We present a new technique to determine distances to major star-forming regions across the Perseus Molecular Cloud , using a combination of stellar photometry , astrometric data , and ^ { 12 } CO spectral-line maps .
Incorporating the Gaia DR2 parallax measurements when available , we start by inferring the distance and reddening to stars from their Pan-STARRS1 and 2MASS photometry , based on a technique presented in and implemented in their 3D “ Bayestar ” dust map of three-quarters of the sky .
We then refine the Green et al .
technique by using the velocity slices of a CO spectral cube as dust templates and modeling the cumulative distribution of dust along the line of sight towards these stars as a linear combination of the emission in the slices .
Using a nested sampling algorithm , we fit these per-star distance-reddening measurements to find the distances to the CO velocity slices towards each star-forming region .
This results in distance estimates explicitly tied to the velocity structure of the molecular gas .
We determine distances to the B5 , IC348 , B1 , NGC1333 , L1448 , and L1451 star-forming regions and find that individual clouds are located between \approx 275 - 300 pc , with typical combined uncertainties of \approx 5 \% .
We find that the velocity gradient across Perseus corresponds to a distance gradient of about 25 pc , with the eastern portion of the cloud farther away than the western portion .
We determine an average distance to the complex of 294 \pm 17 pc , about 60 pc higher than the distance derived to the western portion of the cloud using parallax measurements of water masers associated with young stellar objects .
The method we present is not limited to the Perseus Complex , but may be applied anywhere on the sky with adequate CO data in the pursuit of more accurate 3D maps of molecular clouds in the solar neighborhood and beyond .