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Sample records for radio-loud active galactic

  1. MAGNETIC FLUX PARADIGM FOR RADIO LOUDNESS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sikora, Marek; Begelman, Mitchell C. E-mail: mitch@jila.colorado.edu

    2013-02-20

    We argue that the magnetic flux threading the black hole (BH), rather than BH spin or Eddington ratio, is the dominant factor in launching powerful jets and thus determining the radio loudness of active galactic nuclei (AGNs). Most AGNs are radio quiet because the thin accretion disks that feed them are inefficient in depositing magnetic flux close to the BH. Flux accumulation is more likely to occur during a hot accretion (or thick disk) phase, and we argue that radio-loud quasars and strong emission-line radio galaxies occur only when a massive, cold accretion event follows an episode of hot accretion. Such an event might be triggered by the merger of a giant elliptical galaxy with a disk galaxy. This picture supports the idea that flux accumulation can lead to the formation of a so-called magnetically choked accretion flow. The large observed range in radio loudness reflects not only the magnitude of the flux pressed against the BH, but also the decrease in UV flux from the disk, due to its disruption by the ''magnetosphere'' associated with the accumulated flux. While the strongest jets result from the secular accumulation of flux, moderate jet activity can also be triggered by fluctuations in the magnetic flux deposited by turbulent, hot inner regions of otherwise thin accretion disks, or by the dissipation of turbulent fields in accretion disk coronae. These processes could be responsible for jet production in Seyferts and low-luminosity AGNs, as well as jets associated with X-ray binaries.

  2. Ultrafast outflows in radio-loud active galactic nuclei

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  3. RADIO-LOUD ACTIVE GALACTIC NUCLEUS: IS THERE A LINK BETWEEN LUMINOSITY AND CLUSTER ENVIRONMENT?

    SciTech Connect

    Ineson, J.; Croston, J. H.; Hardcastle, M. J.; Jarvis, M.; Kraft, R. P.; Evans, D. A.

    2013-06-20

    We present here the first results from the Chandra ERA (Environments of Radio-loud AGN) Large Project, characterizing the cluster environments of a sample of 26 radio-loud active galactic nuclei (AGNs) at z {approx} 0.5 that covers three decades of radio luminosity. This is the first systematic X-ray environmental study at a single epoch, and has allowed us to examine the relationship between radio luminosity and cluster environment without the problems of Malmquist bias. We have found a weak correlation between radio luminosity and host cluster X-ray luminosity, as well as tentative evidence that this correlation is driven by the subpopulation of low-excitation radio galaxies, with high-excitation radio galaxies showing no significant correlation. The considerable scatter in the environments may be indicative of complex relationships not currently included in feedback models.

  4. Kepler Photometry of Four Radio-loud Active Galactic Nuclei in 2010-2012

    NASA Astrophysics Data System (ADS)

    Wehrle, Ann E.; Wiita, Paul J.; Unwin, Stephen C.; Di Lorenzo, Paolo; Revalski, Mitchell; Silano, Daniel; Sprague, Dan

    2013-08-01

    We have used Kepler photometry to characterize variability in four radio-loud active galactic nuclei (AGN; three quasars and one object tentatively identified as a Seyfert 1.5 galaxy) on timescales from minutes to months, comparable to the light crossing time of the accretion disk around the central supermassive black hole or the base of the relativistic jet. Kepler's almost continuous observations provide much better temporal coverage than is possible from ground-based observations. We report the first such data analyzed for quasars. We have constructed power spectral densities using eight Kepler quarters of long-cadence (30-minute) data for three AGN, six quarters for one AGN and two quarters of short-cadence (1-minute) data for all four AGN. On timescales longer than about 0.2-0.6 days, we find red noise with mean power-law slopes ranging from -1.8 to -1.2, consistent with the variability originating in turbulence either behind a shock or within an accretion disk. Each AGN has a range of red noise slopes which vary slightly by month and quarter of observation. No quasi-periodic oscillations of astrophysical origin were detected. We detected flares of several days long when brightness increased by 3%-7% in two objects. No flares on timescales of minutes to hours were detected. Our observations imply that the duty cycle for enhanced activity in these radio-loud AGN is small. These well-sampled AGN light curves provide an impetus to develop more detailed models of turbulence in jets and instabilities in accretion disks.

  5. KEPLER PHOTOMETRY OF FOUR RADIO-LOUD ACTIVE GALACTIC NUCLEI IN 2010-2012

    SciTech Connect

    Wehrle, Ann E.; Wiita, Paul J.; Di Lorenzo, Paolo; Revalski, Mitchell; Silano, Daniel; Sprague, Dan; Unwin, Stephen C.

    2013-08-20

    We have used Kepler photometry to characterize variability in four radio-loud active galactic nuclei (AGN; three quasars and one object tentatively identified as a Seyfert 1.5 galaxy) on timescales from minutes to months, comparable to the light crossing time of the accretion disk around the central supermassive black hole or the base of the relativistic jet. Kepler's almost continuous observations provide much better temporal coverage than is possible from ground-based observations. We report the first such data analyzed for quasars. We have constructed power spectral densities using eight Kepler quarters of long-cadence (30-minute) data for three AGN, six quarters for one AGN and two quarters of short-cadence (1-minute) data for all four AGN. On timescales longer than about 0.2-0.6 days, we find red noise with mean power-law slopes ranging from -1.8 to -1.2, consistent with the variability originating in turbulence either behind a shock or within an accretion disk. Each AGN has a range of red noise slopes which vary slightly by month and quarter of observation. No quasi-periodic oscillations of astrophysical origin were detected. We detected flares of several days long when brightness increased by 3%-7% in two objects. No flares on timescales of minutes to hours were detected. Our observations imply that the duty cycle for enhanced activity in these radio-loud AGN is small. These well-sampled AGN light curves provide an impetus to develop more detailed models of turbulence in jets and instabilities in accretion disks.

  6. An X-Ray Spectral Survey of Radio-loud Active Galactic Nuclei with ASCA

    NASA Astrophysics Data System (ADS)

    Sambruna, Rita M.; Eracleous, Michael; Mushotzky, Richard F.

    1999-11-01

    We present a uniform and systematic analysis of the 0.6-10 keV X-ray spectra of radio-loud active galactic nuclei (AGNs) observed by ASCA. The sample, which is not statistically complete, includes 10 broad-line radio galaxies (BLRGs), five radio-loud quasars (QSRs), nine narrow-line radio galaxies (NLRGs), and 10 radio galaxies (RGs) of mixed FR I and FR II types. For several sources the ASCA data are presented here for the first time. The exposure times of the observations and the fluxes of the objects vary over a wide range; as a result, so does the signal-to-noise ratio of the individual X-ray spectra. At soft X-rays, about 50% of NLRGs and 100% of RGs exhibit thermal plasma emission components, with bimodal distributions of temperatures and luminosities. This indicates that the emission in such an object arises in hot gas either in a surrounding cluster or loose group or in a hot corona, consistent with previous ROSAT and optical results. At energies above 2 keV, a hard power-law component (photon index Γ~1.7-1.8) is detected in 90% of cases. The power-law photon indices and luminosities in BLRGs, QSRs, and NLRGs are similar. This is consistent with simple orientation-based unification schemes for lobe-dominated radio-loud sources in which BLRGs, QSRs, and NLRGs harbor the same type of central engine. Moreover, excess cold absorption in the range 1021-1024 cm-2 is detected in most (but not all) NLRGs, consistent with absorption by obscuring tori, as postulated by unification scenarios. The ASCA data provide initial evidence that the immediate gaseous environment of the X-ray source of BLRGs may be different than in Seyfert 1 galaxies: absorption edges of ionized oxygen, common in the latter, are detected in only one BLRG. Instead we detect large columns of cold gas in a fraction (~44%-60%) of BLRGs and QSRs, comparable to the columns detected in NLRGs, which is puzzling. This difference hints at different physical and/or geometrical properties of the medium

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

    SciTech Connect

    Worpel, Hauke; Brown, Michael J. I.; Jones, D. Heath; Floyd, David J. E.; Beutler, Florian

    2013-07-20

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

  8. Fermi-LAT γ-ray anisotropy and intensity explained by unresolved radio-loud active galactic nuclei

    SciTech Connect

    Mauro, Mattia Di; Cuoco, Alessandro; Donato, Fiorenza; Siegal-Gaskins, Jennifer M. E-mail: alessandro.cuoco@to.infn.it E-mail: jsg@tapir.caltech.edu

    2014-11-01

    Radio-loud active galactic nuclei (AGN) are expected to contribute substantially to both the intensity and anisotropy of the isotropic γ-ray background (IGRB). In turn, the measured properties of the IGRB can be used to constrain the characteristics of proposed contributing source classes. We consider individual subclasses of radio-loud AGN, including low-, intermediate-, and high-synchrotron-peaked BL Lacertae objects, flat-spectrum radio quasars, and misaligned AGN. Using updated models of the γ-ray luminosity functions of these populations, we evaluate the energy-dependent contribution of each source class to the intensity and anisotropy of the IGRB. We find that collectively radio-loud AGN can account for the entirety of the IGRB intensity and anisotropy as measured by the Fermi Large Area Telescope (LAT). Misaligned AGN provide the bulk of the measured intensity but a negligible contribution to the anisotropy, while high-synchrotron-peaked BL Lacertae objects provide the dominant contribution to the anisotropy. In anticipation of upcoming measurements with the Fermi-LAT and the forthcoming Cherenkov Telescope Array, we predict the anisotropy in the broader energy range that will be accessible to future observations.

  9. Radio-Loud Narrow-Line Seyfert 1 as a New Class of Gamma-Ray Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T. H.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cecchi, C.; Çelik, Ö.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; Dermer, C. D.; de Palma, F.; Silva, E. do Couto e.; Drell, P. S.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Foschini, L.; Frailis, M.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giebels, B.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kadler, M.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kerr, M.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Pelassa, V.; Pepe, M.; Persic, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Rochester, L. S.; Rodriguez, A. Y.; Ryde, F.; Sadrozinski, H. F.-W.; Sambruna, R.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sgrò, C.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Tagliaferri, G.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Tibolla, O.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.; Fermi/LAT Collaboration; Ghisellini, G.; Maraschi, L.; Tavecchio, F.

    2009-12-01

    We report the discovery with Fermi/LAT of γ-ray emission from three radio-loud narrow-line Seyfert 1 galaxies: PKS 1502+036 (z = 0.409), 1H 0323+342 (z = 0.061), and PKS 2004 - 447 (z = 0.24). In addition to PMN J0948+0022 (z = 0.585), the first source of this type to be detected in γ rays, they may form an emerging new class of γ-ray active galactic nuclei (AGNs). These findings can have strong implications on our knowledge about relativistic jets and the unified model of the AGN.

  10. GALAXY CLUSTERS AROUND RADIO-LOUD ACTIVE GALACTIC NUCLEI AT 1.3 < z < 3.2 AS SEEN BY SPITZER

    SciTech Connect

    Wylezalek, Dominika; Stern, Daniel; Eisenhardt, Peter R. M.; Galametz, Audrey; Vernet, Joeel; De Breuck, Carlos; Seymour, Nick; Brodwin, Mark; Gonzalez, Anthony H.; Hatch, Nina; Jarvis, Matt; Rettura, Alessandro; Stanford, Spencer A.; Stevens, Jason A.

    2013-05-20

    We report the first results from the Clusters Around Radio-Loud AGN program, a Cycle 7 and 8 Spitzer Space Telescope snapshot program to investigate the environments of a large sample of obscured and unobscured luminous radio-loud active galactic nuclei (AGNs) at 1.2 < z < 3.2. These data, obtained for 387 fields, reach 3.6 and 4.5 {mu}m depths of [3.6]{sub AB} = 22.6 and [4.5]{sub AB} = 22.9 at the 95% completeness level, which is two to three times fainter than L* in this redshift range. By using the color cut [3.6] - [4.5] > -0.1 (AB), which efficiently selects high-redshift (z > 1.3) galaxies of all types, we identify galaxy cluster member candidates in the fields of the radio-loud AGN. The local density of these Infrared Array Camera (IRAC)-selected sources is compared to the density of similarly selected sources in blank fields. We find that 92% of the radio-loud AGN reside in environments richer than average. The majority (55%) of the radio-loud AGN fields are found to be overdense at a {>=}2{sigma} level; 10% are overdense at a {>=}5{sigma} level. A clear rise in surface density of IRAC-selected sources toward the position of the radio-loud AGN strongly supports an association of the majority of the IRAC-selected sources with the radio-loud AGN. Our results provide solid statistical evidence that radio-loud AGN are likely beacons for finding high-redshift galaxy (proto-)clusters. We investigate how environment depends on AGN type (unobscured radio-loud quasars versus obscured radio galaxies), radio luminosity and redshift, finding no correlation with either AGN type or radio luminosity. We find a decrease in density with redshift, consistent with galaxy evolution for this uniform, flux-limited survey. These results are consistent with expectations from the orientation-driven AGN unification model, at least for the high radio luminosity regimes considered in this sample.

  11. Radio-Loudness of Active Galactic Nuclei: Observational Facts and Theoretical Implications

    SciTech Connect

    Sikora, Marek; Stawarz, Lukasz; Lasota, Jean-Pierre; /Paris, Inst. Astrophys.

    2007-01-30

    We investigate how the total radio luminosity of AGN-powered radio sources depends on their accretion luminosity and the central black hole mass. Our studies cover about seven orders of magnitude in accretion luminosity (expressed in Eddington units, i.e. as Eddington ratios) and the full range of AGN black hole masses. We find that AGNs form two distinct and well separated sequences on the radio-loudness--Eddington-ratio plane. The ''upper'' sequence is formed by radio selected AGNs, the ''lower'' sequence contains mainly optically selected objects. Whereas an apparent ''gap'' between the two sequences may be an artifact of selection effects, the sequences themselves mark the real upper bounds of radio-loudness of two distinct populations of AGNs: those hosted respectively by elliptical and disk galaxies. Both sequences show the same dependence of the radio-loudness on the Eddington ratio (an increase with decreasing Eddington ratio), which suggests that the normalization of this dependence is determined by the black hole spin. This implies that central black holes in giant elliptical galaxies have (on average) much larger spins than black holes in spiral/disc galaxies. This galaxy-morphology related radio-dichotomy breaks down at high accretion rates where the dominant fraction of luminous quasars hosted by elliptical galaxies is radio quiet. This led to speculations in the literature that formation of powerful jets at high accretion rates is intermittent and related to switches between two disk accretion modes, as directly observed in some BH X-ray binaries. We argue that such intermittency can be reconciled with the spin paradigm, provided that successful formation of relativistic jets by rotating black holes requires collimation by MHD outflows from accretion disks.

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

    NASA Astrophysics Data System (ADS)

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

    2010-02-01

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

  13. FROM THE BLAZAR SEQUENCE TO THE BLAZAR ENVELOPE: REVISITING THE RELATIVISTIC JET DICHOTOMY IN RADIO-LOUD ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Meyer, Eileen T.; Fossati, Giovanni; Georganopoulos, Markos; Lister, Matthew L.

    2011-10-20

    We revisit the concept of a blazar sequence that relates the synchrotron peak frequency ({nu}{sub peak}) in blazars with synchrotron peak luminosity (L{sub peak}, in {nu}L{sub {nu}}) using a large sample of radio-loud active galactic nuclei. We present observational evidence that the blazar sequence is formed from two populations in the synchrotron {nu}{sub peak}-L{sub peak} plane, each forming an upper edge to an envelope of progressively misaligned blazars, and connecting to an adjacent group of radio galaxies having jets viewed at much larger angles to the line of sight. When binned by jet kinetic power (L{sub kin}; as measured through a scaling relationship with extended radio power), we find that radio core dominance decreases with decreasing synchrotron L{sub peak}, revealing that sources in the envelope are generally more misaligned. We find population-based evidence of velocity gradients in jets at low kinetic powers ({approx}10{sup 42}-10{sup 44.5} erg s{sup -1}), corresponding to Fanaroff-Riley (FR) I radio galaxies and most BL Lac objects. These low jet power 'weak-jet' sources, thought to exhibit radiatively inefficient accretion, are distinguished from the population of non-decelerating, low synchrotron-peaking (LSP) blazars and FR II radio galaxies ('strong' jets) which are thought to exhibit radiatively efficient accretion. The two-population interpretation explains the apparent contradiction of the existence of highly core-dominated, low-power blazars at both low and high synchrotron peak frequencies, and further implies that most intermediate synchrotron peak sources are not intermediate in intrinsic jet power between LSP and high synchrotron-peaking (HSP) sources, but are more misaligned versions of HSP sources with similar jet powers.

  14. The X-ray view of radio-loud active galactic nuclei: The central engine and its environment

    NASA Astrophysics Data System (ADS)

    Donato, Davide

    The non-thermal emission from many Active Galactic Nuclei (AGN) is obscured by optically thick circumnuclear matter, particularly at optical and ultraviolet wavelengths. In radio-loud (RL) sources, the AGN activity is coupled with the presence of a bipolar jet that emit radio through g-ray light which is relativistically beamed along the jet axes. The combination of absorption and beaming produces highly anisotropic radiation. The understanding of the origin and magnitude of this radiation allows astronomers to unify different classes of AGN; that is, to identify each single, underlying AGN type that gives rise to different classes through different orientations with respect to the jet axis. This is the fundamental notion behind what are called "unification models" of AGN. Although this general idea is well accepted, many aspects remain matter of debate. In fact, the explanation of the wide and complex variety of AGN phenomena must be searched in a combination of apparent differences (like orientation) and real differences in a number of physical parameters (like gas/dust content and distribution, luminosity, etc.). The goal of this thesis is to address some of the RL unification open questions using X-ray data. The improved sensitivity and angular resolution of a new generation of satellites, combined with the fact that X-rays provide useful information on a variety of AGN phenomena, will allow me to: (1) Study the broadband X-ray continua of BL Lacertae objects (BL Lacs) and Flat Spectrum Radio Quasars (FSRQs); (2) Probe the emission from the very inner region of an AGN; (3) Determine the presence and characteristic of extended X-ray emission from the AGN environment. The results obtained from theses studies will provide me insights into (1) the X-ray average spectral properties of BL Lacs and FSRQs and the physical processes responsible of the emission; (2) the presence of the obscuring torus and the amount of absorption, (3) the nature of X-ray emission, and (4

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

    We present the results of a comparison between the optical morphologies of a complete sample of 46 southern 2 Jy radio galaxies at intermediate redshifts (0.05 < z < 0.7) and those of two control samples of quiescent early-type galaxies: 55 ellipticals at redshifts z ≤ 0.01 from the Observations of Bright Ellipticals at Yale (OBEY) survey, and 107 early-type galaxies at redshifts 0.2 < z < 0.7 in the Extended Groth Strip (EGS). Based on these comparisons, we discuss the role of galaxy interactions in the triggering of powerful radio galaxies (PRGs). We find that a significant fraction of quiescent ellipticals at low and intermediate redshifts show evidence for disturbed morphologies at relatively high surface brightness levels, which are likely the result of past or on-going galaxy interactions. However, the morphological features detected in the galaxy hosts of the PRGs (e.g. tidal tails, shells, bridges, etc.) are up to 2 mag brighter than those present in their quiescent counterparts. Indeed, if we consider the same surface brightness limits, the fraction of disturbed morphologies is considerably smaller in the quiescent population (53 per cent at z < 0.2 and 48 per cent at 0.2 ≤ z < 0.7) than in the PRGs (93 per cent at z < 0.2 and 95 per cent at 0.2 ≤ z < 0.7 considering strong-line radio galaxies only). This supports a scenario in which PRGs represent a fleeting active phase of a subset of the elliptical galaxies that have recently undergone mergers/interactions. However, we demonstrate that only a small proportion (≲20 per cent) of disturbed early-type galaxies are capable of hosting powerful radio sources.

  16. Constraining the population of radio-loud active galactic nuclei at high redshift with the power spectrum of the 21 cm Forest

    NASA Astrophysics Data System (ADS)

    Ewall-Wice, Aaron; Dillon, Joshua S.; Mesinger, Andrei; Hewitt, Jacqueline N.

    2014-06-01

    The 21 cm forest, the absorption by the intergalactic medium (IGM) towards a high redshift radio-loud source, is a probe of the thermal state of the IGM. To date, the literature has focused on line-of-sight spectral studies of a single quasar known to have a large redshift. We instead examine many sources in a wide field of view, and show that the imprint from the 21 cm forest absorption of these sources is detectible in the power spectrum. The properties of the power spectrum can reveal information on the population of the earliest radio loud sources that may have existed during the pre-reionization epoch at z>10.Using semi-numerical simulations of the IGM and a semi-empirical source population, we show that the 21 cm forest dominates, in a distinctive region of Fourier space, the brightness temperature power spectrum that many contemporary experiments aim to measure. In particular, the forest dominates the diffuse emission on smaller spatial scales along the line of sight. Exploiting this separation, one may constrain the IGM thermal history, such as heating by the first X-ray sources, on large spatial scales and the absorption of radio loud active galactic nuclei on small ones.Using realistic simulations of noise and foregrounds, we show that planned instruments on the scale of the Hydrogen Epoch of Reionization Array (HERA) with a collecting area of one tenth of a square kilometer can detect the 21cm forest in this small spatial scale region with high signal to noise. We develop an analytic toy model for the signal and explore its detectability over a large range of thermal histories and potential high redshift source scenarios.

  17. Radiation Mechanism and Jet Composition of Gamma-Ray Bursts and GeV-TeV-selected Radio-loud Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Zhang, Jin; Liang, En-Wei; Sun, Xiao-Na; Zhang, Bing; Lu, Ye; Zhang, Shuang-Nan

    2013-09-01

    Gamma-ray bursts (GRBs) and GeV-TeV-selected radio-loud active galactic nuclei (AGNs) are compared based on our systematic modeling of the observed spectral energy distributions of a sample of AGNs with a single-zone leptonic model. We show that the correlation between the jet power (P jet) and the prompt gamma-ray luminosity (L jet) of GRBs is consistent, within the uncertainties, with the correlation between jet power and the synchrotron peak luminosity (L s, jet) of flat spectrum radio quasars (FSRQs). Their radiation efficiencies (ε) are also comparable (>10% for most sources), which increase with the bolometric jet luminosity (L bol, jet) for FSRQs and with the L jet for GRBs with similar power-law indices. BL Lac objects (BL Lacs) do not follow the P jet-L s, jet relation of FSRQs. They have lower ε and L bol, jet values than FSRQs, and a tentative L bol, jet-ε relation is also found, with a power-law index different from that of the FSRQs. The magnetization parameters (σ) of FSRQs are on average larger than that of BL Lacs. They are anti-correlated with ε for the FSRQs, but positively correlated with ε for the BL Lacs. GeV narrow-line Seyfert 1 galaxies potentially share similar properties with FSRQs. Based on the analogy between GRBs and FSRQs, we suggest that the prompt gamma-ray emission of GRBs is likely produced by the synchrotron process in a magnetized jet with high radiation efficiency, similar to FSRQs. The jets of BL Lacs, on the other hand, are less efficient and are likely more matter-dominated.

  18. 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)

    NASA Technical Reports Server (NTRS)

    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.

  19. 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)

    SciTech Connect

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

    2013-07-20

    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 s{sup -1} and 10{sup 44.9} erg s{sup -1} (14-195 keV), respectively. Based on the radio core luminosity, we estimate that the X-ray spectrum of 3C 206 contains a significant ({approx}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}({identical_to} {Omega}/2{pi}) = 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, < 71 eV, constrains the column density in the equatorial plane to N{sub H}{sup eq} <10{sup 23} cm{sup -2}, or the half-opening angle to {theta}{sub oa} > 80 Degree-Sign if N{sub H}{sup eq} =10{sup 24} cm{sup -2} is assumed. That of PKS 0707-35, 72 {+-} 36 eV, is consistent with N{sub H}{sup eq} {approx}10{sup 23} cm{sup -2}. 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.

  20. MULTI-WAVELENGTH OBSERVATIONS OF A SAMPLE OF INTERMEDIATE-LUMINOSITY RADIO-LOUD ACTIVE GALAXIES

    SciTech Connect

    Lewis, Karen T.; Sambruna, Rita M.; Cheung, Chi C.; Eracleous, Michael; Kadler, Matthias

    2011-07-15

    We present the results from exploratory (12-23 ks) XMM-Newton observations of six optically selected, radio-loud active galactic nuclei (AGNs), together with new radio data and a reanalysis of their archival SDSS spectra. The sources were selected in an effort to expand the current sample of radio-loud AGNs suitable for detailed X-ray spectroscopy studies. The sample includes three broad-line and three narrow-line sources, with X-ray luminosities of the order of L{sub 2-10keV} {approx} 10{sup 43} erg s{sup -1}. The EPIC spectra of the broad-lined sources can be described by single power laws with photon indices {Gamma} {approx} 1.6 and little to negligible absorption (N{sub H} {approx}<10{sup 21} cm{sup -2}); on the contrary, significant absorption is detected in the narrow-lined objects, N{sub H} {approx} 10{sup 23} cm{sup -2}, one of which displays a prominent (equivalent width {approx}2 keV) Fe K{alpha} emission line. Studying their location in several luminosity-luminosity diagrams for radio-loud AGNs, we find that the sources fall at the lower end of the distribution for bright, classical radio-loud AGNs and close to LINER-like sources. As such, and as indicated by the ratios of their optical emission lines, we conclude that the sources of our sample fall on the border between radiatively efficient and inefficient accretion flows. Future deeper studies of these targets at X-rays and longer wavelengths will expand our understanding of the central engines of radio-loud AGNs at a critical transition region.

  1. Radio Loud AGNs are Mergers

    NASA Astrophysics Data System (ADS)

    Chiaberge, Marco; Gilli, Roberto; Lotz, Jennifer M.; Norman, Colin

    2015-06-01

    We measure the merger fraction of Type 2 radio-loud and radio-quiet active galactic nuclei (AGNs) at z\\gt 1 using new samples. The objects have Hubble Space Telescope (HST) images taken with Wide Field Camera 3 (WFC3) in the IR channel. These samples are compared to the 3CR sample of radio galaxies at z\\gt 1 and to a sample of non-active galaxies. We also consider lower redshift radio galaxies with HST observations and previous generation instruments (NICMOS and WFPC2). The full sample spans an unprecedented range in both redshift and AGN luminosity. We perform statistical tests to determine whether the different samples are differently associated with mergers. We find that all (92%-14%+8%) radio-loud galaxies at z\\gt 1 are associated with recent or ongoing merger events. Among the radio-loud population there is no evidence for any dependence of the merger fraction on either redshift or AGN power. For the matched radio-quiet samples, only 38%-15+16 are merging systems. The merger fraction for the sample of non-active galaxies at z\\gt 1 is indistinguishable from radio-quiet objects. This is strong evidence that mergers are the triggering mechanism for the radio-loud AGN phenomenon and the launching of relativistic jets from supermassive black holes (SMBHs). We speculate that major black hole (BH)–BH mergers play a major role in spinning up the central SMBHs in these objects.

  2. Radio-Loud and Radio-Quiet Gamma-Ray Pulsars from the Galactic Plane and the Gould Belt

    SciTech Connect

    Gonthier, P. L.

    2005-03-17

    We present recent results of a pulsar population synthesis study in the polar cap model that includes the Parkes Multibeam Pulsar Survey, realistic beam geometries for radio and {gamma}-ray emission from neutron stars born in the Galactic disc as well as the local Gould Belt. We include nine radio surveys to normalize the simulated results from the Galactic disc to the number of radio pulsars observed by the group of selected surveys. In normalizing the contribution of the Gould Belt, we use results from a recent study that indicates a supernova rate in the Gould Belt of 3 to 5 times that of the local region of the Galactic plane leading to {approx}100 neutron stars born in the Gould Belt during the last 5 Myr. Our simulations include the dynamical evolution of the Gould Belt where neutron stars are produced in the plane of the Gould Belt during the past 5 Myr. We discuss the simulated numbers of radio-quiet (those below flux threshold of radio surveys) and radio-loud, {gamma}-ray pulsars from the Galactic disc and the Gould belt observed by {gamma}-ray telescopes EGRET, AGILE and GLAST. They suggest that about 35 of the unidentified EGRET sources could be (mostly radio-loud) {gamma}-ray pulsars with 2/3 of them born in the Galactic disc and 1/3 in the Gould Belt.

  3. A New Radio Loudness Diagnostic for Active Galaxies: A Radio-to-Mid-Infrared Parameter

    NASA Technical Reports Server (NTRS)

    Melendez, Marcio B.; Kraemer, S. B.; Schmitt, H. R.

    2010-01-01

    We have studied the relationship between the nuclear (high-resolution) radio emission, at 8.4GHz (3.6cm) and 1.4GHz (20cm), the [O IV) (gamma)25.89 micron, [Ne III] (gamma)l5.56 micron and [Ne II] (gamma)l2.81 micron emission lines and the black hole mass accretion rate for a sample of Seyfert galaxies. In order to characterize the radio contribution for the Seyfert nuclei we used the 8.4 GHz/[O IV] ratio, assuming that [0 IV] scales with the luminosity of the active galactic nuclei (AGN). From this we find that Seyfert 1 s (i.e. Seyfert 1.0s, 1.2s and 1.5s) and Seyfert 2s (i.e. Seyfert 1.8s, 1.9s and 2.0s) have similar radio contributions, relative to the AGN. On the other hand, sources in which the [Ne u] emission is dominated either by the AGN or star formation have statistically different radio contributions, with star formation dominated sources more 'radio loud', by a factor of approx.2.8 on average, than AGN dominated sources. We show that star formation dominated sources with relatively larger radio contribution have smaller mass accretion rates. Overall, we suggest that 8.4 GHz/[O IV], or alternatively, 1.4 GHz/[O IV] ratios, can be used to characterize the radio contribution, relative to the AGN, without the limitation of previous methods that rely on optical observables. Key words: Galaxy: stellar content - galaxies: Seyfert - infrared: galaxies

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

    NASA Technical Reports Server (NTRS)

    Romanishin, W.; Hintzen, Paul

    1989-01-01

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

  5. Constraining the Radio-loud Fraction of Quasars at z > 5.5

    NASA Astrophysics Data System (ADS)

    Bañados, E.; Venemans, B. P.; Morganson, E.; Hodge, J.; Decarli, R.; Walter, F.; Stern, D.; Schlafly, E.; Farina, E. P.; Greiner, J.; Chambers, K. C.; Fan, X.; Rix, H.-W.; Burgett, W. S.; Draper, P. W.; Flewelling, J.; Kaiser, N.; Metcalfe, N.; Morgan, J. S.; Tonry, J. L.; Wainscoat, R. J.

    2015-05-01

    Radio-loud active galactic nuclei at z˜ 2-4 are typically located in dense environments and their host galaxies are among the most massive systems at those redshifts, providing key insights for galaxy evolution. Finding radio-loud quasars at the highest accessible redshifts (z˜ 6) is important to the study of their properties and environments at even earlier cosmic time. They could also serve as background sources for radio surveys intended to study the intergalactic medium beyond the epoch of reionization in HI 21 cm absorption. Currently, only five radio-loud (R={{f}ν ,5 GHz}/{{f}ν ,4400 \\overset{\\circA }}\\gt 10) quasars are known at z˜ 6. In this paper we search for 5.5≲ z≲ 7.2 quasars by cross-matching the optical Panoramic Survey Telescope & Rapid Response System 1 and radio Faint Images of the Radio Sky at Twenty cm surveys. The radio information allows identification of quasars missed by typical color-based selections. While we find no good 6.4≲ z≲ 7.2 quasar candidates at the sensitivities of these surveys, we discover two new radio-loud quasars at z˜ 6. Furthermore, we identify two additional z˜ 6 radio-loud quasars that were not previously known to be radio-loud, nearly doubling the current z˜ 6 sample. We show the importance of having infrared photometry for z\\gt 5.5 quasars to robustly classify them as radio-quiet or radio-loud. Based on this, we reclassify the quasar J0203+0012 (z = 5.72), previously considered radio-loud, to be radio-quiet. Using the available data in the literature, we constrain the radio-loud fraction of quasars at z˜ 6, using the Kaplan-Meier estimator, to be 8.1-3.2+5.0%. This result is consistent with there being no evolution of the radio-loud fraction with redshift, in contrast to what has been suggested by some studies at lower redshifts.

  6. Quasar Radio-Loudness and the Elliptical Core Problem

    NASA Astrophysics Data System (ADS)

    Hamilton, Timothy S.

    2010-01-01

    The dichotomy between radio-loud and radio-quiet QSOs is not simply one of host morphology. While radio-louds are almost always found in elliptical hosts, radio-quiets are known to reside in both elliptical and spiral galaxies. We find that what determines whether a given elliptical galaxy will host either a radio-loud or radio-quiet QSO is a combination of accretion rate and host scale. QSOs with high x-ray luminosities (above 10e44.9 erg/s at 0.5 keV) are nearly all found to be radio-loud. But those with low luminosities divide fairly neatly along the Kormendy law, the correlation between re and μe. Those larger than about 10 kpc are radio-loud, while smaller ones are radio-quiet. It has recently been found that core and coreless ellipticals are also divided at about this limit. This implies that for low-luminosity QSOs, radio-louds are found in core ellipticals, while radio-quiets are in coreless ellipticals and spirals. This segregation shows up particularly strongly for low-redshift objects. Since the presence or absence of a core may be tied to the galactic merger history, we have an evolutionary explanation for the differences between radio-loud and radio-quiet QSOs.

  7. Radio Loudness of AGNs: Host Galaxy Morphology and the Spin Paradigm

    SciTech Connect

    Stawarz, L.; Sikora, M.; Lasota, J.-P.

    2007-10-15

    We investigate how the total radio luminosity of AGN-powered radio sources depends on their accretion luminosity and the central black hole mass. We find that AGNs form two distinct and well separated sequences on the radio-loudness -- Eddington-ratio plane. We argue that these sequences mark the real upper bounds of radio-loudness of two distinct populations of AGNs: those hosted respectively by elliptical and disk galaxies. Both sequences show the same dependence of the radio-loudness on the Eddington ratio (an increase with decreasing Eddington ratio), which suggests that another parameter in addition to the accretion rate must play a role in determining the jet production efficiency in active galactic nuclei, and that this parameter is related to properties of the host galaxy. The revealed host-related radio dichotomy breaks down at high accretion rates where the dominant fraction of luminous quasars hosted by elliptical galaxies is radio quiet. We argue that the huge difference between the radio-loudness reachable by AGNs in disc and elliptical galaxies can be explained by the scenario according to which the spin of a black hole determines the outflows power, and central black holes can reach large spins only in early type galaxies (following major mergers), and not (in a statistical sense) in spiral galaxies.

  8. The Radio-Loud Narrow-Line Quasar SDSS J172206.03+565451.6

    NASA Astrophysics Data System (ADS)

    Komossa, Stefanie; Voges, Wolfgang; Adorf, Hans-Martin; Xu, Dawei; Mathur, Smita; Anderson, Scott F.

    2006-03-01

    We report identification of the radio-loud narrow-line quasar SDSS J172206.03+565451.6, which we found in the course of a search for radio-loud narrow-line active galactic nuclei (AGNs). SDSS J172206.03+565451.6 is only about the fourth securely identified radio-loud narrow-line quasar and the second-most radio loud, with a radio index R1.4~100-700. Its black hole mass, MBH~=(2-3)×107 Msolar estimated from Hβ line width and 5100 Å luminosity, is unusually small given its radio loudness, and the combination of mass and radio index puts SDSS J172206.03+565451.6 in a scarcely populated region of MBH-R diagrams. SDSS J172206.03+565451.6 is a classical narrow-line Seyfert 1-type object with FWHMHβ~=1490 km s-1, an intensity ratio of [O III]/Hβ~=0.7, and Fe II emission complexes with Fe II λ4570/Hβ~=0.7. The ionization parameter of its narrow-line region, estimated from the line ratio [O II]/[O III], is similar to Seyferts, and its high ratio of [Ne V]/[Ne III] indicates a strong EUV-to-soft X-ray excess. We advertise the combined usage of [O II]/[O III] and [Ne V]/[Ne III] diagrams as a useful diagnostic tool to estimate ionization parameters and to constrain the EUV-soft X-ray continuum shape relatively independently from other parameters.

  9. Intranight polarization variability in radio-loud and radio-quiet AGN

    NASA Astrophysics Data System (ADS)

    Villforth, Carolin; Nilsson, Kari; Østensen, Roy; Heidt, Jochen; Niemi, Sami-Matias; Pforr, Janine

    2009-08-01

    Intranight polarization variability in active galactic nuclei (AGN) has not been studied extensively so far. Studying the variability in polarization makes it possible to distinguish between different emission mechanisms. Thus, it can help answering the question if intranight variability in radio-loud and radio-quiet AGN is of the same or of fundamentally different origin. In this paper, we investigate intranight polarization variability in AGN. Our sample consists of 28 AGN at low to moderate redshifts (0.048 <= z <= 1.036), 12 of which are radio-quiet quasars (RQQs) and 16 are radio-loud blazars. The subsample of blazars consists of eight flat-spectrum radio-quasars (FSRQs) and eight BL Lac objects. Each AGN was observed for a time-span of ~4h in the R band to measure polarization and variability. Using statistical methods, we determine duty cycles for polarized emission and polarization intranight variability. We find clear differences between the two samples. A majority of the radio-loud AGN show moderate to high degrees of polarization, more than half of them also show variability in polarization. There seems to be a dividing line for polarization intranight variability at P ~ 5 per cent over which all objects vary in polarization. We did not find clear correlations between the strength of the variability and the redshift or degree of polarization. Only two out of 12 RQQs show polarized emission, both at levels of P < 1 per cent. The lack of polarization intranight variability in radio-quiet AGN points towards accretion instabilities being the cause for intranight flux variability whereas the high duty cycle of polarization variability in radio-loud objects is more likely caused by instabilities in the jet or changes of physical conditions in the jet plasma. We were able to constrain the time-scale of the detected variations to >4 h. Further studies of intranight polarization variability will be necessary to reveal exact physical conditions behind this

  10. The Disk-Jet Connection in Radio-Loud AGN: The X-Ray Perspective

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita

    2008-01-01

    Unification schemes assume that radio-loud active galactic nuclei (AGN) contain an accretion disk and a relativistic jet perpendicular to the disk, and an obscuring molecular torus. The jet dominance decreases with larger viewing angles from blazars to Broad-Line and Narrow-Line Radio Galaxies. A fundamental question is how accretion and ejecta are related. The X-rays provide a convenient window to study these issues, as they originate in the innermost nuclear regions and penetrate large obscuring columns. I review the data, using observations by Chandra but also from other currently operating high-energy experiments. Synergy with the upcoming GLAST mission will also be highlighted.

  11. Dark bubbles around high-redshift radio-loud active galactic nucleus

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Sbarrato, T.

    2016-09-01

    At redshift larger than 3 there is a disagreement between the number of blazars (whose jet is pointing at us) and the number of expected parents (whose jet is pointing elsewhere). Now we strengthen this claim because (i) the number of blazars identified within the Sloan Digital Sky Survey (SDSS)+Faint Images of the Radio Sky at Twenty-cm (FIRST) survey footprint increased, demanding a more numerous parent population, and (ii) the detected blazars have a radio flux large enough to be above the FIRST flux limit even if the jet is slightly misaligned. The foreseen number of these slightly misaligned jets, in principle detectable, is much larger than the radio-detected sources in the FIRST+SDSS survey (at redshift larger than 4). This argument is independent of the presence of an isotropic radio component, such as the hotspot or the radio lobe, and does not depend on the bulk Lorentz factor Γ. We propose a scenario that ascribes the lack of slightly misaligned sources to an overobscuration of the nucleus by a `bubble' of dust, possibly typical of the first high-redshift quasars.

  12. Parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Berton, M.; Foschini, L.; Ciroi, S.; Cracco, V.; La Mura, G.; Lister, M. L.; Mathur, S.; Peterson, B. M.; Richards, J. L.; Rafanelli, P.

    2015-06-01

    Flat-spectrum radio-loud narrow-line Seyfert 1 galaxies (NLS1s) are a recently discovered class of γ-ray emitting active galactic nuclei (AGN), that exhibit some blazar-like properties which are explained with the presence of a relativistic jet viewed at small angles. When blazars are observed at larger angles they appear as radio-galaxies, and we expect to observe an analogue parent population for beamed NLS1s. However, the number of known NLS1s with the jet viewed at large angles is not enough. Therefore, we tried to understand the origin of this deficit. Current hypotheses about the nature of parent sources are steep-spectrum radio-loud NLS1s, radio-quiet NLS1s and disk-hosted radio-galaxies. To test these hypotheses we built three samples of candidate sources plus a control sample, and calculated their black hole mass and Eddington ratio using their optical spectra. We then performed a Kolmogorov-Smirnov statistical test to investigate the compatibility of our different samples with a beamed population. Our results indicate that, when the inclination angle increases, a beamed source appears as a steep-spectrum radio-loud NLS1, or possibly even as a disk-hosted radio-galaxy with low black hole mass and high Eddington ratio. Further investigations, involving larger complete samples and observations at radio frequency, are needed to understand the incidence of disk-hosted radio-galaxies in the parent population, and to assess whether radio-quiet NLS1s can play a role, as well. Appendix A is available in electronic form at http://www.aanda.org

  13. Continuum reverberation mapping in a z = 1.41 radio-loud quasar

    NASA Astrophysics Data System (ADS)

    Goicoechea, L. J.; Shalyapin, V. N.; Gil-Merino, R.; Braga, V. F.

    2012-07-01

    Q0957+561 was the first discovered gravitationally lensed quasar. The mirage shows two images of a radio-loud quasar at redshift z = 1.41. The time lag between these two images is well established around one year. We detected a very prominent variation in the optical brightness of Q0957+561A at the beginning of 2009, which allowed us to predict the presence of significant intrinsic variations in multi-wavelength light curves of Q0957+561B over the first semester of 2010. To study the predicted brightness fluctuations of Q0957+561B, we conducted an X-ray, NUV, optical and NIR monitoring campaign using both ground-based and space-based facilities. The continuum NUV-optical light curves revealed evidence of a centrally irradiated, standard accretion disk. In this paper, we focus on the radial structure of the standard accretion disk and the nature of the central irradiating source in the distant radio-loud active galactic nucleus (AGN).

  14. First direct comparison of high and low ionization line kinematics in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Sulentic, J. W.; Marziani, P.; Dultzin-Hacyan, D.; Calvani, M.; Moles, M.

    1995-01-01

    We present first results of a comparison of emission line shift properties for the high (HILs) and low (LILs) ionization lines in 43 low-reshift quasars. We identify a core sample of C IV lambda 1549 and hydrogen beta profiles with a wide distribution of red- and blueshifts (less than or equal to +/- 1000 km/sec). We also identify two tails in this distribution: one with large hydrogen beta redshifts (greater than or equal to 2000 km/sec) and another with large C IV blueshifts (greater than or equal to 1500 km/sec). The tails are mutually exclusive. All objects with extreme hydrogen beta redshift are radio loud, and all objects with extreme C IV blueshift are radio quiet. The core samples of smaller shifts can be most simply divided into: (1) hydrogen beta - a redshifted radio-loud population (related to the tail) and a radio-quiet population with mean shift near zero, and (2) C IV - a blueshifted radio-quiet population (related to the tail) and a radio-loud population with mean shift near zero. The results suggest fundamentally different kinematics for the HILs and LILs. They also suggest very different kinematics for radio-loud and radio-quiet active galactic nuclei. They also favor a predominance of radial motion in a large fraction of the sample.

  15. A Comparison of Radio-loud and Radio-quiet E+A Galaxies

    NASA Astrophysics Data System (ADS)

    Camacho, Yssavo; Wallack, Nicole; Learis, Anna; Liu, Charles

    2015-01-01

    E+A galaxies are systems undergoing an important evolutionary transition. Their optical spectra show significant numbers of A-type stars in an elliptical galaxy that has little to no star formation (SF). These galaxies have likely experienced a recent starburst (< 1 Gyr) followed by an even more recent quench in their SF. What caused their recent SF quench remains one of the most prominent questions surrounding E+A galaxies. Within the Goto (2007, MNRAS 381,187) catalogue of 564 E+A galaxies, there is a small fraction (~3%) that have detectable radio continuum emission from FIRST or NVSS. One possible cause for the observed radio continuum is active galactic nuclei (AGN). AGN feedback is believed to be important in galaxy evolution, including SF quenching (Dubois et al. 2013, MNRAS 433, 3297). In an effort to understand better the differences between radio-loud and radio-quiet E+As, we obtained and compared their spectral energy distributions (SEDs) using the publicly available data from SDSS, 2MASS, and WISE. We also compared them to the SEDs of other known galaxy types. We find that the radio-loud and radio-quiet samples exhibit statistically insignificant differences in the optical, near-infrared, and mid-infrared bands. We also compare the two samples on a (J-H) vs. (H-K) color-color diagram. This work was supported by the National Science Foundation via grant AST-1004583 to the CUNY College of Staten Island, and grant AST-1004591 to the American Museum of Natural History.

  16. Properties of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Foschini, L.; Berton, M.; Caccianiga, A.; Ciroi, S.; Cracco, V.; Peterson, B. M.; Angelakis, E.; Braito, V.; Fuhrmann, L.; Gallo, L.; Grupe, D.; Järvelä, E.; Kaufmann, S.; Komossa, S.; Kovalev, Y. Y.; Lähteenmäki, A.; Lisakov, M. M.; Lister, M. L.; Mathur, S.; Richards, J. L.; Romano, P.; Sievers, A.; Tagliaferri, G.; Tammi, J.; Tibolla, O.; Tornikoski, M.; Vercellone, S.; La Mura, G.; Maraschi, L.; Rafanelli, P.

    2015-03-01

    We have conducted a multiwavelength survey of 42 radio loud narrow-1ine Seyfert 1 galaxies (RLNLS1s), selected by searching among all the known sources of this type and omitting those with steep radio spectra. We analyse data from radio frequencies to X-rays, and supplement these with information available from online catalogues and the literature in order to cover the full electromagnetic spectrum. This is the largest known multiwavelength survey for this type of source. We detected 90% of the sources in X-rays and found 17% at γ rays. Extreme variability at high energies was also found, down to timescales as short as hours. In some sources, dramatic spectral and flux changes suggest interplay between a relativistic jet and the accretion disk. The estimated masses of the central black holes are in the range ~106-8 M⊙, lower than those of blazars, while the accretion luminosities span a range from ~0.01 to ~0.49 times the Eddington limit, with an outlier at 0.003, similar to those of quasars. The distribution of the calculated jet power spans a range from ~1042.6 to ~1045.6 erg s-1, generally lower than quasars and BL Lac objects, but partially overlapping with the latter. Once normalised by the mass of the central black holes, the jet power of the three types of active galactic nuclei are consistent with each other, indicating that the jets are similar and the observational differences are due to scaling factors. Despite the observational differences, the central engine of RLNLS1s is apparently quite similar to that of blazars. The historical difficulties in finding radio-loud narrow-line Seyfert 1 galaxies might be due to their low power and to intermittent jetactivity. Tables 4-9 and Figs. 8-13 are available in electronic form at http://www.aanda.org

  17. The Suzaku Observation of the Nucleus of the Radio Loud Active Galaxy Centaurus A: Constraints on Abundances in the Accreting Material

    NASA Technical Reports Server (NTRS)

    Markowitz, A.; Takahashi, T.A; Watanabe, S.; Nakazawa, K.; Fukazawa, Y.; Kokubun, M.; Makishima, K.; Awaki, H.; Bamba, A.; Isobe, N.; Kataoka, J.; Madejski, G.; Mushotzky, R.; Okajima, T.; Ptak, A.; Reeves, J. N.; Ueda, Y.; Yamasaki, T.; Yaqoob, T.

    2007-01-01

    A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The hard X-rays are fit by two power laws, absorbed by columns of 1.5 and 7 x 10(exp 23) per square centimeter. The dual power-laws are consistent with previous suggestions that the powerlaw components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, or are consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature VAPEC model, plus a third power-law component to account for scattered nuclear emission, kpc-scale jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The width of the Fe Ka line yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. K-shell absorption edges due to Fe, Ca, and S are detected. Elemental abundances are constrained via the fluorescent lines strengths, absorption edge depths and the diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.l) of the circumnuclear material compared to that in the metal-poor outer halo suggests that the accreting material could not have originated in the outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

  18. The Suzaku Observation of the Nucleus of theRadio-Loud Active Galaxy Centaurus A: Constraints on Abundances of the Accreting Material

    SciTech Connect

    Markowitz, A.; Takahashi, T.; Watanabe, S.; Nakazawa, K.; Fukazawa, Y.; Kokubun, M.; Makishima, K.; Awaki, H.; Bamba, A.; Isobe, N.; Kataoka, J.; Madejski, G.; Mushotzky, R.; Okajima, T.; Ptak, A.; Reeves, J.N.; Ueda, Y.; Yamasaki, T.; Yaqoob, T.

    2007-06-27

    A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3 to 250 keV. The net exposure times after screening were: 70 ks per X-ray Imaging Spectrometer (XIS) camera, 60.8 ks for the Hard X-ray Detector (HXD) PIN, and 17.1 ks for the HXD-GSO. The hard X-rays are fit by two power-laws of the same slope, absorbed by columns of 1.5 and 7 x 10{sup 23} cm{sup -2} respectively. The spectrum is consistent with previous suggestions that the power-law components are X-ray emission from the sub-pc VLBI jet and from Bondi accretion at the core, but it is also consistent with a partial covering interpretation. The soft band is dominated by thermal emission from the diffuse plasma and is fit well by a two-temperature vapec model, plus a third power-law component to account for scattered nuclear emission, jet emission, and emission from X-ray Binaries and other point sources. Narrow fluorescent emission lines from Fe, Si, S, Ar, Ca and Ni are detected. The Fe K{alpha} line width yields a 200 light-day lower limit on the distance from the black hole to the line-emitting gas. Fe, Ca, and S K-shell absorption edges are detected. Elemental abundances are constrained via absorption edge depths and strengths of the fluorescent and diffuse plasma emission lines. The high metallicity ([Fe/H]=+0.1) of the circumnuclear material suggests that it could not have originated in the relatively metal-poor outer halo unless enrichment by local star formation has occurred. Relative abundances are consistent with enrichment from Type II and Ia supernovae.

  19. Multiphase ISM in Radio Loud Early Type Galaxies

    NASA Astrophysics Data System (ADS)

    Sahu, Sheetal Kumar; Chaware, Laxmikant; Pandey, S. K.

    We present optical, IR and X-ray photometric study of a sample of radio loud early type galaxies chosen from B2 sample. To get radial profiles of various photometric and geometrical parameters, We per- formed multiband surface photometry on CCD images of our sample gala- xies in ’BVR’ broad band filter and Hα narrow band filter obtained from IUCAA Girawali Observatory(IGO 2m telescope) Pune(INDIA),that descri- be elliptical isophotes fitted to the 2D light distribution of the galaxies. The main focus of our study is to analyze radial profiles of quantities such as the (local) surface brightness, the ellipticity, and the deviations from elliptical isophotes parametrized by the Fourier coefficients. We generated color maps,residual maps,dust extinction maps, Hα emission maps and x-ray diffuse maps (obtained from CHANDRA data archive) of the galaxies to study the morphology of the dust, ionized and hot gas content present in the galaxies. We carried out detailed analysis of the dust properties(mass and temperature of the dust) for sample galaxies. We also made use of the HST(WFPC2) archival optical images to investigate properties of the dust in the central region(˜10 arcsec) of our sample galaxies, including this we also estimated molecular gas mass, mass loss by red giant stars and mass loss rate from evolved stars in the sample galaxies obtained from IRAS fluxes. This multiwavelength study of our sample galaxies enabled us to find physical correlation among different phases of ISM also to address various issues related to dust i.e origin, nature and ate(evolution)of dust in radio-loud early type galaxies, coexistence of multiphase ISM in extra-galactic environment and its possible implications for the scenarios of formation and evolution of galaxies.

  20. Radio-Loud AGN: The Suzaku View

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita

    2009-01-01

    We review our Suzaku observations of Broad-Line Radio Galaxies (BLRGs). The continuum above 2 approx.keV in BLRGs is dominated by emission from an accretion flow, with little or no trace of a jet, which is instead expected to emerge at GeV energies and be detected by Fermi. Concerning the physical conditions of the accretion disk, BLRGs are a mixed bag. In some sources the data suggest relatively high disk ionization, in others obscuration of the innermost regions, perhaps by the jet base. While at hard X-rays the distinction between BLRGs and Seyferts appears blurry, one of the cleanest observational differences between the two classes is at soft X-rays, where Seyferts exhibit warm absorbers related to disk winds while BLRGs do not. We discuss the possibility that jet formation inhibits disk winds, and thus is related to the remarkable dearth of absorption features at soft X-rays in BLRGs and other radio-loud AGN.

  1. Toward a New Paradigm for the Unification of Radio Loud AGN and its Connection to Accretion

    NASA Technical Reports Server (NTRS)

    Georganpoulos, Markos; Meyer, Eileen T.; Fossati, Giovanni; Lister, Matthew L.

    2012-01-01

    We recently argued [21J that the collective properties. of radio loud active galactic nuclei point to the existence of two families of sources, one of powerful sources with single velocity jets and one of weaker jets with significant velocity gradients in the radiating plasma. These families also correspond to different accretion modes and therefore different thermal and emission line intrinsic properties: powerful sources have radiatively efficient accretion disks, while in weak sources accretion must be radiatively inefficient. Here, after we briefly review of our recent work, we present the following findings that support our unification scheme: (i) along the broken sequence of aligned objects, the jet kinetic power increases. (ii) in the powerful branch of the sequence of aligned objects the fraction of BLLs decreases with increasing jet power. (iii) for powerful sources, the fraction of BLLs increases for more un-aligned objects, as measured by the core to extended radio emission. Our results are also compatible with the possibility that a given accretion power produces jets of comparable kinetic power.

  2. Investigating powerful jets in radio-loud narrow-line Seyfert 1s

    NASA Astrophysics Data System (ADS)

    Orienti, M.; D'Ammando, F.; Larsson, J.; Finke, J.; Giroletti, M.; Dallacasa, D.; Isacsson, T.; Stoby Hoglund, J.

    2015-11-01

    We report results on multiband observations from radio to γ-rays of the two radio-loud narrow-line Seyfert 1 (NLSy1) galaxies PKS 2004-447 and J1548+3511. Both sources show a core-jet structure on parsec scale, while they are unresolved at the arcsecond scale. The high core dominance and the high variability brightness temperature make these NLSy1 galaxies good γ-ray source candidates. Fermi-Large Area Telescope detected γ-ray emission only from PKS 2004-447, with a γ-ray luminosity comparable to that observed in blazars. No γ-ray emission is observed for J1548+3511. Both sources are variable in X-rays. J1548+3511 shows a hardening of the spectrum during high activity states, while PKS 2004-447 has no spectral variability. A spectral steepening likely related to the soft excess is hinted below 2 keV for J1548+3511, while the X-ray spectra of PKS 2004-447 collected by XMM-Newton in 2012 are described by a single power law without significant soft excess. No additional absorption above the Galactic column density or the presence of an Fe line is detected in the X-ray spectra of both sources.

  3. Reverberation Mapping Campaign of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Anirban

    In this dissertation, I present results of black hole mass (M BH) measurements of four active galactic nuclei (AGN). AGN activity plays a key part in galaxy formation and evolution as evidenced by relationships like MBH-sigmastar. Accurate measurements of MBH is thus required to better understand these relationships. Luminosity of AGNs is also related to the radius of the broad line region (BLR). I have used reverberation mapping (RM) to obtain measurements of the radius of BLR and MBH of four AGNs. Reverberation data were collected over a period of 180-day span in 2012. None of these objects have been reverberation mapped before. We have also placed our objects on the Radius-Luminosity relationship and three out of four fall on the relationship. The fourth object lies above the Radius-Luminosity relationship and is a minor outlier. Two of these objects are Radio-Loud, which have orientation information available. This has increased the sample of radio-loud AGNs, which have RM from 5 to 7. We have increased the overall sample size of AGNs that have mass measurements from 62 to 66. We obtain masses for these following objects 3C 382 (MBH)= 30.1 -8.7+12.61 x 107 M O, PG2209+184 (MBH)=14.53-8.7 +5.79 x 107 MO, MARK 1040 (MBH)= 30.1-8.7+12.61 x 107 MO and 1ES0206+52(MBH)= 517.3-280+214 x 107 M O.

  4. Accretion disc/corona emission from a radio-loud narrow-line Seyfert 1 galaxy PKS 0558-504

    NASA Astrophysics Data System (ADS)

    Ghosh, R.; Dewangan, G. C.; Raychaudhuri, B.

    2016-02-01

    Approximately 10-20 per cent of active galactic nuclei (AGN) are known to eject powerful jets from the innermost regions. There is very little observational evidence if the jets are powered by spinning black holes and if the accretion discs extend to the innermost regions in radio-loud AGN. Here, we study the soft X-ray excess, the hard X-ray spectrum and the optical/UV emission from the radio-loud narrow-line Seyfert 1 galaxy PKS 0558-504 using Suzaku and Swift observations. The broad-band X-ray continuum of PKS 0558-504 consists of a soft X-ray excess emission below 2 keV that is well described by a blackbody (kT ˜ 0.13 keV) and high-energy emission that is well described by a thermal Comptonization (compps) model with kTe ˜ 250 keV, optical depth τ ˜ 0.05 (spherical corona) or kTe ˜ 90 keV, τ ˜ 0.5 (slab corona). The Comptonizing corona in PKS 0558-504 is likely hotter than in radio-quiet Seyferts such as IC 4329A and Swift J2127.4+5654. The observed soft X-ray excess can be modelled as blurred reflection from an ionized accretion disc or optically thick thermal Comptonization in a low-temperature plasma. Both the soft X-ray excess emission when interpreted as the blurred reflection and the optical/UV to soft X-ray emission interpreted as intrinsic disc Comptonized emission implies spinning (a > 0.6) black hole. These results suggest that disc truncation at large radii and retrograde black hole spin both are unlikely to be the necessary conditions for launching the jets.

  5. Ultra-Fast Outflows in Radio-Loud AGN: New Constraints on Jet-Disk Connection

    NASA Astrophysics Data System (ADS)

    Sambruna, Rita

    There is strong observational and theoretical evidence that outflows/jets are coupled to accretion disks in black hole accreting systems, from Galactic to extragalactic sizes. While in radio-quiet AGN there is ample evidence for the presence of Ultra-Fast Outflows (UFOs) from the presence of blue-shifted absorption features in their 4-10~keV spectra, sub-relativistic winds are expected on theoretical basis in radio-loud AGN but have not been observed until now. Our recent Suzaku observations of 5 bright Broad- Line Radio Galaxies (BLRGs, the radio-loud counterparts of Seyferts) has started to change this picture. We found strong evidence for UFOs in 3 out of 5 BLRGs, with ionization parameters, column densities, and velocities of the absorber similar to Seyferts. Moreover, the outflows in BLRGs are likely to be energetically very significant: from the Suzaku data of the three sources, outflow masses similar to the accretion masses and kinetic energies of the wind similar to the X-ray luminosity and radio power of the jet are inferred. Clearly, UFOs in radio-loud AGN represent a new key ingredient to understand their central engines and in particular, the jet-disk linkage. Our discovery of UFOs in a handful of BLRGs raises the questions of how common disk winds are in radio-loud AGN, what the absorber physical and dynamical characteristics are, and what is the outflow role in broader picture of galaxy-black hole connection for radio sources, i.e., for large-scale feedback models. To address these and other issues, we propose to use archival XMM-Newton and Suzaku spectra to search for Ultra-Fast Outflows in a large number of radio sources. Over a period of two years, we will conduct a systematic, uniform analysis of the archival X-ray data, building on our extensive experience with a similar previous project for Seyferts, and using robust analysis and statistical methodologies. As an important side product, we will also obtain accurate, self- consistent measurements

  6. X-RAYS FROM A RADIO-LOUD COMPACT BROAD ABSORPTION LINE QUASAR 1045+352 AND THE NATURE OF OUTFLOWS IN RADIO-LOUD BROAD ABSORPTION LINE QUASARS

    SciTech Connect

    Kunert-Bajraszewska, Magdalena; Katarzynski, Krzysztof; Siemiginowska, Aneta; Janiuk, Agnieszka

    2009-11-10

    We present new results on X-ray properties of radio-loud broad absorption line (BAL) quasars and focus on broadband spectral properties of a high-ionization BAL (HiBAL) compact steep spectrum (CSS) radio-loud quasar 1045+352. This HiBAL quasar has a very complex radio morphology indicating either strong interactions between a radio jet and the surrounding interstellar medium or a possible re-start of the jet activity. We detected 1045+352 quasar in a short 5 ksec Chandra ACIS-S observation. We applied theoretical models to explain spectral energy distribution of 1045+352 and argue that non-thermal, inverse-Compton (IC) emission from the innermost parts of the radio jet can account for a large fraction of the observed X-ray emission. In our analysis, we also consider a scenario in which the observed X-ray emission from radio-loud BAL quasars can be a sum of IC jet X-ray emission and optically thin corona X-ray emission. We compiled a sample of radio-loud BAL quasars that were observed in X-rays to date and report no correlation between their X-ray and radio luminosity. However, the radio-loud BAL quasars show a large range of X-ray luminosities and absorption columns. This is consistent with the results obtained earlier for radio-quiet BAL quasars and may indicate an orientation effect in BAL quasars or more complex dependence between X-ray emission, radio emission, and an orientation based on the radio morphology.

  7. THE EDDINGTON LIMIT IN COSMIC RAYS: AN EXPLANATION FOR THE OBSERVED LACK OF LOW-MASS RADIO-LOUD QUASARS AND THE M{sub .}-M{sub *} RELATION

    SciTech Connect

    Sironi, Lorenzo; Socrates, Aristotle E-mail: socrates@ias.ed

    2010-02-20

    We present a feedback mechanism for supermassive black holes and their host bulges that operates during epochs of radio-loud quasar activity. In the radio cores of relativistic quasar jets, internal shocks convert a fraction of ordered bulk kinetic energy into randomized relativistic ions, or in other words cosmic rays. By employing a phenomenologically motivated jet model, we show that enough 1-100 GeV cosmic rays escape the radio core into the host galaxy to break the Eddington limit in cosmic rays. As a result, hydrostatic balance is lost and a cosmic ray momentum-driven wind develops, expelling gas from the host galaxy and thus self-limiting the black hole and bulge growth. Although the interstellar cosmic ray power is much smaller than the quasar photon luminosity, cosmic rays provide a stronger feedback than UV photons, since they exchange momentum with the galactic gas much more efficiently. The amount of energy released into the host galaxy as cosmic rays, per unit of black hole rest mass energy, is independent of black hole mass. It follows that radio-loud jets should be more prevalent in relatively massive systems since they sit in galaxies with relatively deep gravitational potentials. Therefore, jet-powered cosmic ray feedback not only self-regulates the black hole and bulge growth, but also provides an explanation for the lack of radio-loud activity in relatively small galaxies. By employing basic known facts regarding the physical conditions in radio cores, we approximately reproduce both the slope and the normalization of the M{sub .}-M{sub *} relation.

  8. SPITZER MID-IR SPECTROSCOPY OF POWERFUL 2 JY AND 3CRR RADIO GALAXIES. I. EVIDENCE AGAINST A STRONG STARBURST-AGN CONNECTION IN RADIO-LOUD AGN

    SciTech Connect

    Dicken, D.; Axon, D.; Robinson, A.; Kharb, P.; Tadhunter, C.; Ramos Almeida, C.; Morganti, R.; Kouwenhoven, M. B. N.; Spoon, H.; Inskip, K. J.; Holt, J.; Nesvadba, N. P. H.

    2012-02-01

    We present deep Spitzer/Infrared Spectrograph (IRS) spectra for complete samples of 46 2 Jy radio galaxies (0.05 < z < 0.7) and 19 3CRR FRII radio galaxies (z < 0.1), and use the detection of polycyclic aromatic hydrocarbon (PAH) features to examine the incidence of contemporaneous star formation and radio-loud active galactic nucleus (AGN) activity. Our analysis reveals PAH features in only a minority (30%) of the objects with good IRS spectra. Using the wealth of complementary data available for the 2 Jy and 3CRR samples we make detailed comparisons between a range of star formation diagnostics: optical continuum spectroscopy, mid- to far-IR (MFIR) color, far-IR excess and PAH detection. There is good agreement between the various diagnostic techniques: most candidates identified to have star formation activity on the basis of PAH detection are also identified using at least two of the other techniques. We find that only 35% of the combined 2 Jy and 3CRR sample show evidence for recent star formation activity (RSFA) at optical and/or MFIR wavelengths. This result argues strongly against the idea of a close link between starburst and powerful radio-loud AGN activity, reinforcing the view that, although a large fraction of powerful radio galaxies may be triggered in galaxy interactions, only a minority are triggered at the peaks of star formation activity in major, gas-rich mergers. However, we find that compact radio sources (D < 15 kpc) show a significantly higher incidence of RSFA (>75%) than their more extended counterparts ( Almost-Equal-To 15%-25%). We discuss this result in the context of a possible bias toward the selection of compact radio sources triggered in gas-rich environments.

  9. Reverberation mapping of two radio-loud quasars

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Anirban; Brotherton, Michael S.; Mason, Michelle; Roberts, Caroline Anna; Singh, Vikram; Johnson-Groh, Mara; Erickson, Nicholas; Lundquist, Michael J.; Alexander, Michael J.; Staudaher, Shawn; Cales, Sabrina; DiPompeo, Michael A.; Smullen, Rachel; Eftekharzadeh, Sarah; Kobulnicky, Henry A.; Nyugen, My; Chatterjee, Ritaban; Chatterjee, Suchetana; Runnoe, Jessie C.; Dale, Daniel A.

    2016-06-01

    We present results of a reverberation mapping (RM) campaign on two radio-loud quasars, 3C 382 and PG 2209+184, using the Wyoming Infrared Observatory (WIRO). For 3C 382 we determine a Hβ time lag of &ea; = 47.2 ^{16.8}_{-30.4} days, with a RMS line dispersion of 2317±195 km s^{-1}, and a corresponding mass of 2.12^{0.92}_{-1.46} × 10^8 M_⊙. For PG 2209+184, we determine a Hβ time lag of τ = 38.9 ^{11.9}_{-21} days, with a RMS line dispersion of 2114±121 km s^{-1}, and a corresponding mass of 1.45^{0.58}_{-0.87} × 10^8 M_⊙. These two objects are consistent with the radius-luminosity relationship for H$β and bring the total of radio-loud quasars reverberation mapped to seven. Radio-loud quasars bring the potential of investigating orientation biases in quasar black hole mass determination.

  10. Reverberation mapping of two radio-loud quasars

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Anirban; Brotherton, Michael S.; Mason, Michelle; Roberts, Caroline Anna; Singh, Vikram; Johnson-Groh, Mara; Erickson, Nicholas; Lundquist, Michael J.; Alexander, Michael J.; Staudaher, Shawn; Cales, Sabrina; DiPompeo, Michael A.; Smullen, Rachel; Eftekharzadeh, Sarah; Kobulnicky, Henry A.; Nyugen, My; Chatterjee, Ritaban; Chatterjee, Suchetana; Runnoe, Jessie C.; Dale, Daniel A.

    2016-06-01

    We present results of a reverberation mapping (RM) campaign on two radio-loud quasars, 3C 382 and PG 2209+184, using the Wyoming Infrared Observatory (WIRO). For 3C 382 we determine a Hβ time lag of η = 47.2 ^{16.8}_{-30.4} days, with a RMS line dispersion of 2317±195 km s^{-1}, and a corresponding mass of 2.12^{0.92}_{-1.46} × 10^8 M_⊙. For PG 2209+184, we determine a Hβ time lag of τ = 38.9 ^{11.9}_{-21} days, with a RMS line dispersion of 2114±121 km s^{-1}, and a corresponding mass of 1.45^{0.58}_{-0.87} × 10^8 M_⊙. These two objects are consistent with the radius-luminosity relationship for H$β and bring the total of radio-loud quasars reverberation mapped to seven. Radio-loud quasars bring the potential of investigating orientation biases in quasar black hole mass determination.

  11. Radio-loud Narrow Line Seyfert 1 under a different perspective: a revised black hole mass estimate from optical spectropolarimetry

    NASA Astrophysics Data System (ADS)

    Baldi, Ranieri D.; Capetti, Alessandro; Robinson, Andrew; Laor, Ari; Behar, Ehud

    2016-05-01

    Several studies indicate that radio-loud (RL) active galactic nuclei (AGNs) are produced only by the most massive black holes (BH), MBH ˜ 108-1010 M⊙. This idea has been challenged by the discovery of RL Narrow Line Seyfert 1 (RL NLSy1), having estimated masses of MBH ˜ 106-107 M⊙. However, these low MBH estimates might be due to projection effects. Spectropolarimetry allows us to test this possibility by looking at RL NLSy1s under a different perspective, i.e. from the viewing angle of the scattering material. We here report the results of a pilot study of Very Large Telescope spectropolarimetric observations of the RL NLSy1 PKS 2004-447. Its polarization properties are remarkably well reproduced by models in which the scattering occurs in an equatorial structure surrounding its broad-line region, seen close to face-on. In particular, we detect a polarized Hα line with a width of ˜9000 km s-1, ˜6 times broader than the width seen in direct light. This corresponds to a revised estimate of MBH ˜ 6 × 108 M⊙, well within the typical range of RL AGN. The double-peaked polarized broad Hα profile of the target suggests that the rare combination of the orientation effects and a broad line region dominated by the rotation might account for this class of objects, casting doubts on the virial estimates of BH mass for type-I AGN.

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

    SciTech Connect

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

    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.

  13. Why Have Many of the Brightest Radio-loud Blazars Not Been Detected in Gamma-Rays by Fermi?

    NASA Astrophysics Data System (ADS)

    Lister, M. L.; Aller, M. F.; Aller, H. D.; Hovatta, T.; Max-Moerbeck, W.; Readhead, A. C. S.; Richards, J. L.; Ros, E.

    2015-09-01

    We use the complete MOJAVE 1.5 Jy sample of active galactic nuclei (AGNs) to examine the gamma-ray detection statistics of the brightest radio-loud blazars in the northern sky. We find that 23% of these AGNs were not detected above 0.1 GeV by the Fermi-LAT during the four-year 3FGL catalog period partly because of an instrumental selection effect and partly due to their lower Doppler boosting factors. Blazars with synchrotron peaks in their spectral energy distributions located below {10}13.4 Hz also tend to have high-energy peaks that lie below the 0.1 GeV threshold of the LAT, and are thus less likely to be detected by Fermi. The non-detected AGNs in the 1.5 Jy sample also have significantly lower 15 GHz radio modulation indices and apparent jet speeds, indicating that they have lower than average Doppler factors. Since the effective amount of relativistic Doppler boosting is enhanced in gamma-rays (particularly in the case of external inverse-Compton scattering), this makes them less likely to appear in the 3FGL catalog. Based on their observed properties, we have identified several bright radio-selected blazars that are strong candidates for future detection by Fermi.

  14. Broad absorption line variability in radio-loud quasars

    NASA Astrophysics Data System (ADS)

    Welling, C. A.; Miller, B. P.; Brandt, W. N.; Capellupo, D. M.; Gibson, R. R.

    2014-05-01

    We investigate C IV broad absorption line (BAL) variability within a sample of 46 radio-loud quasars (RLQs), selected from Sloan Digital Sky Survey (SDSS)/Faint Images of the Radio Sky at Twenty-Centimeters (FIRST) data to include both core-dominated (39) and lobe-dominated (7) objects. The sample consists primarily of high-ionization BAL quasars, and a substantial fraction have large BAL velocities or equivalent widths; their radio luminosities and radio-loudness values span ˜2.5 orders of magnitude. We have obtained 34 new Hobby-Eberly Telescope spectra of 28 BAL RLQs to compare to earlier SDSS data, and we also incorporate archival coverage (primarily dual-epoch SDSS) for a total set of 78 pairs of equivalent width measurements for 46 BAL RLQs, probing rest-frame time-scales of ˜80-6000 d (median 500 d). In general, only modest changes in the depths of segments of absorption troughs are observed, akin to those seen in prior studies of BAL radio-quiet quasars (RQQs). Also similar to previous findings for RQQs, the RLQs studied here are more likely to display BAL variability on longer rest-frame time-scales. However, typical values of |{Δ}EW| and |{Δ}EW|/ are ˜40 ± 20 per cent lower for BAL RLQs when compared with those of a time-scale-matched sample of BAL RQQs. Optical continuum variability is of similar amplitude in BAL RLQs and BAL RQQs; for both RLQs and RQQs, continuum variability tends to be stronger on longer time-scales. BAL variability in RLQs does not obviously depend upon their radio luminosities or radio-loudness values, but we do find tentative evidence for greater fractional BAL variability within lobe-dominated RLQs. Enhanced BAL variability within more edge-on (lobe-dominated) RLQs supports some geometrical dependence to the outflow structure.

  15. Elliptical accretion disks in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Eracleous, Michael; Livio, Mario; Halpern, Jules P.; Storchi-Bergmann, Thaisa

    1995-01-01

    We present a calculation of the profiles of emission lines originating in a relativistic, eccentric disk, and show examples of the resulting model profiles. Our calculations are motivated by the fact that in about one-quarter of the double-peaked emission lines observed in radio-loud active galactic nuclei (and in the mildly active nucleus of NGC 1097), the red peak is stronger than the blue peak, which is contrary to the prediction of relativistic, circular disk models. Using the eccentric disk model we fit some of the observed profiles that cannot be fitted with a circular disk model. We propose two possible scenarios for the formation of an eccentric disk in an active galactic nucleus: (a) tidal perturbation of the disk around a supermassive black hole by a smaller binary companion, and (b) formation of an elliptical disk from the debris resulting from the tidal disruption of a star by the central black hole. In the former case we show that the eccentricity can be long-lived because of the presence of the binary companion. In the latter case, although the inner parts of the disk may circularize quickly, we estimate that the outer parts will maintain their eccentricity for times much longer than the local viscous time. We suggest that it may be possible to detect profile variability on much shorter timescales than those ranging from a decade to several centuries by comparing the evolution of the line profile with detailed model predictions. We argue that line-profile variability may also be the most promising discriminant among competing models for the origin of asymmetric, double-peaked emission lines.

  16. Fossil shell emission in dying radio loud AGNs

    NASA Astrophysics Data System (ADS)

    Kino, M.; Ito, H.; Kawakatu, N.; Orienti, M.; Nagai, H.; Wajima, K.; Itoh, R.

