Effects of Orientation on Proxies for the M-σ* Relation in Quasars, The
presentationposted on 06.05.2016, 00:00 authored by Vikram Singh
The correlation between central black hole mass (M) and stellar velocity dispersion (σ*) in both active and quiescent galaxies suggests an evolutionary relationship between nuclei and their hosts. Direct measurement of both black hole masses and stellar velocity dispersions in the same object is often challenging. In quasars, indirect methods can be employed. Single-epoch scaling relationships permit the estimation of black hole mass based on broad-line velocity width and continuum luminosity, while the velocity width of narrow emission lines permit the estimation of stellar velocity dispersion. We use Sloan Digital Sky Survey Data Release 7 quasar spectra with z < 0.75 to estimate M and σ* in a sample of about 400 radio-loud quasars to investigate how these quantities depend on orientation. We use FIRST Survey maps at 20 cm to measure radio core dominance, an orientation indicator. Conventional scaling relationships that use broad Hβ to estimate black hole mass have a strong orientation bias, likely the result of a flattened broad-line region, and this in turn accounts for a large amount of scatter in the M-σ* relation when measured with these techniques. Turning this around, we suggest that this ratio of M/σ*proxies is itself an orientation indicator that can be used for both radio-loud and radio-quiet quasars.