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

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 −1 . The observation of 21 cm emission with the Giant Metrewave Radio Telescope provides strong evidence of interaction between the pair of dwarf galaxies in terms of neutral hydrogen (H i ) morphology and kinematics. In particular, the H i 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 H i 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.