Mathematics – Logic
Scientific paper
Aug 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008aipc.1035...33o&link_type=abstract
THE EVOLUTION OF GALAXIES THROUGH THE NEUTRAL HYDROGEN WINDOW. AIP Conference Proceedings, Volume 1035, pp. 33-39 (2008).
Mathematics
Logic
Origin And Formation Of The Universe, Galaxy Clusters, Interstellar Medium And Nebulae In External Galaxies, Origin, Formation, Evolution, Age, And Star Formation, Circumstellar Shells, Clouds, And Expanding Envelopes, Circumstellar Masers
Scientific paper
We revisit the composition of neutral hydrogen, i.e. atomic (HI) and molecular (H2), in the local Universe, with focus on the H2-to-HI mass ratio ɛgal in various galaxies and the H2-mass function (MF). First, we derive the H2-MF from the CO-luminosity function (LF) of the FCRAO Extragalactic CO Survey, using a variable CO-to-H2 conversion fitted to nearby observations. This implies a universal H2 density ΩH2 = (6.9+/-2.7).10-5 h-1 and ΩH2/ΩHI = 0.26+/-0.11, which could, however, suffer from incompleteness of the CO-sample. Therefore, a second approach derives the H2-MF from a HI-sample with well described completeness (HIPASS). This premisses an estimation of ɛgal, for which we introduce a set of phenomenological models based on a sample of 245 galaxies drawn from the literature. Our best model in terms of statistical scatter describes ɛgal as a function of galaxy type and cold gas mass. This model leads to an H2-MF that matches the one derived from the CO-LF, thus supporting that model and settling completeness uncertainties.
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