2018ApJ...869L..38T

We present the first spatially resolved (∼0.5 kpc) measurements of the molecular gas depletion time τ_depl across the disk of the interacting spiral galaxy NGC 2276, a system with an asymmetric morphology in various star formation rate (SFR) tracers. To estimate τ_depl, we use new NOEMA observations of the ¹²CO(1-0) emission tracing the bulk molecular gas reservoir in NGC 2276, and extinction-corrected Hα measurements obtained with the PMAS/PPaK integral field unit for robust estimates of the SFR. We find a systematic decrease in τ_depl of 1-1.5 dex across the disk of NGC 2276, with a further, abrupt drop in τ_depl of ∼1 dex along the galaxy's western edge. The global τ_depl in NGC 2776 is τ_depl=0.55Gyr, consistent with literature measurements for the nearby galaxy population. Such a large range in τ_depl on subkiloparsec scales has never previously been observed within an individual isolated or premerger system. When using a metallicity-dependent molecular gas conversion factor X_CO the variation decreases by 0.5 dex. We attribute the variation in τ_depl to the influence of galactic-scale tidal forces and ram pressure on NGC 2276's molecular interstellar medium. Our observations add to the growing body of numerical and observational evidence that galaxy-galaxy interactions significantly modify the molecular gas properties and star-forming activity within galactic disks throughout the interaction, and not just during the final merger phase.