A Comprehensive Radio and Optical Study of Abell 2256: Activity from an Infalling Group

摘要: Abell 2256 is a nearby (z~0.06), rich cluster of galaxies with fascinating observed properties across range wavelengths. Long believed to represent merger, recent X-ray and optical results have suggested that in addition the primary subcluster there evidence for third, poorer system. We present wide-field, high sensitivity 1.4 GHz VLA radio observations conjunction imaging additional spectroscopy. Over 40 are identified, spectroscopy indicating emission source (star formation or AGN) most them. While overall fraction exhibiting consistent large sample other clusters, we find an increase activity level belonging third system (hereafter, ``Group''). Specifically, Group has relatively more star than both main subcluster. The position also coincident relic. suggest recently (~0.3 Gyr) merged this not ongoing merger subcluster, might be responsible many unusual 2256. Furthermore, greater suggests infall groups important driver galaxy evolution clusters.