    2016-02-01

    We investigate shell emission associated with dying radio loud AGNs. First, based on our recent work by Ito et al. (2015), we describe the dynamical and spectral evolution of shells after stopping the jet energy injection. We find that the shell emission overwhelms that of the radio lobes soon after stopping the jet energy injection because fresh electrons are continuously supplied into the shell via the forward shock, while the radio lobes rapidly fade out without jet energy injection. We find that such fossil shells can be a new class of target sources for SKA telescope. Next, we apply the model to the nearby radio source 3C84. Then, we find that the fossil shell emission in 3C84 is less luminous in the radio band while it is bright in the TeV γ-ray band and can be detectable by CTA. Data from STELLA

  17. Radio-Loud Coronal Mass Ejections without Shocks near Earth

    NASA Astrophysics Data System (ADS)

    Akiyama, S.; Gopalswamy, N.; Xie, H.; Yashiro, S.; Makela, P. A.; St Cyr, O. C.; MacDowall, R. J.; Kaiser, M. L.

    2010-12-01

    Type II radio bursts are produced by low energy electrons accelerated in shocks driven by coronal mass ejections (CMEs). One can infer shocks near the Sun, in the Interplanetary medium, and near Earth depending on the wavelength range in which the type II bursts are produced. In fact, type II bursts are good indicators of CMEs that produce solar energetic particles. If the type II burst occurs from a source on the Earth-facing side of the solar disk, it is highly likely that a shock arrives at Earth in 2-3 days and hence can be used to predict shock arrival at Earth. However, a significant fraction of CMEs producing type II bursts were not associated shocks at Earth, even though the CMEs originated close to the disk center. There are several reasons for the lack of shock at 1 AU. CMEs originating at large central meridian distances (CMDs) may be driving a shock, but the shock may not be extended sufficiently to reach to the Sun-Earth line. Another possibility is CME cannibalism because of which shocks merge and one observes a single shock at Earth. Finally, the CME-driven shock may become weak and dissipate before reaching 1 AU. We examined a set of 30 type II bursts observed by the Wind/WAVES experiment that had the solar sources very close to the disk center (within a CMD of 15 degrees), but did not have shock at Earth. We find that the near-Sun speeds of the associated CMEs average to ~600 km/s, only slightly higher than the average speed of CMEs associated with radio-quiet shocks. However, the fraction of halo CMEs is only ~28%, compared to 40% for radio-quiet shocks and 72% for all radio-loud shocks. We conclude that the disk-center radio loud CMEs with no shocks at 1 AU are generally of lower energy and they drive shocks only close to the Sun.

  18. ENSEMBLE VARIABILITY OF NEAR-INFRARED-SELECTED ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Kouzuma, S.; Yamaoka, H. E-mail: yamaoka@phys.kyushu-u.ac.jp

    2012-03-01

    We present the properties of the ensemble variability V for nearly 5000 near-infrared active galactic nuclei (AGNs) selected from the catalog of Quasars and Active Galactic Nuclei (13th Edition) and the SDSS-DR7 quasar catalog. From three near-infrared point source catalogs, namely, Two Micron All Sky Survey (2MASS), Deep Near Infrared Survey (DENIS), and UKIDSS/LAS catalogs, we extract 2MASS-DENIS and 2MASS-UKIDSS counterparts for cataloged AGNs by cross-identification between catalogs. We further select variable AGNs based on an optimal criterion for selecting the variable sources. The sample objects are divided into subsets according to whether near-infrared light originates by optical emission or by near-infrared emission in the rest frame; and we examine the correlations of the ensemble variability with the rest-frame wavelength, redshift, luminosity, and rest-frame time lag. In addition, we also examine the correlations of variability amplitude with optical variability, radio intensity, and radio-to-optical flux ratio. The rest-frame optical variability of our samples shows negative correlations with luminosity and positive correlations with rest-frame time lag (i.e., the structure function, SF), and this result is consistent with previous analyses. However, no well-known negative correlation exists between the rest-frame wavelength and optical variability. This inconsistency might be due to a biased sampling of high-redshift AGNs. Near-infrared variability in the rest frame is anticorrelated with the rest-frame wavelength, which is consistent with previous suggestions. However, correlations of near-infrared variability with luminosity and rest-frame time lag are the opposite of these correlations of the optical variability; that is, the near-infrared variability is positively correlated with luminosity but negatively correlated with the rest-frame time lag. Because these trends are qualitatively consistent with the properties of radio-loud quasars reported

  19. Radio-Loud Coronal Mass Ejections Without Shocks Near Earth

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N.; SaintCyr, O. C.; MacDowall, R. J.; Kaiser, M. L.; Xie, H.; Makela, P.; Akiyama, S.

    2010-01-01

    Type II radio bursts are produced by low energy electrons accelerated in shocks driven by corona) mass ejections (CMEs). One can infer shocks near the Sun, in the Interplanetary medium, and near Earth depending on the wavelength range in which the type II bursts are produced. In fact, type II bursts are good indicators of CMEs that produce solar energetic particles. If the type 11 burst occurs from a source on the Earth-facing side of the solar disk, it is highly likely that a shock arrives at Earth in 2-3 days and hence can be used to predict shock arrival at Earth. However, a significant fraction of CMEs producing type II bursts were not associated shocks at Earth, even though the CMEs originated close to the disk center. There are several reasons for the lack of shock at 1 AU. CMEs originating at large central meridian distances (CMDs) may be driving a shock, but the shock may not be extended sufficiently to reach to the Sun-Earth line. Another possibility is CME cannibalism because of which shocks merge and one observes a single shock at Earth. Finally, the CME-driven shock may become weak and dissipate before reaching 1 AU. We examined a set of 30 type II bursts observed by the Wind/WAVES experiment that had the solar sources very close to the disk center (within a CMD of 15 degrees), but did not have shock at Earth. We find that the near-Sun speeds of the associated CMEs average to approx.600 km/s, only slightly higher than the average speed of CMEs associated with radio-quiet shocks. However, the fraction of halo CMEs is only approx.28%, compared to 40% for radio-quiet shocks and 72% for all radio-loud shocks. We conclude that the disk-center radio loud CMEs with no shocks at 1 AU are generally of lower energy and they drive shocks only close to the Sun.

  20. Fermi LAT detection of increasing gamma-ray emission from the radio-loud NLSy1 PKS 1502+036

    NASA Astrophysics Data System (ADS)

    D'Ammando, Filippo; Ciprini, Stefano

    2015-12-01

    The Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope, has observed gamma-ray flaring activity from a source positionally consistent with the radio-loud narrow-line Seyfert 1 PKS 1502+036 (also known as 3FGL J1505.1+0326, Acero et al. 2015, ApJS, 218, 23), with radio coordinates (J2000.0), R.A.: 226.2769879 deg, Dec.: 3.4418922 deg (Fey et al. 2004, AJ, 127, 3587) at redshift z = 0.4078 (Hewett & Wild 2010, MNRAS, 405, 2302).

  1. Swift Observations Of High-z Radio-loud Quasars Detected With Bat

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita M.; Tueller, J.; Markwardt, C.; Mushotzky, R.; Tavecchio, F.

    2006-01-01

    We present follow-up Swift observations of 4 high-z radio-loud quasars detected with the BAT during the 15-month survey in 15-150 keV. The 0.5-8-keV spectra are best fitted either with a power law with no excess absorption over the Galactic value (0212+735, 0836+710, 2149--307 in higher state) or by a downward-curved broken power law model (0537--286, 2149--307 in lower state). The BAT spectra integrated over the whole 15 months of the survey are fitted with a single power law, with a range of spectral slopes, Gamma=l.3-2.3. Comparison with previous SAX observations shows that there is a trend for the 15-150-keV continuum to soften with fading intensity; on the contrary, little or no spectral variations are observed at medium-hard X-rays. This may suggest either/both dramatic variability above 10-keV, or/and two separate spectral components.

  2. Active galactic nuclei

    PubMed Central

    Fabian, Andrew C.

    1999-01-01

    Active galactic nuclei are the most powerful, long-lived objects in the Universe. Recent data confirm the theoretical idea that the power source is accretion into a massive black hole. The common occurrence of obscuration and outflows probably means that the contribution of active galactic nuclei to the power density of the Universe has been generally underestimated. PMID:10220363

  3. Compact radio cores in radio-quiet active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Maini, A.; Prandoni, I.; Norris, R. P.; Giovannini, G.; Spitler, L. R.

    2016-04-01

    Context. The mechanism of radio emission in radio-quiet (RQ) active galactic nuclei (AGNs) is still debated and might arise from the central AGN, from star formation activity in the host, or from either of these sources. A direct detection of compact and bright radio cores embedded in sources that are classified as RQ can unambiguously determine whether a central AGN significantly contributes to the radio emission. Aims: We search for compact, high-surface-brightness radio cores in RQ AGNs that are caused unambiguously by AGN activity. Methods: We used the Australian Long Baseline Array to search for compact radio cores in four RQ AGNs located in the Extended Chandra Deep Field South (ECDFS). We also targeted four radio-loud (RL) AGNs as a control sample. Results: We detected compact and bright radio cores in two AGNs that are classified as RQ and in one that is classified as RL. Two RL AGNs were not imaged because the quality of the observations was too poor. Conclusions: We report on a first direct evidence of radio cores in RQ AGNs at cosmological redshifts. Our detections show that some of the sources that are classified as RQ contain an active AGN that can contribute significantly (~50% or more) to the total radio emission.

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

    NASA Astrophysics Data System (ADS)

    Pollack, Maxwell; Pauls, David; Wiita, Paul J.

    2016-03-01

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

  5. Diffuse γ-Ray Emission from Misaligned Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Di Mauro, M.; Calore, F.; Donato, F.; Ajello, M.; Latronico, L.

    2014-01-01

    Active galactic nuclei (AGNs) with jets seen at small viewing angles are the most luminous and abundant objects in the γ-ray sky. AGNs with jets misaligned along the line of sight appear fainter in the sky but are more numerous than the brighter blazars. We calculate the diffuse γ-ray emission due to the population of misaligned AGNs (MAGNs) unresolved by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). A correlation between the γ-ray luminosity and the radio-core luminosity is established and demonstrated to be physical by statistical tests, as well as compatible with upper limits based on Fermi-LAT data for a large sample of radio-loud MAGNs. We constrain the derived γ-ray luminosity function by means of the source-count distribution of the radio galaxies detected by the Fermi-LAT. We finally calculate the diffuse γ-ray flux due to the whole MAGN population. Our results demonstrate that MAGNs can contribute from 10% up to nearly the entire measured isotropic gamma-ray background. We evaluate a theoretical uncertainty on the flux of almost an order of magnitude.

  6. Diffuse γ-ray emission from misaligned active galactic nuclei

    SciTech Connect

    Di Mauro, M.; Donato, F.; Calore, F.; Ajello, M.; Latronico, L.

    2014-01-10

    Active galactic nuclei (AGNs) with jets seen at small viewing angles are the most luminous and abundant objects in the γ-ray sky. AGNs with jets misaligned along the line of sight appear fainter in the sky but are more numerous than the brighter blazars. We calculate the diffuse γ-ray emission due to the population of misaligned AGNs (MAGNs) unresolved by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope (Fermi). A correlation between the γ-ray luminosity and the radio-core luminosity is established and demonstrated to be physical by statistical tests, as well as compatible with upper limits based on Fermi-LAT data for a large sample of radio-loud MAGNs. We constrain the derived γ-ray luminosity function by means of the source-count distribution of the radio galaxies detected by the Fermi-LAT. We finally calculate the diffuse γ-ray flux due to the whole MAGN population. Our results demonstrate that MAGNs can contribute from 10% up to nearly the entire measured isotropic gamma-ray background. We evaluate a theoretical uncertainty on the flux of almost an order of magnitude.

  7. 3C 57 as an atypical radio-loud quasar: implications for the radio-loud/radio-quiet dichotomy

    NASA Astrophysics Data System (ADS)

    Sulentic, J. W.; Martínez-Carballo, M. A.; Marziani, P.; del Olmo, A.; Stirpe, G. M.; Zamfir, S.; Plauchu-Frayn, I.

    2015-06-01

    Lobe-dominated radio-loud (LD RL) quasars occupy a restricted domain in the 4D Eigenvector 1 (4DE1) parameter space which implies restricted geometry/physics/kinematics for this subclass compared to the radio-quiet (RQ) majority of quasars. We discuss how this restricted domain for the LD RL parent population supports the notion for a RQ-RL dichotomy among type 1 sources. 3C 57 is an atypical RL quasar that shows both uncertain radio morphology and falls in a region of 4DE1 space where RL quasars are rare. We present new radio flux and optical spectroscopic measures designed to verify its atypical optical/UV spectroscopic behaviour and clarify its radio structure. The former data confirms that 3C 57 falls off the 4DE1 quasar `main sequence' with both extreme optical Fe II emission (R_{Fe II} ˜ 1) and a large C IV λ1549 profile blueshift (˜-1500 km s-1). These parameter values are typical of extreme Population A sources which are almost always RQ. New radio measures show no evidence for flux change over a 50+ year time-scale consistent with compact steep-spectrum (or young LD) over core-dominated morphology. In the 4DE1 context where LD RL are usually low L/LEdd quasars, we suggest that 3C 57 is an evolved RL quasar (i.e. large blackhole mass) undergoing a major accretion event leading to a rejuvenation reflected by strong Fe II emission, perhaps indicating significant heavy metal enrichment, high bolometric luminosity for a low-redshift source and resultant unusually high Eddington ratio giving rise to the atypical C IV λ1549.

  8. EXAMINING THE RADIO-LOUD/RADIO-QUIET DICHOTOMY WITH NEW CHANDRA AND VLA OBSERVATIONS OF 13 UGC GALAXIES

    SciTech Connect

    Kharb, P.; Axon, D. J.; Robinson, A.; Capetti, A.; Balmaverde, B.; Chiaberge, M.; Macchetto, D.; Grandi, P.; Giovannini, G.; Montez, R.

    2012-04-15

    We present the results from new {approx}15 ks Chandra-ACIS and 4.9 GHz Very Large Array (VLA) observations of 13 galaxies hosting low-luminosity active galactic nuclei (AGNs). This completes the multiwavelength study of a sample of 51 nearby early-type galaxies described in Capetti and Balmaverde and Balmaverde and Capetti. The aim of the three previous papers was to explore the connection between the host galaxies and AGN activity in a radio-selected sample. We detect nuclear X-ray emission in eight sources and radio emission in all but one (viz., UGC 6985). The new VLA observations improve the spatial resolution by a factor of 10: the presence of nuclear radio sources in 12 of the 13 galaxies confirms their AGN nature. As previously indicated, the behavior of the X-ray and radio emission in these sources depends strongly on the form of their optical surface brightness profiles derived from Hubble Space Telescope imaging, i.e., on their classification as 'core', 'power-law', or 'intermediate' galaxies. With more than twice the number of 'power-law' and 'intermediate' galaxies compared to previous work, we confirm with a much higher statistical significance that these galaxies lie well above the radio-X-ray correlation established in Fanaroff-Riley type I radio galaxies and the low-luminosity 'core' galaxies. This result highlights the fact that the 'radio-loud/radio-quiet' dichotomy is a function of the host galaxy's optical surface brightness profile. We present radio-optical-X-ray spectral indices for all 51 sample galaxies. Survival statistics point to significant differences in the radio-to-optical and radio-to-X-ray spectral indices between the 'core' and 'power-law galaxies (Gehan's Generalized Wilcoxon test probability p for the two classes being statistically similar is <10{sup -5}), but not in the optical-to-X-ray spectral indices (p = 0.25). Therefore, the primary difference between the 'core' and 'power-law' galaxies is in their ability to launch

  9. The radio-loud AGN population at z ≳ 1 in the COSMOS field. I. selection and spectral energy distributions

    NASA Astrophysics Data System (ADS)

    Baldi, Ranieri D.; Capetti, Alessandro; Chiaberge, Marco; Celotti, Annalisa

    2014-07-01

    We select a sample of radio galaxies at high redshifts (z ≳ 1) in the COSMOS field by cross-matching optical and infrared (IR) images with the FIRST radio data. The aim of this study is to explore the high-z radio-loud (RL) active galactic nuclei (AGN) population at much lower luminosities than the classical samples of distant radio sources, which are similar to those of the local population of radio galaxies. Precisely, we extended a previous analysis focused on low-luminosity radio galaxies. The wide multiwavelength coverage provided by the COSMOS survey allows us to derive their spectral energy distributions (SEDs). We model them with our own developed technique 2SPD that includes old and young stellar populations and dust emission. When added to those previously selected, we obtain a sample of 74 RL AGN. The SED modeling returns several important quantities associated with the AGN and host properties. The resulting photometric redshifts range from z ~ 0.7 to 3. The sample mostly includes compact radio sources but also 21 FR IIs sources; the radio power distribution of the sample covers ~1031.5 - 1034.3 erg s-1 Hz-1, thus straddling the local FR I/FR II break. The inferred range of stellar mass of the hosts is ~1010 - 1011.5M⊙. The SEDs are dominated by the contribution from an old stellar population with an age of ~1 - 3 Gyr for most of the sources. However, UV and mid-IR (MIR) excesses are observed for half of the sample. The dust luminosities inferred from the MIR excesses are in the range, Ldust ~ 1043 - 1045.5 erg s-1, which are associated with temperatures approximately of 350-1200 K. Estimates of the UV component yield values of ~1041.5 - 1045.5 erg s-1 at 2000 Å. The UV emission is significantly correlated with both IR and radio luminosities; the former being the stronger link. However, the origin of UV and dust emission, whether it is produced by the AGN of by star formation, is still unclear. Our results show that this RL AGN population at high

  10. The extreme ultraviolet spectra of low-redshift radio-loud quasars

    NASA Astrophysics Data System (ADS)

    Punsly, Brian; Reynolds, Cormac; Marziani, Paola; O'Dea, Christopher P.

    2016-07-01

    This paper reports on the extreme ultraviolet (EUV) spectrum of three low-redshift (z ˜ 0.6) radio-loud quasars, 3C 95, 3C 57 and PKS 0405-123. The spectra were obtained with the Cosmic Origins Spectrograph of the Hubble Space Telescope. The bolometric thermal emission, Lbol, associated with the accretion flow is a large fraction of the Eddington limit for all of these sources. We estimate the long-term time-averaged jet power, overline{Q}, for the three sources. overline{Q}/L_{bol}, is shown to lie along the correlation of overline{Q}/L_{bol}, and αEUV found in previous studies of the EUV continuum of intermediate and high-redshift quasars, where the EUV continuum flux density between 1100 and 700 Å is defined by F_{ν } ˜ ν ^{-α _{EUV}}. The high Eddington ratios of the three quasars extend the analysis into a wider parameter space. Selecting quasars with high Eddington ratios has accentuated the statistical significance of the partial correlation analysis of the data. Namely, the correlation of overline{Q}/L_{bol} and αEUV is fundamental, and the correlation of overline{Q} and αEUV is spurious at a very high statistical significance level (99.8 per cent). This supports the regulating role of ram pressure of the accretion flow in magnetically arrested accretion models of jet production. In the process of this study, we use multifrequency and multiresolution Very Large Array radio observations to determine that one of the bipolar jets in 3C 57 is likely frustrated by galactic gas that keeps the jet from propagating outside the host galaxy.

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

    NASA Astrophysics Data System (ADS)

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

    2016-08-01

    We present deep near-infrared (NIR) images of a sample of 19 intermediate-redshift (0.3 < z < 1.0) radio-loud active galactic nuclei (AGN) with powerful relativistic jets (L1.4 GHz > 1027 W Hz-1), previously classified as flat-spectrum radio quasars. We also compile host galaxy and nuclear magnitudes for blazars from literature. The combined sample (this work and compilation) contains 100 radio-loud AGN with host galaxy detections and a broad range of radio luminosities L1.4 GHz ˜ 1023.7-1028.3 W Hz-1, allowing us to divide our sample into high-luminosity blazars (HLBs) and low-luminosity blazars (LLBs). The host galaxies of our sample are bright and seem to follow the μe-Reff relation for ellipticals and bulges. The two populations of blazars show different behaviours in the MK,nuclear -MK,bulge plane, where a statistically significant correlation is observed for HLBs. Although it may be affected by selection effects, this correlation suggests a close coupling between the accretion mode of the central supermassive black hole and its host galaxy, which could be interpreted in terms of AGN feedback. Our findings are consistent with semi-analytical models where low-luminosity AGN emit the bulk of their energy in the form of radio jets, producing a strong feedback mechanism, and high-luminosity AGN are affected by galaxy mergers and interactions, which provide a common supply of cold gas to feed both nuclear activity and star formation episodes.

  12. The far-infrared emission of the radio-loud quasar 3C 318

    NASA Astrophysics Data System (ADS)

    Podigachoski, P.; Barthel, P. D.; Peletier, R. F.; Steendam, S.

    2016-01-01

    3C 318, a radio-loud quasar at z = 1.574, is a subgalactic-sized radio source, and a good test-bed for the interplay between black hole and galaxy growth in the high-z Universe. Based on its IRAS, ISO, and SCUBA detections, it has long been considered as one of the most intrinsically luminous (LIR > 1013 L⊙) infrared sources in the Universe. Recent far-infrared data from the Herschel Space Observatory reveal that most of the flux associated with 3C 318, measured with earlier instruments, in fact comes from a bright nearby source. Optical imaging and spectroscopy show that this infrared-bright source is a strongly star-forming pair of interacting galaxies at z = 0.35. Adding existing Spitzer and SDSS photometry, we perform a spectral energy distribution analysis of the pair, and find that it has a combined infrared luminosity of LIR = 1.5 × 1012 L⊙, comparable to other intermediate-redshift ultra-luminous infrared galaxies studied with Herschel. Isolating the emission from 3C 318's host, we robustly constrain the level of star formation to a value a factor of three lower than that published earlier, which is more in line with the star formation activity found in other Herschel-detected 3CR objects at similar redshift.

  13. WHAT GOVERNS THE BULK VELOCITY OF THE JET COMPONENTS IN ACTIVE GALACTIC NUCLEI?

    SciTech Connect

    Chai Bo; Cao Xinwu; Gu Minfeng E-mail: cxw@shao.ac.cn

    2012-11-10

    We use a sample of radio-loud active galactic nuclei (AGNs) with measured black hole masses to explore the jet formation mechanisms in these sources. Based on Koenigl's inhomogeneous jet model, the jet parameters, such as the bulk motion Lorentz factor, magnetic field strength, and electron density in the jet, can be estimated with the very long baseline interferometry and X-ray data.. We find a significant correlation between black hole mass and the bulk Lorentz factor of the jet components for this sample, while no significant correlation is present between the bulk Lorentz factor and the Eddington ratio. The massive black holes will be spun up through accretion, as the black holes acquire mass and angular momentum simultaneously through accretion. Recent investigation indeed suggested that most supermassive black holes in elliptical galaxies have on average higher spins than the black holes in spiral galaxies, where random, small accretion episodes (e.g., tidally disrupted stars, accretion of molecular clouds) might have played a more important role. If this is true, then the correlation between black hole mass and the bulk Lorentz factor of the jet components found in this work implies that the motion velocity of the jet components is probably governed by the black hole spin. No correlation is found between the magnetic field strength at 10R {sub S} (R {sub S} = 2GM/c {sup 2} is the Schwarzschild radius) in the jets and the bulk Lorentz factor of the jet components for this sample. This is consistent with the black hole spin scenario, i.e., the faster moving jets are magnetically accelerated by the magnetic fields threading the horizon of more rapidly rotating black holes. The results imply that the Blandford-Znajek mechanism may dominate over the Blandford-Payne mechanism for the jet acceleration, at least in these radio-loud AGNs.

  14. The innermost dusty structure in active galactic nuclei as probed by the Keck interferometer

    NASA Astrophysics Data System (ADS)

    Kishimoto, M.; Hönig, S. F.; Antonucci, R.; Barvainis, R.; Kotani, T.; Tristram, K. R. W.; Weigelt, G.; Levin, K.

    2011-03-01

    We are now exploring the inner region of type 1 active galactic nuclei (AGNs) with the Keck interferometer in the near-infrared. Adding to the four targets previously studied, we report measurements of the K-band (2.2 μm) visibilities for four more targets, namely AKN120, IC 4329A, Mrk6, and the radio-loud QSO 3C 273 at z = 0.158. The observed visibilities are quite high for all the targets, which we interpret as an indication of the partial resolution of the dust sublimation region. The effective ring radii derived from the observed visibilities scale approximately with L1/2, where L is the AGN luminosity. Comparing the radii with those from independent optical-infrared reverberation measurements, these data support our previous claim that the interferometric ring radius is either roughly equal to or slightly larger than the reverberation radius. We interpret the ratio of these two radii for a given L as an approximate probe of the radial distribution of the inner accreting material. We show tentative evidence that this inner radial structure might be closely related to the radio-loudness of the central engine. Finally, we re-observed the brightest Seyfert 1 galaxy NGC 4151. Its marginally higher visibility at a shorter projected baseline, compared to our previous measurements obtained one year before, further supports the partial resolution of the inner structure. We did not detect any significant change in the implied emission size when the K-band flux was brightened by a factor of 1.5 over a time interval of one year.

  15. RADIO PROPERTIES OF LOW-REDSHIFT BROAD-LINE ACTIVE GALACTIC NUCLEI INCLUDING EXTENDED RADIO SOURCES

    SciTech Connect

    Rafter, Stephen E.; Crenshaw, D. Michael; Wiita, Paul J.

    2011-03-15

    We present a study of the extended radio emission in a sample of 8434 low-redshift (z < 0.35) broad-line active galactic nuclei (AGNs) from the Sloan Digital Sky Survey. To calculate the jet and lobe contributions to the total radio luminosity, we have taken the 846 radio core sources detected in our previous study of this sample and performed a systematic search in the FIRST database for extended radio emission that is likely associated with the optical counterparts. We found that 51 out of 846 radio core sources have extended emission (>4'' from the optical AGN) that is positively associated with the AGN, and we have identified an additional 12 AGNs with extended radio emission but no detectable radio core emission. Among these 63 AGNs, we found 6 giant radio galaxies, with projected emission exceeding 750 kpc in length, and several other AGNs with unusual radio morphologies also seen in higher redshift surveys. The optical spectra of many of the extended sources are similar to those of typical broad-line radio galaxy spectra, having broad H{alpha} emission lines with boxy profiles and large M{sub BH}. With extended emission taken into account, we find strong evidence for a bimodal distribution in the radio-loudness parameter R ({identical_to}{nu}{sub radio} L{sub radio}/{nu}{sub opt} L{sub opt}), where the lower radio luminosity core-only sources appear as a population separate from the extended sources, with a dividing line at log(R) {approx}1.75. This dividing line ensures that these are indeed the most radio-loud AGNs, which may have different or extreme physical conditions in their central engines when compared to the more numerous radio-quiet AGNs.

  16. Phenomenology of Broad Emission Lines in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Sulentic, J. W.; Marziani, P.; Dultzin-Hacyan, D.

    Broad emission lines hold fundamental clues about the kinematics and structure of the central regions in AGN. In this article we review the most robust line profile properties and correlations emerging from the best data available. We identify fundamental differences between the profiles of radio-quiet and radio-loud sources as well as differences between the high- and low-ionization lines, especially in the radio-quiet majority of AGN. An Eigenvector 1 correlation space involving FWHM Hβ, W(FeIIopt)/W(Hβ), and the soft X-ray spectral index provides optimal discrimination between all principal AGN types (from narrow-line Seyfert 1 to radio galaxies). Both optical and radio continuum luminosities appear to be uncorrelated with the E1 parameters. We identify two populations of radio-quiet AGN: Population A sources (with FWHM(Hβ) <~ 4000 km s-1, generally strong FeII emission and a soft X-ray excess) show almost no parameter space overlap with radio-loud sources. Population B shows optical properties largely indistinguishable from radio-loud sources, including usually weak FeII emission, FWHM(Hβ) >~ 4000 km s-1 and lack of a soft X-ray excess. There is growing evidence that a fundamental parameter underlying Eigenvector 1 may be the luminosity-to-mass ratio of the active nucleus (L/M), with source orientation playing a concomitant role.

  17. Selection of High-z Radio-Loud Quasars, and Their Luminosity Function

    NASA Astrophysics Data System (ADS)

    Tuccillo, D.; González-Serrano, J. I.; Benn, C. R.

    We present the selection techniques based on the use of Neural Networks and on the cross match between FIRST and SDSS that lead to the spectroscopic identification of 15 new Radio Loud QSOs in the redshift range 3. 6 ≤ z ≤ 4. 4. These QSOs did not have previous spectroscopical identification in SDSS or other works. Our selection method is highly complete (97 %) and it allows the estimation of the binned luminosity function of radio-loud quasar at z ˜ 4 with unprecedented accuracy. Our luminosity function is compared with the results of other samples of RL QSOs in similar ranges of redshift and with the whole population of QSOs (RL+RQ). The evolution of the luminosity function with redshift was for many years interpreted as a flattening of the bright end slope, but has recently been re-interpreted as strong evolution of the break luminosity for high-z QSOs and our results, for the radio-loud population, are consistent with this. We also find indications of a constant radio-loud fraction for QSOs at high z. Our next investigation will select RL QSOs candidates in the range of redshift 4. 4 ≤ z ≤ 5. 7, and will make use of data in the radio (FIRST), in the optical (SDSS DR10) and in the infrared (UKIDSS Large Area Survey DR10, and WISE).

  18. SHALON observations of Active Galactic Nuclei at red shift from z = 0.0179 to z = 2.979

    NASA Astrophysics Data System (ADS)

    Sinitsyna, V. G.; Alaverdyan, A. Y.; Andreeva, M. S.; Balygin, K. A.; Borisov, S. S.; Ivanov, I. A.; Kirichenko, A. M.; Klimov, A. I.; Kozhukhova, I. P.; Mirzafatikhov, R. M.; Moseiko, N. I.; Nikolsky, S. I.; Ostashev, I. E.; Palamarchuk, A. I.; Sinitsyna, V. Y.; Volokh, I. G.

    2016-05-01

    The radio-loud active galactic nuclei having the radio emission arising from a core region rather than from lobes are often referred to as “blazars” and include Flat Spectrum Radio Quasars (FSRQ) and BL Lacertae (BL Lac) objects. During the period 1992 - 2015, SHALON has been used for observations of the metagalactic sources NGC1275, Mkn421, Mkn501, Mkn180, 3c382, 4c+31.63, OJ 287, 3c454.3, 4c+55.17, 1739+522. We present results of long term observations of FSRQ: among them are known object 3c454.3, high-red shifted quasar 1739+522 as well as BL Lac type objects. The observation results are presented with integral spectra, images and spectral energy distributions for each of sources at energies > 800 GeV. A number of variability periods in different wavelengths including VHE γ-rays were found.

  19. Compact steep-spectrum sources as the parent population of flat-spectrum radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Berton, M.; Caccianiga, A.; Foschini, L.; Peterson, B. M.; Mathur, S.; Terreran, G.; Ciroi, S.; Congiu, E.; Cracco, V.; Frezzato, M.; La Mura, G.; Rafanelli, P.

    2016-06-01

    Narrow-line Seyfert 1 galaxies (NLS1s) are an interesting subclass of active galactic nuclei (AGN), which tipically does not exhibit any strong radio emission. Seven percent of them, though, are radio-loud and often show a flat radio-spectrum (F-NLS1s). This, along to the detection of γ-ray emission coming from them, is usually interpreted as a sign of a relativistic beamed jet oriented along the line of sight. An important aspect of these AGN that must be understood is the nature of their parent population, in other words how do they appear when observed under different angles. In the recent literature it has been proposed that a specific class of radio-galaxies, compact-steep sources (CSS) classified as high excitation radio galaxies (HERG), can represent the parent population of F-NLS1s. To test this hypothesis in a quantitative way,in this paper we analyzed the only two statistically complete samples of CSS/HERGs and F-NLS1s available in the literature. We derived the black hole mass and Eddington ratio distributions, and we built for the first time the radio luminosity function of F-NLS1s. Finally, we applied a relativistic beaming model to the luminosity function of CSS/HERGs, and compared the result with the observed function of F-NLS1s. We found that compact steep-spectrum sources are valid parent candidates and that F-NLS1s, when observed with a different inclination, might actually appear as CSS/HERGs.

  20. The effect of Compton drag on the dynamics of dissipative Poynting-dominated flows: implications for the unification of radio loud AGN

    NASA Astrophysics Data System (ADS)

    Levinson, A.; Globus, N.

    2016-05-01

    The dynamics of a dissipative Poynting-dominated flow subject to a radiation drag due to Compton scattering of ambient photons by relativistic electrons accelerated in reconnecting current sheets is studied. It is found that the efficiency at which magnetic energy is converted to radiation is limited to a maximum value of ɛc = 3ldis σ0/4(σ0 + 1), where σ0 is the initial magnetization of the flow and ldis ≤ 1 the fraction of initial Poynting flux that can dissipate. The asymptotic Lorentz factor satisfies Γ∞ ≥ Γ0(1 + ldis σ0/4), where Γ0 is the initial Lorentz factor. This limit is approached in cases where the cooling time is shorter than the local dissipation time. A somewhat smaller radiative efficiency is expected if radiative losses are dominated by synchrotron and Synchrotron Self-Compton emissions. It is suggested that under certain conditions magnetic field dissipation may occur in two distinct phases: On small scales, asymmetric magnetic fields that are advected into the polar region and dragged out by the outflow dissipate to a more stable configuration. The dissipated energy is released predominantly as gamma rays. On much larger scales, the outflow encounters a flat density profile medium and re-collimates. This leads to further dissipation and wobbling of the jet head by the kink instability, as found recently in 3D magnetohydrodynamic simulations. Within the framework of a model proposed recently to explain the dichotomy of radio loud active galactic nuclei (AGN), this scenario can account for the unification of gamma-ray blazars with Fanaroff-Riley type I and Fanaroff-Riley type II radio sources.

  1. New insights on the QSO radio-loud/radio-quiet dichotomy: SDSS spectra in the context of the 4D eigenvector1 parameter space

    NASA Astrophysics Data System (ADS)

    Zamfir, S.; Sulentic, J. W.; Marziani, P.

    2008-06-01

    We search for a dichotomy/bimodality between radio-loud (RL) and radio-quiet (RQ) type 1 active galactic nuclei (AGN). We examine several samples of Slogan Digital Sky Survey (SDSS) quasi-stellar objects (QSOs) with high signal-to-noise ratio optical spectra and matching Faint Images of the Radio Sky at Twenty-cm/NRAO VLA Sky Survey (FIRST/NVSS) radio observations. We use the radio data to identify the weakest RL sources with a Fanaroff-Riley type II (FRII) structure to define a RL/RQ boundary which corresponds to log L1.4GHz = 31.6 ergs-1 Hz-1. We measure the properties of broad-line Hβ and FeII emission to define the optical plane of a 4DE1 spectroscopic diagnostic space. The RL quasars occupy a much more restricted domain in this optical plane compared to the RQ sources, which a 2D Kolmogorov-Smirnov test finds to be highly significant. This tells us that the range of broad-line region kinematics and structure for RL sources is more restricted than for the RQ QSOs, which supports the notion of dichotomy. FRII and CD RL sources also show significant 4DE1 domain differences that likely reflect differences in line-of-sight orientation (inclined versus face-on, respectively) for these two classes. The possibility of a distinct radio-intermediate (RI) population between RQ and RL source is disfavoured because a 4DE1 diagnostic space comparison shows no difference between RI and RQ sources. We show that searches for dichotomy in radio versus bolometric luminosity diagrams will yield ambiguous results mainly because in a reasonably complete sample, the radio brightest RQ sources will be numerous enough to blur the gap between RQ and RL sources. Within resolution constraints of NVSS and FIRST, we find no FRI sources among the broad-line quasar population.

  2. Accretion disc-corona and jet emission from the radio-loud narrow-line Seyfert 1 galaxy RX J1633.3+4719

    NASA Astrophysics Data System (ADS)

    Mallick, Labani; Dewangan, G. C.; Gandhi, P.; Misra, R.; Kembhavi, A. K.

    2016-08-01

    We perform X-ray/ultraviolet (UV) spectral and X-ray variability studies of the radio-loud narrow-line Seyfert 1 (NLS1) galaxy RX J1633.3+4719 using XMM-Newton and Suzaku observations from 2011 and 2012. The 0.3-10 keV spectra consist of an ultrasoft component described by an accretion disc blackbody (kT_in = 39.6^{+11.2}_{-5.5} eV) and a power law due to the thermal Comptonization (Γ = 1.96^{+0.24}_{-0.31}) of the disc emission. The disc temperature inferred from the soft excess is at least a factor of 2 lower than that found for the canonical soft excess emission from radio-quiet NLS1s. The UV spectrum is described by a power law with photon index 3.05^{+0.56}_{-0.33}. The observed UV emission is too strong to arise from the accretion disc or the host galaxy, but can be attributed to a jet. The X-ray emission from RX J1633.3+4719 is variable with fractional variability amplitude Fvar = 13.5 ± 1.0 per cent. In contrast to radio-quiet active galactic nuclei (AGN), X-ray emission from the source becomes harder with increasing flux. The fractional rms variability increases with energy and the rms spectrum is well described by a constant disc component and a variable power-law continuum with the normalization and photon index being anticorrelated. Such spectral variability cannot be caused by variations in the absorption and must be intrinsic to the hot corona. Our finding of possible evidence for emission from the inner accretion disc, jet and hot corona from RX J1633.3+4719 in the optical to X-ray bands makes this object an ideal target to probe the disc-jet connection in AGN.

  3. The Peculiar Radio-loud Narrow Line Seyfert 1 Galaxy 1H 0323+342

    NASA Astrophysics Data System (ADS)

    Paliya, Vaidehi S.; Sahayanathan, S.; Parker, M. L.; Fabian, A. C.; Stalin, C. S.; Anjum, Ayesha; Pandey, S. B.

    2014-07-01

    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.

  4. The peculiar radio-loud narrow line Seyfert 1 galaxy 1H 0323+342

    SciTech Connect

    Paliya, Vaidehi S.; Stalin, C. S.; Sahayanathan, S.; Parker, M. L.; Fabian, A. C.; Anjum, Ayesha; Pandey, S. B.

    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.

  5. CMB quenching of high-redshift radio-loud AGNs

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Haardt, F.; Ciardi, B.; Sbarrato, T.; Gallo, E.; Tavecchio, F.; Celotti, A.

    2015-10-01

    The very existence of more than a dozen of high-redshift (z ≳ 4) blazars indicates that a much larger population of misaligned powerful jetted active galactic nucleus (AGN) was already in place when the Universe was ≲1.5 Gyr old. Such parent population proved to be very elusive, and escaped direct detection in radio surveys so far. High-redshift blazars themselves seem to be failing in producing extended radio lobes, raising questions about the connection between such class and the vaster population of radio galaxies. We show that the interaction of the jet electrons with the intense cosmic microwave background (CMB) radiation explains the lack of extended radio emission in high-redshift blazars and in their parent population, helping to explain the apparently missing misaligned counterparts of high-redshift blazars. On the other hand, the emission from the more compact and more magnetized hotspots are less affected by the enhanced CMB energy density. By modelling the spectral energy distribution of blazar lobes and hotspots, we find that most of them should be detectable by low-frequency deep radio observations, e.g. by LOw-Frequency ARray for radio astronomy and by relatively deep X-ray observations with good angular resolution, e.g. by the Chandra satellite. At high redshifts, the emission of a misaligned relativistic jet, being debeamed, is missed by current large sky area surveys. The isotropic flux produced in the hotspots can be below ˜1 mJy and the isotropic lobe radio emission is quenched by the CMB cooling. Consequently, even sources with very powerful jets can go undetected in current radio surveys, and misclassified as radio-quiet AGNs.

  6. Fermi monitoring of radio-loud narrow-line Seyfert 1 galaxies

    SciTech Connect

    Paliya, Vaidehi S.; Stalin, C. S.; Ravikumar, C. D.

    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.

  7. Radio-loud narrow-line Seyfert 1 galaxies with high-velocity outflows

    NASA Astrophysics Data System (ADS)

    Komossa, S.; Xu, D.; Zensus, J. A.

    2016-02-01

    We have studied four radio-loud Narrow-line Seyfert 1 (NLS1) galaxies with extreme optical emission-line shifts, indicating radial outflow velocities of up 2450 km s-1. The shifts are accompanied by strong line broadening, up to 2270 km s-1 in [NeV]. A significant ionization stratification (higher line shift at higher ionization potential) of most ions implies that we see a large-scale wind rather than single, localized jet-cloud interactions. The observations are consistent with a scenario, where the signatures of outflows are maximized because of a pole-on view into the central engine of these radio-loud NLS1 galaxies.

  8. Covering factors of the dusty obscurers in radio-loud and radio-quiet quasars

    NASA Astrophysics Data System (ADS)

    Gupta, Maitrayee; Sikora, Marek; Nalewajko, Krzysztof

    2016-09-01

    We compare covering factors of circumnuclear dusty obscurers in radio-loud and radio-quiet quasars. The radio-loud quasars are represented by a sample of FR II quasars obtained by cross-matching a catalog of the FR II radio sources selected by van Velzen et al. with the SDSS DR7 catalog of quasars. Covering factors of FR II quasars are compared with covering factors of the radio-quiet quasars matched with them in redshift, black hole mass, and Eddington-ratio. We found that covering factors, proxied by the infrared-to-bolometric luminosity ratio, are on average slightly smaller in FR II quasars than in radio-quiet quasars, however, this difference is statistically significant only for the highest Eddington ratios. For both samples, no statistically significant dependence of a median covering factor on Eddington ratio, black hole mass, nor redshift can be claimed.

  9. The Optical-UV Emissivity of Quasars: Dependence on Black Hole Mass and Radio Loudness

    NASA Astrophysics Data System (ADS)

    Shankar, Francesco; Calderone, Giorgio; Knigge, Christian; Matthews, James; Buckland, Rachel; Hryniewicz, Krzysztof; Sivakoff, Gregory; Dai, Xinyu; Richardson, Kayleigh; Riley, Jack; Gray, James; La Franca, Fabio; Altamirano, Diego; Croston, Judith; Gandhi, Poshak; Hönig, Sebastian; McHardy, Ian; Middleton, Matthew

    2016-02-01

    We analyzed a large sample of radio-loud and radio-quiet quasar spectra at redshift 1.0 ≤ z ≤ 1.2 to compare the inferred underlying quasar continuum slopes (after removal of the host galaxy contribution) with accretion disk models. The latter predict redder (decreasing) α3000 continuum slopes ({L}ν \\propto {ν }α at 3000 Å) with increasing black hole mass, bluer α3000 with increasing luminosity at 3000 Å, and bluer α3000 with increasing spin of the black hole, when all other parameters are held fixed. We find no clear evidence for any of these predictions in the data. In particular, we find the following. (i) α3000 shows no significant dependence on black hole mass or luminosity. Dedicated Monte Carlo tests suggest that the substantial observational uncertainties in the black hole virial masses can effectively erase any intrinsic dependence of α3000 on black hole mass, in line with some previous studies. (ii) The mean slope α3000 of radio-loud sources, thought to be produced by rapidly spinning black holes, is comparable to, or even redder than, that of radio-quiet quasars. Indeed, although quasars appear to become more radio loud with decreasing luminosity, we still do not detect any significant dependence of α3000 on radio loudness. The predicted mean α3000 slopes tend to be bluer than in the data. Disk models with high inclinations and dust extinction tend to produce redder slopes closer to empirical estimates. Our mean α3000 values are close to the ones independently inferred at z < 0.5, suggesting weak evolution with redshift, at least for moderately luminous quasars.

  10. X-RAY EMISSION FROM OPTICALLY SELECTED RADIO-INTERMEDIATE AND RADIO-LOUD QUASARS

    SciTech Connect

    Miller, B. P.; Brandt, W. N.; Schneider, D. P.; Wu Jianfeng; Gibson, R. R.; Steffen, A. T. E-mail: niel@astro.psu.edu E-mail: jfwu@astro.psu.edu E-mail: rgibson@astro.washington.edu

    2011-01-01

    We present the results of an investigation into the X-ray properties of radio-intermediate and radio-loud quasars (RIQs and RLQs, respectively). We combine large, modern optical (e.g., SDSS) and radio (e.g., FIRST) surveys with archival X-ray data from Chandra, XMM-Newton, and ROSAT to generate an optically selected sample that includes 188 RIQs and 603 RLQs. This sample is constructed independently of X-ray properties but has a high X-ray detection rate (85%); it provides broad and dense coverage of the l-z plane, including at high redshifts (22% of objects have z = 2-5), and it extends to high radio-loudness values (33% of objects have R* = 3-5, using logarithmic units). We measure the 'excess' X-ray luminosity of RIQs and RLQs relative to radio-quiet quasars (RQQs) as a function of radio loudness and luminosity, and parameterize the X-ray luminosity of RIQs and RLQs both as a function of optical/UV luminosity and also as a joint function of optical/UV and radio luminosity. RIQs are only modestly X-ray bright relative to RQQs; it is only at high values of radio loudness (R* {approx}> 3.5) and radio luminosity that RLQs become strongly X-ray bright. We find no evidence for evolution in the X-ray properties of RIQs and RLQs with redshift (implying jet-linked IC/CMB emission does not contribute substantially to the nuclear X-ray continuum). Finally, we consider a model in which the nuclear X-ray emission contains both disk/corona-linked and jet-linked components and demonstrate that the X-ray jet-linked emission is likely beamed but to a lesser degree than applies to the radio jet. This model is used to investigate the increasing dominance of jet-linked X-ray emission at low inclinations.

  11. Diffuse neutrino intensity from the inner jets of active galactic nuclei: Impacts of external photon fields and the blazar sequence

    NASA Astrophysics Data System (ADS)

    Murase, Kohta; Inoue, Yoshiyuki; Dermer, Charles D.

    2014-07-01

    We study high-energy neutrino production in inner jets of radio-loud active galactic nuclei (AGN), taking into account effects of external photon fields and the blazar sequence. We show that the resulting diffuse neutrino intensity is dominated by quasar-hosted blazars, in particular, flat spectrum radio quasars, and that PeV-EeV neutrino production due to photohadronic interactions with broadline and dust radiation is unavoidable if the AGN inner jets are ultrahigh-energy cosmic-ray (UHECR) sources. Their neutrino spectrum has a cutoff feature around PeV energies since target photons are due to Lyα emission. Because of infrared photons provided by the dust torus, neutrino spectra above PeV energies are too hard to be consistent with the IceCube data unless the proton spectral index is steeper than 2.5, or the maximum proton energy is ≲100 PeV. Thus, the simple model has difficulty in explaining the IceCube data. For the cumulative neutrino intensity from blazars to exceed ˜10-8 GeV cm-2 s-1 sr-1, their local cosmic-ray energy generation rate would be ˜10-100 times larger than the local UHECR emissivity but is comparable to the averaged γ-ray blazar emissivity. Interestingly, future detectors such as the Askaryan Radio Array can detect ˜0.1-1 EeV neutrinos even in more conservative cases, allowing us to indirectly test the hypothesis that UHECRs are produced in the inner jets. We find that the diffuse neutrino intensity from radio-loud AGN is dominated by blazars with γ-ray luminosity of ≳1048 erg s-1, and the arrival directions of their ˜1-100 PeV neutrinos correlate with the luminous blazars detected by Fermi.

  12. The Formation of Galactic Bulges

    NASA Astrophysics Data System (ADS)

    Carollo, C. Marcella; Ferguson, Henry C.; Wyse, Rosemary F. G.

    2000-03-01

    Part I. Introduction: What are galactic bulges?; Part II. The Epoch of Bulge Formation: Origin of bulges; Deep sub-mm surveys: High-z ULIRGs and the formation of spheroids; Ages and metallicities for stars in the galactic bulge; Integrated stellar populations of bulges: First results; HST-NICMOS observations of galactic bulges: Ages and dust; Inside-out bulge formation and the origin of the Hubble sequence; Part III. The Timescales of Bulge Formation: Constraints on the bulge formation timescale from stellar populations; Bulge building with mergers and winds; Role of winds, starbursts, and activity in bulge formation; Dynamical timescales of bulge formation; Part IV. Physical Processes in Bulge Formation: the role of bars for secular bulge formation; Bars and boxy/peanut-shaped bulges: an observational point of view; Boxy- and peanut-shaped bulges; A new class of bulges; The role of secondary bars in bulge formation; Radial transport of molecular gas to the nuclei of spiral galaxies; Dynamical evolution of bulge shapes; Two-component stellar systems: Phase-space constraints; Central NGC 2146 - a firehose-type bending instability?; Bulge formation: the role of the multi-phase ISM; Global evolution of a self-gravitating multi-phase ISM in the central kpc region of galaxies; Part V. Bulge Phenomenology: Bulge-disk decomposition of spiral galaxies in the near-infrared; The triaxial bulge of NGC 1371; The bulge-disk orthogonal decoupling in galaxies: NGC 4698 and NGC 4672; The kinematics and the origin of the ionized gas in NGC 4036; Optically thin thermal plasma in the galactic bulge; X-ray properties of bulges; The host galaxies of radio-loud AGN; The centers of radio-loud early-type galaxies with HST; Central UV spikes in two galactic spheroids; Conference summary: where do we stand?

  13. Morphological research on radio loud AGN 4C39.25 using KaVA observations

    NASA Astrophysics Data System (ADS)

    Yoo, Hyemin; Sohn, Bong Won; Yi, Sukyoung; KaVA AGN WG members

    2016-01-01

    4C39.25 (0923+392) is a distant radio loud AGN placed at redshift 0.695. Its kilo-parsec scale jet observed by VLBA(Kollgaard et al. 1990) and parsec scale jet observed by VLBA(Kellermann et al. 1998) are misaligned. This might indicate episodic-jet activity which recently turned on. This object currently shows two stationary compact parsec-scale components:a bright jet component on the east and less luminous core on the west. Also, it is known that there have been superluminal jet components which are flowing from the core toward east, and then merging with the bright jet component (Marscher et al. 1991, Alberdi et al. 2000, Lister et al. 2013). Including the detection of broad emission lines(SDSS), its viewing angle was concluded to be small. However, the jet component being more luminous than the core is abnormal for a source with a small viewing angle. Furthermore, it has young radio galaxy-like properties such as non-variation in total flux(Alberdi et al. 1997, 2000, MOJAVE database) and a high frequency peak in the spectral energy distribution(Orienti et al 2007). In this case, it is more reliable to think that viewing angle of 4C39.25 is large. Korean VLBI Network (KVN) and VLBI Exploration of Radio Astronomy (VERA) Array (KaVA) is a cooperated VLBI system of Korea and Japan which provides high-frequency (23GHz and 43GHz) and high spatial resolution(1.2mas and 0.6mas). Their advantages of multi-wavelength and relatively high S/N ratio relative to its number of baseline allow us to discover the central region and dim structures of 4C39.25. We present results of several epochs observed during 2013 to 2014, focusing on morphological changes of 4C39.25 using KaVA images. According to these results, we were able to find a recently emitted counter-jet component for images of first 6 epochs. Also the counter-jet component propagates along a curved trajectory, and it shows an extreme superluminal motion. This might indicate a necessity of relatively large viewing

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

    SciTech Connect

    Tanaka, Masaomi; Morokuma, Tomoki; Doi, Mamoru; Kikuchi, Yuki; Itoh, Ryosuke; Akitaya, Hiroshi; Tanaka, Yasuyuki T.; Kawabata, Koji S.; Tominaga, Nozomu; Saito, Yoshihiko; Kawai, Nobuyuki; Stawarz, Łukasz; Gandhi, Poshak; Ali, Gamal; Essam, Ahmad; Hamed, Gamal; Aoki, Tsutomu; Contreras, Carlos; Hsiao, Eric Y.; Iwata, Ikuru; 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.

  15. Investigating the Variability of Active Galactic Nuclei Using Combined Multi-quarter Kepler Data

    NASA Astrophysics Data System (ADS)

    Revalski, Mitchell; Nowak, Dawid; Wiita, Paul J.; Wehrle, Ann E.; Unwin, Stephen C.

    2014-04-01

    We used photometry from the Kepler satellite to characterize the variability of four radio-loud active galactic nuclei (AGNs) on timescales from years to minutes. The Kepler satellite produced nearly continuous high precision data sets which provided better temporal coverage than possible with ground based observations. We have now accumulated 11 quarters of data, eight of which were reported in our previous paper. In addition to constructing power spectral densities (PSDs) and characterizing the variability of the last three quarters, we have linked together the individual quarters using a multiplicative scaling process, providing data sets spanning ~2.8 yr with >98% coverage at a 30 minute sampling rate. We compute PSDs on these connected data sets that yield power law slopes at low frequencies in the approximate range of -1.5 to -2.0, with white noise seen at higher frequencies. These PSDs are similar to those of both the individual quarters and to those of ground-based optical observations of other AGNs. We also have explored a PSD binning method intended to reduce a bias toward shallow slope fits by evenly distributing the points within the PSDs. This tends to steepen the computed PSD slopes, especially when the low frequencies are relatively poorly fit. We detected flares lasting several days in which the brightness increased by ~15%-20% in one object, as well a smaller flare in another. Two AGNs showed only small, ~1%-2%, fluctuations in brightness.

  16. Investigating the variability of active galactic nuclei using combined multi-quarter Kepler data

    SciTech Connect

    Revalski, Mitchell; Nowak, Dawid; Wiita, Paul J.; Wehrle, Ann E.; Unwin, Stephen C.

    2014-04-10

    We used photometry from the Kepler satellite to characterize the variability of four radio-loud active galactic nuclei (AGNs) on timescales from years to minutes. The Kepler satellite produced nearly continuous high precision data sets which provided better temporal coverage than possible with ground based observations. We have now accumulated 11 quarters of data, eight of which were reported in our previous paper. In addition to constructing power spectral densities (PSDs) and characterizing the variability of the last three quarters, we have linked together the individual quarters using a multiplicative scaling process, providing data sets spanning ∼2.8 yr with >98% coverage at a 30 minute sampling rate. We compute PSDs on these connected data sets that yield power law slopes at low frequencies in the approximate range of –1.5 to –2.0, with white noise seen at higher frequencies. These PSDs are similar to those of both the individual quarters and to those of ground-based optical observations of other AGNs. We also have explored a PSD binning method intended to reduce a bias toward shallow slope fits by evenly distributing the points within the PSDs. This tends to steepen the computed PSD slopes, especially when the low frequencies are relatively poorly fit. We detected flares lasting several days in which the brightness increased by ∼15%-20% in one object, as well a smaller flare in another. Two AGNs showed only small, ∼1%-2%, fluctuations in brightness.

  17. RMS Spectral Modelling - a powerful tool to probe the origin of variability in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Mallick, Labani; Dewangan, Gulab chand; Misra, Ranjeev

    2016-07-01

    The broadband energy spectra of Active Galactic Nuclei (AGN) are very complex in nature with the contribution from many ingredients: accretion disk, corona, jets, broad-line region (BLR), narrow-line region (NLR) and Compton-thick absorbing cloud or TORUS. The complexity of the broadband AGN spectra gives rise to mean spectral model degeneracy, e.g, there are competing models for the broad feature near 5-7 keV in terms of blurred reflection and complex absorption. In order to overcome the energy spectral model degeneracy, the most reliable approach is to study the RMS variability spectrum which connects the energy spectrum with temporal variability. The origin of variability could be pivoting of the primary continuum, reflection and/or absorption. The study of RMS (Root Mean Square) spectra would help us to connect the energy spectra with the variability. In this work, we study the energy dependent variability of AGN by developing theoretical RMS spectral model in ISIS (Interactive Spectral Interpretation System) for different input energy spectra. In this talk, I would like to present results of RMS spectral modelling for few radio-loud and radio-quiet AGN observed by XMM-Newton, Suzaku, NuSTAR and ASTROSAT and will probe the dichotomy between these two classes of AGN.

  18. The Far-Infrared Emission of Radio Loud and Radio Quiet Quasars

    NASA Technical Reports Server (NTRS)

    Polletta, M.; Courvoisier, T. J.-L.; Wilkes, B. J.; Hooper, E. J.

    2000-01-01

    Continuum observations at radio, millimeter, infrared and soft X-ray energies are presented for a sample of 22 quasars, consisting of flat and steep spectrum radio loud, radio intermediate and radio quiet objects. The primary observational distinctions, among the different kinds of quasars in the radio and IR energy domains are studied using large observational datasets provided by ISOPHOT on board the Infrared Space Observatory, by the IRAM interferometer, by the sub-millimetre array SCUBA on JCMT, and by the European Southern Observatory (ESO) facilities IRAC1 on the 2.2 m telescope and SEST. The spectral energy distributions of all quasars from radio to IR energies are analyzed and modeled with non-thermal and thermal spectral components. The dominant mechanism emitting in the far/mid-IR is thermal dust emission in all quasars, with the exception of flat spectrum radio loud quasars for which the presence of thermal IR emission remains rather uncertain, since it is difficult to separate it from the bright non-thermal component. The dust is predominantly heated by the optical/ultraviolet radiation emitted from the external components of the AGN. A starburst contributes to the IR emission at different levels, but always less than the AGN (<= 27%). The distribution of temperatures, sizes, masses, and luminosities of the emitting dust are independent of the quasar type.

  19. Discovery of a z = 6.1 Radio-Loud Quasar in the NDWFS

    SciTech Connect

    McGreer, I D; Becker, R H; Helfand, D J; White, R L

    2006-07-24

    From examination of only 4 deg{sup 2} of sky in the NOAO Deep Wide-Field Survey (NDWFS) region, we have identified the first radio-loud quasar at a redshift z > 6. The object, FIRST J1427385+331241, was discovered by matching the FLAMEX IR survey to FIRST survey radio sources with NDWFS counterparts. One candidate z > 6 quasar was found, and spectroscopy with the Keck II telescope confirmed its identification, yielding a redshift z = 6.12. The object is a Broad Absorption Line (BAL) quasar with an optical luminosity of M{sub B} {approx} -26.9 and a radio-to-optical flux ratio {approx} 60. Two Mg II absorptions systems are present at redshifts of z = 2.18 and z = 2.20. We briefly discuss the implications of this discovery for the high-redshift quasar population.

  20. Radio-loud CMEs from the Disk Center Lacking Shocks at 1 AU

    NASA Technical Reports Server (NTRS)

    Gopalswamy, N; Makela, P.; Akiyama, S.; Yashiro, S.; Xie, H.; MacDowall, R. J.; Kaiser, M. L.

    2013-01-01

    A coronal mass ejection (CME) associated with a type II burst and originating close to the center of the solar disk typically results in a shock at Earth in 2-3 days and hence can be used to predict shock arrival at Earth. However, a significant fraction (about 28%) of such CMEs producing type II bursts were not associated with shocks at Earth. We examined a set of 21 type II bursts observed by the Wind/WAVES experiment at decameter-hectometric (DH) wavelengths that had CME sources very close to the disk center (within a central meridian distance of 30 degrees), but did not have a shock at Earth. We find that the near-Sun speeds of these CMEs average to 644 km/s, only slightly higher than the average speed of CMEs associated with radio-quiet shocks. However, the fraction of halo CMEs is only 30%, compared to 54% for the radio-quiet shocks and 91% for all radio-loud shocks. We conclude that the disk-center radio-loud CMEs with no shocks at 1 AU are generally of lower energy and they drive shocks only close to the Sun and dissipate before arriving at Earth. There is also evidence for other possible processes that lead to the lack of shock at 1 AU: (i) overtaking CME shocks merge and one observes a single shock at Earth, and (ii) deflection by nearby coronal holes can push the shocks away from the Sun-Earth line, such that Earth misses these shocks. The probability of observing a shock at 1 AU increases rapidly above 60% when the CME speed exceeds 1000 km/s and when the type II bursts propagate to frequencies below 1 MHz.

  1. Disclosing the Radio Loudness Distribution Dichotomy in Quasars: An Unbiased Monte Carlo Approach Applied to the SDSS-FIRST Quasar Sample

    NASA Astrophysics Data System (ADS)

    Baloković, M.; Smolčić, V.; Ivezić, Ž.; Zamorani, G.; Schinnerer, E.; Kelly, B. C.

    2012-11-01

    We investigate the dichotomy in the radio loudness distribution of quasars by modeling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with (12 ± 1)% of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average louder, and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations.

  2. DISCLOSING THE RADIO LOUDNESS DISTRIBUTION DICHOTOMY IN QUASARS: AN UNBIASED MONTE CARLO APPROACH APPLIED TO THE SDSS-FIRST QUASAR SAMPLE

    SciTech Connect

    Balokovic, M.; Smolcic, V.; Ivezic, Z.; Zamorani, G.; Schinnerer, E.; Kelly, B. C.

    2012-11-01

    We investigate the dichotomy in the radio loudness distribution of quasars by modeling their radio emission and various selection effects using a Monte Carlo approach. The existence of two physically distinct quasar populations, the radio-loud and radio-quiet quasars, is controversial and over the last decade a bimodal distribution of radio loudness of quasars has been both affirmed and disputed. We model the quasar radio luminosity distribution with simple unimodal and bimodal distribution functions. The resulting simulated samples are compared to a fiducial sample of 8300 quasars drawn from the SDSS DR7 Quasar Catalog and combined with radio observations from the FIRST survey. Our results indicate that the SDSS-FIRST sample is best described by a radio loudness distribution which consists of two components, with (12 {+-} 1)% of sources in the radio-loud component. On the other hand, the evidence for a local minimum in the loudness distribution (bimodality) is not strong and we find that previous claims for its existence were probably affected by the incompleteness of the FIRST survey close to its faint limit. We also investigate the redshift and luminosity dependence of the radio loudness distribution and find tentative evidence that at high redshift radio-loud quasars were rarer, on average louder, and exhibited a smaller range in radio loudness. In agreement with other recent work, we conclude that the SDSS-FIRST sample strongly suggests that the radio loudness distribution of quasars is not a universal function, and that more complex models than presented here are needed to fully explain available observations.

  3. NUCLEAR RADIO JET FROM A LOW-LUMINOSITY ACTIVE GALACTIC NUCLEUS IN NGC 4258

    SciTech Connect

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

    2013-03-01

    The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak radio continuum component at the galactic center. We investigate its radio spectral properties on the basis of our new observations using the Nobeyama Millimeter Array at 100 GHz and archival data from the Very Large Array at 1.7-43 GHz and the James Clerk Maxwell telescope at 347 GHz. The NGC 4258 nuclear component exhibits (1) an intra-month variable and complicated spectral feature at 5-22 GHz and (2) a slightly inverted spectrum at 5-100 GHz ({alpha} {approx} 0.3; F {sub {nu}}{proportional_to}{nu}{sup {alpha}}) in time-averaged flux densities, which are also apparent in the closest LLAGN M81. These similarities between NGC 4258 and M81 in radio spectral natures in addition to previously known core shift in their AU-scale jet structures produce evidence that the same mechanism drives their nuclei. We interpret the observed spectral property as the superposition of emission spectra originating at different locations with frequency-dependent opacity along the nuclear jet. Quantitative differences between NGC 4258 and M81 in terms of jet/counter jet ratio, radio loudness, and degree of core shift can be consistently understood by fairly relativistic speeds ({Gamma} {approx}> 3) of jets and their quite different inclinations. The picture established from the two closest LLAGNs is useful for understanding the physical origin of unresolved and flat/inverted spectrum radio cores that are prevalently found in LLAGNs, including Sgr A*, with starved supermassive black holes in the present-day universe.

  4. Nuclear Radio Jet from a Low-luminosity Active Galactic Nucleus in NGC 4258

    NASA Astrophysics Data System (ADS)

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

    2013-03-01

    The nearby low-luminosity active galactic nucleus (LLAGN) NGC 4258 has a weak radio continuum component at the galactic center. We investigate its radio spectral properties on the basis of our new observations using the Nobeyama Millimeter Array at 100 GHz and archival data from the Very Large Array at 1.7-43 GHz and the James Clerk Maxwell telescope at 347 GHz. The NGC 4258 nuclear component exhibits (1) an intra-month variable and complicated spectral feature at 5-22 GHz and (2) a slightly inverted spectrum at 5-100 GHz (α ~ 0.3; F νvpropνα) in time-averaged flux densities, which are also apparent in the closest LLAGN M81. These similarities between NGC 4258 and M81 in radio spectral natures in addition to previously known core shift in their AU-scale jet structures produce evidence that the same mechanism drives their nuclei. We interpret the observed spectral property as the superposition of emission spectra originating at different locations with frequency-dependent opacity along the nuclear jet. Quantitative differences between NGC 4258 and M81 in terms of jet/counter jet ratio, radio loudness, and degree of core shift can be consistently understood by fairly relativistic speeds (Γ >~ 3) of jets and their quite different inclinations. The picture established from the two closest LLAGNs is useful for understanding the physical origin of unresolved and flat/inverted spectrum radio cores that are prevalently found in LLAGNs, including Sgr A*, with starved supermassive black holes in the present-day universe.

  5. MOJAVE: MONITORING OF JETS IN ACTIVE GALACTIC NUCLEI WITH VLBA EXPERIMENTS. V. MULTI-EPOCH VLBA IMAGES

    SciTech Connect

    Lister, M. L.; Aller, H. D.; Aller, M. F. E-mail: haller@umich.edu

    2009-03-15

    We present images from a long-term program (MOJAVE: Monitoring of Jets in active galactic nuclei (AGNs) with VLBA Experiments) to survey the structure and evolution of parsec-scale jet phenomena associated with bright radio-loud active galaxies in the northern sky. The observations consist of 2424 15 GHz Very Long Baseline Array (VLBA) images of a complete flux-density-limited sample of 135 AGNs above declination -20{sup 0}, spanning the period 1994 August to 2007 September. These data were acquired as part of the MOJAVE and 2 cm Survey programs, and from the VLBA archive. The sample-selection criteria are based on multi-epoch parsec-scale (VLBA) flux density, and heavily favor highly variable and compact blazars. The sample includes nearly all the most prominent blazars in the northern sky, and is well suited for statistical analysis and comparison with studies at other wavelengths. Our multi-epoch and stacked-epoch images show 94% of the sample to have apparent one-sided jet morphologies, most likely due to the effects of relativistic beaming. Of the remaining sources, five have two-sided parsec-scale jets, and three are effectively unresolved by the VLBA at 15 GHz, with essentially all of the flux density contained within a few tenths of a milliarcsecond.

  6. Are the hosts of VLBI-selected radio-AGN different to those of radio-loud AGN?

    NASA Astrophysics Data System (ADS)

    Rees, G. A.; Norris, R. P.; Spitler, L. R.; Herrera-Ruiz, N.; Middelberg, E.

    2016-05-01

    Recent studies have found that radio-AGN selected by radio-loudness show little difference in terms of their host galaxy properties when compared to non-AGN galaxies of similar stellar mass and redshift. Using new 1.4 GHz very long baseline interferometry (VLBI) observations of the Cosmological Evolution Survey field, we find that approximately 49 ± 8 per cent of high-mass (M > 1010.5 M⊙), high-luminosity (L1.4 > 1024 W Hz-1) radio-AGN possess a VLBI-detected counterpart. These objects show no discernible bias towards specific stellar masses, redshifts or host properties other than what is shown by the radio-AGN population in general. Radio-AGN that are detected in VLBI observations are not special, but form a representative sample of the radio-loud AGN population.

  7. SDSS J013127.34-032100.1: A Newly Discovered Radio-loud Quasar at z = 5.18 with Extremely High Luminosity

    NASA Astrophysics Data System (ADS)

    Yi, Wei-Min; Wang, Feige; Wu, Xue-Bing; Yang, Jinyi; Bai, Jin-Ming; Fan, Xiaohui; Brandt, William N.; Ho, Luis C.; Zuo, Wenwen; Kim, Minjin; Wang, Ran; Yang, Qian; Zhang, Ju-jia; Wang, Fang; Wang, Jian-Guo; Ai, Yanli; Fan, Yu-Feng; Chang, Liang; Wang, Chuan-Jun; Lun, Bao-Li; Xin, Yu-Xin

    2014-11-01

    Very few of the z > 5 quasars discovered to date have been radio-loud, with radio-to-optical flux ratios (radio-loudness parameters) higher than 10. Here we report the discovery of an optically luminous radio-loud quasar, SDSS J013127.34-032100.1 (J0131-0321 in short), at z = 5.18 ± 0.01 using the Lijiang 2.4 m and Magellan telescopes. J0131-0321 has a spectral energy distribution consistent with that of radio-loud quasars. With an i-band magnitude of 18.47 and a radio flux density of 33 mJy, its radio-loudness parameter is ~100. The optical and near-infrared spectra taken by Magellan enable us to estimate its bolometric luminosity to be L bol ~ 1.1 × 1048 erg s-1, approximately 4.5 times greater than that of the most distant quasar known to date. The black hole mass of J0131-0321 is estimated to be 2.7 × 109 M ⊙, with an uncertainty up to 0.4 dex. Detailed physical properties of this high-redshift, radio-loud, potentially super-Eddington quasar can be probed in the future with more dedicated and intensive follow-up observations using multi-wavelength facilities.

  8. SDSS J013127.34–032100.1: A NEWLY DISCOVERED RADIO-LOUD QUASAR AT z = 5.18 WITH EXTREMELY HIGH LUMINOSITY

    SciTech Connect

    Yi, Wei-Min; Bai, Jin-Ming; Zhang, Ju-jia; Wang, Fang; Wang, Jian-Guo; Fan, Yu-Feng; Chang, Liang; Wang, Chuan-Jun; Lun, Bao-Li; Wang, Feige; Wu, Xue-Bing; Yang, Jinyi; Ho, Luis C.; Zuo, Wenwen; Yang, Qian; Ai, Yanli; Fan, Xiaohui; Brandt, William N.; Kim, Minjin; Wang, Ran; and others

    2014-11-10

    Very few of the z > 5 quasars discovered to date have been radio-loud, with radio-to-optical flux ratios (radio-loudness parameters) higher than 10. Here we report the discovery of an optically luminous radio-loud quasar, SDSS J013127.34–032100.1 (J0131–0321 in short), at z = 5.18 ± 0.01 using the Lijiang 2.4 m and Magellan telescopes. J0131–0321 has a spectral energy distribution consistent with that of radio-loud quasars. With an i-band magnitude of 18.47 and a radio flux density of 33 mJy, its radio-loudness parameter is ∼100. The optical and near-infrared spectra taken by Magellan enable us to estimate its bolometric luminosity to be L {sub bol} ∼ 1.1 × 10{sup 48} erg s{sup –1}, approximately 4.5 times greater than that of the most distant quasar known to date. The black hole mass of J0131–0321 is estimated to be 2.7 × 10{sup 9} M {sub ☉}, with an uncertainty up to 0.4 dex. Detailed physical properties of this high-redshift, radio-loud, potentially super-Eddington quasar can be probed in the future with more dedicated and intensive follow-up observations using multi-wavelength facilities.

  9. The compact radio structure of radio-loud NLS1 galaxies and the relationship to CSS sources

    NASA Astrophysics Data System (ADS)

    Gu, M.; Chen, Y.; Komossa, S.; Yuan, W.; Shen, Z.

    2016-02-01

    Narrow-line Seyfert 1 galaxies are thought to be young AGNs with relatively small black hole masses and high accretion rates. Radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s) are very special, because some of them show blazar-like characteristics, while others resemble compact steep-spectrum sources. Relativistic jets were shown to exist in a few RLNLS1s based on VLBI observations and confirmed by the gamma-ray flaring of some of them. These properties may possibly be contrary to typical radio-loud AGNs, in light of the low black-hole masses, and high accretion rates. We present the compact radio structure of fourteen RLNLS1 galaxies from Very Long Baseline Array observations at 5 GHz in 2013. Although all these sources are very radio-loud with {R > 100}, their jet properties are diverse, in terms of their milli-arcsecond (mas) scale (pc scale) morphology and their overall radio spectral shape. The core brightness temperatures of our sources are significantly lower than those of blazars, therefore, the beaming effect is generally not significant in our sources, compared to blazars. This implies that the bulk jet speed may likely be low in our sources. The relationship between RLNLS1s and compact steep-spectrum sources, and the implications on jet formation are discussed based on the pc-scale jet properties.

  10. THE WISE BLAZAR-LIKE RADIO-LOUD SOURCES: AN ALL-SKY CATALOG OF CANDIDATE γ-RAY BLAZARS

    SciTech Connect

    D'Abrusco, R.; Paggi, A.; Smith, H. A.; Massaro, F.; Masetti, N.

    2014-11-01

    We present a catalog of radio-loud candidate γ-ray emitting blazars with WISE mid-infrared colors similar to the colors of confirmed γ-ray blazars. The catalog is assembled from WISE sources detected in all four WISE filters, with colors compatible with the three-dimensional locus of the WISE γ-ray emitting blazars, and which can be spatially cross-matched with radio sources from one of the three radio surveys: NVSS, FIRST, and/or SUMSS. Our initial WISE selection uses a slightly modified version of previously successful algorithms. We then select only the radio-loud sources using a measure of the radio-to-IR flux, the q {sub 22} parameter, which is analogous to the q {sub 24} parameter known in the literature but which instead uses the WISE band-four flux at 22 μm. Our final catalog contains 7855 sources classified as BL Lacs, FSRQs, or mixed candidate blazars; 1295 of these sources can be spatially re-associated as confirmed blazars. We describe the properties of the final catalog of WISE blazar-like radio-loud sources and consider possible contaminants. Finally, we discuss why this large catalog of candidate γ-ray emitting blazars represents a new and useful resource to address the problem of finding low-energy counterparts to currently unidentified high-energy sources.

  11. THE ROLE OF THE ACCRETION DISK, DUST, AND JETS IN THE IR EMISSION OF LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Mason, R. E.; Ramos Almeida, C.; Alonso-Herrero, A.

    2013-11-10

    We use recent high-resolution infrared (IR; 1-20 μm) photometry to examine the origin of the IR emission in low-luminosity active galactic nuclei (LLAGN). The data are compared with published model fits that describe the spectral energy distribution (SED) of LLAGN in terms of an advection-dominated accretion flow, truncated thin accretion disk, and jet. The truncated disk in these models is usually not luminous enough to explain the observed IR emission, and in all cases its spectral shape is much narrower than the broad IR peaks in the data. Synchrotron radiation from the jet appears to be important in very radio-loud nuclei, but the detection of strong silicate emission features in many objects indicates that dust must also contribute. We investigate this point by fitting the IR SED of NGC 3998 using dusty torus and optically thin (τ{sub mid-IR} ∼ 1) dust shell models. While more detailed modeling is necessary, these initial results suggest that dust may account for the nuclear mid-IR emission of many LLAGN.

