroshima Astrophysical Science Center, Hiroshima University, Higashi-Hiroshima, Hiroshima 739-8526 (Japan); Tominaga, Nozomu [Department of Physics, Faculty of Science and Engineering, Konan University, Kobe, Hyogo 658-8501 (Japan); Saito, Yoshihiko; Kawai, Nobuyuki [Department of Physics, Tokyo Institute of Technology, Meguro-ku, Tokyo 152-8551 (Japan); Stawarz, Łukasz [Institute of Space and Astronautical Science, JAXA, Sagamihara, Kanagawa 252-5210 (Japan); Gandhi, Poshak [Department of Physics, Durham University, Durham DH1-3LE (United Kingdom); Ali, Gamal; Essam, Ahmad; Hamed, Gamal [National Research Institute of Astronomy and Geophysics, Helwan, Cairo (Egypt); Aoki, Tsutomu [Kiso Observatory, Institute of Astronomy, School of Science, The University of Tokyo, Kiso, Nagano 397-0101 (Japan); Contreras, Carlos; Hsiao, Eric Y. [Carnegie Observatories, Las Campanas Observatory, Colina El Pino, Casilla 601 (Chile); Iwata, Ikuru, E-mail: masaomi.tanaka@nao.ac.jp [Subaru Telescope, National Astronomical Observatory of Japan, Hilo, HI 96720 (United States); and others

2014-10-01

We present our discovery of dramatic variability in SDSS J1100+4421 by the high-cadence transient survey Kiso Supernova Survey. The source brightened in the optical by at least a factor of three within about half a day. Spectroscopic observations suggest that this object is likely a narrow-line Seyfert 1 galaxy (NLS1) at z = 0.840, however, with unusually strong narrow emission lines. The estimated black hole mass of ∼10{sup 7} M {sub ☉} implies bolometric nuclear luminosity close to the Eddington limit. SDSS J1100+4421 is also extremely radio-loud, with a radio loudness parameter of R ≅ 4 × 10{sup 2}-3 × 10{sup 3}, which implies the presence of relativistic jets. Rapid and large-amplitude optical variability of the target, reminiscent of that found in a few radio- and γ-ray-loud NLS1s, is therefore produced most likely in a blazar-like core. The 1.4 GHz radio image of the source shows an extended structure with a linear size of about 100 kpc. If SDSS J1100+4421 is a genuine NLS1, as suggested here, this radio structure would then be the largest ever discovered in this type of active galaxies.

The Dynamics and Cold Gas Content of Luminous Infrared Galaxy Mergers in the Local Universe

Science.gov (United States)

Privon, G. C.

2014-08-01

Luminous Infrared Galaxies (LIRGs; 10^11 ≤ L_IR [8 - 1000 μm]/L_sun systems in the local universe, both in terms of their absolute star formation rates—ten to several hundred times that of ``normal'' galaxies—and their star formation rate densities. Many U/LIRGs are interacting or merging disk galaxies undergoing enhanced star formation and/or nuclear activity, likely triggered as the objects transform into massive S0 and elliptical merger remnants. The LIRG population also contains a significant number of apparently isolated disk galaxies which are undergoing enhanced star formation, providing a window on secular galaxy evolution. This work examines nearby U/LIRGs chosen from the Great Observatories All-sky LIRG Survey (GOALS), an infrared flux and luminosity selected sample. The proximity of these systems enables high spatial resolution study of active galactic nuclei (AGN) and extreme star formation in these objects. New maps of the neutral hydrogen (HI) emission are presented for systems morphologically classified in the optical and mid-infrared as non-merging or pre-merger systems. The results of this study suggests that some infrared-selected galaxies may be minor mergers or interactions which are being viewed so soon after first pass that the stellar disk has not yet been significantly disturbed. Galaxy mergers appear to drive much of the enhanced activity observed in U/LIRGs; understanding the merger state of these systems provides a context for observations of star formation and AGN properties. In order to constrain the merger stage, dynamical models for a sample of nine systems were matched to the observed kinematics and morphology as obtained from optical imaging and interferometric HI maps. The resulting models are used not only to constrain the merger stage, but also the encounter geometry of the precursor. Based on these dynamical models a new merger stage classification is presented, which re-scales objects to a common timeline is used to

Emission-line galaxies and quasars in the southern hemisphere. I. Description and applications of an objective-prism survey

International Nuclear Information System (INIS)

Smith, M.G.

1975-01-01

A selection of objects from the first plates of a low-dispersion, objective-prism survey for emission-line galaxies and quasars is used to illustrate the application of the survey to the following lines of research in extragalactic astronomy: quasi-stellar objects, Seyfert galaxies, instabilities in galaxies produced by tidal interaction or explosive events, and rates of star formation and the general chemical evolution of galaxies. Included in the discussion is a description of how the survey provides a new, purely optical, color-independent method for the direct isolation of bright, high-redshift QSOs with strong emission lines (Lα is often directly visible on the Schmidt-survey plates). The newly discovered objects used for illustration are a radio-quiet QSO of redshift 2.07, a luminous, class 2 Seyfert galaxy, a compact blue emission-line galaxy with a jet or streamer, yet with no obvious interacting companion, and a blue galaxy with Hβ flux 50 times that of 30 Doradus, and low metal abundances, which is undergoing a very intense burst of star formation. These objects are to be discussed in greater detail in subsequent papers in this series

A CHANDRA PERSPECTIVE ON GALAXY-WIDE X-RAY BINARY EMISSION AND ITS CORRELATION WITH STAR FORMATION RATE AND STELLAR MASS: NEW RESULTS FROM LUMINOUS INFRARED GALAXIES

International Nuclear Information System (INIS)

Lehmer, B. D.; Jenkins, L. P.; Alexander, D. M.; Goulding, A. D.; Roberts, T. P.; Bauer, F. E.; Brandt, W. N.; Ptak, A.

