Star formation and dust obscuration in the tidally distorted galaxy NGC 2442

TL;DR

This study uses multi-wavelength observations to analyze star formation and dust obscuration in the tidally distorted galaxy NGC 2442, revealing higher star formation rates and complex structures like superbubbles and circumnuclear rings.

Contribution

It provides the first detailed multi-wavelength analysis of NGC 2442's star formation distribution and dust properties, highlighting the impact of tidal interactions on star formation activity.

Findings

Star formation rate estimated between 6-11 solar masses per year.

Identification of a large superbubble (~1.7 kpc) with ongoing star formation.

Discovery of an 8um circumnuclear PAH ring with associated Hα emission.

Abstract

Abridged: We present a detailed investigation of the morphological distribution and level of star formation and dust obscuration in the nearby tidally distorted galaxy NGC2442. Spitzer images in the IR at 3.6, 4.5, 5.8, 8.0um, and 24um and GALEX images at 1500\AA{} and 2300\AA{} allow us to resolve the galaxy on scales between 240-600pc. We supplement these with archival data in the B, J, H, and K bands. We use the 8um, 24um and FUV (1500\AA) emission to study the star formation rate (SFR). We find that globally, these tracers of star formation give a range of results of ~6-11\msun/yr, with the dust-corrected FUV giving the highest value of SFR. We can reconcile the UV and IR-based estimates by adopting a steeper UV extinction curve that lies in between the starburst (Calzetti) and SMC extinction curves. However, the regions of highest SFR intensity along the spiral arms are consistent with a starburst-like extinction. Overall, the level of star-formation we find is higher than previously published for this galaxy, by about a factor of two, which, contrary to previous conclusions, implies that the interaction that caused the distorted morphology of NGC2442 likely also triggered increased levels of star-formation activity. Outside of the spiral arms, we discover what appears to be a superbubble, ~1.7kpc across in the IRAC images. Significant H{\alpha}, UV and IR emission in the area also suggest vigorous ongoing star-formation. A known, recent supernova (SN1999ga) is located at the edge of this superbubble. Although speculative at this stage, this area suggests a large star-forming region with a morphology shaped by generations of supernovae. Lastly, we discover an 8um (PAH) circumnuclear ring with an ~0.8kpc radius. The H{\alpha} emission is largely concentrated inside that ring and shows a vague spiral structure in the rest of the galaxy.