FUSE survey of H_2_ in the Galactic disk

DOI

We report results from a Far Ultraviolet Spectrographic Explorer (FUSE) survey of interstellar molecular hydrogen (H_2_) in the Galactic disk toward 139 O-type and early B-type stars at Galactic latitudes |b|<=10{deg}, with updated photometric and parallax distances. H_2_ absorption is measured using the far-UV Lyman and Werner bands, including strong R(0), R(1), and P(1) lines from rotational levels J=0 and J=1 and excited states up to J=5 (sometimes J=6 and 7). For each sight line, we report column densities N_H2_, N_HI_, N(J), and N_H_=N_HI_+2N_H2_ and the molecular fraction f_H2_=2N_H2_/N_H_. Our survey extends the 1977 Copernicus H_2_ survey up to N_H_~5x10^21^cm^-2^. The lowest rotational states have excitation temperatures and rms dispersions =88+/-20K and =77+/-18K, suggesting that J=0, 1, 2 are coupled to the gas kinetic temperature. Populations of higher-J states exhibit mean excitation temperatures =237+/-91K and =304+/-108K, produced primarily by UV radiative pumping. Correlations of f_H2_ with E(B-V) and N_H_ show a transition to f_H2_>=0.1 at N_H_>~10^21^cm^-2^ and E(B-V)>~0.2, interpreted with an analytic model of H_2_ formation-dissociation equilibrium and attenuation of the far-UV radiation field by self-shielding and dust opacity. Results of this disk survey are compared to previous FUSE studies of H_2_ in translucent clouds, at high Galactic latitudes, and in the Magellanic Clouds. Using updated distances to the target stars, we find average sight-line values =0.20 and =6.07x10^21^cm^-2^/mag.

Cone search capability for table J/ApJ/911/55/table1 (Stellar parameters and distances)

Identifier
DOI http://doi.org/10.26093/cds/vizier.19110055
Source https://dc.g-vo.org/rr/q/lp/custom/CDS.VizieR/J/ApJ/911/55
Related Identifier https://cdsarc.cds.unistra.fr/viz-bin/cat/J/ApJ/911/55
Related Identifier https://vizier.cds.unistra.fr/viz-bin/VizieR-2?-source=J/ApJ/911/55
Metadata Access http://dc.g-vo.org/rr/q/pmh/pubreg.xml?verb=GetRecord&metadataPrefix=oai_b2find&identifier=ivo://CDS.VizieR/J/ApJ/911/55
Provenance
Creator Shull J.M.; Danforth C.W.; Anderson K.L.
Publisher CDS
Publication Year 2022
Rights https://cds.unistra.fr/vizier-org/licences_vizier.html
OpenAccess true
Contact CDS support team <cds-question(at)unistra.fr>
Representation
Resource Type Dataset; AstroObjects
Discipline Astrophysics and Astronomy; Galactic and extragalactic Astronomy; Interdisciplinary Astronomy; Interstellar medium; Natural Sciences; Observational Astronomy; Physics; Stellar Astronomy