2010-01-01

We present new Chandra observations that complete a sample of seventeen (17) luminous infrared galaxies (LIRGs) with D H ∼ 20 cm -2 . The LIRGs in our sample have total infrared (8-1000 μm) luminosities in the range of L IR ∼ (1-8) x 10 11 L sun . The high-resolution imaging and X-ray spectral information from our Chandra observations allow us to measure separately X-ray contributions from active galactic nuclei and normal galaxy processes (e.g., X-ray binaries and hot gas). We utilized total infrared plus UV luminosities to estimate star formation rates (SFRs) and K-band luminosities and optical colors to estimate stellar masses (M * ) for the sample. Under the assumption that the galaxy-wide 2-10 keV luminosity (L gal HX ) traces the combined emission from high-mass X-ray binaries (HMXBs) and low-mass X-ray binaries, and that the power output from these components is linearly correlated with SFR and M * , respectively, we constrain the relation L gal HX = αM * + βSFR. To achieve this, we construct a Chandra-based data set composed of our new LIRG sample combined with additional samples of less actively star-forming normal galaxies and more powerful LIRGs and ultraluminous infrared galaxies (ULIRGs) from the literature. Using these data, we measure best-fit values of α = (9.05 ± 0.37) x 10 28 erg s -1 M -1 sun and β = (1.62 ± 0.22) x 10 39 erg s -1 (M sun yr -1 ) -1 . This scaling provides a more physically meaningful estimate of L gal HX , with ∼0.1-0.2 dex less scatter, than a direct linear scaling with SFR. Our results suggest that HMXBs dominate the galaxy-wide X-ray emission for galaxies with SFR/M * ∼>5.9 x 10 -11 yr -1 , a factor of ∼2.9 times lower than previous estimates. We find that several of the most powerful LIRGs and ULIRGs, with SFR/M * ∼> 10 -9 yr -1 , appear to be X-ray underluminous with respect to our best-fit relation. We argue that these galaxies are likely to contain X-ray binaries residing in compact star-forming regions

The 'seven-sister' BCG - A tale of a cD galaxy in the making?

Science.gov (United States)

Lal, Dharam

2015-09-01

We propose Chandra observations of the most complex known multiple-nucleus system, the peculiar "inner nuclei" in the poor cluster A407. This object has many compact nuclei embedded in a luminous matrix; and provides us with a case of a cD galaxy in the making. We are fortunate to have found it! Our proposed 45 ks Chandra observation will provide definitive answers about the origin of such objects. Additionally, we will probe the gas properties, make estimates of temperatures and matallicities, search for substructures or surface brightness edges and correlate them with radio morphology, etc. for A407.

The Taipan Galaxy Survey: Scientific Goals and Observing Strategy

Science.gov (United States)

da Cunha, Elisabete; Hopkins, Andrew M.; Colless, Matthew; Taylor, Edward N.; Blake, Chris; Howlett, Cullan; Magoulas, Christina; Lucey, John R.; Lagos, Claudia; Kuehn, Kyler; Gordon, Yjan; Barat, Dilyar; Bian, Fuyan; Wolf, Christian; Cowley, Michael J.; White, Marc; Achitouv, Ixandra; Bilicki, Maciej; Bland-Hawthorn, Joss; Bolejko, Krzysztof; Brown, Michael J. I.; Brown, Rebecca; Bryant, Julia; Croom, Scott; Davis, Tamara M.; Driver, Simon P.; Filipovic, Miroslav D.; Hinton, Samuel R.; Johnston-Hollitt, Melanie; Jones, D. Heath; Koribalski, Bärbel; Kleiner, Dane; Lawrence, Jon; Lorente, Nuria; Mould, Jeremy; Owers, Matt S.; Pimbblet, Kevin; Tinney, C. G.; Tothill, Nicholas F. H.; Watson, Fred

2017-10-01

The Taipan galaxy survey (hereafter simply `Taipan') is a multi-object spectroscopic survey starting in 2017 that will cover 2π steradians over the southern sky (δ ≲ 10°, |b| ≳ 10°), and obtain optical spectra for about two million galaxies out to z growth rate of structure to 5%; (ii) to make the most extensive map yet constructed of the total mass distribution and motions in the local Universe, using peculiar velocities based on improved Fundamental Plane distances, which will enable sensitive tests of gravitational physics; and (iii) to deliver a legacy sample of low-redshift galaxies as a unique laboratory for studying galaxy evolution as a function of dark matter halo and stellar mass and environment. The final survey, which will be completed within 5 yrs, will consist of a complete magnitude-limited sample (i ⩽ 17) of about 1.2 × 106 galaxies supplemented by an extension to higher redshifts and fainter magnitudes (i ⩽ 18.1) of a luminous red galaxy sample of about 0.8 × 106 galaxies. Observations and data processing will be carried out remotely and in a fully automated way, using a purpose-built automated `virtual observer' software and an automated data reduction pipeline. The Taipan survey is deliberately designed to maximise its legacy value by complementing and enhancing current and planned surveys of the southern sky at wavelengths from the optical to the radio; it will become the primary redshift and optical spectroscopic reference catalogue for the local extragalactic Universe in the southern sky for the coming decade.

