Multi-wavelength and Multi-CO View of The Minor Merger Driven Star
  Formation in the Nearby LIRG NGC 3110
  We present Atacama Large Millimeter/submillimeter Array observations of
multiple CO(1-0), $^{13}$CO(1-0), and C$^{18}$O(1-0) lines and 2.9 mm and 1.3
mm continuum emission toward the nearby interacting luminous infrared galaxy
NGC 3110, supplemented with similar spatial resolution H$\alpha$, 1.4GHz
continuum, and $K$-band data. We estimate the typical CO-to-H$_2$ conversion
factor of 1.7 $M_{\odot}$ (K km s$^{-1}$ pc$^2$)$^{-1}$ within the disk using
LTE-based and dust-based H$_2$ column densities, and measure the 1-kpc scale
surface densities of star formation rate ($\Sigma_{\rm SFR}$), super star
clusters ($\Sigma_{\rm SSC}$), molecular gas mass, and star formation
efficiency (SFE) toward the entire gas disk. These parameters show a peak at
the southern part of the southern spiral arm (SFE $\sim$ 10$^{-8.2}$ yr$^{-1}$,
$\Sigma_{\rm SFR}$ $\sim$ 10$^{-0.6}$ $M_{\odot}$ kpc$^{-2}$ yr$^{-1}$,
$\Sigma_{\rm SSC}$ $\sim$ 6.0 kpc$^{-2}$), which is likely attributed to the
on-going tidal interaction with the companion galaxy MCG-01-26-013, as well as
toward the circumnuclear region. We also find that thermal free-free emission
contributes to a significant fraction of the millimeter continuum emission at
the southern peak position. Those measurements imply that the peak of the
southern arm is an active and young star-forming region, whereas the central
part of NGC 3110 is a site of long-continued star formation. We suggest that,
during the early stage of the galaxy-galaxy interaction with large mass ratio
that in NGC 3110, fragmentation along the main galaxy's arms is an important
driver of merger-induced star formation and massive gas inflow results in dusty
nuclear starbursts.
