Constraints on the Thermal Contents of the X-Ray Cavities of Cluster MS 0735.6+7421 with Sunyaev–Zel'dovich Effect Observations
Outbursts from active galactic nuclei (AGN) can inflate cavities in the intracluster medium (ICM) of galaxy clusters and are believed to play the primary role in offsetting radiative cooling in the ICM. However, the details of how the energy from AGN feedback thermalizes to heat the ICM is not well understood, partly due to the unknown composition and energetics of the cavities. The Sunyaev–Zel'dovich (SZ) effect, a measure of the integrated pressure along the line of sight, provides a means of measuring the thermal contents of the cavities, to discriminate between thermal, nonthermal, and other sources of pressure support. Here we report measurements of the SZ effect at 30 GHz toward the galaxy cluster MS 0735.6+7421 (MS0735), using the Combined Array for Research in Millimeter-wave Astronomy (CARMA). MS0735 hosts the most energetic AGN outburst known and lobes of radio synchrotron emission coincident with a pair of giant X-ray cavities ~200 kpc across. Our CARMA maps show a clear deficit in the SZ signal coincident with the X-ray identified cavities, when compared to a smooth X-ray derived pressure model. We find that the cavities have very little SZ-contributing material, suggesting that they are either supported by very diffuse thermal plasma with temperature in excess of hundreds of keV, or are not supported thermally. Our results represent the first detection (with 4.4σ significance) of this phenomenon with the SZ effect.
© 2019. The American Astronomical Society. Received 2018 June 4; revised 2018 December 12; accepted 2018 December 13; published 2019 January 31. We thank Adrian Vantyghem for supplying the latest Chandra X-ray images and profiles of MS0735 presented in Vantyghem et al. (2014). We thank Laura Birzan and Brian McNamara for supplying the VLA observations of MS0735 presented in Bîrzan et al. (2008). We thank Damiano Capriolli for his insightful comments. We thank the anonymous referee for helpful comments. Support for CARMA construction was derived from the Gordon and Betty Moore Foundation; the Kenneth T. and Eileen L. Norris Foundation; the James S. McDonnell Foundation; the Associates of the California Institute of Technology; the University of Chicago; the states of California, Illinois, and Maryland; and the National Science Foundation. CARMA development and operations were supported by NSF under a cooperative agreement and by the CARMA partner universities; the work at Chicago was supported by NSF grant AST-1140019. Additional support was provided by PHY-0114422.
Submitted - 1806.05050.pdf
Published - Abdulla_2019_ApJ_871_195.pdf