Structure and kinematics of the Taurus star-forming region from Gaia-DR2 and VLBI astrometry

TL;DR

This study uses Gaia-DR2 and VLBI astrometry to analyze the 3D structure and kinematics of the Taurus star-forming region, revealing depth effects, substructure distances, and the dynamics of molecular clouds and stars.

Contribution

It provides a detailed 3D map of Taurus, showing depth variations and kinematic properties, utilizing hierarchical clustering and combining Gaia and VLBI data for the first time at this scale.

Findings

Molecular clouds are at different distances, confirming depth effects.

Closest and most remote substructures are B 215 and L 1558, respectively.

Stars and gas are tightly coupled with minimal velocity difference.

Abstract

Aims:We take advantage of the second data release of the Gaia space mission and the state-of-the-art astrometry delivered from very long baseline interferometry observations to revisit the structure and kinematics of the nearby Taurus star-forming region. Methods: We apply a hierarchical clustering algorithm for partitioning the stars in our sample into groups (i.e., clusters) that are associated with the various molecular clouds of the complex, and derive the distance and spatial velocity of individual stars and their corresponding molecular clouds. Results: We show that the molecular clouds are located at different distances and confirm the existence of important depth effects in this region reported in previous studies. For example, we find that the L 1495 molecular cloud is located at $d=129.9^{+0.4}_{-0.3}$ pc, while the filamentary structure connected to it (in the plane of the sky) is at $d=160.0^{+1.2}_{-1.2}$ pc. We report B 215 and L 1558 as the closest ($d=128.5^{+1.6}_{-1.6}$ pc) and most remote ($d=198.1^{+2.5}_{-2.5}$ pc) substructures of the complex, respectively. The median inter-cloud distance is 25 pc and the relative motion of the subgroups is on the order of a few km/s. We find no clear evidence for expansion (or contraction) of the Taurus complex, but signs of the potential effects of a global rotation. Finally, we compare the radial velocity of the stars with the velocity of the underlying $^{13}$CO molecular gas and report a mean difference of $0.04\pm0.12$ km/s (with r.m.s. of 0.63 km/s) confirming that the stars and the gas are tightly coupled.