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The 60 micron to 20 centimeter infrared-to-radio ratio within spiral galaxiesA detailed comparison is presented of the distribution of 60 micron IR and 20 cm radio continuum emission within 25 galaxies, mostly disk spirals. Local maxima in the thermal IR and nonthermal radio emission are found to be spatially coincident on scales of less than about 0.4 kpc in the nearest sample galaxies. The IR-red disk in normal spirals appears to be characterized by a shorter scale length than that of the radio continuum disk, suggesting that the IR-to-radio ratio should decrease as a function of radius. A model that successfully accounts for the observations is introduced which is based on the assumptions of steady-state star formation activity within the disk on kpc scales and a tight coupling between the origins of the dust-heating radiation and the radio-emitting cosmic-ray electrons. The underlying source is described as an exponential disk. The results also suggest that a random walk process cannot by itself describe the temporal evolution of cosmic rays.
Document ID
Document Type
Reprint (Version printed in journal)
External Source(s)
Bicay, M. D.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA, United States)
Helou, G.
(JPL; California Institute of Technology Pasadena, United States)
Date Acquired
August 14, 2013
Publication Date
October 10, 1990
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 362
ISSN: 0004-637X
Subject Category
Accession Number
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