2003/05/01 by P. Richter, K. R. Sembach, J. C. Howk · 4 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics and Star Formation Studies #Scientific Research and Discoveries #astro-ph
paper · pdf · doi:10.1051/0004-6361:20030722
published as Astron.Astrophys.405:1013-1024,2003 · 12 pages, 6 figures; accepted for publication in A&A
arxiv created 2003/05/01 · openalex publication_date 2003/06/30 · arxiv updated 2011/05/23 · openalex created_date 2019/06/27 · openalex updated_date 2026/07/31
We investigate interstellar absorption from molecular hydrogen (H2) and metals in an intermediate-velocity cloud (IVC) in the direction of the LMC star Sk -68 80 (HD 36521), based on data from the Far Ultraviolet Spectroscopic Explorer (FUSE) satellite. H2 absorption from the Lyman and Werner bands is detected in 30 lines at radial velocities km s-1 in this IVC that is presumably located in the Milky Way halo. We obtain a total logarithmic H2 column density of log H along with a very low Doppler parameter of km s-1. The presence of molecular material in this cloud is suprising, given the fact that the O i column density (log O i) implies a very low neutral gas column density of cm-2 (assuming a solar oxygen abundance). If the H2 column density represents its abundance in a formation-dissociation equilibrium, the data imply that the molecular gas resides in a small, dense filament at a volume density of ∼800 cm-3 and a thickness of only 41 Astronomical Units (AU). The molecular filament possibly corresponds to the tiny-scale atomic structures (TSAS) in the diffuse interstellar medium observed in high-resolution optical data, H i 21 cm absorption, and in CO emission.