A cold globule with a Class 0/I embedded source

ISO observations of the dark cloud DC 303.8–14.2

¹ Observatory, Tähtitorninmäki, PO Box 14, 00014 University of Helsinki, Finland e-mail: kimmo.lehtinen@helsinki.fi
² Max-Planck-Institut für Astronomie, Königstuhl 17, 69117 Heidelberg, Germany

Received: 23 August 2004
Accepted: 25 February 2005

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  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 . 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.