Using a sample of 24 264 optically selected active galactic nuclei (AGNs) from the SDSS DR7 data base, we characterize how the profile of the O iii λ5007 emission line relates to bolometric ...luminosity (L
AGN), Eddington ratio, radio loudness, radio luminosity (L
1.4 GHz) and optical class (i.e. broad/narrow-line Seyfert 1, type 2) to determine what drives the kinematics of this kpc-scale line emitting gas. First, we use spectral stacking to characterize how the average O iii λ5007 profile changes as a function of these five variables. After accounting for the known correlation between L
AGN and L
1.4 GHz, we report that L
1.4 GHz has the strongest influence on the O iii λ5007 profile, with AGNs of moderate radio luminosity (L
1.4 GHz = 1023-1025 W Hz−1) having the broadest O iii λ5007 profiles. Conversely, we find only a modest change in the O iii λ5007 profile with increasing radio loudness and find no significant difference between the O iii λ5007 profiles of broad- and narrow-line Seyfert 1s. When binned according to Eddington ratio, only the AGNs in our highest bin (i.e. >0.3) show any signs of having broadened O iii λ5007 profiles, although the small numbers of such extreme AGNs in our sample mean we cannot rule out that other processes (e.g. radio jets) are responsible for this broadening. The O iii λ5007 profiles of type 1 and type 2 AGNs show the same trends in terms of line width, but type 1 AGNs display a much stronger 'blue wing', which we interpret as evidence of outflowing ionized gas. We perform multicomponent fitting to the Hβ, O iii λλ4959, 5007, N ii λλ6548, 6584 and Hα lines for all the AGNs in our sample to calculate the proportions of AGNs with broad O iii λ5007 profiles. The individual fits confirm the results from our stacked spectra; AGNs with L
1.4 GHz > 1023 W Hz−1 are roughly five times more likely to have extremely broad O iii λ5007 lines (full width at half-maximum, FWHMAvg > 1000 km s−1) compared to lower L
1.4 GHz AGNs, and the width of the O iii λ5007 line peaks in moderate-radio-luminosity AGNs (L
1.4 GHz ∼ 1024 W Hz−1). Our results are consistent with the most disturbed gas kinematics being induced by compact radio cores (rather than powerful radio jets), although broadened O iii λ5007 lines are also present, but much rarer, in low-L
1.4 GHz systems. Our catalogue of multicomponent fits is freely available as an online resource for statistical studies of the kinematics and luminosities of the narrow- and broad-line AGN regions and the identification of potential targets for follow-up observations at http://sites.google.com/site/sdssalpaka.
In this study, we investigate the relationship between the star formation rate (SFR) and AGN luminosity (
$\mathrel {L_{\rm AGN}}$
) for ∼2000 X-ray detected AGN. The AGN span over three orders of ...magnitude in X-ray luminosity (
$10^{42} <\, \mathrel {L_{2{\rm -}8\,\mathrm{keV}}}\,< 10^{45.5} \mathrel {\,\rm erg \; s^{-1}}$
) and are in the redshift range z = 0.2–2.5. Using infrared (IR) photometry (8–500
$\mathrel {\,\rm \mu m}$
), including deblended Spitzer and Herschel images and taking into account photometric upper limits, we decompose the IR spectral energy distributions into AGN and star formation components. Using the IR luminosities due to star formation, we investigate the average SFRs as a function of redshift and AGN luminosity. In agreement with previous studies, we find a strong evolution of the average SFR with redshift, tracking the observed evolution of the overall star-forming galaxy population. However, we find that the relationship between the average SFR and AGN luminosity is broadly flat at all redshifts and across all the AGN luminosities investigated; in comparison to previous studies, we find less scatter amongst the average SFRs across the wide range of AGN luminosities investigated. By comparing to empirical models, we argue that the observed flat relationship is due to short time-scale variations in AGN luminosity, driven by changes in the mass accretion rate, which wash out any underlying correlations between SFR and
$\mathrel {L_{\rm AGN}}$
. Furthermore, we show that the exact form of the predicted relationship between SFR and AGN luminosity (and its normalization) is highly sensitive to the assumed intrinsic Eddington ratio distribution.
