A study of the merging dwarf galaxy VCC322

Galaxy interactions and mergers can enhance or reduce star formation, but a complete understanding of the involved processes is still lacking. The effect of dwarf galaxy mergers is even less clear than their massive counterpart. We present a study on a dwarf merger remnant in the Virgo cluster, VCC322, which might form a triple system with VCC334 and VCC319. We identify a prominent long and straight tail-like substructure that has a size comparable to its host galaxy VCC322. By comparing the color-color ($g-r$ vs. $r-H$) distribution with simple stellar population models, we infer that the metallicity and stellar age of this tail are $Z_\star \sim 0.02~Z_\odot$ and $t_\star \sim 10$~Gyr, respectively. In VCC319, we find a sign of isophotal twisting. This suggests that VCC319 may be subject to tidal interaction. An analysis of the SDSS optical spectra of VCC322 indicates mass- and light-weighted ages of about 10$^{9.8}$ yr and 10$^{7.5}$ yr, respectively, indicating an ongoing star formation activity. However, the star formation in VCC322 seems suppressed when compared to other star-forming dwarfs of comparable stellar masses. Our finding of shock excitation of optical emission lines indicates that interaction-induced shock may contribute to the heating of cold gas and suppression of star formation.
Comment: 12 pages, 7 figures. Accepted for publication in ApJ