Cooke, Elizabeth A. and Hatch, Nina A. and Rettura, A. and Wylezalek, D. and Galametz, A. and Stern, D. and Brodwin, M. and Muldrew, S.I. and Almaini, O. and Conselice, C.J. and Eisenhardt, P.R. and Hartley, W.G. and Jarvis, M. and Seymour, N. and Stanford, S.A.
The formation history of massive cluster galaxies as revealed by CARLA.
Monthly Notices of the Royal Astronomical Society, 452
We use a sample of 37 of the densest clusters and protoclusters across 1.3 ≤ z ≤ 3.2 from the Clusters Around Radio-Loud AGN (CARLA) survey to study the formation of massive cluster galaxies. We use optical i′-band and infrared 3.6 and 4.5 μm images to statistically select sources within these protoclusters and measure their median observed colours; 〈i′ − [3.6]〉. We find the abundance of massive galaxies within the protoclusters increases with decreasing redshift, suggesting these objects may form an evolutionary sequence, with the lower redshift clusters in the sample having similar properties to the descendants of the high-redshift protoclusters. We find that the protocluster galaxies have an approximately unevolving observed-frame i′ − [3.6] colour across the examined redshift range. We compare the evolution of the 〈i′ − [3.6]〉 colour of massive cluster galaxies with simplistic galaxy formation models. Taking the full cluster population into account, we show that the formation of stars within the majority of massive cluster galaxies occurs over at least 2 Gyr, and peaks at z ∼ 2–3. From the median i′ − [3.6] colours, we cannot determine the star formation histories of individual galaxies, but their star formation must have been rapidly terminated to produce the observed red colours. Finally, we show that massive galaxies at z > 2 must have assembled within 0.5 Gyr of them forming a significant fraction of their stars. This means that few massive galaxies in z > 2 protoclusters could have formed via dry mergers.
||This article has been accepted for publication in Monthly Notices of the Royal Astronomical Society ©: 2015 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. All rights reserved
||galaxies: clusters: general; galaxies: evolution; galaxies: formation; galaxies: high-redshift
||University of Nottingham, UK > Faculty of Science > School of Physics and Astronomy
||12 Jul 2016 08:11
||26 Sep 2016 15:35
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