  12. SPECTRAL SURVEY OF X-RAY BRIGHT ACTIVE GALACTIC NUCLEI FROM THE ROSSI X-RAY TIMING EXPLORER

    SciTech Connect

    Rivers, Elizabeth; Markowitz, Alex; Rothschild, Richard

    2011-03-15

    Using long-term monitoring data from the Rossi X-ray Timing Explorer (RXTE), we have selected 23 active galactic nuclei (AGNs) with sufficient brightness and overall observation time to derive broadband X-ray spectra from 3 to {approx}>100 keV. Our sample includes mainly radio-quiet Seyferts, as well as seven radio-loud sources. Given the longevity of the RXTE mission, the greater part of our data is spread out over more than a decade, providing truly long-term average spectra and eliminating inconsistencies arising from variability. We present long-term average values of absorption, Fe line parameters, Compton reflection strengths, and photon indices, as well as fluxes and luminosities for the hard and very hard energy bands, 2-10 keV and 20-100 keV, respectively. We find tentative evidence for high-energy rollovers in three of our objects. We improve upon previous surveys of the very hard X-ray energy band in terms of accuracy and sensitivity, particularly with respect to confirming and quantifying the Compton reflection component. This survey is meant to provide a baseline for future analysis with respect to the long-term averages for these sources and to cement the legacy of RXTE, and especially its High Energy X-ray Timing Experiment, as a contributor to AGN spectral science.

  13. THE EXTREME ULTRAVIOLET DEFICIT AND MAGNETICALLY ARRESTED ACCRETION IN RADIO-LOUD QUASARS

    SciTech Connect

    Punsly, Brian

    2014-12-20

    The Hubble Space Telescope composite quasar spectra presented in Telfer et al. show a significant deficit of emission in the extreme ultraviolet for the radio-loud component of the quasar population (RLQs) compared to the radio-quiet component of the quasar population. The composite quasar continuum emission between 1100 Å and ∼580 Å is generally considered to be associated with the innermost regions of the accretion flow onto the central black hole. The deficit between 1100 Å and 580 Å in RLQs has a straightforward interpretation as a missing or a suppressed innermost region of local energy dissipation in the accretion flow. It is proposed that this can be the result of islands of large-scale magnetic flux in RLQs that are located close to the central black hole that remove energy from the accretion flow as Poynting flux (sometimes called magnetically arrested accretion). These magnetic islands are natural sites for launching relativistic jets. Based on the Telfer et al. data and the numerical simulations of accretion flows in Penna et al., the magnetic islands are concentrated between the event horizon and an outer boundary of <2.8 M (in geometrized units) for rapidly rotating black holes and <5.5 M for modestly rotating black holes.

  14. Expected level of self-Compton scattering in radio loud quasars

    NASA Technical Reports Server (NTRS)

    Bloom, Steven D.; Marscher, Alan P.

    1992-01-01

    Radio-loud quasars usually contain parsec-scale nonthermal jets. The most compact emission region ('the core'), and perhaps some of the moving 'knots', are expected to be efficient producers of inverse Compton scattered X-rays and gamma-rays since many of the synchrotron photons will upscatter before escaping. Through multifrequency flux density observations and Very Long Baseline Interferometry (VLBI) measurements of angular sizes, one can predict the flux density of this self-Compton high-energy emission. It is not always the case that the brightest synchrotron sources are also the brightest X-ray and gamma-ray sources. Perhaps a better predictor of high-energy brightness is the ratio of hard X-ray to high-frequency radio emission. Using the synchrotron self-Compton relations, we predict the gamma-ray fluxes of several sources we expect to be detected by the Energetic Gamma Ray Experiment Telescope (EGRET). More accurate predictions will be made when we complete a program of contemporaneous radio-submillimeter and X-ray observations during the course of the EGRET all-sky survey.

  15. New Insights on the Accretion Disk-Winds Connection in Radio-Loud AGNs from Suzaku

    NASA Technical Reports Server (NTRS)

    Tombesi, F.; Sambruna, R. M.; Reeves, J. N.; Braito, V.; Cappi, M.; Reynolds, S.; Mushotzky, R. F.

    2011-01-01

    From the spectral analysis of long Suzaku observations of five radio-loud AGNs we have been able to discover the presence of ultra-fast outflows with velocities ,,approx.0.1 c in three of them, namely 3C III, 3C 120 and 3C 390.3. They are consistent with being accretion disk winds/outflows. We also performed a follow-up on 3C III to monitor its outflow on approx.7 days time-scales and detected an anti-correlated variability of a possible relativistic emission line with respect to blue-shifted Fe K features, following a flux increase. This provides the first direct evidence for an accretion disc-wind connection in an AGN. The mass outflow rate of these outflows can be comparable to the accretion rate and their mechanical power can correspond to a significant fraction of the bolometric luminosity and is comparable to their typical jet power. Therefore, they can possibly play a significant role in the expected feedback from AGNs and can give us further clues on the relation between the accretion disk and the formation of winds/jets.

  16. The Correlations of Jet Power with Black Hole Mass and Spin in Radio Loud Quasars

    NASA Astrophysics Data System (ADS)

    Xu, Zhang; Hao-jing, Zhang; Xiong, Zhang

    2016-04-01

    The formation of jets is closely related with the black hole mass and black hole spin, to study the correlations of jet power with the black hole mass and black hole spin is of significant importance for understanding the jet formation and structure. We have collected 65 radio loud quasars from the literature. The sample includes 35 Steep Spectrum Radio Quasars (SSRQs) and 30 Flat Spectrum Radio Quasars (FSRQs) with the redshifts ranging from about zero to two. We present here the correlation analysis of jet power with the black hole mass and back hole spin based on the sample data. Our conclusions are as follows: (1) The black hole mass has a strong correlation with the jet power; (2) The black hole spin is also strongly correlated with the jet power, especially for the magnetic field strength B = BEDD, where BEDD is the Eddington magnetic field strength, and the correlation coefficient is higher than that between black hole mass and jet power; (3) There are certain differences between the distributions of spin data of SSRQs and FSRQs; (4) This study has further confirmed that the jet energy is related not only with the black hole mass, but also with the spin energy of the black hole. The formation of black hole jet may be very possibly resulted by the joint effect of black hole mass and black hole spin. These results are consistent with the previous results obtained by other methods.

  17. AN INFRARED EXCESS IDENTIFIED IN RADIO-LOUD BROAD ABSORPTION LINE QUASARS

    SciTech Connect

    DiPompeo, M. A.; Runnoe, J. C.; Brotherton, M. S.; Myers, A. D.

    2013-01-10

    If broad absorption line (BAL) quasars represent a high-covering-fraction evolutionary state (even if this is not the sole factor governing the presence of BALs), it is expected that they should show an excess of mid-infrared radiation compared to normal quasars. Some previous studies have suggested that this is not the case. We perform the first analysis of the IR properties of radio-loud BAL quasars, using IR data from WISE and optical (rest-frame ultraviolet) data from SDSS, and compare the BAL quasar sample with a well-matched sample of unabsorbed quasars. We find a statistically significant excess in the mid- to near-infrared luminosities of BAL quasars, particularly at rest-frame wavelengths of 1.5 and 4 {mu}m. Our sample was previously used to show that BALs are observed along many lines of sight toward quasars, but with an overabundance of more edge-on sources, suggesting that orientation factors into the appearance of BALs. The evidence here-of a difference in IR luminosities between BAL quasars and unabsorbed quasars-can be ascribed to evolution. This suggests that a merging of the current BAL paradigms is needed to fully describe the class.

  18. GPU-based Monte Carlo Dust Radiative Transfer Scheme Applied to Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Heymann, Frank; Siebenmorgen, Ralf

    2012-05-01

    A three-dimensional parallel Monte Carlo (MC) dust radiative transfer code is presented. To overcome the huge computing-time requirements of MC treatments, the computational power of vectorized hardware is used, utilizing either multi-core computer power or graphics processing units. The approach is a self-consistent way to solve the radiative transfer equation in arbitrary dust configurations. The code calculates the equilibrium temperatures of two populations of large grains and stochastic heated polycyclic aromatic hydrocarbons. Anisotropic scattering is treated applying the Heney-Greenstein phase function. The spectral energy distribution (SED) of the object is derived at low spatial resolution by a photon counting procedure and at high spatial resolution by a vectorized ray tracer. The latter allows computation of high signal-to-noise images of the objects at any frequencies and arbitrary viewing angles. We test the robustness of our approach against other radiative transfer codes. The SED and dust temperatures of one- and two-dimensional benchmarks are reproduced at high precision. The parallelization capability of various MC algorithms is analyzed and included in our treatment. We utilize the Lucy algorithm for the optical thin case where the Poisson noise is high, the iteration-free Bjorkman & Wood method to reduce the calculation time, and the Fleck & Canfield diffusion approximation for extreme optical thick cells. The code is applied to model the appearance of active galactic nuclei (AGNs) at optical and infrared wavelengths. The AGN torus is clumpy and includes fluffy composite grains of various sizes made up of silicates and carbon. The dependence of the SED on the number of clumps in the torus and the viewing angle is studied. The appearance of the 10 μm silicate features in absorption or emission is discussed. The SED of the radio-loud quasar 3C 249.1 is fit by the AGN model and a cirrus component to account for the far-infrared emission.

  19. GPU-BASED MONTE CARLO DUST RADIATIVE TRANSFER SCHEME APPLIED TO ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Heymann, Frank; Siebenmorgen, Ralf

    2012-05-20

    A three-dimensional parallel Monte Carlo (MC) dust radiative transfer code is presented. To overcome the huge computing-time requirements of MC treatments, the computational power of vectorized hardware is used, utilizing either multi-core computer power or graphics processing units. The approach is a self-consistent way to solve the radiative transfer equation in arbitrary dust configurations. The code calculates the equilibrium temperatures of two populations of large grains and stochastic heated polycyclic aromatic hydrocarbons. Anisotropic scattering is treated applying the Heney-Greenstein phase function. The spectral energy distribution (SED) of the object is derived at low spatial resolution by a photon counting procedure and at high spatial resolution by a vectorized ray tracer. The latter allows computation of high signal-to-noise images of the objects at any frequencies and arbitrary viewing angles. We test the robustness of our approach against other radiative transfer codes. The SED and dust temperatures of one- and two-dimensional benchmarks are reproduced at high precision. The parallelization capability of various MC algorithms is analyzed and included in our treatment. We utilize the Lucy algorithm for the optical thin case where the Poisson noise is high, the iteration-free Bjorkman and Wood method to reduce the calculation time, and the Fleck and Canfield diffusion approximation for extreme optical thick cells. The code is applied to model the appearance of active galactic nuclei (AGNs) at optical and infrared wavelengths. The AGN torus is clumpy and includes fluffy composite grains of various sizes made up of silicates and carbon. The dependence of the SED on the number of clumps in the torus and the viewing angle is studied. The appearance of the 10 {mu}m silicate features in absorption or emission is discussed. The SED of the radio-loud quasar 3C 249.1 is fit by the AGN model and a cirrus component to account for the far-infrared emission.

  20. Discovery of millimetre-wave excess emission in radio-quiet active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Behar, Ehud; Baldi, Ranieri D.; Laor, Ari; Horesh, Assaf; Stevens, Jamie; Tzioumis, Tasso

    2015-07-01

    The physical origin of radio emission in radio-quiet active galactic nuclei (RQ AGN) remains unclear, whether it is a downscaled version of the relativistic jets typical of radio-loud (RL) AGN, or whether it originates from the accretion disc. The correlation between 5 GHz and X-ray luminosities of RQ AGN, which follows LR = 10-5LX observed also in stellar coronae, suggests an association of both X-ray and radio sources with the accretion disc corona. Observing RQ AGN at higher (mm-wave) frequencies, where synchrotron self-absorption is diminished, and smaller regions can be probed, is key to exploring this association. Eight RQ AGN, selected based on their high X-ray brightness and variability, were observed at 95 GHz with the CARMA (Combined Array for Research in Millimetre-wave Astronomy) and ATCA (the Australia Telescope Compact Array) telescopes. All targets were detected at the 1-10 mJy level. Emission excess at 95 GHz of up to ×7 is found with respect to archival low-frequency steep spectra, suggesting a compact, optically thick core superimposed on the more extended structures that dominate at low frequencies. Though unresolved, the 95 GHz fluxes imply optically thick source sizes of 10-4-10-3 pc, or ˜10-1000 gravitational radii. The present sources lie tightly along an LR (95 GHz) = 10-4LX (2-10 keV) correlation, analogous to that of stellar coronae and RQ AGN at 5 GHz, while RL AGN are shown to have higher LR/LX ratios. The present observations argue that simultaneous mm-wave and X-ray monitoring of RQ AGN features a promising method for understanding accretion disc coronal emission.

  1. Radio observations of a hard X-ray selected sample of active galaxies

    NASA Technical Reports Server (NTRS)

    Unger, S. W.; Lawrence, A.; Wilson, A. S.; Elvis, M.; Wright, A. E.

    1987-01-01

    Radio observations of a hard X-ray selected sample of active galaxies obtained with the VLA and Parkes radio telescopes are discussed, and the ratio of the radio to X-ray flux density is used to determine the degree of radio-loudness of the galaxies. A continuous distribution of the degree of radio loudness is found amongst the sample galaxies, and no evidence for distinct radio-quiet and radio-loud populations is noted. The X-ray and radio luminosity is shown to be nonlinearly correlated, with the radio-loud objects all having high X-ray luminosity.

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

    SciTech Connect

    Richards, Joseph L.; Lister, Matthew L.

    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.

  3. Suzaku Discovery of Ultra-fast Outflows in Radio-loud AGN

    NASA Astrophysics Data System (ADS)

    Sambruna, Rita M.; Tombesi, F.; Reeves, J.; Braito, V.; Gofford, J.; Cappi, M.

    2010-03-01

    We present the results of an analysis of the 3.5--10.5 keV spectra of five bright Broad-Line Radio Galaxies (BLRGs) using proprietary and archival Suzaku observations. In three sources -- 3C 111, 3C 120, and 3C 390.3 -- we find evidence, for the first time in a radio-loud AGN, for absorption features at observed energies 7 keV and 8--9 keV, with high significance according to both the F-test and extensive Monte Carlo simulations (99% or larger). In the remaining two BLRGs, 3C 382 and 3C 445, there is no evidence for such absorption features in the XIS spectra. If interpreted as due to Fe XXV and/or Fe XXVI K-shell resonance lines, the absorption features in 3C 111, 3C 120, and 3C 390.3 imply an origin from an ionized gas outflowing with velocities in the range v 0.04-0.15c, reminiscent of Ultra-Fast Outflows (UFOs) previously observed in radio-quiet Seyfert galaxies. A fit with specific photoionization models gives ionization parameters log ξ 4--5.6 erg s-1 cm and column densities of NH 1022-23 cm-2, similar to the values observed in Seyferts. Based on light travel time arguments, we estimate that the UFOs in the three BLRGs are located within 20--500 gravitational radii from the central black hole, and thus most likely are connected to disk winds/outflows. Our estimates show that the UFOs mass outflow rate is comparable to the accretion rate and their kinetic energy a significant fraction of the AGN bolometric luminosity, making these outflows significant for the global energetic of these systems, in particular for mechanisms of jet formation.

  4. Investigating the radio-loud phase of broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    Bruni, G.; González-Serrano, J. I.; Pedani, M.; Benn, C. R.; Mack, K.-H.; Holt, J.; Montenegro-Montes, F. M.; Jiménez-Luján, F.

    2014-09-01

    Context. Broad absorption lines (BALs) are present in the spectra of ~20% of quasars (QSOs); this indicates fast outflows (up to 0.2c) that intercept the observer's line of sight. These QSOs can be distinguished again into radio-loud (RL) BAL QSOs and radio-quiet (RQ) BAL QSOs. The first are very rare, even four times less common than RQ BAL QSOs. The reason for this is still unclear and leaves open questions about the nature of the BAL-producing outflows and their connection with the radio jet. Aims: We explored the spectroscopic characteristics of RL and RQ BAL QSOs with the aim to find a possible explanation for the rarity of RL BAL QSOs. Methods: We identified two samples of genuine BAL QSOs from SDSS optical spectra, one RL and one RQ, in a suitable redshift interval (2.5 < z < 3.5) that allowed us to observe the Mg ii and Hβ emission lines in the adjacent near-infrared (NIR) band. We collected NIR spectra of the two samples using the Telescopio Nazionale Galileo (TNG, Canary Islands). By using relations known in the literature, we estimated the black-hole mass, the broad-line region radius, and the Eddington ratio of our objects and compared the two samples. Results: We found no statistically significant differences from comparing the distributions of the cited physical quantities. This indicates that they have similar geometries, accretion rates, and central black-hole masses, regardless of whether the radio-emitting jet is present or not. Conclusions: These results show that the central engine of BAL QSOs has the same physical properties with and without a radio jet. The reasons for the rarity of RL BAL QSOs must reside in different environmental or evolutionary variables. Figure 3 is available in electronic form at http://www.aanda.org

  5. Multiwavelength Study of Radio Loud Early-Type Galaxies from the B2 Sample

    NASA Astrophysics Data System (ADS)

    Sahu, Sheetal Kumar; Chaware, Laxmikant; Pandey, S. K.; Kulkarni, Samridhi; Pandge, M. B.; Chakradhari, N. K.

    2014-07-01

    We present multiwavelength study of a sample of radio loud early-type galaxies chosen from the B2 sample. We performed surface photometry in BVR broad band filters and Hα narrow band filter on CCD images of sample galaxies using IGO 2m telescope, Pune (INDIA), to get radial profiles of various photometric and geometrical parameters that describe elliptical isophotes fitted to the 2D light distribution of the galaxies. The analysis of radial profiles of quantities such as the (local) surface brightness, the ellipticity, and the deviations from elliptical isophotes parametrized by the Fourier coefficients are main focus of our study. We generated color maps, residual maps, and dust extinction maps, Hα emission maps of the galaxies to study the morphology of the dust and ionized gas content present in the galaxies. We carried out detailed analysis of the properties of the dust present in our sample galaxies. Additionaly, we investigated properties of the dust in the central ~10 arcsec region of our sample galaxies using optical images available from the HST (WFPC2) data archive. We estimated mass and temperature of the dust, molecular gas mass, in the sample galaxies using FIR fluxes of the galaxies obtained from IRAS. We used spectroscopic data available from the SDSS (DR7) to get an estimate of the mass of the central super massive black-hole for B2 1257+28 (NGC 4874). We plotted rotation curve for coma cluster (Abell 1656), which indicates the presence of dark matter halo around the galaxy B2 1257+28.

  6. THE VLA SURVEY OF CHANDRA DEEP FIELD SOUTH. V. EVOLUTION AND LUMINOSITY FUNCTIONS OF SUB-MILLIJANSKY RADIO SOURCES AND THE ISSUE OF RADIO EMISSION IN RADIO-QUIET ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Padovani, P.; Mainieri, V.; Rosati, P.; Miller, N.; Kellermann, K. I.; Tozzi, P.

    2011-10-10

    We present the evolutionary properties and luminosity functions of the radio sources belonging to the Chandra Deep Field South Very Large Array survey, which reaches a flux density limit at 1.4 GHz of 43 {mu}Jy at the field center and redshift {approx}5 and which includes the first radio-selected complete sample of radio-quiet active galactic nuclei (AGNs). We use a new, comprehensive classification scheme based on radio, far- and near-IR, optical, and X-ray data to disentangle star-forming galaxies (SFGs) from AGNs and radio-quiet from radio-loud AGNs. We confirm our previous result that SFGs become dominant only below 0.1 mJy. The sub-millijansky radio sky turns out to be a complex mix of SFGs and radio-quiet AGNs evolving at a similar, strong rate; non-evolving low-luminosity radio galaxies; and declining radio powerful (P {approx}> 3 x 10{sup 24} W Hz{sup -1}) AGNs. Our results suggest that radio emission from radio-quiet AGNs is closely related to star formation. The detection of compact, high brightness temperature cores in several nearby radio-quiet AGNs can be explained by the coexistence of two components, one non-evolving and AGN related and one evolving and star formation related. Radio-quiet AGNs are an important class of sub-millijansky sources, accounting for {approx}30% of the sample and {approx}60% of all AGNs, and outnumbering radio-loud AGNs at {approx}< 0.1 mJy. This implies that future, large area sub-millijansky surveys, given the appropriate ancillary multiwavelength data, have the potential of being able to assemble vast samples of radio-quiet AGNs, bypassing the problems of obscuration that plague the optical and soft X-ray bands.

  7. The VLA Survey of Chandra Deep Field South. V. Evolution and Luminosity Functions of Sub-millijansky Radio Sources and the Issue of Radio Emission in Radio-quiet Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Padovani, P.; Miller, N.; Kellermann, K. I.; Mainieri, V.; Rosati, P.; Tozzi, P.

    2011-10-01

    We present the evolutionary properties and luminosity functions of the radio sources belonging to the Chandra Deep Field South Very Large Array survey, which reaches a flux density limit at 1.4 GHz of 43 μJy at the field center and redshift ~5 and which includes the first radio-selected complete sample of radio-quiet active galactic nuclei (AGNs). We use a new, comprehensive classification scheme based on radio, far- and near-IR, optical, and X-ray data to disentangle star-forming galaxies (SFGs) from AGNs and radio-quiet from radio-loud AGNs. We confirm our previous result that SFGs become dominant only below 0.1 mJy. The sub-millijansky radio sky turns out to be a complex mix of SFGs and radio-quiet AGNs evolving at a similar, strong rate; non-evolving low-luminosity radio galaxies; and declining radio powerful (P >~ 3 × 1024 W Hz-1) AGNs. Our results suggest that radio emission from radio-quiet AGNs is closely related to star formation. The detection of compact, high brightness temperature cores in several nearby radio-quiet AGNs can be explained by the coexistence of two components, one non-evolving and AGN related and one evolving and star formation related. Radio-quiet AGNs are an important class of sub-millijansky sources, accounting for ~30% of the sample and ~60% of all AGNs, and outnumbering radio-loud AGNs at <~ 0.1 mJy. This implies that future, large area sub-millijansky surveys, given the appropriate ancillary multiwavelength data, have the potential of being able to assemble vast samples of radio-quiet AGNs, bypassing the problems of obscuration that plague the optical and soft X-ray bands.

  8. The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS 2004-447. II. The radio view

    NASA Astrophysics Data System (ADS)

    Schulz, R.; Kreikenbohm, A.; Kadler, M.; Ojha, R.; Ros, E.; Stevens, J.; Edwards, P. G.; Carpenter, B.; Elsässer, D.; Gehrels, N.; Großberger, C.; Hase, H.; Horiuchi, S.; Lovell, J. E. J.; Mannheim, K.; Markowitz, A.; Müller, C.; Phillips, C.; Plötz, C.; Quick, J.; Trüstedt, J.; Tzioumis, A. K.; Wilms, J.

    2016-04-01

    Context. Γ-ray-detected radio-loud narrow-line Seyfert 1 (γ-NLS1) galaxies constitute a small but interesting sample of the γ-ray-loud AGN. The radio-loudest γ-NLS1 known, PKS 2004-447, is located in the southern hemisphere and is monitored in the radio regime by the multiwavelength monitoring programme TANAMI. Aims: We aim for the first detailed study of the radio morphology and long-term radio spectral evolution of PKS 2004-447, which are essential for understanding the diversity of the radio properties of γ-NLS1s. Methods: The TANAMI VLBI monitoring program uses the Australian Long Baseline Array (LBA) and telescopes in Antarctica, Chile, New Zealand, and South Africa to monitor the jets of radio-loud active galaxies in the southern hemisphere. Lower resolution radio flux density measurements at multiple radio frequencies over four years of observations were obtained with the Australia Telescope Compact Array (ATCA). Results: The TANAMI VLBI image at 8.4 GHz shows an extended one-sided jet with a dominant compact VLBI core. Its brightness temperature is consistent with equipartition, but it is an order of magnitude below other γ-NLS1s with the sample value varying over two orders of magnitude. We find a compact morphology with a projected large-scale size < 11 kpc and a persistent steep radio spectrum with moderate flux-density variability. Conclusions: PKS 2004-447 appears to be a unique member of the γ-NLS1 sample. It exhibits blazar-like features, such as a flat featureless X-ray spectrum and a core-dominated, one-sided parsec-scale jet with indications for relativistic beaming. However, the data also reveal properties atypical for blazars, such as a radio spectrum and large-scale size consistent with compact-steep-spectrum (CSS) objects, which are usually associated with young radio sources. These characteristics are unique among all γ-NLS1s and extremely rare among γ-ray-loud AGN. The VLBI images shown in Figs. 3 and 4 (as FITS files) and the ATCA

  9. The gamma-ray emitting radio-loud narrow-line Seyfert 1 galaxy PKS 2004-447. I. The X-ray View

    NASA Astrophysics Data System (ADS)

    Kreikenbohm, A.; Schulz, R.; Kadler, M.; Wilms, J.; Markowitz, A.; Chang, C. S.; Carpenter, B.; Elsässer, D.; Gehrels, N.; Mannheim, K.; Müller, C.; Ojha, R.; Ros, E.; Trüstedt, J.

    2016-01-01

    As part of the TANAMI multiwavelength progam, we discuss new X-ray observations of the γ-ray and radio-loud narrow line Seyfert 1 galaxy (γ-NLS1) PKS 2004-447. The active galaxy is a member of a small sample of radio-loud NLS1s detected in γ-rays by the Fermi Large Area Telescope. It stands out for being the radio-loudest and the only southern-hemisphere source in this sample. We present results from our X-ray monitoring program comprised of Swift snapshot observations from 2012 through 2014 and two new X-ray observations with XMM-Newton in 2012. Supplemented by archival data from 2004 and 2011, our data set allows for a careful analysis of the X-ray spectrum and variability of this peculiar source. The (0.5-10) keV spectrum is described well by a power law (Γ ~ 1.6), which can be interpreted as non-thermal emission from a relativistic jet. The source exhibits moderate flux variability on timescales of both months and years. Correlated brightness variations in the (0.5-2) keV and (2-10) keV bands are explained by a single variable spectral component, such as the one from the jet. A possible soft excess seen in the data from 2004 cannot be confirmed by the new XMM-Newton observations taken during low-flux states. Any contribution to the total flux in 2004 is less than 20% of the power-law component. The (0.5-10) keV luminosities of PKS 2004-447 are in the range of (0.5-2.7) × 1044 erg s-1. A comparison of the X-ray properties among the known γ-NLS1 galaxies shows that in four out of five cases the X-ray spectrum is dominated by a flat power law without intrinsic absorption. These objects are moderately variable in their brightness, while spectral variability is observed in at least two sources. The major difference across the X-ray spectra of γ-NLS1s is the luminosity, which spans a range of almost two orders of magnitude from 1044 erg s-1 to 1046 erg s-1 in the (0.5-10) keV band.

  10. Theory of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shields, G. A.

    1986-01-01

    The involvement of accretion disks around supermassive black holes in the theory of active galactic nuclei (AGN) is discussed. The physics of thin and thick accretion disks is discussed and the partition between thermal and nonthermal energy production in supermassive disks is seen as uncertain. The thermal limit cycle may operate in supermassive disks (Shields, 1985), with accumulation of gas in the disk for periods of 10 to the 4th to 10 to the 7th years, punctuated by briefer outbursts during which the mass is rapidly transferred to smaller radii. An extended X-ray source in AGN is consistent with observations (Tennant and Mushotsky, 1983), and a large wind mass loss rate exceeding the central accretion rate means that only a fraction of the mass entering the disk will reach the central object; the rest being lost to the wind. Controversy in the relationship between the broad lines and the disk is also discussed.

  11. The Radio luminosity Function of Radio-Loud Quasars from the 7C Redshift Survey

    NASA Technical Reports Server (NTRS)

    Willott, Chris J.; Rawlings, Steve; Blundell, Katherine M.; Lacy, Mark

    1998-01-01

    We present a complete sample of 24 radio-loud quasars (RLQs) from the new 7C Redshift Survey. Every quasar with a low-frequency (151 MHz) radio flux-density S(sub 151) > 0.5 Jy in two regions of the sky covering 0.013 sr is included; 23 of these have sufficient extended flux to meet the selection criteria, 18 of these have steep radio spectra (hereafter denoted as SSQs). The key advantage of this sample over most samples of RLQs is the lack of an optical magnitude limit. By combining the 7C and 3CRR samples, we have investigated the properties of RLQs as a function of redshift z and radio luminosity L(sub 151). We derive the radio luminosity function (RLF) of RLQs and find that the data are well fitted by a single power-law with slope alpha(sub 1) = 1.9 +/- 0.1 (for H(sub 0) = 50 km/s.Mpc, OMEGA(sub M) = 1, OMEGA(sub DELTA) = 0). We find that there must be a break in the RLQ RLF at log(sub 10)(L(sub 151)/W Hz.sr) approximately < or = 27, in order for the models to be consistent with the 7C and 6C source counts. The z-dependence of the RLF follows a one-tailed gaussian which peaks at z = 1.7 +/- 0.2. We find no evidence for a decline in the co-moving space density of RLQs at higher redshifts. A positive correlation between the radio and optical luminosities of SSQs is observed, confirming a result of Serjeant. We are able to rule out this correlation being due to selection effects or biases in our combined sample. The radio-optical correlation and best-fit model RLF enable us to estimate the distribution of optical magnitudes of quasars in samples selected at low radio frequencies, We con- clude that for samples with S(sub 151) approximately < or = 1 Jy one must use optical data significantly deeper than the POSS-I limit (R approximately equal 20), in order to avoid severe incompleteness.

  12. An Optical-Infrared Study of Radio-Loud Quasar Environments

    NASA Astrophysics Data System (ADS)

    Hall, Patrick Brian

    1998-06-01

    I present the data for an optical/near-infrared study of radio-loud quasar environments from z = 0.6-2.0, and the analysis of the data from z = 1.0-2.0. I thoroughly discuss the sample selection, observing, data reduction, and object cataloging. Even accounting for possible systematic offsets, I find a significant excess of K/ ~ 19 galaxies in the fields of z = 1-2 RLQs, on two spatial scales. One component is at θ <40&prime‧ from the quasars and is significant compared to the galaxy surface density at θ >40'' in the same fields. The other component appears roughly uniform across the fields (to θ~100'') and is significant compared to the galaxy surface density seen in random-field surveys in the literature. The r-K color distributions of the excess galaxy populations are indistinguishable, and are significantly redder than the color distribution of the field population. The excess galaxy population is thus consistent with being predominantly early-type galaxies at the quasar redshifts. The average excess within 0.5h 75-1 Mpc (~ 65'') of the quasars corresponds to Abell richness class ~0 compared to the galaxy surface density at >0.5h75-1 Mpc from the quasars, and to Abell richness class ~1 compared to that from the literature. I estimate -0.65-0.55+0.41 magnitudes of evolution in MK* to \\bar z = 1.67 by assuming the excess galaxies are at the quasar redshifts. I discuss the spectral energy distributions (SEDs) of galaxies in fields with data in several passbands. Most candidate quasar-associated galaxies are consistent with being 2-3 Gyr old early-types at the quasar redshifts of z~ 1.5. However, some objects have SEDs similar to extremely late-type stars; others have SEDs consistent with being 4-5 Gyr old at z~ 1.5 and others are consistent with old but dust-reddened galaxies at the quasar redshifts. These potentially different galaxy types suggest there may be considerable dispersion in the properties of early-type cluster galaxies at z~ 1.5. There is also

  13. The parsec-scale structure of radio-loud broad absorption line quasars

    NASA Astrophysics Data System (ADS)

    Bruni, G.; Dallacasa, D.; Mack, K.-H.; Montenegro-Montes, F. M.; González-Serrano, J. I.; Holt, J.; Jiménez-Luján, F.

    2013-06-01

    Context. Broad absorption line quasars (BAL QSOs) belong to a class of objects not well-understood as yet. Their UV spectra show BALs in the blue wings of the UV resonance lines, owing to ionized gas with outflow velocities up to 0.2 c. They can have radio emission that is difficult to characterize and that needs to be studied at various wavelengths and resolutions. Aims: We aim to study the pc-scale properties of their synchrotron emission and, in particular, to determine their core properties. Methods: We performed observations in the Very Long Baseline Interferometry (VLBI) technique, using both the European VLBI Network (EVN) at 5 GHz, and the Very Long Baseline Array (VLBA) at 5 and 8.4 GHz to map the pc-scale structure of the brightest radio-loud objects of our sample, allowing a proper morphological interpretation. Results: A variety of morphologies have been found: 9 BAL QSOs on a total of 11 observed sources have a resolved structure. Core-jet, double, and symmetric objects are present, suggesting different orientations. In some cases the sources can be young GPS or CSS. The projected linear size of the sources, also considering observations from our previous work for the same objects, can vary from tens of pc to hundreds of kpc. In some cases, a diffuse emission can be supposed from the missing flux-density with respect to previous lower resolution observations. Finally, the magnetic field strength does not significantly differ from the values found in the literature for radio sources with similar sizes. Conclusions: These results are not easily interpreted with the youth scenario for BAL QSOs, in which they are generally compact objects still expelling a dust cocoon. The variety of orientations, morphologies, and extensions found are presumably related to different possible angles for the BAL producing outflows, with respect to the jet axis. Moreover, the phenomenon could be present in various phases of the QSO evolution. Table 3 is available in

  14. Direct Microlensing-Reverberation Observations of the Intrinsic Magnetic Structure of Active Galactic Nuclei in Different Spectral States: A Tale of Two Quasars

    NASA Astrophysics Data System (ADS)

    Schild, Rudolph E.; Leiter, Darryl J.; Robertson, Stanley L.

    2008-03-01

    We show how direct microlensing-reverberation analysis performed on two well-known quasars (Q2237, the Einstein Cross, and Q0957, the Twin) can be used to observe the inner structure of two quasars which are in significantly different spectral states. These observations allow us to measure the detailed internal structure of Q2237 in a radio-quiet high-soft state, and compare it to Q0957 in a radio-loud low-hard state. When taken together we find that the observed differences in the spectral states of these two quasars can be understood as being due to the location of the inner radii of their accretion disks relative to the co-rotation radii of the magnetospheric eternally collapsing objects (MECO) in the centers of these quasars. The radiating structures observed in these quasars are associated with standard accretion disks and outer outflow structures, where the latter are the major source of UV-optical continuum radiation. While the observed inner accretion disk structure of the radio-quiet quasar Q2237 is consistent with either a MECO or a black hole, the observed inner structure of the radio-loud quasar Q0957 can only be explained by the action of the intrinsic magnetic propeller of a MECO with its accretion disk. Hence a simple and unified answer to the long-standing question: "Why are some quasars radio loud?" is found if the central objects of quasars are MECO, with radio-loud and radio-quiet spectral states similar to the case of galactic black hole candidates.

  15. XMM-Newton Observations of the Radio-Loud Broad Absorption Line Quasar FBQS J131213.5+231958

    NASA Astrophysics Data System (ADS)

    Mathur, Smita; Dai, Xinyu

    2010-12-01

    We present XMM-Newton observations of the broad absorption line (BAL) quasar FBQS J131213.5+231958. The X-ray spectrum of the source can be well described by an absorbed power-law model in which the absorber is either ionized or only partially covers the continuum source. This can explain the apparent lack of absorption observed in the Chandra spectrum with low signal-to-noise ratio. While the power-law slope of the spectrum is similar to that of non-BAL radio-loud quasars, the Eddington luminosity ratio is likely to be significantly higher than the mean. This shows that in high-mass black holes (BHs), high Eddington accretion may not result in as steep of a spectrum as in lower-mass BHs. This provides important constraints for accretion disk models. It also provides support to the idea that BAL quasars, at least their radio-loud subclass, represent an early evolutionary stage of quasars.

  16. Super- and sub-critical regions in shocks driven by radio-loud and radio-quiet CMEs

    NASA Astrophysics Data System (ADS)

    Bemporad, Alessandro; Mancuso, Salvatore

    2013-05-01

    White-light coronagraphic images of Coronal Mass Ejections (CMEs) observed by SOHO/LASCO C2 have been used to estimate the density jump along the whole front of two CME-driven shocks. The two events are different in that the first one was a "radio-loud" fast CME, while the second one was a "radio quiet" slow CME. From the compression ratios inferred along the shock fronts, we estimated the Alfvén Mach numbers for the general case of an oblique shock. It turns out that the "radio-loud" CME shock is initially super-critical around the shock center, while later on the whole shock becomes sub-critical. On the contrary, the shock associated with the "radio-quiet" CME is sub-critical at all times. This suggests that CME-driven shocks could be efficient particle accelerators at the shock nose only at the initiation phases of the event, if and when the shock is super-critical, while at later times they lose their energy and the capability to accelerate high energetic particles.

  17. Reduction and analysis of VLA maps for 281 radio-loud quasars using the UNLV Cray Y-MP supercomputer

    NASA Technical Reports Server (NTRS)

    Ding, Ailian; Hintzen, Paul; Weistrop, Donna; Owen, Frazer

    1993-01-01

    The identification of distorted radio-loud quasars provides a potentially very powerful tool for basic cosmological studies. If large morphological distortions are correlated with membership of the quasars in rich clusters of galaxies, optical observations can be used to identify rich clusters of galaxies at large redshifts. Hintzen, Ulvestad, and Owen (1983, HUO) undertook a VLA A array snapshot survey at 20 cm of 123 radio-loud quasars, and they found that among triple sources in their sample, 17 percent had radio axes which were bent more than 20 deg and 5 percent were bent more than 40 deg. Their subsequent optical observations showed that excess galaxy densities within 30 arcsec of 6 low-redshift distorted quasars were on average 3 times as great as those around undistorted quasars (Hintzen 1984). At least one of the distorted quasars observed, 3C275.1, apparently lies in the first-ranked galaxy at the center of a rich cluster of galaxies (Hintzen and Romanishin, 1986). Although their sample was small, these results indicated that observations of distorted quasars could be used to identify clusters of galaxies at large redshifts. The purpose of this project is to increase the available sample of distorted quasars to allow optical detection of a significant sample of quasar-associated clusters of galaxies at large redshifts.

  18. Determining the radio active galactic nuclei contribution to the radio-far-infrared correlation using the black hole Fundamental Plane relation

    NASA Astrophysics Data System (ADS)

    Wong, O. Ivy; Koss, M. J.; Schawinski, K.; Kapińska, A. D.; Lamperti, I.; Oh, K.; Ricci, C.; Berney, S.; Trakhtenbrot, B.

    2016-08-01

    We investigate the 1.4-GHz radio properties of 92 nearby (z < 0.05) ultra-hard X-ray selected active galactic nuclei (AGNs) from the Swift Burst Alert Telescope (BAT) sample. Through the ultra-hard X-ray selection, we minimize the biases against obscured or Compton-thick AGNs as well as confusion with emission derived from star formation that typically affect AGN samples selected from the ultraviolet, optical and infrared wavelengths. We find that all the objects in our sample of nearby, ultra-hard X-ray selected AGNs are radio quiet; 83 per cent of the objects are classed as high-excitation galaxies and 17 per cent as low-excitation galaxies. While these low-z BAT sources follow the radio-far-infrared correlation in a similar fashion to star-forming galaxies, our analysis finds that there is still significant AGN contribution in the observed radio emission from these radio-quiet AGNs. In fact, the majority of our BAT sample occupy the same X-ray-radio Fundamental Plane as has been observed in other samples, which include radio-loud AGNs - evidence that the observed radio emission (albeit weak) is connected to the AGN accretion mechanism, rather than star formation.

  19. A statistical analysis of the broadband 0.1 to 3.5 keV spectral properties of X-ray-selected active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Thompson, R. J.; Cordova, F. A.

    1994-01-01

    We survey the broadband spectral properties of approximately 500 X-ray-selected active galactic nuclei (AGNs) observed with the Einstein Observatory. Included in this survey are the approximately 450 AGNs in the Extended Medium Sensitivity Survey (EMSS) of Gioia et al. (1990) and the approximately 50 AGNs in the Ultrasoft Survey of Cordova et al. (1992). We present a revised version of the latter sample, based on the post publication discovery of a software error in the Einstein Rev-1b processing. We find that the mean spectral index of the AGNs between 0.1 and 0.6 keV is softer, and the distribution of indices wider, than previous estimates based on analyses of the X-ray spectra of optically selected AGNs. A subset of these AGNs exhibit flux variabiulity, some on timescales as short as 0.05 days. A correlation between radio and hard X-ray luminosity is confirmed, but the data do not support a correlation between the radio and soft X-ray luminosities, or between radio loudness and soft X-ray spectral slope. Evidence for physically distinct soft and hard X-ray components is found, along with the possibility of a bias in previous optically selected samples toward selection of AGNs with flatter X-ray spectra.

  20. A Radial Velocity Test for Supermassive Black Hole Binaries as an Explanation for Broad, Double-peaked Emission Lines in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Liu, Jia; Eracleous, Michael; Halpern, Jules P.

    2016-01-01

    One of the proposed explanations for the broad, double-peaked Balmer emission lines observed in the spectra of some active galactic nuclei (AGNs) is that they are associated with sub-parsec supermassive black hole (SMBH) binaries. Here, we test the binary broad-line region hypothesis through several decades of monitoring of the velocity structure of double-peaked Hα emission lines in 13 low-redshift, mostly radio-loud AGNs. This is a much larger set of objects compared to an earlier test by Eracleous et al. and we use much longer time series for the three objects studied in that paper. Although systematic changes in radial velocity can be traced in many of their lines, they are demonstrably not like those of a spectroscopic binary in a circular orbit. Any spectroscopic binary period must therefore be much longer than the span of the monitoring (assuming a circular orbit), which in turn would require black hole masses that exceed by 1-2 orders of magnitude the values obtained for these objects using techniques such as reverberation mapping and stellar velocity dispersion. Moreover, the response of the double-peaked Balmer line profiles to fluctuations of the ionizing continuum and the shape of the Lyα profiles are incompatible with an SMBH binary. The binary broad-line region hypothesis is therefore disfavored. Other processes evidently shape these line profiles and cause the long-term velocity variations of the double peaks.

  1. Observational signatures of galactic winds powered by active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Nims, Jesse; Quataert, Eliot; Faucher-Giguère, Claude-André

    2015-03-01

    We predict the observational signatures of galaxy scale outflows powered by active galactic nuclei (AGN). Most of the emission is produced by the forward shock driven into the ambient interstellar medium (ISM) rather than by the reverse shock. AGN-powered galactic winds with energetics suggested by phenomenological feedback arguments should produce spatially extended ˜1-10 keV X-ray emission ˜ 1041-44 erg s- 1, significantly in excess of the spatially extended X-ray emission associated with normal star-forming galaxies. The presence of such emission is a direct test of whether AGN outflows significantly interact with the ISM of their host galaxy. We further show that even radio-quiet quasars should have a radio luminosity comparable to or in excess of the far-infrared-radio correlation of normal star-forming galaxies. This radio emission directly constrains the total kinetic energy flux in AGN-powered galactic winds. Radio emission from AGN wind shocks can also explain the recently highlighted correlations between radio luminosity and the kinematics of AGN narrow-line regions in radio-quiet quasars.

  2. X-raying the Winds of Luminous Active Galaxies

    NASA Astrophysics Data System (ADS)

    Brandt, W. N.; Chartas, G.; Gallagher, S. C.; Gibson, R. R.; Miller, B. P.

    2009-12-01

    We briefly describe some recent observational results, mainly at X-ray wavelengths, on the winds of luminous active galactic nuclei (AGNs). These winds likely play a significant role in galaxy feedback. Topics covered include (1) Relations between X-ray and UV absorption in Broad Absorption Line (BAL) and mini-BAL quasars; (2) X-ray absorption in radio-loud BAL quasars; and (3) Evidence for relativistic iron K BALs in the X-ray spectra of a few bright quasars. We also mention some key outstanding problems and prospects for future advances; e.g., with the International X-ray Observatory (IXO).

  3. Sampling Studies Of Quasars, Radio-loud Galaxies, & Radio-quiet Galaxies -- Searching For The Cause Of Radio Emission

    NASA Astrophysics Data System (ADS)

    Coldwell, G.; Salois, Amee; Soechting, I.; Smith, M.

    2011-01-01

    Comparing the environments of Radio-Loud Galaxies, Radio-Quiet Galaxies, and Quasars offers an opportunity to study the evolution of these objects. Our samples have been carefully chosen from Data Release 7 of the Sloan Digital Sky Survey, which also includes samples studied in the FIRST survey, and have been cut to determine the best possible results. Our study includes three samples. The Quasar sample currently contains 69 objects, the Radio-Loud Galaxy (RLG) sample has 1,335 objects, and the Radio-Quiet Galaxy (RQG) sample contains 2,436 objects (any updates will be given at the meeting). A number of trims were made to produce (smaller) samples with characteristics suited for precise results. By comparing the environments of these three samples we will be able to see any similarities or differences between them. If similarities are detected it suggests that the central object has evolved according to 'nature' - in an isolated manner with little environmental feedback, which may or may not have an effect on its evolution, as supposed by Coldwell et al. (2009). If differences are detected it suggests that the central object has evolved according to `nurture’ and that the environment may have played an important role in the development of their properties. We employ similar procedures used by Coldwell et al. (2009) in their study of blue and red AGNs. Upon the completion of an accurate sample, future work will be pursued studying a number of properties of the environments including studies of: the stellar masses, star formation rates, sersic morphologies, as well as densities and ages of the environments.

  4. The Jet/Disk Connection in AGN: Chandra and XMM-Newton Observations of Three Powerful Radio-Loud Quasars

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita; Gliozzi, Mario; Tavecchio, F.; Maraschi, L.; Foschini, Luigi

    2007-01-01

    The connection between the accretion process that powers AGN and the formation of jets is still poorly understood. Here we tackle this issue using new, deep Chandra and XMM-Newton observations of tlie cores of three powerful radio loud quasars: 1136-135, 1150+497 (Chandra), and 0723+679 (XMM-Newton), in the redshift range z=0.3-0.8. These sources are known from our previous Chandra siiapsliot survey to liave kpc-scale X-ray jets. In 1136-135 and 1150-1+497; evidence is found for the presence of diffuse thermal X-ray emission around the cores; on scales of 40-50 kpc and with luminosity L(sub 0.3-2 kev approx. 10(sup 43) erg per second, suggesting thermal emission from the host galaxy or a galaxy group. The X-ray continua of the cores in the three sources are described by an upward-curved (concave) broken power law, with photon indices GAMMA (sub soft) approx. 1.8 - 2.1 and GAMMA (sub hard) approx. 1.7 below and above approx. equal to 2 keV, respectively. There is evidence for an uiiresolved Fe K alpha line with EW approx. 70 eV in the three quasars. The Spectral Energy Distributions of the sources can be well described by a mix of jet and disk emission, with the jet dominating the radio and hard X-rays (via synchrotron and external Compton) and the disk dominating the optical/UV through soft X-rays. The ratio of the jet-to-disk powers is approx. 1, consistent with those derived for a number of gamma ray emitting blazars. This indicates that near equality of accretion and jet power may be common in powerful radio-loud AGN.

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  6. THE NUCLEAR INFRARED EMISSION OF LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Mason, R. E.; Lopez-Rodriguez, E.; Packham, C.; Alonso-Herrero, A.; Elitzur, M.; Aretxaga, I.; Roche, P. F.; Oi, N.

    2012-07-15

    We present high-resolution mid-infrared (MIR) imaging, nuclear spectral energy distributions (SEDs), and archival Spitzer spectra for 22 low-luminosity active galactic nuclei (LLAGNs; L{sub bol} {approx}< 10{sup 42} erg s{sup -1}). Infrared (IR) observations may advance our understanding of the accretion flows in LLAGNs, the fate of the obscuring torus at low accretion rates, and, perhaps, the star formation histories of these objects. However, while comprehensively studied in higher-luminosity Seyferts and quasars, the nuclear IR properties of LLAGNs have not yet been well determined. We separate the present LLAGN sample into three categories depending on their Eddington ratio and radio emission, finding different IR characteristics for each class. (1) At the low-luminosity, low-Eddington-ratio (log L{sub bol}/L{sub Edd} < -4.6) end of the sample, we identify 'host-dominated' galaxies with strong polycyclic aromatic hydrocarbon bands that may indicate active (circum-)nuclear star formation. (2) Some very radio-loud objects are also present at these low Eddington ratios. The IR emission in these nuclei is dominated by synchrotron radiation, and some are likely to be unobscured type 2 AGNs that genuinely lack a broad-line region. (3) At higher Eddington ratios, strong, compact nuclear sources are visible in the MIR images. The nuclear SEDs of these galaxies are diverse; some resemble typical Seyfert nuclei, while others lack a well-defined MIR 'dust bump'. Strong silicate emission is present in many of these objects. We speculate that this, together with high ratios of silicate strength to hydrogen column density, could suggest optically thin dust and low dust-to-gas ratios, in accordance with model predictions that LLAGNs do not host a Seyfert-like obscuring torus. We anticipate that detailed modeling of the new data and SEDs in terms of accretion disk, jet, radiatively inefficient accretion flow, and torus components will provide further insights into the nuclear

  7. The physics of galactic winds driven by active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Faucher-Giguère, Claude-André; Quataert, Eliot

    2012-09-01

    Active galactic nuclei (AGN) drive fast winds in the interstellar medium of their host galaxies. It is commonly assumed that the high ambient densities and intense radiation fields in galactic nuclei imply short cooling times, thus making the outflows momentum conserving. We show that cooling of high-velocity shocked winds in AGN is in fact inefficient in a wide range of circumstances, including conditions relevant to ultraluminous infrared galaxies (ULIRGs), resulting in energy-conserving outflows. We further show that fast energy-conserving outflows can tolerate a large amount of mixing with cooler gas before radiative losses become important. For winds with initial velocity vin ≳ 10 000 km s-1, as observed in ultraviolet and X-ray absorption, the shocked wind develops a two-temperature structure. While most of the thermal pressure support is provided by the protons, the cooling processes operate directly only on the electrons. This significantly slows down inverse Compton cooling, while free-free cooling is negligible. Slower winds with vin ˜ 1000 km s-1, such as may be driven by radiation pressure on dust, can also experience energy-conserving phases but under more restrictive conditions. During the energy-conserving phase, the momentum flux of an outflow is boosted by a factor ˜vin/2vs by work done by the hot post-shock gas, where vs is the velocity of the swept-up material. Energy-conserving outflows driven by fast AGN winds (vin ˜ 0.1c) may therefore explain the momentum fluxes Ṗ≫LAGN/c of galaxy-scale outflows recently measured in luminous quasars and ULIRGs. Shocked wind bubbles expanding normal to galactic discs may also explain the large-scale bipolar structures observed in some systems, including around the Galactic Centre, and can produce significant radio, X-ray and γ-ray emission. The analytic solutions presented here will inform implementations of AGN feedback in numerical simulations, which typically do not include all the important

  8. THE GALACTIC CENTER: NOT AN ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    An, Deokkeun; Ramirez, Solange V.; Sellgren, Kris

    2013-06-01

    We present 10 {mu}m-35 {mu}m Spitzer spectra of the interstellar medium in the Central Molecular Zone (CMZ), the central 210 pc Multiplication-Sign 60 pc of the Galactic center (GC). We present maps of the CMZ in ionic and H{sub 2} emission, covering a more extensive area than earlier spectroscopic surveys in this region. The radial velocities and intensities of ionic lines and H{sub 2} suggest that most of the H{sub 2} 0-0 S(0) emission comes from gas along the line-of-sight, as found by previous work. We compare diagnostic line ratios measured in the Spitzer Infrared Nearby Galaxies Survey to our data. Previous work shows that forbidden line ratios can distinguish star-forming galaxies from low-ionization nuclear emission-line regions (LINERs) and active galactic nuclei (AGNs). Our GC line ratios agree with star-forming galaxies and not with LINERs or AGNs.

  9. A CLOSER VIEW OF THE RADIO-FIR CORRELATION: DISENTANGLING THE CONTRIBUTIONS OF STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY

    SciTech Connect

    Moric, I.; Smolcic, V.; Riechers, D. A.; Scoville, N.; Kimball, A.; Ivezic, Z.

    2010-11-20

    We extend the Unified Radio Catalog, a catalog of sources detected by various (NVSS, FIRST, WENSS, GB6) radio surveys, and SDSS, to IR wavelengths by matching it to the IRAS Point and Faint Source catalogs. By fitting each NVSS-selected galaxy's NUV-NIR spectral energy distribution (SED) with stellar population synthesis models we add to the catalog star formation rates (SFRs), stellar masses, and attenuations. We further add information about optical emission-line properties for NVSS-selected galaxies with available SDSS spectroscopy. Using an NVSS 20 cm (F{sub 1.4{sub GHz}} {approx}> 2.5 mJy) selected sample, matched to the SDSS spectroscopic ('main' galaxy and quasar) catalogs and IRAS data (0.04 < z {approx}< 0.2) we perform an in-depth analysis of the radio-FIR correlation for various types of galaxies, separated into (1) quasars, (2) star-forming, (3) composite, (4) Seyfert, (5) LINER, and (6) absorption line galaxies using the standard optical spectroscopic diagnostic tools. We utilize SED-based SFRs to independently quantify the source of radio and FIR emission in our galaxies. Our results show that Seyfert galaxies have FIR/radio ratios lower than, but still within the scatter of, the canonical value due to an additional (likely active galactic nucleus (AGN)) contribution to their radio continuum emission. Furthermore, IR-detected absorption and LINER galaxies are on average strongly dominated by AGN activity in both their FIR and radio emission; however their average FIR/radio ratio is consistent with that expected for star-forming galaxies. In summary, we find that most AGN-containing galaxies in our NVSS-IRAS-SDSS sample have FIR/radio flux ratios indistinguishable from those of the star-forming galaxies that define the radio-FIR correlation. Thus, attempts to separate AGNs from star-forming galaxies by their FIR/radio flux ratios alone can separate only a small fraction of the AGNs, such as the radio-loud quasars.

  10. Star formation around active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Keel, William C.

    1987-01-01

    Active galactic nuclei (Seyfert nuclei and their relatives) and intense star formation can both deliver substantial amounts of energy to the vicinity of a galactic nucleus. Many luminous nuclei have energetics dominated by one of these mechanisms, but detailed observations show that some have a mixture. Seeing both phenomena at once raises several interesting questions: (1) Is this a general property of some kinds of nuclei? How many AGNs have surround starbursts, and vice versa? (2) As in 1, how many undiscovered AGNs or starbursts are hidden by a more luminous instance of the other? (3) Does one cause the other, and by what means, or do both reflect common influences such as potential well shape or level of gas flow? (4) Can surrounding star formation tell us anything about the central active nuclei, such as lifetimes, kinetic energy output, or mechanical disturbance of the ISM? These are important points in the understanding of activity and star formation in galactic nuclei. Unfortunately, the observational ways of addressing them are as yet not well formulated. Some preliminary studies are reported, aimed at clarifying the issues involved in study of the relationships between stellar and nonstellar excitement in galactic nuclei.

  11. The Role of Star Formation in Radio-Loud Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Herbst, Hanna; Wilcots, E.; Hess, K.

    2010-01-01

    X-ray observations have shown that additional non-gravitational processes are required to explain the heating of the intergalactic medium in galaxy groups. The two most likely processes are galactic outflows from starbursts and feedback from AGN. Here, we look at star formation as a possible additional heating mechanism in X-ray luminous groups such as NGC 741, NGC 1052, NGC 524, and NGC 1587. We report on the results of optical imaging of these groups carried out using the WIYN 3.5m telescope with a specific emphasis on measuring the star formation rates of the resident galaxies in each group and estimating the impact of that star formation on the thermodynamics of the intragroup medium.

  12. Gravitational lensing of active galactic nuclei.

    PubMed Central

    Hewitt, J N

    1995-01-01

    Most of the known cases of strong gravitational lensing involve multiple imaging of an active galactic nucleus. The properties of lensed active galactic nuclei make them promising systems for astrophysical applications of gravitational lensing; in particular, they show structure on scales of milliseconds of arc to tens of seconds of arc, they are variable, and they are polarized. More than 20 cases of strong gravitational lenses are now known, and about half of them are radio sources. High-resolution radio imaging is making possible the development of well-constrained lens models. Variability studies at radio and optical wavelengths are beginning to yield results of astrophysical interest, such as an independent measure of the distance scale and limits on source sizes. PMID:11607613

  13. Ambartsumyan's concept of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Khachikian, E. Ye.

    2010-01-01

    As Victor Ambartsumyan, himself, noted, the concept of active galactic nuclei occupies a special place among his scientific ideas. It was proposed more than half a century ago and was recognized by the U.S. National Academy of Sciences as revolutionary, on a copernican scale. However, by no means all of its propositions were accepted at once by large parts of the astronomy community. Nevertheless, as the American astrophysicist A. R. Sandage has written, “today, not one astronomer would deny the mystery surrounding the nuclei of galaxies or that the first to recognize the rich reward held in this treasury was Viktor Ambartsumian.” The purpose of this article is to acquaint the reader with the major stages in the formation and development of the concept of active galactic nuclei and with some of the work on this topic done at the Byurakan and other astrophysical observatories throughout the world.

  14. Gamma rays from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes

    1990-01-01

    The general properties of Active Galactic Nuclei (AGN) and quasars are reviewed with emphasis on their continuum spectral emission. Two general classes of models for the continuum are outlined and critically reviewed in view of the impending GRO (Gamma Ray Observatory) launch and observations. The importance of GRO in distinguishing between these models and in general in furthering the understanding of AGN is discussed. The very broad terms the status of the current understanding of AGN are discussed.

  15. From the Blazar Sequence to the Blazar Envelope: Revisiting the Relativistic Jet Dichotomy in Radio-Loud AGN

    NASA Technical Reports Server (NTRS)

    Meyer, Eileen T.; Fossati, Giovanini; Georganopoulos, Markos; Lister, Matthew L.

    2012-01-01

    We revisit the concept of a blazar sequence that relates the synchrotron peak frequency (Vpeak) in blazars with synchrotron peak luminosity (Lpeak, in vLv) using a large sample of radio-loud AGN. We present observational evidence that the blazar sequence is formed from two populations in the synchrotron Vpeak - Lpeak plane, each forming an upper edge to an envelope of progressively misaligned blazars, and connecting to an adjacent group of radio galaxies having jets viewed at much larger angles to the line of sight. When binned by jet kinetic power (Lkin; as measured through a scaling relationship with extended radio power), we find that radio core dominance decreases with decreasing synchrotron Lpeak, revealing that sources in the envelope are generally more misaligned. We find population-based evidence of velocity gradients in jets at low kinetic powers (approximately 10(exp 42) - 10(exp 44.5) erg s(exp -1)), corresponding to FR I radio galaxies and most BL Lacs. These low jet power 'weak jet' sources, thought to exhibit radiatively inefficient accretion, are distinguished from the population of non-decelerating, low synchrotron-peaking (LSP) blazars and FR II radio galaxies ('strong' jets) which are thought to exhibit radiatively efficient accretion. The two-population interpretation explains the apparent contradiction of the existence of highly core-dominated, low-power blazars at both low and high synchrotron peak frequencies, and further implies that most intermediate synchrotron peak (ISP) sources are not intermediate in intrinsic jet power between LSP and high synchrotron-peaking (HSP) sources, but are more misaligned versions of HSP sources with similar jet powers.

  16. The fuelling of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shlosman, Isaac; Begelman, Mitchell C.; Frank, Julian

    1990-01-01

    Accretion mechanisms for powering the central engines of active galactic nuclei (AGN) and possible sources of fuel are reviewed. It is a argued that the interstellar matter in the main body of the host galaxy is channeled toward the center, and the problem of angular momentum transport is addressed. Thin accretion disks are not a viable means of delivering fuel to luminous AGN on scales much larger than a parsec because of the long inflow time and effects of self-gravity. There are also serious obstacles to maintaining and regulating geometrically thick, hot accretion flows. The role of nonaxisymmetric perturbations of the gravitational potential on galactic scales and their triggers is emphasized. A unified model is outlined for fueling AGN, in which the inflow on large scales is driven by gravitational torques, and on small scales forms a mildly self-gravitating disk of clouds with inflow driven by magnetic torques or cloud-cloud collisions.

  17. Search for correlations between the optical and radio polarization of active galactic nuclei - I. VLBA polarization data at 15 + 22 + 43 GHz

    NASA Astrophysics Data System (ADS)

    Algaba, J. C.; Gabuzda, D. C.; Smith, P. S.

    2011-02-01

    Although the continua of radio-loud active galactic nuclei (AGNs) are typically dominated by synchrotron radiation over virtually the entire spectrum, it is not clear whether the radio and higher frequency emission originates in the same or different parts of the jet. In some inhomogeneous synchrotron source models, the radio and ultraviolet-optical-infrared emission may be co-spatial, depending on the model parameters considered. Indeed, several different radio-optical correlations based on polarization data have been found recently, suggesting that the optical and radio polarization may be closely related in some AGNs, and that the corresponding emission regions may be co-spatial. Our joint analysis of optical and 15 + 22 + 43 GHz Very Long Baseline Array (VLBA) polarization data for a sample of about 40 AGNs shows that, after correction for the inferred VLBA core Faraday rotations, about 50-55 per cent of BL Lac objects and high-polarization quasars, and about 65 per cent of high-polarization quasars (LPQs) have aligned VLBA-core and optical polarization angles to within 20°; a considerable number of objects also show no obvious relationship between their VLBA-core and optical polarization angles. This may indicate that only some AGNs have co-spatial regions of optical and radio emission in their jets. However, another possibility is that some of the 15-43 GHz VLBA cores have Faraday rotations of the order of several tens of thousand of rad m-2, which were not properly fitted using our three-frequency data due to n×π ambiguities in the observed polarization angles, leading to inaccurate subtraction of the effects of the core Faraday rotation and so incorrect ‘zero-wavelength' radio polarization angles.

  18. MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VI. Kinematics Analysis of a Complete Sample of Blazar Jets

    NASA Astrophysics Data System (ADS)

    Lister, M. L.; Cohen, M. H.; Homan, D. C.; Kadler, M.; Kellermann, K. I.; Kovalev, Y. Y.; Ros, E.; Savolainen, T.; Zensus, J. A.

    2009-12-01

    We discuss the jet kinematics of a complete flux-density-limited sample of 135 radio-loud active galactic nuclei (AGNs) resulting from a 13 year program to investigate the structure and evolution of parsec-scale jet phenomena. Our analysis is based on new 2 cm Very Long Baseline Array (VLBA) images obtained between 2002 and 2007, but includes our previously published observations made at the same wavelength, and is supplemented by VLBA archive data. In all, we have used 2424 images spanning the years 1994-2007 to study and determine the motions of 526 separate jet features in 127 jets. The data quality and temporal coverage (a median of 15 epochs per source) of this complete AGN jet sample represent a significant advance over previous kinematics surveys. In all but five AGNs, the jets appear one-sided, most likely the result of differential Doppler boosting. In general, the observed motions are directed along the jet ridge line, outward from the optically thick core feature. We directly observe changes in speed and/or direction in one third of the well-sampled jet components in our survey. While there is some spread in the apparent speeds of separate features within an individual jet, the dispersion is about three times smaller than the overall dispersion of speeds among all jets. This supports the idea that there is a characteristic flow that describes each jet, which we have characterized by the fastest observed component speed. The observed maximum speed distribution is peaked at ~10c, with a tail that extends out to ~50c. This requires a distribution of intrinsic Lorentz factors in the parent population that range up to ~50. We also note the presence of some rare low-pattern speeds or even stationary features in otherwise rapidly flowing jets that may be the result of standing re-collimation shocks, and/or a complex geometry and highly favorable Doppler factor.

  19. X-RAY OBSERVATIONAL SIGNATURE OF A BLACK HOLE ACCRETION DISK IN AN ACTIVE GALACTIC NUCLEUS RX J1633+4718

    SciTech Connect

    Yuan, W.; Liu, B. F.; Zhou, H.; Wang, T. G.

    2010-11-01

    We report the discovery of a luminous ultra-soft X-ray excess in a radio-loud narrow-line Seyfert 1 galaxy, RX J1633+4718, from archival ROSAT observations. The thermal temperature of this emission, when fitted with a blackbody, is as low as 32.5{sup +8.0}{sub -6.0} eV. This is in remarkable contrast to the canonical temperatures of {approx}0.1-0.2 keV found hitherto for the soft X-ray excess in active galactic nuclei (AGNs) and is interestingly close to the maximum temperature predicted for a postulated accretion disk in this object. If this emission is indeed blackbody in nature, the derived luminosity (3.5{sup +3.3}{sub -1.5} x 10{sup 44} erg s{sup -1}) infers a compact emitting area with a size ({approx}5 x 10{sup 12} cm or 0.33 AU in radius) that is comparable to several times the Schwarzschild radius of a black hole (BH) at the mass estimated for this AGN ({approx}3 x 10{sup 6} M{sub sun}). In fact, this ultra-steep X-ray emission can be well fitted as the (Compton scattered) Wien tail of the multi-temperature blackbody emission from an optically thick accretion disk, whose inferred parameters (BH mass and accretion rate) are in good agreement with independent estimates using the optical emission-line spectrum. We thus consider this feature as a signature of the long-sought X-ray radiation directly from a disk around a supermassive BH, presenting observational evidence for a BH accretion disk in the AGN. Future observations with better data quality, together with improved independent measurements of the BH mass, may constrain the spin of the BH.

  20. INFRARED AND HARD X-RAY DIAGNOSTICS OF ACTIVE GALACTIC NUCLEUS IDENTIFICATION FROM THE SWIFT/BAT AND AKARI ALL-SKY SURVEYS

    SciTech Connect

    Matsuta, K.; Dotani, T.; Yamamura, I.; Gandhi, P.; Nakagawa, T.; Isobe, N.; Stawarz, L.; Ueda, Y.; Ichikawa, K.; Terashima, Y.; Oyabu, S.

    2012-07-10

    We combine data from two all-sky surveys in order to study the connection between the infrared and hard X-ray (>10 keV) properties for local active galactic nuclei (AGNs). The Swift Burst Alert Telescope all-sky survey provides an unbiased, flux-limited selection of hard X-ray-detected AGNs. Cross-correlating the 22 month hard X-ray survey with the AKARI all-sky survey, we studied 158 AGNs detected by the AKARI instruments. We find a strong correlation for most AGNs between the infrared (9, 18, and 90 {mu}m) and hard X-ray (14-195 keV) luminosities, and quantify the correlation for various subsamples of AGNs. Partial correlation analysis confirms the intrinsic correlation after removing the redshift contribution. The correlation for radio galaxies has a slope and normalization identical to that for Seyfert 1 galaxies, implying similar hard X-ray/infrared emission processes in both. In contrast, Compton-thick (CT) sources show a large deficit in the hard X-ray band, because high gas column densities diminish even their hard X-ray luminosities. We propose two photometric diagnostics for source classification: one is an X-ray luminosity versus infrared color diagram, in which type 1 radio-loud AGNs are well isolated from the others in the sample. The other uses the X-ray versus infrared color as a useful redshift-independent indicator for identifying CT AGNs. Importantly, CT AGNs and starburst galaxies in composite systems can also be differentiated in this plane based upon their hard X-ray fluxes and dust temperatures. This diagram may be useful as a new indicator to classify objects in new and upcoming surveys such as WISE and NuSTAR.

  1. Active galactic nuclei cores in infrared-faint radio sources. Very long baseline interferometry observations using the Very Long Baseline Array

    NASA Astrophysics Data System (ADS)

    Herzog, A.; Middelberg, E.; Norris, R. P.; Spitler, L. R.; Deller, A. T.; Collier, J. D.; Parker, Q. A.

    2015-06-01

    Context. Infrared-faint radio sources (IFRS) form a new class of galaxies characterised by radio flux densities between tenths and tens of mJy and faint or absent infrared counterparts. It has been suggested that these objects are radio-loud active galactic nuclei (AGNs) at significant redshifts (z ≳ 2). Aims: Whereas the high redshifts of IFRS have been recently confirmed based on spectroscopic data, the evidence for the presence of AGNs in IFRS is mainly indirect. So far, only two AGNs have been unquestionably confirmed in IFRS based on very long baseline interferometry (VLBI) observations. In this work, we test the hypothesis that IFRS contain AGNs in a large sample of sources using VLBI. Methods: We observed 57 IFRS with the Very Long Baseline Array (VLBA) down to a detection sensitivity in the sub-mJy regime and detected compact cores in 35 sources. Results: Our VLBA detections increase the number of VLBI-detected IFRS from 2 to 37 and provide strong evidence that most - if not all - IFRS contain AGNs. We find that IFRS have a marginally higher VLBI detection fraction than randomly selected sources with mJy flux densities at arcsec-scales. Moreover, our data provide a positive correlation between compactness - defined as the ratio of milliarcsec- to arcsec-scale flux density - and redshift for IFRS, but suggest a decreasing mean compactness with increasing arcsec-scale radio flux density. Based on these findings, we suggest that IFRS tend to contain young AGNs whose jets have not formed yet or have not expanded, equivalent to very compact objects. We found two IFRS that are resolved into two components. The two components are spatially separated by a few hundred milliarcseconds in both cases. They might be components of one AGN, a binary black hole, or the result of gravitational lensing.

  2. Invisible Active Galactic Nuclei. II. Radio Morphologies and Five New H i 21cm Absorption Line Detectors

    NASA Astrophysics Data System (ADS)

    Yan, Ting; Stocke, John T.; Darling, Jeremy; Momjian, Emmanuel; Sharma, Soniya; Kanekar, Nissim

    2016-03-01

    This is the second paper directed toward finding new highly redshifted atomic and molecular absorption lines at radio frequencies. To this end, we selected a sample of 80 candidates for obscured radio-loud active galactic nuclei (AGNs) and presented their basic optical/near-infrared (NIR) properties in Paper I. In this paper, we present both high-resolution radio continuum images for all of these sources and H i 21 cm absorption spectroscopy for a few selected sources in this sample. A-configuration 4.9 and 8.5 GHz Very Large Array continuum observations find that 52 sources are compact or have substantial compact components with size <0.″5 and flux densities >0.1 Jy at 4.9 GHz. The 36 most compact sources were then observed with the Very Long Baseline Array at 1.4 GHz. One definite and 10 candidate Compact Symmetric Objects (CSOs) are newly identified, which is a detection rate of CSOs ∼three times higher than the detection rate previously found in purely flux-limited samples. Based on possessing compact components with high flux densities, 60 of these sources are good candidates for absorption-line searches. Twenty-seven sources were observed for H i 21 cm absorption at their photometric or spectroscopic redshifts with only six detections (five definite and one tentative). However, five of these were from a small subset of six CSOs with pure galaxy optical/NIR spectra (i.e., any AGN emission is obscured) and for which accurate spectroscopic redshifts place the redshifted 21 cm line in a radio frequency intereference (RFI)-free spectral “window” (i.e., the percentage of H i 21 cm absorption-line detections could be as high as ∼90% in this sample). It is likely that the presence of ubiquitous RFI and the absence of accurate spectroscopic redshifts preclude H i detections in similar sources (only 1 detection out of the remaining 22 sources observed, 13 of which have only photometric redshifts); that is, H i absorption may well be present but is masked by

  3. The subarcsecond mid-infrared view of local active galactic nuclei - II. The mid-infrared-X-ray correlation

    NASA Astrophysics Data System (ADS)

    Asmus, D.; Gandhi, P.; Hönig, S. F.; Smette, A.; Duschl, W. J.

    2015-11-01

    We present an updated mid-infrared (MIR) versus X-ray correlation for the local active galactic nuclei (AGN) population based on the high angular resolution 12 and 18μm continuum fluxes from the AGN subarcsecond MIR atlas and 2-10 keV and 14-195 keV data collected from the literature. We isolate a sample of 152 objects with reliable AGN nature and multi-epoch X-ray data and minimal MIR contribution from star formation. Although the sample is not homogeneous or complete, we show that our results are unlikely to be affected by significant biases. The MIR-X-ray correlation is nearly linear and within a factor of 2 independent of the AGN type and the wavebands used. The observed scatter is <0.4 dex. A possible flattening of the correlation slope at the highest luminosities probed (˜1045 erg s-1) towards low MIR luminosities for a given X-ray luminosity is indicated but not significant. Unobscured objects have, on average, an MIR-X-ray ratio that is only ≤0.15 dex higher than that of obscured objects. Objects with intermediate X-ray column densities (22 < log NH < 23) actually show the highest MIR-X-ray ratio on average. Radio-loud objects show a higher mean MIR-X-ray ratio at low luminosities while the ratio is lower than average at high luminosities. This may be explained by synchrotron emission from the jet contributing to the MIR at low luminosities and additional X-ray emission at high luminosities. True Seyfert 2 candidates do not show any deviation from the general behaviour suggesting that they possess a dusty obscurer as in other AGN. Double AGN also do not deviate. Finally, we show that the MIR-X-ray correlation can be used to investigate the AGN nature of uncertain objects. Specifically, we give equations that allow us to determine the intrinsic 2-10 keV luminosities and column densities for objects with complex X-ray properties to within 0.34 dex. These techniques are applied to the uncertain objects of the remaining AGN MIR atlas, demonstrating the

  4. The unusual near-infrared morphology of the radio-loud quasar 4C+09.17

    NASA Astrophysics Data System (ADS)

    Armus, L.; Neugebauer, G.; Lehnert, M. D.; Matthews, K.

    1997-08-01

    Near-infrared images of the luminous, high-redshift (z=2.1108), radio-loud quasar 4C+09.17 reveal a complex structure. The quasar (K=15.76 mag) is surrounded by three `companion' objects having 17.91.5. If this object is at the redshift of 4C+09.17, it has a luminosity of about 7L*. The faintest companion has colours which are unlike those expected from either a spiral or an E/S0 galaxy at any redshift associated with the 4C+09.17 system. Since this object lies along the same direction as the radio jet/lobe of 4C+09.17, as well as the extended Lyalpha emission mapped by Heckman et al., we suggest that this component can be explained as a combination of strong line emission and scattered QSO light. The resolved, diffuse emission surrounding 4C+09.17 is bright, K~17.0 mag, and about 1 mag redder in J-K than the quasar. If this emission is starlight, a very luminous elliptical host galaxy is implied for 4C+09.17. Scattered and reddened AGN light, emission-line gas, and flux from absorbing galaxies along the line of sight may all contribute to this emission.

