A LARGE-SCALE SPECTROSCOPIC SURVEY OF METHANOL AND OH LINE EMISSION FROM THE GALACTIC CENTER: OBSERVATIONS AND DATA

Class I methanol masers are collisionally pumped and are generally correlated with outflows in star-forming sites in the Galaxy. Using the Very Large Array in its A-array configuration, we present a spectral line survey to identify methanol J = 4(-1) -> 3(0)E emission at 36.169 GHz. Over 900 pointings were used to cover a region 66' x 13' along the inner Galactic plane. A shallow survey of OH at 1612, 1665, 1667, and 1720 MHz was also carried out over the area covered by our methanol survey. We provide a catalog of 2240 methanol masers with narrow line-widths of similar to 1 km s(-1), spatial resolutions of similar to 0 ''.14 x 0 ''.05,. and rms noises similar to 20 mJy beam(-1) per channel. Lower limits on the brightness temperature range from 27,000 to 10,000,000 K, showing that the emission is of non-thermal origin. We also provide a list of 23 OH (1612), 14 OH (1665), 5 OH (1667), and 5 OH (1720 MHz) masers. The origin of such a large number of methanol masers is not clear. Many methanol masers appear to be associated with infrared dark clouds, though it appears unlikely that the entire population of these masers traces the early phase of star formation in the Galactic center.