The Balloon-borne Large Aperture Submillimeter Telescope (BLAST) 2005: A 4 deg2 Galactic Plane Survey in Vulpecula (l = 59°)

We present the first results from a new 250, 350, and 500 μm Galactic plane survey taken with the Balloon-borne Large-Aperture Submillimeter Telescope (BLAST) in 2005. This survey's primary goal is to identify and characterize high-mass protostellar objects (HMPOs). The region studied here covers 4 deg² near the open cluster NGC 6823 in the constellation Vulpecula (l = 59°). We find 60 compact sources (<60^'' diameter) detected simultaneously in all three bands. Their SEDs are constrained through BLAST, IRAS, Spitzer MIPS, and MSX photometry, with inferred dust temperatures spanning ~12-40 K assuming a dust emissivity index β = 1.5. The luminosity-to-mass ratio, a distance-independent quantity, spans ~0.2-130 L_⊙ M^-1_⊙. Distances are estimated from coincident ¹³CO(1→ 0) velocities combined with a variety of other velocity and morphological data in the literature. In total, 49 sources are associated with a molecular cloud complex encompassing NGC 6823 (distance ~2.3 kpc), 10 objects with the Perseus arm (~8.5 kpc), and one object is probably in the outer Galaxy (~14 kpc). Near NGC 6823, the inferred luminosities and masses of BLAST sources span ~40-10⁴ L_⊙ and ~15-700 M_⊙, respectively. The mass spectrum is compatible with molecular gas masses in other high-mass star-forming regions. Several luminous sources appear to be ultracompact H II regions powered by early B stars. However, many of the objects are cool, massive gravitationally bound clumps with no obvious internal radiation from a protostar, and hence excellent HMPO candidates.