  5. A multi-wavelength investigation of the radio-loud supernova PTF11qcj and its circumstellar environment

    SciTech Connect

    Corsi, A.; Ofek, E. O.; Gal-Yam, A.; Xu, D.; Frail, D. A.; Kulkarni, S. R.; Horesh, A.; Carpenter, J.; Arcavi, I.; Cao, Y.; Mooley, K.; Sesar, B.; Fox, D. B.; Kasliwal, M. M.; Sullivan, M.; Maguire, K.; Pan, Y.-C.; Cenko, S. B.; Sternberg, A.; Bersier, D.; and others

    2014-02-10

    We present the discovery, classification, and extensive panchromatic (from radio to X-ray) follow-up observations of PTF11qcj, a supernova (SN) discovered by the Palomar Transient Factory (PTF). Our observations with the Karl G. Jansky Very Large Array show that this event is radio-loud: PTF11qcj reached a radio peak luminosity comparable to that of the famous gamma-ray-burst-associated SN 1998bw (L {sub 5} {sub GHz} ≈ 10{sup 29} erg s{sup –1} Hz{sup –1}). PTF11qcj is also detected in X-rays with the Chandra Observatory, and in the infrared band with Spitzer. Our multi-wavelength analysis probes the SN interaction with circumstellar material. The radio observations suggest a progenitor mass-loss rate of ∼10{sup –4} M {sub ☉} yr{sup –1} × (v{sub w} /1000 km s{sup –1}), and a velocity of ≈0.3-0.5 c for the fastest moving ejecta (at ≈10 days after explosion). However, these estimates are derived assuming the simplest model of SN ejecta interacting with a smooth circumstellar wind, and do not account for possible inhomogeneities in the medium and asphericity of the explosion. The radio data show deviations from such a simple model, as well as a late-time re-brightening. The X-ray flux from PTF11qcj is compatible with the high-frequency extrapolation of the radio synchrotron emission (within the large uncertainties). A light echo from pre-existing dust is in agreement with our infrared data. Our pre-explosion data from the PTF suggest that a precursor eruption of absolute magnitude M{sub r} ≈ –13 mag may have occurred ≈2.5 yr prior to the SN explosion. Overall, PTF11qcj fits the expectations from the explosion of a Wolf-Rayet star. Precursor eruptions may be a feature characterizing the final pre-explosion evolution of such stars.

  6. The physical fundamental plane of black hole activity: revisited

    NASA Astrophysics Data System (ADS)

    Liu, Xiang; Han, Zhenhua; Zhang, Zhen

    2016-01-01

    The correlation between the jet power and accretion disk luminosity is investigated for active galactic nuclei (AGNs) and black hole X-ray binaries (BHXBs) from the literature. The power-law correlation index is steep (μ˜1.0 -1.4) for radio loud quasars and the `outliers' of BHXBs, and it is flatter (μ˜ 0.3 -0.6) for radio loud galaxies and the standard BHXBs. The steep-index groups are mostly at higher accretion rates (peaked at Eddington ratio > 0.01) and the flatter-index groups are at relatively low accretion rates (peaked at Eddington ratio < 0.01), implying that the former groups could be dominated by the inner disk accretion of black hole, while the jet in latter groups would be a hybrid production of the accretion and black hole spin. We could still have a fundamental plane of black hole activity for the BHXBs and AGNs with diverse (maybe two kinds of) correlation indices. It is noted that the fundamental plane of black hole activity should be referred to the correlation between the jet power and disk luminosity or equivalently to the correlation between jet power, Eddington ratio and black hole mass, rather than the jet power, disk luminosity and black hole mass.

  7. STELLAR TRANSITS IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Beky, Bence; Kocsis, Bence E-mail: bkocsis@cfa.harvard.edu

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 10{sup 6} solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or {approx}10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  8. Stellar Transits in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Béky, Bence; Kocsis, Bence

    2013-01-01

    Supermassive black holes (SMBHs) are typically surrounded by a dense stellar population in galactic nuclei. Stars crossing the line of site in active galactic nuclei (AGNs) produce a characteristic transit light curve, just like extrasolar planets do when they transit their host star. We examine the possibility of finding such AGN transits in deep optical, UV, and X-ray surveys. We calculate transit light curves using the Novikov-Thorne thin accretion disk model, including general relativistic effects. Based on the expected properties of stellar cusps, we find that around 106 solar mass SMBHs, transits of red giants are most common for stars on close orbits with transit durations of a few weeks and orbital periods of a few years. We find that detecting AGN transits requires repeated observations of thousands of low-mass AGNs to 1% photometric accuracy in optical, or ~10% in UV bands or soft X-ray. It may be possible to identify stellar transits in the Pan-STARRS and LSST optical and the eROSITA X-ray surveys. Such observations could be used to constrain black hole mass, spin, inclination, and accretion rate. Transit rates and durations could give valuable information on the circumnuclear stellar clusters as well. Transit light curves could be used to image accretion disks with unprecedented resolution, allowing us to resolve the SMBH silhouette in distant AGNs.

  9. Starbursts in Low Luminosity Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    González Delgado, Rosa M.; Cid Fernandes, Roberto

    2005-05-01

    Low Luminosity Active Galactic Nuclei (LLAGN), which comprise low-ionization nuclear emission-line regions (LINERs) and transition-type objects (TOs), represent the most common type of nuclear activity. Here, we search for spectroscopic signatures of starbursts and post-starbursts in LLAGN, and investigate their relationship to the ionization mechanism in LLAGN. The method used is based on the stellar population synthesis of the circumnuclear optical continuum of these galaxies. We have found that intermediate-age populations (108-109 yr) are very common in weak-[O I] LLAGN, but that very young stars (≤107 yr) contribute very little to the central optical continuum of these objects. However, ˜ 1 Gyr ago these nuclei harboured starbursts of size ˜ 100 pc and masses 107-108 M⊙. Meanwhile, most of the strong-[O I] LLAGN have predominantly old stellar populations.

  10. Reverberation mapping of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Peterson, Bradley M.

    1993-01-01

    The broad emission lines in the spectra of active galactic nuclei respond to variations in the luminosity of the central continuum source with a delay due to light-travel time effects within the emission-line region. It is therefore possible through the process of 'reverberation mapping' to determine the geometry and kinematics of the emission-line region by careful monitoring of the continuum variations and the resulting emission-line response. In this review, I will discuss progress in application of the reverberation mapping technique. I will describe the underlying assumptions and limitations of the method, discuss how the results obtained to date are changing our understanding of active nuclei, and outline several new questions that might be addressed through further reverberation mapping programs.

  11. THE JET-DRIVEN OUTFLOW IN THE RADIO GALAXY SDSS J1517+3353: IMPLICATIONS FOR DOUBLE-PEAKED NARROW-LINE ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    Rosario, D. J.; Taylor, G. B. E-mail: shieldsga@mail.utexas.ed E-mail: krista@mail.utexas.ed

    2010-06-10

    We report on the study of an intriguing active galaxy that was selected as a potential multiple supermassive black hole merger in the early-type host SDSS J151709.20+335324.7 (z = 0.135) from a complete search for double-peaked [O III] lines from the SDSS spectroscopic quasi-stellar object (QSO) database. Ground-based SDSS imaging reveals two blue structures on either side of the photometric center of the host galaxy, separated from each other by about 5.7 kpc. From a combination of SDSS fiber and Keck/HIRES long-slit spectroscopy, it is demonstrated that, in addition to these two features, a third distinct structure surrounds the nucleus of the host galaxy. All three structures exhibit highly ionized line emission with line ratios characteristic of Seyfert II active galactic nuclei. The analysis of spatially resolved emission-line profiles from the HIRES spectrum reveal three distinct kinematic subcomponents, one at rest and the other two moving at -350 km s{sup -1} and 500 km s{sup -1} with respect to the systemic velocity of the host galaxy. A comparison of imaging and spectral data confirm a strong association between the kinematic components and the spatial knots, which implies a highly disturbed and complex active region in this object. A comparative analysis of the broadband positions, colors, kinematics, and spectral properties of the knots in this system lead to two plausible explanations: (1) a multiple active galactic nucleus (AGN) produced due to a massive dry merger, or (2) a very powerful radio jet-driven outflow. Subsequent VLA radio imaging reveals a clear jet aligned with the emission-line gas, confirming the latter explanation. We use the broadband radio measurements to examine the impact of the jet on the interstellar medium of the host galaxy, and find that the energy in the radio lobes can heat a significant fraction of the gas to the virial temperature. Finally, we discuss tests that may help future surveys distinguish between jet

  12. Echo Mapping of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Peterson, B. M.; Horne, K.

    2004-01-01

    Echo mapping makes use of the intrinsic variability of the continuum source in active galactic nuclei to map out the distribution and kinematics of line-emitting gas from its light travel time-delayed response to continuum changes. Echo mapping experiments have yielded sizes for the broad line-emitting region in about three dozen AGNs. The dynamics of the line-emitting gas seem to be dominated by the gravity of the central black hole, enabling measurement of the black-hole masses in AGNs. We discuss requirements for future echo-mapping experiments that will yield the high quality velocity-delay maps of the broad-line region that are needed to determine its physical nature.

  13. Relativistic neutrons in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Sikora, Marek; Begelman, Mitchell C.; Rudak, Bronislaw

    1989-01-01

    The acceleration of protons to relativistic energies in active galactic nuclei leads to the creation of relativistic neutrons which escape from the central engine. The neutrons decay at distances of up to 1-100 pc, depositing their energies and momenta in situ. Energy deposition by decaying neutrons may inhibit spherical accretion and drive a wind, which could be responsible for the velocity fields in emission-line regions and the outflow of broad absorption line systems. Enhanced pressure in the neutron decay region may also help to confine emission line clouds. A fraction of the relativistic proton energy is radiated in gamma-rays with energies which may be as large as about 100,000 GeV.

  14. DUST EMISSION FROM UNOBSCURED ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Thompson, G. D.; Levenson, N. A.; Uddin, S. A.; Sirocky, M. M.

    2009-05-20

    We use mid-infrared (MIR) spectroscopy of unobscured active galactic nuclei (AGNs) to reveal their native dusty environments. We concentrate on Seyfert 1 galaxies, observing a sample of 31 with the Infrared Spectrograph aboard the Spitzer Space Telescope, and compare them with 21 higher luminosity quasar counterparts. Silicate dust reprocessing dominates the MIR spectra, and we generally measure the 10 and 18 {mu}m spectral features weakly in emission in these galaxies. The strengths of the two silicate features together are sensitive to the dust distribution. We present numerical radiative transfer calculations that distinguish between clumpy and smooth geometries, which are applicable to any central heating source, including stars as well as AGNs. In the observations, we detect the obscuring 'torus' of unified AGN schemes, modeling it as compact and clumpy. We also determine that star formation increases with AGN luminosity, although the proportion of the galaxies' bolometric luminosity attributable to stars decreases with AGN luminosity.

  15. Dust Emission from Unobscured Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Thompson, G. D.; Levenson, N. A.; Uddin, S. A.; Sirocky, M. M.

    2009-05-01

    We use mid-infrared (MIR) spectroscopy of unobscured active galactic nuclei (AGNs) to reveal their native dusty environments. We concentrate on Seyfert 1 galaxies, observing a sample of 31 with the Infrared Spectrograph aboard the Spitzer Space Telescope, and compare them with 21 higher luminosity quasar counterparts. Silicate dust reprocessing dominates the MIR spectra, and we generally measure the 10 and 18 μm spectral features weakly in emission in these galaxies. The strengths of the two silicate features together are sensitive to the dust distribution. We present numerical radiative transfer calculations that distinguish between clumpy and smooth geometries, which are applicable to any central heating source, including stars as well as AGNs. In the observations, we detect the obscuring "torus" of unified AGN schemes, modeling it as compact and clumpy. We also determine that star formation increases with AGN luminosity, although the proportion of the galaxies' bolometric luminosity attributable to stars decreases with AGN luminosity.

  16. Multiwavelength Monitoring of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Peterson, Bradley M.

    2001-01-01

    By intensive monitoring of AGN variability over a large range in wavelength, we can probe the structure and physics of active galactic nuclei on microarcsecond angular scales. For example, multi-wavelength variability data allow us (a) to establish causal relationships between variations in different wavebands, and thus determine which physical processes are primary and which spectral changes are induced by variations at other wavelengths, and (b) through reverberation mapping of the UV/optical emission lines, to determine the structure and kinematics of the line-emitting region, and thus accurately determine the central masses in AGNs. Multiwavelength monitoring is resource-intensive, and is difficult to implement with general-purpose facilities. As a result, virtually all programs undertaken to date have been either sparsely sampled, or short in duration, or both. The potentially high return on this type of investigation, however, argues for dedicated facilities for multiwavelength monitoring programs.

  17. Particle Acceleration in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Miller, James A.

    1997-01-01

    The high efficiency of energy generation inferred from radio observations of quasars and X-ray observations of Seyfert active galactic nuclei (AGNs) is apparently achieved only by the gravitational conversion of the rest mass energy of accreting matter onto supermassive black holes. Evidence for the acceleration of particles to high energies by a central engine is also inferred from observations of apparent superluminal motion in flat spectrum, core-dominated radio sources. This phenomenon is widely attributed to the ejection of relativistic bulk plasma from the nuclei of active galaxies, and accounts for the existence of large scale radio jets and lobes at large distances from the central regions of radio galaxies. Reports of radio jets and superluminal motion from galactic black hole candidate X-ray sources indicate that similar processes are operating in these sources. Observations of luminous, rapidly variable high-energy radiation from active galactic nuclei (AGNs) with the Compton Gamma Ray Observatory show directly that particles are accelerated to high energies in a compact environment. The mechanisms which transform the gravitational potential energy of the infalling matter into nonthermal particle energy in galactic black hole candidates and AGNs are not conclusively identified, although several have been proposed. These include direct acceleration by static electric fields (resulting from, for example, magnetic reconnection), shock acceleration, and energy extraction from the rotational energy of Kerr black holes. The dominant acceleration mechanism(s) operating in the black hole environment can only be determined, of course, by a comparison of model predictions with observations. The purpose of the work proposed for this grant was to investigate stochastic particle acceleration through resonant interactions with plasma waves that populate the magnetosphere surrounding an accreting black hole. Stochastic acceleration has been successfully applied to the

  18. A GMRT study of Seyfert galaxies NGC 4235 and NGC 4594: evidence of episodic activity?

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Low-frequency observations at 325 and 610 MHz have been carried out for two `radio-loud' Seyfert galaxies, NGC 4235 and NGC 4594 (Sombrero galaxy), using the Giant Meterwave Radio Telescope (GMRT). The 610 MHz total intensity and 325-610 MHz spectral index images of NGC 4235 tentatively suggest the presence of a `relic' radio lobe, most likely from a previous episode of active galactic nucleus (AGN) activity. This makes NGC 4235 only the second known Seyfert galaxy after Mrk 6 to show signatures of episodic activity. Spitzer and Herschel infrared spectral energy distribution (SED) modelling using the CLUMPYDREAM code predicts star formation rates (SFRs) that are an order of magnitude lower than those required to power the radio lobes in these Seyferts (˜0.13-0.23 M⊙ yr-1 compared to the required SFR of ˜2.0-2.7 M⊙ yr-1 in NGC 4594 and NGC 4235, respectively). This finding along with the detection of parsec and sub-kpc radio jets in both Seyfert galaxies, that are roughly along the same position angles as the radio lobes, strongly support the suggestion that Seyfert lobes are AGN powered. SED modelling supports the `true' type 2 classification of NGC 4594: this galaxy lacks significant dust obscuration as well as a prominent broad-line region. Between the two Seyfert galaxies, there is an inverse relation between their radio-loudness and Eddington ratio and a direct relation between their Eddington-scaled jet power and bolometric power.

  19. An X-Ray and Multiwavelength Survey of Highly Radio-loud Quasars at z > 4: Jet-linked Emission in the Brightest Radio Beacons of the Early Universe

    NASA Astrophysics Data System (ADS)

    Wu, Jianfeng; Brandt, W. N.; Miller, Brendan P.; Garmire, Gordon P.; Schneider, Donald P.; Vignali, Cristian

    2013-02-01

    We present a systematic study of the X-ray and multiwavelength properties of a sample of 17 highly radio-loud quasars (HRLQs) at z > 4 with sensitive X-ray coverage from new Chandra and archival Chandra, XMM-Newton, and Swift observations. Eight of the new and archival observations are reported in this work for the first time. New Chandra observations of two moderately radio-loud and highly optically luminous quasars at z >~ 4 are also reported. Our HRLQ sample represents the top ~5% of radio-loud quasars (RLQs) in terms of radio loudness. We found that our HRLQs have an X-ray emission enhancement over HRLQs at lower redshifts (by a typical factor of ≈3), and this effect, after controlling for several factors which may introduce biases, has been solidly estimated to be significant at the 3σ-4σ level. HRLQs at z = 3-4 are also found to have a similar X-ray emission enhancement over z < 3 HRLQs, which further supports the robustness of our results. We discuss models for the X-ray enhancement's origin including a fractional contribution from inverse Compton scattering of cosmic microwave background photons. No strong correlations are found between the relative X-ray brightness and optical/UV emission-line rest-frame equivalent widths (REWs) for RLQs. However, the line REWs are positively correlated with radio loudness, which suggests that relativistic jets make a negligible contribution to the optical/UV continua of these HRLQs (contrary to the case where the emission lines are diluted by the relativistically boosted continuum). Our HRLQs are generally consistent with the known anti-correlation between radio loudness and X-ray power-law photon index. We also found that the two moderately radio-loud quasars appear to have the hardest X-ray spectra among our objects, suggesting that intrinsic X-ray absorption (N H ~ 1023 cm-2) may be present. Our z > 4 HRLQs generally have higher X-ray luminosities than those for the composite broadband spectral energy distributions

  20. Launching of Active Galactic Nuclei Jets

    NASA Astrophysics Data System (ADS)

    Tchekhovskoy, Alexander

    As black holes accrete gas, they often produce relativistic, collimated outflows, or jets. Jets are expected to form in the vicinity of a black hole, making them powerful probes of strong-field gravity. However, how jet properties (e.g., jet power) connect to those of the accretion flow (e.g., mass accretion rate) and the black hole (e.g., black hole spin) remains an area of active research. This is because what determines a crucial parameter that controls jet properties—the strength of large-scale magnetic flux threading the black hole—remains largely unknown. First-principles computer simulations show that due to this, even if black hole spin and mass accretion rate are held constant, the simulated jet powers span a wide range, with no clear winner. This limits our ability to use jets as a quantitative diagnostic tool of accreting black holes. Recent advances in computer simulations demonstrated that accretion disks can accumulate large-scale magnetic flux on the black hole, until the magnetic flux becomes so strong that it obstructs gas infall and leads to a magnetically-arrested disk (MAD). Recent evidence suggests that central black holes in jetted active galactic nuclei and tidal disruptions are surrounded by MADs. Since in MADs both the black hole magnetic flux and the jet power are at their maximum, well-defined values, this opens up a new vista in the measurements of black hole masses and spins and quantitative tests of accretion and jet theory.

  1. Active galactic nuclei and galaxy interactions

    NASA Astrophysics Data System (ADS)

    Alonso, M. Sol; Lambas, Diego G.; Tissera, Patricia; Coldwell, Georgina

    2007-03-01

    We perform a statistical analysis of active galactic nucleus (AGN) host characteristics and nuclear activity for AGNs in pairs and without companions. Our study concerns a sample of AGNs derived from the Sloan Digital Sky Survey Data Release 4 data by Kauffmann et al. and pair galaxies obtained from the same data set by Alonso et al. An eye-ball classification of images of 1607 close pairs (rp < 25 kpc h-1,ΔV < 350 km s-1) according to the evidence of interaction through distorted morphologies and tidal features provides us with a more confident assessment of galaxy interactions from this sample. We notice that, at a given luminosity or stellar mass content, the fraction of AGNs is larger for pair galaxies exhibiting evidence for strong interaction and tidal features which also show signs of strong star formation activity. Nevertheless, this process accounts only for a ~10per cent increase of the fraction of AGNs. As in previous works, we find AGN hosts to be redder and with a larger concentration morphological index than non-AGN galaxies. This effect does not depend on whether AGN hosts are in pairs or in isolation. The OIII luminosity of AGNs with strong interaction features is found to be significantly larger than that of other AGNs, either in pairs or in isolation. Estimations of the accretion rate, L[OIII]/MBH, show that AGNs in merging pairs are actively feeding their black holes, regardless of their stellar masses. We also find that the luminosity of the companion galaxy seems to be a key parameter in the determination of the black hole activity. At a given host luminosity, both the OIII luminosity and the L[ OIII]/MBH are significantly larger in AGNs with a bright companion (Mr < -20) than otherwise.

  2. Spectroscopy of 7 radio-loud QSOs at 2 < z < 6: giant Lyman α emission nebulae accreting on to host galaxies

    NASA Astrophysics Data System (ADS)

    Roche, Nathan; Humphrey, Andrew; Binette, Luc

    2014-10-01

    We performed long-slit optical spectroscopy (Gran Telescopio Canarias-Optical System for Imaging and low Resolution Integrated Spectroscopy) of 6 radio-loud quasi-stellar objects (QSOs) at redshifts 2 < z < 3, known to have giant (˜50-100 kpc) Lyman α emitting nebulae, and detect extended Lyman α emission for 4, with surface brightness ˜10-16 erg cm-2 s-1 arcsec-2 and line full width at half-maximum 400-1100 (mean 863) km s- 1. We also observed the z ≃ 5.9 radio-loud QSO, SDSS J2228+0110, and found evidence of a ≥10 kpc extended Lyman α emission nebula, a new discovery for this high-redshift object. Spatially resolved kinematics of the 5 nebulae are examined by fitting the Lyman α wavelength at a series of positions along the slit. We found the line-of-sight velocity Δ(v) profiles to be relatively flat. However, 3 of the nebulae appear systematically redshifted by 250-460 km s- 1 relative to the Lyman α line of the QSO (with no offset for the other two), which we argue is evidence for infall. One of these (Q0805+046) had a small (˜100 km s- 1) velocity shift across its diameter and a steep gradient at the centre. Differences in line-of-sight kinematics between these 5 giant nebulae and similar nebulae associated with high-redshift radio galaxies (which can show steep velocity gradients) may be due to an orientation effect, which brings infall/outflow rather than rotation into greater prominence for the sources observed `on-axis' as QSOs.

  3. TESTING TESTS ON ACTIVE GALACTIC NUCLEI MICROVARIABILITY

    SciTech Connect

    De Diego, Jose A.

    2010-03-15

    Literature on optical and infrared microvariability in active galactic nuclei (AGNs) reflects a diversity of statistical tests and strategies to detect tiny variations in the light curves of these sources. Comparison between the results obtained using different methodologies is difficult, and the pros and cons of each statistical method are often badly understood or even ignored. Even worse, improperly tested methodologies are becoming more and more common, and biased results may be misleading with regard to the origin of the AGN microvariability. This paper intends to point future research on AGN microvariability toward the use of powerful and well-tested statistical methodologies, providing a reference for choosing the best strategy to obtain unbiased results. Light curves monitoring has been simulated for quasars and for reference and comparison stars. Changes for the quasar light curves include both Gaussian fluctuations and linear variations. Simulated light curves have been analyzed using {chi}{sup 2} tests, F tests for variances, one-way analyses of variance and C-statistics. Statistical Type I and Type II errors, which indicate the robustness and the power of the tests, have been obtained in each case. One-way analyses of variance and {chi}{sup 2} prove to be powerful and robust estimators for microvariations, while the C-statistic is not a reliable methodology and its use should be avoided.

  4. Warped circumbinary disks in active galactic nuclei

    SciTech Connect

    Hayasaki, Kimitake; Sohn, Bong Won; Jung, Taehyun; Zhao, Guangyao; Okazaki, Atsuo T.; Naito, Tsuguya

    2014-07-20

    We study a warping instability of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on a circular orbit. Such a circumbinary disk is subject to not only tidal torques due to the binary gravitational potential but also radiative torques due to radiation emitted from an accretion disk around each black hole. We find that a circumbinary disk initially aligned with the binary orbital plane is unstable to radiation-driven warping beyond the marginally stable warping radius, which is sensitive to both the ratio of vertical to horizontal shear viscosities and the mass-to-energy conversion efficiency. As expected, the tidal torques give no contribution to the growth of warping modes but tend to align the circumbinary disk with the orbital plane. Since the tidal torques can suppress the warping modes in the inner part of circumbinary disk, the circumbinary disk starts to be warped at radii larger than the marginally stable warping radius. If the warping radius is of the order of 0.1 pc, a resultant semi-major axis is estimated to be of the order of 10{sup –2} pc to 10{sup –4} pc for 10{sup 7} M{sub ☉} black hole. We also discuss the possibility that the central objects of observed warped maser disks in active galactic nuclei are binary supermassive black holes with a triple disk: two accretion disks around the individual black holes and one circumbinary disk surrounding them.

  5. Probing the Physics of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Peterson, Bradley M.

    2004-01-01

    As a result of a number of large multiwavelength monitoring campaigns that have taken place since the late 1980s, there are now several very large data sets on bright variable active galactic nuclei (AGNs) that are well-sampled in time and can be used to probe the physics of the AGN continuum source and the broad-line emitting region. Most of these data sets have been underutilized, as the emphasis thus far has been primarily on reverberation-mapping issues alone. Broader attempts at analysis have been made on some of the earlier IUE data sets (e.g., data from the 1989 campaign on NGC5 548) , but much of this analysis needs to be revisited now that improved versions of the data are now available from final archive processing. We propose to use the multiwavelength monitoring data that have been accumulated to undertake more thorough investigations of the AGN continuum and broad emission lines, including a more detailed study of line-profile variability, making use of constraints imposed by the reverberation results.

  6. Dielectronic Recombination In Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Lukic, D. V.; Schnell, M.; Savin, D. W.; Altun, Z.; Badnell, N.; Brandau, C.; Schmidt, E. W.; Mueller, A.; Schippers, S.; Sprenger, F.; Lestinsky, M.; Wolf, A.

    2006-01-01

    XMM-Newton and Chandra observations of active galactic nuclei (AGN) show rich spectra of X-ray absorption lines. These observations have detected a broad unresolved transition array (UTA) between approx. 15-17 A. This is attributed to inner-shell photoexcitation of M-shell iron ions. Modeling these UTA features is currently limited by uncertainties in the low-temperature dielectronic recombination (DR) data for M-shell iron. In order to resolve this issue, and to provide reliable iron M-shell DR data for plasma modeling, we are carrying out a series of laboratory measurements using the heavy-ion Test Storage Ring (TSR) at the Max-Plank-Institute for Nuclear Physics in Heidelberg, Germany. Currently, laboratory measurements of low temperature DR can only be performed at storage rings. We use the DR data obtained at TSR, to calculate rate coefficients for plasma modeling and to benchmark theoretical DR calculations. Here we report our recent experimental results for DR of Fe XIV forming Fe XIII.

  7. Reevaluating Active Galactic Nuclei in Rich Clusters

    NASA Astrophysics Data System (ADS)

    Way, M. J.; Flores, R.; Quintana, H.

    1999-06-01

    We have selected 42 candidate Active Galactic Nuclei in 19 Rich Abell Clusters. The candidates were selected using the criteria of Dressler, Thompson & Shectman (1985; DTS) in their analysis of the statistics of 22 AGN in 14 rich cluster fields, which are based on the equivalent width of [OII]3727Å, H β, and [OIII]5007Å emission. These AGN are then separated from HII galaxies in the manner developed by Veilleux & Osterbrock (1987; VO) using the additional information provided by Hα and [NII]6583Å or Hα and [SII]6716 + 6731Å emission, in order to test the reliability of the selection criteria used by DTS. Our sample is very comparable to that of DTS before we discriminate AGN from HII galaxies, and would lead to similar conclusions. However, we find that their method inevitably mixes HII galaxies with AGN. Over the years many authors have attempted to quantify the relative fraction of cluster to field AGN since the study of DTS (Hill & Oegerle 1993; Biviano et al. 1997) and have reached similar conclusions, but using criteria similar to that of DTS to select AGN (or using the [OIII]5007Å/H β flux ratio test that also mixes HII galaxies with AGN).

  8. Quasi periodic oscillations in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Alston, W.; Fabian, A.; Markevičiutė, J.; Parker, M.; Middleton, M.; Kara, E.

    2016-05-01

    Quasi-periodic oscillations (QPOs) are coherent peaks of variability power observed in the X-ray power spectra (PSDs) of stellar mass X-ray binaries (XRBs). A scale invariance of the accretion process implies they should be present in the active galactic nuclei. The first robust detection was a ∼ 1 h periodicity in the Seyfert galaxy RE J1034+396 from a ∼ 90 ks XMM-Newton observation; however, subsequent observations failed to detect the QPO in the 0.3-10.0 keV band. In this talk we present the recent detection of the ∼ 1 h periodicity in the 1.0-4.0 keV band of 4 further low-flux/spectrally-harder observations of RE J1034+396 (see Alston et al. 2014). We also present recent work on the discovery of a QPO in the Seyfert galaxy, MS 2254.9-3712, which again is only detected in energy bands associated with the primary power-law continuum emission (Alston et al. 2015). We conclude these features are most likely analogous to the high-frequency QPOs observed in XRBs. In both sources, we also see evidence for X-ray reverberation at the QPO frequency, where soft X-ray bands and Iron Kα emission lag the primary X-ray continuum. These time delays may provide another diagnostic for understanding the underlying QPO mechanism observed in accreting black holes.

  9. Particle Acceleration in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Miller, James A.

    1996-01-01

    The investigation of stochastic particle acceleration through resonant interactions with plasma waves that populate the magnetosphere surrounding an accreting black hole is presented. Stochastic acceleration has been successfully applied to the problem of ion and electron energization in solar flares, and is capable of accounting for a wide range of both neutral and charged particle emissions. It is also a component in diffusive shock acceleration, since pitch-angle scattering (which is necessary for multiple shock crossings) is accompanied by diffusion in momentum space, which in turn yields a net systematic energy gain; however, stochastic energization will dominate the first-order shock process only in certain parameter regimes. Although stochastic acceleration has been applied to particle energization in the lobes of radio galaxies, its application to the central regions of AGNs (active galactic nuclei) has only recently been considered, but not in detail. We proposed to systematically investigate the plasma processes responsible for stochastic particle acceleration in black hole magnetospheres along with the energy-loss processes which impede particle energization. To this end, we calculated acceleration rates and escape time scales for protons and electrons resonating with Alfven waves, and for electrons resonating with whistlers. We also considered the "hot" topic of gamma-ray line emission from the Orion complex. We proposed that the observed gamma-ray lines are produced by energetic ions that are stochastically accelerated by cascading Alfven waves in the accretion plasma near a black hole. Related research papers that were published in journals are listed.

  10. Warped Circumbinary Disks in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Hayasaki, Kimitake; Sohn, Bong Won; Okazaki, Atsuo T.; Jung, Taehyun; Zhao, Guangyao; Naito, Tsuguya

    2014-07-01

    We study a warping instability of a geometrically thin, non-self-gravitating disk surrounding binary supermassive black holes on a circular orbit. Such a circumbinary disk is subject to not only tidal torques due to the binary gravitational potential but also radiative torques due to radiation emitted from an accretion disk around each black hole. We find that a circumbinary disk initially aligned with the binary orbital plane is unstable to radiation-driven warping beyond the marginally stable warping radius, which is sensitive to both the ratio of vertical to horizontal shear viscosities and the mass-to-energy conversion efficiency. As expected, the tidal torques give no contribution to the growth of warping modes but tend to align the circumbinary disk with the orbital plane. Since the tidal torques can suppress the warping modes in the inner part of circumbinary disk, the circumbinary disk starts to be warped at radii larger than the marginally stable warping radius. If the warping radius is of the order of 0.1 pc, a resultant semi-major axis is estimated to be of the order of 10-2 pc to 10-4 pc for 107 M ⊙ black hole. We also discuss the possibility that the central objects of observed warped maser disks in active galactic nuclei are binary supermassive black holes with a triple disk: two accretion disks around the individual black holes and one circumbinary disk surrounding them.

  11. What is the Nature of Accretion in Active Galactic Nuclei?

    NASA Technical Reports Server (NTRS)

    Krolik, Julian H.

    1998-01-01

    The purpose of this grant was to support theoretical research on the nature of accretion in active galactic nuclei. In the brief time of the award, four papers that appeared in refereed journals were written, as well as two invited reviews in conference proceedings. These papers significantly advanced our understanding of the structure of the most important parts of bright accretion disks around accreting black holes, such as active galactic nuclei.

  12. Research on the Nature of Accretion in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Krolik, J. H.

    1999-01-01

    he purpose of this grant was to support theoretical research on the nature of accretion in active galactic nuclei. In the brief time of the award (one year), four papers that appeared in refereed journals were written, as well as two invited reviews in conference proceedings These papers significantly advanced our understanding of the structure of the most important parts of bright accretion disks around accreting black holes, such as active galactic nuclei.

  13. A NIR Atlas of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Rodríguez-Ardila, A.; Riffel, R.; Pastoriza, M. G.

    2006-06-01

    We present the most comprehensive atlas of near-infrared (NIR) mid-resolution (R=1000) spectra of active galactic nuclei (AGN) made to date in the interval 0.8-2.4 μm. The aim of this work is to provide a homogeneous database suitable to study the nuclear NIR properties of AGN in a region poorly studied spectroscopically but that keeps useful constraints to model the AGN physics. The sample is composed of 49 objects, 39 of them with z <0.05, distributed between 7 quasars, 25 Seyfert 1 (classical and narrow-line Seyfert 1) and 17 Seyfert 2 galaxies. A few LINERS and Starburst galaxies are also included for comparative purposes. The spectra are dominated by strong emission lines of H I, He I, He II, [S III] and conspicuous forbidden lines of low and high ionization species, including coronal lines. In addition, rotational/vibrational lines of H_2 are detected in most objects. Overall, the continuum of quasars and Seyfert 1s are rather similar, being essentially flat or slightly steep in the H and K bands. In J, the shape of the continuum is different from object to object, varying from that displaying a steep rise in flux towards shorter wavelengths, from 1.1 μm bluewards, to that remaining flat. In Seyfert 2s, the continuum smoothly decreases in flux with wavelength, from 1.2 μm redwards. Bluewards, the continuum flux steeply rises in some sources while in others it decreases towards shorter wavelengths, suggesting reddening. Independently of the AGN type, stellar absorption features of CO, Si I and Mg I are present in the H and K bands. They are found to be particularly strong in Seyfert 2s. Line identification and remarks on the most important characteristics observed in the sample are given.

  14. The softest Einstein AGN (active galactic nuclei)

    SciTech Connect

    Cordova, F.A.; Kartje, J.; Mason, K.O.; Mittaz, J.P.D.; Chicago Univ., IL; University Coll., London . Mullard Space Science Lab.)

    1989-01-01

    We have undertaken a coarse spectral study to find the softest sources detected with the Imaging Proportional Counter (IPC) on the Einstein Observatory. Of the nearly 7700 IPC sources, 226 have color ratios that make them candidate ultrasoft'' sources; of these, 83 have small enough errors that we can say with confidence that they have a spectral component similar to those of the white dwarfs Sirius and HZ 43, nearby stars such as {alpha} Cen and Procyon, and typical polar'' cataclysmic variables. By means of catalog searches and ground-based optical and radio observations we have thus far identified 96 of the 226 candidate soft sources; 37 of them are active galactic nuclei (AGN). In the more selective subset of 83 sources, 47 have been identified, 12 of them with AGN. The list of 47 identifications is given in Cordova et al. For one QSO in our sample, E0132.8--411, we are able to fit the pulse-height data to a power-law model and obtain a best fit for the energy spectral index of 2. 2{sub {minus}0.4}{sup +0.6}. For the remainder of the AGN in the higher confidence sample we are able to infer on the basis of their x-ray colors that they have a similar spectral component. Two-thirds of the AGN are detected below 0.5 keV only, while the remainder evidence a flatter spectral component in addition to the ultra-soft component. 14 refs., 5 figs.

  15. The Structure of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Kriss, Gerard A.

    1997-01-01

    We are continuing our systematic investigation of the nuclear structure of nearby active galactic nuclei (AGN). Upon completion, our study will characterize hypothetical constructs such as narrow-line clouds, obscuring tori, nuclear gas disks. and central black holes with physical measurements for a complete sample of nearby AGN. The major scientific goals of our program are: (1) the morphology of the NLR; (2) the physical conditions and dynamics of individual clouds in the NLR; (3) the structure and physical conditions of the warm reflecting gas; (4) the structure of the obscuring torus; (5) the population and morphology of nuclear disks/tori in AGN; (6) the physical conditions in nuclear disks; and (7) the masses of central black holes in AGN. We will use the Hubble Space Telescope (HST) to obtain high-resolution images and spatially resolved spectra. Far-UV spectroscopy of emission and absorption in the nuclear regions using HST/FOS and the Hopkins Ultraviolet Telescope (HUT) will help establish physical conditions in the absorbing and emitting gas. By correlating the dynamics and physical conditions of the gas with the morphology revealed through our imaging program, we will be able to examine mechanisms for fueling the central engine and transporting angular momentum. The kinematics of the nuclear gas disks may enable us to measure the mass of the central black hole. Contemporaneous X-ray observations using ASCA will further constrain the ionization structure of any absorbing material. Monitoring of variability in the UV and X-ray absorption will be used to determine the location of the absorbing gas, possibly in the outflowing warm reflecting gas, or the broad-line region, or the atmosphere of the obscuring torus. Supporting ground-based observations in the optical, near-IR, imaging polarimetry, and the radio will complete our picture of the nuclear structures. With a comprehensive survey of these characteristics in a complete sample of nearby AGN, our

  16. What powers the radio-loud narrow-line Seyfert 1 galaxy RX J2314.9+2243?. A view onto its central engine from radio to X-rays

    NASA Astrophysics Data System (ADS)

    Komossa, S.; Xu, Dawei; Fuhrmann, L.; Grupe, D.; Yao, S.; Fan, Z.; Myserlis, I.; Angelakis, E.; Karamanavis, V.; Yuan, W.; Zensus, J. A.

    2015-02-01

    Aims: Radio-loud narrow-line type 1 galaxies provide us with a fresh look at the blazar phenomenon, the causes of radio loudness, and the physics of jet formation. We present a multi-wavelength study of the radio-loud narrow-line type 1 quasar RX J2314.9+2243, which exhibits some remarkable multi-wavelength properties. It is among the few radio-loud narrow-line type 1 galaxies, with a tentative γ-ray detection, is luminous in the infrared, and shows an exceptionally broad and blueshifted [OIII]λ5007 emission-line component. Methods: In order to understand the nature of this source, we have obtained optical, UV, X-ray, and radio observations of RX J2314.9+2243. Results: Its spectral energy distribution (SED) shows a broad hump extending between the IR and far-UV, a steep radio spectrum and flat X-ray spectrum. Its IR to far-UV SED is consistent with a scenario, in which synchrotron emission from a jet dominates the broadband emission, even though an absorption scenario cannot yet be fully excluded. The high blueshift of its very broad [OIII] component, 1260 km s-1, is consistent with a face-on view, with the jet (and outflow) pointing towards us. RX J2314.9+2243 likely represents an extreme case of AGN induced feedback in the local universe. The optical spectrum (FITS format) is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/A121

  17. Three Candidate Clusters Around High Redshift Radio-loud Sources: MG1 J04426+0202, 3C 068.2, and MS 1426.9+1052

    NASA Astrophysics Data System (ADS)

    Franck, J. R.; McGaugh, S. S.; Schombert, J. M.

    2015-08-01

    We present near-infrared observations of the environments around three radio-loud sources (MG1 J0442+0202, 3C 068.2, and MS 1426.9+1052) at redshifts z = 1.10, 1.57, and 1.83 (respectively) that are surrounded by near-infrared galaxy overdensities. Overdensities with respect to field counts were found to be significant up to 19σ, with 12 times the expected number of galaxies within the inner regions of the densest proto-cluster. Color-magnitude relations are constructed in Ks, J - Ks, with each candidate cluster exhibiting a feature consistent with the beginnings of a red sequence (RS). Galaxy models based on the redshift of the radio source are used to compare expected CMRs for a given formation epoch with the observed RS of each candidate, and are found to be consistent with an old ({z}f \\gt 5) formation epoch for a few bright, red galaxies on the RS.

  18. 21 cm absorption by compact hydrogen discs around black holes in radio-loud nuclei of galaxies

    SciTech Connect

    Loeb, Abraham

    2008-05-15

    The clumpy maser discs observed in some galactic nuclei mark the outskirts of the accretion disc that fuels the central black hole and provide a potential site of nuclear star formation. Unfortunately, most of the gas in maser discs is currently not being probed; large maser gains favor paths that are characterized by a small velocity gradient and require rare edge-on orientations of the disc. Here we propose a method for mapping the atomic hydrogen distribution in nuclear discs through its 21 cm absorption against the radio continuum glow around the central black hole. In NGC 4258, the 21 cm optical depth may approach unity for high angular resolution (VLBI) imaging of coherent clumps which are dominated by thermal broadening and have the column density inferred from x-ray absorption data, {approx}10{sup 23} cm{sup -2}. Spreading the 21 cm absorption over the full rotation velocity width of the material in front of the narrow radio jets gives a mean optical depth of {approx}0.1. Spectroscopic searches for the 21 cm absorption feature in other galaxies can be used to identify the large population of inclined gaseous discs which are not masing in our direction. Follow-up imaging of 21 cm silhouettes of accelerating clumps within these discs can in turn be used to measure cosmological distances.

  19. Environment and properties of obscured and unobscured active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Taormina, M.; Bornancini, C.

    We analyze the properties of obscured and unobscured active galactic nuclei selected using mid-infrared colors in the redshift range 1 < z < 3. We find that obscured objects are located in a denser local galaxy environment compared to the unobscured sample.

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

    SciTech Connect

    Petrović, Jovana; Serpico, Pasquale Dario; Zaharijaš, Gabrijela E-mail: serpico@lapth.cnrs.fr

    2014-10-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

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

  2. Chandra X-Ray Observations of the Two Brightest Unidentified High Galactic Latitude Fermi-LAT Gamma-Ray Sources

    NASA Technical Reports Server (NTRS)

    Cheung, C. C.; Donato, D.; Gehrels, N.; Sokolovsky, K. V.; Giroletti, M.

    2012-01-01

    We present Chandra ACIS-I X-ray observations of 0FGL J1311.9-3419 and 0FGL J1653.4-0200, the two brightest high Galactic latitude (absolute value (beta) >10 deg) gamma-ray sources from the three-month Fermi Large Area Telescope (LAT) bright source list that are still unidentified. Both were also detected previously by EGRET, and despite dedicated multi-wavelength follow-up, they are still not associated with established classes of gamma-ray emitters like pulsars or radio-loud active galactic nuclei. X-ray sources found in the ACIS-I fields of view are cataloged, and their basic properties are determined. These are discussed as candidate counterparts to 0FGL J1311.9-3419 and 0FGL J1653.4-0200, with particular emphasis on the brightest of the 9 and 13 Chandra sources detected within the respective Fermi-LAT 95% confidence regions. Further follow-up studies, including optical photometric and spectroscopic observations, are necessary to identify these X-ray candidate counterparts in order to ultimately reveal the nature of these enigmatic gamma-ray objects.

  3. Constraints on Galactic Center Activity: A Search for Enhanced Galactic Center Lithium and Boron

    NASA Astrophysics Data System (ADS)

    Lubowich, D. A.; Turner, B. E.; Hobbs, L. M.

    1998-12-01

    The abundances of lithium and boron provide important information about big bang nucleosynthesis, Galactic chemical evolution, stellar evolution, and cosmic-ray spallation reactions. We conducted the first search for the ground-state hyperfine-structure transitions of Li I (2S1/2; F = 2-1 803 MHz) and B I (2P1/2; F = 2-1 732 MHz). We used the 43 m NRAO radio telescope to search for enhanced Galactic center (GC) Li and B expected from models of Galactic activity. We did not detect Li I or B I and obtained upper limits of N(Li I) < 1.9 × 1016 cm-2, (Li/H) < 3.9 × 10-8, N(B I) < 2.2 × 1018 cm-2, and (B/H) < 9.2 × 10-6 for the dense 20 km s-1 Sgr A molecular cloud where our largest sources of uncertainties are Li I/Li, B I/B, and N(H). Our observations imply (Li/H)GC < 22 (Li/H)disk, (Li/H)GC < 39 (Li/H)disk-spallation, (B/H)GC < 1.2 × 104 (B/H)disk, (B/H)GC < 1.5 × 104 (B/H)disk-spallation. For a simple model combining mass loss from AGB stars (only for Li), spallation reactions, and SN ν-nucleosynthesis, we estimate (Li/H)GC = 1.3 × 10-8 (13 times enhancement) and (B/H)GC = 7.4 × 10-9 (10 times enhancement). If Li is primarily produced via spallation reactions from a cosmic-ray proton flux φp(t) with the same energy and trapping as in the disk, then [\\smallint φp(t)dt]GC < 13[\\smallint φp(t)dt]disk. Comparing our results to AGN models, we conclude that the GC has not had an extended period of AGN activity containing a large cosmic-ray flux (LCR <= 1044 ergs s-1 for 108 yr), a large low-energy cosmic-ray flux (less than 100 times the disk flux), or a large γ-ray flux (Lγ < 1042 ergs s-1 for 109 yr). Furthermore, since any Galactic deuterium production will significantly enhance the abundances of Li and B, our results imply that there are no sources of D in the GC or Galaxy. Therefore, all the Galactic D originated from the infall of primordial matter with the current D/H reduced by astration and mixing.

  4. Investigation on Radio-Quiet and Radio-Loud Fast CMEs and Their Associated Flares During Solar Cycles 23 and 24

    NASA Astrophysics Data System (ADS)

    Suresh, K.; Shanmugaraju, A.

    2015-03-01

    We present the results of a detailed analysis on the differences between radio-loud (RL) and radio-quiet (RQ) fast coronal mass ejections (CMEs) ( V≥900 km s-1) observed during the period 1996 - 2012. The analysis consists of three different steps in which we examined the properties of (i) RL and RQ CMEs, (ii) accelerating (class-A) and decelerating (class-D) CMEs among RL and RQ CMEs, and (iii) associated flares. The last two steps and events from a longer period are the extensions of the earlier work on RL and RQ CMEs that mainly aimed to determine the reason for the radio-quietness of some fast CMEs. During this period, we found that 38 % of fast CMEs are RL and 62 % of fast CMEs are RQ. Moreover, fewer RQ CMEs occur around the disc centre. The average speeds of RL and RQ CMEs are 1358 km s-1 and 1092 km s-1. Around 10 % of the RQ events are halo CMEs, but ≈ 66 % of RL events are halo CMEs. The mean acceleration or deceleration value of RL-CMEs is slightly greater than that of RQ-CMEs. When we divide these events based on their acceleration behaviour into class A and class D, there are no considerable differences between classes A and D of RL-CMEs or between classes A and D of RQ CMEs, except for their initial acceleration values. But there are significant differences among their associated flare properties. According to our study here, the RQ CMEs are less energetic than RL CMEs, and they are not associated with flares as strong as those associated with RL CMEs. This confirms the previous results that RQ CMEs do not often exceed the critical Alfvén speed of 1000 km s-1 in the outer corona that is needed to produce type II radio bursts.

  5. On the statistical characteristics of radio-loud and radio-quiet halo coronal mass ejections and their associated flares during solar cycles 23 and 24

    NASA Astrophysics Data System (ADS)

    Mittal, Nishant; Sharma, Joginder; Verma, Virendar Kumar; Garg, Vijay

    2016-08-01

    We have studied the characteristics of radio-loud (RL) and radio-quiet (RQ) front side halo coronal mass ejections (HCMEs) (angular width 360°) observed between the time period years 1996-2014. RL-HCMEs are associated with type II radio bursts, while RQ-HCMEs are not associated with type II radio bursts. CMEs near the Sun in the interplanetary medium associated with radio bursts also affect the magnetosphere. The type II radio burst data was observed by WIND/WAVES instrument and HCMEs were observed by LASCO/ SOHO instruments. In our study, we have examined the properties of RL-HCMEs and RQ-HCMEs and found that RL-HCMEs follow the solar cycle variation. Our study also shows that the 26% of slow speed HCMEs and 82% of fast speed HCMEs are RL. The average speed of RL-HCMEs and RQ-HCMEs are 1370 km/s and 727 km/s, respectively. Most of the RQ-HCMEs occur around the solar disc center while most of RL-HCMEs are uniformly distributed across the solar disc. The mean value of acceleration of RL-HCMEs is more than twice that of RQ-HCMEs and mean value of deceleration of RL- HCMEs is very small compare to RQ-HCMEs events. It is also found that RQ-HCMEs events are associated with C- and M-class of SXR flares, while RL-HCMEs events are associated with M and X-class of SXR flares, which indicates that the RQ-HCMEs are less energetic than the RL-HCMEs. We have also discussed the various results obtained in present investigation in view of recent scenario of solar physics.

  6. Accretion disc-corona and jet emission from the radio-loud Narrow Line Seyfert 1 galaxy RXJ1633.3+4719

    NASA Astrophysics Data System (ADS)

    Mallick, Labani; Dewangan, G. C.; Gandhi, P.; Misra, R.; Kembhavi, A. K.

    2016-05-01

    We perform X-ray/UV spectral and X-ray variability studies of the radio-loud Narrow Line Seyfert 1 (NLS1) galaxy RXJ1633.3+4719 using XMM-Newton and Suzaku observations from 2011 and 2012. The 0.3-10 keV spectra consist of an ultra-soft component described by an accretion disc blackbody (kT_in = 39.6^{+11.2}_{-5.5} eV) and a power-law due to the thermal Comptonization (Γ =1.96^{+0.24}_{-0.31}) of the disc emission. The disc temperature inferred from the soft excess is at least a factor of two lower than that found for the canonical soft excess emission from radio-quiet NLS1s. The UV spectrum is described by a power-law with photon index 3.05^{+0.56}_{-0.33}. The observed UV emission is too strong to arise from the accretion disc or the host galaxy, but can be attributed to a jet. The X-ray emission from RXJ1633.3+4719 is variable with fractional variability amplitude Fvar=13.5±1.0%. In contrast to radio-quiet AGN, X-ray emission from the source becomes harder with increasing flux. The fractional RMS variability increases with energy and the RMS spectrum is well described by a constant disc component and a variable power-law continuum with the normalization and photon index being anti-correlated. Such spectral variability cannot be caused by variations in the absorption and must be intrinsic to the hot corona. Our finding of possible evidence for emission from the inner accretion disc, jet and hot corona from RXJ1633.3+4719 in the optical to X-ray bands makes this object an ideal target to probe the disc-jet connection in AGN.

  7. The X-ray spectroscopy of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R.

    1985-01-01

    The scientific goals of X-ray spectroscopy of active galactic nuclei are discussed. The underlying energy source, the regions responsible for the optical emission lines, the different types of active galaxies, and cosmology are considered. The requirements for an X-ray mission of broad band width, large collecting area, modest spatial resolution and good spectral resolution are outlined. It is concluded that the ESA XMM mission meets these requirements.

  8. UNDERSTANDING DUAL ACTIVE GALACTIC NUCLEUS ACTIVATION IN THE NEARBY UNIVERSE

    SciTech Connect

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Vasudevan, Ranjan; Trippe, Margaret; Treister, Ezequiel

    2012-02-20

    We study the fraction of dual active galactic nuclei (AGNs) in a sample of 167 nearby (z < 0.05), moderate-luminosity, ultra-hard X-ray-selected AGNs from the all-sky Swift Burst Alert Telescope (BAT) survey. Combining new Chandra and Gemini observations together with optical and X-ray observations, we find that the dual AGN frequency at scales <100 kpc is {approx}10% (16/167). Of the 16 dual AGNs, only 3 (19%) were detected using X-ray spectroscopy and were not detected using emission line diagnostics. Close dual AGNs (<30 kpc) tend to be more common among the most X-ray luminous systems. In dual AGNs, the X-ray luminosity of both AGNs increases strongly with decreasing galaxy separation, suggesting that the merging event is key in powering both AGNs. Fifty percent of the AGNs with a very close companion (<15 kpc) are dual AGNs. We also find that dual AGNs are more likely to occur in major mergers and tend to avoid absorption line galaxies with elliptical morphologies. Finally, we find that SDSS Seyferts are much less likely than BAT AGNs (0.25% versus 7.8%) to be found in dual AGNs at scales <30 kpc because of a smaller number of companion galaxies, fiber collision limits, a tendency for AGNs at small separations to be detected only in X-rays, and a higher fraction of dual AGN companions with increasing AGN luminosity.

  9. Dense Clouds near the Central Engine of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Sivron, R.; Tsuruta, S

    1993-01-01

    A model is presented which assumes the existence of cold dense clouds near the central engine of Active Galactic Nuclei (AGNs). The effects of such clouds on the observed spectrum are explored. It is shown that this model is consistent with the complicated observed spectra and variability behavior of most extensively studied Seyfert nuclei. The results are compared with other proposed models. The existing observational evidence appears to support the "cloud-model."

  10. Stellar populations in Active Galactic Nuclei III

    NASA Astrophysics Data System (ADS)

    Boisson, C.; Joly, M.; Pelat, D.; Ward, M. J.

    2004-12-01

    In this paper we apply the stellar population synthesis method previously described in Boisson et al. (\\cite{Boisson2000}) to five more AGN. The analysis of these new data strengthen our previous conclusions: i) homogeneity of the stellar population within a class of nuclear activity regardless of the morphological type of the host galaxy; ii) populations within the nuclear regions of LINERs and Seyfert 2s are different: LINERs have a very old metal-rich population while in the Seyfert 2s a contribution of a weak burst of star formation is observed together with the old high metallicity component; iii) in the circum-nuclar region (200 pc ≤D≤1 kpc) of all the active galaxies in our sample, except for NGC 2992, we detect an old burst of star formation (0.2-1 Gyr),which is contrary to what is observed in normal galaxies. We note that the broad OIλ8446 Å emission line detected in the spectrum of the nucleus of NGC 2992 confirms its classification as a Seyfert 1. Based on observations collected at the New Technology Telescope of the European Southern Observatory, La Silla, Chile.

  11. Ultraviolet/X-ray Variability and the Extended X-ray Emission of the Radio-loud Broad Absorption Line Quasar PG 1004+130

    NASA Astrophysics Data System (ADS)

    Scott, A. E.; Brandt, W. N.; Miller, B. P.; Luo, B.; Gallagher, S. C.

    2015-06-01

    We present the results of recent Chandra, XMM-Newton, and Hubble Space Telescope observations of the radio-loud (RL), broad absorption line (BAL) quasar PG 1004+130. We compare our new observations to archival X-ray and UV data, creating the most comprehensive, high signal-to-noise, multi-epoch, spectral monitoring campaign of a RL BAL quasar to date. We probe for variability of the X-ray absorption, the UV BAL, and the X-ray jet, on month-year timescales. The X-ray absorber has a low column density of {N}H=8× {10}20-4× {10}21 {{cm}}-2 when it is assumed to be fully covering the X-ray emitting region, and its properties do not vary significantly between the four observations. This suggests that the observed absorption is not related to the typical “shielding gas” commonly invoked in BAL quasar models, but is likely due to material further from the central black hole. In contrast, the C iv BAL shows strong variability. The equivalent width (EW) in 2014 is {EW}=11.24+/- 0.56 \\AA, showing a fractional increase of Δ {EW}/< {EW}> =1.16+/- 0.11 from the 2003 observation, 3183 days earlier in the rest-frame. This places PG 1004+130 among the most highly variable BAL quasars. By combining Chandra observations we create an exposure that is 2.5 times deeper than studied previously, with which to investigate the nature of the X-ray jet and extended diffuse X-ray emission. An X-ray knot, likely with a synchrotron origin, is detected in the radio jet ˜ 8\\prime\\prime (30 kpc) from the central X-ray source with a spatial extent of ˜ 4\\prime\\prime (15 kpc). No similar X-ray counterpart to the counterjet is detected. Asymmetric, non-thermal diffuse X-ray emission, likely due to inverse Compton scattering of Cosmic Microwave Background photons, is also detected.

  12. Black holes in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Valtonen, M. J.; Mikkola, S.; Merritt, D.; Gopakumar, A.; Lehto, H. J.; Hyvönen, T.; Rampadarath, H.; Saunders, R.; Basta, M.; Hudec, R.

    2010-01-01

    Supermassive black holes are common in centers of galaxies. Among the active galaxies, quasars are the most extreme, and their black hole masses range as high as to 6ṡ1010M⊙. Binary black holes are of special interest but so far OJ287 is the only confirmed case with known orbital elements. In OJ287, the binary nature is confirmed by periodic radiation pulses. The period is twelve years with two pulses per period. The last four pulses have been correctly predicted with the accuracy of few weeks, the latest in 2007 with the accuracy of one day. This accuracy is high enough that one may test the higher order terms in the Post Newtonian approximation to General Relativity. The precession rate per period is 39°.1 ± 0°.1, by far the largest rate in any known binary, and the (1.83 ± 0.01)ṡ1010M⊙ primary is among the dozen biggest black holes known. We will discuss the various Post Newtonian terms and their effect on the orbit solution. The over 100 year data base of optical variations in OJ287 puts limits on these terms and thus tests the ability of Einstein's General Relativity to describe, for the first time, dynamic binary black hole spacetime in the strong field regime. The quadrupole-moment contributions to the equations of motion allows us to constrain the ‘no-hair’ parameter to be 1.0 ± 0.3 which supports the black hole no-hair theorem within the achievable precision.

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

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.; Edelson, R.; Baumgartner, W. H.; Gandhi, P.

    2012-01-01

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

  14. Active galactic nucleus feedback in clusters of galaxies.

    PubMed

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

    2010-04-20

    Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves. PMID:20351250

  15. High-energy neutrinos from active galactic nuclei

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

    The spectrum and high-energy neutrino background flux from photomeson production in active galactic nuclei (AGN) is calculated using the recent UV and X-ray observations to define the photon fields and an accretion-disk shock-acceleration model for producing high-energy particles. Collectively, AGN produce the dominant isotropic neutrino background between 10,000 and 10 to the 10th GeV, detectable with current instruments. AGN neutrinos should produce a sphere of stellar disruption which may explain the 'broad-line region' seen in AGN.

  16. Active galactic nucleus feedback in clusters of galaxies

    PubMed Central

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

    2010-01-01

    Observations made during the last ten years with the Chandra X-ray Observatory have shed much light on the cooling gas in the centers of clusters of galaxies and the role of active galactic nucleus (AGN) heating. Cooling of the hot intracluster medium in cluster centers can feed the supermassive black holes found in the nuclei of the dominant cluster galaxies leading to AGN outbursts which can reheat the gas, suppressing cooling and large amounts of star formation. AGN heating can come in the form of shocks, buoyantly rising bubbles that have been inflated by radio lobes, and the dissipation of sound waves. PMID:20351250

  17. FRESH ACTIVITY IN OLD SYSTEMS: RADIO AGNs IN FOSSIL GROUPS OF GALAXIES

    SciTech Connect

    Hess, Kelley M.; Wilcots, Eric M.; Hartwick, Victoria L. E-mail: ewilcots@astro.wisc.edu

    2012-08-15

    We present the first systematic 1.4 GHz Very Large Array radio continuum survey of fossil galaxy group candidates. These are virialized systems believed to have assembled over a gigayear in the past through the merging of galaxy group members into a single, isolated, massive elliptical galaxy and featuring an extended hot X-ray halo. We use new photometric and spectroscopic data from Sloan Digital Sky Survey Data Release 7 to determine that three of the candidates are clearly not fossil groups. Of the remaining 30 candidates, 67% contain a radio-loud (L{sub 1.4GHz} > 10{sup 23} W Hz{sup -1}) active galactic nucleus (AGN) at the center of their dominant elliptical galaxy. We find a weak correlation between the radio luminosity of the AGN and the X-ray luminosity of the halo suggesting that the AGN contributes to energy deposition into the intragroup medium. We only find a correlation between the radio and optical luminosity of the central elliptical galaxy when we include X-ray-selected, elliptically dominated non-fossil groups, indicating a weak relationship between AGN strength and the mass assembly history of the groups. The dominant elliptical galaxy of fossil groups is on average roughly an order of magnitude more luminous than normal group elliptical galaxies in optical, X-ray, and radio luminosities and our findings are consistent with previous results that the radio-loud fraction in elliptical galaxies is linked to the stellar mass of a population. The current level of activity in fossil groups suggests that AGN fueling continues long after the last major merger. We discuss several possibilities for fueling the AGN at the present epoch.

  18. What obscures low-X-ray-scattering active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Hönig, S. F.; Gandhi, P.; Asmus, D.; Mushotzky, R. F.; Antonucci, R.; Ueda, Y.; Ichikawa, K.

    2014-02-01

    X-ray surveys have revealed a new class of active galactic nuclei (AGN) with a very low observed fraction of scattered soft X-rays, fscat <0.5 per cent. Based on X-ray modelling, these `X-ray new-type', or low observed X-ray-scattering (hereafter, `low-scattering') sources have been interpreted as deeply buried AGN with a high covering factor of gas. In this paper, we address the questions whether the host galaxies of low-scattering AGN may contribute to the observed X-ray properties, and whether we can find any direct evidence for high covering factors from the infrared (IR) emission. We find that X-ray low-scattering AGN are preferentially hosted by highly inclined galaxies or merger systems as compared to other Seyfert galaxies, increasing the likelihood that the line of sight towards the AGN intersects with high columns of host-galactic gas and dust. Moreover, while a detailed analysis of the IR emission of low-scattering AGN ESO 103-G35 remains inconclusive, we do not find any indication of systematically higher dust covering factors in a sample of low-scattering AGN based on their IR emission. For ESO 103-G35, we constrained the temperature, mass and location of the IR emitting dust which is consistent with expectations for the dusty torus. However, a deep silicate absorption feature probably from much cooler dust suggests an additional screen absorber on larger scales within the host galaxy. Taking these findings together, we propose that the low fscat observed in low-scattering AGN is not necessarily the result of circumnuclear dust but could originate from interference of host-galactic gas with a column density of the order of 1022 cm-2 with the line of sight. We discuss implications of this hypothesis for X-ray models, high-ionization emission lines and observed star formation activity in these objects.

  19. The effects of the local environment on active galactic nuclei

    SciTech Connect

    Manzer, L. H.; De Robertis, M. M. E-mail: mmdr@yorku.ca

    2014-06-20

    There continues to be significant controversy regarding the mechanism(s) responsible for the initiation and maintenance of activity in galactic nuclei. In this paper we will investigate possible environmental triggers of nuclear activity through a statistical analysis of a large sample of galaxy groups. The focus of this paper is to identify active galactic nuclei (AGNs) and other emission-line galaxies in these groups and to compare their frequency with a sample of over 260,000 isolated galaxies from the same catalog. The galaxy groups are taken from the catalog of Yang et al., in which over 20,000 virialized groups of galaxies (2 ≤ N ≤ 20) with redshifts between 0.01 and 0.20 are from the Sloan Digital Sky Survey. We first investigate the completeness of our data set and find, though biases are a concern particularly at higher redshift, that our data provide a fair representation of the local universe. After correcting emission-line equivalent widths for extinction and underlying Balmer stellar absorption, we classify galaxies in the sample using traditional emission-line ratios, while incorporating measurement uncertainties. We find a significantly higher fraction of AGNs in groups compared with the isolated sample. Likewise, a significantly higher fraction of absorption-line galaxies are found in groups, while a higher fraction of star-forming galaxies prefer isolated environments. Within grouped environments, AGNs and star-forming galaxies are found more frequently in small- to medium-richness groups, while absorption-line galaxies prefer groups with larger richnesses. Groups containing only emission-line galaxies have smaller virial radii, velocity dispersions, and masses compared with those containing only absorption-line galaxies. Furthermore, the AGN fraction increases with decreasing distance to the group centroid, independent of galaxy morphology. Using properties obtained from Galaxy Zoo, there is an increased fraction of AGNs within merging systems

  20. X-Ray Reprocessing in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.

    2004-01-01

    This is the final report for research entitled "X-ray reprocessing in active galactic nuclei," into X-ray absorption and emission in various classes of active galaxy via X-ray spectral signatures. The fundamental goal of the research was to use these signatures as probes of the central engine structure and circumnuclear environment of active galactic nuclei. The most important accomplishment supported by this grant involved the detailed analysis and interpretation of the XMM data for the bright Seyfert 1 galaxy MCG-6-30-15. This work was performed by Drs. Christopher Reynolds and Mitchell Begelman in collaboration with Dr. Jorn Wilms (University of Tubingen, Germany; PI of the XMM observation) and other European scientists. With XMM we obtained medium resolution X-ray spectra of unprecedented quality for this Seyfert galaxy. Modeling the X-ray spectrum within the framework of accretion disk reflection models produced the first evidence for energy extraction from the spin of a black hole. Specifically, we found that the extreme gravitational redshifts required to explain the X-ray spectrum suggests that the bulk of the energy dissipation is concentrated very close to the black hole, in contrast with the expectations of any pure accretion disk model. In a second paper we addressed the low- energy spectral complexity and used RXTE specta to pin down the high-energy spectral index, thus firming up our initial interpretation. Additionally, we carried out detailed spectral and variability analyses of a number of Seyfert and radio galaxies (e.g., NGC 5548 and 3C 111) and developed general techniques that will be useful in performing X-ray reverberation mapping of accretion disks in AGN, once adequate data becomes available. A list of papers supported by this research is included.

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

    SciTech Connect

    Mushotzky, R. F.; Edelson, R.; Baumgartner, W.

    2011-12-10

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

  2. Photometric Monitoring of the Active Galactic Nucleus in NGC 7469

    NASA Astrophysics Data System (ADS)

    Roberts, Caroline A.; Bentz, M. C.; Stare Collaboration

    2014-01-01

    Reverberation mapping is a technique by which black hole masses in active galactic nuclei (AGN) are determined. The method determines an average radius for the broad line region by measuring the time delay between continuum and emission signatures in an object’s spectrum. Coupled with the broad line region cloud velocity values taken from Doppler emission line broadening and a correction for the angle at which the AGN is viewed, the black hole mass can be constrained. As part of a reverberation mapping campaign targeting NGC 7469, optical B and V photometry was obtained over the span of a 6-month period during the second half of 2011 using 14 different telescopes in the former bandwidth and 15 in the latter. Differential photometry was performed with IRAF and the light curves were compared with those obtained using the image subtraction program ISIS.

  3. DISCOVERY OF 5000 ACTIVE GALACTIC NUCLEI BEHIND THE MAGELLANIC CLOUDS

    SciTech Connect

    Kozlowski, Szymon; Kochanek, Christopher S. E-mail: ckochanek@astronomy.ohio-state.edu

    2009-08-10

    We show that using mid-IR color selection to find active galactic nuclei (AGNs) is as effective in dense stellar fields such as the Magellanic Clouds as it is in extragalactic fields with low stellar densities using comparisons between the Spitzer Deep Wide Field Survey data for the NOAO Deep Wide Field Survey Boeotes region and the SAGE Survey of the Large Magellanic Cloud. We use this to build high-purity catalogs of {approx}5000 AGN candidates behind the Magellanic Clouds. Once confirmed, these quasars will expand the available astrometric reference sources for the Clouds and the numbers of quasars with densely sampled, long-term (>decade) monitoring light curves by well over an order of magnitude and potentially identify sufficiently bright quasars for absorption line studies of the interstellar medium of the Clouds.

  4. Neutrinos in IceCube from active galactic nuclei

    SciTech Connect

    Kalashev, O.; Semikoz, D.; Tkachev, I.

    2015-03-15

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

  5. X-ray emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R.

    1985-01-01

    It is often held that the X-ray emission from active galactic nuclei (AGN) arises from a region close to the central energy source. Thus X-ray observations may provide the best constraints on the central engine. In particular, the shape of the X-ray continuum gives information about the mechanism for photon generation, X-ray time variability data can constrain the size and mass of the continuum source, and X-ray occultation data give constraints on the relative sizes of the continuum source and the intervening absorbing material (often assumed to be the broad line clouds). In addition, since a fair fraction of the total energy of an AGN is emitted at X-ray wavelengths, direct measurement of the amount and spectral form of this radiation is important for modeling of the optically emitting clouds.

  6. Time Delay Evolution of Five Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  7. A NEW COSMOLOGICAL DISTANCE MEASURE USING ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Watson, D.; Denney, K. D.; Vestergaard, M.; Davis, T. M.

    2011-10-20

    Accurate distances to celestial objects are key to establishing the age and energy density of the universe and the nature of dark energy. A distance measure using active galactic nuclei (AGNs) has been sought for more than 40 years, as they are extremely luminous and can be observed at very large distances. We report here the discovery of an accurate luminosity distance measure using AGNs. We use the tight relationship between the luminosity of an AGN and the radius of its broad-line region established via reverberation mapping to determine the luminosity distances to a sample of 38 AGNs. All reliable distance measures up to now have been limited to moderate redshift-AGNs will, for the first time, allow distances to be estimated to z {approx} 4, where variations of dark energy and alternate gravity theories can be probed.

  8. Pair Plasmas in the Central Engine of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Tsuruta, S.; Tritz, B. G.

    1993-01-01

    As the most promising model for the X-ray emission from a class of Active Galactic Nuclei (AGNs) represented by radio-quiet quasars and Seyfert nuclei, here we introduce the non-thermal pair cascade model, where soft photons are Comptonized by non-thermal electron-positron pair plasmas produced by (gamma)-rays. After summarizing the simplest model of this kind, the "homogeneous spherical cascade model", our most recent work on the "surface cascade model" is presented, where a geometrical effect is introduced. Many characteristics of this model are qualitatively similar to the homogeneous cascade model. However, an important difference is that (gamma)-ray depletion is much more efficient in the surface cascade, and consequently this model naturally satisfies the severe observational constraint imposed by the (gamma)-ray background radiation.

  9. Unwrapping the X-ray spectra of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Reynolds, C. S.

    2016-05-01

    Active galactic nuclei (AGN) are complex phenomena. At the heart of an AGN is a relativistic accretion disk around a spinning supermassive black hole (SMBH) with an X-ray emitting corona and, sometimes, a relativistic jet. On larger scales, the outer accretion disk and molecular torus act as the reservoirs of gas for the continuing AGN activity. And on all scales from the black hole outwards, powerful winds are seen that probably affect the evolution of the host galaxy as well as regulate the feeding of the AGN itself. In this review article, we discuss how X-ray spectroscopy can be used to study each of these components. We highlight how recent measurements of the high-energy cutoff in the X-ray continuum by NuSTAR are pushing us to conclude that X-ray coronae are radiatively-compact and have electron temperatures regulated by electron-positron pair production. We show that the predominance of rapidly-rotating objects in current surveys of SMBH spin is entirely unsurprising once one accounts for the observational selection bias resulting from the spin-dependence of the radiative efficiency. We review recent progress in our understanding of fast (v˜ (0.1-0.3)c, highly-ionized (mainly visible in Fe XXV and Fe XXVI lines), high-column density winds that may dominate quasar-mode galactic feedback. Finally, we end with a brief look forward to the promise of Astro-H and future X-ray spectropolarimeters.

  10. OBSERVABILITY OF DUAL ACTIVE GALACTIC NUCLEI IN MERGING GALAXIES

    SciTech Connect

    Van Wassenhove, Sandor; Volonteri, Marta; Bellovary, Jillian; Mayer, Lucio; Callegari, Simone; Dotti, Massimo

    2012-03-20

    Supermassive black holes (SMBHs) have been detected in the centers of most nearby massive galaxies. Galaxies today are not only the products of billions of years of galaxy mergers, but also billions of years of SMBH activity as active galactic nuclei (AGNs) that is connected to galaxy mergers. In this context, detection of AGN pairs should be relatively common. Observationally, however, dual AGNs are scant, being just a few percent of all AGNs. In this Letter, we investigate the triggering of AGN activity in merging galaxies via a suite of high-resolution hydrodynamical simulations. We follow the dynamics and accretion onto the SMBHs as they move from separations of tens of kiloparsecs to tens of parsecs. Our resolution, cooling, and star formation implementation produce an inhomogeneous, multi-phase interstellar medium, allowing us to accurately trace star formation and accretion onto the SMBHs. We study the impact of gas content, morphology, and mass ratio, focusing on AGN activity and dynamics across a wide range of relevant conditions. We test when the two AGNs are simultaneously detectable, for how long and at which separations. We find that strong dual AGN activity occurs during the late phases of the mergers, at small separations (<1-10 kpc) below the resolution limit of most surveys. Much of the SMBH accretion is not simultaneous, limiting the dual AGN fraction detectable through imaging and spectroscopy to a few percent, in agreement with observational samples.

  11. Molecular Abundances in the Disk of AN Active Galactic Nucleus

    NASA Astrophysics Data System (ADS)

    Harada, N.; Thompson, T. A.; Herbst, E.

    2011-06-01

    There are galactic nuclei that emit high luminosities L˜1044-46 erg S-1 including luminosity produced by X-rays from high mass accretion onto the central black holes. These nuclei are called active galactic nuclei (AGNs), and they are accompanied by molecular disks. Observations show high abundances of CN and HCN in the disks; the molecules are proposed to be probes of X-ray dominated regions (XDRs) created by the X-rays from AGNs. We have constructed a spatially-dependent chemical-abundance model of the molecular disk in NGC 1068, a typical AGN-dominated galaxy. Recently, new observations of CN and HCN have been made at much higher spatial resolution, and there are also detections of polyatomic molecules such as HC3N, c-C3H2, and C2H. We discuss how these observations and our simulations can help us to better understand the physical conditions, the disk structure, and conditions for star formation within molecular disks, which are still uncertain. We also include a comparison with other types of galaxies such as (ultra-) luminous infrared galaxies. Usero et al.Astronomy and Astrophysics. 419 (897), 2004. Initial results were presented at the International Symposium on Molecular Spectroscopy 2010, RF05 Garcia-Burillo et al. Astronomy and Astrophysics. 519 (2), 2010. Garcia-Burillo et al. Journal of Physics Conference Series, 131 (12031), 2008. Costagliola et al. ArXiv e-print arXiv:1101.2122, 2011. Nakajima et al. Astrophysical Journal Letters 728 (L38), 2008.

  12. DUAL ACTIVE GALACTIC NUCLEI: DEPROJECTING THE BINARY CORES

    SciTech Connect

    Wang, X.-W.; Zhou, H.-Y.

    2012-10-01

    Dual active galactic nuclei (AGNs) as a population in a special phase during the evolution of merging galaxies have been found largely from candidates selected from the Sloan Digital Sky Survey (SDSS). In this paper, we develop a simple model of dual AGNs, which are composed of two optically thin spheres emitting narrow lines and co-rotating governed by gravity between them. In order to show how profiles are sensitive to the orientation angles of the orbiting plane and phase angles, we make detailed calculations of profiles for a large space of the two angles. The dual AGNs observationally appear as ones with double-peaked profiles of emission lines, but there are still quite large ranges of orientation and phase angles where they appear only with a single-peaked profile. This implies a large fraction of dual AGN candidate missed by selecting AGNs with double-peaked profiles. We show that the highly sensitive dependence of profiles on orientation and phase angles makes them robust to deproject dual AGN systems. Deprojection by the present model has potential implications for discussion of the triggering mechanism of black hole activity in light of the deprojected distance. We apply the present model to two dual AGN, SDSS J095207.6+255257 and J171544.05+600835.7, for deprojection of the binary cores.

