2022ApJ...929..100K

We present Atacama Large Millimeter/submillimeter Array observations of multiple ¹²CO, ¹³CO, and C¹⁸O 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 Hα, 1.4 GHz continuum, and K-band data. We estimate the typical CO-to-H₂ conversion factor of 1.7 M_☉ (K km s^–1 pc²)^–1 within the disk using local thermal equilibrium-based and dust-based H₂ column densities, and measure the 1 kpc scale surface densities of the star formation rate (Σ_SFR), super star clusters (Σ_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 ∼ 10^–8.2 yr^–1, Σ_SFR ∼ 10^–0.6M_☉ kpc^–2 yr^–1, Σ_SSC ∼ 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.