[45.02] A Radio Study of Abell 2255: Star Formation and AGN in a Cluster Merger

AAS 200th meeting, Albuquerque, NM, June 2002
Session 45. The New Radio Universe
Display, Tuesday, June 4, 2002, 10:00am-6:30pm, SW Exhibit Hall

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[45.02] A Radio Study of Abell 2255: Star Formation and AGN in a Cluster Merger

N.A. Miller (NASA's GSFC), F.N. Owen (NRAO)

Deep 1.4 GHz radio continuum imaging of Abell 2255 is presented. This cluster is among the better nearby candidates for rich cluster- cluster merger systems, with evidence including an elongated X-ray morphology, the presence of a radio halo, and substructure present in its galaxy distribution. Our radio observations reach an rms sensitivity of ~40 microJansky per beam, enabling us to detect (at 5-sigma) star formation rates as low as 1.4 solar masses per year from the center of the cluster out to a radial distance of 3h₇₅^-1 Mpc. The radio data are complemented by optical imaging and a large spectroscopic database, allowing us to separate all galaxies brighter than M_R=-20 into cluster members and foreground/background galaxies. The spectra are also used to associate the galaxies' radio emission with either star formation or AGN. By comparing Abell 2255 to other nearby clusters, we demonstrate an unusual amount of activity in this cluster. It appears that the merger strongly effects the evolution of cluster members, including both the powerful AGN and the optically-faint star-forming galaxies.

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