The dust temperature distribution in prestellar cores

We have computed the dust temperature distribution to be expected in a pre- protostellar core in the phase prior to the onset of gravitational instabil ity. We have done this under the approximation that the heating of the dust grains is solely due to the attenuated external radiation field and that t he core is optically thin to its own radiation. This permits us to consider non spherically symmetric geometries. We predict the intensity distributio ns of our model cores at millimeter and sub{millimeter wavelengths and comp are then with observations of the well studied object L1544. We have also d eveloped an analytical approximation for the temperature at the center of s pherically symmetric cores and we compare this with the numerical calculati ons. Our results show (in agreement with Evans et al. 2001) that the temper atures in the nuclei of cores of high visual extinction (>30 mag) are reduc ed to values of below similar to 8 K or roughly half of the surface tempera ture. This has the consequence that maps at wavelengths shortward of 1.3 mm see predominantly the low density exterior of pre{protostellar cores. It i s extremely difficult to deduce the true density distribution from such map s alone. We have computed the intensity distribution expected on the basis of the models of Ciolek & Basu (2000) and compared with the observations of L1544. The agreement is good with a preference for higher inclinations (37 degrees instead of 16 degrees) than that adopted by Ciolek & Basu (2000). We find that a simple extension of the analytic approximation allows a reas onably accurate calculation of the dust temperature as a function of radius in cores with density distributions approximating those expected for Bonno r-Ebert spheres and suggest that this may be a useful tool for future calcu lations of the gas temperature in such cores.