Mass distributions in disk galaxies

NARCIS (Netherlands)

Martinsson, Thomas; Verheijen, Marc; Bershady, Matthew; Westfall, Kyle; Andersen, David; Swaters, Rob

We present results on luminous and dark matter mass distributions in disk galaxies from the DiskMass Survey. As expected for normal disk galaxies, stars dominate the baryonic mass budget in the inner region of the disk; however, at about four optical scale lengths (hR ) the atomic gas starts to

Diffuse radio emission in the Coma cluster and Abell 1367: observations at 430 and 1400 MHz

International Nuclear Information System (INIS)

Hanisch, R.J.

1980-01-01

Two rich clusters of galaxies, Abell 1656 (the Coma cluster) and Abell 1367, have been mapped at both 430 and 1400 MHz with the 305-m telescope at Arecibo. The contribution to the observed radio emission due to known discrete sources has been calculated by convolving interferometrically determined source lists with observed Arecibo beam patterns, and maps of the diffuse radio emission alone have been constructed. Both clusters contain regions of diffuse radio emission, although the source in Coma is larger and much more luminous than the source in Abell 1367. The linear extent of the diffuse emission and its dependence on frequency have been used to study particle propagation rates and modes of diffusion in the intracluster medium. The possible correlations between the diffuse radio emission and x-ray emission in these clusters have been investigated, and it has been found that the observed x-ray luminosities can be accounted for if the intracluster gas is heated through Coulomb interactions with the relativistic electrons responsible for the diffuse radio emission

VizieR Online Data Catalog: Galaxy clusters: radio halos, relics and parameters (Yuan+, 2015)

Science.gov (United States)

Yuan, Z. S.; Han, J. L.; Wen, Z. L.

2017-10-01

A large number of radio halos, relics, and mini-halos have been discovered and measured in recent decades through observations with VLA (e.g., Giovannini & Feretti 2000NewA....5..335G; van Weeren et al. 2011A&A...533A..35V), GMRT (e.g., Venturi et al. 2007A&A...463..937V; Kale et al. 2015A&A...579A..92K), WSRT (e.g., van Weeren et al. 2010Sci...330..347V; Trasatti et al. 2015A&A...575A..45T), and also ATCA (e.g., Shimwell et al. 2014MNRAS.440.2901S, 2015MNRAS.449.1486S). We have checked the radio images of radio halos, relics, and mini-halos in the literature and collected in Table 1 the radio flux Sν at frequencies within a few per cent around 1.4 GHz, 610 MHz, and 325 MHz; we have interpolated the flux at an intermediate frequency if measurements are available at higher and lower frequencies. To establish reliable scaling relations, we include only the very firm detection of diffuse radio emission in galaxy clusters, and omit questionable detections or flux estimates due to problematic point-source subtraction. (3 data files).

Magnetic fields in barred galaxies I. The atlas

CERN Document Server

Beck, R; Ehle, M; Harnett, J I; Haynes, R F; Shukurov, A M; Sokoloff, D D; Thierbach, M

2002-01-01

The total and polarized radio continuum emission of 20 barred galaxies was observed with the Very Large Array (VLA) at 3, 6, 18 and 22 cm and with the Australia Telescope Compact Array (ATCA) at 6 cm and 13 cm. Maps at 30 arcsec angular resolution are presented here. Polarized emission (and therefore a large-scale regular magnetic field) was detected in 17 galaxies. Most galaxies of our sample are similar to non-barred galaxies with respect to the radio/far-infrared flux correlation and equipartition strength of the total magnetic field. Galaxies with highly elongated bars are not always radio-bright. We discuss the correlation of radio properties with the aspect ratio of the bar and other measures of the bar strength. We introduce a new measure of the bar strength, \\Lambda, related to the quadrupole moment of the bar's gravitational potential. The radio surface brightness I of the barred galaxies in our sample is correlated with \\Lambda, I \\propto \\Lambda^0.4+/-0.1, and thus is highest in galaxies with a lon...

Observations of Ultra-Luminous X-ray Sources, and Implications

Science.gov (United States)

Colbert, E. J. M.

2004-05-01

I will review observations of Ultra-Luminous X-ray Sources (ULXs; Lx > 1E39 erg/s), in particular those observations that have helped reveal the nature of these curious objects. Some recent observations suggest that ULXs are a heterogenous class. Although ULX phenomenology is not fully understood, I will present some examples from the (possibly overlapping) sub-classes. Since ULXs are the most luminous objects in starburst galaxies, they, and ``normal'' luminous black-hole high-mass X-ray binaries are intimately tied to the global galaxian X-ray-star-formation connection. Further work is needed to understand how ULXs form, and how they are associated with the putative population of intermediate-mass black holes.

Studying the highly bent spectra of FR II-type radio galaxies with the KDA EXT model

Science.gov (United States)

Kuligowska, Elżbieta

2018-04-01

Context. The Kaiser, Dennett-Thorpe & Alexander (KDA, 1997, MNRAS, 292, 723) EXT model, that is, the extension of the KDA model of Fanaroff & Riley (FR) II-type source evolution, is applied and confronted with the observational data for selected FR II-type radio sources with significantly aged radio spectra. Aim. A sample of FR II-type radio galaxies with radio spectra strongly bent at their highest frequencies is used for testing the usefulness of the KDA EXT model. Methods: The dynamical evolution of FR II-type sources predicted with the KDA EXT model is briefly presented and discussed. The results are then compared to the ones obtained with the classical KDA approach, assuming the source's continuous injection and self-similarity. Results: The results and corresponding diagrams obtained for the eight sample sources indicate that the KDA EXT model predicts the observed radio spectra significantly better than the best spectral fit provided by the original KDA model.

