Growing a `cosmic beast': observations and simulations of MACS J0717.5+3745
Date Issued
2018
Author(s)
Jauzac, M.
•
Eckert, D.
•
Schaller, M.
•
Schwinn, J.
•
Massey, R.
•
Bahé, Y.
•
Baugh, C.
•
Barnes, D.
•
Dalla Vecchia, C.
•
Ebeling, H.
•
Harvey, D.
•
Jullo, E.
•
Kay, S. T.
•
Kneib, J. -P.
•
Limousin, M.
•
Medezinski, E.
•
Natarajan, P.
•
•
Robertson, A.
•
Tam, S. I.
•
Umetsu, K.
Description
MN acknowledges PRIN INAF 2014 1.05.01.94.02.
Abstract
We present a gravitational lensing and X-ray analysis of a massive galaxy cluster and its surroundings. The core of MACS J0717.5+3745 (M(R<1 Mpc)∼ 2 × 10^{15} M_{☉ }, z = 0.54) is already known to contain four merging components. We show that this is surrounded by at least seven additional substructures with masses ranging 3.8{-}6.5× 10^{13} M_{☉}, at projected radii 1.6-4.9 Mpc. We compare MACS J0717 to mock lensing and X-ray observations of similarly rich clusters in cosmological simulations. The low gas fraction of substructures predicted by simulations turns out to match our observed values of 1-4{{ per cent}}. Comparing our data to three similar simulated haloes, we infer a typical growth rate and substructure infall velocity. That suggests MACS J0717 could evolve into a system similar to, but more massive than, Abell 2744 by z = 0.31, and into a ∼ 10^{16} M_{☉} supercluster by z = 0. The radial distribution of infalling substructure suggests that merger events are strongly episodic; however, we find that the smooth accretion of surrounding material remains the main source of mass growth even for such massive clusters.
Volume
481
Issue
3
Start page
2901
Issn Identifier
0035-8711
Ads BibCode
2018MNRAS.481.2901J
Rights
open.access
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