DUST AND HCO+ GAS IN THE STAR-FORMING CORE W3-SE

We report new results from recent Combined Array for Research in Millimeter-wave Astronomy (CARMA) observations of both continuum and HCO+(1–0) line emission at λ3.4 mm from W3-SE, a molecular core of intermediate mass, together with the observations of continuum emission at λ1.1 and λ0.85/λ0.45 mm with the Submillimeter Array (SMA) and the James Clerk Maxwell Telescope, respectively. A continuum emission core elongated from SE to NW, with a size of ∼10″, has been observed at the millimeter and submillimeter wavelengths. The dust core has been resolved into a double source with the SMA at λ1.1 mm. The angular separation between the two components is ∼4″. Together with the measurements from the Spitzer Space Telescope and the Midcourse Space Experiment at mid-IR wavelengths, we determined the spectral energy distribution (SED) of the continuum emission from W3-SE and fit it with a thermal dust emission model. Our best fitting of the SED suggests the presence of two dust components with different temperatures. The emission at millimeter/submillimeter wavelengths is dominated by a major component that is characterized by a temperature of Td = 41 ± 6 K with a mass of 65 ± 10 M☉. In addition, there is a weaker hot component (∼ 400 K) which accounts for emission in the mid-IR, suggesting that a small fraction of dust has been heated by newly formed stars. We also imaged the molecular core in the HCO+(1–0) line using CARMA at an angular resolution ∼6″. In the central region of ∼50″, the integrated HCO+(1–0) line emission shows a main component A that coincides with the dust core, as well as two substructures B and C which are located N and SE of the dust core, respectively. With the CARMA observations, we have verified the presence of a blue-dominated double peak profile toward this core. The line profile cannot be explained by infall alone. The broad velocity wings of the line profile suggest that other kinematics such as outflows within the central 6″ of the core likely dominate the resulting spectrum. The kinematics of the substructures of B and C suggest that the molecular gas outside the main component A appears to be dominated by the bipolar outflow originated from the dust core with a dynamical age of >3 × 104 yr. Our analysis, based on the observations at wavelengths from millimeter, submillimeter, to mid-IR, suggest that the molecular core W3-SE hosts a group of newly formed young stars and protostars.