Optical Spectral Properties of Swift BAT Hard X-ray Selected Active Galactic Nuclei Sources

TL;DR

This study analyzes optical spectra of 64 Swift BAT-selected AGNs, revealing differences in luminosity and accretion rates between types, and examining host galaxy properties and correlations with X-ray luminosity.

Contribution

It provides a comprehensive optical spectral analysis of hard X-ray selected AGNs, including classifications, luminosities, black hole masses, and host galaxy characteristics.

Findings

Type 2 AGNs are less luminous and have lower accretion rates than type 1s.

LINERs and H II galaxies have the lowest luminosities.

Weak correlation between optical [O III] and X-ray luminosities.

Abstract

The Swift Burst Alert Telescope (BAT) survey of Active Galactic Nuclei (AGN) is providing an unprecedented view of local AGNs (<z> = 0.03) and their host galaxy properties. In this paper, we present an analysis of the optical spectra of a sample of 64 AGNs from the 9-month survey, detected solely based on their 14-195 keV flux. Our analysis includes both archived spectra from the Sloan Digital Sky Survey and our own observations from the 2.1-m Kitt Peak National Observatory telescope. Among our results, we include line ratio classifications utilizing standard emission line diagnostic plots, [O III] 5007 A luminosities, and H-beta derived black hole masses. As in our X-ray study, we find the type 2 sources to be less luminous (in [O III] 5007 A and 14-195 keV luminosities) with lower accretion rates than the type 1 sources. We find that the optically classified LINERs, H II/composite galaxies, and ambiguous sources have the lowest luminosities, while both broad line and narrow line Seyferts have similar luminosities. From a comparison of the hard X-ray (14-195 keV) and [O III] luminosities, we find that both the observed and extinction-corrected [O III] luminosities are weakly correlated with X-ray luminosity. In a study of the host galaxy properties from both continuum fits and measurements of the stellar absorption indices, we find that the hosts of the narrow line sources have properties consistent with late type galaxies.