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Sample records for active galaxy nuclei

  1. New southern galaxies with active nuclei

    SciTech Connect

    Maia, M.A.G.; Da costa, L.N.; Willmer, C.; Pellegrini, P.S.; Rite, C.

    1987-03-01

    A list of AGN candidates, identified from optical spectra taken as part of an ongoing redshift survey of southern galaxies, is presented. The identification, coordinates, morphological type, measured heliocentric radial velocity, and proposed emission type are given for the galaxies showing evidence of nonstellar nuclear activity. Using standard diagnostics, several new Seyferts and low-ionization nuclear-emission regions (LINERs) are identified among the emission-line galaxies observed. 14 references.

  2. Active galactic nuclei and galaxy interactions

    NASA Astrophysics Data System (ADS)

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

    2007-03-01

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

  3. Colliding Galaxies Create Active Galactic Nuclei

    NASA Video Gallery

    This simulation follows the collision of two spiral galaxies that harbor giant black holes. The collision merges the black holes and stirs up gas in both galaxies. The merged black hole gorges on t...

  4. Active Galactic Nuclei in Dwarf Galaxies

    NASA Astrophysics Data System (ADS)

    Hein, Megan; Secrest, N.; Satyapal, S.

    2014-01-01

    Supermassive black holes (SMBHs) one million to a few billion times the mass of our sun are thought to reside in the center of most, if not all, bulge-dominated galaxies. It has been observed that the mass of these SMBHs is strongly correlated with the mass of these bulges, leading to the popular view that these central black holes are formed by galaxy mergers, which induce the growth of the galaxy's bulge and provide matter with which to feed the black hole. Although these properties and their possible consequences have been studied extensively in high mass galaxies and galaxies with large bulges, there is very little research on the possible existence and subsequent properties of SMBHs in low mass galaxies or galaxies with small or no central bulges. This is a significant weakness in the research of these objects as the study of this population of galaxies would allow us to gain valuable insight into SMBH seeds, black holes thought to have formed in the early universe. Strong X-rays are a good indicator of an accreting black hole, because they require more energy to produce and SMBHs are highly energetic, as well as being easier to see due to their ability to penetrate matter more easily than other forms of radiation. In this poster, I will present the results from an X-ray investigation using data matched from the Chandra X-ray observatory to a sample of low mass galaxies (with a mass of log(M) < 9).

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

    SciTech Connect

    Haan, Sebastian; Schinnerer, Eva; Mundell, Carole G.; García-Burillo, Santiago; Combes, Francoise E-mail: schinner@mpia.de E-mail: burillo@oan.es

    2008-01-01

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

  6. 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.

  7. 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.

  8. 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.

  9. Mass Loss from the Nuclei of Active Galaxies

    NASA Technical Reports Server (NTRS)

    Crenshaw, Michael; Kraemer, Steven B.; George, Ian M.

    2003-01-01

    Blueshifted absorption lines in the UV and X-ray spectra of active galaxies reveal the presence of massive outflows of ionized gas from their nuclei. The intrinsic UV and X-ray absorbers show large global covering factors of the central continuum source, and the inferred mass loss rates are comparable to the mass accretion rates. Many absorbers show variable ionic column densities which are attributed to a combination of variable ionizing flux and motion of gas into and out of the line of sight . Detailed studies of the intrinsic absorbers. with the assistance of monitoring observations and photoionization models. provide constraints on their kinematics] physical conditions. and locations relative to the central continuum source. which range from the inner nucleus (approx.0.01 pc) to the galactic disk or halo (approx.10 kpc) . Dynamical models that make use of thermal winds. radiation pressure. and/or hydromagnetic flows have reached a level of sophistication that permits comparisons with the observational constraints .

  10. Hidden Active Galactic Nuclei in Early-type Galaxies

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2012-02-01

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

  12. 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.

  13. Simulating Galaxies and Active Galactic Nuclei in the LSST Image Simulation Effort

    NASA Astrophysics Data System (ADS)

    Pizagno, James; Ahmad, Z.; Bankert, J.; Bard, D.; Connolly, A.; Chang, C.; Gibson, R. R.; Gilmore, K.; Grace, E.; Hannel, M.; Jernigan, J. G.; Jones, L.; Kahn, S. M.; Krughoff, S. K.; Lorenz, S.; Marshall, S.; Shmakova, S. M.; Sylvestri, N.; Todd, N.; Young, M.

    2011-01-01

    We present an extragalactic source catalog, which includes galaxies and Active Galactic Nuclei, that is used for the Large Survey Synoptic Telescope Imaging Simulation effort. The galaxies are taken from the De Lucia et. al. (2006) semi-analytic modeling (SAM) of the Millennium Simulation. The LSST Image Simulation effort requires full SED information and galaxy morphological information, which is added to the catalog by fitting Bruzual & Charlot (2003) stellar population models, with Cardelli, Clayton, Mathis (1989) dust models, to the BVRIK colors provided by the De Lucia et. al. (2006) SAM. Galaxy morphology is modeled as a double Sersic profile for the disk and bulge. Galaxy morphological information and number counts are matched to existing observations. The catalog contains galaxies with a limiting r-band magnitude of mr=28, which results in roughly 1E6 galaxies per square degree. An existing AGN catalog (MacLeod et. al. 2010) is matched to galaxy hosts in the galaxy catalog using SDSS observations. AGN are morphologically modeled as variable point sources located at the center of the host galaxy. We demonstrate how this extragalactic source catalog allows LSST to plan for extended object extraction, variable extragalactic source detection, sensitivity level determination after image stacking, and perform various other cosmological tests.

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

    SciTech Connect

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

    2012-07-10

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

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

    SciTech Connect

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

    2011-09-01

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

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

    NASA Technical Reports Server (NTRS)

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

    2012-01-01

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

  18. Optical versus infrared studies of dusty galaxies and active galactic nuclei - I. Nebular emission lines

    NASA Astrophysics Data System (ADS)

    Wild, Vivienne; Groves, Brent; Heckman, Timothy; Sonnentrucker, Paule; Armus, Lee; Schiminovich, David; Johnson, Benjamin; Martins, Lucimara; Lamassa, Stephanie

    2011-01-01

    Optical nebular emission lines are commonly used to estimate the star formation rate of galaxies and the black hole accretion rate of their central active nuclei. The accuracy of the conversion from line strengths to physical properties depends upon the accuracy to which the lines can be corrected for dust attenuation. For studies of single galaxies with normal amounts of dust, most dust corrections result in the same derived properties within the errors. However, for statistical studies of populations of galaxies, or for studies of galaxies with higher dust contents, such as might be found in some classes of ‘transition’ galaxies, significant uncertainty arises from the dust attenuation correction. In this paper, we compare the strength of the predominantly unobscured mid-infrared [Ne II] λ15.5 μ m+[Ne III] λ12.8 μ m emission lines to the optical Hα emission lines in four samples of galaxies: (i) ordinary star-forming galaxies (80 galaxies); (ii) optically selected dusty galaxies (11); (iii) ultraluminous infrared galaxies (6); and (iv) Seyfert 2 galaxies (20). We show that a single dust attenuation curve applied to all samples can correct the Hα luminosity for dust attenuation to a factor better than 2. Similarly, we compare [O IV] and [O III] luminosities to find that [O III] can be corrected to a factor better than 3. This shows that the total dust attenuation suffered by the active galactic nucleus narrow-line region is not significantly different from that suffered by the star-forming H II regions in the galaxy. We provide explicit dust attenuation corrections, together with errors, for [O II], [O III] and Hα. The best-fitting average attenuation curve is slightly greyer than the Milky Way extinction law, indicating either that external galaxies have slightly different typical dust properties from those of the Milky Way or that there is a significant contribution from scattering. Finally, we uncover an intriguing correlation between silicate

  19. OCCUPATION OF X-RAY-SELECTED GALAXY GROUPS BY X-RAY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Allevato, V.; Finoguenov, A.; Hasinger, G.; Cappelluti, N.; Miyaji, T.; Salvato, M.; Brusa, M.; Zamorani, G.; Gilli, R.; George, M. R.; Tanaka, M.; Silverman, J.; Civano, F.; Elvis, M.; Shankar, F.

    2012-10-10

    We present the first direct measurement of the mean halo occupation distribution (HOD) of X-ray-selected active galactic nuclei (AGNs) in the COSMOS field at z {<=} 1, based on the association of 41 XMM and 17 C-COSMOS AGNs with member galaxies of 189 X-ray-detected galaxy groups from XMM-Newton and Chandra data. We model the mean AGN occupation in the halo mass range log M{sub 200} [M{sub Sun }] = 13-14.5 with a rolling-off power law with the best-fit index {alpha} = 0.06(- 0.22; 0.36) and normalization parameter f{sub a} 0.05(0.04; 0.06). We find the mean HOD of AGNs among central galaxies to be modeled by a softened step function at log M{sub h} > log M{sub min} = 12.75(12.10, 12.95) M{sub Sun} while for the satellite AGN HOD we find a preference for an increasing AGN fraction with M{sub h} , suggesting that the average number of AGNs in satellite galaxies grows slower ({alpha}{sub s} < 0.6) than the linear proportion ({alpha}{sub s} = 1) observed for the satellite HOD of samples of galaxies. We present an estimate of the projected autocorrelation function (ACF) of galaxy groups over the range of r{sub p} = 0.1-40 h {sup -1} Mpc at (z) = 0.5. We use the large-scale clustering signal to verify the agreement between the group bias estimated by using the observed galaxy groups ACF and the value derived from the group mass estimates. We perform a measurement of the projected AGN-galaxy-group cross-correlation function, excluding from the analysis AGNs that are within galaxy groups and we model the two-halo term of the clustering signal with the mean AGN HOD based on our results.

  20. 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.

  1. X-ray variability in active galaxy nuclei and quasars in less than one day

    NASA Technical Reports Server (NTRS)

    Elvis, M.; Feigelson, E.; Griffiths, R. E.; Henry, J. P.; Tananbaum, H.

    1980-01-01

    Data obtained from the Einstein Observatory demonstrating variations in X-ray emission from the nuclei of active galaxies and quasars on time scales of hours rather than previously observed days or years is presented. Light curves obtained from the Einstein imaging proportional counter for the Seyfert 1 galaxy NGC 6814 and from the High Resolution Imager for the quasars OX 169 and 3C 273 are illustrated, and variations by factors greater than two on time scales less than 20,000 sec for the first two objects and by a factor of 10% on a time scale over 50,000 sec for 3C 273 are pointed out. The measurements are also used to determine that thermal bremsstrahlung cannot be the cause of the intensity decay in OX 169, and that, in the absence of relativistic effects, the efficiency for energy release in the matter involved in the emission of 3C 273 is at least 0.1.

  2. The Study of Active Galactic Nuclei and Galaxy Structure Using SDSS Spectroscopy

    NASA Astrophysics Data System (ADS)

    Roig, Benjamin

    Two distinct projects involving spectroscopic data from the Sloan Digital Sky Survey are presented. Data from both the Legacy (SDSS-II) and BOSS (SDSS-III) surveys are used to study stellar populations and active galactic nuclei in old, red galaxies. In the first project, we infer stellar metallicity and abundance ratio gradients for a sample of red galaxies in the Sloan Digital Sky Survey (SDSS) Main galaxy sample. Because this sample does not have multiple spectra at various radii in a single galaxy, we measure these gradients statistically. This method is possible because for a fixed aperture size and a varying redshift range, the aperture will cover different physical sizes on each galaxy dependent on redshift. We stack galaxy spectra in relatively narrow redshift bins and calculate several absorption line indices in projected annuli by differencing spectra in neighboring redshift bins. After determining the line indices, we use stellar population modeling from the EZ_Ages software to calculate ages, metallicities, and abundance ratios within each annulus. Our data covers the central regions of these galaxies, out to slightly higher than 1 Re. We find detectable gradients in metallicity and relatively shallow gradients in abundance ratios, similar to results found for direct measurements of individual galaxies. We compare this data to previous observations and find general agreement, and then briefly to several theoretical studies simulating galaxy evolution models to see what the metallicity gradients and abundance ratios imply about the evolutionary track of these red galaxies. This project also involves developing a code framework to verify this method, with potential more generally applicable future uses. For the second project, we examine the sample of luminous galaxies in the Baryon Oscillation Spectroscopic Survey (BOSS). We find a potentially new observational class of AGN, one with strong and broad MgII 2799A line emission, but very weak emission in

  3. Radio active galactic nuclei in galaxy clusters: Feedback, merger signatures, and cluster tracers

    NASA Astrophysics Data System (ADS)

    Paterno-Mahler, Rachel Beth

    Galaxy clusters, the largest gravitationally-bound structures in the universe, are composed of 50-1000s of galaxies, hot X-ray emitting gas, and dark matter. They grow in size over time through cluster and group mergers. The merger history of a cluster can be imprinted on the hot gas, known as the intracluster medium (ICM). Merger signatures include shocks, cold fronts, and sloshing of the ICM, which can form spiral structures. Some clusters host double-lobed radio sources driven by active galactic nuclei (AGN). First, I will present a study of the galaxy cluster Abell 2029, which is very relaxed on large scales and has one of the largest continuous sloshing spirals yet observed in the X-ray, extending outward approximately 400 kpc. The sloshing gas interacts with the southern lobe of the radio galaxy, causing it to bend. Energy injection from the AGN is insufficient to offset cooling. The sloshing spiral may be an important additional mechanism in preventing large amounts of gas from cooling to very low temperatures. Next, I will present a study of Abell 98, a triple system currently undergoing a merger. I will discuss the merger history, and show that it is causing a shock. The central subcluster hosts a double-lobed AGN, which is evacuating a cavity in the ICM. Understanding the physical processes that affect the ICM is important for determining the mass of clusters, which in turn affects our calculations of cosmological parameters. To further constrain these parameters, as well as models of galaxy evolution, it is important to use a large sample of galaxy clusters over a range of masses and redshifts. Bent, double-lobed radio sources can potentially act as tracers of galaxy clusters over wide ranges of these parameters. I examine how efficient bent radio sources are at tracing high-redshift (z>0.7) clusters. Out of 646 sources in our high-redshift Clusters Occupied by Bent Radio AGN (COBRA) sample, 282 are candidate new, distant clusters of galaxies based on

  4. 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.

  5. Compact Nuclei in Galaxies at Moderate Redshift

    NASA Astrophysics Data System (ADS)

    Sarajedini, Vicki Lynn

    The purpose of this study is to understand the space density and properties of active galaxies to z ≃ 0.8. We have investigated the frequency and nature of unresolved nuclei in galaxies at moderate redshift as indicators of nuclear activity such as Active Galactic Nuclei (AGN) or starbursts. Candidates are selected by fitting imaged galaxies with multi-component models using maximum likelihood estimate techniques to determine the best model fit. We select those galaxies requiring an unresolved, point source component in the galaxy nucleus, in addition to a disk and/or bulge component, to adequately model the galaxy light. We have searched 70 WFPC2 images primarily from the Medium Deep Survey for galaxies containing compact nuclei. In our survey of 1033 galaxies, the fraction containing an unresolved nuclear component ≥3% of the total galaxy light is 16±3% corrected for incompleteness and 9±1% for nuclei ≥5% of the galaxy light. Most of the nuclei are ~<20% of the total galaxy light. The majority of the host galaxies are spirals with little or no bulge component. The V-I colors of the nuclei are compared with synthetic colors for Seyferts and starburst nuclei to help differentiate between AGNs and starbursts in our sample. Spectroscopic redshifts have been obtained for 35 of our AGN/starburst candidates and photometric redshifts are estimated to an accuracy of σz≃0.1 for the remaining sample. We present the upper limit luminosity function (LF) for low-luminosity AGN (LLAGN) in two redshift bins to z = 0.8. We detect mild number density evolution of the form φ∝ (1+z)1.9 for nuclei at -18 ~galaxies could have hosted a LLAGN at some point in their lives. We estimate the likely

  6. Offset active galactic nuclei as tracers of galaxy mergers and supermassive black hole growth

    SciTech Connect

    Comerford, Julia M.; Greene, Jenny E.

    2014-07-10

    Offset active galactic nuclei (AGNs) are AGNs that are in ongoing galaxy mergers, which produce kinematic offsets in the AGNs relative to their host galaxies. Offset AGNs are also close relatives of dual AGNs. We conduct a systematic search for offset AGNs in the Sloan Digital Sky Survey by selecting AGN emission lines that exhibit statistically significant line-of-sight velocity offsets relative to systemic. From a parent sample of 18,314 Type 2 AGNs at z < 0.21, we identify 351 offset AGN candidates with velocity offsets of 50 km s{sup –1} < |Δv| < 410 km s{sup –1}. When we account for projection effects in the observed velocities, we estimate that 4%-8% of AGNs are offset AGNs. We designed our selection criteria to bypass velocity offsets produced by rotating gas disks, AGN outflows, and gravitational recoil of supermassive black holes, but follow-up observations are still required to confirm our candidates as offset AGNs. We find that the fraction of AGNs that are offset candidates increases with AGN bolometric luminosity, from 0.7% to 6% over the luminosity range 43 < log (L{sub bol}) [erg s{sup –1}] <46. If these candidates are shown to be bona fide offset AGNs, then this would be direct observational evidence that galaxy mergers preferentially trigger high-luminosity AGNs. Finally, we find that the fraction of AGNs that are offset AGN candidates increases from 1.9% at z = 0.1 to 32% at z = 0.7, in step with the growth in the galaxy merger fraction over the same redshift range.

  7. CO Spectral Line Energy Distributions of Infrared-Luminous Galaxies and Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Papadopoulos, Padeli P.; van der Werf, Paul; Isaak, Kate; Xilouris, Emmanuel M.

    2010-06-01

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

  8. The Intrinsic Eddington Ratio Distribution of Active Galactic Nuclei in Young Galaxies from SDSS

    NASA Astrophysics Data System (ADS)

    Jones, Mackenzie L.; Hickox, Ryan C.; Black, Christine; Hainline, Kevin Nicholas; DiPompeo, Michael A.

    2016-04-01

    An important question in extragalactic astronomy concerns the distribution of black hole accretion rates, i.e. the Eddington ratio distribution, of active galactic nuclei (AGN). Specifically, it is matter of debate whether AGN follow a broad distribution in accretion rates, or if the distribution is more strongly peaked at characteristic Eddington ratios. Using a sample of galaxies from SDSS DR7, we test whether an intrinsic Eddington ratio distribution that takes the form of a broad Schechter function is in fact consistent with previous work that suggests instead that young galaxies in optical surveys have a more strongly peaked lognormal Eddington ratio distribution. Furthermore, we present an improved method for extracting the AGN distribution using BPT diagnostics that allows us to probe over one order of magnitude lower in Eddington ratio, counteracting the effects of dilution by star formation. We conclude that the intrinsic Eddington ratio distribution of optically selected AGN is consistent with a power law with an exponential cutoff, as is observed in the X-rays. This work was supported in part by a NASA Jenkins Fellowship.

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

    SciTech Connect

    Goulding, A. D.; Forman, W. R.; Jones, C.; Murray, S. S.; Paggi, A.; Ashby, M. L. N.; Huang, J.-S.; Kraft, R.; Willner, S. P.; Hickox, R. C.; Coil, A. L.; Cooper, M. C.; Newman, J. A.; Weiner, B. J.

    2014-03-01

    We present the results of a combined galaxy population analysis for the host galaxies of active galactic nuclei (AGN) identified at 0 < z < 1.4 within the Sloan Digital Sky Survey, Boötes, and DEEP2 surveys. We identified AGN in a uniform and unbiased manner at X-ray, infrared, and radio wavelengths. Supermassive black holes undergoing radiatively efficient accretion (detected as X-ray and/or infrared AGN) appear to be hosted in a separate and distinct galaxy population than AGN undergoing powerful mechanically dominated accretion (radio AGN). Consistent with some previous studies, radiatively efficient AGN appear to be preferentially hosted in modest star-forming galaxies, with little dependence on AGN or galaxy luminosity. AGN exhibiting radio-emitting jets due to mechanically dominated accretion are almost exclusively observed in massive, passive galaxies. Crucially, we now provide strong evidence that the observed host-galaxy trends are independent of redshift. In particular, these different accretion-mode AGN have remained as separate galaxy populations throughout the last 9 Gyr. Furthermore, it appears that galaxies hosting AGN have evolved along the same path as galaxies that are not hosting AGN with little evidence for distinctly separate evolution.

  10. AN OBSERVED LINK BETWEEN ACTIVE GALACTIC NUCLEI AND VIOLENT DISK INSTABILITIES IN HIGH-REDSHIFT GALAXIES

    SciTech Connect

    Bournaud, Frederic; Juneau, Stephanie; Le Floc'h, Emeric; Mullaney, James; Daddi, Emanuele; Duc, Pierre-Alain; Elbaz, David; Salmi, Fadia; Dekel, Avishai; Dickinson, Mark

    2012-09-20

    We provide evidence for a correlation between the presence of giant clumps and the occurrence of active galactic nuclei (AGNs) in disk galaxies. Giant clumps of 10{sup 8}-10{sup 9} M{sub Sun} arise from violent gravitational instability in gas-rich galaxies, and it has been proposed that this instability could feed supermassive black holes (BHs). We use emission line diagnostics to compare a sample of 14 clumpy (unstable) disks and a sample of 13 smoother (stable) disks at redshift z {approx} 0.7. The majority of clumpy disks in our sample have a high probability of containing AGNs. Their [O III] {lambda}5007 emission line is strongly excited, inconsistent with low-metallicity star formation (SF) alone. [Ne III] {lambda}3869 excitation is also higher. Stable disks rarely have such properties. Stacking ultra sensitive Chandra observations (4 Ms) reveals an X-ray excess in clumpy galaxies, which confirms the presence of AGNs. The clumpy galaxies in our intermediate-redshift sample have properties typical of gas-rich disk galaxies rather than mergers, being in particular on the main sequence of SF. This suggests that our findings apply to the physically similar and numerous gas-rich unstable disks at z > 1. Using the observed [O III] and X-ray luminosities, we conservatively estimate that AGNs hosted by clumpy disks have typical bolometric luminosities of the order of a few 10{sup 43} erg s{sup -1}, BH growth rates m-dot{sub BH}{approx}10{sup -2} M{sub Sun} yr{sup -1}, and that these AGNs are substantially obscured in X-rays. This moderate-luminosity mode could provide a large fraction of today's BH mass with a high duty cycle (>10%), accretion bursts with higher luminosities being possible over shorter phases. Violent instabilities at high redshift (giant clumps) are a much more efficient driver of BH growth than the weak instabilities in nearby spirals (bars), and the evolution of disk instabilities with mass and redshift could explain the simultaneous downsizing of

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  12. Cosmological Studies with Galaxy Clusters, Active Galactic Nuclei, and Strongly Lensed Quasars

    NASA Astrophysics Data System (ADS)

    Rumbaugh, Nicholas Andrew

    The large-scale structure (LSS) of the universe provides scientists with one of the best laboratories for studying Lambda Cold Dark Matter (LambdaCDM) cosmology. Especially at high redshift, we see increased rates of galaxy cluster and galaxy merging in LSS relative to the field, which is useful for studying the hierarchical merging predicted by LambdaCDM. The largest identified bound structures, superclusters, have not yet virialized. Despite the wide range of dynamical states of their constituent galaxies, groups, and clusters, they are all still actively evolving, providing an ideal laboratory in which to study cluster and galaxy evolution. In this dissertation, I present original research on several aspects of LSS and LambdaCDM cosmology. Three separate studies are included, each one focusing on a different aspect. In the first study, we use X-ray and optical observations from nine galaxy clusters at high redshift, some embedded in larger structures and some isolated, to study their evolutionary states. We extract X-ray gas temperatures and luminosities as well as optical velocity dispersions. These cluster properties are compared using low-redshift scaling relations. In addition, we employ several tests of substructure, using velocity histograms, Dressler-Shectman tests, and centroiding offsets. We conclude that two clusters out of our sample are most likely unrelaxed, and find support for deviations from self-similarity in the redshift evolution of the Lx-T relation. Our numerous complementary tests of the evolutionary state of clusters suggest potential under-estimations of systematic error in studies employing only a single such test. In the second study, we use multi-band imaging and spectroscopy to study active galactic nuclei (AGN) in high-redshift LSS. The AGN were identified using X-ray imaging and matched to optical catalogs that contained spectroscopic redshifts to identify members of the structures. AGN host galaxies tended to be associated with the

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

    SciTech Connect

    Papadopoulos, Padeli P.; Van der Werf, Paul; Isaak, Kate; Xilouris, Emmanuel M. E-mail: pvdwerf@strw.leidenuniv.n E-mail: xilouris@astro.noa.g

    2010-06-01

    We report on new sensitive CO J = 6-5 line observations of several luminous infrared galaxies (LIRGs; L {sub IR}(8-1000 {mu}m) {approx}> 10{sup 11} L {sub sun}), 36% (8/22) of them ultraluminous infrared galaxies (ULIRGs) (L {sub IR}>10{sup 12} L {sub sun}), and two powerful local active galactic nuclei (AGNs)-the optically luminous QSO PG 1119+120 and the powerful radio galaxy 3C 293-using the James Clerk Maxwell Telescope on Mauna Kea in Hawaii. We combine these observations with existing low-J CO data and dust emission spectral energy distributions in the far-infrared-submillimeter from the literature to constrain the properties of the star-forming interstellar medium (ISM) in these systems. We then build the first local CO spectral line energy distributions (SLEDs) for the global molecular gas reservoirs that reach up to high J-levels. These CO SLEDs are neither biased by strong lensing (which affects many of those constructed for high-redshift galaxies), nor suffer from undersampling of CO-bright regions (as most current high-J CO observations of nearby extended systems do). We find: (1) a significant influence of dust optical depths on the high-J CO lines, suppressing the J = 6-5 line emission in some of the most IR-luminous LIRGs, (2) low global CO line excitation possible even in vigorously star-forming systems, (3) the first case of a shock-powered high-excitation CO SLED in the radio galaxy 3C 293 where a powerful jet-ISM interaction occurs, and (4) unusually highly excitated gas in the optically powerful QSO PG 1119+120. In Arp 220 and possibly other (U)LIRGs very faint CO J = 6-5 lines can be attributed to significant dust optical depths at short submillimeter wavelengths immersing those lines in a strong dust continuum, and also causing the C{sup +} line luminosity deficit often observed in such extreme starbursts. Re-analysis of the CO line ratios available for submillimeter galaxies suggests that similar dust opacities also may be present in these

  14. Bursty stellar populations and obscured active galactic nuclei in galaxy bulges

    NASA Astrophysics Data System (ADS)

    Wild, Vivienne; Kauffmann, Guinevere; Heckman, Tim; Charlot, Stéphane; Lemson, Gerard; Brinchmann, Jarle; Reichard, Tim; Pasquali, Anna

    2007-10-01

    We investigate trends between the recent star formation history and black hole growth in galaxy bulges in the Sloan Digital Sky Survey. The galaxies lie at 0.01 < z < 0.07 where the fibre aperture covers only the central 0.6-4.0 kpc diameter of the galaxy. We find strong trends between black hole growth, as measured by dust-attenuation-corrected [O III] luminosity, and the recent star formation history of the bulges. 56 per cent of the bulges are quiescent with no signs of recent or ongoing star formation and, while almost half of all active galactic nuclei (AGN) lie within these bulges, they contribute only ~10 per cent to the total black hole growth in the local Universe. At the other extreme, the AGN contained within the ~4 per cent of galaxy bulges that are undergoing or have recently undergone the strongest starbursts, contribute at least 10-20 per cent of the total black hole growth. Much of this growth occurs in AGN with high amounts of dust extinction and thus the precise numbers remain uncertain. The remainder of the black hole growth (>60 per cent) is contributed by bulges with more moderate recent or ongoing star formation. The strongest accreting black holes reside in bulges with a wide range in recent star formation history. We conclude that our results support the popular hypothesis for black hole growth occurring through gas inflow into the central regions of galaxies, followed by a starburst and triggering of the AGN. However, while this is a significant pathway for the growth of black holes, it is not the dominant one in the present-day Universe. More unspectacular processes are apparently responsible for the majority of this growth. In order to arrive at these conclusions we have developed a set of new high signal-to-noise ratio (S/N) optical spectral indicators, designed to allow a detailed study of stellar populations which have undergone recent enhanced star formation. Working in the rest-frame wavelength range 3750-4150 Å, ideally suited to

  15. GOODS-HERSCHEL: SEPARATING HIGH-REDSHIFT ACTIVE GALACTIC NUCLEI AND STAR-FORMING GALAXIES USING INFRARED COLOR DIAGNOSTICS

    SciTech Connect

    Kirkpatrick, Allison; Pope, Alexandra; Charmandaris, Vassilis; Daddi, Emmanuele; Elbaz, David; Pannella, Maurilio; Aussel, Herve; Dasyra, Kalliopi; Leiton, Roger; Scott, Douglas; Magnelli, Benjamin; Popesso, Paola; Altieri, Bruno; Coia, Daniela; Valtchanov, Ivan; Dannerbauer, Helmut; Dickinson, Mark; Kartaltepe, Jeyhan; Magdis, Georgios

    2013-02-15

    We have compiled a large sample of 151 high-redshift (z = 0.5-4) galaxies selected at 24 {mu}m (S {sub 24} > 100 {mu}Jy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-infrared spectrum into contributions from star formation and activity in the galactic nuclei. In addition, we have a wealth of photometric data from Spitzer IRAC/MIPS and Herschel PACS/SPIRE. We explore how effective different infrared color combinations are at separating our mid-IR spectroscopically determined active galactic nuclei from our star-forming galaxies. We look in depth at existing IRAC color diagnostics, and we explore new color-color diagnostics combining mid-IR, far-IR, and near-IR photometry, since these combinations provide the most detail about the shape of a source's IR spectrum. An added benefit of using a color that combines far-IR and mid-IR photometry is that it is indicative of the power source driving the IR luminosity. For our data set, the optimal color selections are S {sub 250}/S {sub 24} versus S {sub 8}/S {sub 3.6} and S {sub 100}/S {sub 24} versus S {sub 8}/S {sub 3.6}; both diagnostics have {approx}10% contamination rate in the regions occupied primarily by star-forming galaxies and active galactic nuclei, respectively. Based on the low contamination rate, these two new IR color-color diagnostics are ideal for estimating both the mid-IR power source of a galaxy when spectroscopy is unavailable and the dominant power source contributing to the IR luminosity. In the absence of far-IR data, we present color diagnostics using the Wide-field Infrared Survey Explorer mid-IR bands which can efficiently select out high-z (z {approx} 2) star-forming galaxies.

  16. Simulations of cosmic-ray feedback by active galactic nuclei in galaxy clusters

    NASA Astrophysics Data System (ADS)

    Sijacki, Debora; Pfrommer, Christoph; Springel, Volker; Enßlin, Torsten A.

    2008-07-01

    Feedback processes by active galactic nuclei (AGN) appear to be a key for understanding the nature of the very X-ray luminous cool cores found in many clusters of galaxies. We investigate a numerical model for AGN feedback where for the first time a relativistic particle population in AGN-inflated bubbles is followed within a full cosmological context. In our high-resolution simulations of galaxy cluster formation, we assume that black hole accretion is accompanied by energy feedback that occurs in two different modes, depending on the accretion rate itself. At high accretion rates, a small fraction of the radiated energy is coupled thermally to the gas surrounding the quasar, while in a low-accretion state, mechanically efficient feedback in the form of hot, buoyant bubbles that are inflated by radio activity is considered. Unlike previous work, we inject a non-thermal particle population of relativistic protons into the AGN bubbles, instead of adopting a purely thermal heating. We then follow the subsequent evolution of the cosmic-ray (CR) plasma inside the bubbles, considering both its hydrodynamical interactions and dissipation processes relevant to the CR population. This permits us to analyse the impact of CR bubbles on the surrounding intracluster medium, and in particular, how this contrasts with the purely thermal case. Due to the different buoyancy of relativistic plasma and the comparatively long CR dissipation time-scale, we find substantial changes in the evolution of clusters as a result of CR feedback. In particular, the non-thermal population can provide significant pressure support in central cluster regions at low thermal temperatures, providing a natural explanation for the decreasing temperature profiles found in cool core clusters. At the same time, the morphologies of the bubbles and of the induced X-ray cavities show a striking similarity to observational findings. AGN feedback with CRs also proves efficient in regulating cluster cooling

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

    NASA Astrophysics Data System (ADS)

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

    2012-01-01

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

  18. Bulgeless galaxies at intermediate redshift: Sample selection, color properties, and the existence of powerful active galactic nuclei

    SciTech Connect

    Bizzocchi, Luca; Leonardo, Elvira; Grossi, Marco; Afonso, José; Fernandes, Cristina; Retrê, João; Filho, Mercedes E.; Lobo, Catarina; Griffith, Roger L.; Anton, Sonia; Bell, Eric F.; Brinchmann, Jarle; Henriques, Bruno; Messias, Hugo

    2014-02-10

    We present a catalog of bulgeless galaxies, which includes 19,225 objects selected in four of the deepest, largest multi-wavelength data sets available—COSMOS, AEGIS, GEMS, and GOODS—at intermediate redshift (0.4 ≤ z ≤ 1.0). The morphological classification was provided by the Advanced Camera for Surveys General Catalog (ACS-GC), which used publicly available data obtained with the ACS instrument on the Hubble Space Telescope. Rest-frame photometric quantities were derived using kcorrect. We analyze the properties of the sample and the evolution of pure-disk systems with redshift. Very massive [log (M {sub *}/M {sub ☉}) > 10.5] bulgeless galaxies contribute to ∼30% of the total galaxy population number density at z ≥ 0.7, but their number density drops substantially with decreasing redshift. We show that only a negligible fraction of pure disks appear to be quiescent systems, and red sequence bulgeless galaxies show indications of dust-obscured star formation. X-ray catalogs were used to search for X-ray emission within our sample. After visual inspection and detailed parametric morphological fitting we identify 30 active galactic nuclei (AGNs) that reside in galaxies without a classical bulge. The finding of such peculiar objects at intermediate redshift shows that while AGN growth in merger-free systems is a rare event (0.2% AGN hosts in this sample of bulgeless galaxies), it can indeed happen relatively early in the history of the universe.

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

    An important question in extragalactic astronomy concerns the distribution of black hole accretion rates of active galactic nuclei (AGNs). Based on observations at X-ray wavelengths, the observed Eddington ratio distribution appears as a power law, while optical studies have often yielded a lognormal distribution. There is increasing evidence that these observed discrepancies may be due to contamination by star formation and other selection effects. Using a sample of galaxies from the Sloan Digital Sky Survey Data Release 7, we test whether or not an intrinsic Eddington ratio distribution that takes the form of a Schechter function is consistent with previous work suggesting that young galaxies in optical surveys have an observed lognormal Eddington ratio distribution. We simulate the optical emission line properties of a population of galaxies and AGNs using a broad, instantaneous luminosity distribution described by a Schechter function near the Eddington limit. This simulated AGN population is then compared to observed galaxies via their positions on an emission line excitation diagram and Eddington ratio distributions. We present an improved method for extracting the AGN distribution using BPT diagnostics that allows us to probe over one order of magnitude lower in Eddington ratio, counteracting the effects of dilution by star formation. We conclude that for optically selected AGNs in young galaxies, the intrinsic Eddington ratio distribution is consistent with a possibly universal, broad power law with an exponential cutoff, as this distribution is observed in old, optically selected galaxies and X-rays.

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

    NASA Astrophysics Data System (ADS)

    Shklovsky, I. S.

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

  1. Host galaxy colour gradients and accretion disc obscuration in AEGIS z ~ 1 X-ray-selected active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Pierce, C. M.; Lotz, J. M.; Salim, S.; Laird, E. S.; Coil, A. L.; Bundy, K.; Willmer, C. N. A.; Rosario, D. J. V.; Primack, J. R.; Faber, S. M.

    2010-10-01

    We describe the effect of active galactic nucleus (AGN) light on host galaxy optical and UV-optical colours, as determined from X-ray-selected AGN host galaxies at z ~ 1, and compare the AGN host galaxy colours to those of a control sample matched to the AGN sample in both redshift and stellar mass. We identify as X-ray-selected AGNs 8.7+4-3 per cent of the red-sequence control galaxies, 9.8 +/- 3 per cent of the blue-cloud control galaxies and 14.7+4-3 per cent of the green-valley control galaxies. The nuclear colours of AGN hosts are generally bluer than their outer colours, while the control galaxies exhibit redder nuclei. AGNs in blue-cloud host galaxies experience less X-ray obscuration, while AGNs in red-sequence hosts have more, which is the reverse of what is expected from general considerations of the interstellar medium. Outer and integrated colours of AGN hosts generally agree with the control galaxies, regardless of X-ray obscuration, but the nuclear colours of unobscured AGNs are typically much bluer, especially for X-ray luminous objects. Visible point sources are seen in many of these, indicating that the nuclear colours have been contaminated by AGN light and that obscuration of the X-ray radiation and visible light are therefore highly correlated. Red AGN hosts are typically slightly bluer than red-sequence control galaxies, which suggests that their stellar populations are slightly younger. We compare these colour data to current models of AGN formation. The unexpected trend of less X-ray obscuration in blue-cloud galaxies and more in red-sequence galaxies is problematic for all AGN feedback models, in which gas and dust is thought to be removed as star formation shuts down. A second class of models involving radiative instabilities in hot gas is more promising for red-sequence AGNs but predicts a larger number of point sources in red-sequence AGNs than is observed. Regardless, it appears that multiple AGN models are necessary to explain the

  2. MOIRCS DEEP SURVEY. III. ACTIVE GALACTIC NUCLEI IN MASSIVE GALAXIES AT z = 2-4

    SciTech Connect

    Yamada, T.; Kajisawa, M.; Akiyama, M.; Ichikawa, T.; Tokoku, C.; Yoshikawa, T.; Konishi, M.; Nishimura, T.; Omata, K.; Suzuki, R.; Tanaka, I.; Uchimoto, Y. K.

    2009-07-10

    We investigate the X-ray properties of the K-band-selected galaxies at redshift 2 < z < 4 by using our deep near-infrared images obtained in the Multi-Object Infrared Camera and Spectrograph Deep Survey project and the published Chandra X-ray source catalog. Sixty-one X-ray sources with the 2-10 keV luminosity L{sub X} = 10{sup 42}-10{sup 44} erg s{sup -1} are identified with the K-selected galaxies and we found that they are exclusively (90%) associated with the massive objects with a stellar mass larger than 10{sup 10.5} M{sub sun}. Our results are consistent with the idea that the M {sub BH}/M{sub str} ratio of the galaxies at z = 2-4 is similar to the present-day value. On the other hand, the active galactic nucleus (AGN) detection rate among the very massive galaxies with a stellar mass larger than 10{sup 11} M{sub sun} is high, 33% (26/78). They are active objects in the sense that the black hole mass accretion rate is {approx}1%-50% of the Eddington limit if they indeed have similar M {sub BH}/M {sub str} ratio with those observed in the local universe. The active duration in the AGN duty cycle of the high-redshift massive galaxies seems large.

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

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark; Dunner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, Erik D.; Wollack, Edward

    2014-01-01

    We present a catalogue of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 and/or 218 GHz in the 2008 Southern survey. Flux densities span 14 - 1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two subpopulations: 167 radio galaxies powered by central active galactic nuclei (AGN) and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97 per cent of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogues. When combined with flux densities from the Australia Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index, alpha(sub 148-218), of 3.7 +0.62/-0.86), and includes both local galaxies and sources with redshift around 6. Dusty sources with no counterpart in existing catalogues likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

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

    NASA Technical Reports Server (NTRS)

    Marsden, Danica; Gralla, Megan; Marriage, Tobias A.; Switzer, Eric R.; Partridge, Bruce; Massardi, Marcella; Morales, Gustavo; Addison, Graeme; Bond, J. Richard; Crichton, Devin; Das, Sudeep; Devlin, Mark; Duenner, Rolando; Hajian, Amir; Hilton, Matt; Hincks, Adam; Hughes, John P.; Irwin, Kent; Kosowsky, Arthur; Menanteau, Felipe; Moodley, Kavilan; Niemack, Michael; Page, Lyman; Reese, EriK D.; Wollack, Edward

    2013-01-01

    We present a catalog of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 GHz and/or 218GHz in the 2008 Southern survey. Flux densities span 14-1700mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two sub-populations: 167 radio galaxies powered by central active galactic nuclei (AGN), and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97% of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogs. When combined with flux densities from the Australian Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148GHz, with the trend continuing to 218GHz. The ACT dust-dominated source population has a median spectral index, alpha(sub 148-218), of 3.7+0.62 or -0.86, and includes both local galaxies and sources with redshifts as great as 5.6. Dusty sources with no counterpart in existing catalogs likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

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

    NASA Technical Reports Server (NTRS)

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

    2014-01-01

    We present a catalogue of 191 extragalactic sources detected by the Atacama Cosmology Telescope (ACT) at 148 and/or 218 GHz in the 2008 Southern survey. Flux densities span 14 -1700 mJy, and we use source spectral indices derived using ACT-only data to divide our sources into two subpopulations: 167 radio galaxies powered by central active galactic nuclei (AGN) and 24 dusty star-forming galaxies (DSFGs). We cross-identify 97 per cent of our sources (166 of the AGN and 19 of the DSFGs) with those in currently available catalogues. When combined with flux densities from the Australia Telescope 20 GHz survey and follow-up observations with the Australia Telescope Compact Array, the synchrotron-dominated population is seen to exhibit a steepening of the slope of the spectral energy distribution from 20 to 148 GHz, with the trend continuing to 218 GHz. The ACT dust-dominated source population has a median spectral index, A(sub 148-218), of 3.7 (+0.62 or -0.86), and includes both local galaxies and sources with redshift around 6. Dusty sources with no counterpart in existing catalogues likely belong to a recently discovered subpopulation of DSFGs lensed by foreground galaxies or galaxy groups.

  6. POLYCYCLIC AROMATIC HYDROCARBONS IN GALAXIES AT z approx 0.1: THE EFFECT OF STAR FORMATION AND ACTIVE GALACTIC NUCLEI

    SciTech Connect

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

    2009-11-01

    We present the analysis of the polycyclic aromatic hydrocarbon (PAH) spectra of a sample of 92 typical star-forming galaxies at 0.03 < z < 0.2 observed with the Spitzer intensified Reticon spectrograph (IRS). We compare the relative strengths of PAH emission features with Sloan Digital Sky Survey optical diagnostics to probe the relationship between PAH grain properties and star formation and active galactic nuclei (AGNs) activity. Short-to-long wavelength PAH ratios, and in particular the 7.7 mum-to-11.3 mum feature ratio, are strongly correlated with the star formation diagnostics D{sub n} (4000) and Halpha equivalent width, increasing with younger stellar populations. This ratio also shows a significant difference between active and non-active galaxies, with the active galaxies exhibiting weaker 7.7 mum emission. A hard radiation field as measured by [O{sub III}]/Hbeta and [Ne{sub III}]{sub 15.6m}u{sub m}/[Ne{sub II}]{sub 12.8m}u{sub m} effects PAH ratios differently depending on whether this field results from starburst activity or an AGN. Our results are consistent with a picture in which larger PAH molecules grow more efficiently in richer media and in which smaller PAH molecules are preferentially destroyed by the AGN.

  7. Galaxy Zoo: Are Bars Responsible for the Feeding of Active Galactic Nuclei at 0.2 < z < 1.0?

    NASA Astrophysics Data System (ADS)

    Cheung, Edmond; Trump, Jonathan; Athanassoula, Lia; Bamford, Steven; Bell, Eric F.; Bosma, Albert; Cardamone, Carolin N.; Casteels, Kevin; Faber, Sandra M.; Fang, Jerome J.; Fortson, Lucy; Kocevski, Dale; Koo, David C.; Laine, Seppo J.; Lintott, Chris; Masters, Karen; Melvin, Tom; Nichol, Robert; Schawinski, Kevin; Simmons, Brooke D.; Smethurst, Rebecca; Willett, Kyle; Galaxy Zoo, Aegis, Cosmos, Goods

    2015-01-01

    We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS, COSMOS, and GOODS-S surveys to create samples of face-on, disk galaxies at 0.2 < z < 1.0. We use a novel method to robustly compare a sample of 120 AGN host galaxies, defined to have 1042 erg s-1 < LX < 1044erg s-1, with inactive control galaxies matched in stellar mass, rest-frame color, size, Sérsic index, and redshift. Using the GZH bar classifications of each sample, we demonstrate that AGN hosts show no statistically significant enhancement in bar fraction or average bar likelihood compared to closely-matched inactive galaxies. In detail, we find that the AGN bar fraction cannot be enhanced above the bar fraction in the control sample by more than a factor of two, at 99.7% confidence. We similarly find no significant difference in the AGN fraction among barred and non-barred galaxies. Thus we find no compelling evidence that large-scale bars directly fuel AGN at 0.2 < z < 1.0. This result, coupled with previous results at z = 0, implies that moderate-luminosity AGN have not been preferentially fed by large-scale bars since z = 1. Furthermore, given the low bar fractions at z > 1, our findings suggest that large-scale bars have likely never directly been a dominant fueling mechanism for supermassive black hole growth.

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

    NASA Astrophysics Data System (ADS)

    Cheung, Edmond; Trump, Jonathan R.; Athanassoula, E.; Bamford, Steven P.; Bell, Eric F.; Bosma, A.; Cardamone, Carolin N.; Casteels, Kevin R. V.; Faber, S. M.; Fang, Jerome J.; Fortson, Lucy F.; Kocevski, Dale D.; Koo, David C.; Laine, Seppo; Lintott, Chris; Masters, Karen L.; Melvin, Thomas; Nichol, Robert C.; Schawinski, Kevin; Simmons, Brooke; Smethurst, Rebecca; Willett, Kyle W.

    2015-02-01

    We present a new study investigating whether active galactic nuclei (AGN) beyond the local universe are preferentially fed via large-scale bars. Our investigation combines data from Chandra and Galaxy Zoo: Hubble (GZH) in the AEGIS (All-wavelength Extended Groth strip International Survey), COSMOS (Cosmological Evolution Survey), and (Great Observatories Origins Deep Survey-South) GOODS-S surveys to create samples of face-on, disc galaxies at 0.2 < z < 1.0. We use a novel method to robustly compare a sample of 120 AGN host galaxies, defined to have 1042 erg s-1 < LX < 1044 erg s-1, with inactive control galaxies matched in stellar mass, rest-frame colour, size, Sérsic index, and redshift. Using the GZH bar classifications of each sample, we demonstrate that AGN hosts show no statistically significant enhancement in bar fraction or average bar likelihood compared to closely-matched inactive galaxies. In detail, we find that the AGN bar fraction cannot be enhanced above the control bar fraction by more than a factor of 2, at 99.7 per cent confidence. We similarly find no significant difference in the AGN fraction among barred and non-barred galaxies. Thus we find no compelling evidence that large-scale bars directly fuel AGN at 0.2 < z < 1.0. This result, coupled with previous results at z = 0, implies that moderate-luminosity AGN have not been preferentially fed by large-scale bars since z = 1. Furthermore, given the low bar fractions at z > 1, our findings suggest that large-scale bars have likely never directly been a dominant fuelling mechanism for supermassive black hole growth.

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

    NASA Astrophysics Data System (ADS)

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

    2013-10-01

    We study the mid- to far-IR properties of a 24 μm-selected flux-limited sample (S24> 5 mJy) of 154 intermediate redshift (⟨ z ⟩ ~ 0.15), infrared luminous galaxies, drawn from the 5 Milli-Jansky Unbiased Spitzer Extragalactic Survey. By combining existing mid-IR spectroscopy and new Herschel SPIRE submm photometry from the Herschel Multi-tiered Extragalactic Survey, we derived robust total infrared luminosity (LIR) and dust mass (Mdust) estimates and infered the relative contribution of the AGN to the infrared energy budget of the sources. We found that the total (8-1000 μm) infrared emission of galaxies with weak 6.2 μm PAH emission (EW6.2 ≤ 0.2 μm) is dominated by AGN activity, while for galaxies with EW6.2> 0.2 μm more than 50% of the LIR arises from star formation. We also found that for galaxies detected in the 250-500 μm Herschel bands an AGN has a statistically insignificant effect on the temperature of the cold dust and the far-IR colours of the host galaxy, which are primarily shaped by star formation activity. For star-forming galaxies we reveal an anti-correlation between the LIR-to-rest-frame 8 μm luminosity ratio, IR8 ≡ LIR/L8 and the strength of PAH features. We found that this anti-correlation is primarily driven by variations in the PAHsemission, and not by variations in the 5-15 μm mid-IR continuum emission. Using the [Ne iii]/[Ne ii] line ratio as a tracer of the hardness of the radiation field, we confirm that galaxies with harder radiation fields tend to exhibit weaker PAH features, and found that they have higher IR8 values and higher dust-mass-weighted luminosities (LIR/Mdust), the latter being a proxy for the dust temperature (Td). We argue that these trends originate either from variations in the environment of the star-forming regions or are caused by variations in the age of the starburst. Finally, we provide scaling relations that will allow estimating LIR, based on single-band observations with the mid-infrared instrument

  10. The luminous polycyclic aromatic hydrocarbon emission features: Applications to high redshift galaxies and active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Shipley, Heath Vernon

    (corrected for attenuation using the mono-chromatic rest-frame 24um emission), with a tight scatter of 0.15 dex. The scatter is comparable to that between SFRs derived from the Paalpha and dust-corrected Halpha emission lines, implying the PAH features may be as accurate a SFR indicator as the Hydrogen recombination lines. Because the PAH features are so bright, our PAH SFR calibration enables an efficient way to measure SFRs in distant galaxies with JWST to SFRs as low as ~10 M; yr-1 to z >~ 2. We use Spitzer/IRS observations of PAH features in lensed star-forming galaxies at 1 < z < 3 to demonstrate the utility of the PAHs to derive SFRs as accurate as those available from Paalpha. Chapter 4 is the application of the PAH SFRs for galaxies with AGN to demonstrate the reliability for studies of the co-evolution of star-formation and SMBH accretion. We present a study of the contribution from star-formation in galaxies of varying AGN activity (from pure star-forming galaxies to quasars) as a function of total IR luminosity using a sample of 220 galaxies. We use mid-IR spectroscopy from the Spitzer/IRS and photometry from the MIPS mum, 70mum and 160mum bands with partial coverage of the sample with the Herschel 160mum band for the quasars. The contribution from star-formation to the total IR luminosity implied by the PAH emission decreases with increasing IR luminosity. We find a similar result to previous studies for the correlation between SFR, i.e. PAH luminosity, and AGN luminosity for quasars of LSF [special characters omitted] for the 11.3mum PAH feature only (which has been shown to be the most reliable PAH feature in the vicinity of AGN). This may indicate the PAH luminosity remains a reliable tracer of the SFR for galaxies with strong AGN contributions (i.e. quasars), as we did not subtract off the AGN component before measuring the SFR from the PAH luminosity.

