Cosmic Vine: A <i>z</i> = 3.44 large-scale structure hosting massive quiescent galaxies
Shuowen Jin, Nikolaj B. Sillassen, G. Magdis, Malte Brinch, Marko Shuntov, Gabriel Brammer, R. Gobat, Francesco Valentino, Adam C. Carnall, Minju Lee, Aswin P. Vijayan, Steven Gillman, Vasily Kokorev, Aurélien Le Bail, T. R. Greve, B. Gullberg, Katriona M. L. Gould, Sune Toft
Abstract
We report the discovery of a large-scale structure at z = 3.44 revealed by JWST data in the Extended Groth Strip (EGS) field. This structure, called the Cosmic Vine, consists of 20 galaxies with spectroscopic redshifts at 3.43 < z < 3.45 and six galaxy overdensities (4 − 7 σ ) with consistent photometric redshifts, making up a vine-like structure extending over a ∼4 × 0.2 pMpc 2 area. The two most massive galaxies ( M * ≈ 10 10.9 M ⊙ ) of the Cosmic Vine are found to be quiescent with bulge-dominated morphologies ( B / T > 70%). Comparisons with simulations suggest that the Cosmic Vine would form a cluster with halo mass M halo > 10 14 M ⊙ at z = 0, and the two massive galaxies are likely forming the brightest cluster galaxies (BCGs). The results unambiguously reveal that massive quiescent galaxies can form in growing large-scale structures at z > 3, thus disfavoring the environmental quenching mechanisms that require a virialized cluster core. Instead, as suggested by the interacting and bulge-dominated morphologies, the two galaxies are likely quenched by merger-triggered starburst or active galactic nucleus (AGN) feedback before falling into a cluster core. Moreover, we found that the observed specific star formation rates of massive quiescent galaxies in z > 3 dense environments are one to two orders of magnitude lower than that of the BCGs in the TNG300 simulation. This discrepancy potentially poses a challenge to the models of massive cluster galaxy formation. Future studies comparing a large sample with dedicated cluster simulations are required to solve the problem.