AGN mass estimates in large spectroscopic surveys: the effect of host galaxy light

TL;DR

This study investigates how host galaxy light influences supermassive black hole mass estimates from quasar spectra, finding minimal impact on virial mass calculations but notable effects on emission line fitting at lower redshifts.

Contribution

It provides a detailed analysis of host galaxy light effects on virial mass estimates using advanced spectral decomposition with QSFit.

Findings

Host galaxy light has little effect on virial mass estimates.

Emission line fitting is more affected at lower redshifts.

Continuum components do not significantly alter virial mass results.

Abstract

Virial-based methods for estimating active supermassive black hole masses are now commonly used on extremely large spectroscopic quasar catalogues. Most spectral analyses, though, do not pay enough attention to a detailed continuum decomposition. To understand how this affects virial mass estimate results, we test the influence of host galaxy light on them, along with Balmer continuum component. A detailed fit with the new spectroscopic analysis software QSFit demonstrated that the presence or absence of continuum components do not affect significantly the virial-based results for our sample. Taking or not in consideration a host galaxy component, instead, affects the emission line fitting in a more pronounced way at lower redshifts, where in fact we observe dimmer quasars and more visible host galaxies.