2001ApJS..136..137L

A survey is presented of the Galactic plane in the J=1-0 transition of ¹³CO. About 73,000 spectra were obtained with the 7 m telescope at Bell Laboratories over a 10 yr period. The coverage of the survey is (l, b)=(-5° to 117°, -1° to 1°), or 244 deg², with a grid spacing of 3' for |b|<0°.5 and a grid spacing of 6' for |b|>0°.5. The data presented here have been resampled onto a 3' grid. For 0.68 km.s^–1 channels, the rms noise level of the survey is 0.1 K on the T^*_R scale. The raw data have been transformed into FITS format, and all the reduction processes, such as correcting for emission in the reference positions, baseline removal, and interpolation, were conducted within IRAF using the FCRAO task package and additional programs. The reduced data are presented here in the form of longitude-velocity color maps at each latitude. These data allow identification and classification of molecular clouds with masses in excess of ∼10³ M_☉ throughout the first quadrant of the Galaxy. Spiral structure is manifested by the locations of the largest and brightest molecular clouds.