Corvus A: A low-mass, isolated galaxy at 3.5 Mpc

TL;DR

Corvus A is a newly discovered, isolated, low-mass galaxy at 3.5 Mpc with complex stellar populations and recent star formation, providing insights into galaxy evolution in low-density environments.

Contribution

This paper reports the discovery and detailed characterization of Corvus A, a low-mass, gas-rich galaxy at 3.5 Mpc, identified through a novel semi-automated search method.

Findings

Corvus A is at 3.48 Mpc distance, making it highly isolated.

It has a stellar mass of about 10^6 solar masses and HI mass of about 10^6.6 solar masses.

Signs of rotation are observed, but detailed kinematics require higher resolution imaging.

Abstract

We report the discovery of Corvus A, a low-mass, gas-rich galaxy at a distance of approximately 3.5 Mpc, identified in DR10 of the Dark Energy Camera Legacy Imaging Survey during the initial phase of our ongoing SEmi-Automated Machine LEarning Search for Semi-resolved galaxies (SEAMLESS). Jansky Very Large Array observations of Corvus A detect HI line emission at a radial velocity of $523\pm2$ km/s. Magellan/Megacam imaging reveals an irregular and complex stellar population with both young and old stars. We detect UV emission in Neil Gehrels Swift observations, indicative of recent star formation. However, there are no signs of HII regions in H$\alpha$ imaging from Steward Observatory's Kuiper telescope. Based on the Megacam color magnitude diagram we measure the distance to Corvus A via the tip-of-the-red-giant-branch standard candle as $3.48\pm0.24$ Mpc. This makes Corvus A remarkably isolated, with no known galaxy within $\sim$1 Mpc. Based on this distance, we estimate the HI and stellar mass of Corvus A to be $\log M_\mathrm{HI}/\mathrm{M_\odot} = 6.59$ and $\log M_\ast/\mathrm{M_\odot} = 6.0$. Although there are some signs of rotation, the HI distribution of Corvus A appears to be close to face-on, analogous to that of Leo T, and we therefore do not attempt to infer a dynamical mass from its HI line width. Higher resolution synthesis imaging is required to confirm this morphology and to draw robust conclusions from its gas kinematics.