Quantifying radial migration in the Milky Way: Inefficient over short time-scales but essential to the very outer disc beyond ∼15 kpc

Jianhui Lian, Gail Zasowski, Sten Hasselquist, Jon A. Holtzman, Nicholas Boardman, Katia Cunha, Jose G. Fernández-Trincado, Peter M. Frinchaboy, D. A. Garcia-Hernandez, Christian Nitschelm, Richard R. Lane, Daniel Thomas, Kai Zhang

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


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 rbirth < 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.

Original languageEnglish (US)
Pages (from-to)5639-5655
Number of pages17
JournalMonthly Notices of the Royal Astronomical Society
Issue number4
StatePublished - Apr 1 2022


  • Galaxy: abundances
  • Galaxy: evolution
  • Galaxy: formation
  • Galaxy: stellar content
  • Galaxy: structure

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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