A Large Extension of the CfA Galactic CO Survey

Abstract

The Galactic CO survey of Dame, Hartmann, & Thaddeus (2001; hereafter DHT) is composed of both large-scale unbiased surveys, mainly concentrated within 10-deg of the Galactic plane, and targeted observations of clouds at higher latitudes. Analysis of all-sky IRAS and 21 cm maps suggests that the DHT survey is nearly complete for clouds larger than ~1 deg, even though roughly half of the total area at |b| < 30 deg was not observed. In October 2001 we began a new survey of all of this unobserved area that is accessible to the northern 1.2 meter telescope, approximately 6,600 deg^2 between l = 0 deg and 230 deg, mainly in the latitude range |b| = 10-30 deg. At least 12 hours per day is being dedicated to this large project, which is sampled every 1/4-deg (every other beamwidth) to an rms sensitivity of 0.19 K at a velocity resolution of 0.65 km/s. As of May 2003, we have obtained 90,000 of the 106,000 spectra required to complete the survey. While, as expected, the new observations do not substantially change the DHT map, ~68 relatively small and isolated molecular clouds at intermediate latitudes have so far been discovered. The survey has also been extended to b < -30 deg in two regions, one in the vicinity of the large MBM clouds 53-55 at l ~ 90 deg and the other south of the Taurus clouds at l ~170 deg. Substantial amounts of molecular gas were detected in both of these high-latitude regions.