NANTEN observations of the Pipe Nebula; A filamentary massive dark cloud with very low star-formation activity

We present molecular line observations toward the "Pipe Nebula" in the J = 1-0 lines of (CO)-C-12, (CO)-C-13, and (CO)-O-18 by using "NANTEN" telescop e. An area of similar to 27 deg(2) was covered at a 4' grid spacing with a 2'7 beam in (CO)-C-12. The (CO)-C-12 velocity-integrated intensity map and channel maps show a filamentary distribution. The total mass of the (CO)-C- 12- and (CO)-C-13-emitting gas is estimated to be similar to 10000 M., and similar to 3000 M., respectively. We have identified 14 (CO)-O-18 cores who se mass is typically similar to 30 M.. Star formation is active only in the B 59 region. This activity is best demonstrated by a newly detected CO out flow toward the center of B 59. We suggest that the dynamical effects of ta u Sco may be responsible for triggering star formation only in the B 59 reg ion. The (CO)-O-18 column density toward B 59 is extremely high compared wi th the rest of the cloud. This confirms that high (CO)-O-18 column density is a necessary condition of star formation as previously suggested. Althoug h the star-formation efficiency is estimated to be quite low, less than or similar to 0.1%, except for B 59, the existence of the (CO)-O-18 cores sugg ests that there is molecular gas that is massive and dense enough to form s tars, and that star formation is likely tea occur in the near future.