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 \(F_{\textrm{X,0.5-2}}>10^{-14}\) erg s\({}^{-1}\) cm\({}^{-2}\)). With this model, we calibrated positional error of the SRG/eROSITA sources detected in the Lockman Hole: \(\sigma_{\textrm{corr}}=0.87\sqrt{\sigma_{\textrm{det}}^{2.53}+1.12^{2}}\). 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.