SPT-CL J2215−3537: A Massive Starburst at the Center of the Most Distant Relaxed Galaxy Cluster

Calzadilla, Michael S.; Bleem, Lindsey E.; McDonald, Michael; Gladders, Michael D.; Mantz, Adam B.; Allen, Steven W.; Bayliss, Matthew B.; Eilers, Anna-Christina; Floyd, Benjamin; Hlavacek-Larrondo, Julie; Khullar, Gourav; Kim, Keunho J.; Mahler, Guillaume; Sharon, Keren; Somboonpanyakul, Taweewat; Stalder, Brian; Stark, Antony A.

Abstract

We present the discovery of the most distant, dynamically relaxed cool core cluster, SPT-CL J2215−3537 (SPT2215), and its central brightest cluster galaxy (BCG) at z = 1.16. Using new X-ray observations, we demonstrate that SPT2215 harbors a strong cool core with a central cooling time of 200 Myr (at 10 kpc) and a maximal intracluster medium cooling rate of 1900 ± 400 M⊙ yr−1. This prodigious cooling may be responsible for fueling the extended, star-forming filaments observed in Hubble Space Telescope imaging. Based on new spectrophotometric data, we detect bright [O ii] emission in the BCG, implying an unobscured star formation rate (SFR) of ${320}_{-140}^{+230}$M⊙ yr−1. The detection of a weak radio source (2.0 ± 0.8 mJy at 0.8 GHz) suggests ongoing feedback from an active galactic nucleus (AGN), though the implied jet power is less than half the cooling luminosity of the hot gas, consistent with cooling overpowering heating. The extreme cooling and SFR of SPT2215 are rare among known cool core clusters, and it is even more remarkable that we observe these at such high redshift, when most clusters are still dynamically disturbed. The high mass of this cluster, coupled with the fact that it is dynamically relaxed with a highly isolated BCG, suggests that it is an exceptionally rare system that must have formed very rapidly in the early universe. Combined with the high SFR, SPT2215 may be a high-z analog of the Phoenix cluster, potentially providing insight into the limits of AGN feedback and star formation in the most massive galaxies.

Citation

Calzadilla, M. S., Bleem, L. E., McDonald, M., Gladders, M. D., Mantz, A. B., Allen, S. W., …Stark, A. A. (2023). SPT-CL J2215−3537: A Massive Starburst at the Center of the Most Distant Relaxed Galaxy Cluster. Astrophysical Journal, 947(2), Article 44. https://doi.org/10.3847/1538-4357/acc6c2

• Journal Article Type: Article
• Acceptance Date: Mar 16, 2023
• Online Publication Date: Apr 19, 2023
• Publication Date: Apr 20, 2023
• Deposit Date: Oct 31, 2023
• Publicly Available Date: Oct 31, 2023
• Journal: The Astrophysical Journal
• Print ISSN: 0004-637X
• Electronic ISSN: 1538-4357
• Publisher: American Astronomical Society
• Peer Reviewed: Peer Reviewed
• Volume: 947
• Issue: 2
• Article Number: 44
• DOI: https://doi.org/10.3847/1538-4357/acc6c2
• Keywords: Space and Planetary Science; Astronomy and Astrophysics
• Public URL: https://durham-repository.worktribe.com/output/1872373