  11. Spitzer Observations of MAMBO Galaxies: Weeding Out Active Nuclei in Starbursting Protoellipticals

    NASA Astrophysics Data System (ADS)

    Ivison, R. J.; Greve, T. R.; Serjeant, S.; Bertoldi, F.; Egami, E.; Mortier, A. M. J.; Alonso-Herrero, A.; Barmby, P.; Bei, L.; Dole, H.; Engelbracht, C. W.; Fazio, G. G.; Frayer, D. T.; Gordon, K. D.; Hines, D. C.; Huang, J.-S.; Le Floc'h, E.; Misselt, K. A.; Miyazaki, S.; Morrison, J. E.; Papovich, C.; Pérez-González, P. G.; Rieke, M. J.; Rieke, G. H.; Rigby, J.; Rigopoulou, D.; Smail, I.; Wilson, G.; Willner, S. P.

    2004-09-01

    We present 3.6-24 μm Spitzer observations of an unbiased sample of nine luminous, dusty galaxies selected at 1200 μm by MAMBO on the IRAM 30 m telescope, a population akin to the well-known submillimeter or SCUBA galaxies (hereafter SMGs). Owing to the coarse resolution of submillimeter/millimeter cameras, SMGs have traditionally been difficult to identify at other wavelengths. We compare our multiwavelength catalogs to show that the overlap between 24 and 1200 μm must be close to complete at these flux levels. We find that all (4/4) of the most secure >=4 σ SMGs have >=4 σ counterparts at 1.4 GHz, while the fraction drops to 7/9 using all >=3 σ SMGs. We show that combining mid-infrared (MIR) and marginal (>=3 σ) radio detections provides plausible identifications in the remaining cases, enabling us to identify the complete sample. Accretion onto an obscured central engine is betrayed by the shape of the MIR continuum emission for several sources, confirming Spitzer's potential to weed out active galaxies. We demonstrate the power of an S24μm/S8μm versus S8μm/S4.5μm color-color plot as a diagnostic for this purpose. However, we conclude that the majority (~75%) of SMGs have rest-frame mid/far-IR spectral energy distributions commensurate with obscured starbursts. Sensitive 24 μm observations are clearly a useful route to identify and characterize reliable counterparts to high-redshift far-IR-bright galaxies, complementing what is possible via deep radio imaging.

  12. THE PRESENCE OF WEAK ACTIVE GALACTIC NUCLEI IN HIGH REDSHIFT STAR-FORMING GALAXIES

    SciTech Connect

    Wright, Shelley A.; Graham, James R.; Ma, C-P; Larkin, James E.

    2010-03-10

    We present [O III 5007 A] observations of the star-forming galaxy (SFG) HDF-BMZ1299 (z = 1.598) using Keck Observatory's adaptive optics system with the near-infrared {integral} field spectrograph OSIRIS. Using previous Halpha and [N II] measurements of the same source, we are able for the first time to use spatially resolved observations to place a high-redshift galaxy's substructure on a traditional H II diagnostic diagram. We find that HDF-BMZ1299's spatially concentrated nebular ratios in the central {approx}1.5 kpc (0.''2) are best explained by the presence of an active galactic nucleus (AGN): log ([N II]/Halpha) = -0.22 +- 0.05 and 2sigma limit of log ([O III]/Hbeta) {approx}>0.26. The dominant energy source of this galaxy is star formation, and integrating a single aperture across the galaxy yields nebular ratios that are composite spectra from both AGN and H II regions. The presence of an embedded AGN in HDF-BMZ1299 may suggest a potential contamination in a fraction of other high-redshift SFGs, and we suggest that this may be a source of the 'elevated' nebular ratios previously seen in seeing-limited metallicity studies. HDF-BMZ1299's estimated AGN luminosity is L{sub Halpha} = (3.7 +- 0.5) x 10{sup 41} erg s{sup -1} and L{sub [O{sub III}]} = (5.8 +- 1.9) x 10{sup 41} erg s{sup -1}, making it one of the lowest luminosity AGNs discovered at this early epoch.

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

    SciTech Connect

    Yuan, W.; Zhou, H.; Dou, L.; Dong, X.-B.; Wang, T.-G.; Fan, X.

    2014-02-10

    We report on Chandra X-ray observations of four candidate low-mass black hole (M {sub bh} ≲ 10{sup 6} M {sub ☉}) active galactic nuclei (AGNs) that have the estimated Eddington ratios among the lowest (∼10{sup –2}) found for this class. The aims are to validate the nature of their AGNs and to confirm the low Eddington ratios that are derived from the broad Hα line, and to explore this poorly studied regime in the AGN parameter space. Among them, two objects with the lowest significance of the broad lines are also observed with the Multi-Mirror Telescope, and the high-quality optical spectra taken confirm them as Seyfert 1 AGNs and as having small black hole masses. X-ray emission is detected from the nuclei of two of the galaxies, which is variable on timescales of ∼10{sup 3} s, whereas no significant (or only marginal at best) detection is found for the remaining two. The X-ray luminosities are on the order of 10{sup 41} erg s{sup –1} or even lower, on the order of 10{sup 40} erg s{sup –1} for non-detections, which are among the lowest regimes ever probed for Seyfert galaxies. The low X-ray luminosities, compared to their black hole masses derived from Hα, confirm their low accretion rates assuming typical bolometric corrections. Our results hint at the existence of a possibly large population of under-luminous low-mass black holes in the local universe. An off-nucleus ultra-luminous X-ray source in one of the dwarf galaxies is detected serendipitously, with a luminosity (6-9)× 10{sup 39} erg s{sup –1} in 2-10 keV.

  14. ENVIRONMENTAL DEPENDENCE OF THE STAR FORMATION RATE, SPECIFIC STAR FORMATION RATE, AND THE PRESENCE OF ACTIVE GALACTIC NUCLEI FOR HIGH STELLAR MASS AND LOW STELLAR MASS GALAXIES

    SciTech Connect

    Deng Xinfa; Song Jun; Chen Yiqing; Jiang Peng; Ding Yingping

    2012-07-10

    Using two volume-limited main galaxy samples of the Sloan Digital Sky Survey Data Release 8 (SDSS DR8), we explore the environmental dependence of the star formation rate (SFR), specific star formation rate (SSFR), and the presence of active galactic nuclei (AGNs) for high stellar mass (HSM) and low stellar mass (LSM) galaxies. It is found that the environmental dependence of the SFR and SSFR for luminous HSM galaxies and faint LSM ones remains very strong: galaxies in the lowest density regime preferentially have higher SFR and SSFR than galaxies in the densest regime, while the environmental dependence of the SFR and SSFR for luminous LSM galaxies is substantially reduced. Our result also shows that the fraction of AGNs in HSM galaxies decreases as a function of density, while the one in LSM galaxies depends very little on local density. In the faint LSM galaxy sample, the SFR and SSFR of galaxies strongly decrease with increasing density, but the fraction of AGNs depends very little on local density. Such a result can rule out that AGNs are fueled by the cold gas in the disk component of galaxies that is also driving the star formation of those galaxies.

  15. THE IMPACT OF INTERACTIONS, BARS, BULGES, AND ACTIVE GALACTIC NUCLEI ON STAR FORMATION EFFICIENCY IN LOCAL MASSIVE GALAXIES

    SciTech Connect

    Saintonge, Amelie; Fabello, Silvia; Wang Jing; Catinella, Barbara; Tacconi, Linda J.; Genzel, Reinhard; Gracia-Carpio, Javier; Wuyts, Stijn; Kramer, Carsten; Moran, Sean; Heckman, Timothy M.; Schiminovich, David; Schuster, Karl

    2012-10-20

    Using atomic and molecular gas observations from the GASS and COLD GASS surveys and complementary optical/UV data from the Sloan Digital Sky Survey and the Galaxy Evolution Explorer, we investigate the nature of the variations in the molecular gas depletion time observed across the local massive galaxy population. The large and unbiased COLD GASS sample allows us for the first time to statistically assess the relative importance of galaxy interactions, bar instabilities, morphologies, and the presence of active galactic nuclei (AGNs) in regulating star formation efficiency. We find that both the H{sub 2} mass fraction and depletion time vary as a function of the distance of a galaxy from the main sequence traced by star-forming galaxies in the SFR-M {sub *} plane. The longest gas depletion times are found in below-main-sequence bulge-dominated galaxies ({mu}{sub *} >5 Multiplication-Sign 10{sup 8} M {sub Sun} kpc{sup -2}, C > 2.6) that are either gas-poor (M{sub H{sub 2}}/M {sub *} <1.5%) or else on average less efficient by a factor of {approx}2 than disk-dominated galaxies at converting into stars any cold gas they may have. We find no link between the presence of AGNs and these long depletion times. In the regime where galaxies are disk-dominated and gas-rich, the galaxies undergoing mergers or showing signs of morphological disruptions have the shortest molecular gas depletion times, while those hosting strong stellar bars have only marginally higher global star formation efficiencies as compared to matched control samples. Our interpretation is that the molecular gas depletion time variations are caused by changes in the ratio between the gas mass traced by the CO(1-0) observations and the gas mass in high-density star-forming cores (as traced by observations of, e.g., HCN(1-0)). While interactions, mergers, and bar instabilities can locally increase pressure and raise the ratio of efficiently star-forming gas to CO-detected gas (therefore lowering the CO

  16. 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}.

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

    SciTech Connect

    Trump, Jonathan R.; Luo, Bin; Brandt, W. N.; Barro, Guillermo; Guo, Yicheng; Koo, David C.; Faber, S. M.; Brammer, Gabriel B.; Ferguson, Henry C.; Grogin, Norman A.; Kartaltepe, Jeyhan; Koekemoer, Anton M.; Bell, Eric F.; Dekel, Avishai; Hopkins, Philip F.; Kocevski, Dale D.; McIntosh, Daniel H.; Momcheva, Ivelina; and others

    2014-10-01

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

  18. POLYCYCLIC AROMATIC HYDROCARBON AND EMISSION LINE RATIOS IN ACTIVE GALACTIC NUCLEI AND STARBURST GALAXIES

    SciTech Connect

    Sales, Dinalva A.; Pastoriza, M. G.; Riffel, R. E-mail: pastoriza@ufrgs.b

    2010-12-10

    We study the polycyclic aromatic hydrocarbon (PAH) bands, ionic emission lines, and mid-infrared continuum properties in a sample of 171 emission line galaxies taken from the literature plus 15 new active galactic nucleus (AGN) Spitzer spectra. We normalize the spectra at {lambda} = 23 {mu}m and grouped them according to the type of nuclear activity. The continuum shape steeply rises for longer wavelengths and can be fitted with a warm blackbody distribution of T {approx} 150-300 K. The brightest PAH spectral bands (6.2, 7.7, 8.6, 11.3, and 12.7 {mu}m) and the forbidden emission lines of [Si II] 34.8 {mu}m, [Ar II] 6.9 {mu}m, [S III] 18.7 and 33.4 {mu}m were detected in all the starbursts and in {approx}80% of the Seyfert 2. Taking under consideration only the PAH bands at 7.7 {mu}m, 11.3 {mu}m, and 12.7 {mu}m, we find that they are present in {approx}80% of the Seyfert 1, while only half of this type of activity show the 6.2 {mu}m and 8.6 {mu}m PAH bands. The observed intensity ratios for neutral and ionized PAHs (6.2 {mu}m/7.7 {mu}m x 11.3 {mu}m/7.7 {mu}m) were compared to theoretical intensity ratios, showing that AGNs have higher ionization fraction and larger PAH molecules ({>=}180 carbon atoms) than SB galaxies. The ratio between the ionized (7.7 {mu}m) and the neutral PAH bands (8.6 {mu}m and 11.3 {mu}m) are distributed over different ranges for AGNs and SB galaxies, suggesting that these ratios could depend on the ionization fraction, as well as on the hardness of the radiation field. The ratio between the 7.7 {mu}m and 11.3 {mu}m bands is nearly constant with the increase of [Ne III]15.5 {mu}m/[Ne II] 12.8 {mu}m, indicating that the fraction of ionized to neutral PAH bands does not depend on the hardness of the radiation field. The equivalent width of both PAH features show the same dependence (strongly decreasing) with [Ne III]/[Ne II], suggesting that the PAH molecules, emitting either ionized (7.7 {mu}m) or neutral (11.3 {mu}m) bands, may be destroyed

  19. DEEP SILICATE ABSORPTION FEATURES IN COMPTON-THICK ACTIVE GALACTIC NUCLEI PREDOMINANTLY ARISE DUE TO DUST IN THE HOST GALAXY

    SciTech Connect

    Goulding, A. D.; Forman, W. R.; Jones, C.; Trichas, M.; Alexander, D. M.; Mullaney, J. R.; Bauer, F. E.; Hickox, R. C.

    2012-08-10

    We explore the origin of mid-infrared (mid-IR) dust extinction in all 20 nearby (z < 0.05) bona fide Compton-thick (N{sub H} > 1.5 Multiplication-Sign 10{sup 24} cm{sup -2}) active galactic nuclei (AGNs) with hard energy (E > 10 keV) X-ray spectral measurements. We accurately measure the silicate absorption features at {lambda} {approx} 9.7 {mu}m in archival low-resolution (R {approx} 57-127) Spitzer Infrared Spectrograph spectroscopy, and show that only a minority ( Almost-Equal-To 45%) of nearby Compton-thick AGNs have strong Si-absorption features (S{sub 9.7} = ln (f{sub int}/f{sub obs}) {approx}> 0.5) which would indicate significant dust attenuation. The majority ( Almost-Equal-To 60%) are star formation dominated (AGN:SB < 0.5) at mid-IR wavelengths and lack the spectral signatures of AGN activity at optical wavelengths, most likely because the AGN emission lines are optically extinguished. Those Compton-thick AGNs hosted in low-inclination-angle galaxies exhibit a narrow range in Si-absorption (S{sub 9.7} {approx} 0-0.3), which is consistent with that predicted by clumpy-torus models. However, on the basis of the IR spectra and additional lines of evidence, we conclude that the dominant contribution to the observed mid-IR dust extinction is dust located in the host galaxy (i.e., due to disturbed morphologies, dust lanes, galaxy inclination angles) and not necessarily a compact obscuring torus surrounding the central engine.

  20. Probing Spectroscopic Variability of Galaxies and Narrow-Line Active Galactic Nuclei in the Sloan Digital Sky Survey

    NASA Astrophysics Data System (ADS)

    Yip, C. W.; Connolly, A. J.; Vanden Berk, D. E.; Scranton, R.; Krughoff, S.; Szalay, A. S.; Dobos, L.; Tremonti, C.; Taghizadeh-Popp, M.; Budavári, T.; Csabai, I.; Wyse, R. F. G.; Ivezić, Ž.

    2009-06-01

    Under the unified model for active galactic nuclei (AGNs), narrow-line (Type 2) AGNs are, in fact, broad-line (Type 1) AGNs but each with a heavily obscured accretion disk. We would therefore expect the optical continuum emission from Type 2 AGNs to be composed mainly of stellar light and nonvariable on the timescales of months to years. In this work we probe the spectroscopic variability of galaxies and narrow-line AGNs using the multiepoch data in the Sloan Digital Sky Survey Data Release 6. The sample contains 18,435 sources for which there exist pairs of spectroscopic observations (with a maximum separation in time of ~700 days) covering a wavelength range of 3900-8900 Å. To obtain a reliable repeatability measurement between each spectral pair, we consider a number of techniques for spectrophotometric calibration resulting in an improved spectrophotometric calibration of a factor of 2. From these data we find no obvious continuum and emission-line variability in the narrow-line AGNs on average—the spectroscopic variability of the continuum is 0.07 ± 0.26 mag in the g band and, for the emission-line ratios log10([N II]/Hα) and log10([O III]/Hβ), the variability is 0.02 ± 0.03 dex and 0.06 ± 0.08 dex, respectively. From the continuum variability measurement we set an upper limit on the ratio between the flux of the varying spectral component, presumably related to AGN activities, and that of the host galaxy to be ~30%. We provide the corresponding upper limits for other spectral classes, including those from the BPT diagram, eClass galaxy classification, stars, and quasars.

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

    SciTech Connect

    Koulouridis, E.; Plionis, M.

    2010-05-10

    We present a study of X-ray active galactic nucleus (AGN) overdensities in 16 Abell clusters, within the redshift range 0.073 < z < 0.279, in order to investigate the effect of the hot inter-cluster environment on the triggering of the AGN phenomenon. The X-ray AGN overdensities, with respect to the field expectations, were estimated for sources with L{sub x} {>=} 10{sup 42} erg s{sup -1} (at the redshift of the clusters) and within an area of 1 h {sup -1} {sub 72} Mpc radius (excluding the core). To investigate the presence or absence of a true enhancement of luminous X-ray AGNs in the cluster area, we also derived the corresponding optical galaxy overdensities, using a suitable range of r-band magnitudes. We always find the latter to be significantly higher (and only in two cases roughly equal) with respect to the corresponding X-ray overdensities. Over the whole cluster sample, the mean X-ray point-source overdensity is a factor of {approx}4 less than that corresponding to bright optical galaxies, a difference which is significant at a >0.995 level, as indicated by an appropriate student's t-test. We conclude that the triggering of luminous X-ray AGNs in rich clusters is strongly suppressed. Furthermore, searching for optical Sloan Digital Sky Survey counterparts of all the X-ray sources, associated with our clusters, we found that about half appear to be background QSOs, while others are background and foreground AGNs or stars. The true overdensity of X-ray point sources, associated with the clusters, is therefore even smaller than what our statistical approach revealed.

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

    NASA Astrophysics Data System (ADS)

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

    2016-09-01

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

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

    NASA Astrophysics Data System (ADS)

    Shipley, Heath V.

    2016-01-01

    For decades, significant work has been applied to calibrating emission from the ultra-violet, nebular emission lines, far-infrared, X-ray and radio as tracers of the star-formation rate (SFR) in distant galaxies. Understanding the exact rate of star-formation and how it evolves with time and galaxy mass has deep implications for how galaxies form. The co-evolution of star-formation and supermassive black hole (SMBH) accretion is one of the key problems in galaxy formation theory. But, many of these SFR indicators are influenced by SMBH accretion in galaxies and result in unreliable SFRs. Utilizing the luminous polycyclic aromatic hydrocarbon (PAH) emission features, I provide a new robust SFR calibration using the luminosity emitted from the PAHs at 6.2μm, 7.7μm and 11.3μm to solve this. The PAH features emit strongly in the mid-infrared (mid-IR; 5-25μm) mitigating dust extinction, containing on average 5-10% of the total IR luminosity in galaxies. I use a sample of 105 star-forming galaxies covering a range of total IR luminosity, LIR = L(8-1000μm) = 109 - 1012 L⊙ and redshift 0 < z < 0.4, with mid-IR spectroscopy from the Spitzer Infrared Spectrograph (IRS), and data covering other SFR indicators (Hα emission and rest-frame 24μm continuum emission). The PAH luminosity correlates linearly with the SFR as measured by the Hα luminosity (corrected for attenuation using the mono-chromatic rest-frame 24μm emission), with a tight scatter of <0.15 dex. The scatter is comparable to that between SFRs derived from the Paα and dust-corrected Hα emission lines. We present a case study in advance of JWST, which will be capable of measuring SFRs (from 8μm rest-frame photometry, i.e. PAHs) in distant galaxies (z ≤ 2) with JWST/MIRI to SFRs as low as ~10 M⊙yr-1, because the PAH features are so bright. We use Spitzer/IRS observations of PAH features in lensed star-forming galaxies at 1 < z < 3 to demonstrate the utility of the PAHs to derive SFRs that agree with

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

    NASA Astrophysics Data System (ADS)

    Shipley, Heath; Papovich, Casey

    2015-08-01

    We provide a new robust star-formation rate (SFR) calibration using the luminosity from polycyclic aromatic hydrogen (PAH) molecules. The PAH features emit strongly in the mid-infrared (mid-IR; 3-19μm), mitigating dust extinction, and they are very luminous, containing 5-10% of the total IR luminosity in galaxies. We derive the calibration of the PAH luminosity as a SFR indicator using a sample of 105 star-forming galaxies covering a range of total IR luminosity, LIR = L(8-1000μm) = 109 - 1012 L⊙ and redshift 0 < z < 0.6. The PAH luminosity correlates linearly with the SFR as measured by the dust-corrected Hα luminosity (using the sum of the Hα and rest-frame 24μm luminosity from Kennicutt et al. 2009), with tight scatter of ~0.15 dex, comparable to the scatter in the dust-corrected Hα SFRs and Paα SFRs. We show this relation is sensitive to galaxy metallicity, where the PAH luminosity of galaxies with Z < 0.7 Z⊙ departs from the linear SFR relationship but in a behaved manor. We derive for this a correction to galaxies below solar metallicity. As a case study for observations with JWST, we apply the PAH SFR calibration to a sample of lensed galaxies at 1 < z < 3 with Spitzer Infrared Spectrograph (IRS) data, and we demonstrate the utility of PAHs to derive SFRs as accurate as those available from any other indicator. This new SFR indicator will be useful for probing the peak of the SFR density of the universe (1 < z < 3) and for studying the coevolution of star-formation and supermassive blackhole accretion contemporaneously in a galaxy.

  5. Multi-wavelength population studies of Active Galactic Nuclei and Galaxies using PRIMUS and AEGIS

    NASA Astrophysics Data System (ADS)

    Mendez, Alexander John

    This dissertation uses large galaxy redshift surveys and multi-wavelength imaging to place observational constraints on the evolution of galaxies and the supermassive black holes that they host since the Universe was roughly half its current age. In the first chapter, we use data from the AEGIS survey to present quantitative morphological measurements of green valley galaxies, to constrain the mechanism(s) responsible for quenching star formation in this transition population and creating elliptical galaxies. We show that green galaxies are generally massive (M*~1010.5M sun) disk galaxies with high concentrations of light. We find that major mergers are not the dominant mechanism responsible for quenching star formation, and we find that either more mild external processes or internal secular processes play a crucial role in halting star formation. In the second chapter, we use data from the PRIMUS survey to investigate Spitzer/IRAC and X-ray AGN selection techniques in order to quantify the overlap, uniqueness, contamination, and completeness of each AGN selection. For roughly similar depth IR and X-ray data, we find that ~75% of IR-selected AGN are also identified as X-ray AGN. For the deepest X-ray data, this fraction increases to ~90%, indicating that at most ~10% of IR-selected AGN may be heavily obscured. While similar overall, the IR-AGN samples preferentially contain more luminous AGN, while the X-ray AGN samples identify AGN with a wider range of accretion rates, where the host galaxy light dominates at IR wavelengths. A more complete AGN sample is created by combining both IR and X-ray selected AGN. Finally, we present a clustering study of X-ray AGN, radio AGN and IR AGN selected AGN using spectroscopic redshifts from the PRIMUS and DEEP2 redshift surveys. Using the cross-correlation of AGN with dense galaxy samples, we find differences in the clustering of AGN selected at different wavelengths. However, we find no significant differences in the

  6. MILLIMETER RADIO CONTINUUM EMISSIONS AS THE ACTIVITY OF SUPERMASSIVE BLACK HOLES IN NEARBY EARLY-TYPE GALAXIES AND LOW-LUMINOSITY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Doi, Akihiro; Nakanishi, Kouichiro; Nagai, Hiroshi; Kohno, Kotaro; Kameno, Seiji

    2011-11-15

    We conducted millimeter continuum observations for samples of nearby early-type galaxies (21 sources) and nearby low-luminosity active galactic nuclei (LLAGNs; 16 sources) at 100 GHz ({lambda}3 mm) using the Nobeyama Millimeter Array (NMA). In addition, we performed quasi-simultaneous observations at 150 GHz ({lambda}2 mm) and 100 GHz for five LLAGNs. Compact nuclear emissions showing flat or inverted spectra at centimeter-to-millimeter wavelengths were found in many LLAGNs and several early-type galaxies. Moreover, significant flux variability was detected in three LLAGNs. These radio properties are similar to Sgr A*. The observed radio luminosities are consistent with the fundamental plane of black hole activity that was suggested on the basis of samples with black hole masses ranging from 10 to 10{sup 10} M{sub Sun }. This implies nuclear jets powered by radiatively inefficient accretion flows onto black holes.

  7. OBSCURED GOODS ACTIVE GALACTIC NUCLEI AND THEIR HOST GALAXIES AT z < 1.25: THE SLOW BLACK HOLE GROWTH PHASE

    SciTech Connect

    Simmons, B. D.; Urry, C. M.; Van Duyne, J.; Treister, E.; Koekemoer, A. M.; Grogin, N. A.

    2011-06-20

    We compute black hole masses and bolometric luminosities for 87 obscured active galactic nuclei (AGNs) in the redshift range 0.25 {<=} z {<=} 1.25, selected from the GOODS deep multi-wavelength survey fields via their X-ray emission. We fit the optical images and obtain morphological parameters for the host galaxy, separating the galaxy from its central point source, thereby obtaining a four-band optical spectral energy distribution (SED) for each active nucleus. We calculate bolometric luminosities for these AGNs by reddening a normalized mean SED of GOODS broad-line AGNs to match the observed central point-source SED of each obscured AGN. This estimate of L{sub bol} has a smaller spread than simple bolometric corrections to the X-ray luminosity or direct integration of the observed multi-wavelength SED, suggesting it is a better measure. We estimate central black hole masses from the bulge luminosities. The black hole masses span a wide range, 7 x 10{sup 6} M{sub sun} to 6 x 10{sup 9} M{sub sun}; the median black hole mass is 5 x 10{sup 8} M{sub sun}. The majority of these AGNs have L/L{sub Edd} {<=} 0.01, and we detect no significant evolution of the mean Eddington ratio to z = 1.25. This implies that the bulk of black hole growth in these obscured AGNs must have occurred at z {approx}> 1 and that we are observing these AGNs in a slow- or no-growth state.

  8. Multi-wavelength properties and smbh's masses of the isolated galaxies with active nuclei in the Local Universe

    NASA Astrophysics Data System (ADS)

    Vavilova, Iryna; Vasylenko, Anatolij; Babyk, Iuri; Pulatova, Nadya

    2016-07-01

    We apply the specially-oriented Astro-Space databases obtained with ground-based telescopes and space observatories to study the multi-wavelength spectral and physical properties of galaxies with active nuclei (AGNs), namely of isolated AGNs that are poorly investigated especially in X-rays. Such a study allowed us 1) to separate the internal evolution mechanisms from the environment influence and consider them as two separate processes related to fueling nuclear activity, 2) to explore absorption features and the X-ray continuum radiation from accretion disks around SMBHs (e.g. to select accretion models). In the case of detecting the Fe K emission line, it was possible to analyze the physical conditions in the AGNs innermost parts in more details. Using the SDSS spectral Hβ-line data we were able to estimate the SMBH masses of several isolated AGNs in the Local Universe, which are systematically lower than the SMBH masses of AGNs located in a dense environment. We present also the results of analysis of the spectral data obtained by XMM-Newton, Swift, Chandra, and INTEGRAL space observatories for several isolated AGNs from 2MIG catalogue, for which the available X-ray data were accessed. Among these objects are CGCG 179-005, NGC 6300, NGC 1050, NGC 2989, WKK 3050, ESO 438-009, ESO 317-038 and others. We determined corresponding spectral models and values of their parameters (spectral index, intrinsic absorption etc.). X-ray spectra for bright galaxies, NGC 6300 and Circinus, were analyzed up to 250 keV and their characteristics of emission features were determined in 6-7 keV range.

  9. The X-Ray Zurich Environmental Study (X-ZENS). I. Chandra and XMM-Newton Observations of Active Galactic Nuclei in Galaxies in nearby Groups

    NASA Astrophysics Data System (ADS)

    Silverman, J. D.; Miniati, F.; Finoguenov, A.; Carollo, C. M.; Cibinel, A.; Lilly, S. J.; Schawinski, K.

    2014-01-01

    We describe X-ray observations with Chandra and XMM-Newton of 18 M group ~ 1-6 × 1013 M ⊙, z ~ 0.05 galaxy groups from the Zurich ENvironmental Study. The X-ray data aim at establishing the frequency and properties, unaffected by host galaxy dilution and obscuration, of active galactic nuclei (AGNs) in central and satellite galaxies, also as a function of halo-centric distance. X-ray point-source detections are reported for 22 of the 177 galaxies, down to a sensitivity level of f 0.5 - 8 keV ~ 5 × 10-15 erg cm-2 s-1, corresponding to a limiting luminosity of L 0.5 - 8 keV ~ 3 × 1040 erg s-1. With the majority of the X-ray sources attributed to AGNs of low-to-moderate levels (L/L Edd >~ 10-4), we discuss the detection rate in the context of the occupation of AGNs to halos of this mass scale and redshift and compare the structural and morphological properties between AGN-active and non-active galaxies. At galaxy mass scales <1011 M ⊙, central galaxies appear to be a factor of ~4 more likely to host AGNs than satellite galaxies of similar mass. This effect, coupled with the tendency for AGNs to be hosted by massive galaxies, explains the (weak) trend for AGNs to be preferentially found in the inner parts of group halos, with no detectable trend with halo-centric distance in the frequency of AGNs within the satellite population. Finally, our data indicate that the rate of decline with redshift of AGN activity in galaxy groups matches that of the global AGN population, indicating that either AGN activity occurs preferentially in group halos or that the evolution rate is independent of halo mass.

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

    SciTech Connect

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

    2013-02-15

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-02-01

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

  12. Towards a complete census of active galactic nuclei in nearby galaxies: the incidence of growing black holes

    NASA Astrophysics Data System (ADS)

    Goulding, A. D.; Alexander, D. M.; Lehmer, B. D.; Mullaney, J. R.

    2010-07-01

    We investigate the local supermassive black hole (SMBH) density function and relative mass accretion rates of all active galactic nuclei (AGNs) identified in a volume-limited sample of infrared (IR) bright galaxies (LIR > 3 × 109Lsolar) to D < 15Mpc. A data base of accurate SMBH mass (MBH) estimates is compiled from literature sources using physically motivated AGN modelling techniques (reverberation mapping, maser mapping and gas kinematics) and well-established indirect MBH estimation methods (the M-σ* and MBH-LK,bul relations). For the three sources without previously published MBH estimates, we use Two Micron All Sky Survey (2MASS) K-band imaging and GALFIT to constrain the bulge luminosities, and hence SMBH masses. In general, we find the AGNs in the sample host SMBHs which are spread over a wide mass range [MBH ~ (0.1-30) × 107Msolar], but with the majority in the poorly studied MBH ~ 106-107Msolar region. Using sensitive hard X-ray (2-10keV) and mid-IR constraints we calculate the bolometric luminosities of the AGNs (LBol,AGN) and use them to estimate relative mass accretion rates. We use these data to calculate the volume-averaged SMBH growth rate of galaxies in the local Universe and find that the AGNs hosting SMBHs in the mass range MBH ~ 106-107Msolar are dominated by optically unidentified AGNs. These relatively small SMBHs are acquiring a significant proportion of their mass in the present day, and are amongst the most rapidly growing in the local Universe (SMBH mass-doubling times of ~6Gyr). Additionally, we find tentative evidence for an increasing volume-weighted AGN fraction with decreasing SMBH mass in the MBH ~ 106-108Msolar range. Overall, we conclude that significant mass accretion on to small SMBHs may be missed in even the most sensitive optical surveys due to absent or weak optical AGN signatures.

  13. Predictions for imaging and spectroscopic surveys of galaxies and Active Galactic Nuclei in the mid-/far-Infrared

    NASA Astrophysics Data System (ADS)

    Bonato, Matteo

    2015-02-01

    detected by large area surveys such as those by Herschel and by SPT can provide key information on the galaxy-AGN co-evolution out to higher redshifts. Finally, as third step of the work, I present predictions for number counts and redshift distributions of galaxies detectable in continuum and in emission lines with the Mid-infrared (MIR) Instrument (SMI) proposed for SPICA. I have considered 24 MIR emission fine-structure lines, four Polycyclic Aromatic Hydrocarbon (PAH) bands (at 6.2, 7.7, 8.6 and 11.3μm) and two silicate bands (in emission and in absorption) at 9.7μm and 18.0μm. Six of these lines are primarily associated with Active Galactic Nuclei (AGNs), the others primarily with star formation. Altogether, they allow us to study the interplay between star formation and super-massive black hole growth. A survey with the SMI spectrometers of 1 hour integration per field-of-view (FoV) over an area of 1 deg 2 will yield 5 σ detections of ≃ 140 AGN lines, produced by ≃ 110 AGNs 1 , and of ≃ 5.2 × 10^4 star-forming galaxies, ≃ 1.6 × 10^4 of which will be detected in at least two lines. The combination of a shallow (20.0 deg 2 , 1.4 × 10^-1 h integration per FoV) and a deep survey (6.9 × 10^-3 deg^2 , 635 h integration time), with the SMI camera, for a total of ∼1000 h, will accurately determine the MIR number counts of galaxies and of AGNs over five orders of magnitude in flux density, reaching values more than one order of magnitude fainter than the Spitzer 24 μm surveys. This will allow us to resolve almost completely the extragalactic background and to determine the cosmic star formation rate (SFR) function down to SFRs more than 100 times fainter than reached by the Herschel Observatory.

  14. The effects of X-rays from active galactic nuclei on the interstellar medium of the surrounding galaxy

    NASA Technical Reports Server (NTRS)

    Begelman, Mitchell C.

    1988-01-01

    The effects of an active nucleus on the large-scale properties of the host galaxy are examined, focusing on the effects of X-ray heating on the host galaxy's interstellar medium. The basic properties of AGNs and several questions concerning AGNs are reviewed. The relationship between X-ray heated winds and coronae is outlined. The case of X-ray heated winds in type 2 Seyfert galaxies is discussed.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    We use CANDELS imaging, 3D-HST spectroscopy, and Chandra X-ray data to investigate if active galactic nuclei (AGNs) are preferentially fueled by violent disk instabilities funneling gas into galaxy centers at 1.3 < z < 2.4. We select galaxies undergoing gravitational instabilities using the number of clumps and degree of patchiness as proxies. The CANDELS visual classification system is used to identify 44 clumpy disk galaxies, along with mass-matched comparison samples of smooth and intermediate morphology galaxies. We note that despite being mass-matched and having similar star formation rates, the smoother galaxies tend to be smaller disks with more prominent bulges compared to the clumpy galaxies. The lack of smooth extended disks is probably a general feature of the z ~ 2 galaxy population, and means we cannot directly compare with the clumpy and smooth extended disks observed at lower redshift. We find that z ~ 2 clumpy galaxies have slightly enhanced AGN fractions selected by integrated line ratios (in the mass-excitation method), but the spatially resolved line ratios indicate this is likely due to extended phenomena rather than nuclear AGNs. Meanwhile, the X-ray data show that clumpy, smooth, and intermediate galaxies have nearly indistinguishable AGN fractions derived from both individual detections and stacked non-detections. The data demonstrate that AGN fueling modes at z ~ 1.85—whether violent disk instabilities or secular processes—are as efficient in smooth galaxies as they are in clumpy galaxies. Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by AURA Inc, under NASA contract NAS 5-26555.

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

    SciTech Connect

    Khabiboulline, Emil T.; Steinhardt, Charles L.; Silverman, John D.; Ellison, Sara L.; Mendel, J. Trevor; Patton, David R.

    2014-11-01

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

  17. Changing Ionization Conditions in SDSS Galaxies with Active Galactic Nuclei as a Function of Environment from Pairs to Clusters

    NASA Astrophysics Data System (ADS)

    Khabiboulline, Emil T.; Steinhardt, Charles L.; Silverman, John D.; Ellison, Sara L.; Mendel, J. Trevor; Patton, David R.

    2014-11-01

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

  18. Triggering active galactic nuclei in hierarchical galaxy formation: disk instability vs. interactions

    NASA Astrophysics Data System (ADS)

    Menci, N.; Gatti, M.; Fiore, F.; Lamastra, A.

    2014-09-01

    Using a state-of-the-art semi analytic model for galaxy formation, we investigated in detail the effects of black hole (BH) accretion triggered by disk instabilities (DI) in isolated galaxies on the evolution of the AGN population. Specifically, we took on, developed, and expanded the Hopkins & Quataert (2011, MNRAS, 411, 1027) model for the mass inflow following disk perturbations, based on a physical description of nuclear inflows and tested against aimed N-body simulations. We compared the evolution of AGN due to such a DI accretion mode with that arising in a scenario where galaxy interactions (IT mode) produce the sudden destabilization of large quantities of gas feeding the AGN; this constitutes the standard AGN feeding mode implemented in the earliest versions of most semi-analytic models. To study the maximal contribution of DI to the evolution of the AGN population, we extended and developed the DI model to assess the effects of changing the assumed disk surface density profile, and to obtain lower limits for the nuclear star formation rates associated to the DI accretion mode. We obtained the following results: i) For AGN with luminosity M1450 ≳ - 26, the DI mode can provide the BH accretion needed to match the observed AGN luminosity functions up to z ≈ 4.5. In such a luminosity range and redshift, it constitutes a viable candidate mechanism to fuel AGN, and can compete with the IT scenario as the main driver of cosmological evolution of the AGN population. ii) The DI scenario cannot provide the observed abundance of high-luminosity QSO with M1450 ≤ -26 AGN, as well as the abundance of high-redhshift z ≳ 4.5 QSO with M1450 ≤ -24. As found in our earliest works, the IT scenario provides an acceptable match to the observed luminosity functions up to z ≈ 6. iii) The dispersion of the distributions of Eddington ratio λ for low- and intermediate-luminosity AGN (bolometric LAGN = 1043-1045 erg s-1) is predicted to be much smaller in the DI

  19. 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

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

    SciTech Connect

    Silverman, J. D.; Miniati, F.; Carollo, C. M.; Cibinel, A.; Lilly, S. J.; Schawinski, K.; Finoguenov, A.

    2014-01-01

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

  1. A two-parameter model for the infrared/submillimeter/radio spectral energy distributions of galaxies and active galactic nuclei

    SciTech Connect

    Dale, Daniel A.; Helou, George; Magdis, Georgios E.; Armus, Lee; Díaz-Santos, Tanio; Shi, Yong

    2014-03-20

    A two-parameter semi-empirical model is presented for the spectral energy distributions of galaxies with contributions to their infrared-submillimeter-radio emission from both star formation and accretion disk-powered activity. This model builds upon a previous one-parameter family of models for star-forming galaxies, and includes an update to the mid-infrared emission using an average template obtained from Spitzer Space Telescope observations of normal galaxies. Star-forming/active galactic nucleus (AGN) diagnostics based on polycyclic aromatic hydrocarbon equivalent widths and broadband infrared colors are presented, and example mid-infrared AGN fractional contributions are estimated from model fits to the Great Observatories All-Sky LIRG Survey sample of nearby U/LIRGS and the Five mJy Unbiased Spitzer Extragalactic Survey sample of 24 μm selected sources at redshifts 0 ≲ z ≲ 4.

  2. Interacting nuclei in distant galaxies

    NASA Technical Reports Server (NTRS)

    Zheng, Wei; Grandi, Steven A.

    1990-01-01

    The N-galaxy 3C 390.3 has been monitored spectroscopically since 1974 (Osterbrock, Koski and Phillips 1975; Oke 1988). From various archives and literature, it is found that the Balmer lines change their intensities and profiles in a dramatic manner. The H alpha profile is very broad and peculiar, and the relative intensities of its two humps changes consistently with time, possibly periodically. Before 1980, the blue hump was significantly stronger than the one in the red. From 1980 to 1983 the blue hump became stronger (see Oke 1988). After 1983 the H alpha profile has returned to its early shape and seems to have completed a full circle. Unlike the rapid (on the order of a month or even less) and aperiodic variation in the continuum and integrated line intensities, the change in broad profile seems slow and consistent. Taking the analogy of cataclysmic variables, the double-horn profiles have been observed in cases of interacting stars. For example, the emission lines, both in He II and hydrogen Balmer lines in GD 552 (Stover 1985) show double-horn profiles and periodical changes in their line profiles, including the change in ratios of two humps. It is understood that the D-wave components (Smak 1976) are the signature of an emitting disk and the S-wave component is from the emission at a hot spot which rotates and results in a moving component in the velocity space. The mass flow from the nearby interacting star provides the stream toward the core of a neutron star or white dwarf. Therefore, it is proposed that the variation of broad line profiles observed in 3C 390.3 may be the result of a pair of interacting massive cores. The rotational velocity dominates and produces a variable double-horn profile. However, the line widths observed in broad line radio galaxies are one order larger than that in interacting stars. The Balmer decrements imply a much smaller density (10(exp 10-12) cm(exp-3)) than that in the cataclysmic variables. The much larger velocity and

  3. The host galaxies of X-ray selected active galactic nuclei to z = 2.5: Structure, star formation, and their relationships from CANDELS and Herschel/PACS

    NASA Astrophysics Data System (ADS)

    Rosario, D. J.; McIntosh, D. H.; van der Wel, A.; Kartaltepe, J.; Lang, P.; Santini, P.; Wuyts, S.; Lutz, D.; Rafelski, M.; Villforth, C.; Alexander, D. M.; Bauer, F. E.; Bell, E. F.; Berta, S.; Brandt, W. N.; Conselice, C. J.; Dekel, A.; Faber, S. M.; Ferguson, H. C.; Genzel, R.; Grogin, N. A.; Kocevski, D. D.; Koekemoer, A. M.; Koo, D. C.; Lotz, J. M.; Magnelli, B.; Maiolino, R.; Mozena, M.; Mullaney, J. R.; Papovich, C. J.; Popesso, P.; Tacconi, L. J.; Trump, J. R.; Avadhuta, S.; Bassett, R.; Bell, A.; Bernyk, M.; Bournaud, F.; Cassata, P.; Cheung, E.; Croton, D.; Donley, J.; DeGroot, L.; Guedes, J.; Hathi, N.; Herrington, J.; Hilton, M.; Lai, K.; Lani, C.; Martig, M.; McGrath, E.; Mutch, S.; Mortlock, A.; McPartland, C.; O'Leary, E.; Peth, M.; Pillepich, A.; Poole, G.; Snyder, D.; Straughn, A.; Telford, O.; Tonini, C.; Wandro, P.

    2015-01-01

    We study the relationship between the structure and star formation rate (SFR) of X-ray selected low and moderate luminosity active galactic nuclei (AGNs) in the two Chandra Deep Fields, using Hubble Space Telescope imaging from the Cosmic Assembly Near Infrared Extragalactic Legacy Survey (CANDELS) and deep far-infrared maps from the PEP+GOODS-Herschel survey. We derive detailed distributions of structural parameters and FIR luminosities from carefully constructed control samples of galaxies, which we then compare to those of the AGNs. At z ~ 1, AGNs show slightly diskier light profiles than massive inactive (non-AGN) galaxies, as well as modestly higher levels of gross galaxy disturbance (as measured by visual signatures of interactions and clumpy structure). In contrast, at z ~ 2, AGNs show similar levels of galaxy disturbance as inactive galaxies, but display a red central light enhancement, which may arise from a more pronounced bulge in AGN hosts or extinguished nuclear light. We undertake a number of tests of both these alternatives, but our results do not strongly favor one interpretation over the other. The mean SFR and its distribution among AGNs and inactive galaxies are similar at z> 1.5. At z< 1, however, clear and significant enhancements are seen in the SFRs of AGNs with bulge-dominated light profiles. These trends suggest an evolution in the relation between nuclear activity and host properties with redshift, towards a minor role for mergers and interactions at z> 1.5. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.Appendices are available in electronic form at http://www.aanda.org

  4. Chandra X-Ray and Hubble Space Telescope Imaging of Optically Selected Kiloparsec-scale Binary Active Galactic Nuclei. II. Host Galaxy Morphology and AGN Activity

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

    Binary active galactic nuclei (AGNs) provide clues to how gas-rich mergers trigger and fuel AGNs and how supermassive black hole (SMBH) pairs evolve in a gas-rich environment. While significant effort has been invested in their identification, the detailed properties of binary AGNs and their host galaxies are still poorly constrained. In a companion paper, we examined the nature of ionizing sources in the double nuclei of four kiloparsec-scale binary AGNs with redshifts between 0.1 and 0.2. Here, we present their host galaxy morphology based on F336W (U-band) and F105W (Y-band) images taken by the Wide Field Camera 3 on board the Hubble Space Telescope. Our targets have double-peaked narrow emission lines and were confirmed to host binary AGNs with follow-up observations. We find that kiloparsec-scale binary AGNs occur in galaxy mergers with diverse morphological types. There are three major mergers with intermediate morphologies and a minor merger with a dominant disk component. We estimate the masses of the SMBHs from their host bulge stellar masses and obtain Eddington ratios for each AGN. Compared with a representative control sample drawn at the same redshift and stellar mass, the AGN luminosities and Eddington ratios of our binary AGNs are similar to those of single AGNs. The U ‑ Y color maps indicate that clumpy star-forming regions could significantly affect the X-ray detection of binary AGNs, e.g., the hardness ratio. Considering the weak X-ray emission in AGNs triggered in merger systems, we suggest that samples of X-ray-selected AGNs may be biased against gas-rich mergers. Based, in part, on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. These observations are associated with program number GO 12363.

  5. Epsiodic Activity in Radio Galaxies

    SciTech Connect

    Saikia, D.J.; Konar, C.; Jamrozy, M.; Machalski, J.; Gupta, Neeraj; Stawarz, L.; Mack, K.-H.; Siemiginowska, A.; /Harvard-Smithsonian Ctr. Astrophys.

    2007-10-15

    One of the interesting issues in our understanding of active galactic nuclei is the duration of their active phase and whether such activity is episodic. In this paper we summarize our recent results on episodic activity in radio galaxies obtained with the GMRT and the VLA.

  6. MOLECULAR GAS IN LENSED z >2 QUASAR HOST GALAXIES AND THE STAR FORMATION LAW FOR GALAXIES WITH LUMINOUS ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Riechers, Dominik A.

    2011-04-01

    We report the detection of luminous CO(J = 2{yields}1), CO(J = 3{yields}2), and CO(J = 4{yields}3) emission in the strongly lensed high-redshift quasars B1938+666 (z = 2.059), HE 0230-2130 (z = 2.166), HE 1104-1805 (z = 2.322), and B1359+154 (z = 3.240), using the Combined Array for Research in Millimeter-wave Astronomy. B1938+666 was identified in a 'blind' CO redshift search, demonstrating the feasibility of such investigations with millimeter interferometers. These galaxies are lensing-amplified by factors of {mu}{sub L} {approx_equal} 11-170, and thus allow us to probe the molecular gas in intrinsically fainter galaxies than currently possible without the aid of gravitational lensing. We report lensing-corrected intrinsic CO line luminosities of L'{sub CO} = 0.65-21x10{sup 9} K km s{sup -1} pc{sup 2}, translating to H{sub 2} masses of M(H{sub 2}) = 0.52-17 x 10{sup 9} ({alpha}{sub CO}/0.8) M{sub sun}. To investigate whether or not the active galactic nucleus (AGN) in luminous quasars substantially contributes to L{sub FIR}, we study the L'{sub CO}-L{sub FIR} relation for quasars relative to galaxies without a luminous AGN as a function of redshift. We find no substantial differences between submillimeter galaxies and high-z quasars, but marginal evidence for an excess in L{sub FIR} in nearby low-L{sub FIR} AGN galaxies. This may suggest that an AGN contribution to L{sub FIR} is significant in systems with relatively low gas and dust content, but only minor in the most far-infrared-luminous galaxies (in which L{sub FIR} is dominated by star formation).

  7. The Biases of Optical Line-Ratio Selection for Active Galactic Nuclei and the Intrinsic Relationship between Black Hole Accretion and Galaxy Star Formation

    NASA Astrophysics Data System (ADS)

    Trump, Jonathan R.; Sun, Mouyuan; Zeimann, Gregory R.; Luck, Cuyler; Bridge, Joanna S.; Grier, Catherine J.; Hagen, Alex; Juneau, Stephanie; Montero-Dorta, Antonio; Rosario, David J.; Brandt, W. Niel; Ciardullo, Robin; Schneider, Donald P.

    2015-09-01

    We use 317,000 emission-line galaxies from the Sloan Digital Sky Survey to investigate line-ratio selection of active galactic nuclei (AGNs). In particular, we demonstrate that “star formation (SF) dilution” by H ii regions causes a significant bias against AGN selection in low-mass, blue, star-forming, disk-dominated galaxies. This bias is responsible for the observed preference of AGNs among high-mass, green, moderately star-forming, bulge-dominated hosts. We account for the bias and simulate the intrinsic population of emission-line AGNs using a physically motivated Eddington ratio distribution, intrinsic AGN narrow line region line ratios, a luminosity-dependent {L}{bol}/L[{{O}} {{III}}] bolometric correction, and the observed {M}{BH}-σ relation. These simulations indicate that, in massive ({log}({M}*/{M}⊙ )≳ 10) galaxies, AGN accretion is correlated with specific star formation rate (SFR) but is otherwise uniform with stellar mass. There is some hint of lower black hole occupation in low-mass ({log}({M}*/{M}⊙ )≲ 10) hosts, although our modeling is limited by uncertainties in measuring and interpreting the velocity dispersions of low-mass galaxies. The presence of SF dilution means that AGNs contribute little to the observed strong optical emission lines (e.g., [{{O}} {{III}}] and {{H}}α ) in low-mass and star-forming hosts. However the AGN population recovered by our modeling indicates that feedback by typical (low- to moderate-accretion) low-redshift AGNs has nearly uniform efficiency at all stellar masses, SFRs, and morphologies. Taken together, our characterization of the observational bias and resultant AGN occupation function suggest that AGNs are unlikely to be the dominant source of SF quenching in galaxies, but instead are fueled by the same gas which drives SF activity.

  8. ACTIVE GALACTIC NUCLEI AS MAIN CONTRIBUTORS TO THE ULTRAVIOLET IONIZING EMISSIVITY AT HIGH REDSHIFTS: PREDICTIONS FROM A {Lambda}-CDM MODEL WITH LINKED AGN/GALAXY EVOLUTION

    SciTech Connect

    Giallongo, E.; Menci, N.; Fiore, F.; Castellano, M.; Fontana, A.; Grazian, A.; Pentericci, L.

