SDSS spectroscopy for blazars in the $Fermi$ LAT bright AGN sample

TL;DR

This study compiles SDSS spectra and photometry for bright AGNs associated with Fermi LAT, analyzing black hole masses, emission lines, and accretion properties to better understand their jet and accretion disk contributions.

Contribution

It provides new measurements of broad emission lines and black hole masses for FSRQs, including first-time measurements for five sources, and investigates their optical emission origins.

Findings

Optical continuum in FSRQs likely dominated by nonthermal jet emission.

Black hole masses range from 10^8.2 to 10^9.9 solar masses.

Eddington ratios suggest presence of thick accretion disks.

Abstract

We have collected all available spectra and photometric data from SDSS catalogue for bright AGNs complied from the first three months of the Fermi large area telescope all-sky survey. Based on the 106 high-confidence and 11 low-confidence association bright AGN list, the photometry data are collected from SDSS DR7 for 28 sources (12 BL Lacs and 16 FSRQs), two of which are low-confidence association bright AGNs. Among these 28 SDSS photometric sources, SDSS spectra are available for 20 sources (6 BL Lacs and 14 FSRQs). The black hole mass M_BH and the broad line region (BLR) luminosity were obtained for 14 FSRQs by measuring the line-width and strength of broad emission lines from SDSS spectra. The broad emission lines measurements of five FSRQs are presented for the first time in this work. The optical continuum emission of these 14 FSRQs is found to be likely dominated by the nonthermal jet emission through comparing the relationship between the broad Mg II line and continuum luminosity to that of radio quiet AGNs. The black hole mass of 14 FSRQs ranges from 10^8.2 to 10^9.9 solar mass, with most of sources larger than 10^9 solar mass. The Eddington ratio L_bol/L_Edd ranges from 10^-1.5 to ~ 1. This implies that the optically thin, geometrically thick accretion disk may exist in these FSRQs.