We sort 4683 molecular clouds between 10°<ℓ<65°from the Bolocam Galactic Plane Survey based on observational diagnostics of star formation activity: compact 70 μm sources, mid-IR color-selected YSOs, H 2 O and CH 3 OH masers, and UCH IIregions. We also present a combined NH 3 -derived gas kinetic temperature and H 2 O maser catalog for 1788 clumps from our own GBT 100 m observations and from the literature. We identify a subsample of 2223 (47.5%) starless clump candidates (SCCs), the largest and most robust sample identified from a blind survey to date. Distributions of flux density, flux concentration, solid angle, kinetic temperature, column density, radius, and mass show strong (>1 dex) progressions when sorted by star formation indicator. The median SCC is marginally subvirial (α∼0.7) with >75% of clumps with known distance being gravitationally bound (α<2). These samples show a statistically significant increase in the median clump mass of ΔM∼170-370 M e from the starless candidates to clumps associated with protostars. This trend could be due to (i) mass growth of the clumps atM 200 440 -M e Myr −1 for an average freefall 0.8 Myr timescale, (ii) a systematic factor of two increase in dust opacity from starless to protostellar phases, and/or (iii)a variation in the ratio of starless to protostellar clump lifetime that scales as ∼M −0.4 . By comparing to the observed number of CH 3 OH maser containing clumps, we estimate the phaselifetime of massive (M>10 3 M e ) starless clumps to be 0.37±0.08 Myr (M/103 M e ) −1; the majority (M<450 M e ) have phaselifetimes longer than their average freefall time.

We present a re-reduction and expansion of the Bolocam Galactic Plane Survey, first presented by Aguirre et al. (2011a) and Rosolowsky et al. (2010a). The BGPS is a 1.1 mm survey of dust emission in the Northern galactic plane, covering longitudes −10 • < < 90 • and latitudes |b| < 0.5 • with a typical 1 − σ 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 a method for selecting z > 4 dusty, star forming galaxies (DSFGs) using Herschel/SPIRE 250/350/500 µm flux densities to search for red sources. We apply this method to 21 deg 2 of data from the HerMES survey to produce a catalog of 38 high-z candidates. Follow-up of the first 5 of these sources confirms that this method is efficient at selecting high-z DSFGs, with 4/5 at z = 4.3 to 6.3 (and the remaining source at z = 3.4), and that they are some of the most luminous dusty sources known. Comparison with previous DSFG samples, mostly selected at longer wavelengths (e.g., 850 µm) and in single-band surveys, shows that our method is much more efficient at selecting high-z DSFGs, in the sense that a much larger fraction are at z > 3. Correcting for the selection completeness and purity, we find that the number of bright (S 500µm ≥ 30 mJy), red Herschel sources is 3.3 ± 0.8 deg −2 . This is much higher than the number predicted by current models, suggesting that the DSFG population extends to higher redshifts than previously believed. If the shape of the luminosity function for high-z DSFGs is similar to that at z ∼ 2, rest-frame UV based studies may be missing a significant component of the star formation density at z = 4 to 6, even after correction for extinction.

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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 N 2 H + 3 − 2, for all 6194 sources in the Bolocam Galactic Plane Survey v1.0.1 catalog between 7.5 • ≤ l ≤ 194 • . 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 N 2 H + 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 -2kinetic temperature derived from previously published NH 3 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 N 2 H + than HCO + integrated intensity, but we find no correlations between the N 2 H + /HCO + ratio and 1.1 mm continuum flux density, gas kinetic temperature, or line width. Selfabsorbed profiles are rare (1.3%).