Speaker
Description
I will present the hard ($2.3-5~$keV) X-ray selected sample of sources detected with eROSITA during the first all-sky survey, comprising 5466 X-ray sources. From this catalog, I have produced a large uniform sample of hard-X-ray selected AGN, and characterised them with supporting multi-wavelength astrometry, photometry and spectroscopy. For the 2863 sources within the sky coverage of the DESI imaging Legacy Survey Data Release 10 (LS10; $>15000$ deg$^2$), counterparts are identified and classified. I also perform comparisons with the Swift-BAT sample and HEAO-1 AGN sample to attempt to better understand the effectiveness and sensitivity of eROSITA in the hard band. A total of 2547 sources within the LS10 area 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 $>10^{23}~$cm$^{-2}$ corresponding to $\sim14\%$ of the full sample, but that the completeness drops rapidly thereafter. A sample of hard-only sources, many of which are likely to be obscured AGN with column densities $\sim10^{23}~$cm$^{-2}$ 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. I will discuss these results in the context of future analyses of hard X-ray selected AGN, and also in the context of future eROSITA all-sky surveys.
