Daftar Isi: Discovery of a Radio Relic in the Massive Merging Cluster SPT-CL J2023-5535 from the ASKAP-EMU Pilot Survey

Daftar Isi:

The ASKAP-EMU survey is a deep wide-field radio continuum survey designed to cover the entire southern sky and a significant fraction of the northern sky up to +30deg. We report a discovery of a radio relic in the merging cluster SPT-CL J2023--5535 at z=0.23 from the ASKAP-EMU pilot 300 sq.deg survey (800 - 1088 MHz). The radio relic is located at the western edge of this radio halo stretched ~0.5 Mpc in the north-south orientation. The integrated spectral index of the radio relic within the narrow bandwidth is alpha (1088 MHz - 800 MHz) = - 0.76 +- 0.06. Our weak-lensing analysis of archival DECam data shows that the system is a massive M200 =(1.04 +- 0.36) 10^15 Msun) merging cluster composed of at least three subclusters. We suggest a scenario, wherein the radio features arise from the collision between the eastern and middle subclusters. Our discovery illustrates the effectiveness of the ASKAP-EMU survey in detecting diffuse emissions in galaxy clusters and when completed, the survey will greatly increase the number of merging cluster detections with diffuse radio emissions.