Postbus 800, NL-9700AV Groningen, the Netherlands
Paper published in February 1999 by the Main Journal of
Astronomy and Astrophysics in vol. 351, pp. 323 - 329.
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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 x 1013 cm-2 for the CO column density is derived
for the C-X band near 1088 Å. The detected H2 absorption
features were used to determine a limit for the H2/CO ratio of
N(CO)/N(12CO) >= 2.0 x 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.
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