Chandra Follow-up Observations of Swift-BAT-selected AGNs II

TL;DR

This study combines Chandra and Swift-BAT data to analyze nine low-redshift AGNs, confirming heavy obscuration and identifying two new candidate Compton-thick AGNs, demonstrating an effective selection strategy for such sources.

Contribution

It introduces a successful methodology for selecting heavily obscured AGNs with a higher success rate than blind surveys.

Findings

All sources are obscured with NH >= 10^22 cm^-2.

Two sources are candidate Compton-thick AGNs with NH >= 10^24 cm^-2.

Selection criteria yield ~20% success rate in discovering heavily obscured AGNs.

Abstract

We present the combined Chandra and Swift-BAT spectral analysis of nine low-redshift (z <= 0.10), candidate heavily obscured active galactic nuclei (AGN) selected from the Swift-BAT 150-month catalog. We located soft (1-10 keV) X-ray counterparts to these BAT sources and joint fit their spectra with physically motivated models.The spectral analysis in the 1-150 keV energy band determined that all sources are obscured, with a line-of-sight column density NH >= 10^22 cm^-2 at a 90% confidence level. Four of these sources show significant obscuration with NH >= 10^23 cm^-2 and two additional sources are candidate Compton-thick Active Galactic Nuclei (CT-AGNs) with NH >= 10^24 cm^-2.These two sources, 2MASX J02051994-0233055 and IRAS 11058-1131, are the latest addition to the previous 3 CT-AGN candidates found using our strategy for soft X-ray follow-up of BAT sources. In here we present the results of our methodology so far, and analyze the effectiveness of applying different selection criteria to discover CT-AGN in the local Universe. Our selection criteria has a ~20% success rate of discovering heavily obscured AGN whose CT nature is confirmed by follow-up NuSTAR observations. This is much higher than the ~5% found in blind surveys.