The Extragalactic Serendipitous Swift Survey (ExSeSS) -- I. Survey definition and measurements of the X-ray number counts
Jack N. Delaney, James Aird, Phil A. Evans, Cassandra Barlow-Hall,, Julian P. Osborne, Michael G. Watson

TL;DR
The ExSeSS survey provides a comprehensive X-ray source catalog and measures the number counts of AGN across a wide flux range, revealing discrepancies with existing models and suggesting a larger obscured AGN population at low redshifts.
Contribution
This work introduces a new, well-defined X-ray source sample from Swift, measures differential number counts, and compares them with models, highlighting the need to account for obscured AGN populations.
Findings
Good agreement with previous high-energy data when accounting for absorption.
Discrepancies with AGN population models suggest missing obscured sources.
Indicates a larger, moderately obscured AGN population at low redshifts.
Abstract
We present the Extragalactic Serendipitous Swift Survey (ExSeSS), providing a new well-defined sample constructed from the observations performed using the Swift X-ray Telescope. The ExSeSS sample consists of 79,342 sources detected in the medium (1-2 keV), hard (2-10 keV) or total (0.3-10 keV) energy bands, covering 2086.6 deg of sky across a flux range of erg s cm. Using the new ExSeSS sample we present measurements of the differential number counts of X-ray sources as a function of 2-10 keV flux that trace the population of Active Galactic Nuclei (AGN) in a previously unexplored regime. We find that taking the line-of-sight absorption column density into account has an effect on the differential number count measurements and is vital to obtain agreement with previous results. In the hard band, we obtain a good agreement…
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Taxonomy
TopicsAstrophysical Phenomena and Observations · Astronomy and Astrophysical Research · Stellar, planetary, and galactic studies
