A Large Catalog of Accurate Distances to Local Molecular Clouds: The
  Gaia DR2 Edition
  We present a uniform catalog of accurate distances to local molecular clouds
informed by the Gaia DR2 data release. Our methodology builds on that of
Schlafly et al. (2014). First, we infer the distance and extinction to stars
along sightlines towards the clouds using optical and near-infrared photometry.
When available, we incorporate knowledge of the stellar distances obtained from
Gaia DR2 parallax measurements. We model these per-star distance-extinction
estimates as being caused by a dust screen with a 2-D morphology derived from
Planck at an unknown distance, which we then fit for using a nested sampling
algorithm. We provide updated distances to the Schlafly et al. (2014)
sightlines towards the Dame et al. (2001) and Magnani et al. (1985) clouds,
finding good agreement with the earlier work. For a subset of 27 clouds, we
construct interactive pixelated distance maps to further study detailed cloud
structure, and find several clouds which display clear distance gradients
and/or are comprised of multiple components. We use these maps to determine
robust average distances to these clouds. The characteristic combined
uncertainty on our distances is approximately 5-6%, though this can be higher
for clouds at farther distances, due to the limitations of our single-cloud
model.
