Dust Continuum Imaging of the HH 24 Region in L1630

Abstract

We have mapped the 1300 and 350 km continuum emission in the region surrounding the Herbig-Haro objects HH 22ÈHH 26 in L1630, which is part of the Orion B molecular cloud complex, using the MPIR bolometer at the IRAM 30 m telescope and the SHARC bolometer camera at the Caltech Sub-millimeter Observatory (CSO). Our observations reveal the presence of a cluster of at least nine pro-tostellar condensations at various evolutionary stages in the region around HH 24ÈHH 26. In addition to two previously identiÐed class 0 protostars, two additional sources with a low 350/1300 km Ñux ratio are detected. Although the lack of far-infrared Ñuxes precludes a deÐnitive determination of their nature, their low 350/1300 km Ñux ratio along with the absence of embedded infrared and radio contin-uum sources suggests that they are likely to be in a very early evolutionary stage. In particular, one of these two sources appears quite compact in the 1300 km image and may be in the short-lived phase of isothermal collapse. In addition, we have detected three millimeter continuum sources in the vicinity of the HH 22ÈHH 23 objects, including a compact source at the origin of the HH 23 optical jet. The bolo-metric luminosity, submillimeter-to-bolometric luminosity ratio, temperature, and mass of this source are all consistent with those of a class 0 protostar. However, the compactness of the source suggests that the continuum emission may be dominated by an unresolved disk, as would be expected for a more evolved protostellar source. No evidence is found for the presence of a molecular outÑow associated with this source in our CO, 13CO, andHC data obtained with the CSO.