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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. The evolution of radio-loud active galactic nuclei as a function of black hole spin

    NASA Astrophysics Data System (ADS)

    Garofalo, D.; Evans, D. A.; Sambruna, R. M.

    2010-08-01

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

  4. 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.

  5. 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.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

    Di Mauro, Mattia; Cuoco, Alessandro; Donato, Fiorenza; Siegal-Gaskins, Jennifer M.

    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.

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

    DOE PAGES

    Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

    2009-12-04

    In this work, 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). Lastly, these findings can have strong implications on our knowledge about relativistic jets and the unified model of the AGN.

  9. A 3.5 mm POLARIMETRIC SURVEY OF RADIO-LOUD ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Agudo, I.; Thum, C.; Wiesemeyer, H.; Krichbaum, T. P. E-mail: thum@iram.f E-mail: tkrichbaum@mpifr-bonn.mpg.d

    2010-07-15

    We present the results from the first large (>100 sources) 3.5 mm polarimetric survey of radio-loud active galactic nuclei (AGNs). This wavelength is favorable within the radio-millimeter range for measuring the intrinsic linearly polarized emission from AGNs, since in general it is only marginally affected by Faraday rotation of the electric vector position angle and depolarization. The I, Q, U, and V Stokes parameter observations were performed with the XPOL polarimeter at the IRAM 30 m Telescope on different observing epochs from 2005 July (when most of the measurements were made) to 2009 October. Our sample consists of 145 flat-radio-spectrum AGNs with declination >-30{sup 0} (J2000.0) and flux density {approx}>1 Jy at {approx}86 GHz, as measured at the IRAM 30 m Telescope from 1978 to 1994. This constraint on the radio spectrum causes our sample to be dominated by blazars, which allows us to conduct new statistical studies on this class of high-luminosity, relativistically beamed emitters. We detect linear and circular polarization (above minimum 3{sigma} levels of {approx}1.5% and {approx}0.3%) for 76% and 6% of the sample, respectively. We find a clear excess in degree of linear polarization detected at 86 GHz with regard to that at 15 GHz by a factor of {approx}2. Over our entire source sample, the luminosity of the jets is anticorrelated with the degree of linear polarization. Consistent with previous findings claiming larger Doppler factors for brighter {gamma}-ray blazars, quasars listed in our sample, and in the Fermi Large Area Telescope Bright Source Catalog (LBAS), show larger luminosities than non-LBAS ones, but our data do not allow us to confirm the same for BL Lac objects. We do not find a clear relation between the linear polarization angle and the jet structural position angle for any source class in our sample. We interpret this as the consequence of a markedly non-axisymmetric character of the 3 mm emitting region in the jets. We find that

  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. EVIDENCE FOR INFRARED-FAINT RADIO SOURCES AS z > 1 RADIO-LOUD ACTIVE GALACTIC NUCLEI

    SciTech Connect

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

    2010-02-10

    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 {mu}m) 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 {approx}> 1) active galactic nuclei.

  14. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2012-12-01

    We present optical, infrared (IR) and radio observations of the powerful Fanaroff-Riley type II (FR II) radio source PKS 0347+05 (z = 0.3390), and demonstrate that it is a rare example of a radio-loud/radio-quiet double active galactic nucleus (AGN) system, comprising a weak-line radio galaxy (WLRG) separated by 25 kpc (in projection) from a Seyfert 1 nucleus at the same redshift. Our deep Gemini optical images show a highly disturbed morphology, with a warped dust lane crossing through the halo and nuclear regions of the radio galaxy host, tidal tails and a bridge connecting the radio galaxy to the Seyfert 1 nucleus. Spectral synthesis modelling of our Gemini optical spectrum of the radio galaxy shows evidence for a reddened young stellar population of age ≤100 Myr. Further evidence for recent star formation activity in this source is provided by the detection of strong polycyclic aromatic hydrocarbon features in mid-IR Spitzer/IRS spectra. Together, these observations support a model in which both AGN have been triggered simultaneously in a major galaxy merger. However, despite the presence of a powerful FR II radio source, and the apparently plentiful supply of fuel provided by the merger, the nucleus of the radio galaxy shows only weak, low-ionization emission-line activity. We speculate that the fuel supply to nuclear regions of the radio galaxy has recently switched off (within the last ˜106 yr), but the information about the resulting decrease in nuclear AGN activity has yet to reach the extended lobes and hotspots of the FR II radio source. Based on this scenario, we derive a lower limit on the typical lifetimes of powerful, intermediate-redshift FR II radio sources of τ FR II ≳5×106 yr. Overall, our observations emphasize that the fuelling of AGN activity in major galaxy mergers is likely to be highly intermittent.

  16. OISTER optical and near-infrared monitoring observations of peculiar radio-loud active galactic nucleus SDSS J110006.07+442144.3

    NASA Astrophysics Data System (ADS)

    Morokuma, Tomoki; Tanaka, Masaomi; Tanaka, Yasuyuki T.; Itoh, Ryosuke; Tominaga, Nozomu; Gandhi, Poshak; Pian, Elena; Mazzali, Paolo; Ohta, Kouji; Matsumoto, Emiko; Shibata, Takumi; Akimoto, Hinako; Akitaya, Hiroshi; Ali, Gamal B.; Aoki, Tsutomu; Doi, Mamoru; Ebisuda, Nana; Essam, Ahmed; Fujisawa, Kenta; Fukushima, Hideo; Goda, Shuhei; Gouda, Yuya; Hanayama, Hidekazu; Hashiba, Yasuhito; Hashimoto, Osamu; Hayashida, Kenzo; Hiratsuka, Yuichiro; Honda, Satoshi; Imai, Masataka; Inoue, Kanichiro; Ishibashi, Michiko; Iwata, Ikuru; Izumiura, Hideyuki; Kanda, Yuka; Kawabata, Miho; Kawaguchi, Kenji; Kawai, Nobuyuki; Kokubo, Mitsuru; Kuroda, Daisuke; Maehara, Hiroyuki; Mito, Hiroyuki; Mitsuda, Kazuma; Miyagawa, Ryota; Miyaji, Takeshi; Miyamoto, Yusuke; Morihana, Kumiko; Moritani, Yuki; Morokuma-Matsui, Kana; Murakami, Kotone; Murata, Katsuhiro L.; Nagayama, Takahiro; Nakamura, Kazuki; Nakaoka, Tatsuya; Niinuma, Kotaro; Nishimori, Takafumi; Nogami, Daisaku; Oasa, Yumiko; Oda, Tatsunori; Ohshima, Tomohito; Saito, Yoshihiko; Sakata, Shuichiro; Sako, Shigeyuki; Sarugaku, Yuki; Sawada-Satoh, Satoko; Seino, Genta; Sorai, Kazuo; Soyano, Takao; Taddia, Francesco; Takahashi, Jun; Takagi, Yuhei; Takaki, Katsutoshi; Takata, Koji; Tarusawa, Ken'ichi; Uemura, Makoto; Ui, Takahiro; Urago, Riku; Ushioda, Kazutoshi; Watanabe, Jun-ichi; Watanabe, Makoto; Yamashita, Satoshi; Yanagisawa, Kenshi; Yonekura, Yoshinori; Yoshida, Michitoshi

    2017-10-01

    We present monitoring campaign observations at optical and near-infrared (NIR) wavelengths for a radio-loud active galactic nucleus (AGN) at z = 0.840, SDSS J110006.07+442144.3 (hereafter, J1100+4421), which was identified during a flare phase in late 2014 February. The campaigns consist of three intensive observing runs from the discovery to 2015 March, mostly within the scheme of the OISTER collaboration. Optical-NIR light curves and simultaneous spectral energy distributions (SEDs) are obtained. Our measurements show the strongest brightening in 2015 March. We found that the optical-NIR SEDs of J1100+4421 show an almost steady shape despite the large and rapid intranight variability. This constant SED shape is confirmed to extend to ˜5 μm in the observed frame using the archival WISE data. Given the lack of absorption lines and the steep power-law spectrum of αν ˜ -1.4, where f_{ν }∝ ν ^{α _{ν }}, synchrotron radiation by a relativistic jet with no or small contributions from the host galaxy and the accretion disk seems most plausible as an optical-NIR emission mechanism. The steep optical-NIR spectral shape and the large amplitude of variability are consistent with this object being a low νpeak jet-dominated AGN. In addition, sub-arcsecond resolution optical imaging data taken with Subaru Hyper Suprime-Cam does not show a clear extended component and the spatial scales are significantly smaller than the large extensions detected at radio wavelengths. The optical spectrum of a possible faint companion galaxy does not show any emission lines at the same redshift, and hence a merging hypothesis for this AGN-related activity is not supported by our observations.

  17. RADIATION MECHANISM AND JET COMPOSITION OF GAMMA-RAY BURSTS AND GeV-TeV-SELECTED RADIO-LOUD ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Zhang Jin; Lu Ye; Zhang Shuangnan; Liang Enwei; Sun Xiaona; Zhang Bing

    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{sub jet}) and the prompt gamma-ray luminosity (L{sub jet}) of GRBs is consistent, within the uncertainties, with the correlation between jet power and the synchrotron peak luminosity (L{sub s,jet}) of flat spectrum radio quasars (FSRQs). Their radiation efficiencies ({epsilon}) are also comparable (>10% for most sources), which increase with the bolometric jet luminosity (L{sub bol,jet}) for FSRQs and with the L{sub jet} for GRBs with similar power-law indices. BL Lac objects (BL Lacs) do not follow the P{sub jet}-L{sub s,jet} relation of FSRQs. They have lower {epsilon} and L{sub bol,jet} values than FSRQs, and a tentative L{sub bol,jet}-{epsilon} relation is also found, with a power-law index different from that of the FSRQs. The magnetization parameters ({sigma}) of FSRQs are on average larger than that of BL Lacs. They are anti-correlated with {epsilon} for the FSRQs, but positively correlated with {epsilon} 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. H I absorption towards low-luminosity radio-loud active galactic nuclei of different accretion modes and WISE colours

    NASA Astrophysics Data System (ADS)

    Chandola, Yogesh; Saikia, D. J.

    2017-02-01

    H I absorption studies of active galaxies enable us to probe their circumnuclear regions and the general interstellar medium and study the supply of gas that may trigger nuclear activity. In this article, we investigate the dependence of the detection rate of H I absorption on the nature of radio galaxies based on their emission-line spectra and on the nature of host galaxies based on WISE colours and their radio structure, which may help us understand the different accretion modes. We find significant differences in the distributions of W2-W3 colour for sources with H I absorption detections and non-detections. We report a high detection rate of H I absorption in those galaxies with WISE infrared colours W2-W3 > 2, typical of gas-rich systems, along with a compact radio structure. The H I detection rate for low-excitation radio galaxies (LERGs) with W2-W3 > 2 and compact radio structure is high (70.6 ± 20.4 per cent). In high-excitation radio galaxies (HERGs), compact radio structure in the nuclear or circumnuclear region could give rise to absorption by gas in the dusty torus, in addition to gas in the interstellar medium. However, the higher specific star-formation rate (sSFR) for LERGs with W2-W3 > 2 suggests that H I absorption may be largely due to star-forming gas in their hosts. LERGs with extended radio structure tend to have significantly lower values of W2-W3 compared with those with compact structure. Extended radio sources and those with W2-W3 < 2 have low H I detection rates.

  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)

    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.

  20. 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.

  1. 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.

  2. Obscuration, orientation, and the infrared properties of radio-loud active galaxies

    NASA Technical Reports Server (NTRS)

    Heckman, Timothy M.; O'Dea, Christopher P.; Baum, Stefi A.; Laurikainen, Eija

    1994-01-01

    We report on a study of the mid- and far-infrared (MFIR) properties of several different classes of radio-loud active galactic nuclei (AGNs) using the IRAS database. Our goal is to try to improve the understanding of the possible relationships between the diverse classes of AGNs. The MFIR and radio properties of radio-loud AGNs are especially useful in this regard, since (excluding the blazar class, which we do not study here) the radio emission is thought to be emitted isotropically, and the radio and MFIR radiation should be much less affected by dust obscuration than radiation at shorter wavelengths. We have first compared samples of 3CR broad-line radio galaxies (BLRGs) and narrow-line radio galaxies (NLRGs) matched in radio flux and mean redshift. We find that the BLRGs are stronger than the NLRGs by a factor of 4-5 in their mid-IR emission but are similar to the NLRGs in the far-IR. This is qualitatively consistent with recent 'unification' models for NLRGs and BLRGs which invoke thermal MFIR emission from dusty 'obscuring tori,' but there may be an additional source of far-IR emission present in the more luminous broad-line objects (the radio-loud quasars) studied previously by Heckman, Chambers & Postman (1992). We have also compared samples of Fanaroff-Riley class I (FRI) and Fanaroff-Riley class II (FRII) radio galaxies matched in radio flux and redshift. The FRII galaxies are stronger MFIR emitters than the FRI galaxies by a factor of about 4. This is consistent with suggestions that the central engine in FRI galaxies produces relatively little radiant energy per unit jet power (expecially since we find that the weak MFIR emission from the FRI galaxies may not be powered by the AGN). Comparing samples of gigahertz-peaked spectrum (GPS) and compact steep spectrum (CSS) sources versus non-GPS-CSS sources, we find that the GPS-CSS and non-GPS-CSS sources have similar MFIR strengths. This suggests that the efficiency of the conversion of jet kinetic energy

  3. Herschel-ATLAS: the connection between star formation and AGN activity in radio-loud and radio-quiet active galaxies

    NASA Astrophysics Data System (ADS)

    Gürkan, G.; Hardcastle, M. J.; Jarvis, M. J.; Smith, D. J. B.; Bourne, N.; Dunne, L.; Maddox, S.; Ivison, R. J.; Fritz, J.

    2015-10-01

    We examine the relationship between star formation and active galactic nuclei (AGN) activity by constructing matched samples of local (0 < z < 0.6) radio-loud and radio-quiet AGN in the Herschel-Astrophysical Terahertz Large Area Survey fields. Radio-loud AGN are classified as high-excitation and low-excitation radio galaxies using their emission lines and WISE 22-μm luminosity. AGN accretion and jet powers in these active galaxies are traced by [O III] emission-line and radio luminosity, respectively. Star formation rates (SFRs) and specific star formation rates (SSFRs) were derived using Herschel 250-μm luminosity and stellar mass measurements from the Sloan Digital Sky Survey-Max Planck Institute for Astrophysics-John Hopkins University catalogue. In the past, star formation studies of AGN have mostly focused on high-redshift sources to observe the thermal dust emission that peaks in the far-infrared, which limited the samples to powerful objects. However, with Herschel we can expand this to low redshifts. Our stacking analyses show that SFRs and SSFRs of both radio-loud and radio-quiet AGN increase with increasing AGN power but that radio-loud AGN tend to have lower SFR. Additionally, radio-quiet AGN are found to have approximately an order of magnitude higher SSFRs than radio-loud AGN for a given level of AGN power. The difference between the star formation properties of radio-loud and -quiet AGN is also seen in samples matched in stellar mass.

  4. 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.

  5. 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

  6. 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.

  7. The Suzaku Observation of the Nucleus of the Radio Loud Active Galaxy Centaurus A

    NASA Astrophysics Data System (ADS)

    Markowitz, A.; Suzaku Cen A Team

    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 × 1023 cm-2 respectively. The spectrum 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, 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 collisional ionization emission 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 Kα line yields a 200 light-day lower limit on the distance from the black hole to the line-emitt ing gas. K-shell absorption edges due to Fe, Ca, and S are detected. The high metallicity ([Fe/H]=+0.1) of the circumnuclear material suggests that the accreting material could not have originated in the metal-poor outer halo unless enrichment by local star formation has occurred. Relative element abundances are consistent with enrichment due to local star formation processes.

  8. 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.

  9. What Distinguishes the Host Galaxies of Radio-loud and Radio-quiet AGNs?

    NASA Astrophysics Data System (ADS)

    Kozieł-Wierzbowska, D.; Vale Asari, N.; Stasińska, G.; Sikora, M.; Goettems, E. I.; Wójtowicz, A.

    2017-09-01

    We compare the optical properties of the host galaxies of radio-quiet (RQ) and radio-loud (RL) Type 2 active galactic nuclei (AGNs) to infer whether the jet production efficiency depends on the host properties or is determined just by intrinsic properties of the accretion flows. We carefully select galaxies from SDSS, FIRST, and NVSS catalogs. We confirm previous findings that the fraction of RL AGNs depends on the black-hole (BH) masses, and on the Eddington ratio. The comparison of the nature of the hosts of RL and RQ AGNs, therefore, requires pair-matching techniques. Matching in BH mass and Eddington ratio allows us to study the differences between galaxies hosting RL and RQ AGNs that have the same basic accretion parameters. We show that these two samples differ predominantly in the host-galaxy concentration index, morphological type (in the RL sample the frequency of elliptical galaxies becoming larger with increasing radio loudness), and nebular extinction (galaxies with highest radio loudness showing only low nebular extinction). Contrary to some previous studies, we find no significant difference between our radio-loud and radio-quiet samples regarding merger/interaction features.

  10. 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.

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

    NASA Astrophysics Data System (ADS)

    Barišić, Ivana; van der Wel, Arjen; Bezanson, Rachel; Pacifici, Camilla; Noeske, Kai; Muñoz-Mateos, Juan C.; Franx, Marijn; Smolčić, Vernesa; Bell, Eric F.; Brammer, Gabriel; Calhau, João; Chauké, Priscilla; van Dokkum, Pieter G.; van Houdt, Josha; Gallazzi, Anna; Labbé, Ivo; Maseda, Michael V.; Muzzin, Adam; Sobral, David; Straatman, Caroline; Wu, Po-Feng

    2017-09-01

    We investigate the stellar kinematics and stellar populations of 58 radio-loud galaxies of intermediate luminosities (L 3 GHz > 1023 W Hz‑1) at 0.6 < z < 1. This sample is constructed by cross-matching galaxies from the deep VLT/VIMOS LEGA-C spectroscopic survey with the VLA 3 GHz data set. The LEGA-C continuum spectra reveal for the first time stellar velocity dispersions and age indicators of z ∼ 1 radio galaxies. We find that z ∼ 1 radio-loud active galactic nucleus (AGN) occur exclusively in predominantly old galaxies with high velocity dispersions: σ * > 175 km s‑1, corresponding to black hole masses in excess of 108 M ⊙. Furthermore, we confirm that at a fixed stellar mass the fraction of radio-loud AGN at z ∼ 1 is five to 10 times higher than in the local universe, suggesting that quiescent, massive galaxies at z ∼ 1 switch on as radio AGN on average once every Gyr. Our results strengthen the existing evidence for a link between high black hole masses, radio loudness, and quiescence at z ∼ 1.

  12. On the two main classes of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Padovani, Paolo

    2017-08-01

    Active galactic nuclei (AGNs) are empirically divided into 'radio-loud' and 'radio-quiet'. These 50-year-old labels are obsolete, misleading and wrong. I argue that AGNs should be classified as 'jetted' and 'non-jetted' based on a physical difference — the presence (or lack) of strong relativistic jets.

  13. Radio-loud and Radio-quiet QSOs

    NASA Astrophysics Data System (ADS)

    Kellermann, K. I.; Condon, J. J.; Kimball, A. E.; Perley, R. A.; Ivezić, Željko

    2016-11-01

    We discuss 6 GHz JVLA observations covering a volume-limited sample of 178 low-redshift (0.2< z< 0.3) optically selected quasi-stellar objects (QSOs). Our 176 radio detections fall into two clear categories: (1) about 20% are radio-loud QSOs (RLQs) with spectral luminosities of {L}6≳ {10}23.2 {{W}} {{Hz}}-1 that are primarily generated in the active galactic nucleus (AGN) responsible for the excess optical luminosity that defines a bona fide QSO; and (2) the remaining 80% that are radio-quiet QSOs (RQQs) that have {10}21≲ {L}6≲ {10}23.2 {{W}} {{Hz}}-1 and radio sizes ≲ 10 {kpc}, and we suggest that the bulk of their radio emission is powered by star formation in their host galaxies. “Radio-silent” QSOs ({L}6≲ {10}21 {{W}} {{Hz}}-1) are rare, so most RQQ host galaxies form stars faster than the Milky Way; they are not “red and dead” ellipticals. Earlier radio observations did not have the luminosity sensitivity of {L}6≲ {10}21 {{W}} {{Hz}}-1 that is needed to distinguish between such RLQs and RQQs. Strong, generally double-sided radio emission spanning \\gg 10 {kpc} was found to be associated with 13 of the 18 RLQ cores with peak flux densities of {S}{{p}}> 5 {mJy} {{beam}}-1 ({log}(L)≳ 24). The radio luminosity function of optically selected QSOs and the extended radio emission associated with RLQs are both inconsistent with simple “unified” models that invoke relativistic beaming from randomly oriented QSOs to explain the difference between RLQs and RQQs. Some intrinsic property of the AGNs or their host galaxies must also determine whether or not a QSO appears radio-loud.

  14. Zooming in on the peculiar radio-loud narrow-line Seyfert 1 galaxy, J1100+4421

    NASA Astrophysics Data System (ADS)

    Gabányu, K. É.; Frey, S.; Paragi, Z.; Tar, I.; An, T.; Tanaka, M.; Morokuma, T.

    2016-08-01

    Narrow-line Seyfert 1 galaxies (NLS1) are interesting subsamples of active galactic nuclei, which are typically thought to contain a relatively smaller supermassive black holes (10^6-10^8 solar masses) and show quite high accretion rate. Only 7% of them are detected in radio. The radio structure of the objects in the extremely radio-loud NLS1 subsample indicates the presence of relativistically beamed jets. Some radio-loud NLS1s were detected even at high energies with the Fermi Large Array Telescope. Therefore these sources are often suggested to be the low-luminosity and younger counterparts of blazars. SDSS J110006.07+442144.3 was identified as an NLS1 at z=0.84 after its dramatic optical brightening discovered by Tanaka et al. (2014) Our dual-frequency (1.6 and 5 GHz) European VLBI Network observations taken one year after this event show a compact structre with brightness temperature of 6 x 10^9 K and a flat spectral index indicating the presence of a compact synchrotron self-absorbed core. Compared with low resolution VLA-FIRST data, the large-scale structure seen there is resolved out in the EVN observation. However the recovered flux density in our L-band EVN observation is significantly higher than the FIRST flux density, which is indicative of brightening in the radio regime. All these results fit into the picture where radio-loud NLS1s are described as faint blazars.

  15. γ-ray variability of radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Calderone, G.; Foschini, L.; Ghisellini, G.; Colpi, M.; Maraschi, L.; Tavecchio, F.; Decarli, R.; Tagliaferri, G.

    2011-06-01

    The recent detection of γ-ray emission from four radio-loud narrow-line Seyfert 1 galaxies suggests that the engine driving the active galactic nuclei (AGN) activity of these objects shares some similarities with that of blazars, namely the presence of a γ-ray emitting, variable jet of plasma closely aligned to the line of sight. In this work we analyse the γ-ray light curves of the four radio-loud narrow-line Seyfert 1 galaxies for which high-energy γ-ray emission has been discovered by Fermi/LAT, in order to study their variability. We find significant flux variability in all the sources. This allows us to exclude a starburst origin of the γ-ray photons and confirms the presence of a relativistic jet. Furthermore, we estimate the minimum e-folding variability time-scale (3-30 d) and infer an upper limit for the size of the emitting region (0.2-2 pc, assuming a relativistic Doppler factor δ= 10 and a jet aperture of θ= 0.1 rad).

  16. 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).

  17. What sparks the radio-loud phase of nearby quasars?

    NASA Astrophysics Data System (ADS)

    Coziol, Roger; Andernach, Heinz; Torres-Papaqui, Juan Pablo; Ortega-Minakata, René Alberto; Moreno del Rio, Froylan

    2017-04-01

    To better constrain the hypotheses proposed to explain why only a few quasars are radio loud (RL), we compare the characteristics of 1958 nearby (z ≤ 0.3) SDSS (Sloan Digital Sky Survey) quasars, covered by the FIRST (Faint Images of the Radio Sky at Twenty-centimeters) and NVSS (NRAO VLA Sky Survey) radio surveys. Only 22 per cent are RL with log (L1.4 GHz) ≥ 22.5 W Hz-1, the majority being compact (C), weak radio sources (WRS), with log (L1.4 GHz) < 24.5 W Hz-1. 15 per cent of the RL quasars have extended radio morphologies: 3 per cent have a core and a jet (J), 2 per cent have a core with one lobe (L), and 10 per cent have a core with two lobes (T), the majority being powerful radio sources (PRS), with log (L1.4 GHz) ≥ 24.5 W Hz-1. In general, RL quasars have higher bolometric luminosities and ionization powers than radio-quiet (RQ) quasars. The WRS have comparable black hole (BH) masses as the RQ quasars, but higher accretion rates or radiative efficiencies. The PRS have higher BH masses than the WRS, but comparable accretion rates or radiative efficiencies. The WRS also have higher FWHM_{[O iii]} than the PRS, consistent with a coupling of the spectral characteristics of the quasars with their radio morphologies. Inspecting the SDSS images and applying a neighbour search algorithm reveal no difference between the RQ and RL quasars of their host galaxies, environments, and interaction. Our results prompt the conjecture that the phenomenon that sparks the RL phase in quasars is transient, intrinsic to the active galactic nuclei, and stochastic, due to the chaotic nature of the accretion process of matter on to the BHs.

  18. Modeling Gyrosynchrotron Coronae of Radio-Loud Stars

    NASA Astrophysics Data System (ADS)

    Peterson, William M.

    2015-01-01

    Fast gyrosynchrotron codes are used to model the emission in close, active binary star systems. Multiple magnetic field topologies, plasma densities, and scale heights for the emitting plasma are tested for in an attempt to duplicate the emission characteristics detected using high-resolution VLBI imaging of the close active binaries UX Arietis and Algol. Also included are effects of occlusion by the companion star. It is found that a co-orbiting coronal loop oriented toward the companion star with its feet anchored on the poles of the active star is consistent with the observed emission from these two radio-loud stars.

  19. The Parsec-scale Structure and Kinematics of Radio-Loud Narrow-Line Seyfert 1 Galaxies

    NASA Astrophysics Data System (ADS)

    Richards, Joseph L; Lister, Matthew L.; Foschini, Luigi; Savolainen, Tuomas; Homan, Daniel C.; Kadler, Matthias; Readhead, Anthony C. S.; Arshakian, Tigran; Chavushyan, Vahram

    2014-08-01

    We have begun a campaign to monitor a sample of 15 radio-loud narrow-line Seyfert 1 galaxies (NLS1s) with the Very Long Baseline Array (VLBA). Here, we present early results from this program, which includes total intensity and polarimetric observations at 1, 2, 4, and 6cm wavelengths. NLS1s are a class of active galactic nuclei that share many observational properties with the much more powerful blazar classes. Despite their low black hole masses and near- or super-Eddington accretion rates, a small minority are radio loud. A growing number of these have been detected in GeV gamma rays, indicating that a relativistic jet has formed in at least some of these sources. This presents a challenge to jet models, but may provide a link between jets found at the small scales of galactic binaries and the large scales of giant quasars. In addition to our VLBA program, we are carrying out complementary fast-cadence single dish 2cm radio monitoring with the Owens Valley Radio Observatory 40m telescope and an optical spectroscopic monitoring campaign using the Guillermo Haro Astrophysics Observatory 2m-class telescope in Cananea, Mexico. Using data from this program, we will expand the currently limited knowledge of the parsec-scale properties and kinematics of this class of sources. Among our first epoch results, we find significant parsec-scale extension in about about two thirds of our sample, many of which are excellent candidates for jet kinematics analysis.

  20. A Mixture Evolution Scenario of the AGN Radio Luminosity Function. II. Do Low- and High-power Radio-loud AGNs Evolve Differently?

    NASA Astrophysics Data System (ADS)

    Yuan, Zunli; Wang, Jiancheng; Zhou, Ming; Qin, Longhua; Mao, Jirong

    2017-09-01

    Following previous work, we further confirm that the cosmic evolution of steep-spectrum radio-loud AGNs (active galactic nuclei) can be reproduced by a simple combination of density evolution (DE) and luminosity evolution (LE). This mixture evolution scenario can naturally explain the luminosity-dependent evolution of radio-loud AGNs. Our models successfully fitted a large amount of data on radio luminosity functions of steep-spectrum sources and multi-frequency source counts. The modeling indicates that the DE slowly increases as {(1+z)}0.3∼ 1.3 out to z∼ 0.8, and then rapidly decreases as {(1+z)}-6.8∼ -5.7, while the LE rapidly increases as {(1+z)}4.8 out to a higher redshift (at least z> 3.5). We find a high-redshift decline (i.e., redshift cutoff) in the number density of steep-spectrum radio sources, but we cannot conclude whether such a decline is sharp or shallow. We believe that whether a redshift cutoff occurs or not depends mainly on DE, while its steepness is decided by LE, which, however, cannot be well constrained due to the lack of high-redshift samples. Most intriguingly, according to our mixture evolution scenario, there appears to be no need for different evolution for the low- and high-power radio-loud AGNs. Both types of sources experience the same combined evolution of DE and LE.

  1. The Fundamental Plane of Radio Loud Quasars and X-ray Binaries

    NASA Astrophysics Data System (ADS)

    Zhang, X.; Zhang, H. J.; Zhang, X.

    2016-05-01

    Several X-ray binaries (X-ray binaries) in low/hard state that follow a track of radio-X-ray correlation have been found in recent years. Dong et al. also found this relation in RQQs (radio quiet quasars). Black hole accretion and jet formation are scale invariants which form the fundamental plane of black hole activity. It is a plane given in the space of the black hole mass and the radio/X-ray luminosities. In this paper, we compile a sample of radio loud active galactic nuclei and find that: (1) The hard X-ray photon indices and Eddington ratios of our sample are positively correlated, similar to XRBs. The Eddington-scaled radio-X-ray correlation of our sample also has that of outliers. A radiatively efficient accretion flow can regulate the positively correlated X-ray spectral evolution and the steep radio-X-ray correlation. (2) We can present a fundamental plane for XRBs. Several XRBs and radio-loud quasars (RLQs) have similarities in the relation formed by the black-hole mass, radio and X-ray luminosities. The fundamental plane is lg LR=0.998+0.045-0.045 lg LX+0.592+0.049-0.049 lg MBH -6.56+1.605-1.605, where LR is the radio luminosity, LX is the X-ray luminosity, and MBH is the black hole mass. (3) The plane can be suitable for the RLQ black hole sources. And the X-ray binaries also agree to the relation.

  2. 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.

  3. 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

  4. 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.; hide

    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.

  5. The Suzaku Observation of the Nucleus of the Radio-loud Active Galaxy Centaurus A: Constraints on Abundances of the Accreting Material

    NASA Astrophysics Data System (ADS)

    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.

    2007-08-01

    A Suzaku observation of the nucleus of the radio-loud AGN Centaurus A in 2005 has yielded a broadband spectrum spanning 0.3-250 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 7×1023 cm-2, respectively. The spectrum is consistent with previous suggestions that the power-law components are X-ray emission from the subparsec 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 Kα line width yields a 200 lt-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.

  6. 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.

  7. 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.

  8. The X-Ray Reflection Spectrum of the Radio-loud Quasar 4C 74.26

    NASA Astrophysics Data System (ADS)

    Lohfink, Anne M.; Fabian, Andrew C.; Ballantyne, David R.; Boggs, S. E.; Boorman, Peter; Christensen, F. E.; Craig, W. W.; Farrah, Duncan; García, Javier; Hailey, C. J.; Harrison, F. A.; Ricci, Claudio; Stern, Daniel; Zhang, W. W.

    2017-06-01

    The relativistic jets created by some active galactic nuclei are important agents of AGN feedback. In spite of this, our understanding of what produces these jets is still incomplete. X-ray observations, which can probe the processes operating in the central regions in the immediate vicinity of the supermassive black hole, the presumed jet launching point, are potentially particularly valuable in illuminating the jet formation process. Here, we present the hard X-ray NuSTAR observations of the radio-loud quasar 4C 74.26 in a joint analysis with quasi-simultaneous, soft X-ray Swift observations. Our spectral analysis reveals a high-energy cutoff of {183}-35+51 keV and confirms the presence of ionized reflection in the source. From the average spectrum we detect that the accretion disk is mildly recessed, with an inner radius of R in = 4-180 R g. However, no significant evolution of the inner radius is seen during the three months covered by our NuSTAR campaign. This lack of variation could mean that the jet formation in this radio-loud quasar differs from what is observed in broad-line radio galaxies.

