The Bolocam Galactic Plane Survey (BGPS) is a 1.1 mm continuum survey of dense clumps of dust throughout the Galaxy covering 170 square degrees. We present spectroscopic observations using the ...Heinrich Hertz Submillimeter Telescope of the dense gas tracers, HCO+ and N2H+ 3-2, for all 6194 sources in the Bolocam Galactic Plane Survey v1.0.1 catalog between 7.5 <= l <= 194 degrees. This is the largest targeted spectroscopic survey of dense molecular gas in the Milky Way to date. We find unique velocities for 3126 (50.5%) of the BGPS v1.0.1 sources observed. Strong N2H+ 3-2 emission (T_{mb} > 0.5 K) without HCO+ 3-2 emission does not occur in this catalog. We characterize the properties of the dense molecular gas emission toward the entire sample. HCO+ is very sub-thermally populated and the 3-2 transitions are optically thick toward most BGPS clumps. The median observed line width is 3.3 km/s consistent with supersonic turbulence within BGPS clumps. We find strong correlations between dense molecular gas integrated intensities and 1.1 mm peak flux and the gas kinetic temperature derived from previously published NH3 observations. These intensity correlations are driven by the sensitivity of the 3-2 transitions to excitation conditions rather than by variations in molecular column density or abundance. We identify a subset of 113 sources with stronger N2H+ than HCO+ integrated intensity, but we find no correlations between the N2H+ / HCO+ ratio and 1.1 mm continuum flux density, gas kinetic temperature, or line width. Self-absorbed profiles are rare (1.3%).
We present a re-reduction and expansion of the Bolocam Galactic Plane Survey, first presented by Aguirre et al. (2011) and Rosolowsky et al. (2010). The BGPS is a 1.1 mm survey of dust emission in ...the Northern galactic plane, covering longitudes -10 < \ell < 90 and latitudes |b| < 0.5 with a typical 1-\sigma RMS sensitivity of 30-100 mJy in a 33" beam. Version 2 of the survey includes an additional 20 square degrees of coverage in the 3rd and 4th quadrants and 2 square degrees in the 1st quadrant. The new data release has improved angular recovery, with complete recovery out to 80" and partial recovery to 300", and reduced negative bowls around bright sources resulting from the atmospheric subtraction process. We resolve the factor of 1.5 flux calibration offset between the v1.0 data release and other data sets and determine that there is no offset between v2.0 and other data sets. The v2.0 pointing accuracy is tested against other surveys and demonstrated to be accurate and an improvement over v1.0. We present simulations and tests of the pipeline and its properties, including measurements of the pipeline's angular transfer function. The Bolocat cataloging tool was used to extract a new catalog, which includes 8594 sources, with 591 in the expanded regions. We have demonstrated that the Bolocat 40" and 80" apertures are accurate even in the presence of strong extended background emission. The number of sources is lower than in v1.0, but the amount of flux and area included in identified sources is larger.
We present the results of observations of 1882 sources in the Bolocam Galactic Plane Survey (BGPS) at 1.1 mm with the 10m Heinrich Hertz Telescope simultaneously in HCO+ J=3-2 and N2H+ J=3-2. We ...detect 77% of these sources in HCO^+ and 51% in N2H+ at greater than 3\(\sigma\). We find a strong correlation between the integrated intensity of both dense gas tracers and the 1.1 mm dust emission of BGPS sources. We determine kinematic distances for 529 sources (440 in the first quadrant breaking the distance ambiguity and 89 in the second quadrant) We derive the size, mass, and average density for this subset of clumps. The median size of BGPS clumps is 0.75 pc with a median mass of 330 M\(_{\odot}\) (assuming T_{Dust}=20 K). The median HCO+ linewidth is 2.9 km s\(^{-1}\) indicating that BGPS clumps are dominated by supersonic turbulence or unresolved kinematic motions. We find no evidence for a size-linewidth relationship for BGPS clumps. We analyze the effects of the assumed dust temperature on the derived clump properties with a Monte Carlo simulation and we find that changing the temperature distribution will change the median source properties (mass, volume-averaged number density, surface density) by factors of a few. The observed differential mass distribution has a power-law slope that is intermediate between that observed for diffuse CO clouds and the stellar IMF. BGPS clumps represent a wide range of objects (from dense cores to more diffuse clumps) and are typically characterized by larger sizes and lower densities than previously published surveys of high-mass star-forming regions. This collection of objects is a less-biased sample of star-forming regions in the Milky Way that likely span a wide range of evolutionary states.
