Optical Identification and Spectroscopic Redshift Measurements of 216 Galaxy Clusters from the SRG/eROSITA All-Sky Survey

We present the results of the optical identification and spectroscopic redshift measurements of 216 galaxy clusters detected in the SRG/eROSITA all-sky X-ray survey. The spectroscopic observations were performed in 2020–2023 with the 6-m BTA telescope at the Special Astrophysical Observatory of the Russian Academy of Sciences, the 2.5-m telescope at the Caucasus Mountain Observatory of the Sternberg Astronomical Institute of the Moscow State University, the 1.6-m AZT-33IK telescope at the Sayan Solar Observatory of the Institute of Solar–Terrestrial Physics of the Siberian Branch of the Russian Academy of Sciences, and the 1.5-m Russian–Turkish telescope (RTT-150) at the TÜBİTAK Observatory. For all of the galaxy clusters presented here the spectroscopic redshift measurements have been obtained for the first time. Of these, 139 galaxy clusters have been detected for the first time in the SRG/eROSITA survey and 22 galaxy clusters are at redshifts z_spec≳ 0.7 , including three at z_spec≳ 1 . Deep direct images with the rizJK filters have also been obtained for four distant galaxy clusters at z_spec>0.7 . For these observations we chose the most massive clusters and, therefore, most of the galaxy clusters presented here with the spectroscopic redshifts measured by us will most likely enter in future into the cosmological samples of galaxy clusters from the SRG/eROSITA survey.