Cloud structure and star formation revealed by the Gould Belt and HOBYS surveys
With its unprecedented spatial resolution and high sensitivity in the far-infrared to submillimetre regime, Herschel is revolutionizing our understanding of star formation. The Gould Belt and HOBYS surveys are Herschel key programs (André et al. 2010; Motte, Zavagno, Bontemps et al. 2010; see http://www.herschel.fr/cea/star-formation/en/) that specifically target nearby burgeoning young stellar objects through multi-wavelength PACS (70, 100 & 160um) and SPIRE (250, 350, 500um) images. Gould Belt aims to obtain complete samples of nearby prestellar cores and Class 0 protostars with robust core mass functions and protostar luminosity functions in molecular clouds at 100-500 pc. HOBYS aims to discover and characterize the progenitors of high-mass stars within complexes at
I will review the first results from the Gould Belt and HOBYS programs. While most star-forming filaments in the Gould Belt clouds have a characteristic width close to the sonic scale (Menshchikov et al. 2010; Arzoumanian et al. 2011), HOBYS cloud complexes harbor a few well-ordered, dominating, and wider ridges which are forming massive stars (e.g. Hill et al. 2011; Nguyen-Luong et al.). Inside these filaments, prestellar cores are found with mass functions that confirm that the stellar IMF is shaped at prestellar stages by cloud fragmentation (Konyves et al. 2010). The associated low-mass protostellar clusters of Gould Belt clouds display protostellar evolutionary diagrams (M_env vs. L_bol) that need to be completed for high-mass protostars using HOBYS images (Bontemps et al. 2010; Hennemann et al. 2010). Moreover, the OB stars and clusters are strongly impacting the HOBYS molecular clouds via heating, pillars formation, and triggered star formation (Schneider et al. 2010; Zavagno et al. 2010; Minier et al.).