    2012-08-20

    We have evaluated the contribution of the active galactic nuclei (AGN) population to the ionization history of the universe based on a semi-analytic model of galaxy formation and evolution in the cold dark matter cosmological scenario. The model connects the growth of black holes and of the ensuing AGN activity to galaxy interactions. In the model we have included a self-consistent physical description of the escape of ionizing UV photons; this is based on the blast-wave model for the AGN feedback we developed in a previous paper to explain the distribution of hydrogen column densities in AGNs of various redshifts and luminosities, due to absorption by the host galaxy gas. The model predicts UV luminosity functions for AGNs that are in good agreement with those derived from the observations especially at low and intermediate redshifts (z {approx} 3). At higher redshifts (z > 5), the model tends to overestimate the data at faint luminosities. Critical biases in both the data and in the model are discussed to explain such apparent discrepancies. The predicted hydrogen photoionization rate as a function of redshift is found to be consistent with that derived from the observations. All of the above suggests that we should reconsider the role of the AGNs as the main driver of the ionization history of the universe.

  9. BLACK HOLE GROWTH AND ACTIVE GALACTIC NUCLEI OBSCURATION BY INSTABILITY-DRIVEN INFLOWS IN HIGH-REDSHIFT DISK GALAXIES FED BY COLD STREAMS

    SciTech Connect

    Bournaud, Frederic; Teyssier, Romain; Daddi, Emanuele; Dekel, Avishai; Cacciato, Marcello; Juneau, Stephanie; Shankar, Francesco E-mail: dekel@phys.huji.ac.il

    2011-11-10

    Disk galaxies at high redshift have been predicted to maintain high gas surface densities due to continuous feeding by intense cold streams leading to violent gravitational instability, transient features, and giant clumps. Gravitational torques between the perturbations drive angular momentum out and mass in, and the inflow provides the energy for keeping strong turbulence. We use analytic estimates of the inflow for a self-regulated unstable disk at a Toomre stability parameter Q {approx} 1, and isolated galaxy simulations capable of resolving the nuclear inflow down to the central parsec. We predict an average inflow rate {approx}10 M{sub Sun} yr{sup -1} through the disk of a 10{sup 11} M{sub Sun} galaxy, with conditions representative of z {approx} 2 stream-fed disks. The inflow rate scales with disk mass and (1 + z){sup 3/2}. It includes clump migration and inflow of the smoother component, valid even if clumps disrupt. This inflow grows the bulge, while only a fraction of {approx}> 10{sup -3} of it needs to accrete onto a central black hole (BH), in order to obey the observed BH-bulge relation. A galaxy of 10{sup 11} M{sub Sun} at z {approx} 2 is expected to host a BH of {approx}10{sup 8} M{sub Sun }, accreting on average with moderate sub-Eddington luminosity L{sub X} {approx} 10{sup 42}-10{sup 43} erg s{sup -1}, accompanied by brighter episodes when dense clumps coalesce. We note that in rare massive galaxies at z {approx} 6, the same process may feed {approx}10{sup 9} M{sub Sun} BH at the Eddington rate. High central gas column densities can severely obscure active galactic nuclei in high-redshift disks, possibly hindering their detection in deep X-ray surveys.

  10. THE RADIUS-LUMINOSITY RELATIONSHIP FOR ACTIVE GALACTIC NUCLEI: THE EFFECT OF HOST-GALAXY STARLIGHT ON LUMINOSITY MEASUREMENTS. II. THE FULL SAMPLE OF REVERBERATION-MAPPED AGNs

    SciTech Connect

    Bentz, Misty C.; Peterson, Bradley M.; Pogge, Richard W.; Netzer, Hagai; Vestergaard, Marianne E-mail: peterson@astronomy.ohio-state.edu E-mail: netzer@wise.tau.ac.il

    2009-05-20

    We present high-resolution Hubble Space Telescope images of all 35 active galactic nuclei (AGNs) with optical reverberation-mapping results, which we have modeled to create a nucleus-free image of each AGN host galaxy. From the nucleus-free images, we determine the host-galaxy contribution to ground-based spectroscopic luminosity measurements at 5100 A. After correcting the luminosities of the AGNs for the contribution from starlight, we re-examine the H{beta} R {sub BLR}-L relationship. Our best fit for the relationship gives a power-law slope of 0.52 with a range of 0.45-0.59 allowed by the uncertainties. This is consistent with our previous findings, and thus still consistent with the naive assumption that all AGNs are simply luminosity-scaled versions of each other. We discuss various consistency checks relating to the galaxy modeling and starlight contributions, as well as possible systematic errors in the current set of reverberation measurements from which we determine the form of the R {sub BLR}-L relationship.

  11. The 4 Ms CHANDRA Deep Field-South Number Counts Apportioned by Source Class: Pervasive Active Galactic Nuclei and the Ascent of Normal Galaxies

    NASA Technical Reports Server (NTRS)

    Lehmer, Bret D.; Xue, Y. Q.; Brandt, W. N.; Alexander, D. M.; Bauer, F. E.; Brusa, M.; Comastri, A.; Gilli, R.; Hornschemeier, A. E.; Luo, B.; Paolillo, M.; Ptak, A.; Shemmer, O.; Schneider, D. P.; Tozzi, P.; Vignali, C.

    2012-01-01

    We present 0.5-2 keV, 2-8 keV, 4-8 keV, and 0.5-8 keV (hereafter soft, hard, ultra-hard, and full bands, respectively) cumulative and differential number-count (log N-log S ) measurements for the recently completed approx. equal to 4 Ms Chandra Deep Field-South (CDF-S) survey, the deepest X-ray survey to date. We implement a new Bayesian approach, which allows reliable calculation of number counts down to flux limits that are factors of approx. equal to 1.9-4.3 times fainter than the previously deepest number-count investigations. In the soft band (SB), the most sensitive bandpass in our analysis, the approx. equal to 4 Ms CDF-S reaches a maximum source density of approx. equal to 27,800 deg(sup -2). By virtue of the exquisite X-ray and multiwavelength data available in the CDF-S, we are able to measure the number counts from a variety of source populations (active galactic nuclei (AGNs), normal galaxies, and Galactic stars) and subpopulations (as a function of redshift, AGN absorption, luminosity, and galaxy morphology) and test models that describe their evolution. We find that AGNs still dominate the X-ray number counts down to the faintest flux levels for all bands and reach a limiting SB source density of approx. equal to 14,900 deg(sup -2), the highest reliable AGN source density measured at any wavelength. We find that the normal-galaxy counts rise rapidly near the flux limits and, at the limiting SB flux, reach source densities of approx. equal to 12,700 deg(sup -2) and make up 46% plus or minus 5% of the total number counts. The rapid rise of the galaxy counts toward faint fluxes, as well as significant normal-galaxy contributions to the overall number counts, indicates that normal galaxies will overtake AGNs just below the approx. equal to 4 Ms SB flux limit and will provide a numerically significant new X-ray source population in future surveys that reach below the approx. equal to 4 Ms sensitivity limit. We show that a future approx. equal to 10 Ms CDF

  12. ON THE COSMIC EVOLUTION OF THE SCALING RELATIONS BETWEEN BLACK HOLES AND THEIR HOST GALAXIES: BROAD-LINE ACTIVE GALACTIC NUCLEI IN THE zCOSMOS SURVEY

    SciTech Connect

    Merloni, A.; Bongiorno, A.; Brusa, M.; Bolzonella, M.; Comastri, A.; Gilli, R.; Lusso, E.; Mignoli, M.; Civano, F.; Elvis, M.; Hao, H.; Fiore, F.; Jahnke, K.; Koekemoer, A. M.; Mainieri, V.; Miyaji, T.; Renzini, A.; Salvato, M.; Silverman, J.; Trump, J.

    2010-01-01

    We report on the measurement of the physical properties (rest-frame K-band luminosity and total stellar mass) of the hosts of 89 broad-line (type-1) active galactic nuclei (AGNs) detected in the zCOSMOS survey in the redshift range 1 < z < 2.2. The unprecedented multi-wavelength coverage of the survey field allows us to disentangle the emission of the host galaxy from that of the nuclear black hole in their spectral energy distributions (SEDs). We derive an estimate of black hole masses through the analysis of the broad Mg II emission lines observed in the medium-resolution spectra taken with VIMOS/VLT as part of the zCOSMOS project. We found that, as compared to the local value, the average black hole to host-galaxy mass ratio appears to evolve positively with redshift, with a best-fit evolution of the form (1+z){sup 0.68+}-{sup 0.12+0.6{sub -0.3}}, where the large asymmetric systematic errors stem from the uncertainties in the choice of initial mass function, in the calibration of the virial relation used to estimate BH masses and in the mean QSO SED adopted. On the other hand, if we consider the observed rest-frame K-band luminosity, objects tend to be brighter, for a given black hole mass, than those on the local M{sub BH}-M{sub K} relation. This fact, together with more indirect evidence from the SED fitting itself, suggests that the AGN hosts are likely actively star-forming galaxies. A thorough analysis of observational biases induced by intrinsic scatter in the scaling relations reinforces the conclusion that an evolution of the M{sub BH}-M{sub *} relation must ensue for actively growing black holes at early times: either its overall normalization, or its intrinsic scatter (or both) appear to increase with redshift. This can be interpreted as signature of either a more rapid growth of supermassive black holes at high redshift, a change of structural properties of AGN hosts at earlier times, or a significant mismatch between the typical growth times of

  13. 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.

  14. RADIO STACKING REVEALS EVIDENCE FOR STAR FORMATION IN THE HOST GALAXIES OF X-RAY-SELECTED ACTIVE GALACTIC NUCLEI AT z < 1

    SciTech Connect

    Pierce, C. M.; Ballantyne, D. R.; Ivison, R. J.

    2011-11-20

    Nuclear starbursts may contribute to the obscuration of active galactic nuclei (AGNs). The predicted star formation rates (SFRs) are modest, and, for the obscured AGNs that form the X-ray background at z < 1, the associated faint radio emission lies just beyond the sensitivity limits of the deepest surveys. Here, we search for this level of star formation by studying a sample of 359 X-ray-selected AGNs at z < 1 from the Cosmic Evolution Survey field that are not detected by current radio surveys. The AGNs are separated into bins based on redshift, X-ray luminosity, obscuration, and mid-infrared characteristics. An estimate of the AGN contribution to the radio flux density is subtracted from each radio image, and the images are then stacked to uncover any residual faint radio flux density. All of the bins containing 24 {mu}m detected AGNs are detected with a signal-to-noise >3{sigma} in the stacked radio images. In contrast, AGNs not detected at 24 {mu}m are not detected in the resulting stacked radio images. This result provides strong evidence that the stacked radio signals are likely associated with star formation. The estimated SFRs derived from the radio stacks range from 3 M{sub Sun} yr{sup -1} to 29 M{sub Sun} yr{sup -1}. Although it is not possible to associate the radio emission with a specific region of the host galaxies, these results are consistent with the predictions of nuclear starburst disks in AGN host galaxies.

  15. The Discovery of H2O Maser Emission in Seven Active Galactic Nuclei and at High Velocities in the Circinus Galaxy

    NASA Astrophysics Data System (ADS)

    Greenhill, L. J.; Kondratko, P. T.; Lovell, J. E. J.; Kuiper, T. B. H.; Moran, J. M.; Jauncey, D. L.; Baines, G. P.

    2003-01-01

    We report the discovery of H2O maser emission at 1.35 cm wavelength in seven active galactic nuclei (at distances of up to 80 Mpc) during a survey conducted at the 70 m diameter antenna of the NASA Deep Space Network near Canberra, Australia. The detection rate was ~4%. Two of the maser sources are particularly interesting because they display satellite high-velocity emission lines, which are a signature of emission from the accretion disks of supermassive black holes when seen edge-on. Three of the masers are coincident, to within uncertainties of 0.2", with continuum emission sources that we observed at about λ=1.3 cm. We also report the discovery of new spectral features in the Circinus galaxy H2O maser that broaden the known velocity range of emission therein by a factor of ~1.7. If the new spectral features originate in the Circinus accretion disk, then molecular material must survive at radii ~3 times smaller than had been believed previously (~0.03 pc or ~2×105 Schwarzschild radii).

  16. Ambartsumyan's concept of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Khachikian, E. Ye.

    2010-01-01

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

  17. 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.

  18. DUST EMISSION FROM UNOBSCURED ACTIVE GALACTIC NUCLEI

    SciTech Connect

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

    2009-05-20

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

  19. Dust Emission from Unobscured Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

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

    2009-05-01

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

  20. Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Arévalo, P.

    2014-10-01

    Accreting supermassive black holes have had a large impact in the evolution of their host galaxies, and even inject significant energy into their host cluster of galaxies. Although the black hole's influence in these large structures is evident, the central engine itself is remarkably difficult to observe. Their extremely compact nature makes it impossible to resolve the final source of fueling, the accretion disc, although interferometric observations have started to reveal important details of the material directly outside this region. In this work I review the techniques that have shed light into the structure and behavior of these central engines in the quest to find out how black hole grow.

  1. The fueling of active galaxies

    NASA Technical Reports Server (NTRS)

    Hernquist, Lars

    1991-01-01

    Collisions of galaxies are often invoked to explain violent phenomena in the universe. The dynamics of interacting galaxies is intrinsically three-dimensional and involves both gas and stellar dynamics. In general, a computational approach is needed to model galactic collisions. Galaxy encounters are studied using a hybrid N-body/hydrodynamics code, capable of integrating systems of stars, gas, and dark matter in a fully self-consistent manner. These experiments demonstrate that gravitational coupling between gas and stars in galactic interactions can drive most of the gas throughout a galaxy into the nucleus of a merger remnant. The high densities in these gas concentrations are likely to result in strong bursts of star formation. Hence, this process may explain the nuclear starbursts in some systems of interacting galaxies. Further collapse of these gas concentrations can trigger even more intense activity if some gas is eventually accreted by a supermassive black hole. Such an evolutionary sequence may account for some quasars and active galactic nuclei.

  2. Starbursts in Low Luminosity Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    González Delgado, Rosa M.; Cid Fernandes, Roberto

    2005-05-01

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

  3. SUZAKU VIEW OF THE SWIFT/BAT ACTIVE GALACTIC NUCLEI. IV. NATURE OF TWO NARROW-LINE RADIO GALAXIES (3C 403 AND IC 5063)

    SciTech Connect

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

    2011-09-01

    We report the results of Suzaku broadband X-ray observations of the two narrow-line radio galaxies, 3C 403 and IC 5063. Combined with the Swift/Burst Alert Telescope (BAT) spectra averaged for 58 months, we are able to accurately constrain their spectral properties over the 0.5-200 keV band. The spectra of both nuclei are well represented with an absorbed cutoff power law, an absorbed reflection component from cold matter with an iron-K emission line, and an unabsorbed soft component, which gives a firm upper limit for the scattered emission. The reflection strength normalized to the averaged BAT flux is R {identical_to} {Omega}/2{pi} {approx} 0.6 in both targets, implying that their tori have a sufficiently large solid angle to produce the reprocessed emission. A numerical torus model with an opening angle of {approx}50{sup 0} well reproduces the observed spectra. We discuss the possibility that the amount of the normal gas responsible for Thomson scattering is systematically smaller in radio galaxies compared with Seyfert galaxies.

  4. Far-infrared properties of Markarian galaxies with multiple nuclei - Warm dust emission in mergers

    NASA Technical Reports Server (NTRS)

    Mazzarella, Joseph M.; Bothun, Gregory D.; Boroson, Todd A.

    1991-01-01

    An investigation of coadded IRAS data is performed on 187 Markarian galaxies where distinguishing morphological characteristics or multiple optical nuclei are present. The far-IR properties of Markarian galaxies are compared to the IRAS Bright Galaxy Sample, and a much higher median dust temperature is found in the multiple nucleus galaxies, suggesting that more far-IR luminosity results from active star formation. Both optical/UV and far-IR selection techniques are necessary to extract complete samples of AGNs since the far-IR two-color plane can miss up to 50 percent of the galaxies. A systematic increase in the contribution of warm dust emission due to active star formation and AGNs is found in a statistical comparison of merger candidates and other galaxy samples. The assumed nature of precursor galaxies determines the assumed enhancement of far-IR luminosity caused by galaxy collisions. A model is presented which describes the properties of the Markarian galaxies in terms of enhanced OB star formation and different grain size distributions. The results of the investigation are shown to be consistent with a 'subdued' interpretation of merging galaxies with high luminosities.

  5. Reevaluating Active Galactic Nuclei in Rich Clusters

    NASA Astrophysics Data System (ADS)

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

    1999-06-01

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

  6. The Host Galaxies of X-Ray Selected Active Galactic Nuclei to z - 2.5: Structure, Star-Formation and Their Relationships from CANDELS and Herschel/Pacs

    NASA Technical Reports Server (NTRS)

    Rosario, D.J.; McIntosh, D. H.; van der Wel, A.; Kartaltepe, J.; Lang, P.; Santini, P.; Wuyts, S.; Lutz, D.; Rafelski, M.; Villforth, C.; Alexander, D. M.; Bauer, F. E.; Bell, E. F.; Berta, S.; Brandt, W. N.; Conselice, C. J.; Dekel, A.; Faber, S. M.; Ferguson, H. C.; Genzel, R.; Grogin, N. A.; Kocevski, D. D.; Koekemoer, A. M.; Koo, D. C.; Straughn, A.

    2014-01-01

    We study the relationship between the structure and star-formation rate (SFR) of X-ray selected low and moderate luminosity active galactic nuclei (AGNs) in the two Chandra Deep Fields, using Hubble Space Telescope imaging from the Cosmic Assembly Near Infrared Extragalactic Legacy Survey (CANDELS) and deep far-infrared maps from the PEP+GOODS-Herschel survey. We derive detailed distributions of structural parameters and FIR luminosities from carefully constructed control samples of galaxies, which we then compare to those of the AGNs. At z is approximately 1, AGNs show slightly diskier light profiles than massive inactive (non-AGN) galaxies, as well as modestly higher levels of gross galaxy disturbance (as measured by visual signatures of interactions and clumpy structure). In contrast, at z 2, AGNs show similar levels of galaxy disturbance as inactive galaxies, but display a red central light enhancement, which may arise due to a more pronounced bulge in AGN hosts or due to extinguished nuclear light. We undertake a number of tests of both these alternatives, but our results do not strongly favour one interpretation over the other. The mean SFR and its distribution among AGNs and inactive galaxies are similar at z greater than 1.5. At z less than 1, however, clear and significant enhancements are seen in the SFRs of AGNs with bulge-dominated light profiles. These trends suggest an evolution in the relation between nuclear activity and host properties with redshift towards a minor role for mergers and interactions at z greater than 15

  7. The nature of active galaxies

    NASA Astrophysics Data System (ADS)

    Chapman, Scott Christopher

    Many details of the structure of Active Galactic Nuclei (AGN) galaxies continue to elude researchers in the field. To shed light on some of the enigmas related to the fueling and classification of AGN, I have studied the core structure of a sample of 37 nearby Seyfert galaxies at high resolution using adaptive optics on the CFHT. This dataset consists of near-IR imaging from 1 to 3 μm (the J, H, and K bands). I first describe the instruments and observing techniques along with a presentation of the galaxy sample properties. I then outline the detailed data reduction and image processing required with adaptive optics observations, highlighting some of the associated unavoidable perils. A detailed multi-wavelength study is pursued for two nearby Seyfert galaxies, NGC3227 and NGC2992. With these objects, the current ideas of Seyfert fueling and unification of Seyfert types are scrutinized, focusing on the high spatial resolution achieved using adaptive optics in the near-IR. The dynamical processes and differing classifications of these galaxies are substantially clarified through their core morphologies. These studies show that scientific results can be established with AO data, in spite of the above mentioned artifact. For NGC2992, a spiral structure within the central 6' and a 1' extended feature are traced down to the core at the resolution of our images. We speculate, based on these observed structures, that multiple radio components are superposed which contribute to the observed figure-8 morphology in the VLA images: one associated with the spiral structure in the galaxy disk, and another flowing out of the galaxy plane. I then address whether the classification of Seyfert galaxy types can be explained via patchy dust at fairly large distances (~100 pc) from the central engine. Maps of dust extinction are constructed with the deep view afforded by the near-IR. These are compared with optical images observed with the Hubble Space Telescope (HST) to aid in

  8. 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

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

    NASA Astrophysics Data System (ADS)

    Taormina, M.; Bornancini, C.

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

  10. Evolution and Distribution of Magnetic Fields from Active Galactic Nuclei in Galaxy Clusters. II. The Effects of Cluster Size and Dynamical State

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Li, Hui; Collins, David C.; Li, Shengtai; Norman, Michael L.

    2011-10-01

    Theory and simulations suggest that magnetic fields from radio jets and lobes powered by their central super massive black holes can be an important source of magnetic fields in the galaxy clusters. This is Paper II in a series of studies where we present self-consistent high-resolution adaptive mesh refinement cosmological magnetohydrodynamic simulations that simultaneously follow the formation of a galaxy cluster and evolution of magnetic fields ejected by an active galactic nucleus. We studied 12 different galaxy clusters with virial masses ranging from 1 × 1014 to 2 × 1015 M sun. In this work, we examine the effects of the mass and merger history on the final magnetic properties. We find that the evolution of magnetic fields is qualitatively similar to those of previous studies. In most clusters, the injected magnetic fields can be transported throughout the cluster and be further amplified by the intracluster medium (ICM) turbulence during the cluster formation process with hierarchical mergers, while the amplification history and the magnetic field distribution depend on the cluster formation and magnetism history. This can be very different for different clusters. The total magnetic energies in these clusters are between 4 × 1057 and 1061 erg, which is mainly decided by the cluster mass, scaling approximately with the square of the total mass. Dynamically older relaxed clusters usually have more magnetic fields in their ICM. The dynamically very young clusters may be magnetized weakly since there is not enough time for magnetic fields to be amplified.

  11. AGN Zoo and Classifications of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.

    2015-07-01

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

  12. Stellar Nuclei and Inner Polar Disks in Lenticular Galaxies

    NASA Astrophysics Data System (ADS)

    Sil’chenko, Olga K.

    2016-09-01

    I analyze statistics of the stellar population properties for stellar nuclei and bulges of nearby lenticular galaxies in different environments by using panoramic spectral data of the integral-field spectrograph SAURON retrieved from the open archive of the Isaac Newton Group. I also estimate the fraction of nearby lenticular galaxies having inner polar gaseous disks by exploring the volume-limited sample of early-type galaxies of the ATLAS-3D survey. By inspecting the two-dimensional velocity fields of the stellar and gaseous components with the running tilted-ring technique, I have found seven new cases of inner polar disks. Together with those, the frequency of inner polar disks in nearby S0 galaxies reaches 10%, which is much higher than the frequency of large-scale polar rings. Interestingly, the properties of the nuclear stellar populations in the inner polar ring hosts are statistically the same as those in the whole S0 sample, implying similar histories of multiple gas-accretion events from various directions.

  13. The Penrose photoproduction scenario for NGC 4151: A black hole gamma-ray emission mechanism for active galactic nuclei and Seyfert galaxies. [Compton scattering and pair production

    NASA Technical Reports Server (NTRS)

    Leiter, D.

    1979-01-01

    A consistent theoretical interpretation is given for the suggestion that a steepening of the spectrum between X-ray and gamma ray energies may be a general, gamma-ray characteristic of Seyfert galaxies, if the diffuse gamma ray spectrum is considered to be a superposition of unresolved contributions, from one or more classes of extragalactic objects. In the case of NGC 4151, the dominant process is shown to be Penrose Compton scattering in the ergosphere of a Kerr black hole, assumed to exist in the Seyfert's active galactic nucleus.

  14. Multifrequency study of the nuclei of SBC galaxies

    NASA Astrophysics Data System (ADS)

    Vila, M. B.; Davies, R. D.; Pedlar, A.; Axon, D. J.; Hummel, E.

    1989-07-01

    A sample of 100 Sbc galaxies has been observed at different wavelengths and resolutions. The ultimate aim of the project is to probe the origin of their nuclear activity (e.g., blackhole, starbust, etc.). The results from radio observations with the VLA (New Mexico) at 20 and 6 cm wavelength, with a resolution of 1-2 arc sec, for the inner kpc of nineteen sources are presented. Six of the galaxies show extended emission consistent with starburst activity. The remaining thirteen are unresolved or marginally resolved compact sources. Their steep spectra indicate synchrotron emission. They show total nuclear energies similar to those found for a sample of Seyfert galaxies. Optical spectroscopic observations with a similar resolution to the radio data have been made for approximately 90 galaxies. A sample of the derived rotation curves is included.

  15. The fuelling of active galactic nuclei

    NASA Technical Reports Server (NTRS)

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

    1990-01-01

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

  16. The dynamics and fueling of active nuclei

    NASA Technical Reports Server (NTRS)

    Norman, C.; Silk, J.

    1983-01-01

    It is generally believed that quasars and active galactic nuclei produce their prodigious luminosities in connection with the release of gravitational energy associated with accretion and infall of matter onto a compact central object. In the present analysis, it is assumed that the central object is a massive black hole. The fact that a black hole provides the deepest possible central potential well does imply that it is the most natural candidate for the central engine. It is also assumed that the quasar is associated with the nucleus of a conventional galaxy. A number of difficulties arise in connection with finding a suitable stellar fueling model. A simple scheme is discussed for resolving these difficulties. Attention is given to fueling in a nonaxisymmetric potential, the effects of a massive accretion disk, and the variability in the disk luminosity caused by star-disk collisions assuming that the energy deposited in the disk is radiated.

  17. The relation between star formation and active nuclei

    NASA Technical Reports Server (NTRS)

    Rieke, G. H.

    1987-01-01

    Three questions relevant to the relation between an active nucleus and surrounding star formation are discussed. The infrared stellar CO absorption bands can be used to identify galaxies with large populations of young, massive stars and thus can identify strong starburst unambiguously, such as in NGC 6240, and can help identify composite active/starburst systems such as Arp 220. An active nucleus is probably not required for LINER spectral characteristics; dusty starburst galaxies, particularly if they are nearly edge-on, can produce LINER spectra through the shock heating of their interstellar media by supernovae combined with the obscuration of their nuclei in the optical. The Galactic Center would be an ideal laboratory for studying the interaction of starbursts and active nuclei, if both could be demonstrated to occur there. Failure to detect a cusp in the stellar distribution raises questions about the presence of an active nucleus, which should be answered by additional observations in the near future.

  18. Quasi periodic oscillations in active galactic nuclei

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  19. The X-ray spectroscopy of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R.

    1985-01-01

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

  20. Galaxy interactions and strength of nuclear activity

    NASA Technical Reports Server (NTRS)

    Simkin, S. M.

    1990-01-01

    Analysis of data in the literature for differential velocities and projected separations of nearby Seyfert galaxies with possible companions shows a clear difference in projected separations between type 1's and type 2's. This kinematic difference between the two activity classes reinforces other independent evidence that their different nuclear characteristics are related to a non-nuclear physical distinction between the two classes. The differential velocities and projected separations of the galaxy pairs in this sample yield mean galaxy masses, sizes, and mass to light ratios which are consistent with those found by the statistical methods of Karachentsev. Although the galaxy sample discussed here is too small and too poorly defined to provide robust support for these conclusions, the results strongly suggest that nuclear activity in Seyfert galaxies is associated with gravitational perturbations from companion galaxies, and that there are physical distinctions between the host companions of Seyfert 1 and Seyfert 2 nuclei which may depend both on the environment and the structure of the host galaxy itself.

  1. The Properties Of The Stellar Nuclei With The Host Galaxy Morphology In The ACSVCS

    NASA Astrophysics Data System (ADS)

    Lee, Hyun-chul

    2012-01-01

    We have revisited the ACS Virgo Cluster Survey (ACSVCS), a Hubble Space Telescope program to obtain ACS/WFC g and z bands imaging for a sample of 100 early-type galaxies in the Virgo Cluster. In this study, we examine 51 nucleated early-type galaxies in the ACSVCS in order to look into the relationship between the photometric and structural properties of stellar nuclei and their host galaxies. We morphologically dissect galaxies into five classes. We note that (1) the stellar nuclei of dwarf early-type galaxies (dS0, dE, and dE,N) are generally fainter and bluer with g > 18.95 and (g-z) < 1.40 compared to some brighter and redder counterparts of the ellipticals (E) and lenticular galaxies (S0), (2) the g-band half-light radii of stellar nuclei of all dwarf early-type galaxies (dS0, dE, and dE,N) are smaller than 20 pc and their average is about 4 pc, and (3) the colors of red stellar nuclei with (g-z) > 1.40 in bright ellipticals and lenticular galaxies are bluer than their host galaxies colors. We also show that most of the unusually RED stellar nuclei with (g-z) > 1.54 in the ACSVCS are the central parts of bright ellipticals and lenticular galaxies.

  2. Theory of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Shields, G. A.

    1986-01-01

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

  3. 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.

  4. 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

  5. Multiwavelength Study of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Singh, Veeresh

    2010-08-01

    Seyfert galaxies are a subclass of active galaxies and are categorized as nearby, low luminosity, radio-quiet Active Galactic Nuclei (AGN) hosted in spiral or lenticular galaxies. Demographically, Seyfert galaxies may account for ~ 10% of the entire population of active galaxies in the nearby universe. Seyfert galaxies are classified mainly into two subclasses named as `type 1' and `type 2' Seyferts, based on the presence and absence of broad permitted emission lines in their optical spectra, respectively. Detection of broad permitted emission lines in some Seyfert type 2s observed in the polarized light laid the foundation of the Seyfert unification scheme, which hypothesizes that Seyfert type 1s and type 2s belong to the same parent population and appear different solely due to the differing orientations of the obscuring material having a torus-like geometry around the AGN (Antonucci and Miller 1985; Antonucci 1993). The primary objective of this thesis work is to examine the validity and limitations of the orientation and obscuration based Seyfert unification scheme using multiwavelength (mainly X-ray and radio) observations. The key issue in testing the Seyfert unification scheme has been acquiring a well defined rigorously selected Seyfert sample. I have argued that the Seyfert samples based on flux limited surveys at optical, IR, UV and X-ray are likely to be biased against obscured and faint sources. In order to test the predictions of Seyfert unification scheme I use a sample based on properties (i.e., cosmological redshift, [OIII] emission line luminosity, absolute bulge magnitude, absolute stellar magnitude of the host galaxy and the Hubble stage of the host galaxy) that are independent to the orientation of the obscuring torus, host galaxy and the AGN axis. Furthermore, two Seyfert subtypes of our sample have matched distributions in the orientation-independent properties and this ensures the intrinsic similarity between two Seyfert subtypes within the

  6. SUBMILLIMETER H{sub 2}O MASER IN CIRCINUS GALAXY-A NEW PROBE FOR THE CIRCUMNUCLEAR REGION OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Hagiwara, Yoshiaki; Miyoshi, Makoto; Doi, Akihiro; Horiuchi, Shinji

    2013-05-10

    We present the first detection of extragalactic submillimeter H{sub 2}O maser in the 321 GHz transition toward the center of Circinus galaxy, the nearby Type 2 Seyfert using the Atacama Large Millimeter/Submillimeter Array. We find that Doppler features of the detected 321 GHz H{sub 2}O maser straddle the systemic velocity of the galaxy as seen in the spectrum of the known 22 GHz H{sub 2}O maser in the galaxy. By comparing the velocities of the maser features in both transitions, it can be deduced that the 321 GHz maser occurs in a region similar to that of the 22 GHz maser, where the sub-parsec-scale distribution of the 22 GHz maser was revealed by earlier very long baseline interferometry observations. The detected maser features remain unresolved at the synthesized beam of {approx}0.''66 ({approx}15 pc) and coincide with the 321 GHz continuum peak within small uncertainties. We also present a tentative detection of the highest velocity feature (redshifts up to {approx}635 km s{sup -1}) in the galaxy. If this high-velocity feature arises from a Keplerian rotating disk well established in this galaxy, it is located at a radius of {approx}0.018 pc ({approx}1.2 Multiplication-Sign 10{sup 5} Schwarzschild radii), which might probe molecular material closest to the central engine.

  7. EVOLUTION AND DISTRIBUTION OF MAGNETIC FIELDS FROM ACTIVE GALACTIC NUCLEI IN GALAXY CLUSTERS. I. THE EFFECT OF INJECTION ENERGY AND REDSHIFT

    SciTech Connect

    Xu Hao; Li Hui; Li Shengtai; Collins, David C.; Norman, Michael L. E-mail: hli@lanl.go E-mail: dcollins@physics.ucsd.ed

    2010-12-20

    We present a series of cosmological magnetohydrodynamic simulations that simultaneously follow the formation of a galaxy cluster and evolution of magnetic fields ejected by an active galactic nucleus (AGN). Specifically, we investigate the influence of both the epoch of the AGN (z {approx} 3-0.5) and the AGN energy ({approx}3 x 10{sup 57}- 2 x 10{sup 60} erg) on the final magnetic field distribution in a relatively massive cluster (M{sub vir} {approx} 10{sup 15} M{sub sun}). We find that as long as the AGN magnetic fields are ejected before the major mergers in the cluster formation history, magnetic fields can be transported throughout the cluster and can be further amplified by the intracluster medium (ICM) turbulence caused by hierarchical mergers during the cluster formation process. The total magnetic energy in the cluster can reach {approx}10{sup 61} erg, with micro Gauss fields distributed over the {approx}Mpc scale. The amplification of the total magnetic energy by the ICM turbulence can be significant, up to {approx}1000 times in some cases. Therefore even weak magnetic fields from AGNs can be used to magnetize the cluster to the observed level. The final magnetic energy in the ICM is determined by the ICM turbulent energy, with a weak dependence on the AGN injection energy. We discuss the properties of magnetic fields throughout the cluster and the synthetic Faraday rotation measure maps they produce. We also show that high spatial resolution over most of the magnetic regions of the cluster is very important to capture the small-scale dynamo process and maintain the magnetic field structure in our simulations.

  8. Evolution and Distribution of Magnetic Fields from Active Galactic Nuclei in Galaxy Clusters. I. The Effect of Injection Energy and Redshift

    NASA Astrophysics Data System (ADS)

    Xu, Hao; Li, Hui; Collins, David C.; Li, Shengtai; Norman, Michael L.

    2010-12-01

    We present a series of cosmological magnetohydrodynamic simulations that simultaneously follow the formation of a galaxy cluster and evolution of magnetic fields ejected by an active galactic nucleus (AGN). Specifically, we investigate the influence of both the epoch of the AGN (z ~ 3-0.5) and the AGN energy (~3 × 1057- 2 × 1060 erg) on the final magnetic field distribution in a relatively massive cluster (M vir ~ 1015 M sun). We find that as long as the AGN magnetic fields are ejected before the major mergers in the cluster formation history, magnetic fields can be transported throughout the cluster and can be further amplified by the intracluster medium (ICM) turbulence caused by hierarchical mergers during the cluster formation process. The total magnetic energy in the cluster can reach ~1061 erg, with micro Gauss fields distributed over the ~Mpc scale. The amplification of the total magnetic energy by the ICM turbulence can be significant, up to ~1000 times in some cases. Therefore even weak magnetic fields from AGNs can be used to magnetize the cluster to the observed level. The final magnetic energy in the ICM is determined by the ICM turbulent energy, with a weak dependence on the AGN injection energy. We discuss the properties of magnetic fields throughout the cluster and the synthetic Faraday rotation measure maps they produce. We also show that high spatial resolution over most of the magnetic regions of the cluster is very important to capture the small-scale dynamo process and maintain the magnetic field structure in our simulations.

  9. The dance of heating and cooling in galaxy clusters: three-dimensional simulations of self-regulated active galactic nuclei outflows

    NASA Astrophysics Data System (ADS)

    Gaspari, M.; Melioli, C.; Brighenti, F.; D'Ercole, A.

    2011-02-01

    It is now widely accepted that heating processes play a fundamental role in galaxy clusters, struggling in an intricate but fascinating ‘dance' with its antagonist, radiative cooling. Last-generation observations, especially X-ray, are giving us tiny hints about the notes of this endless ballet. Cavities, shocks, turbulence and wide absorption lines indicate that the central active nucleus is injecting a huge amount of energy in the intracluster medium. However, which is the real dominant engine of self-regulated heating? One of the models we propose is massive subrelativistic outflows, probably generated by a wind disc or just the result of the entrainment on kpc scale by the fast radio jet. Using a modified version of the adaptive mesh refinement code FLASH 3.2, we have explored several feedback mechanisms that self-regulate the mechanical power. Two are the best schemes that answer our primary question, that is, quenching cooling flow and at the same time preserving a cool core appearance for a long-term evolution (7 Gyr): one is more explosive (with efficiencies ˜ 5 × 10-3-10-2), triggered by central cooled gas, and the other is gentler, ignited by hot gas Bondi accretion (with ɛ= 0.1). These three-dimensional simulations show that the total energy injected is not the key aspect, but the results strongly depend on how energy is given to the intracluster medium. We follow the dynamics of the best models (temperature, density, surface brightness maps and profiles) and produce many observable predictions: buoyant bubbles, ripples, turbulence, iron abundance maps and hydrostatic equilibrium deviation. We present an in-depth discussion of the merits and flaws of all our models, with a critical eye towards observational concordance.

  10. A NIR Atlas of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

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

    2006-06-01

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

  11. IRAS observations of active galaxies

    NASA Technical Reports Server (NTRS)

    Neugebauer, G.; Soifer, B. T.; Rowan-Robinson, M.

    1985-01-01

    The IRAS survey gives an unbiased view of the infrared properties of the active galaxies. Seyfert galaxies occupy much the same area in color-color plots as to normal infrared bright galaxies, but extend the range towards flatter 60 to 25 mm slopes. Statistically the Seyfert 1 galaxies can be distinguished from the Seyfert 2 galaxies, lying predominantly closer to the area with constant slopes between 25 and 200 mm. The infrared measurements of the Seyfert galaxies cannot distinguish between the emission mechanisms in these objects although they agree with the currently popular ideas; they do provide a measure of the total luminosity of the Seyferts. The quasar's position in the color-color diagrams continue the trend of the Seyferts. The quasar 3C48 is shown to be exceptional among the radio loud quasars in that it has a high infrared luminosity which dominates the power output of the quasar and is most likely associated with the underlying host galaxy.

  12. Not Dead Yet: Low-Level Star Formation and Active Nuclei in the Continued Evolution of Nearby Early-Type Galaxies

    NASA Astrophysics Data System (ADS)

    Nyland, Kristina; Young, Lisa; Wrobel, Joan; Morganti, Raffaella; Atlas-3D

    2015-01-01

    We present the results of sensitive Jansky Very Large Array continuum observations of nearby early-type galaxies (ETGs) at 1.4 and 5 GHz. Our sample comprises a subset of the volume- and magnitude-limited ATLAS-3D survey of ETGs, which has a rich database of ancillary data including CO observations. The 1.4 GHz observations were designed to explore the properties of star formation (SF) in ETGs at ~5' (~300 pc) spatial resolution. Here, we find that some CO-rich ETGs have radio luminosities consistent with extrapolations from H2 mass-derived SF rates (SFRs) and standard radio-SFR calibrations. However, at low H2 masses, many have weaker radio emission than expected. The infrared-radio relation shows similar behavior at low luminosities, with a systematic tendency for ETGs to lie below the standard infrared-radio relation developed for spirals, even when substantial reservoirs of H2 are available. Thus, many nearby ETGs are radio deficient compared to both their H2 and infrared emission. Several mechanisms likely conspire to cause this, but evidence is most compelling for a combination of decreased SF efficiency, a bottom-heavy IMF, weak magnetic fields, and higher incidence of environmental effects compared to spirals.We also study the prevalence and properties of 5~GHz radio cores at subarcsecond (~30 pc) resolution for two distinct kinematic classes: slow rotators (SRs) and fast rotators (FRs). SRs preferentially host nuclear radio emission compared to FRs, and they also host the most powerful radio sources in our sample, consistent with previous findings for ellipticals. In contrast to FRs, SRs also show signs of relationships between radio luminosity and stellar mass. In both FRs and SRs, the presence of dust and ionized gas are strong predictors of the detection of a radio core. All of this suggests that the nuclear activity in ETGs is related to their formation histories. In this picture, FRs are built-up by minor mergers and interactions that leave behind

  13. Particle Acceleration in Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Miller, James A.

    1996-01-01

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

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

    PubMed

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

    2012-05-10

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

  15. Astrochemistry and star formation in nearby galaxies: from galaxy disks to hot nuclei

    NASA Astrophysics Data System (ADS)

    Aalto, S.

    2016-05-01

    Studying the molecular phase of the interstellar medium in galaxies is fundamental for the understanding of the onset and evolution of compact and extended star formation, and of the growth of supermassive black holes. Molecular line emission is an excellent tracer of chemical, physical and dynamical conditions in the cold neutral gas. Key molecules in extragalactic studies are e.g. HCN, HCO+, HC3N, SiO, CH3OH, H2O. Furthermore, we can use IR excited molecular emission to probe the very inner regions of luminous infrared galaxies allowing us to get past the optically thick dust barrier of the compact obscured nuclei where lines of CO, HCN and HCO+ in their vibrational ground state (ν=0) may be self-absorbed. Finally, molecular outflows and their chemistry are briefly discussed - including new ALMA results on for example the outflow of the lenticular galaxy NGC1377 and a study of the chemistry of the outflow of the quasar Mrk231.

  16. (12)CO (3-2) & (1-0) emission line observations of nearby starburst galaxy nuclei

    NASA Technical Reports Server (NTRS)

    Devereux, Nicholas; Taniguchi, Yoshiaki; Sanders, D. B.; Nakai, N.; Young, J. S.

    1994-01-01

    New measurements of the (12)CO (1-0) and (12)CO (3-2) line emission are presented for the nuclei of seven nearby starburst galaxies selected from a complete sample of 21 nearby starburst galaxies for which the nuclear star formation rates are measured to be comparable to the archetype starburst galaxies M82 and NGC 253. The new observations capitalize on the coincidence between the beam size of the 45 m Nobeyama telescope at 115 GHz and that of the 15 m James Clerk Maxwell Telescope at 345 GHz to measure the value of the (12)CO (3-2)/(1-0) emission line ratio in a 15 sec (less than or equal to 2.5 kpc) diameter region centered on the nuclear starburst. In principle, the (12)CO (3-2)/(1-0) emission line ratio provides a measure of temperature and optical depth for the (12)CO gas. The error weighted mean value of the (12)CO (3-2)/(1-0) emission line ratio measured for the seven starburst galaxy nuclei is -0.64 +/- 0.06. The (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is significantly higher than the average value measured for molecular gas in the disk of the Galaxy, implying warmer temperatures for the molecular gas in starburst galaxy nuclei. On the other hand, the (12)CO (3-2)/(1-0) emission line ratio measured for the starburst galaxy nuclei is not as high as would be expected if the molecular gas were hot, greater than 20 K, and optically thin, tau much less than 1. The total mass of molecular gas contained within the central 1.2-2.8 kpc diameter region of the starburst galaxy nuclei ranges from 10(exp 8) to 10(exp 9) solar mass. While substantial, the molecular gas mass represents only a small percentage, approximately 9%-16%, of the dynamical mass in the same region.

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

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

    SciTech Connect

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

    2011-12-01

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

  19. 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.

  20. Reverberation Mapping Campaign of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Bhattacharjee, Anirban

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

  1. 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.

  2. 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

  3. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

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

  5. Destruction and survival of polycyclic aromatic hydrocarbons in active galaxies

    NASA Technical Reports Server (NTRS)

    Voit, G. M.

    1992-01-01

    Infrared spectra of dusty galactic environments often contain emission features attributed to polycyclic aromatic hydrocarbons or PAHs, which can be considered to be very small grains or very large molecules. Although IR spectra of starburst galaxies almost always show these emission features, similar spectra of active galaxies are usually featureless. Even in those active galaxies that do exhibit PAH emission, the PAHs still appear to be eradicated from the nuclear region. This dichotomy suggests that PAHs are destroyed by the intense hard radiation field from an AGN. Laboratory experiments show that certain PAHs are, in fact, so effectively destroyed by individual EUV and X-ray photons that they cannot survive even at kiloparsec distances from active nuclei. Regions within active galaxies that do show PAH emission must therefore be shielded from the central X-ray source by a substantial column density of X-ray absorbing gas.

  6. Statistics of Active Galactic Nuclei in Rich Clusters Revisited

    NASA Astrophysics Data System (ADS)

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

    1998-07-01

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

  7. 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.

  8. Thick discs, and an outflow, of dense gas in the nuclei of nearby Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Lin, Ming-Yi; Davies, R. I.; Burtscher, L.; Contursi, A.; Genzel, R.; González-Alfonso, E.; Graciá-Carpio, J.; Janssen, A.; Lutz, D.; Orban de Xivry, G.; Rosario, D.; Schnorr-Müller, A.; Sternberg, A.; Sturm, E.; Tacconi, L.

    2016-05-01

    We discuss the dense molecular gas in central regions of nearby Seyfert galaxies, and report new arcsec resolution observations of HCN (1-0) and HCO+ (1-0) for three objects. In NGC 3079, the lines show complex profiles as a result of self-absorption and saturated continuum absorption. H13CN reveals the continuum absorption profile, with a peak close to the galaxy's systemic velocity that traces disc rotation, and a second feature with a blue wing extending to -350 km s-1 that most likely traces a nuclear outflow. The morphological and spectral properties of the emission lines allow us to constrain the dense gas dynamics. We combine our kinematic analysis for these three objects, as well as another with archival data, with a previous comparable analysis of four other objects, to create a sample of eight Seyferts. In seven of these, the emission line kinematics imply thick disc structures on radial scales of ˜100 pc, suggesting such structures are a common occurrence. We find a relation between the circum-nuclear LHCN and Mdyn that can be explained by a gas fraction of 10 per cent and a conversion factor αHCN ˜ 10 between gas mass and HCN luminosity. Finally, adopting a different perspective to probe the physical properties of the gas around active galactic nuclei, we report on an analysis of molecular line ratios which indicates that the clouds in this region are not self-gravitating.

  9. Miller-Urey Synthesis in The Nuclei of Galaxies

    NASA Astrophysics Data System (ADS)

    Wickramasinghe, N. C.; Hoyle, F.

    1999-10-01

    The most promising venues for the synthesis of prebiotic molecules by Miller-Urey type processes may be found near the centres of galaxies. Explosions of supermassive stars would produce the basic chemical elements necessary to make molecules in high-density mass flows that are then acted upon by ionizing radiation, thus simulating the conditions needed for Miller-Urey type processing.

  10. Miller-Urey Synthesis in the Nuclei of Galaxies

    NASA Astrophysics Data System (ADS)

    Wickramasinghe, N. C.; Hoyle, F.

    1998-06-01

    The most promising venues for the synthesis of prebiotic molecules by Miller-Urey type processes may be found near the centres of galaxies. Explosions of supermassive stars would produce the basic chemical elements necessary to make molecules in high-density mass flows that are then acted upon by ionizing radiation, thus simulating the conditions needed for Miller-Urey type processing.

  11. 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.

  12. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-02-01

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

  14. Active galaxies and the diffuse Gamma-Ray background

    NASA Technical Reports Server (NTRS)

    Kazanas, D.; Protheroe, R. J.

    1983-01-01

    A model for the origin of relativistic particles and gamma rays in active galactic nuclei and quasars, together with recent HEAO-1 observations of the spectra of active galaxies from 2 to 165 keV, provide the basis for a reexamination of the nature of the extragalactic gamma ray background. Active galaxies account for the observed background if their X-ray spectra steepen to E.021 above 100 keV, as observed in Cen-A, together with a further steepening to E.021 as a result of absorption of gamma rays by photon-photon pair production interactions with X-ray photons. The compactness of active galaxies required to give this steepening is consistent with estimates of their typical luminosity and radius.

  15. Active galactic nucleus feedback in clusters of galaxies.

    PubMed

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

    2010-04-20

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

  16. Active galactic nucleus feedback in clusters of galaxies

    PubMed Central

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

    2010-01-01

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

  17. 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.

  18. Stellar populations in Active Galactic Nuclei III

    NASA Astrophysics Data System (ADS)

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

    2004-12-01

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

  19. Optical positions of active galaxies

    NASA Astrophysics Data System (ADS)

    Meurs, E. J. A.

    1984-04-01

    Optical positions are calculated for 26 active galaxies (mainly Markarian dn Arakelian objects), using the plate-measuring apparatus at Leiden Observatory on the O plates of the Palomar Sky Survey and applying AGK-3 data in the reductions. The results are presented in a table and have accuracy 0.5 arcsec; a comparison with the positions determined by Clements (1981, 1983) for 19 objects reveals a possible offset of -0.28 arcsec in the right-ascension determinations.

  20. 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.

  1. Paired galaxies with different activity levels and their supernovae

    NASA Astrophysics Data System (ADS)

    Nazaryan, T. A.; Petrosian, A. R.; Hakobyan, A. A.; Adibekyan, V. Z.; Kunth, D.; Mamon, G. A.; Turatto, M.; Aramyan, L. S.

    2013-10-01

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

  2. NUCLEAR ACTIVITY IS MORE PREVALENT IN STAR-FORMING GALAXIES

    SciTech Connect

    Rosario, D. J.; Lutz, D.; Berta, S.; Popesso, P.; Genzel, R.; Saintonge, A.; Tacconi, L.; Wuyts, S. E-mail: lutz@mpe.mpg.de E-mail: popesso@mpe.mpg.de E-mail: amelie@mpe.mpg.de E-mail: swuyts@mpe.mpg.de; and others

    2013-07-01

    We explore the question of whether low and moderate luminosity active galactic nuclei (AGNs) are preferentially found in galaxies that are undergoing a transition from active star formation (SF) to quiescence. This notion has been suggested by studies of the UV-optical colors of AGN hosts, which find them to be common among galaxies in the so-called Green Valley, a region of galaxy color space believed to be composed mostly of galaxies undergoing SF quenching. Combining the deepest current X-ray and Herschel/PACS far-infrared (FIR) observations of the two Chandra Deep Fields with redshifts, stellar masses, and rest-frame photometry derived from the extensive and uniform multi-wavelength data in these fields, we compare the rest-frame U - V color distributions and star formation rate distributions of AGNs and carefully constructed samples of inactive control galaxies. The UV-to-optical colors of AGNs are consistent with equally massive inactive galaxies at redshifts out to z {approx} 2, but we show that such colors are poor tracers of SF. While the FIR distributions of both star-forming AGNs and star-forming inactive galaxies are statistically similar, we show that AGNs are preferentially found in star-forming host galaxies, or, in other words, AGNs are less likely to be found in weakly star-forming or quenched galaxies. We postulate that, among X-ray-selected AGNs of low and moderate accretion luminosities, the supply of cold gas primarily determines the accretion rate distribution of the nuclear black holes.

