English

Possible environmental quenching in an interacting little red dot pair at $z\sim7$

Astrophysics of Galaxies 2025-07-21 v2

Abstract

We report the discovery of a z7z\sim7 group of galaxies that contains two little red dots (LRDs) just 3.3 kpc apart, along with three potential satellite galaxies, as part of the Canadian NIRISS Unbiased Cluster Survey (CANUCS). The spectral energy distributions (SEDs) of this LRD pair show evidence of a Balmer break, consistent with a recent (100\sim 100 Myr) quenching of star formation. In contrast, the satellites are compatible with a recent-onset (100\sim 100 Myr), ongoing burst of star formation. LRD1's SED is consistent with a dust-free active galactic nucleus (AGN) being the source of the UV excess in the galaxy. The optical continuum would be powered by the emission from an obscured post-starburst and the AGN at a subdominant level. LRD2's SED is more ambiguous, but it could also be indicative of a dust-free AGN. In this scenario, these LRDs would be massive (M1010MM_\star\sim10^{10}\,M_\odot) and dusty (A(V) >1>1 mag) and the three satellites would be lower-mass objects (M1089MM_\star\sim10^{8-9}\,M_\odot) subject to low dust attenuations. The proximity of the two LRDs suggests that their interaction is responsible for their recent star formation histories, which can be interpreted as environmental bursting and quenching in the epoch of reionization.

Keywords

Cite

@article{arxiv.2501.17925,
  title  = {Possible environmental quenching in an interacting little red dot pair at $z\sim7$},
  author = {Rosa M. Mérida and Gaia Gaspar and Marcin Sawicki and Yoshihisa Asada and Guillaume Desprez and Gregor Rihtaršič and Jacqueline Antwi-Danso and Roberta Tripodi and Chris J. Willott and Maruša Bradač and Gabriel B. Brammer and Kartheik G. Iyer and Nicholas S. Martis and Adam Muzzin and Gaël Noirot and Ghassan T. E. Sarrouh and Vladan Markov},
  journal= {arXiv preprint arXiv:2501.17925},
  year   = {2025}
}

Comments

20 pages, 13 figures, 7 tables, A&A