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arXiv · 1504.05191

Star Formation and Relaxation in 379 Nearby Galaxy Clusters

Seth A. Cohen·Ryan C. Hickox·Gary A. Wegner
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Abstract

We investigate the relationship between star formation (SF) and level of relaxation in a sample of 379 galaxy clusters at z < 0.2. We use data from the Sloan Digital Sky Survey to measure cluster membership and level of relaxation, and to select star-forming galaxies based on mid-infrared emission detected with the Wide-Field Infrared Survey Explorer. For galaxies with absolute magnitudes M_r < -19.5, we find an inverse correlation between SF fraction and cluster relaxation: as a cluster becomes less relaxed, its SF fraction increases. Furthermore, in general, the subtracted SF fraction in all unrelaxed clusters (0.117 +/- 0.003) is higher than that in all relaxed clusters (0.097 +/- 0.005). We verify the validity of our SF calculation methods and membership criteria through analysis of previous work. Our results agree with previous findings that a weak correlation exists between cluster SF and dynamical state, possibly because unrelaxed clusters are less evolved relative to relaxed clusters.

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Seth A. Cohen, Ryan C. Hickox, Gary A. Wegner. 2015-04-20. Star Formation and Relaxation in 379 Nearby Galaxy Clusters. https://doi.org/10.1088/0004-637x%2F806%2F1%2F85

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