Distances to Dark Clouds: Comparing Extinction Distances to Maser Parallax Distances

TL;DR

This study evaluates near-infrared extinction methods for estimating dark cloud distances by comparing them with precise maser parallax measurements, finding extinction methods generally reliable and superior to kinematic distances.

Contribution

The paper validates two extinction distance estimation methods against maser parallax measurements, demonstrating their accuracy and potential for broader application.

Findings

Extinction distances agree with maser parallaxes 66-100% of the time.

Extinction methods outperform kinematic distances in accuracy.

Extinction methods avoid the kinematic distance ambiguity.

Abstract

We test two different methods of using near-infrared extinction to estimate distances to dark clouds in the first quadrant of the Galaxy using large near infrared (2MASS and UKIDSS) surveys. VLBI parallax measurements of masers around massive young stars provide the most direct and bias-free measurement of the distance to these dark clouds. We compare the extinction distance estimates to these maser parallax distances. We also compare these distances to kinematic distances, including recent re-calibrations of the Galactic rotation curve. The extinction distance methods agree with the maser parallax distances (within the errors) between 66% and 100% of the time (depending on method and input survey) and between 85% and 100% of the time outside of the crowded Galactic center. Although the sample size is small, extinction distance methods reproduce maser parallax distances better than kinematic distances; furthermore, extinction distance methods do not suffer from the kinematic distance ambiguity. This validation gives us confidence that these extinction methods may be extended to additional dark clouds where maser parallaxes are not available.