  3. 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

  4. IGM Heating and AGN activity in Fossil Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Miraghaei, H.; Khosroshahi, H. G.; Klöckner, H.-R.; Ponman, T. J.; Jetha, N. N.; Raychaudhury, S.

    2014-07-01

    Fossil galaxy groups are energetically and morphologically ideal environments to study the intergalactic medium (IGM) heating, because their inter-galactic gas is undisturbed due to the lack of recent group scale mergers. We study the role of active galactic nuclei (AGN) in heating the IGM in a sample of five fossil galaxy groups by employing properties at 610 MHz and 1.4 GHz. We find that two of the dominant galaxies in fossil groups, ESO 3060170 and RX J1416.4+2315, are associated with the radio lobes. We evaluate the PdV work of the radio lobes and their corresponding heating power and compare to the X-ray emission loss within cooling radius. Our results show that the power due to mechanical heating is not sufficiently high to suppress the cooling.

  5. Gravitational lensing of active galactic nuclei.

    PubMed Central

    Hewitt, J N

    1995-01-01

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

  6. 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.

  7. Stellar Transits in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Béky, Bence; Kocsis, Bence

    2013-01-01

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

  8. Quasars and Active Galaxies: A Reading List.

    ERIC Educational Resources Information Center

    Fraknoi, Andrew

    1988-01-01

    Contains the annotated bibliographies of introductory books and sections of books, recent introductory articles, more advanced articles, and more advanced books dealing with quasars and active galaxies. (CW)

  9. 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

  10. THE ACS FORNAX CLUSTER SURVEY. VI. THE NUCLEI OF EARLY-TYPE GALAXIES IN THE FORNAX CLUSTER

    SciTech Connect

    Turner, Monica L.; Cote, Patrick; Ferrarese, Laura; Blakeslee, John P.; Jordan, Andres; Mei, Simona; Peng, Eric W.; West, Michael J.

    2012-11-15

    The Advanced Camera for Surveys (ACS) Fornax Cluster Survey is a Hubble Space Telescope program to image 43 early-type galaxies in the Fornax cluster, using the F475W and F850LP bandpasses of the ACS. We employ both one-dimensional and two-dimensional techniques to characterize the properties of the stellar nuclei in these galaxies, defined as the central 'luminosity excesses', relative to a Sersic model fitted to the underlying host. We find 72% {+-} 13% of our sample (31 galaxies) to be nucleated, with only three of the nuclei offset by more than 0.''5 from their galaxy photocenter, and with the majority of nuclei having colors bluer than their hosts. The nuclei are observed to be larger, and brighter, than typical Fornax globular clusters and to follow different structural scaling relations. A comparison of our results to those from the ACS Virgo Cluster Survey reveals striking similarities in the properties of the nuclei belonging to these different environments. We briefly review a variety of proposed formation models and conclude that, for the low-mass galaxies in our sample, the most important mechanism for nucleus growth is probably infall of star clusters through dynamical friction, while for higher mass galaxies, gas accretion triggered by mergers, accretions, and tidal torques is likely to dominate, with the relative importance of these two processes varying smoothly as a function of galaxy mass. Some intermediate-mass galaxies in our sample show a complexity in their inner structure that may be the signature of the 'hybrid nuclei' that arose through parallel formation channels.

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

    SciTech Connect

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

    2014-07-01

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

  12. Echo Mapping of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Peterson, B. M.; Horne, K.

    2004-01-01

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

  13. Relativistic neutrons in active galactic nuclei

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

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

  14. 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.

  15. Are the globular clusters with significant internal [Fe/H] spreads all former dwarf galaxy nuclei?

    NASA Astrophysics Data System (ADS)

    Da Costa, Gary Stewart

    2015-08-01

    In this presentation I will advance the idea that the 'globular clusters' with significant internal [Fe/H] dispersions are in fact the former nuclei or nuclear star clusters of dwarf galaxies that have been disrupted during the formation of the Galactic halo. I'll discuss the characteristics of these clusters, particularly their common properties, and indicate that at present the number of such clusters known is broadly consistent with the disruption hypothesis. Identification of significantly more clusters with large internal [Fe/H] abundance ranges may, however, cast doubt on the hypothesis, if the stars of the disrupted dwarfs remain in the Galactic halo.

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

    NASA Astrophysics Data System (ADS)

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

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

  17. Black holes in active galactic nuclei

    NASA Astrophysics Data System (ADS)

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

    2010-01-01

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

  18. HUBBLE CAPTURES AN EXTRAORDINARY AND POWERFUL ACTIVE GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    Resembling a swirling witch's cauldron of glowing vapors, the black hole-powered core of a nearby active galaxy appears in this colorful NASA Hubble Space Telescope image. The galaxy lies 13 million light-years away in the southern constellation Circinus. This galaxy is designated a type 2 Seyfert, a class of mostly spiral galaxies that have compact centers and are believed to contain massive black holes. Seyfert galaxies are themselves part of a larger class of objects called Active Galactic Nuclei or AGN. AGN have the ability to remove gas from the centers of their galaxies by blowing it out into space at phenomenal speeds. Astronomers studying the Circinus galaxy are seeing evidence of a powerful AGN at the center of this galaxy as well. Much of the gas in the disk of the Circinus spiral is concentrated in two specific rings -- a larger one of diameter 1,300 light-years, which has already been observed by ground-based telescopes, and a previously unseen ring of diameter 260 light-years. In the Hubble image, the smaller inner ring is located on the inside of the green disk. The larger outer ring extends off the image and is in the plane of the galaxy's disk. Both rings are home to large amounts of gas and dust as well as areas of major 'starburst' activity, where new stars are rapidly forming on timescales of 40 - 150 million years, much shorter than the age of the entire galaxy. At the center of the starburst rings is the Seyfert nucleus, the believed signature of a supermassive black hole that is accreting surrounding gas and dust. The black hole and its accretion disk are expelling gas out of the galaxy's disk and into its halo (the region above and below the disk). The detailed structure of this gas is seen as magenta-colored streamers extending towards the top of the image. In the center of the galaxy and within the inner starburst ring is a V-shaped structure of gas. The structure appears whitish-pink in this composite image, made up of four filters. Two

  19. Launching of Active Galactic Nuclei Jets

    NASA Astrophysics Data System (ADS)

    Tchekhovskoy, Alexander

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

  20. Rapid X-Ray Variability of Active Galaxies. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Tennant, A. F., Jr.

    1983-01-01

    Active galactic nuclei are luminous sources of X-rays. The thesis that the X-rays are generated within 10 gravitational radii from the central object is tested. A very sensitive search for rapid ( 1 day) X-ray variability from active galaxies was made.

  1. DUAL ACTIVE GALACTIC NUCLEI: DEPROJECTING THE BINARY CORES

    SciTech Connect

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

    2012-10-01

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

  2. 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.

  3. The M bh-σ Diagram and the Offset Nature of Barred Active Galaxies

    NASA Astrophysics Data System (ADS)

    Graham, Alister W.; Li, I.-hui

    2009-06-01

    From a sample of 50 predominantly inactive galaxies with direct supermassive black hole mass measurements, it has recently been established that barred galaxies tend to reside rightward of the M bh-σ relation defined by nonbarred galaxies. Either black holes in barred galaxies tend to be anemic or the central velocity dispersions in these galaxies have a tendency to be elevated by the presence of the bar. The latter option is in accord with studies connecting larger velocity dispersions in galaxies with old bars, while the former scenario is at odds with the observation that barred galaxies do not deviate from the M bh-luminosity relation. Using a sample of 88 galaxies with active galactic nuclei, whose supermassive black hole masses have been estimated from their associated emission lines, we reveal for the first time that they also display this same general behavior in the M bh-σ diagram depending on the presence of a bar or not. A new symmetrical and nonsymmetrical "barless" M bh-σ relation is derived using 82 nonbarred galaxies. The barred galaxies are shown to reside on or up to ~1 dex below this relation. This may explain why narrow-line Seyfert 1 galaxies appear offset from the "barless" M bh-σ relation, and has far-reaching implications given that over half of the disk galaxy population are barred.

  4. 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.

  5. Chandra Finds Surprising Black Hole Activity In Galaxy Cluster

    NASA Astrophysics Data System (ADS)

    2002-09-01

    bright active galaxies, often referred to as Active Galactic Nuclei, or AGN. Many astronomers think that all galaxies have central, supermassive black holes, yet only a small percent show activity. What is needed to power the AGN is fuel in the form of a nearby reservoir of gas and dust. Galaxy clusters contain hundreds to thousands of galaxies. They are the largest known structures in the universe and serve as a microcosm for the mechanics of the Universe at large. The galaxies in clusters are often old, reddish elliptically shaped galaxies, distinct from blue, spiral galaxies like our own. These old galaxies also do not have many young stars. The theory now in question is that as galaxies enter into clusters at high speeds, they are stripped of their interstellar gas, much as a strong wind strips leaves from a tree. Galaxies may also collide with one another and use up all of their gas in one huge burst of star formation triggered by this interaction. These processes remove most, if not all, of the gas that isn't locked up in stars. As they no longer have the raw material to form new stars, the stellar population slowly gets old and the Galaxy appears red. No gas is left to fuel an AGN. Previous surveys of galaxy clusters with optical telescopes have found that about only one percent of the galaxies in a cluster have AGN. This latest Chandra observation if typical, however, bumps the count up to about 5 percent. The team found six red galaxies with high X-ray activity during a nearly 14-hour Chandra observation of a galaxy cluster named Abell 2104, over 700 million light years from Earth. Based on previous optical surveys, only one was expected. "If we relied on optical data alone, we would have missed these hidden monsters," said co-author Dr. John Mulchaey. Only one of the six AGN, in fact, had the optical spectral properties typical of AGN activity. "The presence of these AGN indicate that supermassive black holes have somehow retained a fuel source, despite the

  6. PROPAGATION OF ULTRAHIGH ENERGY NUCLEI IN CLUSTERS OF GALAXIES: RESULTING COMPOSITION AND SECONDARY EMISSIONS

    SciTech Connect

    Kotera, K.; Allard, D.; Dubois, Y.; Pierog, T.

    2009-12-10

    We study the survival of ultrahigh energy nuclei injected in clusters of galaxies, as well as their secondary neutrino and photon emissions, using a complete numerical propagation method and a realistic modeling of the magnetic, baryonic, and photonic backgrounds. It is found that the survival of heavy nuclei highly depends on the injection position and on the profile of the magnetic field. Taking into account the limited lifetime of the central source could also lead in some cases to the detection of a cosmic-ray afterglow, temporally decorrelated from neutrino and gamma-ray emissions. We calculate that the diffusive neutrino flux around 1 PeV coming from clusters of galaxies may have a chance to be detected by current instruments. The observation of single sources in neutrinos and in gamma rays produced by ultrahigh energy cosmic rays will be more difficult. Signals coming from lower energy cosmic rays (E approx< 1 PeV), if they exist, might however be detected by Fermi, for reasonable sets of parameters.

  7. TESTING TESTS ON ACTIVE GALACTIC NUCLEI MICROVARIABILITY

    SciTech Connect

    De Diego, Jose A.

    2010-03-15

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

  8. 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.

  9. 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.

  10. 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.

  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. Elliptical accretion disks in active galactic nuclei

    NASA Technical Reports Server (NTRS)

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

    1995-01-01

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

  13. Deep Chandra observations of HCG 16. I. Active nuclei, star formation, and galactic winds

    SciTech Connect

    O'Sullivan, E.; Zezas, A.; Vrtilek, J. M.; David, L. P.; Giacintucci, S.; Trevisan, M.; Ponman, T. J.; Raychaudhury, S.; Mamon, G. A.

    2014-10-01

    We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610 MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation, and high-luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect for the first time an Fe Kα emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infrared and ultraviolet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ∼400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ∼0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.

  14. Deep Chandra Observations of HCG 16. I. Active Nuclei, Star Formation, and Galactic Winds

    NASA Astrophysics Data System (ADS)

    O'Sullivan, E.; Zezas, A.; Vrtilek, J. M.; Giacintucci, S.; Trevisan, M.; David, L. P.; Ponman, T. J.; Mamon, G. A.; Raychaudhury, S.

    2014-10-01

    We present new, deep Chandra X-ray and Giant Metrewave Radio Telescope 610 MHz observations of the spiral-galaxy-rich compact group HCG 16, which we use to examine nuclear activity, star formation, and high-luminosity X-ray binary populations in the major galaxies. We confirm the presence of obscured active nuclei in NGC 833 and NGC 835, and identify a previously unrecognized nuclear source in NGC 838. All three nuclei are variable on timescales of months to years, and for NGC 833 and NGC 835 this is most likely caused by changes in accretion rate. The deep Chandra observations allow us to detect for the first time an Fe Kα emission line in the spectrum of the Seyfert 2 nucleus of NGC 835. We find that NGC 838 and NGC 839 are both starburst-dominated systems, with only weak nuclear activity, in agreement with previous optical studies. We estimate the star formation rates in the two galaxies from their X-ray and radio emission, and compare these results with estimates from the infrared and ultraviolet bands to confirm that star formation in both galaxies is probably declining after galaxy-wide starbursts were triggered ~400-500 Myr ago. We examine the physical properties of their galactic superwinds, and find that both have temperatures of ~0.8 keV. We also examine the X-ray and radio properties of NGC 848, the fifth largest galaxy in the group, and show that it is dominated by emission from its starburst.

  15. X-raying the Winds of Luminous Active Galaxies

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  16. Microvariabilty in Active Galactic Nuclei at Centimeter Wavelengths

    NASA Astrophysics Data System (ADS)

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

    2007-12-01

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

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

    NASA Astrophysics Data System (ADS)

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

    2014-01-01

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

  18. Highlights from the VERITAS Active Galactic Nuclei Observing Program

    NASA Astrophysics Data System (ADS)

    Fortson, Lucy; VERITAS Collaboration

    2016-01-01

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

  19. High-energy spectra of active nuclei. 1: The catalog

    NASA Technical Reports Server (NTRS)

    Malaguti, G.; Bassani, L.; Caroli, E.

    1994-01-01

    This paper presents a catalog of high-energy spectra (E is greater than or equal to 0.01 keV) of active galactic nuclei (AGNs). The catalog contains 209 objects (140 Seyfert galaxies, 65 quasars, and 4 objects otherwise classified), for a total of 1030 spectra. Most of the data have been collected from the literature over a period spanning more than 20 yr starting from the early 1970s up to the end of 1992. For a numbner of objects (17), EXOSAT/ME data have been extracted and analyzed, and the 27 spectra obtained have been added to the database. For each object we report individual observation spectral fit parameters using a power-law model corrected for cold gas absorption along the line of sight (photon index, 1 keV intensity and hydrogen column density), plus other relevant data. It is hoped that this database can become a useful tool for the study of the AGN phenomenon in its various aspects.

  20. 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.

  1. 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.

  2. 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.

  3. The rise and fall of galaxy activity in dark matter haloes

    NASA Astrophysics Data System (ADS)

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

    2009-03-01

    We use the catalogue of galaxy groups constructed from the Sloan Digital Sky Survey (SDSS DR4) by Yang et al. to study the dependence of galaxy activity on stellar mass, M*, halo mass, Mh, and group hierarchy (central versus satellite galaxies). The wealth of data provided by the SDSS allows us to split the sample on the basis of galaxy activity in star-forming galaxies, galaxies with optical active galactic nuclei (AGN), composite galaxies (both star formation and optical AGN activity) and radio sources. We find a smooth transition in halo mass as the activity of central galaxies changes from star formation to optical AGN activity to radio emission. Star-forming centrals preferentially reside in haloes with Mh < 1012h-1Msolar, central galaxies with optical AGN activity typically inhabit haloes with Mh ~ 1013h-1Msolar and centrals emitting in the radio mainly reside in haloes more massive than 1014h-1Msolar. Although this seems to suggest that the environment (halo mass) determines the type of activity of its central galaxy, we find a similar trend with stellar mass: central star formers typically have stellar masses less than 1010h-2Msolar, while optical AGN hosts and central radio sources have characteristic stellar masses of ~1010.8 and ~1011.6h-2Msolar, respectively. Since more massive haloes typically host more massive centrals, it is unclear whether the activity of a central galaxy is causally connected to its stellar mass or to its halo mass. In general, satellite galaxies have their activity suppressed with respect to central galaxies of the same stellar mass. This holds not only for star formation activity, but also for AGN activity in the optical and the radio. At fixed stellar mass, we find that the activity of satellite galaxies depends only weakly on halo mass. In fact, using a set of reduced conditional probability functions, we find that for satellite galaxies the dependence of galaxy activity on halo mass is more than four times weaker than the

  4. Probing the central regions of active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Lohfink, Anne Maria

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

  5. 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

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

    NASA Technical Reports Server (NTRS)

    Krolik, Julian H.

    1998-01-01

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

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

    NASA Technical Reports Server (NTRS)

    Krolik, J. H.

    1999-01-01

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

  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. DETECTING ACTIVE GALACTIC NUCLEI USING MULTI-FILTER IMAGING DATA. II. INCORPORATING ARTIFICIAL NEURAL NETWORKS

    SciTech Connect

    Dong, X. Y.; De Robertis, M. M.

    2013-10-01

    This is the second paper of the series Detecting Active Galactic Nuclei Using Multi-filter Imaging Data. In this paper we review shapelets, an image manipulation algorithm, which we employ to adjust the point-spread function (PSF) of galaxy images. This technique is used to ensure the image in each filter has the same and sharpest PSF, which is the preferred condition for detecting AGNs using multi-filter imaging data as we demonstrated in Paper I of this series. We apply shapelets on Canada-France-Hawaii Telescope Legacy Survey Wide Survey ugriz images. Photometric parameters such as effective radii, integrated fluxes within certain radii, and color gradients are measured on the shapelets-reconstructed images. These parameters are used by artificial neural networks (ANNs) which yield: photometric redshift with an rms of 0.026 and a regression R-value of 0.92; galaxy morphological types with an uncertainty less than 2 T types for z ≤ 0.1; and identification of galaxies as AGNs with 70% confidence, star-forming/starburst (SF/SB) galaxies with 90% confidence, and passive galaxies with 70% confidence for z ≤ 0.1. The incorporation of ANNs provides a more reliable technique for identifying AGN or SF/SB candidates, which could be very useful for large-scale multi-filter optical surveys that also include a modest set of spectroscopic data sufficient to train neural networks.

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

    NASA Technical Reports Server (NTRS)

    Kallman, T.; Mushotzky, R.

    1985-01-01

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

  11. Penrose photoproduction processes - A high efficiency energy mechanism for active galactic nuclei and quasars

    NASA Technical Reports Server (NTRS)

    Leiter, D.; Kafatos, M.

    1979-01-01

    Recent observations of NGC 4151 and 3C273 suggest that the nuclei of active galaxies have very high gamma ray efficiencies. In addition, optical studies of M87 have indicated the possibility of a massive black hole in its central region. The above facts have led to study of a new physical mechanism, Penrose Photoproduction Processes, in the ergospheres of massive Kerr black holes, as a way to account for the fluctuating, high efficiency, energy production associated with active galaxies and quasars. Observational signatures, associated with this mechanism, occur in the form of approximately 2 MeV and approximately 2 GeV gamma ray cutoffs which might be corroborated by the observed spectra of NGC 4151 and 3C273, respectively.

  12. 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.

  13. The Stellar Populations of Nuclei, Globular Clusters, and Stars in dE Galaxies in Virgo and Fornax

    NASA Astrophysics Data System (ADS)

    Whitfield Miller, Bryan; Hyazinth Puzia, Thomas; Hilker, Michael; Sanchez-Janssen, Ruben; Kissler-Patig, Markus

    2015-08-01

    We present ages and metallicities for globular clusters, nuclei, and underlying stars in nucleated dwarf elliptical galaxies (dE,N) in the Virgo and Fornax Cluster based on Lick/IDS index measurements and SSP models. Gemini/GMOS spectroscopy shows that the globular clusters are mostly old and metal-poor, very similar to the globular clusters in the Milky Way halo. The nuclei and underlying stars tend to be more metal-rich than the globular clusters and have a wide range of ages. The [α/Fe] ratios for both the globular clusters and nuclei range between 0.0 and 0.3. Formation scenarios for globular clusters and nuclei will be discussed.

  14. Chemistry in the Molecular Disks of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Harada, Nanase; Herbst, Eric

    2010-06-01

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

  15. Dwarf Galaxies with Active Massive Black Holes

    NASA Astrophysics Data System (ADS)

    Reines, Amy E.; Greene, J. E.; Geha, M. C.

    2014-01-01

    Supermassive black holes (BHs) live at the heart of essentially all massive galaxies with bulges, power AGN, and are thought to be important agents in the evolution of their hosts. However, the birth and growth of the first supermassive BH "seeds" is far from understood. While direct observations of these distant BHs in the infant Universe are unobtainable with current capabilities, massive BHs in present-day dwarf galaxies can place valuable constraints on the masses, formation path, and hosts of supermassive BH seeds. Using optical spectroscopy from the SDSS, we have systematically assembled the largest sample of dwarf galaxies hosting active massive BHs to date. These dwarf galaxies have stellar masses comparable to the Magellanic Clouds and contain some of the least-massive supermassive BHs known.

  16. 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."

  17. Multiwavelength Search and Studies of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2016-06-01

    Since 1950s, Byurakan Astrophysical Observatory (BAO) has always been one of the centres for surveys and studies of active galaxies. Here I review our search and studies of active galaxies during last 30 years using various wavelength ranges, as well as some recent related works. These projects since late 1980s were focused on multiwavelength search and studies of AGN and Starbursts (SB). 1103 blue stellar objects (BSOs) on the basis of their UV-excess were selected using Markarian Survey (First Byurakan Survey, FBS) plates and Markarian's criteria used for the galaxies. Among many blue stars, QSOs and Seyfert galaxies were found by follow-up observations. 1577 IRAS point sources were optically identified using FBS low-dispersion spectra and many AGN, SB and high-luminosity IR galaxies (LIRG/ULIRG) were discovered. 32 extremely high IR/opt flux ratio galaxies were studies with Spitzer. 2791 ROSAT FSC sources were optically identified using Hamburg Quasar Survey (HQS) low-dispersion spectra and many AGN were discovered by follow-up observations. Fine analysis of emission line spectra was carried out using spectral line decomposition software to establish true profiles and calculate physical parameters for the emitting regions, as well as to study the spectral variability of these objects. X-ray and radio selection criteria were used to find new AGN and variable objects for further studies. Multiwavelength approach allowed revealing many new AGN and SB and obtaining a number of interesting relations using their observational characteristics and physical properties.

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

    NASA Astrophysics Data System (ADS)

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

    2008-06-01

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

  19. Polarization insights for active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Antonucci, Robert

    Optical spectropolarimetry and broadband polarimetry in other wavebands has been a key to understanding many diverse aspects of AGN. In some cases polarization is due to synchrotron radiation, and in other cases it's due to scattering. Recognition of relativistically beamed optical synchrotron emission by polarization was vital for understanding blazars (BL Lacs and Optically Violently Variable quasars), both physically and geometrically. Radio polarimetry of quiescent AGN is equally important, again for both purposes. Scattering polarization was central to the Unified Model for Seyferts, Radio Galaxies and (high ionization) Ultraluminous Infrared Galaxies. It provides a periscope for viewing AGN from other directions. Finally, if we could understand its message, polarization would also provide major insights regarding the nature of the AGN "Featureless Continuum" and Broad (emission) Line Region. I point out that high ionization ULIRGs have all the exact right properties to the called Quasar 2s. Mid-IR observations generally don't penetrate to the nucleus, greatly reducing their ability to diagnose the energy source. In particular, LINER ULIRGs aren't necessarily starburst-dominated, as has been claimed.

  20. 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.

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

    SciTech Connect

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

    2010-10-01

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

  2. 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.

  3. A SiO 2-1 SURVEY TOWARD GAS-RICH ACTIVE GALAXIES

    SciTech Connect

    Wang, Junzhi; Zhang, Jiangshui; Shi, Yong; Zhang, Zhiyu

    2013-12-01

    In order to study the feedback from active galactic nuclei (AGNs), we performed a survey of SiO J = 2-1 (v = 0) transition toward ten gas-rich active galaxies with the IRAM 30 m telescope. As the first survey of SiO in such galaxies, we detected SiO J = 2-1 (v = 0) emission in six galaxies above the 3σ level and one galaxy (NGC 3690) at the 2.7σ level. The detection rate is not related to the AGN type or to star formation activity. In comparison with M82, which is a pure star-forming galaxy without nuclear activity, our SiO detections could not be completely ascribed to being due to star formation activity. This suggests that the AGN feedback may be efficient in producing SiO molecules in such galaxies. Further surveys with large single-dish millimeter telescopes and interferometers are necessary for understanding the origin of SiO in galaxies with nuclear activity.

  4. 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.

  5. Chemical Fingerprints of Star Forming Regions and Active Galaxies

    NASA Astrophysics Data System (ADS)

    Pérez-Beaupuits, Juan-Pablo

    2010-10-01

    This thesis is devoted to the study of the physical conditions of the interstellar medium (ISM) in active galactic nuclei (AGNs) and Galactic star-forming regions, using mostly single-dish millimeter observations. I first study the excitation conditions of dense gas in a group of Seyfert galaxies using radiative transfer models (Chapter 2). I then study the galaxy NGC 1068, and try to distinguish signatures of the contributions from the AGN and the starburst ring by incorporating observations of high-J transitions of dense gas tracers (Chapter 3). Later, I venture into the mid-infrared spectral region to study different aspects of the AGN and starburst components in the galaxy NGC 4945 (Chapter 4). In Chapter 5 I delve into theoretical aspects of the dynamical evolution of gas in an AGN torus. I use a 3D hydrodynamic simulation with chemical abundances driven by X-rays. The aim is to understand the effects of X-ray irradiation by the AGN on the temperature, formation and destruction of the molecular gas. I finally explore a Galactic star-forming region, the Omega Nebula, with high resolution single dish observations, to study the properties of the warm gas and to constrain chemical models (Chapters 6 and 7).

  6. Active Galactic Nuclei Probed by QSO Absorption Lines

    NASA Astrophysics Data System (ADS)

    Misawa, Toru

    2007-07-01

    Quasars are the extremely bright nuclei found in about 10% of galaxies. A variety of absorption features (known collectively as quasar absorption lines) are detected in the rest-frame UV spectra of these objects. While absorption lines that have very broad widths originate in gas that is probably physocally related to the quasars, narrow absorption lines (NALs) were thought to arise in galaxies and/or in the intter-alacttic medium between the quasars and us. Using high-resolution spectra of quasars, it is found that a substantial fraction of NALs arise in gas in the immediate vicinity of the quasars. A dramatically variable, moderately-broad absorption line in the spectrum of the quasar HS 1603+3820l is also found. The variability of this line is monitored in a campaign with Subaru telescope. These observational results are compared to models for outflows from the quasars, specifically, models for accretion disk winds and evaporating obscuring tori. It is quite important to determine the mechanism of outflow because of its cosmological implications. The outflow could expel angular momentum from the accretion disk and enable quasars to accrete and shine. In addition, the outflow may also regulate star formation in the early stages of the assembly of the host galaxy and enrich the interstellar and intergalactic medium with metals.

  7. Active galaxies and radiative heating.

    PubMed

    Ostriker, Jeremiah P; Ciotti, Luca

    2005-03-15

    There is abundant evidence that heating processes in the central regions of elliptical galaxies have both prevented large-scale cooling flows and assisted in the expulsion of metal rich gas. We now know that each such spheroidal system harbours in its core a massive black hole weighing ca. 0.13% of the mass in stars and also know that energy was emitted by each of these black holes with an efficiency exceeding 10% of its rest mass. Since, if only 0.5% of that radiant energy were intercepted by the ambient gas, its thermal state would be drastically altered, it is worth examining in detail the interaction between the out-flowing radiation and the equilibrium or inflowing gas. On the basis of detailed hydrodynamic computations we find that relaxation oscillations are to be expected with the radiative feedback quite capable of regulating both the growth of the central black hole and also the density and thermal state of the gas in the galaxy. Mechanical input of energy by jets may assist or dominate over these radiative effects. We propose specific observational tests to identify systems which have experienced strong bursts of radiative heating from their central black holes. PMID:15681285

  8. A far-infrared spectral line survey of 23 infrared-bright Galaxy nuclei

    NASA Technical Reports Server (NTRS)

    Lord, Steven D.; Hollenbach, David J.; Colgan, Sean W. J.; Haas, Michael R.; Rubin, Robert H.; Madden, Suzanne C.; Steiman-Cameron, Thomas Y.; Carral, Patricia; Maloney, Philip R.; Erickson, Edwin F.

    1995-01-01

    We present results from a KAO survey of fine-structure lines observed in 23 infrared-luminous galaxies. One or more of the following lines was observed and/or detected in each galaxy: (S III) 19, 33 microns, (Ne V) 24 microns, (O IV) 26 microns, (Fe II) 26 microns, (Si II) 35 microns, (O III) 52, 88 microns, (0 I) 63, 146 microns, (N III) 57 micro ns, (N II) 122, 205 microns, (C II) 158 microns. The galaxies span a wide range of morphologies (irregular to grand design), have varying metallicities, and include mergers, AGN's, and starburst systems. The observations were made beginning in 1988 using the facility Cryogenic Grating Spectrometer onboard the KAO at a typical resolution of approximately 60-140 km/s and with a 30-44 deg beam. We interpret the (C II) and (O I) fluxes, along with previous measurements of the IR continuum fluxes, in the context of photo dissociation region (PDR) models (Tielens & Hollenbach 1985; Wolfire et al. 1990). With these models, we obtain estimates of the typical interstellar UV fields incident on the line emitting regions (102-104 times the local interstellar radiation field) and the total masses (10(exp 7)-10(exp 8) Solar Mass), densities (10(exp 3)-10(exp 4)/cu cm), and temperatures (100-250 K) of the warm atomic gas. The (O III) (52/88) and (S III) (33/19) line flux ratios constrain the range of electron densities and pressures found within the ionized regions. The (O III) and (S III) lines also provide estimates of the effective temperature of the ionizing stars and elemental abundances within the ionized regions of these galactic nuclei. Our measurements imply typical gas pressures of nT approximately 5 x 10(exp 6)/cu cm K and typical upper mass cutoffs of 25-35 Solar Mass. The low-metallicity systems show high (C II)/CO and (O I)/CO flux ratios, 3-5 times the Milky Way value, indicating that they contain a larger fraction of photodissociated gas relative to the molecular material.

  9. IDENTIFYING LUMINOUS ACTIVE GALACTIC NUCLEI IN DEEP SURVEYS: REVISED IRAC SELECTION CRITERIA

    SciTech Connect

    Donley, J. L.; Koekemoer, A. M.; Brusa, M.; Salvato, M.; Capak, P.; Cardamone, C. N.; Civano, F.; Ilbert, O.; Impey, C. D.; Kartaltepe, J. S.; Miyaji, T.; Sanders, D. B.; Trump, J. R.

    2012-04-01

    Spitzer/IRAC selection is a powerful tool for identifying luminous active galactic nuclei (AGNs). For deep IRAC data, however, the AGN selection wedges currently in use are heavily contaminated by star-forming galaxies, especially at high redshift. Using the large samples of luminous AGNs and high-redshift star-forming galaxies in COSMOS, we redefine the AGN selection criteria for use in deep IRAC surveys. The new IRAC criteria are designed to be both highly complete and reliable, and incorporate the best aspects of the current AGN selection wedges and of infrared power-law selection while excluding high-redshift star-forming galaxies selected via the BzK, distant red galaxy, Lyman-break galaxy, and submillimeter galaxy criteria. At QSO luminosities of log L{sub 2-10keV}(erg s{sup -1}) {>=}44, the new IRAC criteria recover 75% of the hard X-ray and IRAC-detected XMM-COSMOS sample, yet only 38% of the IRAC AGN candidates have X-ray counterparts, a fraction that rises to 52% in regions with Chandra exposures of 50-160 ks. X-ray stacking of the individually X-ray non-detected AGN candidates leads to a hard X-ray signal indicative of heavily obscured to mildly Compton-thick obscuration (log N{sub H} (cm{sup -2}) = 23.5 {+-} 0.4). While IRAC selection recovers a substantial fraction of luminous unobscured and obscured AGNs, it is incomplete to low-luminosity and host-dominated AGNs.

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

    NASA Astrophysics Data System (ADS)

    Feltre, Anna

    2013-07-01

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

  11. Two Active Nuclei in 3C 294

    NASA Astrophysics Data System (ADS)

    Stockton, Alan; Canalizo, Gabriela; Nelan, E. P.; Ridgway, Susan E.

    2004-01-01

    The z=1.786 radio galaxy 3C 294 lies < 10" from a 12 mag star and has been the target of at least three previous investigations using adaptive optics (AO) imaging. A major problem in interpreting these results is the uncertainty in the precise alignment of the radio structure with the H- or K-band AO imaging. Here we report observations of the position of the AO guide star with the Hubble Space Telescope Fine Guidance Sensor, which, together with positions from the second United States Naval Observatory's CCD Astrograph Catalog (UCAC2), allow us to register the infrared and radio frames to an accuracy of better than 0.1". The result is that the nuclear compact radio source is not coincident with the brightest discrete object in the AO image, an essentially unresolved source on the eastern side of the light distribution, as Quirrenbach and coworkers had suggested. Instead, the radio source is centered about 0.9" to the west of this object, on one of the two apparently real peaks in a region of diffuse emission. Nevertheless, the conclusion of Quirrenbach and coworkers that 3C 294 involves an ongoing merger appears to be correct: analysis of a recent deep Chandra image of 3C 294 obtained from the archive shows that the nucleus comprises two X-ray sources, which are coincident with the radio nucleus and the eastern stellar object. The X-ray/optical flux ratio of the latter makes it extremely unlikely that it is a foreground Galactic star. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy (AURA), Inc., under NASA contract NAS5-26555. These observations are associated with proposal 08315. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a

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

    NASA Astrophysics Data System (ADS)

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

    2015-11-01

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

  13. 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

  14. Compton thick active galactic nuclei in Chandra surveys

    NASA Astrophysics Data System (ADS)

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

    2014-09-01

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

  15. 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.

  16. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  18. Recurrent Activity in Radio Galaxies

    SciTech Connect

    Jamrozy, Marek; Konar, Chiranjib; Machalski, Jerzy; Mack, Karl-Heinz; Saikia, Dhruba; Siemiginowska, Aneta; Stawarz, Lukasz; /KIPAC, Menlo Park /Jagiellonian U.

    2007-10-15

    One of the outstanding issues concerning extragalactic radio sources is the total duration of their active phase and the possible existence of duty cycles of their nuclear activity. A duty cycle can be recognized if there is a mechanism which preserves the information of past activity for a sufficiently long time after a new activity has started up. If a new cycle starts before the radio lobes created during a former activity period have faded, we can recognize this by the observations of a young radio source embedded in an old relic structure.

  19. Galaxy interactions and the stimulation of nuclear activity

    NASA Technical Reports Server (NTRS)

    Heckman, Timothy M.

    1990-01-01

    The author discusses the idea that interactions between galaxies can lead to enhanced galactic activity. He discusses whether, apart from the observational evidence, there is a strong theoretical or heuristic motivation for investigating galaxy interactions as stimulators of nuclear activity in galaxies. Galactic interactions as mechanisms for triggering nuclear starbursts are covered.

  20. NASA's Fermi Shows How Active Galaxies Can Be

    NASA Video Gallery

    Active galaxies called blazars make up the largest class of objects detected by Fermi's Large Area Telescope (LAT). Massive black holes in the hearts of these galaxies fire particle jets in our dir...

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

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

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

  2. The Broad-Line Region and Dust Torus Structure of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Pozo Nuñez, Francisco

    2014-06-01

    I present the results from optical and infrared multi-month monitoring campaigns at the Universitätssternwarte Bochum (USB) in Chile to explore the structure of the central engine in active galactic nuclei (AGN). I apply and test photometric reverberation mapping (PRM) for measuring the time delay between variations in the continuum and Hbeta, Halpha emission lines. This time delay is used to infer the size of the broad-line region (BLR) for three Seyfert 1 galaxies. I place the results in context of the known BLR size luminosity relationship from spectroscopic reverberation mapping (SRM) and discuss its potential application to constrain cosmological parameters. The BLR size and the velocity dispersion of the emission line are used to calculate the virial mass of the supermassive black hole (SMBH). Through the direct modelling of PRM data, I infer the geometry type of the BLR allowing the determination of the geometry scaling factor used to constrain the real black hole mass. I find strong evidence for a disk-like BLR geometry. If this result holds for Seyfert galaxies in general, then the determination of the geometry scaling factor and the black hole mass can be remarkably improved. I discuss deviations of Seyfert-1 galaxies from the SMBH-bulge velocity dispersion relation MBH - sigma* for quiescent galaxies. Finally, I perform dust-reverberation mapping to determine the dust-torus size for the Seyfert 1 galaxy WPVS48. The light curves in the optical and near-infrared revealed unexpected variations which allow to solve an old puzzle on the geometry of the dusttorus.

  3. Exploring the Environs of Compact Symmetric Objects in the Nuclei of Galaxies and Quasars

    NASA Astrophysics Data System (ADS)

    Taylor, G. B.; Xu, W.; Readhead, A. C. S.; Pearson, T. J.

    1994-12-01

    Two large Caltech--Jodrell Bank VLBI surveys at 5 GHz have recently been completed (CJ1 -- Xu et al. 1994, ApJS, submitted; CJ2 -- Taylor et al. 1994, ApJS, in press; Henstock et al. 1994, ApJS, submitted). Together with the Pearson--Readhead survey (1988, ApJ, 328, 114) these provide ~ 1 mas resolution images for a flux limited sample of 321 sources. One of the most interesting findings of these surveys was the discovery of three confirmed compact symmetric objects (CSOs) and forty additional candidate CSOs. These are compact (size ~ 100 pc) sources with emission on both sides of the central engine that is thought to be free of beaming effects. To account for their small sizes the CSOs must be either young or severely confined by a dense neutral medium. If these objects are young (ages ~ 3000 yrs) and growing at rates typical of equally luminous, but 1000 times larger, radio galaxies like Cygnus A then they must be a common phase in the evolution of galaxies, or perhaps a recurrent one. Alternatively, if the CSOs are strongly confined and longer lived then the large amount of material required for their confinement should have several observational consequences -- large amounts of neutral and molecular gas, high induced Faraday rotations, and possibly severe reddening and distortions of the starlight from the host galaxy. In an effort to discriminate between the above models we have performed deep infrared imaging of a number of CSOs and CSO candidates. We also report on high-dynamic range imaging with the VLA to look for large Faraday rotation measures, or for extended components that might be the result of a previous active phase. We have also observed one nearby CSO candidate in CO 1-0 with the Owens Valley millimeter array to search for molecular gas.

  4. 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.

  5. 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.

  6. 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.

  7. 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

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

    NASA Astrophysics Data System (ADS)

    Tombesi, F.

    2016-05-01

    Powerful winds driven by active galactic nuclei (AGN) are often invoked to play a fundamental role in the evolution of both supermassive black holes (SMBHs) and their host galaxies, quenching star formation and explaining the tight SMBH-galaxy relations. A strong support of this ``quasar mode'' feedback came from the recent X-ray observation of a mildly relativistic accretion disk wind in a ultraluminous infrared galaxy (ULIRG) and its connection with a large-scale molecular outflow, providing a direct link between the SMBH and the gas out of which stars form. Spectroscopic observations, especially in the X-ray band, show that such accretion disk winds may be common in local AGN and quasars. However, their origin and characteristics are still not fully understood. Detailed theoretical models and simulations focused on radiation, magnetohydrodynamic (MHD) or a combination of these two processes to investigate the possible acceleration mechanisms and the dynamics of these winds. Some of these models have been directly compared to X-ray spectra, providing important insights into the wind physics. However, fundamental improvements on these studies will come only from the unprecedented energy resolution and sensitivity of the upcoming X-ray observatories, namely ASTRO-H (launch date early 2016) and Athena (2028).

  9. ON THE ANISOTROPY OF NUCLEI MID-INFRARED RADIATION IN NEARBY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Yang, Huan; Wang, JunXian; Liu, Teng E-mail: jxw@ustc.edu.cn

    2015-01-20

    In the center of active galactic nuclei (AGNs), the dusty torus absorbs the radiation from the central engine and reemits in mid-infrared (MIR). Observations have detected moderate anisotropy in the dust MIR emission, in the way that type 1 AGNs (type1s) are mildly brighter in MIR comparing with type 2 sources (type2s). However, type1s and type2s were found to follow statistically the same tight MIR-hard X-ray correlation, suggesting that the MIR emission is highly isotropic assuming that the hard X-ray radiation is inclination independent. We argue that this discrepancy could be solved considering that the hard X-ray emission in AGNs is also mildly anisotropic, as we recently discovered. To verify this diagram, we compare the subarcsecond 12 μm flux densities of type1s and type2s using the [O IV] λ25.89 μm emission line as an isotropic luminosity indicator. We find that on average type1s are brighter in nuclei 12 μm radiation by a factor of 2.6 ± 0.6 than type2s at given [O IV] λ25.89 μm luminosities, confirming the mild anisotropy of the nuclei 12 μm emission. We show that the anisotropy of the 12 μm emission we detected is in good agreement with radiative transfer models of clumpy tori. The fact that type1s and type2s follow the same tight MIR-hard X-ray correlation instead supports that both the MIR emission and hard X-ray emission in AGNs are mildly anisotropic.

  10. The line-emitting gas in active galaxies - A probe of the nuclear engine

    NASA Technical Reports Server (NTRS)

    Veilleux, Sylvain

    1993-01-01

    This paper reviews some of the basic questions regarding the structure of the engine powering active galactic nuclei (AGN), the nature of the interaction between the AGN and the host galaxy, and the origin and evolution of AGN. The study of the dynamics and physical characteristics of the line-emitting gas in these objects has proven fruitful in addressing many of these issues. Recent advances in optical and infrared detector technology combined with the development of superior ground-based instruments have produced efficient new tools for the study of the line-emitting gas on nuclear and Galactic scales. Programs which take advantage of two of these new techniques, Fabry-Perot imaging spectroscopy and infrared spectroscopy, are described in this paper. The origin of nuclear activity in galaxies is also addressed in a third project which aims at determining the nature of luminous infrared galaxies.

  11. Constraining the Active Galactic Nucleus Contribution in a Multiwavelength Study of Seyfert Galaxies

    NASA Technical Reports Server (NTRS)

    Melendez, M.; Kraemer, S.B.; Schmitt, H.R.; Crenshaw, D.M.; Deo, R.P.; Mushotzky, R.F.; Bruhweiler, F.C.

    2008-01-01

    We have studied the relationship between the high- and low-ionization [O IV] (lambda)25.89 microns, [Ne III] (lambda)15.56 microns, and [Ne II] (lambda)12.81 microns emission lines with the aim of constraining the active galactic nuclei (AGNs) and star formation contributions for a sample of 103 Seyfert galaxies.We use the [O IV] and [Ne II] emission as tracers for the AGN power and star formation to investigate the ionization state of the emission-line gas.We find that Seyfert 2 galaxies have, on average, lower [O IV]/[Ne II] ratios than Seyfert 1 galaxies. This result suggests two possible scenarios: (1) Seyfert 2 galaxies have intrinsically weaker AGNs, or (2) Seyfert 2 galaxies have relatively higher star formation rates than Seyfert 1 galaxies. We estimate the fraction of [Ne II] directly associated with the AGNs and find that Seyfert 2 galaxies have a larger contribution from star formation, by a factor of approx.1.5 on average, than what is found in Seyfert 1 galaxies. Using the stellar component of [Ne II] as a tracer of the current star formation, we found similar star formation rates in Seyfert 1 and Seyfert 2 galaxies.We examined the mid- and far-infrared continua and found that [Ne II] is well correlated with the continuum luminosity at 60 microns and that both [Ne III] and [O IV] are better correlated with the 25 micron luminosities than with the continuum at longer wavelengths, suggesting that the mid-infrared continuum luminosity is dominated by the AGN, while the far-infrared luminosity is dominated by star formation. Overall, these results test the unified model of AGNs and suggest that the differences between Seyfert galaxies cannot be solely due to viewing angle dependence.

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

    SciTech Connect

    Diaz Tello, J.; Donzelli, C.; Padilla, N.; Fujishiro, N.; Yoshikawa, T.; Hanami, H.; Hatsukade, B.

    2013-07-01

    We present a spectroscopic study with the derivation of the physical properties of 37 Balmer break galaxies, which have the necessary lines to locate them in star-forming-active galactic nuclei (AGNs) diagnostic diagrams. These galaxies span a redshift range from 0.045 to 0.93 and are somewhat less massive than similar samples of previous works. The studied sample has multiwavelength photometric data coverage from the ultraviolet to mid-infrared (MIR) Spitzer bands. We investigate the connection between star formation and AGN activity via optical, mass-excitation (MEx), and MIR diagnostic diagrams. Through optical diagrams, 31 (84%) star-forming galaxies, two (5%) composite galaxies, and three (8%) AGNs were classified, whereas from the MEx diagram only one galaxy was classified as AGN. A total of 19 galaxies have photometry available in all the IRAC/Spitzer bands. Of these, three AGN candidates were not classified as AGN in the optical diagrams, suggesting they are dusty/obscured AGNs, or that nuclear star formation has diluted their contributions. By fitting the spectral energy distribution of the galaxies, we derived the stellar masses, dust reddening E(B - V), ages, and UV star formation rates (SFRs). Furthermore, the relationship between SFR surface density ({Sigma}{sub SFR}) and stellar mass surface density per time unit ({Sigma}{sub M{sub */{tau}}}) as a function of redshift was investigated using the [O II] {lambda}3727, 3729, H{alpha} {lambda}6563 luminosities, which revealed that both quantities are larger for higher redshift galaxies. We also studied the SFR and specific SFR (SSFR) versus stellar mass and color relations, with the more massive galaxies having higher SFR values but lower SSFR values than less massive galaxies. These results are consistent with previous ones showing that, at a given mass, high-redshift galaxies have on average larger SFR and SSFR values than low-redshift galaxies. Finally, bluer galaxies have larger SSFR values than redder

  13. Empirical measurements of massive galaxy and active galaxy evolution

    NASA Astrophysics Data System (ADS)

    Cool, Richard Jacob

    Using new wide-area galaxy redshift surveys, we explore the evolution of the most massive galaxies and the most luminous quasars in the universe over much of cosmic history. Quasars and massive red galaxies both are extremes; the most luminous high redshift quasars likely play a key role in shaping their nearby environment and the universe as a whole. The most massive galaxies represent the end points of galaxy evolution and contain a fossil record of the galaxy evolution process. Using the AGES redshift survey completed with the MMT and the Hectospec multi- object spectrograph as well as new z -band observations of the NOAO Deep Wide- Field Survey Bootes field, we report the discovery of three new quasars at z > 5. We explore new mid-infrared selection in light of these three new quasars and place constraints on the slope of the high-redshift quasar luminosity function. At lower redshift (0.1< z <0.4) we measure the scatter in red galaxy colors around the optical red-sequence using imaging and spectroscopy from the Sloan Digital Sky Survey. With our sample of nearly 20,000 massive early-type galaxies ( L [Special characters omitted.] 2.2 L *), we find that the scatter around the color-magnitude relation is quite small in colors studied. Each of three model star formation histories can reproduce the scatter we measure, none of the models produce color distributions matching those observed. We measure the evolution of the LRG luminosity function in the redshift range 0.1< z <0.9. We find that the LRG population has evolved little beyond the passive fading of its stellar populations since z ~ 0.9. The most massive (L > 3 L *) red galaxies have grown by less than 50% (at 99% confidence) since z = 0.9 in stark contrast to the factor of 2 to 4 growth observed in the L * red galaxy population over the same epoch. Finally, we introduce the PRIsm MUlti-object Survey (PRIMUS), a new redshift survey aimed at collecting ~300,000 galaxy spectra over 10 deg 2 to z ~ 1. We

  14. COSMIC EVOLUTION OF RADIO SELECTED ACTIVE GALACTIC NUCLEI IN THE COSMOS FIELD

    SciTech Connect

    Smolcic, V.; Salvato, M.; Scoville, N.; Zamorani, G.; Bardelli, S.; Ciliegi, P.; Schinnerer, E.; Bondi, M.; BIrzan, L.; Carilli, C. L.; Elvis, M.; Impey, C. D.; Trump, J. R.; Koekemoer, A. M.; Merloni, A.; Scodeggio, M.; Paglione, T

    2009-05-01

    We explore the cosmic evolution of radio luminous active galactic nuclei (AGNs) with low radio powers (L {sub 1.4GHz} {approx}< 5 x 10{sup 25} W Hz{sup -1}) out to z = 1.3 using to date the largest sample of {approx}600 low-luminosity radio AGN at intermediate redshift drawn from the VLA-COSMOS survey. We derive the radio-luminosity function for these AGNs, and its evolution with cosmic time assuming two extreme cases: (1) pure luminosity and (2) pure density evolution. The former and latter yield L {sub *} {proportional_to} (1 + z){sup 0.8} {sup {+-}} {sup 0.1}, and {phi}{sub *} {proportional_to} (1 + z){sup 1.1} {sup {+-}} {sup 0.1}, respectively, both implying a fairly modest change in properties of low-radio-power AGNs since z = 1.3. We show that this is in stark contrast with the evolution of powerful (L {sub 1.4GHz} > 5 x 10{sup 25} W Hz{sup -1}) radio AGN over the same cosmic time interval, constrained using the 3CRR, 6CE, and 7CRS radio surveys by Willot et al. We demonstrate that this can be explained through differences in black hole fueling and triggering mechanisms, and a dichotomy in host galaxy properties of weak and powerful AGNs. Our findings suggest that high- and low-radio-power AGN activities are triggered in different stages during the formation of massive red galaxies. We show that weak radio AGN occur in the most massive galaxies already at z {approx} 1, and they may significantly contribute to the heating of their surrounding medium and thus inhibit gas accretion onto their host galaxies, as recently suggested for the 'radio mode' in cosmological models.

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  16. Active galaxies and their evolution: As observed in the FIRST and Sloan Digital Sky Surveys

    NASA Astrophysics Data System (ADS)

    Reviglio, Pietro M.

