Ram-pressure Stripping of a Dwarf Galaxy by the Cosmic Web

Galaxies undergo many processes over the lifetime of the Universe, but one of the more striking events can be the “quenching”, or halting of star formation. Quenching can happen for a variety of reasons, but observations of low-mass (dwarf) galaxies suggest that most dwarf galaxies are forming stars unless they are close to a much larger galaxy (or galaxy group or cluster). In “Caught in the Cosmic Web: Evidence for Ram-Pressure Stripping of a Low-Mass Galaxy by the Cosmic Web” (Luber+) we present observations of the atomic gas in a dwarf galaxy that is seemingly isolated from a more massive system. The gas is asymmetrically distributed and appears to be in the process of being removed from the galaxy.

We explored whether this could be due to a collision/interaction with another galaxy but could not identify a sufficiently close companion. Instead, looking at the large-scale distribution of galaxies shows that the gas “tail” is pointing back towards the intersections of filaments of galaxies. These filaments may be filled with hot gas and, as the dwarf galaxy passed through a filament, the cold gas in the galaxy felt drag against the hot gas while the stars continued on, essentially unaffected. In the future, this quick removal of gas may result in the quenching of star formation in this dwarf.

We conclude that this could be an important process for at least some dwarf galaxies. The paper has been accepted for publication in the Astrophysical Journal Letters and a preprint is available at the link above.