A Quenched and Relatively Isolated Dwarf Galaxy in the Local Volume

TL;DR

This study presents detailed observations of the isolated, quenched dwarf galaxy CVn C, challenging the idea that environment alone causes galaxy quenching, and explores possible mechanisms behind its star formation cessation.

Contribution

It provides new HST data and analysis of CVn C, an isolated quenched dwarf galaxy, highlighting the role of past interactions and other mechanisms in galaxy quenching.

Findings

CVn C is a low-mass, isolated galaxy with no recent star formation.

No detectable gas in CVn C, indicating quenching.

Possible past interaction with a larger galaxy may have caused quenching.

Abstract

An increasing number of discoveries of isolated and quenched dwarf galaxies are challenging the idea that the present-day local environment of low-mass systems is the main determinant of their quenching. We present new Hubble Space Telescope (HST) data of one such system, the dwarf galaxy Canes Venatici C (CVn C). CVn C is a low-mass (3.4(+4.2-2.6)*10^6 M_sun) galaxy with a Tip of the Red Giant Branch distance of 8.43(+0.47-0.32) Mpc determined from the resolved stars in the HST imaging, which we also use to derive CVn C's structural parameters. CVn C's distance places CVn C in the Local Volume and in an isolated environment with the most tidally influential L* galaxy > 5Rvir away. Additional constraints from the HST color-magnitude diagram, archival Far-Ultraviolet (FUV), and neutral hydrogen (HI) data show that CVn C is quenched, with no evidence of star formation in the last 100 Myr and no detectable gas (MHI < 1.5*10^6 M_sun). Circumstantial evidence suggests that CVn C may have quenched via past interactions with the L* galaxy NGC 4631 (L_K = 10^10.4 L_sun), and was possibly sent on an extreme backsplash orbit by the tidal dissolution of a subhalo group. However, other quenching mechanisms-such as stripping via the cosmic web-cannot be ruled out. CVn C adds to the growing number of quenched dwarf galaxies in under-dense environments, a population that will be critical to defining the mass and environment regimes in which different quenching mechanisms operate.