The Bolocam Galactic Plane Survey. XII. Distance Catalog Expansion Using
  Kinematic Isolation of Dense Molecular Cloud Structures With 13CO(1-0)
  We present an expanded distance catalog for 1,710 molecular cloud structures
identified in the Bolocam Galactic Plane Survey (BGPS) version 2, representing
a nearly threefold increase over the previous BGPS distance catalog. We
additionally present a new method for incorporating extant data sets into our
Bayesian distance probability density function (DPDF) methodology. To augment
the dense-gas tracers (e.g., HCO+(3-2), NH3(1,1)) used to derive line-of-sight
velocities for kinematic distances, we utilize the Galactic Ring Survey
13CO(1-0) data to morphologically extract velocities for BGPS sources. The
outline of a BGPS source is used to select a region of the GRS 13CO data, along
with a reference region to subtract enveloping diffuse emission, to produce a
line profile of 13CO matched to the BGPS source. For objects with a HCO+(3-2)
velocity, \approx 95% of the new 13CO(1-0) velocities agree with that of the
dense gas. A new prior DPDF for kinematic distance ambiguity (KDA) resolution,
based on a validated formalism for associating molecular cloud structures with
known objects from the literature, is presented. We demonstrate this prior
using catalogs of masers with trigonometric parallaxes and HII regions with
robust KDA resolutions. The distance catalog presented here contains
well-constrained distance estimates for 20% of BGPS V2 sources, with typical
distance uncertainties \lesssim 0.5 kpc. Approximately 75% of the
well-constrained sources lie within 6 kpc of the Sun, concentrated in the
Scutum-Centarus arm. Galactocentric positions of objects additionally trace out
portions of the Sagittarius, Perseus, and Outer arms in the first and second
Galactic quadrants, and we also find evidence for significant regions of
interarm dense gas.