CONNECTION BETWEEN THE ACCRETION DISK AND JET IN THE RADIO GALAXY 3C 111

International Nuclear Information System (INIS)

Chatterjee, Ritaban; Marscher, Alan P.; Jorstad, Svetlana G.; Harrison, Brandon; Agudo, Ivan; Taylor, Brian W.; Markowitz, Alex; Rivers, Elizabeth; Rothschild, Richard E.; McHardy, Ian M.; Aller, Margo F.; Aller, Hugh D.; Laehteenmaeki, Anne; Tornikoski, Merja; Gomez, Jose L.; Gurwell, Mark

2011-01-01

We present the results of extensive multi-frequency monitoring of the radio galaxy 3C 111 between 2004 and 2010 at X-ray (2.4-10 keV), optical (R band), and radio (14.5, 37, and 230 GHz) wave bands, as well as multi-epoch imaging with the Very Long Baseline Array (VLBA) at 43 GHz. Over the six years of observation, significant dips in the X-ray light curve are followed by ejections of bright superluminal knots in the VLBA images. This shows a clear connection between the radiative state near the black hole, where the X-rays are produced, and events in the jet. The X-ray continuum flux and Fe line intensity are strongly correlated, with a time lag shorter than 90 days and consistent with zero. This implies that the Fe line is generated within 90 lt-day of the source of the X-ray continuum. The power spectral density function of X-ray variations contains a break, with a steeper slope at shorter timescales. The break timescale of 13 +12 -6 days is commensurate with scaling according to the mass of the central black hole based on observations of Seyfert galaxies and black hole X-ray binaries (BHXRBs). The data are consistent with the standard paradigm, in which the X-rays are predominantly produced by inverse Compton scattering of thermal optical/UV seed photons from the accretion disk by a distribution of hot electrons-the corona-situated near the disk. Most of the optical emission is generated in the accretion disk due to reprocessing of the X-ray emission. The relationships that we have uncovered between the accretion disk and the jet in 3C 111, as well as in the Fanaroff-Riley class I radio galaxy 3C 120 in a previous paper, support the paradigm that active galactic nuclei and Galactic BHXRBs are fundamentally similar, with characteristic time and size scales proportional to the mass of the central black hole.

Radio galaxies radiation transfer, dynamics, stability and evolution of a synchrotron plasmon

CERN Document Server

Pacholczyk, A G

1977-01-01

Radio Galaxies: Radiation Transfer, Dynamics, Stability and Evolution of a Synchrotron Plasmon deals with the physics of a region in space containing magnetic field and thermal and relativistic particles (a plasmon). The synchrotron emission and absorption of this region are discussed, along with the properties of its spectrum; its linear and circular polarization; transfer of radiation through such a region; its dynamics and expansion; and interaction with external medium.Comprised of eight chapters, this volume explores the stability, turbulence, and acceleration of particles in a synchrotro

Genesis of dwarf galaxies in interacting system

International Nuclear Information System (INIS)

Duc, Pierre-Alain

1995-01-01

This research thesis addresses the study of interacting and merging galaxies, and more particularly the associated stellar formation episodes. The author first reports an analysis of the central regions of these objects by studying a specific class among them, i.e. galaxies discovered by the IRAS satellite which are ultra-luminous in the far infrared. The author presents results obtained by optical and infrared imagery and spectroscopy of a complete sample of objects located in the southern hemisphere. In the second part, the author focusses on outside regions of interacting galaxies, discusses the observation of filaments formed under the influence of tidal forces acting during galactic collisions, and of condensations which are as luminous as dwarf galaxies. Then a multi-wavelength study of several neighbouring systems revealed the existence of a specific class of objects, the tidal dwarf galaxies, which are formed from stellar and gaseous material snatched from the disk of interacting galaxies. Gas-rich tidal dwarf galaxies contain, like dwarf irregular galaxies or blue compact galaxies, newly formed stars. But, in opposition with these ones, they are richer in heavy elements: this is one of the consequences of a specific mode of galactic formation based on a cosmic recycling [fr

The peculiar radio-loud narrow line Seyfert 1 galaxy 1H 0323+342

Energy Technology Data Exchange (ETDEWEB)

Paliya, Vaidehi S.; Stalin, C. S. [Indian Institute of Astrophysics, Block-II, Koramangala, Bangalore-560034 (India); Sahayanathan, S. [Astrophysical Science Division, Bhabha Atomic Research Center, Mumbai-400085 (India); Parker, M. L.; Fabian, A. C. [Institute of Astronomy, Madingley Road, Cambridge CB3 0HA (United Kingdom); Anjum, Ayesha [Department of Physics, Christ University, Bangalore-560029 (India); Pandey, S. B., E-mail: vaidehi@iiap.res.in [Aryabhatta Research Institute of Observational Sciences, Manora peak, Nainital-263129 (India)

