Birth sites of young stellar associations and recent star formation in a flocculent corrugated disc. Issue 4 (15th October 2020)

• Record Type: Journal Article
• Authors: Quillen, Alice C; Pettitt, Alex R; Chakrabarti, Sukanya; Zhang, Yifan; Gagné, Jonathan; Minchev, Ivan
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 499:Issue 4(2020)
• Page Start: 5623
• Page End: 5640
• Publication Date: 2020-10-15
• Subjects: Galaxy: disc -- Galaxy: kinematics and dynamics -- solar neighbourhood -- open clusters and associations: general; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/staa3189
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: With backwards orbit integration, we estimate birth locations of young stellar associations and moving groups identified in the solar neighbourhood that are younger than 70 Myr. The birth locations of most of these stellar associations are at a smaller galactocentric radius than the Sun, implying that their stars moved radially outwards after birth. Exceptions to this rule are the Argus and Octans associations, which formed outside the Sun's galactocentric radius. Variations in birth heights of the stellar associations suggest that they were born in a filamentary and corrugated disc of molecular clouds, similar to that inferred from the current filamentary molecular cloud distribution and dust extinction maps. Multiple spiral arm features with different but near corotation pattern speeds and at different heights could account for the stellar association birth sites. We find that the young stellar associations are located in between peaks in the radial/tangential (UV) stellar velocity distribution for stars in the solar neighbourhood. This would be expected if they were born in a spiral arm, which perturbs stellar orbits that cross it. In contrast, stellar associations seem to be located near peaks in the vertical phase-space distribution, suggesting that the gas in which stellar associations are born moves vertically together with the low-velocity dispersion disc stars.