Post-merger cluster A2255 membership

There are changes in color, morphology, and star formation properties when galaxies fall into groups and clusters, but the specifics of how and where these modifications occur are not fully understood. To look for answers, we focused on star-forming galaxies in A2255, an unrelaxed cluster thought to have recently experienced a merger with another cluster or large group.

We used H{alpha}, MIPS 24 {mu}m, and WISE 22 {mu}m to estimate total star formation rates (SFRs) and Sloan Digital Sky Survey photometry to find stellar masses (M_*_) for galaxies out to ~5 r_200_. We compared the star-forming cluster galaxies with the field SFR-mass distribution and found no enhancement or suppression of star formation in currently star-forming galaxies of high mass (log(M_*_/M_{sun}_)>~10). This conclusion holds out to very large distances from the cluster center.