Enhanced rates of stellar radial migration in gas-rich discs at high redshift
(2026) In Monthly Notices of the Royal Astronomical Society 549(4).- Abstract
Radial migration and dynamical heating redistribute stars within galactic discs and thereby modify the chemo-kinematic structure of their host galaxies. Usually, these secular processes are studied in N-body and hydrodynamical simulations of Milky Way analogues with stellar-dominated discs. In contrast, discs at high redshift are gas rich, which may qualitatively change how secular evolution proceeds. We use the Nexus framework to construct and evolve a suite of isolated galaxies with fixed halo and disc mass but varying initial disc gas fraction, from 0 to 100 per cent. We show that in gas-rich models, the root-mean-square change in stellar angular momentum is up to a factor of 2 larger than in gas-poor analogues and is accompanied by... (More)
Radial migration and dynamical heating redistribute stars within galactic discs and thereby modify the chemo-kinematic structure of their host galaxies. Usually, these secular processes are studied in N-body and hydrodynamical simulations of Milky Way analogues with stellar-dominated discs. In contrast, discs at high redshift are gas rich, which may qualitatively change how secular evolution proceeds. We use the Nexus framework to construct and evolve a suite of isolated galaxies with fixed halo and disc mass but varying initial disc gas fraction, from 0 to 100 per cent. We show that in gas-rich models, the root-mean-square change in stellar angular momentum is up to a factor of 2 larger than in gas-poor analogues and is accompanied by stronger radial and vertical heating, leading to enhanced radial mixing. We further dissect the role of gas in specific migration channels. For bar-driven migration, corotation-resonance dragging dominates in gas-poor discs, whereas in gas-rich discs stars more readily reach and accumulate at the outer Lindblad resonance, which acts as a barrier. The high radial mixing efficiency in gas-rich phases can flatten the stellar metallicity gradient relative to that of the initial gaseous disc within only a few orbital time-scales. Together, these results imply that radial mixing in early, gas-rich discs is substantially more vigorous than in late-time, gas-poor discs, naturally producing distinct evolutionary tracks for chemically bimodal discs such as that of the Milky Way.
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- author
- Zhang, Han Yuan ; Tepper-García, Thor ; Belokurov, Vasily ; Evans, N. Wyn ; Tsukui, Takafumi ; Davis, Hillary ; Bland-Hawthorn, Joss LU ; Sanders, Jason L. and Agertz, Oscar LU
- organization
- publishing date
- 2026-07
- type
- Contribution to journal
- publication status
- published
- subject
- keywords
- galaxies: evolution, galaxies: kinematics and dynamics, Galaxy: disc, Galaxy: evolution
- in
- Monthly Notices of the Royal Astronomical Society
- volume
- 549
- issue
- 4
- article number
- stag1082
- publisher
- Oxford University Press
- external identifiers
-
- scopus:105042411047
- ISSN
- 0035-8711
- DOI
- 10.1093/mnras/stag1082
- language
- English
- LU publication?
- yes
- id
- f29eaada-4a4b-43d6-8a89-da80226eee0b
- date added to LUP
- 2026-07-02 12:12:52
- date last changed
- 2026-07-02 12:13:44
@article{f29eaada-4a4b-43d6-8a89-da80226eee0b,
abstract = {{<p>Radial migration and dynamical heating redistribute stars within galactic discs and thereby modify the chemo-kinematic structure of their host galaxies. Usually, these secular processes are studied in N-body and hydrodynamical simulations of Milky Way analogues with stellar-dominated discs. In contrast, discs at high redshift are gas rich, which may qualitatively change how secular evolution proceeds. We use the Nexus framework to construct and evolve a suite of isolated galaxies with fixed halo and disc mass but varying initial disc gas fraction, from 0 to 100 per cent. We show that in gas-rich models, the root-mean-square change in stellar angular momentum is up to a factor of 2 larger than in gas-poor analogues and is accompanied by stronger radial and vertical heating, leading to enhanced radial mixing. We further dissect the role of gas in specific migration channels. For bar-driven migration, corotation-resonance dragging dominates in gas-poor discs, whereas in gas-rich discs stars more readily reach and accumulate at the outer Lindblad resonance, which acts as a barrier. The high radial mixing efficiency in gas-rich phases can flatten the stellar metallicity gradient relative to that of the initial gaseous disc within only a few orbital time-scales. Together, these results imply that radial mixing in early, gas-rich discs is substantially more vigorous than in late-time, gas-poor discs, naturally producing distinct evolutionary tracks for chemically bimodal discs such as that of the Milky Way.</p>}},
author = {{Zhang, Han Yuan and Tepper-García, Thor and Belokurov, Vasily and Evans, N. Wyn and Tsukui, Takafumi and Davis, Hillary and Bland-Hawthorn, Joss and Sanders, Jason L. and Agertz, Oscar}},
issn = {{0035-8711}},
keywords = {{galaxies: evolution; galaxies: kinematics and dynamics; Galaxy: disc; Galaxy: evolution}},
language = {{eng}},
number = {{4}},
publisher = {{Oxford University Press}},
series = {{Monthly Notices of the Royal Astronomical Society}},
title = {{Enhanced rates of stellar radial migration in gas-rich discs at high redshift}},
url = {{http://dx.doi.org/10.1093/mnras/stag1082}},
doi = {{10.1093/mnras/stag1082}},
volume = {{549}},
year = {{2026}},
}