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 x 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 ᴠɪ 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 x 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.

Document Type


Publication Date


Notes/Citation Information

Published in The Astrophysical Journal, v. 811, no. 2, article 111, p. 1-18.

© 2015. The American Astronomical Society. All rights reserved.

The copyright holders have granted the permission for posting the article here.

Digital Object Identifier (DOI)


Funding Information

M.M. acknowledges support by NASA through contracts HST-GO-13456.002A (Hubble) and GO4-15122A (Chandra), and Hubble Fellowship grant HST-HF51308.01-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS 5-26555. The Guaranteed Time Observations (GTO) included here were selected by the ACIS Instrument Principal Investigator, Gordon P. Garmire, of the Huntingdon Institute for X-ray Astronomy, LLC, which is under contract to the Smithsonian Astrophysical Observatory; Contract SV2-82024. J.E.C. acknowledges support from National Science Foundation grants PLR-1248097 and PHY-1125897. B.R.M. acknowledges generous financial support from the Natural Sciences and Engineering Research Council of Canada. R.J.W. is supported by NASA through the Einstein Postdoctoral grant number PF2-130104 awarded by the Chandra X-ray Center, which is operated by the Smithsonian Astrophysical Observatory for NASA under contract NAS8-03060. J.H.-L. is supported by NSERC through the discovery grant and Canada Research Chair programs, as well as FRQNT. D.A. acknowledges support from the DLR under projects 50 OR 1210 and 1407, and from the DFG under project AP 253/1-1. A.C.E. acknowledges support from STFC grant ST/I001573/1.