  13. DISCOVERY OF FOUR kpc-SCALE BINARY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Liu Xin; Greene, Jenny E.; Strauss, Michael A.; Shen Yue

    2010-05-20

    We report the discovery of four kpc-scale binary active galactic nuclei (AGNs). These objects were originally selected from the Sloan Digital Sky Survey based on double-peaked [O III] {lambda}{lambda}4959, 5007 emission lines in their fiber spectra. The double peaks could result from pairing active supermassive black holes (SMBHs) in a galaxy merger or could be due to bulk motions of narrow-line region gas around a single SMBH. Deep near-infrared (NIR) images and optical slit spectra obtained from the Magellan 6.5 m and the Apache Point Observatory 3.5 m telescopes strongly support the binary SMBH scenario for the four objects. In each system, the NIR images reveal tidal features and double stellar components with a projected separation of several kpc, while optical slit spectra show two Seyfert 2 nuclei spatially coincident with the stellar components, with line-of-sight velocity offsets of a few hundred km s{sup -1}. These objects were drawn from a sample of only 43 objects, demonstrating the efficiency of this technique to find kpc-scale binary AGNs.

  14. Active galactic nuclei at gamma-ray energies

    NASA Astrophysics Data System (ADS)

    Dermer, Charles Dennison; Giebels, Berrie

    2016-06-01

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

  15. ON THE 10 mum SILICATE FEATURE IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Nikutta, Robert; Elitzur, Moshe; Lacy, Mark E-mail: moshe@pa.uky.ed

    2009-12-20

    The 10 mum silicate feature observed with Spitzer in active galactic nuclei (AGNs) reveals some puzzling behavior. It (1) has been detected in emission in type 2 sources, (2) shows broad, flat-topped emission peaks shifted toward long wavelengths in several type 1 sources, and (3) is not seen in deep absorption in any source observed so far. We solve all three puzzles with our clumpy dust radiative transfer formalism. Addressing (1), we present the spectral energy distribution (SED) of SST1721+6012, the first type 2 quasar observed to show a clear 10 mum silicate feature in emission. Such emission arises in models of the AGN torus easily when its clumpy nature is taken into account. We constructed a large database of clumpy torus models and performed extensive fitting of the observed SED. We find that the cloud radial distribution varies as r {sup -1.5} and the torus contains 2-4 clouds along radial equatorial rays, each with optical depth at visual approx60-80. The source bolometric luminosity is approx3 x 10{sup 12} L{sub sun}. Our modeling suggests that approx<35% of objects with tori sharing these characteristics and geometry would have their central engines obscured. This relatively low obscuration probability can explain the clear appearance of the 10 mum emission feature in SST1721+6012 together with its rarity among other QSO2. Investigating (2), we also fitted the SED of PG1211+143, one of the first type 1 QSOs with a 10 mum silicate feature detected in emission. Together with other similar sources, this QSO appears to display an unusually broadened feature whose peak is shifted toward longer wavelengths. Although this led to suggestions of non-standard dust chemistry in these sources, our analysis fits such SEDs with standard galactic dust; the apparent peak shifts arise from simple radiative transfer effects. Regarding (3), we find additionally that the distribution of silicate feature strengths among clumpy torus models closely resembles the observed

  16. Microvariabilty in Active Galactic Nuclei at Centimeter Wavelengths

    NASA Astrophysics Data System (ADS)

    Atwood, James W.; Pannuti, T. G.

    2007-12-01

    Active Galactic Nuclei (AGNs) are some of the most distant objects known in the universe. Quasars, Blazars, and Seyfert galaxies are all categorized as AGNs. One of the interesting characteristics of AGNs is that they vary in brightness over a variety of time scales, ranging from long term (years or decades), to intraday (days or weeks), to extremely short (hours or minutes). Using the Morehead State University 21m Space Tracking Antenna we can measure short term variations (microvariability) of the radio frequency radiation of these distant objects. By monitoring variability we may be able to determine if this observed phenomenon originates from the internal processes of these objects or due to the intervening medium, and to provide insight into the nature and process associated with the AGN central engines. Initial observations of a set of target AGNs have been undertaken. Additional observations of these target objects will be made at 1.4, 2.4, and 12GHz to measure microvariability and to produce data points for broadband SEDs of these AGNs. Few observations have been made in the 12GHz region for these objects. These data sets will be correlated with simultaneous optical (Bell observatory) and The Gamma Ray Large Area Space Telescope (GLAST) observations to produce broad band, multiwavelength observations of a selected target set of AGNs. An additional goal of this project is to become a node in the NASA GLAST network.

  17. AN OFF-CENTERED ACTIVE GALACTIC NUCLEUS IN NGC 3115

    SciTech Connect

    Menezes, R. B.; Steiner, J. E.; Ricci, T. V.

    2014-11-20

    NGC 3115 is an S0 galaxy that has always been considered to have a pure absorption-line spectrum. Some recent studies have detected a compact radio-emitting nucleus in this object, coinciding with the photometric center and with a candidate for the X-ray nucleus. This is evidence of the existence of a low-luminosity active galactic nucleus (AGN) in the galaxy, although no emission line has ever been observed. We report the detection of an emission-line spectrum of a type 1 AGN in NGC 3115, with an Hα luminosity of L {sub Hα} = (4.2 ± 0.4) × 10{sup 37} erg s{sup –1}. Our analysis revealed that this AGN is located at a projected distance of ∼0.''29 ± 0.''05 (corresponding to ∼14.3 ± 2.5 pc) from the stellar bulge center, which is coincident with the kinematic center of this object's stellar velocity map. The black hole corresponding to the observed off-centered AGN may form a binary system with a black hole located at the stellar bulge center. However, it is also possible that the displaced black hole is the merged remnant of the binary system coalescence, after the ''kick'' caused by the asymmetric emission of gravitational waves. We propose that certain features in the stellar velocity dispersion map are the result of perturbations caused by the off-centered AGN.

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

    NASA Technical Reports Server (NTRS)

    Dwek, E.

    2012-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-01-01

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

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

    SciTech Connect

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

    2013-01-20

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

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

    NASA Astrophysics Data System (ADS)

    Ellison, Sara L.; Teimoorinia, Hossen; Rosario, David J.; Mendel, J. Trevor

    2016-05-01

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

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

    PubMed

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

    2012-05-10

    The old, red stars that constitute the bulges of galaxies, and the massive black holes at their centres, are the relics of a period in cosmic history when galaxies formed stars at remarkable rates and active galactic nuclei (AGN) shone brightly as a result of accretion onto black holes. It is widely suspected, but unproved, that the tight correlation between the mass of the black hole and the mass of the stellar bulge results from the AGN quenching the surrounding star formation as it approaches its peak luminosity. X-rays trace emission from AGN unambiguously, whereas powerful star-forming galaxies are usually dust-obscured and are brightest at infrared and submillimetre wavelengths. Here we report submillimetre and X-ray observations that show that rapid star formation was common in the host galaxies of AGN when the Universe was 2-6 billion years old, but that the most vigorous star formation is not observed around black holes above an X-ray luminosity of 10(44) ergs per second. This suppression of star formation in the host galaxy of a powerful AGN is a key prediction of models in which the AGN drives an outflow, expelling the interstellar medium of its host and transforming the galaxy's properties in a brief period of cosmic time. PMID:22575961

  3. Continuum radiation from active galactic nuclei: A statistical study

    NASA Technical Reports Server (NTRS)

    Isobe, T.; Feigelson, E. D.; Singh, K. P.; Kembhavi, A.

    1986-01-01

    The physics of the continuum spectrum of active galactic nuclei (AGNs) was examined using a large data set and rigorous statistical methods. A data base was constructed for 469 objects which include radio selected quasars, optically selected quasars, X-ray selected AGNs, BL Lac objects, and optically unidentified compact radio sources. Each object has measurements of its radio, optical, X-ray core continuum luminosity, though many of them are upper limits. Since many radio sources have extended components, the core component were carefully selected out from the total radio luminosity. With survival analysis statistical methods, which can treat upper limits correctly, these data can yield better statistical results than those previously obtained. A variety of statistical tests are performed, such as the comparison of the luminosity functions in different subsamples, and linear regressions of luminosities in different bands. Interpretation of the results leads to the following tentative conclusions: the main emission mechanism of optically selected quasars and X-ray selected AGNs is thermal, while that of BL Lac objects is synchrotron; radio selected quasars may have two different emission mechanisms in the X-ray band; BL Lac objects appear to be special cases of the radio selected quasars; some compact radio sources show the possibility of synchrotron self-Compton (SSC) in the optical band; and the spectral index between the optical and the X-ray bands depends on the optical luminosity.

  4. Radiation-pressure-supported obscuring tori around active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Pier, Edward A.; Krolik, Julian H.

    1992-01-01

    Radiation pressure acting on dust grains can support the vertical thickness of the obscuring tori believed to exist in active galactic nuclei. Using the results of 2D radiation transfer calculations, we evaluate the radiation force acting on these tori. We find that on the inner edge of the torus the radiation force is about 350 l(E) times the gravitational force of the nucleus, where l(E) is the Eddington ratio. Beyond a few torus heights from the inner edge, the radiation force is negligible with respect to gravity. However, between these two extremes lies a region of considerable size where the ratio of radiation force to gravity is nearly constant and can be of order unity for l(E) about 0.1. If the distribution of material within the torus is sufficiently lumpy, there is a significant time-varying component to the radiation force. This drives the random motions of the constituent clouds, thickening the torus at lower values of l(E).

  5. Implosive accretion and outbursts of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Lovelace, R. V. E.; Romanova, M. M.; Newman, W. I.

    1994-01-01

    A model and simulation code have been developed for time-dependent axisymmetric disk accretion onto a compact object including for the first time the influence of an ordered magnetic field. The accretion rate and radiative luminosity of the disk are naturally coupled to the rate of outflow of energy and angular momentum in magnetically driven (+/- z) winds. The magnetic field of the wind is treated in a phenomenological way suggested by self-consistent wind solutions. The radial accretion speed u(r, t) of the disk matter is shown to be the sum of the usual viscous contribution and a magnetic contribution proportional to r(exp 3/2)(B(sub p exp 2))/sigma, where B(sub p)(r,t) is the poloidal field threading the disk and sigma(r,t) is the disk's surface mass density. An enhancement or variation in B(sub p) at a large radial distance leads to the formation of a soliton-like structure in the disk density, temperature, and B-field which propagates implosively inward. The implosion gives a burst in the power output in winds or jets and a simultaneous burst in the disk radiation. The model is pertinent to the formation of discrete fast-moving components in jets observed by very long baseline interferometry. These components appear to originate at times of optical outbursts of the active galactic nucleus.

  6. Accretion disks and periodic outbursts of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Lin, D. N. C.; Shields, G. A.

    1986-01-01

    The local thermal stability of accretion disks around supermassive black holes in active galactic nuclei is examined. Such disks are unstable at radii where the surface temperature is several thousand degrees. Supermassive disks therefore should undergo limit-cycle outbursts similar to those believed to occur in dwarf novae. Operating on a time scale of about 10,000 to 10 million yr and at radii of about 10 to the 15th to 10 to the 16th cm, this mechanism will result in alternating periods of higher and lower accretion rate onto the black hole and, consequently, higher and lower luminosity. Quasi-periodic outbursts on this time scale may be recorded in the structure of extended radio sources, a possible example being 4C 29.47. For accretion rates greater than 0.1 solar masses/yr, the situation is complicated by instabilities caused by self-gravitation and by the dominance of radiation pressure and electron scattering opacity.

  7. Highlights from the VERITAS Active Galactic Nuclei Observing Program

    NASA Astrophysics Data System (ADS)

    Fortson, Lucy; VERITAS Collaboration

    2016-01-01

    The VERITAS Observatory, located at the Fred Lawrence Whipple Observatory near Tucson, Arizona is one of the world's most sensitive detectors of very-high-energy (VHE; E>100GeV) gamma rays. With an array of four 12-m telescopes, VERITAS detects the Cherenkov light emitted from air showers initiated by astrophysical gamma rays. A sequence of upgrades completed in 2012 aimed at lowering the energy threshold resulted in the instrument being sensitive to gamma rays between 85 GeV and 30 TeV. Fully operational since 2007, VERITAS has so far detected 54 VHE gamma-ray objects in eight different source classes. The active galactic nuclei (AGN) class comprises the majority of these detections, with 34 sources that include several radio galaxies but are predominantly blazars (AGN with relativistic jets pointing towards Earth). The scientific importance of VHE detections of AGN includes studying the details of emission mechanisms in blazars and elucidating whether they are sources of ultra-high-energy cosmic rays and astrophysical neutrinos. Additionally VHE gamma-ray observations can be used to gain cosmological insights such as placing limits on the intergalactic magnetic field (IGMF) and the extragalactic background light (EBL), which comprises all the diffuse starlight in the universe. This presentation will summarize the VERITAS AGN observing program and highlight a few recent results.

  8. Effects of Active galactic nuclei feedback in galaxy population

    NASA Astrophysics Data System (ADS)

    Lagos, C.; Cora, S.; Padilla, N.

    We analyze the effects of feedback from Active Galactic Nuclei (AGN) on the formation and evolution of galaxies, which is assumed to quench cooling flows in massive halos. With this aim we use an hybrid model that combines a cosmological Lambda CDM simulation with a semi-analytic model of galaxy formation. We consider the semi-analytic model described by Cora (2006) (SAMC06) which has been improved by including AGNs, which are associated with the presence of supermassive black holes (BHs). Modellization of BH includes gas accretion during merger-driven starbursts and black hole mergers (Malbon et al., 2006), accretion during starbursts triggered by disk instabilities (Bower et al. 2006), and accretion of cooling gas from quasi-hydrostatically cooling haloes (Croton et al. 2006); Eddington limit is applied in all accretion processes. It is assumed that feedback from AGNs operates in the later case. We show that this new model can simultaneously explain: (i) the bright-end of the galaxy luminosity function (LF); (ii) the observed older population of stars in massive galaxies, thus reproducing the stellar mass function (SMF); (iii) a star formation rate (SFR) seemingly showing an anti-hierarchical galaxy growth. The success of our model is mainly due to the ability of AGN feedback to suppress further cooling and SF in the most massive structures.

  9. Fermi Observations of TeV-Selected Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Atwood, W. B.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Baring, M. G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T. H.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cominsky, L. R.; Conrad, J.; Cutini, S.; de Angelis, A.; de Palma, F.; Di Bernardo, G.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Finke, J.; Focke, W. B.; Fortin, P.; Foschini, L.; Frailis, M.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giavitto, G.; Giebels, B.; Giglietto, N.; Giommi, P.; Giordano, F.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grondin, M.-H.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; Johnson, R. P.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocian, M. L.; Kuss, M.; Lande, J.; Latronico, L.; Lemoine-Goumard, M.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reposeur, T.; Reyes, L. C.; Ritz, S.; Rochester, L. S.; Rodriguez, A. Y.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Schalk, T. L.; Sellerholm, A.; Sgrò, C.; Shaw, M. S.; Siskind, E. J.; Smith, D. A.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Tajima, H.; Takahashi, H.; Takahashi, T.; Tanaka, T.; Tanaka, Y.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Ziegler, M.

    2009-12-01

    We report on observations of TeV-selected active galactic nuclei (AGNs) made during the first 5.5 months of observations with the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope (Fermi). In total, 96 AGNs were selected for study, each being either (1) a source detected at TeV energies (28 sources) or (2) an object that has been studied with TeV instruments and for which an upper limit has been reported (68 objects). The Fermi observations show clear detections of 38 of these TeV-selected objects, of which 21 are joint GeV-TeV sources, and 29 were not in the third EGRET catalog. For each of the 38 Fermi-detected sources, spectra and light curves are presented. Most can be described with a power law of spectral index harder than 2.0, with a spectral break generally required to accommodate the TeV measurements. Based on an extrapolation of the Fermi spectrum, we identify sources, not previously detected at TeV energies, which are promising targets for TeV instruments. Evidence for systematic evolution of the γ-ray spectrum with redshift is presented and discussed in the context of interaction with the extragalactic background light.

  10. MOMENTUM DRIVING: WHICH PHYSICAL PROCESSES DOMINATE ACTIVE GALACTIC NUCLEUS FEEDBACK?

    SciTech Connect

    Ostriker, Jeremiah P.; Choi, Ena; Novak, Gregory S.; Ciotti, Luca; Proga, Daniel

    2010-10-10

    The deposition of mechanical feedback from a supermassive black hole (SMBH) in an active galactic nucleus into the surrounding galaxy occurs via broad-line winds which must carry mass and radial momentum as well as energy. The effect can be summarized by the dimensionless parameter {eta}= M-dot{sub outf}/ M-dot{sub acc}=2{epsilon}{sub w}c{sup 2}/v{sub w}{sup 2} where {epsilon}{sub w} ({identical_to} E-dot{sub w}/(M-dot{sub acc}c{sup 2})) is the efficiency with which accreted matter is turned into wind energy in the disk surrounding the central SMBH. The outflowing mass and momentum are proportional to {eta}, and many prior treatments have essentially assumed that {eta} = 0. We perform one- and two-dimensional simulations and find that the growth of the central SMBH is very sensitive to the inclusion of the mass and momentum driving but is insensitive to the assumed mechanical efficiency. For example in representative calculations, the omission of momentum and mass feedback leads to a hundred-fold increase in the mass of the SMBH to over 10{sup 10} M{sub sun}. When allowance is made for momentum driving, the final SMBH mass is much lower and the wind efficiencies that lead to the most observationally acceptable results are relatively low with {epsilon}{sub w} {approx}< 10{sup -4}.

  11. On the efficient acceleration of clouds in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Waters, Tim; Proga, Daniel

    2016-07-01

    In the broad line region of active galactic nuclei (AGN), acceleration occurs naturally when a cloud condenses out of the hot confining medium due to the increase in line opacity as the cloud cools. However, acceleration by radiation pressure is not very efficient when the flux is time-independent, unless the flow is 1D. Here, we explore how acceleration is affected by a time-varying flux, as AGN are known to be highly variable. If the period of flux oscillations is longer than the thermal time-scale, we expect the gas to cool during the low flux state, and therefore line opacity should quickly increase. The cloud will receive a small kick due to the increased radiation force. We perform hydrodynamical simulations using ATHENA to confirm this effect and quantify its importance. We find that despite the flow becoming turbulent in 2D due to hydrodynamic instabilities, a 20 per cent modulation of the flux leads to a net increase in acceleration - by more than a factor of 2 - in both 1D and 2D. We show that this acceleration is sufficient to produce the observed line widths, although we only consider optically thin clouds. We discuss the implications of our results for photoionization modelling and reverberation mapping.

  12. THE NATURE OF OPTICALLY DULL ACTIVE GALACTIC NUCLEI IN COSMOS

    SciTech Connect

    Trump, Jonathan R.; Impey, Chris D.; Gabor, Jared M.; Taniguchi, Yoshi; Nagao, Tohru; Shioya, Yasuhiro; Brusa, Marcella; Civano, Francesca; Elvis, Martin; Kelly, Brandon C.; Huchra, John P.; Jahnke, Knud; Koekemoer, Anton M.; Salvato, Mara; Capak, Peter; Scoville, Nick Z.; Kartaltepe, Jeyhan S.; Lanzuisi, Giorgio; McCarthy, Patrick J.; Maineri, Vincenzo

    2009-11-20

    We present infrared, optical, and X-ray data of 48 X-ray bright, optically dull active galactic nuclei (AGNs) in the COSMOS field. These objects exhibit the X-ray luminosity of an AGN but lack broad and narrow emission lines in their optical spectrum. We show that despite the lack of optical emission lines, most of these optically dull AGNs are not well described by a typical passive red galaxy spectrum: instead they exhibit weak but significant blue emission like an unobscured AGN. Photometric observations over several years additionally show significant variability in the blue emission of four optically dull AGNs. The nature of the blue and infrared emission suggest that the optically inactive appearance of these AGNs cannot be caused by obscuration intrinsic to the AGNs. Instead, up to approx70% of optically dull AGNs are diluted by their hosts, with bright or simply edge-on hosts lying preferentially within the spectroscopic aperture. The remaining approx30% of optically dull AGNs have anomalously high f{sub X} /f{sub O} ratios and are intrinsically weak, not obscured, in the optical. These optically dull AGNs are best described as a weakly accreting AGN with a truncated accretion disk from a radiatively inefficient accretion flow.

  13. Active Galactic Nuclei:. Sources for Ultra High Energy Cosmic Rays

    NASA Astrophysics Data System (ADS)

    Biermann, P. L.; Becker, J. K.; Caramete, L.; Gergely, L.; Mariş, I. C.; Meli, A.; de Souza, V.; Stanev, T.

    Ultra high energy cosmic ray events presently show a spectrum, which we interpret here as galactic cosmic rays due to a starburst, in the radio galaxy Cen A which is pushed up in energy by the shock of a relativistic jet. The knee feature and the particles with energy immediately higher in galactic cosmic rays then turn into the bulk of ultra high energy cosmic rays. This entails that all ultra high energy cosmic rays are heavy nuclei. This picture is viable if the majority of the observed ultra high energy events come from the radio galaxy Cen A, and are scattered by intergalactic magnetic fields across much of the sky.

  14. Chemistry in the Molecular Disks of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Harada, Nanase; Herbst, Eric

    2010-06-01

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

  15. THE EVOLUTION OF ACTIVE GALACTIC NUCLEI AND THEIR SPINS

    SciTech Connect

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

    2013-10-01

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

  16. Obscuration-dependent Evolution of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Buchner, Johannes; Georgakakis, Antonis; Nandra, Kirpal; Brightman, Murray; Menzel, Marie-Luise; Liu, Zhu; Hsu, Li-Ting; Salvato, Mara; Rangel, Cyprian; Aird, James; Merloni, Andrea; Ross, Nicholas

    2015-04-01

    We aim to constrain the evolution of active galactic nuclei (AGNs) as a function of obscuration using an X-ray-selected sample of ~2000 AGNs from a multi-tiered survey including the CDFS, AEGIS-XD, COSMOS, and XMM-XXL fields. The spectra of individual X-ray sources are analyzed using a Bayesian methodology with a physically realistic model to infer the posterior distribution of the hydrogen column density and intrinsic X-ray luminosity. We develop a novel non-parametric method that allows us to robustly infer the distribution of the AGN population in X-ray luminosity, redshift, and obscuring column density, relying only on minimal smoothness assumptions. Our analysis properly incorporates uncertainties from low count spectra, photometric redshift measurements, association incompleteness, and the limited sample size. We find that obscured AGNs with N H > 1022 cm-2 account for {77}+4-5% of the number density and luminosity density of the accretion supermassive black hole population with L X > 1043 erg s-1, averaged over cosmic time. Compton-thick AGNs account for approximately half the number and luminosity density of the obscured population, and {38}+8-7% of the total. We also find evidence that the evolution is obscuration dependent, with the strongest evolution around N H ≈ 1023 cm-2. We highlight this by measuring the obscured fraction in Compton-thin AGNs, which increases toward z ~ 3, where it is 25% higher than the local value. In contrast, the fraction of Compton-thick AGNs is consistent with being constant at ≈35%, independent of redshift and accretion luminosity. We discuss our findings in the context of existing models and conclude that the observed evolution is, to first order, a side effect of anti-hierarchical growth.

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

    NASA Astrophysics Data System (ADS)

    Mao, Jirong; Kim, Minsun

    2016-09-01

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

  18. The dust covering factor in active galactic nuclei

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    The primary source of emission of active galactic nuclei (AGNs), the accretion disc, is surrounded by an optically and geometrically thick dusty structure (`the so-called dusty torus'). The infrared radiation emitted by the dust is nothing but a reprocessed fraction of the accretion disc emission, so the ratio of the torus to the AGN luminosity (Ltorus/LAGN) should corresponds to the fraction of the sky obscured by dust, i.e. the covering factor. We undertook a critical investigation of the Ltorus/LAGN as the dust covering factor proxy. Using state-of-the-art 3D Monte Carlo radiative transfer code, we calculated a grid of spectral energy distributions (SEDs) emitted by the clumpy two-phase dusty structure. With this grid of SEDs, we studied the relation between Ltorus/LAGN and the dust covering factor for different parameters of the torus. We found that in the case of type 1 AGNs the torus anisotropy makes Ltorus/LAGN underestimate low covering factors and overestimate high covering factors. In type 2 AGNs Ltorus/LAGN always underestimates covering factors. Our results provide a novel easy-to-use method to account for anisotropy and obtain correct covering factors. Using two samples from the literature, we demonstrated the importance of our result for inferring the obscured AGN fraction. We found that after the anisotropy is properly accounted for, the dust covering factors show very weak dependence on LAGN, with values in the range of ≈0.6-0.7. Our results also suggest a higher fraction of obscured AGNs at high luminosities than those found by X-ray surveys, in part owing to the presence of a Compton-thick AGN population predicted by population synthesis models.

  19. Statistics of Active Galactic Nuclei in Rich Clusters Revisited

    NASA Astrophysics Data System (ADS)

    Way, M. J.; Flores, R. A.; Quintana, H.

    1998-07-01

    Using the spectrophotometry of a large sample of galaxies in 19 Abell clusters, we have selected 42 candidate active galactic nuclei (AGNs) using the criteria used by Dressler and coworkers in their analysis of the statistics of 22 AGNs in 14 rich cluster fields, which are based on the equivalent width of [O II] 3727 Å, Hβ, and [O III] 5007 Å emission. We have then discriminated AGNs from H II region-like galaxies (hereafter H II galaxies) in the manner developed by Veilleux & Osterbrock using the additional information provided by Hα and [N II] 6583 Å or Hα and [S II] 6716 + 6731 Å emission, in order to test the reliability of the selection criteria used by Dressler and coworkers. We find that before we discriminate AGNs from H II galaxies, our sample is very similar to that of Dressler and coworkers and it leads to similar conclusions. However, we find that their method inevitably mixes H II galaxies with AGNs, even for the most luminous objects in our sample. We estimate a contamination of at least 38% at a formal 90% confidence level. Since the study of Dressler and coworkers, other authors have attempted to quantify the relative fraction of cluster-to-field AGNs and have reached similar conclusions, but they have used criteria similar to Dressler and coworkers to select AGNs (or have used the [O III] 5007 Å/Hβ flux ratio test that also mixes H II galaxies with AGNs). Our sample of true AGNs remains too small to reach statistically meaningful conclusions, therefore a new study with a more time-consuming method that includes the other lines will be required to quantify the true relative fraction of cluster-to-field AGNs.

  20. Probing the central regions of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Lohfink, Anne Maria

    Active Galactic Nuclei (AGN) are one of the key players in the Universe. Their energy output can strongly affect the growth of their host galaxy and can promote or suppress star formation on galactic scales. Most of the processes that determine the power of an AGN as well as the form in which that power is released take place in the immediate surroundings of its supermassive black hole, a region that is still not entirely understood. A comprehension of these inner regions is, however, crucial to any ultimate understanding of the AGN's vast influence. This dissertation explores these close-in environments of the black hole using two approaches: X-ray spectroscopy and variability studies. We begin by summarizing our current understanding of why AGN play such a significant role in galaxy formation. This is followed by a discussion of why X-ray spectroscopy is one of the best means to investigate them. We point out that, in particular, the X-ray reflection spectrum is interesting as it can directly probe parameters such as the black hole spin or the inclination of the accretion disk. Since the reflection spectrum is a broad band component, that usually only contributes a fraction of the total observed X-ray flux, the entire X-ray spectrum requires careful modeling. To perform such modeling and gain access to the parameters of the reflection spectrum, we first select a target in which the spectral decomposition is simplified by the absence of absorption - the Seyfert 1 galaxy Fairall 9. We apply a multi-epoch fitting method that uses more than one spectrum at a time to get the best possible results on the parameters of the reflection spectrum that are invariant on human timescales. This technique enables us to tightly constrain the reflection parameters and leads us to conclude that Fairall 9 most likely possesses a composite soft X-ray excess, consisting of blurred reflection and a separate component such as Comptonization. The reflection spectrum also provides a way

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

    SciTech Connect

    Donoso, E.; Yan, Lin; Stern, D.; Assef, R. J.

    2014-07-01

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

  2. Steps Toward Unveiling the True Population of Active Galactic Nuclei: Photometric Characterization of Active Galactic Nuclei in COSMOS

    NASA Astrophysics Data System (ADS)

    Schneider, Evan E.; Impey, Christopher D.; Trump, Jonathan R.; Salvato, Mara

    2013-04-01

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

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

    SciTech Connect

    Schneider, Evan E.; Impey, Christopher D.; Trump, Jonathan R.

    2013-04-01

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

  4. BAR EFFECTS ON CENTRAL STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY

    SciTech Connect

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

    2012-01-01

    Galactic bars are often suspected to be channels of gas inflow to the galactic center and to trigger central star formation and active galactic nucleus (AGN) activity. However, the current status on this issue based on empirical studies is unsettling, especially regarding AGNs. We investigate this question based on the Sloan Digital Sky Survey Data Release 7. From the nearby (0.01 < z < 0.05) bright (M{sub r} < -19) database, we have constructed a sample of 6658 relatively face-on late-type galaxies through visual inspection. We found 36% of them to have a bar. Bars are found to be more common in galaxies with earlier morphology. This makes sample selection critical. Parameter-based selections would miss a large fraction of barred galaxies of early morphology. Bar effects on star formation or AGNs are difficult to understand properly because multiple factors (bar frequency, stellar mass, black hole mass, gas contents, etc.) seem to contribute to them in intricate manners. In the hope of breaking these degeneracies, we inspect bar effects for fixed galaxy properties. Bar effects on central star formation seem higher in redder galaxies. Bar effects on AGNs on the other hand are higher in bluer and less massive galaxies. These effects seem more pronounced with increasing bar length. We discuss possible implications in terms of gas contents, bar strength, bar evolution, fueling timescale, and the dynamical role of supermassive black hole.

  5. Hidden Active Galactic Nuclei in Early-type Galaxies

    NASA Astrophysics Data System (ADS)

    Paggi, Alessandro; Fabbiano, Giuseppina; Civano, Francesca; Pellegrini, Silvia; Elvis, Martin; Kim, Dong-Woo

    2016-06-01

    We present a stacking analysis of the complete sample of early-type galaxies (ETGs) in the Chandra COSMOS (C-COSMOS) survey, to explore the nature of the X-ray luminosity in the redshift and stellar luminosity ranges 0\\lt z\\lt 1.5 and {10}9\\lt {L}K/{L}ȯ \\lt {10}13. Using established scaling relations, we subtract the contribution of X-ray binary populations to estimate the combined emission of hot ISM and active galactic nuclei (AGNs). To discriminate between the relative importance of these two components, we (1) compare our results with the relation observed in the local universe {L}X,{gas}\\propto {L}K4.5 for hot gaseous halos emission in ETGs, and (2) evaluate the spectral signature of each stacked bin. We find two regimes where the non-stellar X-ray emission is hard, consistent with AGN emission. First, there is evidence of hard, absorbed X-ray emission in stacked bins including relatively high z (∼1.2) ETGs with average high X-ray luminosity ({L}X {- {LMXB}}≳ 6× {10}42 {{erg}} {{{s}}}-1). These luminosities are consistent with the presence of highly absorbed “hidden” AGNs in these ETGs, which are not visible in their optical–IR spectra and spectral energy distributions. Second, confirming the early indication from our C-COSMOS study of X-ray detected ETGs, we find significantly enhanced X-ray luminosity in lower stellar mass ETGs ({L}K≲ {10}11{L}ȯ ), relative to the local {L}X,{gas}\\propto {L}K4.5 relation. The stacked spectra of these ETGs also suggest X-ray emission harder than expected from gaseous hot halos. This emission is consistent with inefficient accretion {10}-5-{10}-4{\\dot{M}}{Edd} onto {M}{BH}∼ {10}6-{10}8 {M}ȯ .

  6. APPLICATION OF THE DISK EVAPORATION MODEL TO ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Liu, B. F.

    2009-12-10

    The disk corona evaporation model extensively developed for the interpretation of observational features of black hole X-ray binaries (BHXRBs) is applied to active galactic nuclei (AGNs). Since the evaporation of gas in the disk can lead to its truncation for accretion rates less than a maximal evaporation rate, the model can naturally account for the soft spectrum in high-luminosity AGNs and the hard spectrum in low-luminosity AGNs. The existence of two different luminosity levels describing transitions from the soft to hard state and from the hard to soft state in BHXRBs, when applied to AGNs, suggests that AGNs can be in either spectral state within a range of luminosities. For example, at a viscosity parameter, alpha, equal to 0.3, the Eddington ratio from the hard-to-soft transition and from the soft-to-hard transition occurs at 0.027 and 0.005, respectively. The differing Eddington ratios result from the importance of Compton cooling in the latter transition, in which the cooling associated with soft photons emitted by the optically thick inner disk in the soft spectral state inhibits evaporation. When the Eddington ratio of the AGN lies below the critical value corresponding to its evolutionary state, the disk is truncated. With decreasing Eddington ratios, the inner edge of the disk increases to greater distances from the black hole with a concomitant increase in the inner radius of the broad-line region, R {sub BLR}. The absence of an optically thick inner disk at low luminosities (L) gives rise to region in the R {sub BLR}-L plane for which the relation R {sub BLR} propor to L {sup 1/2} inferred at high luminosities is excluded. As a result, a lower limit to the accretion rate is predicted for the observability of broad emission lines, if the broad-line region is associated with an optically thick accretion disk. Thus, true Seyfert 2 galaxies may exist at very low accretion rates/luminosities. The differences between BHXRBs and AGNs in the framework of

  7. Compton thick active galactic nuclei in Chandra surveys

    NASA Astrophysics Data System (ADS)

    Brightman, Murray; Nandra, Kirpal; Salvato, Mara; Hsu, Li-Ting; Aird, James; Rangel, Cyprian

    2014-09-01

    We present the results from an X-ray spectral analysis of active galactic nuclei (AGN) in the Chandra Deep Field-South, All-wavelength Extended Groth-strip International Survey (AEGIS)-Deep X-ray survey (XD) and Chandra-Cosmic Evolution Surveys (COSMOS), focusing on the identification and characterization of the most heavily obscured, Compton thick (CT, NH > 1024 cm-2) sources. Our sample is comprised of 3184 X-ray selected extragalactic sources, which has a high rate of redshift completeness (96.6 per cent), and includes additional spectroscopic redshifts and improved photometric redshifts over previous studies. We use spectral models designed for heavily obscured AGN which self-consistently include all major spectral signatures of heavy absorption. We validate our spectral fitting method through simulations, identify CT sources not selected through this method using X-ray colours and take considerations for the constraints on NH given the low count nature of many of our sources. After these considerations, we identify a total of 100 CT AGN with best-fitting NH > 1024 cm-2 and NH constrained to be above 1023.5 cm-2 at 90 per cent confidence. These sources cover an intrinsic 2-10 keV X-ray luminosity range of 1042-3 × 1045 erg s-1 and a redshift range of z = 0.1-4. This sample will enable characterization of these heavily obscured AGN across cosmic time and to ascertain their cosmological significance. These survey fields are sites of extensive multiwavelength coverage, including near-infrared Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) data and far-infrared Herschel data, enabling forthcoming investigations into the host properties of CT AGN. Furthermore, by using the torus models to test different covering factor scenarios, and by investigating the inclusion of the soft scattered emission, we find evidence that the covering factor of the obscuring material decreases with LX for all redshifts, consistent with the receding torus model

  8. Line-driven disk winds in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Proga, D.; Stone, J. M.; Kallman, T. R.

    2001-01-01

    We present the results of axisymmetric time-dependent hydrodynamic calculations of line-driven winds from accretion disks in active galactic nuclei (AGN). We assume the disk is flat, Keplerian, geometrically thin, and optically thick, radiating according to the α-disk prescription. The central engine of the AGN is a source of both ionizing X-rays and wind-driving ultraviolet (UV) photons. To calculate the radiation force, we take into account radiation from the disk and the central engine. The gas temperature and ionization state in the wind are calculated self-consistently from the photoionization and heating rate of the central engine. We find that a disk accreting onto a 10 8 M ⊙ yr -1 black hole at the rate of 1.8 M ⊙ yr -1 can launch a wind at ˜ 10 16 cm from the central engine. The X-rays from the central object are significantly attenuated by the disk atmosphere so they cannot prevent the local disk radiation from pushing matter away from the disk. However in the supersonic portion of the flow high above the disk, the X-rays can overionize the gas and decrease the wind terminal velocity. For a reasonable X-ray opacity, e.g., κ X = 40 g -1 cm 2, the disk wind can be accelerated by the central UV radiation to velocities of up to 15000 km s -1 at a distance of ˜ 10 17 cm from the central engine. The covering factor of the disk wind is ˜ 0.2. The wind is unsteady and consists of an opaque, slow vertical flow near the disk that is bounded on the polar side by a high-velocity, stream. A typical column density through the fast stream is a few 10 23 cm -2 so the stream is optically thin to the UV radiation. This low column density is precisely why gas can be accelerated to high velocities. The fast stream contributes nearly 100% to the total wind mass loss rate of 0.5 M ⊙ yr -1.

  9. New detections of Galactic molecular absorption systems toward ALMA calibrator sources

    NASA Astrophysics Data System (ADS)

    Ando, Ryo; Kohno, Kotaro; Tamura, Yoichi; Izumi, Takuma; Umehata, Hideki; Nagai, Hiroshi

    2016-02-01

    We report on Atacama Large Millimeter/submillimeter Array (ALMA) detections of molecular absorption lines in Bands 3, 6, and 7 toward four radio-loud quasars, which were observed as the bandpass and complex gain calibrators. The absorption systems, three of which are newly detected, are found to be Galactic origin. Moreover, HCO absorption lines toward two objects are detected, which almost doubles the number of HCO absorption samples in the Galactic diffuse medium. In addition, high HCO-to-H13CO+ column density ratios are found, suggesting that the interstellar media (ISM) observed toward the two calibrators are in photodissociation regions, which observationally illustrates the chemistry of diffuse ISM driven by ultraviolet (UV) radiation. These results demonstrate that calibrators in the ALMA Archive are potential sources for the quest for new absorption systems and for detailed investigation of the nature of the ISM.

  10. HST/COS OBSERVATIONS OF GALACTIC HIGH-VELOCITY CLOUDS: FOUR ACTIVE GALACTIC NUCLEUS SIGHT LINES THROUGH COMPLEX C

    SciTech Connect

    Shull, J. Michael; Stevans, Matthew; Danforth, Charles; Penton, Steven V.; Lockman, Felix J.; Arav, Nahum E-mail: matthew.stevans@colorado.edu E-mail: steven.penton@colorado.edu E-mail: arav@vt.edu

    2011-10-01

    We report ultraviolet spectra of Galactic high-velocity clouds (HVCs) in Complex C, taken by the Cosmic Origins Spectrograph (COS) on the Hubble Space Telescope (HST), together with new 21 cm spectra from the Green Bank Telescope. The wide spectral coverage and higher signal-to-noise ratio, compared to previous HST spectra, provide better velocity definition of the HVC absorption, additional ionization species (including high ions), and improved abundances in this halo gas. Complex C has a metallicity of 10%-30% solar and a wide range of ions, suggesting dynamical and thermal interactions with hot gas in the Galactic halo. Spectra in the COS medium-resolution G130M (1133-1468 A) and G160M (1383-1796 A) gratings detect ultraviolet absorption lines from eight elements in low-ionization states (O I, N I, C II, S II, Si II, Al II, Fe II, P II) and three elements in intermediate- and high-ionization states (Si III, Si IV, C IV, N V). Our four active galactic nucleus sight lines toward Mrk 817, Mrk 290, Mrk 876, and PG 1259+593 have high-velocity H I and O VI column densities, log N{sub Hi}= 19.39-20.05 and log N{sub Ovi}= 13.58-14.10, with substantial amounts of kinematically associated photoionized gas. The high-ion abundance ratios are consistent with cooling interfaces between photoionized and collisionally ionized gas: N(C IV)/N(O VI) {approx} 0.3-0.5, N(Si IV)/N(O VI) {approx} 0.05-0.11, N(N V)/N(O VI) {approx} 0.07-0.13, and N(Si IV)/N(Si III) {approx}0.2.

  11. GIANT GAMMA-RAY BUBBLES FROM FERMI-LAT: ACTIVE GALACTIC NUCLEUS ACTIVITY OR BIPOLAR GALACTIC WIND?

    SciTech Connect

    Su Meng; Slatyer, Tracy R.; Finkbeiner, Douglas P.

    2010-12-01

    Data from the Fermi-LAT reveal two large gamma-ray bubbles, extending 50{sup 0} above and below the Galactic center (GC), with a width of about 40{sup 0} in longitude. The gamma-ray emission associated with these bubbles has a significantly harder spectrum (dN/dE {approx} E {sup -2}) than the inverse Compton emission from electrons in the Galactic disk, or the gamma rays produced by the decay of pions from proton-interstellar medium collisions. There is no significant spatial variation in the spectrum or gamma-ray intensity within the bubbles, or between the north and south bubbles. The bubbles are spatially correlated with the hard-spectrum microwave excess known as the WMAP haze; the edges of the bubbles also line up with features in the ROSAT X-ray maps at 1.5-2 keV. We argue that these Galactic gamma-ray bubbles were most likely created by some large episode of energy injection in the GC, such as past accretion events onto the central massive black hole, or a nuclear starburst in the last {approx}10 Myr. Dark matter annihilation/decay seems unlikely to generate all the features of the bubbles and the associated signals in WMAP and ROSAT; the bubbles must be understood in order to use measurements of the diffuse gamma-ray emission in the inner Galaxy as a probe of dark matter physics. Study of the origin and evolution of the bubbles also has the potential to improve our understanding of recent energetic events in the inner Galaxy and the high-latitude cosmic ray population.

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

    SciTech Connect

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

    2013-08-10

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

  13. High-energy gamma-ray observations of active galaxies

    NASA Technical Reports Server (NTRS)

    Fichtel, Carl E.

    1994-01-01

    During the period from 1992 May to early 1992 November, the Energetic Gamma-Ray Experiment Telescope (EGRET) on board the Compton Gamma Ray Observatory obtained high-energy gamma-ray data for most of the sky. A total of 18 active galaxies have been seen with high certainty, and it is expected that more will be found in the data when a more thorough analysis is complete. All of those that have been seen are radio-loud quasars or BL Lacertae objects; most have already been identified as blazars. No Seyfert galaxies have been found thus far. If the spectra are represented as a power law in energy, spectral slopes ranging from approximately -1.7 to -2.4 are found. A wide range of z-values exits in the observed sample, eight having values in excess of 1.0. Time variations have been seen, with the timescale for a significant change being as short as days in at least one case. These results imply the existence of very large numbers of relativistic particles, probably close to the central object. Although a large extrapolation is required, their existence also suggests that these active galactic nuclei may be the source of the extragalactic cosmic rays.

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

    NASA Astrophysics Data System (ADS)

    Bartos, Imre

    2016-06-01

    Galactic nuclei are expected to harbor the densest population of stellar-mass black holes, accounting for as much as ∼ 2% of the mass of the nuclear stellar cluster. A significant fraction (∼ 30%) of these black holes can reside in binaries. We discuss the fate of the black hole binaries in active galactic nuclei, which get trapped in the inner region of the accretion disk around the central supermassive black hole. Binary black holes can migrate into and then rapidly merge within the disk. The binaries also accrete a significant amount of gas from the disk, potentially leading to detectable X-ray or gamma-ray emission.

  15. Centrifugally driven MHD-winds in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Camenzind, M.

    1986-02-01

    When the prime mover in quasars is a supermassive magnetized and rapidly rotating object, the centrifugal instability can drive strong MHD-winds away from the equatorial region and extract angular momentum and rotational energy from the central object. The author shows that the necessary magnetic fields are produced, when this central object has been formed from the central part of a galactic disc. The position of the light cylinder for these objects requires a relativistic description for the corresponding MHD-winds. The author discusses the relevant equations for any stationary and axisymmetric spacetime and derives explicitly the position of the Alfvén point in the flow. He finds that centrifugally driven winds from supermassive objects carry a Poynting flux comparable with the kinetic energy flux. In addition, the magnetic field structure in the open wind zone requires the existence of a global current topology, which might explain the necessary magnetic collimation for escaping jet material. As a result, centrifugally driven winds from rapidly rotating supermassive objects carry the energy necessary to power the non-thermal emission of BLR AGNs and the material required to fuel the broad emission line clouds and the thermal jets.

  16. PeV Neutrinos Observed by IceCube from Cores of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Stecker, Floyd W.

    2013-01-01

    I show that the high energy neutrino flux predicted to arise from active galactic nuclei cores can explain the PeV neutrinos detected by IceCube without conflicting with the constraints from the observed extragalactic cosmic-ray and gamma-ray backgrounds.

  17. Fermi/LAT Observations of Swift/BAT Seyfert Galaxies: On the Contribution of Radio-Quiet Active Galactic Nuclei to the Extragalactic gamma-Ray Background

    NASA Technical Reports Server (NTRS)

    Teng, Stacy H.; Mushotzky, Richard F.; Sambruna, Rita M.; Davis, David S.; Reynolds, Christopher S.

    2011-01-01

    We present the analysis of 2.1 years of Fermi Large Area Telescope (LAT) data on 491 Seyfert galaxies detected by the Swift Burst Alert Telescope (BAT) survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi first year catalog, are detected. Using Swift/BAT and radio 20 cm fluxes, we define a new radio-loudness parameter R(sub X,BAT) where radio-loud objects have logR(sub X,BAT) > -4.7. Based on this parameter, only radio-loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be approx.2x10(exp -11) photons/sq cm/s, approximately seven times lower than the observed flux of NGC 1068. Assuming a median redshift of 0.031, this implies an upper limit to the gamma-ray (1-100 GeV) luminosity of < approx.3x10(exp 41) erg/s. In addition, we identified 120 new Fermi/LAT sources near the Swift/BAT Seyfert galaxies with significant Fermi/LAT detections. A majority of these objects do not have Swift/BAT counterparts, but their possible optical counterparts include blazars, flat-spectrum radio quasars, and quasars.

  18. FERMI/LAT OBSERVATIONS OF SWIFT/BAT SEYFERT GALAXIES: ON THE CONTRIBUTION OF RADIO-QUIET ACTIVE GALACTIC NUCLEI TO THE EXTRAGALACTIC {gamma}-RAY BACKGROUND

    SciTech Connect

    Teng, Stacy H.; Mushotzky, Richard F.; Reynolds, Christopher S.; Sambruna, Rita M.; Davis, David S.

    2011-12-01

    We present the analysis of 2.1 years of Fermi Large Area Telescope (LAT) data on 491 Seyfert galaxies detected by the Swift Burst Alert Telescope (BAT) survey. Only the two nearest objects, NGC 1068 and NGC 4945, which were identified in the Fermi first year catalog, are detected. Using Swift/BAT and radio 20 cm fluxes, we define a new radio-loudness parameter R{sub X,BAT} where radio-loud objects have log R{sub X,BAT} > -4.7. Based on this parameter, only radio-loud sources are detected by Fermi/LAT. An upper limit to the flux of the undetected sources is derived to be {approx}2 Multiplication-Sign 10{sup -11} photons cm{sup -2} s{sup -1}, approximately seven times lower than the observed flux of NGC 1068. Assuming a median redshift of 0.031, this implies an upper limit to the {gamma}-ray (1-100 GeV) luminosity of {approx}< 3 Multiplication-Sign 10{sup 41} erg s{sup -1}. In addition, we identified 120 new Fermi/LAT sources near the Swift/BAT Seyfert galaxies with significant Fermi/LAT detections. A majority of these objects do not have Swift/BAT counterparts, but their possible optical counterparts include blazars, flat-spectrum radio quasars, and quasars.

  19. Studies of Low Luminosity Active Galactic Nuclei with Monte Carlo and Magnetohydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Hilburn, Guy Louis

    Results from several studies are presented which detail explorations of the physical and spectral properties of low luminosity active galactic nuclei. An initial Sagittarius A* general relativistic magnetohydrodynamic simulation and Monte Carlo radiation transport model suggests accretion rate changes as the dominant flaring method. A similar study on M87 introduces new methods to the Monte Carlo model for increased consistency in highly energetic sources. Again, accretion rate variation seems most appropriate to explain spectral transients. To more closely resolve the methods of particle energization in active galactic nuclei accretion disks, a series of localized shearing box simulations explores the effect of numerical resolution on the development of current sheets. A particular focus on numerically describing converged current sheet formation will provide new methods for consideration of turbulence in accretion disks.

  20. Masses of Black Holes in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Peterson, Bradley M.

    2003-01-01

    We present a progress report on a project whose goal is to improve both the precision and accuracy of reverberation-based black-hole masses. Reverberation masses appear to be accurate to a factor of about three, and the black-hole mass/bulge velocity dispersion (M-sigma) relationship appears to be the same in active and quiescent galaxies.

  1. Near Infrared Spectroscopy of Active Galactic Nuclei Using FSpec

    NASA Astrophysics Data System (ADS)

    Frechem, Joshua; Pessev, Peter

    2015-01-01

    Using data from the 2.3 meter Bok telescope on Kitt Peak and the FRANKENSpec spectrograph, we aim to investigate the circumnuclear region of over twenty active galaxies in the J, H, and K passbands in order to obtain high signal to noise spectra with reasonable investment of observing time. The sample is selected to cover a wide range of AGN types of activity in luminous nearby galaxies. The primary goal of this project was to sort and process the 9,000+ spectra, including dark subtraction, flat fielding, and creation of and application of bad pixel masks. The 2-D spectra were processed to a 1-D spectra and wavelength calibrated to reveal the exact wavelength of each peak in the spectra. Using standard stars is of utmost importance so the atmospheric lines can be corrected for and the data can be used for precise analysis. With the reduced and calibrated spectra, we measure the Paschen α, β, and γ Hydrogen lines, the Brackett γ Hydrogen line and the FeII line in the near infrared emitted from the circumnuclear regions of the galaxies. These data unveil details of what the environment is like in the area surrounding the supermassive black holes that are found in the heart of each of these galaxies.

  2. A study of ultraviolet absorption lines through the complete Galactic halo by the analysis of HST faint object spectrograph spectra of active Galactic nuclei, 1

    NASA Technical Reports Server (NTRS)

    Burks, Geoffrey S.; Bartko, Frank; Shull, J. Michael; Stocke, John T.; Sachs, Elise R.; Burbidge, E. Margaret; Cohen, Ross D.; Junkkarinen, Vesa T.; Harms, Richard J.; Massa, Derck

    1994-01-01

    The ultraviolet (1150 - 2850 A) spectra of a number of active galactic nuclei (AGNs) observed with the Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) have been used to study the properties of the Galactic halo. The objects that served as probes are 3C 273, PKS 0454-220, Pg 1211+143, CSO 251, Ton 951, and PG 1351+640. The equivalent widths of certain interstellar ions have been measured, with special attention paid to the C IV/C II and Si IV/Si II ratios. These ratios have been intercompared, and the highest values are found in the direction of 3C 273, where C IV/C II = 1.2 and Si IV/Si II greater than 1. These high ratios may be due to a nearby supernova remnant, rather than to ionized gas higher up in the Galactic halo. Our data give some support to the notion that QSO metal-line systems may arise from intervening galaxies which contain high supernova rates, galactic fountains, and turbulent mixing layers.

  3. Stability of narrow emission line clouds in active galactic nuclei

    SciTech Connect

    Mathews, W.G.; Veilleux, S.

    1989-01-01

    The effects of the lateral flow and Rayleigh-Taylor instabilities on clouds in the narrow-line region of active galaxies are considered using cloud densities and velocities based on observations. A simplified model for the lateral flow instability governed only by overpressures is discussed. The associated radiative acceleration is considered, and parameters describing the narrow-line region and the central nonstellar continuum are presented. It is shown that many otherwise acceptable narrow-line clouds are unstable to lateral flows, particularly if their column depths are small. It is argued that the most likely narrow-line clouds have column densities of about 10 to the 23rd/sq cm and that these clouds are accelerated by winds in the intercloud medium. Arguments are made against models in which narrow-line clouds move inward. 22 references.

  4. Astrophysical bags - A new paradigm for active galactic nuclei?

    NASA Technical Reports Server (NTRS)

    Wilson, Thomas L.

    1992-01-01

    Active galaxies are believed to consist of a compact nucleus, the standard model for which is a massive black hole or a cluster of black holes. A different paradigm is considered here, deriving from quark confinement theory in QCD. It is an 'astrophysical bag', modelled after the 'hadron bags' of particle physics which have already been studied in astrophysics as quark stars. Another interpretation of the cosmological constant in general relativity, and possibly a new quasar redshift formula, are introduced. As a highly-energetic object, this model may resolve the baryonic matter problem for fuelling AGN accretion processes which black hole paradigms cannot account for. Here, baryons, cosmic rays, and neutrinos are free.

  5. DOUBLE-PEAKED NARROW-LINE ACTIVE GALACTIC NUCLEI. II. THE CASE OF EQUAL PEAKS

    SciTech Connect

    Smith, K. L.; Shields, G. A.; Salviander, S.; Stevens, A. C.; Rosario, D. J. E-mail: shields@astro.as.utexas.edu E-mail: acs0196@mail.utexas.edu

    2012-06-10

    Active galactic nuclei (AGNs) with double-peaked narrow lines (DPAGNs) may be caused by kiloparsec-scale binary AGNs, bipolar outflows, or rotating gaseous disks. We examine the class of DPAGNs in which the two narrow-line components have closely similar intensity as being especially likely to involve disks or jets. Two spectroscopic indicators support this likelihood. For DPAGNs from Smith et al., the 'equal-peaked' objects (EPAGNs) have [Ne V]/[O III]ratios lower than for a control sample of non-double-peaked AGNs. This is unexpected for a pair of normal AGNs in a galactic merger, but may be consistent with [O III] emission from a rotating ring with relatively little gas at small radii. Also, [O III]/H{beta} ratios of the redshifted and blueshifted systems in the EPAGN are more similar to each other than in a control sample, suggestive of a single ionizing source and inconsistent with the binary interpretation.

  6. CO Line Emission from Compact Nuclear Starburst Disks around Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Armour, J. N.; Ballantyne, D. R.

    2012-06-01

    There is substantial evidence for a connection between star formation in the nuclear region of a galaxy and growth of the central supermassive black hole. Furthermore, starburst activity in the region around an active galactic nucleus (AGN) may provide the obscuration required by the unified model of AGNs. Molecular line emission is one of the best observational avenues to detect and characterize dense, star-forming gas in galactic nuclei over a range of redshift. This paper presents predictions for the carbon monoxide (CO) line features from models of nuclear starburst disks around AGNs. These small-scale (lsim 100 pc), dense and hot starbursts have CO luminosities similar to scaled-down ultra-luminous infrared galaxies and quasar host galaxies. Nuclear starburst disks that exhibit a pc-scale starburst and could potentially act as the obscuring torus show more efficient CO excitation and higher brightness temperature ratios than those without such a compact starburst. In addition, the compact starburst models predict strong absorption when J Upper >~ 10, a unique observational signature of these objects. These findings allow for the possibility that CO spectral line energy distributions (SLEDs) could be used to determine if starburst disks are responsible for the obscuration in z <~ 1 AGNs. Directly isolating the nuclear CO line emission of such compact regions around AGNs from galactic-scale emission will require high-resolution imaging or selecting AGN host galaxies with weak galactic-scale star formation. Stacking individual CO SLEDs will also be useful in detecting the predicted high-J features.

  7. Probing active galactic nuclei with H2O megamasers.

    PubMed Central

    Moran, J; Greenhill, L; Herrnstein, J; Diamond, P; Miyoshi, M; Nakai, N; Inque, M

    1995-01-01

    We describe the characteristics of the rapidly rotating molecular disk in the nucleus of the mildly active galaxy NGC4258. The morphology and kinematics of the disk are delineated by the point-like watervapor emission sources at 1.35-cm wavelength. High angular resolution [200 microas where as is arcsec, corresponding to 0.006 parsec (pc) at 6.4 million pc] and high spectral resolution (0.2 km.s-1 or nu/Deltanu = 1.4 x 10(6)) with the Very-Long-Baseline Array allow precise definition of the disk. The disk is very thin, but slightly warped, and is viewed nearly edge-on. The masers show that the disk is in nearly perfect Keplerian rotation within the observable range of radii of 0.13-0.26 pc. The approximately random deviations from the Keplerian rotation curve among the high-velocity masers are approximately 3.5 km.s-1 (rms). These deviations may be due to the masers lying off the midline by about +/-4 degrees or variations in the inclination of the disk by +/-4 degrees. Lack of systematic deviations indicates that the disk has a mass of <4 x 10(6) solar mass (M[symbol: see text]). The gravitational binding mass is 3.5 x 10(7) M[symbol: see text], which must lie within the inner radius of the disk and requires that the mass density be >4 x 10(9) M[symbol: see text].pc-3. If the central mass were in the form of a star cluster with a density distribution such as a Plummer model, then the central mass density would be 4 x 10(12) M[symbol: see text].pc-3. The lifetime of such a cluster would be short with respect to the age of the galaxy [Maoz, E. (1995) Astrophys. J. Lett. 447, L91-L94]. Therefore, the central mass may be a black hole. The disk as traced by the systemic velocity features is unresolved in the vertical direction, indicating that its scale height is <0.0003 pc (hence the ratio of thickness to radius, H/R, is <0.0025). For a disk in hydrostatic equilibrium the quadrature sum of the sound speed and Alfven velocity is <2.5 km.s-1, so that the temperature of

  8. A Mid-infrared Census of Star Formation Activity in Bolocam Galactic Plane Survey Sources

    NASA Astrophysics Data System (ADS)

    Dunham, Miranda K.; Robitaille, Thomas P.; Evans, Neal J., II; Schlingman, Wayne M.; Cyganowski, Claudia J.; Urquhart, James

    2011-04-01

    We present the results of a search for mid-infrared signs of star formation activity in the 1.1 mm sources in the Bolocam Galactic Plane Survey (BGPS). We have correlated the BGPS catalog with available mid-IR Galactic plane catalogs based on the Spitzer Space Telescope GLIMPSE legacy survey and the Midcourse Space Experiment (MSX) Galactic plane survey. We find that 44% (3712 of 8358) of the BGPS sources contain at least one mid-IR source, including 2457 of 5067 (49%) within the area where all surveys overlap (10° < ell < 65°). Accounting for chance alignments between the BGPS and mid-IR sources, we conservatively estimate that 20% of the BPGS sources within the area where all surveys overlap show signs of active star formation. We separate the BGPS sources into four groups based on their probability of star formation activity. Extended Green Objects and Red MSX Sources make up the highest probability group, while the lowest probability group is comprised of "starless" BGPS sources which were not matched to any mid-IR sources. The mean 1.1 mm flux of each group increases with increasing probability of active star formation. We also find that the "starless" BGPS sources are the most compact, while the sources with the highest probability of star formation activity are on average more extended with large skirts of emission. A subsample of 280 BGPS sources with known distances demonstrates that mass and mean H2 column density also increase with probability of star formation activity.

  9. MID-INFRARED SPECTRAL INDICATORS OF STAR FORMATION AND ACTIVE GALACTIC NUCLEUS ACTIVITY IN NORMAL GALAXIES

    SciTech Connect

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

    2010-08-20

    We investigate the use of mid-infrared (MIR) polycyclic aromatic hydrocarbon (PAH) bands, the continuum, and emission lines as probes of star formation (SF) and active galactic nucleus (AGN) activity in a sample of 100 'normal' and local (z {approx} 0.1) emission-line galaxies. The MIR spectra were obtained with the Spitzer Space Telescope Infrared Spectrograph as part of the Spitzer-SDSS-GALEX Spectroscopic Survey, which includes multi-wavelength photometry from the ultraviolet to the far-infrared and optical spectroscopy. The continuum and features were extracted using PAHFIT, a decomposition code which we find to yield PAH equivalent widths (EWs) up to {approx}30 times larger than the commonly used spline methods. Despite the lack of extreme objects in our sample (such as strong AGNs, low-metallicity galaxies, or ULIRGs), we find significant variations in PAH, continuum, and emission-line properties, and systematic trends between these MIR properties and optically derived physical properties, such as age, metallicity, and radiation field hardness. We revisit the diagnostic diagram relating PAH EWs and [Ne II]12.8 {mu}m/[O IV]25.9 {mu}m line ratios and find it to be in much better agreement with the standard optical SF/AGN classification than when spline decompositions are used, while also potentially revealing obscured AGNs. The luminosity of individual PAH components, of the continuum, and, with poorer statistics, of the neon emission lines and molecular hydrogen lines are found to be tightly correlated to the total infrared (TIR) luminosity, making individual MIR components good gauges of the total dust emission in SF galaxies. Like the TIR luminosity, these individual components can be used to estimate dust attenuation in the UV and in H{alpha} lines based on energy balance arguments. We also propose average scaling relations between these components and dust-corrected, H{alpha}-derived SF rates.

  10. DUST IN ACTIVE GALACTIC NUCLEI: ANOMALOUS SILICATE TO OPTICAL EXTINCTION RATIOS?

    SciTech Connect

    Lyu, Jianwei; Hao, Lei; Li, Aigen

    2014-09-01

    Dust plays a central role in the unification theory of active galactic nuclei (AGNs). However, little is known about the nature (e.g., size, composition) of the dust that forms a torus around the AGN. In this Letter, we report a systematic exploration of the optical extinction (A{sub V} ) and the silicate absorption optical depth (Δτ{sub 9.7}) of 110 type 2 AGNs. We derive A{sub V} from the Balmer decrement based on the Sloan Digital Sky Survey data, and Δτ{sub 9.7} from the Spitzer/InfraRed Spectrograph data. We find that with a mean ratio of (A{sub V} /Δτ{sub 9.7}) ≲ 5.5, the optical-to-silicate extinction ratios of these AGNs are substantially lower than that of the Galactic diffuse interstellar medium (ISM) for which A{sub V} /Δτ{sub 9.7} ≈ 18.5. We argue that the anomalously low A{sub V} /Δτ{sub 9.7} ratio could be due to the predominance of larger grains in the AGN torus compared to that in the Galactic diffuse ISM.

  11. A ∼ 3.8 hr PERIODICITY FROM AN ULTRASOFT ACTIVE GALACTIC NUCLEUS CANDIDATE

    SciTech Connect

    Lin, Dacheng; Irwin, Jimmy A.; Godet, Olivier; Webb, Natalie A.; Barret, Didier

    2013-10-10

    Very few galactic nuclei are found to show significant X-ray quasi-periodic oscillations (QPOs). After carefully modeling the noise continuum, we find that the ∼3.8 hr QPO in the ultrasoft active galactic nucleus candidate 2XMM J123103.2+110648 was significantly detected (∼5σ) in two XMM-Newton observations in 2005, but not in the one in 2003. The QPO root mean square (rms) is very high and increases from ∼25% in 0.2-0.5 keV to ∼50% in 1-2 keV. The QPO probably corresponds to the low-frequency type in Galactic black hole X-ray binaries, considering its large rms and the probably low mass (∼10{sup 5} M {sub ☉}) of the black hole in the nucleus. We also fit the soft X-ray spectra from the three XMM-Newton observations and find that they can be described with either pure thermal disk emission or optically thick low-temperature Comptonization. We see no clear X-ray emission from the two Swift observations in 2013, indicating lower source fluxes than those in XMM-Newton observations.

  12. Related investigations on the physics of high energy emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Margon, Bruce

    1991-01-01

    The Final Technical Report on a number of related investigations on the physics of high energy emission from active galactic nuclei, such as Seyfert galaxies and quasi-stellar objects is presented. The chief conclusions of the work are briefly described, and citations to the papers supported by this grant and published in the refereed scientific literature are provided. Areas of research included: 'warm' galaxies observed in x rays; x ray/infrared correlations in galaxies; the contribution of active galaxies to the cosmic x ray background radiation; and an unusual x ray emitting starburst galaxy.

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

    NASA Astrophysics Data System (ADS)

    Lyu, Yang; Liu, Xin

    2016-08-01

    One percent of redshift z ˜ 0.1 Active Galactic Nuclei (AGNs) show velocity splitting of a few hundred km s-1 in the narrow emission lines in spatially integrated spectra. Such line profiles have been found to arise from the bulk motion of ionized gas clouds associated with galactic-scale outflows, merging pairs of galaxies each harboring a supermassive black hole (SMBH), and/or galactic-scale disk rotation. It remains unclear, however, how the frequency of narrow-line velocity splitting may depend on AGN luminosity. Here we study the correlation between the fraction of Type 2 AGNs with double-peaked narrow emission lines and AGN luminosity as indicated by [O III]λ5007 emission-line luminosity L[O III]. We combine the sample of Liu et al. (2010a) at z ˜ 0.1 with a new sample of 178 Type 2 AGNs with double-peaked [O III] emission lines at z ˜ 0.5. We select the new sample from a parent sample of 2089 Type 2 AGNs from the SDSS-III/Baryon Oscillation Spectroscopic Survey. We find a statistically significant (˜4.2σ) correlation between L[O III] and the fraction of objects that exhibit double-peaked narrow emission lines among all Type 2 AGNs, corrected for selection bias and incompleteness due to [O III] line width, equivalent width, splitting velocity, and/or equivalent width ratio between the two velocity components. Our result suggests that galactic-scale outflows and/or merging pairs of SMBHs are more prevalent in more powerful AGNs, although spatially resolved follow up observations are needed to resolve the origin(s) for the narrow-line velocity splitting for individual AGNs.

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

    SciTech Connect

    Olsen, Karen P.; Rasmussen, Jesper; Toft, Sune; Zirm, Andrew W.

    2013-02-10

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

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

    NASA Astrophysics Data System (ADS)

    Vollmer, B.; Davies, R. I.

    2013-08-01

    Galactic gas-gas collisions involving a turbulent multiphase interstellar medium (ISM) share common ISM properties: dense extraplanar gas visible in CO, large linewidths (≳50 km s-1), strong mid-infrared H2 line emission, low star formation activity, and strong radio continuum emission. Gas-gas collisions can occur in the form of ram pressure stripping caused by the rapid motion of a spiral galaxy within the intracluster medium, galaxy head-on collisions, compression of the intragroup gas and/or galaxy ISM by an intruder galaxy which flies through the galaxy group at a high velocity, or external gas accretion on an existing gas torus in a galactic center. We suggest that the common theme of all these gas-gas interactions is adiabatic compression of the ISM leading to an increase of the turbulent velocity dispersion of the gas. The turbulent gas clouds are then overpressured and star formation is quenched. Within this scenario we developed a model for turbulent clumpy gas disks where the energy to drive turbulence is supplied by external infall or the gain of potential energy by radial gas accretion within the disk. The cloud size is determined by the size of a continuous (C-type) shock propagating in dense molecular clouds with a low ionization fraction at a given velocity dispersion. We give expressions for the expected volume and area filling factors, mass, density, column density, and velocity dispersion of the clouds. The latter is based on scaling relations of intermittent turbulence whose open parameters are estimated for the circumnuclear disk in the Galactic center. The properties of the model gas clouds (~0.1 pc, ~100 M⊙, Δv ≳ 6 km s-1) and the external mass accretion rate necessary for the quenching of the star formation rate due to adiabatic compression (Ṁ ~ 1-10 M⊙ yr-1) are consistent with those derived from high-resolution H2 2.12 μm line observations. Based on these findings, a scenario for the evolution of gas tori in galactic centers is

  16. An Axisymmetric, Hydrodynamical Model for the Torus Wind in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Dorodnitsyn, A.; Kallman, T.; Proga, D.

    2008-01-01

    We report on time-dependent axisymmetric simulations of an X-ray-excited flow from a parsec-scale, rotating, cold torus around an active galactic nucleus. Our simulations account for radiative heating and cooling and radiation pressure force. The simulations follow the development of a broad biconical outflow induced mainly by X-ray heating. We compute synthetic spectra predicted by our simulations. The wind characteristics and the spectra support the hypothesis that a rotationally supported torus can serve as the source of a wind which is responsible for the warm absorber gas observed in the X-ray spectra of many Seyfert galaxies.

  17. On the origin of power-law X-ray spectra of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Schlosman, I.; Shaham, J.; Shaviv, G.

    1984-01-01

    In the present analytical model for a power law X-ray continuum production in active galactic nuclei, the dissipation of turbulent energy flux above the accretion disk forms an optically thin transition layer with an inverted temperature gradient. The emitted thermal radiation has a power law spectrum in the 0.1-100 keV range, with a photon energy spectral index gamma of about 0.4-1.0. Thermal X-ray contribution from the layer is 5-10 percent of the total disk luminosity. The gamma value of 0.75 is suggested as a 'natural' power law index for Seyfert galaxies and QSOs.

  18. CCD Observing and Dynamical Time Series Analysis of Active Galactic Nuclei.

    NASA Astrophysics Data System (ADS)

    Nair, Achotham Damodaran

    1995-01-01

    The properties, working and operations procedure of the Charge Coupled Device (CCD) at the 30" telescope at Rosemary Hill Observatory (RHO) are discussed together with the details of data reduction. Several nonlinear techniques of time series analysis, based on the behavior of the nearest neighbors, have been used to analyze the time series of the quasar 3C 345. A technique using Artificial Neural Networks based on prediction of the time series is used to study the dynamical properties of 3C 345. Finally, a heuristic model for variability of Active Galactic Nuclei is discussed.

  19. THE PREVALENCE OF NARROW OPTICAL Fe II EMISSION LINES IN TYPE 1 ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Dong Xiaobo; Wang Jianguo; Wang Tinggui; Wang Huiyuan; Zhou Hongyan; Ho, Luis C.; Fan Xiaohui

    2010-10-01

    From detailed spectral analysis of a large sample of low-redshift active galactic nuclei (AGNs) selected from the Sloan Digital Sky Survey, we demonstrate-statistically for the first time-that narrow optical Fe II emission lines, both permitted and forbidden, are prevalent in type 1 AGNs. Remarkably, these optical lines are completely absent in type 2 AGNs, across a wide luminosity range, from Seyfert 2 galaxies to type 2 quasars. We suggest that the narrow Fe II-emitting gas is confined to a disk-like geometry in the innermost regions of the narrow-line region on physical scales smaller than the obscuring torus.

  20. Disk-Corona Model of Active Galactic Nuclei with Nonthermal Pairs

    NASA Technical Reports Server (NTRS)

    Tsuruta, Sachiko; Kellen, Michael

    1995-01-01

    As a promising model for the X-ray emission from radio-quiet quasars and Seyfert 1 nuclei, we present a nonthermal disk-corona model, where soft photons from a disk are Comptonized by the nonthermal electron-positron pairs in a coronal region above the disk. Various characteristics of our model are qualitatively similar to the homogeneous, spherical, nonthermal pair models previously studied, but the important difference is that in our disk-corona model gamma-ray depletion is far more efficient, and, moreover, the gamma-ray annihilation line is much less prominent. Consequently, this model naturally satisfies the observed constraints on active galactic nuclei.

  1. Optical evidence for the unification of active galactic nuclei and quasi-stellar objects.

    PubMed Central

    Miller, J S

    1995-01-01

    There is a variety of optical evidence for some unification of different types of active galactic nuclei and quasi-stellar objects (QSOs). The case is very strong for the unification of at least some Seyfert galaxies, where polarization data show that the type assigned to the Seyfert galaxy must depend on viewing direction. It has been proposed that Fanaroff-Riley type 2 (FR2) radio galaxies are quasars seen in a direction from which the quasar is obscured, and there is some limited direct evidence for this picture. The broad absorption line QSOs may be normal QSOs seen from a special direction. Some of the sources observed to have high luminosities in the far infrared could be obscured QSOs and active nuclei. Mergers and interactions are likely to play an important role in nuclear activity, and active galaxies and QSOs could change their apparent types through these encounters followed by subsequent evolution. PMID:11607611

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

    NASA Astrophysics Data System (ADS)

    Serafinelli, R.; Vagnetti, F.; Middei, R.

    2016-02-01

    The variability of the X-Ray spectra of active galactic nuclei (AGN) usually includes a change of the spectral slope. This has been investigated for a small sample of local AGNs by Sobolewska and Papadakis [1], who found that slope variations are well correlated with flux variations, and that the spectra are typically steeper in the bright phase (softer when brighter behaviour). Not much information is available for the spectral variability of high-luminosity AGNs and quasars. In order to investigate this phenomenon, we use data from the XMM-Newton Serendipitous Source Catalogue, Data Release 5, which contains X- Ray observations for a large number of active galactic nuclei in a wide luminosity and redshift range, for several different epochs. This allows to perform an ensemble analysis of the spectral variability for a large sample of quasars. We quantify the spectral variability through the spectral variability parameter β, defined by Trevese and Vagnetti [2] as the ratio between the change in spectral slope and the corresponding logarithmic flux variation. We find that the spectral variability of quasars has a softer when brighter behaviour, similarly to local AGNs.

  3. Neutrino-heated stars and broad-line emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Macdonald, James; Stanev, Todor; Biermann, Peter L.

    1991-01-01

    Nonthermal radiation from active galactic nuclei indicates the presence of highly relativistic particles. The interaction of these high-energy particles with matter and photons gives rise to a flux of high-energy neutrinos. In this paper, the influence of the expected high neutrino fluxes on the structure and evolution of single, main-sequence stars is investigated. Sequences of models of neutrino-heated stars in thermal equilibrium are presented for masses 0.25, 0.5, 0.8, and 1.0 solar mass. In addition, a set of evolutionary sequences for mass 0.5 solar mass have been computed for different assumed values for the incident neutrino energy flux. It is found that winds driven by the heating due to high-energy particles and hard electromagnetic radiation of the outer layers of neutrino-bloated stars may satisfy the requirements of the model of Kazanas (1989) for the broad-line emission clouds in active galactic nuclei.

  4. Interpreting Broad Double-Peaked Emission Lines in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Halpern, Jules; Chen, Kaiyou

    1999-01-01

    The principal objectives of this project were to probe the inner regions of active galactic nuclei and to test general relativity in the strong-field limit. The approach takes advantage of broad atomic line emission observed from material deep in the potential well of an active galactic nucleus which contains key information as to the physics of the system. Line profiles in a wide range of wavebands from optical to X-ray have provided compelling evidence of the existence of a relativistic accretion disk around a supermassive black hole in a number of galaxies. The simplest model posits a geometrically thin disk in Keplerian orbit, with general relativistic effects in evidence. This model is the point of departure for the proposed work. We developed a high-performance numerical code to calculate photon trajectories in a Schwarzschild or Kerr metric and implemented it on parallel supercomputers. This code includes a general purpose ray tracer that calculates line profiles, light curves, and other observable quantities for a wide variety of emitter configurations. The versatility comes from the fact that the ray tracing algorithm does not depend on any symmetries regarding emitter locations. The speed comes from parallel implementation which enables us to sample hitherto unattainable volumes of disk model parameter space. During the period 1 March 1997 through 28 February 1998, two papers, supported in whole or in part by this grant, were published in refereed journals. They are reproduced in their entirety in the next two sections of this report.

