Mid-Infrared Properties of the Swift Burst Alert Telescope Active Galactic Nuclei Sample of the Local Universe. 1. Emission-Line Diagnostics
Abstract
We compare mid-infrared emission-line properties from high-resolution Spitzer spectra of a hard X-ray (14-195 keV) selected sample of nearby (z < 0.05) active galactic nuclei (AGNs) detected by the Burst Alert Telescope (BAT) aboard Swift. The luminosity distribution for the mid-infrared emission lines, [Oiv] 25.89 microns,[Ne ii] 12.81 microns [Ne iii] 15.56 microns and [Ne v] 14.32/24.32 microns and hard X-ray continuum show no differences between Seyfert 1 and Seyfert 2 populations; however, six newly discovered BAT AGNs are under-luminous in [O iv], most likely the result of dust extinction in the host galaxy. The overall tightness of the mid-infrared correlations and BAT fluxes and luminosities suggests that the emission lines primarily arise in gas ionized by the AGNs. We also compare the mid-infrared emission lines in the BAT AGNs with those from published studies of ULIRGs,Palomar-Green quasars, star-forming galaxies, and LINERs.We find that the BAT AGN sample falls into a distinctive region when comparing the [Ne iii]/[Ne ii] and the [Oiv]/[Ne iii] ratios. These line ratios are lower in sources that have been previously classified in the mid-infrared/optical as AGNs than those found for the BAT AGNs, suggesting that, in our X-ray selected sample, the AGNs represent the main contribution to the observed line emission. These ratios represent a new emission line diagnostic for distinguishing between AGNs and star-forming galaxies.
Document Details
- Document Type
- Technical Report
- Publication Date
- Jun 20, 2010
- Accession Number
- ADA540104
Entities
People
- C. Markwardt
- Ciprian T. Berghea
- E. Malumuth
- J. Tueller
- K. A. Weaver
- K. Engle
- M. Melendez
- R. F. Mushotzky
- R. P. Dudik
- S. B. Kraemer
Organizations
- United States Naval Observatory