  9. The X-Ray Reflection Spectrum of the Radio-Loud Quasar 4C 74.26

    NASA Technical Reports Server (NTRS)

    Lohfink, Ann M.; Fabian, Andrew C.; Ballantyne, David R.; Boggs, S. E.; Boorman, Peter; Christensen, F. E.; Craig, W. W.; Farrah, Duncan; Garcia, Javier; Hailey, C. J.; hide

    2017-01-01

    The relativistic jets created by some active galactic nuclei are important agents of AGN feedback. In spite of this, our understanding of what produces these jets is still incomplete. X-ray observations, which can probe the processes operating in the central regions in the immediate vicinity of the supermassive black hole, the presumed jet launching point, are potentially particularly valuable in illuminating the jet formation process. Here, we present the hard X-ray NuSTAR observations of the radio-loud quasar 4C 74.26 in a joint analysis with quasi-simultaneous, soft X-ray Swift observations. Our spectral analysis reveals a high-energy cutoff of -183+3551 keV and confirms the presence of ionized reflection in the source. From the average spectrum we detect that the accretion disk is mildly recessed, with an inner radius of Rin4180 Rg. However, no significant evolution of the inner radius is seen during the three months covered by our NuSTAR campaign. This lack of variation could mean that the jet formation in this radio-loud quasar differs from what is observed in broad-line radio galaxies.

  10. 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.

  11. Phenomenology of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Leahy, J. P.

    1999-04-01

    I review the observational data on AGN, focusing especially on results that may be relevant to sub-parsec discs. After emphasizing the essential unity of the different AGN, from LINERs to quasars, I review several observational tracers which have been claimed to be produced by accretion discs. In most cases the interpretation of these data is ambiguous, but the recent detections of redshifted Fe K alpha by ASCA provide convincing evidence for discs. I briefly review the phenomenology of jets in AGN, and emphasize that jets are detected in all classes of AGN, and in radio-loud AGN comprise a major component of the energy budget. Evidence that jets are relativistic is now compelling for all types of radio-loud AGN and is accumulating even for radio-quiet objects. Data on jets provide a long-term record of AGN activity which constrains aspects of disc history including start-up times, alignment stability and precession, lifetimes, and recurrent activity. Finally, I discuss the distinction between radio-quiet and radio loud AGN, which is broad enough to suggest two fundamentally different types of central engine, although it may not be as clear-cut as is sometimes claimed. At present there is no consensus on the nature of this difference. I draw attention to the broad absorption line (BAL) phenomenon, which signposts powerful but uncollimated outflows in radio-quiet AGN, which may correspond to the powerful jets in the radio-loud objects.

  12. The Eddington Limit in Cosmic Rays: An Explanation for the Observed Lack of Low-Mass Radio-Loud Quasars and The M •-M sstarf Relation

    NASA Astrophysics Data System (ADS)

    Sironi, Lorenzo; Socrates, Aristotle

    2010-02-01

    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 •-M sstarf relation.

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

    DOE PAGES

    Orienti, M.; D'Ammando, F.; Larsson, J.; ...

    2015-09-14

    Here, 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. Furthermore, 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. There was no γ-ray emission observed for J1548+3511. Both sources are variable in X-rays. J1548+3511 shows a hardening of themore » 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.« less

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

    SciTech Connect

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

    2015-09-14

    Here, 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. Furthermore, 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. There was no γ-ray emission 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.

  15. 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.

  16. 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

  17. HST Grism Confirmation of Two z ˜ 2 Structures from the Clusters around Radio-loud AGN (CARLA) Survey

    NASA Astrophysics Data System (ADS)

    Noirot, Gaël; Vernet, Joël; De Breuck, Carlos; Wylezalek, Dominika; Galametz, Audrey; Stern, Daniel; Mei, Simona; Brodwin, Mark; Cooke, Elizabeth A.; Gonzalez, Anthony H.; Hatch, Nina A.; Rettura, Alessandro; Stanford, Spencer Adam

    2016-10-01

    Using Hubble Space Telescope slitless grism data, we report the spectroscopic confirmation of two distant structures at z˜ 2 associated with powerful high-redshift radio-loud active galactic nuclei (AGNs). These rich structures, likely (forming) clusters, are among the most distant structures currently known, and were identified on the basis of Spitzer/IRAC [3.6]-[4.5] color. We spectroscopically confirm nine members in the field of MRC 2036-254, comprising eight star-forming galaxies and the targeted radio galaxy. The median redshift is z = 2.000. We spectroscopically confirm 10 members in the field of B3 0756+406, comprising 8 star-forming galaxies and 2 AGNs, including the targeted radio-loud quasar. The median redshift is z = 1.986. All confirmed members are within 500 kpc (1 arcmin) of the targeted AGNs. We derive median (mean) star-formation rates of ˜ 35 {M}⊙ {{yr}}-1 (˜ 50 {M}⊙ {{yr}}-1) for the confirmed star-forming members of both structures based on their [O iii]λ 5007 luminosities, and estimate average galaxy stellar masses ≲ 1× {10}11 {M}⊙ based on mid-infrared fluxes and spectral energy distribution modeling. Most of our confirmed members are located above the star-forming main sequence toward starburst galaxies, consistent with clusters at these early epochs being the sites of significant levels of star formation. The structure around MRC 2036-254 shows an overdensity of IRAC-selected candidate galaxy cluster members consistent with being quiescent galaxies, while the structure around B3 0756+406 shows field values, albeit with many lower limits to colors that could allow an overdensity of faint red quiescent galaxies. The structure around MRC 2036-254 shows a red sequence of passive galaxy candidates.

  18. The Parsec-scale Structure and Kinematics of Radio-Loud Narrow-Line Seyfert 1 Galaxies

    NASA Astrophysics Data System (ADS)

    Richards, Joseph L.; Lister, M. L.; Foschini, L.; Savolainen, T.; Homan, D. C.; Kadler, M.; Hovatta, T.; Readhead, A. C.; Arshakian, T.; Chavushyan, V.

    2014-01-01

    Narrow-line Seyfert 1 galaxies (NLS1) are a class of active galactic nuclei that share many observational properties with the much more powerful blazar classes. Despite their low black hole masses (typically 10^6-10^8 solar masses) and near- or super-Eddington accretion rates, a small minority are radio loud (RLNLS1s). A growing number of these have been detected in GeV gamma rays by the Fermi Large Area Telescope (LAT), indicating that a relativistic jet has formed in at least some of these sources. This presents a challenge to jet models, but may provide a link between jets found at the small scales of galactic binaries and the large scales of giant quasars. We are carrying out a multifrequency polarimetric radio monitoring campaign of a sample of 15 RLNLS1s using the Very Long Baseline Array (VLBA). Using data from this program, we will expand the currently limited knowledge of the parsec-scale properties and kinematics of this class of sources. We are complementing this campaign with fast-cadence single dish radio monitoring with the Owens Valley Radio Observatory 40m telescope and an optical spectroscopic monitoring campaign using the GHAO 2m-class telescope in Cananea, Mexico.

  19. 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.

  20. First Detection of 350 Micron Polarization from a Radio-loud AGN

    NASA Astrophysics Data System (ADS)

    Lee, Sang-Sung; Kang, Sincheol; Byun, Do-Young; Chapman, Nicholas; Novak, Giles; Trippe, Sascha; Algaba, Juan Carlos; Kino, Motoki

    2015-07-01

    We report the first detection of linearly polarized emission at an observing wavelength of 350 μm from the radio-loud active galactic nucleus 3C 279. We conducted polarization observations for 3C 279 using the SHARP polarimeter in the Caltech Submillimeter Observatory on 2014 March 13 and 14. For the first time, we detected the linear polarization with the degree of polarization of 13.3% ± 3.4% (3.9σ) and the electric vector position angle (EVPA) of 34.°7 ± 5.°6. We also observed 3C 279 simultaneously at 13, 7, and 3.5 mm in dual polarization with the Korean very long baseline interferometry (VLBI) Network on 2014 March 6 (single dish) and imaged in milliarcsecond (mas) scales at 13, 7, 3.5, and 2.3 mm on March 22 (VLBI). We found that the degree of linear polarization increases from 10% to 13% at 13 mm to 350 μm and the EVPAs at all observing frequencies are parallel within <10° to the direction of the jet at mas scale, implying that the integrated magnetic fields are perpendicular to the jet in the innermost regions. We also found that the Faraday rotation measures RM are in a range of -6.5 × 102 ˜ -2.7 × 103 rad m-2 between 13 and 3.5 mm, and are scaled as a function of wavelength: | {RM}| \\propto {λ }-2.2. These results indicate that the millimeter and sub-millimeter polarization emission are generated in the compact jet within 1 mas scale and affected by a Faraday screen in or in the close proximity of the jet.

  1. J0906+6930: a radio-loud quasar in the early Universe

    NASA Astrophysics Data System (ADS)

    Zhang, Yingkang; An, Tao; Frey, Sándor; Gabányi, Krisztina É.; Paragi, Zsolt; Gurvits, Leonid I.; Sohn, Bong Won; Jung, Taehyun; Kino, Motoki; Lao, Baoqiang; Lu, Yang; Mohan, Prashanth

    2017-06-01

    Radio-loud high-redshift quasars (HRQs), although only a few of them are known to date, are crucial for studies of the growth of supermassive black holes (SMBHs) and the evolution of active galactic nuclei at early cosmological epochs. Radio jets offer direct evidence of SMBHs, and their radio structures can be studied with the highest angular resolution using very long baseline interferometry (VLBI). Here we report on the observations of three HRQs (J0131-0321, J0906+6930 and J1026+2542) at z > 5 using the Korean VLBI Network and VLBI Exploration of Radio Astrometry Arrays (together known as KaVA) with the purpose of studying their pc-scale jet properties. The observations were carried out at 22 and 43 GHz in 2016 January among the first-batch open-use experiments of KaVA. The quasar J0906+6930 was detected at 22 GHz but not at 43 GHz. The other two sources were not detected and upper limits to their compact radio emission are given. Archival VLBI imaging data and the single-dish 15-GHz monitoring light curve of J0906+6930 were also acquired as complementary information. J0906+6930 shows a moderate-level variability at 15 GHz. The radio image is characterized by a core-jet structure with a total detectable size of ˜5 pc in projection. The brightness temperature, ≳1.9 × 1011 K, indicates relativistic beaming of the jet. The radio properties of J0906+6930 are consistent with a blazar. Follow-up VLBI observations will be helpful for determining its structural variation.

  2. Spectral energy distributions of radio-loud AGN

    NASA Astrophysics Data System (ADS)

    Hardcastle, Martin

    2013-10-01

    With this proposal we will construct a comprehensive library of X-ray to mid-IR radio-loud quasar spectral energy distributions for a single epoch (z=1), using a sample that is precisely matched to a companion sample of radio quiet quasars. In doing so, we will decouple luminosity effects from evolutionary effects and so determine the amount of radiation that is absorbed and reprocessed by the torus, and how this depends on luminosity. The SED library will represent a fundamental resource for future investigations of the accretion history of massive black holes, and will allow us to reconcile conflicting results on AGN obscuration at different wavelengths and to answer key questions about the radio-loud/radio-quiet dichotomy.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. The puzzling case of the radio-loud QSO 3C 186: a gravitational wave recoiling black hole in a young radio source?

    NASA Astrophysics Data System (ADS)

    Chiaberge, M.; Ely, J. C.; Meyer, E. T.; Georganopoulos, M.; Marinucci, A.; Bianchi, S.; Tremblay, G. R.; Hilbert, B.; Kotyla, J. P.; Capetti, A.; Baum, S. A.; Macchetto, F. D.; Miley, G.; O'Dea, C. P.; Perlman, E. S.; Sparks, W. B.; Norman, C.

    2017-04-01

    Context. Radio-loud active galactic nuclei with powerful relativistic jets are thought to be associated with rapidly spinning black holes (BHs). BH spin-up may result from a number of processes, including accretion of matter onto the BH itself, and catastrophic events such as BH-BH mergers. Aims: We study the intriguing properties of the powerful (Lbol 1047 erg s-1) radio-loud quasar 3C 186. This object shows peculiar features both in the images and in the spectra. Methods: We utilize near-IR Hubble Space Telescope (HST) images to study the properties of the host galaxy, and HST UV and Sloan Digital Sky Survey optical spectra to study the kinematics of the source. Chandra X-ray data are also used to better constrain the physical interpretation. Results: HST imaging shows that the active nucleus is offset by 1.3 ± 0.1 arcsec (i.e. 11 kpc) with respect to the center of the host galaxy. Spectroscopic data show that the broad emission lines are offset by -2140 ± 390 km s-1 with respect to the narrow lines. Velocity shifts are often seen in QSO spectra, in particular in high-ionization broad emission lines. The host galaxy of the quasar displays a distorted morphology with possible tidal features that are typical of the late stages of a galaxy merger. Conclusions: A number of scenarios can be envisaged to account for the observed features. While the presence of a peculiar outflow cannot be completely ruled out, all of the observed features are consistent with those expected if the QSO is associated with a gravitational wave (GW) recoiling BH. Future detailed studies of this object will allow us to confirm this type of scenario and will enable a better understanding of both the physics of BH-BH mergers and the phenomena associated with the emission of GW from astrophysical sources.

  8. SDSS J143244.91+301435.3: a link between radio-loud narrow-line Seyfert 1 galaxies and compact steep-spectrum radio sources?

    NASA Astrophysics Data System (ADS)

    Caccianiga, A.; Antón, S.; Ballo, L.; Dallacasa, D.; Della Ceca, R.; Fanali, R.; Foschini, L.; Hamilton, T.; Kraus, A.; Maccacaro, T.; Mack, K.-H.; Marchã, M. J.; Paulino-Afonso, A.; Sani, E.; Severgnini, P.

    2014-06-01

    We present SDSS J143244.91+301435.3, a new case of a radio-loud narrow-line Seyfert 1 (RL NLS1) with a relatively high radio power (P1.4 GHz = 2.1 × 1025 W Hz-1) and large radio-loudness parameter (R1.4 = 600 ± 100). The radio source is compact with a linear size below ˜1.4 kpc but, in contrast to most of the RL NLS1 discovered so far with such a high R1.4, its radio spectrum is very steep (α = 0.93, Sν ∝ ν-α) and does not support a `blazar-like' nature. Both the small mass of the central supermassive black hole and the high accretion rate relative to the Eddington limit estimated for this object (3.2 × 107 M⊙ and 0.27, respectively, with a formal error of ˜0.4 dex for both quantities) are typical of the NLS1 class. Through modelling the spectral energy distribution of the source, we have found that the galaxy hosting SDSS J143244.91+301435.3 is undergoing quite intense star formation (SFR = 50 M⊙ yr-1), which, however, is expected to contribute only marginally (˜1 per cent) to the observed radio emission. The radio properties of SDSS J143244.91+301435.3 are remarkably similar to those of compact steep-spectrum (CSS) radio sources, a class of active galactic nuclei (AGN) mostly composed of young radio galaxies. This may suggest a direct link between these two classes of AGN, with CSS sources possibly representing the misaligned version (the so-called `parent population') of RL NLS1 showing blazar characteristics.

  9. The warm absorber in the radio-loud quasar 4C +74.26

    NASA Astrophysics Data System (ADS)

    Di Gesu, L.; Costantini, E.

    2016-10-01

    Outflows of photoionized gas are commonly detected in the X-ray spectra of Seyfert 1 galaxies. However, the evidence for this phenomenon in broad line radio galaxies, which are analogous to Seyfert 1 galaxies in the radio-loud regime, has so far been scarce. Here, we present the analysis of the X-ray absorption in the radio-loud quasar 4C +74.26. With the aim of characterizing the kinetic and the ionization conditions of the absorbing material, we fitted jointly the XMM-Newton Reflection Grating Spectrometer (RGS) and the Chandra High Energy Transmission Grating Spectrometer (HETGS) spectra, which were taken 4 months apart. The intrinsic continuum flux did not vary significantly during this time lapse. The spectrum shows the absorption signatures (e.g., Fe-UTA, O vii, and Ne vii-Ne x) of a photoionized gas outflow (NH ~ 3.5 × 1021 cm-2, log ξ ~ 2.6, vout ~ 3600 km s-1) located at the redshift of source. We estimate that the gas is located outside the broad line region but within the boundaries of the putative torus. This ionized absorber is consistent with the X-ray counterpart of a polar scattering outflow reported in the optical band for this source. The kinetic luminosity carried by the outflow is insufficient to produce a significant feedback is this quasar. Finally, we show that the heavy soft X-ray absorption that was noticed in the past for this source arises mostly in the Galactic interstellar medium.

  10. Intergenerational preferences for radio loudness during automobile driving.

    PubMed

    Hanser, Frederick Howard Bateman; Adjei Boakye, Eric; Mikulec, Anthony Alan

    2017-07-01

    The comparative contribution to human noise exposure from the vehicular radio is unknown, as are the radio volume preferences of different generations when driving an automobile. A single vehicle was used to measure radio listening level in decibels of three generations (age 16-17 years, age 32-50 years, and age 51-73 years) in various conditions, ranging from engine off with windows closed to 60 miles per hour (mph) with windows open. No differences in radio loudness based on the sex of the driver were found. Statistically significant differences were identified in preferred signal to noise ratio among multiple vehicular paradigms, with the youngest generation preferring the largest signal to noise ratio in conditions with low background noise. The youngest generation favored the largest signal to noise ratio (radio level above background noise), a preference which waned with increasing background noise. Copyright © 2017 Elsevier B.V. All rights reserved.

  11. The X-ray nuclei of radio-loud AGN from the 2Jy sample

    NASA Astrophysics Data System (ADS)

    Hardcastle, Martin

    2009-10-01

    X-ray observations of AGN samples provide crucial information about both the AGN themselves and the material that obscures them. Understanding the properties of the active nuclei of radio-loud AGN is particularly vital given that these objects seem likely to have a key role in models of galaxy formation and evolution. The 2Jy sample of radio galaxies and quasars has uniquely good multiwavelength data, but until recently has been poorly studied in the X-ray. We have recently been awarded time to observe all the low-z 2Jy steep-spectrum sample with Chandra, and here propose short observations of the high-z half of the sample with XMM which will give us a complete picture of the nuclear activity in these objects, and allow a wide range of projects to be carried out.

  12. The X-ray nuclei of radio-loud AGN from the 2Jy sample

    NASA Astrophysics Data System (ADS)

    Hardcastle, Martin

    2010-10-01

    X-ray observations of AGN samples provide crucial information about both the AGN themselves and the material that obscures them. Understanding the properties of the active nuclei of radio-loud AGN is particularly vital given that these objects seem likely to have a key role in models of galaxy formation and evolution. The 2Jy sample of radio galaxies and quasars has uniquely good multiwavelength data, but until recently has been poorly studied in the X-ray. We have recently been awarded time to observe all the low-z 2Jy steep-spectrum sample with Chandra, and here propose short observations of the high-z half of the sample with XMM which will give us a complete picture of the nuclear activity in these objects, and allow a wide range of projects to be carried out.

  13. Search for Differences between Radio-loud and Radio-quiet Gamma-Ray Pulsar Populations with Fermi-LAT Data

    NASA Astrophysics Data System (ADS)

    Sokolova, E. V.; Rubtsov, G. I.

    2016-12-01

    Observations by the Fermi-Large Area Telescope (LAT) have enabled us to explore the population of non-recycled gamma-ray pulsars with a set of 112 objects. It was recently noted that there are apparent differences in the properties of radio-quiet and radio-loud subsets. In particular, the average observed radio-loud pulsar is younger than the average radio-quiet one and is located at lower Galactic latitude. Even so, the analysis based on the full list of pulsars may suffer from selection effects. Namely, most radio-loud pulsars are first discovered in the radio band, while radio-quiet ones are found using the gamma-ray data. In this work we perform a blind search for gamma-ray pulsars using the Fermi-LAT data alone, using all point sources from the 3FGL catalog as the candidates. Unlike our previous work, the present catalog is constructed with a semi-coherent method based on the time-differencing technique and covers the full range of characteristic ages down to 1 kyr. The search resulted in a catalog of 40 non-recycled pulsars, 25 of which are radio-quiet. All pulsars found in the search were previously known gamma-ray pulsars. We find no statistically significant differences in age or in distributions in Galactic latitude for the radio-loud and radio-quiet pulsars, while the distributions in rotation period are marginally different with a statistical probability of 4× {10}-3. The fraction of radio-quiet pulsars is estimated as {ε }{RQ}=(63+/- 8) % . The results are in agreement with the predictions of the outer magnetosphere models, while the polar cap models are disfavored.

  14. Radiation Mechanism and Jet Composition of Gamma-Ray Bursts and GeV-TeV-Selected Radio-Loud Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Zhang, J.; Liang, E. W.; Sun, X. N.; Zhang, B.; Lu, Y.; Zhang, S. N.

    2016-10-01

    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.

  15. 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.

  16. Resolving the Geometry of the Innermost Relativistic Jets in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Algaba, J. C.; Nakamura, M.; Asada, K.; Lee, S. S.

    2017-01-01

    In the current paradigm, it is believed that the compact VLBI radio core of radio-loud active galactic nuclei (AGNs) represents the innermost upstream regions of relativistic outflows. These regions of AGN jets have generally been modeled by a conical outflow with a roughly constant opening angle and flow speed. Nonetheless, some works suggest that a parabolic geometry would be more appropriate to fit the high energy spectral distribution properties and it has been recently found that, at least in some nearby radio galaxies, the geometry of the innermost regions of the jet is parabolic. We compile here multi-frequency core sizes of archival data to investigate the typically unresolved upstream regions of the jet geometry of a sample of 56 radio-loud AGNs. Data combined from the sources considered here are not consistent with the classic picture of a conical jet starting in the vicinity of the super-massive black hole (SMBH), and may exclude a pure parabolic outflow solution, but rather suggest an intermediate solution with quasi-parabolic streams, which are frequently seen in numerical simulations. Inspection of the large opening angles near the SMBH and the range of the Lorentz factors derived from our results support our analyses. Our result suggests that the conical jet paradigm in AGNs needs to be re-examined by millimeter/sub-millimeter VLBI observations.

  17. Results from selection of high redshift radio-loud quasars

    NASA Astrophysics Data System (ADS)

    Tuccillo, D.; Gonzalez-Serrano, J. I.; Carballo, R.

    2013-05-01

    We present results on reliable selection of Radio Loud Quasars (RLQ) at high redshift (z>3.6), based on the combined use of the surveys FIRST and SDSS. We explore the redshift range 3.6

  18. 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.

  19. 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.

  20. Multiwavelength monitoring of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Urry, C. M.

    1993-01-01

    Recent multiwavelength monitoring of active galactic nuclei (AGN), particularly with the IUE satellite, has produced extraordinay advances in our understanding of the energy-generation mechanism(s) in the central engine and of the structure of the surrounding material. Examples discussed here include both ordinary AGN and blazars (the collective name for highly variable, radio-loud AGN like BL Lac objects and Optically Violently Variable quasars). In the last decade, efforts to obtain single-epoch multiwavelength spectra led to fundamentally new models for the structure of AGN, involving accretion disks for AGN and relativistic jets for blazars. Recent extensions of multiwavelength spectroscopy into the temporal domain have shown that while these general pictures may be correct, the details were probably wrong. Campaigns to monitor Seyfert 1 galaxies like NGC 4151, NGC 5548 and Fairall 9 at infrared, optical, ultraviolet and X-ray wavelengths indicate that broad-emission line regions are stratified by ionization, density, and velocity; argue against a standard thin accretion disk model; and suggest that X-rays represent primary rather than reprocessed radiation. For blazars, years of radio monitoring indicated emission from an inhomogeneous synchrotron-emitting plasma, which could also produce at least some of the shorter-wavelength emission. The recent month-long campaign to observe the BL Lac object PKS 2155-304 has revealed remarkably rapid variability that extends from the infrared through the X-ray with similar amplitude and little or no discernible lag. This lends strong support to relativistic jet models and rules out the proposed accretion disk model for the ultraviolet-X-ray continuum.

  1. 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).

  2. 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.

  3. The prospects of X-ray polarimetry for Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Goosmann, René W.

    2016-08-01

    Polarimetry at optical and other wavelength continues to play an important role in our struggle to develop (super-)unification schemes for active galactic nuclei (AGN). Therefore, radio-loud and radio-quiet AGN are important targets for the future small and medium-size X-ray polarimetry missions that are currently under phase A study at NASA and ESA. After briefly pointing out the detection principle of polarization imaging in the soft X-ray band, I am going to review the prospects of X-ray polarimetry for our understanding of AGN ejection (winds and blazar jets) and accretion flows (accretion disk and corona). The X-ray polarimetry signal between 2 and 8 keV is going to give us important new constraints on the geometry of the central engine as well as on the acceleration effects in AGN jets, in particular when combined with spectral and/or polarization information at other wavelengths.

  4. 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

  5. Probing the radio loud/quiet AGN dichotomy with quasar clustering

    NASA Astrophysics Data System (ADS)

    Retana-Montenegro, E.; Röttgering, H. J. A.

    2017-04-01

    We investigate the clustering properties of 45 441 radio-quiet quasars (RQQs) and 3493 radio-loud quasars (RLQs) drawn from a joint use of the Sloan Digital Sky Survey (SDSS) and Faint Images of the Radio Sky at 20 cm (FIRST) surveys in the range 0.3 < z < 2.3. This large spectroscopic quasar sample allow us to investigate the clustering signal dependence on radio-loudness and black hole (BH) virial mass. We find that RLQs are clustered more strongly than RQQs in all the redshift bins considered. We find a real-space correlation length of and for RQQs and RLQs, respectively, for the full redshift range. This implies that RLQs are found in more massive host haloes than RQQs in our samples, with mean host halo masses of 4.9 × 1013h-1M⊙ and 1.9 × 1012h-1M⊙, respectively. Comparison with clustering studies of different radio source samples indicates that this mass scale of ≳ 1 × 1013h-1M⊙ is characteristic for the bright radio-population, which corresponds to the typical mass of galaxy groups and galaxy clusters. The similarity we find in correlation lengths and host halo masses for RLQs, radio galaxies and flat-spectrum radio quasars agrees with orientation-driven unification models. Additionally, the clustering signal shows a dependence on BH mass, with the quasars powered by the most massive BHs clustering more strongly than quasars having less massive BHs. We suggest that the current virial BH mass estimates may be a valid BH proxies for studying quasar clustering. We compare our results to a previous theoretical model that assumes that quasar activity is driven by cold accretion via mergers of gas-rich galaxies. While the model can explain the bias and halo masses for RQQs, it cannot reproduce the higher bias and host halo masses for RLQs. We argue that other BH properties such as BH spin, environment, magnetic field configuration, and accretion physics must be considered to fully understand the origin of radio-emission in quasars and its relation to

  6. What is the difference between radio-loud and radio-quiet quasi-stellar objects?

    NASA Technical Reports Server (NTRS)

    Hutchings, J. B.; Janson, T.; Neff, S. G.

    1989-01-01

    Measures of the nuclear and host galaxy luminosities and colors and a morphological discussion of the host galaxies are presented for a sample of low-redshift, high-luminosity, radio-quiet QSOs whose redshift and luminosity distribution matches that of a radio-loud sample previously discussed. Radio-quiet QSOs are found to reside in galaxies which are smaller, fainter, and redder than the host galaxies of radio-loud QSOs. These properties are generally consistent with the suggestion that radio-quiet QSOs are located in spiral-type galaxies and radio-loud QSOs are located in more elliptical-type galaxies. Significantly less evidence is found for tidal interactions among the radio-quiet objects, although they appear to reside in somewhat richer environments in terms of nearby companions.

  7. 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

  8. 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.

  9. Mapping the Polarization of the Radio-Loud Lyα Nebula B3 J2330+3927

    NASA Astrophysics Data System (ADS)

    You, Chang; Zabludoff, Ann; Smith, Paul; Yang, Yujin; Kim, Eunchong; Jannuzi, Buell; Prescott, Moire K. M.; Matsuda, Yuichi; Lee, Myung Gyoon

    2017-01-01

    Lyα nebulae, or "Lyα blobs," are extended (up to ˜100 kpc), bright (LLyα ≳ 1043 erg s-1) clouds of Lyα emitting gas that tend to lie in overdense regions at z ˜ 2-5. The origin of the Lyα emission remains unknown, but recent theoretical work suggests that measuring the polarization might discriminate among powering mechanisms. Here we present the first narrowband imaging polarimetry of a radio-loud Lyα nebula, B3 J2330+3927, at z = 3.09, with an embedded active galactic nucleus (AGN). The AGN lies near the blob’s Lyα emission peak, and its radio lobes align roughly with the blob's major axis. With the SPOL polarimeter on the 6.5 m MMT telescope, we map the total (Lyα + continuum) polarization in a grid of circular apertures of a radius of 0.″6 (4.4 kpc), detecting a significant (>2σ) polarization fraction P% in nine apertures and achieving strong upper limits (as low as 2%) elsewhere. P% increases from <2% at ˜5 kpc from the blob center to 17% at ˜15-25 kpc. The detections are distributed asymmetrically, roughly along the nebula's major axis. The polarization angles θ are mostly perpendicular to this axis. Comparing the Lyα flux to that of the continuum and conservatively assuming that the continuum is highly polarized (20%-100%) and aligned with the total polarization, we place lower limits on the polarization of the Lyα emission P%,Lyα ranging from no significant polarization at ˜5 kpc from the blob center to 3%-17% at 10-25 kpc. Like the total polarization, the Lyα polarization detections occur more often along the blob's major axis. The observations reported here were obtained at the MMT Observatory, a joint facility of the University of Arizona and the Smithsonian Institution.

  10. Geoeffectiveness and flare properties of radio-loud CMEs

    NASA Astrophysics Data System (ADS)

    Prakash, O.; Shanmugaraju, A.; Michalek, G.; Umapathy, S.

    2014-03-01

    A detailed investigation on geoeffective CMEs associated with meter to Deca-Hectometer (herein after m- and DH-type-II) wavelengths range type-II radio bursts observed during the period 1997-2005 is presented. The study consists of three steps: i) the characteristics of m-and DH-type-II bursts associated with flares and geoeffective CMEs; ii) characteristics of geo and non-geoeffective radio-loud and quiet CMEs, iii) the relationships between the geoeffective CMEs and flares properties. Interestingly, we found that 92 % of DH-type-II bursts are extension of m-type-II burst which are associated with faster and wider geoeffective DH-CMEs and also associated with longer/stronger flares. The geoeffective CME-associated m-type-II bursts have higher starting frequency, lower ending frequency and larger bandwidth compared to the general population of m-type-II bursts. The geoeffective CME-associated DH-type-II bursts have longer duration ( P≪1 %), lower ending frequency ( P=2 %) and lower drift rates ( P=2 %) than that of DH-type-IIs associated with non-geoeffective CMEs. The differences in mean speed of geoeffective DH-CMEs and non-geoeffective DH-CMEs (1327 km s-1 and 1191 km s-1, respectively) is statistically insignificant ( P=20 %).However, the mean difference in width (339∘ and 251∘, respectively) is high statistical significant ( P=0.8 %). The geo-effective general populations of LASCO CMEs speeds (545 km s-1 and 450 km s-1, respectively) and widths (252∘ and 60∘, respectively) is higher than the non geo-effective general populations of LASCO CMEs ( P=3 % and P=0.02 %, respectively). The geoeffective CMEs associated flares have longer duration, and strong flares than non-geoeffective DH-CMEs associated flares ( P=0.8 % and P=1 %, respectively). We have found a good correlation between the geo-effective flare and DH-CMEs properties: i) CMEs speed—acceleration ( R=-0.78, where R is a linear correlation coefficient), ii) acceleration—flare peak flux ( R

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

    SciTech Connect

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

    2013-12-20

    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. Here, 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). Furthermore, 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. These 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.

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

    SciTech Connect

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

    2016-03-20

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

  13. 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.

