Dm. Elmegreen et al., Hubble Space Telescope observations of dust and star-forming regions in the ocular galaxy IC 2163 and its spiral companion NGC 2207, ASTRONOM J, 121(1), 2001, pp. 182-197
Hubble Space Telescope observations in U, B, V, and I passbands of the inte
racting spiral galaxies IC 2163 and NGC 2207 are used to measure extinction
s in the cloud and intercloud regions and ages and luminosities of the star
-forming regions. The extinction in the part of NGC 2207 seen in projection
against IC 2163 was determined by using the method of White & Keel. The ex
tinctions there and elsewhere were also determined from radiative transfer
models of the magnitude differences between clouds and their surroundings.
The intercloud extinction in V band ranges from 0.5 to 1 mag on the line of
sight, and the cloud extinction ranges from 1 to 2 mag. The measured star-
forming regions in these galaxies have a power-law relation between size an
d luminosity and a power-law luminosity distribution function. These power
laws are consistent with a fractal dimension for the star formation that is
the same as that for interstellar gas, D similar to 2.2, extending over sc
ales ranging from 20 to 1000 pc. Fifteen compact massive star clusters that
are analogous to super-star clusters found in starburst regions are in the
spiral arms of NGC 2207. Nothing is peculiar about these regions except fo
r a high H I velocity dispersion (similar to 50 km s(-1)). Two more super-s
tar clusters are in the tidally compressed oval of IC 2163. These clusters
have masses ranging from similar to 10(4) to 2 x 10(5) M-. and ages of a fe
w times 10(6) yr.