We present measurements of the radial profile of mass and galaxy number density around x-ray selected ROSAT All Sky Survey-Multi-Component Matched Filter galaxy clusters using Year 3 data from the Dark Energy Survey. We measure the projected cross-correlation signal of the RedMaGiC “high density” galaxies around an approximately volume-limited sample of 255 galaxy clusters at a median redshift of $z=0.4$ and an x-ray luminosity $L_X>{10}^{44}\mathrm{ergs}{\mathrm{s}}^{-1}{\mathrm{h}}^{-2}$. This cross-correlation signal measured with a signal-to-noise ratio of 16.41 allows us to infer a 3D number density profile, which shows a significant steepening at the edges of these galaxy clusters, namely the splashback radius of $r_{\mathrm{sp}}/h^{-1}\mathrm{Mpc}=2.19_{-0.43}^{+0.50}$. We present the dependence of the splashback radius value over a range of absolute galaxy magnitude cuts to look for any evidence of dynamical friction affecting these results. The weak lensing signal around our galaxy clusters measured with a signal-to-noise ratio of 32.19 allows us to infer a halo mass $\log (M_{200\mathrm{m}}/h^{-1}{M}_{\odot })=14.68_{-0.04}^{+0.04}$. Comparison of the location of the splashback radius with the spherical overdensity boundary $r_{200\mathrm{m}}$ shows consistency with the $\mathrm{\Lambda }$ cold dark matter predictions. We present the first inference of the average mass accretion rate of galaxy clusters using our measurements of the splashback radius.

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• Cosmological parameters
• Large scale structure of the Universe
• Massive compact halo objects
• Galaxy clusters
• Astrophysical & cosmological simulations