  Distance measurements to molecular clouds are important, but are often made
separately for each cloud of interest, employing very different different data
and techniques. We present a large, homogeneous catalog of distances to
molecular clouds, most of which are of unprecedented accuracy. We determine
distances using optical photometry of stars along lines of sight toward these
clouds, obtained from PanSTARRS-1. We simultaneously infer the reddenings and
distances to these stars, tracking the full probability distribution function
using a technique presented in Green et al. (2014). We fit these star-by-star
measurements using a simple dust screen model to find the distance to each
cloud. We thus estimate the distances to almost all of the clouds in the
Magnani et al. (1985) catalog, as well as many other well-studied clouds,
including Orion, Perseus, Taurus, Cepheus, Polaris, California, and Monoceros
R2, avoiding only the inner Galaxy. Typical statistical uncertainties in the
distances are 5%, though the systematic uncertainty stemming from the quality
of our stellar models is about 10%. The resulting catalog is the largest
catalog of accurate, directly-measured distances to molecular clouds. Our
distance estimates are generally consistent with available distance estimates
from the literature, though in some cases the literature estimates are off by a
factor of more than two.

Astrophysics of Galaxies