A search for localized sources of noncosmological deuterium near the Galactic Centre

Abstract

The VLA at the 92 cm D I hyperfine transition was used to search for a possible localized concentration of atomic deuterium near the Galactic center over a velocity range of + or - 180 km/s. The search yielded an upper limit for the D column density N(D) = 7.78 x 10 to the 16th T(s)/sq cm where T(s) is the spin temperature of the D I hyperfine lines. For the smaller velocity range of + or - 30 km/s, a more sensitive upper limit of N(D) = 3.12 x 10 to the 16th T(s)/sq cm is obtained. If D is associated with the H I clouds to the Galactic center, an upper limit for the D/H ratio of 0.0043 is obtained for the clouds at V = 20 km/s and 50 km/s. If a significant fraction of the D exists in atomic form in molecular clouds, the upper limits are 1.2 x 10 to the -7th for the V = 20 km/s molecular cloud near the Galactic center and 8.3 x 10 to the -7th for the V = 50 km/s molecular cloud near the Galactic center. These results are consistent with the D observed in the Galactic center and the ISM being primarily cosmological in origin.