2024/01/30 by Sophia G. H. Waddell, Waddell, Sophia G. H., Johannes Büchner +27
Engineering · Physics and Astronomy · #Astronomical Observations and Instrumentation #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #FOS: Physical sciences #High Energy Astrophysical Phenomena (astro-ph.HE)
paper · pdf · doi:10.48550/arxiv.2401.17306
openalex publication_date 2024/01/30 · openalex created_date 2024/02/01 · openalex updated_date 2026/07/28
The eROSITA instrument aboard the Spectrum Roentgen Gamma (SRG) satellite has performed its first all-sky survey between December 2019 and June 2020. This paper presents the resulting hard X-ray (2.3-5 keV) sample, the first created from an all-sky imaging survey in the 2-8 keV band, for sources within western galactic sky. The 5466 hard X-ray selected sources detected with eROSITA are presented and discussed. The Bayesian statistics-based code NWAY is used to identify the counterparts for the X-ray sources. These sources are classified based on their multiwavelength properties, and the literature is searched to identify spectroscopic redshifts, which further inform the source classification. A total of 2547 sources are found to have good-quality counterparts, and 111 of these are detected only in the hard band. Comparing with other hard X-ray selected surveys, the eROSITA hard sample covers a larger redshift range and probes dimmer sources, providing a complementary and expanded sample as compared to Swift-BAT. Examining the column density distribution of missed and detected eROSITA sources present in the follow-up catalog of Swift BAT 70 month sources, it is demonstrated that eROSITA can detect obscured sources with column densities >1024 cm-2, but that the completeness drops rapidly after 1023 cm-2. A sample of hard-only sources, many of which are likely to be heavily obscured AGN, is also presented and discussed. X-ray spectral fitting reveals that these sources have extremely faint soft X-ray emission and their optical images suggest that they are found in more edge-on galaxies with lower b/a. The resulting X-ray catalog is demonstrated to be a powerful tool for understanding AGN, in particular heavily obscured AGN found in the hard-only sample.