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For refcode 1990ApJ...364...77P:
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Copyright by American Astronomical Society. Reproduced by permission
1990ApJ...364...77P MOLECULAR AND ATOMIC HYDROGEN LINE EMISSION FROM STAR-FORMING GALAXIES P. J. PUXLEY Institute for Astronomy, Honolulu T. G. HAWARDEN Joint Astronomy Centre, Hilo AND C. M. MOUNTAIN Royal Observatory, Blackford Hill, Edinburgh Received 1989 November 27; accepted 1990 May 17 ABSTRACT Models of the generation of molecular and atomic hydrogen line emission from star-forming regions are discussed. These take into account the variations in the efficiency with which fluorescent H_2_ emission is produced as the ratio of the incident soft UV to the gas density changes (the lower this ratio, the higher the efficiency). The models deal with hot stars embedded within molecular clouds, large compact clusters of young stars generating intense UV fields, and emission from clouds bathed in a relatively diffuse UV field. The results from the models are compared with the ratio of the observed intensities of the H_2_ v = 1-0 S(1) and Br{gamma} lines from the nuclear regions for a sample of 29 galaxies whose optical spectra are dominated by H II regions. Unlike previous investigators, we find that the scatter in the ratio of the two lines is quite small, suggesting a common mechanism for the H_2_ excitation. The line ratios are found to be consistent with H_2_ emission from photodissociation zones and in most of the sample can be understood in terms of ensembles of hot stars intimately mixed with molecular clouds, and perhaps forming blisters at their surface, although a few galaxies require much higher ratios of the UV intensity to the gas density, conditions which imply the presence of large numbers of massive stars in compact clusters. Subject headings: galaxies: interstellar matter - interstellar: molecules - radiation mechanisms - stars: formation ############################################################################ 1991ApJ...372..733P ERRATUM In the paper "Molecular and Atomic Hydrogen Line Emission from Star- forming Galaxies" by P. J. Puxley, T. G. Hawarden, and C. M. Mountain (ApJ, 364, 77 [1990]), there is an error in a footnote to Table 1. Footnote d to that table should read "log_10_ UV intensity at the edge of the Stromgren sphere for an electron density of 100 cm^- 3^, relative to the background in the solar neighborhood" rather than "10^4^ cm^- 3^." The entries in the table were calculated using the correct value, and thus the remainder of the paper is unaffected by this change.
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