Rejuvenating Star Formation Activity in an Early-type Dwarf Galaxy, LEDA 1915372, with Accreted HI Gas

TL;DR

This study documents a rare case where an early-type dwarf galaxy is rejuvenated by accreting gas from a nearby star-forming dwarf galaxy, leading to renewed central star formation.

Contribution

It provides observational evidence of gas transfer and interaction between dwarf galaxies, revealing a new pathway for blue-cored dwarf galaxy formation.

Findings

Detection of a gas bridge connecting the galaxies.

Shared rotation of HI components in both galaxies.

Deviation of HI emission peak indicating tidal interaction.

Abstract

We report a rare astrophysical phenomenon, in which an early-type dwarf galaxy (dE), LEDA 1915372, is accreting gas from a nearby star-forming dwarf galaxy, MRK 0689, and is rejuvenating star-formation activity at the center. Both LEDA 1915372 and MRK 0689 have similar brightness of $M_{r}$ = $-$16.99 and $-$16.78 mag, respectively. They are located in a small group environment, separated by a sky-projected distance of 20.27 kpc (up to 70 kpc in three dimension), and have a relative line-of-sight radial velocity of 6 km/s. The observation of 21 cm emission with the Giant Metrewave Radio Telescope provides strong evidence of interaction between the pair dwarf galaxies in terms of neutral hydrogen (HI) morphology and kinematics. In particular, the HI map reveals that the two galaxies are clearly connected by a gas bridge, and the gas components of both LEDA 1915372 and MRK 0689 share a common direction of rotation. We also find that the HI emission peak deviates from LEDA 1915372 toward its optical blue plume, suggesting a tidal origin of ongoing central star formation. Our findings provide a new path to the formation of blue-cored dEs.