We use infrared spectroscopy and photometry to empirically define the intrinsic mid- to far-infrared spectral energy distribution (i.e. 6-100 μm SED) of thermal emission produced by typical (i.e. ...2-10 keV luminosity, L
2-10 keV∼ 1042-1044 erg s−1) active galactic nuclei (hereafter AGNs). The average infrared SED of typical AGNs is best described as a broken power law at ≲40 μ m that falls steeply at ≳40 μm (i.e. at far-infrared wavelengths). Despite this fall-off at long wavelengths, at least three of the 11 AGNs in our sample have demonstrated SEDs that are AGN dominated even at 60 μ m, demonstrating the importance of accounting for any AGN contribution when calculating galaxy infrared luminosities. We find that the average intrinsic AGN 6-100 μ m SED gets bluer with increasing X-ray luminosity - a trend seen both within our sample and also when we compare it with the intrinsic SEDs of more luminous quasars (i.e. L
2-10 keV≳ 1044 erg s−1). The range of intrinsic AGN SEDs is more closely matched by clumpy, rather than continuous, torus models. Using our intrinsic AGN SEDs we define a set of correction factors to convert either monochromatic infrared or X-ray luminosities into total (i.e. 8-1000 μm) AGN infrared luminosities. We outline a procedure that uses our newly defined intrinsic AGN infrared SEDs, in conjunction with a selection of host-galaxy templates, to measure the AGN contribution to the infrared output of composite galaxies from photometry alone. We verify the accuracy of our SED-fitting procedure by comparing our results to two independent measures of AGN contribution: (1) 12-μm luminosities obtained from high spatial resolution observations of nearby galaxies and (2) the equivalent width of the 11.25-μm PAH feature. Our SED-fitting procedure opens up the possibility of measuring the intrinsic AGN luminosities for large numbers of galaxies with well-sampled infrared data (e.g. IRAS, ISO, Spitzer and Herschel).
The bolometric quasar luminosity function at z = 0–7 Shen, Xuejian; Hopkins, Philip F; Faucher-Giguère, Claude-André ...
Monthly notices of the Royal Astronomical Society,
07/2020, Letnik:
495, Številka:
3
Journal Article
Recenzirano
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ABSTRACT
In this paper, we provide updated constraints on the bolometric quasar luminosity function (QLF) from z = 0 to z = 7. The constraints are based on an observational compilation that includes ...observations in the rest-frame IR, B band, UV, soft, and hard X-ray in past decades. Our method follows Hopkins et al. with an updated quasar SED model and bolometric and extinction corrections. The new best-fitting bolometric quasar luminosity function behaves qualitatively different from the old Hopkins model at high redshift. Compared with the old model, the number density normalization decreases towards higher redshift and the bright-end slope is steeper at z ≳ 2. Due to the paucity of measurements at the faint end, the faint end slope at z ≳ 5 is quite uncertain. We present two models, one featuring a progressively steeper faint-end slope at higher redshift and the other featuring a shallow faint-end slope at z ≳ 5. Further multiband observations of the faint-end QLF are needed to distinguish between these models. The evolutionary pattern of the bolometric QLF can be interpreted as an early phase likely dominated by the hierarchical assembly of structures and a late phase likely dominated by the quenching of galaxies. We explore the implications of this model on the ionizing photon production by quasars, the CXB spectrum, the SMBH mass density, and mass functions. The predicted hydrogen photoionization rate contributed by quasars is subdominant during the epoch of reionization and only becomes important at z ≲ 3. The predicted CXB spectrum, cosmic SMBH mass density, and SMBH mass function are generally consistent with existing observations.
What drives the growth of black holes? Alexander, D.M.; Hickox, R.C.
New astronomy reviews,
June 2012, 2012-6-00, 20120601, Letnik:
56, Številka:
4
Journal Article
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Massive black holes (BHs) are at once exotic and yet ubiquitous, residing at the centers of massive galaxies in the local Universe. Recent years have seen remarkable advances in our understanding of ...how these BHs form and grow over cosmic time, during which they are revealed as Active Galactic Nuclei (AGN). However, despite decades of research, we still lack a coherent picture of the physical drivers of BH growth, the connection between the growth of BHs and their host galaxies, the role of large-scale environment on the fueling of BHs, and the impact of BH-driven outflows on the growth of galaxies. In this paper we review our progress in addressing these key issues, motivated by the science presented at the “What drives the growth of black holes?” workshop held at Durham on 26–29th July 2010, and discuss how these questions may be tackled with current and future facilities.
We use a coupled model of the formation and evolution of galaxies and black holes (BHs) to study the evolution of active galactic nuclei (AGNs) in a cold dark matter universe. The model is embedded ...in the galaxy formation code galform and predicts the masses, spins and mass accretion histories of BHs in tandem with the formation of their host galaxies. BHs grow by accretion during starbursts, triggered by discs becoming dynamically unstable or by galaxy mergers, and accretion from quasi-hydrostatic hot gas haloes. Using an empirical law for AGN obscuration, our model matches the observed luminosity functions (LFs) of AGNs over a wide range of redshifts. Due to the suppression of cooling in massive haloes by AGN feedback, at low redshift (z≲ 2), the brightest quasars (L
bol≳ 1046 erg s−1) are predicted preferentially to inhabit haloes with masses
. The model predicts a hierarchical buildup of BH mass, with the typical mass of actively growing BHs increasing with decreasing redshift. Nevertheless, the model displays clear 'downsizing' as reflected in the differential evolution of the space density of faint and bright AGNs. This arises naturally from the interplay between the starburst and hot gas halo accretion modes. The faint end of the LF is dominated by massive BHs accreting at low rates via a thick disc, primarily during the hot-halo mode. The bright end is populated by BHs accreting close to or above the Eddington limit during the starburst mode. Obscuration plays a central role in determining the observed abundance of AGNs and, hence, in their implied cosmic evolution.
