南方基地知识库

A clear link between a dwarf-dwarf merger event and enhanced star formation (SF) in the recent past was recently identified in the gas-dominated merger remnant VCC 848, offering by far the clearest view of a gas-rich late-stage dwarf-dwarf merger. We present a joint analysis of JVLA Hi emission line mapping, optical imaging, and numerical simulations of VCC 848 in order to examine the effect of the merger on the stellar and gaseous distributions. VCC 848 has less than 30% of its Hi gas concentrated within the central high-surface-brightness star-forming region, while the remaining Hi is entrained in outlying tidal features. Particularly, a well-defined tidal arm reachesN(Hi) comparable to the galaxy center but lacks SF. The molecular gas mass inferred from the current SF rate (SFR) dominates over the atomic gas mass in the central similar to 1.5 kpc. VCC 848 is consistent with being a main-sequence star-forming galaxy for itscurrentstellar mass and SFR. The Hii region luminosity distribution largely agrees with that of normal dwarf irregulars with similar luminosities, except that the brightest Hii region is extraordinarily luminous. OurN-body/hydrodynamical simulations imply that VCC 848 is a merger between a gas-dominated primary progenitor and a gas-bearing star-dominated secondary. The progenitors had their first passage on a near-radial noncoplanar orbit more than 1 Gyr ago. The merger did not build up a core as compact as typical compact dwarfs with a centralized starburst, which may be partly ascribed to the star-dominated nature of the secondary and, in a general sense, a negative stellar feedback following intense starbursts triggered at early stages of the merger.