NGC 2207/IC 2163: A Grazing Encounter with Large Scale Shocks
  Radio continuum, Spitzer infrared, optical and XMM-Newton X-ray and UVM2
observations 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 shock front
along the rim of the ocular oval in IC 2163 has produced vigorous star
formation in a dusty environment. In the outer part of the companion side of
NGC 2207, a large-scale front attributed to disk or halo scraping is
particularly bright in the radio continuum but not in any tracers of recent
star formation or in X-rays. This radio continuum front may be mainly in the
halo on the back side of NGC 2207 between the two galaxies. Values of the flux
density ratio S(8 um)/S(6 cm) of kpc-sized, Spitzer IRAC star-forming clumps in
NGC 2207/IC 2163 are compared with those of giant H II regions in M81. We find
evidence that in 2001 a radio supernova was present in the core of feature i, a
mini-starburst on an outer arm of NGC 2207. X-ray emission is detected from the
NGC 2207 nucleus and from nine discrete sources, one of which corresponds to SN
1999ec, and another may be a radio supernova or a background quasar. The X-ray
luminosity and X-ray spectrum of the NGC 2207 nucleus suggests it is a highly
absorbed, low luminosity AGN.
