2009/01/31 by M. Dietrich, Matthias Dietrich, Smita Mathur +3
Physics and Astronomy · #Accretion (finance) #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Black hole (networking) #Emission spectrum #Galaxies: Formation, Evolution, Phenomena #Galaxy #Gamma-ray bursts and supernovae #Luminosity #Metallicity #Physics #Quasar #Redshift #Solar mass #Spectral line #astro-ph.CO
paper · pdf · doi:10.1088/0004-637x/696/2/1998
published as Astrophys.J.696:1998-2013,2009 · 48 pages, 16 figures, accepted for publication in ApJ
arxiv created 2009/02/20 · openalex publication_date 2009/04/28 · arxiv updated 2014/11/18 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present near-infrared spectra of 10 luminous, intermediate-redshift quasars ( z ≃2; L bol ≃ 10 47 erg s −1 ), observed with SofI at the NTT of ESO/La Silla. With these rest-frame optical spectra we probe the Hβ–[O iii ] emission line region. Using the standard scaling relation involving the width of the Hβ line and the continuum luminosity, we measure black hole (BH) masses in the range of ∼2 × 10 9 ≲ M bh ≲ 10 10 M ☉ for these sources. We also used Sloan Digital Sky Survey spectra to probe Mg ii λ2798 and C iv λ1549 emission lines and used these for BH mass measurements as well. The BH mass estimates using C iv λ1549 are on average smaller by about 60% than those based on Hβ. The massive BHs we observe could not have grown by simple radiatively efficient accretion at the observed accretion rate starting from seeds of up to a thousand solar masses. About 10% of the observed BH mass must have been accumulated by earlier merger events and radiatively inefficient accretion. Radiatively efficient accretion would further grow these BHs to masses of several 10 9 M ☉ in 2–3 e -folding times, i.e., in several 10 8 yr. This scenario is consistent with recent models of BH growth. The Hβ-based Eddington luminosity ratios are in the range of ∼0.2–0.7, with an average of 〈 L bol / L edd 〉 = 0.39 ± 0.05. The L bol / L edd ratio distribution follows a lognormal distribution which is consistent with prior studies of quasars with comparable luminosity. We also find that the gas metallicity of the broad-line region is super-solar with ∼3 Z / Z ☉ , based on N iii ]λ1750/O iii ]λ1663 and N v λ1240/C iv λ1549 emission line ratios. We find no correlation of the gas metallicity with the optical Fe ii emission line strength in our small sample, contrary to a recent suggestion.