BLAST: THE MASS FUNCTION, LIFETIMES, AND PROPERTIES OF INTERMEDIATE MASS CORES FROM A 50 deg2SUBMILLIMETER GALACTIC SURVEY IN VELA (ℓ ≈ 265°)

Abstract

We present first results from an unbiased 50 deg2 submillimeter Galactic survey at 250, 350, and 500 μm from the 2006 flight of the Balloon-borne Large Aperture Submillimeter Telescope. The map has resolution ranging from 36'' to 60'' in the three submillimeter bands spanning the thermal emission peak of cold starless cores. We determine the temperature, luminosity, and mass of more than 1000 compact sources in a range of evolutionary stages and an unbiased statistical characterization of the population. From comparison with C18O data, we find the dust opacity per gas mass, κr= 0.16 cm2 g–1 at 250 μm, for cold clumps. We find that 2% of the mass of the molecular gas over this diverse region is in cores colder than 14 K, and that the mass function for these cold cores is consistent with a power law with index α = –3.22 ± 0.14 over the mass range 14 M < M < 80 M . Additionally, we infer a mass-dependent cold core lifetime of tc (M) = 4 × 106(M/20 M )–0.9 yr—longer than what has been found in previous surveys of either low or high-mass cores, and significantly longer than free fall or likely turbulent decay times. This implies some form of non-thermal support for cold cores during this early stage of star formation.