2014-07-10

We present a multiwavelength study of the radio-loud narrow-line Seyfert 1 galaxy (NLSy1) 1H 0323+342, detected by the Fermi Gamma-Ray Space Telescope. Multiband light curves show many orphan X-ray and optical flares having no corresponding γ-ray counterparts. Such anomalous variability behavior can be due to different locations of the emission region from the central source. During a large flare, a γ-ray flux doubling timescale as small as ∼3 hr is noticed. We built spectral energy distributions (SEDs) during different activity states and modeled them using a one-zone leptonic model. The shape of the optical/UV component of the SEDs is dominated by accretion disk emission in all the activity states. In the X-ray band, significant thermal emission from the hot corona is inferred during quiescent and first flaring states; however, during subsequent flares, the nonthermal jet component dominates. The γ-ray emission in all the states can be well explained by inverse-Compton scattering of accretion disk photons reprocessed by the broad-line region. The source showed violent intra-night optical variability, coinciding with one of the high γ-ray activity states. An analysis of the overall X-ray spectrum fitted with an absorbed power-law plus relativistic reflection component hints at the presence of an Fe Kα line and returns a high black hole spin value of a = 0.96 ± 0.14. We argue that 1H 0323+342 possesses dual characteristics, akin to both flat-spectrum radio quasars (FSRQs) and radio-quiet NLSy1 galaxies, though at a low jet power regime compared to powerful FSRQs.

Search for low-frequency diffuse radio emission around a shock in the massive galaxy cluster MACS J0744.9+3927

Science.gov (United States)

Wilber, A.; Brüggen, M.; Bonafede, A.; Rafferty, D.; Savini, F.; Shimwell, T.; van Weeren, R. J.; Botteon, A.; Cassano, R.; Brunetti, G.; De Gasperin, F.; Wittor, D.; Hoeft, M.; Birzan, L.

2018-05-01

Merging galaxy clusters produce low-Mach-number shocks in the intracluster medium. These shocks can accelerate electrons to relativistic energies that are detectable at radio frequencies. MACS J0744.9+3927 is a massive [M500 = (11.8 ± 2.8) × 1014 M⊙], high-redshift (z = 0.6976) cluster where a Bullet-type merger is presumed to have taken place. Sunyaev-Zel'dovich maps from MUSTANG indicate that a shock, with Mach number M = 1.0-2.9 and an extension of ˜200 kpc, sits near the centre of the cluster. The shock is also detected as a brightness and temperature discontinuity in X-ray observations. To search for diffuse radio emission associated with the merger, we have imaged the cluster with the LOw Frequency ARray (LOFAR) at 120-165 MHz. Our LOFAR radio images reveal previously undetected AGN emission, but do not show clear cluster-scale diffuse emission in the form of a radio relic nor a radio halo. The region of the shock is on the western edge of AGN lobe emission from the brightest cluster galaxy. Correlating the flux of known shock-induced radio relics versus their size, we find that the radio emission overlapping the shocked region in MACS J0744.9+3927 is likely of AGN origin. We argue against the presence of a relic caused by diffusive shock acceleration and suggest that the shock is too weak to accelerate electrons from the intracluster medium.

Exploring the luminosity evolution and stellar mass assembly of 2SLAQ luminous red galaxies between redshifts 0.4 and 0.8

Science.gov (United States)

Banerji, Manda; Ferreras, Ignacio; Abdalla, Filipe B.; Hewett, Paul; Lahav, Ofer

2010-03-01

We present an analysis of the evolution of 8625 luminous red galaxies (LRGs) between z = 0.4 and 0.8 in the 2dF and Sloan Digital Sky Survey LRG and QSO (2SLAQ) survey. The LRGs are split into redshift bins and the evolution of both the luminosity and stellar mass function with redshift is considered and compared to the assumptions of a passive evolution scenario. We draw attention to several sources of systematic error that could bias the evolutionary predictions made in this paper. While the inferred evolution is found to be relatively unaffected by the exact choice of spectral evolution model used to compute K + e corrections, we conclude that photometric errors could be a source of significant bias in colour-selected samples such as this, in particular when using parametric maximum likelihood based estimators. We find that the evolution of the most massive LRGs is consistent with the assumptions of passive evolution and that the stellar mass assembly of the LRGs is largely complete by z ~ 0.8. Our findings suggest that massive galaxies with stellar masses above 1011Msolar must have undergone merging and star formation processes at a very early stage (z >~ 1). This supports the emerging picture of downsizing in both the star formation as well as the mass assembly of early-type galaxies. Given that our spectroscopic sample covers an unprecedentedly large volume and probes the most massive end of the galaxy mass function, we find that these observational results present a significant challenge for many current models of galaxy formation.

Alignment between galaxies and large-scale structure

International Nuclear Information System (INIS)

Faltenbacher, A.; Li Cheng; White, Simon D. M.; Jing, Yi-Peng; Mao Shude; Wang Jie

