TiNy Titans: The Role of Dwarf-Dwarf Interactions in the Evolution of Low Mass Galaxies (1412.4796v1)

Abstract: We introduce TiNy Titans (TNT), the first systematic study of star formation and the subsequent processing of the interstellar medium in interacting dwarf galaxies. Here we present the first results from a multiwavelength observational program based on a sample of 104 dwarf galaxy pairs selected from a range of environments within the SDSS and caught in various stages of interaction. The TNT dwarf pairs span mass ratios of M1/M2 <10, projected separations <50 kpc, and pair member masses of 7< log(M_*/Msun) <9.7. The dwarf-dwarf merger sequence, as defined by TNT, demonstrates conclusively and for the first time that the star formation enhancement observed for massive galaxy pairs also extends to dwarfs. Star formation is enhanced in paired dwarfs in otherwise isolated environments by a factor of 2.3 (+/- 0.7) at pair separations < 50 kpc relative to unpaired analogs. Starbursts, with Ha EQW >100 A, occur in 20% of TNT dwarf pairs, regardless of environment, compared to only 6-8% of matched unpaired dwarfs. Starbursts can be triggered throughout the merger (out to large pair separations) and not just approaching coalescence. Despite their enhanced star formation, most TNT dwarf pairs have similar gas fractions relative to unpaired dwarfs. Thus, there may be significant reservoirs of diffuse, non-starforming gas surrounding the dwarf pairs or the gas consumption timescales may be long in the starburst phase. The only TNT dwarf pairs with low gas fractions (fgas <0.4) and the only dwarfs with Ha EQW <2 A are found near massive galaxy hosts. Thus, dwarf-dwarf interactions are significant drivers of dwarf galaxy evolution, but ultimately environment is responsible for the quenching of star formation. This work is a precursor to an ongoing high resolution HI and optical imaging program to constrain the spatial distribution of star formation and gas throughout the dwarf-dwarf merger sequence.