The Gould's Belt Distances Survey (GOBELINS). V. Distances and Kinematics of the Perseus molecular cloud

TL;DR

This study combines VLBA and Gaia data to accurately determine the distances and kinematics of the Perseus molecular cloud, revealing a smaller line-of-sight extent and no significant internal motions.

Contribution

It provides precise distance measurements for IC 348 and Gaia-based distances for NGC 1333, improving understanding of the cloud's structure and stellar motions.

Findings

Distance to IC 348 is 321+/-10 pc, consistent with Gaia.

Distance to NGC 1333 is 293+/-22 pc from Gaia.

The cloud's line-of-sight extent is about 30 pc, smaller than previously thought.

Abstract

We derive the distance and structure of the Perseus molecular cloud by combining trigonometric parallaxes from Very Long Baseline Array (VLBA) observations, taken as part of the GOBELINS survey, and Gaia Data Release 2. Based on our VLBA astrometry, we obtain a distance of 321+/-10 pc for IC 348. This is fully consistent with the mean distance of 320+/-26 measured by Gaia. The VLBA observations toward NGC 1333 are insufficient to claim a successful distance measurement to this cluster. Gaia parallaxes, on the other hand, yield a mean distance of 293+/-22 pc. Hence, the distance along the line of sight between the eastern and western edges of the cloud is ~30 pc, which is significantly smaller than previously inferred. We use Gaia proper motions and published radial velocities to derive the spatial velocities of a selected sample of stars. The average velocity vectors with respect to the LSR are (u,v,w) = (-6.1+/-1.6, 6.8+/-1.1, -0.9+/-1.2) and (-6.4+/-1.0, 2.1+/-1.4, -2.4+/-1.0) km/s for IC 348 and NGC 1333, respectively. Finally, our analysis of the kinematics of the stars has shown that there is no clear evidence of expansion, contraction, or rotational motions within the clusters.