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

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