Estimating black hole masses in quasars using broad optical and UV emission lines

Abstract

We review past work using broad emission lines as virial estimators of black hole masses in quasars. Basically one requires estimates of the emitting region radius and virial velocity dispersion to obtain black hole masses. The three major ways to estimate the broad-line emitting region (BLR) radius involve: (1) direct reverberation mapping, (2) derivation of BLR radius for larger samples using the radius-luminosity correlation derived from reverberation measures, and (3) estimates of BLR radius using the definition of the ionization parameter solved for BLR radius (photoionization method). At low redshift (z < ∼ 0.7) FWHM Hβ serves as the most widely used estimator of virial velocity dispersion. FWHM Hβ can provide estimates for tens of thousands of quasars out to z ≈ 3.8 (IR spectroscopy beyond z ≈ 1). A new photoionization method also shows promise for providing many reasonable estimates of BLR radius via high S/N IR spectroscopy of the UV region 1300 -2000Å. FWHM Mgiiλ2800 can serve as a surrogate for FWHM Hβ in the range 0.4 < ∼ z < ∼ 6.5 while Civλ1549 is affected by broadening due to non-virial motions and best avoided (i.e. there is no clear conversion factor between FWHM Hβ and FWHM Civλ1549). Most quasars yield mass estimates in the range 7 < ∼ log M BH < ∼ 9.7. There is no strong evidence for values above 10.0 and there may be evidence for a turnover in the maximum black hole mass near z ≈ 5.

Microlensing of the broad line region in 17 lensed quasars

“…(1) but for the C iv line. Black-hole mass estimates derived from that line are more controversial because of uncertainties on the geometry of the C iv emitting region, because of the contamination from a putative narrow C iv emission and because virial equilibrium is not expected to hold perfectly for such high ionization lines (Richards et al 2002;Bachev et al 2004;Marziani et al 2006;Fine et al 2011;Assef et al 2011;Wang et al 2011;Richards et al 2011;Marziani & Sulentic 2012). For two systems (H1413+117 and J1131-1231), we also used H β to calculate M BH .…”

Gamma-ray opacity of the anisotropic stratified broad-line regions in blazars

“…Here we assumed that 10 per cent of quasar luminosity is reprocessed in the BLR to photons of average energy 10 eV. The photon density is uncertain by an order of magnitude, because of the uncertainties on the BLR radius determined using different emission lines (Peterson & Wandel 1999;Marziani & Sulentic 2012).…”

Blue outliers among intermediate redshift quasars

“…A/narrow line Seyfert 1 (NLSy1) nuclei (Z02). Use of the [Oiii]λλ-4959,5007 line width as a proxy of the bulge stellar component velocity dispersion should be avoided for population A sources in the spectral types A2, A3, A4 (e.g., Marziani and Sulentic 2012, and references therein). The narrow line region (NLR) in sources whose [Oiii]-λλ4959,5007 profile is blueshifted and semi-broad is unlikely to be dynamically related to the host-galaxy stellar bulge.…”