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

    DOE PAGES

    Di Mauro, M.; Calore, F.; Donato, F.; ...

    2013-12-20

    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. Here, 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). Furthermore, 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 uppermore » 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. These 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.« less

  15. THE COMPACT RADIO STRUCTURE OF RADIO-LOUD NARROW LINE SEYFERT 1 GALAXIES

    SciTech Connect

    Gu Minfeng; Chen Yongjun

    2010-06-15

    We present the compact radio structure of three radio-loud narrow line Seyfert 1 galaxies from the Very Long Baseline Array archive data at 2.3, 5, and 8.4 GHz. In RXS J16290+4007, the radio structure is mostly unresolved. The combination of compact radio structure, high brightness temperature, and inverted spectrum between simultaneous 2.3 and 8.4 GHz strongly favors jet relativistic beaming. Combined with the very long baseline interferometry data at 1.6 and 8.4 GHz from the literature, we argue that RXS J16333+4718 also may harbor a relativistic jet, with resolved core-jet structure in 5 GHz. B3 1702+457 is clearly resolved with a well-defined jet component. The overall radio steep spectrum indicates that B3 1702+457 is likely a source optically defined as NLS1 with radio definition of compact steep spectrum sources. From these three sources, we found that radio loud NLS1s can be either intrinsically radio loud (e.g., B3 1702+457) or apparently radio loud due to jet beaming effects (e.g., RXS J16290+4007 and RXS J16333+4718).

  16. The Radio-loud Fraction of Quasars with Faint Optical Luminosities

    NASA Astrophysics Data System (ADS)

    Hooper, E. J.; Impey, C. D.; Foltz, C. B.; Hewett, P. C.

    1994-12-01

    The observed radio-loud fraction of optically selected quasars decreases for absolute blue magnitudes fainter than M_B ~ -24, a phenomenon which has been attributed to a selection effect in quasar surveys (e.g., Peacock et al. 1986, MNRAS, 218, 265). A similar decrease was found (Hooper et al. 1995, ApJ, submitted) in a sample of the optically selected Large Bright Quasar Survey (LBQS; Hewett et al. 1995, in preparation) observed at radio wavelengths. The change in radio-loud fraction within the LBQS cannot be explained by the proposed selection bias against quasars with large radio luminosities and small optical luminosities, implying that the effect is a real physical change in the quasar population. An additional sample of LBQS quasars was observed with the VLA and combined with the earlier data to verify this effect and to better determine the form of the change in radio-loud fraction. The radio-loud (8.4 GHz luminosity > 10^25 W/Hz) fraction is 2/70 (3%) for M_B fainter than -24, compared to 30/289 (10%) among the more optically luminous objects, a difference significant at the 98% confidence level.

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

    NASA Astrophysics Data System (ADS)

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

    2017-10-01

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

  18. 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.

  19. 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.

  20. 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.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. The jet detection in radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Gu, Minfeng

    With relatively small black hole masses and high accretion rates, narrow-line Seyfert 1 galaxies are thought to be young AGNs. About 7% of them are radio-loud narrow-line Seyfert 1 galaxies (RLNLS1s). RLNLS1s allow us to re-address some of the key questions regarding the physics of jet formation. As the first step of the systematic study on the jet properties of RLNLS1s, we present the radio structure of fourteen RLNLS1s from VLBA 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 pc-scale morphology and 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, compared to blazars. This implies that the bulk jet speed may likely be low in our sources.

  7. Active Galactic Nucleus

    NASA Image and Video Library

    2017-09-14

    SCI2017_0007: Artist illustration of the thick ring of dust that can obscure the energetic processes that occur near the supermassive black hole of an active galactic nuclei. The SOFIA studies suggest that the dust distribution is about 30 percent smaller than previously thought. Credit: NASA/SOFIA/Lynette Cook

  8. 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.

  9. On the Radio Dichotomy of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Cao, Xinwu

    2016-12-01

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

  10. Active Galactic Nuclei Feedback and Galactic Outflows

    NASA Astrophysics Data System (ADS)

    Sun, Ai-Lei

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

  11. 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

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

    SciTech Connect

    Gu, Minfeng; Chen, Yongjun; Shen, Zhiqiang; Komossa, S.; Zensus, J. A.; Yuan, Weimin; Wajima, Kiyoaki; Zhou, Hongyan

    2015-11-15

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

  13. 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.

  14. Discovery of Dramatic Optical Variability in SDSS J1100+4421: A Peculiar Radio-loud Narrow-line Seyfert 1 Galaxy?

    NASA Astrophysics Data System (ADS)

    Tanaka, Masaomi; Morokuma, Tomoki; Itoh, Ryosuke; Akitaya, Hiroshi; Tominaga, Nozomu; Saito, Yoshihiko; Stawarz, Łukasz; Tanaka, Yasuyuki T.; Gandhi, Poshak; Ali, Gamal; Aoki, Tsutomu; Contreras, Carlos; Doi, Mamoru; Essam, Ahmad; Hamed, Gamal; Hsiao, Eric Y.; Iwata, Ikuru; Kawabata, Koji S.; Kawai, Nobuyuki; Kikuchi, Yuki; Kobayashi, Naoto; Kuroda, Daisuke; Maehara, Hiroyuki; Matsumoto, Emiko; Mazzali, Paolo A.; Minezaki, Takeo; Mito, Hiroyuki; Miyata, Takashi; Miyazaki, Satoshi; Mori, Kensho; Moritani, Yuki; Morokuma-Matsui, Kana; Morrell, Nidia; Nagao, Tohru; Nakada, Yoshikazu; Nakata, Fumiaki; Noma, Chinami; Ohsuga, Ken; Okada, Norio; Phillips, Mark M.; Pian, Elena; Richmond, Michael W.; Sahu, Devendra; Sako, Shigeyuki; Sarugaku, Yuki; Shibata, Takumi; Soyano, Takao; Stritzinger, Maximilian D.; Tachibana, Yutaro; Taddia, Francesco; Takaki, Katsutoshi; Takey, Ali; Tarusawa, Ken'ichi; Ui, Takahiro; Ukita, Nobuharu; Urata, Yuji; Walker, Emma S.; Yoshii, Taketoshi

    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 ~107 M ⊙ 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 × 102-3 × 103, 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. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Linking the central engine to the jet properties in radio loud AGN

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    We explore the connection between the black hole mass and its relativistic jet for a sample of radio-loud AGN (z < 1), in which the relativistic jet parameters are well estimated by means of long term monitoring with the 14m Metsähovi millimeter wave telescope and the Very Long Base-line Array (VLBA). NIR host galaxy images taken with the NOTCam on the Nordic Optical Telescope (NOT) and retrieved from the 2MASS all-sky survey allowed us to perform a detailed surface brightness decomposition of the host galaxies in our sample and to estimate reliable black hole masses via their bulge luminosities. We present early results on the correlations between black hole mass and the relativistic jet parameters. Our preliminary results suggest that the more massive the black hole is, the faster and the more luminous jet it produces.

  1. HUBBLE SPACE TELESCOPE Imaging of the Host Galaxies of High-RedshiftRadio-loud Quasars

    NASA Astrophysics Data System (ADS)

    Lehnert, Matthew D.; van Breugel, Wil J. M.; Heckman, Timothy M.; Miley, George K.

    1999-09-01

    We present rest-frame UV and Lyα images of spatially resolved structures (``hosts'') around five high-redshift radio-loud quasars obtained with the WFPC2 camera on the Hubble Space Telescope (HST). The quasars were imaged with the PC1 through the F555W (``V''-band) filter, which at the redshifts of the quasars (2.1radio-loud quasars at high redshift have prominent host galaxies that appeared to have properties similar to those of high-redshift radio galaxies. Our HST observations allow a more detailed investigation of quasar host morphologies and a comparison with similar HST studies of radio galaxies by others. Using several methods to measure and quantify the host properties we find that all five quasars are extended and that this ``fuzz'' contains ~5%-40% of the total continuum flux and 15%-65% of the Lyα flux within a radius of about 1.5". The rest-frame UV luminosities of the hosts are log λPλ~11.9-12.5 Lsolar (assuming no internal dust extinction), comparable to the luminous radio galaxies at similar redshifts and a factor 10 higher than both radio-quiet field galaxies at z~2-3 and the most UV-luminous low-redshift starburst galaxies. The Lyα luminosities of the hosts are log LLyα~44.3-44.9 ergs s-1, which are also similar to the those of luminous high-redshift radio galaxies and considerably larger than the Lyα luminosities of high-redshift field galaxies. To generate the Lyα luminosities of the hosts would require roughly a few percent of the total observed ionizing luminosity of the quasar. The UV continuum morphologies of the hosts appear complex and knotty at the relatively high surface brightness levels of our exposures (about 24 V mag arcsec-2). In two quasars we find evidence for foreground galaxies that confuse the

  2. 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.

  3. 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.

  4. Optical spectroscopy of the radio-loud nuclei of spiral galaxies: Starbursts or monsters

    SciTech Connect

    Heckman, T.M.; Van Breugel, W.; Miley, G.K.; Butcher, H.R.

    1983-08-01

    We present optical spectroscopic data pertaining to the physical state, kinematics, and spatial extent of the emission-line gas near the radio-loud nuclei of spiral galaxies. These data are combined with published optical, radio, and infrared data to evaluate the suggestions by Condon et al. (1982) that the nuclear radio emission in this class of galaxy is produced by multiple supernova remnants generated as a consequence of a nuclear starburst. As a whole, the radio-loud nuclei have stronger emission lines than radio-quiet nuclei of galaxies of similar Hubble/de Vaucouleurs type. This emission-line gas is generally at least as spatially extended as the radio continuum emission. However, we find that only about 1/3 of the spiral galaxies examined have optical spectroscopic properties consistent with those of ''extranuclear starbursts'' (i.e., giant H II regions). The majority of the nuclei seem to require a form of energy input to the ionized gas which is ''harder'' than the Lyman continuum radiation of OB stars, as their emission-line spectra are of the Seyfert or Liner variety. The nuclei with H II region spectra are distinct from the nuclei with Seyfert spectra in terms of radio morphology and radio spectral index, and tend to occur in spiral galaxies of much later Hubble type than do the Seyfert or Liner nuclei (Sc vs Sa). Moreover, the most luminous nuclear radio sources in our sample (PMHz> or =10/sup 22/ Watts Hz/sup -1/ Sr/sup -1/) are not associated with H II region nuclei. We summarize evidence that the putative nuclear starbursts must differ significantly from extranuclear starbursts.

  5. 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.

  6. Differences between Radio-loud and Radio-quiet Gamma-ray Pulsars as Revealed by Fermi

    NASA Astrophysics Data System (ADS)

    Hui, C. Y.; Lee, Jongsu; Takata, J.; Ng, C. W.; Cheng, K. S.

    2017-01-01

    By comparing the properties of non-recycled radio-loud γ-ray pulsars and radio-quiet γ-ray pulsars, we have searched for the differences between these two populations. We found that the γ-ray spectral curvature of radio-quiet pulsars can be larger than that of radio-loud pulsars. Based on the full sample of non-recycled γ-ray pulsars, their distributions of the magnetic field strength at the light cylinder are also found to be different. We note that this might result from an observational bias. By reexamining the previously reported difference of γ-ray-to-X-ray flux ratios, we found that the significance can be hampered by their statistical uncertainties. In the context of the outer gap model, we discuss the expected properties of these two populations and compare with the possible differences that are identified in our analysis.

  7. VizieR Online Data Catalog: A 3.5mm polarimetric survey of radio-loud AGNs (Agudo+, 2010)

    NASA Astrophysics Data System (ADS)

    Agudo, I.; Thum, C.; Wiesemeyer, H.; Krichbaum, T. P.

    2010-09-01

    In Table 1, we present our sample of 145 observed sources (see also Fig. 1) which has been built essentially from the 138 radio-loud AGNs in the IRAM pointing sources that were contained in the 1Jy catalog (Kuhr et al. 1981, Cat. VIII/5) and/or in the catalog of 404 compact radio sources by Perley (1982, Cat. J/AJ/87/859). (2 data files).

  8. 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.

  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. 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.

  12. 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.

  13. 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.

  14. 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.

  15. Unifying Black Hole Jets: The Connection between radio-loud AGNs and Gamma-ray Bursts

    NASA Astrophysics Data System (ADS)

    Nemmen, Rodrigo

    2012-07-01

    Radio-loud AGNs and gamma-ray bursts produce powerful relativistic jets and their central engines share the same basic astrophysical ingredients, despite the vastly different mass scales. An outstanding question is how the jet physics scales from GRBs up to AGNs.Using Fermi and Swift observations as well as data obtained with several other observatories, we show that the jets produced by blazars and long-duration GRBs exhibit similar correlations between the kinetic power and apparent gamma-ray luminosity, with AGNs and GRBs lying at the low and high-luminosity end, respectively, of the trend. After carrying out the beaming correction for these two populations, we find evidence that blazars and GRBs follow the same correlation between the intrinsic gamma-ray luminosity and kinetic power. This result implies that jet production and energy dissipation mechanisms are remarkably similar across over 9 orders of magnitude in jet power, establishing a physical analogy between AGN and GRBs. Our results indicate that these jets convert their internal energy into radiation with efficiencies exceeding 10%. We will discuss the implications of these results in terms of the properties of the central engines of AGNs and GRBs, in particular the bulk Lorentz factor, jet opening angles and mass accretion rates.

  16. THE SPATIAL CLUSTERING OF ROSAT ALL-SKY SURVEY ACTIVE GALACTIC NUCLEI. III. EXPANDED SAMPLE AND COMPARISON WITH OPTICAL ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Krumpe, Mirko; Coil, Alison L.; Miyaji, Takamitsu; Aceves, Hector

    2012-02-10

    This is the third paper in a series that reports on our investigation of the clustering properties of active galactic nuclei (AGNs) identified in the ROSAT All-Sky Survey (RASS) and the Sloan Digital Sky Survey (SDSS). In this paper, we extend the redshift range to 0.07 < z < 0.50 and measure the clustering amplitudes of both X-ray-selected and optically selected SDSS broad-line AGNs with and without radio detections as well as for X-ray-selected narrow-line RASS/SDSS AGNs. We measure the clustering amplitude through cross-correlation functions (CCFs) with SDSS galaxies and derive the bias by applying a halo occupation distribution model directly to the CCFs. We find no statistically convincing difference in the clustering of X-ray-selected and optically selected broad-line AGNs, as well as with samples in which radio-detected AGNs are excluded. This is in contrast to low-redshift optically selected narrow-line AGNs, where radio-loud AGNs are found in more massive halos than optical AGNs without a radio detection. The typical dark matter halo masses of our broad-line AGNs are log (M{sub DMH}/[h{sup -1} M{sub Sun }]) {approx} 12.4-13.4, consistent with the halo mass range of typical non-AGN galaxies at low redshifts. We find no significant difference between the clustering of X-ray-selected narrow-line AGNs and broad-line AGNs. We confirm the weak dependence of the clustering strength on AGN X-ray luminosity at a {approx}2{sigma} level. Finally, we summarize the current picture of AGN clustering to z {approx} 1.5 based on three-dimensional clustering measurements.

  17. 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.

  18. 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.

  19. 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

  20. 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.

  1. The contribution of unresolved radio-loud AGN to the extragalactic diffuse gamma-ray background

    NASA Astrophysics Data System (ADS)

    Mücke, A.; Pohl, M.

    2000-02-01

    We present a calculation of the blazar contribution to the extragalactic diffuse γ-ray background (EGRB) in the EGRET energy range. Our model is based on inverse-Compton scattering as the dominant γ-ray production process in the jets of flat spectrum radio quasars (FSRQs) and BL Lac objects, and on the unification scheme of radio-loud AGN. According to this picture, blazars represent the beamed fraction of the Fanaroff-Riley radio galaxies (FR galaxies). The observed logN-logS distribution and redshift distribution of both FSRQs and BL Lacs constrain our model. Depending slightly on the evolutionary behaviour of blazars, we find that unresolved AGN underproduce the intensity of the extragalactic background radiation. With our model only 20-40per cent of the extragalactic background emission can be explained by unresolved blazars if we integrate to a maximum redshift of Zmax=3. For Zmax=5, blazars could account for 40-80per cent of the EGRB. Roughly 70-90per cent of the AGN contribution to the EGRB would result from BL Lacs. While the systematic uncertainties in our estimate for the FSRQ contribution appear small, in the case of BL Lacs our model parameters are not consistent with the results from studies in other wavelength regimes, and therefore may have larger systematic uncertainties. Thus we end up with two possibilities, depending on whether we underpredict or overpredict the BL Lac contribution: either unresolved AGN cannot account for the entire EGRB, or unresolved BL Lacs produce the observed background. We predict a significant flattening of the γ-ray logN-logS function in the next two decades of flux below the EGRET threshold.

  2. Kiloparsec-Scale Jets in Three Radio-Loud Narrow-Line Seyfert 1 Galaxies

    NASA Astrophysics Data System (ADS)

    Richards, Joseph L.; Lister, Matthew L.

    2015-02-01

    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 (≲1010 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}6}-107 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. 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.

  4. 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.

  5. 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.

  6. The invisible AGN catalogue: a mid-infrared-radio selection method for optically faint active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Truebenbach, Alexandra E.; Darling, Jeremy

    2017-06-01

    A large fraction of active galactic nuclei (AGN) are 'invisible' in extant optical surveys due to either distance or dust-obscuration. The existence of this large population of dust-obscured, infrared (IR)-bright AGN is predicted by models of galaxy-supermassive black hole coevolution and is required to explain the observed X-ray and IR backgrounds. Recently, IR colour cuts with Wide-field Infrared Survey Explorer have identified a portion of this missing population. However, as the host galaxy brightness relative to that of the AGN increases, it becomes increasingly difficult to differentiate between IR emission originating from the AGN and from its host galaxy. As a solution, we have developed a new method to select obscured AGN using their 20-cm continuum emission to identify the objects as AGN. We created the resulting invisible AGN catalogue by selecting objects that are detected in AllWISE (mid-IR) and FIRST (20 cm), but are not detected in SDSS (optical) or 2MASS (near-IR), producing a final catalogue of 46 258 objects. 30 per cent of the objects are selected by existing selection methods, while the remaining 70 per cent represent a potential previously unidentified population of candidate AGN that are missed by mid-IR colour cuts. Additionally, by relying on a radio continuum detection, this technique is efficient at detecting radio-loud AGN at z ≥ 0.29, regardless of their level of dust obscuration or their host galaxy's relative brightness.

  7. 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.

  8. 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.

  9. 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

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

    NASA Technical Reports Server (NTRS)

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

    2016-01-01

    Context. gamma-ray-detected radio-loud narrow-line Seyfert 1 (gamma-NLS1) galaxies constitute a small but interesting sample of the gamma-ray-loud AGN. The radio-loudest gamma-NLS1 known, PKS2004447, 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 PKS2004447, which are essential for understanding the diversity of the radio properties of gamma-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 8.4GHz 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 gamma-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. PKS2004447 appears to be a unique member of the gamma-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 gamma-NLS1s and extremely rare among gamma-ray-loud AGN.

  11. 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.

  12. 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.

  13. XMM-NEWTON OBSERVATIONS OF THE RADIO-LOUD BROAD ABSORPTION LINE QUASAR FBQS J131213.5+231958

    SciTech Connect

    Mathur, Smita; Dai Xinyu E-mail: dai@nhn.ou.ed

    2010-12-15

    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.

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

    PubMed

    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.

  15. 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.

  16. Star formation in accretion discs: from the Galactic center to active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Collin, S.; Zahn, J.-P.

    2008-01-01

    Context: Keplerian accretion discs around massive black holes (MBHs) are gravitationally unstable beyond a few hundredths of a parsec, and they should collapse to form stars. It has indeed been shown recently that an accretion/star formation episode took place a few million years ago in the Galactic center (GC). This raises the question of how the disc can survive in AGN and quasars and continue to transport matter towards the black hole. Aims: We study the accretion/star formation process in quasars and AGN with one aim in mind: to show that a spectrum similar to the observed one can be produced by the disc. Methods: We compute models of stationary accretion discs that are either continuous or clumpy. Continuous discs must be maintained in a state of marginal stability so that the rate of star formation remains modest and the disc is not immediately destroyed. The disc then requires additional heating and additional transport of angular momentum. In clumpy discs, the momentum transport is provided by cloud interactions. Results: Non-viscous heating can be provided by stellar illumination, but in the case of continuous discs, even momentum transport by supernovae is insufficient for sustaining a marginal state, except at the very periphery of the disc. In clumpy discs it is possible to account for the required accretion rate through interactions between clouds, but this model is unsatisfactory because its parameters are tightly constrained without any physical justification. Conclusions: Finally one must appeal to non-stationary discs with intermittent accretion episodes like those that occurred in the GC, but such a model is probably not applicable either to luminous high redshift quasars or to radio-loud quasars.

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

    PubMed

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

    2006-12-07

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

  18. 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.

  19. 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.

  20. CHANDRA X-RAY OBSERVATIONS OF THE REDSHIFT 1.53 RADIO-LOUD QUASAR 3C 270.1

    SciTech Connect

    Wilkes, Belinda J.; Lal, Dharam V.; Willner, S. P.; Ashby, M. L. N.; Fazio, G. G.; Worrall, D. M.; Birkinshaw, Mark; Haas, Martin; Chini, Rolf; Antonucci, Robert; Avara, Mark; Barthel, Peter; Hardcastle, Martin; Lawrence, Charles; Leipski, Christian; Ogle, Patrick; Schulz, Bernhard

    2012-01-20

    Chandra X-ray observations of the high redshift (z = 1.532) radio-loud quasar 3C 270.1 in 2008 February show the nucleus to have a power-law spectrum, {Gamma} = 1.66 {+-} 0.08, typical of a radio-loud quasar, and a marginally detected Fe K{alpha} emission line. The data also reveal extended X-ray emission, about half of which is associated with the radio emission from this source. The southern emission is co-spatial with the radio lobe and peaks at the position of the double radio hot spot. Modeling this hot spot, including Spitzer upper limits, rules out synchrotron emission from a single power-law population of electrons, favoring inverse Compton emission with a field of {approx}11 nT, roughly a third of the equipartition value. The northern emission is concentrated close to the location of a 40 Degree-Sign bend where the radio jet is presumed to encounter an external medium. It can be explained by inverse Compton emission involving cosmic microwave background photons with a field of {approx}3 nT, a factor of 7-10 below the equipartition value. The remaining, more diffuse X-ray emission is harder (HR = -0.09 {+-} 0.22). With only 22.8 {+-} 5.6 counts, the spectral form cannot be constrained. Assuming thermal emission with a temperature of 4 keV yields an estimate for the luminosity of 1.8 Multiplication-Sign 10{sup 44} erg s{sup -1}, consistent with the luminosity-temperature relation of lower-redshift clusters. However, deeper Chandra X-ray observations are required to delineate the spatial distribution and better constrain the spectrum of the diffuse emission to verify that we have detected X-ray emission from a high-redshift cluster.

  1. Piecing together the X-ray background: bolometric corrections for active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Vasudevan, R. V.; Fabian, A. C.

    2007-11-01

    The X-ray background can be used to constrain the accretion history of supermassive black holes (SMBHs) in active galactic nuclei (AGN), with the SMBH mass density related to the energy density due to accretion. A knowledge of the hard X-ray bolometric correction, κ2-10keV, is a vital input into these studies, as it allows us to constrain the parameters of the accretion responsible for SMBH growth. Earlier studies assumed a constant bolometric correction for all AGN, and more recent work has suggested accounting for a dependence on AGN luminosity. Until recently, the variations in the disc emission in the ultraviolet (UV) have not been taken into account in this calculation; we show that such variations are important by construction of optical-to-X-ray spectral energy distributions for 54 AGN. In particular, we use Far Ultraviolet Spectroscopic Explorer (FUSE) UV and X-ray data from the literature to constrain the disc emission as well as possible. We find evidence for very significant spread in the bolometric corrections, with no simple dependence on luminosity being evident. Populations of AGN such as narrow-line Seyfert 1 nuclei, radio-loud and X-ray-weak AGN may have bolometric corrections which differ systematically from the rest of the AGN population. We identify other sources of uncertainty including intrinsic extinction in the optical-UV, X-ray and UV variability and uncertainties in SMBH mass estimates. Our results suggest a more well-defined relationship between the bolometric correction and Eddington ratio in AGN, with a transitional region at an Eddington ratio of ~0.1, below which the bolometric correction is typically 15-25, and above which it is typically 40-70. We consider the potential-implied parallels with the low/hard and high/soft states in Galactic black hole (GBH) accretion, and present bolometric corrections for the GBH binary GX 339-4 for comparison. Our findings reinforce previous studies proposing a multistate description of AGN

  2. 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.

  3. A RADIAL VELOCITY TEST FOR SUPERMASSIVE BLACK HOLE BINARIES AS AN EXPLANATION FOR BROAD, DOUBLE-PEAKED EMISSION LINES IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

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

    2016-01-20

    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.

  4. 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

  5. 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

  6. X-ray Observations of the Radio-loud Narrow-Line Seyfert 1 Galaxy PMN J0948+0022

    NASA Astrophysics Data System (ADS)

    Brenneman, Laura; Reynolds, Christopher S.; Markoff, Sera; Parker, Michael; Miller, Jon M.

    2017-08-01

    We report on the 200-ks NuSTAR observation of the narrow-line Seyfert 1 (NLS1) AGN, PMN J0948+0022, executed simultaneously with an 80-ks XMM-Newton observation in 2016. PMN J0948+0022 was chosen because it is one of seven known, powerfully-jetted radio-loud (RL) NLS1s that have been observed with Fermi. We will detail our progress toward meeting the following campaign objectives with the analysis of these datasets: (1) Confirming the presence of the soft excess and look for any evidence of reflection, either in Fe K emission or the Compton hump above 10 keV; (2) Determining the correct spectral model across the entire X-ray bandpass (e.g., Comptonization vs. blurred reflection for the soft excess); (3) Measuring the coronal parameters (temperature, optical depth, compactness) by constraining the high-energy cutoff of the power-law and the low-energy UV/optical data simultaneously; (4) Looking for any correlations between the corona, jet and accretion properties by examining radio and Fermi monitoring of the source contemporaneous with the X-ray and UV/optical data and comparing fits to pure disk/corona models vs. jet models; (5) Furthering our understanding of the jet emission mechanism(s) in RLNLS1s by adding new information to the SED modeling of this source.

  7. RADIO-QUIET AND RADIO-LOUD PULSARS: SIMILAR IN GAMMA-RAYS BUT DIFFERENT IN X-RAYS

    SciTech Connect

    Marelli, M.; Mignani, R. P.; Luca, A. De; Salvetti, D.; Parkinson, P. M. Saz; Hartog, P. R. Den

    2015-04-01

    We present new Chandra and XMM-Newton observations of a sample of eight radio-quiet (RQ) γ-ray pulsars detected by the Fermi Large Area Telescope. For all eight pulsars we identify the X-ray counterpart, based on the X-ray source localization and the best position obtained from γ-ray pulsar timing. For PSR J2030+4415 we found evidence for a ∼10″-long pulsar wind nebula. Our new results consolidate the work from Marelli et al. and confirm that, on average, the γ-ray-to-X-ray flux ratios (F{sub γ}/F{sub X}) of RQ pulsars are higher than for the radio-loud (RL) ones. Furthermore, while the F{sub γ}/F{sub X} distribution features a single peak for the RQ pulsars, the distribution is more dispersed for the RL ones, possibly showing two peaks. We discuss possible implications of these different distributions based on current models for pulsar X-ray emission.

  8. 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.

  9. 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.

  10. A Closer View of the Radio-FIR Correlation: Disentangling the Contributions of Star Formation and Active Galactic Nucleus Activity

    NASA Astrophysics Data System (ADS)

    Morić, I.; Smolčić, V.; Kimball, A.; Riechers, D. A.; Ivezić, Ž.; Scoville, N.

    2010-11-01

    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 1.4 GHz >~ 2.5 mJy) selected sample, matched to the SDSS spectroscopic ("main" galaxy and quasar) catalogs and IRAS data (0.04 < z <~ 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. Based on observations with the National Radio Astronomy

  11. Nuclear obscuration in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Ramos Almeida, Cristina; Ricci, Claudio

    2017-09-01

    The material surrounding accreting supermassive black holes connects the active galactic nucleus with its host galaxy and, besides being responsible for feeding the black hole, provides important information on the feedback that nuclear activity produces on the galaxy. In this Review, we summarize our current understanding of the close environment of accreting supermassive black holes obtained from studies of local active galactic nuclei carried out in the infrared and X-ray regimes. The structure of this circumnuclear material is complex, clumpy and dynamic, and its covering factor depends on the accretion properties of the active galactic nucleus. In the infrared, this obscuring material is a transition zone between the broad- and narrow-line regions, and, at least in some galaxies, it consists of two structures: an equatorial disk/torus and a polar component. In the X-ray regime, the obscuration is produced by multiple absorbers across various spatial scales, mostly associated with the torus and the broad-line region. In the coming decade, the new generation of infrared and X-ray facilities will greatly contribute to our understanding of the structure and physical properties of nuclear obscuration in active galactic nuclei.

  12. Nuclear obscuration in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Almeida, Cristina Ramos; Ricci, Claudio

    2017-10-01

    The material surrounding accreting supermassive black holes connects the active galactic nucleus with its host galaxy and, besides being responsible for feeding the black hole, provides important information on the feedback that nuclear activity produces on the galaxy. In this Review, we summarize our current understanding of the close environment of accreting supermassive black holes obtained from studies of local active galactic nuclei carried out in the infrared and X-ray regimes. The structure of this circumnuclear material is complex, clumpy and dynamic, and its covering factor depends on the accretion properties of the active galactic nucleus. In the infrared, this obscuring material is a transition zone between the broad- and narrow-line regions, and, at least in some galaxies, it consists of two structures: an equatorial disk/torus and a polar component. In the X-ray regime, the obscuration is produced by multiple absorbers across various spatial scales, mostly associated with the torus and the broad-line region. In the coming decade, the new generation of infrared and X-ray facilities will greatly contribute to our understanding of the structure and physical properties of nuclear obscuration in active galactic nuclei.

  13. Interplanetary Proton and Electron Enhancements Associated with Radio-loud and Radio-quiet CME-driven Shocks

    NASA Astrophysics Data System (ADS)

    Makela, P. A.; Gopalswamy, N.; Xie, H.; Akiyama, S.; Yashiro, S.

    2009-12-01

    We present the results on electron and proton acceleration in association with radio-quiet (RQ) and radio-loud (RL) shocks driven by coronal mass ejections (CMEs) during 1996-2006. The CME-driven shocks are classified into RL or RQ shocks based on the presence or the lack of type II radio bursts in the metric and decameter-hectometric wavelength range. We studied proton flux enhancements at L1 in the 66 keV - 50 MeV energy range observed by the ACE/EPAM and SOHO/ERNE instruments. Electron flux enhancements were studied in the 38-53~keV energy channel of EPAM. In general, the RL shocks are more likely to be associated with an energetic storm particle (ESP) event than RQ shocks. Approximately one third of RQ shocks and slightly over a half of RL shocks produced an ESP event at energies above 1.8 MeV. In overall both RQ and RL electron ESP events are rarer, but they follow a similar pattern to the proton observations, i.e. ESP events are observed in approximately one fifth versus two fifths of shocks, respectively. We also studied correlations of ESP event size with CME and shock properties. As expected, the ESP events associated with the RQ shocks are less intense than those with RL shocks. In addition, particle acceleration in RQ shocks occurs predominately in quasi-perpendicular shocks. There is a modest positive correlation between ESP event size and the CME and shock speed and the Mach number. Again, the correlations are stronger for the RL shocks. It appears that shocks can accelerate particles, although less efficiently, even when they do not produce observable type II radio bursts. The variation between the presence of type IIs and ESP events is probably connected to variations in the coronal conditions of shock formation and to the consequent evolution of the shock as it travels through diverse coronal and interplanetary plasmas.

  14. 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.

  15. 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.

  16. The emission line spectrum of active galactic nuclei and the unifying scheme

    NASA Astrophysics Data System (ADS)

    Véron-Cetty, M. P.; Véron, P.

