Abstract
We explore the possibility of using the external regions of galaxy clusters to measure their mass accretion rate (MAR). The main goal is to provide a method to observationally investigate the growth of structures on the nonlinear scales of galaxy clusters. We derive the MAR by using the mass profile beyond the splashback radius, evaluating the mass of a spherical shell and the time it takes to fall in. The infall velocity of the shell is extracted from N-body simulations. The average MAR returned by our prescription in the redshift range z = [ 0 , 2 ] is within 20%–40% of the average MAR derived from the merger trees of dark matter haloes in the reference N-body simulations. Our result suggests that the external regions of galaxy clusters can be used to measure the mean MAR of a sample of clusters.
Highlights
After the discovery of a steepening in the density profiles of halos at ∼0.5–1 R200m (R∆m is the radius of a sphere of mass M∆m and average density ∆ times the mean density of the Universe, ρm = ρc Ωm, where ρc ≡ 3H 2 (z)/8πG is the critical density of the Universe and H is the Hubble parameter) in numerical simulations [1], the outskirts of galaxy clusters have gathered much attention
Our result suggests that the external regions of galaxy clusters can be used to measure the mean mass accretion rate (MAR) of a sample of clusters
We rely on N-body simulations of dark matter haloes and compare the MAR obtained with our method with the “true” MAR obtained from the merger trees for the same sample of clusters
Summary
This could be the reason why at radii larger than Rsp , the profiles are more self-similar when rescaled by R200m than when rescaled by R200c Another important radius in the outer regions of galaxy clusters that has been studied as an alternative definition of the splashback radius and of the halo boundary is the so-called infall radius Rinf ; i.e., the radius where the mean radial velocity is more negative. Before applying our method to real data, we have to check whether it is capable of recovering the true MAR of objects for which the latter is well known For this reason, we rely on N-body simulations of dark matter haloes and compare the MAR obtained with our method with the “true” MAR obtained from the merger trees for the same sample of clusters
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