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Stellar splashback: the edge of the intracluster light

Deason, Alis J. and Oman, Kyle A. and Fattahi, Azadeh and Schaller, Matthieu and Jauzac, Mathilde and Zhang, Yuanyuan and Montes, Mireia and Bahé, Yannick M. and Dalla Vecchia, Claudio and Kay, Scott T. and Evans, Tilly A. (2021) 'Stellar splashback: the edge of the intracluster light.', Monthly notices of the Royal Astronomical Society, 500 (3). pp. 4181-4192.


We examine the outskirts of galaxy clusters in the C-EAGLE simulations to quantify the ‘edges’ of the stellar and dark matter distribution. The radius of the steepest slope in the dark matter, commonly used as a proxy for the splashback radius, is located at ∼r200m⁠; the strength and location of this feature depends on the recent mass accretion rate, in good agreement with previous work. Interestingly, the stellar distribution (or intracluster light, ICL) also has a well-defined edge, which is directly related to the splashback radius of the halo. Thus, detecting the edge of the ICL can provide an independent measure of the physical boundary of the halo, and the recent mass accretion rate. We show that these caustics can also be seen in the projected density profiles, but care must be taken to account for the influence of substructures and other non-diffuse material, which can bias and/or weaken the signal of the steepest slope. This is particularly important for the stellar material, which has a higher fraction bound in subhaloes than the dark matter. Finally, we show that the ‘stellar splashback’ feature is located beyond current observational constraints on the ICL, but these large projected distances (≫1 Mpc) and low surface brightnesses (μ ≫ 32 mag arcsec−2) can be reached with upcoming observational facilities such as the Vera C. Rubin Observatory, the Nancy Grace Roman Space Telescope, and Euclid.

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Publisher statement:This article has been accepted for publication in Monthly Notices of the Royal astronomical Society ©: 2020 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:13 November 2020
Date deposited:29 June 2021
Date of first online publication:19 November 2020
Date first made open access:29 June 2021

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