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

¹ Università degli Studi di Milano–Bicocca, Dipartimento di Fisica “G. Occhialini”, Piazza della Scienza 3, 20126 Milano, Italy
e-mail: l.varisco4@campus.unimib.it
² INAF – Osservatorio Astronomico di Trieste, via Tiepolo 11, 34131 Trieste, Italy
³ INFN, Sezione di Milano–Bicocca, Piazza della Scienza 3, 20126 Milano, Italy

Received: 17 January 2018
Accepted: 16 March 2018

Abstract

Virial–based methods for estimating active supermassive black hole masses are now commonly used on extremely large spectroscopic quasar catalogs. Most spectral analyses, though, do not pay enough attention to the detailed continuum decomposition. To understand how this affects virial mass estimates, we test the influence of host galaxy light on them, along with a Balmer continuum component. A detailed fit with the new spectroscopic analysis software QSFIT demonstrates that the presence or absence of continuum components does not significantly affect the virial-based results for our sample. Taking a host galaxy component into consideration or not, 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.