2009-01-01

Based on the Sloan Digital Sky Survey DR6 (SDSS) and the Millennium Simulation (MS), we investigate the alignment between galaxies and large-scale structure. For this purpose, we develop two new statistical tools, namely the alignment correlation function and the cos(2θ)-statistic. The former is a two-dimensional extension of the traditional two-point correlation function and the latter is related to the ellipticity correlation function used for cosmic shear measurements. Both are based on the cross correlation between a sample of galaxies with orientations and a reference sample which represents the large-scale structure. We apply the new statistics to the SDSS galaxy catalog. The alignment correlation function reveals an overabundance of reference galaxies along the major axes of red, luminous (L ∼ * ) galaxies out to projected separations of 60 h- 1 Mpc. The signal increases with central galaxy luminosity. No alignment signal is detected for blue galaxies. The cos(2θ)-statistic yields very similar results. Starting from a MS semi-analytic galaxy catalog, we assign an orientation to each red, luminous and central galaxy, based on that of the central region of the host halo (with size similar to that of the stellar galaxy). As an alternative, we use the orientation of the host halo itself. We find a mean projected misalignment between a halo and its central region of ∼ 25 deg. The misalignment decreases slightly with increasing luminosity of the central galaxy. Using the orientations and luminosities of the semi-analytic galaxies, we repeat our alignment analysis on mock surveys of the MS. Agreement with the SDSS results is good if the central orientations are used. Predictions using the halo orientations as proxies for central galaxy orientations overestimate the observed alignment by more than a factor of 2. Finally, the large volume of the MS allows us to generate a two-dimensional map of the alignment correlation function, which shows the reference

Fermi monitoring of radio-loud narrow-line Seyfert 1 galaxies

Energy Technology Data Exchange (ETDEWEB)

Paliya, Vaidehi S.; Stalin, C. S. [Indian Institute of Astrophysics, Block II, Koramangala, Bangalore-560034 (India); Ravikumar, C. D., E-mail: vaidehi@iiap.res.in [Department of Physics, University of Calicut, Malappuram-673635 (India)

2015-02-01

We present detailed analysis of the γ-ray flux variability and spectral properties of the five radio-loud narrow line Seyfert 1 (RL-NLSy1) galaxies, detected by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope, namely 1H 0323+342, SBS 0846+513, PMN J0948+0022, PKS 1502+036, and PKS 2004−447. The first three sources show significant flux variations, including the rapid variability of a few hours by 1H 0323+342. The average γ-ray spectrum of 1H 0323+342 and PMN J0948+0022 shows deviation from a simple power-law (PL) behavior, whereas the PL model gives a better fit for the other three sources. The spectra of 1H 0323+342, SBS 0846+513, and PMN J0948+0022, which are in low, flaring, and moderately active states, respectively, show significant curvature. Such curvature in the γ-ray spectrum of 1H 0323+342 and PMN J0948+0022 could be due to the emission region located inside the broad line region (BLR) where the primary mechanism of the γ-ray emission is inverse-Compton (IC) scattering of BLR photons occurring in the Klein–Nishina regime. The γ-ray emission of SBS 0846+513 is explained by IC scattering of dusty torus photons, which puts the emission region outside the BLR and thus under the Thomson regime. Therefore, the observed curvature of SBS 0846+513 could be intrinsic to the particle energy distribution. The presence of curvature in the γ-ray spectrum and flux variability amplitudes of some of the RL-NLSy1 galaxies suggests that these sources could be akin to low/moderate jet power flat spectrum radio quasars.

Fermi monitoring of radio-loud narrow-line Seyfert 1 galaxies

International Nuclear Information System (INIS)

Paliya, Vaidehi S.; Stalin, C. S.; Ravikumar, C. D.

2015-01-01

We present detailed analysis of the γ-ray flux variability and spectral properties of the five radio-loud narrow line Seyfert 1 (RL-NLSy1) galaxies, detected by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope, namely 1H 0323+342, SBS 0846+513, PMN J0948+0022, PKS 1502+036, and PKS 2004−447. The first three sources show significant flux variations, including the rapid variability of a few hours by 1H 0323+342. The average γ-ray spectrum of 1H 0323+342 and PMN J0948+0022 shows deviation from a simple power-law (PL) behavior, whereas the PL model gives a better fit for the other three sources. The spectra of 1H 0323+342, SBS 0846+513, and PMN J0948+0022, which are in low, flaring, and moderately active states, respectively, show significant curvature. Such curvature in the γ-ray spectrum of 1H 0323+342 and PMN J0948+0022 could be due to the emission region located inside the broad line region (BLR) where the primary mechanism of the γ-ray emission is inverse-Compton (IC) scattering of BLR photons occurring in the Klein–Nishina regime. The γ-ray emission of SBS 0846+513 is explained by IC scattering of dusty torus photons, which puts the emission region outside the BLR and thus under the Thomson regime. Therefore, the observed curvature of SBS 0846+513 could be intrinsic to the particle energy distribution. The presence of curvature in the γ-ray spectrum and flux variability amplitudes of some of the RL-NLSy1 galaxies suggests that these sources could be akin to low/moderate jet power flat spectrum radio quasars.

A radio and optical study of Molonglo radio sources

Science.gov (United States)

Ishwara-Chandra, C. H.; Saikia, D. J.; McCarthy, P. J.; van Breugel, W. J. M.

2001-05-01

We present multi-wavelength radio observations with the Very Large Array, and narrow- and broad-band optical observations with the 2.5-m telescope at the Las Campanas Observatory, of a well-defined sample of high-luminosity Fanaroff-Riley class II radio galaxies and quasars, selected from the Molonglo Reference Catalogue 1-Jy sample. These observations were carried out as part of a programme to investigate the effects of orientation and environment on some of the observed properties of these sources. We examine the dependence of the Liu-Pooley relationship, which shows that radio lobes with flatter radio spectra are less depolarized, on size, identification and redshift, and show that it is significantly stronger for smaller sources, with the strength of the relationship being similar for both radio galaxies and quasars. In addition to Doppler effects, there appear to be intrinsic differences between the lobes on opposite sides. We discuss the asymmetry in brightness and location of the hotspots, and present estimates of the ages and velocities from matched-resolution observations in the L and C bands. Narrow- and broad-band optical images of some of these sources were made to study their environments and correlate with the symmetry parameters. An extended emission-line region is seen in a quasar, and in four of the objects possible companion galaxies are seen close to the radio axis.

