Towards a complete picture of the Sco-Cen outflow

Abstract

Previous studies have presented strong evidence that the Sun is crossing an outflow originating from the Scorpius-Centaurus OB association (Sco-Cen). Understanding this outflow’s origin and structure illuminates how massive star formation shapes the interstellar medium (ISM) and helps predict future Galactic conditions that will affect our Solar System. We analysed H I emission and optical ISM absorption lines towards 47 early-type stars around the Upper Sco region to refine the map of the Sco-Cen outflow. Combined with data for nearby stars, we find that the outflow has at least two components: a faster, low-density component traced by Ca II, and a slower, possibly lower-density component traced by Mg II and Fe II in the UV that is passing through the Earth. A constant flow model successfully describes both components with (l, b, |v|) = (335.4°, −6.8°, 14.0 km s−1) and (305.5°, +17.6°, 21.2 km s−1), respectively. The origin of the faster component is possibly related to the Sco-Cen 15 Myr population, which is consistent with the origin of the slower component within 2 σ. A simple model comparison indicates that a constant flow is favoured over a spherical flow geometry, implying an extended distribution of feedback sources within Sco-Cen. We also find that a poorly studied 25 pc long H I cloud at a distance of 107 pc belongs to the established Sco-Cen flow.