A CO Survey of the Most Extensive Translucent Molecular Cloud Complex, MBM 53-55

摘要

We present a new, sensitive CO J = 1 → 0 survey of the large translucent molecular cloud complex, MBM 53-55 using the CfA 1.2 m millimeter-wave telescope. A region extending from l = 84° to 97° and b = -44° to -30° was observed every 1/4°—roughly every other beamwidth—to an rms noise of 0.15 K per 0.65 km s?1 channel, for a total of 2968 spectra. Detected at velocities ranging from -15 to 0 km s?1, CO is concentrated in an arc-shaped structure over 10° long. Comparison with H I data suggests that this complex coincides with the edge of an expanding H I shell, as previously noted by Gir, Blitz, & Magnani (1994). This complex is also seen in IRAS 100 μm observations. We derive an integrated mass of 1.3 x 103 Msolar assuming a distance of 150 pc (Welty et al 1989). An atomic mass of 3.3 x 103 Msolar was similarly derived from the H I emission integrated over the velocity range -15 to 0 km s?1.