Low-Frequency VLA Observations of Abell 754: Evidence for a Cluster Radio Halo and Possible Radio Relics

摘要

We present 74 and 330 MHz VLA observations of Abell 754. Diffuse, halo-like emission is detected from the center of the cluster at both frequencies. At 330 MHz, the resolution of 90' distinguishes this extended emission from previously known point sources. In addition to the halo, and at a much lower level, outlying steep-spectrum emission regions straddle the cluster center and are seen only at 74 MHz. The location, morphology, and spectrum of this emission are all highly suggestive of at least one, and possibly two, cluster radio relics. Easily obtained higher resolution, higher sensitivity VLA observations at both frequencies are required to confirm the extended nature of the halo-like emission and the 74 MHz relic detections. However, since there is prior evidence that this cluster is or has recently been in the process of a major merger event, the possible discovery of relics in this system is of great interest in light of recent observational and theoretical evidence in favor of a merger-relic connection. We discuss the possible role that the merger shock waves, which are seen in the X-ray emission, may have played in the formation of the halo and radio relics in A754.