1994A&A...288..591O

We present the first maps of the ¹²CO J=1->0, ¹³CO J=1->0 and CS J=2->1 molecular lines of three selected PMS candidates in the nearby Chamaeleon II dark cloud: IRAS F12452-7709, IRAS F12479-7634 and IRAS 12553-7651. Our aim is to see if high density molecular material is associated with these low luminosity objects. The first two are unclassified sources detected at 60 and 100µm only, whilst the third may be an embedded (proto)stellar object. The three molecular lines have been detected in all three fields, except for CS in IRAS F12452-7709, for which we have a 3σ upper limit of 0.2K. The ¹²CO line is optically thick. It gives the kinetic temperature of the large scale molecular cloud (9 K), but does not give information on substructures associated with the FIR sources. The ¹³CO spectra show always two line components in the three observed regions. By using the velocity information in IRAS 12553-7651 a clump around the IRAS source can be isolated from the large scale molecular cloud. In IRAS F12479-7634 the line components seem to come from two distinct molecular clouds, whose interface goes approximately through the IRAS source. In IRAS F12452-7709 ¹³CO shows quite a complex morphology. The CS J=2->1 line is always very weak (0.5 K at maximum, in IRAS 12553-7651). Its emission is extended and centred on the FIR source in IRAS 12553-7651, but offset in velocity with respect to the ¹³CO component. In IRAS F12479-7634 it peaks at a slightly offset position. Our observations suggest that IRAS 12553-7651 is indeed a young low luminosity stellar object, which has formed near the centre of a molecular condensation.