Multiwavelength and Multi-CO View of the Minor Merger Driven Star Formation in the Nearby LIRG NGC 3110

Abstract

We present Atacama Large Millimeter/submillimeter Array observations of multiple (CO)-C-12, (CO)-C-13, and (CO)-O-18 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, 1.4 GHz continuum, and K-band data. We estimate the typical CO-to-H-2 conversion factor of 1.7 M (circle dot) (K km s(-1) pc(2))(-1) within the disk using local thermal equilibrium-based and dust-based H-2 column densities, and measure the 1 kpc scale surface densities of the star formation rate (sigma(SFR)), super star clusters (sigma(SSC)), molecular gas mass, and star formation efficiency (SFE) toward the entire gas disk. These parameters show a peak in the southern part of the southern spiral arm (SFE similar to 10(-8.2) yr(-1), sigma(SFR) similar to 10(-0.6) M (circle dot) kpc(-2) yr(-1), sigma(SSC) similar to 6.0 kpc(-2)), which is likely attributable to the ongoing 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 position of the southern peak. These 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 in which the mass ratio was high in NGC 3110, fragmentation along the main galaxy arms is an important driver of merger-induced star formation, and that massive gas inflow results in dusty nuclear starbursts.