BLACK HOLE MASSES OF INTERMEDIATE-REDSHIFT QUASARS: NEAR-INFRARED SPECTROSCOPY

Journal Article · Sun May 10 04:00:00 EDT 2009 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/696/2/1998; COUNTRY OF INPUT: INTERNATIONAL ATOMIC ENERGY AGENCY (IAEA)· OSTI ID:21300622

Dietrich, Matthias; Mathur, Smita ^[1]; Grupe, Dirk ^[2]; Komossa, Stefanie ^[3]

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1. Department of Astronomy, Ohio State University, 140 West 18th Avenue, Columbus, OH 43 210 (United States)
2. Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16 802 (United States)
3. MPI fuer extraterrestrische Physik, Giessenbachstr., D-85 748 Garching (Germany)

We present near-infrared spectra of 10 luminous, intermediate-redshift quasars (z {approx_equal}2; L {sub bol} {approx_equal} 10{sup 47} erg s{sup -1}), observed with SofI at the NTT of ESO/La Silla. With these rest-frame optical spectra we probe the H{beta}-[O III] emission line region. Using the standard scaling relation involving the width of the H{beta} line and the continuum luminosity, we measure black hole (BH) masses in the range of {approx}2 x 10{sup 9}{approx}< M {sub bh} {approx}< 10{sup 10} M {sub sun} for these sources. We also used Sloan Digital Sky Survey spectra to probe Mg II {lambda}2798 and C IV {lambda}1549 emission lines and used these for BH mass measurements as well. The BH mass estimates using C IV {lambda}1549 are on average smaller by about 60% than those based on H{beta}. 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{sup 9} M {sub sun} in 2-3 e-folding times, i.e., in several 10{sup 8} yr. This scenario is consistent with recent models of BH growth. The H{beta}-based Eddington luminosity ratios are in the range of {approx}0.2-0.7, with an average of (L {sub bol}/L {sub edd}) = 0.39 {+-} 0.05. The L {sub bol}/L {sub 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 {approx}3 Z/Z {sub sun}, based on N III]{lambda}1750/O III]{lambda}1663 and N V {lambda}1240/C IV {lambda}1549 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.

• OSTI ID: 21300622
• Journal Information: Astrophysical Journal, Journal Name: Astrophysical Journal Journal Issue: 2 Vol. 696; ISSN ASJOAB; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTRONOMY AND ASTROPHYSICS
99 GENERAL AND MISCELLANEOUS
ABSORPTION SPECTROSCOPY
BLACK HOLES
GALAXIES
INFRARED SPECTRA
LUMINOSITY
MASS
QUASARS
RED SHIFT