Astronomy and Astrophysics – Astronomy
Scientific paper
Jul 1993
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1993apj...412..127r&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 412, no. 1, p. 127-145.
Astronomy and Astrophysics
Astronomy
13
Far Infrared Radiation, Point Sources, H Ii Regions, Infrared Astronomy Satellite, Molecular Clouds, Nebulae, Protostars
Scientific paper
Sources discovered by the Infrared Astronomical Satellite with spectra that rise steeply from 60 to 100 microns are a mixed sample of external galaxies, condensations in the interstellar medium, and potentially unknown astronomical objects. Sources in regions of low total H I column density (as determined with the all-sky 21-cm line surveys), and with no nearby cataloged external galaxy, were observed for presence of 20-cm continuum emission (with the NRAO VLA), enhanced 21-cm H I line emission (with the NAIC Arecibo 305 m), and molecular line emission (with the NRAO 12 m, HCRO 6 m, and FCRAO 14 m). Based on the CO detection rate, 70 percent of our sample are small interstellar molecular clouds. The remainder are mostly faint external galaxies. The dust column densities of the interstellar condensations were determined from the IR flux, using a spherical-cloud model for the radiative transfer of the interstellar radiation field (ISRF). The CO column densities were determined using the large-velocity-gradient model for the excitation and radiative transfer of the rotational transitions. About half of the interstellar sources have normal dust-to-gas ratios and ISRF heating. Sources with excess infrared emission, compared to the molecular column density, are protostellar candidates.
Heiles Carl
Koo Bon-Chul
Reach William T.
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