    Recent papers dealing with the most controversial aspects of AGNs are reviewed. They suggest interesting conclusions: all Seyferts can be described by a single parameter, the X-ray column density; radio loud AGNs may host a rapidly spinning black hole and radio quiet AGNs a slowly spinning black hole; high-ionization AGNs (Seyfert galaxies and QSOs) contain an optically thick, geometrically thin accretion disk, while low-ionization AGNs (Liners) contain an optically thin, geometrically thick accretion disk; a number of blazars have been classified as BLLs on the basis of insufficient data; most objects with weak broad emission lines are in fact HPQs; many objects have been called Liners although they are not AGNs but rather the result of stellar activity; type 2 QSOs exist, but are quite inconspicuous if radio quiet.

  17. HI absorption towards low luminosity radio-loud AGNs of different accretion modes and WISE colours

    NASA Astrophysics Data System (ADS)

    Chandola, Yogesh; Saikia, D. J.

    2016-08-01

    HI absorption studies of active galaxies enable us to probe their circumnuclear regions and the general interstellar medium, and study the supply of gas which may trigger the nuclear activity. We investigated the detection rate of HI absorption on the nature of radio galaxies based on their emission-line spectra, nature of the host galaxies based on the WISE colours and their radio structure, which may help understand the different accretion modes. The highest detection rate of HI absorption is found in the `late-type' galaxies with WISE infrared colours W2-W3 > 2, which is typical of gas-rich systems, along with a compact radio structure. Almost all the high-excitation radio galaxies (HERGs) in our sample have W2-W3 > 2. The HI detection rate for low-excitation radio galaxies (LERGs) with W2-W3 > 2 and compact radio structure is high (~ 71 %). This is similar to compact HERGs with W2-W3 > 2 where, although the numbers are small, all three sources are detected with HI absorption. In HERGs, compact radio structure in the nuclear or circumnuclear region could give rise to absorption by gas in the dusty torus in addition to gas in the interstellar medium. However, higher specific star formation rate (sSFR) for the LERGs with W2-W3 > 2 suggests that HI absorption may be largely due to star-forming gas in their hosts.

  18. Fermi LAT Detection of a GeV Flare from the Radio-Loud Narrow-Line Sy1 1H 0323+342

    NASA Astrophysics Data System (ADS)

    Carpenter, Bryce; Ojha, Roopesh

    2013-08-01

    The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray flux from a source positionally consistent with 1H 0323+342 (RA=03h24m41.1613s, Dec=+34d10m45.856s, J2000; Beasley et al. 2002, ApJS, 141, 13) at z= 0.061 (Marcha et al. 1996, MNRAS, 281, 425). This is the second nearest radio-loud Narrow-Line Seyfert 1 galaxy, a small and important class of gamma-ray loud AGN (Abdo et al.

  19. A CHANDRA SURVEY OF THE X-RAY PROPERTIES OF BROAD ABSORPTION LINE RADIO-LOUD QUASARS

    SciTech Connect

    Miller, B. P.; Brandt, W. N.; Garmire, G. P.; Gibson, R. R.; Shemmer, O. E-mail: niel@astro.psu.edu E-mail: rgibson@astro.washington.edu

    2009-09-10

    This work presents the results of a Chandra study of 21 broad absorption line (BAL) radio-loud quasars (RLQs). We conducted a Chandra snapshot survey of 12 bright BAL RLQs selected from Sloan Digital Sky Survey Data/Faint Images of the Radio Sky data and possessing a wide range of radio and C IV absorption properties. Optical spectra were obtained nearly contemporaneously with the Hobby-Eberly Telescope; no strong flux or BAL variability was seen between epochs. In addition to the snapshot targets, we include in our sample nine additional BAL RLQs possessing archival Chandra coverage. We compare the properties of (predominantly high-ionization) BAL RLQs to those of non-BAL RLQs as well as to BAL radio-quiet quasars (RQQs) and non-BAL RQQs for context. All 12 snapshots and 8/9 archival BAL RLQs are detected, with observed X-ray luminosities less than those of non-BAL RLQs having comparable optical/UV luminosities by typical factors of 4.1-8.5. (BAL RLQs are also X-ray weak by typical factors of 2.0-4.5 relative to non-BAL RLQs having both comparable optical/UV and radio luminosities.) However, BAL RLQs are not as X-ray weak relative to non-BAL RLQs as are BAL RQQs relative to non-BAL RQQs. While some BAL RLQs have harder X-ray spectra than typical non-BAL RLQs, some have hardness ratios consistent with those of non-BAL RLQs, and there does not appear to be a correlation between X-ray weakness and spectral hardness, in contrast to the situation for BAL RQQs. RLQs are expected to have X-ray continuum contributions from both accretion-disk corona and small-scale jet emission. While the entire X-ray continuum in BAL RLQs cannot be obscured to the same degree as in BAL RQQs, we calculate that the jet is likely partially covered in many BAL RLQs. We comment briefly on implications for geometries and source ages in BAL RLQs.

  20. 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.

  1. Tidal events and galactic activity

    NASA Technical Reports Server (NTRS)

    Hutchings, J. B.; Neff, S. G.

    1990-01-01

    Researchers report some results from recent and ongoing work which relate to the connection between nuclear activity and tidal interactions. They suggest that tidal events are in general a necessary but not sufficient condition for nuclear activation. They also suggest that nuclear activity generally develops at a 'late stage' of a tidal encounter, following star-formation and dust evaporation, and when the most obvious morphological disturbances may have disappeared. The quantitative results from quasi-stellar object imaging, radio source evolution, HI observations, and an Infrared Astronomy Satellite (IRAS) source survey are given in tabular form.

  2. 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.

  3. Fantastic Clusters and Where to Find Them: The Densest Structures at 1.4 < z < 2.8 from the Clusters Around Radio-Loud AGN (CARLA) Survey

    NASA Astrophysics Data System (ADS)

    Galametz, A.; Noirot, G.; Stern, D.; De Breuck, C.; Vernet, J.; . Cooke, E.; Wylezalek, D.; Mei, S.; Hatch, N.; Rettura, A.; Brodwin, M.; Gonzalez, A.; Jarvis, M.; Seymour, N.; Standord, S. A.; Eisenhardt, P.

    2017-07-01

    There is a rich tradition of surveys that aimed at identifying clusters of galaxies at higher and higher z. Although searches have preferentially looked for concentrations of red sequence and/or massive galaxies, or looking for signatures of the hot intracluster gas, they are exceedingly time-depending and require both depth and coverage as searches go to increasingly higher z. The limit of known clusters currently reaches z 2, also identified as a crucial epoch for cluster formation. A targeted cluster search would reduce the strain on telescope time. Our Spitzer/IRAC survey CARLA (Clusters Around Radio-Loud AGN) has, in that regard, targeted high-z radio-loud AGN, which are known to reside in dense environments. I will summarize a series of results and on-going studies from the CARLA collaboration that aimed at identifying cluster candidates in the field of RLAGN, investigating the formation scenario of the most massive cluster members by analyzing the evolution of the cluster luminosity function or red sequence color with redshift. I will also present CARLA-HST and CARLALMA, respectively the HST spectroscopic confirmation campaign and on-going ALMA follow-up of CARLA clusters.

  4. Clustering, cosmology and a new era of black hole demographics- II. The conditional luminosity functions of Type 2 and Type 1 active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Ballantyne, D. R.

    2017-01-01

    The orientation-based unification model of active galactic nuclei (AGNs) posits that the principle difference between obscured (Type 2) and unobscured (Type 1) AGNs is the line of sight into the central engine. If this model is correct then there should be no difference in many of the properties of AGN host galaxies (e.g. the mass of the surrounding dark matter haloes). However, recent clustering analyses of Type 1 and Type 2 AGNs have provided some evidence for a difference in the halo mass, in conflict with the orientation-based unified model. In this work, a method to compute the conditional luminosity function (CLF) of Type 2 and Type 1 AGNs is presented. The CLF allows many fundamental halo properties to be computed as a function of AGN luminosity, which we apply to the question of the host halo masses of Type 1 and 2 AGNs. By making use of the total AGN CLF, the Type 1 X-ray luminosity function, and the luminosity-dependent Type 2 AGN fraction, the CLFs of Type 1 and 2 AGNs are calculated at z ≈ 0 and 0.9. At both z, there is no statistically significant difference in the mean halo mass of Type 2 and 1 AGNs at any luminosity. There is marginal evidence that Type 1 AGNs may have larger halo masses than Type 2s, which would be consistent with an evolutionary picture where quasars are initially obscured and then subsequently reveal themselves as Type 1s. As the Type 1 lifetime is longer, the host halo will increase somewhat in mass during the Type 1 phase. The CLF technique will be a powerful way to study the properties of many AGNs subsets (e.g. radio-loud, Compton-thick) as future wide-area X-ray and optical surveys substantially increase our ability to place AGNs in their cosmological context.

  5. 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.

  6. 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.

  7. Galaxy NGC 1448 with Active Galactic Nucleus

    NASA Image and Video Library

    2017-01-07

    NGC 1448, a galaxy with an active galactic nucleus, is seen in this image combining data from the Carnegie-Irvine Galaxy Survey in the optical range and NuSTAR in the X-ray range. This galaxy contains an example of a supermassive black hole hidden by gas and dust. X-ray emissions from NGC 1448, as seen by NuSTAR and Chandra, suggests for the first time that, like IC 3639 in PIA21087, there must be a thick layer of gas and dust hiding the active black hole in this galaxy from our line of sight. http://photojournal.jpl.nasa.gov/catalog/PIA21086

  8. 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

  9. INVISIBLE ACTIVE GALACTIC NUCLEI. II. RADIO MORPHOLOGIES AND FIVE NEW H i 21 cm ABSORPTION LINE DETECTORS

    SciTech Connect

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

    2016-03-15

    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

  10. Active Galactic Nuclei and Gamma Rays

    NASA Astrophysics Data System (ADS)

    Giebels, Berrie; Aharonian, Felix; Sol, Hélène

    The supermassive black holes harboured in active galactic nuclei are at the origin of powerful jets which can emit copious amounts of γ-rays. The exact interplay between the infalling matter, the black hole and the relativistic outflow is still poorly known, and this parallel session of the 12th Marcel Grossman meeting intended to offer the most up to date status of observational results with the latest generation of ground and space-based instruments, as well as the theoretical developments relevant for the field.

  11. 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.

  12. 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.

  13. 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.

  14. The parsec-scale structure, kinematics, and polarization of radio-loud narrow-line Seyfert 1 galaxies

    NASA Astrophysics Data System (ADS)

    Richards, J. L.; Lister, M. L.; Savolainen, T.; Homan, D. C.; Kadler, M.; Hovatta, T.; Readhead, A. C. S.; Arshakian, T. G.; Chavushyan, V.

    2015-03-01

    Several narrow-line Seyfert 1 galaxies (NLS1s) have now been detected in gamma rays, providing firm evidence that at least some of this class of active galactic nuclei (AGN) produce relativistic jets. The presence of jets in NLS1s is surprising, as these sources are typified by comparatively small black hole masses and near- or super-Eddington accretion rates. This challenges the current understanding of the conditions necessary for jet production. Comparing the properties of the jets in NLS1s with those in more familiar jetted systems is thus essential to improve jet production models. We present early results from our campaign to monitor the kinematics and polarization of the parsec-scale jets in a sample of 15 NLS1s through multifrequency observations with the Very Long Baseline Array. These observations are complemented by fast-cadence 15 GHz monitoring with the Owens Valley Radio Observatory 40 m telescope and optical spectroscopic monitoring with with the 2 m class telescope at the Guillermo Haro Astrophysics Observatory in Cananea, Mexico.

  15. 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.

  16. Dielectronic Recombination In Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

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

    2006-05-01

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

  17. 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.

  18. 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.

  19. 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.

  20. Echo Mapping of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Horne, K.

    Echo mapping exploits light travel time delays, revealed by multi-wavelength variability studies, to map the geometry, kinematics, and physical conditions of reprocessing sites in photo-ionized gas flows. In active galactic nuclei (AGN), the ultraviolet to near infrared light arises in part from reprocessing of EUV and X-ray light from a compact and erratically variable source in the nucleus. The observed time delays, 0.1-2 days for the continuum and 1-100 days for the broad emission lines, probe regions only micro-arcseconds from the nucleus. Emission-line delays reveal radially stratified ionization zones, identify the nature of the gas motions, and estimate the masses of the central black holes. Continuum time delays map the temperature-radius structure of AGN accretion discs, and provide distances that may be accurate enough to realize the potential of AGNs as cosmological probes.

  1. 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

  2. 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.

  3. Silicate Dust in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Xie, Yanxia; Li, Aigen; Hao, Lei

    2017-01-01

    The unification theory of active galactic nuclei (AGNs) hypothesizes that all AGNs are surrounded by an anisotropic dust torus and are essentially the same objects but viewed from different angles. However, little is known about the dust that plays a central role in the unification theory. There are suggestions that the AGN dust extinction law appreciably differs from that of the Galaxy. Also, the silicate emission features observed in type 1 AGNs appear anomalous (i.e., their peak wavelengths and widths differ considerably from that of the Galaxy). In this work, we explore the dust properties of 147 AGNs of various types at redshifts z≲ 0.5, with special attention paid to 93 AGNs that exhibit the 9.7 and 18 μm silicate emission features. We model their silicate emission spectra obtained with the Infrared Spectrograph aboard the Spitzer Space Telescope. We find that 60/93 of the observed spectra can be well explained with “astronomical silicate,” while the remaining sources favor amorphous olivine or pyroxene. Most notably, all sources require the dust to be micron-sized (with a typical size of ∼1.5 ± 0.1 μm), much larger than submicron-sized Galactic interstellar grains, implying a flat or “gray” extinction law for AGNs. We also find that, while the 9.7 μm emission feature arises predominantly from warm silicate dust of temperature T ∼ 270 K, the ∼5–8 μm continuum emission is mostly from carbon dust of T ∼ 640 K. Finally, the correlations between the dust properties (e.g., mass, temperature) and the AGN properties (e.g., luminosity, black hole mass) have also been investigated.

  4. Environmental properties related to active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Manzer, Lianne H.

    There continues to be significant controversy regarding the mechanisms responsible for the initiation of activity in galactic nuclei. It is well understood that the non-thermal energy produced by an AGN is due to accretion onto a supermassive black hole. It has not yet been determined, however, what leads particular galaxies to become active. An accurate exploration into what triggers an AGN demands an analysis of a large sample of galaxies across a diverse set of environments. In this work, we investigate possible environmental influences by carrying out a statistical investigation of galaxy groups. Using the catalogue of Yang et al. (2007), in which groups of galaxies containing between 2 and 20 members with redshifts between 0.01 -- 0.20 were taken from the Sloan Digital Sky Survey, we investigate the fraction of active galactic nuclei (AGN) within these groups and compare it to the sample of isolated galaxies also obtained from Yang et al. (2007). After correcting our spectroscopic data for extinction and underlying stellar absorption, we classify the galaxy sample using relevant emission-line ratios. We propose an alternate method for classifying emission-line galaxies, including AGN, which builds upon standard diagnostic utilities used for optical classification and includes uncertainties. Such classification probabilities offer a more robust and consistent method of investigating the effect of group environments with galaxy type. We find our sample to be a fair representation of the local universe by comparing the luminosity function of our entire data set to that of Blanton et al. (2001), Blanton et al. (2003b), and Montero-Dorta & Prada (2009). The evidence also suggests that the luminosity function of galaxies differs between isolated galaxies and galaxies in groups. We find a significant increase in the fraction of AGNs identified in grouped environments. On the other hand, we find a higher fraction of starforming galaxies within isolated systems. We

  5. ACTIVE GALACTIC NUCLEUS FEEDBACK WORKS BOTH WAYS

    SciTech Connect

    Zinn, P.-C.; Middelberg, E.; Dettmar, R.-J.; Norris, R. P.

    2013-09-01

    Simulations of galaxy growth need to invoke strong negative feedback from active galactic nuclei (AGNs) to suppress the formation of stars and thus prevent the over-production of very massive systems. While some observations provide evidence for such negative feedback, other studies find either no feedback or even positive feedback, with increased star formation associated with higher AGN luminosities. Here we report an analysis of several hundred AGNs and their host galaxies in the Chandra Deep Field South using X-ray and radio data for sample selection. Combined with archival far-infrared data as a reliable tracer of star formation activity in the AGN host galaxies, we find that AGNs with pronounced radio jets exhibit a much higher star formation rate (SFR) than the purely X-ray-selected ones, even at the same X-ray luminosities. This difference implies that positive AGN feedback plays an important role, too, and therefore has to be accounted for in all future simulation work. We interpret this to indicate that the enhanced SFR of radio-selected AGNs arises because of jet-induced star formation, as is suggested by the different jet powers among our AGN samples, while the suppressed SFR of X-ray selected AGN is caused by heating and photo-dissociation of molecular gas by the hot AGN accretion disk.

  6. 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.

  7. Dielectronic Recombination In Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

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

    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 ˜ 15-17 Å. 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.

  8. 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.

  9. Active galactic nuclei: what's in a name?

    NASA Astrophysics Data System (ADS)

    Padovani, P.; Alexander, D. M.; Assef, R. J.; De Marco, B.; Giommi, P.; Hickox, R. C.; Richards, G. T.; Smolčić, V.; Hatziminaoglou, E.; Mainieri, V.; Salvato, M.

    2017-08-01

    Active galactic nuclei (AGN) are energetic astrophysical sources powered by accretion onto supermassive black holes in galaxies, and present unique observational signatures that cover the full electromagnetic spectrum over more than twenty orders of magnitude in frequency. The rich phenomenology of AGN has resulted in a large number of different "flavours" in the literature that now comprise a complex and confusing AGN "zoo". It is increasingly clear that these classifications are only partially related to intrinsic differences between AGN and primarily reflect variations in a relatively small number of astrophysical parameters as well the method by which each class of AGN is selected. Taken together, observations in different electromagnetic bands as well as variations over time provide complementary windows on the physics of different sub-structures in the AGN. In this review, we present an overview of AGN multi-wavelength properties with the aim of painting their "big picture" through observations in each electromagnetic band from radio to γ -rays as well as AGN variability. We address what we can learn from each observational method, the impact of selection effects, the physics behind the emission at each wavelength, and the potential for future studies. To conclude, we use these observations to piece together the basic architecture of AGN, discuss our current understanding of unification models, and highlight some open questions that present opportunities for future observational and theoretical progress.

  10. 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.

  11. 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.

  12. Deep Surveys of Obscured Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Chatzichristou, Eleni T.

    2006-08-01

    Several key goals require measuring the number of all Active Galactic Nuclei (AGN) in the Universe, and the evolution of the ratio of obscured to unobscured AGN with redshift. This reflects the structure of AGN and thus the development in the heart of all galaxies. Hard X-rays can penetrate most obscuring dust columns to reveal the AGN that remains hidden in all other wavelengths. Mid-IR surveys probe the thermal dust emission, that is, the continuum light from the central source after it is reprocessed by dust, and this emission dominates the bolometric luminosities of dusty high-redshift galaxies. Thus, combining deep mid-IR and hard X-ray surveys can provide us with accurate demographics of AGN especially at high redshifts. Multi-wavelength surveys aim to address these science goals by exploiting the unprecedented combination of great observatories such as HST, Chandra and SIRTF to survey the distant universe to the faintest flux limits across the broadest range of wavelengths. In this paper I discuss some of the results coming from multi-wavelength surveys placing particular focus on the systematic study of obscured AGN.

  13. 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.

  14. Testing Tests on Active Galactic Nucleus Microvariability

    NASA Astrophysics Data System (ADS)

    de Diego, José A.

    2010-03-01

    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 χ2 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 χ2 prove to be powerful and robust estimators for microvariations, while the C-statistic is not a reliable methodology and its use should be avoided.

  15. Unobscured Type 2 Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Shi, Yong; Rieke, George H.; Smith, Paul; Rigby, Jane; Hines, Dean; Donley, Jennifer; Schmidt, Gary; Diamond-Stanic, Aleksandar M.

    2010-05-01

    Type 2 active galactic nuclei (AGNs) with intrinsically weak broad emission lines (BELs) would be exceptions to the unified model. After examining a number of proposed candidates critically, we find that the sample is contaminated significantly by objects with BELs of strengths indicating that they actually contain intermediate-type AGNs, plus a few Compton-thick sources as revealed by extremely low ratios of X-ray to nuclear IR luminosities. We develop quantitative metrics that show two (NGC 3147 and NGC 4594) of the remaining candidates to have BELs 2-3 orders of magnitude weaker than those of typical type 1 AGNs. Several more galaxies remain as candidates to have anomalously weak BELs, but this status cannot be confirmed with the existing information. Although the parent sample is poorly defined, the two confirmed objects are well under 1% of its total number of members, showing that the absence of a BEL is possible, but very uncommon in AGN. We evaluate these two objects in detail using multi-wavelength measurements including new IR data obtained with Spitzer and ground-based optical spectropolarimeteric observations. They have little X-ray extinction with N H < ~1021 cm-2. Their IR spectra show strong silicate emission (NGC 4594) or weak aromatic features on a generally power-law continuum with a suggestion of silicates in emission (NGC 3147). No polarized BEL is detected in NGC 3147. These results indicate that the two unobscured type 2 objects have circumnuclear tori that are approximately face-on. Combined with their X-ray and optical/UV properties, this behavior implies that we have an unobscured view of the nuclei and thus that they have intrinsically weak BELs. We compare their properties with those of the other less-extreme candidates. We then compare the distributions of bolometric luminosities and accretion rates of these objects with theoretical models that predict weak BELs.

  16. 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.

  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. Megamaser Disks in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Kartje, John F.; Königl, Arieh; Elitzur, Moshe

    1999-03-01

    Recent spectroscopic and VLBI-imaging observations of bright extragalactic H2O maser sources have revealed that the megamaser emission often originates in thin circumnuclear disks near the centers of active galactic nuclei (AGNs). Using general radiative and kinematic considerations and taking account of the observed flux variability, we argue that the maser emission regions are clumpy, a conclusion that is independent of the detailed mechanism (X-ray heating, shocks, etc.) driving the collisionally pumped masers. We examine scenarios in which the clumps represent discrete gas condensations (i.e., clouds) and do not merely correspond to velocity irregularities in the disk. We show that even two clouds that overlap within the velocity-coherence length along the line of sight could account (through self-amplification) for the entire maser flux of a high-velocity ``satellite'' feature in sources like NGC 4258 and NGC 1068, and we suggest that cloud self-amplification likely contributes also to the flux of the background-amplifying ``systemic'' features in these objects. Analogous interpretations have previously been proposed for water maser sources in Galactic star-forming regions. We argue that this picture provides a natural explanation of the time-variability characteristics of extragalactic megamaser sources and of their apparent association with Seyfert 2-like galaxies. We also show that the requisite cloud space densities and internal densities are consistent with the typical values of nuclear (broad emission line region type) clouds. We examine two scenarios of clumpy disks in which the maser emission is excited by a central continuum source. This excitation mechanism was first considered in the context of megamaser disks by Neufeld & Maloney, but our proposed models are clearly distinct from their warped, homogeneous disk interpretation. In our first scenario we consider an annular disk (or ``ring'') whose inner edge corresponds to the innermost radius of the

  19. 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

  20. Decaying globular cluster systems and galactic nuclear activity

    NASA Astrophysics Data System (ADS)

    Capuzzo-Dolcetta, R.

    Globular cluster are systems that evolve dissipatively in non symmetric galactic potentials, losing energy and angular momentum. As a consequence, the GCS radial profile in a galaxy evolves significantly, so to differ from the one of the collisionless stellar bulge phase: this can explain the observations, which indicate how the GCS distribution in galaxies is usually more extended than the underlining stellar distribution. Moreover, the GCS orbital decay implies that a significant quantity of mass is carried toward the mother galaxy's central galactic region in a time scale short compared to the Hubble time. We show that this mass can accrete a galactic nucleus and fuel its activity in early stages of galactic life.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. The under-explored radio-loudness of quasars and the possibility of radio-source-environment interactions

    NASA Astrophysics Data System (ADS)

    Blundell, Katherine M.

    2003-10-01

    I demonstrate that radio observations in the literature to date of optically-selected quasars are largely inadequate to reveal the full extent of their jet-activity. I discuss a recent example of an optically-powerful quasar, which is radio-quiet according to all the standard classifications, which Blundell and Rawlings discovered to have a >100 kpc jet, and show that other than being the first FR I quasar to be identified, there is no reason to presume it is exceptional. I also discuss a possible new probe of accounting for the interactions of radio sources with their environments. This tool could help to avoid over-estimating magnetic fields strengths within cluster gas. I briefly describe recent analyses by Rudnick and Blundell which confront claims in the literature of cluster gas B-fields >10 μG.

  7. The Physics and Evolution of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Netzer, Hagai

    2013-11-01

    Preface; 1. Observations of active galactic nuclei; 2. Nonthermal radiation processes; 3. Black holes; 4. Accretion disks; 5. Physical processes in AGN gas and dust; 6. The AGN family; 7. Main components of AGN; 8. Host galaxies of AGN; 9. Formation and evolution of AGN; 10. Outstanding questions; References; Index.

  8. Near infrared study of shrouded active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Hearty, Frederick R.

    2007-08-01

    In this work, I consider the astronomical search for active galactic nuclei which has been predominately conducted in the optical portion of the electromagnetic spectrum and propose a multi-wavelength approach. I describe the opto-mechanical systems of the Near Infrared Camera and Fabry-Perot Spectrometer (NIC-FPS) which I, as part of a team, designed, built, and commissioned, and which I then used for this scientific investigation. This investigation had two purposes: (1) to demonstrate the state-of-theart capability of NIC-FPS, and (2) to examine the large population of astronomical radio sources that remain undetected in optical observations. My broadband near infrared imaging, when combined with archival optical, mid-infrared, and radio data, revealed large numbers of active galactic nuclei and related quasi- stellar objects which may, in part, be hidden by shrouds of gas and dust. This newly revealed population is likely to outnumber the optically selected population, and may indicate a phase of galactic nuclear activation which has been strongly selected against by existing surveys. Such objects are critical to our scientific understanding because they can be used as probes of the most distant regions of the observable Universe. Additionally, I propose a life cycle model for active galactic nuclei which accounts for the shrouded phase and for the disparity between the optically detected and near infrared detected radio sources.

  9. 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.

  10. Galaxy IC 3639 with Obscured Active Galactic Nucleus

    NASA Image and Video Library

    2017-01-07

    IC 3639, a galaxy with an active galactic nucleus, is seen in this image combining data from the Hubble Space Telescope and the European Southern Observatory. This galaxy contains an example of a supermassive black hole hidden by gas and dust. Researchers analyzed NuSTAR data from this object and compared them with previous observations from NASA's Chandra X-Ray Observatory and the Japanese-led Suzaku satellite. The findings from NuSTAR, which is more sensitive to higher energy X-rays than these observatories, confirm the nature of IC 3639 as an active galactic nucleus that is heavily obscured, and intrinsically much brighter than observed. http://photojournal.jpl.nasa.gov/catalog/PIA21087

  11. Infrared-ultraviolet spectra of active galactic nuclei

    NASA Technical Reports Server (NTRS)

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

    1987-01-01

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

  12. 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."

  13. High-energy radiation from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Sikora, Marek

    1994-01-01

    Two recent findings concerning high-energy radiation properties of active galactic nuclei -- discovery of breaks in hard X-ray spectra of Seyfert galaxies, and discovery of huge fluxes of hard gamma rays from blazars -- seem to press us to change our standard views about radiation production in these objects. I review briefly the existing radiation models, confront them with the newest observations, and discuss newly emerging theoretical pictures which attempt to account for the discoveries.

  14. Feedback by AGN Jets and Wide-angle Winds on a Galactic Scale

    NASA Astrophysics Data System (ADS)

    Dugan, Zachary; Gaibler, Volker; Silk, Joseph

    2017-07-01

    To investigate the differences in mechanical feedback from radio-loud and radio-quiet active galactic nuclei on the host galaxy, we perform 3D AMR hydrodynamic simulations of wide-angle, radio-quiet winds with different inclinations on a single, massive, gas-rich disk galaxy at a redshift of 2-3. We compare our results to hydrodynamic simulations of the same galaxy but with a jet. The jet has an inclination of 0° (perpendicular to the galactic plane), and the winds have inclinations of 0°, 45°, and 90°. We analyze the impact on the host’s gas, star formation, and circumgalactic medium. We find that jet feedback is energy-driven and wind feedback is momentum-driven. In all the simulations, the jet or wind creates a cavity mostly devoid of dense gas in the nuclear region where star formation is then quenched, but we find strong positive feedback in all the simulations at radii greater than 3 kpc. All four simulations have similar SFRs and stellar velocities with large radial and vertical components. However, the wind at an inclination of 90° creates the highest density regions through ram pressure and generates the highest rates of star formation due to its ongoing strong interaction with the dense gas of the galactic plane. With increased wind inclination, we find greater asymmetry in gas distribution and resulting star formation. Our model generates an expanding ring of triggered star formation with typical velocities of the order of 1/3 of the circular velocity, superimposed on the older stellar population. This should result in a potentially detectable blue asymmetry in stellar absorption features at kiloparsec scales.

  15. Cosmic ray feedback in galaxies and active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Pfrommer, C.; Pakmor, R.; Schaal, K.; Simpson, C. M.; Springel, V.

    2017-01-01

    Recent cosmological simulations of galaxy formation have demonstrated that feedback by star formation, supernovae and active galactic nuclei appears to be critical in obtaining realistic disk galaxies, to slow down star formation to the small observed rates, to move gas and metals out of galaxies, and to balance radiative cooling of low-entropy gas at the centers of galaxy clusters. However the particular physical processes underlying these feedback processes still remain elusive. In particular, these simulations neglected cosmic rays (CRs) and magnetic fields, which provide a comparable pressure support in comparison to turbulence in our Galaxy, and are known to couple dynamically and thermally to the gas. We will present our recent efforts to model CR physics in the cosmological simulation code arepo and demonstrate that CRs matter on all scales relevant for galaxy formation. Presenting global simulations of galaxy formation that couple CRs to the magneto-hydrodynamics, we show how CRs can launch powerful galactic winds, which reduces the available amount of gas for star formation. In particular, we highlight the importance of the γ-ray window in understanding the properties of galactic winds and discuss the non-thermal radio and γ-ray emission of Milky-Way like galaxies with bubble-shaped outflows. On scales of galaxy clusters, we show that cosmic-ray heating can balance radiative cooling of the low-entropy gas at the centers of galaxy clusters and helps in mitigating the star formation of the brightest cluster galaxies. Combining low-frequency radio and γ-ray emission of M87, the closest active galaxy interacting with the cooling cluster plasma, enable us to put forward a comprehensive, physics-based model of feedback by active galactic nuclei.

  16. Metal-poor Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Bicalho, I. C.; Telles, E.

    2014-10-01

    Active galaxies are considered to be metal-rich, with metallicity ranging from solar to slightly supersolar. This is due to the fact that the active galaxy nuclei are usually found in supermassive galaxies. We aim to test this statement by obtaining near infrared spectra of peculiar dwarf galaxies to see if they host an AGN. We present the results based on analysis of data from Gemini Near Infrared Integral Field Spectrograph (NIFS) of the metal-poor HII galaxy SDSS J1047+0739 (12 + log O/H ˜ 7.85 ± 0.02). The spectrum of this galaxy shows strong permitted emission lines with extended wings, which is atypical for HII regions. We use unconventional methods such as PCA tomography due to the benefits that it provides to data cube analysis. We are studying the kinematics of the nuclear region and the regions of star formation surrounding it, mostly through the Paschen-α and He lines. We find that the broad line emission comes only from the unresolved central region. The results of this analysis agree well with the existence of an AGN in this metal-poor galaxy.

