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The relationship between the carbon monoxide intensity and the radio continuum emission in spiral galaxiesThe relationship between the velocity-integrated CO emission and the nonthermal radio continuum brightness in the disks of normal spiral galaxies is examined on a variety of length scales. On a global scale, the total CO intensity correlates strongly with the total radio continuum flux density for a sample of 31 galaxies. On scales of about 2 kpc or more in the disk of individual galaxies, it is found that the ratio I(CO)/T(20) remains fairly constant over the entire disk as well as from galaxy to galaxy. For the eight spirals in the sample, the disk-averaged values of I(CO)/T(20) range from 0.6-2.4, with the average over all eight galaxies being 1.3 +/- 0.6. It is concluded that what these various length scales actually trace are differences in the primary heating mechanism of the gas in the beam. The observed relationship between CO and nonthermal radio continuum emission can be explained by assuming that molecular gas in galactic disks is heated primarily by cosmic rays. The observed relationship is used to show that the brightness of synchrotron emission is proportional to n(cr) exp 0.4 - 0.9 in galactic disks.
Document ID
19920031985
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Adler, David S.
(Illinois Univ. Urbana, IL, United States)
Lo, K. Y.
(Illinois, University Urbana, United States)
Allen, Ronald J.
(Space Telescope Science Institute Baltimore, MD, United States)
Date Acquired
August 15, 2013
Publication Date
December 1, 1991
Publication Information
Publication: Astrophysical Journal, Part 1
Volume: 382
ISSN: 0004-637X
Subject Category
Astrophysics
Accession Number
92A14609
Funding Number(s)
CONTRACT_GRANT: NSF AST-87-15905
CONTRACT_GRANT: NAS5-26555
Distribution Limits
Public
Copyright
Other

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