Distances to molecular clouds in the second Galactic quadrant

Purple Mountain Observatory and Key Laboratory of Radio Astronomy, Chinese Academy of Sciences, 10 Yuanhua Road, Qixia District, Nanjing 210033, PR China
e-mail: jiyang@pmo.ac.cn; qzyan@pmo.ac.cn

Received: 27 October 2020
Accepted: 16 December 2020

Abstract

We present distances to 76 medium-sized molecular clouds and an extra large-scale molecular cloud in the second Galactic quadrant (104. °75 < l < 150. °25 and |b| < 5. °25), 73 of which are accurately measured for the first time. Molecular cloud samples are drawn from l-b-V space (− 95 < V_LSR < 25 km s⁻¹) with the density-based spatial clustering of applications with noise algorithm, and distances are measured with the background-eliminated extinction-parallax method using extinctions and Gaia DR2 parallaxes. The range of the measured distances to the 76 molecular clouds is from 211 to 2631 pc, and the extra large-scale molecular cloud appears to be a coherent structure at about 1 kpc, across about 40° (~700 pc) in the Galactic longitude.