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Register a new userNo significant evolution of relations between Black hole mass and Galaxy total stellar mass up to z~2.5
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We investigate the cosmic evolution of the ratio between black hole mass (MBH) and host galaxy total stellar mass (Mstellar) out to z~2.5 for a sample of 100 X-ray-selected moderate-luminosity, broad-line active galactic nuclei (AGNs) in the Chandra-COSMOS Legacy Survey. By taking advantage of the deep multi-wavelength photometry and spectroscopy in the COSMOS field, we measure in a uniform way the galaxy total stellar mass using a SED decomposition technique and the black hole mass based on broad emission line measurements and single-epoch virial estimates. Our sample of AGN host galaxies has total stellar masses of 10^10-12Msun, and black hole masses of 10^7.0-9.5Msun. Combining our sample with the relatively bright AGN samples from the literature, we find no significant evolution of the MBH-Mstellar relation with black hole-to-host total stellar mass ratio of MBH/Mstellar~0.3% at all redshifts probed. We conclude that the average black hole-to-host stellar mass ratio appears to be consistent with the local value within the uncertainties, suggesting a lack of evolution of the MBH-Mstellar relation up to z~2.5.
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At the highest redshifts, z>6, several tens of luminous quasars have been detected. The search for fainter AGN, in deep X-ray surveys, has proven less successful, with few candidates to date. An extrapolation of the relationship between black hole (BH) and bulge mass would predict that the sample of z>6 galaxies host relatively massive BHs (>1e6 Msun), if one assumes that total stellar mass is a good proxy for bulge mass. At least a few of these BHs should be luminous enough to be detectable in the 4Ms CDFS. The relation between BH and stellar mass defined by local moderate-luminosity AGN in low-mass galaxies, however, has a normalization that is lower by approximately an order of magnitude compared to the BH-bulge mass relation. We explore how this scaling changes the interpretation of AGN in the high-z Universe. Despite large uncertainties, driven by those in the stellar mass function, and in the extrapolation of local relations, one can explain the current non-detection of moderate-luminosity AGN in Lyman Break Galaxies if galaxies below 1e11 Msun are characterized by the low-normalization scaling, and, even more so, if their Eddington ratio is also typical of moderate-luminosity AGN rather than luminous quasars. AGN being missed by X-ray searches due to obscuration or instrinsic X-ray weakness also remain a possibility.
Supermassive Black Holes (BHs) residing in brightest cluster galaxies (BCGs) are overly massive when considering the local relationships between the BH mass and stellar bulge mass or velocity dispersion. Due to the location of these BHs within the cluster, large-scale cluster processes may aid the growth of BHs in BCGs. In this work, we study a sample of 71 galaxy clusters to explore the relationship between the BH mass, stellar bulge mass of the BCG, and the total gravitating mass of the host clusters. Due to difficulties in obtaining dynamically measured BH masses in distant galaxies, we use the Fundamental Plane relationship of BHs to infer their masses. We utilize X-ray observations taken by $Chandra$ to measure the temperature of the intra-cluster medium (ICM), which is a proxy for the total mass of the cluster. We analyze the $rm M_{BH}-kT$ and $rm M_{BH}-M_{Bulge}$ relationships and establish the best-fitting power laws:$log_{10}(M_{rm BH} /10^9 M_{odot})=-0.35+2.08 log_{10}(kT / 1 rm keV)$ and $log_{10}(rm M_{BH}/10^9M_{odot})= -1.09+ 1.92 log_{10}(M_{rm bulge}/10^{11}M_{odot})$. Both relations are comparable with that established earlier for a sample of brightest group/cluster galaxies with dynamically measured BH masses. Although both the $rm M_{BH}-kT$ and the $rm M_{BH}-M_{Bulge}$ relationships exhibit large intrinsic scatter, based on Monte Carlo simulations we conclude that dominant fraction of the scatter originates from the Fundamental Plane relationship. We split the sample into cool core and non-cool core resembling clusters, but do not find statistically significant differences in the $rm M_{BH}-kT$ relation. We speculate that the overly massive BHs in BCGs may be due to frequent mergers and cool gas inflows onto the cluster center.
