Dependence between some spectral and physical characteristics of quasars

TL;DR

This study investigates how spectral and physical characteristics of quasars are interrelated, revealing dependencies between emission line strengths and spectral index, but no link between black hole mass and spectral index.

Contribution

It provides new insights into the spectral dependencies of quasars by analyzing composite spectra binned in spectral index and luminosity, highlighting specific emission line behaviors.

Findings

Emission line equivalent widths depend on spectral index for certain lines.

No correlation between black hole mass and spectral index.

Spectral index influences emission line properties, but not black hole mass.

Abstract

Using 192 composite spectra stacked from subsamples of individual SDSS DR7 quasar spectra binned in spectral index, $\alpha_{\lambda}$, and logarithm of monochromatic luminosity at 1450 \AA, $\log{l_{1450}}$, we found that there is a dependence of the emission line equivalent width (EW) on spectral index (correlation or anti-correlation) for some lines, mostly for those lines for which the Baldwin effect is detected. We also show that there is no dependence between the virial mass of the central supermassive black hole of a quasar and its spectral index $\alpha_{\lambda}$.