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M. J. Griffin (Cardiff University, UK), P. Andre (CEA, Saclay, France), P. Saraceno (IFSI, Rome, Italy), SPIRE and PACS Instrument Collaboration
Understanding star formation on both small and large scales is a major unsolved problem of modern astrophysics. In particular, we still lack a self-consistent theory for the fragmentation of molecular clouds into prestellar dense cores,the subsequent collapse of prestellar cores into protostars, and the origin of the stellar initial mass function (IMF). Since prestellar cores and young protostars emit the bulk of their luminosity between ~80 and ~350 \mum, Herschel will be uniquely suited to studying the early stages of star formation and make progress on these fundamental issues. With an angular resolution ~7"-25" at 80-350 \mum comparable to, or better than, the largest ground-based single-dish radiotelescopes at ~1 mm, the two Herschel imaging instruments PACS and SPIRE will make possible deep, unbiased surveys for pre-proto-stellar condensations in a large fraction of both active and quiescent regions of nearby (d < 0.5-1 kpc) molecular cloud complexes. These surveys, covering on the order of ~ 150 sq. deg. with SPIRE at 250-500 \mum and ~ 15 sq. deg. with PACS at 90-170 \mum to the cirrus confusion limit, will provide, for the first time, the mass and luminosity functions for complete samples of thousands of cold condensations down to the proto-brown dwarf regime. On small scales, the temperature and density structure of the nearest condensations (distance within 0.2 kpc) will be resolved, setting detailed constraints on the initial conditions for individual protostellar collapse. On a more global level, the large spatial dynamic range of the planned Herschel surveys will provide a unique view of the formation of dense cores and protoclusters within cloud complexes, by probing the link between diffuse cirrus-like structures and compact self-gravitating condensations. Key information on the evolution of dust properties from the diffuse ISM to dense cloud cores will also be obtained.
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Bulletin of the American Astronomical Society, 36 #2
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