2006A&A...454L..71H

The feasibility of observing the C¹⁸O(3-2) spectral line in cold clouds with the APEX telescope has been tested. As the line at 329.330GHz lies in the wing of a strong atmospheric H₂O absorption it can be observed only at high altitude observatories. Using the three lowest rotational levels instead of only two helps to narrow down the physical properties of dark clouds and globules. The centres of two C¹⁸O maxima in the high latitude low mass star forming region CG 12 were mapped in C¹⁸O(3-2) and the data were analyzed together with spectral line data from the SEST. The T_MB(3-2)/T_MB(2-1) ratio in the northern C¹⁸O maximum, CG 12-N, is 0.8, and in the southern maximum, CG 12-S, ∼2. CG 12-N is modelled as a 120" diameter (0.4pc) cold core with a mass of 27M_☉. A small size maximum with a narrow, 0.8km/s, C¹⁸O(3-2) spectral line with a peak temperature of T_MB∼11K was detected in CG 12-S. This maximum is modelled as a 60"-80" diameter (∼0.2pc) hot (80K≲T_ex≲200K) ∼1.6M_☉ clump. The source lies on the axis of a highly collimated bipolar molecular outflow near its driving source. This is the first detection of such a compact, warm object in a low mass star forming region.