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[61.18] FUSE Survey of Interstellar Molecular Hydrogen toward 130 Galactic Disk Sightlines

J.M. Shull, K. Anderson (Univ. Colorado, CASA), J. Tumlinson (Univ. Chicago), FUSE Science Team

We present the results of a Far Ultraviolet Spectroscopic Explorer (FUSE) survey of interstellar molecular hydrogen in the Galactic disk. The survey includes 130 sightlines toward O- and B-type stars at Galactic latitudes b < 10 degrees. The targets stars range in distance from 0.5 to 5 kpc. We measure interstellar absorption in the H₂ Lyman and Werner bands between 912 and 1120 Å, down to a column density threshold log N(H₂) > 14.0. For each sightline, we report N(H₂), together with column densities N(J) for rotation levels J = 0-6. These results are supplemented with N(H I) from a combination of 21 cm and Lyman-beta measurements. We use these column densities to derive the molecular fraction [mean f(H₂) = 0.18], rotational temperature (mean T₀₁ = 88 K), and rotational excitation conditions (T_exc ranges from 600 K to 140 K for J = 2-6).

This work was supported by the FUSE Mission, with financial support from NASA Contract NAS5-32985 to Johns Hopkins University and a sub-contract to the University of Colorado at Boulder.

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Bulletin of the American Astronomical Society, 36 #2
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