MC<sup>2</sup>:Boosted AGN and star formation activity in CIZA J2242.8+5301, a massive post-merger cluster at z = 0.19

Sobral, David and Stroe, Andra and Dawson, William A. and Wittman, David and James Jee, M. and Röttgering, Huub and van Weeren, Reinout J. and Brüggen, Marcus (2015) MC<sup>2</sup>:Boosted AGN and star formation activity in CIZA J2242.8+5301, a massive post-merger cluster at z = 0.19. Monthly Notices of the Royal Astronomical Society, 450 (1). pp. 630-645. ISSN 0035-8711

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Abstract

Cluster mergers may play a fundamental role in the formation and evolution of cluster galaxies. Stroe et al. revealed unexpected overdensities of candidate Hα emitters near the ~1-Mpc-wide shock fronts of the massive (~2 × 10<sup>15</sup> M<inf>⊙</inf>) 'Sausage' merging cluster, CIZA J2242.8+5301. We used the Keck/Deep Imaging Multi-Object Spectrograph and the William Herschel Telescope/AutoFib2+WYFFOS to confirm 83 Hα emitters in and around the merging cluster. We find that cluster star-forming galaxies in the hottest X-ray gas and/or in the cluster subcores (away from the shock fronts) show high [S II]6716/[S II]6761 and high [S II] 6716/Hα, implying very low electron densities (<30 × lower than all other star-forming galaxies outside the cluster) and/or significant contribution from supernovae, respectively. All cluster star-forming galaxies near the cluster centre show evidence of significant outflows (blueshifted Na D ~200-300 km s<sup>-1</sup>), likely driven by supernovae. Strong outflows are also found for the cluster Hα active galactic nucleus (AGN). Hα star-forming galaxies in the merging cluster follow the z ~ 0 mass-metallicity relation, showing systematically higher metallicity (~0.15-0.2 dex) than Hα emitters outside the cluster (projected R > 2.5 Mpc). This suggests that the shock front may have triggered remaining metal-rich gas which galaxies were able to retain into forming stars. Our observations show that the merger of impressively massive (~10<sup>15</sup> M<inf>⊙</inf>) clusters can provide the conditions for significant star formation and AGN activity, but, as we witness strong feedback by star-forming galaxies and AGN (and given how massive the merging cluster is), such sources will likely quench in a few 100 Myr.

Item Type:
Journal Article
Journal or Publication Title:
Monthly Notices of the Royal Astronomical Society
Uncontrolled Keywords:
/dk/atira/pure/subjectarea/asjc/3100/3103
Subjects:
ID Code:
77718
Deposited By:
Deposited On:
15 Jan 2016 10:16
Refereed?:
Yes
Published?:
Published
Last Modified:
31 Jul 2020 00:43