  5. Analysis of nearly simultaneous x-ray and optical observations of active galactic nuclei

    SciTech Connect

    Webb, J.R.

    1988-01-01

    Rosemary Hill optical and EINSTEIN X-ray observations of a sample of 36 galactic nuclei (AGN) were reduced and analyzed. Seventy-two x-ray observations of these sources were reduced, nineteen of which yielded spectral information. Of these spectra observations, significant hydrogen column densities above the galactic value were required for nine of the active galactic nuclei. X-ray variability was detected in eight of the eleven sources which were observed more than once by EINSTEIN. Correlations between the x-ray and optical luminosities were investigated using the Jefferys method of least squares. This method allows for errors in both variables. The results indicate a strong correlation between the x-ray and optical luminosities for the entire sample. Division of the sample into groups with similar optical variability characteristics show that the less violently violent variable AGN are more highly correlated than the violently variable blazars. Infrared and radio observations were combined with the x-ray and optical observations of six AGN. These sources were modelled in terms of the synchrotron-self-Compton model. The turnover frequency falls between the infrared and radio data and reliable estimates of this parameter are difficult to estimate. Therefore the results were found as a function of the turnover frequency. Four sources required relativistic bulk motion or beaming. Multifrequency spectra made at different times for one individual source, 0235+164, required different amounts of beaming to satisfy the x-ray observations. Sizes of the emitting regions for the sources modelled ranged from 0.5 parsec to 1.0 parsec.

  6. Galactic Winds

    NASA Astrophysics Data System (ADS)

    Veilleux, Sylvain

    Galactic winds have become arguably one of the hottest topics in extragalactic astronomy. This enthusiasm for galactic winds is due in part to the detection of winds in many, if not most, high-redshift galaxies. Galactic winds have also been invoked by theorists to (1) suppress the number of visible dwarf galaxies and avoid the "cooling catastrophe" at high redshift that results in the overproduction of massive luminous galaxies, (2) remove material with low specific angular momentum early on and help enlarge gas disks in CDM + baryons simulations, (3) reduce the dark mass concentrations in galaxies, (4) explain the mass-metallicity relation of galaxies from selective loss of metal-enriched gas from smaller galaxies, (5) enrich and "preheat" the ICM, (6) enrich the IGM without disturbing the Lyαforest significantly, and (7) inhibit cooling flows in galaxy clusters with active cD galaxies. The present paper highlights a few key aspects of galactic winds taken from a recent ARAA review by Veilleux, Cecil, &Bland-Hawthorn (2005; herafter VCBH). Readers interested in a more detailed discussion of this topic are encouraged to refer to the original ARAA article.

  7. MID-INFRARED SELECTION OF ACTIVE GALACTIC NUCLEI WITH THE WIDE-FIELD INFRARED SURVEY EXPLORER. I. CHARACTERIZING WISE-SELECTED ACTIVE GALACTIC NUCLEI IN COSMOS

    SciTech Connect

    Stern, Daniel; Assef, Roberto J.; Eisenhardt, Peter; Benford, Dominic J.; Blain, Andrew; Cutri, Roc; Griffith, Roger L.; Jarrett, T. H.; Masci, Frank; Tsai, Chao-Wei; Yan, Lin; Dey, Arjun; Lake, Sean; Petty, Sara; Wright, E. L.; Stanford, S. A.; Harrison, Fiona; Madsen, Kristin

    2012-07-01

    The Wide-field Infrared Survey Explorer (WISE) is an extremely capable and efficient black hole finder. We present a simple mid-infrared color criterion, W1 - W2 {>=} 0.8 (i.e., [3.4]-[4.6] {>=}0.8, Vega), which identifies 61.9 {+-} 5.4 active galactic nucleus (AGN) candidates per deg{sup 2} to a depth of W2 {approx} 15.0. This implies a much larger census of luminous AGNs than found by typical wide-area surveys, attributable to the fact that mid-infrared selection identifies both unobscured (type 1) and obscured (type 2) AGNs. Optical and soft X-ray surveys alone are highly biased toward only unobscured AGNs, while this simple WISE selection likely identifies even heavily obscured, Compton-thick AGNs. Using deep, public data in the COSMOS field, we explore the properties of WISE-selected AGN candidates. At the mid-infrared depth considered, 160 {mu}Jy at 4.6 {mu}m, this simple criterion identifies 78% of Spitzer mid-infrared AGN candidates according to the criteria of Stern et al. and the reliability is 95%. We explore the demographics, multiwavelength properties and redshift distribution of WISE-selected AGN candidates in the COSMOS field.

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

    SciTech Connect

    Yoast-Hull, Tova M.; Zweibel, Ellen G.; Gallagher III, J. S.; Everett, John E.

    2014-01-10

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

  9. New active galactic nuclei among the INTEGRAL and SWIFT X-ray sources

    NASA Astrophysics Data System (ADS)

    Burenin, R. A.; Mescheryakov, A. V.; Revnivtsev, M. G.; Sazonov, S. Yu.; Bikmaev, I. F.; Pavlinsky, M. N.; Sunyaev, R. A.

    2008-06-01

    We present the results of our optical identifications of a set of X-ray sources from the INTEGRAL and SWIFT all-sky surveys. The optical data have been obtained with the 1.5-m Russian-Turkish Telescope (RTT-150). Nine X-ray sources have been identified with active galactic nuclei (AGNs). Two of them are located in the nearby spiral galaxies MCG-01-05-047 and NGC 973 seen almost edge-on. One source, IGR J16562-3301, is probably a BL Lac object (blazar). The remaining AGNs are observed as the starlike nuclei of spiral galaxies whose spectra exhibit broad emission lines. The relation between the hard X-ray (17-60 keV) luminosity and the [O III] 5007 line luminosity, log L x/ L [O III] ≈ 2.1, holds good for most of the AGNs detected in hard X rays. However, the luminosities of some AGNs deviate from this relation. The fraction of such objects can reach ˜20%. In particular, the [O III] line flux is lower for two nearby edge-on spiral galaxies. This can be explained by the effect of absorption in the galactic disks.

  10. THE FIRST HARD X-RAY POWER SPECTRAL DENSITY FUNCTIONS OF ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    Shimizu, T. Taro; Mushotzky, Richard F.

    2013-06-10

    We present results of our power spectral density (PSD) analysis of 30 active galactic nuclei (AGNs) using the 58 month light curves from Swift's Burst Alert Telescope (BAT) in the 14-150 keV band. PSDs were fit using a Monte Carlo based algorithm to take into account windowing effects and measurement error. All but one source were found to be fit very well using an unbroken power law with a slope of {approx} - 1, consistent at low frequencies with previous studies in the 2-10 keV band, with no evidence of a break in the PSD. For five of the highest signal-to-noise ratio sources, we tested the energy dependence of the PSD and found no significant difference in the PSD at different energies. Unlike previous studies of X-ray variability in AGNs, we do not find any significant correlations between the hard X-ray variability and different properties of the AGN including luminosity and black hole mass. The lack of break frequencies and correlations seem to indicate that AGNs are similar to the high state of Galactic black holes.

  11. Ion-heated thermal Comptonization models and x-ray spectral correlations in active galactic nuclei

    SciTech Connect

    Dermer, C.D.

    1989-11-01

    Recent Ginga observations of the Seyfert 1 galaxies NGC 4051 and MCG 6-30-15 show a positive correlation between the 2-10 keV luminosity and photon spectral index {alpha}. Similar behavior has also been reported in Exosat and Einstein observations of other active galactic nuclei, and is suggested in hard x-ray low-state data of the galactic black-hole candidate Cygnus X-1. A two-temperature thermal Comptonization model with internal soft-photon production provides a simple explanation for this correlation. The electron temperature, determined by a balance between ion heating and radiative cooling, decreases in response to an enhancement of the soft photon flux, resulting in a softening of the spectrum and an increase in the soft x-ray luminosity. The bulk of the soft photons are produced through pion production in collisions between the hot ions. Pivoting of the spectrum at photon energies {var epsilon} > 50 keV is a consequence of variations in the ion temperature. An important test of the model would be time correlations between soft and hard x-ray bands. 17 refs., 9 figs., 1 tab.

  12. Analysis of nearly simultaneous X-ray and optical observations of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Webb, James Raymond

    Rosemary Hill optical and EINSTEIN X-ray observations of a sample of 36 active galactic nuclei (AGN) were reduced and analyzed. Seventy-two X-ray observations of these sources were reduced, nineteen of which yielded spectral information. Of these spectral observations, significant hydrogen column densities above the galactic value were required for nine of the eleven sources which were observed more than once by EINSTEIN. Correlations between the X-ray and optical luminosities were investigated using the Jefferys method of least squares. This method allows for errors in both variables. The results indicate a strong correlation between the X-ray and optical luminosities for the entire sample. Division of the sample into groups with similar optical variability characteristics show that the less violently violent variable AGN are more highly correlated than the violently variable blazars. Infrared and radio observations were combined with the X-ray and optical observations of six AGN. These sources were modelled in terms of the synchrotron-self-Compton model. The turnover frequency falls between the infrared and radio data and reliable estimates of this parameter are difficult to estimate. Therefore the results were found as a function of the turnover frequency. Four sources required relativistic bulk motion or beaming. Multifrequency spectra made at different times for one individual source, 0235+164, required different amounts of beaming to satisfy the X-ray observations. Sizes of the emitting regions for the sources modelled ranged from 0.5 parsec to 1.0 parsec.

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

    SciTech Connect

    Collaboration, The Pierre auger

    2007-12-01

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

  14. Gamma-ray blazars and active galactic nuclei seen by the Fermi-LAT

    NASA Astrophysics Data System (ADS)

    Lott, B.; Cavazzuti, E.; Ciprini, S.; Cutini, S.; Gasparrini, D.

    2015-03-01

    The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected with a test statistic (TS) greater than 25 using the first 4 years of data. The 3LAC includes 1591 AGNs located at high Galactic latitudes, |b| > 10 (with 28 duplicate associations, thus corresponding to 1563 gamma-ray sources among 2192 sources in the 3FGL catalog), a 71% increase over the second catalog based on 2 years of data. A very large majority of these AGNs (98%) are blazars. About half of the newly detected blazars are of unknown type, i.e., they lack spectroscopic information of sufficient quality to determine the strength of their emission lines. The general properties of the 3LAC sample confirm previous findings from earlier catalogs, but some new subclasses (e.g., intermediate- and high-synchrotron-peaked FSRQs) have now been significantly detected.

  15. Consequences of hot gas in the broad line region of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Kallman, T.; Mushotzky, R.

    1985-01-01

    Models for hot gas in the broad line region of active galactic nuclei are discussed. The results of the two phase equilibrium models for confinement of broad line clouds by Compton heated gas are used to show that high luminosity quasars are expected to show Fe XXVI L alpha line absorption which will be observed with spectrometers such as those planned for the future X-ray spectroscopy experiments. Two phase equilibrium models also predict that the gas in the broad line clouds and the confining medium may be Compton thick. It is shown that the combined effects of Comptonization and photoabsorption can suppress both the broad emission lines and X-rays in the Einstein and HEAO-1 energy bands. The observed properties of such Compton thick active galaxies are expected to be similar to those of Seyfert 2 nuclei. The implications for polarization and variability are also discussed.

  16. Galactic cosmic ray flux in the mid of 1700 from 44Ti activity of Agen meteorite

    NASA Astrophysics Data System (ADS)

    Taricco, Carla; Sinha, Neeharika; Bhandari, Narendra; Colombetti, Paolo; Mancuso, Salvatore; Rubinetti, Sara; Barghini, Dario

    2016-04-01

    Cosmogenic isotopes produced by galactic cosmic rays (GCR) in meteorites offer the opportunity to reveal the heliospheric magnetic field modulation in the interplanetary space between heliocentric distances of 1 and 3 AU. We present the gamma-activity measurement of Agen meteorite, a H5 chondrite that fell on September 5, 1814 in Aquitaine, France. Its 44Ti activity reflects GCR flux integrated since the mid of 1700 to the time of fall and confirms the decreasing trend of GCR flux that we previously suggested on the basis of measurements of other meteorites which fell in the last 250 years as well as the centennial modulation of GCR due to the Gleissberg solar cycle This result was obtained thanks to the high-efficiency and selective configuration of the gamma-ray spectrometer (HPGe+NaI) operating at the underground Laboratory of Monte dei Cappuccini (OATo, INAF) in Torino, Italy.

  17. Activity in galactic nuclei of cluster and field galaxies in the local universe

    NASA Astrophysics Data System (ADS)

    Hwang, H. S.; Park, C.; Elbaz, D.; Choi, Y.-Y.

    2012-02-01

    Aims: We study the environmental effects on the activity in galactic nuclei by comparing galaxies in clusters and in the field. Methods: Using a spectroscopic sample of galaxies in Abell clusters from the Sloan Digital Sky Survey Data Release 7, we investigate the dependence of nuclear activity on the physical parameters of clusters as well as the nearest neighbor galaxy. We also compare galaxy properties between active galactic nuclei (AGNs) hosts and non-AGN galaxies. Results: We find that the AGN fraction of early-type galaxies starts to decrease around one virial radius of clusters (r200,cl) as decreasing clustercentric radius, while that of late types starts to decrease close to the cluster center (R ~ 0.1-0.5r200,cl). The AGN fractions of early-type cluster galaxies, on average, are found to be lower than those of early-type field galaxies by a factor ~3. However, the mean AGN fractions of late-type cluster galaxies are similar to those of late-type field galaxies. The AGN fraction of early-type brightest cluster galaxies lies between those of other early-type, cluster and field galaxies with similar luminosities. In the field, the AGN fraction is strongly dependent on the morphology of and the distance to the nearest neighbor galaxy. We find an anti-correlation between the AGN fraction and the velocity dispersion of clusters for all subsamples divided by morphology and luminosity of host galaxies. The AGN power indicated by L [OIII] /MBH is found to depend strongly on the mass of host galaxies rather than the clustercentric radius. The difference in physical parameters such as luminosity, (u - r) colors, star formation rates, and (g - i) color gradients between AGN hosts and non-AGN galaxies is seen for both early and late types at all clustercentric radii, while the difference in structure parameters between the two is significant only for late types. Conclusions: These results support the idea that the activity in galactic nuclei is triggered through

  18. Multi-band Emission of Active Galactic Nuclei: the Relationship of Stellar and Gravitational-Accretion Activity

    NASA Astrophysics Data System (ADS)

    Feltre, Anna

    2013-07-01

    One of the remaining open issues in the context of the analysis of active galactic nuclei is the evidence that nuclear gravitational accretion is often accompanied by a concurrent starburst activity. What is, in this picture, the role played by the obscuring dust around the nucleus and what does the state of the art models have to say? Can the infrared data provided by Spitzer and Herschel help us in extensively investigate both phenomena and, if so, how and with what limitations? Does the presence of an active nucleus have an impact in the mid- and far-infrared properties of galaxies? Which are the effects of simultaneous nuclear gravitational accretion and starburst activities in these same galaxies? This Thesis presents our contribution to the efforts of answering these questions. I report on results coming from a comparative study of various approaches adopted while modelling active galactic nuclei, focusing mostly on the much-debated issue about the morphology of the dust distribution in the toroidal structure surrounding their nuclear centre. We largely illustrate that properties of dust in active galactic nuclei as measured by matching observations (be it broad band infrared photometry or infrared spectra) with models strongly depend on the choice of the dust distribution. Further, I describe a spectral energy distribution fitting tool appositely developed to derive simultaneously the physical properties of active nuclei and coexisting starbursts. The procedure was developed to make the best use of Spitzer and Herschel mid- and far-infrared observations. Such data play a crucial role in this context, providing much stronger constraints on the models with respect to the previous observing facilities. The tool has been applied to a large sample of extragalactic sources representing the Herschel/Multi-tiered Extragalactic Survey population with mid-infrared spectra from Spitzer and with a plethora of multi-wavelength data (SDSS, Spitzer and Herschel/SPIRE). The

  19. THE EFFECTS OF X-RAY FEEDBACK FROM ACTIVE GALACTIC NUCLEI ON HOST GALAXY EVOLUTION

    SciTech Connect

    Hambrick, D. Clay; Ostriker, Jeremiah P.; Naab, Thorsten; Johansson, Peter H.

    2011-09-01

    Hydrodynamic simulations of galaxies with active galactic nuclei (AGNs) have typically employed feedback that is purely local, i.e., an injection of energy to the immediate neighborhood of the black hole (BH). We perform GADGET-2 simulations of massive elliptical galaxies with an additional feedback component: an observationally calibrated X-ray radiation field which emanates from the BH and heats gas out to large radii from the galaxy center. We find that including the heating and radiation pressure associated with this X-ray flux in our simulations enhances the effects which are commonly reported from AGN feedback. This new feedback model is twice as effective as traditional feedback at suppressing star formation, produces three times less star formation in the last 6 Gyr, and modestly lowers the final BH mass (30%). It is also significantly more effective than an X-ray background in reducing the number of satellite galaxies.

  20. X-ray spectroscopy of AGN with the AXAF 'Microcalorimeter'. [Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Holt, Stephen S.

    1987-01-01

    A novel technique for X-ray spectroscopy has been configured as part of the definition payload of the AXAF Observatory. It is basically a calorimeter which, operating at 0.1 K, senses the total conversion of single photoelectrically absorbed X-rays via the differential temperature rise of the absorber. The technique promises to achieve less than 10 eV FWHM with near-unit efficiency simultaneously over the entire AXAF bandpass. This combination of high resolution and high efficiency allows for the possibility of investigating thermal, fluorescent and absorption X-ray line features in many types of X-ray source, including a large sample of active galactic nuclei.

  1. RELATIVISTIC BROADENING OF IRON EMISSION LINES IN A SAMPLE OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Brenneman, Laura W.; Reynolds, Christopher S.

    2009-09-10

    We present a uniform X-ray spectral analysis of eight type-1 active galactic nuclei that have been previously observed with relativistically broadened iron emission lines. Utilizing data from the XMM-Newton European Photon Imaging Camera (EPIC-pn) we carefully model the spectral continuum, taking complex intrinsic absorption and emission into account. We then proceed to model the broad Fe K{alpha} feature in each source with two different accretion disk emission line codes, as well as a self-consistent, ionized accretion disk spectrum convolved with relativistic smearing from the inner disk. Comparing the results, we show that relativistic blurring of the disk emission is required to explain the spectrum in most sources, even when one models the full reflection spectrum from the photoionized disk.

  2. On the X-Ray Low- and High-Velocity Outflows in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Ramirez, J. M.; Tombesi, F.

    2012-01-01

    An exploration of the relationship between bolometric luminosity and outflow velocity for two classes of X-ray outflows in a large sample of active galactic nuclei has been performed. We find that line radiation pressure could be one physical mechanism that might accelerate the gas we observe in warm absorber, v approx. 100-1000 km/s, and on comparable but less stringent grounds the ultrafast outflows, v approx. 0.03-0.3c. If comparable with the escape velocity of the system, the first is naturally located at distances of the dusty torus, '" I pc, and the second at subparsec scales, approx.0.01 pc, in accordance with large set of observational evidence existing in the literature. The presentation of this relationship might give us key clues for our understanding of the different physical mechanisms acting in the centre of galaxies, the feedback process and its impact on the evolution of the host galaxy.

  3. The cosmological evolution and luminosity function of X-ray selected active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Maccacaro, T.; Gioia, I. M.; Avni, Y.; Giommi, P.; Griffiths, R. E.; Liebert, J.; Stocke, J.; Danziger, J.

    1983-01-01

    The cosmological evolution and the X-ray luminosity function of X-ray selected active galactic nuclei (AGNs) are derived and discussed. The sample used consists of 31 AGNs extracted from a fully identified sample of X-ray sources from the Einstein Observatory Medium Sensitivity Survey and is therefore exclusively defined by its X-ray properties. The distribution in space is found to be strongly nonuniform. The amount of cosmological evolution required by the X-ray data is derived in the framework of pure luminosity evolution and is found to be smaller than the amount determined from optically selected samples. The X-ray luminosity function is derived. It can be satisfactorily represented by a single power law only over a limited range of absolute luminosities. Evidence that the luminosity function flattens at low luminosity or steepens at high luminosity, or both, is presented and discussed.

  4. A new approach to the variability characterization of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Middei, R.; Vagnetti, F.; Antonucci, M.; Serafinelli, R.

    2016-02-01

    The normalized excess variance is a popular method used by many authors to estimate the variability of active galactic nuclei (AGNs), especially in the X-ray band. We show that this estimator is affected by the cosmological time dilation, so that it should be appropriately corrected when applied to AGN samples distributed in wide redshift intervals. We propose a formula to modify this estimator, based on the use of the structure function. To verify the presence of the cosmological effect and the reliability of the proposed correction, we use data extracted from the XMM-Newton Serendipitous Source Catalogue, data release 5 (XMMSSC-DR5), and cross-matched with the Sloan Digital Sky Survey quasar catalogue, of data release 7 and 12.

  5. Photon-photon absorption and the uniqueness of the spectra of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Kazanas, D.

    1984-01-01

    The effects of the feedback of e(+)-e(-) pair reinjection in a plasma due to photon-photon absorption of its own radiation was examined. Under the assumption of continuous electron injection with a power law spectrum E to the minus gamma power and Compton losses only, it is shown that for gamma 2 the steady state electron distribution function has a unique form independent of the primary injection spectrum. This electron distribution function can, by synchrotron emission, reproduce the general characteristics of the observed radio to optical active galactic nuclei spectra. Inverse Compton scattering of the synchrotron photons by the same electron distribution can account for their X-ray spectra, and also implies gamma ray emission from these objects. This result is invoked to account for the similarity of these spectra, and it is consistent with observations of the diffuse gamma ray background.

  6. Search for correlations between HiRes stereo events and active galactic nuclei

    NASA Astrophysics Data System (ADS)

    High Resolution Fly'S Eye Collaboration; Abbasi, R. U.; Abu-Zayyad, T.; Allen, M.; Amman, J. F.; Archbold, G.; Belov, K.; Belz, J. W.; Benzvi, S. Y.; Bergman, D. R.; Blake, S. A.; Boyer, J. H.; Brusova, O. A.; Burt, G. W.; Cannon, C.; Cao, Z.; Deng, W.; Fedorova, Y.; Findlay, J.; Finley, C. B.; Gray, R. C.; Hanlon, W. F.; Hoffman, C. M.; Holzscheiter, M. H.; Hughes, G.; Hüntemeyer, P.; Ivanov, D.; Jones, B. F.; Jui, C. C. H.; Kim, K.; Kirn, M. A.; Knapp, B. C.; Loh, E. C.; Maestas, M. M.; Manago, N.; Mannel, E. J.; Marek, L. J.; Martens, K.; Matthews, J. N.; Moore, S. A.; O'Neill, A.; Painter, C. A.; Perera, L.; Reil, K.; Riehle, R.; Roberts, M. D.; Rodriguez, D.; Sasaki, N.; Schnetzer, S. R.; Scott, L. M.; Seman, M.; Sinnis, G.; Smith, J. D.; Snow, R.; Sokolsky, P.; Song, C.; Springer, R. W.; Stokes, B. T.; Stratton, S. R.; Thomas, J. R.; Thomas, S. B.; Thomson, G. B.; Tupa, D.; Wiencke, L. R.; Zech, A.; Zhang, X.; High Resolution Fly's Eye Collaboration

    2008-11-01

    We have searched for correlations between the pointing directions of ultrahigh energy cosmic rays observed by the High Resolution Fly's Eye experiment and active galactic nuclei (AGN) visible from its northern hemisphere location. No correlations, other than random correlations, have been found. We report our results using search parameters prescribed by the Pierre Auger collaboration. Using these parameters, the Auger collaboration concludes that a positive correlation exists for sources visible to their southern hemisphere location. We also describe results using two methods for determining the chance probability of correlations: one in which a hypothesis is formed from scanning one half of the data and tested on the second half, and another which involves a scan over the entire data set. The most significant correlation found occurred with a chance probability of 24%.

  7. Nonthermal electron-positron pairs and cold matter in the central engines of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Zdziarski, Andrzej A.

    1992-01-01

    The nonthermal e(+/-) pair model of the central engine of active galactic nuclei (AGNs) is discussed. The model assumes that nonthermal e(+/-) pairs are accelerated to highly relativistic energies in a compact region close to the central black hole and in the vicinity of some cold matter. The model has a small number of free parameters and explains a large body of AGN observations from EUV to soft gamma-rays. In particular, the model explains the existence of the UV bump, the soft X-rays excess, the canonical hard X-ray power law, the spectral hardening above about 10 keV, and some of the variability patterns in the soft and hard X-rays. In addition, the model explains the spectral steepening above about 50 keV seen in NGC 4151.

  8. Relativistic particles and gamma-rays in quasars and active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Protheroe, R. J.; Kazanas, D.

    1983-01-01

    A model for a class of quasars and active galactic nuclei is described in which a shock around a massive black hole randomizes the infall kinetic energy of spherically accreting matter producing a nonthermal spectrum of high energy protons. These protons may be responsible for the secondary production (via tau + or - decay) of the radio emitting high energy electrons and also of high energy gamma rays (via Pi decay and inverse Compton interactions of the electrons). The correlation between radio and gamma ray emission implied by the model is in good agreement with observations of 3C273. Observation of the flux of high energy neutrinos from quasars may provide a test for the model.

  9. Relativistic particles and gamma-ray in quasars and active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Protheroe, R. J.; Kazanas, D.

    1982-01-01

    A model for a class of quasars and active galactic nuclei is described in which a shock around a massive black hole randomizes the infall kinetic energy of spherically accreting matter producing a nonthermal spectrum of high energy protons. These protons may be responsible for the secondary production (via tau + or - decay) of the radio emitting high energy electrons and also of high energy gamma rays (via pi decay and inverse Compton interactions of the electrons). The correlation between radio and gamma ray emission implied by the model is in good agreement with observations of 3C273. Observation of the flux of high energy neutrinos from quasars may provide a test for the model.

  10. Time-dependent behavior of active galactic nuclei with pair production

    NASA Technical Reports Server (NTRS)

    Li, H.; Dermer, C. D.

    1994-01-01

    We study the properties of coupled partial differential equations describing the time-dependent behavior of the photon and electron occupation numbers for conditions likely to be found near active galactic nuclei (AGN). The processes governing electron acceleration are modeled by a stochastic accelerator, and we include acceleration by Alfvenic and whistler turbulence. The acceleration of electrons is limited by Compton and synchrotron losses, and the number density of electrons depends on pair production and annihilation processes. We also treat particle escape from the system. We examine the steady, (possibly) oscillatory, and unstable solutions that arise for various choices of parameters. We examine instabilities related to pair production and trapping and consider the formation of pair jets.

  11. Evolution of self-gravitating accretion disks in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shlosman, Isaac; Begelman, Mitchell C.

    1989-01-01

    The evolution of self-gravitating gaseous disks in active galactic nuclei on scales of about 10-1000 pc is investigated. Star formation is a plausible outcome of the Jeans instability operating in a disk which violates the criterion for local stability. Even a low efficiency of star formation would deplete the gaseous disk on a short time scale and create a flat stellar system. These systems can evolve (sphericalize) secularly by means of stellar encounters but this process appears to be too slow to be important. Such flattened stellar systems may be common in the circumnuclear regions of disk galaxies. Conventional viscosities are inefficient in building anew the accretion process even in a cosmological time. Strongly self-gravitating disks are unstable to global nonaxisymmetric modes, which can induce radial inflow of gas in a short dynamical time. The latter effect is studied in a separate paper.

  12. Spectropolarimetric test of the relativistic disk model for the broad emission lines of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Chen, Kaiyou; Halpern, Jules P.

    1990-01-01

    Previously, it was claimed that the broad emission lines of the radio galaxy Arp 102B can be fitted by the line profile from a simple relativistic Keplerian thin disk. It was argued that the lines originating from the relativistic accretion disk could be polarized due to electron scattering, which is likely to be the dominant opacity in the line-emitting region of Arp 102B. In the present work, the expected polarization properties of these broad emission lines are calculated. The percentage of polarization depends strongly on the inclination angle. For some angles, the red peak of the polarized, double-peaked line profile can be higher than the blue peak. This is in contrast to the total line profile, in which the blue peak is always higher than the red one. Spectropolarimetric observations could, therefore, provide an independent test of the relativistic disk model for the broad emission lines of Arp 102B and other active galactic nuclei.

  13. Correlation Analysis of Optical and Radio Light Curves for a Large Sample of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Clements, S. D.; Smith, A. G.; Aller, H. D.; Aller, M. F.

    1995-08-01

    The Rosemary Hill Observatory has accumulated internally consistent light curves extending over as much as 26 years for a large sample of active galactic nuclei. Forty-six of these optical records have been compared with similar radio records from the University of Michigan Radio Astronomy Observatory and the Algonquin Radio Observatory. For 18 objects, pairs of records were sufficiently long and unconfused to allow reliable application of the Discrete Correlation Function analysis; this group included 8 BL Lacertids, 8 quasars, and 2 Seyfert galaxies. Nine of the 18 sources showed positive radio-optical correlations, with the radio events lagging the optical by intervals ranging from 0 to 14 months. Consistent with the relativistic beaming model of the BL Lacertids, the group displaying correlations was dominated by this type of object.

  14. Photon damping in cosmic-ray acceleration in active galactic nuclei

    SciTech Connect

    Colgate, S.A.

    1983-04-07

    The usual assumption of the acceleration of ultra high energy cosmic rays, greater than or equal to 10/sup 18/ eV in quasars, Seyfert galaxies and other active galactic nuclei is challenged on the basis of the photon interactions with the accelerated nucleons. This is similar to the effect of the black body radiation on particles > 10/sup 20/ eV for times of the age of the universe except that the photon spectrum is harder and the energy density greater by approx. = 10/sup 15/. Hence, a single traversal, radial or circumferential, of radiation whose energy density is no greater than the emitted flux will damp an ultra high energy. Hence, it is unlikely that any reasonable configuration of acceleration can void disastrous photon energy loss. A different site for ultra high energy cosmic ray acceleration must be found.

  15. Innermost structure and near-infrared radiation of dusty clumpy tori in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Kawaguchi, Toshihiro

    2012-12-01

    The dusty clumpy torus surrounds the central black hole (BH) and the accretion disk in active galactic nuclei, and governs the growth of super-massive BHs via gas fueling towards the central engine. Near-infrared (NIR) monitoring observations have revealed that the torus inner radius is determined by the dust sublimation process. However, the observed radii are systematically smaller than the theoretical predictions by a factor of three. We take into account the anisotropic illumination by the central accretion disk to the torus, and calculate the innermost structure of the torus and the NIR time variability. We then show that the anisotropy naturally solves the systematic discrepancy and that the viewing angle is the primary source to produce an object-to-object scatter of the NIR time delay. Dynamics of clumps at the innermost region of the torus will be unveiled via future high- resolution X-ray spectroscopy (e.g., Astro-H)

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

    NASA Astrophysics Data System (ADS)

    Geballe, T. R.; Mason, R. E.; Oka, T.

    2015-10-01

    Spectra of the archetypal Type II Seyfert galaxy NGC 1068 in a narrow wavelength interval near 3.7 μm have revealed a weak absorption feature due to two lines of the molecular ion {{{H}}}3+. The observed wavelength of the feature corresponds to a velocity of -70 km s-1 relative to the systemic velocity of the galaxy, implying an outward flow from the nucleus along the line of sight. The absorption by H{}3+ along with the previously known broad hydrocarbon absorption at 3.4μm are probably formed in diffuse gas that is in close proximity to the continuum source, i.e., within a few tens of parsecs of the central engine. Based on that conclusion and the measured H{}3+ absorption velocity and with the assumption of a spherically symmetric wind we estimate a rate of mass outflow from the active galactic nucleus of ˜1 M⊙ yr-1.

  17. A polarimetric method for measuring black hole masses in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  18. Scientific Highlights from Observations of Active Galactic Nuclei with the MAGIC Telescope

    SciTech Connect

    Wagner, Robert

    2008-12-24

    Since 2004, the MAGIC {gamma}-ray telescope has newly discovered 6 TeV blazars. The total set of 13 MAGIC-detected active galactic nuclei includes well-studied objects at other wavelengths like Markarian 501 and the giant radio galaxy M 87, but also the distant the flat-spectrum radio quasar 3C 279, and the newly discovered TeV {gamma}-ray emitter S5 0716+71. In addition, also long-term and multi-wavelength studies on well-known TeV blazars and systematic searches for new TeV blazars have been carried out. Here we report selected highlights from recent MAGIC observations of extragalactic TeV {gamma}-ray sources, emphasizing the new physics insights MAGIC was able to contribute.

  19. The largest mid-infrared atlas of active galactic nuclei at sub-arcsecond spatial scales

    NASA Astrophysics Data System (ADS)

    Asmus, Daniel; Gandhi, Poshak; Honig, Sebastian F.; Smette, Alain

    2012-12-01

    We present the largest mid-infrared atlas of active galactic nuclei at sub-arcsecond spatial scales containing 249 objects. It comprises all ground-based HR MIR observations performed to date. This catalog includes a large number of new observations. The photometry in multiple filters allows for characterizing the properties of the dust emission for most objects. Because of its size and characteristics, this sample is very well-suited for AGN unification studies. In particular, we discuss the enlarged MIR-X-ray correlation which extends over six orders of magnitude in luminosity and potentially probes different physical mechanisms. Finally, tests for intrinsic differences between the AGN types are presented and we discuss dependencies of MIR-X-ray properties with respect to fundamental AGN parameters such as accretion rate and the column density and covering factor of obscuring material.

  20. THE FERMI BUBBLES: SUPERSONIC ACTIVE GALACTIC NUCLEUS JETS WITH ANISOTROPIC COSMIC-RAY DIFFUSION

    SciTech Connect

    Yang, H.-Y. K.; Ruszkowski, M.; Ricker, P. M.; Zweibel, E.; Lee, D.

    2012-12-20

    The Fermi Gamma-Ray Space Telescope reveals two large bubbles in the Galaxy, which extend nearly symmetrically {approx}50 Degree-Sign above and below the Galactic center. Using three-dimensional (3D) magnetohydrodynamic simulations that self-consistently include the dynamical interaction between cosmic rays (CRs) and thermal gas and anisotropic CR diffusion along the magnetic field lines, we show that the key characteristics of the observed gamma-ray bubbles and the spatially correlated X-ray features in the ROSAT 1.5 keV map can be successfully reproduced by recent jet activity from the central active galactic nucleus. We find that after taking into account the projection of the 3D bubbles onto the sky the physical heights of the bubbles can be much smaller than previously thought, greatly reducing the formation time of the bubbles to about a Myr. This relatively small bubble age is needed to reconcile the simulations with the upper limit of bubble ages estimated from the cooling time of high-energy electrons. No additional physical mechanisms are required to suppress large-scale hydrodynamic instabilities because the evolution time is too short for them to develop. The simulated CR bubbles are edge-brightened, which is consistent with the observed projected flat surface brightness distribution. Furthermore, we demonstrate that the sharp edges of the observed bubbles can be due to anisotropic CR diffusion along magnetic field lines that drape around the bubbles during their supersonic expansion, with suppressed perpendicular diffusion across the bubble surface. Possible causes of the slight bends of the Fermi bubbles to the west are also discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    We investigate and quantify the observed scatter in the empirical relationship between the broad line region size R and the luminosity of the active galactic nucleus, in order to better understand its origin. This study is motivated by the indispensable role of this relationship in the mass estimation of cosmologically distant black holes, but may also be relevant to the recently proposed application of this relationship for measuring cosmic distances. We study six nearby reverberation-mapped active galactic nuclei (AGNs) for which simultaneous UV and optical monitoring data exist. We also examine the long-term optical luminosity variations of the Seyfert 1 galaxy NGC 5548 and employ Monte Carlo simulations to study the effects of the intrinsic variability of individual objects on the scatter in the global relationship for a sample of ~40 AGNs. We find the scatter in this relationship has a correctable dependence on color. For individual AGNs, the size of the Hβ emitting region has a steeper dependence on the nuclear optical luminosity than on the UV luminosity, which can introduce a scatter of ~0.08 dex into the global relationship, due the nonlinear relationship between the variations in the ionizing continuum and those in the optical continuum. Also, our analysis highlights the importance of understanding and minimizing the scatter in the relationship traced by the intrinsic variability of individual AGNs since it propagates directly into the global relationship. We find that using the UV luminosity as a substitute for the ionizing luminosity can reduce a sizable fraction of the current observed scatter of ~0.13 dex.

  2. The Hubble Space Telescope Quasar Absorption Line Key Project. 10: Galactic H I 21 centimeter emission toward 143 quasars and active Galactic nuclei

    NASA Technical Reports Server (NTRS)

    Lockman, Felix J.; Savage, Blair D.

    1995-01-01

    Sensitive H I 21 cm emission line spectra have been measured for the directions to 143 quasars and active galactic nuclei (AGNs) chosen from the observing lists for the Hubble Space Telescope (HST) Quasar Absorption Line Key Project. Narrow-band and wide-band data were obtained with the National Radio Astronomy Observatory (NRAO) 43 m radio telescope for each object. The narrow-band data have a velocity resolution of 1 km/s, extend from -220 to +170 km/s, and are corrected for stray 21 cm radiation. The wide-band data have a resolution of 4 km/s and extend from -1000 to +1000 km/s. The data are important for the interpretation of ultraviolet absorption lines near zero redshift in Key Project spectra. Twenty-two percent of the quasars lie behind Galactic high-velocity H I clouds with absolute value of V(sub LSR) greater than 100 km/s whose presence can increase the equivalent width of interstellar absorption lines significantly. This paper contains the emission spectra and measures of the H I velocities and column densities along the sight line to each quasar. We discuss how the measurements can be used to estimate the visual and ultraviolet extinction toward each quasar and to predict the approximate strength of the strong ultraviolet resonance lines of neutral gas species in the HST Key Project spectra.

  3. A statistical method to search for recoiling supermassive black holes in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Raffai, P.; Haiman, Z.; Frei, Z.

    2016-01-01

    We propose an observational test for gravitationally recoiling supermassive black holes (BHs) in active galactic nuclei, based on a correlation between the velocities of BHs relative to their host galaxies, |Δv|, and their obscuring dust column densities, Σdust (both measured along the line of sight). We use toy models for the distribution of recoil velocities, BH trajectories, and the geometry of obscuring dust tori in galactic centres, to simulate 2.5 × 105 random observations of recoiling quasars. BHs with recoil velocities comparable to the escape velocity from the galactic centre remain bound to the nucleus, and do not fully settle back to the centre of the torus due to dynamical friction in a typical quasar lifetime. We find that |Δv| and Σdust for these BHs are positively correlated. For obscured (Σdust > 0) and for partially obscured (0 < Σdust ≲ 2.3 g m-2) quasars with |Δv| ≥ 45 km s-1, the sample correlation coefficient between log10(|Δv|) and Σdust is r45 = 0.28 ± 0.02 and r45 = 0.13 ± 0.02, respectively. Allowing for random ± 100 km s- 1 errors in |Δv| unrelated to the recoil dilutes the correlation for the partially obscured quasars to r45 = 0.026 ± 0.004 measured between |Δv| and Σdust. A random sample of ≳ 3500 obscured quasars with |Δv| ≥ 45 km s-1 would allow rejection of the no-correlation hypothesis with 3σ significance 95 per cent of the time. Finally, we find that the fraction of obscured quasars, {F_obs} (|Δv|), decreases with |Δv| from {F_obs} (<10 km s-1) ≳ 0.8 to {F_obs} (>103 km s-1) ≲ 0.4. This predicted trend can be compared to the observed fraction of type II quasars, and can further test combinations of recoil, trajectory, and dust torus models.

  4. GSFC Contributions to the NATO X-ray Astronomy Institute, Erice, July 1979. [X-ray spectra of supernova remants, galactic X-ray sources, active galactic nuclei, and clusters of galaxies

    NASA Technical Reports Server (NTRS)

    Holt, S. S.; Mushotzky, R. F.

    1979-01-01

    An overview of X-ray astronomical spectroscopy in general is presented and results obtained by HEAO 1 and 2 as well as earlier spacecraft are examined. Particular emphasis is given to the spectra of supernova remnants; galactic binary X-ray sources, cataclysmic variables, bulges, pulsars, and stars; the active nuclei of Seyfert 1 galaxy, BL Lac, and quasars; the diffuse X-ray background; and galactic clusters.

  5. Modeling Hot Gas Flow in the Low-luminosity Active Galactic Nucleus of NGC 3115

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Roman V.; Wong, Ka-Wah; Irwin, Jimmy A.; Reynolds, Christopher S.

    2014-02-01

    Based on the dynamical black hole (BH) mass estimates, NGC 3115 hosts the closest billion solar mass BH. Deep studies of the center revealed a very underluminous active galactic nucleus (AGN) immersed in an old massive nuclear star cluster. Recent 1 Ms Chandra X-ray visionary project observations of the NGC 3115 nucleus resolved hot tenuous gas, which fuels the AGN. In this paper we connect the processes in the nuclear star cluster with the feeding of the supermassive BH. We model the hot gas flow sustained by the injection of matter and energy from the stars and supernova explosions. We incorporate electron heat conduction as the small-scale feedback mechanism, the gravitational pull of the stellar mass, cooling, and Coulomb collisions. Fitting simulated X-ray emission to the spatially and spectrally resolved observed data, we find the best-fitting solutions with χ2/dof = 1.00 for dof = 236 both with and without conduction. The radial modeling favors a low BH mass <1.3 × 109 M ⊙. The best-fitting supernova rate and the best-fitting mass injection rate are consistent with their expected values. The stagnation point is at r st <~ 1'', so that most of the gas, including the gas at a Bondi radius rB = 2''-4'', outflows from the region. We put an upper limit on the accretion rate at 2 × 10-3 M ⊙ yr-1. We find a shallow density profile nvpropr -β with β ≈ 1 over a large dynamic range. This density profile is determined in the feeding region 0.''5-10'' as an interplay of four processes and effects: (1) the radius-dependent mass injection, (2) the effect of the galactic gravitational potential, (3) the accretion flow onset at r <~ 1'', and (4) the outflow at r >~ 1''. The gas temperature is close to the virial temperature Tv at any radius.

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

    NASA Technical Reports Server (NTRS)

    Fiore, Fabrizio; White, Nicholas (Technical Monitor)

    2000-01-01

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

  7. A CORRELATION BETWEEN THE HIGHEST ENERGY COSMIC RAYS AND NEARBY ACTIVE GALACTIC NUCLEI DETECTED BY FERMI

    SciTech Connect

    Nemmen, Rodrigo S.; Bonatto, Charles; Storchi-Bergmann, Thaisa

    2010-10-10

    We analyze the correlation of the positions of {gamma}-ray sources in the Fermi Large Area Telescope (LAT) First Source Catalog (1FGL) and the First LAT Active Galactic Nuclei (AGNs) Catalog (1LAC) with the arrival directions of ultra-high-energy cosmic rays (UHECRs) observed with the Pierre Auger Observatory, in order to investigate the origin of UHECRs. We find that Galactic sources and blazars identified in the 1FGL are not significantly correlated with UHECRs, while the 1LAC sources display a mild correlation (2.6{sigma} level) on an {approx}2.{sup 0}4 angular scale. When selecting only the 1LAC AGNs closer than 200 Mpc, we find a strong association (5.4{sigma}) between their positions and the directions of UHECRs on an {approx}17{sup 0} angular scale; the probability of the observed configuration being due to an isotropic flux of cosmic rays is 5 x 10{sup -8}. There is also a 5{sigma} correlation with nearby 1LAC sources on a 6.{sup 0}5 scale. We identify seven '{gamma}-ray loud' AGNs which are associated with UHECRs within {approx}17{sup 0} and are likely candidates for the production sites of UHECRs: Centaurus A, NGC 4945, ESO 323-G77, 4C+04.77, NGC 1218, RX J0008.0+1450, and NGC 253. We interpret these results as providing additional support to the hypothesis of the origin of UHECRs in nearby extragalactic objects. As the angular scales of the correlations are large, we discuss the possibility that intervening magnetic fields might be considerably deflecting the trajectories of the particles on their way to Earth.

  8. A CANDIDATE ACTIVE GALACTIC NUCLEUS WITH A PURE SOFT THERMAL X-RAY SPECTRUM

    SciTech Connect

    Terashima, Yuichi; Kamizasa, Naoya; Awaki, Hisamitsu; Kubota, Aya; Ueda, Yoshihiro

    2012-06-20

    We report the discovery of a candidate active galactic nucleus (AGN), 2XMM J123103.2+110648 at z = 0.13, with an X-ray spectrum represented purely by soft thermal emission reminiscent of Galactic black hole (BH) binaries in the disk-dominated state. This object was found in the second XMM-Newton serendipitous source catalog as a highly variable X-ray source. In three separate observations, its X-ray spectrum can be represented either by a multicolor disk blackbody model with an inner temperature of kT{sub in} Almost-Equal-To 0.16-0.21 keV or a Wien spectrum Comptonized by an optically thick plasma with kT Almost-Equal-To 0.14-0.18 keV. The soft X-ray luminosity in the 0.5-2 keV band is estimated to be (1.6-3.8) Multiplication-Sign 10{sup 42} erg s{sup -1}. Hard emission above {approx}2 keV is not detected. The ratio of the soft to hard emission is the strongest among AGNs observed thus far. Spectra selected in high/low-flux time intervals are examined in order to study spectral variability. In the second observation with the highest signal-to-noise ratio, the low-energy (below 0.7 keV) spectral regime flattens when the flux is high, while the shape of the high-energy part (1-1.7 keV) remains unchanged. This behavior is qualitatively consistent with being caused by strong Comptonization. Both the strong soft excess and spectral change consistent with Comptonization in the X-ray spectrum imply that the Eddington ratio is large, which requires a small BH mass (smaller than {approx}10{sup 5} M{sub Sun }).

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

    NASA Astrophysics Data System (ADS)

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

    2015-09-01

    The third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC) is presented. It is based on the third Fermi-LAT catalog (3FGL) of sources detected between 100 MeV and 300 GeV with a Test Statistic greater than 25, between 2008 August 4 and 2012 July 31. The 3LAC includes 1591 AGNs located at high Galactic latitudes (| b| \\gt 10^\\circ ), a 71% increase over the second catalog based on 2 years of data. There are 28 duplicate associations, thus 1563 of the 2192 high-latitude gamma-ray sources of the 3FGL catalog are AGNs. Most of them (98%) are blazars. About half of the newly detected blazars are of unknown type, i.e., they lack spectroscopic information of sufficient quality to determine the strength of their emission lines. Based on their gamma-ray spectral properties, these sources are evenly split between flat-spectrum radio quasars (FSRQs) and BL Lacs. The most abundant detected BL Lacs are of the high-synchrotron-peaked (HSP) type. About 50% of the BL Lacs have no measured redshifts. A few new rare outliers (HSP-FSRQs and high-luminosity HSP BL Lacs) are reported. The general properties of the 3LAC sample confirm previous findings from earlier catalogs. The fraction of 3LAC blazars in the total population of blazars listed in BZCAT remains non-negligible even at the faint ends of the BZCAT-blazar radio, optical, and X-ray flux distributions, which hints that even the faintest known blazars could eventually shine in gamma-rays at LAT-detection levels. The energy-flux distributions of the different blazar populations are in good agreement with extrapolation from earlier catalogs.

  10. Grain physics and infrared dust emission in active galactic nucleus environments

    SciTech Connect

    Hensley, Brandon S.; Ostriker, Jeremiah P.; Ciotti, Luca

    2014-07-01

    We study the effects of a detailed dust treatment on the properties and evolution of early-type galaxies containing central black holes, as determined by active galactic nucleus (AGN) feedback. We find that during cooling flow episodes, radiation pressure on the dust in and interior to infalling shells of cold gas can greatly impact the amount of gas able to be accreted and therefore the frequency of AGN bursts. However, the overall hydrodynamic evolution of all models, including mass budget, is relatively robust to the assumptions on dust. We find that IR re-emission from hot dust can dominate the bolometric luminosity of the galaxy during the early stages of an AGN burst, reaching values in excess of 10{sup 46} erg s{sup –1}. The AGN-emitted UV is largely absorbed, but the optical depth in the IR does not exceed unity, so the radiation momentum input never exceeds L {sub BH}/c. We constrain the viability of our models by comparing the AGN duty cycle, broadband luminosities, dust mass, black hole mass, and other model predictions to current observations. These constraints force us towards models wherein the dust to metals ratios are ≅ 1% of the Galactic value, and only models with a dynamic dust to gas ratio are able to produce both quiescent galaxies consistent with observations and high obscured fractions during AGN 'on' phases. During AGN outbursts, we predict that a large fraction of the FIR luminosity can be attributed to warm dust emission (≅ 100 K) from dense dusty gas within ≤1 kpc reradiating the AGN UV emission.

  11. Signs of active galactic nucleus quenching in a merger remnant with radio jets

    NASA Astrophysics Data System (ADS)

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

    2016-02-01

    We investigate optical, infrared, and radio active galactic nucleus (AGN) signs in the merger remnant Arp 187, which hosts luminous jets launched in the order of 105 yr ago but whose present-day AGN activity is still unknown. We find AGN signs from the optical Baldwin-Phillips-Telervich diagram and infrared [O IV] 25.89 μm line, originating from the narrow line regions of AGN. On the other hand, Spitzer/IRS show host galaxy dominated spectra, suggesting that the thermal emission from the AGN torus is considerably small or already diminished. Combining the black hole mass, the upper limit of radio luminosity of the core, and the fundamental plane of the black hole enables us to estimate X-ray luminosity, which gives <1040 erg s-1. Those results suggest that the AGN activity of Arp 187 has already been quenched, but the narrow line region is still alive owing to the time delay of emission from the past AGN activity.

  12. MOIRCS DEEP SURVEY. III. ACTIVE GALACTIC NUCLEI IN MASSIVE GALAXIES AT z = 2-4

    SciTech Connect

    Yamada, T.; Kajisawa, M.; Akiyama, M.; Ichikawa, T.; Tokoku, C.; Yoshikawa, T.; Konishi, M.; Nishimura, T.; Omata, K.; Suzuki, R.; Tanaka, I.; Uchimoto, Y. K.

    2009-07-10

    We investigate the X-ray properties of the K-band-selected galaxies at redshift 2 < z < 4 by using our deep near-infrared images obtained in the Multi-Object Infrared Camera and Spectrograph Deep Survey project and the published Chandra X-ray source catalog. Sixty-one X-ray sources with the 2-10 keV luminosity L{sub X} = 10{sup 42}-10{sup 44} erg s{sup -1} are identified with the K-selected galaxies and we found that they are exclusively (90%) associated with the massive objects with a stellar mass larger than 10{sup 10.5} M{sub sun}. Our results are consistent with the idea that the M {sub BH}/M{sub str} ratio of the galaxies at z = 2-4 is similar to the present-day value. On the other hand, the active galactic nucleus (AGN) detection rate among the very massive galaxies with a stellar mass larger than 10{sup 11} M{sub sun} is high, 33% (26/78). They are active objects in the sense that the black hole mass accretion rate is {approx}1%-50% of the Eddington limit if they indeed have similar M {sub BH}/M {sub str} ratio with those observed in the local universe. The active duration in the AGN duty cycle of the high-redshift massive galaxies seems large.

  13. Penrose pair production as a power source of quasars and active galactic nuclei. [black hole mechanisms

    NASA Technical Reports Server (NTRS)

    Kafatos, M.; Leiter, D.

    1979-01-01

    Penrose pair production in massive canonical Kerr black holes (those with a/M equal to 0.998) is proposed as a way to explain the nature of the vast fluctuating energy production associated with active galactic nuclei and quasars. It is assumed that a Kerr black hole with a mass of the order of 100 million solar masses lies at the center of an active nucleus and that an accretion disk is formed. Penrose pair production in the inner ergosphere of such a massive canonical Kerr black hole is analyzed. The results indicate that: (1) particle pairs are ejected within a 40 deg angle relative to the equator; (2) the particle energy is of the order of 1 GeV per pair; (3) the pressure of the electron-positron relativistic gas is proportional to the electron-positron number density; (4) pair production may occur in bursts; and (5) the overall lifetime of an active nucleus would depend on the time required to exhaust the disk of its matter content. A test of the theory is suggested which involves observation of the 0.5-MeV pair-annihilation gamma rays that would be generated by annihilating particle pairs.

  14. RADIATION-DRIVEN FOUNTAIN AND ORIGIN OF TORUS AROUND ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Wada, Keiichi

    2012-10-10

    We propose a plausible mechanism to explain the formation of the so-called obscuring tori around active galactic nuclei (AGNs) based on three-dimensional hydrodynamic simulations including radiative feedback from the central source. The X-ray heating and radiation pressure on the gas are explicitly calculated using a ray-tracing method. This radiation feedback drives a 'fountain', that is, a vertical circulation of gas in the central few to tens parsecs. Interaction between the non-steady outflows and inflows causes the formation of a geometrically thick torus with internal turbulent motion. As a result, the AGN is obscured for a wide range of solid angles. In a quasi-steady state, the opening angles for the column density toward a black hole <10{sup 23} cm{sup -2} are approximately {+-}30 Degree-Sign and {+-}50 Degree-Sign for AGNs with 10% and 1% Eddington luminosity, respectively. Mass inflows through the torus coexist with the outflow and internal turbulent motion, and the average mass accretion rate to the central parsec region is 2 Multiplication-Sign 10{sup -4} {approx} 10{sup -3} M{sub Sun} yr{sup -1}; this is about 10 times smaller than accretion rate required to maintain the AGN luminosity. This implies that relatively luminous AGN activity is intrinsically intermittent or that there are other mechanisms, such as stellar energy feedback, that enhance the mass accretion to the center.

  15. Alignments Of Black Holes with Their Warped Accretion Disks and Episodic Lifetimes of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Li, Yan-Rong; Wang, Jian-Min; Cheng, Cheng; Qiu, Jie

    2015-05-01

    Warped accretion disks have attracted intense attention because of their critical role in shaping the spin of supermassive massive black holes (SMBHs) through the Bardeen-Petterson effect, a general relativistic effect that leads to final alignments or anti-alignments between black holes and warped accretion disks. We study such alignment processes by explicitly taking into account the finite sizes of accretion disks and the episodic lifetimes of active galactic nuclei (AGNs) that delineate the duration of gas fueling onto accretion disks. We employ an approximate global model to simulate the evolution of accretion disks, allowing us to determine the gravitomagnetic torque that drives the alignments in a simple way. We then track down the evolutionary paths for mass and spin of black holes both in a single activity episode and over a series of episodes. Given with randomly and isotropically oriented gas fueling over episodes, we calculate the spin evolution with different episodic lifetimes and find that it is quite sensitive to the lifetimes. We therefore propose that the spin distribution of SMBHs can place constraints on the episodic lifetimes of AGNs and vice versa. The applications of our results on the observed spin distributions of SMBHs and the observed episodic lifetimes of AGNs are discussed, although both measurements at present are too ambiguous for us to draw a firm conclusion. Our prescription can be easily incorporated into semi-analytic models for black hole growth and spin evolution.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  17. MID- AND FAR-INFRARED PROPERTIES OF A COMPLETE SAMPLE OF LOCAL ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Ichikawa, Kohei; Ueda, Yoshihiro; Terashima, Yuichi; Oyabu, Shinki; Gandhi, Poshak; Nakagawa, Takao; Matsuta, Keiko

    2012-07-20

    We investigate the mid- (MIR) to far-infrared (FIR) properties of a nearly complete sample of local active galactic nuclei (AGNs) detected in the Swift/Burst Alert Telescope (BAT) all-sky hard X-ray (14-195 keV) survey, based on the cross correlation with the AKARI infrared survey catalogs complemented by those with Infrared Astronomical Satellite and Wide-field Infrared Survey Explorer. Out of 135 non-blazer AGNs in the Swift/BAT nine-month catalog, we obtain the MIR photometric data for 128 sources either in the 9, 12, 18, 22, and/or 25 {mu}m band. We find good correlation between their hard X-ray and MIR luminosities over three orders of magnitude (42 < log {lambda}L{sub {lambda}}(9, 18 {mu}m) < 45), which is tighter than that with the FIR luminosities at 90 {mu}m. This suggests that thermal emission from hot dusts irradiated by the AGN emission dominate the MIR fluxes. Both X-ray unabsorbed and absorbed AGNs follow the same correlation, implying isotropic infrared emission, as expected in clumpy dust tori rather than homogeneous ones. We find excess signals around 9 {mu}m in the averaged infrared spectral energy distribution from heavy obscured 'new type' AGNs with small scattering fractions in the X-ray spectra. This could be attributed to the polycyclic aromatic hydrocarbon emission feature, suggesting that their host galaxies have strong starburst activities.

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

    SciTech Connect

    Juneau, Stephanie; Bournaud, Frederic; Daddi, Emanuele; Elbaz, David; Alexander, David M.; Mullaney, James R.; Magnelli, Benjamin; Hwang, Ho Seong; Willner, S. P.; Coil, Alison L.; Rosario, David J.; Trump, Jonathan R.; Faber, S. M.; Kocevski, Dale D.; Cooper, Michael C.; Frayer, David T.; and others

    2013-02-20

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

  19. A census of gas outflows in type 2 active galactic nuclei

    SciTech Connect

    Bae, Hyun-Jin; Woo, Jong-Hak E-mail: woo@astro.snu.ac.kr

    2014-11-01

    We perform a census of ionized gas outflows using a sample of ∼23,000 type 2 active galactic nuclei (AGNs) out to z ∼ 0.1. By measuring the velocity offset of narrow emission lines, i.e., [O III] λ5007 and Hα, with respect to the systemic velocity measured from the stellar absorption lines, we find that 47% of AGNs display an [O III] line-of-sight velocity offset ≥ 20 km s{sup –1}. The fraction of the [O III] velocity offset in type 2 AGNs is comparable to that in type 1 AGNs after considering the projection effect. AGNs with a large [O III] velocity offset preferentially have a high Eddington ratio, implying that the detected velocity offsets are related to black hole activity. The distribution of the host galaxy inclination is clearly different between the AGNs with blueshifted [O III] and the AGNs with redshifted [O III], supporting the combined model of the biconical outflow and dust obscuration. In addition, for ∼3% of AGNs, [O III] and Hα show comparable large velocity offsets, indicating a more complex gas kinematics than decelerating outflows in a stratified narrow-line region.

  20. Spectral-luminosity evolution of active galactic nuclei and the cosmic X- and gamma ray background

    NASA Technical Reports Server (NTRS)

    Leiter, Darryl; Boldt, Elihu

    1992-01-01

    Coherent electromagnetic dynamo acceleration processes, which act on charge particles within the context of black hole accretion disk scenarios, are generally regarded as the underlying central power source for active galactic nuclei (AGN). If the precursor active galaxies (PAG) for such AGN are formed at high redshift and contain initial seed black holes with mass approximately equal to 10(exp 4) solar masses, then the Eddington limited X-ray radiation emitted during their lifetime will undergo the phenomenon of 'spectral-luminosity evolution'. When accretion disks are first formed at the onset of galaxy formation the accretion rate occurs at very high values of luminosity/size compactness parameter L/R greater than 10(exp 30) erg/cm-sec. In the absence of extended structure, such high values of L/R generate dynamic constraints which suppress coherent, black hole/accretion disk dynamo particle acceleration processes. This inhibits nonthermal radiation processes and causes the spectrum of X-radiation emitted by PAG to be predominantly thermal. A superposition of PAG sources at z is greater than or equal to 6 can account for the residual cosmic X-ray background (CXB) obtained from the total CXB after subtraction of foreground AGN sources associated with present epoch Seyfert galaxies. The manner in which the PAG undergo spectral-luminosity evolution into Seyfert galaxies is investigated.

  1. ANISOTROPIC METAL-ENRICHED OUTFLOWS DRIVEN BY ACTIVE GALACTIC NUCLEI IN CLUSTERS OF GALAXIES

    SciTech Connect

    Kirkpatrick, C. C.; McNamara, B. R.; Cavagnolo, K. W.

    2011-04-20

    We present an analysis of the spatial distribution of metal-rich gas in 10 galaxy clusters using deep observations from the Chandra X-ray Observatory. The brightest cluster galaxies (BCGs) have experienced recent active galactic nucleus activity in the forms of bright radio emission, cavities, and shock fronts embedded in the hot atmospheres. The heavy elements are distributed anisotropically and are aligned with the large-scale radio and cavity axes. They are apparently being transported from the halo of the BCG into the intracluster medium along large-scale outflows driven by the radio jets. The radial ranges of the metal-enriched outflows are found to scale with jet power as R{sub Fe} {proportional_to} P {sup 0.42}{sub jet}, with a scatter of only 0.5 dex. The heavy elements are transported beyond the extent of the inner cavities in all clusters, suggesting that this is a long-lasting effect sustained over multiple generations of outbursts. Black holes in BCGs will likely have difficulty ejecting metal-enriched gas beyond 1 Mpc unless their masses substantially exceed 10{sup 9} M{sub sun}.

  2. THE CONNECTION BETWEEN 3.3 {mu}m POLYCYCLIC AROMATIC HYDROCARBON EMISSION AND ACTIVE GALACTIC NUCLEUS ACTIVITY

    SciTech Connect

    Woo, Jong-Hak; Park, Dawoo; Kim, Ji Hoon; Imanishi, Masatoshi

    2012-02-15

    We investigate the connection between starburst and active galactic nucleus (AGN) activity by comparing 3.3 {mu}m polycyclic aromatic hydrocarbon (PAH) emission with AGN properties. Utilizing the slitless spectroscopic capability of the AKARI space telescope, we observe a moderate-luminosity Type I AGN at z {approx} 0.4 to measure global starburst activity. The 3.3 {mu}m PAH emissions are detected for 7 out of 26 target galaxies. We find no strong correlation between the 3.3 {mu}m PAH emission and AGN luminosity in the limited range of the observed AGN luminosity, suggesting that global star formation may not be closely related to AGN activity. Combining our measurements with previous 3.3 {mu}m measurements of low-redshift Type I AGNs in the literature, we investigate the connection between nuclear starburst and AGN activity. In contrast to global star formation, the 3.3 {mu}m PAH luminosity measured from the central part of galaxies correlates with AGN luminosity, implying that starburst activity and AGN activity are directly connected in the nuclear region.

  3. Flares from Galactic Centre pulsars: a new class of X-ray transients?

    NASA Astrophysics Data System (ADS)

    Giannios, Dimitrios; Lorimer, Duncan R.

    2016-06-01

    Despite intensive searches, the only pulsar within 0.1 pc of the central black hole in our Galaxy, Sgr A*, is a radio-loud magnetar. Since magnetars are rare among the Galactic neutron star population, and a large number of massive stars are already known in this region, the Galactic Centre (GC) should harbour a large number of neutron stars. Population syntheses suggest several thousand neutron stars may be present in the GC. Many of these could be highly energetic millisecond pulsars which are also proposed to be responsible for the GC gamma-ray excess. We propose that the presence of a neutron star within 0.03 pc from Sgr A* can be revealed by the shock interactions with the disc around the central black hole. As we demonstrate, these interactions result in observable transient non-thermal X-ray and gamma-ray emission over time-scales of months, provided that the spin-down luminosity of the neutron star is Lsd ˜ 1035 erg s-1. Current limits on the population of normal and millisecond pulsars in the GC region suggest that a number of such pulsars are present with such luminosities.

  4. Aspects of Supermassive Black Hole Growth in Nearby Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Lena, Davide

    Super-massive black holes (SBHs) have long been identified as the engines of active galactic nuclei (AGNs) and are now considered to play a key role in galaxy evolution. In this dissertation I present results from two observational studies conducted on nearby AGNs with the aim of furthering our understanding of SBH growth and their interplay with the host galaxies. The first study is an observational search for SBHs spatially offset from the center of their host galaxies. Such offsets can be considered signatures of gravitational recoil following the coalescence of an SBH binary system (formed in the aftermath of a galaxy merger) due to emission of gravitational waves. The study is based on a photometric analysis of fourteen nearby elliptical galaxies observed with the Hubble Space Telescope. I find that parsec-scale offsets are common. However, while these are individually consistent with residual gravitational recoil oscillations, there is a high probability that larger offsets than those actually observed should have been found in the sample as a whole. There are a number of possible explanations for this result: the galaxy merger rate may be lower than current estimates; SBH-binaries may reach the merger stage with a configuration which minimizes recoil velocities; or the SBH oscillations are more quickly damped than predicted. In the second study I use integral field spectroscopy obtained with the Gemini South telescope to investigate the kinematics of the circum-nuclear ionized gas in two active galaxies: NGC 1386, a Seyfert 2, and NGC 1365, a Seyfert 1. The goal of the study is to investigate outflows in low-luminosity AGNs, and the mechanisms channeling gas (the SBH fuel) from the inner kiloparsec down to a few tens of parsecs from the SBH. I find that the dominant kinematic components can be explained as a combination of rotation in the large-scale galactic disk and compact outflows along the axis of the AGN "radiation cone". However, in the case of NGC

  5. The stellar populations of low-luminosity active galactic nuclei - III. Spatially resolved spectral properties

    NASA Astrophysics Data System (ADS)

    Cid Fernandes, R.; González Delgado, R. M.; Storchi-Bergmann, T.; Martins, L. Pires; Schmitt, H.

    2005-01-01

    In a recently completed survey of the stellar population properties of low-ionization nuclear emission-line regions (LINERs) and LINER/HII transition objects (TOs), we have identified a numerous class of galactic nuclei which stand out because of their conspicuous 108-9 yr populations, traced by high-order Balmer absorption lines and other stellar indices. These objects are called `young-TOs', because they all have TO-like emission-line ratios. In this paper we extend this previous work, which concentrated on the nuclear properties, by investigating the radial variations of spectral properties in low-luminosity active galactic nuclei (LLAGNs). Our analysis is based on high signal-to-noise ratio (S/N) long-slit spectra in the 3500-5500 Å interval for a sample of 47 galaxies. The data probe distances of typically up to 850 pc from the nucleus with a resolution of ~100 pc (~1 arcsec) and S/N ~ 30. Stellar population gradients are mapped by the radial profiles of absorption-line equivalent widths and continuum colours along the slit. These variations are further analysed by means of a decomposition of each spectrum in terms of template galaxies representative of very young (<=107 yr), intermediate age (108-9 yr) and old (1010 yr) stellar populations. This study reveals that young-TOs also differ from old-TOs and old-LINERs in terms of the spatial distributions of their stellar populations and dust. Specifically, our main findings are as follows. (i) Significant stellar population gradients are found almost exclusively in young-TOs. (ii) The intermediate age population of young-TOs, although heavily concentrated in the nucleus, reaches distances of up to a few hundred pc from the nucleus. Nevertheless, the half width at half-maximum of its brightness profile is more typically 100 pc or less. (iii) Objects with predominantly old stellar populations present spatially homogeneous spectra, be they LINERs or TOs. (iv) Young-TOs have much more dust in their central regions

  6. On different types of instabilities in black hole accretion discs: implications for X-ray binaries and active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Janiuk, Agnieszka; Czerny, Bożena

    2011-07-01

    We discuss two important instability mechanisms that may lead to the limit-cycle oscillations of the luminosity of the accretion discs around compact objects: ionization instability and radiation pressure instability. Ionization instability is well established as a mechanism of X-ray novae eruptions in black hole binary systems, but its applicability to active galactic nuclei (AGN) is still problematic. Radiation pressure theory has still a very weak observational background in any of these sources. In this paper, we attempt to confront the parameter space of these instabilities with the observational data. At the basis of this simple survey of sources properties, we argue that the radiation pressure instability is likely to be present in several Galactic sources with the Eddington ratios being above 0.15 and in AGN with the Eddington ratio above 0.025. Our results favour the parametrization of the viscosity through the geometrical mean of the radiation and gas pressure in both Galactic sources and AGN. More examples of the quasi-regular outbursts in the time-scales of 100 s in Galactic sources and hundreds of years in AGN are needed to formulate firm conclusions. We also show that the disc sizes in the X-ray novae are consistent with the ionization instability. This instability may also considerably influence the lifetime cycle and overall complexity in the supermassive black hole environment.

  7. Spitzer and JCMT Observations of the Active Galactic Nucleus in the Sombrero Galaxy (NGC 4594)

    NASA Astrophysics Data System (ADS)

    Bendo, George J.; Buckalew, Brent A.; Dale, Daniel A.; Draine, Bruce T.; Joseph, Robert D.; Kennicutt, Robert C., Jr.; Sheth, Kartik; Smith, John-David T.; Walter, Fabian; Calzetti, Daniela; Cannon, John M.; Engelbracht, Charles W.; Gordon, Karl D.; Helou, George; Hollenbach, David; Murphy, Eric J.; Roussel, Hélène

    2006-07-01

    We present Spitzer 3.6-160 μm images, Spitzer mid-infrared spectra, and JCMT SCUBA 850 μm images of the Sombrero Galaxy (NGC 4594), an Sa galaxy with a 109 Msolar low-luminosity active galactic nucleus (AGN). The brightest infrared sources in the galaxy are the nucleus and the dust ring. The spectral energy distribution of the AGN demonstrates that, while the environment around the AGN is a prominent source of mid-infrared emission, it is a relatively weak source of far-infrared emission, as had been inferred for AGNs in previous research. The weak nuclear 160 μm emission and the negligible polycyclic aromatic hydrocarbon emission from the nucleus also implies that the nucleus is a site of only weak star formation activity and the nucleus contains relatively little cool interstellar gas needed to fuel such activity. We propose that this galaxy may be representative of a subset of low-ionization nuclear emission region galaxies that are in a quiescent AGN phase because of the lack of gas needed to fuel circumnuclear star formation and Seyfert-like AGN activity. Surprisingly, the AGN is the predominant source of 850 μm emission. We examine the possible emission mechanisms that could give rise to the 850 μm emission and find that neither thermal dust emission, CO line emission, bremsstrahlung emission, nor the synchrotron emission observed at radio wavelengths can adequately explain the measured 850 μm flux density by themselves. The remaining possibilities for the source of the 850 μm emission include a combination of known emission mechanisms, synchrotron emission that is self-absorbed at wavelengths longer than 850 μm, or unidentified spectral lines in the 850 μm band.

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

    SciTech Connect

    Davies, R. I.; Erwin, P.; Burtscher, L.; Lin, M.; Orban de Xivry, G.; Rosario, D. J.; Schnorr-Müller, A.; Maciejewski, W.; Hicks, E. K. S.; Emsellem, E.; Dumas, G.; Malkan, M. A.; Müller-Sánchez, F.; Tran, A.

    2014-09-10

    We analyze the two-dimensional distribution and kinematics of the stars as well as molecular and ionized gas in the central few hundred parsecs of five active and five matched inactive galaxies. The equivalent widths of the Brγ line indicate that there is no ongoing star formation in their nuclei, although recent (terminated) starbursts are possible in the active galaxies. The stellar velocity fields show no signs of non-circular motions, while the 1-0 S(1) H{sub 2} kinematics exhibit significant deviations from simple circular rotation. In the active galaxies the H{sub 2} kinematics reveal inflow and outflow superimposed on disk rotation. Steady-state circumnuclear inflow is seen in three active galactic nuclei (AGNs), and hydrodynamical models indicate it can be driven by a large-scale bar. In three of the five AGNs, molecular outflows are spatially resolved. The outflows are oriented such that they intersect, or have an edge close to, the disk, which may be the source of molecular gas in the outflow. The relatively low speeds imply the gas will fall back onto the disk, and with moderate outflow rates, they will have only a local impact on the host galaxy. H{sub 2} was detected in two inactive galaxies. These exhibit chaotic circumnuclear dust morphologies and have molecular structures that are counter-rotating with respect to the main gas component, which could lead to gas inflow in the near future. In our sample, all four galaxies with chaotic dust morphology in the circumnuclear region exist in moderately dense groups with 10-15 members where accretion of stripped gas can easily occur.

  9. Modeling Hot Gas Flow in the Low-Luminosity Active Galactic Nucleus of NGC3115

    NASA Astrophysics Data System (ADS)

    Shcherbakov, Roman V.; Wong, K.; Irwin, J.; Reynolds, C. S.

    2014-01-01

    Based on the dynamical estimates of the black hole (BH) mass, NGC3115 hosts the closest billion solar mass BH. Deep studies of the center revealed a very underluminous active galactic nucleus (AGN) immersed in an old massive nuclear star cluster. Recent 1Ms Chandra X-ray visionary project observations of the NGC3115 nucleus resolved hot tenuous gas, which fuels the AGN. In this work we connect the processes in the nuclear star cluster with the feeding of the supermassive BH. We model the hot gas flow sustained by the injection of matter and energy by the stars and supernova explosions. We incorporate electron heat conduction, the gravitational pull of the stellar mass, cooling, and Coulomb collisions. We reach reduced χi^2=1 fitting simulated X-ray emission to the spatially and spectrally resolved observed X-ray data. Radial modeling favors a low BH mass <1.3*10^{9}Msun. The best-fitting supernova rate and the best-fitting mass injection rate are consistent with their expected values. The stagnation point is at r_ s 1arcsec, so that most of gas, including the gas at a Bondi radius r_B=2-4arcsec, outflows from the region. We put an upper limit on the accretion rate at 2*10^{-3}Msun/yr. We find a shallow density profile r^{-β} with β 1 over a large dynamic range. This density profile is determined in the feeding region 0.5-10arcsec as an interplay of four processes and effects: (1) the radius-dependent mass injection, (2) the effect of the galactic gravitational potential, (3) the accretion flow onset at r<1arcsec, and (4) the outflow at r>1arcsec. Conduction makes the density profile shallow only very close to the BH at r<0.1arcsec. The gas temperature is close to the virial temperature T_v at any radius. The temperature profile is shallow outside of the Bondi radius because the enclosed stellar mass is proportional to radius M_en r, which leads to flat virial temperature profile.

  10. Modeling hot gas flow in the low-luminosity active galactic nucleus of NGC 3115

    SciTech Connect

    Shcherbakov, Roman V.; Reynolds, Christopher S.; Wong, Ka-Wah; Irwin, Jimmy A.

