| Description |
Herschel provides a unique opportunity to study the earliest stages of star formation.What is the origin of the stellar initial mass function (IMF)? This issue is central inlocal star formation research and for understanding whether the IMF is truly universal oris likely to depend on metallicity, pressure, or temperature. As prestellar cores andyoung (Class 0) protostars emit the bulk of their luminosity at virgul80-400 microns, theHerschel imaging instruments SPIRE and PACS are ideal for taking a census of such objectsdown to virgul0.01-0.1 Msun in the nearby (<0.5 kpc) molecular cloud complexes.We propose an extensive imaging survey of the densest portions of the Gould Belt withSPIRE at 250-500 and PACS at 110-170 microns down to a 5-sigma column sensitivityNH2virgul10^21 cm^-2 or Avvirgul1. Our goal is to make a complete, homogeneous mapping of the Av>3regions with SPIRE and of the Av>6 regions with PACS, and representative areas at Avvirgul1-3levels with both instruments. The survey sensitivity is well matched to the expectedcirrus confusion limit, so we should detect structures throughout the maps. The targetclouds span a range of physical conditions, from active, cluster-forming complexes toquiescent regions with lower star formation activity.We should detect hundreds Class 0 protostars and thousands prestellar condensations in theentire virgul145 deg^2 SPIRE survey, i.e. virgul10 times more cold objects than already identifiedfrom the ground. These numbers should allow us to derive an accurate prestellar core massfunction. The temperature and density structures of the nearest (< 0.2 kpc) cores will beresolved, revealing the initial conditions for individual protostellar collapse. The largespatial dynamic range of the proposed survey will probe the link between diffusecirrus-like structures and compact self-gravitating cores. Our main scientific goal is toelucidate the physical mechanisms for the formation of prestellar cores out of the diffusemedium, crucial for understanding the origin of stellar masses. |
