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• 1611.03512v1

Rights statement: This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated versionAndra Stroe, David Sobral, Ana Paulino-Afonso, Lara Alegre, João Calhau, Sergio Santos, Reinout van Weeren; A large Hα survey of star formation in relaxed and merging galaxy cluster environments at z ∼ 0.15–0.3. Mon Not R Astron Soc 2017; 465 (3): 2916-2935. doi: 10.1093/mnras/stw2939 is available online at: https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/stw2939

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## A large H$α$ survey of star formation in relaxed and merging galaxy cluster environments at $z\sim0.15-0.3$

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Journal publication date 03/2017 Monthly Notices of the Royal Astronomical Society 3 465 20 2916-2935 Published 17/11/16 English

### Abstract

We present the first results from the largest H$\alpha$ survey of star formation and AGN activity in galaxy clusters. Using 9 different narrow band filters, we select $>3000$ H$\alpha$ emitters within $19$ clusters and their larger scale environment over a total volume of $1.3\times10^5$ Mpc$^3$. The sample includes both relaxed and merging clusters, covering the $0.15-0.31$ redshift range and spanning from $5\times10^{14}$ $M_{\odot}$ to $30\times10^{14}$ $M_{\odot}$. We find that the H$\alpha$ luminosity function (LF) for merging clusters has a higher characteristic density $\phi^*$ compared to relaxed clusters. $\phi^*$ drops from cluster core to cluster outskirts for both merging and relaxed clusters, with the merging cluster values $\sim0.3$ dex higher at each projected radius. The characteristic luminosity $L^*$ drops over the $0.5-2.0$ Mpc distance from the cluster centre for merging clusters and increases for relaxed objects. Among disturbed objects, clusters hosting large-scale shock waves (traced by radio relics) are overdense in H$\alpha$ emitters compared to those with turbulence in their intra-cluster medium (traced by radio haloes). We speculate that the increase in star formation activity in disturbed, young, massive galaxy clusters can be triggered by interactions between gas-rich galaxies, shocks and/or the intra-cluster medium, as well as accretion of filaments and galaxy groups. Our results indicate that disturbed clusters represent vastly different environments for galaxy evolution compared to relaxed clusters or average field environments.

### Bibliographic note

This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated versionAndra Stroe, David Sobral, Ana Paulino-Afonso, Lara Alegre, João Calhau, Sergio Santos, Reinout van Weeren; A large Hα survey of star formation in relaxed and merging galaxy cluster environments at z ∼ 0.15–0.3. Mon Not R Astron Soc 2017; 465 (3): 2916-2935. doi: 10.1093/mnras/stw2939 is available online at: https://academic.oup.com/mnras/article-lookup/doi/10.1093/mnras/stw2939