    2014-02-20

    Based on the dynamical black hole (BH) mass estimates, NGC 3115 hosts the closest billion solar mass BH. Deep studies of the center revealed a very underluminous active galactic nucleus (AGN) immersed in an old massive nuclear star cluster. Recent 1 Ms Chandra X-ray visionary project observations of the NGC 3115 nucleus resolved hot tenuous gas, which fuels the AGN. In this paper we connect the processes in the nuclear star cluster with the feeding of the supermassive BH. We model the hot gas flow sustained by the injection of matter and energy from the stars and supernova explosions. We incorporate electron heat conduction as the small-scale feedback mechanism, the gravitational pull of the stellar mass, cooling, and Coulomb collisions. Fitting simulated X-ray emission to the spatially and spectrally resolved observed data, we find the best-fitting solutions with χ{sup 2}/dof = 1.00 for dof = 236 both with and without conduction. The radial modeling favors a low BH mass <1.3 × 10{sup 9} M {sub ☉}. The best-fitting supernova rate and the best-fitting mass injection rate are consistent with their expected values. The stagnation point is at r {sub st} ≲ 1'', so that most of the gas, including the gas at a Bondi radius r{sub B} = 2''-4'', outflows from the region. We put an upper limit on the accretion rate at 2 × 10{sup –3} M {sub ☉} yr{sup –1}. We find a shallow density profile n∝r {sup –β} with β ≈ 1 over a large dynamic range. This density profile is determined in the feeding region 0.''5-10'' as an interplay of four processes and effects: (1) the radius-dependent mass injection, (2) the effect of the galactic gravitational potential, (3) the accretion flow onset at r ≲ 1'', and (4) the outflow at r ≳ 1''. The gas temperature is close to the virial temperature T{sub v} at any radius.

  11. X-ray color analysis of the spectra of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Netzer, Hagai; Turner, T. J.; George, Ian M.

    1994-01-01

    The identification and detection of X-ray absorption and emission features depends on the resolution and the signal-to-noise ratio (S/N) of the observation, the understanding of the instrument response, and the Galactic line-of-sight absorption. Since many of the active galactic nucleus (AGN) data sets are limited in their S/N and full modeling of the physical conditions is rather complicated, we suggest a new analysis method based on 'X-ray colors.' The two sets of X-ray colors, defined for low (ROSAT Position Sensitive Proportional Counter (PSPC)) and medium (Broad Band X-Ray Telescope (BBXRT)) and ASCA Solid-State Imaging Spectrometers (SIS) resolution experiments, are used to separate regions of different physical conditions in a two-dimensional color-color plane. They are similar but superior to previous methods using the X-ray 'hardness ratio' in being able to reveal more of the physical properties of the source. We illustrate the use of such diagrams by studying a number of AGNs suspected of showing absorption features. A sample of 14 AGNs observed by the ROSAT PSPC is presented which includes several objects with suspected 'warm absorbers' along the line-of-sight to the nucleus, several others exhibiting intrinsic continuum variations, and a number of control objects thought to be featureless. Our new observations show, for the first time, the color variation as a function of time for three of the Seyfert 1 sources: NGC 4051, Mrk 335, and Mrk 766. The variations suggest that in two sources we are witnessing real changes in continuum shape, while one (NGC 4051) is consistent with having a warm absorber. Four of the objects observed by BBXRT are reanalyzed using our X-ray colors. Out of these, we discuss in detail the case of NGC 4151 and show that the color-color analysis agrees very well with previous, detailed spectral fitting methods. In particular, we confirm that the observed BBXRT observation of this source is not consistent with the warm absorber

  12. The origins of active galactic nuclei obscuration: the 'torus' as a dynamical, unstable driver of accretion

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Hayward, Christopher C.; Narayanan, Desika; Hernquist, Lars

    2012-02-01

    Recent multiscale simulations have made it possible to follow gas inflows responsible for high-Eddington ratio accretion on to massive black holes (BHs) from galactic scales to the BH accretion disc. When sufficient gas is driven towards a BH, gravitational instabilities generically form lopsided, eccentric discs that propagate inwards from larger radii. The lopsided stellar disc exerts a strong torque on the gas, driving inflows that fuel the growth of the BH. Here, we investigate the possibility that the same disc, in its gas-rich phase, is the putative 'torus' invoked to explain obscured active galactic nuclei (AGN) and the cosmic X-ray background. The disc is generically thick and has characteristic ˜1-10 pc sizes and masses resembling those required of the torus. Interestingly, the scale heights and obscured fractions of the predicted torii are substantial even in the absence of strong stellar feedback providing the vertical support. Rather, they can be maintained by strong bending modes and warps/twists excited by the inflow-generating instabilities. A number of other observed properties commonly attributed to 'feedback' processes may in fact be explained entirely by dynamical, gravitational effects: the lack of alignment between torus and host galaxy, correlations between local star formation rate (SFR) and turbulent gas velocities and the dependence of obscured fractions on AGN luminosity or SFR. We compare the predicted torus properties with observations of gas surface density profiles, kinematics, scale heights and SFR densities in AGN, and find that they are consistent in all cases. We argue that it is not possible to reproduce these observations and the observed column density distribution without a clumpy gas distribution, but allowing for simple clumping on small scales the predicted column density distribution is in good agreement with observations from NH˜ 1020-1027 cm-2. We examine how the NH distribution scales with galaxy and AGN properties

  13. X-ray spectra and time variability of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.

    1984-01-01

    The X-ray spectra of broad line active galactic nuclei (AGN) of all types (Seyfert I's, NELG's, broadline radio galaxies) are well fit by a power law in the .5 to 100 keV band of man energy slope alpha = .68 + or - .15. There is, as yet, no strong evidence for time variability of this slope in a given object. The constraints that this places on simple models of the central energy source are discussed. BL Lac objects have quite different X-ray spectral properties and show pronounced X-ray spectral variability. On time scales longer than 12 hours most radio quiet AGN do not show strong, delta I/I .5, variability. The probability of variability of these AGN seems to be inversely related to their luminosity. However characteristics timescales for variability have not been measured for many objects. This general lack of variability may imply that most AGN are well below the Eddington limit. Radio bright AGN tend to be more variable than radio quiet AGN on long, tau approx 6 month, timescales.

  14. ACTIVE GALACTIC NUCLEI SELECTED FROM GALEX SPECTROSCOPY: THE IONIZING SOURCE SPECTRUM AT z {approx} 1 ,

    SciTech Connect

    Barger, Amy J.; Cowie, Lennox L. E-mail: cowie@ifa.hawaii.ed

    2010-08-01

    We use a complete sample of Ly{alpha}-emission-line-selected active galactic nuclei (AGNs) obtained from nine deep blank fields observed with the grism spectrographs on the Galaxy Evolution Explorer (GALEX) satellite to measure the normalization and the spectral shape of the AGN contribution to the ionizing background (rest-frame wavelengths 700-900 A) at z {approx} 1. Our sample consists of 139 sources selected in the redshift range z = 0.65-1.25 in the near-ultraviolet (NUV; 2371 A central wavelength) channel. The area covered is 8.2 deg{sup 2} to a NUV magnitude of 20.5 (AB) and 0.92 deg{sup 2} at the faintest magnitude limit of 21.8. The GALEX AGN luminosity function agrees well with those obtained using optical and X-ray AGN samples, and the measured redshift evolution of the ionizing volume emissivity is similar to that previously obtained by measuring the GALEX far-ultraviolet (FUV; 1528 A central wavelength) magnitudes of an X-ray-selected sample. For the first time, we are able to construct the shape of the ionizing background at z {approx} 1 in a fully self-consistent way.

  15. X-ray refelection from photoionized media in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Zycki, Piotr T.; Krolik, Julian H.; Zdziarski, Andrzej A.; Kallman, Timothy R.

    1994-01-01

    We calculate the spectrum of X-ray radiation and reprocessed by a partly ionized optically thick medium in an active galactic nucleus. We self-consistently calculate the ionization balance and thermal balance in the medium along with the distribution of X-ray intensity with optical depth. In addition to absorption or scattering of the incident X-rays, we also compute the spectrum of X-rays emitted by the material, including lines, edges, and bremsstrahlung. The albedo of the medium depends primarily on the X-ray ionization parameter (ratio of incident flux to gas density, zeta(sub Chi), and secondarily on the UV flux generated by dissipation inside the disk; we locate the critical range of zeta(sub Chi) over which the albedo increases from small to nearly unity. While the continuum reflection is very weak below 10 keV when zeta(sub Chi) is small, significnat fluxes are emitted in atomic lines and edges in this energy range. In the limit of large zeta(sub Chi), the albedo below 10 keV increases, but reflection in this band is never gray: some photoelectric absorption remains up to rather large values of zeta(sub Chi), while at still higher values, inverse Compton scattering amplifies the soft X-ray flux. These features are sufficiently sharp that current and near-future X-ray experiments should permit diagnostic measures of zeta(sub Chi).

  16. FULL SPECTRAL SURVEY OF ACTIVE GALACTIC NUCLEI IN THE ROSSI X-RAY TIMING EXPLORER ARCHIVE

    SciTech Connect

    Rivers, Elizabeth; Markowitz, Alex; Rothschild, Richard

    2013-08-01

    We have analyzed spectra for all active galactic nuclei (AGNs) in the Rossi X-ray Timing Explorer archive. We present long-term average values of absorption, Fe line equivalent width (EW), Compton reflection, and photon index, and calculate fluxes and luminosities in the 2-10 keV band for 100 AGN with sufficient brightness and overall observation time to yield high-quality spectral results. We compare these parameters across the different classifications of Seyferts and blazars. Our distributions of photon indices for Seyfert 1s and 2s are consistent with the idea that Seyferts share a common central engine; however, our distributions of Compton reflection hump strengths do not support the classical picture of absorption by a torus and reflection off a Compton-thick disk with type depending only on inclination angle. We conclude that a more complex reflecting geometry such as a combined disk and torus or clumpy torus is likely a more accurate picture of the Compton-thick material. We find that Compton reflection is present in {approx}85% of Seyferts and by comparing Fe line EW's to Compton reflection hump strengths we have found that on average 40% of the Fe line arises in Compton thick material; however, this ratio was not consistent from object to object and did not seem to be dependent on optical classification.

  17. DETERMINING INCLINATIONS OF ACTIVE GALACTIC NUCLEI VIA THEIR NARROW-LINE REGION KINEMATICS. I. OBSERVATIONAL RESULTS

    SciTech Connect

    Fischer, T. C.; Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.

    2013-11-01

    Active galactic nuclei (AGNs) are axisymmetric systems to first order; their observed properties are likely strong functions of inclination with respect to our line of sight (LOS). However, except for a few special cases, the specific inclinations of individual AGNs are unknown. We have developed a promising technique for determining the inclinations of nearby AGNs by mapping the kinematics of their narrow-line regions (NLRs), which are often easily resolved with Hubble Space Telescope [O III] imaging and long-slit spectra from the Space Telescope Imaging Spectrograph. Our studies indicate that NLR kinematics dominated by radial outflow can be fit with simple biconical outflow models that can be used to determine the inclination of the bicone axis, and hence the obscuring torus, with respect to our LOS. We present NLR analysis of 53 Seyfert galaxies and the resulting inclinations from models of 17 individual AGNs with clear signatures of biconical outflows. Our model results agree with the unified model in that Seyfert 1 AGNs have NLRs inclined further toward our LOS than Seyfert 2 AGNs. Knowing the inclinations of these AGN NLRs, and thus their accretion disk and/or torus axes, will allow us to determine how their observed properties vary as a function of polar angle. We find no correlation between the inclinations of the AGN NLRs and the disks of their host galaxies, indicating that the orientation of the gas in the torus is independent of that of the host disk.

  18. ORIENTATION EFFECTS ON THE INNER REGION OF DUSTY TORUS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Kawaguchi, Toshihiro; Mori, Masao

    2010-12-01

    A sublimation process governs the innermost region of the dusty torus of active galactic nuclei. However, the observed inner radius of the torus is systematically smaller than the expected radius by a factor of {approx}1/3. We show that the anisotropy of the emission from accretion disks resolves this conflict naturally and quantitatively. An accretion disk emits lesser radiation in the direction closer to its equatorial plane (i.e., to the torus). We find that the anisotropy makes the torus inner region closer to the central black hole and concave. Moreover, the innermost edge of the torus may connect with the outermost edge of the disk continuously. Considering the anisotropic emission of each clump in the torus, we calculate the near-infrared flux variation in response to a UV flash. For an observer at the polar angle {theta}{sub obs} = 25{sup 0}, the centroid of the time delay is found to be 37% of the delay expected in the case of isotropic illumination, which explains the observed systematic deviation.

  19. Echo mapping of active galactic nuclei broad-line regions: Fundamental algorithms

    NASA Technical Reports Server (NTRS)

    Vio, Roberto; Horne, Keith; Wamsteker, Willem

    1994-01-01

    We formulate and test a series of algorithms for echo mapping the emission-line regions near active galactic nuclei from measurements of correlated variability in their line and continuum light curves. The linear regularization method (LRM) employs a direct inversion of evenly spaced light-curve data, with a regularization parameter that can be used to control the trade-off between noise and resolution. Matrix formulas express the formal solution as well as its variance and covariance in terms of uncertainties in the measurements. Unlike the maximum-entropy method (MEM), LRM applies to kernels with both positive and negative values, but the results are somewhat limited by ringing effects. A positivity constraint proves effective in controlling the ringing. MEM combines regularization and positivity in a natural way, but similar results are also found using positivity constraints with nonentropic regularization functions. Direct inversions of unevenly sampled light curves require interpolating the noisy data. In this case better results are found by solving for both the continuum light curve and kernel function in a simultaneous fit to the data. Our conclusion is that while echo mapping currently gives ambiguous results, the algorithms are not the limiting factor. Progress depends on efforts to increase the accuracy and completeness of sampling of the observed light curves.

  20. Simulating Galaxies and Active Galactic Nuclei in the LSST Image Simulation Effort

    NASA Astrophysics Data System (ADS)

    Pizagno, James; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Chang, C.; Gibson, R. R.; Gilmore, K.; Grace, E.; Hannel, M.; Jernigan, J. G.; Jones, L.; Kahn, S. M.; Krughoff, S. K.; Lorenz, S.; Marshall, S.; Shmakova, S. M.; Sylvestri, N.; Todd, N.; Young, M.

    2011-01-01

    We present an extragalactic source catalog, which includes galaxies and Active Galactic Nuclei, that is used for the Large Survey Synoptic Telescope Imaging Simulation effort. The galaxies are taken from the De Lucia et. al. (2006) semi-analytic modeling (SAM) of the Millennium Simulation. The LSST Image Simulation effort requires full SED information and galaxy morphological information, which is added to the catalog by fitting Bruzual & Charlot (2003) stellar population models, with Cardelli, Clayton, Mathis (1989) dust models, to the BVRIK colors provided by the De Lucia et. al. (2006) SAM. Galaxy morphology is modeled as a double Sersic profile for the disk and bulge. Galaxy morphological information and number counts are matched to existing observations. The catalog contains galaxies with a limiting r-band magnitude of mr=28, which results in roughly 1E6 galaxies per square degree. An existing AGN catalog (MacLeod et. al. 2010) is matched to galaxy hosts in the galaxy catalog using SDSS observations. AGN are morphologically modeled as variable point sources located at the center of the host galaxy. We demonstrate how this extragalactic source catalog allows LSST to plan for extended object extraction, variable extragalactic source detection, sensitivity level determination after image stacking, and perform various other cosmological tests.

  1. Relativistic hadrons and the origin of relativistic outflows in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Contopoulos, John; Kazanas, D.

    1995-01-01

    We examine the hydrodynamic origin of relativistic outflows in active galactic nuclei (AGN). Specifically, we propose that the presence of a population of relativistic hadrons in the AGN 'central engine' and the associated neutron production suffices to produce outflows which under rather general conditions could be relativistic. The main such condition is that the size of the neutron production region be larger than the neutron flight path tau(sub n) approximately 3 x 10(exp 13) cm. This condition guarantees that the mean energy per particle in the proton fluid, resulting from the decay of the neutrons outside their production region, be greater than the proton rest mass. The expansion of this fluid can then lead naturally to a relativistic outflow by conversion of its internal energy to directed motion. We follow the development of such flows by solving the mass, energy as well as the kinetic equation for the proton gas in steady state, taking into account the source terms due to compute accurately the adiabatic index of the expanding gas, and in conjunction with Bernoulli's equation the detailed evolution of the bulk Lorentz factor. We further examine the role of large-scale magnetic fields in confining these outflows to produce the jets observed at larger scales.

  2. Modeling active galactic nucleus feedback in cool-core clusters: The formation of cold clumps

    SciTech Connect

    Li, Yuan; Bryan, Greg L.

    2014-07-10

    We perform high-resolution (15-30 pc) adaptive mesh simulations to study the impact of momentum-driven active galactic nucleus (AGN) feedback in cool-core clusters, focusing in this paper on the formation of cold clumps. The feedback is jet-driven with an energy determined by the amount of cold gas within 500 pc of the super-massive black hole. When the intracluster medium in the core of the cluster becomes marginally stable to radiative cooling, with the thermal instability to the free-fall timescale ratio t{sub TI}/t{sub ff} < 3-10, cold clumps of gas start to form along the propagation direction of the AGN jets. By tracing the particles in the simulations, we find that these cold clumps originate from low entropy (but still hot) gas that is accelerated by the jet to outward radial velocities of a few hundred km s{sup –1}. This gas is out of hydrostatic equilibrium and so can cool. The clumps then grow larger as they decelerate and fall toward the center of the cluster, eventually being accreted onto the super-massive black hole. The general morphology, spatial distribution, and estimated Hα morphology of the clumps are in reasonable agreement with observations, although we do not fully replicate the filamentary morphology of the clumps seen in the observations, probably due to missing physics.

  3. Hard-X-ray spectra of active galactic nuclei in the INTEGRAL complete sample

    NASA Astrophysics Data System (ADS)

    Molina, M.; Bassani, L.; Malizia, A.; Stephen, J. B.; Bird, A. J.; Bazzano, A.; Ubertini, P.

    2013-08-01

    In this paper, we present the hard-X-ray spectral analysis of a complete sample of active galactic nuclei (AGNs) detected by INTEGRAL/IBIS. In conjunction with IBIS spectra, we make use of Swift/BAT data, with the aim of cross-calibrating the two instruments, studying source variability and constraining some important spectral parameters. We find that flux variability is present in at least 14 per cent of the sample, while spectral variability is found only in one object. There is general good agreement between BAT and IBIS spectra, despite a systematic mismatch of about 22 per cent in normalization. When fitted with a simple power-law model, type 1 and type 2 sources appear to have very similar average photon indices, suggesting that they are powered by the same mechanism. As expected, we also find that a simple power law does not always describe the data sufficiently well, thus indicating a certain degree of spectral complexity, which can be ascribed to features like a high energy cut-off and/or a reflection component. Fixing the reflection to be 0, 1 or 2, we find that our sample covers quite a large range in photon indices as well as cut-off energies; however, the spread is due only to a small number of objects, while the majority of the AGNs lie within well-defined boundaries of photon index (1 ≤ Γ ≤ 2) and cut-off energy (30 ≤ Ecut ≤ 300 keV).

  4. Radiation-driven Outflows from and Radiative Support in Dusty Tori of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Chan, Chi-Ho; Krolik, Julian H.

    2016-07-01

    Substantial evidence points to dusty, geometrically thick tori obscuring the central engines of active galactic nuclei (AGNs), but so far no mechanism satisfactorily explains why cool dust in the torus remains in a puffy geometry. Near-Eddington infrared (IR) and ultraviolet (UV) luminosities coupled with high dust opacities at these frequencies suggest that radiation pressure on dust can play a significant role in shaping the torus. To explore the possible effects of radiation pressure, we perform three-dimensional radiative hydrodynamics simulations of an initially smooth torus. Our code solves the hydrodynamics equations, the time-dependent multi–angle group IR radiative transfer (RT) equation, and the time-independent UV RT equation. We find a highly dynamic situation. IR radiation is anisotropic, leaving primarily through the central hole. The torus inner surface exhibits a break in axisymmetry under the influence of radiation and differential rotation; clumping follows. In addition, UV radiation pressure on dust launches a strong wind along the inner surface; when scaled to realistic AGN parameters, this outflow travels at ˜ 5000 {(M/{10}7{M}ȯ )}1/4 {[{L}{UV}/(0.1{L}{{E}})]}1/4 {km} {{{s}}}-1 and carries ˜ 0.1 {(M/{10}7{M}ȯ )}3/4 {[{L}{UV}/(0.1{L}{{E}})]}3/4 M ⊙ yr‑1, where M, {L}{UV}, and {L}{{E}} are the mass, UV luminosity, and Eddington luminosity of the central object respectively.

  5. The effect of active galactic nuclei feedback on the halo mass function

    NASA Astrophysics Data System (ADS)

    Cui, Weiguang; Borgani, Stefano; Murante, Giuseppe

    2014-06-01

    We investigate baryon effects on the halo mass function (HMF), with emphasis on the role played by active galactic nuclei (AGN) feedback. Haloes are identified with both friends-of-friends (FoF) and spherical overdensity (SO) algorithms. We embed the standard SO algorithm into a memory-controlled frame program and present the Python spherIcAl Overdensity code - PIAO (Chinese character: ). For both FoF and SO haloes, the effect of AGN feedback is that of suppressing the HMFs to a level even below that of dark matter (DM) simulations. The ratio between the HMFs in the AGN and in the DM simulations is ˜0.8 at overdensity Δc = 500, a difference that increases at higher overdensity Δc = 2500, with no significant redshift and mass dependence. A decrease of the halo masses ratio with respect to the DM case induces the decrease of the HMF in the AGN simulation. The shallower inner density profiles of haloes in the AGN simulation witnesses that mass reduction is induced by the sudden displacement of gas induced by thermal AGN feedback. We provide fitting functions to describe halo mass variations at different overdensities, which can recover the HMFs with a residual random scatter ≲5 per cent for halo masses larger than 1013 h-1 M⊙.

  6. Gamma-ray active galactic nucleus type through machine-learning algorithms

    NASA Astrophysics Data System (ADS)

    Hassan, T.; Mirabal, N.; Contreras, J. L.; Oya, I.

    2013-01-01

    The Fermi Gamma-ray Space Telescope (Fermi) is producing the most detailed inventory of the gamma-ray sky to date. Despite tremendous achievements approximately 25 per cent of all Fermi extragalactic sources in the Second Fermi Large Area Telescope Catalogue (2FGL) are listed as active galactic nuclei (AGN) of uncertain type. Typically, these are suspected blazar candidates without a conclusive optical spectrum or lacking spectroscopic observations. Here, we explore the use of machine-learning algorithms - random forests and support vector machines - to predict specific AGN subclass based on observed gamma-ray spectral properties. After training and testing on identified/associated AGN from the 2FGL we find that 235 out of 269 AGN of uncertain type have properties compatible with gamma-ray BL Lacertae and flat-spectrum radio quasars with accuracy rates of 85 per cent. Additionally, direct comparison of our results with class predictions made after following the infrared colour-colour space of Massaro et al. shows that the agreement rate is over four-fifths for 54 overlapping sources, providing independent cross-validation. These results can help tailor follow-up spectroscopic programmes and inform future pointed surveys with ground-based Cherenkov telescopes.

  7. X-ray induced stellar mass loss near active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Voit, G. Mark; Shull, J. Michael

    1988-01-01

    The effects of UV and X-ray radiation on stars in active galactic nuclei (AGN) are critically evaluated. Mass loss rates in X-ray-induced winds are evaluated for realistic red giant models, and the effects of the ablation of stellar envelopes by radiation pressure are considered. The importance of X-ray-induced mass loss in the standard quasar model is evaluated and whether it can provide a source of accretion fuel or emission-line clouds is discussed. It is concluded that thermal winds driven by X-ray heating are a minor total supply of mass to AGN, but that thermal plus line-driven winds and stellar ablation may increase the mass loss and improve the chances for supplying a fraction of the necessary mass supply to the central object. It is speculated that when steady winds are inefficient, complex time-dependent processes due to X-ray energy injection deep into a stellar atmosphere could still release significant mass from stars.

  8. The standard model and some new directions. [for scientific theory of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Blandford, R. D.; Rees, M. J.

    1992-01-01

    A 'standard' model of Active Galactic Nuclei (AGN), based upon a massive black hole surrounded by a thin accretion disk, is defined. It is argued that, although there is good evidence for the presence of black holes and orbiting gas, most of the details of this model are either inadequate or controversial. Magnetic field may be responsible for the confinement of continuum and line-emitting gas, for the dynamical evolution of accretion disks and for the formation of jets. It is further argued that gaseous fuel is supplied in molecular form and that this is responsible for thermal re-radiation, equatorial obscuration and, perhaps, the broad line gas clouds. Stars may also supply gas close to the black hole, especially in low power AGN and they may be observable in discrete orbits as probes of the gravitational field. Recent observations suggest that magnetic field, stars, dusty molecular gas and orientation effects must be essential components of a complete description of AGN. The discovery of quasars with redshifts approaching 5 is an important clue to the mechanism of galaxy formation.

  9. Spectral evolution of active galactic nuclei: A unified description of the X-ray and gamma

    NASA Technical Reports Server (NTRS)

    Leiter, D.; Boldt, E.

    1982-01-01

    A model for spectral evolution is presented whereby active galactic nuclei (AGN) of the type observed individually emerge from an earlier stage at z approx = 4 in which they are the thermal X-ray sources responsible for most of the cosmic X-ray background (CXB). The conjecture is pursued that these precursor objects are initially supermassive Schwarzschild black holes with accretion disks radiating near the Eddington luminosity limit. It is noted that after approx. 10 to the 8th power years these central black holes are spun-up to a canonical Kerr equilibrium state (A/M = 0.998; Thorne 1974) and shown how they then can lead to spectral evolution involving non-thermal emission extending to gamma rays, at the expense of reduced thermal disk radiation. That major portion of the CXB remaining after the contribution of usual AGN are considered, while a superposition of AGN sources at z 1 can account for the gamma ray background. Extensive X-ray measurements carried out with the HEAO 1 and 2 missions as well as gamma ray and optical data are shown to compare favorably with principal features of this model.

  10. The Intrinsic Eddington Ratio Distribution of Active Galactic Nuclei in Young Galaxies from SDSS

    NASA Astrophysics Data System (ADS)

    Jones, Mackenzie L.; Hickox, Ryan C.; Black, Christine; Hainline, Kevin Nicholas; DiPompeo, Michael A.

    2016-04-01

    An important question in extragalactic astronomy concerns the distribution of black hole accretion rates, i.e. the Eddington ratio distribution, of active galactic nuclei (AGN). Specifically, it is matter of debate whether AGN follow a broad distribution in accretion rates, or if the distribution is more strongly peaked at characteristic Eddington ratios. Using a sample of galaxies from SDSS DR7, we test whether an intrinsic Eddington ratio distribution that takes the form of a broad Schechter function is in fact consistent with previous work that suggests instead that young galaxies in optical surveys have a more strongly peaked lognormal Eddington ratio distribution. Furthermore, we present an improved method for extracting the AGN distribution using BPT diagnostics that allows us to probe over one order of magnitude lower in Eddington ratio, counteracting the effects of dilution by star formation. We conclude that the intrinsic Eddington ratio distribution of optically selected AGN is consistent with a power law with an exponential cutoff, as is observed in the X-rays. This work was supported in part by a NASA Jenkins Fellowship.

  11. Active galactic nucleus black hole mass estimates in the era of time domain astronomy

    SciTech Connect

    Kelly, Brandon C.; Treu, Tommaso; Pancoast, Anna; Malkan, Matthew; Woo, Jong-Hak

    2013-12-20

    We investigate the dependence of the normalization of the high-frequency part of the X-ray and optical power spectral densities (PSDs) on black hole mass for a sample of 39 active galactic nuclei (AGNs) with black hole masses estimated from reverberation mapping or dynamical modeling. We obtained new Swift observations of PG 1426+015, which has the largest estimated black hole mass of the AGNs in our sample. We develop a novel statistical method to estimate the PSD from a light curve of photon counts with arbitrary sampling, eliminating the need to bin a light curve to achieve Gaussian statistics, and we use this technique to estimate the X-ray variability parameters for the faint AGNs in our sample. We find that the normalization of the high-frequency X-ray PSD is inversely proportional to black hole mass. We discuss how to use this scaling relationship to obtain black hole mass estimates from the short timescale X-ray variability amplitude with precision ∼0.38 dex. The amplitude of optical variability on timescales of days is also anticorrelated with black hole mass, but with larger scatter. Instead, the optical variability amplitude exhibits the strongest anticorrelation with luminosity. We conclude with a discussion of the implications of our results for estimating black hole mass from the amplitude of AGN variability.

  12. The Invariant Twist of Magnetic Fields in the Relativistic Jets of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Contopoulos, Ioannis; Christodoulou, Dimitris M.; Kazanas, Demosthenes; Gabuzda, Denise C.

    2009-01-01

    The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in Active Galactic Nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1 %. This lends support to the hypothesis that the Universe is seeded by B fields that are generated in AGN via this mechanism

  13. X-ray spectral parameters for a sample of 95 active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Vasylenko, A. A.; Zhdanov, V. I.; Fedorova, E. V.

    2015-12-01

    We present a broadband X-ray analysis of a new homogeneous sample of 95 active galactic nuclei (AGN) from the 22-month Swift/BAT all-sky survey. For this sample we treated jointly the X-ray spectra observed by XMM-Newton and INTEGRAL missions for the total spectral range of 0.5-250 keV. Photon index \\varGamma, relative reflection R, equivalent width of Fe K_{α} line EW_{FeK}, hydrogen column density NH, exponential cut-off energy Ec and intrinsic luminosity L_{corr} are determined for all objects of the sample. We investigated correlations \\varGamma-R, EW_{FeK}-L_{corr}, \\varGamma-Ec, EW_{FeK}-NH. Dependence "\\varGamma-R" for Seyfert 1/2 galaxies has been investigated separately. We found that the relative reflection parameter at low power-law indexes for Seyfert 2 galaxies is systematically higher than for Seyfert 1 ones. This can be related to an increasing contribution of the reflected radiation from the gas-dust torus. Our data show that there exists some anticorrelation between EW_{FeK} and L_{corr}, but it is not strong. We have not found statistically significant deviations from the AGN Unified Model.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    Graham et al. found a sample of active galactic nuclei (AGNs) and quasars from the Catalina Real-time Transient Survey (CRTS) that have long-term periodic variations in optical continuum. The nature of the periodicity remains uncertain. We investigate the periodic variability characteristics of the sample by testing the relations of the observed variability periods with AGN optical luminosity, black hole mass and accretion rates, and find no significant correlations. We also test the observed periods in several different aspects related to accretion discs surrounding single black holes, such as the Keplerian rotational periods of 5100 Å photon-emission regions and self-gravity dominated regions and the precessing period of warped discs. These tests shed new lights on understanding AGN variability in general. Under the assumption that the periodic behaviour is associated with supermassive black hole binary systems in particular, we compare the separations (r {D}_{bullet }) against characteristic radii of broad-line regions (R_riptscriptstyle BLR) of the binaries and find r {D}_{bullet }≈ 0.05R_riptscriptstyle BLR. This interestingly implies that these binaries have only circumbinary BLRs.

  15. Long Term Optical and Infrared Reverberation Mapping of High and Low Luminosity Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Gorjian, Varoujan; Barth, Aaron; Brandt, Niel; Dawson, Kyle; Green, Paul; Ho, Luis; Horne, Keith; Jiang, Linhua; Joner, Mike; Kenney, John; McGreer, Ian; Nordgren, Tyler; Schneider, Donald; Shen, Yue; Tao, Charling

    2016-08-01

    Previous Spitzer reverberation monitoring projects looking for UV/optical light absorbed and re-emitted in the IR by dust have been limited to very low luminosity active galactic nuclei (AGN) that could potentially show reverberation within a single cycle (~1 year). Cycle 11-12's two year baseline allowed for the reverberation mapping of 17 high luminosity quasars from the Sloan Digital Sky Survey Reverberation Mapping project. By combining ground based monitoring from Pan-STARRS, CFHT, and Steward Observatory telescopes with Spitzer data we have for the first time detected dust reverberation in quasars. We propose to continue this project to capitalize on the continuing optical motnoring from the ground and to increase the confidence in the detected lags. Additionally, the Call for Proposals asks for up to 1000 hours of observations in the Spitzer CVZ to accommodate battery charging needs. We propose to add to our quasar sample five lower luminosity Seyfert galaxies from the Pan-STARRS ground based optical survey that are in the Spitzer CVZ, which will increase the luminosity range of AGN we are studying and, combined with additional ground based observatories, provide for a continuous monitoring campaign lasting 2 years and thus provide the most detailed study of dust around AGN to date.

  16. SWIFT J195509+261406: Dramatic Flaring Activity from a New Galactic Magnetar

    NASA Astrophysics Data System (ADS)

    de Ugarte Postigo, A.; Castro-Tirado, A. J.; Gorosabel, J.; Fatkhullin, T. A.; Sokolov, V. V.; Jelínek, M.; Sluse, D.; Ferrero, P.; Kann, D. A.; Klose, S.; Bremer, M.; Winters, J. M.; Nurenberger, D.; Pérez-Ramírez, D.; Guerrero, M. A.; French, J.; Melady, G.; Hanlon, L.; McBreen, B.; Aceituno, F. J.; Cunniffe, R.; Kubánek, P.; Vitek, S.; Schulze, S.; Wilson, A. C.; Hudec, R.; González-Pérez, J. M.; Shahbaz, T.; Guziy, S.; Pavlenko, L.; Sonbas, E.; Trushkin, S.; Bursov, N.; Nizhelskij, N. A.; Sabau-Graziati, L.

    Most of the transient sources that are detected in the gamma-ray sky are produced by extragalactic gamma-ray bursts (GRBs). However, it is known that there are some other astronomical objects that can produce high-energy bursts within the Milky Way. SWIFT J195509+261406, just one degree off the Galactic plane, is one of them. It was discovered on the 10th July 2007 by the Swift satellite and was since then observable for a period of a fortnight. During this time SWIFT J195509+261406 experimented dramatic flaring activity that could be observed in near infrared, optical and X-rays. We gathered multi-wavelength observations of SWIFT J195509+261406 including optical, near infrared, millimeter and radio observations. Our dataset covers the time from 1 min after the burst onset to more than 4 months later. Following the initial burst in the gamma-ray band, we recorded more than 40 flaring episodes in the optical bands (reaching up to I c ˜ 15) over a time span of 3 days, plus a faint infrared flare that was observed at late times. After this time, the source slowly faded away until it became undetectable. Using the observations compiled in this work we propose that this source is part of the magnetar family, linking soft gamma-ray repeaters and anomalous X-ray pulsars to dim isolated neutron stars.

  17. Stochastic non-circular motion and outflows driven by magnetic activity in the Galactic bulge region

    NASA Astrophysics Data System (ADS)

    Suzuki, Takeru K.; Fukui, Yasuo; Torii, Kazufumi; Machida, Mami; Matsumoto, Ryoji

    2015-12-01

    By performing a global magnetohydrodynamical simulation for the Milky Way with an axisymmetric gravitational potential, we propose that spatially dependent amplification of magnetic fields possibly explains the observed noncircular motion of the gas in the Galactic centre region. The radial distribution of the rotation frequency in the bulge region is not monotonic in general. The amplification of the magnetic field is enhanced in regions with stronger differential rotation, because magnetorotational instability and field-line stretching are more effective. The strength of the amplified magnetic field reaches ≳0.5 mG, and radial flows of the gas are excited by the inhomogeneous transport of angular momentum through turbulent magnetic field that is amplified in a spatially dependent manner. In addition, the magnetic pressure-gradient force also drives radial flows in a similar manner. As a result, the simulated position-velocity diagram exhibits a time-dependent asymmetric parallelogram-shape owing to the intermittency of the magnetic turbulence; the present model provides a viable alternative to the bar-potential-driven model for the parallelogram shape of the central molecular zone. This is a natural extension into the central few 100 pc of the magnetic activity, which is observed as molecular loops at radii from a few 100 pc to 1 kpc. Furthermore, the time-averaged net gas flow is directed outward, whereas the flows are highly time dependent, which we discuss from a viewpoint of the outflow from the bulge.

  18. OBSERVATIONAL LIMITS ON TYPE 1 ACTIVE GALACTIC NUCLEUS ACCRETION RATE IN COSMOS

    SciTech Connect

    Trump, Jonathan R.; Impey, Chris D.; Gabor, Jared; Kelly, Brandon C.; Elvis, Martin; Hao Heng; Huchra, John P.; Merloni, Andrea; Bongiorno, Angela; Brusa, Marcella; Cappelluti, Nico; McCarthy, Patrick J.; Koekemoer, Anton; Nagao, Tohru; Salvato, Mara; Scoville, Nick Z.

    2009-07-20

    We present black hole masses and accretion rates for 182 Type 1 active galactic nuclei (AGNs) in COSMOS. We estimate masses using the scaling relations for the broad H {beta}, Mg II, and C IV emission lines in the redshift ranges 0.16 < z < 0.88, 1 < z < 2.4, and 2.7 < z < 4.9. We estimate the accretion rate using an Eddington ratio L{sub I}/L{sub Edd} estimated from optical and X-ray data. We find that very few Type 1 AGNs accrete below L{sub I} /L{sub Edd} {approx} 0.01, despite simulations of synthetic spectra which show that the survey is sensitive to such Type 1 AGNs. At lower accretion rates the broad-line region may become obscured, diluted, or nonexistent. We find evidence that Type 1 AGNs at higher accretion rates have higher optical luminosities, as more of their emission comes from the cool (optical) accretion disk with respect to shorter wavelengths. We measure a larger range in accretion rate than previous works, suggesting that COSMOS is more efficient at finding low accretion rate Type 1 AGNs. However, the measured range in accretion rate is still comparable to the intrinsic scatter from the scaling relations, suggesting that Type 1 AGNs accrete at a narrow range of Eddington ratio, with L{sub I} /L{sub Edd} {approx} 0.1.

  19. HOT-DUST-POOR TYPE 1 ACTIVE GALACTIC NUCLEI IN THE COSMOS SURVEY

    SciTech Connect

    Hao Heng; Elvis, Martin; Civano, Francesca; Lanzuisi, Giorgio; Brusa, Marcella; Bongiorno, Angela; Lusso, Elisabeta; Zamorani, Gianni; Comastri, Andrea; Impey, Chris D.; Trump, Jonathan R.; Koekemoer, Anton M.; Le Floc'h, Emeric; Sanders, David; Salvato, Mara; Vignali, Cristian E-mail: elvis@cfa.harvard.ed

    2010-11-20

    We report a sizable class of type 1 active galactic nuclei (AGNs) with unusually weak near-infrared (1-3 {mu}m) emission in the XMM-COSMOS type 1 AGN sample. The fraction of these 'hot-dust-poor' AGNs increases with redshift from 6% at low redshift (z < 2) to 20% at moderate high redshift (2 < z < 3.5). There is no clear trend of the fraction with other parameters: bolometric luminosity, Eddington ratio, black hole mass, and X-ray luminosity. The 3 {mu}m emission relative to the 1 {mu}m emission is a factor of 2-4 smaller than the typical Elvis et al. AGN spectral energy distribution (SED), which indicates a 'torus' covering factor of 2%-29%, a factor of 3-40 smaller than required by unified models. The weak hot dust emission seems to expose an extension of the accretion disk continuum in some of the source SEDs. We estimate the outer edge of their accretion disks to lie at (0.3-2.0) x 10{sup 4} Schwarzschild radii, {approx}10-23 times the gravitational stability radii. Formation scenarios for these sources are discussed.

  20. Detailed Shape and Evolutionary Behavior of the X-Ray Luminosity Function of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Miyaji, T.; Hasinger, G.; Salvato, M.; Brusa, M.; Cappelluti, N.; Civano, F.; Puccetti, S.; Elvis, M.; Brunner, H.; Fotopoulou, S.; Ueda, Y.; Griffiths, R. E.; Koekemoer, A. M.; Akiyama, M.; Comastri, A.; Gilli, R.; Lanzuisi, G.; Merloni, A.; Vignali, C.

    2015-05-01

    We construct the rest-frame 2-10 keV intrinsic X-ray luminosity function (XLF) of active galactic nuclei (AGNs) from a combination of X-ray surveys from the all-sky Swift BAT survey to the Chandra Deep Field South. We use ˜3200 AGNs in our analysis, which covers six orders of magnitude in flux. The inclusion of XMM and Chandra COSMOS data has allowed us to investigate the detailed behavior of the XLF and evolution. In deriving our XLF, we take into account realistic AGN spectrum templates, absorption corrections, and probability density distributions in photometric redshift. We present an analytical expression for the overall behavior of the XLF in terms of the luminosity-dependent density evolution, smoothed two-power-law expressions in 11 redshift shells, three-segment power-law expression of the number density evolution in four luminosity classes, and binned XLF. We observe a sudden flattening of the low luminosity end slope of the XLF slope at z ≳0.6. Detailed structures of the AGN downsizing have also been revealed, where the number density curves have two clear breaks at all luminosity classes above log {{L}X}\\gt 43. The two-break structure is suggestive of two-phase AGN evolution, consisting of major merger triggering and secular processes.

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

    PubMed

    Kalashev, Oleg E; Kusenko, Alexander; Essey, Warren

    2013-07-26

    The observed very high energy spectra of distant blazars are well described by secondary gamma rays produced in line-of-sight interactions of cosmic rays with background photons. In the absence of the cosmic-ray contribution, one would not expect to observe very hard spectra from distant sources, but the cosmic ray interactions generate very high energy gamma rays relatively close to the observer, and they are not attenuated significantly. The same interactions of cosmic rays are expected to produce a flux of neutrinos with energies peaked around 1 PeV. We show that the diffuse isotropic neutrino background from many distant sources can be consistent with the neutrino events recently detected by the IceCube experiment. We also find that the flux from any individual nearby source is insufficient to account for these events. The narrow spectrum around 1 PeV implies that some active galactic nuclei can accelerate protons to EeV energies. PMID:23931348

  2. A Simple test for the existence of two accretion modes in active galactic nuclei

    SciTech Connect

    Jester, Sebastian; /Fermilab

    2005-02-01

    By analogy to the different accretion states observed in black-hole X-ray binaries (BHXBs), it appears plausible that accretion disks in active galactic nuclei (AGN) undergo a state transition between a radiatively efficient and inefficient accretion flow. If the radiative efficiency changes at some critical accretion rate, there will be a change in the distribution of black hole masses and bolometric luminosities at the corresponding transition luminosity. To test this prediction, the author considers the joint distribution of AGN black hole masses and bolometric luminosities for a sample taken from the literature. The small number of objects with low Eddington-scaled accretion rates m < 0.01 and black hole masses M{sub BH} < 10{sup 9} M{sub {circle_dot}} constitutes tentative evidence for the existence of such a transition in AGN. Selection effects, in particular those associated with flux-limited samples, systematically exclude objects in particular regions of the (M{sub BH}, L{sub bol}) plane. Therefore, they require particular attention in the analysis of distributions of black hole mass, bolometric luminosity, and derived quantities like the accretion rate. The author suggests further observational tests of the BHXB-AGN unification scheme which are based on the jet domination of the energy output of BHXBs in the hard state, and on the possible equivalence of BHXB in the very high (or steep power-law) state showing ejections and efficiently accreting quasars and radio galaxies with powerful radio jets.

  3. THE INVARIANT TWIST OF MAGNETIC FIELDS IN THE RELATIVISTIC JETS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Contopoulos, Ioannis; Christodoulou, Dimitris M.; Kazanas, Demosthenes E-mail: dimitris_christodoulou@uml.edu E-mail: gabuzda@physics.ucc.ie

    2009-09-10

    The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in active galactic nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1%. This lends support to the hypothesis that the universe is seeded by B fields that are generated in AGNs via this mechanism and subsequently injected into intergalactic space by the jet outflows.

  4. Tomography of Accretion Flows in Binary Stars and Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Livio, Mario

    2001-01-01

    Under this project, a variety of accretion problems have been studied, with two in particular. In the first, astrophysical jets are observed in many objects ranging from young stars to Active Galactic Nuclei. A major unsolved problem is how do these jets originate from accretion disks. In a series of works, I have examined the launching of outflows from magnetized disks, the extraction of energy from black holes, and the formation of jets in systems like Cataclysmic Variables and supermassive accreting black holes. The results of these works were published in a number of papers. In the second, I examined the potential role of vortices in accretion disks around Young Stellar Objects, for the formation of planets and for angular momentum transport. I showed that vortices are surprisingly stable, and that they are able to concentrate dust in their cores. I also examined the development of spiral shocks in disks. Finally, I studied the evolution of magnetically layered protoplanetary disks, and showed that they exhibit outbursts which could 'pump' the jets that are observed in Herbig-Haro objects. The results of these works were published in a number of papers as well. Additional information on the published papers is contained in the original abstract.

  5. Study of torus structure of low-luminosity active galactic nuclei with Suzaku

    NASA Astrophysics Data System (ADS)

    Kawamuro, T.

    2015-09-01

    We investigate the nature of the torus structure of eight low-luminosity active galactic nuclei (LLAGNs; NGC 1566, NGC 2655, NGC 3718, NGC 3998, NGC 4138, NGC 4941, NGC 5273 and NGC 5643) based on the broad band X-ray spectra (0.5-200 keV) obtained with Suzaku and Swift/BAT. Their X-ray luminosities are smaller than 1e 42 erg/s, while the Eddington ratios span a range from 1e-4 to 1e-2. No significant iron- Kalpha line is detected in the spectra of two LLAGNs with the lowest Eddington ratios (<3e-4) in our sample (NGC 3718 and NGC 3998), suggesting that their tori are little developed. The others show the iron-Kalpha equivalent widths larger than 100 eV. For these six LLAGNs, we utilize the Monte-Carlo based simulation code by Ikeda 09 to constrain the torus parameters by assuming a nearly spherical geometry. The torus solid- angles in three sources (NGC 2655, NGC 4138, and NGC 4941) are constrained to be Omega/2pi > 0.34, and the rest are found to have torus column-densities of logNrmH > 22.7. These results suggest that there are two types of LLAGNs, (1) those where the torus is very small and little mass accretion takes place, and (2) those where the torus is moderately developed and a sufficient amount of gas is supplied to the black hole.

  6. THE GLOBAL IMPLICATIONS OF THE HARD X-RAY EXCESS IN TYPE 1 ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Tatum, M. M.; Turner, T. J.; Reeves, J. N.; Miller, L.

    2013-01-10

    Recent evidence for a strong 'hard excess' of flux at energies {approx}> 20 keV in some Suzaku observations of type 1 active galactic nuclei (AGNs) has motivated an exploratory study of the phenomenon in the local type 1 AGN population. We have selected all type 1 AGNs in the Swift Burst Alert Telescope 58 month catalog and cross-correlated them with the holdings of the Suzaku public archive. We find the hard excess phenomenon to be a ubiquitous property of type 1 AGNs. Taken together, the spectral hardness and equivalent width of Fe K{alpha} emission are consistent with reprocessing by an ensemble of Compton-thick clouds that partially cover the continuum source. In the context of such a model, {approx}80% of the sample has a hardness ratio consistent with >50% covering of the continuum by low-ionization, Compton-thick gas. A more detailed study of the three hardest X-ray spectra in our sample reveal a sharp Fe K absorption edge at {approx}7 keV in each of them, indicating that blurred reflection is not responsible for the very hard spectral forms. Simple considerations place the distribution of Compton-thick clouds at or within the optical broad-line region.

  7. Submillimeter recombination lines in dust-obscured starbursts and active galactic nuclei

    SciTech Connect

    Scoville, N.; Murchikova, L.

    2013-12-10

    We examine the use of submillimeter (submm) recombination lines of H, He, and He{sup +} to probe the extreme ultraviolet (EUV) luminosity of starbursts (SBs) and active galactic nuclei (AGNs). We find that the submm recombination lines of H, He, and He{sup +} are in fact extremely reliable and quantitative probes of the EUV continuum at 13.6 eV to above 54.6 eV. At submm wavelengths, the recombination lines originate from low energy levels (n = 20-50). The maser amplification, which poses significant problems for quantitative interpretation of the higher n, radio frequency recombination lines, is insignificant. Lastly, at submm wavelengths, the dust extinction is minimal. The submm line luminosities are therefore directly proportional to the emission measures (EM{sub ION} = n{sub e} × n {sub ion} × volume) of their ionized regions. We also find that the expected line fluxes are detectable with ALMA and can be imaged at ∼0.''1 resolution in low redshift ultraluminous infrared galaxies. Imaging of the H I lines will provide accurate spatial and kinematic mapping of the star formation distribution in low-z IR-luminous galaxies, and the relative fluxes of the H I and He II recombination lines will strongly constrain the relative contributions of SBs and AGNs to the luminosity. The H I lines should also provide an avenue to constraining the submm dust extinction curve.

  8. Intrinsic physical conditions and structure of relativistic jets in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Nokhrina, E. E.; Beskin, V. S.; Kovalev, Y. Y.; Zheltoukhov, A. A.

    2015-03-01

    The analysis of the frequency dependence of the observed shift of the cores of relativistic jets in active galactic nuclei (AGNs) allows us to evaluate the number density of the outflowing plasma ne and, hence, the multiplicity parameter λ = ne/nGJ, where nGJ is the Goldreich-Julian number density. We have obtained the median value for λmed = 3 × 1013 and the median value for the Michel magnetization parameter σM, med = 8 from an analysis of 97 sources. Since the magnetization parameter can be interpreted as the maximum possible Lorentz factor Γ of the bulk motion which can be obtained for relativistic magnetohydrodynamic (MHD) flow, this estimate is in agreement with the observed superluminal motion of bright features in AGN jets. Moreover, knowing these key parameters, one can determine the transverse structure of the flow. We show that the poloidal magnetic field and particle number density are much larger in the centre of the jet than near the jet boundary. The MHD model can also explain the typical observed level of jet acceleration. Finally, casual connectivity of strongly collimated jets is discussed.

  9. The Case for Standard Irradiated Accretion Disks in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Chelouche, Doron

    2013-07-01

    We analyze the broadband photometric light curves of Seyfert 1 galaxies from the Sergeev et al. sample and find that (1) perturbations propagating across the continuum emitting region are a general phenomenon securely detected in most cases, (2) it is possible to obtain reliable time delays between continuum emission in different wavebands, which are not biased by the contribution of broad emission lines to the signal, and (3) such lags are consistent with the predictions of standard irradiated accretion disk models, given the optical luminosity of the sources. These findings provide new and independent support for standard accretion disks being responsible for the bulk of the (rest) optical emission in low-luminosity active galactic nuclei (AGNs). We interpret our lag measurements in individual objects within the framework of this model and estimate the typical mass accretion rate to be <~ 0.1 M ⊙ yr&-1, with little dependence on the black hole mass. Assuming bolometric corrections typical of type I sources, we find tentative evidence for the radiative efficiency of accretion flows being a rising function of the black hole mass. With upcoming surveys that will regularly monitor the sky, we may be able to better quantify possible departures from standard self-similar models, and identify other modes of accretion in AGNs.

  10. DETECTING ACTIVE GALACTIC NUCLEI USING MULTI-FILTER IMAGING DATA. II. INCORPORATING ARTIFICIAL NEURAL NETWORKS

    SciTech Connect

    Dong, X. Y.; De Robertis, M. M.

    2013-10-01

    This is the second paper of the series Detecting Active Galactic Nuclei Using Multi-filter Imaging Data. In this paper we review shapelets, an image manipulation algorithm, which we employ to adjust the point-spread function (PSF) of galaxy images. This technique is used to ensure the image in each filter has the same and sharpest PSF, which is the preferred condition for detecting AGNs using multi-filter imaging data as we demonstrated in Paper I of this series. We apply shapelets on Canada-France-Hawaii Telescope Legacy Survey Wide Survey ugriz images. Photometric parameters such as effective radii, integrated fluxes within certain radii, and color gradients are measured on the shapelets-reconstructed images. These parameters are used by artificial neural networks (ANNs) which yield: photometric redshift with an rms of 0.026 and a regression R-value of 0.92; galaxy morphological types with an uncertainty less than 2 T types for z ≤ 0.1; and identification of galaxies as AGNs with 70% confidence, star-forming/starburst (SF/SB) galaxies with 90% confidence, and passive galaxies with 70% confidence for z ≤ 0.1. The incorporation of ANNs provides a more reliable technique for identifying AGN or SF/SB candidates, which could be very useful for large-scale multi-filter optical surveys that also include a modest set of spectroscopic data sufficient to train neural networks.

  11. Changing-Look Active Galactic Nuclei With The Time Domain Spectroscopic Survey (TDSS)

    NASA Astrophysics Data System (ADS)

    Runnoe, J.

    2015-09-01

    Changing-look active galactic nuclei (CL-AGNs) present a unique opportunity to study AGN unification and physics. They are observed to transformation between the Type 1 and 2 classifications, supporting a picture in which both orientation to the observer and intrinsic spectral and luminosity evolution can play important roles in unification. In the same spirit, CL-AGNs also offer a way to study behavior brought about by abrupt changes in the accretion rate and may represent a previously unappreciated mode of quasar variability: prolonged "on-" and "off-states". CL-AGNs are uncommon, with only a handful identified to date, but several have been discovered in the Time Domain Spectroscopic Survey (TDSS), and these are likely just the tip of the iceberg. The TDSS offers a promising way of discovering substantial numbers of CL-AGN because it will revisit several thousand objects with previous spectra from the SDSS, many of which are selected based on substantial photometric variability. A statistical sample of these objects will allow us to move beyond the detailed case studies and start to understand the underlying physical mechanisms responsible for these dramatic spectral changes. I will describe our systematic search for CL-AGN in the TDSS and discuss what we have learned from a growing sample of these objects.

  12. THE BALDWIN EFFECT IN THE NARROW EMISSION LINES OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Zhang, Kai; Wang, Ting-Gui; Dong, Xiao-Bo; Gaskell, C. Martin E-mail: twang@ustc.edu.cn E-mail: martin.gaskell@uv.cl

    2013-01-01

    The anti-correlations between the equivalent widths of emission lines and the continuum luminosity in active galactic nuclei (AGNs), known as the Baldwin effect, are well established for broad lines, but are less well studied for narrow lines. In this paper we explore the Baldwin effect of narrow emission lines over a wide range of ionization levels and critical densities using a large sample of broad-line, radio-quiet AGNs taken from Sloan Digital Sky Survey Data Release 4. These type 1 AGNs span three orders of magnitude in continuum luminosity. We show that most narrow lines show a similar Baldwin effect slope of about -0.2, while the significant deviations of the slopes for [N II] {lambda}6583, [O II] {lambda}3727, [Ne V] {lambda}3425, and the narrow component of H{alpha} can be explained by the influence of metallicity, star formation contamination, and possibly by the difference in the shape of the UV-optical continuum. The slopes do not show any correlation with either the ionization potential or the critical density. We show that a combination of 50% variations in continuum near 5100 A and a lognormal distribution of observed luminosity can naturally reproduce a constant Baldwin effect slope of -0.2 for all narrow lines. The variations of the continuum could be due to variability, intrinsic anisotropic emission, or an inclination effect.

  13. A NEW COSMOLOGICAL DISTANCE MEASURE USING ACTIVE GALACTIC NUCLEUS X-RAY VARIABILITY

    SciTech Connect

    Franca, Fabio La; Bianchi, Stefano; Branchini, Enzo; Matt, Giorgio; Ponti, Gabriele

    2014-05-20

    We report the discovery of a luminosity distance estimator using active galactic nuclei (AGNs). We combine the correlation between the X-ray variability amplitude and the black hole (BH) mass with the single-epoch spectra BH mass estimates which depend on the AGN luminosity and the line width emitted by the broad-line region. We demonstrate that significant correlations do exist that allow one to predict the AGN (optical or X-ray) luminosity as a function of the AGN X-ray variability and either the Hβ or the Paβ line widths. In the best case, when the Paβ is used, the relationship has an intrinsic dispersion of ∼0.6 dex. Although intrinsically more disperse than supernovae Ia, this relation constitutes an alternative distance indicator potentially able to probe, in an independent way, the expansion history of the universe. With respect to this, we show that the new mission concept Athena should be able to measure the X-ray variability of hundreds of AGNs and then constrain the distance modulus with uncertainties of 0.1 mag up to z ∼ 0.6. We also discuss how our estimator has the prospect of becoming a cosmological probe even more sensitive than the current supernovae Ia samples by using a new dedicated wide-field X-ray telescope able to measure the variability of thousands of AGNs.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

    Graham et al. found a sample of active galactic nuclei (AGNs) and quasars from the Catalina Real-time Transient Survey (CRTS) that have long-term periodic variations in optical continuum, the nature of the periodicity remains uncertain. We investigate the periodic variability characteristics of the sample by testing the relations of the observed variability periods with AGN optical luminosity, black hole mass and accretion rates, and find no significant correlations. We also test the observed periods in several different aspects related to accretion disks surrounding single black holes, such as the Keplerian rotational periods of 5100 Å photon-emission regions and self-gravity dominated regions and the precessing period of warped disks. These tests shed new lights on understanding AGN variability in general. Under the assumption that the periodic behavior is associated with SMBHB systems in particular, we compare the separations (D_{bullet }) against characteristic radii of broad-line regions (RBLR) of the binaries and find D_{bullet }≈ 0.05R_{BLR}. This interestingly implies that these binaries have only circumbinary BLRs.

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

    NASA Astrophysics Data System (ADS)

    Tombesi, F.

    2016-05-01

    Powerful winds driven by active galactic nuclei (AGN) are often invoked to play a fundamental role in the evolution of both supermassive black holes (SMBHs) and their host galaxies, quenching star formation and explaining the tight SMBH-galaxy relations. A strong support of this ``quasar mode'' feedback came from the recent X-ray observation of a mildly relativistic accretion disk wind in a ultraluminous infrared galaxy (ULIRG) and its connection with a large-scale molecular outflow, providing a direct link between the SMBH and the gas out of which stars form. Spectroscopic observations, especially in the X-ray band, show that such accretion disk winds may be common in local AGN and quasars. However, their origin and characteristics are still not fully understood. Detailed theoretical models and simulations focused on radiation, magnetohydrodynamic (MHD) or a combination of these two processes to investigate the possible acceleration mechanisms and the dynamics of these winds. Some of these models have been directly compared to X-ray spectra, providing important insights into the wind physics. However, fundamental improvements on these studies will come only from the unprecedented energy resolution and sensitivity of the upcoming X-ray observatories, namely ASTRO-H (launch date early 2016) and Athena (2028).

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

    NASA Astrophysics Data System (ADS)

    Giomi, Matteo; Gerard, Lucie; Maier, Gernot

    2016-07-01

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

  17. Long-term variability of active galactic nuclei from the "Planck" catalog

    NASA Astrophysics Data System (ADS)

    Volvach, A. E.; Kardashev, N. S.; Larionov, M. G.; Volvach, L. N.

    2016-07-01

    A complete sample of 104 bright active galactic nuclei (AGNs) from the "Planck" catalog (early results) were observed at 36.8 GHz with the 22-m radio telescope of the Crimean Astrophysical Observatory (CrAO).Variability indices of the sources at this frequency were determined based on data from theWMAP space observatory, theMetsa¨ hovi RadioObservatory (Finland), and the CrimeanAstrophysical Observatory. New observational results confirm that the variability of these AGNs is stronger in the millimeter than at other radio wavelengths. The variability indices probably change as a result of the systematic decrease in the AGN flux densities in the transition to the infrared. Some radio sources demonstrate significant flux-density variations, including decreases, which sometimes cause them to fall out of the analysed sample. The change of the variability index in the millimeter is consistent with the suggestion that this variability is due to intrinsic processes in binary supermassive black holes at an evolutionary stage close to coalescence. All 104 of the sources studied are well known objects that are included in various radio catalogs and have flux densities exceeding 1 Jy at 36.8 GHz.

  18. Highlights of recent results from the VERITAS Active Galactic Nuclei Observing Program

    NASA Astrophysics Data System (ADS)

    Abeysekara, Udara; VERITAS Collaboration

    2016-03-01

    Active Galactic Nuclei (AGN) are the dominant class of the Very High Energy (VHE) gamma-ray sources. The VERITAS Observatory dedicates about 430 hr/year of dark time and 200 hr/year of observations under moonlight, on the AGN observing program. VERITAS is located at the Fred Lawrence Whipple Observatory near Tucson, Arizona, and is sensitive to gamma rays with energies between of 85 GeV and 30 TeV. VERITAS became fully operational in 2007, and has since then detected 34 very high energy (VHE) AGN. The majority of the detected galaxies are blazars, in addition to a few radio galaxies. The VHE emission mechanism, and the location of the VHE emission zone of AGN are still poorly understood. Detailed observations of VHE AGN are necessary for understanding these uncertainties. AGN are plausible source candidates for ultra-high-energy cosmic rays and astrophysical neutrinos. VHE gamma-rays from AGN can also be used as probes to place limits on extragalactic background light density. This presentation will report the most recent results from the VERITAS AGN program including newly discovered AGN, and VHE flares of known TeV AGN. Udara Abeysekara for the VERITAS Collaboration.

  19. The Fundamental Plane of the Broad-line Region in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Du, Pu; Wang, Jian-Min; Hu, Chen; Ho, Luis C.; Li, Yan-Rong; Bai, Jin-Ming

    2016-02-01

    Broad emission lines in active galactic nuclei (AGNs) mainly arise from gas photoionized by continuum radiation from an accretion disk around a central black hole. The shape of the broad-line profile, described by {{ D }}{{H}β }={{FWHM}}/{σ }{{H}β }, the ratio of full width at half maximum to the dispersion of broad Hβ, reflects the dynamics of the broad-line region (BLR) and correlates with the dimensionless accretion rate (\\overset{\\quad \\cdot }{{M}}) or Eddington ratio ({L}{{bol}}/{L}{{Edd}}). At the same time, \\overset{\\quad \\cdot }{{M}} and {L}{{bol}}/{L}{{Edd}} correlate with {{ R }}{{Fe}}, the ratio of optical Fe ii to Hβ line flux emission. Assembling all AGNs with reverberation mapping measurements of broad Hβ, both from the literature and from new observations reported here, we find a strong bivariate correlation of the form {log}(\\overset{\\quad \\cdot }{{M}},{L}{{bol}}/{L}{{Edd}})=α +β {{ D }}{{H}β }+γ {{ R }}{{Fe}}, where α = (2.47, 0.31), β = -(1.59, 0.82), and γ = (1.34, 0.80). We refer to this as the fundamental plane of the BLR. We apply the plane to a sample of z < 0.8 quasars to demonstrate the prevalence of super-Eddington accreting AGNs are quite common at low redshifts.

  20. The hunt for red active galactic nuclei: a new infrared diagnostic

    NASA Astrophysics Data System (ADS)

    Fadda, Dario; Rodighiero, Giulia

    2014-10-01

    We introduce a new infrared diagnostic to separate galaxies on the basis of their dominant infrared emission: stellar or nuclear. The main novelty with respect to existing diagnostics is the use of a broad band encompassing at the same time the 9.7-μm silicate absorption feature and one of the adjacent broad polycyclic aromatic hydrocarbon (PAH) features. This provides a robust estimate of the near- to mid-infrared continuum slope and enables a clear distinction among different classes of galaxies up to a redshift z ˜ 2.5. The diagnostic can be applied to a wealth of archival data from the ISO, Spitzer and Akari surveys, as well as future James Webb Space Telescope surveys. Based on data in the Great Observatories Origins Deep Survey (GOODS), Lockman Hole and North Ecliptic Pole fields, we find that approximately 70 per cent of active galactic nuclei (AGNs) detected with X-ray and optical spectroscopy dominate the total mid-infrared emission. Finally, we estimate that AGNs contribute less than 30 per cent of the mid-infrared extragalactic integrated emission.

  1. The location and kinematics of the coronal-line emitting regions in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Mullaney, J. R.; Ward, M. J.; Done, C.; Ferland, G. J.; Schurch, N.

    2009-03-01

    We use the photoionization code CLOUDY to determine both the location and the kinematics of the optical forbidden, high-ionization line (hereafter, FHIL) emitting gas in the narrow line Seyfert 1 galaxy Ark 564. The results of our models are compared with the observed properties of these emission lines to produce a physical model that is used to explain both the kinematics and the source of this gas. The main features of this model are that the FHIL emitting gas is launched from the putative dusty torus and is quickly accelerated to its terminal velocity of a few hundred km s-1. Iron-carrying grains are destroyed during this initial acceleration. This velocity is maintained by a balance between radiative forces and gravity in this super-Eddington source. Eventually the outflow is slowed at large radii by the gravitational forces of and interactions with the host galaxy. In this model, FHIL emission traces the transition between the active galactic nucleus (AGN) and bulge zones of influence.

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

    SciTech Connect

    Secrest, N. J.; Satyapal, S.; Gliozzi, M.; Moran, S. M.; Cheung, C. C.; Giroletti, M.; Bergmann, M. P.; Seth, A. C.

    2013-11-10

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

  3. EVIDENCE FOR ACTIVE GALACTIC NUCLEUS DRIVEN OUTFLOWS IN YOUNG RADIO QUASARS

    SciTech Connect

    Kim, Minjin; Ho, Luis C.; Lonsdale, Carol J.; Lacy, Mark; Kimball, Amy E.; Blain, Andrew W.

    2013-05-01

    We present near-infrared spectra of young radio quasars (P{sub 1.4GHz} Almost-Equal-To 26-27 W Hz{sup -1}) selected from the Wide-Field Infrared Survey Explorer. The detected objects have typical redshifts of z Almost-Equal-To 1.6-2.5 and bolometric luminosities {approx}10{sup 47} erg s{sup -1}. Based on the intensity ratios of narrow emission lines, we find that these objects are mainly powered by active galactic nuclei (AGNs), although star formation contribution cannot be completely ruled out. The host galaxies experience moderate levels of extinction, A{sub V} Almost-Equal-To 0-1.3 mag. The observed [O III] {lambda}5007 luminosities and rest-frame J-band magnitudes constrain the black hole masses to lie in the range {approx}10{sup 8.9}-10{sup 9.7} M{sub Sun }. From the empirical correlation between black hole mass and host galaxy mass, we infer stellar masses of {approx}10{sup 11.3}-10{sup 12.2} M{sub Sun }. The [O III] line is exceptionally broad, with FWHM {approx}1300-2100 km s{sup -1}, significantly larger than that of ordinary distant quasars. We argue that these large line widths can be explained by jet-induced outflows, as predicted by theoretical models of AGN feedback.

  4. The effects of irradiation on cloud evolution in active galactic nuclei

    SciTech Connect

    Proga, Daniel; Smith, Daniel; Jiang, Yan-Fei; Stone, James M.; Davis, Shane W.

    2014-01-01

    We report on the first phase of a study of cloud irradiation. We study irradiation by means of numerical, two-dimensional, time-dependent radiation hydrodynamic simulations of a strongly irradiated cloud. We adopt a very simple treatment of the opacity, neglect photoionization and gravity, and focus instead on assessing the role of the type and magnitude of the opacity on the cloud evolution. Our main result is that even relatively dense clouds that are radiatively heated (i.e., with significant absorption opacity) do not move as a whole; instead, they undergo very rapid and major evolution in shape, size, and physical properties. In particular, the cloud and its remnants become optically thin in less than 1 sound-crossing time and before they can travel a significant distance (a few initial-cloud radii). We also find that a cloud can be accelerated as a whole under quite extreme conditions, i.e., the opacity must be dominated by scattering. However, the acceleration due to the radiation force is relatively small, and unless the cloud is optically thin, it quickly undergoes changes in size and shape. We discuss implications for the modeling and interpretation of the broad-line regions of active galactic nuclei.

  5. Radiation-driven Outflows from and Radiative Support in Dusty Tori of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Chan, Chi-Ho; Krolik, Julian H.

    2016-07-01

    Substantial evidence points to dusty, geometrically thick tori obscuring the central engines of active galactic nuclei (AGNs), but so far no mechanism satisfactorily explains why cool dust in the torus remains in a puffy geometry. Near-Eddington infrared (IR) and ultraviolet (UV) luminosities coupled with high dust opacities at these frequencies suggest that radiation pressure on dust can play a significant role in shaping the torus. To explore the possible effects of radiation pressure, we perform three-dimensional radiative hydrodynamics simulations of an initially smooth torus. Our code solves the hydrodynamics equations, the time-dependent multi–angle group IR radiative transfer (RT) equation, and the time-independent UV RT equation. We find a highly dynamic situation. IR radiation is anisotropic, leaving primarily through the central hole. The torus inner surface exhibits a break in axisymmetry under the influence of radiation and differential rotation; clumping follows. In addition, UV radiation pressure on dust launches a strong wind along the inner surface; when scaled to realistic AGN parameters, this outflow travels at ∼ 5000 {(M/{10}7{M}ȯ )}1/4 {[{L}{UV}/(0.1{L}{{E}})]}1/4 {km} {{{s}}}-1 and carries ∼ 0.1 {(M/{10}7{M}ȯ )}3/4 {[{L}{UV}/(0.1{L}{{E}})]}3/4 M ⊙ yr‑1, where M, {L}{UV}, and {L}{{E}} are the mass, UV luminosity, and Eddington luminosity of the central object respectively.

  6. Photon-axion mixing within the jets of active galactic nuclei and prospects for detection

    SciTech Connect

    Harris, J.; Chadwick, P.M. E-mail: p.m.chadwick@durham.ac.uk

    2014-10-01

    Very high energy γ-ray observations of distant active galactic nuclei (AGN) generally result in higher fluxes and harder spectra than expected, resulting in some tension with the level of the extragalactic background light (EBL). If hypothetical axions or axion-like particles (ALPs) were to exist, this tension could be relieved since the oscillation of photons to ALPs would mitigate the effects of EBL absorption and lead to softer inferred intrinsic AGN spectra. In this paper we consider the effect of photon-ALP mixing on observed spectra, including the photon-ALP mixing that would occur within AGN jets. We then simulate observations of three AGN with the Cherenkov Telescope Array (CTA), a next generation γ-ray telescope, to determine its prospects for detecting the signatures of photon-ALP mixing on the spectra. We conclude that prospects for CTA detecting these signatures or else setting limits on the ALP parameter space are quite promising. We find that prospects are improved if photon-ALP mixing within the jet is properly considered and that the best target for observations is PKS 2155-304.

  7. NO EVIDENCE FOR A SYSTEMATIC Fe II EMISSION LINE REDSHIFT IN TYPE 1 ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sulentic, Jack W.; Marziani, Paola; Zamfir, Sebastian; Meadows, Zachary A. E-mail: paola.marziani@oapd.inaf.it E-mail: Zachary.A.Meadows@uwsp.edu

    2012-06-10

    We test the recent claim by Hu et al. that Fe II emission in type 1 active galactic nuclei shows a systematic redshift relative to the local source rest frame and broad-line H{beta}. We compile high signal-to-noise median composites using Sloan Digital Sky Survey spectra from both the Hu et al. sample and our own sample of the 469 brightest DR5 spectra. Our composites are generated in bins of FWHM H{beta} and Fe II strength as defined in our 4D Eigenvector 1 formalism. We find no evidence for a systematic Fe II redshift and consistency with previous assumptions that Fe II shift and width (FWHM) follow H{beta} shift and FWHM in virtually all sources. This result is consistent with the hypothesis that Fe II emission (quasi-ubiquitous in type 1 sources) arises from a broad-line region with geometry and kinematics the same as that producing the Balmer lines.

  8. Reflections of Active Galactic Nucleus Outbursts in the Gaseous Atmosphere of M87

    NASA Astrophysics Data System (ADS)

    Forman, W.; Nulsen, P.; Heinz, S.; Owen, F.; Eilek, J.; Vikhlinin, A.; Markevitch, M.; Kraft, R.; Churazov, E.; Jones, C.

    2005-12-01

    We combined deep Chandra, ROSAT HRI, and XMM-Newton observations of M87 to study the impact of active galactic nucleus (AGN) outbursts on its gaseous atmosphere. Many X-ray features appear to be a direct result of repetitive AGN outbursts. In particular, the X-ray cavities around the jet and counterjet are likely due to the expansion of radio plasma, while rings of enhanced emission at 14 and 17 kpc are probably shock fronts associated with outbursts that began 1-2×107 yr ago. The effects of these shocks are also seen in brightenings within the prominent X-ray arms. On larger scales, ~50 kpc from the nucleus, depressions in the surface brightness may be remnants of earlier outbursts. As suggested for the Perseus Cluster by Fabian and his coauthors, our analysis of the energetics of the M87 outbursts argues that shocks may be the most significant channel for AGN energy input into the cooling-flow atmospheres of galaxies, groups, and clusters. For M87, the mean power driving the shock outburst, 2.4×1043 ergs s-1, is 3 times greater than the radiative losses from the entire cooling flow. Thus, even in the absence of other energy inputs, outbursts every 3×107 yr are sufficient to quench the flow.

  9. Clumpy tori around type II active galactic nuclei as revealed by X-ray fluorescent lines

    NASA Astrophysics Data System (ADS)

    Liu, Jiren; Liu, Yuan; Li, Xiaobo; Xu, Weiwei; Gou, Lijun; Cheng, Cheng

    2016-06-01

    The reflection spectrum of a torus around an active galactic nucleus (AGN) is characterized by X-ray fluorescent lines, which are most prominent for type II AGNs. A clumpy torus allows photons reflected from the back-side of the torus to leak through the front regions that are free of obscuration. The observed X-ray fluorescent lines are therefore sensitive to the clumpiness of the torus. We analysed a sample of type II AGNs observed with the Chandra High Energy Transmission Grating Spectrometer (HETGS), and measured the fluxes for the Si Kα and Fe Kα lines. The measured Fe Kα/Si Kα ratios, spanning a range between 5 and 60, are far smaller than the ratios predicted from simulations of smooth tori, indicating that the tori of the studied sources have clumpy distributions rather than smooth ones. We compared the measured Fe Kα/Si Kα ratios with simulation results of clumpy tori. The Circinus galaxy has a Fe Kα/Si Kα ratio of ˜60, which is close to the simulation results for N = 5, where N is the average number of clumps along the line of sight. The Fe Kα/Si Kα ratios of the other sources are all below the simulation results for N = 2. Overall, this shows that the non-Fe fluorescent lines in the soft X-ray band are a potentially powerful probe of the clumpiness of tori around AGNs.

  10. Low-mass Active Galactic Nuclei with Rapid X-Ray Variability

    NASA Astrophysics Data System (ADS)

    Ho, Luis C.; Kim, Minjin

    2016-04-01

    We present a detailed study of the optical spectroscopic properties of 12 active galactic nuclei (AGNs) with candidate low-mass black holes (BHs) selected by Kamizasa et al. through rapid X-ray variability. The high-quality, echellette Magellan spectra reveal broad Hα emission in all the sources, allowing us to estimate robust virial BH masses and Eddington ratios for this unique sample. We confirm that the sample contains low-mass BHs accreting at high rates: the median MBH = 1.2 × 106 M⊙ and median Lbol/LEdd = 0.44. The sample follows the MBH–σ* relation, within the considerable scatter typical of pseudobulges, the probable hosts of these low-mass AGNs. Various lines of evidence suggest that ongoing star formation is prevalent in these systems. We propose a new strategy to estimate star formation rates in AGNs hosted by low-mass, low-metallicity galaxies, based on modification of an existing method using the strength of [O ii] λ3727, [O iii] λ5007, and X-rays.

