The physics and chemistry of low-mass cores

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Low–mass molecular cloud cores are the birthplaces of solar–type stars. Therefore, a thorough understanding of star–formation requires detailed knowledge of their initial properties. Nearby, small and isolated clouds, like Bok globules, are ideal laboratories for studying the physical and chemical properties of such star–forming cores because they are free from the complicating effects present in more clustered star–forming regions and are relatively straight–forward to model. Despite this relative simplicity, we still lack robust measurements of two fundamental physical parameters of such cores: temperature and density. These two parameters regulate the chemical and dynamical evolution and the subsequent gravitational collapse and fragmentation. The data from our Herschel project “EPOS” allow us for the first time to directly measure the temperature and density structure in a sample of 14 isolated star–forming cores. In order to measure gas–grain coupling processes and the role of turbulence and magnetic support, we have already acquired a set of complementary molecular line maps of different CO isotopes and N2H+ and propose further observations of at least NH3, CS, HCO+. When combined, these observations present the unique opportunity to model, in an unprecedented way, the chemical and dynamical state of the densest and coldest star–forming units in the interstellar medium. Our aim is to derive a new — coherent — modeling approach in which the highly accurate physical structure derived from the dust continuum data serves as independent input for the state–of–the–art chemical models, which in turn allow us to constrain the chemical evolution of such star–forming cores.