    2008-10-01

    We present a multiwavelength study of more than 150000 galaxies of the local universe observed by the Sloan Digital Sky Survey aimed at clarifying the properties of active galaxies and their nuclei. We have investigated the systematics of spectroscopic selection of AGN by comparing a spectroscopically selected sample with a radio-selected sample of AGN. We have shown that pollution from the host galaxy light significantly biases the classification of low signal-to-noise systems if a constant threshold in line signal-to-noise is used to classify emission-line systems throughout the survey. We have developed a method to quantify this incompleteness in the spectroscopic classification of star-forming galaxies and AGN and have discussed a simple correction for this bias. We have used the corrected sample to investigate the evolution of those nuclei and their hosts in the look-back time of the SDSS. We have shown that significant evolution in the strength of both the emission lines and the radio emission can be detected, with the luminosity of these nuclei declining over time. Interestingly, we find that nuclei residing in lower luminosity hosts have undergone a more significant variation in their luminosities over the past 2 Gyrs than nuclei hosted by more luminous galaxies. Our study likely traces the low-redshift tail of downsizing in AGN activity observed at higher redshifts. This evolution in the AGN properties is accompanied by the evolution of the host properties. We have presented evidence of an increase in the concentration of the host light. The magnitude of this evolution towards more bulgy systems is dependent on the luminosity of the host as well, with less luminous galaxies evolving more significantly in the past 2 Gyrs than bigger systems, suggesting that, while spheroids and disks are stable configuration, the combination of the two is not and tends to evolve more rapidly towards the more concentrated distribution typical of spheroids. We have classified

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    Powerful winds driven by active galactic nuclei are often thought to affect the evolution of both supermassive black holes and their host galaxies, quenching star formation and explaining the close relationship between black holes and galaxies. Recent observations of large-scale molecular outflows in ultraluminous infrared galaxies support this quasar-feedback idea, because they directly trace the gas from which stars form. Theoretical models suggest that these outflows originate as energy-conserving flows driven by fast accretion-disk winds. Proposed connections between large-scale molecular outflows and accretion-disk activity in ultraluminous galaxies were incomplete because no accretion-disk wind had been detected. Conversely, studies of powerful accretion-disk winds have until now focused only on X-ray observations of local Seyfert galaxies and a few higher-redshift quasars. Here we report observations of a powerful accretion-disk wind with a mildly relativistic velocity (a quarter that of light) in the X-ray spectrum of IRAS F11119+3257, a nearby (redshift 0.189) optically classified type 1 ultraluminous infrared galaxy hosting a powerful molecular outflow. The active galactic nucleus is responsible for about 80 per cent of the emission, with a quasar-like luminosity of 1.5 × 1046 ergs per second. The energetics of these two types of wide-angle outflows is consistent with the energy-conserving mechanism that is the basis of the quasar feedback in active galactic nuclei that lack powerful radio jets (such jets are an alternative way to drive molecular outflows).

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

    PubMed

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

    2015-03-26

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

  19. THE STAR FORMATION IN RADIO SURVEY: GBT 33 GHz OBSERVATIONS OF NEARBY GALAXY NUCLEI AND EXTRANUCLEAR STAR-FORMING REGIONS

    SciTech Connect

    Murphy, E. J.; Bremseth, J.; Mason, B. S.; Condon, J. J.; Schinnerer, E.; Aniano, G.; Armus, L.; Helou, G.; Turner, J. L.; Jarrett, T. H.

    2012-12-20

    We present 33 GHz photometry of 103 galaxy nuclei and extranuclear star-forming complexes taken with the Green Bank Telescope as part of the Star Formation in Radio Survey. Among the sources without evidence for an active galactic nucleus, and also having lower frequency radio data, we find a median thermal fraction at 33 GHz of Almost-Equal-To 76% with a dispersion of Almost-Equal-To 24%. For all sources resolved on scales {approx}<0.5 kpc, the thermal fraction is even larger, being {approx}>90%. This suggests that the rest-frame 33 GHz emission provides a sensitive measure of the ionizing photon rate from young star-forming regions, thus making it a robust star formation rate (SFR) indicator. Taking the 33 GHz SFRs as a reference, we investigate other empirical calibrations relying on different combinations of warm 24 {mu}m dust, total infrared (IR; 8-1000 {mu}m), H{alpha} line, and far-UV continuum emission. The recipes derived here generally agree with others found in the literature, albeit with a large dispersion that most likely stems from a combination of effects. Comparing the 33 GHz to total IR flux ratios as a function of the radio spectral index, measured between 1.7 and 33 GHz, we find that the ratio increases as the radio spectral index flattens which does not appear to be a distance effect. Consequently, the ratio of non-thermal to total IR emission appears relatively constant, suggesting only moderate variations in the cosmic-ray electron injection spectrum and ratio of synchrotron to total cooling processes among star-forming complexes. Assuming that this trend solely arises from an increase in the thermal fraction sets a maximum on the scatter of the non-thermal spectral indices among the star-forming regions of {sigma}{sub {alpha}{sup N}{sup T}}{approx}<0.13.

  20. Origin and properties of dual and offset active galactic nuclei in a cosmological simulation at z=2

    NASA Astrophysics Data System (ADS)

    Steinborn, Lisa K.; Dolag, Klaus; Comerford, Julia M.; Hirschmann, Michaela; Remus, Rhea-Silvia; Teklu, Adelheid F.

    2016-05-01

    In the last few years, it became possible to observationally resolve galaxies with two distinct nuclei in their centre. For separations smaller than 10 kpc, dual and offset active galactic nuclei (AGN) are distinguished: in dual AGN, both nuclei are active, whereas in offset AGN only one nucleus is active. To study the origin of such AGN pairs, we employ a cosmological, hydrodynamic simulation with a large volume of (182 Mpc)3 from the set of Magneticum Pathfinder Simulations. The simulation self-consistently produces 35 resolved black hole (BH) pairs at redshift z = 2, with a comoving distance smaller than 10 kpc. 14 of them are offset AGN and nine are dual AGN, resulting in a fraction of (1.2 ± 0.3) per cent AGN pairs with respect to the total number of AGN. In this paper, we discuss fundamental differences between the BH and galaxy properties of dual AGN, offset AGN and inactive BH pairs and investigate their different triggering mechanisms. We find that in dual AGN the BHs have similar masses and the corresponding BH from the less massive progenitor galaxy always accretes with a higher Eddington ratio. In contrast, in offset AGN the active BH is typically more massive than its non-active counterpart. Furthermore, dual AGN in general accrete more gas from the intergalactic medium than offset AGN and non-active BH pairs. This highlights that merger events, particularly minor mergers, do not necessarily lead to strong gas inflows and thus, do not always drive strong nuclear activity.

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

    NASA Technical Reports Server (NTRS)

    Tsuruta, S.; Tritz, B. G.

    1993-01-01

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

  2. LONG-TERM OPTICAL CONTINUUM COLOR VARIABILITY OF NEARBY ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Sakata, Yu; Minezaki, Takeo; Yoshii, Yuzuru; Uchimoto, Yuka Katsuno; Sugawara, Shota; Kobayashi, Yukiyasu; Koshida, Shintaro; Aoki, Tsutomu; Tomita, Hiroyuki; Enya, Keigo; Suganuma, Masahiro

    2010-03-01

    We examine whether the spectral energy distribution of optical continuum emission of active galactic nuclei (AGNs) changes during flux variation, based on accurate and frequent monitoring observations of 11 nearby Seyfert galaxies and QSOs carried out in the B, V, and I bands for seven years by the MAGNUM telescope. The multi-epoch flux data in any two different bands obtained on the same night show a very tight linear flux-to-flux relationship for all target AGNs. The flux of the host galaxy within the photometric aperture is carefully estimated by surface brightness fitting to available high-resolution Hubble Space Telescope images and MAGNUM images. The flux of narrow emission lines in the photometric bands is also estimated from available spectroscopic data. We find that the non-variable component of the host galaxy plus narrow emission lines for all target AGNs is located on the fainter extension of the linear regression line of multi-epoch flux data in the flux-to-flux diagram. This result strongly indicates that the spectral shape of AGN continuum emission in the optical region ({approx}4400-7900 A) does not systematically change during flux variation. The trend of spectral hardening that optical continuum emission becomes bluer as it becomes brighter, which has been reported by many studies, is therefore interpreted as the domination of the variable component of the nearly constant spectral shape of an AGN as it brightens over the non-variable component of the host galaxy plus narrow lines, which is usually redder than AGN continuum emission.

  3. 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.

  4. Spectropolarimetric test of the relativistic disk model for the broad emission lines of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Chen, Kaiyou; Halpern, Jules P.

    1990-01-01

    Previously, it was claimed that the broad emission lines of the radio galaxy Arp 102B can be fitted by the line profile from a simple relativistic Keplerian thin disk. It was argued that the lines originating from the relativistic accretion disk could be polarized due to electron scattering, which is likely to be the dominant opacity in the line-emitting region of Arp 102B. In the present work, the expected polarization properties of these broad emission lines are calculated. The percentage of polarization depends strongly on the inclination angle. For some angles, the red peak of the polarized, double-peaked line profile can be higher than the blue peak. This is in contrast to the total line profile, in which the blue peak is always higher than the red one. Spectropolarimetric observations could, therefore, provide an independent test of the relativistic disk model for the broad emission lines of Arp 102B and other active galactic nuclei.

  5. 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.

  6. Photon damping in cosmic-ray acceleration in active galactic nuclei

    SciTech Connect

    Colgate, S.A.

    1983-04-07

    The usual assumption of the acceleration of ultra high energy cosmic rays, greater than or equal to 10/sup 18/ eV in quasars, Seyfert galaxies and other active galactic nuclei is challenged on the basis of the photon interactions with the accelerated nucleons. This is similar to the effect of the black body radiation on particles > 10/sup 20/ eV for times of the age of the universe except that the photon spectrum is harder and the energy density greater by approx. = 10/sup 15/. Hence, a single traversal, radial or circumferential, of radiation whose energy density is no greater than the emitted flux will damp an ultra high energy. Hence, it is unlikely that any reasonable configuration of acceleration can void disastrous photon energy loss. A different site for ultra high energy cosmic ray acceleration must be found.

  7. 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.

  8. Emission Line Assimetry in Active Galaxies: Mrk 533 and Mrk 110

    NASA Astrophysics Data System (ADS)

    Gavrilovic, N.

    2009-09-01

    In this work emission line asymmetries detected in two different types of Active Galactic Nuclei (AGN) - Seyfert 1 galaxy Mrk 110 and Seyfert 2 galaxy Mrk 533 were analyzed. Since emission lines in two galaxies arise in different emitting regions, detailed spectrum analysis gave the insight into kinematical properties of the Narrow Line and the Broad Line region (NLR and BLR) of this galaxies. We used several methods in the analysis procedure: (a) in order to analyse line profiles we performed profile decomposition into Gaussian components, (b) to study kinematical properties of the gas in the stellar disk, we used the model of "tilted-rings" (Begeman 1989), (c) to determine the sources of ionization of emitting region, we used the Veilleux and Osterbrock diagnostic diagram (Veilleux and Osterbrock 1987), (d) thermodynamical properties of the BLR were determined using the Boltzman plot method (Popović 2003). We showed that the red-shift and asymmetry of emission lines in Mrk 110 are probable caused by the strong gravitational field of the super massive black hole in the center of this galaxy. On the other hand, detailed analysis of 3D spectrophotometric observation of Mrk 533 made possible to map the outflow velocities from the very center of this galaxy, as well as shock waves in the circum-nuclear region, and to analyse the increase of the blue asymmetry with the increase of the outflow velocity (in more details see Smirnova et al. 2007).

  9. Three-dimensional Relativistic MHD Simulations of Active Galactic Nuclei Jets: Magnetic Kink Instability and Fanaroff-Riley Dichotomy

    NASA Astrophysics Data System (ADS)

    Tchekhovskoy, Alexander; Bromberg, Omer

    2016-04-01

    Energy deposition by active galactic nuclei jets into the ambient medium can affect galaxy formation and evolution, the cooling of gas flows at the centres of galaxy clusters, and the growth of the supermassive black holes. However, the processes that couple jet power to the ambient medium and determine jet morphology are poorly understood. For instance, there is no agreement on the cause of the well-known Fanaroff-Riley (FR) morphological dichotomy of jets, with FRI jets being shorter and less stable than FRII jets. We carry out global 3D magnetohydrodynamic simulations of relativistic jets propagating through the ambient medium. We show that the flat density profiles of galactic cores slow down and collimate the jets, making them susceptible to the 3D magnetic kink instability. We obtain a critical power, which depends on the galaxy core mass and radius, below which jets become kink-unstable within the core, stall, and inflate cavities filled with relativistically-hot plasma. Jets above the critical power stably escape the galaxy cores and form powerful backflows. Thus, the kink instability controls the jet morphology and can lead to the FR dichotomy. The model-predicted dependence of the critical power on the galaxy optical luminosity agrees well with observations.

  10. Abdominal surgery activates nesfatin-1 immunoreactive brain nuclei in rats.

    PubMed

    Stengel, Andreas; Goebel, Miriam; Wang, Lixin; Taché, Yvette

    2010-02-01

    Abdominal surgery-induced postoperative gastric ileus is well established to induce Fos expression in specific brain nuclei in rats within 2-h after surgery. However, the phenotype of activated neurons has not been thoroughly characterized. Nesfatin-1 was recently discovered in the rat hypothalamus as a new anorexigenic peptide that also inhibits gastric emptying and is widely distributed in rat brain autonomic nuclei suggesting an involvement in stress responses. Therefore, we investigated whether abdominal surgery activates nesfatin-1-immunoreactive (ir) neurons in the rat brain. Two hours after abdominal surgery with cecal palpation under short isoflurane anesthesia or anesthesia alone, rats were transcardially perfused and brains processed for double immunohistochemical labeling of Fos and nesfatin-1. Abdominal surgery, compared to anesthesia alone, induced Fos expression in neurons of the supraoptic nucleus (SON), paraventricular nucleus (PVN), locus coeruleus (LC), Edinger-Westphal nucleus (EW), rostral raphe pallidus (rRPa), nucleus of the solitary tract (NTS) and ventrolateral medulla (VLM). Double Fos/nesfatin-1 labeling showed that of the activated cells, 99% were nesfatin-1-immunoreactive in the SON, 91% in the LC, 82% in the rRPa, 74% in the EW and VLM, 71% in the anterior parvicellular PVN, 47% in the lateral magnocellular PVN, 41% in the medial magnocellular PVN, 14% in the NTS and 9% in the medial parvicellular PVN. These data established nesfatin-1 immunoreactive neurons in specific nuclei of the hypothalamus and brainstem as part of the neuronal response to abdominal surgery and suggest a possible implication of nesfatin-1 in the alterations of food intake and gastric transit associated with such a stressor. PMID:19944727

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

    NASA Astrophysics Data System (ADS)

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

    2002-06-01

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

  12. 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.

  13. 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.

  14. Star formation and black hole accretion activity in rich local clusters of galaxies

    NASA Astrophysics Data System (ADS)

    Bianconi, Matteo; Marleau, Francine R.; Fadda, Dario

    2016-04-01

    Context. We present a study of star formation and central black hole accretion activity of galaxies that are hosted in the two nearby (z ~ 0.2) rich galaxy clusters Abell 983 and 1731. Aims: We aim to quantify both the obscured and unobscured star formation rates, as well as the presence of active galactic nuclei (AGN) as a function of the environment in which the galaxy is located. Methods: We targeted the clusters with unprecedented deep infrared Spitzer observations (0.2 mJy at 24 micron), near-IR Palomar imaging and optical WIYN spectroscopy. The extent of our observations (~3 virial radii) covers the vast range of possible environments, from the very dense cluster centre to the very rarefied cluster outskirts and accretion regions. Results: The star-forming members of the two clusters present star formation rates that are comparable with those measured in coeval field galaxies. Analysis of the spatial arrangement of the spectroscopically confirmed members reveals an elongated distribution for A1731 with respect to the more uniform distribution of A983. The emerging picture is compatible with A983 being a fully evolved cluster, in contrast with the still actively accreting A1731. Conclusions: Analysis of the specific star formation rate reveals evidence of ongoing galaxy pre-processing along A1731's filament-like structure. Furthermore, the decrease in the number of star-forming galaxies and AGN towards the cluster cores suggests that the cluster environment is accelerating the ageing process of the galaxies and blocking further accretion of the cold gas that fuels both star formation and black hole accretion activity. The catalogue and the reduced images (FITS files) are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/588/A105

  15. Infrared Polarimetry of Galaxies

    NASA Astrophysics Data System (ADS)

    Jones, T. J.

    2005-12-01

    Imaging polarimetry at near infrared wavelengths can probe the magnetic field geometry in external galaxies in regions of high extinction inaccessible to optical techniques. Polarization of starlight from deep into dustlanes, blowouts, and dust enshrouded nuclei can be measured. A total of twelve galaxies showing only interstellar polarization have been observed to date. Normal galaxies such as NGC 4565 show a magnetic field geometry lying in the plane of the disk and a polarization strength very similar to what is observed in the Milky Way. Ultraluminous galaxies and galaxies with starburst nuclei show a polar magnetic field geometry in the nucleus, causing a crossed polaroid effect and reduced polarization. Interestingly, galaxies with active disks, but otherwise normal, such as NGC 891 show the effects of blowouts in the polarization maps.

  16. Symbiotic starburst-black hole active galactic nuclei - I. Isothermal hydrodynamics of the mass-loaded interstellar medium

    NASA Astrophysics Data System (ADS)

    Williams, R. J. R.; Baker, A. C.; Perry, Judith J.

    1999-12-01

    Compelling evidence associates the nuclei of active galaxies and massive starbursts. The symbiosis between a compact nuclear starburst stellar cluster and a massive black hole can self-consistently explain the properties of active nuclei. The young stellar cluster has a profound effect on the most important observable properties of active galaxies through its gravity, and by mass injection through stellar winds, supernovae and stellar collisions. This mass loss, injected throughout the nucleus, creates a hot nuclear interstellar medium (nISM). The cluster both acts as an optically thin fuel reservoir and enriches the nISM with the products of nucleosynthesis. The nISM flows under gravitational and radiative forces until it leaves the nucleus or is accreted on to the black hole or accretion disc. The radiative force exerted by the black hole-accretion disc radiation field is not spherically symmetric. This results in complex flows in which regions of inflow can coexist with high Mach number outflowing winds and hydrodynamic jets. We present two-dimensional hydrodynamic models of such nISM flows, which are highly complex and time-variable. Shocked shells, jets and explosive bubbles are produced, with bipolar winds driving out from the nucleus. Our results graphically illustrate why broad-emission-line studies have consistently failed to identify any simple, global flow geometry. The real structure of the flows is inevitably yet more complex. The structure of these nISM flows is principally determined by two dimensionless quantities. The first is the magnitude of the stellar cluster velocity dispersion relative to the sound speed in the nISM. These speeds measure the gravitational and thermal energies in the nISM respectively, and, therefore, whether the gas is initially bound or escapes in a thermal wind. The second parameter is the Mach number of the ill-collimated nISM flow which is driven away from the central black hole. We discuss a two-parameter classification

  17. DETERMINING INCLINATIONS OF ACTIVE GALACTIC NUCLEI VIA THEIR NARROW-LINE REGION KINEMATICS. I. OBSERVATIONAL RESULTS

    SciTech Connect

    Fischer, T. C.; Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.

    2013-11-01

    Active galactic nuclei (AGNs) are axisymmetric systems to first order; their observed properties are likely strong functions of inclination with respect to our line of sight (LOS). However, except for a few special cases, the specific inclinations of individual AGNs are unknown. We have developed a promising technique for determining the inclinations of nearby AGNs by mapping the kinematics of their narrow-line regions (NLRs), which are often easily resolved with Hubble Space Telescope [O III] imaging and long-slit spectra from the Space Telescope Imaging Spectrograph. Our studies indicate that NLR kinematics dominated by radial outflow can be fit with simple biconical outflow models that can be used to determine the inclination of the bicone axis, and hence the obscuring torus, with respect to our LOS. We present NLR analysis of 53 Seyfert galaxies and the resulting inclinations from models of 17 individual AGNs with clear signatures of biconical outflows. Our model results agree with the unified model in that Seyfert 1 AGNs have NLRs inclined further toward our LOS than Seyfert 2 AGNs. Knowing the inclinations of these AGN NLRs, and thus their accretion disk and/or torus axes, will allow us to determine how their observed properties vary as a function of polar angle. We find no correlation between the inclinations of the AGN NLRs and the disks of their host galaxies, indicating that the orientation of the gas in the torus is independent of that of the host disk.

  18. The Invariant Twist of Magnetic Fields in the Relativistic Jets of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Contopoulos, Ioannis; Christodoulou, Dimitris M.; Kazanas, Demosthenes; Gabuzda, Denise C.

    2009-01-01

    The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in Active Galactic Nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1 %. This lends support to the hypothesis that the Universe is seeded by B fields that are generated in AGN via this mechanism

  19. X-ray spectral parameters for a sample of 95 active galactic nuclei

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

    We present a broadband X-ray analysis of a new homogeneous sample of 95 active galactic nuclei (AGN) from the 22-month Swift/BAT all-sky survey. For this sample we treated jointly the X-ray spectra observed by XMM-Newton and INTEGRAL missions for the total spectral range of 0.5-250 keV. Photon index \\varGamma, relative reflection R, equivalent width of Fe K_{α} line EW_{FeK}, hydrogen column density NH, exponential cut-off energy Ec and intrinsic luminosity L_{corr} are determined for all objects of the sample. We investigated correlations \\varGamma-R, EW_{FeK}-L_{corr}, \\varGamma-Ec, EW_{FeK}-NH. Dependence "\\varGamma-R" for Seyfert 1/2 galaxies has been investigated separately. We found that the relative reflection parameter at low power-law indexes for Seyfert 2 galaxies is systematically higher than for Seyfert 1 ones. This can be related to an increasing contribution of the reflected radiation from the gas-dust torus. Our data show that there exists some anticorrelation between EW_{FeK} and L_{corr}, but it is not strong. We have not found statistically significant deviations from the AGN Unified Model.

  20. THE INVARIANT TWIST OF MAGNETIC FIELDS IN THE RELATIVISTIC JETS OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Contopoulos, Ioannis; Christodoulou, Dimitris M.; Kazanas, Demosthenes E-mail: dimitris_christodoulou@uml.edu E-mail: gabuzda@physics.ucc.ie

    2009-09-10

    The origin of cosmic magnetic (B) fields remains an open question. It is generally believed that very weak primordial B fields are amplified by dynamo processes, but it appears unlikely that the amplification proceeds fast enough to account for the fields presently observed in galaxies and galaxy clusters. In an alternative scenario, cosmic B fields are generated near the inner edges of accretion disks in active galactic nuclei (AGNs) by azimuthal electric currents due to the difference between the plasma electron and ion velocities that arises when the electrons are retarded by interactions with photons. While dynamo processes show no preference for the polarity of the (presumably random) seed field that they amplify, this alternative mechanism uniquely relates the polarity of the poloidal B field to the angular velocity of the accretion disk, resulting in a unique direction for the toroidal B field induced by disk rotation. Observations of the toroidal fields of 29 AGN jets revealed by parsec-scale Faraday rotation measurements show a clear asymmetry that is consistent with this model, with the probability that this asymmetry came about by chance being less than 1%. This lends support to the hypothesis that the universe is seeded by B fields that are generated in AGNs via this mechanism and subsequently injected into intergalactic space by the jet outflows.

  1. Submillimeter recombination lines in dust-obscured starbursts and active galactic nuclei

    SciTech Connect

    Scoville, N.; Murchikova, L.

    2013-12-10

    We examine the use of submillimeter (submm) recombination lines of H, He, and He{sup +} to probe the extreme ultraviolet (EUV) luminosity of starbursts (SBs) and active galactic nuclei (AGNs). We find that the submm recombination lines of H, He, and He{sup +} are in fact extremely reliable and quantitative probes of the EUV continuum at 13.6 eV to above 54.6 eV. At submm wavelengths, the recombination lines originate from low energy levels (n = 20-50). The maser amplification, which poses significant problems for quantitative interpretation of the higher n, radio frequency recombination lines, is insignificant. Lastly, at submm wavelengths, the dust extinction is minimal. The submm line luminosities are therefore directly proportional to the emission measures (EM{sub ION} = n{sub e} × n {sub ion} × volume) of their ionized regions. We also find that the expected line fluxes are detectable with ALMA and can be imaged at ∼0.''1 resolution in low redshift ultraluminous infrared galaxies. Imaging of the H I lines will provide accurate spatial and kinematic mapping of the star formation distribution in low-z IR-luminous galaxies, and the relative fluxes of the H I and He II recombination lines will strongly constrain the relative contributions of SBs and AGNs to the luminosity. The H I lines should also provide an avenue to constraining the submm dust extinction curve.

  2. Highlights of recent results from the VERITAS Active Galactic Nuclei Observing Program

    NASA Astrophysics Data System (ADS)

    Abeysekara, Udara; VERITAS Collaboration

    2016-03-01

    Active Galactic Nuclei (AGN) are the dominant class of the Very High Energy (VHE) gamma-ray sources. The VERITAS Observatory dedicates about 430 hr/year of dark time and 200 hr/year of observations under moonlight, on the AGN observing program. VERITAS is located at the Fred Lawrence Whipple Observatory near Tucson, Arizona, and is sensitive to gamma rays with energies between of 85 GeV and 30 TeV. VERITAS became fully operational in 2007, and has since then detected 34 very high energy (VHE) AGN. The majority of the detected galaxies are blazars, in addition to a few radio galaxies. The VHE emission mechanism, and the location of the VHE emission zone of AGN are still poorly understood. Detailed observations of VHE AGN are necessary for understanding these uncertainties. AGN are plausible source candidates for ultra-high-energy cosmic rays and astrophysical neutrinos. VHE gamma-rays from AGN can also be used as probes to place limits on extragalactic background light density. This presentation will report the most recent results from the VERITAS AGN program including newly discovered AGN, and VHE flares of known TeV AGN. Udara Abeysekara for the VERITAS Collaboration.

  3. The hunt for red active galactic nuclei: a new infrared diagnostic

    NASA Astrophysics Data System (ADS)

    Fadda, Dario; Rodighiero, Giulia

    2014-10-01

    We introduce a new infrared diagnostic to separate galaxies on the basis of their dominant infrared emission: stellar or nuclear. The main novelty with respect to existing diagnostics is the use of a broad band encompassing at the same time the 9.7-μm silicate absorption feature and one of the adjacent broad polycyclic aromatic hydrocarbon (PAH) features. This provides a robust estimate of the near- to mid-infrared continuum slope and enables a clear distinction among different classes of galaxies up to a redshift z ˜ 2.5. The diagnostic can be applied to a wealth of archival data from the ISO, Spitzer and Akari surveys, as well as future James Webb Space Telescope surveys. Based on data in the Great Observatories Origins Deep Survey (GOODS), Lockman Hole and North Ecliptic Pole fields, we find that approximately 70 per cent of active galactic nuclei (AGNs) detected with X-ray and optical spectroscopy dominate the total mid-infrared emission. Finally, we estimate that AGNs contribute less than 30 per cent of the mid-infrared extragalactic integrated emission.

  4. Long-term Evolution of Massive Black Hole Binaries. IV. Mergers of Galaxies with Collisionally Relaxed Nuclei

    NASA Astrophysics Data System (ADS)

    Gualandris, Alessia; Merritt, David

    2012-01-01

    We simulate mergers between galaxies containing collisionally relaxed nuclei around massive black holes (MBHs). Our galaxies contain four mass groups, representative of old stellar populations; a primary goal is to understand the distribution of stellar-mass black holes (BHs) after the merger. Mergers are followed using direct-summation N-body simulations, assuming a mass ratio of 1:3 and two different orbits. Evolution of the binary MBH is followed until its separation has shrunk by a factor of 20 below the hard-binary separation. During the galaxy merger, large cores are carved out in the stellar distribution, with radii several times the influence radius of the massive binary. Much of the pre-existing mass segregation is erased during this phase. We follow the evolution of the merged galaxies for approximately three central relaxation times after coalescence of the massive binary; both standard and top-heavy mass functions are considered. The cores that were formed in the stellar distribution persist, and the distribution of the stellar-mass BHs evolves against this essentially fixed background. Even after one central relaxation time, these models look very different from the relaxed, multi-mass models that are often assumed to describe the distribution of stars and stellar remnants near a massive BH. While the stellar BHs do form a cusp on roughly a relaxation timescale, the BH density can be much smaller than in those models. We discuss the implications of our results for the extreme-mass-ratio inspiral problem and for the existence of Bahcall-Wolf cusps.

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

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  6. Hidden starbursts and active galactic nuclei at 0 < z < 4 from the Herschel-VVDS-CFHTLS-D1 field: Inferences on coevolution and feedback

    NASA Astrophysics Data System (ADS)

    Lemaux, B. C.; Le Floc'h, E.; Le Fèvre, O.; Ilbert, O.; Tresse, L.; Lubin, L. M.; Zamorani, G.; Gal, R. R.; Ciliegi, P.; Cassata, P.; Kocevski, D. D.; McGrath, E. J.; Bardelli, S.; Zucca, E.; Squires, G. K.

    2014-12-01

    We investigate of the properties of ~2000 Herschel/SPIRE far-infrared-selected galaxies from 0 galaxies are compared to optically-selected galaxies at a variety of redshifts. Herschel-selected galaxies are observed to span a range of stellar masses, colors, and absolute magnitudes equivalent to galaxies undetected in SPIRE. Though many Herschel galaxies appear to be in transition, such galaxies are largely consistent with normal star-forming galaxies when rest-frame colors are utilized. The nature of the star-forming "main sequence" is studied and we warn against adopting this framework unless the main sequence is determined precisely. Herschel galaxies at different total infrared luminosities (LTIR) are compared. Bluer optical colors, larger nebular extinctions, and larger contributions from younger stellar populations are observed for galaxies with larger LTIR, suggesting that low-LTIR galaxies are undergoing rejuvenated starbursts while galaxies with higher LTIR are forming a larger percentage of their stellar mass. A variety of methods are used to select powerful active galactic nuclei (AGN). Galaxies hosting all types of AGN are observed to be undergoing starbursts more commonly and vigorously than a matched sample of galaxies without powerful AGN and, additionally, the fraction of galaxies with an AGN increases with increasing star formation rate at all redshifts. At all redshifts (0 galaxies are found to contain the highest fraction of powerful AGN. For redshift bins that allow a comparison (z> 0.5), the highest LTIR galaxies in a given redshift bin are unobserved by SPIRE at subsequently lower redshifts, a trend linked to downsizing. In conjunction with other

  7. 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

  8. Observational model of the ionized gas in Seyfert and radio-galaxy nuclei*

    PubMed Central

    Osterbrock, Donald E.

    1978-01-01

    Equivalent widths of the total emission-line Hβ in Seyfert 1, Seyfert 2, and intermediate-type Seyfert galaxies, expressed in terms of the featureless continuum, all have approximately the same frequency distribution. This suggests that the energy-input mechanism to both the narrow-line, low-density gas and the broad-line, high-density gas is photoionization by the featureless continuum. The reason for the weakness of the narrow emission lines in extreme Seyfert 1 galaxies is then the absorption of most of the ionizing photons in the dense gas near the central source. The statistics of line widths can be fitted by a model in which the dense gas has typical rotational velocity 5000 km/sec and typical turbulent velocity 2000 km/sec. A model is proposed in which the dense gas forms a rotating, turbulent disk with dimension ≈0.1 pc and height/diameter ≈2/5. Seyfert 2 galaxies are objects with little dense gas, and intermediate-type Seyfert galaxies are objects in which the dense gas is optically thin to ionizing radiation at least along the poles. Most radio galaxies have strong narrow emission lines, suggesting that escape of radio plasma can only occur where some ionizing photons can also escape from the dense gas. Other predictions, implications, and tests of this model are discussed. Images PMID:16592488

  9. NO CLEAR SUBMILLIMETER SIGNATURE OF SUPPRESSED STAR FORMATION AMONG X-RAY LUMINOUS ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Harrison, C. M.; Alexander, D. M.; Mullaney, J. R.; Del Moro, A.; Rovilos, E.; Altieri, B.; Coia, D.; Charmandaris, V.; Daddi, E.; Le Floc'h, E.; Leiton, R.; Dasyra, K.; Dickinson, M.; Kartaltepe, J.; Hickox, R. C.; Ivison, R. J.; Magnelli, B.; Popesso, P.; Rosario, D.; and others

    2012-11-20

    Many theoretical models require powerful active galactic nuclei (AGNs) to suppress star formation in distant galaxies and reproduce the observed properties of today's massive galaxies. A recent study based on Herschel-SPIRE submillimeter observations claimed to provide direct support for this picture, reporting a significant decrease in the mean star formation rates (SFRs) of the most luminous AGNs (L{sub X} >10{sup 44} erg s{sup -1}) at z Almost-Equal-To 1-3 in the Chandra Deep Field-North (CDF-N). In this Letter, we extend these results using Herschel-SPIRE 250 {mu}m data in the COSMOS and Chandra Deep Field-South fields to achieve an order-of-magnitude improvement in the number of sources at L{sub X} >10{sup 44} erg s{sup -1}. On the basis of our analysis, we find no strong evidence for suppressed star formation in L{sub X} >10{sup 44} erg s{sup -1} AGNs at z Almost-Equal-To 1-3. The mean SFRs of the AGNs are constant over the broad X-ray luminosity range of L{sub X} Almost-Equal-To 10{sup 43}-10{sup 45} erg s{sup -1} (with mean SFRs consistent with typical star-forming galaxies at z Almost-Equal-To 2; (SFRs) Almost-Equal-To 100-200 M{sub Sun} yr{sup -1}). We suggest that the previous CDF-N results were likely due to low number statistics. We discuss our results in the context of current theoretical models.

  10. Radio-selected Binary Active Galactic Nuclei from the Very Large Array Stripe 82 Survey

    NASA Astrophysics Data System (ADS)

    Fu, Hai; Myers, A. D.; Djorgovski, S. G.; Yan, Lin; Wrobel, J. M.; Stockton, A.

    2015-01-01

    Galaxy mergers play an important role in the growth of galaxies and their supermassive black holes. Simulations suggest that tidal interactions could enhance black hole accretion, which can be tested by the fraction of binary active galactic nuclei (AGNs) among galaxy mergers. However, determining the fraction requires a statistical sample of binaries. We have identified kiloparsec-scale binary AGNs directly from high-resolution radio imaging. Inside the 92 deg2 covered by the high-resolution Very Large Array survey of the Sloan Digital Sky Survey (SDSS) Stripe 82 field, we identified 22 grade A and 30 grade B candidates of binary radio AGNs with angular separations less than 5'' (10 kpc at z = 0.1). Eight of the candidates have optical spectra for both components from the SDSS spectroscopic surveys and our Keck program. Two grade B candidates are projected pairs, but the remaining six candidates are all compelling cases of binary AGNs based on either emission line ratios or the excess in radio power compared to the Hα-traced star formation rate. Only two of the six binaries were previously discovered by an optical spectroscopic search. Based on these results, we estimate that ~60% of our binary candidates would be confirmed once we obtain complete spectroscopic information. We conclude that wide-area high-resolution radio surveys offer an efficient method to identify large samples of binary AGNs. These radio-selected binary AGNs complement binaries identified at other wavelengths and are useful for understanding the triggering mechanisms of black hole accretion. Some of the data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.

  11. RADIO-SELECTED BINARY ACTIVE GALACTIC NUCLEI FROM THE VERY LARGE ARRAY STRIPE 82 SURVEY

    SciTech Connect

    Fu, Hai; Myers, A. D.; Djorgovski, S. G.; Yan, Lin; Wrobel, J. M.; Stockton, A.

    2015-01-20

    Galaxy mergers play an important role in the growth of galaxies and their supermassive black holes. Simulations suggest that tidal interactions could enhance black hole accretion, which can be tested by the fraction of binary active galactic nuclei (AGNs) among galaxy mergers. However, determining the fraction requires a statistical sample of binaries. We have identified kiloparsec-scale binary AGNs directly from high-resolution radio imaging. Inside the 92 deg{sup 2} covered by the high-resolution Very Large Array survey of the Sloan Digital Sky Survey (SDSS) Stripe 82 field, we identified 22 grade A and 30 grade B candidates of binary radio AGNs with angular separations less than 5'' (10 kpc at z = 0.1). Eight of the candidates have optical spectra for both components from the SDSS spectroscopic surveys and our Keck program. Two grade B candidates are projected pairs, but the remaining six candidates are all compelling cases of binary AGNs based on either emission line ratios or the excess in radio power compared to the Hα-traced star formation rate. Only two of the six binaries were previously discovered by an optical spectroscopic search. Based on these results, we estimate that ∼60% of our binary candidates would be confirmed once we obtain complete spectroscopic information. We conclude that wide-area high-resolution radio surveys offer an efficient method to identify large samples of binary AGNs. These radio-selected binary AGNs complement binaries identified at other wavelengths and are useful for understanding the triggering mechanisms of black hole accretion.

  12. Spectroscopic Active Galaxies and Clusters Explorer

    NASA Astrophysics Data System (ADS)

    Ferrari, L.; Bagliani, D.; Bardi, A.; Battistelli, E.; Birkinshaw, M.; Colafrancesco, S.; Conte, A.; Debernardis, P.; Degregori, S.; Depetris, M.; de Zotti, G.; Donati, A.; Franceschini, A.; Gatti, F.; Gervasi, M.; Gonzalez-Nuevo, J.; Lamagna, L.; Luzzi, G.; Maiolino, M.; Marchegiani, P.; Mariani, A.; Masi, S.; Massardi, M.; Mauskopf, P.; Nati, L.; Nati, F.; Natoli, P.; Piacentini, F.; Polenta, G.; Porciani, M.; Savini, G.; Schillaci, A.; Spinelli, S.; Tartari, A.; Tavanti, M.; Tortora, A.; Vaccari, M.; Vaccarone, R.; Zannoni, M.

    2009-12-01

    We present a concept for the payload SAGACE, the Spectroscopic Active Galaxies And Cluster Explorer, devoted to study the evolution of Universe structures using different observables, all of them in the mm/submm wavelength. The SAGACE payload is made of a passively cooled 3 m telescope, a cryogenic Fourier Transform Spectrometer (FTS) and detector arrays to be operated at 0.3 K by a 3He fridge. The detectors are Ti/Au Transition Edge Sensor (TES) bolometers with a NEP<10-17 W/Hz12. A phase-A study has been recently completed for this experiment, in the framework of the call for small missions of the Italian Space Agency.

  13. What Fraction of Active Galaxies Actually Show Outflows?

    NASA Astrophysics Data System (ADS)

    Ganguly, Rajib; Brotherton, M. S.

    2007-12-01

    Outflows from active galactic nuclei (AGNs) seem to be common and are thought to be important from a variety of perspectives: as an agent of chemical enhancement of the interstellar and intergalactic media, as an agent of angular momentum removal from the accreting central engine, and as an agent limiting star formation in starbursting systems by blowing out gas and dust from the host galaxy. To understand these processes, we must determine what fraction of AGNs feature outflows and understand what forms they take. We examine recent surveys of outflows detected in ultraviolet absorption over the entire range of velocities and velocity widths (i.e., broad absorption lines, associated absorption lines, and high-velocity narrow absorption lines). While the fraction of specific forms of outflows depends on AGN properties, the overall fraction displaying outflows is fairly constant, approximately 60%, over many orders of magnitude in luminosity. We discuss implications of this result and ways to refine our understanding of outflows. We acknowledge support from the US National Science Foundation through grant AST 05-07781.

  14. Multiwavelength data for bright active galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.; Abrahamyan, Hayk V.; Paronyan, Gurgen M.; Harutyunyan, Gohar S.

    2012-08-01

    The spectral energy distribution (SED) gives a complete picture of the radiation of space objects and may result in correct classifications compared to those based only on optical (or other local) spectra. This is especially crucial for active galaxies, both AGN and Starbursts (SB). For this, multiwavelength (MW) data are needed taken from available surveys and catalogs. We have cross-correlated the Catalogue of quasars and active galaxies with all-sky or large-area MW catalogues, such as X-ray ROSAT (BSC and FSC), UV GALEX (MIS and AIS), optical APM, MAPS, USNO-B1.0, GSC 2.3.2, and SDSS DR8, NIR 2MASS, MIR/FIR WISE, IRAS (PSC and FSC) and AKARI (IRC and FIS), radio GB6, NVSS, FIRST, and WENSS. We have established accurate positions and photometry for a few thousands of objects that appeared in the catalog with poor data, as well as achieved the best astrometric and photometric data for all objects. This allowed correct cross-correlations and establishing correct MW data for these objects. As a result, we obtained 34 photometric points from X-rays to radio and using VO tools built SEDs for some 10,000 bright objects. Some data from other surveys were also used, such as Chandra, XMM, Spitzer, etc. All objects were grouped into several forms of SED and were compared to the known optical classes given in the catalog (QSO, BLL, Sy1, Sy1.2-1.9, Sy2, LINER, SB, and HII). This allowed reveal obscured AGN, as well as find previously misclassified objects. A homogeneous classification for these objects was established. The first part of this project is presented; establishment of accurate positions and photometry and cross-correlations with MW catalogs.

  15. THE REST-FRAME ULTRAVIOLET SPECTRA OF UV-SELECTED ACTIVE GALACTIC NUCLEI AT z {approx} 2-3

    SciTech Connect

    Hainline, Kevin N.; Shapley, Alice E.; Greene, Jenny E.; Steidel, Charles C.

    2011-05-20

    We present new results for a sample of 33 narrow-lined UV-selected active galactic nuclei (AGNs), identified in the course of a spectroscopic survey for star-forming galaxies at z {approx} 2-3. The rest-frame UV composite spectrum for our AGN sample shows several emission lines characteristic of AGNs, as well as interstellar absorption features detected in star-forming Lyman break galaxies (LBGs). We report a detection of N IV] {lambda}1486, which has been observed in high-redshift radio galaxies, as well as in rare optically selected quasars. The UV continuum slope of the composite spectrum is significantly redder than that of a sample of non-AGN UV-selected star-forming galaxies. Blueshifted Si IV absorption provides evidence for outflowing highly ionized gas in these objects at speeds of {approx}10{sup 3} km s{sup -1}, quantitatively different from what is seen in the outflows of non-AGN LBGs. Grouping the individual AGNs by parameters such as the Ly{alpha} equivalent width, redshift, and UV continuum magnitude allows for an analysis of the major spectroscopic trends within the sample. Stronger Ly{alpha} emission is coupled with weaker low-ionization absorption, which is similar to what is seen in the non-AGN LBGs, and highlights the role that cool interstellar gas plays in the escape of Ly{alpha} photons. However, the AGN composite does not show the same trends between Ly{alpha} strength and extinction seen in the non-AGN LBGs. These results represent the first such comparison at high redshift between star-forming galaxies and similar galaxies that host AGN activity.

  16. Histidine kinase activity in nuclei of Physarum polycephalum

    SciTech Connect

    Matthews, H.R.; Pesis, K. Wei, Y.

    1987-05-01

    Nuclei of the true slime mold Physarum polycephalum, contain a kinase that specifically phosphorylates the 1-nitrogen of histidine-75 of histone H4, in vitro. Phosphohistidine is alkali stable and acid labile. Similar alkali stable phosphorylation has been observed with beef heart extracts and S-100 extracts from S. cerevisiae. The activity may be similar to that previously reported by R.A. Smith and his colleagues in several mammalian tissues. They have begun a search for nuclear proteins that contain phosphohistidine. Cultures of Physarum were grown in the presence of /sup 32/P-phosphate using several different labeling protocols. Labeled nuclear proteins were fractionated on a Superose-12 column. Alkali stable phosphate label eluted close to the position of histone H1, although it was not on H1 itself. No alkali stable phosphate eluted at the position of histone H4, which was obtained in high yield by this procedure. The absence of alkali-stable phosphorylation of histone H4 was confirmed by gel electrophoresis of the crude nuclear proteins. The fraction containing alkali-stable phosphate was shown to contain phosphohistidine by amino acid analysis of a total alkaline hydrolysate. They conclude that Physarum nuclei possess at least one protein that contains phosphohistidine in vivo and that histone H4 does not contain phosphohistidine in this system.

  17. GOODS-HERSCHEL: IMPACT OF ACTIVE GALACTIC NUCLEI AND STAR FORMATION ACTIVITY ON INFRARED SPECTRAL ENERGY DISTRIBUTIONS AT HIGH REDSHIFT

    SciTech Connect

    Kirkpatrick, Allison; Pope, Alexandra; Alexander, David M.; Charmandaris, Vassilis; Daddi, Emmanuele; Elbaz, David; Gabor, Jared; Mullaney, James; Pannella, Maurilio; Aussel, Herve; Bournaud, Frederic; Dasyra, Kalliopi; Hwang, Ho Seong; Ivison, Rob; Scott, Douglas; Altieri, Bruno; Coia, Daniela; Buat, Veronique; Dannerbauer, Helmut; and others

    2012-11-10

    We explore the effects of active galactic nuclei (AGNs) and star formation activity on the infrared (0.3-1000 {mu}m) spectral energy distributions (SEDs) of luminous infrared galaxies from z = 0.5 to 4.0. We have compiled a large sample of 151 galaxies selected at 24 {mu}m (S {sub 24} {approx}> 100 {mu}Jy) in the GOODS-N and ECDFS fields for which we have deep Spitzer IRS spectroscopy, allowing us to decompose the mid-IR spectrum into contributions from star formation and AGN activity. A significant portion ({approx}25%) of our sample is dominated by an AGN (>50% of the mid-IR luminosity) in the mid-IR. Based on the mid-IR classification, we divide our full sample into four sub-samples: z {approx} 1 star-forming (SF) sources, z {approx} 2 SF sources, AGNs with clear 9.7 {mu}m silicate absorption, and AGNs with featureless mid-IR spectra. From our large spectroscopic sample and wealth of multi-wavelength data, including deep Herschel imaging at 100, 160, 250, 350, and 500 {mu}m, we use 95 galaxies with complete spectral coverage to create a composite SED for each sub-sample. We then fit a two-temperature component modified blackbody to the SEDs. We find that the IR SEDs have similar cold dust temperatures, regardless of the mid-IR power source, but display a marked difference in the warmer dust temperatures. We calculate the average effective temperature of the dust in each sub-sample and find a significant ({approx}20 K) difference between the SF and AGN systems. We compare our composite SEDs to local templates and find that local templates do not accurately reproduce the mid-IR features and dust temperatures of our high-redshift systems. High-redshift IR luminous galaxies contain significantly more cool dust than their local counterparts. We find that a full suite of photometry spanning the IR peak is necessary to accurately account for the dominant dust temperature components in high-redshift IR luminous galaxies.

  18. A water-vapour giga-maser in the active galaxy TXFS2226-184.

    PubMed

    Koekemoer, A M; Henkel, C; Greenhill, L J; Dey, A; van Breugel, W; Codella, C; Antonucci, R

    1995-12-14

    Active galactic nuclei are thought to be powered by gas falling into a massive black hole; the different types of active galaxy may arise because we view them through a thick torus of molecular gas at varying angles of inclination. One way to determine whether the black hole is surrounded by a torus, which would obscure the accretion disk around the black hole along certain lines of sight, is to search for water masers, as these exist only in regions with plentiful molecular gas. Since the first detection of an extra-galactic water maser in 1979, they have come to be associated primarily with active galaxies, and have even been used to probe the mass of the central engine. Here we report the detection of a water giga-maser in the radio galaxy TXFS2226-184. The strength of the emission supports a recently proposed theory of maser pumping that allows for even more powerful masers, which might be detectable at cosmological distances. Water masers may accordingly provide a way to determine distances to galaxies outside the usual distance ladder, providing an independent calibration of the Hubble constant. PMID:7501016

  19. Three-dimensional relativistic MHD simulations of active galactic nuclei jets: magnetic kink instability and Fanaroff-Riley dichotomy

    NASA Astrophysics Data System (ADS)

    Tchekhovskoy, Alexander; Bromberg, Omer

    2016-09-01

    Energy deposition by active galactic nuclei jets into the ambient medium can affect galaxy formation and evolution, the cooling of gas flows at the centres of galaxy clusters, and the growth of the supermassive black holes. However, the processes that couple jet power to the ambient medium and determine jet morphology are poorly understood. For instance, there is no agreement on the cause of the well-known Fanaroff-Riley (FR) morphological dichotomy of jets, with FRI jets being shorter and less stable than FRII jets. We carry out global 3D magnetohydrodynamic simulations of relativistic jets propagating through the ambient medium. We show that the flat density profiles of galactic cores slow down and collimate the jets, making them susceptible to the 3D magnetic kink instability. We obtain a critical power, which depends on the galaxy core mass and radius, below which jets become kink-unstable within the core, stall, and inflate cavities filled with relativistically hot plasma. Jets above the critical power stably escape the core and form powerful backflows. Thus, the kink instability controls the jet morphology and can lead to the FR dichotomy. The model-predicted dependence of the critical power on the galaxy optical luminosity agrees well with observations.

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

    SciTech Connect

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

    2011-12-10

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

  1. 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.

  2. 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.

  3. X-ray emission from active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R.

    1985-01-01

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

  4. Time Delay Evolution of Five Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

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

    2015-12-01

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

  5. 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.

  6. Suprachiasmatic nuclei and Circadian rhythms. The role of suprachiasmatic nuclei on rhythmic activity of neurons in the lateral hypothalamic area, ventromedian nuclei and pineal gland

    NASA Technical Reports Server (NTRS)

    Nishino, H.

    1977-01-01

    Unit activity of lateral hypothalamic area (LHA) and Ventromedian nuclei (VMN) was recorded in urethane anesthetized male rats. A 5 to 10 sec. a 3-5 min and a circadian rhythmicity were observed. In about 15% of all neurons, spontaneous activity of LHA and VMN showed reciprocal relationships. Subthreshold stimuli applied at a slow rate in the septum and the suprachiasmatic nuclei (SCN) suppressed the rhythms without changing firing rates. On the other hand, stimulation of the optic nerve at a rate of 5 to 10/sec increased firing rates in 1/3 of neurons of SCN. Iontophoretically applied acetylcholine increased 80% of tested neurons of SCN, whereas norepinephrine, dopamine and 5 HT inhibited 64, 60 and 75% of SCN neurons respectively. These inhibitions were much stronger in neurons, the activity of which was increased by optic nerve stimulation. Stimulation of the SCN inhibited the tonic activity in cervical sympathetic nerves.

