A cold globule with a Class 0/I embedded source

Abstract

Infrared observations of the dark cloud DC 303.8-14.2 and the embedded point source IRAS 13036-7644 have been made with the ISOPHOT instrument aboard ISO at 7.7 μm, 60 μm, 100 μm and 200 μm. We have compared the properties of dust in DC 303.8-14.2 and the Thumbprint Nebula (TPN), a morphologically similar globule but without star formation. The dust temperature at the center of DC 303.8-14.2 has a minimum of 14.6 ± 1 K, similar to that in the TPN. A comparison of far-infrared radial optical depth distributions between these clouds at angular scales of ~1.5'-3' shows no difference. The observations suggest that there is a bright rim of 7.7 μm emission that peaks just outside the optical bright rim of the cloud, indicating a halo of very small dust particles or PAHs around the cloud. The bolometric luminosity of the IRAS source is estimated to be about 1.0 L_⊙. The heating of the cloud by the IRAS source is negligible; the thermal structure of the cloud is dominated by external heating. We have studied the evolutionary status of the IRAS source and find it to be located between Class 0 and Class I, at a late accretion phase. The source was detected at 7.7 μm and we suggest that this emission is due to the 7.7 μm UIR band. We also give a compilation of small molecular clouds whose extended FIR emission has been mapped with ISO.