|
|
|
|
|
Benny Trakhtenbrot |
|
"Probing the Cosmic
Evolution of Black Hole Mass and Acrretion Rate in AGNs" |
|
The existence of Super-Massive Black Holes in the centers of galaxies, which grow by episodes of radiative efficient accretion has now become common wisdom. I will present black-hole mass (M_BH) and accretion rate (L/L_Edd) measurements in several samples of type-I AGNs in the redshift range 0-4.8. Using SDSS data a significant evolution of L/L_Edd is found for all BHs up to z~2. Ground-based NIR spectroscopy in three redshift bands is used to measure M_BH and L/L_Edd reliably at higher redshifts. Two samples, at z~2.3 and z~3.4, clearly show a broad range of L/L_Edd values, far below the Eddington limit, in contrast to several theoretical models. The first phase of fast growth of some of the objects must have occurred at z>3.4. I will also present preliminary results from our latest VLT & Gemini campaign, aiming at a relatively large, well defined sample at z~4.8. The combination of the three high redshift samples can constrain the first cycle of merger-driven nuclear activity and the initial phases of growth of the most massive BHs. |