The Structure of Prestellar Cores as derived from ISO Observations

Observations of dark cloud cores have been carried out in the mid-infrared using ISOCAM and in the far-infrared using ISOPHOT, both aboard the Infrared Space Observatory. The cores are in most cases detected in emission at 200 and 170 micron, remain undetected at 90 micron and are seen in absorption against the diffuse mid-infrared background at 7 micron. The observations are consistent with the cores being pre-stellar and not having a central heating source, and yield core temperatures of ~ 11-13 K. We were able to determine the density structure of the cores up to radii that extend beyond the sensitivity limit of previous submillimetre studies. The column density profiles of the cores studied here flatten out in the centre, as shown by previous submillimetre continuum results, and interestingly, in a few cases, the profiles steepen with radius beyond ~ 5000-10000 AU and present sharp edges. This could indicate that these cores are decoupled from their parent molecular cloud and represent finite reservoirs of mass for subsequent accretion