NGC 2207/IC 2163: A GRAZING ENCOUNTER WITH LARGE-SCALE SHOCKS
- Department of Physics, Ohio State University, 191 West Woodruff Ave, Columbus, OH 43210 (United States)
- Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802 (United States)
- IBM Research Division, T. J. Watson Research Center, P.O. Box 218, Yorktown Heights, NY 10598 (United States)
- Department of Physics and Astronomy, Vassar College, 124 Raymond Ave., Poughkeepsie, NY 12604 (United States)
- Department of Physics and Astronomy, Iowa State University, Ames, IA 50011 (United States)
- Centre for Astrophysics Research, University of Hertfordshire, College Lane, Hatfield AL10 9AB (United Kingdom)
Radio continuum, Spitzer infrared, optical, and XMM-Newton X-ray and ultraviolet observations (UVW1 and UVM2) are used to study large-scale shock fronts, young star complexes, and the galactic nuclei in the interacting galaxies NGC 2207/IC 2163. There are two types of large-scale shock fronts in this galaxy pair. The large-scale shock front along the rim of the ocular oval in IC 2163 has produced vigorous star formation in a dusty environment, bright in the Spitzer 8 {mu}m and 24 {mu}m images. In the outer part of the companion side of NGC 2207, a large-scale front attributed to halo scraping is particularly bright in the {lambda}6 cm and {lambda}20 cm radio continuum but not in any tracers of recent star formation (H{alpha}, 8 {mu}m, 24 {mu}m, or ultraviolet emission) or in X-rays. This radio-continuum front may be from compression of the halo magnetic field on the back side of NGC 2207, between the two galaxies. The X-ray emission sets an upper limit to the gas density in the halo. Values of the flux density ratio S{sub {nu}}(8 {mu}m)/S{sub {nu}}(6 cm) of prominent, kiloparsec-size, Spitzer/IRAC star-forming clumps in NGC 2207/IC 2163 are compared with those of giant radio H II regions in M81. For the bright clumps in NGC 2207, the mean value of this ratio is the same as for the M81 H II regions, whereas for the bright clumps on the rim of the IC 2163 ocular oval, the mean value is nearly a factor of two greater. Possible explanations for this are discussed. The galaxy pair has global values of the ratios of infrared-to-radio continuum flux density in the Spitzer 8 {mu}m, 24 {mu}m, and 70 {mu}m bands, and the IRAS FIR significantly below the medians/means for large samples of galaxies. Feature i, a mini-starburst on an outer arm of NGC 2207 on its anti-companion side, is the most luminous 8 {mu}m, 24 {mu}m, 70 {mu}m, radio continuum, and H{alpha} source in the galaxy pair. We find evidence that a radio supernova was present in the core of feature i in 2001. X-ray emission is detected from the nucleus of NGC 2207 and from nine discrete sources whose X-ray luminosities make them possible candidates for Ultraluminous X-ray sources. One of these corresponds with the Type Ib SN 1999ec, which is also bright in the ultraviolet, and another may be a radio supernova or a background quasar. The X-ray luminosity of the NGC 2207 nucleus is log L{sub 0.3-10.0keV} = 40.6 erg s{sup -1}, which, together with its X-ray spectrum, suggests that this is a highly absorbed, low-luminosity, active galactic nucleus.
- OSTI ID:
- 22089817
- Journal Information:
- Astronomical Journal (New York, N.Y. Online), Vol. 144, Issue 5; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1538-3881
- Country of Publication:
- United States
- Language:
- English
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