A Compendium of Distances to Molecular Clouds in the Star Formation Handbook

TL;DR

This paper presents a new Bayesian method combining stellar photometry and Gaia data to accurately measure distances to nearby molecular clouds, resulting in a comprehensive catalog that aligns well with maser parallax measurements.

Contribution

The authors developed and refined a Bayesian approach to determine molecular cloud distances, producing a large, homogeneous catalog with high accuracy for the first time.

Findings

Distances agree with maser parallaxes within 10%

Method achieves ~5% accuracy in distance measurements

Catalog covers clouds from 150 pc to 2.5 kpc

Abstract

Accurate distances to local molecular clouds are critical for understanding the star and planet formation process, yet distance measurements are often obtained inhomogeneously on a cloud-by-cloud basis. We have recently developed a method which combines stellar photometric data with Gaia DR2 parallax measurements in a Bayesian framework to infer the distances of nearby dust clouds to a typical accuracy of $\sim5\%$. After refining the technique to target lower latitudes and incorporating deep optical data from DECam in the southern Galactic plane, we have derived a catalog of distances to molecular clouds in Reipurth (2008, Star Formation Handbook, vols I and II) which contains a large fraction of the molecular material in the solar neighborhood. Comparison with distances derived from maser parallax measurements towards the same clouds shows our method produces consistent distances with $\lesssim10\%$ scatter for clouds across our entire distance spectrum (150 pc $-$ 2.5 kpc). We hope this catalog of homogeneous distances will serve as a baseline for future work.