Herschel Far-Infrared Photometry of the Swift Burst Alert Telescope Active Galactic Nuclei Sample of the Local Universe. I. PACS Observations

TL;DR

This study presents Herschel PACS far-infrared photometry for 313 nearby AGN from the Swift BAT catalog, exploring the relationship between FIR emission, star formation, and AGN activity, with implications for understanding dust heating mechanisms.

Contribution

First comprehensive FIR photometry of a large, hard X-ray selected AGN sample, analyzing correlations between FIR emission, AGN power, and star formation indicators.

Findings

FIR luminosity distributions are similar for Seyfert 1 and 2 galaxies.

Significant correlation between AGN power and FIR emission in Seyfert 1s.

No correlation between AGN power and FIR in Seyfert 2s.

Abstract

Far-Infrared (FIR) photometry from the the Photodetector Array Camera and Spectrometer (PACS) on the Herschel Space Observatory is presented for 313 nearby, hard X-ray selected galaxies from the 58-month Swift Burst Alert Telescope (BAT) Active Galactic catalog. The present data do not distinguish between the FIR luminosity distributions at 70 and 160um for Seyfert 1 and Seyfert 2 galaxies. This result suggests that if the FIR emission is from the nuclear obscuring material surrounding the accretion disk, then it emits isotropically, independent of orientation. Alternatively, a significant fraction of the 70 and 160um could be from star formation, independent of AGN type. Using a non-parametric test for partial correlation with censored data, we find a statistically significant correlation between the AGN intrinsic power (in the 14-195 keV band ) and the FIR emission at 70 and 160um for Seyfert 1 galaxies. We find no correlation between the 14-195 keV and FIR luminosities in Seyfert 2 galaxies. The observed correlations suggest two possible scenarios: (i) if we assume that the FIR luminosity is a good tracer of star formation, then there is a connection between star formation and the AGN at sub-kiloparsec scales, or (ii) dust heated by the AGN has a statistically significant contribution to the FIR emission. Using a Spearman rank-order analysis, the 14-195 keV luminosities for the Seyfert 1 and 2 galaxies are weakly statistically correlated with the F70/F160 ratios.