Unveiling the Sources of X-Ray Luminosity in DESI Galaxy Groups: Insights from the SRG/eROSITA All-sky Survey

Abstract We use the first eROSITA all-sky survey to investigate the contributions of active galactic nuclei (AGN) and extended gas to the total X-ray luminosity ( L X ) of galaxy groups with different halo masses ( M h ) at different redshifts. The presence of AGN in their central galaxies is identified using multiwavelength catalogs, including the X-ray counterparts, the ASKAP radio catalog, and the DESI spectroscopic measurements. We apply the stacking method to obtain sufficient statistics for the X-ray surface brightness profile and the L X for groups with different central AGN properties. We find that the X-ray groups exhibit the highest L X , followed by groups with QSO, radio, Baldwin–Phillips–Terlevich AGN, and non-AGN centrals. Moreover, the L X of the M h ≲ 10 13 h −1 M ⊙ groups is dominated by the central AGN, while the X-ray emission from extended gas tends to be more prominent in the M h ≳ 10 13 h −1 M ⊙ groups. In groups where the AGN play a major role in X-ray emission, the contribution from extended gas is minor, resulting in significant uncertainties concerning the extended X-ray emission. When the subset containing the X-ray-detected counterparts is excluded, the extended gas component becomes easier to obtain. A correlation has been identified between the X-ray luminosity of the central AGN and extended gas. However, once we account for the positional offset, their correlation becomes less prominent. Currently, the results are not conclusive enough to confirm whether there is a connection between the AGN feedback and extended gas. However, they provide a new perspective on the feedback processes in the history of group assembly.