Carbon monoxide in the inner galaxy

Emission from the J=1..-->..0 rotational transition of /sup 12/C/sup 16/O has been surveyed at b=0/sup 0/ in the region 10/sup 0/> or =l> or =352/sup 0/ with high angular (..delta..l=0/sup 0/.2, using a 65'' beamwidth) and velocity ..delta..v=2.6 km s/sup -1/) resolution. Because CO observations provide a means of tracing the large-scale distribution and kinematics of H/sub 2/ and because most of the gaseous mass in the interstellar medium is either H I or H/sub 2/, the comparison of CO and H I surveys can in principle provide a complete determination of the gas distribution. Although CO emission is more clumped in (l, v) -space than is the 21 cm radiation, a detailed comparison of the observations in the inner Galaxy reveals that there is no large-scale CO feature which is not also seen in H I. The longitude dependence of the CO centroid velocity suggests that the CO in the inner Galaxy rotates at velocities consistent with the observed 21 cm rotation curve. The integrated intensity and kinematics of the observed CO imply that the inner 2 kpc of the Galaxy contains, outside of 300 pc, only a few molecular clouds with N (CO) > or approx. =2 xmore » 10/sup 16/ cm/sup -2/, the sensitivity limit of the survey. The bulk of the CO within 3--4 kpc of the center is found in the nuclear region (R<300 pc, M (H/sub 2/) 9 or approx. =7 x 10/sup 8/ M/sub sun)/The parameters GAMMA, q, and Omega-bar governing the Breit-Wigner resonance are determined by fitting the observed line shapes of each of the two bands in the cesium and potassium intercalate spectra.« less