  17. Active galactic nuclei and their panchromatic beauty.

    NASA Astrophysics Data System (ADS)

    Lusso, Elisabeta

    2016-08-01

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

  18. Fueling active galactic nuclei by magnetic braking

    NASA Technical Reports Server (NTRS)

    Krolik, Julian H.; Meiksin, Avery

    1990-01-01

    Recent detections of massive concentrations of molecular gas near the centers of galaxies hosting active nuclei suggest that these concentrations may be the source of accretion fuel for the nucleus. However, for that to be true, an angular momentum barrier must be overcome before the material in such a cloud can reach the nucleus. It is suggested that magnetic braking of the cloud may remove sufficient angular momentum to permit its material to draw considerably closer to the central object. The mechanism is particularly effective in the limit that the gas becomes self-gravitating because removal of a fraction of the initial angular momentum can lead to dynamical instability and collapse. Any small misalignment between the initial rotation axis of the cloud and the rotation axis of the galaxy can be substantially amplified as a result of the braking. It is argued that mass accretion onto the central object may occur in episodes, in some cases with a constant mass accretion rate during each episode.

  19. Observational distinction between two types of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Xie, G. Z.; Liu, F. K.; Liu, B. F.; Li, K. H.; Lu, R. W.; Lu, J. F.

    1991-01-01

    Using three criteria, the observational distinction between relativistic beaming and pure accretion for 69 active galaxies, including Seyferts, Quasars, and BL Lac objects are discussed. The first criterion is whether the inferred efficiency of the conversion of accreted matter into energy is greater than 0.1 or not. The second one is whether the observed flux is larger than the classical Eddington luminosity or not. The third is concerned in the strong coupling of geometrical and physical effects in jets. The result suggests distinguishing active galactic nuclei into two types.

  20. 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.

  1. Statistics of Superluminal Motion in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Zhang, Yong-Wei; Fan, Jun-Hui

    2008-08-01

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

  2. 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.

  3. Nuclear Structure and Galactic γ-Ray Activity.

    PubMed

    Görres, J

    2000-01-01

    The observation of galactic γ lines following the decay of radioactive nuclei provides a direct link between nuclear physics experiments in earth-based laboratories and astrophysical observations with space-based observatories. Two examples are presented to illustrate this interplay: the measurement of the lifetime of (44)Ti to allow an improved determination of the (44)Ti mass of the supernova remnant Cassiopeia A from the observed γ ray activity and the measurements of excited states in (24)Si to determine the reaction rate of (23)Al(p, γ)(24)Si which might be important for a reduced production of (22)Na in novae.

  4. Magnetic fields in the central engines of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.

    1989-01-01

    Important physical processes which may occur in the central engines of active galactic nuclei and which rely on the presence of a strong magnetic field are discussed. These processes include those involved in the plasma physics of hot tenuous accretion flows, the production of nonthermal continuum radiation, and the radiative manifestation of hydromagnetic jet production. The main arguments which support the hypothesis that supermassive black holes are the prime movers in the central engines are reviewed, and some major deduction regarding the physical state of the accreting gas are pointed out.

  5. 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.

  6. Microlensing and the structure of active galactic nucleus accretion disks

    NASA Technical Reports Server (NTRS)

    Rauch, Kevin P.; Blandford, Roger D.

    1991-01-01

    Rapid variability has been reported in two of the four gravitationally lensed images of Q2237 + 0305, and this is attributed to microlensing caused by the intervening stars. The associated constraints on the source size and properties are studied and compared with a variety of stationary accretion disk models. The reported microlensing variation in Q2237 + 0305 requires the disk size to be over 3 times smaller than a blackbody disk of similar luminosity, implying that the optical emission is either nonthermal or optically tin. An exploration of nonstationary disk models including orbiting, transient hot spots leads to a similar conclusion. Implications for models of active galactic nucleus optical continua are briefly discussed.

  7. Variability of the central region in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Wallinder, F. H.; Kato, S.; Abramowicz, M. A.

    We review implications of the observed optical and X-ray variability (periodicities and light-curves), relevant for the understanding of physical conditions in the deep interiors of active galactic nuclei. We discuss in detail kinematical, hydrodynamical, thermal and radiative transfer effects which are theorized to be responsible for observed variability patterns. We put emphasis on theoretical options which can predict basic accretion parameters, such as the mass of the central black hole, the accretion rate, and the inclination angle, in terms of observable quantities. Closed analytical results are given whenever available.

  8. Physics and structure of photoionised outflows in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Kaastra, Jelle

    2012-07-01

    I discuss the recent progress in the study of outflows from active galactic nuclei. Using long and deep monitoring observations, it is now possible to get a detailed view on the structure and location of the outflow, as well as its impact on the environment of the AGN. Focus will be on the nature of the outflow components in terms of number of components, and on time-dependent photoionisation modeling as a tool to constrain the location of these components. I will illustrate this using the results of a large monitoring campaign on Mrk 509 with XMM-Newton, Integral, Chandra, HST, Swift and ground-based observatories.

  9. 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

  10. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

  12. Fresh Activity in Old Systems: Radio AGNs in Fossil Groups of Galaxies

    NASA Astrophysics Data System (ADS)

    Hess, Kelley M.; Wilcots, Eric M.; Hartwick, Victoria L.

    2012-08-01

    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 1.4 GHz > 1023 W Hz-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.

  13. Relativistic Jets in Active Galactic Nuclei and Microquasars

    NASA Astrophysics Data System (ADS)

    Romero, Gustavo E.; Boettcher, M.; Markoff, S.; Tavecchio, F.

    2017-07-01

    Collimated outflows (jets) appear to be a ubiquitous phenomenon associated with the accretion of material onto a compact object. Despite this ubiquity, many fundamental physics aspects of jets are still poorly understood and constrained. These include the mechanism of launching and accelerating jets, the connection between these processes and the nature of the accretion flow, and the role of magnetic fields; the physics responsible for the collimation of jets over tens of thousands to even millions of gravitational radii of the central accreting object; the matter content of jets; the location of the region(s) accelerating particles to TeV (possibly even PeV and EeV) energies (as evidenced by γ-ray emission observed from many jet sources) and the physical processes responsible for this particle acceleration; the radiative processes giving rise to the observed multi-wavelength emission; and the topology of magnetic fields and their role in the jet collimation and particle acceleration processes. This chapter reviews the main knowns and unknowns in our current understanding of relativistic jets, in the context of the main model ingredients for Galactic and extragalactic jet sources. It discusses aspects specific to active Galactic nuclei (especially blazars) and microquasars, and then presents a comparative discussion of similarities and differences between them.

  14. High energy neutrinos from radio-quiet active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Alvarez-Muñiz, Jaime; Mészáros, Peter

    2004-12-01

    Most active galactic nuclei (AGN) lack prominent jets, and show modest radio emission and significant x-ray emission which arises mainly from the galactic core, very near the central black hole. We use a quantitative scenario of such core-dominated radio-quiet AGN, which attributes a substantial fraction of the x-ray emission to the presence of abortive jets involving the collision of gas blobs in the core. Here we investigate the consequences of the acceleration of protons in the shocks from such collisions. We find that protons will be accelerated up to energies above the pion photoproduction threshold on both the x rays and the UV photons from the accretion disk. The secondary charged pions decay, producing neutrinos. We predict significant fluxes of TeV-PeV neutrinos, and show that the AMANDA II detector is already constraining several important astrophysical parameters of these sources. Larger cubic kilometer detectors such as IceCube will be able to detect such neutrinos in less than one year of operation, or otherwise rule out this scenario.

  15. Relativistic Jets in Active Galactic Nuclei and Microquasars

    NASA Astrophysics Data System (ADS)

    Romero, Gustavo E.; Boettcher, M.; Markoff, S.; Tavecchio, F.

    2017-01-01

    Collimated outflows (jets) appear to be a ubiquitous phenomenon associated with the accretion of material onto a compact object. Despite this ubiquity, many fundamental physics aspects of jets are still poorly understood and constrained. These include the mechanism of launching and accelerating jets, the connection between these processes and the nature of the accretion flow, and the role of magnetic fields; the physics responsible for the collimation of jets over tens of thousands to even millions of gravitational radii of the central accreting object; the matter content of jets; the location of the region(s) accelerating particles to TeV (possibly even PeV and EeV) energies (as evidenced by γ-ray emission observed from many jet sources) and the physical processes responsible for this particle acceleration; the radiative processes giving rise to the observed multi-wavelength emission; and the topology of magnetic fields and their role in the jet collimation and particle acceleration processes. This chapter reviews the main knowns and unknowns in our current understanding of relativistic jets, in the context of the main model ingredients for Galactic and extragalactic jet sources. It discusses aspects specific to active Galactic nuclei (especially blazars) and microquasars, and then presents a comparative discussion of similarities and differences between them.

  16. The MIXR sample: AGN activity versus star formation across the cross-correlation of WISE, 3XMM, and FIRST/NVSS

    NASA Astrophysics Data System (ADS)

    Mingo, B.; Watson, M. G.; Rosen, S. R.; Hardcastle, M. J.; Ruiz, A.; Blain, A.; Carrera, F. J.; Mateos, S.; Pineau, F.-X.; Stewart, G. C.

    2016-11-01

    We cross-correlate the largest available mid-infrared (Wide-field Infrared Survey Explorer - WISE), X-ray (3XMM) and radio (Faint Images of the Radio Sky at Twenty centimetres+NRAO VLA Sky Survey) catalogues to define the MIXR sample of AGN and star-forming galaxies. We pre-classify the sources based on their positions on the WISE colour/colour plot, showing that the MIXR triple selection is extremely effective to diagnose the star formation and AGN activity of individual populations, even on a flux/magnitude basis, extending the diagnostics to objects with luminosities and redshifts from SDSS DR12. We recover the radio/mid-IR star formation correlation with great accuracy, and use it to classify our sources, based on their activity, as radio-loud and radio-quiet active galactic nuclei (AGN), low excitation radio galaxies/low ionization nuclear emission line regions, and non-AGN galaxies. These diagnostics can prove extremely useful for large AGN and galaxy samples, and help develop ways to efficiently triage sources when data from the next generation of instruments becomes available. We study bias in detail, and show that while the widely used WISE colour selections for AGN are very successful at cleanly selecting samples of luminous AGN, they miss or misclassify a substantial fraction of AGN at lower luminosities and/or higher redshifts. MIXR also allows us to test the relation between radiative and kinetic (jet) power in radio-loud AGN, for which a tight correlation is expected due to a mutual dependence on accretion. Our results highlight that long-term AGN variability, jet regulation, and other factors affecting the Q/Lbol relation, are introducing a vast amount of scatter in this relation, with dramatic potential consequences on our current understanding of AGN feedback and its effect on star formation.

  17. 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

  18. 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.

  19. 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.

  20. EUV energy distributions of accretion disks in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Storzer, H.; Hauschildt, P. H.

    1994-01-01

    We have calculated UV/EUV (300 A less than or = lambda less than or = 1500 A) continuous energy distributions of accretion disks in the centers of active galactic nuclei (AGNs) for disk luminosities in the range 0.1 L(sub Edd) and central masses ranging from 10(exp 8) solar mass to 10(exp 10) solar mass. The vertical gas pressure structure of the disk is obtained analytically, the temperature stratification and the resulting continuum radiation fields are calculated numerically. We show that weak Lyman edges are an intrinsic feature of such disks. The strength of the H I Lyman edge decreases for increasing accretion rate and fixed mass of the central black hole. It increases for increasing central mass and fixed luminosity in terms of the Eddington luminosity.

  1. A New Cosmological Distance Measure Using Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

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

    2011-10-01

    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 ~ 4, where variations of dark energy and alternate gravity theories can be probed.

  2. 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.

  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. Active galactic nuclei horizons from the gamma-ray perspective

    NASA Astrophysics Data System (ADS)

    Taylor, Andrew M.

    2017-08-01

    Recent results in the field of high energy active galactic nuclei (AGN) astrophysics, benefiting from improvements to gamma-ray instruments and observational strategies, have revealed a surprising wealth of unexpected phenomena. These developments have been brought about both through observational efforts to discover new very high energy gamma-ray emitters, as well as from further in-depth observations of previously detected and well studied objects. I here focus specifically on the discovery of repeated temporal structures observed in AGN lightcurves, and new hard spectral components within the spectral energy distributions of other AGN systems. The challenges that these new features place on the modeling of the sources are highlighted, along with some reflections on what these results tell us about the underlying nature of the emission processes at play.

  5. 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.

  6. Variability Analysis and the Structure of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Krolik, Julian H.

    1998-01-01

    This five-year Long-Term Space Astrophysics grant provided the support for several major steps in advancing our knowledge of the internal structure of active galactic nuclei. The single largest portion of this program had to do with the development and application of techniques for "reverberation mapping", the use of spectral monitoring of several different bands related by radiation reprocessing to infer the internal geometry of sources. Major steps were taken in this regard, particularly in establishing the distribution in radius of emission line material, and in relating the apparent reprocessing of continuum bands to the underlying structure of the accretion disk. Another major effort built directly upon these results. Once the case for continuum reprocessing was made by the monitoring, it next behooved us to understand the spectral output of AGN as a result of this reprocessing. As a result, our view of continuum production in AGN is now much better focussed on the key problems. A third focus of effort had to do with the nature of X-ray variability in AGN, and what it can tell us about the dynamics of extremely hot material in the immediate outskirts of the supermassive black holes that form the central engines of active galactic nuclei. In addition to these primary efforts, this grant also supported many other, smaller projects. Several of these were demonstrations of how the material spewed out of AGN in relativistic.ets generate the radiation by which we observe them. J Finally, the portion of this study that had to do with continuum production by accretion disks in AGN led naturally to several papers in which new developments were presented having to do with "advection-dominated accretion disks", those disks in which accretion appears to proceed at a substantial rate, but in which radiation processes are weak.

  7. Variability Analysis and the Structure of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Krolik, Julian H.

    1998-01-01

    This five-year Long-Term Space Astrophysics grant provided the support for several major steps in advancing our knowledge of the internal structure of active galactic nuclei. The single largest portion of this program had to do with the development and application of techniques for 'reverberation mapping, the use of spectral monitoring of several different bands related by radiation reprocessing to infer the internal geometry of sources. Major steps were taken in d-ds regard, particularly in establishing the distribution in radius of emission line material, and in relating the apparent reprocessing of continuum bands to the underlying structure of the accretion disk. Another major effort built directly upon these results. Once the case for continuum reprocessing was made by the monitoring, it next behooved us to understand the spectral output of AGN as a result of this reprocessing. As a result, our view of continuum production in AGN is now much better focussed on the key problems. A third focus of effort had to do with the nature of X-ray variability in AGN, and what it can tell us about the dynamics of extremely hot material in the immediate outskirts of the supermassive black holes that form the central engines of active galactic nuclei. In addition to these primary efforts, this grant also supported many other, smaller projects. Several of these were demonstrations of how the material spewed out of AGN in relativistic jets generate the radiation by which we observe them. Finally, the portion of this study that had to do with continuum production by accretion disks in AGN led naturally to several papers in which new developments were presented having to do with 'advection-dominated accretion disks', those disks in which accretion appears to proceed at a substantial rate, but in which radiation processes are weak.

  8. 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.

  9. 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.

  10. Galactic Winds in Galaxies with Active Black Holes

    NASA Astrophysics Data System (ADS)

    Lee, Lin; Yesuf, Hassen Mohammed

    2017-01-01

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

  11. 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.

  12. Optically thin broad-line clouds in active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shields, Joseph C.; Ferland, Gary J.; Peterson, Bradley M.

    1995-01-01

    The broad-line region (BLR) in Seyfert galaxy nuclei exhibits correlated variations in continuum and emission-line luminosity that are qualitatively consistent with photoionization of ionization-bounded (optically thick) clouds. However, evidence is growing that a nonnegligible fraction of the BLR cloud population is optically thin to the Lyman continuum and fully ionized in hydrogen. We consider the implications of this nebular component for observed line emission and find that inclusion of thin clouds in photoionization calculations can resolve several outstanding puzzles of Seyfert variability, notably the behavior of the C IV lambda 1549/Ly-alpha ratio as a function of continuum luminosity. A similar population of thin clouds located along our line of sight can account for observed ultraviolet absorption features and 'warm absorber' behavior at X-ray energies. The Baldwin effect for active galaxies, a negative correlation between ultraviolet emission-line equivalent width and continuum luminosity, can also be explained in detail by a decrease in the covering factor of an optically thin component with increasing source luminosity. The luminosity dependence of covering factor may result from outflows of thin clouds that proceed more efficiently in intrinsically brighter sources. The presence of absorption features in active galactic nuclei (AGNs) that are blueshifted and attain the highest velocities in broad absorption line features associated with luminous QSOs would be consistent with this interpretation.

  13. 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

  14. A study of warm absorbers in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Ashton, Ceri Ellen

    This thesis explores the 'warm absorber' phenomenon observed in Active Galactic Nuclei (AGN). Warm absorbers are clouds of ionised gas within AGN, that cause absorption at soft X-ray wavelengths. They are observed in half of all Type 1 AGN, hence they play an important part in the framework of our under standing of Active Galactic Nuclei. Observations with the satellite XMM-Newton have given us the highest signal-to-noise data yet. XMM-Newton observations of the quasars PG 1114+445 and PG 1309+355 are studied. Both quasars exhibit evidence for absorption by warm material in the line-of-sight. We define a 'phase' of absorption to have a single ionisation param eter and column density. From fits to the data, the absorption in PG 1114+445 is found to be in two phases, a 'hot' phase with a log ionisation parameter f of 2.57 and a column of 1022 cm-2, and a 'cooler' one with log f of 0.83 and a column of 1021 cm-2. The absorption in PG 1309+355 consists of a single phase, with log f of 1.87 and a column of 1021 cm-2. The absorbing gas lies at distances of 1019 - 1022 cm from the continuum radiation sources in these AGN, suggesting origins in a wind emanating from a molecular torus, according to the 'Standard Model' of AGN. The kinetic luminosities of the outflowing absorbers represent insignificant fractions (< 10 3) of the energy budgets of the AGN. Using data for the Seyfert 1 H 0557 385, the warm absorption is characterised by two phases, a phase with log £ of 0.48 and a column of 1021 cm-2, and a phase with log f of 1.63 and a column of 1022 cm-2. Neutral absorption is also present in the source, and possible origins for this are discussed. For a large sample, observations of warm absorbers are collated and compared with models.

  15. 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.

  16. 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

    2012-05-09

    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.

  17. 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.

  18. 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.

  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. BARYON LOADING OF ACTIVE GALACTIC NUCLEUS JETS MEDIATED BY NEUTRONS

    SciTech Connect

    Toma, K.; Takahara, F.

    2012-08-01

    Plasmas of geometrically thick, black hole (BH) accretion flows in active galactic nuclei (AGNs) are generally collisionless for protons, and involve magnetic field turbulence. Under such conditions a fraction of protons can be accelerated stochastically and create relativistic neutrons via nuclear collisions. These neutrons can freely escape from the accretion flow and decay into protons in the dilute polar region above the rotating BH to form relativistic jets. We calculate geometric efficiencies of the neutron energy and mass injections into the polar region, and show that this process can deposit luminosity as high as L{sub j}{approx}2 Multiplication-Sign 10{sup -3} M-dot c{sup 2} and mass loading M-dot{sub j}{approx}6 Multiplication-Sign 10{sup -4} M-dot for the case of the BH mass M {approx} 10{sup 8} M{sub Sun }, where M-dot is the mass accretion rate. The terminal Lorentz factors of the jets are {Gamma} {approx} 3, and they may explain the AGN jets having low luminosities. For higher luminosity jets, which can be produced by additional energy inputs such as Poynting flux, the neutron decay still can be a dominant mass loading process, leading to, e.g., {Gamma} {approx} 50 for L{sub j,tot}{approx}3 Multiplication-Sign 10{sup -2} M-dot c{sup 2}.

  2. 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.

  3. 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.

  4. Simulating electromagnetic cascades in magnetospheres of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Wendel, Christoph; Glawion, Dorit; Shukla, Amit; Mannheim, Karl

    2017-01-01

    Context: At the low accretion-rates typical for BL Lac-objects, magnetospheres of active galactic nuclei can develop vacuum gaps with strong electric fields accelerating charged seed particles parallel to the magnetic fields up to ultra-relativistic energies. The seed particles sustain electromagnetic cascades by inverse-Compton-scattering and subsequent pair-production in soft background-radiation-fields from the accretion-disk and/or photo-ionised clouds, along the direction of the primary particle beams. Method: The one-dimensional kinetic equation describing this linear inverse-Compton-Klein-Nishina-pair-cascade is inferred. We have developed a novel code, that can numerically solve this kinetic equation for an ample variety of input-parameters. By this, quasi-stationary particle- and photon-spectra are obtained. Application: We use the code to model the cascaded interaction of electrons, that have been accelerated in a vacuum gap in the magnetosphere of Mrk 501, with Lyman-alpha-photons. The resulting spectrum on top of a synchrotron-self-Compton-background can cause a narrow TeV-bump in the spectrum of of Mrk 501.

  5. Microvariabilty in Active Galactic Nuclei at 1420 MHz

    NASA Astrophysics Data System (ADS)

    Atwood, James W.

    2006-12-01

    Active Galactic Nuclei (AGNs) are some of the most distant objects known in the universe. Quasars, blazers, 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 including long term (years or decades), intraday (days or weeks), and very short periods (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 the microvariability in the atomic hydrogen line at 1420 MHz we may be able to determine if the variability is due the internal processes of these objects or due to the intervening medium, and to provide insight into the nature and process of the AGN central engines. Initial observations of a set of target AGNs have been undertaken. These data sets will be correlated with simultaneous optical (Bell observatory) and gamma ray (GLAST) observations to produce broad band, multiwavelength observations of a target set of AGNs. This project is supported by the Kentucky Space Grants Consortium.

  6. 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.

  7. 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.

  8. Dusty Winds in Active Galactic Nuclei: Reconciling Observations with Models

    NASA Astrophysics Data System (ADS)

    Hönig, Sebastian F.; Kishimoto, Makoto

    2017-04-01

    This Letter presents a revised radiative transfer model for the infrared (IR) emission of active galactic nuclei (AGNs). While current models assume that the IR is emitted from a dusty torus in the equatorial plane of the AGNs, spatially resolved observations indicate that the majority of the IR emission from ≲100 pc in many AGNs originates from the polar region, contradicting classical torus models. The new model CAT3D-WIND builds upon the suggestion that the dusty gas around the AGNs consists of an inflowing disk and an outflowing wind. Here, it is demonstrated that (1) such disk+wind models cover overall a similar parameter range of observed spectral features in the IR as classical clumpy torus models, e.g., the silicate feature strengths and mid-IR spectral slopes, (2) they reproduce the 3–5 μm bump observed in many type 1 AGNs unlike torus models, and (3) they are able to explain polar emission features seen in IR interferometry, even for type 1 AGNs at relatively low inclination, as demonstrated for NGC3783. These characteristics make it possible to reconcile radiative transfer models with observations and provide further evidence of a two-component parsec-scale dusty medium around AGNs: the disk gives rise to the 3–5 μm near-IR component, while the wind produces the mid-IR emission. The model SEDs will be made available for download.

  9. 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.

  10. 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.

  11. Investigating the Structure of Active Galactic Nuclei: The Dusty Torus

    NASA Astrophysics Data System (ADS)

    Stalevski, Marko

    2012-11-01

    Active galactic nuclei Nowadays it is widely accepted that every massive galaxy harbors a supermassive black hole (SMBH) at its center. A number of apparent correlations between SMBH mass and host galaxy structural and dynamical properties have been observed. The correlation between the masses of SMBHs and their host galactic bulges suggest a link between their growth (Kormendy & Richstone, 1995; Kormendy & Gebhardt, 2001). Active galactic nucleus (AGN) represents a phase in the life of a galaxy, during which the SMBH growth is directly observable. The term AGN encompasses a variety of energetic phenomena in galactic centers triggered by the matter spiralling into a SMBH at a relatively high rate. The radiation coming from AGNs originates in the conversion of gravitational potential energy into thermal energy as matter spirals towards the SMBH through an accretion disk (Lynden- Bell, 1969). Their luminosity can be up to 10000 greater then the total luminosity of a normal galaxy. The radiated AGN continuum covers a broad range of spectrum, from the X to radio domain, it is partially polarized and variable in time. Radiation from the central engine is ionizing the surrounding medium, creating conditions for the strong emission line spectrum, superimposed on the continuum. Sometimes, highly collimated and fast outflows (“jets”) emerge perpendicular to the accretion disk. Since the discovery of Keel (1980) that the orientation of Seyfert 1 galaxies is not random, it xxx has been recognized that the appearance of an AGN varies with the viewing angle. This has led to the picture of “orientation unification” (see Antonucci, 1993; Urry & Padovani, 1995) where the structure of AGNs is believed to be basically similar but what we see is a strong function of orientation (see Fig. 9). In this unified model, the central black hole is surrounded by a geometrically-thin accretion disk which is the source of the strong X-ray emission and UV/optical continuum (see Jovanovic

  12. 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).

  13. FERMI Observations of TeV-Selected Active Galactic Nuclei

    DOE PAGES

    Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

    2009-12-04

    Here, 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 thirdmore » 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. Finally, 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.« less

  14. Momentum Driving: Which Physical Processes Dominate Active Galactic Nucleus Feedback?

    NASA Astrophysics Data System (ADS)

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

    2010-10-01

    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 η ={\\dot{M}_outf}/{\\dot{M}_acc}= {2 ɛ_wc^2}/{v_w^2} where epsilonw (≡ \\dot{E}_w/(\\dot{M}_accc^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 η, and many prior treatments have essentially assumed that η = 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 1010 M 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 epsilonw <~ 10-4.

  15. The Intermediate-line Region in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Adhikari, T. P.; Różańska, A.; Czerny, B.; Hryniewicz, K.; Ferland, G. J.

    2016-11-01

    We show that the recently observed suppression of the gap between the broad-line region (BLR) and the narrow-line region (NLR) in some active galactic nuclei (AGNs) can be fully explained by an increase of the gas density in the emitting region. Our model predicts the formation of the intermediate-line region (ILR) that is observed in some Seyfert galaxies by the detection of emission lines with intermediate-velocity FWHM ˜ 700-1200 km s-1. These lines are believed to be originating from an ILR located somewhere between the BLR and NLR. As was previously proved, the apparent gap is assumed to be caused by the presence of dust beyond the sublimation radius. Our computations with the use of the cloudy photoionization code show that the differences in the shape of the spectral energy distribution from the central region of AGNs do not diminish the apparent gap in the line emission in those objects. A strong discontinuity in the line emission versus radius exists for all lines at the dust sublimation radius. However, increasing the gas density to ˜{10}11.5 cm-3 at the sublimation radius provides the continuous line emission versus radius and fully explains the recently observed lack of apparent gap in some AGNs. We show that such a high density is consistent with the density of upper layers of an accretion disk atmosphere. Therefore, the upper layers of the disk atmosphere can give rise to the formation of observed emission-line clouds.

  16. Testing Unification Models in Dual Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Muller-Sanchez, Francisco

    Dual active galactic nuclei (AGNs), which are kpc-scale separation AGN pairs in galaxy mergers, are ideal targets for testing unification models and models of galaxy evolution. By definition, the AGN nature of the two nuclei suggests that they must be consistent with standard unification models (i.e, a dusty torus obscures the central engine in type 2 AGN). At the same time, they are the result of merger-induced nuclear activity. Galaxy evolution models suggest that merger-induced AGNs are heavily obscured for long periods by the high gas densities powering them. Eventually, feedback drives away material, creating a brief window in time in which the AGN is not obscured. Therefore, in these models, there is no need for a small-scale torus. We are constructing for the first time the spectral energy distributions (SEDs) of the two AGNs in dual AGN systems using data from Hubble and Chandra telescopes, in combination with VLA, Keck and VLT data. However, a critical missing component is dust emission at 30-40 microns, which can only be achieved by SOFIA. We propose FORCAST 31.5 and 37.1 microns observations of the complete sample of 5 confirmed dual AGNs with angular separations >3.5". As suggested by current models, the best wavelength to detect thermal emission from a torus would be between 30-40 microns, where both the non-thermal core and the stellar emission sharply decline, and the torus emission peaks. Thus, FORCAST provides 1) the best angular resolution between 30-40 microns of the current suite of instruments, crucial to separate the emission from the two AGNs, and 2) the largest constraining power for torus models, crucial to characterize the properties of the torus in AGNs.

  17. The OPTX Project. V. Identifying Distant Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Trouille, L.; Barger, A. J.; Tremonti, C.

    2011-11-01

    The Baldwin, Phillips, and Terlevich emission-line ratio diagnostic ([O III]/Hβ versus [N II]/Hα, hereafter BPT diagram) efficiently separates galaxies whose signal is dominated by star formation (BPT-SF) from those dominated by active galactic nucleus (AGN) activity (BPT-AGN). Yet this BPT diagram is limited to z < 0.5, the redshift at which [N II]λ6584 leaves the optical spectral window. Using the Sloan Digital Sky Survey (SDSS), we construct a new diagnostic, or TBT diagram, that is based on rest-frame g - z color, [Ne III]λ3869, and [O II]λλ3726 + 3729 and can be used for galaxies out to z < 1.4. The TBT diagram identifies 98.7% of the SDSS BPT-AGN as TBT-AGN and 97% of the SDSS BPT-SF as TBT-SF. Furthermore, it identifies 97% of the OPTX Chandra X-ray-selected AGNs as TBT-AGN. This is in contrast to the BPT diagram, which misidentifies 20% of X-ray-selected AGNs as BPT-SF. We use the Great Observatories Origins Deep Survey North and Lockman Hole galaxy samples, with their accompanying deep Chandra imaging, to perform X-ray and infrared stacking analyses to further validate our TBT-AGN and TBT-SF selections; that is, we verify the dominance of AGN activity in the former and star formation activity in the latter. Finally, we address the inclusion of the majority of the BPT-comp (sources lying between the BPT-SF and BPT-AGN regimes) in our TBT-AGN regime. We find that the stacked BPT-comp source is X-ray hard (langΓeffrang = 1.0+0.4 -0.4) and has a high X-ray luminosity to total infrared luminosity ratio. This suggests that, on average, the X-ray signal in BPT-comp is dominated by obscured or low accretion rate AGN activity rather than by star formation, supporting their inclusion in the TBT-AGN regime. 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

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  19. 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.

  20. Fermi Large Area Telescope Observations Of Misaligned Active Galactic Nuclei

    DOE PAGES

    Abdo, A. A.

    2010-08-13

    Analysis is presented for 15 months of data taken with the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope for 11 non-blazar active galactic nuclei (AGNs), including seven FRI radio galaxies and four FRII radio sources consisting of two FRII radio galaxies and two steep spectrum radio quasars. The broad line FRI radio galaxy 3C 120 is reported here as a γ-ray source for the first time. The analysis is based on directional associations of LAT sources with radio sources in the 3CR, 3CRR, and MS4 (collectively referred to as 3C-MS) catalogs. Seven of the eleven LAT sourcesmore » associated with 3C-MS radio sources have spectral indices larger than 2.3 and, except for the FRI radio galaxy NGC 1275 that shows possible spectral curvature, are well described by a power law. No evidence for time variability is found for any sources other than NGC 1275. The γ-ray luminosities of FRI radio galaxies are significantly smaller than those of the BL Lac objects detected by the LAT, whereas the γ-ray luminosities of the FRII sources are quite similar to those of FSRQs, which could reflect different beaming factors for the γ-ray emission. A core dominance (CD) study of the 3CRR sample indicates that sources closer to the jet axis are preferentially detected with the Fermi LAT, insofar as the γ-ray-detected misaligned AGNs have larger CD at a given average radio flux. The results are discussed in view of the AGN unification scenario.« less

  1. 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.

  2. Spatially Offset Active Galactic Nuclei. II. Triggering in Galaxy Mergers

    NASA Astrophysics Data System (ADS)

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

    2017-04-01

    Galaxy mergers are likely to play a role in triggering active galactic nuclei (AGNs), but the conditions under which this process occurs are poorly understood. In Paper I, we constructed a sample of spatially offset X-ray AGNs that represent galaxy mergers hosting a single AGN. In this paper, we use our offset AGN sample to constrain the parameters that affect AGN observability in galaxy mergers. We also construct dual-AGN samples with similar selection properties for comparison. We find that the offset AGN fraction shows no evidence for a dependence on AGN luminosity, while the dual-AGN fractions show stronger evidence for a positive dependence, suggesting that the merger events forming dual AGNs are more efficient at instigating accretion onto supermassive black holes than those forming offset AGNs. We also find that the offset and dual-AGN fractions both have a negative dependence on nuclear separation and are similar in value at small physical scales. This dependence may become stronger when restricted to high AGN luminosities, although a larger sample is needed for confirmation. These results indicate that the probability of AGN triggering increases at later merger stages. This study is the first to systematically probe down to nuclear separations of <1 kpc (∼0.8 kpc) and is consistent with predictions from simulations that AGN observability peaks in this regime. We also find that the offset AGNs are not preferentially obscured compared to the parent AGN sample, suggesting that our selection may be targeting galaxy mergers with relatively dust-free nuclear regions.

