Cookies

We use cookies to ensure that we give you the best experience on our website. You can change your cookie settings at any time. Otherwise, we'll assume you're OK to continue.

Durham University

Department of Physics

Staff profile

Publication details for Prof Richard Massey

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., Nonino, M., Robertson, A., Tam, S. I. & Umetsu, K. (2018). Growing a ‘cosmic beast’ observations and simulations of MACS J0717.5+3745. Monthly Notices of the Royal Astronomical Society 481(3): 2901-2917.

Author(s) from Durham

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<1Mpc)∼ 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 × 1015 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 × 1013 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 ∼ 1016 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.   2×1015M⊙ , 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 3.8−6.5×1013M⊙ , 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 ∼  1016M⊙ 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.