The Bolocam Galactic Plane Survey and Formaldehyde Densitometry Survey
Jeremy Darling, John Bally, Cara Battersby, Jason Glenn
The Bolocam Galactic Plane Survey (BGPS) is a 1.1 mm survey of the northern Galactic plane (−10°<l<90°, |b|<0.5°) performed with the Bolocam instrument at the Caltech Submillimeter Observatory with resolution ~33". We discuss the calibration of the survey and concerns relevant to comparison with Hi-Gal. We review some of the major results from the BGPS and discuss future possibilities. We report results of a follow-up survey of formaldehyde (H2CO) in Galactic UCHII regions and outer-galaxy dust clumps. The formaldehyde 1−1 and 2−2 K-doublet inversion transitions are sensitive to the gas density n(H2) and are seen in absorption against the CMB, providing an unbiased densitometer to probe gas density in dust clumps in different evolutionary states. We discuss the density measurements, their relationship to temperature measurements performed with the NH3 thermometer, and implications for the relative lifetime of different evolutionary states of molecular clumps.