Inferences on the Relations Between Central Black Hole Mass and Total Galaxy Stellar Mass in the High-redshift Universe
Abstract
At the highest redshifts, z\gt 6, several tens of luminous quasars have been detected. The search for fainter active galactic nucleus (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\gt 6 galaxies host relatively massive BHs (\gt {10}6 {M}⊙ ), 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 AGNs 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 AGNs 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 AGNs in Lyman Break Galaxies if galaxies below {10}11 {M}⊙ are characterized by the low-normalization scaling, and, even more so, if their Eddington ratio is also typical of moderate-luminosity AGNs rather than luminous quasars. AGNs being missed by X-ray searches due to obscuration or instrinsic X-ray weakness also remain a possibility.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- March 2016
- DOI:
- 10.3847/2041-8205/820/1/L6
- arXiv:
- arXiv:1602.05711
- Bibcode:
- 2016ApJ...820L...6V
- Keywords:
-
- galaxies: active;
- galaxies: evolution;
- galaxies: high-redshift;
- Astrophysics - Astrophysics of Galaxies;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- Accepted for publication in ApJ Letters