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arXiv · 1606.02362

Recent galaxy mergers and residual star formation of red sequence galaxies in galaxy clusters

Yun-Kyeong Sheen·Sukyoung K. Yi·Chang H. Ree·Yara Jaffé·Ricardo Demarco·Ezequiel Treister
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Abstract

This study explored the GALEX ultraviolet (UV) properties of optical red sequence galaxies in 4 rich Abell clusters at z \leq 0.1. In particular, we tried to find a hint of merger-induced recent star formation (RSF) in red sequence galaxies. Using the NUV - r' colors of the galaxies, RSF fractions were derived based on various criteria for post-merger galaxies and normal galaxies. Following k-correction, about 36% of the post-merger galaxies were classified as RSF galaxies with a conservative criterion (NUV - r' \leq 5), and that number was doubled (~ 72%) when using a generous criterion (NUV - r' \leq 5.4). The trend was the same when we restricted the sample to galaxies within 0.5xR_{200}. Post-merger galaxies with strong UV emission showed more violent, asymmetric features in the deep optical images. The RSF fractions did not show any trend along the clustocentric distance within R_{200}. We performed a Dressler-Shectman test to check whether the RSF galaxies had any correlation with the sub-structures in the galaxy clusters. Within R_{200} of each cluster, the RSF galaxies did not appear to be preferentially related to the clusters' sub-structures. Our results suggested that only 30% of RSF red sequence galaxies show morphological hints of recent galaxy mergers. This implies that internal processes (e.g., stellar mass-loss or hot gas cooling) for the supply of cold gas to early-type galaxies may play a significant role in the residual star formation of early-type galaxies at a recent epoch.

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Yun-Kyeong Sheen, Sukyoung K. Yi, Chang H. Ree, Yara Jaffé, Ricardo Demarco, Ezequiel Treister. 2016-06-08. Recent galaxy mergers and residual star formation of red sequence galaxies in galaxy clusters. https://doi.org/10.3847/0004-637x%2F827%2F1%2F32

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