  7. An Atlas of Warm Active Galactic Nuclei and Starbursts from the IRAS Deep Fields

    NASA Astrophysics Data System (ADS)

    Keel, William C.; Irby, Bryan K.; May, Alana; Miley, George K.; Golombek, Daniel; de Grijp, M. H. K.; Gallimore, Jack F.

    2005-06-01

    We present a set of 180 active galactic nucleus (AGN) candidates based on color selection from the IRAS slow-scan deep observations, with color criteria broadened from the initial Point Source Catalog samples so as to include similar objects with redshifts up to z=1 and allowing for two-band detections. Spectroscopic identifications have been obtained for 80 (44%); some additional identifications are secure based on radio detections or optical morphology, although yet unobserved spectroscopically. These spectroscopic identifications include 13 type 1 Seyfert galaxies, 17 type 2 Seyferts, 29 starburst galaxies, 7 LINER systems, and 13 emission-line galaxies so heavily reddened as to remain of ambiguous classification. The optical magnitudes range from R=12.0 to 20.5; the counts suggest that incompleteness is important fainter than R=15.5. Redshifts extend to z=0.51, with a significant part of the sample at z>0.2. Even with the relaxed color criteria, this sample includes slightly more AGNs than star-forming systems among those where the spectra contain enough diagnostic feature to make the distinction. The active nuclei include several broad-line objects with strong Fe II emission, and composite objects with the absorption-line signatures of fading starbursts. These AGNs with warm far-IR colors have little overlap with the ``red AGNs'' identified with 2MASS; only a single Seyfert 1 was detected by 2MASS with J-K>2. Some reliable IRAS detections have either very faint optical counterparts or only absorption-line galaxies, potentially being deeply obscured AGNs. The IRAS detections include a newly identified symbiotic star, and several possible examples of the ``Vega phenomenon,'' including dwarfs as cool as type K. Appendices detail these candidate stars, and the optical-identification content of a particularly deep set of high-latitude IRAS scans (probing the limits of optical identification from IRAS data alone). Based on observations from the European Southern

  8. The mid-infrared emission of narrow-line active galactic nuclei: Star formation, nuclear activity, and two populations revealed by WISE

    SciTech Connect

    Rosario, David J.; Burtscher, Leonard; Davies, Richard; Genzel, Reinhard; Lutz, Dieter; Tacconi, Linda J.

    2013-12-01

    We explore the nature of the long-wavelength mid-infrared (MIR) emission of a sample of 13,000 local Type II (narrow-line) active galactic nuclei (AGNs) from the Sloan Digital Sky Survey (SDSS) using 12 μm and 22 μm photometry from the WISE all-sky survey. In combination with FIRST 1.4 GHz photometry, we show that AGNs divide into two relatively distinct populations or 'branches' in the plane of MIR and radio luminosity. Seyfert galaxies lie almost exclusively on an MIR-bright branch (Branch A), while low-ionization nuclear emission line galaxies (LINERs) are split evenly into Branch A and the MIR-faint Branch B. We devise various tests to constrain the processes that define the branches, including a comparison to the properties of pure star-forming inactive galaxies on the MIR-radio plane. We demonstrate that the total MIR emission of objects on Branch A, including most Seyfert galaxies, is governed primarily by host star formation, with ≈15% of the 22 μm luminosity coming from AGN-heated dust. This implies that ongoing dusty star formation is a general property of Seyfert host galaxies. We show that the 12 μm broadband luminosity of AGNs on Branch A is suppressed with respect to star-forming galaxies, possibly due to the destruction of PAHs or deeper 10 μm Si absorption in AGNs. We uncover a correlation between the MIR luminosity and [O III] λ5007 luminosity in AGNs. This suggests a relationship between the star formation rate and nuclear luminosity in the AGN population, but we caution on the importance of selection effects inherent to such AGN-dominated emission-line galaxies in driving such a correlation. We highlight the MIR-radio plane as a useful tool in comparative studies of star formation and nuclear activity in AGNs.

  9. INVESTIGATION OF DUAL ACTIVE NUCLEI, OUTFLOWS, SHOCK-HEATED GAS, AND YOUNG STAR CLUSTERS IN MARKARIAN 266

    SciTech Connect

    Mazzarella, J. M.; Chan, B. H. P.; Iwasawa, K. E-mail: bchan@ipac.caltech.edu; and others

    2012-11-01

    Results of observations with the Spitzer, Hubble, GALEX, Chandra, and XMM-Newton space telescopes are presented for the luminous infrared galaxy (LIRG) merger Markarian 266. The SW (Seyfert 2) and NE (LINER) nuclei reside in galaxies with Hubble types SBb (pec) and S0/a (pec), respectively. Both companions are more luminous than L* galaxies and they are inferred to each contain a Almost-Equal-To 2.5 Multiplication-Sign 10{sup 8} M{sub Sun} black hole. Although the nuclei have an observed hard X-ray flux ratio of f{sub X} (NE)/f{sub X} (SW) = 6.4, Mrk 266 SW is likely the primary source of a bright Fe K{alpha} line detected from the system, consistent with the reflection-dominated X-ray spectrum of a heavily obscured active galactic nucleus (AGN). Optical knots embedded in an arc with aligned radio continuum radiation, combined with luminous H{sub 2} line emission, provide evidence for a radiative bow shock in an AGN-driven outflow surrounding the NE nucleus. A soft X-ray emission feature modeled as shock-heated plasma with T {approx} 10{sup 7} K is cospatial with radio continuum emission between the galaxies. Mid-infrared diagnostics provide mixed results, but overall suggest a composite system with roughly equal contributions of AGN and starburst radiation powering the bolometric luminosity. Approximately 120 star clusters have been detected, with most having estimated ages less than 50 Myr. Detection of 24 {mu}m emission aligned with soft X-rays, radio continuum, and ionized gas emission extending {approx}34'' (20 kpc) north of the galaxies is interpreted as {approx}2 Multiplication-Sign 10{sup 7} M{sub Sun} of dust entrained in an outflowing superwind. At optical wavelengths this Northern Loop region is resolved into a fragmented morphology indicative of Rayleigh-Taylor instabilities in an expanding shell of ionized gas. Mrk 266 demonstrates that the dust 'blow-out' phase can begin in a LIRG well before the galaxies fully coalesce during a subsequent

  10. Misaligned Disks as Obscurers in Active Galaxies

    SciTech Connect

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

    2010-06-02

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

  11. MISALIGNED DISKS AS OBSCURERS IN ACTIVE GALAXIES

    SciTech Connect

    Lawrence, Andy; Elvis, Martin

    2010-05-01

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

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

    SciTech Connect

    Mathews, W.G.; Veilleux, S.

    1989-01-01

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

  13. 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.

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

    NASA Astrophysics Data System (ADS)

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

    2014-10-01

    A strong X-ray emission is one of the defining signatures of nuclear activity in galaxies. According to the Unified Model for Active Galactic Nuclei (AGN), both the X-ray radiation and the prominent broad emission lines, characterizing the optical and UV spectra of Type 1 AGNs, are originated in the innermost regions of the sources, close to the Super Massive Black Holes (SMBH), which power the central engine. Since the emission is concentrated in a very compact region (with typical size r⩽0.1 pc) and it is not possible to obtain resolved images of the source, spectroscopic studies of this radiation represent the only valuable key to constrain the physical properties of matter and its structure in the center of active galaxies. Based on previous studies on the physics of the Broad Line Region (BLR) and on the X-ray spectra of broad (FWHMHβ ⩾ 2000 km s-1) and narrow line (1000 km s-1 ⩽FWHMHβ ⩽ 2000 km s-1) emitting objects, it has been observed that the kinematic and ionization properties of matter close to the SMBHs are related together, and, in particular, that ionization is higher in narrow line sources. Here we report on the study of the optical and X-ray spectra of a sample of Type 1 AGNs, selected from the Sloan Digital Sky Survey (SDSS) database, within an upper redshift limit of z=0.35, and detected at X-ray energies. We present analysis of the broad emission line fluxes and profiles, as well as the properties of the X-ray continuum and Fe Kα emission and we use these parameters to assess the consistency of our current AGN understanding.

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

    SciTech Connect

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

    2013-12-10

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

  16. ADAPTIVE OPTICS IMAGING OF QUASI-STELLAR OBJECTS WITH DOUBLE-PEAKED NARROW LINES: ARE THEY DUAL ACTIVE GALACTIC NUCLEI?

    SciTech Connect

    Rosario, D. J.; McGurk, R. C.; Max, C. E.; Shields, G. A.; Smith, K. L.; Ammons, S. M. E-mail: mcgurk@ucsc.edu E-mail: shieldsga@mail.utexas.edu E-mail: ammons@as.arizona.edu

    2011-09-20

    Active galaxies hosting two accreting and merging supermassive black holes (SMBHs)-dual active galactic nuclei (AGNs)-are predicted by many current and popular models of black-hole-galaxy co-evolution. We present here the results of a program that has identified a set of probable dual AGN candidates based on near-infrared laser guide star adaptive optics imaging with the Keck II telescope. These candidates are selected from a complete sample of radio-quiet quasi-stellar objects (QSOs) drawn from the Sloan Digital Sky Survey (SDSS), which show double-peaked narrow AGN emission lines. Of the 12 AGNs imaged, we find 6 with double galaxy structure, of which four are in galaxy mergers. We measure the ionization of the two velocity components in the narrow AGN lines to test the hypothesis that both velocity components come from an active nucleus. The combination of a well-defined parent sample and high-quality imaging allows us to place constraints on the fraction of SDSS QSOs that host dual accreting black holes separated on kiloparsec scales: {approx}0.3%-0.65%. We derive from this fraction the time spent in a QSO phase during a typical merger and find a value that is much lower than estimates that arise from QSO space densities and galaxy merger statistics. We discuss possible reasons for this difference. Finally, we compare the SMBH mass distributions of single and dual AGNs and find little difference between the two within the limited statistics of our program, hinting that most SMBH growth happens in the later stages of a merger process.

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

    NASA Astrophysics Data System (ADS)

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

    2016-04-01

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

  18. Galaxies

    SciTech Connect

    Not Available

    1981-01-01

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

  19. Chandra Observations of the Nuclei of Radio Galaxies: 3C 295 and Hydra A

    NASA Technical Reports Server (NTRS)

    Harris, D. E.; McNamara, B. R.; David, L. P.; Lavoie, Anthony R. (Technical Monitor)

    2000-01-01

    The angular resolution available with Chandra allows us to isolate the X-ray emission from the nucleus of many radio galaxies and obtain their spectra. As expected from unification schemes, spectra so far obtained can best be interpreted as heavily absorbed power laws. We present the spectral parameters so derived for 3C 295 and Hydra A and compare them to data obtained at other wavelengths.

  20. Evolution of galaxy properties across the peak of cosmic activity in cosmological hydrodynamics simulations

    NASA Astrophysics Data System (ADS)

    Devriendt, Julien

    2015-08-01

    In this talk I will review how numerical hydrodynamics simulations predict galaxies evolve in the redshift range 1galaxy spins and the large scale cosmic web filaments in which they are embedded. Relative contributions to property evolution will be split between major and minor, gas rich and gas poor mergers as well as smooth accretion, and quantitatively assessed. Finally, switching from nurture to nature, I will also discuss the role played by various feedback processes, whether of stellar origin or driven by active nuclei, in driving such changes or freezing them in.

  1. Disk-driven hydromagnetic winds as a key ingredient of active galactic nuclei unification schemes

    NASA Technical Reports Server (NTRS)

    Konigl, Arieh; Kartje, John F.

    1994-01-01

    Centrifugally driven winds from the surfaces of magnetized accretion disks have been recognized as an attractive mechanism of removing the angular momentum of the accreted matter and of producing the bipolar outflows and jets that are often associated with compact astronomical objects. As previously suggested in the context of young stellar objects, such winds have unique observational manifestations stemming from their highly stratified density and velocity structure and from their exposure to the strong continuum radiation field of the compact object. We have applied this scenario to active galactic nuclei (AGNs) and investigated the properties of hydromagnetic outflows that originate within approximately 10(M(sub 8)) pc of the central 10(exp 8)(M(sub 8)) solar mass black hole. On the basis of our results, we propose that hydromagnetic disk-driven winds may underlie the classification of broad-line and narrow-line AGNs (e.g., the Seyfert 1/Seyfert 2 dichotomy) as well as the apparent dearth of luminous Seyfert 2 galaxies. More generally, we demonstrate that such winds could strongly influence the spectral characteristics of Seyfert galaxies, QSOs, and BL Lac objects (BLOs). In our picture, the torus is identified with the outer regions of the wind where dust uplifted from the disk surfaces by gas-grain collisions is embedded in the outflow. Using an efficient radiative transfer code, we show that the infrared emission of Seyfert galaxies and QSOs can be attributed to the reprocessing of the UV/soft X-ray AGN continuum by the dust in the wind and the disk. We demonstrate that the radiation pressure force flattens the dust distribution in objects with comparatively high (but possibly sub-Eddington) bolometric luminosities, and we propose this as one likely reason for the apparent paucity of narrow-line objects among certain high-luminosity AGNs. Using the XSTAR photoionization code, we show that the inner regions of the wind could naturally account for the warm

  2. THE 1.6 {mu}m NEAR-INFRARED NUCLEI OF 3C RADIO GALAXIES: JETS, THERMAL EMISSION, OR SCATTERED LIGHT?

    SciTech Connect

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

    2010-12-20

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

  3. The incidence of nuclear activity in galaxy pairs with different morphologies (E+E), (E+S) and (S+S)

    NASA Astrophysics Data System (ADS)

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

    2016-06-01

    We analysed 385 Sloan Digital Sky Survey Data Release 7 (SDSS-DR7) galactic spectra that belong to the catalogue of isolated pairs of galaxies by Karachentsev. The spectra correspond to physical pairs of galaxies defined by a difference in velocity ≤1200 km s-1 and a pair separation ≤100 kpc. We study the incidence of nuclear activity, both star formation and non-thermal - active galactic nuclei (AGNs). After a careful extraction of the nuclear spectra, we use diagnostic diagrams and find that the incidence of AGNs is 48 per cent in emission line paired galaxies and 40 per cent for the total sample (as compared to ˜43 per cent and 41 per cent, respectively, in a sample of isolated galaxies). These results remain after dissecting the effects of morphological type and galactic stellar mass (with only a small, non significant, enhancement of the AGN fraction in galaxy pairs). These results suggest that weak interactions are not necessary and/or sufficient to trigger low-luminosity AGN. Since the fraction of AGN is predominant in early-type spiral galaxies, we conclude that the role of a bulge, and a large gas reservoir are both essential for the triggering of nuclear activity. The most striking result is that Type 1 nuclei are absent from the AGN sample. This result is in conflict with the Unified Model, and suggests that high accretion rates are essential to form the broad line region in active galaxies.

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

    NASA Astrophysics Data System (ADS)

    Mao, Jirong; Kim, Minsun

    2016-09-01

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

  5. Les galaxies

    NASA Astrophysics Data System (ADS)

    Combes, Francoise

    2016-08-01

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

  6. THE BLACK HOLE-BULGE MASS RELATION OF ACTIVE GALACTIC NUCLEI IN THE EXTENDED CHANDRA DEEP FIELD-SOUTH SURVEY

    SciTech Connect

    Schramm, Malte; Silverman, John D.

    2013-04-10

    We present results from a study to determine whether relations-established in the local universe-between the mass of supermassive black holes (SMBHs) and their host galaxies are in place at higher redshifts. We identify a well-constructed sample of 18 X-ray-selected, broad-line active galactic nuclei (AGNs) in the Extended Chandra Deep Field-South Survey with 0.5 < z < 1.2. This redshift range is chosen to ensure that Hubble Space Telescope (HST) imaging is available with at least two filters that bracket the 4000 A break, thus providing reliable stellar mass estimates of the host galaxy by accounting for both young and old stellar populations. We compute single-epoch, virial black hole (BH) masses from optical spectra using the broad Mg II emission line. For essentially all galaxies in our sample, their total stellar mass content agrees remarkably well, given their BH masses, with local relations of inactive galaxies and active SMBHs. We further decompose the total stellar mass into bulge and disk components separately with full knowledge of the HST point-spread function. We find that {approx}80% of the sample is consistent with the local M{sub BH}-M{sub *,{sub Bulge}} relation even with 72% of the host galaxies showing the presence of a disk. In particular, bulge-dominated hosts are more aligned with the local relation than those with prominent disks. We further discuss the possible physical mechanisms that are capable of building up the stellar mass of the bulge from an extended disk of stars over the subsequent 8 Gyr.

  7. The stellar populations of low-luminosity active galactic nuclei - III. Spatially resolved spectral properties

    NASA Astrophysics Data System (ADS)

    Cid Fernandes, R.; González Delgado, R. M.; Storchi-Bergmann, T.; Martins, L. Pires; Schmitt, H.

    2005-01-01

    In a recently completed survey of the stellar population properties of low-ionization nuclear emission-line regions (LINERs) and LINER/HII transition objects (TOs), we have identified a numerous class of galactic nuclei which stand out because of their conspicuous 108-9 yr populations, traced by high-order Balmer absorption lines and other stellar indices. These objects are called `young-TOs', because they all have TO-like emission-line ratios. In this paper we extend this previous work, which concentrated on the nuclear properties, by investigating the radial variations of spectral properties in low-luminosity active galactic nuclei (LLAGNs). Our analysis is based on high signal-to-noise ratio (S/N) long-slit spectra in the 3500-5500 Å interval for a sample of 47 galaxies. The data probe distances of typically up to 850 pc from the nucleus with a resolution of ~100 pc (~1 arcsec) and S/N ~ 30. Stellar population gradients are mapped by the radial profiles of absorption-line equivalent widths and continuum colours along the slit. These variations are further analysed by means of a decomposition of each spectrum in terms of template galaxies representative of very young (<=107 yr), intermediate age (108-9 yr) and old (1010 yr) stellar populations. This study reveals that young-TOs also differ from old-TOs and old-LINERs in terms of the spatial distributions of their stellar populations and dust. Specifically, our main findings are as follows. (i) Significant stellar population gradients are found almost exclusively in young-TOs. (ii) The intermediate age population of young-TOs, although heavily concentrated in the nucleus, reaches distances of up to a few hundred pc from the nucleus. Nevertheless, the half width at half-maximum of its brightness profile is more typically 100 pc or less. (iii) Objects with predominantly old stellar populations present spatially homogeneous spectra, be they LINERs or TOs. (iv) Young-TOs have much more dust in their central regions

  8. Active galactic nuclei emission line diagnostics and the mass-metallicity relation up to redshift z ∼ 2: The impact of selection effects and evolution

    SciTech Connect

    Juneau, Stéphanie; Bournaud, Frédéric; Daddi, Emanuele; Elbaz, David; Duc, Pierre-Alain; Gobat, Raphael; Jean-Baptiste, Ingrid; Le Floc'h, Émeric; Pannella, Maurilio; Schreiber, Corentin; Trump, Jonathan R.; Dickinson, Mark

    2014-06-10

    Emission line diagnostic diagrams probing the ionization sources in galaxies, such as the Baldwin-Phillips-Terlevich (BPT) diagram, have been used extensively to distinguish active galactic nuclei (AGN) from purely star-forming galaxies. However, they remain poorly understood at higher redshifts. We shed light on this issue with an empirical approach based on a z ∼ 0 reference sample built from ∼300,000 Sloan Digital Sky Survey galaxies, from which we mimic selection effects due to typical emission line detection limits at higher redshift. We combine this low-redshift reference sample with a simple prescription for luminosity evolution of the global galaxy population to predict the loci of high-redshift galaxies on the BPT and Mass-Excitation (MEx) diagnostic diagrams. The predicted bivariate distributions agree remarkably well with direct observations of galaxies out to z ∼ 1.5, including the observed stellar mass-metallicity (MZ) relation evolution. As a result, we infer that high-redshift star-forming galaxies are consistent with having normal interstellar medium (ISM) properties out to z ∼ 1.5, after accounting for selection effects and line luminosity evolution. Namely, their optical line ratios and gas-phase metallicities are comparable to that of low-redshift galaxies with equivalent emission-line luminosities. In contrast, AGN narrow-line regions may show a shift toward lower metallicities at higher redshift. While a physical evolution of the ISM conditions is not ruled out for purely star-forming galaxies and may be more important starting at z ≳ 2, we find that reliably quantifying this evolution is hindered by selections effects. The recipes provided here may serve as a basis for future studies toward this goal. Code to predict the loci of galaxies on the BPT and MEx diagnostic diagrams and the MZ relation as a function of emission line luminosity limits is made publicly available.

  9. The evolution of galaxy star formation activity in massive haloes

    NASA Astrophysics Data System (ADS)

    Popesso, P.; Biviano, A.; Finoguenov, A.; Wilman, D.; Salvato, M.; Magnelli, B.; Gruppioni, C.; Pozzi, F.; Rodighiero, G.; Ziparo, F.; Berta, S.; Elbaz, D.; Dickinson, M.; Lutz, D.; Altieri, B.; Aussel, H.; Cimatti, A.; Fadda, D.; Ilbert, O.; Le Floch, E.; Nordon, R.; Poglitsch, A.; Xu, C. K.

    2015-02-01

    Context. There is now a large consensus that the current epoch of the cosmic star formation history (CSFH) is dominated by low mass galaxies while the most active phase, between redshifts 1 and 2, is dominated by more massive galaxies, which evolve more quickly. Aims: Massive galaxies tend to inhabit very massive haloes, such as galaxy groups and clusters. We aim to understand whether the observed "galaxy downsizing" could be interpreted as a "halo downsizing", whereas the most massive haloes, and their galaxy populations, evolve more rapidly than the haloes with lower mass. Methods: We studied the contribution to the CSFH of galaxies inhabiting group-sized haloes. This is done through the study of the evolution of the infra-red (IR) luminosity function of group galaxies from redshift 0 to redshift ~1.6. We used a sample of 39 X-ray-selected groups in the Extended Chandra Deep Field South (ECDFS), the Chandra Deep Field North (CDFN), and the COSMOS field, where the deepest available mid- and far-IR surveys have been conducted with Spitzer MIPS and with the Photodetector Array Camera and Spectrometer (PACS) on board the Herschel satellite. Results: Groups at low redshift lack the brightest, rarest, and most star forming IR-emitting galaxies observed in the field. Their IR-emitting galaxies contribute ≤10% of the comoving volume density of the whole IR galaxy population in the local Universe. At redshift ≳1, the most IR-luminous galaxies (LIRGs and ULIRGs) are mainly located in groups, and this is consistent with a reversal of the star formation rate (SFR) vs. density anti-correlation observed in the nearby Universe. At these redshifts, group galaxies contribute 60-80% of the CSFH, i.e. much more than at lower redshifts. Below z ~ 1, the comoving number and SFR densities of IR-emitting galaxies in groups decline significantly faster than those of all IR-emitting galaxies. Conclusions: Our results are consistent with a "halo downsizing" scenario and highlight the

  10. DWARF GALAXIES WITH OPTICAL SIGNATURES OF ACTIVE MASSIVE BLACK HOLES

    SciTech Connect

    Reines, Amy E.; Greene, Jenny E.; Geha, Marla

    2013-10-01

    We present a sample of 151 dwarf galaxies (10{sup 8.5} ∼< M{sub *} ∼< 10{sup 9.5} M{sub ☉}) that exhibit optical spectroscopic signatures of accreting massive black holes (BHs), increasing the number of known active galaxies in this stellar-mass range by more than an order of magnitude. Utilizing data from the Sloan Digital Sky Survey Data Release 8 and stellar masses from the NASA-Sloan Atlas, we have systematically searched for active BHs in ∼25,000 emission-line galaxies with stellar masses comparable to the Magellanic Clouds and redshifts z < 0.055. Using the narrow-line [O III]/Hβ versus [N II]/Hα diagnostic diagram, we find photoionization signatures of BH accretion in 136 galaxies, a small fraction of which also exhibit broad Hα emission. For these broad-line active galactic nucleus (AGN) candidates, we estimate BH masses using standard virial techniques and find a range of 10{sup 5} ∼< M{sub BH} ∼< 10{sup 6} M{sub ☉} and a median of M{sub BH} ∼ 2 × 10{sup 5} M{sub ☉}. We also detect broad Hα in 15 galaxies that have narrow-line ratios consistent with star-forming galaxies. Follow-up observations are required to determine if these are true type 1 AGN or if the broad Hα is from stellar processes. The median absolute magnitude of the host galaxies in our active sample is M{sub g} = –18.1 mag, which is ∼1-2 mag fainter than previous samples of AGN hosts with low-mass BHs. This work constrains the smallest galaxies that can form a massive BH, with implications for BH feedback in low-mass galaxies and the origin of the first supermassive BH seeds.

  11. 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.

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

    NASA Technical Reports Server (NTRS)

    Halpern, Jules; Chen, Kaiyou

    1999-01-01

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

  13. 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.

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

    SciTech Connect

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

    2012-03-01

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

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

    NASA Technical Reports Server (NTRS)

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

    1994-01-01

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

  16. Broad Hβ Emission-line Variability in a Sample of 102 Local Active Galaxies

    NASA Astrophysics Data System (ADS)

    Runco, Jordan N.; Cosens, Maren; Bennert, Vardha N.; Scott, Bryan; Komossa, S.; Malkan, Matthew A.; Lazarova, Mariana S.; Auger, Matthew W.; Treu, Tommaso; Park, Daeseong

    2016-04-01

    A sample of 102 local (0.02 ≤ z ≤ 0.1) Seyfert galaxies with black hole masses MBH > 107M⊙ was selected from the Sloan Digital Sky Survey (SDSS) and observed using the Keck 10 m telescope to study the scaling relations between MBH and host galaxy properties. We study profile changes of the broad Hβ emission line within the three to nine year time frame between the two sets of spectra. The variability of the broad Hβ emission line is of particular interest, not only because it is used to estimate MBH, but also because its strength and width are used to classify Seyfert galaxies into different types. At least some form of broad-line variability (in either width or flux) is observed in the majority (∼66%) of the objects, resulting in a Seyfert-type change for ∼38% of the objects, likely driven by variable accretion and/or obscuration. The broad Hβ line virtually disappears in 3/102 (∼3%) extreme cases. We discuss potential causes for these changing look active galactic nuclei. While similar dramatic transitions have previously been reported in the literature, either on a case-by-case basis or in larger samples focusing on quasars at higher redshifts, our study provides statistical information on the frequency of Hβ line variability in a sample of low-redshift Seyfert galaxies.

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

    SciTech Connect

    Toba, Y.; Matsuhara, H.; Oyabu, S.; Malkan, M. A.; Gandhi, P.; Nakagawa, T.; Isobe, N.; Shirahata, M.; Oi, N.; Takita, S.; Yano, K.; Ohyama, Y.; Yamauchi, C.

    2014-06-10

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

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

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

  19. 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.

  20. 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.

  1. The systematic search for z ≳ 5 active galactic nuclei in the Chandra Deep Field South

    NASA Astrophysics Data System (ADS)

    Weigel, Anna K.; Schawinski, Kevin; Treister, Ezequiel; Urry, C. Megan; Koss, Michael; Trakhtenbrot, Benny

    2015-04-01

    We investigate early black hole (BH) growth through the methodical search for z ≳ 5 active galactic nuclei (AGN) in the Chandra Deep Field South. We base our search on the Chandra 4-Ms data with flux limits of 9.1 × 10-18 (soft, 0.5-2 keV) and 5.5 × 10-17 erg s-1 cm-2 (hard, 2-8 keV). At z ˜ 5, this corresponds to luminosities as low as ˜1042 (˜1043) erg s-1 in the soft (hard) band and should allow us to detect Compton-thin AGN with MBH > 107 M⊙ and Eddington ratios >0.1. Our field (0.03 deg2) contains over 600z ˜ 5 Lyman Break Galaxies. Based on lower redshift relations, we would expect ˜20 of them to host AGN. After combining the Chandra data with Great Observatories Origins Deep Survey (GOODS)/Advanced Camera for Surveys (ACS), CANDELS/Wide Field Camera 3 and Spitzer/Infrared Array Camera data, the sample consists of 58 high-redshift candidates. We run a photometric redshift code, stack the GOODS/ACS data, apply colour criteria and the Lyman Break Technique and use the X-ray Hardness Ratio. We combine our tests and using additional data find that all sources are most likely at low redshift. We also find five X-ray sources without a counterpart in the optical or infrared which might be spurious detections. We conclude that our field does not contain any convincing z ≳ 5 AGN. Explanations for this result include a low BH occupation fraction, a low AGN fraction, short, super-Eddington growth modes, BH growth through BH-BH mergers or in optically faint galaxies. By searching for z ≳ 5 AGN, we are setting the foundation for constraining early BH growth and seed formation scenarios.

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

    SciTech Connect

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

    2011-03-15

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

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

    NASA Technical Reports Server (NTRS)

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

    2010-01-01

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

  4. Spin orientation of supermassive black holes in active galaxies

    NASA Astrophysics Data System (ADS)

    Kollatschny, W.

    2003-12-01

    Accretion of gas onto a central supermassive black hole is generally accepted to be the source of the emitted energy in active galactic nuclei. The broad emission lines we observe in their optical spectra are probably formed in the wind of an accretion disk at distances of light days to light years from the central black hole. The variable fraction of the emission lines originates at typical distances of only 1 to 50 light days from the central supermassive black hole. We derived a central black hole mass of Morbital1.8+/- 0.4x 107 Msun in the Seyfert galaxy Mrk 110 assuming the broad emission lines are generated in gas clouds orbiting within an accretion disk. This figure depends on the inclination angle of the accretion disk. Here we report on the detection of gravitational redshifted emission in the variable fraction of the broad emission lines. We derive a central black hole mass of Mgrav=14.0+/- 3.0x 107 Msun. These measurements are independent on the orientation of the accretion disk. The comparison of both black hole mass estimates allows to determine the projection of the central accretion disk angle i to 21+/-5 deg in Mrk 110 and therefore the orientation of the spin axis of the central black hole. Based on observations obtained with the Hobby-Eberly Telescope, which is a joint project of the University of Texas at Austin, the Pennsylvania State University, Stanford University, Ludwig-Maximilians-Universität München, and Georg-August-Universität Göttingen. This paper is dedicated to Frank Bash without whose efforts the Hobby-Eberly Telescope would not have been possible.

  5. Variability Selected Low-Luminosity Active Galactic Nuclei in the 4 Ms Chandra Deep Field-South

    NASA Technical Reports Server (NTRS)

    Young, M.; Brandt, W. N.; Xue, Y. Q.; Paolillo, D. M.; Alexander, F. E.; Bauer, F. E.; Lehmer, B. D.; Luo, B.; Shemmer, O.; Schneider, D. P.; Vignail, C.

    2012-01-01

    The 4 Ms Chandra Deep Field-South (CDF-S) and other deep X-ray surveys have been highly effective at selecting active galactic nuclei (AGN). However, cosmologically distant low-luminosity AGN (LLAGN) have remained a challenge to identify due to significant contribution from the host galaxy. We identify long-term X ray variability (approx. month years, observed frame) in 20 of 92 CDF-S galaxies spanning redshifts approx equals 00.8 - 1.02 that do not meet other AGN selection criteria. We show that the observed variability cannot be explained by X-ray binary populations or ultraluminous X-ray sources, so the variability is most likely caused by accretion onto a supermassive black hole. The variable galaxies are not heavily obscured in general, with a stacked effective power-law photon index of Gamma(sub Stack) approx equals 1.93 +/- 0.13, and arc therefore likely LLAGN. The LLAGN tend to lie it factor of approx equal 6-89 below the extrapolated linear variability-luminosity relation measured for luminous AGN. This may he explained by their lower accretion rates. Variability-independent black-hole mass and accretion-rate estimates for variable galaxies show that they sample a significantly different black hole mass-accretion-rate space, with masses a factor of 2.4 lower and accretion rates a factor of 22.5 lower than variable luminous AGNs at the same redshift. We find that an empirical model based on a universal broken power-law power spectral density function, where the break frequency depends on SMBH mass and accretion rate, roughly reproduces the shape, but not the normalization, of the variability-luminosity trends measured for variable galaxies and more luminous AGNs.

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

    NASA Astrophysics Data System (ADS)

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

    2016-03-01

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

  7. Active targets for the study of nuclei far from stability

    NASA Astrophysics Data System (ADS)

    Beceiro-Novo, S.; Ahn, T.; Bazin, D.; Mittig, W.

    2015-09-01

    Weakly bound nuclear systems can be considered to represent a good testing-ground of our understanding of non-perturbative quantum systems. Reactions leading to bound and unbound states in systems with very unbalanced neutron-to-proton ratios are used to understand the properties of these systems. Radioactive beams with energies from below the Coulomb barrier up to several hundreds MeV/nucleon are now available, and with these beams, a broad variety of studies of nuclei near the drip-line can be performed. To compensate for the low intensity of secondary beams as compared to primary beams, thick targets and high efficiency detection is necessary. In this context, a new generation of detectors was developed, called active target detectors: the detector gas is used as target, and the determination of the reaction vertex in three dimensions allows for good resolution even with thick targets. The reaction products can be measured over essentially 4 π. The physics explored with these detectors together with the technology developed will be described.

  8. 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.

  9. 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).

  10. Accretion disks and periodic outbursts of active galactic nuclei

    NASA Technical Reports Server (NTRS)

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

    1986-01-01

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

  11. Fermi Observations of TeV-Selected Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

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

    2009-12-01

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

  12. 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.

  13. Velocity dispersions in galaxies. V - The nuclei of M31 and M32

    NASA Technical Reports Server (NTRS)

    Morton, D. C.; Elmergreen, B. G.

    1976-01-01

    Stigmatic spectra between 4160 and 4385 A of the central regions of M31 and M32 as well as the K0 III star 51 Ori are presented which were obtained using a SEC-vidicon integrating television tube and the coude spectrograph of the Hale telescope. Line-of-sight velocity dispersions of approximately 130 and 55 km/s are determined for the nuclei of M31 and M32, respectively, by directly comparing their spectra with Gaussian-broadened spectra of 51 Ori. The analytical techniques are outlined, and alternative methods for estimating velocity dispersions are evaluated, including least-squares fitting of intensities and division of Fourier transforms. It is noted that the broadened spectrum of 51 Ori fits the nucleus of M32 and the bulge of M31 much better than the nucleus of M31 in the region between 4180 and 4370 A.

  14. Spatial Correlation Function of the Chandra Selected Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Yang, Y.; Mushotzky, R. F.; Barger, A. J.; Cowie, L. L.

    2006-01-01

    two groups. We have also found that the correlation between X-ray luminosity and clustering amplitude is weak, which, however, is fully consistent with the expectation using the simplest relations between X-ray luminosity, black hole mass, and dark halo mass. We study the evolution of the AGN clustering by dividing the samples into 4 redshift bins over 0.1 Mpc< z <3.0 Mpc. We find a very mild evolution in the clustering amplitude, which show the same evolution trend found in optically selected quasars in the 2dF survey. We estimate the evolution of the bias, and find that the bias increases rapidly with redshift (b(z = 0.45) = 0.95 +/- 0.15 and b(z = 2.07) = 3.03 +/- 0.83): The typical mass of the dark matter halo derived from the bias estimates show little change with redshift. The average halo mass is found to be log (M(sub halo)/M(sun))approximates 12.1. Subject headings: cosmology: observations - large-scale structure of the universe - x-rays: diffuse background - galaxies: nuclei

  15. Byurakan-IRAS galaxies as massive galaxies with nuclear and starburst activity

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.; Harutyunyan, Gohar S.

    2013-07-01

    Byurakan-IRAS Galaxies (BIG) (Mickaelian 1995) are the result of optical identifications of IRAS PSC sources at high-galactic latitudes using the First Byurakan Survey (FBS) low-dispersion spectra (Markarian et al. 1989). Among the 1577 targets, 1178 galaxies have been identified. Most are dusty spiral galaxies and there is a number of ULIRGs among these objects. Our spectroscopic observations, carried out with three telescopes (Byurakan Astrophysical Observatory 2.6m, Russian Special Astrophysical Observatory 6m and Observatoire de Haute Provence 1.93m; Mickaelian & Sargsyan 2010), for 172 galaxies, as well as the SDSS DR8 spectra for 83 galaxies make up the list of 255 spectroscopically studied BIG objects. The classification regarding activity type for narrow-line emission galaxies has been carried out using the diagnostic diagrams by Veilleux & Osterbrock (1987). All possible physical characteristics have been measured and/or calculated, including radial velocities and distances, angular and physical sizes, absolute magnitudes and luminosities (both optical and IR). IR luminosities and star-formation rates have been calculated from the IR fluxes (Duc et al. 1997).

  16. Far-infrared activity and starburst galaxies

    NASA Technical Reports Server (NTRS)

    Belfort, P.; Mochkovitch, R.; Dennefeld, M.

    1987-01-01

    After the IRAS discovery of galaxies with large far-infrared to blue luminosity ratio, it has been proposed that an enhanced star formation could be the origin of the far-infrared emission through dust heating. Whether a simple photometric model is able to account for the FIR and optical properties of IRAS galaxies was investigated. The L sub IR/L sub B ratio, (B-V) color and H sub alpha equivalent width of normal spirals are well reproduced with smooth star formation histories. In the case of starburst galaxies, several theoretical diagrams allow us to estimate the burst strength and extinction. L sub IR/L sub B ratio up to 100 can be rather easily reached, whereas extreme values probably require IMF truncated at the low end.

  17. Gravitational-wave bursts from the nuclei of distant galaxies and quasars: Proposal for detection using Doppler tracking of interplanetary spacecraft

    NASA Technical Reports Server (NTRS)

    Thorne, K. S.; Braginsky, V. B.

    1974-01-01

    Supermassive black holes which exist in the nuclei of many quasars and galaxies are examined along with the collapse which forms these holes and subsequent collisions between them which produce strong, broad-band bursts of gravitational waves. Such bursts might arrive at earth as often as 50 times per year--or as rarely as once each 300 years. The detection of such bursts with dual-frequency Doppler tracking of interplanetary spacecraft is considered.

  18. The effect of suprathermal protons on the physical conditions in Seyfert galaxy nuclei II

    NASA Technical Reports Server (NTRS)

    Stoner, R.; Ptak, R.

    1975-01-01

    The radiative transfer of Ly-alpha, Ly-beta, and H-alpha in a hydrogen gas containing dust was considered with application to the nuclear gas in Seyfert galaxies. By neglecting the direct escape of line radiation and by averaging over the gas, the radiation transfer in space is suppressed and the frequency transfer only is considered. The dust degrades the line radiation via frequency-independent absorption, converting the energy to infrared luminosity. The source functions in the lines were solved, using appropriate approximations, in order to determine under what conditions the narrow component of the Balmer line radiation from the gas can be self-absorbed and degraded without similar degradation of the broad component, which originates from the suprathermals themselves. The results are used to find self-consistent values for the temperature and ionization of the gas for various amounts of dust and various concentrations of suprathermal particles.

  19. The effect of suprathermal protons on the physical conditions in Seyfert galaxy nuclei

    NASA Technical Reports Server (NTRS)

    Ptak, R.; Stoner, R.

    1974-01-01

    The physical conditions in a high density hydrogen gas heated and ionized by suprathermal protons were investigated, with application to the gas in the nuclear region of Seyfert galaxies. The gas is assumed optically thick to Lyman and Balmer line radiation. Mechanisms by which the radiation from the gas can balance the heating by the fast protons were investigated, and minimum values for the mass of gas were estimated. Under certain conditions, the suprathermal atoms themselves can cool the ambient gas by rescattering the line radiation into the optically thin region in the wings of the line. This mechanism, called optical reverberation, can enhance the broad component of the hydrogen lines produced by inelastic atomic collisions and yield line widths consistent with those observed in Seyfert and quasar spectra. Also discussed is the possibility of achieving dynamic equilibrium of the ambient gas by balancing the momentum transfer from the suprathermals with gravitational attraction of a massive central source.

  20. An Initial Investigation of Active Galaxies in RESOLVE and ECO

    NASA Astrophysics Data System (ADS)

    Norman, Dara J.; Kannappan, Sheila; Bittner, Ashley; Yarber, Aara'L.; Hoversten, Erik A.; Stark, David; RESOLVE Team

    2016-01-01

    The volume-limited REsolved Spectroscopy Of a Local VolumE (RESOLVE) survey and its complementary Environmental COntext (ECO) catalog are dominated by low mass, gas-rich galaxies, as is typical of the bulk of large-scale structure in the local universe. These surveys, therefore, provide an excellent opportunity to investigate the complete large-scale environments of low-redshift AGN and nuclear starbursts in such galaxies, in order to search for external triggering, examine activity in relation to gas supply, and investigate the role of feedback. By data-mining multi-wavelength catalogs that use varied techniques, we identify known AGN in RESOLVE and ECO, including a population of gas-dominated low-mass galaxies. We take advantage of these surveys' multi-wavelength supporting data to investigate triggering, feedback, and the roles of environment and gas supply in this initial sample of active galaxies. Because biases in standard AGN candidate selection techniques (e.g. BPT, X-ray luminosity) make them individually poor selectors of AGN activity in star-forming and low mass (<10^10 Msun) host galaxies, we also seek to improve the identification of nuclear activity in such galaxies via combined analysis of star formation and AGN signatures. RESOLVE is supported by NSF grant AST-0955368

  1. 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.

  2. X-ray spectra and time variability of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.

    1984-01-01

    The X-ray spectra of broad line active galactic nuclei (AGN) of all types (Seyfert I's, NELG's, broadline radio galaxies) are well fit by a power law in the .5 to 100 keV band of man energy slope alpha = .68 + or - .15. There is, as yet, no strong evidence for time variability of this slope in a given object. The constraints that this places on simple models of the central energy source are discussed. BL Lac objects have quite different X-ray spectral properties and show pronounced X-ray spectral variability. On time scales longer than 12 hours most radio quiet AGN do not show strong, delta I/I .5, variability. The probability of variability of these AGN seems to be inversely related to their luminosity. However characteristics timescales for variability have not been measured for many objects. This general lack of variability may imply that most AGN are well below the Eddington limit. Radio bright AGN tend to be more variable than radio quiet AGN on long, tau approx 6 month, timescales.

  3. ACTIVE GALACTIC NUCLEI SELECTED FROM GALEX SPECTROSCOPY: THE IONIZING SOURCE SPECTRUM AT z {approx} 1 ,

    SciTech Connect

    Barger, Amy J.; Cowie, Lennox L. E-mail: cowie@ifa.hawaii.ed

    2010-08-01

    We use a complete sample of Ly{alpha}-emission-line-selected active galactic nuclei (AGNs) obtained from nine deep blank fields observed with the grism spectrographs on the Galaxy Evolution Explorer (GALEX) satellite to measure the normalization and the spectral shape of the AGN contribution to the ionizing background (rest-frame wavelengths 700-900 A) at z {approx} 1. Our sample consists of 139 sources selected in the redshift range z = 0.65-1.25 in the near-ultraviolet (NUV; 2371 A central wavelength) channel. The area covered is 8.2 deg{sup 2} to a NUV magnitude of 20.5 (AB) and 0.92 deg{sup 2} at the faintest magnitude limit of 21.8. The GALEX AGN luminosity function agrees well with those obtained using optical and X-ray AGN samples, and the measured redshift evolution of the ionizing volume emissivity is similar to that previously obtained by measuring the GALEX far-ultraviolet (FUV; 1528 A central wavelength) magnitudes of an X-ray-selected sample. For the first time, we are able to construct the shape of the ionizing background at z {approx} 1 in a fully self-consistent way.

  4. The standard model and some new directions. [for scientific theory of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Blandford, R. D.; Rees, M. J.

    1992-01-01

    A 'standard' model of Active Galactic Nuclei (AGN), based upon a massive black hole surrounded by a thin accretion disk, is defined. It is argued that, although there is good evidence for the presence of black holes and orbiting gas, most of the details of this model are either inadequate or controversial. Magnetic field may be responsible for the confinement of continuum and line-emitting gas, for the dynamical evolution of accretion disks and for the formation of jets. It is further argued that gaseous fuel is supplied in molecular form and that this is responsible for thermal re-radiation, equatorial obscuration and, perhaps, the broad line gas clouds. Stars may also supply gas close to the black hole, especially in low power AGN and they may be observable in discrete orbits as probes of the gravitational field. Recent observations suggest that magnetic field, stars, dusty molecular gas and orientation effects must be essential components of a complete description of AGN. The discovery of quasars with redshifts approaching 5 is an important clue to the mechanism of galaxy formation.

  5. Long Term Optical and Infrared Reverberation Mapping of High and Low Luminosity Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Gorjian, Varoujan; Barth, Aaron; Brandt, Niel; Dawson, Kyle; Green, Paul; Ho, Luis; Horne, Keith; Jiang, Linhua; Joner, Mike; Kenney, John; McGreer, Ian; Nordgren, Tyler; Schneider, Donald; Shen, Yue; Tao, Charling

    2016-08-01

    Previous Spitzer reverberation monitoring projects looking for UV/optical light absorbed and re-emitted in the IR by dust have been limited to very low luminosity active galactic nuclei (AGN) that could potentially show reverberation within a single cycle (~1 year). Cycle 11-12's two year baseline allowed for the reverberation mapping of 17 high luminosity quasars from the Sloan Digital Sky Survey Reverberation Mapping project. By combining ground based monitoring from Pan-STARRS, CFHT, and Steward Observatory telescopes with Spitzer data we have for the first time detected dust reverberation in quasars. We propose to continue this project to capitalize on the continuing optical motnoring from the ground and to increase the confidence in the detected lags. Additionally, the Call for Proposals asks for up to 1000 hours of observations in the Spitzer CVZ to accommodate battery charging needs. We propose to add to our quasar sample five lower luminosity Seyfert galaxies from the Pan-STARRS ground based optical survey that are in the Spitzer CVZ, which will increase the luminosity range of AGN we are studying and, combined with additional ground based observatories, provide for a continuous monitoring campaign lasting 2 years and thus provide the most detailed study of dust around AGN to date.

  6. A Simple test for the existence of two accretion modes in active galactic nuclei

    SciTech Connect

    Jester, Sebastian; /Fermilab

    2005-02-01

    By analogy to the different accretion states observed in black-hole X-ray binaries (BHXBs), it appears plausible that accretion disks in active galactic nuclei (AGN) undergo a state transition between a radiatively efficient and inefficient accretion flow. If the radiative efficiency changes at some critical accretion rate, there will be a change in the distribution of black hole masses and bolometric luminosities at the corresponding transition luminosity. To test this prediction, the author considers the joint distribution of AGN black hole masses and bolometric luminosities for a sample taken from the literature. The small number of objects with low Eddington-scaled accretion rates m < 0.01 and black hole masses M{sub BH} < 10{sup 9} M{sub {circle_dot}} constitutes tentative evidence for the existence of such a transition in AGN. Selection effects, in particular those associated with flux-limited samples, systematically exclude objects in particular regions of the (M{sub BH}, L{sub bol}) plane. Therefore, they require particular attention in the analysis of distributions of black hole mass, bolometric luminosity, and derived quantities like the accretion rate. The author suggests further observational tests of the BHXB-AGN unification scheme which are based on the jet domination of the energy output of BHXBs in the hard state, and on the possible equivalence of BHXB in the very high (or steep power-law) state showing ejections and efficiently accreting quasars and radio galaxies with powerful radio jets.

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

    SciTech Connect

    Dermer, C.D.

    1989-11-01

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

  8. The Case for Standard Irradiated Accretion Disks in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Chelouche, Doron

    2013-07-01

    We analyze the broadband photometric light curves of Seyfert 1 galaxies from the Sergeev et al. sample and find that (1) perturbations propagating across the continuum emitting region are a general phenomenon securely detected in most cases, (2) it is possible to obtain reliable time delays between continuum emission in different wavebands, which are not biased by the contribution of broad emission lines to the signal, and (3) such lags are consistent with the predictions of standard irradiated accretion disk models, given the optical luminosity of the sources. These findings provide new and independent support for standard accretion disks being responsible for the bulk of the (rest) optical emission in low-luminosity active galactic nuclei (AGNs). We interpret our lag measurements in individual objects within the framework of this model and estimate the typical mass accretion rate to be <~ 0.1 M ⊙ yr&-1, with little dependence on the black hole mass. Assuming bolometric corrections typical of type I sources, we find tentative evidence for the radiative efficiency of accretion flows being a rising function of the black hole mass. With upcoming surveys that will regularly monitor the sky, we may be able to better quantify possible departures from standard self-similar models, and identify other modes of accretion in AGNs.

  9. 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.

  10. Low-mass Active Galactic Nuclei with Rapid X-Ray Variability

    NASA Astrophysics Data System (ADS)

    Ho, Luis C.; Kim, Minjin

    2016-04-01

    We present a detailed study of the optical spectroscopic properties of 12 active galactic nuclei (AGNs) with candidate low-mass black holes (BHs) selected by Kamizasa et al. through rapid X-ray variability. The high-quality, echellette Magellan spectra reveal broad Hα emission in all the sources, allowing us to estimate robust virial BH masses and Eddington ratios for this unique sample. We confirm that the sample contains low-mass BHs accreting at high rates: the median MBH = 1.2 × 106 M⊙ and median Lbol/LEdd = 0.44. The sample follows the MBH–σ* relation, within the considerable scatter typical of pseudobulges, the probable hosts of these low-mass AGNs. Various lines of evidence suggest that ongoing star formation is prevalent in these systems. We propose a new strategy to estimate star formation rates in AGNs hosted by low-mass, low-metallicity galaxies, based on modification of an existing method using the strength of [O ii] λ3727, [O iii] λ5007, and X-rays.

  11. 21 cm absorption by compact hydrogen discs around black holes in radio-loud nuclei of galaxies

    SciTech Connect

    Loeb, Abraham

    2008-05-15

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

  12. A TALE OF TWO POPULATIONS: THE CONTRIBUTION OF MERGER AND SECULAR PROCESSES TO THE EVOLUTION OF ACTIVE GALACTIC NUCLEI

    SciTech Connect

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

    2012-05-20

    Due to the co-evolution of supermassive black holes and their host galaxies, understanding the mechanisms that trigger active galactic nuclei (AGNs) is imperative to understanding galaxy evolution and the formation of massive galaxies. It is observationally difficult to determine the trigger of a given AGN due to the difference between the AGN lifetime and triggering timescales. Here, we utilize AGN population synthesis modeling to determine the importance of different AGN triggering mechanisms. An AGN population model is computed by combining an observationally motivated AGN triggering rate and a theoretical AGN light curve. The free parameters of the AGN light curve are constrained by minimizing a {chi}{sup 2} test with respect to the observed AGN hard X-ray luminosity function. The observed black hole space density, AGN number counts, and X-ray background spectrum are also considered as observational constraints. It is found that major mergers are not able to account for the entire AGN population. Therefore, non-merger processes, such as secular mechanisms, must also trigger AGNs. Indeed, non-merger processes are the dominant AGN triggering mechanism at z {approx}< 1-1.5. Furthermore, the shape and evolution of the black hole mass function of AGNs triggered by major mergers are intrinsically different from the shape and evolution of the black hole mass function of AGNs triggered by secular processes.

