First ALMA Detection of a Galaxy Cluster Merger Shock

Journal
Date Issued
2016
Author(s)
Basu, K.
•
Sommer, M.
•
Erler, J.
•
Eckert, D.
•
•
Magnelli, B.
•
Bertoldi, F.
•
Abstract
We report on the first ALMA measurement of a galaxy cluster merger shock, observed at the location of a radio relic in the famous El Gordo galaxy cluster at redshift z 0.9. Located at about half the current age of the Universe, this is also the most distant example of a directly measured astrophysical shock. ALMA Band 3 was utilised to measure the Sunyaev-Zel'dovich (SZ) effect signature that confirms a small-scale change in pressure as expected from the passage of a shock in the intracluster medium. The results support a previous radio-based estimate of the shock Mach number and display similarities, and also some mild tensions, with the X-ray based results. Most importantly, these results show the potential of ALMA to detect galaxy cluster shocks, observations that will advance our knowledge of cluster formation, non-thermal particle acceleration and amplification of magnetic fields across the entire observable Universe where such relic shocks can be found.
Volume
166
Start page
53
Uri
Url
Issn Identifier
0722-6691
Ads BibCode
2016Msngr.166...53B
Rights
open.access
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