Merging and Clustering of the Swift BAT AGN Sample

Abstract

We discuss the merger rate, close galaxy environment, and clustering on scales up to a Mpc of the SWIFT BAT hard X-ray sample of nearby (z<0.05), moderate-luminosity active galactic nuclei (AGN). We find a higher incidence of galaxies with signs of disruption compared to a matched control sample (18% versus 1%) and of close pairs within 30 kpc (24% versus 1%). We also find a larger fraction with companions compared to normal galaxies and optical emission line selected AGN at scales up to 250 kpc. We hypothesize that these merging AGN may not be identified using optical emission line diagnostics because of optical extinction and dilution by star formation. In support of this hypothesis, in merging systems we find a higher hard X-ray to [OIII] flux ratio, as well as emission line diagnostics characteristic of composite or star-forming galaxies, and a larger IRAS 60 um to stellar mass ratio.

15 pages, 4 figures, published in the Astrophysical Journal Letters

References in corpus (6)

• The Host Galaxies and Classification of Active Galactic Nuclei
• K-corrections and filter transformations in the ultraviolet, optical, and near infrared
• The Luminosity Dependence of the Galaxy Merger Rate
• The clustering of narrow-line AGN in the local Universe
• The Small-Scale Environment of Quasars
• Infrared Properties of Close Pairs of Galaxies

Cited by in corpus (5)

• The Mean Star Formation Rate of X-ray selected Active Galaxies and its Evolution from z=2.5: Results from PEP-Herschel
• HST WFC3/IR Observations of Active Galactic Nucleus Host Galaxies at z~2: Supermassive Black Holes Grow in Disk Galaxies
• Active Galactic Nucleus Pairs from the Sloan Digital Sky Survey. I. The Frequency on ~ 5-100 kpc Scales
• Chandra Discovery of a Binary Active Galactic Nucleus in Mrk 739
• The merger fraction of active and inactive galaxies in the local Universe through an improved non-parametric classification