  3. IUEAGN: A database of ultraviolet spectra of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Pike, G.; Edelson, R.; Shull, J. M.; Saken, J.

    1993-01-01

    In 13 years of operation, IUE has gathered approximately 5000 spectra of almost 600 Active Galactic Nuclei (AGN). In order to undertake AGN studies which require large amounts of data, we are consistently reducing this entire archive and creating a homogeneous, easy-to-use database. First, the spectra are extracted using the Optimal extraction algorithm. Continuum fluxes are then measured across predefined bands, and line fluxes are measured with a multi-component fit. These results, along with source information such as redshifts and positions, are placed in the IUEAGN relational database. Analysis algorithms, statistical tests, and plotting packages run within the structure, and this flexible database can accommodate future data when they are released. This archival approach has already been used to survey line and continuum variability in six bright Seyfert 1s and rapid continuum variability in 14 blazars. Among the results that could only be obtained using a large archival study is evidence that blazars show a positive correlation between degree of variability and apparent luminosity, while Seyfert 1s show an anti-correlation. This suggests that beaming dominates the ultraviolet properties for blazars, while thermal emission from an accretion disk dominates for Seyfert 1s. Our future plans include a survey of line ratios in Seyfert 1s, to be fitted with photoionization models to test the models and determine the range of temperatures, densities and ionization parameters. We will also include data from IRAS, Einstein, EXOSAT, and ground-based telescopes to measure multi-wavelength correlations and broadband spectral energy distributions.

  4. SPECTROSCOPICALLY SELECTED SPITZER 24 {mu}m ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Choi, P. I.; Yan Lin; Helou, G.; Storrie-Lombardi, L. J.; Shim, H.; Fadda, D.; Im, M.

    2011-05-01

    We investigate the active galactic nucleus (AGN) sub-population of a 24 {mu}m flux-limited galaxy sample in the Spitzer Extragalactic First Look Survey. Using deep Keck optical spectroscopy and a series of emission-line diagnostics, we identify AGN-dominated systems over broad redshift 0 < z < 3.5 and luminosity 9 < log (L{sub TIR}) < 14 ranges, with sample means of (z) = 0.85 and (log (L{sub TIR})) = 11.5. We find that down to the flux limits of our Spitzer MIPS sample (f{sub 24} > 200 {mu}Jy), 15%-20% of sources exhibit strong AGN signatures in their optical spectra. At this flux limit, the AGN population accounts for as much as 25%-30% of the integrated 24 {mu}m flux. This corresponds to an MIR AGN contribution {approx}2-3 x greater than that found in ISOCAM 15 {mu}m studies that used X-ray AGN identifications. Based on our spectroscopically selected AGN sample, we also investigate the merits of Infrared Array Camera (IRAC) color selection for AGN identification. Our comparison reveals that although there is considerable overlap, a significant fraction of spectroscopic AGNs are not identifiable based on their MIR colors alone. Both the measured completeness and reliability of the IRAC color selections are found to be strongly dependent on the MIR flux limit. Finally, our spectroscopic AGN sample implies as much as a 3 x higher AGN surface density at high redshift (z > 1.2) than that of recent optical surveys at comparable optical flux limits, suggestive of a population of heavily obscured, optical/UV reddened AGNs.

  5. The Evolution of Active Galactic Nuclei and their Spins

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

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

  6. Gamma-ray properties of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Schoenfelder, V.

    1994-01-01

    Recent observations by the Compton Observatory (CGRO) have increased our knowledge about the gamma-ray emission from Active Galactic Nuclei (AGN) considerably. The three most important findings of CGRO with respect to AGNs are: first, no Seyfert 1 galaxy has been found to show emission above 500 keV. The by far strongest Seyfert 1 galaxy NGC 4151 shows a spectrum which falls off exponentially with an e-folding energy of 39 keV between 65 and 500 keV. OSSE so far has detected or has indications of detections for seven additional Seyfert 1 galaxies, which, however, all show very weak hard X-ray emission compared to NGC 4151. No annihilation feature has been seen from any Seyfert galaxy to this date. Second, the radio galaxy Cen A shows a power-law energy spectrum from hard X-ray energies of about 150 keV to at least 3 MeV. It has not been seen at EGRET-energies. Third, a new class of AGN was discovered at energies above 100 MeV by EGRET. The power of these objects in gamma-rays can dominate the luminosity in other spectral ranges. These objects are associated with extragalactic sources that have blazar properties. The high-energy gamma-ray emission is probably produced in relativistically outflowing jets. At hard X-ray energies the objects are rather weak. Spectral breaks at MeV energies were found by COMPTEL for three of these objects (3C 273, 3C 279, and PKS 0528+134).

  7. Investigating a model of optimized active galactic nucleus feedback

    NASA Astrophysics Data System (ADS)

    Pope, Edward C. D.

    2011-07-01

    The feedback heating from active galactic nuclei (AGNs) in massive galaxies and galaxy clusters can be thought of as a naturally occurring control system which plays a significant role in regulating both star formation rates and the X-ray luminosity of the surrounding hot gas. In the simplest case, negative feedback can be viewed as a system response that is 'optimized' to minimize deviations from equilibrium, such that the system rapidly evolves towards a steady state. However, a general solution of this form appears to be incompatible with radio observations which indicate intermittent AGN outbursts. Here, we explore an energetically favourable scenario in which feedback is required to both balance X-ray gas cooling and minimize the sum of the energy radiated by the gas and the energy injected by the AGN. This specification is equivalent to ensuring that AGN heating balances the X-ray gas cooling with the minimum black hole growth. It is shown that minimum energy heating occurs in discrete events and not at a continuous, constant level. Furthermore, systems with stronger feedback experience proportionally more powerful heating events, but correspondingly smaller duty cycles. Interpreting observations from this perspective would imply that stronger feedback occurs in less-massive objects - elliptical galaxies rather than galaxy clusters. One direct consequence of this effect would be that AGN heating events are sufficiently powerful to expel hot gas from the gravitational potential of a galaxy, but not a galaxy cluster, which is consistent with theoretical explanations for the steepening of the LX-T relation at temperatures below 1-2 keV.

  8. Surface Photometry of Reverberation-Mapped Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Bower, Gary A.

    2015-01-01

    I present a statistical analysis of the surface photometry obtained for a sample of Hubble Space Telescope (HST) archival images of the host galaxies containing active galactic nuclei (AGN), whose time-delay between continuum and broad emission line variations have been analyzed (i.e., reverberation mapping). For quiescent galaxies, strong correlations exist between central black hole mass and host galaxy structure. If there are similar correlations for AGN between central black hole masses derived from reverberation mapping and the host galaxy structure that I have derived from archival HST images, this would imply some validation of the assumptions underlying reverberation mapping concerning the structure, kinematics, and orientation of the broad line regions in AGN.The correlations for quiescent galaxies bewteen central black hole mass and host galaxy structure imply that there might be a strong causal connection between the formation and evolution of the black hole and the galaxy bulge. A current hypothesis is that bulges, black holes, and quasars formed, grew, or turned on as parts of the same process, in part because the collapse or merger of bulges might provide a rich fuel supply to a central black hole. One way of testing this hypothesis would be to plot AGN as a function of redshift on these correlations. However, two severe obstacles limit the ability to measure black hole masses in AGN using HST to analyze the central stellar and/or gas dynamics: (1) since spatial resolution becomes more limited at larger distances, only two reverberation-mapped AGN are close enough to Earth to render the analysis feasible, and (2) it isdifficult to obtain useful spectra of the stars and/or gas in the presence of the bright nonstellar nucleus. The most useful alternative is to exploit reverberation mapping, which uses the time delay in a given AGN between variations in the continuum emission and broad emission lines.

  9. X-Ray Eclipses of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Zhang, Fupeng; Yu, Qingjuan; Lu, Youjun

    2017-08-01

    X-ray variation is a ubiquitous feature of active galactic nuclei (AGNs); however, its origin is not well understood. In this paper, we show that the X-ray flux variations in some AGNs, and correspondingly, the power spectral densities (PSDs) of the variations, may be interpreted as being caused by absorptions of eclipsing clouds or clumps in the broad-line region (BLR) and the dusty torus. By performing Monte Carlo simulations for a number of plausible cloud models, we systematically investigate the statistics of the X-ray variations resulting from the cloud eclipsing and the PSDs of the variations. For these models, we show that the number of eclipsing events can be significant and the absorption column densities due to those eclipsing clouds can be in the range from 1021 to {10}24 {{cm}}-2, leading to significant X-ray variations. We find that the PSDs obtained from the mock observations for the X-ray flux and the absorption column density resulting from these models can be described by a broken double power law, similar to those directly measured from observations of some AGNs. The shape of the PSDs depend strongly on the kinematic structures and the intrinsic properties of the clouds in AGNs. We demonstrate that the X-ray eclipsing model can naturally lead to a strong correlation between the break frequencies (and correspondingly the break timescales) of the PSDs and the masses of the massive black holes (MBHs) in the model AGNs, which can be well consistent with the one obtained from observations. Future studies of the PSDs of the AGN X-ray (and possibly also the optical-UV) flux and column density variations may provide a powerful tool to constrain the structure of the BLR and the torus and to estimate the MBH masses in AGNs.

  10. Active Galactic Nuclei at the Smallest Scales: Infall and Obscuration

    NASA Astrophysics Data System (ADS)

    Storchi-Bergmann, T.

    2014-09-01

    Active Galactic Nuclei (AGN) probe crucial phases in the evolution of galaxies, which seem to regulate both the growth of the Supermassive Black Hole (SMBH) via mass accretion and of the galaxy via AGN feedback. The relevant physical processes occur at scales ranging from 10-6 parsecs (pc) (Event Horizon) through 10-3 pc (Accretion Disk), 10-2 pc (Broad Line Region—BLR), and 10-1-100 pc (Dusty Torus) to 101 -103 pc ( Narrow-Line Region—NLR). Studies using the technique of near-IR interferometry are already probing the dusty torus in the closest AGN. On larger scales (10-100 pc), observations with Integral Field Units (IFUs) at large (8m) telescopes are being used not only to map the usual outflows (feedback) observed in the NLR but also to look for inflows that feed the AGN. In the near-IR, observations with the Gemini instrument NIFS and Very Large Telescope instrument SINFONI reveal structures in hot (2000K) molecular hydrogen whose kinematics are dominated by rotation or inflow, suggesting that they are fueling the AGN. In the optical, Hubble Space Telescope imaging shows dusty spirals and filaments, interpreted as being tracers of fueling flows to the AGN, what has been confirmed in a few cases via optical IFU spectroscopy using ionized gas emission lines. These IFU observations are providing the first estimates of mass inflow rates to the AGN as well as the mapping of the inflow processes. These studies will be complemented in the near future with observations of the cold molecular gas with the Atacama Large Millimeter Array—ALMA. But further progress—to scales smaller than those of the torus, such as that of the BLR (0.01 pc), will only be possible using the technique of optical and near-infrared interferometry.

  11. Emission line galaxies and active galactic nuclei in WINGS clusters

    NASA Astrophysics Data System (ADS)

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

    2017-03-01

    We present the analysis of the emission line galaxies members of 46 low-redshift (0.04 < z < 0.07) clusters observed by WINGS (WIde-field Nearby Galaxy cluster Survey). Emission line galaxies were identified following criteria that are meant to minimize biases against non-star-forming galaxies and classified employing diagnostic diagrams. We examined the emission line properties and frequencies of star-forming galaxies, transition objects, and active galactic nuclei (AGNs: LINERs and Seyferts), unclassified galaxies with emission lines, and quiescent galaxies with no detectable line emission. A deficit of emission line galaxies in the cluster environment is indicated by both a lower frequency, and a systematically lower Balmer emission line equivalent width and luminosity with respect to control samples; this implies a lower amount of ionized gas per unit mass and a lower star formation rate if the source is classified as Hii region. A sizable population of transition objects and of low-luminosity LINERs (≈ 10-20% of all emission line galaxies) are detected among WINGS cluster galaxies. These sources are a factor of ≈1.5 more frequent, or at least as frequent, as in control samples with respect to Hii sources. Transition objects and LINERs in clusters are most affected in terms ofline equivalent width by the environment and appear predominantly consistent with so-called retired galaxies. Shock heating can be a possible gas excitation mechanism that is able to account for observed line ratios. Specific to the cluster environment, we suggest interaction between atomic and molecular gas and the intracluster medium as a possible physical cause of line-emitting shocks. The data whose description is provided in Table B.1, and emission line catalog of the WINGS database are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/599/A83

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

    NASA Astrophysics Data System (ADS)

    Ryan, Christopher J.

    2009-06-01

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

  13. 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.

  14. Active Galactic Nuclei and X-ray Ovservations

    NASA Astrophysics Data System (ADS)

    Vasylenko, A. A.; Zhdanov, V. I.; Fedorova, E. V.

    2016-11-01

    Active galactic nuclei (AGN) are the brightest objects in the Universe and their brightness is mainly caused by accretion of m atter onto supermassive black holes (SMBH). This is the common reason of the AGN activity. However, every AGN has differences and fine features, which are the subject of an intensive investigation. The occurrence of such highly-relativistic objects as SMBH residing at the AGN core makes them an excellent laboratory for testing the fundamental physical theories. The X-rays and gamma-rays generated in a corona of an accretion disc around SMBH yield valuable information for these tests, the radiation in the range of 1-100 keV being at present the most informative source. However, there are a number of obstacles for such a study due to different physical processes that complicate the interpretation of observations in different bands of the electromagnetic radiation. In this paper, we review the current concepts concerning the structure of AGNs with a focus on the central part of these objects th at require relativistic theories for their understanding. The basic notions of the unified AGN schemes are considered; some modifications are reviewed. The paper contains the following sections. I. Introduction; II. Observational manifestations and classification of galaxies with active nuclei (II.A. Optical observations; II.B. Radio observations; II.C. X-ray data; II.D Infrared data; II.E. AGN anatomy with multywave data); III. AGN "central machine"; III.A. Black holes; III.B. Accretion disc types; III.C. Corona; III.D. AGN unified scheme); IV. Simulation X-ray AGN spectra (IV.A. The power-law contimuum and the exponential cut-off; IV.B. The absorption of X-rays; IV.C. Reflection; IV.D. Fe K a line; IV.E. Spin paradigm); V. AGN as a laboratory to test the fundamental interactions (V.A. Strong gravitational fields; V.B. Dynamic dark energy near compact astrophysical objects

  15. 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.

  16. 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.

  17. PAH features within few hundred parsecs of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Jensen, J. J.; Hönig, S. F.; Rakshit, S.; Alonso-Herrero, A.; Asmus, D.; Gandhi, P.; Kishimoto, M.; Smette, A.; Tristram, K. R. W.

    2017-09-01

    Spectral features from polycyclic aromatic hydrocarbon (PAH) molecules observed in the mid-infrared (mid-IR) range are typically used to infer the amount of recent and ongoing star formation on kiloparsec scales around active galactic nuclei (AGN) where more traditional methods fail. This method assumes that the observed PAH features are excited predominantly by star formation. With current ground-based telescopes and the upcoming James Webb Space Telescope, much smaller spatial scales can be probed and we aim at testing if this assumption still holds in the range of few tens to few hundreds of parsecs. For that, we spatially map the emitted 11.3 μm PAH surface flux as a function of distance from 0.4-4 arcsec from the centre in 28 nearby AGN using ground-based high-angular-resolution mid-IR spectroscopy. We detect and extract the 11.3 μm PAH feature in 13 AGN. The fluxes within each aperture are scaled to a luminosity-normalized distance from the nucleus to be able to compare intrinsic spatial scales of AGN radiation spanning about two orders of magnitude in luminosity. For this, we establish an empirical relation between the absorption-corrected X-ray luminosity and the sublimation radius in these sources. Once normalized, the radial profiles of the emitted PAH surface flux show similar radial slopes, with a power-law index of approximately -1.1, and similar absolute values, consistent within a factor of a few of each other as expected from the uncertainty in the intrinsic scale estimate. We interpret this as evidence that the profiles are caused by a common compact central physical process, either the AGN itself or circumnuclear star formation linked in strength to the AGN power. A photoionization-based model of an AGN exciting dense clouds in its environment can reproduce the observed radial slope and confirms that the AGN radiation field is strong enough to explain the observed PAH surface fluxes within ∼10-500 pc of the nucleus. Our results advice caution

  18. 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

  19. Characterizing the population of active galactic nuclei in dwarf galaxies

    NASA Astrophysics Data System (ADS)

    Baldassare, Vivienne F.; Reines, Amy E.; Gallo, Elena; Greene, Jenny E.

    2017-01-01

    Clues to super-massive black hole (BH) formation and growth reside in the population and properties of BHs in local dwarf galaxies. The masses of BHs in these systems are our best observational constraint on the masses of the first BH "seeds" at high redshift. Moreover, present-day dwarf galaxies are unlikely to have undergone major mergers, making them a relatively pristine testbed for studying triggers of BH accretion. However, in order to find BHs in dwarf galaxies outside the Local Group, it is necessary to search for signatures of accretion, i.e., active galactic nuclei (AGN). Until recently, only a handful of dwarf galaxies were known to contain AGN. However, large surveys such as the SDSS have led to the production of samples of over a hundred dwarf galaxies with AGN signatures (see e.g., Reines et al. 2013). My dissertation work has involved in-depth, multi-wavelength follow-up of nearby (z<0.055) dwarf galaxies with optical spectroscopic AGN signatures in SDSS.I analyzed high resolution spectra of dwarf galaxies with narrow-line AGN, which led to the discovery of a 50,000 MSun BH in the nucleus of RGG 118 - the smallest BH yet reported in a galaxy nucleus (Baldassare et al. 2015). I also used multi-epoch optical spectroscopy to study the nature of broad H-alpha emission in dwarf galaxies. A characteristic signature of dense gas orbiting around a BH, broad emission can also be produced by transient stellar processes. I showed that broad H-alpha in star-forming dwarf galaxies fades over a baseline of 5-10 years, and is likely produced by e.g., a Type II SN as opposed to an AGN. However, broad emission in dwarf galaxies with AGN/composite narrow lines is persistent and consistent across observations, suggesting an AGN origin (Baldassare et al. 2016). Finally, I analyzed X-ray and UV observations of dwarf galaxies with broad and narrow-line AGN signatures. All targets had nuclear X-ray detections at levels significantly higher than expected from X-ray binaries

  20. On the Feedback Efficiency of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Kurosawa, Ryuichi; Proga, Daniel; Nagamine, Kentaro

    2009-12-01

    We measure and analyze the energy, momentum, and mass feedback efficiencies due to radiation from active galactic nuclei (AGNs) in relatively large-scale outflows (from ~0.01 to ~10 pc). Our measurements are based on the two-dimensional (axisymmetric) and time-dependent radiation-hydrodynamical simulations recently presented in Kurosawa & Proga. In that paper, we studied outflows from a slowly rotating (sub-Keplerian) infalling gas driven by the energy and pressure of the radiation emitted by the AGNs. These simulations follow the dynamics of gas under the influence of the gravity of the central 108 M sun black hole (BH) on scales from ~0.01 to ~10 pc. They self-consistently couple the accretion luminosity with the mass inflow rate at the smallest radius (our proxy for the mass-accretion rate, \\dot{M}_{a}). Over 30 simulations have been performed to investigate how the results depend on the gas density at the outer radius, ρo. A key feature of these simulations is that the radiation field and consequently the gas dynamics are axisymmetric, but not spherically symmetric. Therefore, the gas inflow and outflow can occur at the same time. We compare our \\dot{M}_{a}-ρo relation with that predicted by the Bondi accretion model. For high luminosities comparable to the Eddington limit, the power-law fit (\\dot{M}_{a} ∝ ρ _{o}^{q}) to our models yields q ≈ 0.5 instead of q = 1.0, which is predicted by the Bondi model. This difference is caused by the outflows which are important for the overall mass budget at high luminosities. The maximum momentum and mass feedback efficiencies found in our models are ~10-2 and ~10-1, respectively. However, the outflows are much less important energetically: the thermal and kinetic powers in units of the radiative luminosity are ~10-5 and ~10-4, respectively. In addition, the efficiencies do not increase monotonically with the accretion luminosity but rather peak around the Eddington limit beyond which a steady-state disk

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

    NASA Astrophysics Data System (ADS)

    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 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.

  2. A new perspective on the radio active zone at the Galactic center - feedback from nuclear activities

    NASA Astrophysics Data System (ADS)

    Zhao, J.-H.; Morris, M. R.; Goss, W. M.

    2014-05-01

    Based on our deep image of Sgr A using broadband data observed with the VLA† at 6 cm, we present a new perspective of the radio bright zone at the Galactic center. We further show the radio detection of the X-ray Cannonball, a candidate neutron star associated with the Galactic center SNR Sgr A East. The radio image is compared with the Chandra X-ray image to show the detailed structure of the radio counterparts of the bipolar X-ray lobes. The bipolar lobes are likely produced by the winds from the activities within Sgr A West, which could be collimated by the inertia of gas in the CND, or by the momentum driving of Sgr A*; and the poloidal magnetic fields likely play an important role in the collimation. The less-collimated SE lobe, in comparison to the NW one, is perhaps due to the fact that the Sgr A East SN might have locally reconfigured the magnetic field toward negative galactic latitudes. In agreement with the X-ray observations, the time-scale of ˜1 × 104 yr estimated for the outermost radio ring appears to be comparable to the inferred age of the Sgr A East SNR.

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

    NASA Astrophysics Data System (ADS)

    Zhao, Jun-Hui; Morris, Mark R.; Goss, W. M.

    2013-11-01

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

  4. ON THE FEEDBACK EFFICIENCY OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Kurosawa, Ryuichi; Proga, Daniel; Nagamine, Kentaro E-mail: dproga@physics.unlv.ed

    2009-12-10

    We measure and analyze the energy, momentum, and mass feedback efficiencies due to radiation from active galactic nuclei (AGNs) in relatively large-scale outflows (from approx0.01 to approx10 pc). Our measurements are based on the two-dimensional (axisymmetric) and time-dependent radiation-hydrodynamical simulations recently presented in Kurosawa and Proga. In that paper, we studied outflows from a slowly rotating (sub-Keplerian) infalling gas driven by the energy and pressure of the radiation emitted by the AGNs. These simulations follow the dynamics of gas under the influence of the gravity of the central 10{sup 8} M {sub sun} black hole (BH) on scales from approx0.01 to approx10 pc. They self-consistently couple the accretion luminosity with the mass inflow rate at the smallest radius (our proxy for the mass-accretion rate, M-dot{sub a}). Over 30 simulations have been performed to investigate how the results depend on the gas density at the outer radius, rho{sub o}. A key feature of these simulations is that the radiation field and consequently the gas dynamics are axisymmetric, but not spherically symmetric. Therefore, the gas inflow and outflow can occur at the same time. We compare our M-dot{sub a}-rho{sub o} relation with that predicted by the Bondi accretion model. For high luminosities comparable to the Eddington limit, the power-law fit M-dot{sub a}propor torho{sub o}{sup q} to our models yields q approx 0.5 instead of q = 1.0, which is predicted by the Bondi model. This difference is caused by the outflows which are important for the overall mass budget at high luminosities. The maximum momentum and mass feedback efficiencies found in our models are approx10{sup -2} and approx10{sup -1}, respectively. However, the outflows are much less important energetically: the thermal and kinetic powers in units of the radiative luminosity are approx10{sup -5} and approx10{sup -4}, respectively. In addition, the efficiencies do not increase monotonically with the

  5. Outflow and Accretion Physics in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    McGraw, Sean Michael

    2016-09-01

    This dissertation focuses on placing observational constraints on outflows and accretion disks in active galactic nuclei (AGN) for the purpose of better understanding the physics of super-massive black holes (SMBHs) and their evolution with the host galaxy over cosmic time. Quasar outflows and their importance in SMBH-host galaxy co-evolution can be further understood by analyzing broad absorption lines (BALs) in rest-frame UV spectra that trace a range of wind conditions. We quantify the properties of the flows by conducting BAL variability studies using multiple-epoch spectra acquired primarily from MDM Observatory and from the Sloan Digital Sky Survey. Iron low-ionization BALs (FeLoBALs) are a rare type of outflow that may represent a transient phase in galaxy evolution, and we analyze the variations in 12 FeLoBAL quasars with redshifts between 0.7 ≤ z ≤ 1.9 and rest frame timescales between ˜10 d to 7.6 yr. We investigate BAL variability in 71 quasar outflows that exhibit P V absorption, a tracer of high column density gas (i.e. NH ≥ 1022 cm -2), in order to quantify the energies and momenta of the flows. We also characterize the variability patterns of 26 quasars with mini-BALs, an interesting class of absorbers that may represent a distinct phase in the evolution of outflows. Low-luminosity AGN (LLAGN) are important objects to study since their prominence in the local Universe suggest a possible evolution from the quasar era, and their low radiative outputs likely indicate a distinct mode of accretion onto the SMBH. We probe the accretion conditions in the LLAGN NGC 4203 by estimating the SMBH mass, which is obtained by modeling the 2-dimensional velocity field of the nebular gas using spectra from the Hubble Space Telescope. We detect significant BAL and mini-BAL variability in a subset of quasars from each of our samples, with measured rest-frame variability time-scales from days to years and over multiple years on average. Variable wavelength

  6. Discovery of the Recombining Plasma in the South of the Galactic Center: A Relic of the Past Galactic Center Activity?

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

    We report Suzaku results for soft X-ray emission to the south of the Galactic center (GC). The emission (hereafter "GC South") has an angular size of ~42' × 16' centered at (l, b) ~ (0.°0, - 1.°4) and is located in the largely extended Galactic ridge X-ray emission (GRXE). The X-ray spectrum of GC South exhibits emission lines from highly ionized atoms. Although the X-ray spectrum of the GRXE can be well fitted with a plasma in collisional ionization equilibrium (CIE), that of GC South cannot be fitted with a plasma in CIE, leaving hump-like residuals at ~2.5 and 3.5 keV, which are attributable to the radiative recombination continua of the K-shells of Si and S, respectively. In fact, GC South spectrum is well fitted with a recombination-dominant plasma model; the electron temperature is 0.46 keV while atoms are highly ionized (kT = 1.6 keV) in the initial epoch, and the plasma is now in a recombining phase at a relaxation scale (plasma density × elapsed time) of 5.3 × 1011 s cm-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 (~8 kpc distance). The size of the plasma, the mean density, and the thermal energy are estimated to be ~97 pc × 37 pc, 0.16 cm-3, and 1.6 × 1051 erg, respectively. We discuss possible origins of the recombination-dominant plasma as a relic of past activity in the GC region.

  7. 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.

  8. 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.

  9. 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.

  10. Anticorrelation of Variability Amplitude with X-Ray Luminosity for Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Bao, Gang; Abramowicz, Marek A.

    1996-07-01

    The bright-spot model for the short-term X-ray variability of active galactic nuclei predicts that, statistically, sources with larger luminosities should have smaller variability amplitudes. This quantitatively agrees with the analysis of the observational data from 12 high-quality EXOSAT long looks performed by Lawrence & Papadakis.

  11. 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.

  12. 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.

  13. 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.

  14. Identification of 1.4 Million Active Galactic Nuclei In the Mid-Infrared Using WISE Data

    DTIC Science & Technology

    2015-11-01

    IDENTIFICATION OF 1.4 MILLION ACTIVE GALACTIC NUCLEI IN THE MID-INFRARED USINGWISE DATA N. J. Secrest, R. P. Dudik, B. N. Dorland, N. Zacharias, V...accepted 2015 September 22; published 2015 October 28 ABSTRACT We present an all-sky sample of≈1.4 million active galactic nuclei (AGNs) meeting a two-color...galaxies – infrared: stars – galaxies: active – quasars: general Supporting material: machine-readable table 1. INTRODUCTION The International Celestial

  15. 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.

  16. Hot bubbles from active galactic nuclei as a heat source in cooling-flow clusters.

    PubMed

    Brüggen, Marcus; Kaiser, Christian R

    2002-07-18

    Hot, X-ray-emitting plasma permeates clusters of galaxies. The X-ray surface brightness often shows a peak near the centre of the cluster that is coincident with a drop in the entropy of the gas. This has been taken as evidence for a 'cooling flow', where the gas cools by radiating away its energy, and then falls to the centre. Searches for this cool gas have revealed significantly less than predicted, indicating that the mass deposition rate is much lower than expected. Most clusters with cooling flows, however, also host an active galactic nucleus at their centres. These active galactic nuclei can inflate large bubbles of hot plasma that subsequently rise through the cluster 'atmosphere', thus stirring the cooling gas and adding energy. Here we report highly resolved hydrodynamic simulations which show that buoyant bubbles increase the cooling time in the inner regions of clusters and significantly reduce the deposition of cold gas.

  17. 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.

  18. 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.

  19. CO-DARK Star Formation and Black Hole Activity in 3C 368 at Z = 1.131: Coeval Growth of Stellar and Supermassive Black Hole Masses

    NASA Astrophysics Data System (ADS)

    Lamarche, C.; Stacey, G.; Brisbin, D.; Ferkinhoff, C.; Hailey-Dunsheath, S.; Nikola, T.; Riechers, D.; Sharon, C. E.; Spoon, H.; Vishwas, A.

    2017-02-01

    We present the detection of four far-infrared fine-structure oxygen lines, as well as strong upper limits for the CO(2–1) and [N ii] 205 μm lines, in 3C 368, a well-studied radio-loud galaxy at z = 1.131. These new oxygen lines, taken in conjunction with previously observed neon and carbon fine-structure lines, suggest a powerful active galactic nucleus (AGN), accompanied by vigorous and extended star formation. A starburst dominated by O8 stars, with an age of ∼6.5 Myr, provides a good fit to the fine-structure line data. This estimated age of the starburst makes it nearly concurrent with the latest episode of AGN activity, suggesting a link between the growth of the supermassive black hole and stellar population in this source. We do not detect the CO(2–1) line, down to a level twelve times lower than the expected value for star-forming galaxies. This lack of CO line emission is consistent with recent star formation activity if the star-forming molecular gas has low metallicity, is highly fractionated (such that CO is photodissociated throughout much of the clouds), or is chemically very young (such that CO has not yet had time to form). It is also possible, although we argue it is unlikely, that the ensemble of fine-structure lines is emitted from the region heated by the AGN.

  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. 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.

  2. Modified viscosity in accretion disks. Application to Galactic black hole binaries, intermediate mass black holes, and active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Grzędzielski, Mikołaj; Janiuk, Agnieszka; Czerny, Bożena; Wu, Qingwen

    2017-07-01

    Aims: Black holes (BHs) surrounded by accretion disks are present in the Universe at different scales of masses, from microquasars up to the active galactic nuclei (AGNs). Since the work of Shakura & Sunyaev (1973, A&A, 24, 337) and their α-disk model, various prescriptions for the heat-production rate are used to describe the accretion process. The current picture remains ad hoc due the complexity of the magnetic field action. In addition, accretion disks at high Eddington rates can be radiation-pressure dominated and, according to some of the heating prescriptions, thermally unstable. The observational verification of their resulting variability patterns may shed light on both the role of radiation pressure and magnetic fields in the accretion process. Methods: We compute the structure and time evolution of an accretion disk, using the code GLADIS (which models the global accretion disk instability). We supplement this model with a modified viscosity prescription, which can to some extent describe the magnetisation of the disk. We study the results for a large grid of models, to cover the whole parameter space, and we derive conclusions separately for different scales of black hole masses, which are characteristic for various types of cosmic sources. We show the dependencies between the flare or outburst duration, its amplitude, and period, on the accretion rate and viscosity scaling. Results: We present the results for the three grids of models, designed for different black hole systems (X-ray binaries, intermediate mass black holes, and galaxy centres). We show that if the heating rate in the accretion disk grows more rapidly with the total pressure and temperature, the instability results in longer and sharper flares. In general, we confirm that the disks around the supermassive black holes are more radiation-pressure dominated and present relatively brighter bursts. Our method can also be used as an independent tool for the black hole mass determination

  3. 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.

