Confirm the kinematic connection between young stars and molecular gas

Determine whether the young stars and molecular gas in the Sh 2-205 subregions share a close kinematic connection, using additional high-precision stellar radial-velocity measurements.

Background

The three-dimensional kinematic analysis of Sh 2-205 adopts molecular-gas radial velocities as proxies for the radial velocities of the individual subregions because only a small fraction of the young stars have precise radial-velocity measurements. Although the available stellar and gas velocities are broadly consistent across the entire region, the subregional comparisons are sensitive to the radial-velocity uncertainty threshold and yield apparent deviations in some subregions.

Consequently, the inferred three-dimensional motions and expansion pattern remain partly dependent on an approximation that has not been independently verified for each subregion. Additional precise stellar radial velocities are needed to establish whether the young stellar populations and molecular clouds are genuinely co-moving.

References

The current data only tentatively suggest that the stellar and gas RVs in the subregions lie within similar ranges. Given the uncertainties, this conclusion remains ambiguous.

— Star Formation in the H II Region Sh 2-205: 3D Morphology and Kinematics from Young Stars and Molecular Gas  (2608.16179 - Dong et al., 17 Aug 2026) in Section 2, subsection “3D Positions and Velocities of star-forming regions in S205”; see also Appendix, Section “Comparison Between Stellar and Molecular Gas Radial Velocities”