Optical and near-infrared observations of the SPT2349-56 proto-cluster core at z = 4.3

K. M. Rotermund, S. C. Chapman, K. A. Phadke, R. Hill, E. Pass, M. Aravena, M. L.N. Ashby, A. Babul, M. Béthermin, R. Canning, C. De Breuck, C. Dong, A. H. Gonzalez, C. C. Hayward, S. Jarugula, D. P. Marrone, D. Narayanan, C. Reuter, D. Scott, J. S. SpilkerJ. D. Vieira, G. Wang, A. Weiss

Research output: Contribution to journalArticlepeer-review

2 Scopus citations

Abstract

We present Gemini-S and Spitzer-IRAC optical-through-near-IR observations in the field of the SPT2349-56 proto-cluster at z = 4.3. We detect optical/IR counterparts for only 9 of the 14 submillimetre galaxies (SMGs) previously identified by ALMA in the core of SPT2349-56. In addition, we detect four z ∼4 Lyman-break galaxies (LBGs) in the 30 arcsec-diameter region surrounding this proto-cluster core. Three of the four LBGs are new systems, while one appears to be a counterpart of one of the nine observed SMGs. We identify a candidate brightest cluster galaxy (BCG) with a stellar mass of (3.2+2.3-1.4)× 1011 M⊙. The stellar masses of the eight other SMGs place them on, above, and below the main sequence of star formation at z ≈ 4.5. The cumulative stellar mass for the SPT2349-56 core is at least (12.2 ± 2.8) × 1011 M⊙, a sizeable fraction of the stellar mass in local BCGs, and close to the universal baryon fraction (0.19) relative to the virial mass of the core (1013 M⊙). As all 14 of these SMGs are destined to quickly merge, we conclude that the proto-cluster core has already developed a significant stellar mass at this early stage, comparable to z = 1 BCGs. Importantly, we also find that the SPT2349-56 core structure would be difficult to uncover in optical surveys, with none of the ALMA sources being easily identifiable or constrained through g, r, and i colour selection in deep optical surveys and only a modest overdensity of LBGs over the more extended structure. SPT2349-56 therefore represents a truly dust-obscured phase of a massive cluster core under formation.

Original languageEnglish (US)
Pages (from-to)1797-1815
Number of pages19
JournalMonthly Notices of the Royal Astronomical Society
Volume502
Issue number2
DOIs
StatePublished - Apr 1 2021

Keywords

  • galaxies: evolution
  • galaxies: high-redshift
  • galaxies: star formation
  • submillimetre: galaxies

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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