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Published November 1, 2010 | Published
Journal Article Open

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

Abstract

We present a detailed investigation of the morphological distribution and level of star formation and dust obscuration in the nearby tidally distorted galaxy NGC 2442. Spitzer images in the IR at 3.6, 4.5, 5.8, 8.0, and 24μm and GALEX images at 1500 Å and 2300 Å allow us to resolve the galaxy on scales between ~240 and 600 pc. We supplement these with archival data in the B, J, H, and K bands. We use the 8μm, 24μm, and FUV (1500 Å) 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 M_⊙ yr^(−1), 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 Small Magellanic Cloud extinction curves. However, the regions of the 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 2, which, contrary to previous conclusions, implies that the interaction that caused the distorted morphology of NGC 2442 likely also triggered increased levels of star formation activity. We also find marked asymmetry in that the north spiral arm has a noticeably higher SFR than the southern arm. The tip of the southern spiral arm shows a likely tidally distorted peculiar morphology. It is UV bright and shows unusual IRAC colors, consistent with other published tidal features IRAC data. Outside of the spiral arms, we discover what appears to be a superbubble, ~1.7 kpc across, which is seen most clearly in the IRAC images. Significant Hα, UV, and IR emission in the area also suggest vigorous ongoing star formation. A known, recent supernova (SN 1999ga) 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 8μm (polycyclic aromatic hydrocarbon) circumnuclear ring with an ~0.8 kpc radius. The Hα emission is largely concentrated inside that ring and shows a vague spiral structure in the rest of the galaxy. The nuclear region shows the highest obscuration levels in the galaxy (A_(1600) ~ 3–4) most likely due to the circumnuclear dust ring.

Additional Information

© 2010 American Astronomical Society. Received 2010 April 27; accepted 2010 August 17; published 2010 October 12. We are grateful to the anonymous referee for their careful reading of our manuscript and thoughtful suggestions that have significantly improved the content and clarity of this paper. We thank Beth Willman and Brian Siana for helpful discussions. Support for this work was provided by NASA through an award issued by JPL/Caltech. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. This work uses observations made by Galaxy Evolution Explorer (GALEX), a NASA Small Explorer, launched in 2003 April and developed in cooperation with the Centre National d'Etudes Spatiales of France and the Korean Ministry of Science and Technology. This work makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This work has also made use of the NASA/IPAC Extragalactic Database (NED) which is operated by the Jet Propulsion Laboratory, California Institute of Technology, under contract with the National Aeronautics and Space Administration.

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August 19, 2023
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