Molecular clouds in the galaxy

The J=1→0 emission of CO has been surveyed in the galactic plane between l=-10degree and +90degree with a 1' beam sampling every degree. Molecular clouds emitting in the CO line are plentiful over the inner region of the Galaxy. Their greatest number occurs in the galactic nucleus and at a radius of 5.5 kpc: a distribution similar to radio H ii regions and galactic γ-ray emission but very different from that previously derived for atomic hydrogen. The total mass in molecular clouds is found to be 1--3times109 M/sub sun/, and each typically has 105 M/sub sun/, an H2 density of 700 cm-3, and a temperature near 7 K. These results suggest that most of the interstellar medium in the interior of the Galaxy is molecular H2