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Date and Time of the Query: 2019-06-19 T17:03:22 PDT
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For refcode 1989ApJ...338L..53B:
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Copyright by American Astronomical Society. Reproduced by permission
1989ApJ...338L..53B THE INFRARED-TO-RADIO RATIO WITHIN NGC 5236 (M83) AND NGC 6946 M. D. BICAY AND G. HELOU Infrared Processing and Analysis Center, California Institute of Technology AND J. J. CONDON National Radio Astronomy Observatory Received 1988 October 26; accepted 1988 December 21 ABSTRACT A detailed comparison of the distribution of 60 micron infrared and 20 cm radio continuum emission within NGC 5236 (M83) and NGC 6946 is presented. Local maxima in the thermal infrared and nonthermal radio maps are found to be spatially coincident on scales <= 0.3h^-1^ kpc. Superposed on this broad correlation, we observe in the disks of both galaxies a slow decrease of the 60 micron-to-20 cm ratio (Q_60_) with increasing radius. Values of Q_60_ within the central regions are enhanced by roughly a factor of 3 with respect to the outer disks, whereas the corresponding enhancement in radio surface brightness is at least a factor of 20. The 100 micron-to-20 cm ratio shows a similar but shallower gradient. To account for these observations, we propose that spiral galaxies are characterized by an infrared disk with a shorter scale length than that of the radio continuum disk, the latter being smeared as a result of cosmic-ray propagation. Subject headings: galaxies: structure - infrared: sources - radio sources: galaxies
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