A Widespread, Clumpy Starburst in the Isolated Ongoing Dwarf Galaxy
  Merger dm1647+21
  Interactions between pairs of isolated dwarf galaxies provide a critical
window into low-mass hierarchical, gas-dominated galaxy assembly and the
buildup of stellar mass in low-metallicity systems. We present the first
VLT/MUSE optical IFU observations of the interacting dwarf pair dm1647+21,
selected from the TiNy Titans survey. The H$\alpha$ emission is widespread and
corresponds to a total unobscured star formation rate (SFR) of 0.44 M$_{\odot}$
yr$^{-1}$, 2.7 times higher than the SFR inferred from SDSS data. The implied
specific SFR (sSFR) for the system is elevated by more than an order of
magnitude above non-interacting dwarfs in the same mass range. This increase is
dominated by the lower-mass galaxy, which has a sSFR enhancement of $>$ 50.
Examining the spatially-resolved maps of classic optical line diagnostics, we
find the ISM excitation can be fully explained by star formation. The velocity
field of the ionized gas is not consistent with simple rotation. Dynamical
simulations indicate that the irregular velocity field and the stellar
structure is consistent with the identification of this system as an ongoing
interaction between two dwarf galaxies. The widespread, clumpy enhancements in
star formation in this system point to important differences in the effect of
mergers on dwarf galaxies, compared to massive galaxies: rather than the
funneling of gas to the nucleus and giving rise to a nuclear starburst,
starbursts in low-mass galaxy mergers may be triggered by large-scale ISM
compression, and thus be more distributed.
