LARGE AMOUNTS OF COLD MOLECULAR-HYDROGEN IN THE SMALL MAGELLANIC CLOUD

From galaxy counts behind the SMC, it has been found that its outer regions exhibit an extinction much larger than predicted from the column density of atomic hydrogen if the dust-to-gas ratio is similar to that in the central, actively star-forming regions. I propose that the excess extinction is associated with large amounts of molecular gas, very difficult to detect otherwise. Independent evidences for this molecular hydrogen are also presented. I suggest that molecular hydrogen might constitute a major part of, and perhaps all the dark matter detected dynamically in irregular galaxies.