  4. 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.

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

    NASA Astrophysics Data System (ADS)

    Estrada-Piedra, T.; Torres-Papaqui, J. P.; Terlevich, R.; Fuentes, O.; Terlevich, E.

    2004-07-01

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

  6. 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.

  7. 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.

  8. High-resolution infrared observations of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Pott, Jörg-Uwe

    2012-07-01

    Interferometric resolution at IR wavelengths offers for the first time the possibility to zoom into the nuclei of galaxies beyond the circumnuclear stellar structures and spatially resolve gas and dust in the innermost regions (0.05-5pc), dominated by the central black hole. Ultimate goal is to reveal new aspects of AGN feeding, and interaction with its host galaxy. After first successes of resolving AGN with infrared interferometry (VLTI, Keck-IF), the second generation of high-resolution interferometric imagers behind 8m class telescopes is currently being built. I will summarize current aspects and successes of the field, and present our activities to provide extended capabilities for VLTI-Midi and -Matisse, LBT-Linc-Nirvana and Keck-Astra to study a larger sample of AGN in greater detail.

  9. Gamma-Ray Observations of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Madejski, Grzegorz (Greg); Sikora, Marek

    2016-09-01

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

  10. Active Galactic Nucleus Feedback at z ~ 2 and the Mutual Evolution of Active and Inactive Galaxies

    NASA Astrophysics Data System (ADS)

    Cimatti, A.; Brusa, M.; Talia, M.; Mignoli, M.; Rodighiero, G.; Kurk, J.; Cassata, P.; Halliday, C.; Renzini, A.; Daddi, E.

    2013-12-01

    The relationship between galaxies of intermediate stellar mass and moderate luminosity active galactic nuclei (AGNs) at 1 < z < 3 is investigated with a Galaxy Mass Assembly ultra-deep Spectroscopic Survey (GMASS) sample complemented with public data in the GOODS-South field. Using X-ray data, hidden AGNs are identified in unsuspected star-forming galaxies with no apparent signs of non-stellar activity. In the color-mass plane, two parallel trends emerge during the ~2 Gyr between the average redshifts z ~ 2.2 and z ~ 1.3: while the red sequence becomes significantly more populated by ellipticals, the majority of AGNs with L(2-10 keV) > 1042.3 erg s-1 disappear from the blue cloud/green valley where they were hosted predominantly by star-forming systems with disk and irregular morphologies. These results are even clearer when the rest-frame colors are corrected for dust reddening. At z ~ 2.2, the ultraviolet spectra of active galaxies (including two Type 1 AGNs) show possible gas outflows with velocities up to about -500 km s-1, which are observed neither in inactive systems at the same redshift, nor at lower redshifts. Such outflows indicate the presence of gas that can move faster than the escape velocities of active galaxies. These results suggest that feedback from moderately luminous AGNs (log LX < 44.5 erg s-1) played a key role at z >~ 2 by contributing to outflows capable of ejecting part of the interstellar medium and leading to a rapid decrease in star formation in host galaxies with stellar masses 10 < log({\\cal M}/M_{\\odot }) 11.

  11. 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

  12. 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.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

    Fujita, Yutaka; Kimura, Shigeo S.; Murase, Kohta

    2017-01-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1984-01-01

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

  16. 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.

  17. 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.

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

    SciTech Connect

    LaMassa, Stephanie M.; Heckman, T. M.; Ptak, A.; Schiminovich, D.; Bertincourt, B.; O'Dowd, M.

    2012-10-10

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

  19. 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.

  20. OUTFLOWING GALACTIC WINDS IN POST-STARBURST AND ACTIVE GALACTIC NUCLEUS HOST GALAXIES AT 0.2 < z < 0.8

    SciTech Connect

    Coil, Alison L.; Aird, James; Weiner, Benjamin J.; Holz, Daniel E.; Cooper, Michael C.; Yan Renbin

    2011-12-10

    We present Keck/LRIS-B spectra for a sample of 10 AEGIS X-ray active galactic nucleus (AGN) host galaxies and 13 post-starburst galaxies from SDSS and DEEP2 at 0.2 < z < 0.8 in order to investigate the presence, properties, and influence of outflowing galactic winds at intermediate redshifts. We focus on galaxies that either host a low-luminosity AGN or have recently had their star formation quenched to test whether these galaxies have winds of sufficient velocity to potentially clear gas from the galaxy. We find, using absorption features of Fe II, Mg II, and Mg I, that six of the ten (60%) X-ray AGN host galaxies and four of the thirteen (31%) post-starburst galaxies have outflowing galactic winds, with typical velocities of {approx}200 km s{sup -1}. We additionally find that most of the galaxies in our sample show line emission, possibly from the wind, in either Fe II* or Mg II. A total of 100% of our X-ray AGN host sample (including four red sequence galaxies) and 77% of our post-starburst sample has either blueshifted absorption or line emission. Several K+A galaxies have small amounts of cool gas absorption at the systemic velocity, indicating that not all of the cool gas has been expelled. We conclude that while outflowing galactic winds are common in both X-ray low-luminosity AGN host galaxies and post-starburst galaxies at intermediate redshifts, the winds are likely driven by supernovae (as opposed to AGNs) and do not appear to have sufficiently high velocities to quench star formation in these galaxies.

  1. 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.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. Ensemble X-ray variability of active galactic nuclei at intermediate and long time lags

    NASA Astrophysics Data System (ADS)

    Vagnetti, Fausto; Middei, Riccardo

    2016-08-01

    We present a variability analysis for a sample of 2700 active galactic nuclei extracted from the latest release of the XMM-Newton serendipitous source catalogue. The structure function of this sample increases up to rest-frame time lags of about 5 years. Moreover, comparing observations performed by the XMM-Newton and ROSAT satellites, we are able to extend the X-ray structure function to 20 years rest-frame, showing a further increase of variability without any evidence of a plateau. Our results are compared with similar analyses in the optical band, and discussed in relation to the physical sizes of the emitting regions.

  7. 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.

  8. Discovery of H2O megamasers in obscured active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Yamauchi, Aya; Miyamoto, Yusuke; Nakai, Naomasa; Terashima, Yuichi; Okumura, Taishi; Zhou, Bin; Taniguchi, Kotomi; Kaneko, Hiroyuki; Matsumoto, Naoko; Salak, Dragan; Nishimura, Atsushi; Ueno, Saeko

    2017-08-01

    A new method to discover obscured active galactic nuclei (AGNs) by utilizing X-ray and infrared data has recently been developed. We carried out a survey of H2O maser emission toward 10 obscured AGNs with the Nobeyama 45 m telescope. We newly detected the maser emission with a signal-noise-ratio (SNR) of above 4 from two AGNs; NGC 1402 and NGC 7738. We also found a tentative detection with SNR > 3 in NGC 5037. The detection rate of 20% is higher than those of previous surveys (usually several percent).

  9. COMBINING SEMIANALYTIC MODELS WITH SIMULATIONS OF GALAXY CLUSTERS: THE NEED FOR HEATING FROM ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Short, C. J.; Thomas, P. A.

    2009-10-20

    We present hydrodynamical N-body simulations of clusters of galaxies with feedback taken from semianalytic models of galaxy formation. The advantage of this technique is that the source of feedback in our simulations is a population of galaxies that closely resembles that found in the real universe. We demonstrate that, to achieve the high entropy levels found in clusters, active galactic nuclei must inject a large fraction of their energy into the intergalactic/intracluster media throughout the growth period of the central black hole. These simulations reinforce the argument of Bower et al., who arrived at the same conclusion on the basis of purely semianalytic reasoning.

  10. Exploring Black Hole Accretion in Active Galactic Nuclei with Simbol-X

    NASA Astrophysics Data System (ADS)

    Goosmann, R. W.; Dovčiak, M.; Mouchet, M.; Czerny, B.; Karas, V.; Gonçalves, A.

    2009-05-01

    A major goal of the Simbol-X mission is to improve our knowledge about black hole accretion. By opening up the X-ray window above 10 keV with unprecedented sensitivity and resolution we obtain new constraints on the X-ray spectral and variability properties of active galactic nuclei. To interpret the future data, detailed X-ray modeling of the dynamics and radiation processes in the black hole vicinity is required. Relativistic effects must be taken into account, which then allow to constrain the fundamental black hole parameters and the emission pattern of the accretion disk from the spectra that will be obtained with Simbol-X.

  11. Search for emission of ultra high energy radiation from active galactic nuclei

    SciTech Connect

    The CYGNUS Collaboration

    1993-05-01

    A search for emission of ultra-high energy gamma radiation from 13 active galactic nuclei that were detected by EGRET, using the CYGNUS extensive air-shower array, is described. The data set has been searched for continuous emission, emission on the time scale of one week, and for on the time scale of out day. No evidence for emission from any of the AGN on any of the time scales examined was found. The 90% C.L. upper limit to the continuous flux from Mrk 421 above 50 TeV is 7.5 {times} 10{sup {minus}14} cm{sup {minus}2}s{sup {minus}1}.

  12. Search for emission of ultra high energy radiation from active galactic nuclei

    SciTech Connect

    Not Available

    1993-01-01

    A search for emission of ultra-high energy gamma radiation from 13 active galactic nuclei that were detected by EGRET, using the CYGNUS extensive air-shower array, is described. The data set has been searched for continuous emission, emission on the time scale of one week, and for on the time scale of out day. No evidence for emission from any of the AGN on any of the time scales examined was found. The 90% C.L. upper limit to the continuous flux from Mrk 421 above 50 TeV is 7.5 [times] 10[sup [minus]14] cm[sup [minus]2]s[sup [minus]1].

  13. 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.

  14. New structures of power density spectra for four Kepler active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Dobrotka, A.; Antonuccio-Delogu, V.; Bajčičáková, I.

    2017-09-01

    Many nearby active galactic nuclei display a significant short-term variability. In this work, we reanalyse photometric data of four active galactic nuclei observed by Kepler in order to study the flickering activity, with our main goal to search for multiple components in the power density spectra. We find that all four objects have similar characteristics, with two break frequencies at approximately log( f /Hz) = -5.2 and -4.7. We consider some physical phenomena whose characteristic time-scales are consistent with those observed, in particular mass accretion fluctuations in the inner geometrically thick disc (hot X-ray corona) and unstable relativistic Rayleigh-Taylor modes. The former is supported by detection of the same break frequencies in the Swift X-ray data of ZW229-15. We also discuss rms-flux relations, and we detect a possible typical linear trend at lower flux levels. Our findings support the hypothesis of a multiplicative character of variability, in agreement with the propagating accretion fluctuation model.

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

    PubMed

    Miller, J S

    1995-12-05

    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.

  16. 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

  17. Can We Reproduce the X-Ray Background Spectral Shape Using Local Active Galactic Nuclei?

    NASA Astrophysics Data System (ADS)

    Vasudevan, Ranjan V.; Mushotzky, Richard F.; Gandhi, Poshak

    2013-06-01

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

  18. Reflection features in the Galactic Center and past activity of Sagittarius A*

    NASA Astrophysics Data System (ADS)

    Clavel, Maïca; Terrier, Regis; Goldwurm, Andrea; Morris, Mark; Jin, Chichuan; Ponti, Gabriele; Chuard, Dimitri

    2016-07-01

    X-ray observations carried out over the past two decades have captured an increasing number of reflection features within the molecular clouds located in the inner regions of our Galaxy. The intensity of these structures along with the correlated variations which are detected over the entire central molecular zone are strong evidence that this diffuse emission is created by the past activity of the supermassive black hole at the Galactic center, Sagittarius A*. In particular, within the last centuries, Sgr A* is likely to have experienced several short outbursts during which the black hole was at least a million times brighter than today. However, the precise description of the corresponding past catastrophic events is difficult to assess, mainly because the properties of the reflection features that they create while propagating away from Sgr A* depend on the line-of-sight distance, the geometry, and the size of the reflecting clouds, all of which are poorly known. I will review the different attempts to reconstruct Sgr A*'s past activity from the constraints obtained through the observation of the reflection features in the Galactic center, including the current Chandra monitoring.

  19. Powerful outflows in the central parsecs of the low-luminosity active galactic nucleus NGC 1386

    NASA Astrophysics Data System (ADS)

    Rodríguez-Ardila, A.; Prieto, M. A.; Mazzalay, X.; Fernández-Ontiveros, J. A.; Luque, R.; Müller-Sánchez, F.

    2017-09-01

    Low-luminosity active galactic nuclei, i.e. L_{bol}/Ledd ∼ 10-6-10-3, constitute the bulk population of active galactic nuclei (AGNs). Powerful jets, common in these objects, are a crucial source of feedback energy-driving mass outflows into the host galaxy and the intergalactic medium. This paper reports the first direct measurement of powerful mass outflows traced by the forbidden high-ionization gas in the low-luminosity AGN NGC 1386 at scales of a few parsecs from the central engine. The high-angular resolution of the data allows us to directly measure the location, morphology and kinematic of the outflow. This has the form of two symmetrical expanding hot gas shells moving in opposite directions along the line of sight. The co-spatiality of the gas shells with radio emission seen at the same parsec scales and with X-rays indicates that this is a shock-driven outflow presumably induced by an incipient core jet. With a minimum number of assumptions, we derive a mass outflow rate of 11 M⊙ yr-1, comparable to those of powerful AGN. The result has strong implications in the global accounting of feedback mass and energy driven by a low-luminosity AGN into the medium and the corresponding galaxy evolution.

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  2. Vertical flows and structures excited by magnetic activity in the Galactic center region

    NASA Astrophysics Data System (ADS)

    Kakiuchi, Kensuke; Suzuki, Takeru K.; Fukui, Yasuo; Torii, Kazufumi; Machida, Mami; Matsumoto, Ryoji

    2017-01-01

    Various observations show peculiar features in the Galactic Center region, such as loops and filamentary structure. It is still unclear how such characteristic features are formed. Magnetic field is believed to play very important roles in the dynamics of gas in the Galaxy Center. Suzuki et al. (2015) performed a global magneto-hydrodynamical simulation focusing on the Galactic Center with an axisymmetric gravitational potential and claimed that non-radial motion is excited by magnetic activity. We further analyzed their simulation data and found that vertical motion is also excited by magnetic activity. In particular, fast down flows with speed of ~100 km/s are triggered near the footpoint of magnetic loops that are buoyantly risen by Parker instability. These downward flows are accelerated by the vertical component of the gravity, falling along inclined field lines. As a result, the azimuthal and radial components of the velocity are also excited, which are observed as high velocity features in a simulated position-velocity diagram. Depending on the viewing angle, these fast flows will show a huge variety of characteristic features in the position-velocity diagram.

  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. NGC 5252: a pair of radio-emitting active galactic nuclei?

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

    The X-ray source CXO J133815.6+043255 has counterparts in the UV, optical, and radio bands. Based on the multiband investigations, it has been recently proposed by Kim et al. as a rarely seen off-nucleus ultraluminous X-ray (ULX) source with a black hole mass of ≥104 M⊙ in the nearby Seyfert galaxy NGC 5252. To explore its radio properties at very high angular resolution, we performed very long-baseline interferometry (VLBI) observations with the European VLBI Network (EVN) at 1.7 GHz. We find that the radio counterpart is remarkably compact among the known ULXs. It does not show a resolved structure with a resolution of a few milliarcsecond (mas), and the total recovered flux density is comparable to that measured in earlier sub-arcsecond-resolution images. The compact radio structure, the relatively flat spectrum, and the high radio luminosity are consistent with a weakly accreting supermassive black hole in a low-luminosity active galactic nucleus. The nucleus of NGC 5252 itself has similar radio properties. We argue that the system represents a relatively rare pair of active galactic nuclei, where both components emit in the radio.

  5. Tracing the Physical Conditions in Active Galactic Nuclei with Time-Dependent Chemistry

    NASA Astrophysics Data System (ADS)

    Meijerink, Rowin; Spaans, Marco; Kamp, Inga; Aresu, Giambattista; Thi, Wing-Fai; Woitke, Peter

    2013-10-01

    We present an extension of the code ProDiMo that allows for a modeling of processes pertinent to active galactic nuclei and to an ambient chemistry that is time dependent. We present a proof-of-concept and focus on a few astrophysically relevant species, e.g., H+, H2+, and H3+; C+ and N+; C and O; CO and H2O; OH+, H2O+, and H3O+; and HCN and HCO+. We find that the freeze-out of water is strongly suppressed and that this affects the bulk of the oxygen and carbon chemistry occurring in the active galactic nucleus (AGN). The commonly used AGN tracer HCN/HCO+ is strongly time-dependent, with ratios that vary over orders of magnitude for times longer than 104 years. Through Atacama large millimeter array observations this ratio can be used to probe how the narrow-line region evolves under large fluctuations in the supermassive black hole accretion rate. Strong evolutionary trends, on time scales of 104-108 years are also found in species such as H3O+, CO, and H2O. These reflect, respectively, time-dependent effects in the ionization balance, the transient nature of the production of molecular gas, and the freeze-out/sublimation of water.

  6. The Complete Infrared View of Active Galactic Nuclei from the 70 Month Swift/BAT Catalog

    NASA Astrophysics Data System (ADS)

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

    2017-01-01

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

  7. 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.

  8. A transient, flat spectrum radio pulsar near the Galactic Centre

    NASA Astrophysics Data System (ADS)

    Dexter, J.; Degenaar, N.; Kerr, M.; Deller, A.; Deneva, J.; Lazarus, P.; Kramer, M.; Champion, D.; Karuppusamy, R.

    2017-06-01

    Recent studies have shown possible connections between highly magnetized neutron stars ('magnetars'), whose X-ray emission is too bright to be powered by rotational energy, and ordinary radio pulsars. In addition to the magnetar SGR J1745-2900, one of the radio pulsars in the Galactic Centre (GC) region, PSR J1746-2850, had timing properties implying a large magnetic field strength and young age, as well as a flat spectrum. All characteristics are similar to those of rare, transient, radio-loud magnetars. Using several deep non-detections from the literature and two new detections, we show that this pulsar is also transient in the radio. Both the flat spectrum and large amplitude variability are inconsistent with the light curves and spectral indices of three radio pulsars with high magnetic field strengths. We further use frequent, deep archival imaging observations of the GC in the past 15 yr to rule out a possible X-ray outburst with a luminosity exceeding the rotational spin-down rate. This source, either a transient magnetar without any detected X-ray counterpart or a young, strongly magnetized radio pulsar producing magnetar-like radio emission, further blurs the line between the two categories. We discuss the implications of this object for the radio emission mechanism in magnetars and for star and compact object formation in the GC.

  9. γ-Ray emission from Arp 220: indications of an active galactic nucleus

    NASA Astrophysics Data System (ADS)

    Yoast-Hull, Tova M.; Gallagher, John S., III; Aalto, Susanne; Varenius, Eskil

    2017-07-01

    Extragalactic cosmic ray populations are important diagnostic tools for tracking the distribution of energy in nuclei and for distinguishing between activity powered by star formation versus active galactic nuclei (AGNs). Here, we compare different diagnostics of the cosmic ray populations of the nuclei of Arp 220 based on radio synchrotron observations and the recent γ-ray detection. We find the γ-ray and radio emission to be incompatible; a joint solution requires at minimum a factor of 4-8 times more energy coming from supernovae and a factor of 40-70 more mass in molecular gas than that is observed. We conclude that this excess of the γ-ray flux in comparison to all other diagnostics of star-forming activity indicates that there is an AGN present that is providing the extra cosmic rays, likely in the western nucleus.

  10. THE SUZAKU VIEW OF THE SWIFT/BAT ACTIVE GALACTIC NUCLEI. II. TIME VARIABILITY AND SPECTRA OF FIVE 'HIDDEN' ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Winter, Lisa M.; Mushotzky, Richard F.; Terashima, Yuichi; Ueda, Yoshihiro

    2009-08-20

    The fraction of Compton-thick sources is one of the main uncertainties left in understanding the active galactic nucleus (AGN) population. The Swift Burst Alert Telescope (BAT) all-sky survey for the first time gives us an unbiased sample of AGNs for all but the most heavily absorbed sources N {sub H} > 10{sup 25} cm{sup -2}). Still, the BAT spectra (14-195 keV) are time averaged over months of observations and therefore hard to compare with softer spectra from the Swift XRT or other missions. This makes it difficult to distinguish between Compton-thin and Compton-thick models. With Suzaku, we have obtained simultaneous hard (>15 keV) and soft (0.3-10 keV) X-ray spectra for five Compton-thick candidate sources. We report on the spectra and a comparison with the BAT and earlier XMM observations. Based on both flux variability and spectral shape, we conclude that these hidden sources are not Compton thick. We also report on a possible correlation between excess variance and Swift BAT luminosity from the 16 day binned light curves, which holds true for a sample of both absorbed (four sources), unabsorbed (eight sources), and Compton-thick (Circinus) AGNs, but is weak in the 64 day binned BAT light curves.

  11. 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.

  12. Jet signatures of black holes: From Sgr A* to active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Britzen, S.; Eckart, A.; Lämmerzahl, C.; Roland, J.; Brockamp, M.; Hackmann, E.; Kunz, J.; Macias, A.; Malchow, R.; Sabha, N.; Shahzamanian, B.

    2015-06-01

    Detailed and long-term VLBI (Very Long Baseline Interferometry) studies of the variable jets of supermassive black holes helps us to understand the emission processes of these fascinating phenomena. When observed and traced precisely, jet component kinematics reveals details about the potential motion of the jet base. Following this motion over decades with VLBI monitoring reveals - in some cases - the signatures of precession. While several processes can cause precession, the most likely cause seems to be a supermassive binary black hole in the central region of the AGN. We present examples of the analysis of high-resolution VLBI observations which provides us with insight into the physics of these objects and reveals evidence for the presence of double black hole cores. EHT (Event Horizon Telescope) observations will probably soon tell us more about the jet origin and launching mechanism at the very centers of nearby active galactic nuclei. An important question to be addressed by the EHT and related observations will be whether Sgr A\\star, the supermassive black hole in the Galactic Center, has a jet as well.

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  15. RADIAL VELOCITY OFFSETS DUE TO MASS OUTFLOWS AND EXTINCTION IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Crenshaw, D. M.; Schmitt, H. R.; Kraemer, S. B.; Mushotzky, R. F.

    2010-01-01

    We present a study of the radial velocity offsets between narrow emission lines and host galaxy lines (stellar absorption and H I 21 cm emission) in Seyfert galaxies with observed redshifts less than 0.043. We find that 35% of the Seyferts in the sample show [O III] emission lines with blueshifts with respect to their host galaxies exceeding 50 km s{sup -1}, whereas only 6% show redshifts this large, in qualitative agreement with most previous studies. We also find that a greater percentage of Seyfert 1 galaxies show blueshifts than Seyfert 2 galaxies. Using Hubble Spce Talescope/Space Telescope Imaging Spectrograph spatially resolved spectra of the Seyfert 2 galaxy NGC 1068 and the Seyfert 1 galaxy NGC 4151, we generate geometric models of their narrow-line regions (NLRs) and inner galactic disks, and show how these models can explain the blueshifted [O III] emission lines in collapsed STIS spectra of these two Seyferts. We conclude that the combination of mass outflow of ionized gas in the NLR and extinction by dust in the inner disk (primarily in the form of dust spirals) is primarily responsible for the velocity offsets in Seyfert galaxies. More exotic explanations are not needed. We discuss the implications of this result for the velocity offsets found in higher redshift active galactic nuclei.

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

    NASA Astrophysics Data System (ADS)

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

    2010-05-01

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

  17. What can Fermi LAT observation of the Galactic Centre tell us about its active past?

    NASA Astrophysics Data System (ADS)

    Zaharijas, Gabrijela; Petrović, Jovana; Serpico, Pasquale

    The Fermi-LAT gamma-ray data in the inner Galaxy region show several prominent features possibly related to the past activity of the Milky Way's super massive black hole. At a large, 50 deg scale, the Fermi LAT revealed symmetric hour glass structures with hard energy spectra extending up to 100 GeV (and dubbed `the Fermi bubbles'). More recently and closer to the Galactic centre, at the 10 deg scale, several groups have claimed evidence for excess gamma-ray emission that appears symmetric around the Galactic center and has an energy spectrum peaking at few GeVs. We explore here the possibility that this emission originates in inverse Compton emission from high-energy electrons produced in a short duration, burst-like event injecting 1052 - 1053 erg, roughly 106 yrs ago. Several lines of evidence suggest that a series of `burst like' events happened in the vicinity of our black hole in the past and gamma-ray observations may offer a new view of that scenario.

  18. 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.

  19. 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.

  20. A SCALING RELATION BETWEEN MEGAMASER DISK RADIUS AND BLACK HOLE MASS IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Wardle, Mark; Yusef-Zadeh, Farhad E-mail: zadeh@northwestern.edu

    2012-05-10

    Several thin, Keplerian, sub-parsec megamaser disks have been discovered in the nuclei of active galaxies and used to precisely determine the mass of their host black holes. We show that there is an empirical linear correlation between the disk radius and the black hole mass. We demonstrate that such disks are naturally formed by the partial capture of molecular clouds passing through the galactic nucleus and temporarily engulfing the central supermassive black hole. Imperfect cancellation of the angular momenta of the cloud material colliding after passing on opposite sides of the hole leads to the formation of a compact disk. The radial extent of the disk is determined by the efficiency of this process and the Bondi-Hoyle capture radius of the black hole, and naturally produces the empirical linear correlation of the radial extent of the maser distribution with black hole mass. The disk has sufficient column density to allow X-ray irradiation from the central source to generate physical and chemical conditions conducive to the formation of 22 GHz H{sub 2}O masers. For initial cloud column densities {approx}< 10{sup 23.5} cm{sup -2} the disk is non-self-gravitating, consistent with the ordered kinematics of the edge-on megamaser disks; for higher cloud columns the disk would fragment and produce a compact stellar disk similar to that observed around Sgr A* at the galactic center.

  1. Constraining black hole masses in low-accreting active galactic nuclei using X-ray spectra

    NASA Astrophysics Data System (ADS)

    Jang, I.; Gliozzi, M.; Hughes, C.; Titarchuk, L.

    2014-09-01

    In a recent work we demonstrated that a novel X-ray scaling method, originally introduced for Galactic black holes (BHs), can be reliably extended to estimate the mass of supermassive BHs accreting at a moderate to high level. Here we investigate the limits of applicability of this method to low-accreting active galactic nuclei (AGN), using a control sample with good-quality X-ray data and dynamically measured mass. For low-accreting AGN (LX/LEdd ≤ 10-4), because the basic assumption that the photon index positively correlates with the accretion rate no longer holds the X-ray scaling method cannot be used. Nevertheless, the inverse correlation in the Γ-LX/LEdd diagram, found in several low-accreting BHs and confirmed by this sample, can be used to constrain MBH within a factor of ˜10 from the dynamically determined values. We provide a simple recipe to determine MBH using solely X-ray spectral data, which can be used as a sanity check for MBH determination based on indirect optical methods.

  2. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2008-04-01

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

  4. Outflow and Metallicity in the Broad-Line Region of Low-Redshift Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Shin, Jaejin; nagao, Tohru; Woo, Jong-Hak

    2017-01-01

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

  5. Nearby active galactic nuclei seen via adaptive optics at the Keck Telescope

    NASA Astrophysics Data System (ADS)

    Max, Claire

    2004-02-01

    In recent years it has become increasingly clear that mergers between galaxies play a critical role in galaxy evolution, in the formation of central black holes, and in the phenomena of active galactic nuclei (AGNs) and quasar activity. The advent of adaptive optics on the new generation of 6-10 m telescopes is making it possible to study nearby AGNs and merging galaxies with spatial resolutions of10 - 100 pc. In this talk I will describe and discuss observations of NGC 6240 and Cygnus A, archetypes of merging disk galaxies and of powerful radiogalaxies respectively. I will make use of infrared observations using the adaptive optics system on the 10-m Keck Telescope, as well as visible-light observations from the Hubble Space Telescope.

  6. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  8. 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.

  9. AVERAGE HEATING RATE OF HOT ATMOSPHERES IN DISTANT CLUSTERS BY RADIO ACTIVE GALACTIC NUCLEUS: EVIDENCE FOR CONTINUOUS ACTIVE GALACTIC NUCLEUS HEATING

    SciTech Connect

    Ma, C.-J.; McNamara, B. R.; Schaffer, R.; Nulsen, P. E. J.; Vikhlinin, A.

    2011-10-20

    We examine atmospheric heating by radio active galactic nuclei (AGNs) in distant X-ray clusters by cross correlating clusters selected from the 400 Square Degree (400SD) X-ray Cluster survey with radio sources in the NRAO VLA Sky Survey. Roughly 30% of the clusters show radio emission above a flux threshold of 3 mJy within a projected radius of 250 kpc. The radio emission is presumably associated with the brightest cluster galaxy. The mechanical jet power for each radio source was determined using scaling relations between radio power and cavity (mechanical) power determined for nearby clusters, groups, and galaxies with hot atmospheres containing X-ray cavities. The average jet power of central radio AGNs is approximately 2 x 10{sup 44} erg s{sup -1}. We find no significant correlation between radio power, and hence mechanical jet power, and the X-ray luminosities of clusters in the redshift range 0.1-0.6. This implies that the mechanical heating rate per particle is higher in lower mass, lower X-ray luminosity clusters. The jet power averaged over the sample corresponds to an atmospheric heating of approximately 0.2 keV per particle within R{sub 500}. Assuming the current AGN heating rate does not evolve but remains constant to redshifts of 2, the heating rate per particle would rise by a factor of two. We find that the energy injected from radio AGNs contribute substantially to the excess entropy in hot atmospheres needed to break self-similarity in cluster scaling relations. The detection frequency of radio AGNs is inconsistent with the presence of strong cooling flows in 400SD clusters, but does not exclude weak cooling flows. It is unclear whether central AGNs in 400SD clusters are maintained by feedback at the base of a cooling flow. Atmospheric heating by radio AGNs may retard the development of strong cooling flows at early epochs.

  10. 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.

  11. 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.

  12. THE EVOLUTION AND EDDINGTON RATIO DISTRIBUTION OF COMPTON THICK ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Draper, A. R.; Ballantyne, D. R.

    2010-06-01

    Previous studies of the active galactic nuclei (AGNs) contribution to the cosmic X-ray background (CXB) consider only observable parameters such as luminosity and absorbing column. Here, for the first time, we extend the study of the CXB to physical parameters including the Eddington ratio of the sources and the black hole mass. In order to calculate the contribution to the CXB of AGN accreting at various Eddington ratios, an evolving Eddington ratio space density model is calculated. In particular, Compton thick (CT) AGNs are modeled as accreting at specific, physically motivated Eddington ratios instead of as a simple extension of the Compton thin type 2 AGN population. Comparing against the observed CT AGN space densities and log N-log S relation indicates that CT AGNs are likely a composite population of AGNs made up of sources accreting either at >90% or <1% of their Eddington rate.

  13. The VSOP 5 GHz Active Galactic Nucleus Survey. V. Imaging Results for the Remaining 140 Sources

    NASA Astrophysics Data System (ADS)

    Dodson, R.; Fomalont, E. B.; Wiik, K.; Horiuchi, S.; Hirabayashi, H.; Edwards, P. G.; Murata, Y.; Asaki, Y.; Moellenbrock, G. A.; Scott, W. K.; Taylor, A. R.; Gurvits, L. I.; Paragi, Z.; Frey, S.; Shen, Z.-Q.; Lovell, J. E. J.; Tingay, S. J.; Rioja, M. J.; Fodor, S.; Lister, M. L.; Mosoni, L.; Coldwell, G.; Piner, B. G.; Yang, J.

