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Register a new userBlack Hole and Galaxy Coevolution in Moderately Luminous Active Galactic Nuclei at z~1.4 in SXDF
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We investigate the relation of black hole mass versus host stellar mass and that of mass accretion rate versus star formation rate (SFR) in moderately luminous ($log L_{rm bol} sim 44.5-46.5 {rm erg s^{-1}}$), X-ray selected broad-line active galactic nuclei (AGNs) at $z=1.18-1.68$ in the Subaru/XMM-Newton Deep Field. The far-infrared to far-ultraviolet spectral energy distributions of 85 AGNs are reproduced with the latest version of Code Investigating GALaxy Emission ({tt CIGALE}), where the AGN clumpy torus model {tt SKIRTOR} is implemented. Most of their hosts are confirmed to be main-sequence star-forming galaxies. We find that the mean ratio of the black hole mass ($M_{rm BH}$) to the total stellar mass ($M_{rm stellar}$) is $log M_{rm BH}/M_{rm stellar} = -2.2$, which is similar to the local black hole-to-bulge mass ratio. This suggests that if the host galaxies of these moderately luminous AGNs at $zsim1.4$ are dominated by bulges, they already established the local black hole mass-bulge mass relation; if they are disk dominant, their black holes are overmassive relative to the bulges. AGN bolometric luminosities and SFR show a good correlation with ratios higher than that expected from the local black hole-to-bulge mass relation, suggesting that these AGNs are in a SMBH-growth dominant phase.
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This is the third paper in a series describing the spectroscopic properties of a sample of 39 AGN at $z sim 1.5$, selected to cover a large range in black hole mass ($M_{BH}$) and Eddington ratio ($L/L_{Edd}$). In this paper, we continue the analysis of the VLT/X-shooter observations of our sample with the addition of 9 new sources. We use an improved Bayesian procedure, which takes into account intrinsic reddening, and improved $M_{BH}$ estimates, to fit thin accretion disc (AD) models to the observed spectra and constrain the spin parameter ($a_*$) of the central black holes. We can fit 37 out of 39 AGN with the thin AD model, and for those with satisfactory fits, we obtain constraints on the spin parameter of the BHs, with the constraints becoming generally less well defined with decreasing BH mass. Our spin parameter estimates range from $sim$$-$0.6 to maximum spin for our sample, and our results are consistent with the spin-up scenario of BH spin evolution. We also discuss how the results of our analysis vary with the inclusion of non-simultaneous GALEX photometry in our thin AD fitting. Simultaneous spectra covering the rest-frame optical through far-UV are necessary to definitively test the thin AD theory and obtain the best constraints on the spin parameter.
The astrophysical origin of gravitational wave (GW) transients is a timely open question in the wake of discoveries by LIGO/Virgo. In active galactic nuclei (AGNs), binaries form and evolve efficiently by interaction with a dense population of stars and the gaseous AGN disk. Previous studies have shown that stellar-mass black hole (BH) mergers in such environments can explain the merger rate and the number of suspected hierarchical mergers observed by LIGO/Virgo. The binary eccentricity distribution can provide further information to distinguish between astrophysical models. Here we derive the eccentricity distribution of BH mergers in AGN disks. We find that eccentricity is mainly due to binary-single (BS) interactions, which lead to most BH mergers in AGN disks having a significant eccentricity at $0.01,mathrm{Hz}$, detectable by LISA. If BS interactions occur in isotropic-3D directions, then $8$--$30%$ of the mergers in AGN disks will have eccentricities at $10,mathrm{Hz}$ above $e_{10,rm Hz}gtrsim 0.03$, detectable by LIGO/Virgo/KAGRA, while $5$--$17%$ of mergers have $e_{10,rm Hz}geq 0.3$. On the other hand, if BS interactions are confined to the AGN-disk plane due to torques from the disk, with 1-20 intermediate binary states during each interaction, or if BHs can migrate to $lesssim10^{-3},mathrm{pc}$ from the central supermassive black hole, then $10$--$70%$ of the mergers will be highly eccentric ($e_{10,rm Hz} geq 0.3$), consistent with the possible high eccentricity in GW190521.
Measuring the spins of supermassive black holes (SMBHs) in active galactic nuclei (AGN) can inform us about the relative role of gas accretion vs. mergers in recent epochs of the life of the host galaxy and its AGN. Recent advances in theory and observation have enabled spin measurements for a handful of SMBHs thus far, but this science is still very much in its infancy. Herein, I discuss how and why we seek to measure black hole spin in AGN, using recent results from long X-ray observing campaigns on three radio-quiet AGN (MCG-6-30-15, NGC 3783 and Fairall 9) to illustrate this process and its caveats. I then present our current knowledge of the distribution of SMBH spins in the local universe. I also address prospects for improving the accuracy, precision and quantity of these spin constraints in the next decade and beyond with instruments such as NuSTAR, Astro-H and a future generation large-area X-ray telescope.
We model the triggering of Active Galactic Nuclei (AGN) in galaxy clusters using the semi- analytic galaxy formation model SAGE (?). We prescribe triggering methods based on the ram pressure galaxies experience as they move throughout the intracluster medium, which is hypothesized to trigger star formation and AGN activity. The clustercentric radius and velocity distribution of the simulated active galaxies produced by these models are compared with that of AGN and galaxies with intense star formation from a sample of low-redshift, relaxed clusters from the Sloan Digital Sky Survey. The ram pressure triggering model that best explains the clustercentric radius and velocity distribution of these observed galaxies has AGN and star formation triggered if $2.5times10^{-14} < P_{ram} < 2.5times10^{-13}$ Pa and $P_{ram} > 2P_{internal}$; this is consistent with expectations from hydrodynamical simulations of ram-pressure induced star formation. Our results show that ram pressure is likely to be an important mechanism for triggering star formation and AGN activity in clusters.
We have measured the stellar velocity dispersions (sigma_*) and estimated the central black hole (BH) masses for over 900 broad-line active galactic nuclei (AGNs) observed with the Sloan Digital Sky Survey. The sample includes objects which have redshifts up to z=0.452, high quality spectra, and host galaxy spectra dominated by an early-type (bulge) component. The AGN and host galaxy spectral components were decomposed using an eigenspectrum technique. The BH masses (M_BH) were estimated from the AGN broad-line widths, and the velocity dispersions were measured from the stellar absorption spectra of the host galaxies. The range of black hole masses covered by the sample is approximately 10^6 < M_BH < 10^9 M_Sun. The host galaxy luminosity-velocity dispersion relationship follows the well-known Faber-Jackson relation for early-type galaxies, with a power-law slope 4.33+-0.21. The estimated BH masses are correlated with both the host luminosities (L_{H}) and the stellar velocity dispersions (sigma_*), similar to the relationships found for low-redshift, bulge-dominated galaxies. The intrinsic scatter in the correlations are large (~0.4 dex), but the very large sample size allows tight constraints to be placed on the mean relationships: M_BH ~ L_H^{0.73+-0.05} and M_BH ~ sigma_*^{3.34+-0.24}. The amplitude of the M_BH-sigma_* relation depends on the estimated Eddington ratio, such that objects with larger Eddington ratios have smaller black hole masses than expected at a given velocity dispersion.
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