Molecular cloud distance determination from deep NIR survey extinction measurements

TL;DR

This paper introduces a method to determine molecular cloud distances using deep near-infrared survey extinction measurements, providing an independent approach that resolves near/far ambiguities and aligns well with existing kinematic methods.

Contribution

The study presents a novel technique for estimating molecular cloud distances from NIR extinction data, independent of kinematic methods, and successfully resolves the near/far ambiguity for multiple clouds.

Findings

Distances for 20 clouds were derived independently.

Results agree with existing kinematic measurements where ambiguity was resolved.

The method effectively resolves near/far distance ambiguities.

Abstract

Using near infrared UKIDSS Galactic Plane Survey data, we make extinction measurements to individual stars along the same line of sight as molecular clouds. Using an existing 3D extinction map of the inner Galaxy, that provides line of sight specific extinction-distance relationships, we convert the measured extinction of molecular clouds to a corresponding distance. These distances are derived independently from kinematic methods, typically used to derive distances to molecular clouds, and as such they have no near/far ambiguity. The near/far distance ambiguity has been resolved for 27 clouds and distances have been derived to 20 clouds. The results are found to be in good agreement with kinematic measurements to molecular clouds where the ambiguity has already been resolved, using HI self-absorption techniques.