Black Hole Mass and Growth Rate and Metal Enrichment at Low and High Redshift
Abstract
Large spectroscopic samples of active galactic nuclei (AGNs), combined with improved methods for calculating black hole mass and accretion rate, enable a eaningful statistical investigation of the mass, accretion rate and metallicity of such sources as a function of redshift. The results shown here are based on the study of about 10,000 z < 0.75 radio-quiet SDSS AGNs and about 30 z=2.3-3.4 high redshift, very high luminosity AGNs. Their combination suggests that: 1. The fraction of more massive active black holes is larger at earlier times. 2. The normalized accretion rate (L/LEdd) is an increasing function of redshift for black holes of all masses. 3. The slope of the accretion rate vs. redshift correlation is similar to the slope of the cosmic star formation rate over the redshift interval 0-0.75. 4. Metallicity as measured by the Nλ 1240/CIVλ 1549 line ratio at high redshifts, and by FeII/Hβ at low redshifts, is an increasing function of L/LEdd. 5. Most AGNs do not have enough time to grow to their present size given their present (observed) accretion rate. 6. There must have been several episodes of increased broad line gas metallicity, as well as of low metallicity, in the history of most active black holes. Thus, the BLR metallicity goes through cycles and is likely correlated with the large scale galactic star formation history.
- Publication:
-
Relativistic Astrophysics Legacy and Cosmology - Einstein's Legacy
- Pub Date:
- 2007
- DOI:
- 10.1007/978-3-540-74713-0_61
- Bibcode:
- 2007ralc.conf..264N