PEARLS: A Potentially Isolated Quiescent Dwarf Galaxy with a Tip of the Red Giant Branch Distance of 30 Mpc

Abstract

A wealth of observations have long suggested that the vast majority of isolated classical dwarf galaxies (M * = 107-109 M ⊙) are currently star forming. However, recent observations of the large abundance of “ultra-diffuse galaxies” beyond the reach of previous large spectroscopic surveys suggest that our understanding of the dwarf galaxy population may be incomplete. Here we report the serendipitous discovery of an isolated quiescent dwarf galaxy in the nearby Universe, which was imaged as part of the JWST PEARLS Guaranteed Time Observation program. Remarkably, individual red-giant branch stars are visible in this near-IR imaging, suggesting a distance of 30 ± 4 Mpc, and a wealth of archival photometry point to an sSFR of 2 × 10−11 yr−1 and star formation rate of 4 × 10−4 M ⊙ yr−1. Spectra obtained with the Lowell Discovery Telescope find a recessional velocity consistent with the Hubble Flow and >1500 km s−1 separated from the nearest massive galaxy in Sloan Digital Sky Survey suggesting that this galaxy was either quenched from internal mechanisms or had a very high-velocity (≳1000 km s−1) interaction with a nearby massive galaxy in the past. This analysis highlights the possibility that many nearby quiescent dwarf galaxies are waiting to be discovered and that JWST has the potential to resolve them. © 2024. The Author(s). Published by the American Astronomical Society.