Interplay between Young Stars and Molecular Clouds in the Ophiuchus Star-forming Complex

TL;DR

This study investigates the spatial and kinematic relationships between young stars and molecular clouds in the Ophiuchus region, revealing how star evolution stages relate to cloud proximity and the influence of external shock fronts.

Contribution

It provides new insights into the spatial distribution and kinematic properties of young stars at different evolutionary stages in relation to molecular clouds in Ophiuchus.

Findings

More evolved stars are farther from clouds.

Younger stars are closely associated with natal clouds.

Star distribution suggests influence of shock fronts from Sco-Cen OB association.

Abstract

We present spatial and kinematic correlation between the young stellar population and the cloud clumps in the Ophiuchus star-forming region. The stellar sample consists of known young objects at various evolutionary stages, taken from the literature, some of which are diagnosed with Gaia EDR3 parallax and proper-motion measurements. The molecular gas is traced by the 850 $\mu$m Submillimetre Common-User Bolometer Array-2 image, reaching $\sim$2.3 mJy beam$^{-1}$, the deepest so far for the region, stacked from the James Clerk Maxwell Telescope/Transient program aiming to detect submillimeter outburst events. Our analysis indicates that the more evolved sources, namely the class II and III young stars, are located further away from clouds than class I and flat-spectrum sources that have ample circumstellar matter and are closely associated with natal clouds. Particularly the class II and III population is found to exhibit a structured spatial distribution indicative of passage of shock fronts from the nearby Sco-Cen OB association thereby compressing clouds to trigger star formation, with the latest starbirth episode occurring now in the densest cloud filaments. The young stars at all evolutionary stages share similar kinematics. This suggests that the stellar patterns trace the relics of parental cloud filaments that now have been dispersed.