Cold and massive cores near ISOSS J18364-0221: Implications for the initial conditions of high-mass star formation

We report the discovery of two very cold and massive molecular cloud cores in the region ISOSS J18364 - 0221. The object has been identified by a systematic search for very early evolutionary stages of high-mass stars using the 170 mu m ISOPHOT Serendipity Survey (ISOSS). Submillimeter continuum and molecular line measurements reveal two compact cores within this region. The first core has a temperature of 16.5 K, shows signs of ongoing infall and outflows, has no near- or mid- infrared counterpart, and is massive enough (M similar to 75 M circle dot) to form at least one O star with an associated cluster. It is therefore considered a candidate for a genuine high- mass protostar and a high- mass analog to the Class 0 objects. The second core has an average gas and dust temperature of only similar to 12 K and a mass of M similar to 280 M circle dot. Its temperature and level of turbulence are below the values found for massive cores so far, and we suggest that this represents the initial conditions from which high- mass star formation occurs.