  13. A Census of Star Formation and Active Galactic Nuclei Populations in Abell 1689

    NASA Astrophysics Data System (ADS)

    Jones, Logan H.; Atlee, David Wesley

    2016-01-01

    A recent survey of low-z galaxy clusters observed a disjunction between X-ray and mid-infrared selected populations of active galactic nuclei (X-ray and IR AGNs) (Atlee+ 2011, ApJ 729, 22.). Here we present an analysis of near-infrared spectroscopic data of star-forming galaxies in cluster Abell 1689 in order to confirm the identity of some of their IR AGN and to provide a check on their reported star formation rates. Our sample consists of 24 objects in Abell 1689. H and K band spectroscopic observations of target objects and standard stars were obtained by David Atlee between 2010 May 17 and 2011 June 6 using the Large Binocular Telescope's LUCI instrument. After undergoing initial reductions, standard stars were corrected for telluric absorption using TelFit (Gullikson+ 2014, AJ, 158, 53). Raw detector counts were converted to physical units using the wavelength-dependent response of the grating and the star's reported H and K band magnitudes to produce conversion factors that fully correct for instrumental effects. Target spectra were flux-calibrated using the airmass-corrected transmission profiles produced by TelFit and the associated H band conversion factor (or the average of the two factors, for nights with two standard stars). Star formation rates were calculated using the SFR-L(Ha) relation reported in Kennicutt (1998), with the measured luminosity of the Pa-a emission line at the luminosity distance of the cluster used as a proxy for L(Ha) (Kennicutt 1998, ARA&A 36, 189; Hummer & Stoney 1987, MNRAS 346, 1055). The line ratios H2 2.121 mm/Brg and [FeII]/Pab were used to classify targets as starburst galaxies, AGNs, or LINERs (Rodriguez-Ardila+ 2005, MNRAS, 364, 1041). Jones was supported by the NOAO/KPNO Research Experience for Undergraduates (REU) Program, which is funded by the National Science Foundation Research Experiences for Undergraduates Program (AST-1262829).

  14. Dust in the nuclei of the Seyfert galaxies Markarian 231 and NGC 4151

    SciTech Connect

    Jones, B.; Worrall, D.M.; Rodriguez-Espinosa, J.M.; Stein, W.A.

    1984-09-01

    Observations carried out with a 8-13 micron grating-spectrometer of Mrk 231 and NGC 4151 are reported. The Mrk 231 data can be fitted to various thermal dust emission models or a single power law, with dust extinction. In all the model fits, except for that of graphite and silicon carbide grain emission, a component of silicate absorption of optical depth of not more than 0.7 is required. Confirming published work, the absorption being at the redshift of the low-redshift absorption-line system is ruled out. The high values of silicate optical depth absorption do not give ratios to the galaxy's visual extinction which are comparable to those of galactic H II regions. Weak evidence for a 10-micron absorption feature in NGC 4151 is also reported. This is somewhat contrary to expectation, since the visual extinction of NGC 4151 is lower than that of Mrk 231, and since there is evidence to support a nonthermal rather than thermal dust origin for the infrared continuum emission. 46 references.

  15. 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

  16. The AMIGA sample of isolated galaxies. XI. Optical characterisation of nuclear activity

    NASA Astrophysics Data System (ADS)

    Sabater, J.; Verdes-Montenegro, L.; Leon, S.; Best, P.; Sulentic, J.

    2012-09-01

    Context. This paper is part of a series involving the AMIGA project (Analysis of the Interstellar Medium of Isolated GAlaxies), which identifies and studies a statistically significant sample of the most isolated galaxies in the northern sky. Aims: We present a catalogue of nuclear activity, traced by optical emission lines, in a well-defined sample of the most isolated galaxies in the local Universe, which will be used as a basis for studying the effect of the environment on nuclear activity. Methods: We obtained spectral data from the 6th Data Release of the Sloan Digital Sky Survey, which were inspected in a semi-automatic way. We subtracted the underlying stellar populations from the spectra (using the software Starlight) and modelled the nuclear emission features. Standard emission-line diagnostics diagrams were applied, using a new classification scheme that takes into account censored data, to classify the type of nuclear emission. Results: We provide a final catalogue of spectroscopic data, stellar populations, emission lines and classification of optical nuclear activity for AMIGA galaxies. The prevalence of optical active galactic nuclei (AGN) in AMIGA galaxies is 20.4%, or 36.7% including transition objects. The fraction of AGN increases steeply towards earlier morphological types and higher luminosities. We compare these results with a matched analysis of galaxies in isolated denser environments (Hickson Compact Groups). After correcting for the effects of the morphology and luminosity, we find that there is no evidence for a difference in the prevalence of AGN between isolated and compact group galaxies, and we discuss the implications of this result. Conclusions: We find that a major interaction is not a necessary condition for the triggering of optical AGN. Full Tables 1-7 and A.1-A.3 are only available in electronic form at http://amiga.iaa.es/ and at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc

  17. 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.

  18. The dust covering factor in active galactic nuclei

    NASA Astrophysics Data System (ADS)

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

    2016-05-01

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

  19. Fractionation of nuclei from brain by zonal centrifugation and a study of the ribonucleic acid polymerase activity in the various classes of nuclei

    PubMed Central

    Austoker, J.; Cox, D.; Mathias, A. P.

    1972-01-01

    1. The nuclei of the cells of the whole rat brain have been fractionated in a B-XIV zonal rotor with a discontinuous gradient of sucrose. Five fractions were obtained. Zone (I) contained neuronal nuclei (70%) and astrocytic nuclei (23%). Zone (II) contained astrocytic nuclei (81%) and neuronal nuclei (15%). Zone (III) contained astrocytic nuclei (84%) and oligodendrocytic nuclei (15%). Zone (IV) contained oligodendrocytic nuclei (92%) and zone (V) contained only oligodendrocytic nuclei. 2. The content of DNA, RNA and protein per nucleus was determined for each zone. Although the amount of DNA per nucleus is constant (7pg) the RNA varies from 4.5 to 2.5pg/nucleus and the protein from 38 to 17.6pg/nucleus. The neuronal nuclei have the greatest amounts of protein. The oligodendrocytic nuclei have the least content of RNA and protein. 3. The effects of pH, ionic strength, and Mg2+ and Mn2+ concentration on the activity of the nuclear system for synthesis in vitro of RNA have been investigated for unfractionated nuclei. From these studies a standard set of conditions for the assay of nuclear RNA polymerase has been established. 4. The activity of the RNA polymerase in each of the zonal fractions has been determined in the presence and in the absence of α-amanitin. Zone (II) is the most active, followed by zone (I). The nuclei of zones (IV) and (V) have comparable activity, which is 40% of that of zone (II). 5. The extent of incorporation of each of the four labelled nucleoside triphosphates by the nuclei from each zone has been measured. These values have been used to calculate the base composition of the RNA synthesized in vitro in each class of nucleus. 6. The effect of changes in the condition of assay of RNA polymerase in the different classes of nuclei has been investigated. Significant differences in the response to concentrations of metal ions and ammonium sulphate have been observed. 7. Homopolymer formation in each zone of brain nuclei has been determined. The

  20. Growth and activity of black holes in galaxy mergers with varying mass ratios

    NASA Astrophysics Data System (ADS)

    Capelo, Pedro R.; Volonteri, Marta; Dotti, Massimo; Bellovary, Jillian M.; Mayer, Lucio; Governato, Fabio

    2015-03-01

    We study supermassive black holes (BHs) in merging galaxies, using a suite of hydrodynamical simulations with very high spatial (˜10 pc) and temporal (˜1 Myr) resolution, where we vary the initial mass ratio, the orbital configuration, and the gas fraction. (i) We address the question of when and why, during a merger, increased BH accretion occurs, quantifying gas inflows and BH accretion rates. (ii) We also quantify the relative effectiveness in inducing active galactic nuclei activity of merger-related versus secular-related causes, by studying different stages of the encounter: the stochastic (or early) stage, the (proper) merger stage, and the remnant (or late) stage. (iii) We assess which galaxy mergers preferentially enhance BH accretion, finding that the initial mass ratio is the most important factor. (iv) We study the evolution of the BH masses, finding that the BH mass contrast tends to decrease in minor mergers and to increase in major mergers. This effect hints at the existence of a preferential range of mass ratios for BHs in the final pairing stages. (v) In both merging and dynamically quiescent galaxies, the gas accreted by the BH is not necessarily the gas with low angular momentum, but the gas that loses angular momentum.

  1. A connection between star formation activity and cosmic rays in the starburst galaxy M82

    NASA Astrophysics Data System (ADS)

    VERITAS Collaboration; Acciari, V. A.; Aliu, E.; Arlen, T.; Aune, T.; Bautista, M.; Beilicke, M.; Benbow, W.; Boltuch, D.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Celik, O.; Cesarini, A.; Chow, Y. C.; Ciupik, L.; Cogan, P.; Colin, P.; Cui, W.; Dickherber, R.; Duke, C.; Fegan, S. J.; Finley, J. P.; Finnegan, G.; Fortin, P.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gibbs, K.; Gillanders, G. H.; Godambe, S.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Holder, J.; Horan, D.; Hui, C. M.; Humensky, T. B.; Imran, A.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Kildea, J.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; Lebohec, S.; Maier, G.; McArthur, S.; McCann, A.; McCutcheon, M.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nagai, T.; Ong, R. A.; Otte, A. N.; Pandel, D.; Perkins, J. S.; Pizlo, F.; Pohl, M.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Schroedter, M.; Sembroski, G. H.; Smith, A. W.; Steele, D.; Swordy, S. P.; Theiling, M.; Thibadeau, S.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wagner, R. G.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Williams, D. A.; Wissel, S.; Wood, M.; Zitzer, B.

    2009-12-01

    Although Galactic cosmic rays (protons and nuclei) are widely believed to be mainly accelerated by the winds and supernovae of massive stars, definitive evidence of this origin remains elusive nearly a century after their discovery. The active regions of starburst galaxies have exceptionally high rates of star formation, and their large size-more than 50 times the diameter of similar Galactic regions-uniquely enables reliable calorimetric measurements of their potentially high cosmic-ray density. The cosmic rays produced in the formation, life and death of massive stars in these regions are expected to produce diffuse γ-ray emission through interactions with interstellar gas and radiation. M82, the prototype small starburst galaxy, is predicted to be the brightest starburst galaxy in terms of γ-ray emission. Here we report the detection of >700-GeV γ-rays from M82. From these data we determine a cosmic-ray density of 250eVcm-3 in the starburst core, which is about 500 times the average Galactic density. This links cosmic-ray acceleration to star formation activity, and suggests that supernovae and massive-star winds are the dominant accelerators.

  2. Active Galactic Nuclei with James Webb Space Telescope (JWST)

    NASA Technical Reports Server (NTRS)

    Rigby, Jane R.

    2011-01-01

    I'll discuss several ways in which JWST will probe the cosmic history of accretion onto supermassive black holes, and the co-evolution of host galaxies. Key investigations include: 1) Measurements of redshift, luminosity, and AGN fraction for obscured AGN candidates identified by other missions. 2) Measurements of AGN hosts at all redshifts, including stellar masses, morphology, interactions, and star formation rates. 3) Measurements of stellar mass and black hole mass in AGN at high redshift, to chart the early history of black hole and galaxy growth.

  3. Evidence for Supermassive Black Holes in Active Galactic Nuclei from Emission-Line Reverberation

    NASA Technical Reports Server (NTRS)

    Peterson, Bradley M.; Wandel, Amri

    2000-01-01

    Emission-line variability data for Seyfert 1 galaxies provide strong evidence for the existence of supermassive black holes in the nuclei of these galaxies and that the line-emitting gas is moving in the gravitational potential of that black hole. The time-delayed response of the emission lines to continuum variations is used to infer the size of the line-emitting region, which is then combined with measurements of the Doppler widths of the variable line components to estimate a virial mass. la the case of the best-studied galaxy, NGC 5548, various emission lines spanning an order of magnitude in distance from the central source show the expected V proportional to r(sup -l/2) correlation between distance and line width and are thus consistent with a single value for the mass. Two other Seyfert galaxies, NGC 7469 and 3C 390.3, show a similar relationship. We compute the ratio of luminosity to mass for these three objects and the narrow-line Seyfert I galaxy NGC 4051 and find that the gravitational force on the line-emitting gas is much stronger than radiation pressure. These results strongly support the paradigm of gravitationally bound broad emission line region clouds.

  4. Discovery of Ultra-steep Spectrum Giant Radio Galaxy with Recurrent Radio Jet Activity in Abell 449

    NASA Astrophysics Data System (ADS)

    Hunik, Dominika; Jamrozy, Marek

    2016-01-01

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

  5. 1.75 h {sup -1} kpc SEPARATION DUAL ACTIVE GALACTIC NUCLEI AT z = 0.36 IN THE COSMOS FIELD

    SciTech Connect

    Comerford, Julia M.; Davis, Marc; Griffith, Roger L.; Stern, Daniel; Gerke, Brian F.; Newman, Jeffrey A.

    2009-09-01

    We present strong evidence for dual active galactic nuclei (AGNs) in the z = 0.36 galaxy COSMOS J100043.15+020637.2. COSMOS Hubble Space Telescope (HST) imaging of the galaxy shows a tidal tail, indicating that the galaxy recently underwent a merger, as well as two bright point sources near the galaxy's center. The luminosities of these sources (derived from the HST image) and their emission line flux ratios (derived from Keck/DEIMOS slit spectroscopy) suggest that both are AGNs and not star-forming regions or supernovae. Observations from zCOSMOS, the Sloan Digital Sky Survey, XMM-Newton, Spitzer, and the Very Large Array fortify the evidence for AGN activity. With HST imaging we measure a projected spatial offset between the two AGNs of 1.75 {+-} 0.03 h {sup -1} kpc, and with DEIMOS we measure a 150 {+-} 40 km s{sup -1} line-of-sight velocity offset between the two AGNs. Combined, these observations provide substantial evidence that COSMOS J100043.15+020637.2 is a merger-remnant galaxy with dual AGNs.

  6. HARD X-RAY LAGS IN ACTIVE GALACTIC NUCLEI: TESTING THE DISTANT REVERBERATION HYPOTHESIS WITH NGC 6814

    SciTech Connect

    Walton, D. J.; Harrison, F. A.; Zoghbi, A.; Reynolds, C. S.; Cackett, E. M.; Uttley, P.; Fabian, A. C.; Kara, E.; Miller, J. M.; Reis, R. C.

    2013-11-10

    We present an X-ray spectral and temporal analysis of the variable active galaxy NGC 6814, observed with Suzaku during 2011 November. Remarkably, the X-ray spectrum shows no evidence for the soft excess commonly observed amongst other active galaxies, despite its relatively low level of obscuration, and is dominated across the whole Suzaku bandpass by the intrinsic powerlaw-like continuum. Despite this, we clearly detect the presence of a low-frequency hard lag of ∼1600 s between the 0.5-2.0 and 2.0-5.0 keV energy bands at greater than 6σ significance, similar to those reported in the literature for a variety of other active galactic nuclei (AGNs). At these energies, any additional emission from, e.g., a very weak, undetected soft excess, or from distant reflection must contribute less than 3% of the observed countrates (at 90% confidence). Given the lack of any significant continuum emission component other than the powerlaw, we can rule out models that invoke distant reprocessing for the observed lag behavior, which must instead be associated with this continuum emission. These results are fully consistent with a propagating fluctuation origin for the low-frequency hard lags, and with the interpretation of the high-frequency soft lags—a common feature seen in the highest quality AGN data with strong soft excesses—as reverberation from the inner accretion disk.

  7. OPTICAL SPECTRAL PROPERTIES OF SWIFT BURST ALERT TELESCOPE HARD X-RAY-SELECTED ACTIVE GALACTIC NUCLEI SOURCES

    SciTech Connect

    Winter, Lisa M.; Keeney, Brian; Lewis, Karen T.; Koss, Michael; Veilleux, Sylvain; Mushotzky, Richard F.

    2010-02-10

    The Swift Burst Alert Telescope survey of active galactic nuclei (AGNs) is providing an unprecedented view of local AGNs ((z) {approx} 0.03) and their host galaxy properties. In this paper, we present an analysis of the optical spectra of a sample of 64 AGNs from the nine month survey, detected solely based on their 14-195 keV flux. Our analysis includes both archived spectra from the Sloan Digital Sky Survey and our own observations from the 2.1 m Kitt Peak National Observatory telescope. Among our results, we include line ratio classifications utilizing standard emission line diagnostic plots, [O III] 5007 A luminosities, and Hbeta-derived black hole masses. As in our X-ray study, we find the type 2 sources to be less luminous (in [O III] 5007 A and 14-195 keV luminosities) with lower accretion rates than the type 1 sources. We find that the optically classified low-ionization narrow emission line regions, H II/composite galaxies, and ambiguous sources have the lowest luminosities, while both broad-line and narrow-line Seyferts have similar luminosities. From a comparison of the hard X-ray (14-195 keV) and [O III] luminosities, we find that both the observed and extinction-corrected [O III] luminosities are weakly correlated with X-ray luminosity. In a study of the host galaxy properties from both continuum fits and measurements of the stellar absorption indices, we find that the hosts of the narrow-line sources have properties consistent with late-type galaxies.

  8. Line-driven disk winds in active galactic nuclei

    NASA Astrophysics Data System (ADS)

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

    2001-01-01

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

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

    SciTech Connect

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

    2009-12-20

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

  10. Chemical complexity in galactic nuclei

    NASA Astrophysics Data System (ADS)

    Martin-Pintado, Jesus

    2007-12-01

    In recent years our knowledge of the chemical complexity in the nuclei of galaxies has dramatically changed. Recent observations of the nucleus of the Milky Way, of the starburst galaxy NGC253 and of the ultraluminous infrared galaxy (ULIRG) Arp220 have shown large abundance of complex organic molecules believed to be formed on grains. The Galactic center appears to be the largest repository of complex organic molecule like aldehydes and alcohols in the galaxy. We also measure large abundance of methanol in starburst galaxies and in ULIRGs suggesting that complex organic molecules are also efficiently produced in the central region of galaxies with strong star formation activity. From the systematic observational studies of molecular abundance in regions dominated by different heating processes like shocks, UV radiation, X-rays and cosmic rays in the center of the Milky Way, we are opening the possibility of using chemistry as a diagnostic tool to study the highly obscured regions of galactic centers. The templates found in the nucleus of the Milky Way will be used to establish the main mechanisms driving the heating and the chemistry of the molecular clouds in galaxies with different type of activity. The role of grain chemistry in the chemical complexity observed in the center of galaxies will be also briefly discussed.

  11. Towards advanced study of Active Galactic Nuclei with visible light adaptive optics

    NASA Astrophysics Data System (ADS)

    Ammons, Stephen Mark

    It is thought that the immense energies associated with accretion of matter onto black holes in Active Galactic Nuclei (AGN) and Quasi-Stellar Objects (QSOs) may "feedback," via intense photon flux or outward motion of gas, and affect certain properties of the host galaxy. In particular, AGN feedback may contribute to "quenching," or ceasing, of star formation by the expulsion or heating of cold gas, causing the host galaxy to evolve onto the red sequence (e.g., Di Matteo et al. 2005, Hopkins et al. 2006). I probe for the effects of feedback on the stellar populations of 60 X-ray-selected AGN hosts at a redshift of 1 in the Great Observatories Origins Deep Survey (GOODS) Southern field. Combining high spatial resolution optical imaging from the Hubble Space Telescope Advanced Camera for Surveys (HST ACS), and high spatial resolution near infrared data from Keck Laser Guide Star Adaptive Optics (AO) and HST Near-Infrared Camera and Multi-Object Spectrograph (NICMOS), I test for the presence of young stars on sub-kiloparsec scales, independent of dust extinction. Testing for correlations between near-ultraviolet/optical ( NUV- R ) colors and gradients and X-ray parameters such as hardness ratio and luminosity reveals new information about the nature of AGN-driven feedback. These AGN hosts display color gradients in rest-frame NUV - R as far inward as ~400 pc, suggesting stellar mixtures with nonuniform age distributions. There is little (< 0.3 mags) difference between the NUV - R gradients of the obscured (hard in X-ray) sources and the unobscured (soft in X-ray) sources, suggesting that the unobscured sources are not increasingly quenched of star formation. I compare the NUV - R colors of spiral galaxies that host AGN to non-active spirals, finding similar color gradients, but redder colors. These observations support the notion that unobscured intermediate-luminosity AGN hosts do not appear to be increasingly quenched of star formation relative to obscured sources

  12. Determining inclinations of active galactic nuclei via their narrow-line region kinematics. II. Correlation with observed properties

    SciTech Connect

    Fischer, T. C.; Crenshaw, D. M.; Kraemer, S. B.; Schmitt, H. R.; Turner, T. J.

    2014-04-10

    Active galactic nuclei (AGNs) are axisymmetric systems to first order; their observed properties are likely strong functions of inclination with respect to our line of sight, yet the specific inclinations of all but a few AGNs are generally unknown. By determining the inclinations and geometries of nearby Seyfert galaxies using the kinematics of their narrow-line regions (NLRs) and comparing them with observed properties, we find strong correlations between inclination and total hydrogen column density, infrared color, and Hβ FWHM. These correlations provide evidence that the orientation of AGNs with respect to our line of sight affects how we perceive them beyond the Seyfert 1/2 dichotomy. They can also be used to constrain three-dimensional models of AGN components such as the broad-line region and torus. Additionally, we find weak correlations between AGN luminosity and several modeled NLR parameters, which suggests that the NLR geometry and kinematics are dependent to some degree on the AGN's radiation field.

  13. Active galaxies observed during the Extreme Ultraviolet Explorer all-sky survey

    NASA Technical Reports Server (NTRS)

    Marshall, H. L.; Fruscione, A.; Carone, T. E.

    1995-01-01

    We present observations of active galactic nuclei (AGNs) obtained with the Extreme Ultraviolet Explorer (EUVE) during the all-sky survey. A total of 13 sources were detected at a significance of 2.5 sigma or better: seven Seyfert galaxies, five BL Lac objects, and one quasar. The fraction of BL Lac objects is higher in our sample than in hard X-ray surveys but is consistent with the soft X-ray Einstein Slew Survey, indicating that the main reason for the large number of BL Lac objects in the extreme ulktraviolet (EUV) and soft X-ray bands is their steeper X-ray spectra. We show that the number of AGNs observed in both the EUVE and ROSAT Wide Field Camera surveys can readily be explained by modelling the EUV spectra with a simple power law in the case of BL Lac objects and with an additional EUV excess in the case of Seyferts and quasars. Allowing for cold matter absorption in Seyfert galaxy hosts drive up the inferred average continuum slope to 2.0 +/- 0.5 (at 90% confidence), compared to a slope of 1.0 usually found from soft X-ray data. If Seyfert galaxies without EUV excesses form a significant fraction of the population, then the average spectrum of those with bumps should be even steeper. We place a conservative limit on neutral gas in BL Lac objects: N(sub H) less than 10(exp 20)/sq cm.

  14. Einstein observations of active galaxies and quasars

    NASA Technical Reports Server (NTRS)

    Schreier, E. J.

    1979-01-01

    The radio galaxies Centaurus A and Signus B are discussed. In both these sources, a comparison of the radio and imaged X-ray flux is allowed for the measurement of the magnetic fields. Einstein observations of quasars are discussed. The number of known X-ray emitting QSO's was increased from 3 to 22 and the distances where these QSO's were seen to correspond to an age of 15 billion years. It was shown that these quasars contributed significantly to the X-ray background.

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

    NASA Astrophysics Data System (ADS)

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

    2013-08-01

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

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

    SciTech Connect

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

    2013-08-20

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

  17. A PHYSICAL LINK BETWEEN JET FORMATION AND HOT PLASMA IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Wu Qingwen; Wang Dingxiong; Cao Xinwu; Ho, Luis C. E-mail: dxwang@hust.edu.cn E-mail: lho@obs.carnegiescience.edu

    2013-06-10

    Recent observations suggest that in black hole X-ray binaries jet/outflow formation is related to the hot plasma in the vicinity of the black hole, either in the form of an advection-dominated accretion flow at low accretion rates or in a disk corona at high accretion rates. We test the viability of this scenario for supermassive black holes using two samples of active galactic nuclei distinguished by the presence (radio-strong) and absence (radio-weak) of well-collimated, relativistic jets. Each is centered on a narrow range of black hole mass but spans a very broad range of Eddington ratios, effectively simulating in a statistical manner the behavior of a single black hole evolving across a wide spread in accretion states. Unlike the relationship between the radio and optical luminosity, which shows an abrupt break between high- and low-luminosity sources at an Eddington ratio of {approx}1%, the radio emission-a measure of the jet power-varies continuously with the hard X-ray (2-10 keV) luminosity, roughly as L{sub R} {proportional_to} L{sub X}{sup 0.6-0.75}. This relation, which holds for both radio-weak and radio-strong active galaxies, is similar to the one seen in X-ray binaries. Jet/outflow formation appears to be closely linked to the conditions that give rise to the hot, optically thin coronal emission associated with accretion flows, both in the regime of low and high accretion rates.

  18. DO MOST ACTIVE GALACTIC NUCLEI LIVE IN HIGH STAR FORMATION NUCLEAR CUSPS?

    SciTech Connect

    Mushotzky, Richard F.; Shimizu, T. Taro; Meléndez, Marcio; Koss, Michael

    2014-02-01

    We present early results of the Herschel PACS (70 and 160 μm) and SPIRE (250, 350, and 500 μm) survey of 313 low redshift (z < 0.05), ultra-hard X-ray (14-195 keV) selected active galactic nuclei (AGNs) from the 58 month Swift/Burst Alert Telescope catalog. Selection of AGNs from ultra-hard X-rays avoids bias from obscuration, providing a complete sample of AGNs to study the connection between nuclear activity and star formation in host galaxies. With the high angular resolution of PACS, we find that >35% and >20% of the sources are ''point-like'' at 70 and 160 μm respectively and many more have their flux dominated by a point source located at the nucleus. The inferred star formation rates (SFRs) of 0.1-100 M {sub ☉} yr{sup –1} using the 70 and 160 μm flux densities as SFR indicators are consistent with those inferred from Spitzer Ne II fluxes, but we find that 11.25 μm polycyclic aromatic hydrocarbon data give ∼3× lower SFR. Using GALFIT to measure the size of the far-infrared emitting regions, we determined the SFR surface density (M {sub ☉} yr{sup –1} kpc{sup –2}) for our sample, finding that a significant fraction of these sources exceed the threshold for star formation driven winds (0.1 M {sub ☉} yr{sup –1} kpc{sup –2})

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

    NASA Astrophysics Data System (ADS)

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

    2015-03-01

    We investigate and quantify the observed scatter in the empirical relationship between the broad line region size R and the luminosity of the active galactic nucleus, in order to better understand its origin. This study is motivated by the indispensable role of this relationship in the mass estimation of cosmologically distant black holes, but may also be relevant to the recently proposed application of this relationship for measuring cosmic distances. We study six nearby reverberation-mapped active galactic nuclei (AGNs) for which simultaneous UV and optical monitoring data exist. We also examine the long-term optical luminosity variations of the Seyfert 1 galaxy NGC 5548 and employ Monte Carlo simulations to study the effects of the intrinsic variability of individual objects on the scatter in the global relationship for a sample of ~40 AGNs. We find the scatter in this relationship has a correctable dependence on color. For individual AGNs, the size of the Hβ emitting region has a steeper dependence on the nuclear optical luminosity than on the UV luminosity, which can introduce a scatter of ~0.08 dex into the global relationship, due the nonlinear relationship between the variations in the ionizing continuum and those in the optical continuum. Also, our analysis highlights the importance of understanding and minimizing the scatter in the relationship traced by the intrinsic variability of individual AGNs since it propagates directly into the global relationship. We find that using the UV luminosity as a substitute for the ionizing luminosity can reduce a sizable fraction of the current observed scatter of ~0.13 dex.

  20. Clues to galaxy activity from rich cluster simulations

    NASA Technical Reports Server (NTRS)

    Evrard, August E.

    1990-01-01

    New simulations of rich cluster evolution are used to evaluate the first infall hypothesis of Gunn and Dressler - the idea that the enhanced fraction of active galaxies seen in high redshift clusters is due to a one-time burst of star formation triggered by the rapid rise in external pressure as a galaxy plows into the hot intracluster medium (ICM). Using three-dimensional simulations which contain both baryonic gas and collisionless dark material, local static pressure histories for test orbits of galaxies are generated and a simple trigger threshold based on dP/dt/P sub ISM is applied to define an active fraction of the population. The results lend qualitative and quantitative support to the first infall interpretation.

  1. Very low luminosity active galaxies and the X-ray background

    NASA Technical Reports Server (NTRS)

    Elvis, M.; Soltan, A.; Keel, W. C.

    1984-01-01

    The properties of very low luminosity active galactic nuclei are not well studied, and, in particular, their possible contribution to the diffuse X-ray background is not known. In the present investigation, an X-ray luminosity function for the range from 10 to the 39th to 10 to the 42.5th ergs/s is constructed. The obtained X-ray luminosity function is integrated to estimate the contribution of these very low luminosity active galaxies to the diffuse X-ray background. The construction of the X-ray luminosity function is based on data obtained by Keel (1983) and some simple assumptions about optical and X-ray properties.

  2. Inefficient Driving of Bulk Turbulence By Active Galactic Nuclei in a Hydrodynamic Model of the Intracluster Medium

    NASA Astrophysics Data System (ADS)

    Reynolds, Christopher S.; Balbus, Steven A.; Schekochihin, Alexander A.

    2015-12-01

    Central jetted active galactic nuclei (AGNs) appear to heat the core regions of the intracluster medium (ICM) in cooling-core galaxy clusters and groups, thereby preventing a cooling catastrophe. However, the physical mechanism(s) by which the directed flow of kinetic energy is thermalized throughout the ICM core remains unclear. We examine one widely discussed mechanism whereby the AGN induces subsonic turbulence in the ambient medium, the dissipation of which provides the ICM heat source. Through controlled inviscid three-dimensional hydrodynamic simulations, we verify that explosive AGN-like events can launch gravity waves (g-modes) into the ambient ICM, which in turn decays to volume-filling turbulence. In our model, however, this process is found to be inefficient, with less than 1% of the energy injected by the AGN activity actually ending up in the turbulence of the ambient ICM. This efficiency is an order of magnitude or more too small to explain the observations of AGN-feedback in galaxy clusters and groups with short central cooling times. Atmospheres in which the g-modes are strongly trapped/confined have an even lower efficiency since, in these models, the excitation of turbulence relies on the g-modes’ ability to escape from the center of the cluster into the bulk ICM. Our results suggest that, if AGN-induced turbulence is indeed the mechanism by which the AGN heats the ICM core, its driving may rely on physics beyond that captured in our ideal hydrodynamic model.

  3. Modelling galaxy and AGN evolution in the infrared: black hole accretion versus star formation activity

    NASA Astrophysics Data System (ADS)

    Gruppioni, C.; Pozzi, F.; Zamorani, G.; Vignali, C.

    2011-09-01

    We present a new backward evolution model for galaxies and active galactic nuclei (AGNs) in the infrared (IR). What is new in this model is the separate study of the evolutionary properties of different IR populations (i.e. spiral galaxies, starburst galaxies, low-luminosity AGNs, 'unobscured' type 1 AGNs and 'obscured' type 2 AGNs) defined through a detailed analysis of the spectral energy distributions (SEDs) of large samples of IR-selected sources. The evolutionary parameters have been constrained by means of all the available observables from surveys in the mid- and far-IR (source counts, redshift and luminosity distributions, luminosity functions). By decomposing the SEDs representative of the three AGN classes into three distinct components (a stellar component emitting most of its power in the optical/near-IR, an AGN component due to the hot dust heated by the central black hole peaking in the mid-IR, and a starburst component dominating the far-IR spectrum), we have disentangled the AGN contribution to the monochromatic and total IR luminosity emitted by different populations considered in our model from that due to star formation activity. We have then obtained an estimate of the total IR luminosity density [and star formation density (SFD) produced by IR galaxies] and the first ever estimate of the black hole mass accretion density (BHAR) from the IR. The derived evolution of the BHAR is in agreement with estimates from X-rays, though the BHAR values we derive from the IR are slightly higher than the X-ray ones. Finally, we have simulated source counts, redshift distributions, and SFD and BHAR that we expect to obtain with the future cosmological surveys in the mid-/far-IR that will be performed with the JWST-MIRI and SPICA-SAFARI. Outputs of the model are available online.1

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

    SciTech Connect

    Esquej, P.; Alonso-Herrero, A.; Hernán-Caballero, A.; González-Martín, O.; Ramos Almeida, C.; Rodríguez Espinosa, J. M.; Roche, P.; Mason, R. E.; Díaz-Santos, T.; Levenson, N. A.; Aretxaga, I.; Packham, C.

    2014-01-01

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

  5. Nuclear Star Formation Activity and Black Hole Accretion in Nearby Seyfert Galaxies

    NASA Astrophysics Data System (ADS)

    Esquej, P.; Alonso-Herrero, A.; González-Martín, O.; Hönig, S. F.; Hernán-Caballero, A.; Roche, P.; Ramos Almeida, C.; Mason, R. E.; Díaz-Santos, T.; Levenson, N. A.; Aretxaga, I.; Rodríguez Espinosa, J. M.; Packham, C.

    2014-01-01

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

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

    NASA Astrophysics Data System (ADS)

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

    1999-11-01

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

  7. Extended chromatin and DNA fibers from active plant nuclei for high-resolution FISH.

    PubMed

    Lavania, U C; Yamamoto, M; Mukai, Y

    2003-10-01

    The conventional protocol for isolation of cell wall free nuclei for release of DNA fibers for plants involves mechanical removal of the cell wall and separation of debris by sieve filtration. The mechanical grinding pressure applied during the process leaves only the more tolerant G(1) nuclei intact, and all other states of active nuclei that may be present in the target tissues (e.g., leaf) are simply crushed/disrupted during the isolation process. Here we describe an alternative enzymatic protocol for isolation of nuclei from root tip tissue. Cell wall free nuclei at a given stage of cell cycle, free of any cell debris, could be realized in suspension that are fit for preparation of extended fibers suitable for fiber FISH applications. The protocol utilizes selective harvest of active nuclei from root tip tissue in liquid suspension under the influence of cell wall-degrading enzymes, and provides opportunities to target cell cycle-specific nuclei from interphase through division phase for the release of extended DNA fibers. Availability of cell cycle-specific fibers may have added value in transcriptional analysis, DNA:RNA hybridization, visualization of DNA replication and replication forks, and improved FISH efficiency. PMID:14500692

  8. X-rays From Quasars and Active Galaxies

    NASA Technical Reports Server (NTRS)

    Lightman, Alan P.

    1981-01-01

    Features of quasars and active galactic nuclei are discussed and include: the nature of the power source, the radiation processes, and the mechanism for the formation and collimation of long-lived jets of matter observed to emanate from the center of these of these objects. The phenomena that produce X-rays are highlighted.

  9. Nuclear activity and the environments of nearby radio galaxies

    NASA Technical Reports Server (NTRS)

    Dey, Arjun; Vanbreugel, Wil

    1993-01-01

    Much of our present understanding of galaxy evolution over a large redshift range is based on the study of samples selected on the basis of non-thermal radio emission. It is therefore necessary to understand the relationship between radio source activity and the host galaxy. Recent observations suggest that there is a connection between radio galaxy (RG) activity and radio galaxy evolution. For example, high-redshift RGs (z approx. greater than 0.7) show evidence for significant populations of young stars, and have optical continuum morphologies nearly always aligned with the radio axis (McCarthy et al. 1987; Chambers et al. 1987). This phenomenon is generally attributed to radio jet induced star formation (DeYoung 1989), but the lack of high S/N spectra of the galaxy continua, and recent detections of polarized light in a few objects make it hard to rule out other processes such as scattering or synchrotron radiation. A detailed study of the continuum light in the distant RGs is difficult as they are optically very faint. However, nearby RGs (z approx. less than 0.1) have bluer B-V colors than radio-quiet ellipticals, presumably due to the presence of young stellar populations (Smith and Heckman 1989) and several have extended UV continuum emitting regions along their radio axes (van Bruegel et al. 1985a, b, di Serego Alighieri et al. 1989), reminiscent of the alignment effect seen in the high redshift RGs. We have almost completed a continuum imaging survey of nearby (and therefore optically brighter), powerful RGs to study any possible relationships between the optical continuum light and radio source activity. In particular we are interested in (1) whether these lower redshift RGs shown any evidence of the alignment effect (in their rest-frame UV light) that is seen in the distant RGs, and (2) the effects that the radio source has on the environment of the host galaxy.

  10. The activity of deoxyribonucleic acid polymerase and deoxyribonucleic acid synthesis in nuclei from brain fractionated by zonal centrifugation

    PubMed Central

    Stambolova, M. A.; Cox, D.; Mathias, A. P.

    1973-01-01

    1. The DNA polymerase (EC 2.7.7.7) activity in purified intact brain nuclei from infant rats was investigated. The effects of pH, Mg2+, glycerol, sonication and storage of the nuclei under different conditions were examined and a suitable assay system was established. 2. The nuclei from infant brain cells were fractionated by zonal centrifugation in a discontinuous sucrose gradient into five zones: zone (I) contained neuronal nuclei (59%) and astrocytic nuclei (41%); zone (II) contained astrocytic nuclei (81%) and neuronal nuclei (19%); zone (III) contained astrocytic nuclei (82%) and oligodendrocytic nuclei (18%); zone (IV) contained oligodendrocytic nuclei (92%) and zone (V) contained oligodendrocytic nuclei (100%). 3. The content of DNA, RNA and protein for each fraction was measured. 4. The distribution of DNA polymerase activity in the fractionated infant and adult rat brain nuclei was determined. The highest activity was found in the neuronal nuclei from zone (I) and the following zones exhibited a progressive decline. In contrast with the nuclei from infant rats those from adults had a much higher activity and expressed a preference for native DNA as template. 5. The deoxyribonuclease activity in all classes of nuclei was measured with [3H]DNA as substrate. A general correspondence in the pattern of the relative activities in the nuclear fractions with the distribution of DNA polymerase was found. 6. The incorporation of [3H]thymidine into nuclear DNA in infant and adult rat brain was investigated. The specific radioactivity of the DNA in the 10-day-old rats was highest in zone (V) whereas in the nuclei of adult rats, which exhibited a comparatively low incorporation, the highest specific radioactivity was associated with zones (I) and (V). PMID:4780694

  11. Supernovae in paired host galaxies

    NASA Astrophysics Data System (ADS)

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

    2014-12-01

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

  12. The origins of active galactic nuclei obscuration: the 'torus' as a dynamical, unstable driver of accretion

    NASA Astrophysics Data System (ADS)

    Hopkins, Philip F.; Hayward, Christopher C.; Narayanan, Desika; Hernquist, Lars

    2012-02-01

    Recent multiscale simulations have made it possible to follow gas inflows responsible for high-Eddington ratio accretion on to massive black holes (BHs) from galactic scales to the BH accretion disc. When sufficient gas is driven towards a BH, gravitational instabilities generically form lopsided, eccentric discs that propagate inwards from larger radii. The lopsided stellar disc exerts a strong torque on the gas, driving inflows that fuel the growth of the BH. Here, we investigate the possibility that the same disc, in its gas-rich phase, is the putative 'torus' invoked to explain obscured active galactic nuclei (AGN) and the cosmic X-ray background. The disc is generically thick and has characteristic ˜1-10 pc sizes and masses resembling those required of the torus. Interestingly, the scale heights and obscured fractions of the predicted torii are substantial even in the absence of strong stellar feedback providing the vertical support. Rather, they can be maintained by strong bending modes and warps/twists excited by the inflow-generating instabilities. A number of other observed properties commonly attributed to 'feedback' processes may in fact be explained entirely by dynamical, gravitational effects: the lack of alignment between torus and host galaxy, correlations between local star formation rate (SFR) and turbulent gas velocities and the dependence of obscured fractions on AGN luminosity or SFR. We compare the predicted torus properties with observations of gas surface density profiles, kinematics, scale heights and SFR densities in AGN, and find that they are consistent in all cases. We argue that it is not possible to reproduce these observations and the observed column density distribution without a clumpy gas distribution, but allowing for simple clumping on small scales the predicted column density distribution is in good agreement with observations from NH˜ 1020-1027 cm-2. We examine how the NH distribution scales with galaxy and AGN properties

  13. Powerful Molecular Outflows in Nearby Active Galaxies

    NASA Astrophysics Data System (ADS)

    Veilleux, Sylvain; Meléndez, Marcio

    2014-07-01

    We report the results from a systematic search for molecular (OH 119 μm) outflows with Herschel-PACS† in a sample of 43 nearby (z < 0.3) galaxy mergers, mostly ultraluminous infrared galaxies (ULIRGs) and QSOs. We find that the character of the OH feature (strength of the absorption relative to the emission) correlates with that of the 9.7-μm silicate feature, a measure of obscuration in ULIRGs. Unambiguous evidence for molecular outflows, based on the detection of OH absorption profiles with median velocities more blueshifted than -50 km s-1, is seen in 26 (70%) of the 37 OH-detected targets, suggesting a wide-angle (~ 145°) outflow geometry. Conversely, unambiguous evidence for molecular inflows, based on the detection of OH absorption profiles with median velocities more redshifted than +50 km s-1, is seen in only 4 objects, suggesting a planar or filamentary geometry for the inflowing gas. Terminal outflow velocities of ~ -1000 km s-1 are measured in several objects, but median outflow velocities are typically ~ -200 km s-1. While the outflow velocities show no statistically significant dependence on the star formation rate, they are distinctly more blueshifted among systems with large AGN fractions and luminosities [log (L AGN/L ⊙) >= 11.8 +/- 0.3]. The quasars in these systems play a dominant role in driving the molecular outflows. In contrast, the most AGN dominated systems, where OH is seen purely in emission, show relatively modest OH line widths, despite their large AGN luminosities, perhaps indicating that molecular outflows subside once the quasar has cleared a path through the obscuring material.

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

    NASA Astrophysics Data System (ADS)

    Lyu, Yang; Liu, Xin

    2016-08-01

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

  15. THE INTEGRAL HIGH-ENERGY CUT-OFF DISTRIBUTION OF TYPE 1 ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Malizia, A.; Molina, M.; Bassani, L.; Stephen, J. B.; Bazzano, A.; Ubertini, P.; Bird, A. J.

    2014-02-20

    In this Letter we present the primary continuum parameters, the photon index Γ, and the high-energy cut-off E {sub c} of 41 type-1 Seyfert galaxies extracted from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) complete sample of active galactic nuclei (AGNs). We performed broadband (0.3-100 keV) spectral analysis by simultaneously fitting the soft and hard X-ray spectra obtained by XMM and INTEGRAL/IBIS-Swift/BAT, respectively, in order to investigate the general properties of these parameters, in particular their distribution and mean values. We find a mean photon index of 1.73 with a standard deviation of 0.17 and a mean high-energy cut-off of 128 keV with a standard deviation of 46 keV for the whole sample. This is the first time that the cut-off energy is constrained in such a large number of AGNs. We have 26 measurements of the cut-off, which corresponds to 63% of the entire sample, distributed between 50 and 200 keV. There are a further 11 lower limits mostly below 300 keV. Using the main parameters of the primary continuum, we have been able to obtain the actual physical parameters of the Comptonizing region, i.e., the plasma temperature kT {sub e} from 20 to 100 keV and the optical depth τ < 4. Finally, with the high signal-to-noise ratio spectra starting to come from NuSTAR it will soon be possible to better constrain the cut-off values in many AGNs, allowing the determination of more physical models and thus better understand the continuum emission and geometry of the region surrounding black holes.

  16. The INTEGRAL High-energy Cut-off Distribution of Type 1 Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Malizia, A.; Molina, M.; Bassani, L.; Stephen, J. B.; Bazzano, A.; Ubertini, P.; Bird, A. J.

    2014-02-01

    In this Letter we present the primary continuum parameters, the photon index Γ, and the high-energy cut-off E c of 41 type-1 Seyfert galaxies extracted from the International Gamma-Ray Astrophysics Laboratory (INTEGRAL) complete sample of active galactic nuclei (AGNs). We performed broadband (0.3-100 keV) spectral analysis by simultaneously fitting the soft and hard X-ray spectra obtained by XMM and INTEGRAL/IBIS-Swift/BAT, respectively, in order to investigate the general properties of these parameters, in particular their distribution and mean values. We find a mean photon index of 1.73 with a standard deviation of 0.17 and a mean high-energy cut-off of 128 keV with a standard deviation of 46 keV for the whole sample. This is the first time that the cut-off energy is constrained in such a large number of AGNs. We have 26 measurements of the cut-off, which corresponds to 63% of the entire sample, distributed between 50 and 200 keV. There are a further 11 lower limits mostly below 300 keV. Using the main parameters of the primary continuum, we have been able to obtain the actual physical parameters of the Comptonizing region, i.e., the plasma temperature kT e from 20 to 100 keV and the optical depth τ < 4. Finally, with the high signal-to-noise ratio spectra starting to come from NuSTAR it will soon be possible to better constrain the cut-off values in many AGNs, allowing the determination of more physical models and thus better understand the continuum emission and geometry of the region surrounding black holes.

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

    NASA Astrophysics Data System (ADS)

    Kacprzak, Glenn G.; Churchill, Christopher W.; Murphy, Michael T.; Cooke, Jeff

    2015-01-01

    We performed a detailed study of the extended cool gas, traced by Mg II absorption [Wr(2796) ≥ 0.3 Å], surrounding 14 narrow-line active galactic nuclei (AGNs) at 0.12 ≤ z ≤ 0.22 using background quasar sightlines. The background quasars probe the AGNs at projected distances of 60 ≤ D ≤ 265 kpc. We find that, between 100 ≤ D ≤ 200 kpc, AGNs appear to have lower Mg II gas covering fractions (0.09^{+0.18}_{-0.08}) than quasars (0.47^{+0.16}_{-0.15}) and possibly lower than inactive field galaxies (0.25^{+0.11}_{-0.09}). We do not find a statistically significant azimuthal angle dependence for the Mg IIcovering fraction around AGNs, though the data hint at one. We also study the `down-the-barrel' outflow properties of the AGNs themselves and detect intrinsic Na ID absorption in 8/8 systems and intrinsic Mg II absorption in 2/2 systems, demonstrating that the AGNs have significant reservoirs of cool gas. We find that 6/8 Na ID and 2/2 Mg II intrinsic systems contain blueshifted absorption with Δv > 50 km s-1, indicating outflowing gas. The 2/2 intrinsic Mg II systems have outflow velocities a factor of ˜4 higher than the Na ID outflow velocities. Our results are consistent with AGN-driven outflows destroying the cool gas within their haloes, which dramatically decreases their cool gas covering fraction, while starburst-driven winds are expelling cool gas into their circumgalactic media (CGM). This picture appears contrary to quasar-quasar pair studies which show that the quasar CGM contains significant amounts of cool gas whereas intrinsic gas found `down-the-barrel' of quasars reveals no cool gas. We discuss how these results are complementary and provide support for the AGN unified model.

  18. Reverberation mapping the dusty torus in Active Galactic Nuclei using Spitzer and optical light curves

    NASA Astrophysics Data System (ADS)

    Robinson, Andrew

    Dusty molecular tori play a central role in unification models for active galactic nuclei (AGN) and are also the dominant source of their mid-IR emission. Our limited knowledge of the size and structure of AGN tori and how these properties vary with luminosity hinders our ability to understand the observed spectral energy distribution and hence AGN demographics. Ultimately this inhibits our ability to understand the obscured AGN population and the cosmic evolution of super-massive black holes. Although the torus is, in general, inaccessible to direct imaging, its properties can be studied by analyzing the time response of the dust emission from the torus with respect to variations in the AGN continuum luminosity; a technique known as reverberation mapping. With this goal, we have completed a 2.5-year monitoring campaign on 12 broad-line AGN, using the Spitzer Space Telescope supported by ground-based optical observations, to measure the temporal response of thetorus 3.5 and 4.6μm mid-IR dust emission to variations in the AGN UV/optical continuum. The data obtained from the first 1.5 years in Spitzer Cycle 8 have been analysed. The aim of this project is to complete the time series analysis of the complete 2.5 year light curves, and to model these light curves in order extract structural and physical information contained in data, such as the size of the torus, its radial depth, opening angle, inclination and dust composition. This project will help to maximize the scientific returns on a significant investment of Spitzer Space Telescope time and supports the NASA strategic goal to "explore the origin and evolution of the galaxies, stars and planets that make up our universe".

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

    NASA Astrophysics Data System (ADS)

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

    2011-03-01

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

  20. DIRECT MEASUREMENT OF THE X-RAY TIME-DELAY TRANSFER FUNCTION IN ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Legg, E.; Miller, L.; Turner, T. J.; Giustini, M.; Reeves, J. N.; Kraemer, S. B.

    2012-11-20

    The origin of the observed time lags, in nearby active galactic nuclei (AGNs), between hard and soft X-ray photons is investigated using new XMM-Newton data for the narrow-line Seyfert I galaxy Ark 564 and existing data for 1H 0707-495 and NGC 4051. These AGNs have highly variable X-ray light curves that contain frequent, high peaks of emission. The averaged light curve of the peaks is directly measured from the time series, and it is shown that (1) peaks occur at the same time, within the measurement uncertainties, at all X-ray energies, and (2) there exists a substantial tail of excess emission at hard X-ray energies, which is delayed with respect to the time of the main peak, and is particularly prominent in Ark 564. Observation (1) rules out that the observed lags are caused by Comptonization time delays and disfavors a simple model of propagating fluctuations on the accretion disk. Observation (2) is consistent with time lags caused by Compton-scattering reverberation from material a few thousand light-seconds from the primary X-ray source. The power spectral density and the frequency-dependent phase lags of the peak light curves are consistent with those of the full time series. There is evidence for non-stationarity in the Ark 564 time series in both the Fourier and peaks analyses. A sharp 'negative' lag (variations at hard photon energies lead soft photon energies) observed in Ark 564 appears to be generated by the shape of the hard-band transfer function and does not arise from soft-band reflection of X-rays. These results reinforce the evidence for the existence of X-ray reverberation in type I AGN, which requires that these AGNs are significantly affected by scattering from circumnuclear material a few tens or hundreds of gravitational radii in extent.