  11. He II EMISSION IN Lyalpha NEBULAE: ACTIVE GALACTIC NUCLEUS OR COOLING RADIATION?

    SciTech Connect

    Scarlata, C.; Colbert, J.; Teplitz, H. I.; Bridge, C.; Francis, P.; Palunas, P.; Siana, B.; Williger, G. M.; Woodgate, B.

    2009-12-01

    We present a study of an extended Lyalpha nebula located in a known overdensity at z approx 2.38. The data include multiwavelength photometry covering the rest-frame spectral range from 0.1 to 250 mum, and deep optical spectra of the sources associated with the extended emission. Two galaxies are associated with the Lyalpha nebula. One of them is a dust enshrouded active galactic nucleus (AGN), while the other is a powerful starburst, forming stars at approx>400 M{sub sun} yr{sup -1}. We detect the He II emission line at 1640 A in the spectrum of the obscured AGN, but detect no emission from other highly ionized metals (C IV or N V) as is expected from an AGN. One scenario that simultaneously reproduces the width of the detected emission lines, the lack of C IV emission, and the geometry of the emitting gas, is that the He II and the Lyalpha emission are the result of cooling gas that is being accreted on the dark matter halo of the two galaxies, Ly1 and Ly2. Given the complexity of the environment associated with our Lyalpha nebula it is possible that various mechanisms of excitation are at work simultaneously.

  12. Evidence for Active Galactic Nucleus Driven Outflows in Young Radio Quasars

    NASA Astrophysics Data System (ADS)

    Kim, Minjin; Ho, Luis C.; Lonsdale, Carol J.; Lacy, Mark; Blain, Andrew W.; Kimball, Amy E.

    2013-05-01

    We present near-infrared spectra of young radio quasars (P 1.4 GHz ≈ 26-27 W Hz-1) selected from the Wide-Field Infrared Survey Explorer. The detected objects have typical redshifts of z ≈ 1.6-2.5 and bolometric luminosities ~1047 erg s-1. Based on the intensity ratios of narrow emission lines, we find that these objects are mainly powered by active galactic nuclei (AGNs), although star formation contribution cannot be completely ruled out. The host galaxies experience moderate levels of extinction, AV ≈ 0-1.3 mag. The observed [O III] λ5007 luminosities and rest-frame J-band magnitudes constrain the black hole masses to lie in the range ~108.9-109.7 M ⊙. From the empirical correlation between black hole mass and host galaxy mass, we infer stellar masses of ~1011.3-1012.2 M ⊙. The [O III] line is exceptionally broad, with FWHM ~1300-2100 km s-1, significantly larger than that of ordinary distant quasars. We argue that these large line widths can be explained by jet-induced outflows, as predicted by theoretical models of AGN feedback. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile.

  13. Radiation pressure confinement - II. Application to the broad-line region in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Baskin, Alexei; Laor, Ari; Stern, Jonathan

    2014-02-01

    Active galactic nuclei (AGN) are characterized by similar broad emission lines properties at all luminosities (1039 - 1047 erg s-1). What produces this similarity over a vast range of 108 in luminosity? Photoionization is inevitably associated with momentum transfer to the photoionized gas. Yet, most of the photoionized gas in the broad-line region (BLR) follows Keplerian orbits, which suggests that the BLR originates from gas with a large enough column for gravity to dominate. The photoionized surface layer of the gas must develop a pressure gradient due to the incident radiation force. We present solutions for the structure of such a hydrostatic photoionized gas layer in the BLR. The gas is stratified, with a low-density highly ionized surface layer, a density rise inwards and a uniform-density cooler inner region, where the gas pressure reaches the incident radiation pressure. This radiation pressure confinement (RPC) of the photoionized layer leads to a universal ionization parameter U ˜ 0.1 in the inner photoionized layer, independent of luminosity and distance. Thus, RPC appears to explain the universality of the BLR properties in AGN. We present predictions for the BLR emission per unit covering factor, as a function of distance from the ionizing source, for a range of ionizing continuum slopes and gas metallicity. The predicted mean strength of most lines (excluding H β), and their different average-emission radii, are consistent with available observations.

  14. THE MICROARCSECOND STRUCTURE OF AN ACTIVE GALACTIC NUCLEUS JET VIA INTERSTELLAR SCINTILLATION

    SciTech Connect

    Macquart, J.-P.; Godfrey, L. E. H.; Bignall, H. E.

    2013-03-10

    We describe a new tool for studying the structure and physical characteristics of ultracompact active galactic nucleus (AGN) jets and their surroundings with {mu}as precision. This tool is based on the frequency dependence of the light curves observed for intra-day variable radio sources, where the variability is caused by interstellar scintillation. We apply this method to PKS 1257-326 to resolve the core-shift as a function of frequency on scales well below {approx}12 {mu}as. We find that the frequency dependence of the position of the scintillating component is r{proportional_to}{nu}{sup -0.1{+-}0.24} (99% confidence interval) and the frequency dependence of the size of the scintillating component is d{proportional_to}{nu}{sup -0.64{+-}0.006}. Together, these results imply that the jet opening angle increases with distance along the jet: d{proportional_to}r{sup n{sub d}} with n{sub d} > 1.8. We show that the flaring of the jet, and flat frequency dependence of the core position is broadly consistent with a model in which the jet is hydrostatically confined and traversing a steep pressure gradient in the confining medium with p{proportional_to}r{sup -n{sub p}} and n{sub p} {approx}> 7. Such steep pressure gradients have previously been suggested based on very long baseline interferometry studies of the frequency dependent core shifts in AGNs.

  15. Deep Chandra observations of HCG 16. I. Active nuclei, star formation, and galactic winds

    SciTech Connect

    O'Sullivan, E.; Zezas, A.; Vrtilek, J. M.; David, L. P.; Giacintucci, S.; Trevisan, M.; Ponman, T. J.; Raychaudhury, S.; Mamon, G. A.

    2014-10-01

    We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610 MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation, and high-luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect for the first time an Fe Kα emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infrared and ultraviolet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ∼400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ∼0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.

  16. THE MERGER HISTORY, ACTIVE GALACTIC NUCLEUS, AND DWARF GALAXIES OF HICKSON COMPACT GROUP 59

    SciTech Connect

    Konstantopoulos, I. S.; Charlton, J. C.; Brandt, W. N.; Eracleous, M.; Gronwall, C.; Gallagher, S. C.; Fedotov, K.; Hill, A. R.; Durrell, P. R.; Tzanavaris, P.; Hornschemeier, A. E.; Zabludoff, A. I.; Maier, M. L.; Johnson, K. E.; Walker, L. M.; Maybhate, A.; English, J.; Mulchaey, J. S.

    2012-01-20

    Compact group galaxies often appear unaffected by their unusually dense environment. Closer examination can, however, reveal the subtle, cumulative effects of multiple galaxy interactions. Hickson Compact Group (HCG) 59 is an excellent example of this situation. We present a photometric study of this group in the optical (Hubble Space Telescope), infrared (Spitzer), and X-ray (Chandra) regimes aimed at characterizing the star formation and nuclear activity in its constituent galaxies and intra-group medium. We associate five dwarf galaxies with the group and update the velocity dispersion, leading to an increase in the dynamical mass of the group of up to a factor of 10 (to 2.8 Multiplication-Sign 10{sup 13} M{sub Sun }), and a subsequent revision of its evolutionary stage. Star formation is proceeding at a level consistent with the morphological types of the four main galaxies, of which two are star-forming and the other are two quiescent. Unlike in some other compact groups, star-forming complexes across HCG 59 closely follow mass-radius scaling relations typical of nearby galaxies. In contrast, the ancient globular cluster populations in galaxies HCG 59A and B show intriguing irregularities, and two extragalactic H II regions are found just west of B. We age-date a faint stellar stream in the intra-group medium at {approx}1 Gyr to examine recent interactions. We detect a likely low-luminosity active galactic nucleus in HCG 59A by its {approx}10{sup 40} erg s{sup -1} X-ray emission; the active nucleus rather than star formation can account for the UV+IR spectral energy distribution. We discuss the implications of our findings in the context of galaxy evolution in dense environments.

  17. Deep Chandra Observations of HCG 16. I. Active Nuclei, Star Formation, and Galactic Winds

    NASA Astrophysics Data System (ADS)

    O'Sullivan, E.; Zezas, A.; Vrtilek, J. M.; Giacintucci, S.; Trevisan, M.; David, L. P.; Ponman, T. J.; Mamon, G. A.; Raychaudhury, S.

    2014-10-01

    We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610 MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation, and high-luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect for the first time an Fe Kα emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infrared and ultraviolet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ~400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ~0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    A strong X-ray emission is one of the defining signatures of nuclear activity in galaxies. According to the Unified Model for Active Galactic Nuclei (AGN), both the X-ray radiation and the prominent broad emission lines, characterizing the optical and UV spectra of Type 1 AGNs, are originated in the innermost regions of the sources, close to the Super Massive Black Holes (SMBH), which power the central engine. Since the emission is concentrated in a very compact region (with typical size r⩽0.1 pc) and it is not possible to obtain resolved images of the source, spectroscopic studies of this radiation represent the only valuable key to constrain the physical properties of matter and its structure in the center of active galaxies. Based on previous studies on the physics of the Broad Line Region (BLR) and on the X-ray spectra of broad (FWHMHβ ⩾ 2000 km s-1) and narrow line (1000 km s-1 ⩽FWHMHβ ⩽ 2000 km s-1) emitting objects, it has been observed that the kinematic and ionization properties of matter close to the SMBHs are related together, and, in particular, that ionization is higher in narrow line sources. Here we report on the study of the optical and X-ray spectra of a sample of Type 1 AGNs, selected from the Sloan Digital Sky Survey (SDSS) database, within an upper redshift limit of z=0.35, and detected at X-ray energies. We present analysis of the broad emission line fluxes and profiles, as well as the properties of the X-ray continuum and Fe Kα emission and we use these parameters to assess the consistency of our current AGN understanding.

  19. A possible WISE blazar counterpart of the faint INTEGRAL active galactic nucleus IGR J02341+0228

    NASA Astrophysics Data System (ADS)

    Massaro, F.; Paggi, A.; D'Abrusco, R.

    2012-05-01

    Following the Swift-XRT identification of the counterpart for the faint INTEGRAL active galactic nucleus IGR J02341+0228, associated with a new extragalactic source: QSO B0231+022 (ATEL #4102), we searched in the Wide-field Infrared Survey Explorer (WISE; Wright et al. 2010 AJ, 140, 1868) catalog at the position of the QSO B0231+022 source for an infrared counterpart.

  20. Anti-hierarchical evolution of the active galactic nucleus space density in a hierarchical universe

    SciTech Connect

    Enoki, Motohiro; Ishiyama, Tomoaki; Kobayashi, Masakazu A. R.; Nagashima, Masahiro

    2014-10-10

    Recent observations show that the space density of luminous active galactic nuclei (AGNs) peaks at higher redshifts than that of faint AGNs. This downsizing trend in the AGN evolution seems to be contradictory to the hierarchical structure formation scenario. In this study, we present the AGN space density evolution predicted by a semi-analytic model of galaxy and AGN formation based on the hierarchical structure formation scenario. We demonstrate that our model can reproduce the downsizing trend of the AGN space density evolution. The reason for the downsizing trend in our model is a combination of the cold gas depletion as a consequence of star formation, the gas cooling suppression in massive halos, and the AGN lifetime scaling with the dynamical timescale. We assume that a major merger of galaxies causes a starburst, spheroid formation, and cold gas accretion onto a supermassive black hole (SMBH). We also assume that this cold gas accretion triggers AGN activity. Since the cold gas is mainly depleted by star formation and gas cooling is suppressed in massive dark halos, the amount of cold gas accreted onto SMBHs decreases with cosmic time. Moreover, AGN lifetime increases with cosmic time. Thus, at low redshifts, major mergers do not always lead to luminous AGNs. Because the luminosity of AGNs is correlated with the mass of accreted gas onto SMBHs, the space density of luminous AGNs decreases more quickly than that of faint AGNs. We conclude that the anti-hierarchical evolution of the AGN space density is not contradictory to the hierarchical structure formation scenario.

  1. NEAR-INFRARED REVERBERATION BY DUSTY CLUMPY TORI IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Kawaguchi, Toshihiro; Mori, Masao

    2011-08-20

    According to recent models, the accretion disk and black hole in active galactic nuclei (AGNs) are surrounded by a clumpy torus. We investigate the NIR flux variation of the torus in response to a UV flash for various geometries. Anisotropic illumination by the disk and the torus self-occultation contrast our study with earlier works. Both the waning effect of each clump and the torus self-occultation selectively reduce the emission from the region with a short delay. Therefore, the NIR delay depends on the viewing angle (where a more inclined angle leads to a longer delay), and the time response shows an asymmetric profile with negative skewness, opposing the results for optically thin tori. The range of the computed delay coincides with the observed one, suggesting that the viewing angle is primarily responsible for the scatter of the observed delay. We also propose that the red NIR-to-optical color of type 1.8/1.9 objects is caused not only by the dust extinction but also the intrinsically red color. Compared with the modest torus thickness, both a thick and a thin tori display weaker NIR emission. A selection bias is thus expected such that NIR-selected AGNs tend to possess moderately thick tori. A thicker torus shows a narrower and more heavily skewed time profile, while a thin torus produces a rapid response. A super-Eddington accretion rate leads to much weaker NIR emission due to the disk self-occultation and the disk truncation by self-gravity. A long delay is expected from an optically thin and/or a largely misaligned torus. Very weak NIR emission, such as in hot-dust-poor active nuclei, can arise from a geometrically thin torus, a super-Eddington accretion rate, or a slightly misaligned torus.

  2. Anti-hierarchical Evolution of the Active Galactic Nucleus Space Density in a Hierarchical Universe

    NASA Astrophysics Data System (ADS)

    Enoki, Motohiro; Ishiyama, Tomoaki; Kobayashi, Masakazu A. R.; Nagashima, Masahiro

    2014-10-01

    Recent observations show that the space density of luminous active galactic nuclei (AGNs) peaks at higher redshifts than that of faint AGNs. This downsizing trend in the AGN evolution seems to be contradictory to the hierarchical structure formation scenario. In this study, we present the AGN space density evolution predicted by a semi-analytic model of galaxy and AGN formation based on the hierarchical structure formation scenario. We demonstrate that our model can reproduce the downsizing trend of the AGN space density evolution. The reason for the downsizing trend in our model is a combination of the cold gas depletion as a consequence of star formation, the gas cooling suppression in massive halos, and the AGN lifetime scaling with the dynamical timescale. We assume that a major merger of galaxies causes a starburst, spheroid formation, and cold gas accretion onto a supermassive black hole (SMBH). We also assume that this cold gas accretion triggers AGN activity. Since the cold gas is mainly depleted by star formation and gas cooling is suppressed in massive dark halos, the amount of cold gas accreted onto SMBHs decreases with cosmic time. Moreover, AGN lifetime increases with cosmic time. Thus, at low redshifts, major mergers do not always lead to luminous AGNs. Because the luminosity of AGNs is correlated with the mass of accreted gas onto SMBHs, the space density of luminous AGNs decreases more quickly than that of faint AGNs. We conclude that the anti-hierarchical evolution of the AGN space density is not contradictory to the hierarchical structure formation scenario.

  3. A PHYSICAL LINK BETWEEN JET FORMATION AND HOT PLASMA IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Wu Qingwen; Wang Dingxiong; Cao Xinwu; Ho, Luis C. E-mail: dxwang@hust.edu.cn E-mail: lho@obs.carnegiescience.edu

    2013-06-10

    Recent observations suggest that in black hole X-ray binaries jet/outflow formation is related to the hot plasma in the vicinity of the black hole, either in the form of an advection-dominated accretion flow at low accretion rates or in a disk corona at high accretion rates. We test the viability of this scenario for supermassive black holes using two samples of active galactic nuclei distinguished by the presence (radio-strong) and absence (radio-weak) of well-collimated, relativistic jets. Each is centered on a narrow range of black hole mass but spans a very broad range of Eddington ratios, effectively simulating in a statistical manner the behavior of a single black hole evolving across a wide spread in accretion states. Unlike the relationship between the radio and optical luminosity, which shows an abrupt break between high- and low-luminosity sources at an Eddington ratio of {approx}1%, the radio emission-a measure of the jet power-varies continuously with the hard X-ray (2-10 keV) luminosity, roughly as L{sub R} {proportional_to} L{sub X}{sup 0.6-0.75}. This relation, which holds for both radio-weak and radio-strong active galaxies, is similar to the one seen in X-ray binaries. Jet/outflow formation appears to be closely linked to the conditions that give rise to the hot, optically thin coronal emission associated with accretion flows, both in the regime of low and high accretion rates.

  4. The typecasting of active galactic nuclei: Mrk 590 no longer fits the role

    SciTech Connect

    Denney, K. D.; De Rosa, G.; Croxall, K.; Gupta, A.; Fausnaugh, M. M.; Grier, C. J.; Martini, P.; Mathur, S.; Peterson, B. M.; Pogge, R. W.; Shappee, B. J.; Bentz, M. C.

    2014-12-01

    We present multiwavelength observations that trace more than 40 yr in the life of the active galactic nucleus (AGN) in Mrk 590, traditionally known as a classic Seyfert 1 galaxy. From spectra recently obtained from Hubble Space Telescope, Chandra, and the Large Binocular Telescope, we find that the activity in the nucleus of Mrk 590 has diminished so significantly that the continuum luminosity is a factor of 100 lower than the peak luminosity probed by our long-baseline observations. Furthermore, the broad emission lines, once prominent in the UV/optical spectrum, have all but disappeared. Since AGN type is defined by the presence of broad emission lines in the optical spectrum, our observations demonstrate that Mrk 590 has now become a 'changing-look' AGN. If classified by recent optical spectra, Mrk 590 would be a Seyfert ∼1.9–2, where the only broad emission line still visible in the optical spectrum is a weak component of Hα. As an additional consequence of this change, we have definitively detected UV narrow-line components in a Type 1 AGN, allowing an analysis of these emission-line components with high-resolution COS spectra. These observations challenge the historical paradigm that AGN type is only a consequence of the line-of-sight viewing angle toward the nucleus in the presence of a geometrically flattened, obscuring medium (i.e., the torus). Our data instead suggest that the current state of Mrk 590 is a consequence of the change in luminosity, which implies the black hole accretion rate has significantly decreased.

  5. DO MOST ACTIVE GALACTIC NUCLEI LIVE IN HIGH STAR FORMATION NUCLEAR CUSPS?

    SciTech Connect

    Mushotzky, Richard F.; Shimizu, T. Taro; Meléndez, Marcio; Koss, Michael

    2014-02-01

    We present early results of the Herschel PACS (70 and 160 μm) and SPIRE (250, 350, and 500 μm) survey of 313 low redshift (z < 0.05), ultra-hard X-ray (14-195 keV) selected active galactic nuclei (AGNs) from the 58 month Swift/Burst Alert Telescope catalog. Selection of AGNs from ultra-hard X-rays avoids bias from obscuration, providing a complete sample of AGNs to study the connection between nuclear activity and star formation in host galaxies. With the high angular resolution of PACS, we find that >35% and >20% of the sources are ''point-like'' at 70 and 160 μm respectively and many more have their flux dominated by a point source located at the nucleus. The inferred star formation rates (SFRs) of 0.1-100 M {sub ☉} yr{sup –1} using the 70 and 160 μm flux densities as SFR indicators are consistent with those inferred from Spitzer Ne II fluxes, but we find that 11.25 μm polycyclic aromatic hydrocarbon data give ∼3× lower SFR. Using GALFIT to measure the size of the far-infrared emitting regions, we determined the SFR surface density (M {sub ☉} yr{sup –1} kpc{sup –2}) for our sample, finding that a significant fraction of these sources exceed the threshold for star formation driven winds (0.1 M {sub ☉} yr{sup –1} kpc{sup –2})

  6. COSMIC EVOLUTION OF RADIO SELECTED ACTIVE GALACTIC NUCLEI IN THE COSMOS FIELD

    SciTech Connect

    Smolcic, V.; Salvato, M.; Scoville, N.; Zamorani, G.; Bardelli, S.; Ciliegi, P.; Schinnerer, E.; Bondi, M.; BIrzan, L.; Carilli, C. L.; Elvis, M.; Impey, C. D.; Trump, J. R.; Koekemoer, A. M.; Merloni, A.; Scodeggio, M.; Paglione, T

    2009-05-01

    We explore the cosmic evolution of radio luminous active galactic nuclei (AGNs) with low radio powers (L {sub 1.4GHz} {approx}< 5 x 10{sup 25} W Hz{sup -1}) out to z = 1.3 using to date the largest sample of {approx}600 low-luminosity radio AGN at intermediate redshift drawn from the VLA-COSMOS survey. We derive the radio-luminosity function for these AGNs, and its evolution with cosmic time assuming two extreme cases: (1) pure luminosity and (2) pure density evolution. The former and latter yield L {sub *} {proportional_to} (1 + z){sup 0.8} {sup {+-}} {sup 0.1}, and {phi}{sub *} {proportional_to} (1 + z){sup 1.1} {sup {+-}} {sup 0.1}, respectively, both implying a fairly modest change in properties of low-radio-power AGNs since z = 1.3. We show that this is in stark contrast with the evolution of powerful (L {sub 1.4GHz} > 5 x 10{sup 25} W Hz{sup -1}) radio AGN over the same cosmic time interval, constrained using the 3CRR, 6CE, and 7CRS radio surveys by Willot et al. We demonstrate that this can be explained through differences in black hole fueling and triggering mechanisms, and a dichotomy in host galaxy properties of weak and powerful AGNs. Our findings suggest that high- and low-radio-power AGN activities are triggered in different stages during the formation of massive red galaxies. We show that weak radio AGN occur in the most massive galaxies already at z {approx} 1, and they may significantly contribute to the heating of their surrounding medium and thus inhibit gas accretion onto their host galaxies, as recently suggested for the 'radio mode' in cosmological models.

  7. HOST GALAXY PROPERTIES OF THE SWIFT BAT ULTRA HARD X-RAY SELECTED ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    Koss, Michael; Mushotzky, Richard; Veilleux, Sylvain; Winter, Lisa M.; Baumgartner, Wayne; Tueller, Jack; Gehrels, Neil; Valencic, Lynne

    2011-10-01

    We have assembled the largest sample of ultra hard X-ray selected (14-195 keV) active galactic nucleus (AGN) with host galaxy optical data to date, with 185 nearby (z < 0.05), moderate luminosity AGNs from the Swift BAT sample. The BAT AGN host galaxies have intermediate optical colors (u - r and g - r) that are bluer than a comparison sample of inactive galaxies and optically selected AGNs from the Sloan Digital Sky Survey (SDSS) which are chosen to have the same stellar mass. Based on morphological classifications from the RC3 and the Galaxy Zoo, the bluer colors of BAT AGNs are mainly due to a higher fraction of mergers and massive spirals than in the comparison samples. BAT AGNs in massive galaxies (log M{sub *} >10.5) have a 5-10 times higher rate of spiral morphologies than in SDSS AGNs or inactive galaxies. We also see enhanced far-infrared emission in BAT AGN suggestive of higher levels of star formation compared to the comparison samples. BAT AGNs are preferentially found in the most massive host galaxies with high concentration indexes indicative of large bulge-to-disk ratios and large supermassive black holes. The narrow-line (NL) BAT AGNs have similar intrinsic luminosities as the SDSS NL Seyferts based on measurements of [O III] {lambda}5007. There is also a correlation between the stellar mass and X-ray emission. The BAT AGNs in mergers have bluer colors and greater ultra hard X-ray emission compared to the BAT sample as a whole. In agreement with the unified model of AGNs, and the relatively unbiased nature of the BAT sources, the host galaxy colors and morphologies are independent of measures of obscuration such as X-ray column density or Seyfert type. The high fraction of massive spiral galaxies and galaxy mergers in BAT AGNs suggest that host galaxy morphology is related to the activation and fueling of local AGN.

  8. Removing Cool Cores and Central Metallicity Peaks in Galaxy Clusters with Powerful Active Galactic Nucleus Outbursts

    NASA Astrophysics Data System (ADS)

    Guo, Fulai; Mathews, William G.

    2010-07-01

    Recent X-ray observations of galaxy clusters suggest that cluster populations are bimodally distributed according to central gas entropy and are separated into two distinct classes: cool core (CC) and non-cool core (NCC) clusters. While it is widely accepted that active galactic nucleus (AGN) feedback plays a key role in offsetting radiative losses and maintaining many clusters in the CC state, the origin of NCC clusters is much less clear. At the same time, a handful of extremely powerful AGN outbursts have recently been detected in clusters, with a total energy ~1061-1062 erg. Using two-dimensional hydrodynamic simulations, we show that if a large fraction of this energy is deposited near the centers of CC clusters, which is likely common due to dense cores, these AGN outbursts can completely remove CCs, transforming them to NCC clusters. Our model also has interesting implications for cluster abundance profiles, which usually show a central peak in CC systems. Our calculations indicate that during the CC to NCC transformation, AGN outbursts efficiently mix metals in cluster central regions and may even remove central abundance peaks if they are not broad enough. For CC clusters with broad central abundance peaks, AGN outbursts decrease peak abundances, but cannot effectively destroy the peaks. Our model may simultaneously explain the contradictory (possibly bimodal) results of abundance profiles in NCC clusters, some of which are nearly flat, while others have strong central peaks similar to those in CC clusters. A statistical analysis of the sizes of central abundance peaks and their redshift evolution may shed interesting insights on the origin of both types of NCC clusters and the evolution history of thermodynamics and AGN activity in clusters.

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

    NASA Astrophysics Data System (ADS)

    Xie, Fu-Guo; Zdziarski, Andrzej A.; Ma, Renyi; Yang, Qi-Xiang

    2016-08-01

    The active galactic nucleus (AGN) NGC 7213 shows a complex correlation between the monochromatic radio luminosity LR and the 2-10 keV X-ray luminosity LX, i.e. the correlation is unusually weak with p ˜ 0 (in the form L_R∝ L_X^p) when LX is below a critical luminosity, and steep with p > 1 when LX is above that luminosity. Such a hybrid correlation in individual AGNs is unexpected as it deviates from the fundamental plane of AGN activity. Interestingly, a similar correlation pattern is observed in the black-hole X-ray binary H1743-322, where it has been modelled by switching between different modes of accretion. We propose that the flat LR-LX correlation of NGC 7213 is due to the presence of a luminous hot accretion flow, an accretion model whose radiative efficiency is sensitive to the accretion rate. Given the low luminosity of the source, LX ˜ 10-4 of the Eddington luminosity, the viscosity parameter is determined to be small, α ≈ 0.01. We also modelled the broad-band spectrum from radio to γ-rays, the time lag between the radio and X-ray light curves, and the implied size and the Lorentz factor of the radio jet. We predict that NGC 7213 will enter into a two-phase accretion regime when L_X⪆ 1.5 × 10^{42} erg s^{-1}. When this happens, we predict a softening of the X-ray spectrum with the increasing flux and a steep radio/X-ray correlation.

  10. Statistical analysis of the correlation between active galactic nuclei and ultra-high energy cosmic rays

    SciTech Connect

    Kim, Hang Bae; Kim, Jihyun E-mail: jihyunkim@hanyang.ac.kr

    2011-03-01

    We develop the statistical methods for comparing two sets of arrival directions of cosmic rays in which the two-dimensional distribution of arrival directions is reduced to the one-dimensional distributions so that the standard one-dimensional Kolmogorov-Smirnov test can be applied. Then we apply them to the analysis of correlation between the ultra-high energy cosmic rays (UHECR) with energies above 5.7 × 10{sup 19} eV, observed by Pierre Auger Observatory (PAO) and Akeno Giant Air Shower Array (AGASA), and the active galactic nuclei (AGN) within the distance 100 Mpc. For statistical test, we set up the simple AGN model for UHECR sources in which a certain fraction of observed UHECR are originated from AGN within a chosen distance, assuming that all AGN have equal UHECR luminosity and smearing angle, and the remaining fraction are from the isotropic background contribution. For the PAO data, our methods exclude not only a hypothesis that the observed UHECR are simply isotropically distributed but also a hypothesis that they are completely originated from the selected AGN. But, the addition of appropriate amount of isotropic component either through the background contribution or through the large smearing effect improves the correlation greatly and makes the AGN hypothesis for UHECR sources a viable one. We also point out that restricting AGN within the distance bin of 40–60 Mpc happens to yield a good correlation without appreciable isotropic component and large smearing effect. For the AGASA data, we don't find any significant correlation with AGN.

  11. INCLINATION-DEPENDENT ACTIVE GALACTIC NUCLEUS FLUX PROFILES FROM STRONG LENSING OF THE KERR SPACETIME

    SciTech Connect

    Chen, Bin; Dai, Xinyu; Baron, E.

    2013-01-10

    Recent quasar microlensing observations have constrained the X-ray emission sizes of quasars to be about 10 gravitational radii, one order of magnitude smaller than the optical emission sizes. Using a new ray-tracing code for the Kerr spacetime, we find that the observed X-ray flux is strongly influenced by the gravity field of the central black hole, even for observers at moderate inclination angles. We calculate inclination-dependent flux profiles of active galactic nuclei in the optical and X-ray bands by combining the Kerr lensing and projection effects for future reference. We further study the dependence of the X-ray-to-optical flux ratio on the inclination angle caused by differential lensing distortion of the X-ray and optical emission, assuming several corona geometries. The strong lensing X-ray-to-optical magnification ratio can change by a factor of {approx}10 for normal quasars in some cases, and a further factor of {approx}10 for broad absorption line (BAL) quasars and obscured quasars. Comparing our results with the observed distributions in normal and BAL quasars, we find that the inclination angle dependence of the magnification ratios can significantly change the X-ray-to-optical flux ratio distributions. In particular, the mean value of the spectrum slope parameter {alpha}{sub ox}, 0.3838log F {sub 2keV}/F {sub 2500A}, can differ by {approx}0.1-0.2 between normal and BAL quasars, depending on corona geometries, suggesting larger intrinsic absorptions in BAL quasars.

  12. Variability-based active galactic nucleus selection using image subtraction in the SDSS and LSST era

    SciTech Connect

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

    2014-02-10

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

  13. NO CLEAR SUBMILLIMETER SIGNATURE OF SUPPRESSED STAR FORMATION AMONG X-RAY LUMINOUS ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Harrison, C. M.; Alexander, D. M.; Mullaney, J. R.; Del Moro, A.; Rovilos, E.; Altieri, B.; Coia, D.; Charmandaris, V.; Daddi, E.; Le Floc'h, E.; Leiton, R.; Dasyra, K.; Dickinson, M.; Kartaltepe, J.; Hickox, R. C.; Ivison, R. J.; Magnelli, B.; Popesso, P.; Rosario, D.; and others

    2012-11-20

    Many theoretical models require powerful active galactic nuclei (AGNs) to suppress star formation in distant galaxies and reproduce the observed properties of today's massive galaxies. A recent study based on Herschel-SPIRE submillimeter observations claimed to provide direct support for this picture, reporting a significant decrease in the mean star formation rates (SFRs) of the most luminous AGNs (L{sub X} >10{sup 44} erg s{sup -1}) at z Almost-Equal-To 1-3 in the Chandra Deep Field-North (CDF-N). In this Letter, we extend these results using Herschel-SPIRE 250 {mu}m data in the COSMOS and Chandra Deep Field-South fields to achieve an order-of-magnitude improvement in the number of sources at L{sub X} >10{sup 44} erg s{sup -1}. On the basis of our analysis, we find no strong evidence for suppressed star formation in L{sub X} >10{sup 44} erg s{sup -1} AGNs at z Almost-Equal-To 1-3. The mean SFRs of the AGNs are constant over the broad X-ray luminosity range of L{sub X} Almost-Equal-To 10{sup 43}-10{sup 45} erg s{sup -1} (with mean SFRs consistent with typical star-forming galaxies at z Almost-Equal-To 2; (SFRs) Almost-Equal-To 100-200 M{sub Sun} yr{sup -1}). We suggest that the previous CDF-N results were likely due to low number statistics. We discuss our results in the context of current theoretical models.

  14. Q2122-444: A NAKED ACTIVE GALACTIC NUCLEUS FULLY DRESSED

    SciTech Connect

    Gliozzi, M.; Satyapal, S.; Panessa, F.; Franca, F. La; Saviane, I.; Monaco, L.; Foschini, L.; Kedziora-Chudczer, L.; Sambruna, R. M.

    2010-12-20

    Based on previous spectral and temporal optical studies, Q2122-444 has been classified as a naked active galactic nucleus (AGN) or true type 2 AGN, that is, an AGN that genuinely lacks a broad-line region (BLR). Its optical spectrum seemed to possess only narrow forbidden emission lines that are typical of type 2 (obscured) AGNs, but the long-term optical light curve, obtained from a monitoring campaign over more than two decades, showed strong variability, apparently ruling out the presence of heavy obscuration. Here we present the results from a {approx}40 ks XMM-Newton observation of Q2122-444 carried out to shed light on the energetics of this enigmatic AGN. The X-ray analysis was complemented with Australia Telescope Compact Array radio data to assess the possible presence of a jet, and with new NTT/EFOSC2 optical spectroscopic data to verify the actual absence of a BLR. The higher-quality optical data revealed the presence of strong and broad Balmer lines that are at odds with the previous spectral classification of this AGN. The lack of detection of radio emission rules out the presence of a jet. The X-ray data combined with simultaneous UV observations carried out by the Optical Monitor (OM) aboard XMM-Newton confirm that Q2122-444 is a typical type 1 AGN without any significant intrinsic absorption. New estimates of the black hole mass independently obtained from the broad Balmer lines and from a new scaling technique based on X-ray spectral data suggest that Q2122-444 is accreting at a relatively high rate in Eddington units.

  15. THE INTEGRAL HIGH-ENERGY CUT-OFF DISTRIBUTION OF TYPE 1 ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Malizia, A.; Molina, M.; Bassani, L.; Stephen, J. B.; Bazzano, A.; Ubertini, P.; Bird, A. J.

    2014-02-20

    In this Letter we present the primary continuum parameters, the photon index Γ, and the high-energy cut-off E {sub c} of 41 type-1 Seyfert galaxies extracted from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) complete sample of active galactic nuclei (AGNs). We performed broadband (0.3-100 keV) spectral analysis by simultaneously fitting the soft and hard X-ray spectra obtained by XMM and INTEGRAL/IBIS-Swift/BAT, respectively, in order to investigate the general properties of these parameters, in particular their distribution and mean values. We find a mean photon index of 1.73 with a standard deviation of 0.17 and a mean high-energy cut-off of 128 keV with a standard deviation of 46 keV for the whole sample. This is the first time that the cut-off energy is constrained in such a large number of AGNs. We have 26 measurements of the cut-off, which corresponds to 63% of the entire sample, distributed between 50 and 200 keV. There are a further 11 lower limits mostly below 300 keV. Using the main parameters of the primary continuum, we have been able to obtain the actual physical parameters of the Comptonizing region, i.e., the plasma temperature kT {sub e} from 20 to 100 keV and the optical depth τ < 4. Finally, with the high signal-to-noise ratio spectra starting to come from NuSTAR it will soon be possible to better constrain the cut-off values in many AGNs, allowing the determination of more physical models and thus better understand the continuum emission and geometry of the region surrounding black holes.

  16. THE POPULATION OF HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI IN THE CHANDRA-COSMOS SURVEY

    SciTech Connect

    Civano, F.; Elvis, M.; Hao, H.; Brusa, M.; Comastri, A.; Zamorani, G.; Gilli, R.; Mignoli, M.; Salvato, M.; Capak, P.; Kakazu, Y.; Masters, D.; Fiore, F.; Ikeda, H.; Kartaltepe, J. S.; Miyaji, T.; Puccetti, S.; Shankar, F.; Silverman, J.; Vignali, C.

    2011-11-10

    We present the high-redshift (3 active galactic nuclei (AGNs) detected in the Chandra Cosmic Evolution Survey. The sample comprises 81 X-ray-detected sources with available spectroscopic (31) and photometric (50) redshifts plus 20 sources with a formal z{sub phot} < 3 but with a broad photometric redshift probability distribution, such that z{sub phot} + 1{sigma} > 3. Eighty-one sources are selected in the 0.5-2 keV band, fourteen are selected in the 2-10 keV and six in the 0.5-10 keV bands. We sample the high-luminosity (log L{sub (2-10keV)} > 44.15 erg s{sup -1}) space density up to z {approx} 5 and a fainter luminosity range (43.5 erg s{sup -1} < log L{sub (2-10keV)} < 44.15 erg s{sup -1}) than previous studies, up to z = 3.5. We weighted the contribution to the number counts and the space density of the sources with photometric redshift by using their probability of being at z > 3. We find that the space density of high-luminosity AGNs declines exponentially at all the redshifts, confirming the trend observed for optically selected quasars. At lower luminosity, the measured space density is not conclusive, and a larger sample of faint sources is needed. Comparisons with optical luminosity functions and black hole formation models are presented together with prospects for future surveys.

  17. Active galactic nucleus and quasar science with aperture masking interferometry on the James Webb Space Telescope

    SciTech Connect

    Ford, K. E. Saavik; McKernan, Barry; Sivaramakrishnan, Anand; Martel, André R.; Koekemoer, Anton; Lafrenière, David; Parmentier, Sébastien

    2014-03-10

    Due to feedback from accretion onto supermassive black holes (SMBHs), active galactic nuclei (AGNs) are believed to play a key role in ΛCDM cosmology and galaxy formation. However, AGNs extreme luminosities and the small angular size of their accretion flows create a challenging imaging problem. We show that the James Webb Space Telescope's Near Infrared Imager and Slitless Spectrograph (JWST-NIRISS) Aperture Masking Interferometry (AMI) mode will enable true imaging (i.e., without any requirement of prior assumptions on source geometry) at ∼65 mas angular resolution at the centers of AGNs. This is advantageous for studying complex extended accretion flows around SMBHs and in other areas of angular-resolution-limited astrophysics. By simulating data sequences incorporating expected sources of noise, we demonstrate that JWST-NIRISS AMI mode can map extended structure at a pixel-to-pixel contrast of ∼10{sup –2} around an L = 7.5 point source, using short exposure times (minutes). Such images will test models of AGN feedback, fueling, and structure (complementary with ALMA observations), and are not currently supported by any ground-based IR interferometer or telescope. Binary point source contrast with NIRISS is ∼10{sup –4} (for observing binary nuclei in merging galaxies), significantly better than current ground-based optical or IR interferometry. JWST-NIRISS's seven-hole non-redundant mask has a throughput of 15%, and utilizes NIRISS's F277W (2.77 μm), F380M (3.8 μm), F430M (4.3 μm), and F480M (4.8 μm) filters. NIRISS's square pixels are 65 mas per side, with a field of view ∼2' × 2'. We also extrapolate our results to AGN science enabled by non-redundant masking on future 2.4 m and 16 m space telescopes working at long-UV to near-IR wavelengths.

  18. MEASURING X-RAY VARIABILITY IN FAINT/SPARSELY SAMPLED ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Allevato, V.; Paolillo, M.; Papadakis, I.; Pinto, C.

    2013-07-01

    We study the statistical properties of the normalized excess variance of variability process characterized by a ''red-noise'' power spectral density (PSD), as in the case of active galactic nuclei (AGNs). We perform Monte Carlo simulations of light curves, assuming both a continuous and a sparse sampling pattern and various signal-to-noise ratios (S/Ns). We show that the normalized excess variance is a biased estimate of the variance even in the case of continuously sampled light curves. The bias depends on the PSD slope and on the sampling pattern, but not on the S/N. We provide a simple formula to account for the bias, which yields unbiased estimates with an accuracy better than 15%. We show that the normalized excess variance estimates based on single light curves (especially for sparse sampling and S/N < 3) are highly uncertain (even if corrected for bias) and we propose instead the use of an ''ensemble estimate'', based on multiple light curves of the same object, or on the use of light curves of many objects. These estimates have symmetric distributions, known errors, and can also be corrected for biases. We use our results to estimate the ability to measure the intrinsic source variability in current data, and show that they could also be useful in the planning of the observing strategy of future surveys such as those provided by X-ray missions studying distant and/or faint AGN populations and, more in general, in the estimation of the variability amplitude of sources that will result from future surveys such as Pan-STARRS and LSST.

  19. Iron Opacity Bump Changes the Stability and Structure of Accretion Disks in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Jiang, Yan-Fei; Davis, Shane W.; Stone, James M.

    2016-08-01

    Accretion disks around supermassive black holes have regions where the Rosseland mean opacity can be larger than the electron scattering opacity due to the large number of bound–bound transitions in iron. We study the effects of this iron opacity “bump” on the thermal stability and vertical structure of radiation-pressure-dominated accretion disks, utilizing three-dimensional radiation magnetohydrodynamic (MHD) simulations in the local shearing box approximation. The simulations self-consistently calculate the heating due to MHD turbulence caused by magneto-rotational instability and radiative cooling by using the radiative transfer module based on a variable Eddington tensor in Athena. For a 5 × 108 solar mass black hole with ˜3% of the Eddington luminosity, a model including the iron opacity bump maintains its structure for more than 10 thermal times without showing significant signs of thermal runaway. In contrast, if only electron scattering and free–free opacity are included as in the standard thin disk model, the disk collapses on the thermal timescale. The difference is caused by a combination of (1) an anti-correlation between the total optical depth and the midplane pressure, and (2) enhanced vertical advective energy transport. These results suggest that the iron opacity bump may have a strong impact on the stability and structure of active galactic nucleus (AGN) accretion disks, and may contribute to a dependence of AGN properties on metallicity. Since this opacity is relevant primarily in UV emitting regions of the flow, it may help to explain discrepancies between observation and theory that are unique to AGNs.

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

    NASA Astrophysics Data System (ADS)

    Bentz, Misty C.; Denney, K.; Grier, C.; Barth, A. J.; Peterson, B. M.; Vestergaard, M.

    2014-01-01

    We present an updated and revised analysis of the relationship between the Hβ broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of nine new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create "AGN-free" images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the Hβ time lag, which is assumed to yield the average Hβ BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of α = 0.533^{+0.035}_{-0.033}, consistent with previous work and with simple photoionization arguments. Only two AGNs appear to be outliers from the relationship, but both of them have monitoring light curves that raise doubt regarding the accuracy of their reported time lags. The scatter around the relationship is found to be 0.19 ± 0.02 dex, but would be decreased to 0.13 dex by the removal of these two suspect measurements. A large fraction of the remaining scatter in the relationship is likely due to the inaccurate distances to the AGN host galaxies. Our results help support the possibility that the R-L relationship could potentially be used to turn the BLRs of AGNs into standardizable candles. This would allow the cosmological expansion of the universe to be probed by a separate population of objects, and over a larger range of redshifts.

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    We present an updated and revised analysis of the relationship between the Hβ broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of nine new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create "AGN-free" images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the Hβ time lag, which is assumed to yield the average Hβ BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R BLR-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of \\alpha = 0.533^{+0.035}_{-0.033}, consistent with previous work and with simple photoionization arguments. Only two AGNs appear to be outliers from the relationship, but both of them have monitoring light curves that raise doubt regarding the accuracy of their reported time lags. The scatter around the relationship is found to be 0.19 ± 0.02 dex, but would be decreased to 0.13 dex by the removal of these two suspect measurements. A large fraction of the remaining scatter in the relationship is likely due to the inaccurate distances to the AGN host galaxies. Our results help support the possibility that the R BLR-L relationship could potentially be used to turn the BLRs of AGNs into standardizable candles. This would allow the cosmological expansion of the universe to be probed by a separate population of objects, and over a larger range of redshifts.

  2. A New Black Hole Mass Estimate for Obscured Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Minezaki, Takeo; Matsushita, Kyoko

    2015-04-01

    We propose a new method for estimating the mass of a supermassive black hole, applicable to obscured active galactic nuclei (AGNs). This method estimates the black hole mass using the width of the narrow core of the neutral FeKα emission line in X-rays and the distance of its emitting region from the black hole based on the isotropic luminosity indicator via the luminosity scaling relation. Assuming the virial relation between the locations and the velocity widths of the neutral FeKα line core and the broad Hβ emission line, the luminosity scaling relation of the neutral FeKα line core emitting region is estimated. We find that the velocity width of the neutral FeKα line core falls between that of the broad Balmer emission lines and the corresponding value at the dust reverberation radius for most of the target AGNs. The black hole mass {{M}BH,FeKα } estimated with this method is then compared with other black hole mass estimates, such as the broad emission-line reverberation mass {{M}BH,rev} for type 1 AGNs, the mass {{M}BH,{{H2}O}} based on the H2O maser, and the single-epoch mass estimate {{M}BH,pol} based on the polarized broad Balmer lines for type 2 AGNs. We find that {{M}BH,FeKα } is consistent with {{M}BH,rev} and {{M}BH,pol}, and find that {{M}BH,FeKα } correlates well with {{M}BH,{{H2}O}}. These results suggest that {{M}BH,FeKα } is a potential indicator of the black hole mass for obscured AGNs. In contrast, {{M}BH,FeKα } is systematically larger than {{M}BH,{{H2}O}} by about a factor of 5, and the possible origins are discussed.

  3. The Broad-Line Region and Dust Torus Structure of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Pozo Nuñez, Francisco

    2014-06-01

    I present the results from optical and infrared multi-month monitoring campaigns at the Universitätssternwarte Bochum (USB) in Chile to explore the structure of the central engine in active galactic nuclei (AGN). I apply and test photometric reverberation mapping (PRM) for measuring the time delay between variations in the continuum and Hbeta, Halpha emission lines. This time delay is used to infer the size of the broad-line region (BLR) for three Seyfert 1 galaxies. I place the results in context of the known BLR size luminosity relationship from spectroscopic reverberation mapping (SRM) and discuss its potential application to constrain cosmological parameters. The BLR size and the velocity dispersion of the emission line are used to calculate the virial mass of the supermassive black hole (SMBH). Through the direct modelling of PRM data, I infer the geometry type of the BLR allowing the determination of the geometry scaling factor used to constrain the real black hole mass. I find strong evidence for a disk-like BLR geometry. If this result holds for Seyfert galaxies in general, then the determination of the geometry scaling factor and the black hole mass can be remarkably improved. I discuss deviations of Seyfert-1 galaxies from the SMBH-bulge velocity dispersion relation MBH - sigma* for quiescent galaxies. Finally, I perform dust-reverberation mapping to determine the dust-torus size for the Seyfert 1 galaxy WPVS48. The light curves in the optical and near-infrared revealed unexpected variations which allow to solve an old puzzle on the geometry of the dusttorus.

  4. Iron Opacity Bump Changes the Stability and Structure of Accretion Disks in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Jiang, Yan-Fei; Davis, Shane W.; Stone, James M.

    2016-08-01

    Accretion disks around supermassive black holes have regions where the Rosseland mean opacity can be larger than the electron scattering opacity due to the large number of bound–bound transitions in iron. We study the effects of this iron opacity “bump” on the thermal stability and vertical structure of radiation-pressure-dominated accretion disks, utilizing three-dimensional radiation magnetohydrodynamic (MHD) simulations in the local shearing box approximation. The simulations self-consistently calculate the heating due to MHD turbulence caused by magneto-rotational instability and radiative cooling by using the radiative transfer module based on a variable Eddington tensor in Athena. For a 5 × 108 solar mass black hole with ∼3% of the Eddington luminosity, a model including the iron opacity bump maintains its structure for more than 10 thermal times without showing significant signs of thermal runaway. In contrast, if only electron scattering and free–free opacity are included as in the standard thin disk model, the disk collapses on the thermal timescale. The difference is caused by a combination of (1) an anti-correlation between the total optical depth and the midplane pressure, and (2) enhanced vertical advective energy transport. These results suggest that the iron opacity bump may have a strong impact on the stability and structure of active galactic nucleus (AGN) accretion disks, and may contribute to a dependence of AGN properties on metallicity. Since this opacity is relevant primarily in UV emitting regions of the flow, it may help to explain discrepancies between observation and theory that are unique to AGNs.

  5. Constraining the Active Galactic Nucleus Contribution in a Multiwavelength Study of Seyfert Galaxies

    NASA Technical Reports Server (NTRS)

    Melendez, M.; Kraemer, S.B.; Schmitt, H.R.; Crenshaw, D.M.; Deo, R.P.; Mushotzky, R.F.; Bruhweiler, F.C.

    2008-01-01

    We have studied the relationship between the high- and low-ionization [O IV] (lambda)25.89 microns, [Ne III] (lambda)15.56 microns, and [Ne II] (lambda)12.81 microns emission lines with the aim of constraining the active galactic nuclei (AGNs) and star formation contributions for a sample of 103 Seyfert galaxies.We use the [O IV] and [Ne II] emission as tracers for the AGN power and star formation to investigate the ionization state of the emission-line gas.We find that Seyfert 2 galaxies have, on average, lower [O IV]/[Ne II] ratios than Seyfert 1 galaxies. This result suggests two possible scenarios: (1) Seyfert 2 galaxies have intrinsically weaker AGNs, or (2) Seyfert 2 galaxies have relatively higher star formation rates than Seyfert 1 galaxies. We estimate the fraction of [Ne II] directly associated with the AGNs and find that Seyfert 2 galaxies have a larger contribution from star formation, by a factor of approx.1.5 on average, than what is found in Seyfert 1 galaxies. Using the stellar component of [Ne II] as a tracer of the current star formation, we found similar star formation rates in Seyfert 1 and Seyfert 2 galaxies.We examined the mid- and far-infrared continua and found that [Ne II] is well correlated with the continuum luminosity at 60 microns and that both [Ne III] and [O IV] are better correlated with the 25 micron luminosities than with the continuum at longer wavelengths, suggesting that the mid-infrared continuum luminosity is dominated by the AGN, while the far-infrared luminosity is dominated by star formation. Overall, these results test the unified model of AGNs and suggest that the differences between Seyfert galaxies cannot be solely due to viewing angle dependence.

  6. Spectral Energy Distribution Models for Low-Luminosity Active Galactic Nuclei in LINERs

    NASA Technical Reports Server (NTRS)

    Nemmen, Rodrigo S.; Storchi-Bergmann, Thaisa; Eracleous, Michael

    2012-01-01

    Low-luminosity active galactic nuclei (LLAGNs) represent the bulk of the AGN population in the present-day universe and they trace the low-level accreting supermassive black holes. In order to probe the accretion and jet physical properties in LLAGNs as a class, we model the broadband radio to X-rays spectral energy distributions (SEDs) of 21 LLAGNs in low-ionization nuclear emission-line regions (LINERs) with a coupled accretion-jet model. The accretion flow is modeled as an inner ADAF outside of which there is a truncated standard thin disk. We find that the radio emission is severely underpredicted by ADAF models and is explained by the relativistic jet. The origin of the X-ray radiation in most sources can be explained by three distinct scenarios: the X-rays can be dominated by emission from the ADAF, or the jet, or the X-rays can arise from a jet-ADAF combination in which both components contribute to the emission with similar importance. For 3 objects both the jet and ADAF fit equally well the X-ray spectrum and can be the dominant source of X-rays whereas for 11 LLAGNs a jet-dominated model accounts better than the ADAF-dominated model for the data. The individual and average SED models that we computed can be useful for different studies of the nuclear emission of LLAGNs. From the model fits, we estimate important parameters of the central engine powering LLAGNs in LINERs, such as the mass accretion rate and the mass-loss rate in the jet and the jet power - relevant for studies of the kinetic feedback from jets.

  7. Radio-selected Binary Active Galactic Nuclei from the Very Large Array Stripe 82 Survey

    NASA Astrophysics Data System (ADS)

    Fu, Hai; Myers, A. D.; Djorgovski, S. G.; Yan, Lin; Wrobel, J. M.; Stockton, A.

    2015-01-01

    Galaxy mergers play an important role in the growth of galaxies and their supermassive black holes. Simulations suggest that tidal interactions could enhance black hole accretion, which can be tested by the fraction of binary active galactic nuclei (AGNs) among galaxy mergers. However, determining the fraction requires a statistical sample of binaries. We have identified kiloparsec-scale binary AGNs directly from high-resolution radio imaging. Inside the 92 deg2 covered by the high-resolution Very Large Array survey of the Sloan Digital Sky Survey (SDSS) Stripe 82 field, we identified 22 grade A and 30 grade B candidates of binary radio AGNs with angular separations less than 5'' (10 kpc at z = 0.1). Eight of the candidates have optical spectra for both components from the SDSS spectroscopic surveys and our Keck program. Two grade B candidates are projected pairs, but the remaining six candidates are all compelling cases of binary AGNs based on either emission line ratios or the excess in radio power compared to the Hα-traced star formation rate. Only two of the six binaries were previously discovered by an optical spectroscopic search. Based on these results, we estimate that ~60% of our binary candidates would be confirmed once we obtain complete spectroscopic information. We conclude that wide-area high-resolution radio surveys offer an efficient method to identify large samples of binary AGNs. These radio-selected binary AGNs complement binaries identified at other wavelengths and are useful for understanding the triggering mechanisms of black hole accretion. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  9. THE LOW-LUMINOSITY END OF THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI

    SciTech Connect

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

    2013-04-20

    We present an updated and revised analysis of the relationship between the H{beta} broad-line region (BLR) radius and the luminosity of the active galactic nucleus (AGN). Specifically, we have carried out two-dimensional surface brightness decompositions of the host galaxies of nine new AGNs imaged with the Hubble Space Telescope Wide Field Camera 3. The surface brightness decompositions allow us to create ''AGN-free'' images of the galaxies, from which we measure the starlight contribution to the optical luminosity measured through the ground-based spectroscopic aperture. We also incorporate 20 new reverberation-mapping measurements of the H{beta} time lag, which is assumed to yield the average H{beta} BLR radius. The final sample includes 41 AGNs covering four orders of magnitude in luminosity. The additions and updates incorporated here primarily affect the low-luminosity end of the R{sub BLR}-L relationship. The best fit to the relationship using a Bayesian analysis finds a slope of {alpha}= 0.533{sup +0.035}{sub -0.033}, consistent with previous work and with simple photoionization arguments. Only two AGNs appear to be outliers from the relationship, but both of them have monitoring light curves that raise doubt regarding the accuracy of their reported time lags. The scatter around the relationship is found to be 0.19 {+-} 0.02 dex, but would be decreased to 0.13 dex by the removal of these two suspect measurements. A large fraction of the remaining scatter in the relationship is likely due to the inaccurate distances to the AGN host galaxies. Our results help support the possibility that the R{sub BLR}-L relationship could potentially be used to turn the BLRs of AGNs into standardizable candles. This would allow the cosmological expansion of the universe to be probed by a separate population of objects, and over a larger range of redshifts.

  10. An optical and near-infrared color-magnitude diagram for type I Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Palmer, Robert J.; Gibbs, John; Gorjian, Varoujan; Pruett, Lee; Young, Diedre; Boyd, Robert; Byrd, Joy; Cheshier, Jaicie; Chung, Stephanie; Clark, Ruby; Fernandez, Joseph; Gonzales, Elyse; Kumar, Anika; McGinnis, Gillian; Palmer, John; Perrine, Luke; Phelps, Brittney; Reginio, Margaret; Richter, Kristi; Sanchez, Elias; Washburn, Claire

    2016-01-01

    This project is seeking another standard candle for measuring cosmic distances by trying to establish a color-magnitude diagram for active galactic nuclei (AGN). Type I AGN selected from the NASA/IPAC Extragalactic Database (NED) were used to establish a correlation between the color and the luminosity of AGN. This work builds on previous NASA/IPAC Teacher Archive Research Program team attempts to establish such a relationship. This is novel in that it uses both optical and 1-2 micron near-infrared (NIR) wavelengths as a better color discriminator of the transition between accretion-dominated and dust/torus-dominated emission.Photometric data from the Sloan Digital Sky Survey (SDSS) and the Two Micron All Sky Survey (2MASS) was extracted and analyzed for type I AGN with redshifts z < 0.20. Our color-magnitude diagram for the area where the dust vaporizes is analogous to a stellar Hertzsprung-Russell (HR) diagram. Data from SDSS and 2MASS were specifically selected to focus on the sublimation boundary between the coolest part of the accretion disk and the hottest region of the inner edge of the dusty torus surrounding the accretion disk to find the greatest ratio for the color. The more luminous the AGN, the more extended the dust sublimation radius, causing a larger hot dust emitting surface area, which corresponds to a greater NIR luminosity.Our findings suggest that the best correlations correspond to colors associated with the Sloan z band and any of the 2MASS bands with slight variations dependent on redshift. This may result in a tool for using AGN as a standard for cosmic distances. This research was made possible through the NASA/IPAC Teacher Archive Research Program (NITARP) and was funded by NASA Astrophysics Data Program.

  11. THE COSMOS ACTIVE GALACTIC NUCLEUS SPECTROSCOPIC SURVEY. I. XMM-NEWTON COUNTERPARTS

    SciTech Connect

    Trump, Jonathan R.; Impey, Chris D.; Gabor, Jared; Kelly, Brandon C.; Elvis, Martin; Huchra, John P.; Civano, Francesca; Hao, Heng; McCarthy, Patrick J.; Scoville, Nick Z.; Smolcic, Vernesa; Brusa, Marcella; Cappelluti, Nico; Hasinger, Gunther; Salvato, Mara; Capak, Peter; Comastri, Andrea; Jahnke, Knud; Schinnerer, Eva; Lilly, Simon J.

    2009-05-10

    We present optical spectroscopy for an X-ray and optical flux-limited sample of 677 XMM-Newton selected targets covering the 2 deg{sup 2} Cosmic Evolution Survey field, with a yield of 485 high-confidence redshifts. The majority of the spectra were obtained over three seasons (2005-2007) with the Inamori Magellan Areal Camera and Spectrograph instrument on the Magellan (Baade) telescope. We also include in the sample previously published Sloan Digital Sky Survey spectra and supplemental observations with MMT/Hectospec. We detail the observations and classification analyses. The survey is 90% complete to flux limits of f {sub 0.5-10keV} > 8 x 10{sup -16} erg cm{sup -2} s{sup -1} and i {sup +} {sub AB} < 22, where over 90% of targets have high-confidence redshifts. Making simple corrections for incompleteness due to redshift and spectral type allows for a description of the complete population to i {sup +} {sub AB} < 23. The corrected sample includes a 57% broad emission line (Type 1, unobscured) active galactic nucleus (AGN) at 0.13 < z < 4.26, 25% narrow emission line (Type 2, obscured) AGN at 0.07 < z < 1.29, and 18% absorption line (host-dominated, obscured) AGN at 0 < z < 1.22 (excluding the stars that made up 4% of the X-ray targets). We show that the survey's limits in X-ray and optical fluxes include nearly all X-ray AGNs (defined by L {sub 0.5-10keV} > 3 x 10{sup 42} erg s{sup -1}) to z < 1, of both optically obscured and unobscured types. We find statistically significant evidence that the obscured-to-unobscured AGN ratio at z < 1 increases with redshift and decreases with luminosity.

  12. The INTEGRAL High-energy Cut-off Distribution of Type 1 Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Malizia, A.; Molina, M.; Bassani, L.; Stephen, J. B.; Bazzano, A.; Ubertini, P.; Bird, A. J.

    2014-02-01

    In this Letter we present the primary continuum parameters, the photon index Γ, and the high-energy cut-off E c of 41 type-1 Seyfert galaxies extracted from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) complete sample of active galactic nuclei (AGNs). We performed broadband (0.3-100 keV) spectral analysis by simultaneously fitting the soft and hard X-ray spectra obtained by XMM and INTEGRAL/IBIS-Swift/BAT, respectively, in order to investigate the general properties of these parameters, in particular their distribution and mean values. We find a mean photon index of 1.73 with a standard deviation of 0.17 and a mean high-energy cut-off of 128 keV with a standard deviation of 46 keV for the whole sample. This is the first time that the cut-off energy is constrained in such a large number of AGNs. We have 26 measurements of the cut-off, which corresponds to 63% of the entire sample, distributed between 50 and 200 keV. There are a further 11 lower limits mostly below 300 keV. Using the main parameters of the primary continuum, we have been able to obtain the actual physical parameters of the Comptonizing region, i.e., the plasma temperature kT e from 20 to 100 keV and the optical depth τ < 4. Finally, with the high signal-to-noise ratio spectra starting to come from NuSTAR it will soon be possible to better constrain the cut-off values in many AGNs, allowing the determination of more physical models and thus better understand the continuum emission and geometry of the region surrounding black holes.

  13. SPATIALLY RESOLVED SPECTROSCOPY OF SDSS J0952+2552: A CONFIRMED DUAL ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    McGurk, R. C.; Max, C. E.; Rosario, D. J.; Shields, G. A.; Smith, K. L.; Wright, S. A. E-mail: max@ucolick.org E-mail: shieldsga@mail.utexas.edu E-mail: saw@astro.berkeley.edu

    2011-09-01

    Most massive galaxies contain supermassive black holes (SMBHs) in their cores. When galaxies merge, gas is driven to nuclear regions and can accrete onto the central black hole. Thus, one expects to see dual active galactic nuclei (AGNs) in a fraction of galaxy mergers. Candidates for galaxies containing dual AGNs have been identified by the presence of double-peaked narrow [O III] emission lines and by high spatial resolution images of close galaxy pairs. Spatially resolved spectroscopy is needed to confirm these galaxy pairs as systems with spatially separated double SMBHs. With the Keck 2 Laser Guide Star Adaptive Optics system and the OH Suppressing InfraRed Imaging Spectrograph near-infrared integral field spectrograph, we obtained spatially resolved spectra for SDSS J09527.62+255257.2, a radio-quiet quasar shown by previous imaging to consist of a galaxy and its close (1.''0) companion. We find that the main galaxy is a Type 1 AGN with both broad and narrow AGN emission lines in its spectrum, while the companion galaxy is a Type 2 AGN with narrow emission lines only. The two AGNs are separated by 4.8 kpc, and their redshifts correspond to those of the double peaks of the [O III] emission line seen in the Sloan Digital Sky Survey spectrum. Line diagnostics indicate that both components of the double emission lines are due to AGN photoionization. These results confirm that J0952+2552 contains two spatially separated AGNs. As one of the few confirmed dual AGNs at an intermediate separation of <10 kpc, this system offers a unique opportunity to study galaxy mergers and their effect on black hole growth.

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

    NASA Astrophysics Data System (ADS)

    Kacprzak, Glenn G.; Churchill, Christopher W.; Murphy, Michael T.; Cooke, Jeff

    2015-01-01

    We performed a detailed study of the extended cool gas, traced by Mg II absorption [Wr(2796) ≥ 0.3 Å], surrounding 14 narrow-line active galactic nuclei (AGNs) at 0.12 ≤ z ≤ 0.22 using background quasar sightlines. The background quasars probe the AGNs at projected distances of 60 ≤ D ≤ 265 kpc. We find that, between 100 ≤ D ≤ 200 kpc, AGNs appear to have lower Mg II gas covering fractions (0.09^{+0.18}_{-0.08}) than quasars (0.47^{+0.16}_{-0.15}) and possibly lower than inactive field galaxies (0.25^{+0.11}_{-0.09}). We do not find a statistically significant azimuthal angle dependence for the Mg IIcovering fraction around AGNs, though the data hint at one. We also study the `down-the-barrel' outflow properties of the AGNs themselves and detect intrinsic Na ID absorption in 8/8 systems and intrinsic Mg II absorption in 2/2 systems, demonstrating that the AGNs have significant reservoirs of cool gas. We find that 6/8 Na ID and 2/2 Mg II intrinsic systems contain blueshifted absorption with Δv > 50 km s-1, indicating outflowing gas. The 2/2 intrinsic Mg II systems have outflow velocities a factor of ˜4 higher than the Na ID outflow velocities. Our results are consistent with AGN-driven outflows destroying the cool gas within their haloes, which dramatically decreases their cool gas covering fraction, while starburst-driven winds are expelling cool gas into their circumgalactic media (CGM). This picture appears contrary to quasar-quasar pair studies which show that the quasar CGM contains significant amounts of cool gas whereas intrinsic gas found `down-the-barrel' of quasars reveals no cool gas. We discuss how these results are complementary and provide support for the AGN unified model.

  15. Spatially Resolved Spectra of the "Teacup" Active Galactic Nucleus: Tracing the History of a Dying Quasar

    NASA Astrophysics Data System (ADS)

    Gagne, J. P.; Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.; Keel, W. C.; Rafter, S.; Fischer, T. C.; Bennert, V. N.; Schawinski, K.

    2014-09-01

    The Sloan Digital Sky Survey (SDSS) Galaxy Zoo project has revealed a number of spectacular galaxies possessing extended emission-line regions (EELRs), the most famous being Hanny's Voorwerp galaxy. We present another EELR object discovered in the SDSS endeavor: the Teacup active galactic nucleus (AGN). Nicknamed for its EELR, which has a "handle"-like structure protruding 15 kpc into the northeast quadrant of the galaxy. We analyze the physical conditions of this galaxy with long-slit, ground-based spectroscopy from the Lowell, Lick, and KPNO observatories. With the Lowell 1.8 m Perkin's telescope we took multiple observations at different offset positions, allowing us to recover spatially resolved spectra across the galaxy. Line diagnostics indicate the ionized gas is photoionized primarily by the AGN. Additionally we are able to derive the hydrogen density from the [S II] λ6716/λ6731 ratio. We generated two-component photoionization models for each spatially resolved Lowell spectrum. These models allow us to calculate the AGN bolometric luminosity seen by the gas at different radii from the nuclear center of the Teacup. Our results show a drop in bolometric luminosity by more than two orders of magnitude from the EELR to the nucleus, suggesting that the AGN has decreased in luminosity by this amount in a continuous fashion over 46,000 yr, supporting the case for a dying AGN in this galaxy independent of any IR based evidence. We demonstrate that spatially resolved photoionization modeling could be applied to EELRs to investigate long timescale variability.

  16. Reverberation mapping the dusty torus in Active Galactic Nuclei using Spitzer and optical light curves

    NASA Astrophysics Data System (ADS)

    Robinson, Andrew

    Dusty molecular tori play a central role in unification models for active galactic nuclei (AGN) and are also the dominant source of their mid-IR emission. Our limited knowledge of the size and structure of AGN tori and how these properties vary with luminosity hinders our ability to understand the observed spectral energy distribution and hence AGN demographics. Ultimately this inhibits our ability to understand the obscured AGN population and the cosmic evolution of super-massive black holes. Although the torus is, in general, inaccessible to direct imaging, its properties can be studied by analyzing the time response of the dust emission from the torus with respect to variations in the AGN continuum luminosity; a technique known as reverberation mapping. With this goal, we have completed a 2.5-year monitoring campaign on 12 broad-line AGN, using the Spitzer Space Telescope supported by ground-based optical observations, to measure the temporal response of thetorus 3.5 and 4.6μm mid-IR dust emission to variations in the AGN UV/optical continuum. The data obtained from the first 1.5 years in Spitzer Cycle 8 have been analysed. The aim of this project is to complete the time series analysis of the complete 2.5 year light curves, and to model these light curves in order extract structural and physical information contained in data, such as the size of the torus, its radial depth, opening angle, inclination and dust composition. This project will help to maximize the scientific returns on a significant investment of Spitzer Space Telescope time and supports the NASA strategic goal to "explore the origin and evolution of the galaxies, stars and planets that make up our universe".

  17. DISSECTING PHOTOMETRIC REDSHIFT FOR ACTIVE GALACTIC NUCLEUS USING XMM- AND CHANDRA-COSMOS SAMPLES

    SciTech Connect

    Salvato, M.; Hasinger, G.; Ilbert, O.; Rau, A.; Brusa, M.; Bongiorno, A.; Civano, F.; Elvis, M.; Zamorani, G.; Vignali, C.; Comastri, A.; Bardelli, S.; Bolzonella, M.; Cappelluti, N.; Aussel, H.; Le Floc'h, E.; Mainieri, V.; Capak, P.; Caputi, K.; and others

    2011-12-01

    In this paper, we release accurate photometric redshifts for 1692 counterparts to Chandra sources in the central square degree of the Cosmic Evolution Survey (COSMOS) field. The availability of a large training set of spectroscopic redshifts that extends to faint magnitudes enabled photometric redshifts comparable to the highest quality results presently available for normal galaxies. We demonstrate that morphologically extended, faint X-ray sources without optical variability are more accurately described by a library of normal galaxies (corrected for emission lines) than by active galactic nucleus (AGN) dominated templates, even if these sources have AGN-like X-ray luminosities. Preselecting the library on the bases of the source properties allowed us to reach an accuracy {sigma}{sub {Delta}z/(1+z{sub s{sub p{sub e{sub c)}}}}}{approx}0.015 with a fraction of outliers of 5.8% for the entire Chandra-COSMOS sample. In addition, we release revised photometric redshifts for the 1735 optical counterparts of the XMM-detected sources over the entire 2 deg{sup 2} of COSMOS. For 248 sources, our updated photometric redshift differs from the previous release by {Delta}z > 0.2. These changes are predominantly due to the inclusion of newly available deep H-band photometry (H{sub AB} = 24 mag). We illustrate once again the importance of a spectroscopic training sample and how an assumption about the nature of a source together, with the number and the depth of the available bands, influences the accuracy of the photometric redshifts determined for AGN. These considerations should be kept in mind when defining the observational strategies of upcoming large surveys targeting AGNs, such as eROSITA at X-ray energies and the Australian Square Kilometre Array Pathfinder Evolutionary Map of the Universe in the radio band.

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

    SciTech Connect

    Liu, Yuan; Li, Xiaobo E-mail: lixb@ihep.ac.cn

    2014-05-20

    We construct an X-ray spectral model for the clumpy torus in an active galactic nucleus (AGN) using Geant4, which includes the physical processes of the photoelectric effect, Compton scattering, Rayleigh scattering, γ conversion, fluorescence line, and Auger process. Since the electrons in the torus are expected to be bounded instead of free, the deviation of the scattering cross section from the Klein-Nishina cross section has also been included, which changes the X-ray spectra by up to 25% below 10 keV. We have investigated the effect of the clumpiness parameters on the reflection spectra and the strength of the fluorescent line Fe Kα. The volume filling factor of the clouds in the clumpy torus only slightly influences the reflection spectra, however, the total column density and the number of clouds along the line of sight significantly change the shapes and amplitudes of the reflection spectra. The effect of column density is similar to the case of a smooth torus, while a small number of clouds along the line of sight will smooth out the anisotropy of the reflection spectra and the fluorescent line Fe Kα. The smoothing effect is mild in the low column density case (N {sub H} = 10{sup 23} cm{sup –2}), whereas it is much more evident in the high column density case (N {sub H} = 10{sup 25} cm{sup –2}). Our model provides a quantitative tool for the spectral analysis of the clumpy torus. We suggest that the joint fits of the broad band spectral energy distributions of AGNs (from X-ray to infrared) should better constrain the structure of the torus.

  19. A Growth-rate Indicator for Compton-thick Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Brightman, M.; Masini, A.; Ballantyne, D. R.; Baloković, M.; Brandt, W. N.; Chen, C.-T.; Comastri, A.; Farrah, D.; Gandhi, P.; Harrison, F. A.; Ricci, C.; Stern, D.; Walton, D. J.

    2016-07-01

    Due to their heavily obscured central engines, the growth rate of Compton-thick (CT) active galactic nuclei (AGNs) is difficult to measure. A statistically significant correlation between the Eddington ratio, λ Edd, and the X-ray power-law index, Γ, observed in unobscured AGNs offers an estimate of their growth rate from X-ray spectroscopy (albeit with large scatter). However, since X-rays undergo reprocessing by Compton scattering and photoelectric absorption when the line of sight to the central engine is heavily obscured, the recovery of the intrinsic Γ is challenging. Here we study a sample of local, predominantly CT megamaser AGNs, where the black hole mass, and thus Eddington luminosity, are well known. We compile results of the X-ray spectral fitting of these sources with sensitive high-energy (E > 10 keV) NuSTAR data, where X-ray torus models, which take into account the reprocessing effects have been used to recover the intrinsic Γ values and X-ray luminosities, L X. With a simple bolometric correction to L X to calculate λ Edd, we find a statistically significant correlation between Γ and λ Edd (p = 0.007). A linear fit to the data yields Γ = (0.41 ± 0.18)log10 λ Edd + (2.38 ± 0.20), which is statistically consistent with results for unobscured AGNs. This result implies that torus modeling successfully recovers the intrinsic AGN parameters. Since the megamasers have low-mass black holes (M BH ≈ 106–107 M ⊙) and are highly inclined, our results extend the Γ–λ Edd relationship to lower masses and argue against strong orientation effects in the corona, in support of AGN unification. Finally this result supports the use of Γ as a growth-rate indicator for accreting black holes, even for CT AGNs.

  20. HerMES: disentangling active galactic nuclei and star formation in the radio source population

    NASA Astrophysics Data System (ADS)

    Rawlings, J. I.; Page, M. J.; Symeonidis, M.; Bock, J.; Cooray, A.; Farrah, D.; Guo, K.; Hatziminaoglou, E.; Ibar, E.; Oliver, S. J.; Roseboom, I. G.; Scott, Douglas; Seymour, N.; Vaccari, M.; Wardlow, J. L.

    2015-10-01

    We separate the extragalactic radio source population above ˜50 μJy into active galactic nuclei (AGN) and star-forming sources. The primary method of our approach is to fit the infrared spectral energy distributions (SEDs), constructed using Spitzer/IRAC (Infrared Array Camera) and Multiband Imaging Photometer for Spitzer (MIPS) and Herschel/SPIRE photometry, of 380 radio sources in the Extended Chandra Deep Field-South. From the fitted SEDs, we determine the relative AGN and star-forming contributions to their infrared emission. With the inclusion of other AGN diagnostics such as X-ray luminosity, Spitzer/IRAC colours, radio spectral index and the ratio of star-forming total infrared flux to k-corrected 1.4 GHz flux density, qIR, we determine whether the radio emission in these sources is powered by star formation or by an AGN. The majority of these radio sources (60 per cent) show the signature of an AGN at some wavelength. Of the sources with AGN signatures, 58 per cent are hybrid systems for which the radio emission is being powered by star formation. This implies that radio sources which have likely been selected on their star formation have a high AGN fraction. Below a 1.4 GHz flux density of 1 mJy, along with finding a strong contribution to the source counts from pure star-forming sources, we find that hybrid sources constitute 20-65 per cent of the sources