Quantifying radial migration in the Milky Way: inefficient over short time-scales but essential to the very outer disc beyond ∼15 kpc. Issue 4 (22nd February 2022)

• Record Type: Journal Article
• Authors: Lian, Jianhui; Zasowski, Gail; Hasselquist, Sten; Holtzman, Jon A; Boardman, Nicholas; Cunha, Katia; Fernández-Trincado, José G; Frinchaboy, Peter M; Garcia-Hernandez, D A; Nitschelm, Christian; Lane, Richard R; Thomas, Daniel; Zhang, Kai
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 511:Issue 4(2022)
• Page Start: 5639
• Page End: 5655
• Publication Date: 2022-02-22
• Subjects: Galaxy: abundances -- Galaxy: evolution -- Galaxy: formation -- Galaxy: stellar content -- Galaxy: structure; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stac479
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Stellar radial migration plays an important role in reshaping a galaxy's structure and the radial distribution of stellar population properties. In this work, we revisit reported observational evidence for radial migration and quantify its strength using the age–[Fe/H] distribution of stars across the Milky Way with APOGEE data. We find a broken age–[Fe/H] relation in the Galactic disc at r > 6 kpc, with a more pronounced break at larger radii. To quantify the strength of radial migration, we assume stars born at each radius have a unique age and metallicity, and then decompose the metallicity distribution function (MDF) of mono-age young populations into different Gaussian components that originated from various birth radii at r birth < 13 kpc. We find that, at ages of 2 and 3 Gyr, roughly half the stars were formed within 1 kpc of their present radius, and very few stars (<5 per cent) were formed more than 4 kpc away from their present radius. These results suggest limited short-distance radial migration and inefficient long-distance migration in the Milky Way during the last 3 Gyr. In the very outer disc beyond 15 kpc, the observed age–[Fe/H] distribution is consistent with the prediction of pure radial migration from smaller radii, suggesting a migration origin of the very outer disc. We also estimate intrinsic metallicity gradients at ages of 2 and 3 Gyr of −0.061 and −0.063 dex kpc −1, respectively.