  1. Bars within bars - A mechanism for fuelling active galactic nuclei

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    A mechanism, applicable to AGN and nuclear starburst galaxies in which there is accretion onto a supermassive black hole (SBH), is proposed which brings in gas from large to small scales by successive dynamical instabilities. On the large scale, a stellar bar sweeps the interstellar medium into a gaseous disk a few hundred pc in radius. Under certain conditions, this disk can become unstable again, allowing material to flow inwards until turbulent viscous processes control angular-momentum transport. This flow pattern may feed viscosity-driven accretion flows around an SBH or lead to the formation of an SBH if none was present initially.

  2. Outflowing X-ray corona in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Wang, Junxian; Liu, Teng; Yang, Huan; Zhu, Feifan; Zhou, Youyuan

    2015-08-01

    Hard X-ray emission in radio-quiet AGNs is believed to be produced via inverse Compton scattering by hot and compact corona near the super massive black hole. However the origin and physical properties of the coronae, including geometry, kinematics and dynamics, yet remain poorly known. Taking [OIV] 25.89um emission line as an isotropic indicator of AGN's intrinsic luminosity, we compare the intrinsic corona X-ray emission between Seyfert 1 and Compton-thin Seyfert 2 galaxies, which are viewed at different inclinations according to the unification scheme. We find that Seyfert 1 galaxies are brighter in "absorption-corrected" 2-10 keV emission by a factor of ~2.8, comparing with Compton-thin Seyfert 2 galaxies. The Seyfert 1 and Compton-thin Seyfert 2 galaxies follow a statistically identical correlation between the absorption-corrected 2-10 keV luminosity and the SWIFT BAT 14-195 keV luminosity, indicating that our absorption correction to the 2-10 keV flux is sufficient. The difference between the two populations thus can not be attributed to X-ray absorption, and instead implies an intrinsic anisotropy in the corona X-ray emission. This striking anisotropy of X-ray emission can be explained by a bipolar outflowing corona with a bulk velocity of ~0.3-0.5c. This would provide a natural link between the so-called coronae and weak jets in these systems. We also show that how this study would affect our understanding to the nature of mid-infrared emission in AGNs and the properties of dusty torus. Furthermore, such anisotropy implies that, contrary to previous understanding based on the assumption of isotropic corona emission, hard X-ray AGN surveys are biased against type 2 AGNs even after absorption-correction, and careful correction for this effect is required to measure the obscured fraction from X-ray surveys. Other interesting consequences of this discovery will also be discussed.

  3. High resolution X-ray spectroscopy of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Krolik, Julian H.

    1990-01-01

    After a brief review of the principal problems of AGN research, selected potential high-resolution observations are discussed with a view toward assessing their scientific value and the degree of resolution they will require. Two classes of observations pertaining directly to AGNs are discussed. Fe K-alpha spectroscopy relevant to the dynamical and thermal character of the emission line zones; and measurement of resonance line absorption by highly-ionized species in BL Lac objects, which should provide information about entrainment of interstellar material by relativistic jets. A third class of potentially important observations uses AGNs as background light sources in order to directly measure the distance to clusters of galaxies.

  4. High-resolution X-ray spectroscopy of four active galaxies - Probing the intercloud medium

    NASA Technical Reports Server (NTRS)

    Lum, Kenneth S. K.; Canizares, Claude R.; Markert, Thomas H.; Arnaud, Keith A.

    1990-01-01

    The focal plane crystal spectrometer (FPCS) on the Einstein Observatory has been used to perform a high-resolution spectroscopic search for oxygen X-ray line emission from four active galaxies: Fairall 9, Mrk 421, Mrk 501, and PKS 0548 - 322. Specifically, O VIII Ly-alpha and Ly-beta, whose unredshifted energies are 653 and 775 eV, respectively, were sought. No narrow-line emission was detected within the energy bands searched. Upper limits are calculated on the line flux from these sources of 30 eV equivalent width and use a photoionization model to place corresponding upper limits on the densities of diffuse gas surrounding the active nuclei. The upper limits on gas density range from about 0.02-50/cu cm and probe various radial distances from the central source. This is the first time high-resolution X-ray spectroscopy has been used to place constraints on the intercloud medium in active galaxies.

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

    PubMed

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

    2014-07-01

    Supermassive black holes in the nuclei of active galaxies expel large amounts of matter through powerful winds of ionized gas. The archetypal active galaxy NGC 5548 has been studied for decades, and high-resolution x-ray and ultraviolet (UV) observations have previously shown a persistent ionized outflow. An observing campaign in 2013 with six space observatories shows the nucleus to be obscured by a long-lasting, clumpy stream of ionized gas not seen before. It blocks 90% of the soft x-ray emission and causes simultaneous deep, broad UV absorption troughs. The outflow velocities of this gas are up to five times faster than those in the persistent outflow, and, at a distance of only a few light days from the nucleus, it may likely originate from the accretion disk. PMID:24994647

  6. SPECTRAL ENERGY DISTRIBUTIONS OF TYPE 1 ACTIVE GALACTIC NUCLEI IN THE COSMOS SURVEY. I. THE XMM-COSMOS SAMPLE

    SciTech Connect

    Elvis, M.; Hao, H.; Civano, F.; Brusa, M.; Salvato, M.; Bongiorno, A.; Cappelluti, N.; Capak, P.; Zamorani, G.; Comastri, A.; Gilli, R.; Jahnke, K.; Lusso, E.; Cisternas, M.; Mainieri, V.; Trump, J. R.; Ho, L. C.; Aussel, H.; Frayer, D.; Hasinger, G. E-mail: hhao@cfa.harvard.edu; and others

    2012-11-01

    The 'Cosmic Evolution Survey' (COSMOS) enables the study of the spectral energy distributions (SEDs) of active galactic nuclei (AGNs) because of the deep coverage and rich sampling of frequencies from X-ray to radio. Here we present an SED catalog of 413 X-ray (XMM-Newton)-selected type 1 (emission line FWHM > 2000 km s{sup -1}) AGNs with Magellan, SDSS, or VLT spectrum. The SEDs are corrected for Galactic extinction, broad emission line contributions, constrained variability, and host galaxy contribution. We present the mean SED and the dispersion SEDs after the above corrections in the rest-frame 1.4 GHz to 40 keV, and show examples of the variety of SEDs encountered. In the near-infrared to optical (rest frame {approx}8 {mu}m-4000 A), the photometry is complete for the whole sample and the mean SED is derived from detections only. Reddening and host galaxy contamination could account for a large fraction of the observed SED variety. The SEDs are all available online.

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

    NASA Technical Reports Server (NTRS)

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

    1991-01-01

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

  8. Morphology, star formation, and nuclear activity in void galaxies

    NASA Astrophysics Data System (ADS)

    Wiedmann, Sophia; Miller, Brendan; Gallo, Elena; Pazar, Beni; Alfvin, Erik

    2015-01-01

    We report on new Chandra observations of six early-type galaxies located within cosmic voids, from a program examining the influence of Mpc-scale environment upon star formation and low-level supermassive black hole activity. Simple feedback prescriptions are predicted to operate independently of the surrounding density once outside the dark matter halo, and further link star formation quenching to black hole activity. Alternatively, mediation of the cold gas supply by the large-scale environment, for example through increased cold-stream accretion and reduced harassment or stripping within more isolated regions, could mutually enhance star formation and (perhaps indirectly) low-level supermassive black hole activity. The six targeted early-type galaxies have comparable stellar masses of 6-9e10 solar, chosen to be near the predicted "critical value" for efficient feedback, but span a wide range of star-formation rates. Specifically, they have SFRs of 6.5, 1.4, 0.45, 0.10, 0.04, and 0.03 solar masses per year. All galaxies are detected in the Chandra ACIS-S observations with 0.3-8 keV X-ray luminosities ranging from 2e39 to 1e41 erg/s. Specifically, they have log Lx values of 40.4, 41.1, 41.1, 39.3, 39.2, and 39.2, again ordered by decreasing SFR. The three galaxies with moderate-to-high star formation rates have nuclear X-ray luminosities that are significantly greater than those of the three galaxies with low star formation rates. This result is more consistent with a symbiotic relationship between current low-level star formation and supermassive black hole activity than with simple feedback quenching models. We additionally situate these galaxies in the context of void and cluster galaxies in the local universe, model their optical surface brightness profiles and color gradients, discuss caveats including the possibility of X-ray binary contamination, and consider other supermassive black hole activity indicators.

  9. Dissecting the Power Sources of Low-Luminosity Emission-Line Galaxy Nuclei via Comparison of HST-STIS and Ground-Based Spectra

    NASA Astrophysics Data System (ADS)

    Constantin, Anca; Shields, Joseph C.; Ho, Luis C.; Barth, Aaron J.; Filippenko, Alexei V.; Castillo, Christopher A.

    2015-12-01

    Using a sample of ∼100 nearby line-emitting galaxy nuclei, we have built the currently definitive atlas of spectroscopic measurements of Hα and neighboring emission lines at subarcsecond scales. We employ these data in a quantitative comparison of the nebular emission in Hubble Space Telescope (HST) and ground-based apertures, which offer an order-of-magnitude difference in contrast, and provide new statistical constraints on the degree to which transition objects and low-ionization nuclear emission-line regions (LINERs) are powered by an accreting black hole at ≲10 pc. We show that while the small-aperture observations clearly resolve the nebular emission, the aperture dependence in the line ratios is generally weak, and this can be explained by gradients in the density of the line-emitting gas: the higher densities in the more nuclear regions potentially flatten the excitation gradients, suppressing the forbidden emission. The transition objects show a threefold increase in the incidence of broad Hα emission in the high-resolution data, as well as the strongest density gradients, supporting the composite model for these systems as accreting sources surrounded by star-forming activity. The narrow-line LINERs appear to be the weaker counterparts of the Type 1 LINERs, where the low accretion rates cause the disappearance of the broad-line component. The enhanced sensitivity of the HST observations reveals a 30% increase in the incidence of accretion-powered systems at z ≈ 0. A comparison of the strength of the broad-line emission detected at different epochs implies potential broad-line variability on a decade-long timescale, with at least a factor of three in amplitude. Based on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555.

  10. The evolution of star formation activity in galaxy groups

    NASA Astrophysics Data System (ADS)

    Erfanianfar, G.; Popesso, P.; Finoguenov, A.; Wuyts, S.; Wilman, D.; Biviano, A.; Ziparo, F.; Salvato, M.; Nandra, K.; Lutz, D.; Elbaz, D.; Dickinson, M.; Tanaka, M.; Mirkazemi, M.; Balogh, M. L.; Altieri, M. B.; Aussel, H.; Bauer, F.; Berta, S.; Bielby, R. M.; Brandt, N.; Cappelluti, N.; Cimatti, A.; Cooper, M.; Fadda, D.; Ilbert, O.; Le Floch, E.; Magnelli, B.; Mulchaey, J. S.; Nordon, R.; Newman, J. A.; Poglitsch, A.; Pozzi, F.

    2014-12-01

    We study the evolution of the total star formation (SF) activity, total stellar mass (ΣM*) and halo occupation distribution (HOD) in massive haloes by using one of the largest X-ray selected sample of galaxy groups with secure spectroscopic identification in the major blank field surveys (ECDFS, CDFN, COSMOS, AEGIS). We provide an accurate measurement of star formation rate (SFR) for the bulk of the star-forming galaxies using very deep mid-infrared Spitzer MIPS and far-infrared Herschel PACS observations. For undetected IR sources, we provide a well-calibrated SFR from spectral energy distribution (SED) fitting. We observe a clear evolution in the level of SF activity in galaxy groups. The total SF activity in the high-redshift groups (0.5 < z < 1.1) is higher with respect to the low-redshift (0.15 < z < 0.5) sample at any mass by 0.8 ± 0.12 dex. A milder difference (0.35 ± 0.1 dex) is observed between the low-redshift bin and the groups at z ˜ 0. We show that the level of SF activity is declining more rapidly in the more massive haloes than in the more common lower mass haloes. We do not observe any evolution in the HOD and total stellar mass-halo mass relations in groups. The picture emerging from our findings suggests that the galaxy population in the most massive systems is evolving faster than galaxies in lower mass haloes, consistently with a `halo downsizing' scenario.

  11. HERSCHEL/SPIRE SUBMILLIMETER SPECTRA OF LOCAL ACTIVE GALAXIES {sup ,}

    SciTech Connect

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

    2013-05-01

    We present the submillimeter spectra from 450 to 1550 GHz of 11 nearby active galaxies observed with the SPIRE Fourier Transform Spectrometer (SPIRE/FTS) on board Herschel. We detect CO transitions from J{sub up} = 4 to 12, as well as the two [C I] fine structure lines at 492 and 809 GHz and the [N II]1461 GHz line. We used radiative transfer models to analyze the observed CO spectral line energy distributions. The FTS CO data were complemented with ground-based observations of the low-J CO lines. We found that the warm molecular gas traced by the mid-J CO transitions has similar physical conditions (n{sub H{sub 2}}{approx} 10{sup 3.2}-10{sup 3.9} cm{sup -3} and T{sub kin} {approx} 300-800 K) in most of our galaxies. Furthermore, we found that this warm gas is likely producing the mid-IR rotational H{sub 2} emission. We could not determine the specific heating mechanism of the warm gas, however, it is possibly related to the star formation activity in these galaxies. Our modeling of the [C I] emission suggests that it is produced in cold (T{sub kin} < 30 K) and dense (n{sub H{sub 2}}>10{sup 3} cm{sup -3}) molecular gas. Transitions of other molecules are often detected in our SPIRE/FTS spectra. The HF J = 1-0 transition at 1232 GHz is detected in absorption in UGC 05101 and in emission in NGC 7130. In the latter, near-infrared pumping, chemical pumping, or collisional excitation with electrons are plausible excitation mechanisms likely related to the active galactic nucleus of this galaxy. In some galaxies, few H{sub 2}O emission lines are present. Additionally, three OH{sup +} lines at 909, 971, and 1033 GHz are identified in NGC 7130.

  12. The development of a color-magnitude diagram for active galactic nuclei (AGN): hope for a new standard candle

    NASA Astrophysics Data System (ADS)

    McGinnis, G.; Chung, S.; Gonzales, E. V.; Gorjian, V.; Pruett, L.

    2015-12-01

    Of the galaxies in our universe, only a small percentage currently have Active Galactic Nuclei (AGN). These galaxies tend to be further out in the universe and older, and are different from inactive galaxies in that they emit high amounts of energy from their central black holes. These AGN can be classified as either Seyferts or quasars, depending on the amount of energy emitted from the center (less or more). We are studying the correlation between the ratio of dust emission and accretion disk emission to luminosities of AGN in order to determine if there is a relationship strong enough to act as a predictive model for distance within the universe. This relationship can be used as a standard candle if luminosity is found to determine distances in space. We have created a color-magnitude diagram depicting this relationship between luminosity and wavelengths, similar to the Hertzsprung-Russell (HR) diagram. The more luminous the AGN, the more dust surface area over which to emit energy, which results in a greater near-infrared (NIR) luminosity. This differs from previous research because we use NIR to differentiate accretion from dust emission. Using data from the Sloan Digital Sky Survey (SDSS) and the Two Micron All Sky Survey (2MASS), we analyzed over one thousand Type 1 Seyferts and quasars. We studied data at different wavelengths in order to show the relationship between color (the ratio of one wavelength to another) and luminosity. It was found that plotting filters i-K (the visible and mid-infrared regions of the electromagnetic spectrum) against the magnitude absolute K (luminosity) showed a strong correlation. Furthermore, the redshift range between 0.14 and 0.15 was the most promising, with an R2 of 0.66.

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

    SciTech Connect

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

    2011-10-20

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

  14. TURBULENT CAULDRON OF STARBIRTH IN NEARBY ACTIVE GALAXY

    NASA Technical Reports Server (NTRS)

    2002-01-01

    NASA's Hubble Space Telescope offers a stunning unprecedented close-up view of a turbulent firestorm of starbirth along a nearly edge-on dust disk girdling Centaurus A, the nearest active galaxy to Earth. A ground-based telescopic view (upper left insert) shows that the dust lane girdles the entire elliptical galaxy. This lane has long been considered the dust remnant of a smaller spiral galaxy that merged with the large elliptical galaxy. The spiral galaxy deposited its gas and dust into the elliptical galaxy, and the shock of the collision compressed interstellar gas, precipitating a flurry of star formation. Resembling looming storm clouds, dark filaments of dust mixed with cold hydrogen gas are silhouetted against the incandescent yellow-orange glow from hot gas and stars behind it. Brilliant clusters of young blue stars lie along the edge of the dark dust rift. Outside the rift the sky is filled with the soft hazy glow of the galaxy's much older resident population of red giant and red dwarf stars. The dusty disk is tilted nearly edge-on, its inclination estimated to be only 10 or 20 degrees from our line-of-sight. The dust lane has not yet had enough time since the recent merger to settle down into a flat disk. At this oblique angle, bends and warps in the dust lane cause us to see a rippled 'washboard' structure. The picture is a mosaic of two Hubble Space Telescope images taken with the Wide Field Planetary Camera 2, on Aug. 1, 1997 and Jan. 10, 1998. The approximately natural color is assembled from images taken in blue, green and red light. Details as small as seven light-years across can be resolved. The blue color is due to the light from extremely hot, newborn stars. The reddish-yellow color is due in part to hot gas, in part to older stars in the elliptical galaxy and in part to scattering of blue light by dust -- the same effect that produces brilliant orange sunsets on Earth. Centaurus A (NGC 5128) Fast Facts: Right Ascension: 13: 25.5 (hours

  15. Activation of raphe nuclei triggers rapid and distinct effects on parallel olfactory bulb output channels.

    PubMed

    Kapoor, Vikrant; Provost, Allison C; Agarwal, Prateek; Murthy, Venkatesh N

    2016-02-01

    The serotonergic raphe nuclei are involved in regulating brain states over timescales of minutes and hours. We examined more rapid effects of raphe activation on two classes of principal neurons in the mouse olfactory bulb, mitral and tufted cells, which send olfactory information to distinct targets. Brief stimulation of the raphe nuclei led to excitation of tufted cells at rest and potentiation of their odor responses. While mitral cells at rest were also excited by raphe activation, their odor responses were bidirectionally modulated, leading to improved pattern separation of odors. In vitro whole-cell recordings revealed that specific optogenetic activation of raphe axons affected bulbar neurons through dual release of serotonin and glutamate. Therefore, the raphe nuclei, in addition to their role in neuromodulation of brain states, are also involved in fast, sub-second top-down modulation similar to cortical feedback. This modulation can selectively and differentially sensitize or decorrelate distinct output channels. PMID:26752161

  16. Activation of raphe nuclei triggers rapid and distinct effects on parallel olfactory bulb output channels

    PubMed Central

    Kapoor, Vikrant; Provost, Allison; Agarwal, Prateek; Murthy, Venkatesh N.

    2015-01-01

    The serotonergic raphe nuclei are involved in regulating brain states over time-scales of minutes and hours. We examined more rapid effects of serotonergic activation on two classes of principal neurons in the mouse olfactory bulb, mitral and tufted cells, which send olfactory information to distinct targets. Brief stimulation of the raphe nuclei led to excitation of tufted cells at rest and potentiation of their odor responses. While mitral cells at rest were also excited by raphe activation, their odor responses were bidirectionally modulated, leading to improved pattern separation of odors. In vitro whole-cell recordings revealed that specific optogenetic activation of raphe axons affected bulbar neurons through dual release of serotonin and glutamate. Therefore, the raphe nuclei, in addition to their role in neuromodulation of brain states, are also involved in fast, sub-second top-down modulation, similar to cortical feedback. This modulation can selectively and differentially sensitize or decorrelate distinct output channels. PMID:26752161

  17. Lambda = 3 mm line survey of nearby active galaxies

    NASA Astrophysics Data System (ADS)

    Aladro, R.; Martín, S.; Riquelme, D.; Henkel, C.; Mauersberger, R.; Martín-Pintado, J.; Weiß, A.; Lefevre, C.; Kramer, C.; Requena-Torres, M. A.; Armijos-Abendaño, R. J.

    2015-07-01

    Aims: We aim to better understand the imprints that the nuclear activity in galaxies leaves in the molecular gas. Methods: We used the IRAM 30 m telescope to observe the frequency range ~[86-116] GHz towards the central regions of the starburst galaxies M 83, M 82, and NGC 253, the galaxies hosting an active galactic nucleus (AGN) M 51, NGC 1068, and NGC 7469, and the ultra-luminous infrared galaxies (ULIRGs) Arp 220 and Mrk 231. Assuming local thermodynamic equilibrium (LTE), we calculated the column densities of 27 molecules and 10 isotopologues (or their upper limits in case of non-detections). Results: Among others, we report the first tentative detections of CH3CHO, HNCO, and NS in M 82 and, for the first time in the extragalactic medium, HC5N in NGC 253. Hα recombination lines were only found in M 82 and NGC 253. Vibrationally excited lines of HC3N were only detected in Arp 220. CH3CCH emission is only seen in the starburst-dominated galaxies. By comparison of the fractional abundances among the galaxies, we looked for the molecules that are best suited to characterise the chemistry of each group of galaxies (starbursts, AGNs and ULIRGs), as well as the differences among galaxies within the same group. Conclusions: Suitable species for characterising and comparing starburst galaxies are CH3OH and HNCO as tracers of large-scale shocks, which dominate early to intermediate starburst stages, and CH3CCH, c-C3H2, and HCO as tracers of UV fields, which control the intermediate-to-old or post starburst phases. M 83 shows signs of a shock-dominated environment. NGC 253 is characterised by both strong shocks and some UV fields. M 82 stands out for its bright photo-dissociated region tracers, which indicate an UV field-dominated environment. Regarding AGNs, the abundances of HCN and CN (previously claimed as enhanced in AGNs) in M 51 are similar to those in starburst galaxies, while the HCN/HCO+ ratio is high in M 51 and NGC 1068, but not in NGC 7469. We did not find

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

    NASA Technical Reports Server (NTRS)

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

    2011-01-01

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

  19. A CANDELS WFC3 GRISM STUDY OF EMISSION-LINE GALAXIES AT z {approx} 2: A MIX OF NUCLEAR ACTIVITY AND LOW-METALLICITY STAR FORMATION

    SciTech Connect

    Trump, Jonathan R.; Kocevski, Dale D.; McGrath, Elizabeth J.; Koo, David C.; Faber, S. M.; Mozena, Mark; Yesuf, Hassen; Scarlata, Claudia; Bell, Eric F.; Laird, Elise S.; Rangel, Cyprian; Yan Renbin; Atek, Hakim; Dickinson, Mark; Donley, Jennifer L.; Ferguson, Henry C.; Grogin, Norman A.; Dunlop, James S.; Finkelstein, Steven L.; and others

    2011-12-20

    We present Hubble Space Telescope Wide Field Camera 3 (WFC3) slitless grism spectroscopy of 28 emission-line galaxies at z {approx} 2, in the GOODS-S region of the Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey. The high sensitivity of these grism observations, with >1{sigma} detections of emission lines to f > 2.5 Multiplication-Sign 10{sup -18} erg s{sup -1} cm{sup -2}, means that the galaxies in the sample are typically {approx}7 times less massive (median M{sub *} = 10{sup 9.5} M{sub Sun }) than previously studied z {approx} 2 emission-line galaxies. Despite their lower mass, the galaxies have [O III]/H{beta} ratios which are very similar to previously studied z {approx} 2 galaxies and much higher than the typical emission-line ratios of local galaxies. The WFC3 grism allows for unique studies of spatial gradients in emission lines, and we stack the two-dimensional spectra of the galaxies for this purpose. In the stacked data the [O III] emission line is more spatially concentrated than the H{beta} emission line with 98.1% confidence. We additionally stack the X-ray data (all sources are individually undetected), and find that the average L{sub [OIII]}/L{sub 0.5-10keV} ratio is intermediate between typical z {approx} 0 obscured active galaxies and star-forming galaxies. Together the compactness of the stacked [O III] spatial profile and the stacked X-ray data suggest that at least some of these low-mass, low-metallicity galaxies harbor weak active galactic nuclei.

  20. Probing the Active Galactic Nuclei using optical spectroscopy

    NASA Astrophysics Data System (ADS)

    Vivek, M.

    Variability studies offer one of the best tools for understanding the physical conditions present in regions close to the central engine in an AGN. We probed the various properties of AGN through time variability studies of spectral lines in the optical wavelengths using the 2m telescope in IUCAA Girawali observatory. The absorption line variability studies are mainly concentrated in understanding the nature of outflows in quasars. Quasar outflows have a huge impact on the evolution of central supermassive blackholes, their host galaxies and the surrounding intergalactic medium. Studying the variability in these Broad Absorption Lines (BALs) can help us understand the structure, evolution, and basic physical properties of these outflows. We conducted a repeated Low ionization BAL monitoring program with 27 LoBALs (Low Ionization BALs) at z 0.3-2.1 covering timescales from 3.22 to 7.69 years in the quasar rest frame. We see a variety of phenomena, including some BALs that either appeared or disappeared completely and some BALs which do not vary over the observation period. In one case, the excited fine structure lines have changed dramatically. One source shows signatures of radiative acceleration. Here, we present the results from this program. Emission line studies are concentrated in understanding the peculiar characteristics of a dual-AGN source SDSS J092712.64+294344.0.

  1. DISCOVERY OF CANDIDATE H{sub 2}O DISK MASERS IN ACTIVE GALACTIC NUCLEI AND ESTIMATIONS OF CENTRIPETAL ACCELERATIONS

    SciTech Connect

    Greenhill, Lincoln J.; Moran, James M.; Tilak, Avanti; Kondratko, Paul T.

    2009-12-10

    Based on spectroscopic signatures, about one-third of known H{sub 2}O maser sources in active galactic nuclei (AGNs) are believed to arise in highly inclined accretion disks around central engines. These 'disk maser candidates' are of interest primarily because angular structure and rotation curves can be resolved with interferometers, enabling dynamical study. We identify five new disk maser candidates in studies with the Green Bank Telescope, bringing the total number published to 30. We discovered two (NGC 1320, NGC 17) in a survey of 40 inclined active galaxies (v {sub sys} < 20, 000 km s{sup -1}). The remaining three disk maser candidates were identified in monitoring of known sources: NGC 449, NGC 2979, and NGC 3735. We also confirm a previously marginal case in UGC 4203. For the disk maser candidates reported here, inferred rotation speeds are 130-500 km s{sup -1}. Monitoring of three more rapidly rotating candidate disks (CG 211, NGC 6264, VV 340A) has enabled measurement of likely orbital centripetal acceleration, and estimation of central masses ((2-7) x10{sup 7} M {sub sun}) and mean disk radii (0.2-0.4 pc). Accelerations may ultimately permit estimation of distances when combined with interferometer data. This is notable because the three AGNs are relatively distant (10,000 km s{sup -1} galaxies, would be small. As signposts of highly inclined geometries at galactocentric radii of approx0.1-1 pc, disk masers also provide robust orientation references that allow analysis of (mis)alignment between AGNs and surrounding galactic stellar disks, even without extensive interferometric mapping. We find no preference among published disk maser candidates to lie in high-inclination galaxies. This provides independent support for conclusions that in late-type galaxies, central engine accretion disks and galactic plane orientations are not

  2. XMM FOLLOW-UP OBSERVATIONS OF THREE SWIFT BAT-SELECTED ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Trippe, M. L.; Reynolds, C. S.; Koss, M.; Mushotzky, R. F.; Winter, L. M.

    2011-08-01

    We present XMM-Newton observations of three active galactic nuclei (AGNs) taken as part of a hunt to find very heavily obscured Compton-thick AGNs. For obscuring columns greater than 10{sup 25} cm{sup -2}, AGNs are only visible at energies below 10 keV via reflected/scattered radiation, characterized by a flat power law. We therefore selected three objects (ESO 417-G006, IRAS 05218-1212, and MCG -01-05-047) from the Swift Burst Alert Telescope (BAT) hard X-ray survey catalog with Swift X-ray Telescope (XRT) 0.5-10 keV spectra with flat power-law indices as candidate Compton-thick sources for follow-up observations with the more sensitive instruments on XMM-Newton. The XMM spectra, however, rule out reflection-dominated models based on the weakness of the observed Fe K{alpha} lines. Instead, the spectra are well fit by a model of a power-law continuum obscured by a Compton-thin absorber plus a soft excess. This result is consistent with previous follow-up observations of two other flat-spectrum BAT-detected AGNs. Thus, out of the six AGNs in the 22 month BAT catalog with apparently flat Swift XRT spectra, all five that have had follow-up observations are not likely Compton thick. We also present new optical spectra of two of these objects, IRAS 05218-1212 and MCG -01-05-047. Interestingly, though both the AGNs have similar X-ray spectra, their optical spectra are completely different, adding evidence against the simplest form of the geometric unified model of AGNs. IRAS 05218-1212 appears in the optical as a Seyfert 1, despite the {approx}8.5 x 10{sup 22} cm{sup -2} line-of-sight absorbing column indicated by its X-ray spectrum. MCG -01-05-047's optical spectrum shows no sign of AGN activity; it appears as a normal galaxy.

  3. Active galaxies and the diffuse gamma-ray background

    NASA Technical Reports Server (NTRS)

    Kazanas, D.; Protheroe, R. J.

    1983-01-01

    Active galaxies are shown to account for the observed gamma ray background radiation if a steepening of the spectra above about 100 keV is present. An analytical model is discussed in which protons undergo Fermi acceleration at a shock in a spherical accretion flow onto a massive black hole. Relativistic protons with power law spectra, nuclear interactions producing gamma rays from neutal pion decay and electrons from pion-mu meson-electron decay, with a power law spectrum above several hundred MeV, synchrotron and inverse Compton losses steepening the electron spectrum, a photon spectrum close to the pion gamma spectrum and a high-energy gamma ray spectrum steepened by photon-photon pair production interactions with X rays are covered in the model. Comparisons are made with HEAO 2 data on active galaxies, which have estimated luminosities and radii consistent with the compactness necessary for producing the steepening predicted by the model. The active galaxies spectra would be described by a spherical accretion-shock model.

  4. Reverberation Mapping of the Dusty Tori in Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Richmond, Michael; Batcheldor, Daniel; Buchanan, Catherine; Capetti, Alessandro; Moshe, Elitzur; Gallimore, Jack; Horne, Keith; Kishimoto, Makoto; Marconi, Alessandro; Mason, Rachel; Maiolino, Robert; Netzer, Hagai; Packham, Christopher; Perez, Enrique; Peterson, Brad; Tadhunter, Clive; Robinson, Andrew; Stirpe, Giovanna; Storchi-Bergmann, Thaisa

    2012-12-01

    Our current understanding of the size and structure of AGN tori is weak, despite their central role in AGN unification models and their importance for studies of supermassive black hole demographics. We propose to use the warm phase of Spitzer to determine the sizes of circum-nuclear dust tori in AGN. To accomplish this we will extend an existing Spitzer monitoring campaign, coordinated with ground-based observations, to measure the 'light echo' as the dust emission responds to variations in the AGN optical/UV continuum. We have selected a sample of 12 bright type 1 nuclei in close proximity to the Spitzer Continuous Viewing Zone which can be observed for at least 70% of the 365 day cycle. We will observe each AGN every 30 days for the whole of Cycle 9, roughly doubling our existing baseline of one year, permitting us to identify optical-IR time lags of many months. We will continue our current ground based monitoring program using a variety of telescopes to determine the AGN light-curves in the optical. These observations will sample the torus more faithfully than previous measurements made in the K-band. Such high fidelity, continuously sampled IR light curves covering ~years cannot be obtained from the ground, and are needed because the expected reverberation timescales are hundreds of days. We will apply well developed techniques to determine the reverberation lag and therefore obtain the characteristic size of the torus in this sample which spans a range of black hole mass and Eddington ratio. Our team contains many leading experts in reverberation mapping of AGN and in the observational study and theoretical modeling of the physics of the dusty torus. We are requesting a total of 14 hours in the cycle to perform our observations. These observations will provide a stringent observational test of current models for the obscuring torus in AGN. The required measurements - long timescales, continuous monitoring in the near-infrared - are possible only with the

  5. Nearby Galaxy is a Hotbed of Star Birth Activity

    NASA Technical Reports Server (NTRS)

    2004-01-01

    This new image taken with NASA's Hubble Space Telescope (HST) is of the nearby dwarf galaxy NGC 1569. This galaxy is a hotbed of vigorous star birth activity which blows huge bubbles that riddle its main body. The bubble structure is sculpted by the galactic super-winds and outflows caused by a colossal input of energy from collective supernova explosions that are linked with a massive episode of star birth. The bubbles seen in this image are made of hydrogen gas that glows when hit by the fierce wind and radiation from hot young stars and is racked by supernova shocks. Its 'star factories' are also manufacturing brilliant blue star clusters. NGC 1569 had a sudden onset of star birth about 25 million years ago, which subsided about the time the very earliest human ancestors appeared on Earth. The Marshall Space Flight Center had responsibility for the design, development, and construction of the HST.

  6. Gamma-ray bursts, QSOs and active galaxies.

    PubMed

    Burbidge, Geoffrey

    2007-05-15

    The similarity of the absorption spectra of gamma-ray burst (GRB) sources or afterglows with the absorption spectra of quasars (QSOs) suggests that QSOs and GRB sources are very closely related. Since most people believe that the redshifts of QSOs are of cosmological origin, it is natural to assume that GRBs or their afterglows also have cosmological redshifts. For some years a few of us have argued that there is much optical evidence suggesting a very different model for QSOs, in which their redshifts have a non-cosmological origin, and are ejected from low-redshift active galaxies. In this paper I extend these ideas to GRBs. In 2003, Burbidge (Burbidge 2003 Astrophys. J. 183, 112-120) showed that the redshift periodicity in the spectra of QSOs appears in the redshift of GRBs. This in turn means that both the QSOs and the GRB sources are similar objects ejected from comparatively low-redshift active galaxies. It is now clear that many of the GRBs of low redshift do appear in, or very near, active galaxies.A new and powerful result supporting this hypothesis has been produced by Prochter et al. (Prochter et al. 2006 Astrophys. J. Lett. 648, L93-L96). They show that in a survey for strong MgII absorption systems along the sightlines to long-duration GRBs, nearly every sightline shows at least one absorber. If the absorbers are intervening clouds or galaxies, only a small fraction should show absorption of this kind. The number found by Prochter et al. is four times higher than that normally found for the MgII absorption spectra of QSOs. They believe that this result is inconsistent with the intervening hypothesis and would require a statistical fluctuation greater than 99.1% probability. This is what we expect if the absorption is intrinsic to the GRBs and the redshifts are not associated with their distances. In this case, the absorption must be associated with gas ejected from the QSO. This in turn implies that the GRBs actually originate in comparatively low

  7. INFRARED CLASSIFICATION AND LUMINOSITIES FOR DUSTY ACTIVE GALACTIC NUCLEI AND THE MOST LUMINOUS QUASARS

    SciTech Connect

    Weedman, Daniel; Sargsyan, Lusine; Houck, James; Barry, Donald; Lebouteiller, Vianney

    2012-12-20

    Mid-infrared spectroscopic measurements from the Infrared Spectrometer (IRS) on Spitzer are given for 125 hard X-ray active galactic nuclei (AGNs; 14-195 keV) from the Swift Burst Alert Telescope (BAT) sample and for 32 AGNs with black hole masses (BHMs) from reverberation mapping. The 9.7 {mu}m silicate feature in emission or absorption defines an infrared AGN classification describing whether AGNs are observed through dust clouds, indicating that 55% of the BAT AGNs are observed through dust. The mid-infrared dust continuum luminosity is shown to be an excellent indicator of intrinsic AGN luminosity, scaling closely with the hard X-ray luminosity, log {nu}L{sub {nu}}(7.8 {mu}m)/L(X) = -0.31 {+-} 0.35, and independent of classification determined from silicate emission or absorption. Dust luminosity scales closely with BHM, log {nu}L{sub {nu}}(7.8 {mu}m) = (37.2 {+-} 0.5) + 0.87 log BHM for luminosity in erg s{sup -1} and BHM in M{sub Sun }. The 100 most luminous type 1 quasars as measured in {nu}L{sub {nu}}(7.8 {mu}m) are found by comparing Sloan Digital Sky Survey (SDSS) optically discovered quasars with photometry at 22 {mu}m from the Wide-Field Infrared Survey Explorer (WISE), scaled to rest frame 7.8 {mu}m using an empirical template determined from IRS spectra. The most luminous SDSS/WISE quasars have the same maximum infrared luminosities for all 1.5 < z < 5, reaching total infrared luminosity L{sub IR} = 10{sup 14.4} L{sub Sun }. Comparing with dust-obscured galaxies from Spitzer and WISE surveys, we find no evidence of hyperluminous obscured quasars whose maximum infrared luminosities exceed the maximum infrared luminosities of optically discovered quasars. Bolometric luminosities L{sub bol} estimated from rest-frame optical or ultraviolet luminosities are compared to L{sub IR}. For the local AGN, the median log L{sub IR}/L{sub bol} = -0.35, consistent with a covering factor of 45% for the absorbing dust clouds. For the SDSS/WISE quasars, the median log L

  8. Proton-synchrotron radiation of large-scale jets in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Aharonian, F. A.

    2002-05-01

    The X-radiation of large-scale extragalactic jets poses a serious challenge for the conventional electron-synchrotron or inverse Compton models suggested to explain the overall non-thermal emission of the resolved knots and hotspots. In this paper I propose an alternative mechanism for X-ray emission - synchrotron radiation by extremely high-energy protons - and discuss implications of this model for the extended jet features resolved by Chandra in several prominent radio galaxies and active galactic nuclei (AGN) - Pictor A, 3C 120, PKS 0637-752 and 3C 273. I show that if protons are indeed accelerated to energies E p >=1018 eV, it is possible to construct a realistic model that allows an effective cooling of protons via synchrotron radiation on quite `comfortable' time-scales of about 107 -108 yr, i.e. on time-scales that provide effective propagation of protons over the jet structures on kpc scales. This explains quite naturally the diffuse character of the observed X-ray emission, as well as the broad range of spectral X-ray indices observed from different objects. Yet, as long as the proton synchrotron cooling time is comparable with both the particle escape time and the age of the jet, the proton-synchrotron model offers an adequate radiation efficiency. The model requires relatively large magnetic field of about 1mG, and proton acceleration rates ranging from L p ~1043 to 1046 ergs-1 . These numbers could be reduced significantly if the jet structures are moving relativistically towards the observer. I discuss also possible contributions of synchrotron radiation by secondary electrons produced at interactions of relatively low energy (E p <=1013 eV) protons with the compressed gas in the jet structures. This is an interesting possibility which however requires a very large product of the ambient gas density and total amount of accelerated protons. Therefore it could be treated as a viable working hypothesis only if one can reduce the intrinsic X

  9. A statistical method to search for recoiling supermassive black holes in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Raffai, P.; Haiman, Z.; Frei, Z.

    2016-01-01

    We propose an observational test for gravitationally recoiling supermassive black holes (BHs) in active galactic nuclei, based on a correlation between the velocities of BHs relative to their host galaxies, |Δv|, and their obscuring dust column densities, Σdust (both measured along the line of sight). We use toy models for the distribution of recoil velocities, BH trajectories, and the geometry of obscuring dust tori in galactic centres, to simulate 2.5 × 105 random observations of recoiling quasars. BHs with recoil velocities comparable to the escape velocity from the galactic centre remain bound to the nucleus, and do not fully settle back to the centre of the torus due to dynamical friction in a typical quasar lifetime. We find that |Δv| and Σdust for these BHs are positively correlated. For obscured (Σdust > 0) and for partially obscured (0 < Σdust ≲ 2.3 g m-2) quasars with |Δv| ≥ 45 km s-1, the sample correlation coefficient between log10(|Δv|) and Σdust is r45 = 0.28 ± 0.02 and r45 = 0.13 ± 0.02, respectively. Allowing for random ± 100 km s- 1 errors in |Δv| unrelated to the recoil dilutes the correlation for the partially obscured quasars to r45 = 0.026 ± 0.004 measured between |Δv| and Σdust. A random sample of ≳ 3500 obscured quasars with |Δv| ≥ 45 km s-1 would allow rejection of the no-correlation hypothesis with 3σ significance 95 per cent of the time. Finally, we find that the fraction of obscured quasars, {F_obs} (|Δv|), decreases with |Δv| from {F_obs} (<10 km s-1) ≳ 0.8 to {F_obs} (>103 km s-1) ≲ 0.4. This predicted trend can be compared to the observed fraction of type II quasars, and can further test combinations of recoil, trajectory, and dust torus models.

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

    NASA Astrophysics Data System (ADS)

    Bartos, Imre

    2016-06-01

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

  11. 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.

  12. 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.

  13. Deficits in the Activation of Human Oculomotor Nuclei in Chronic Traumatic Brain Injury

    PubMed Central

    Tyler, Christopher W.; Likova, Lora T.; Mineff, Kristyo N.; Nicholas, Spero C.

    2015-01-01

    Binocular eye movements form a finely tuned system that requires accurate coordination of the oculomotor dynamics of the brainstem control nuclei when tracking the fine binocular disparities required for 3D vision. They are particularly susceptible to disruption by brain injury and other neural dysfunctions. Here, we report functional magnetic resonance imaging activation of the brainstem oculomotor control nuclei by binocular saccadic and vergence eye movements, and significant reductions in their response amplitudes in mild or diffuse traumatic brain injury (dTBI). Bilateral signals were recorded from a non-TBI control group (n = 11) in the oculomotor control system of the superior colliculi, the oculomotor nuclei, the abducens nuclei, and in the supra-oculomotor area (SOA), which mediate vergence eye movements. Signals from these nuclei were significantly reduced overall in a dTBI group (n = 12) and in particular for the SOA for vergence movements, which also showed significant decreases in velocity for both the convergence and divergence directions. PMID:26379615

  14. Herschel Far-infrared Photometry of the Swift Burst Alert Telescope Active Galactic Nuclei Sample of the Local Universe. I. PACS Observations

    NASA Astrophysics Data System (ADS)

    Meléndez, M.; Mushotzky, R. F.; Shimizu, T. T.; Barger, A. J.; Cowie, L. L.

    2014-10-01

    Far-Infrared (FIR) photometry from the Photodetector Array Camera and Spectrometer on the Herschel Space Observatory is presented for 313 nearby, hard X-ray selected galaxies from the 58 month Swift Burst Alert Telescope (BAT) Active Galactic Nuclei catalog. The present data do not distinguish between the FIR luminosity distributions at 70 and 160 μm for Seyfert 1 and Seyfert 2 galaxies. This result suggests that if the FIR emission is from the nuclear obscuring material surrounding the accretion disk, then it emits isotropically, independent of orientation. Alternatively, a significant fraction of the 70 and 160 μm luminosity could be from star formation, independent of active galactic nucleus (AGN) type. Using a non-parametric test for partial correlation with censored data, we find a statistically significant correlation between the AGN intrinsic power (in the 14-195 keV band) and the FIR emission at 70 and 160 μm for Seyfert 1 galaxies. We find no correlation between the 14-195 keV and FIR luminosities in Seyfert 2 galaxies. The observed correlations suggest two possible scenarios: (1) if we assume that the FIR luminosity is a good tracer of star formation, then there is a connection between star formation and the AGN at sub-kiloparsec scales, or (2) dust heated by the AGN has a statistically significant contribution to the FIR emission. Using a Spearman rank-order analysis, the 14-195 keV luminosities for the Seyfert 1 and 2 galaxies are weakly statistically correlated with the F 70/F 160 ratios. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA.

  15. Herschel far-infrared photometry of the swift burst alert telescope active galactic nuclei sample of the local universe. I. PACS observations

    SciTech Connect

    Meléndez, M.; Mushotzky, R. F.; Shimizu, T. T.; Barger, A. J.; Cowie, L. L.

    2014-10-20

    Far-Infrared (FIR) photometry from the Photodetector Array Camera and Spectrometer on the Herschel Space Observatory is presented for 313 nearby, hard X-ray selected galaxies from the 58 month Swift Burst Alert Telescope (BAT) Active Galactic Nuclei catalog. The present data do not distinguish between the FIR luminosity distributions at 70 and 160 μm for Seyfert 1 and Seyfert 2 galaxies. This result suggests that if the FIR emission is from the nuclear obscuring material surrounding the accretion disk, then it emits isotropically, independent of orientation. Alternatively, a significant fraction of the 70 and 160 μm luminosity could be from star formation, independent of active galactic nucleus (AGN) type. Using a non-parametric test for partial correlation with censored data, we find a statistically significant correlation between the AGN intrinsic power (in the 14-195 keV band) and the FIR emission at 70 and 160 μm for Seyfert 1 galaxies. We find no correlation between the 14-195 keV and FIR luminosities in Seyfert 2 galaxies. The observed correlations suggest two possible scenarios: (1) if we assume that the FIR luminosity is a good tracer of star formation, then there is a connection between star formation and the AGN at sub-kiloparsec scales, or (2) dust heated by the AGN has a statistically significant contribution to the FIR emission. Using a Spearman rank-order analysis, the 14-195 keV luminosities for the Seyfert 1 and 2 galaxies are weakly statistically correlated with the F {sub 70}/F {sub 160} ratios.

  16. Reversible, activity-dependent targeting of profilin to neuronal nuclei

    SciTech Connect

    Birbach, Andreas . E-mail: andreas.birbach@lbicr.lbg.ac.at; Verkuyl, J. Martin; Matus, Andrew . E-mail: aim@fmi.ch

    2006-07-15

    The actin cytoskeleton in pyramidal neurons plays a major role in activity-dependent processes underlying neuronal plasticity. The small actin-binding protein profilin shows NMDA receptor-dependent accumulation in dendritic spines, which is correlated with suppression of actin dynamics and long-term stabilization of synaptic morphology. Here we show that following NMDA receptor activation profilin also accumulates in the nucleus of hippocampal neurons via a process involving rearrangement of the actin cytoskeleton. This simultaneous targeting to dendritic spines and the cell nucleus suggests a novel mechanism of neuronal plasticity in which profilin both tags activated synapses and influences nuclear events.

  17. X-ray Spectroscopy of Low-Luminosity Active Galactic Nuclei with XMM

    NASA Technical Reports Server (NTRS)

    DiMatteo, Tiziana; Mushotzky, Richard (Technical Monitor)

    2002-01-01

    The measurement of black hole masses in nearby galaxies has transformed our understanding of these systems, allowing us to quantify the relevant scales of power, length and time and explore how the activity of black holes is linked to their environments and to the evolution of their host galaxies. In this project, Dr. Tiziana Di Matteo has the primary responsibility for developing and investigating theoretical models for the origin of the X-ray emission observed in low-luminosity AGN. Dr. Di Matteo has been involved in interpreting X-ray data and assessing accretion models throughout the project.

  18. 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.

  19. Supernovae in paired galaxies

    NASA Astrophysics Data System (ADS)

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

    2014-07-01

    We investigate the influence of close neighbor galaxies on the properties of supernovae (SNe) and their host galaxies using 56 SNe located in pairs of galaxies with different levels of star formation (SF) and nuclear activity. The mean distance of type II SNe from nuclei of hosts is greater by about a factor of 2 than that of type Ibc SNe. The distributions and mean distances of SNe are consistent with previous results compiled with the larger sample. For the first time it is shown that SNe Ibc are located in pairs with significantly smaller difference of radial velocities between components than pairs containing SNe Ia and II. We consider this as a result of higher star formation rate (SFR) of these closer systems of galaxies.

  20. 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.

  1. In vivo metabolic activity of hamster suprachiasmatic nuclei: use of anesthesia

    SciTech Connect

    Schwartz, W.J.

    1987-02-01

    In vivo glucose utilization was measured in the suprachiasmatic nuclei (SCN) of Golden hamsters using the /sup 14/C-labeled deoxyglucose technique. A circadian rhythm of SCN metabolic activity could be measured in this species, but only during pentobarbital sodium anesthesia when the surrounding background activity of adjacent hypothalamus was suppressed. Both the SCN's metabolic oscillation and its time-keeping ability are resistant to general anesthesia.

  2. Neuromedin U in the paraventricular and arcuate hypothalamic nuclei increases non-exercise activity thermogenesis.

    PubMed

    Novak, C M; Zhang, M; Levine, J A

    2006-08-01

    Brain neuromedin U (NMU) has been associated with the regulation of both energy intake and expenditure. We hypothesized that NMU induces changes in spontaneous physical activity and nonexercise activity thermogenesis (NEAT) through its actions on hypothalamic nuclei. We applied increasing doses of NMU directly to the paraventricular (PVN) and arcuate hypothalamic nuclei using chronic unilateral guide cannulae. In both nuclei, NMU significantly and dose-dependently increased physical activity and NEAT. Moreover, NMU increased physical activity and NEAT during the first hour of the dark phase, indicating that the reduction of sleep is unlikely to account for the increased physical activity seen with NMU treatment. As a positive control, we demonstrated that paraventricular NMU also significantly decreased food intake, as well as body weight. These data demonstrate that NMU is positively associated with NEAT through its actions in the PVN and arcuate nucleus. In co-ordination with its suppressive effects on feeding, the NEAT-activating effects of NMU make it a potential candidate in the combat of obesity. PMID:16867180

  3. Highly Active Ice Nuclei from Tree Leaf Litters Retain Activity for Decades

    NASA Astrophysics Data System (ADS)

    Schnell, R. C.; Hill, T. C. J.

    2015-12-01

    Biogenic ice nuclei (IN) studied since the 1960s were first observed in tree leaf litters, in a few bacteria species and later in fungi and lichens. Recently, viable IN bacteria in precipitation have been used as a metric of their possible role in precipitation formation. Although bacterial IN activity is deactivated by a variety of common environmental stresses, we present data showing that IN found in a potpourri of decayed plant leaves, bacteria, molds and fungi etc. in plant litters are exceptionally stable and active over decades while in storage. As such, their atmospheric IN potential is worthy of further study due to their environmental persistence. In August 1970 litter collected in a grove of deciduous trees near Red Deer, AB, Canada was tested for IN (drop freezing technique). The sample initiated ice at -4C with 109 IN per gram of litter active at -10C. A few kilograms were stored in a plastic bag and tested every few years for IN content; the IN activity remained essential