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Abstract

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.