COSMOS-dw1: A quenched, isolated low mass dwarf galaxy outside of the Local Group environment
Low mass dwarf galaxies are thought to quench primarily due to environmental mechanisms, such as galaxy-galaxy interactions, stripping, or harassment. As a result, it is very unusual to find a quiescent dwarf galaxy in the field. In this paper, we present the third such example (and the first outside of the Local Group), which is also the youngest and most isolated. We posit that star formation shut off only recently, and the clump of bright blue stars in the NE may represent the site of the stellar feedback event that has temporarily quenched COSMOS-dw1.
Because it was found serendipitously in an extremely well-studied part of the sky, we anticipate that the number density of these small, quiescent galaxies is much higher than previously thought. The similarities in the three galaxy-sample and the likelihood that star formation has shut off temporarily due to internal feedback also indicate that quenched, isolated galaxies with a stellar mass of approximately one million to 10 million solar masses generally have luminosity-weighted ages of ~1 Gyr.
This work also got some popular interest and was also picked up by astrobites (as well as AAS Nova) and the Yale Scientific Magazine.