A DETAILED STUDY OF THE LOBES OF ELEVEN POWERFUL RADIO GALAXIES

International Nuclear Information System (INIS)

Daly, Ruth A.; Mory, Matthew P.; McKane, Justin; Altenderfer, Christopher; Beury, Michael; Kharb, Preeti; O'Dea, Christopher P.; Baum, Stefi A.

2010-01-01

Radio lobes of a sample of 11 very powerful classical double radio galaxies were studied. Each source was rotated so that the symmetry axis of the source was horizontal, and vertical cross-sectional cuts were taken across the source at intervals of one beam size. These were used to study the cross-sectional surface brightness profiles, the width of each slice, radio emissivity as a function of position across each slice, the first and second moments, and the average surface brightness, minimum-energy magnetic field strength, and pressure of each slice. Typically, a Gaussian provides a good description of the surface brightness profile of cross-sectional slices. The Gaussian full width at half-maximum (FWHM) as a function of distance from the hot spot first increases and then decreases with increasing distance from the hot spot. The width as a function of distance from the hot spot is generally highly symmetric on each side of the source. The radio emissivity is often close to flat across a slice, indicating a roughly constant emissivity and pressure for that slice. Some slices show variations in radio emissivity that indicate an 'edge-peaked' pressure profile for that slice. When this occurs, it is generally found in slices near the local maxima of the bridge width. The emissivity does not exhibit any signature of emission from a jet. The first moment is generally quite close to zero indicating only small excursions of the ridgeline from the symmetry axis of the source. The second moment indicates the same source shape as is found using the Gaussian FWHM. The average surface brightness is peaked at the hot spot, and is fairly flat across most of the radio lobes. The average magnetic field strength and pressure peak at the hot spot and gradually decrease with increasing distance from the hot spot, reaching a roughly constant value at a location that is typically just before the location of a local maximum of the bridge width. These results are interpreted in terms

Large-Scale Outflows in Seyfert Galaxies

Science.gov (United States)

Colbert, E. J. M.; Baum, S. A.

1995-12-01

\\catcode`\\@=11 \\ialign{m @th#1hfil ##hfil \\crcr#2\\crcr\\sim\\crcr}}} \\catcode`\\@=12 Highly collimated outflows extend out to Mpc scales in many radio-loud active galaxies. In Seyfert galaxies, which are radio-quiet, the outflows extend out to kpc scales and do not appear to be as highly collimated. In order to study the nature of large-scale (>~1 kpc) outflows in Seyferts, we have conducted optical, radio and X-ray surveys of a distance-limited sample of 22 edge-on Seyfert galaxies. Results of the optical emission-line imaging and spectroscopic survey imply that large-scale outflows are present in >~{{1} /{4}} of all Seyferts. The radio (VLA) and X-ray (ROSAT) surveys show that large-scale radio and X-ray emission is present at about the same frequency. Kinetic luminosities of the outflows in Seyferts are comparable to those in starburst-driven superwinds. Large-scale radio sources in Seyferts appear diffuse, but do not resemble radio halos found in some edge-on starburst galaxies (e.g. M82). We discuss the feasibility of the outflows being powered by the active nucleus (e.g. a jet) or a circumnuclear starburst.

POWERFUL ACTIVITY IN THE BRIGHT AGES. I. A VISIBLE/IR SURVEY OF HIGH REDSHIFT 3C RADIO GALAXIES AND QUASARS

Energy Technology Data Exchange (ETDEWEB)

Hilbert, B.; Chiaberge, M.; Kotyla, J. P.; Sparks, W. B.; Macchetto, F. D. [Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218 (United States); Tremblay, G. R. [Yale University, Department of Astronomy, 260 Whitney Avenue, New Haven, CT 06511 (United States); Stanghellini, C. [INAF—Istituto di Radioastronomia, Via P. Gobetti, 101 I-40129 Bologna (Italy); Baum, S.; O’Dea, C. P. [University of Manitoba, Dept of Physics and Astronomy, 66 Chancellors Circle, Winnipeg, MB R3T 2N2 (Canada); Capetti, A. [Osservatorio Astronomico de Torino, Corso Savona, I-10024 Moncalieri TO (Italy); Miley, G. K. [Universiteit Leiden, Rapenburg 70, 2311 EZ Leiden (Netherlands); Perlman, E. S. [Florida Institute of Technology, 150 W University Boulevard, Melbourne, FL 32901 (United States); Quillen, A. [Rochester Institute of Technology, School of Physics and Astronomy, 84 Lomb Memorial Drive, Rochester, NY 14623 (United States)

2016-07-01

We present new rest-frame UV and visible observations of 22 high- z (1 < z < 2.5) 3C radio galaxies and QSOs obtained with the Hubble Space Telescope ’s Wide Field Camera 3 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 reveal that brighter QSOs generally tend to be 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 and radio axes alignment.