We present new stellar mass functions at $zsim6$, $zsim7$, $zsim8$, $zsim9$ and, for the first time, $zsim10$, constructed from $sim800$ Lyman-Break galaxies previously identified over the XDF/UDF, parallels and the five CANDELS fields. Our study is distinctive due to (1) the much deeper ($sim200$ hour) wide-area Spitzer/IRAC imaging at $3.6mu$m and $4.5mu$m from the GOODS Re-ionization Era wide Area Treasury from Spitzer (GREATS) program and (2) consideration of $zsim6-10$ sources over a $3times$ larger area than previous HST+Spitzer studies. The Spitzer/IRAC data enable $ge2sigma$ rest-frame optical detections for an unprecedented $50%$ of galaxies down to a stellar mass limit of $sim10^{8}mathcal{M}_odot$ across all redshifts. Schechter fits to our volume densities suggest a combined evolution in characteristic mass $mathcal{M}^*$ and normalization factor $phi^*$ between $zsim6$ and $zsim8$. The stellar mass density (SMD) increases by $sim1000times$ in the $sim500$ Myr between $zsim10$ and $zsim6$, with indications of a steeper evolution between $zsim10$ and $zsim8$, similar to the previously-reported trend of the star-formation rate density. Strikingly, abundance matching to the Bolshoi-Planck simulation indicates halo mass densities evolving at approximately the same rate as the SMD between $zsim10$ and $zsim4$. Our results show that the stellar-to-halo mass ratios, a proxy for the star-formation efficiency, do not change significantly over the huge stellar mass build-up occurred from $zsim10$ to $zsim6$, indicating that the assembly of stellar mass closely mirrors the build-up in halo mass in the first $sim1$ Gyr of cosmic history. JWST is poised to extend these results into the first galaxy epoch at $zgtrsim10$.
We derive the growth of SMBHs relative to the stellar content of their host galaxy predicted under the assumption of BH accretion triggered by galaxy encounters occurring during their merging histories. We show that, within this framework, the ratio Gamma=(M_BH/M_*)(z)/(M_BH/M_*)(z=0) between the Black Hole mass and the galactic stellar mass (normalized to the local value) depends on both BH mass and redshift. While the average value and the spread of Gamma(z) increase with z, such an effect is larger for massive BHs, reaching values Gamma=5 for massive Black Holes (M>10^9 M_{odot}) at z>4, in agreement with recent observations of high-redshift QSOs; this is due to the effectiveness of interactions in triggering BH accretion in high-density environments at high redshifts. To test such a model against observations, we worked out specific predictions for sub-samples of the simulated galaxies corresponding to the different observational samples for which measurements of Gamma have been obtained. We found that for Broad Line AGNs at 1<z<2 values of Gamma=2 are expected, with a mild trend toward larger value for increasing BH mass. Instead, when we select from our Monte Carlo simulations only extremely gas rich, rapidly star forming galaxies at 2<z<3, we find low values 0.3<Gamma<1.5, consistent with recent observational findings on samples of sub-mm galaxies; in the framework of our model, these objects end up at z=0 in low-to-intermediate mass BHs (M<10^9 M_{odot}), and they do not represent typical paths leading to local massive galaxies. The latter have formed preferentially through paths passing above the local M_*-M_BH relation. We discuss how the global picture emerging from the model is consistent with a downsizing scenario, where massive BHs accrete a larger fraction of their final mass at high redshifts z>4.
Strongly lensed active galactic nuclei (AGN) provide a unique opportunity to make progress in the study of the evolution of the correlation between the mass of supermassive black holes ($mathcal M_{BH}$) and their host galaxy luminosity ($L_{host}$). We demonstrate the power of lensing by analyzing two systems for which state-of-the-art lens modelling techniques have been applied to Hubble Space Telescope imaging data. We use i) the reconstructed images to infer the total and bulge luminosity of the host and ii) published broad-line spectroscopy to estimate $mathcal M_{BH}$ using the so-called virial method. We then enlarge our sample with new calibration of previously published measurements to study the evolution of the correlation out to z~4.5. Consistent with previous work, we find that without taking into account passive luminosity evolution, the data points lie on the local relation. Once passive luminosity evolution is taken into account, we find that BHs in the more distant Universe reside in less luminous galaxies than today. Fitting this offset as $mathcal M_{BH}$/$L_{host}$ $propto$ (1+z)$^{gamma}$, and taking into account selection effects, we obtain $gamma$ = 0.6 $pm$ 0.1 and 0.8$pm$ 0.1 for the case of $mathcal M_{BH}$-$L_{bulge}$ and $mathcal M_{BH}$-$L_{total}$, respectively. To test for systematic uncertainties and selection effects we also consider a reduced sample that is homogeneous in data quality. We find consistent results but with considerably larger uncertainty due to the more limited sample size and redshift coverage ($gamma$ = 0.7 $pm$ 0.4 and 0.2$pm$ 0.5 for $mathcal M_{BH}$-$L_{bulge}$ and $mathcal M_{BH}$-$L_{total}$, respectively), highlighting the need to gather more high-quality data for high-redshift lensed quasar hosts. Our result is consistent with a scenario where the growth of the black hole predates that of the host galaxy.
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