ORFEUS II echelle spectra: On the H2/CO ratio in the LMC towards LH 10
Abstract
ORFEUS far UV echelle spectra have been used to investigate HI, H2 and CO absorption lines along the line of sight towards LH 10:3120 in the LMC, extending the study presented by de Boer et al. (1998). While H2 absorption is clearly visible, no CO absorption at LMC velocities is detected, but an upper limit of N(CO) < 3.3 1013 cm-2 for the CO column density is derived for the C-X band near 1088 A. The detected H2 absorption features were used to determine a limit for the H2/CO ratio of N(H2)/N(CO) > 2.0 105 for the LMC gas along this individual line of sight. Generally, the fraction of gas in molecular form in the LMC is low compared to interstellar gas in the Milky Way with the same total gas quantity. We compare the absorption spectroscopy with SEST CO emission line measurements. It is found that most of the CO emission comes from gas behind LH 10:3120. We discuss our results in view of the possible scenario, in which the low dust content limits the amount of molecular hydrogen in the diffuse LMC gas.
Turn this paper into a full lesson
ArcXiv compiles a staged curriculum from this paper: 8-12 lessons across beginner → advanced, synthesised section guides, visuals, flashcards, a quiz, exercises, and on-demand deep dives per section. Grounded in the abstract, never invented.