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Deep Chandra, HST-COS, and Megacam observations of the Phoenix cluster : extreme star formation and AGN feedback on hundred kiloparsec scales.

McDonald, M. and McNamara, B.R. and van Weeren, R.J. and Applegate, D.E. and Bayliss, M. and Bautz, M.W. and Benson, B.A. and Carlstrom, J.E. and Bleem, L.E. and Chatzikos, M. and Edge, A.C. and Fabian, A.C. and Garmire, G.P. and Hlavacek-Larrondo, J. and Jones-Forman, C. and Mantz, A.B. and Miller, E.D. and Stalder, B. and Veilleux, S. and ZuHone, J.A. (2015) 'Deep Chandra, HST-COS, and Megacam observations of the Phoenix cluster : extreme star formation and AGN feedback on hundred kiloparsec scales.', Astrophysical journal., 811 (2). p. 111.


We present new ultraviolet, optical, and X-ray data on the Phoenix galaxy cluster (SPT-CLJ2344-4243). Deep optical imaging reveals previously undetected filaments of star formation, extending to radii of ~50–100 kpc in multiple directions. Combined UV-optical spectroscopy of the central galaxy reveals a massive (2 × 109 M⊙), young (~4.5 Myr) population of stars, consistent with a time-averaged star formation rate of 610 ± 50 M⊙ yr−1. We report a strong detection of O vi λλ1032,1038, which appears to originate primarily in shock-heated gas, but may contain a substantial contribution (>1000 M⊙ yr−1) from the cooling intracluster medium (ICM). We confirm the presence of deep X-ray cavities in the inner ~10 kpc, which are among the most extreme examples of radio-mode feedback detected to date, implying jet powers of 2–7 × 1045 erg s−1. We provide evidence that the active galactic nucleus inflating these cavities may have only recently transitioned from "quasar-mode" to "radio-mode," and may currently be insufficient to completely offset cooling. A model-subtracted residual X-ray image reveals evidence for prior episodes of strong radio-mode feedback at radii of ~100 kpc, with extended "ghost" cavities indicating a prior epoch of feedback roughly 100 Myr ago. This residual image also exhibits significant asymmetry in the inner ~200 kpc (0.15R500), reminiscent of infalling cool clouds, either due to minor mergers or fragmentation of the cooling ICM. Taken together, these data reveal a rapidly evolving cool core which is rich with structure (both spatially and in temperature), is subject to a variety of highly energetic processes, and yet is cooling rapidly and forming stars along thin, narrow filaments.

Item Type:Article
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Publisher statement:© 2015. The American Astronomical Society. All rights reserved.
Date accepted:21 August 2015
Date deposited:12 November 2015
Date of first online publication:October 2015
Date first made open access:No date available

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