Other
Scientific paper
Dec 1999
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1999aas...195.5311m&link_type=abstract
American Astronomical Society, 195th AAS Meeting, #53.11; Bulletin of the American Astronomical Society, Vol. 31, p.1455
Other
1
Scientific paper
We present measurements of FIR cooling lines from neutral and ionized ISM of 60 normal, star-forming galaxies, selected to span a range in morphology, FIR colors indicating dust temperatures, and FIR/Blue ratios (indicating star-formation activity, optical depth). From the trends seen in the data and comparison with theoretical models we draw the following main conclusions: (1) The ratio of [CII](158 μ m)/FIR declines with increasing dust temperature and star-forming activity in galaxies; spannning a factor of more than 50 in [CII]/FIR with [CII] deficient galaxies at its extreme end. (2) The ratio of [OI]/[CII] lines increases for galaxies with higher F60/F100. In galaxies with warmer dust, there is less cooling via the [CII] line, while [OI] at 63 μ m remains a major coolant. This trend is explained in PDR models by an increase in UV radiation field G0, which raises both the gas and dust temperature. (3) [NII] (122 μ m) from ionized regions, shows behavior similar to [CII], i.e. the ratio [NII]/FIR declines with F60/F100 and L(FIR)/L(B). This suggests that a fair fraction of [CII] comes from ionized gas. We derive theoretical scaling between [NII](122 μ m) and [CII] from ionized gas and use that scaling to estimate the [CII] flux from neutral regions [CII]c. (4) By comparing the observed ratios of [OI](63μ m) and [CII]c lines and the ratio of line to the total FIR continuum from dust with a grid of PDR models, we derive the UV radiation density G0 and gas densities n in the sample galaxies. G0 and n correlate with each other and G0 increases as n1.4. Since G0 can be used as a measure of current star-formation, this directly confirms Schmidt law of star-formation where the star-formation increases with gas density to some power.
Brauher James
Contursi Alessandra
Dale Daniel
Helou George
Hollenbach David
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