Improved Measurements of Molecular Cloud Distances Based on Global Search

TL;DR

This paper introduces an improved global search method, BEEP-II, for measuring molecular cloud distances using extinction and parallax data, enabling efficient large-scale mapping in complex dust environments.

Contribution

The paper presents an enhanced BEEP-II method that improves the efficiency and applicability of molecular cloud distance measurements across large samples and complex environments.

Findings

Measured 238 molecular cloud distances across three regions.

BEEP-II outperforms previous methods in efficiency and complexity handling.

Suitable for large-scale molecular cloud distance surveys.

Abstract

The principle of the background-eliminated extinction-parallax (BEEP) method is examining the extinction difference between on- and off-cloud regions to reveal the extinction jump caused by molecular clouds, thereby revealing the distance in complex dust environments. The BEEP method requires high-quality images of molecular clouds and high-precision stellar parallaxes and extinction data, which can be provided by the Milky Way Imaging Scroll Painting (MWISP) CO survey and the Gaia DR2 catalog, as well as supplementary AV extinction data. In this work, the BEEP method is further improved (BEEP-II) to measure molecular cloud distances in a global search manner. Applying the BEEP-II method to three regions mapped by the MWISP CO survey, we collectively measured 238 distances for 234 molecular clouds. Compared with previous BEEP results, the BEEP-II method measures distances efficiently, particularly for those molecular clouds with large angular size or in complicated environments, making it suitable for distance measurements of molecular clouds in large samples.