THE ORIGIN OF THE INFRARED EMISSION IN RADIO GALAXIES. II. ANALYSIS OF MID- TO FAR-INFRARED SPITZER OBSERVATIONS OF THE 2JY SAMPLE

International Nuclear Information System (INIS)

Dicken, D.; Tadhunter, C.; Axon, D.; Morganti, R.; Inskip, K. J.; Holt, J.; Groves, B.; Delgado, R. Gonzalez

2009-01-01

We present an analysis of deep mid- to far-infrared (MFIR) Spitzer photometric observations of the southern 2Jy sample of powerful radio sources (0.05 < z < 0.7), conducting a statistical investigation of the links between radio jet, active galactic nucleus (AGN), starburst activity and MFIR properties. This is part of an ongoing extensive study of powerful radio galaxies that benefits from both complete optical emission line information and a uniquely high detection rate in the far-infrared (far-IR). We find tight correlations between the MFIR and [O III]λ5007 emission luminosities, which are significantly better than those between MFIR and extended radio luminosities, or between radio and [O III] luminosities. Since [O III] is a known indicator of intrinsic AGN power, these correlations confirm AGN illumination of the circumnuclear dust as the primary heating mechanism for the dust producing thermal MFIR emission at both 24 and 70 μm. We demonstrate that AGN heating is energetically feasible, and identify the narrow-line region clouds as the most likely location of the cool, far-IR emitting dust. Starbursts make a major contribution to the heating of the cool dust in only 15%-28% of our targets. We also investigate the orientation dependence of the continuum properties, finding that the broad- and narrow-line objects in our sample with strong emission lines have similar distributions of MFIR luminosities and colors. Therefore our results are entirely consistent with the orientation-based unified schemes for powerful radio galaxies. However, the weak line radio galaxies form a separate class of objects with intrinsically low-luminosity AGNs in which both the optical emission lines and the MFIR continuum are weak.

The radio universe

International Nuclear Information System (INIS)

Worvill, R.

1977-01-01

Elementary description of the development of radioastronomy, radio waves from the sun and planets, the use of radio telescopes and the detection of nebulae, supernova, radio galaxies and quasars is presented. A brief glossary of terms is included. (UK)

The extreme flare in III Zw 2: evolution of a radio jet in a Seyfert galaxy

NARCIS (Netherlands)

Brunthaler, A.; Falcke, H.D.E.; Bower, G.C.; Aller, M.F.; Aller, H.D.; Teraesranta, H.

2005-01-01

A very detailed monitoring of a radio flare in the Seyfert I galaxy III Zw 2 with the VLA and the VLBA is presented. The relative astrometry in the VLBA observations was precise on a level of a few microarcseconds. Spectral and spatial evolution of the source are closely linked and these

Understanding the radio spectral indices of galaxy cluster relics by superdiffusive shock acceleration

Science.gov (United States)

Zimbardo, Gaetano; Perri, Silvia

2018-06-01

Galaxy cluster merger shocks are the likely source of relativistic electrons, but many observations do not fit into the standard acceleration models. In particular, there is a long-standing discrepancy between the radio derived Mach numbers M_radio and the Mach numbers derived from X-ray measurements, M_X. Here, we show how superdiffusive electron transport and superdiffusive shock acceleration (SSA) can help to solve this problem. We present a heuristic derivation of the superlinear time growth of the mean square displacement of particles, ⟨Δx2⟩∝tβ, and of the particle energy spectral index in the framework of SSA. The resulting expression for the radio spectral index α is then used to determine the superdiffusive exponent β from the observed values of α and of the compression ratio for a number of radio relics. Therefore, the fact that M_radio>M_X can be explained by SSA without the need to make assumptions on the energy spectrum of the seed electrons to be re-accelerated. We also consider the acceleration times obtained in the diffusive case, based both on the Bohm diffusion coefficient and on the quasilinear diffusion coefficient. While in the latter case the acceleration time is consistent with the estimated electron energy loss time, the former case it is much shorter.

Twin radio relics in the nearby low-mass galaxy cluster Abell 168

Science.gov (United States)

Dwarakanath, K. S.; Parekh, V.; Kale, R.; George, L. T.

2018-06-01

We report the discovery of twin radio relics in the outskirts of the low-mass merging galaxy cluster Abell 168 (redshift=0.045). One of the relics is elongated with a linear extent ˜800 kpc and projected width of ˜80 kpc and is located ˜900 kpc towards the north of the cluster centre, oriented roughly perpendicular to the major axis of the X-ray emission. The second relic is ring-shaped with a size ˜220 kpc and is located near the inner edge of the elongated relic at a distance of ˜600 kpc from the cluster centre. These radio sources were imaged at 323 and 608 MHz with the Giant Meterwave Radio Telescope and at 1520 MHz with the Karl G. Jansky Very Large Array (VLA). The elongated relic was detected at all frequencies, with a radio power of 1.38 ± 0.14 × 1023 W Hz-1 at 1.4 GHz and a power law in the frequency range 70-1500 MHz (S ∝ να, α = -1.1 ± 0.04). This radio power is in good agreement with that expected from the known empirical relation between the radio powers of relics and host cluster masses. This is the lowest mass (M500 = 1.24 × 1014 M⊙) cluster in which relics due to merger shocks are detected. The ring-shaped relic has a steeper spectral index (α) of -1.74 ± 0.29 in the frequency range 100-600 MHz. We propose this relic to be an old plasma, revived due to adiabatic compression by the outgoing shock that produced the elongated relic.

Galaxy Cluster Outskirts from the Thermal SZ and Non-Thermal Synchrotron Link

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