MaNGA 8313-1901: gas accretion observed in a blue compact dwarf galaxy?

TL;DR

This study presents observational evidence of gas accretion in a Blue Compact Dwarf galaxy, highlighting a low-metallicity, star-forming clump with detached gas kinematics, suggesting external gas inflow rather than internal processes.

Contribution

First direct observational evidence of ongoing gas accretion in a BCD galaxy, identified through distinct kinematic and metallicity features of an off-centered clump.

Findings

Detection of a low-metallicity, star-forming NE clump with detached gas kinematics.

Spectral analysis indicates recent star formation from accreted cold gas.

Potential shared origin of gas accretion for multiple clumps.

Abstract

Gas accretion is an important process in the evolution of galaxies, but it has limited direct observational evidences. In this paper, we report the detection of a possible ongoing gas accretion event in a Blue Compact Dwarf (BCD) galaxy, MaNGA 8313-1901, observed by the Mapping Nearby Galaxies and Apache Point Observatory (MaNGA) program. This galaxy has a distinct off-centered blue clump to the northeast (the NE clump) that shows low metallicity and enhanced star-formation. The kinematics of the gas in the NE clump also seems to be detached from the host BCD galaxy. Together with the metallicity drop of the NE clump, it suggests that the NE clump likely has an external origin, such as the gas accretion or galaxy interaction, rather than an internal origin, such as an \hii~complex in the disk. After removing the underlying host component, we find that the spectrum of the "pure" clump can match very well with a modeled spectrum containing a stellar population of the young stars ($\le 7$ Myr) only. This may imply that the galaxy is experiencing an accretion of cold gas, instead of a merger event involving galaxies with significant pre-existing old stars. We also find signs of another clump (the SW clump) at the south-west corner of the host galaxy, and the two clumps may share the same origin of gas accretion.