A Large Scale Survey of the Subnmillimeter-wave Emission of Atomic Carbon at Northrn Chile

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The principal aim of this project is a large-scale survey observation of the neutral carbon atom with a new transportable 18 cm submillimeter-wave telescope operated at Pampa la Bola (alt. 4800m) in northern Chi I e. For this purpose, we have first developed a compact submillimeter-wave receiver by using a GN 2 stage refrigerator. The receiver noise temperature achieved was as low as 200 K. With this telescope, we conducted the test observations three times during the project period (March 2001, September 2001, and September 2002).In the first run, we had a serious trouble in the Az driving system of the telescope during transportation, and we only confirmed the performance of individual instruments at the Pampa la Bola site. In the second run, we successfully observed the continuum emission from the moon and the sun at 492 GHz, and also observed the ozone emission from the upper atmosphere. In the third run, we finally succeeded in detecting the submillimeter-wave line (492 GHz) of the neutral carbon atom toward the pOph molecular cloud with this telescope system. Furthermore, we observed several molecular clouds including NGC6334 and M17. Particularly awing emission with the velocity width of 40 km/s has been detected clearly in M17. Since this wing emission is spatially extended, it cannot be ascribed to the molecular outflow from protostars in this region. Rather this emission may represent a new type of interstellar clouds that has not been recognized yet.As described above, we have established the 18 cm telescope system, and have obtained new scientific results of astrophysical importance.