Dust Temperature Profiles in Dense Cores Associated With Massive Star-Forming Regions

Abstract

Using the APEX-12m telescope, continuum maps at 350~$\mu$m of eight gas-dust clouds from the southern hemisphere are obtained. Clouds are associated with the regions of massive star and star cluster formation and have dense cores. Core sizes estimated at the half maximum level are $\sim 0.1-0.2$~pc, core masses and mean gas densities lie in the ranges: $\sim 20-1000~M_{\odot}$ and $\sim (0.3-7.3)\times 10^6$~cm$^{-3}$, respectively. Comparison of the 350~$\mu$m data with the data of observations at 1.2~mm has been performed. From the ratios of intensities at two wavelengths convolved to the same angular resolution, spatial distributions of dust temperatures averaged over the line of sight are calculated. Dust temperature maps for most objects correlate with spatial distributions of intensities at 350~$\mu$m. A decrease in dust temperature with a distance from the center is detected in the cores. Dust temperature profiles in most cases are close to linear ones. Using a simple spherically-symmetric cloud model it is shown that temperature profiles similar to the observed ones can be obtained in a model with internal source by varying density profile parameters and setting $\beta$, a power-law index of the dust emissivity dependence on frequency, constant. It is shown that the dust temperatures estimates strongly depend on the accepted value of $\beta$. It is considered how possible variations of $\beta$ in a cloud can affect the results obtained.