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Mapping substructure in the HST Frontier Fields cluster lenses and in cosmological simulations.

Natarajan, Priyamvada and Chadayammuri, Urmila and Jauzac, Mathilde and Richard, Johan and Kneib, Jean-Paul and Ebeling, Harald and Jiang, Fangzhou and van den Bosch, Frank and Limousin, Marceau and Jullo, Eric and Atek, Hakim and Pillepich, Annalisa and Popa, Cristina and Marinacci, Federico and Hernquist, Lars and Meneghetti, Massimo and Vogelsberger, Mark (2017) 'Mapping substructure in the HST Frontier Fields cluster lenses and in cosmological simulations.', Monthly notices of the Royal Astronomical Society., 468 (2). pp. 1962-1980.

Abstract

We map the lensing-inferred substructure in the first three clusters observed by the Hubble Space Telescope Frontier Fields (HSTFF) Initiative: Abell 2744 (z = 0.308), MACSJ 0416, (z = 0.396) and MACSJ 1149 (z = 0.543). Statistically resolving dark matter subhaloes down to ∼109.5M⊙ ∼109.5M⊙ , we compare the derived subhalo mass functions (SHMFs) to theoretical predictions from analytical models and with numerical simulations in a Lambda cold dark matter (LCDM) cosmology. Mimicking our observational cluster member selection criteria in the HSTFF, we report excellent agreement in both amplitude and shape of the SHMF over four decades in subhalo mass ( 109−13M⊙ 109−13M⊙ ). Projection effects do not appear to introduce significant errors in the determination of SHMFs from simulations. We do not find evidence for a substructure crisis, analogous to the missing satellite problem in the Local Group, on cluster scales, but rather excellent agreement of the count-matched HSTFF SHMF down to Msubhalo/Mhalo ∼ 10−5. However, we do find discrepancies in the radial distribution of subhaloes inferred from HSTFF cluster lenses compared to determinations from simulated clusters. This suggests that although the selected simulated clusters match the HSTFF sample in mass, they do not adequately capture the dynamical properties and complex merging morphologies of these observed cluster lenses. Therefore, HSTFF clusters are likely observed in a transient evolutionary stage that is presently insufficiently sampled in cosmological simulations. The abundance and mass function of dark matter substructure in cluster lenses continues to offer an important test of the LCDM paradigm, and at present we find no tension between model predictions and observations.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1093/mnras/stw3385
Publisher statement:This article has been accepted for publication in Monthly notices of the Royal Astronomical Society ©: 2017 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved.
Date accepted:30 December 2016
Date deposited:24 August 2017
Date of first online publication:06 February 2017
Date first made open access:24 August 2017

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