Measuring the X-ray luminosities of DESI groups from eROSITA Final Equatorial-Depth Survey: I. X-ray luminosity -- halo mass scaling relation

Abstract

We use the eROSITA Final Equatorial-Depth Survey (eFEDS) to measure the rest-frame 0.1-2.4 keV band X-ray luminosities of $\sim$ 600,000 DESI groups using two different algorithms in the overlap region of the two observations. These groups span a large redshift range of $0.0\le z_g\le 1.0$ and group mass range of $10^{10.76}{h}^{-1}{M}_{\odot }\le M_h\le 10^{15.0}{h}^{-1}{M}_{\odot }$. (1) Using the blind detection pipeline of eFEDS, we find that 10932 X-ray emission peaks can be cross matched with our groups, $\sim 38\%$ of which have signal-to-noise ratio $\mathrm{S}/\mathrm{N}\ge 3$ in X-ray detection. Comparing to the numbers reported in previous studies, this matched sample size is a factor of $\sim 6$ larger. (2) By stacking X-ray maps around groups with similar masses and redshifts, we measure the average X-ray luminosity of groups as a function of halo mass in five redshift bins. We find, in a wide halo mass range, the X-ray luminosity, $L_{\mathrm{X}}$, is roughly linearly proportional to $M_h$, and is quite independent to the redshift of the groups. (3) We use a Poisson distribution to model the X-ray luminosities obtained using two different algorithms and obtain best-fit $L_{\mathrm{X}}=10^{28.46\pm 0.03}{M}_h^{1.024\pm 0.002}$ and $L_{\mathrm{X}}=10^{26.73\pm 0.04}{M}_h^{1.140\pm 0.003}$ scaling relations, respectively. The best-fit slopes are flatter than the results previously obtained, but closer to a self-similar prediction.

15 pages, 13 figures, Monthly Notices of the Royal Astronomical Society, Volume 523, Issue 4, pp.4909-4922