A recent star formation event far into the Milky Way halo: spectroscopic follow-up and implications for the Milky Way hot halo
Abstract
We report high-resolution spectroscopic measurements of 27 stars in the recently discovered young (~116 Myr) stellar association Price-Whelan 1 (PW 1), which was found in the vicinity of the Leading Arm (LA) of the Magellanic Stream. We find that the mean metallicity of PW 1 is [Fe/H] = -1.16 and the mean radial velocity is Vhel = 273.9 km/s with a dispersion of 10.7 km/s. PW 1 is spatially offset by only ~6 deg from the tip of the Leading Arm II (LA II) complex and offset in velocity by ~30 km/s. In addition, there is a strong correlation between the spatial pattern of the PW 1 stars and the LA II gas with an offset of ~10 deg. The similarity in metallicity, velocity, and spatial patterns indicates that PW 1 likely originated in LA II and is therefore the first detection of stars born in the gaseous Magellanic Stream system. We find that the spatial and kinematic separation between LA II and PW 1 can be explained by ram pressure from Milky Way gas. Using orbit integrations, we constrain the MW hot halo density to be 4.5E-3 atoms/cm3 at a radius of 17 kpc, significantly higher than typically assumed.
- Publication:
-
American Astronomical Society Meeting Abstracts #235
- Pub Date:
- January 2020
- Bibcode:
- 2020AAS...23541503N