Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 2009
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2009apjs..180..125r&link_type=abstract
The Astrophysical Journal Supplement, Volume 180, Issue 1, pp. 125-137 (2009).
Astronomy and Astrophysics
Astronomy
41
Ism: Abundances, Ism: Clouds, Ism: Lines And Bands, Ism: Molecules, Ultraviolet: Ism
Scientific paper
We report total abundances and related parameters for the full sample of the Far Ultraviolet Spectroscopic Explorer survey of molecular hydrogen in 38 translucent lines of sight. New results are presented for the "second half" of the survey involving 15 lines of sight to supplement data for the first 23 lines of sight already published. We assess the correlations between molecular hydrogen and various extinction parameters in the full sample, which covers a broader range of conditions than the initial sample. In particular, we are now able to confirm that many, but not all, lines of sight with shallow far-UV extinction curves and large values of the total-to-selective extinction ratio, RV = AV /E(B - V)—characteristic of larger than average dust grains—are associated with particularly low hydrogen molecular fractions (f_H_2). In the lines of sight with large RV , there is in fact a wide range in molecular fractions, despite the expectation that the larger grains should lead to less H2 formation. However, we see specific evidence that the molecular fractions in this sub-sample are inversely related to the estimated strength of the UV radiation field and thus the latter factor is more important in this regime. We have provided an update to previous values of the gas-to-dust ratio, N(Htot)/E(B - V), based on direct measurements of N(H2) and N(H I). Although our value is nearly identical to that found with Copernicus data, it extends the relationship by a factor of 2 in reddening. Finally, as the new lines of sight generally show low-to-moderate molecular fractions, we still find little evidence for single monolithic "translucent clouds" with f_H_2 ˜ 1.
Destree Joshua D.
Ferlet Roger
Friedman Scott David
Gry Cecile
Jenkins Edward B.
No associations
LandOfFree
Molecular Hydrogen in the Far Ultraviolet Spectroscopic Explorer Translucent Lines of Sight: The Full Sample does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Molecular Hydrogen in the Far Ultraviolet Spectroscopic Explorer Translucent Lines of Sight: The Full Sample, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Molecular Hydrogen in the Far Ultraviolet Spectroscopic Explorer Translucent Lines of Sight: The Full Sample will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1783322