Two Orders of Magnitude Variation in the Star Formation Efficiency across the Premerger Galaxy NGC 2276
Abstract
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}=0.55 {Gyr}, 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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- December 2018
- DOI:
- 10.3847/2041-8213/aaf810
- arXiv:
- arXiv:1812.05048
- Bibcode:
- 2018ApJ...869L..38T
- Keywords:
-
- galaxies: individual: NGC 2276;
- galaxies: ISM;
- galaxies: star formation;
- Astrophysics - Astrophysics of Galaxies
- E-Print:
- This paper has 6 pages, 4 figures, 1 table Comments: We deleted the 2nd affiliation of the co-author Christopher Faesi from the previous version of the published paper. Comments: We added to the paper an additional acknowledgment from the co-author Jerome Pety