SPT-CL J2040-4451: AN SZ-SELECTED GALAXY CLUSTER AT z = 1.478 WITH SIGNIFICANT ONGOING STAR FORMATION

• Main Authors: Bautz, Marshall W. (Contributor), McDonald, Michael A. (Contributor), Miller, Eric D (Author)
• Other Authors: MIT Kavli Institute for Astrophysics and Space Research (Contributor), Miller, Eric D. (Contributor)
• Format: Article
• Language: English
• Published: IOP Publishing, 2015-02-18T15:58:14Z.
• Subjects: Article
• Online Access: Get fulltext

 SPT-CL J2040-4451-spectroscopically confirmed at z = 1.478-is the highest-redshift galaxy cluster yet discovered via the Sunyaev-Zel'dovich effect. SPT-CL J2040-4451 was a candidate galaxy cluster identified in the first 720 deg[superscript 2] of the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey, and has been confirmed in follow-up imaging and spectroscopy. From multi-object spectroscopy with Magellan-I/Baade+IMACS we measure spectroscopic redshifts for 15 cluster member galaxies, all of which have strong [O II] λλ3727 emission. SPT-CL J2040-4451 has an SZ-measured mass of M [subscript 500, SZ] = 3.2 ± 0.8 × 10[superscript 14] M [subscript ☉] h [-1 over 70], corresponding to M [subscript 200, SZ] = 5.8 ± 1.4 × 10[superscript 14] M [subscript ☉] h [-1 over 70]. The velocity dispersion measured entirely from blue star-forming members is σ [subscript v] = 1500 ± 520 km s[superscript -1]. The prevalence of star-forming cluster members (galaxies with >1.5 M [subscript ☉] yr[superscript -1]) implies that this massive, high-redshift cluster is experiencing a phase of active star formation, and supports recent results showing a marked increase in star formation occurring in galaxy clusters at z [> over ~] 1.4. We also compute the probability of finding a cluster as rare as this in the SPT-SZ survey to be >99%, indicating that its discovery is not in tension with the concordance ΛCDM cosmological model.