Anatomy of a Cooling Flow: The Feedback Response to Pure Cooling in the Core of the Phoenix Cluster

• Published in: The Astrophysical journal 2019-11, Vol.885 (1), p.63
• Main Authors: McDonald, M., McNamara, B. R., Voit, G. M., Bayliss, M., Benson, B. A., Brodwin, M., Canning, R. E. A., Florian, M. K., Garmire, G. P., Gaspari, M., Gladders, M. D., Hlavacek-Larrondo, J., Kara, E., Reichardt, C. L., Russell, H. R., Saro, A., Sharon, K., Somboonpanyakul, T., Tremblay, G. R., Weeren, R. J. van
• Format: Article
• Language: English
• Subjects: Active galactic nuclei; Angular resolution; Astrophysics; Clusters; Computational fluid dynamics; Cooling; Cooling flows (astrophysics); Entropy; Feedback; Galaxies; galaxies: clusters: individual (SPT-CLJ2344-4243); galaxies: clusters: intracluster medium; Hubble Space Telescope; Multiphase; Power law; Radio jets (astronomy); Radio waves; Soft x rays; Space telescopes; Uplift; Wavelengths; X-rays; X-rays: galaxies: clusters
• ISSN: 0004-637X; 1538-4357
• DOI: 10.3847/1538-4357/ab464c

We present new, deep observations of the Phoenix cluster from Chandra, the Hubble Space Telescope, and the Karl Jansky Very Large Array. These data provide an order-of-magnitude improvement in depth and/or angular resolution over previous observations at X-ray, optical, and radio wavelengths. We find that the one-dimensional temperature and entropy profiles are consistent with expectations for pure-cooling models. In particular, the entropy profile is well fit by a single power law at all radii, with no evidence for excess entropy in the core. In the inner ∼10 kpc, the cooling time is shorter than any other known cluster by an order of magnitude, while the ratio of the cooling time to freefall time (tcool/tff) approaches unity, signaling that the intracluster medium is unable to resist multiphase condensation on kpc scales. The bulk of the cooling in the inner ∼20 kpc is confined to a low-entropy filament extending northward from the central galaxy, with tcool/tff ∼ 1 over the length of the filament. In this filament, we find evidence for ∼1010 M in cool (∼104 K) gas (as traced by the [O ii]λλ3726,3729 doublet), which is coincident with the low-entropy filament and absorbing soft X-rays. The bulk of this cool gas is draped around and behind a pair of X-ray cavities, presumably bubbles that have been inflated by radio jets. These data support a picture in which active galactic nucleus feedback is promoting the formation of a multiphase medium via uplift of low-entropy gas, either via ordered or chaotic (turbulent) motions.