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Date and Time of the Query: 2019-08-20 T18:25:50 PDT
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For refcode 1988AJ.....96..877B:
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1988AJ.....96..877B OBSERVATIONS WITH THE PARKING LOT CAMERA. I. SURFACE PHOTOMETRY AND COLOR DISTRIBUTION OF THE MAGELLANIC CLOUDS GREGORY D. BOTHUN Department of Astronomy, The University of Michigan, Ann Arbor, Michigan 48109 IAN B. THOMPSON Mount Wilson and Las Campanas Observatories, 813 Santa Barbara Street, Pasadena, California 91101 Received 8 March 1988;revised 10 May 1988 ABSTRACT We have obtained B, V, and R CCD images of the SMC and LMC using an optical system that yields a field size of 6^deg^ x 10^deg^. These data allow for the study of the integrated-light and color distributions for both galaxies. From these distributions, we find that the SMC shows a coherent, connected pattern of current (or very recent) star formation and has overall properties like those of star-forming dwarf elliptical galaxies in the Virgo Cluster. In contrast, the LMC exhibits a largely random pattern of star formation, although some hierarchical clustering of different age (color) regions is evident and there is a suggestion in the data that star formation is migrating outwards from the bar region. Neither galaxy, however, shows much evidence for a globally large star-formation rate (e.g., a burst) at the present epoch since (1) they exhibit nominal (~B=21.5 mag arcsec^-2^) central surface brightnesses and (2) their overall colors are significantly redder than those typically measured for other Type I irregular galaxies (e.g., NGC 2366, NGC 4449). The distribution of light in the outermost regions of the SMC falls off exponentially, but there is a conspicuous excess of light in the inner regions due to current star formation. The blue-light distribution in the inner regions of the LMC is well fit by an exponential of scale length 1.5 kpc, which is quite large for a galaxy that does not exhibit obvious spiral structure. Furthermore, this luminosity profile shows a substantial deficit of light, relative to the exponential extrapolation, beginning at 1.65 scale lengths. If the mass distribution of the LMC was once exponential in form, then our data suggest that beyond the 1/2 mass radius, approximately 30% of this mass has been removed. If this mass were still intact, we predict a B = 25.0 mag arcsec^-2^ diameter of 11.2^deg^, similar to the diameter defined by the outermost clusters of the LMC. Finally, we find values for integrated colors and isophotal sizes of the clouds that agree to within 10% of those derived 30 yr earlier by de Vaucouleurs on the basis of photographic photometry.
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