ABSTRACT
We present integral field spectroscopy observations, covering the O iii λλ4959, 5007 emission‐line doublet of eight high‐redshift (z = 1.4–3.4) ultraluminous infrared galaxies (ULIRGs) that ...host active galactic nucleus (AGN) activity, including known submillimetre luminous galaxies. The targets have moderate radio luminosities that are typical of high‐redshift ULIRGs (L1.4 GHz = 1024–1025 W Hz−1) and therefore are not radio‐loud AGNs. We decouple kinematic components due to the galaxy dynamics and mergers from those due to outflows. We find evidence in the four most luminous systems (LO III ≳1043 erg s−1) for the signatures of large‐scale energetic outflows: extremely broad O iii emission (full width at half‐maximum ≈ 700–1400 km s−1) across ≈4–15 kpc, with high velocity offsets from the systemic redshifts (up to ≈850 km s−1). The four less luminous systems have lower quality data displaying weaker evidence for spatially extended outflows. We estimate that these outflows are potentially depositing energy into their host galaxies at considerable rates (Ė≈1043–1045 erg s−1); however, due to the lack of constraints on the density of the outflowing material and the structure of the outflow, these estimates should be taken as illustrative only. Based on the measured maximum velocities (vmax ≈ 400–1400 km s−1) the outflows observed are likely to unbind some fraction of the gas from their host galaxies, but are unlikely to completely remove gas from the galaxy haloes. By using a combination of energetic arguments and a comparison to ULIRGs without clear evidence for AGN activity, we show that the AGN activity could be the dominant power source for driving all of the observed outflows, although star formation may also play a significant role in some of the sources.
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 x 10 super(24) cm super(-2)) active galactic nuclei (AGNs) with hard ...energy (E > 10 keV) X-ray spectral measurements. We accurately measure the silicate absorption features at lambda ~ 9.7 mu m in archival low-resolution (R ~ 57-127) Spitzer Infrared Spectrograph spectroscopy, and show that only a minority (approx =45%) of nearby Compton-thick AGNs have strong Si-absorption features (S sub(9.7) = ln (functionof sub(int)/functionof sub(obs)) > ~0.5) which would indicate significant dust attenuation. The majority (approx =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) ~ 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.
ABSTRACT We present a sample of accreting supermassive black holes (SMBHs) in dwarf galaxies at . We identify dwarf galaxies in the NEWFIRM Medium Band Survey with stellar masses of that have ...spectroscopic redshifts from the DEEP2 survey and lie within the region covered by deep (flux limit of ) archival Chandra X-ray data. From our sample of 605 dwarf galaxies, 10 exhibit X-ray emission consistent with that arising from active galactic nucleus (AGN) activity. If black-hole mass scales roughly with stellar mass, then we expect that these AGNs are powered by SMBHs with masses of and typical Eddington ratios of . Furthermore, we find an AGN fraction consistent with extrapolations of other searches of for and . Our AGN fraction is in good agreement with a semi-analytic model, suggesting that, as we search larger volumes, we may use comparisons between observed AGN fractions and models to understand seeding mechanisms in the early universe.
We present the first full catalog and science results for the Nuclear Spectroscopic Telescope Array (NuSTAR) serendipitous survey. The catalog incorporates data taken during the first 40 months of ...NuSTAR operation, which provide 20 Ms of effective exposure time over 331 fields, with an areal coverage of 13 deg2, and 497 sources detected in total over the 3-24 keV energy range. There are 276 sources with spectroscopic redshifts and classifications, largely resulting from our extensive campaign of ground-based spectroscopic follow-up. We characterize the overall sample in terms of the X-ray, optical, and infrared source properties. The sample is primarily composed of active galactic nuclei (AGNs), detected over a large range in redshift from z = 0.002 to 3.4 (median of ), but also includes 16 spectroscopically confirmed Galactic sources. There is a large range in X-ray flux, from to −11, and in rest-frame 10-40 keV luminosity, from to 46, with a median of 44.1. Approximately 79% of the NuSTAR sources have lower-energy (<10 keV) X-ray counterparts from XMM-Newton, Chandra, and Swift XRT. The mid-infrared (MIR) analysis, using WISE all-sky survey data, shows that MIR AGN color selections miss a large fraction of the NuSTAR-selected AGN population, from 15% at the highest luminosities ( erg s−1) to 80% at the lowest luminosities ( erg s−1). Our optical spectroscopic analysis finds that the observed fraction of optically obscured AGNs (i.e., the type 2 fraction) is , for a well-defined subset of the 8-24 keV selected sample. This is higher, albeit at a low significance level, than the type 2 fraction measured for redshift- and luminosity-matched AGNs selected by <10 keV X-ray missions.
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