    2008-04-01

    In 1997 February, the Japanese radio astronomy satellite HALCA was launched to provide the space-bourne element for the VLBI Space Observatory Program (VSOP) mission. Approximately 25% of the mission time was dedicated to the VSOP survey of bright compact active galactic nuclei (AGNs) at 5 GHz. This paper, the fifth in the series, presents images and models for the remaining 140 sources not included in the third paper in the series, which contained 102 sources. For most sources, the plots of the (u,v) coverage, the visibility amplitude versus (u,v) distance, and the high-resolution image are presented. Model fit parameters to the major radio components are determined, and the brightness temperature of the core component for each source is calculated. The brightness temperature distributions for all of the sources in the VSOP AGN survey are discussed.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-12-01

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

  20. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

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

  2. Radius-luminosity and mass-luminosity relationships for active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Koratkar, Anuradha P.; Gaskell, C. Martin

    1991-01-01

    Broad-line region (BLR) sizes derived from spectral variability and BLR line widths are used to directly derive the mass (M) of the central objects of ten active galactic nuclei (AGNs) in a uniform manner. It is shown that the luminosity-weighted C IV 1549-emitting BLR radius (R) correlates with the bolometric luminosity L(Bol) and is consistent with R about sq rt L(Bol). The measurements also permit a verification of the Dibai mass-luminosity (M-L) relationship (previously derived indirectly). It is found that L(Bol) is proportional to M exp (1.1 + or - 0.3). It is found that the efficiency factor epsilon, defined as the ratio of L(Bol) to the Eddington luminosity increases from 0.03 in the low-luminosity Seyferts up to 0.06 in the most luminous objects in the sample.

  3. A MAGNETIC RECONNECTION ORIGIN FOR THE SOFT X-RAY EXCESS IN AN ACTIVE GALACTIC NUCLEUS

    SciTech Connect

    Zhong Xiaogu; Wang Jiancheng

    2013-08-10

    We present a new scenario to explain the soft X-ray excess in an active galactic nucleus (AGN). Magnetic reconnection could happen in a thin layer on the surface of an accretion disk. Electrons are accelerated by a shock wave and turbulence is triggered by magnetic reconnection. Inverse Compton scattering then takes place above the accretion disk, producing soft X-rays. Based on the standard disk model, we estimate the magnetic field strength and the energy released by magnetic reconnection along the accretion disk and find that the luminosity arising from magnetic reconnection is mostly emitted in the inner disk, which is dominated by radiation pressure. We then apply the model to fit the spectra of AGNs with strong soft X-ray excess.

  4. Difficulties in Estimating the Physical Parameters of Compact Radio Sources in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Artyukh, V. S.

    2016-12-01

    The various factors influencing estimates of the physical parameters of compact radio sources in active galactic nuclei (AGN) using a methods based on uniform models of synchrotron radiation sources are analyzed. It is found that the form of the relativistic electron energy density distribution as a function of magnetic energy density (Ee-EH) in the radio sources is determined by the shape of the electron energy spectrum. It is shown that the very large observed deviations of the estimated energies of the field and relativistic particles from equipartition are mainly caused by nonuniformity of the radio sources. In order to obtain correct estimates of the physical parameters of nonuniform radio sources, it is necessary to know their angular sizes at low frequencies (in the opaque region) and their Doppler factors.

  5. 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.

  6. 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.

  7. Very-High-Energy Gamma-Ray Observations of Active Galactic Nuclei with VERITAS

    NASA Astrophysics Data System (ADS)

    Quinn, John

    2016-08-01

    VERITAS is an array of four imaging atmospheric Cherenkov telescopes for very-high-energy (VHE, E>100 GeV) gamma-ray astronomy that has been in full scientific operation since 2007. The VERITAS collaboration is conducting several key science projects, one of which is the study of active galactic nuclei (AGN). So far, VERITAS has invested more than 3000 hours in observations of AGN, with approximately 150 objects observed. The program has resulted in the successful detection of 34 AGN as VHE gamma-ray sources, with the majority belonging to the blazar AGN subclass. Significant effort is made to acquire multiwavelength data coincident with the VERITAS observations. An overview of the VERITAS AGN program and its key results will be presented.

  8. 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.

  9. ON THE SCATTER IN THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Kilerci Eser, E.; Vestergaard, M.; Peterson, B. M.; Denney, K. D.; Bentz, M. C. E-mail: vester@dark-cosmology.dk E-mail: peterson@astronomy.ohio-state.edu

    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.

  10. 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.

  11. Swift/XRT detects renewed activity of the Galactic center transient CXOGC J174540.0-290005

    NASA Astrophysics Data System (ADS)

    Degenaar, N.; Reynolds, M. T.; Wijnands, R.; Miller, J. M.; Kennea, J. A.

    2017-03-01

    In our daily Swift/XRT monitoring observations of the Galactic center (Degenaar et al. 2015, JHEAp, 7, 137) we detect X-ray activity of a transient source located 20" to the north of Sgr A*, at a position consistent with that of the known X-ray transient CXOGC J174540.0-290005/Swift J174540.2-290005.

  12. The first catalog of active galactic nuclei detected by the FERMI large area telescope

    DOE PAGES

    Abdo, A. A.; Ackermann, M.; Ajello, M.; ...

    2010-04-29

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

  13. 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 }).

  14. The Second Catalog Of Active Galactic Nuclei Detected By The Fermi Large Area Telescope

    DOE PAGES

    Ackermann, M.

    2011-12-02

    The second catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT) in two years of scientific operation is presented. The Second LAT AGN Catalog (2LAC) includes 1017 γ-ray sources located at high Galactic latitudes (|b| > 10°) that are detected with a test statistic (TS) greater than 25 and associated statistically with AGNs. However some of these are affected by analysis issues and some are associated with multiple AGNs. Consequently we define a clean sample which includes 886 AGNs, comprising 395 BL Lacertae objects (BL Lacs), 310 flat-spectrum radio quasars (FSRQs), 157 candidate blazars ofmore » unknown type (i.e., with broad-band blazar characteristics but with no optical spectral measurement yet), eight misaligned AGNs, four narrow-line Seyfert 1 (NLS1s), 10 AGNs of other types and two starburst galaxies. Where possible, the blazars have been further classified based on their spectral energy distributions (SEDs) as archival radio, optical, and X-ray data permit. While almost all FSRQs have a synchrotron-peak frequency < 1014 Hz, about half of the BL Lacs have a synchrotron-peak frequency > 1015 Hz. The 2LAC represents a significant improvement relative to the First LAT AGN Catalog (1LAC), with 52% more associated sources. The full characterization of the newly detected sources will require more broad-band data. Various properties, such as γ-ray fluxes and photon power law spectral indices, redshifts, γ-ray luminosities, variability, and archival radio luminosities—and their correlations are presented and discussed for the different blazar classes. The general trends observed in 1LAC are confirmed.« less

  15. The third catalog of active galactic nuclei detected by the Fermi large area telescope

    DOE PAGES

    Ackermann, M.; Ajello, M.; Atwood, W. B.; ...

    2015-08-25

    We present the third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC). 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 (more » $$| b| \\gt 10^\\circ $$), 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. There were about 50% of the BL Lacs that had 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. Furthermore, the energy-flux distributions of the different blazar populations are in good agreement with extrapolation from earlier catalogs.« less

  16. A Candidate Dual Active Galactic Nucleus at z = 1.175

    NASA Astrophysics Data System (ADS)

    Barrows, R. Scott; Stern, Daniel; Madsen, Kristin; Harrison, Fiona; Assef, Roberto J.; Comerford, Julia M.; Cushing, Michael C.; Fassnacht, Christopher D.; Gonzalez, Anthony H.; Griffith, Roger; Hickox, Ryan; Kirkpatrick, J. Davy; Lagattuta, David J.

    2012-01-01

    The X-ray source CXOXBJ142607.6+353351 (CXOJ1426+35), which was identified in a 172 ks Chandra image in the Boötes field, shows double-peaked rest-frame optical/UV emission lines, separated by 0farcs69 (5.5 kpc) in the spatial dimension and by 690 km s-1 in the velocity dimension. The high excitation lines and emission line ratios indicate both systems are ionized by an active galactic nucleus (AGN) continuum, and the double-peaked profile resembles that of candidate dual AGNs. At a redshift of z = 1.175, this source is the highest redshift candidate dual AGN yet identified. However, many sources have similar emission line profiles for which other interpretations are favored. We have analyzed the substantial archival data available in this field as well as acquired near-infrared (NIR) adaptive optics (AO) imaging and NIR slit spectroscopy. The X-ray spectrum is hard, implying a column density of several 1023 cm-2. Though heavily obscured, the source is also one of the brightest in the field, with an absorption-corrected 2-10 keV luminosity of ~1045 erg s-1. Outflows driven by an accretion disk may produce the double-peaked lines if the central engine accretes near the Eddington limit. However, we may be seeing the narrow line regions of two AGNs following a galactic merger. While the AO image reveals only a single source, a second AGN would easily be obscured by the significant extinction inferred from the X-ray data. Understanding the physical processes producing the complex emission line profiles seen in CXOJ1426+35 and related sources is important for interpreting the growing population of dual AGN candidates.

  17. 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.

  18. Feedback from Mass Outflows in Nearby Active Galactic Nuclei. I. Ultraviolet and X-Ray Absorbers

    NASA Astrophysics Data System (ADS)

    Crenshaw, D. M.; Kraemer, S. B.

    2012-07-01

    We present an investigation into the impact of feedback from outflowing UV and X-ray absorbers in nearby (z < 0.04) active galactic nuclei (AGNs). From studies of the kinematics, physical conditions, and variability of the absorbers in the literature, we calculate the possible ranges in the total mass outflow rate (\\dot{M}_{out}) and kinetic luminosity (L KE) for each AGN, summed over all of its absorbers. These calculations make use of values (or limits) for the radial locations of the absorbers determined from variability, excited-state absorption, and other considerations. From a sample of 10 Seyfert 1 galaxies with detailed photoionization models for their absorbers, we find that 7 have sufficient constraints on the absorber locations to determine \\dot{M}_{out} and L KE. For the low-luminosity AGN NGC 4395, these values are low, although we do not have sufficient constraints on the X-ray absorbers to make definitive conclusions. At least five of the six Seyfert 1s with moderate bolometric luminosities (L bol = 1043 - 1045 erg s-1) have mass outflow rates that are 10-1000 times the mass accretion rates needed to generate their observed luminosities, indicating that most of the mass outflow originates from outside the inner accretion disk. Three of these (NGC 4051, NGC 3516, and NGC 3783) have L KE in the range 0.5%-5% L bol, which is the range typically required by feedback models for efficient self-regulation of black hole and galactic bulge growth. At least two of the other three (NGC 5548, NGC 4151, and NGC 7469) have L KE >~ 0.1%L bol, although these values may increase if radial locations can be determined for more of the absorbers. We conclude that the outflowing UV and X-ray absorbers in moderate-luminosity AGNs have the potential to deliver significant feedback to their environments.

  19. The third catalog of active galactic nuclei detected by the Fermi large area telescope

    SciTech Connect

    Ackermann, M.; Ajello, M.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Gonzalez, J. Becerra; 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.; Angelis, A. de; Desiante, R.; Digel, S. W.; Venere, L. Di; 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.; Mura, G. La; 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.

    2015-08-25

    We present the third catalog of active galactic nuclei (AGNs) detected by the Fermi-LAT (3LAC). 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. There were about 50% of the BL Lacs that had 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. Furthermore, the energy-flux distributions of the different blazar populations are in good agreement with extrapolation from earlier catalogs.

  20. 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.

  1. 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.

  2. Grain Physics and Infrared Dust Emission in Active Galactic Nucleus Environments

    NASA Astrophysics Data System (ADS)

    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 1046 erg s-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 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 (sime 100 K) from dense dusty gas within <=1 kpc reradiating the AGN UV emission.

  3. THE SECOND CATALOG OF ACTIVE GALACTIC NUCLEI DETECTED BY THE FERMI LARGE AREA TELESCOPE

    SciTech Connect

    Ackermann, M.; Ajello, M.; Allafort, A.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Antolini, E.; Bonamente, E.; Atwood, W. B.; Bouvier, A.; Axelsson, M.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Ballet, J.; Bastieri, D. E-mail: sarac@slac.stanford.edu E-mail: charles.dermer@nrl.navy.mil; and others

    2011-12-20

    The second catalog of active galactic nuclei (AGNs) detected by the Fermi Large Area Telescope (LAT) in two years of scientific operation is presented. The second LAT AGN catalog (2LAC) includes 1017 {gamma}-ray sources located at high Galactic latitudes (|b| > 10 Degree-Sign ) that are detected with a test statistic (TS) greater than 25 and associated statistically with AGNs. However, some of these are affected by analysis issues and some are associated with multiple AGNs. Consequently, we define a Clean Sample which includes 886 AGNs, comprising 395 BL Lacertae objects (BL Lac objects), 310 flat-spectrum radio quasars (FSRQs), 157 candidate blazars of unknown type (i.e., with broadband blazar characteristics but with no optical spectral measurement yet), 8 misaligned AGNs, 4 narrow-line Seyfert 1 (NLS1s), 10 AGNs of other types, and 2 starburst galaxies. Where possible, the blazars have been further classified based on their spectral energy distributions (SEDs) as archival radio, optical, and X-ray data permit. While almost all FSRQs have a synchrotron-peak frequency <10{sup 14} Hz, about half of the BL Lac objects have a synchrotron-peak frequency >10{sup 15} Hz. The 2LAC represents a significant improvement relative to the first LAT AGN catalog (1LAC), with 52% more associated sources. The full characterization of the newly detected sources will require more broadband data. Various properties, such as {gamma}-ray fluxes and photon power-law spectral indices, redshifts, {gamma}-ray luminosities, variability, and archival radio luminosities and their correlations are presented and discussed for the different blazar classes. The general trends observed in 1LAC are confirmed.

  4. 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).

  5. Observational Evidence for Active Galactic Nuclei Feedback at the Parsec Scale

    NASA Astrophysics Data System (ADS)

    Yuan, Feng; Li, Miao

    2011-08-01

    In a hot accretion flow, the radiation from the innermost region of the flow propagates outward and heats the electrons at large radii via Compton scattering. It has been shown in previous works that if the radiation is strong enough, L >~ 2%L Edd, the electrons at the Bondi radius (rB ~ 105 rs ) will be heated to above the virial temperature; thus, the accretion will be stopped. The accretion will recover after the gas cools down. This results in the oscillation of the black hole activity. In this paper, we show that this mechanism is the origin of the intermittent activity of some compact young radio sources. Such intermittency is required to explain the population of these sources. We calculate the timescales of the black hole oscillation and find that the durations of active and inactive phases are 3 × 104(0.1/α)(M/108 M sun)(L/2%L Edd)-1/2 yr and 105(α/0.1)(M/108 M sun) yr, respectively, consistent with those required to explain observations. Such feedback occurring at the parsec scale should be common in low-luminosity active galactic nuclei and should be considered when we consider their matter and energy output.

  6. 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.

  7. Population statistics of radio and γ-ray pulsars from the Galactic disk

    NASA Astrophysics Data System (ADS)

    Gonthier, Peter L.; Story, Sarah A.; Clow, Brian D.; Harding, Alice K.

    2008-01-01

    We present results of our population synthesis of normal and millisecond pulsars from the Galactic disk. Over the past several years, a program has been developed to simulate pulsar birth, evolution, and emission using Monte Carlo techniques. We have added to the program the capability to simulate millisecond pulsars, which are old, recycled pulsars with extremely short periods. We model the spatial distribution of millisecond pulsars by assuming they start with a random kick velocity and then evolve through the Galactic potential. We use a polar cap/slot gap model for gamma-ray emission from both millisecond and normal pulsars. We also include gamma-ray emission from an outer-gap model to compare the statistics of radio-loud and radio-faint gamma-ray pulsars on the same footing as pulsars from our polar cap/slot gap model. From our studies of radio pulsars that have clearly identifiable core and cone components, in which we fit the polarization sweep as well as the pulse profiles to constrain the viewing geometry, we develop a model describing the ratio of radio core-to-cone peak fluxes. In this model, short period pulsars are more cone-dominated than in our previous studies. We present the preliminary results of our recent study including comparisons between these two groups of pulsars and the implications for observing these pulsars with GLAST and AGILE. GLAST should detect significant numbers of millisecond pulsars.

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

    SciTech Connect

    Comerford, Julia M.; Gerke, Brian F.; Cooper, Michael C.; Weiner, Benjamin J.; Newman, Jeffrey A.; Madsen, Kristin; Barrows, R. Scott

    2012-07-01

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

  9. Kiloparsec-scale Spatial Offsets in Double-peaked Narrow-line Active Galactic Nuclei. I. Markers for Selection of Compelling Dual Active Galactic Nucleus Candidates

    NASA Astrophysics Data System (ADS)

    Comerford, Julia M.; Gerke, Brian F.; Stern, Daniel; Cooper, Michael C.; Weiner, Benjamin J.; Newman, Jeffrey A.; Madsen, Kristin; Barrows, R. Scott

    2012-07-01

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

  10. MHD SIMULATIONS OF ACTIVE GALACTIC NUCLEUS JETS IN A DYNAMIC GALAXY CLUSTER MEDIUM

    SciTech Connect

    Mendygral, P. J.; Jones, T. W.; Dolag, K.

    2012-05-10

    We present a pair of three-dimensional magnetohydrodynamical simulations of intermittent jets from a central active galactic nucleus (AGN) in a galaxy cluster extracted from a high-resolution cosmological simulation. The selected cluster was chosen as an apparently relatively relaxed system, not having undergone a major merger in almost 7 Gyr. Despite this characterization and history, the intracluster medium (ICM) contains quite active 'weather'. We explore the effects of this ICM weather on the morphological evolution of the AGN jets and lobes. The orientation of the jets is different in the two simulations so that they probe different aspects of the ICM structure and dynamics. We find that even for this cluster, which can be characterized as relaxed by an observational standard, the large-scale, bulk ICM motions can significantly distort the jets and lobes. Synthetic X-ray observations of the simulations show that the jets produce complex cavity systems, while synthetic radio observations reveal bending of the jets and lobes similar to wide-angle tail radio sources. The jets are cycled on and off with a 26 Myr period using a 50% duty cycle. This leads to morphological features similar to those in 'double-double' radio galaxies. While the jet and ICM magnetic fields are generally too weak in the simulations to play a major role in the dynamics, Maxwell stresses can still become locally significant.

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

    NASA Astrophysics Data System (ADS)

    Nandra, K.; Iwasawa, K.

    2007-11-01

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

  12. 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.

  13. 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.

  14. 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.

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

    DOE PAGES

    Bufanda, E.; Hollowood, D.; Jeltema, T. E.; ...

    2016-12-13

    The correlation between active galactic nuclei (AGN) and environment provides important clues to AGN fueling and the relationship of black hole growth to galaxy evolution. Here, we analyze the fraction of galaxies in clusters hosting AGN as a function of redshift and cluster richness for X-ray detected AGN associated with clusters of galaxies in Dark Energy Survey (DES) Science Verification data. The present sample includes 33 AGN with L_X > 1043 ergs s-1 in non-central, host galaxies with luminosity greater than 0.5 L* from a total sample of 432 clusters in the redshift range of 0.10.7. Our result is inmore » good agreement with previous work and parallels the increase in star formation in cluster galaxies over the same redshift range. But, the AGN fraction in clusters is observed to have no significant correlation with cluster mass. Future analyses with DES Year 1 through Year 3 data will be able to clarify whether AGN activity is correlated to cluster mass and will tightly constrain the relationship between cluster AGN populations and redshift.« less

  17. X-Ray Detected Active Galactic Nuclei in Dwarf Galaxies at 0 < z < 1

    NASA Astrophysics Data System (ADS)

    Pardo, K.; Goulding, A. D.; Greene, J. E.; Somerville, R. S.; Gallo, E.; Hickox, R. C.; Miller, B. P.; Reines, A. E.; Silverman, J. D.

    2016-11-01

    We present a sample of accreting supermassive black holes (SMBHs) in dwarf galaxies at z\\lt 1. We identify dwarf galaxies in the NEWFIRM Medium Band Survey with stellar masses of {M}\\star \\lt 3× {10}9 {M}⊙ that have spectroscopic redshifts from the DEEP2 survey and lie within the region covered by deep (flux limit of ˜ 5× {10}-17{--}6× {10}-16 {erg} {{cm}}-2 {{{s}}}-1) archival Chandra X-ray data. From our sample of 605 dwarf galaxies, 10 exhibit X-ray emission consistent with that arising from active galactic nucleus (AGN) activity. If black-hole mass scales roughly with stellar mass, then we expect that these AGNs are powered by SMBHs with masses of ˜ {10}5{--}{10}6 {M}⊙ and typical Eddington ratios of ˜ 5 % . Furthermore, we find an AGN fraction consistent with extrapolations of other searches of ˜ 0.6 % {--}3 % for {10}9 {M}⊙ ≤slant {M}\\star ≤slant 3× {10}9 {M}⊙ and 0.1\\lt z\\lt 0.6. Our AGN fraction is in good agreement with a semi-analytic model, suggesting that, as we search larger volumes, we may use comparisons between observed AGN fractions and models to understand seeding mechanisms in the early universe.

  18. 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.

  19. Stability of cloud orbits in the broad-line region of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Krause, Martin; Burkert, Andreas; Schartmann, Marc

    2011-02-01

    We investigate the global dynamic stability of spherical clouds in the broad-line region (BLR) of active galactic nuclei (AGN), exposed to radial radiation pressure, gravity of the central black hole (BH) and centrifugal forces assuming the clouds adapt their size according to the local pressure. We consider both isotropic and anisotropic light sources. In both cases, stable orbits exist also for very sub-Keplerian rotation for which the radiation pressure contributes substantially to the force budget. We demonstrate that highly eccentric, very sub-Keplerian stable orbits may be found. This gives further support for the model of Marconi et al., who pointed out that BH masses might be significantly underestimated if radiation pressure is neglected. That model improved the agreement between BH masses derived in certain active galaxies based on BLR dynamics, and BH masses derived by other means in other galaxies by inclusion of a luminosity-dependent term. For anisotropic illumination, energy is conserved for averages over long time intervals only, but not for individual orbits. This leads to Rosetta orbits that are systematically less extended in the direction of maximum radiation force. Initially isotropic relatively low column density systems would therefore turn into a disc when an anisotropic AGN is switched on.

  20. 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}.

  1. DYNAMO ACTIVITIES DRIVEN BY MAGNETOROTATIONAL INSTABILITY AND THE PARKER INSTABILITY IN GALACTIC GASEOUS DISKS

    SciTech Connect

    Machida, Mami; Nakamura, Kenji E.; Kudoh, Takahiro; Akahori, Takuya; Sofue, Yoshiaki; Matsumoto, Ryoji

    2013-02-10

    We carried out global three-dimensional magnetohydrodynamic simulations of dynamo activities in galactic gaseous disks without assuming equatorial symmetry. Numerical results indicate the growth of azimuthal magnetic fields non-symmetric to the equatorial plane. As the magnetorotational instability (MRI) grows, the mean strength of magnetic fields is amplified until the magnetic pressure becomes as large as 10% of the gas pressure. When the local plasma {beta} (=p {sub gas}/p {sub mag}) becomes less than 5 near the disk surface, magnetic flux escapes from the disk by the Parker instability within one rotation period of the disk. The buoyant escape of coherent magnetic fields drives dynamo activities by generating disk magnetic fields with opposite polarity to satisfy the magnetic flux conservation. The flotation of the azimuthal magnetic flux from the disk and the subsequent amplification of disk magnetic field by the MRI drive quasi-periodic reversal of azimuthal magnetic fields on a timescale of 10 rotation periods. Since the rotation speed decreases with radius, the interval between the reversal of azimuthal magnetic fields increases with radius. The rotation measure computed from the numerical results shows symmetry corresponding to a dipole field.

  2. ALIGNMENTS OF BLACK HOLES WITH THEIR WARPED ACCRETION DISKS AND EPISODIC LIFETIMES OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Li, Yan-Rong; Wang, Jian-Min; Qiu, Jie; Cheng, Cheng

    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.

  3. The different neighbours around Type-1 and Type-2 active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Villarroel, Beatriz; Korn, Andreas J.

    2014-06-01

    One of the most intriguing open issues in galaxy evolution is the structure and evolution of active galactic nuclei (AGN) that emit intense light believed to come from an accretion disk near a super massive black hole. To understand the zoo of different AGN classes, it has been suggested that all AGN are the same type of object viewed from different angles. This model--called AGN unification--has been successful in predicting, for example, the existence of hidden broad optical lines in the spectrum of many narrow-line AGN. But this model is not unchallenged and it is debatable whether more than viewing angle separates the so-called Type-1 and Type-2 AGN. Here we report the first large-scale study that finds strong differences in the galaxy neighbours to Type-1 and Type-2 AGN with data from the Sloan Digital Sky Survey (SDSS; ref. ) Data Release 7 (DR7; ref. ) and Galaxy Zoo. We find strong differences in the colour and AGN activity of the neighbours to Type-1 and Type-2 AGN and in how the fraction of AGN residing in spiral hosts changes depending on the presence or not of a neighbour. These findings suggest that an evolutionary link between the two major AGN types might exist.

  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. Impact of red giant/AGB winds on active galactic nucleus jet propagation

    NASA Astrophysics Data System (ADS)

    Perucho, M.; Bosch-Ramon, V.; Barkov, M. V.

    2017-10-01

    Context. Dense stellar winds may mass-load the jets of active galactic nuclei, although it is unclear on what time and spatial scales the mixing takes place. Aims: Our aim is to study the first steps of the interaction between jets and stellar winds, and also the scales on which the stellar wind mixes with the jet and mass-loads it. Methods: We present a detailed 2D simulation - including thermal cooling - of a bubble formed by the wind of a star designed to study the initial stages of jet-star interaction. We also study the first interaction of the wind bubble with the jet using a 3D simulation in which the star enters the jet. Stability analysis is carried out for the shocked wind structure to evaluate the distances over which the jet-dragged wind, which forms a tail, can propagate without mixing with the jet flow. Results.The 2D simulations point to quick wind bubble expansion and fragmentation after about one bubble shock crossing time. Three-dimensional simulations and stability analysis point to local mixing in the case of strong perturbations and relatively low density ratios between the jet and the jet dragged-wind, and to a possibly more stable shocked wind structure at the phase of maximum tail mass flux. Analytical estimates also indicate that very early stages of the star jet-penetration time may be also relevant for mass-loading. The combination of these and previous results from the literature suggests highly unstable interaction structures and efficient wind-jet flow mixing on the scale of the jet interaction height. Conclusions: The winds of stars with strong mass loss can efficiently mix with jets from active galactic nuclei. In addition, the initial wind bubble shocked by the jet leads to a transient, large interaction surface. The interaction between jets and stars can produce strong inhomogeneities within the jet. As mixing is expected to be effective on large scales, even individual asymptotic giant branch stars can significantly contribute to

  6. Measuring the kinetic power of active galactic nuclei in the radio mode

    NASA Astrophysics Data System (ADS)

    Merloni, Andrea; Heinz, Sebastian

    2007-10-01

    We have studied the relationship among nuclear radio and X-ray power, Bondi rate and the kinetic luminosity of sub-Eddington active galactic nucleus (AGN) jets, as estimated from the pdV work done to inflate the cavities and bubbles observed in the hot X-ray-emitting atmospheres of their host galaxies and clusters. Besides the recently discovered correlation between jet kinetic and Bondi power, we show that a clear correlation exists also between Eddington-scaled kinetic power and bolometric luminosity, given by log(Lkin/LEdd) = (0.49 +/- 0.07) log(Lbol/LEdd) - (0.78 +/- 0.36). The measured slope suggests that these objects are in a radiatively inefficient accretion mode, and have been used to put stringent constraints on the properties of the accretion flow. Interestingly, we found no statistically significant correlations between Bondi power and bolometric AGN luminosity, apart from that induced by their common dependence on Lkin, thus confirming the idea that most of the accretion power emerges from these systems in kinetic form. We have then analysed the relation between kinetic power and radio core luminosity. Combining the measures of jet power with estimators of the unbeamed radio flux of the jet cores as, for example, the so-called Fundamental Plane of active black holes, we are able to determine, in a statistical sense, both the probability distribution of the mean jet Lorentz factor, which peaks at Γm ~ 7, and the intrinsic relationship between kinetic and radio core luminosity (and thus the jet radiative efficiency), which we estimate as logLkin = (0.81 +/- 0.11) logLR + 11.9+4.1-4.4, in good agreement with theoretical predictions of synchrotron jet models. With the aid of these findings, quantitative assessments of kinetic feedback from supermassive black holes in the radio mode (i.e. at low dimensionless accretion rates) will be possible based on accurate determinations of the central engine properties alone, such as mass, radio core and/or X

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

    NASA Astrophysics Data System (ADS)

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

    2005-12-01

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

  8. THE ORIGIN OF [O II] EMISSION IN RECENTLY QUENCHED ACTIVE GALACTIC NUCLEUS HOSTS

    SciTech Connect

    Kocevski, Dale D.; Lemaux, Brian C.; Lubin, Lori M.; Shapley, Alice E.; Gal, Roy R.; Squires, Gordon K.

    2011-08-20

    We have employed emission-line diagnostics derived from DEIMOS and NIRSPEC spectroscopy to determine the origin of the [O II] emission line observed in six active galactic nucleus (AGN) hosts at z {approx} 0.9. These galaxies are a subsample of AGN hosts detected in the Cl1604 supercluster that exhibit strong Balmer absorption lines in their spectra and appear to be in a post-starburst or post-quenched phase, if not for their [O II] emission. Examining the flux ratio of the [N II] to H{alpha} lines, we find that in five of the six hosts the dominant source of ionizing flux is AGN continuum emission. Furthermore, we find that four of the six galaxies have over twice the [O II] line luminosity that could be generated by star formation alone given their H{alpha} line luminosities. This strongly suggests that AGN-excited narrow-line emission is contaminating the [O II] line flux. A comparison of star formation rates calculated from extinction-corrected [O II] and H{alpha} line luminosities indicates that the former yields a five-fold overestimate of the current activity in these galaxies. Our findings reveal the [O II] line to be a poor indicator of star formation activity in a majority of these moderate-luminosity Seyferts. This result bolsters our previous findings that an increased fraction of AGN at high redshifts is hosted by galaxies in a post-starburst phase. The relatively high fraction of AGN hosts in the Cl1604 supercluster that show signs of recently truncated star formation activity may suggest that AGN feedback plays an increasingly important role in suppressing ongoing activity in large-scale structures at high redshift.

  9. 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.

  10. 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.

  11. FEEDBACK FROM MASS OUTFLOWS IN NEARBY ACTIVE GALACTIC NUCLEI. I. ULTRAVIOLET AND X-RAY ABSORBERS

    SciTech Connect

    Crenshaw, D. M.; Kraemer, S. B.

    2012-07-01

    We present an investigation into the impact of feedback from outflowing UV and X-ray absorbers in nearby (z < 0.04) active galactic nuclei (AGNs). From studies of the kinematics, physical conditions, and variability of the absorbers in the literature, we calculate the possible ranges in the total mass outflow rate (M-dot{sub out}) and kinetic luminosity (L{sub KE}) for each AGN, summed over all of its absorbers. These calculations make use of values (or limits) for the radial locations of the absorbers determined from variability, excited-state absorption, and other considerations. From a sample of 10 Seyfert 1 galaxies with detailed photoionization models for their absorbers, we find that 7 have sufficient constraints on the absorber locations to determine M-dot{sub out} and L{sub KE}. For the low-luminosity AGN NGC 4395, these values are low, although we do not have sufficient constraints on the X-ray absorbers to make definitive conclusions. At least five of the six Seyfert 1s with moderate bolometric luminosities (L{sub bol} = 10{sup 43} - 10{sup 45} erg s{sup -1}) have mass outflow rates that are 10-1000 times the mass accretion rates needed to generate their observed luminosities, indicating that most of the mass outflow originates from outside the inner accretion disk. Three of these (NGC 4051, NGC 3516, and NGC 3783) have L{sub KE} in the range 0.5%-5% L{sub bol}, which is the range typically required by feedback models for efficient self-regulation of black hole and galactic bulge growth. At least two of the other three (NGC 5548, NGC 4151, and NGC 7469) have L{sub KE} {approx}> 0.1%L{sub bol}, although these values may increase if radial locations can be determined for more of the absorbers. We conclude that the outflowing UV and X-ray absorbers in moderate-luminosity AGNs have the potential to deliver significant feedback to their environments.

  12. 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.

  13. 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