SRGz: building an optical cross-match model for the X-ray SRG/eROSITA sources using the Lockman Hole data

Abstract

We present a probabilistic model built for the optical cross-match between the SRG/eROSITA X-ray sources and photometric data from the DESI Legacy Imaging Surveys. The model relies both on positional and photometric information on optical objects nearby X-ray sources and allows performing selection with precision and recall $\approx 94$% (for $F_{\mathrm{X},0.5-2}>10^{-14}$ erg/s/cm${}^2$). With this model, we calibrated positional error of the SRG/eROSITA sources detected in the Lockman Hole: ${\sigma }_{\mathrm{corr}}=0.87\sqrt{{\sigma }_{\det }^{2.53}+1.12^2}$. The model will become a part of the SRGz system for data analysis of the X-ray data obtained from the all-sky SRG/eROSITA survey.

19 pages, 18 figures, published in Astronomy Letters