GASTRO Library. II. Exploring Chemical Bimodalities in Disk Galaxies with GSE-like Mergers and Massive Star-forming Clumps
Abstract
We use several smoothed particle hydrodynamics+ N -body models as part of the GASTRO library to study the role of high-density star-forming clumpy regions and a single merger on the formation of the α -rich and α -poor populations in the disk galaxies. These experiments are tailored to mimic what is expected to be the Gaia-Sausage/Enceladus (GSE) accretion event, which occurred circa 10 Gyr ago in the Milky Way (MW). We find that either an early clumpy phase or a retrograde merger significantly reduces the star formation rate (SFR) of the disk, giving rise to a chemical bimodality qualitatively similar to the MW’s. The decrease of the SFR as the cause of the chemical bimodality is consistent with previous idealized and cosmological simulations. On the other hand, a prograde radial merger does not significantly modify the SFR of the disk, resulting in no clear chemical bimodality. We further show that stars originating from the inner regions ( R form < 4 kpc) do not create the disk’s chemical bimodality, although they can enhance it. Finally, only the models with an early clumpy phase can produce a significant fraction of old, age >11 Gyr, α- poor stars with disk-like orbits, similar to what has been recently observed in the MW. Our results strengthen the case of clumpy disky galaxies observed at redshift z ≈ 1–2 as likely progenitors of our Galaxy.
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BibTeX
@article{amarante2026gastro,
title = {{GASTRO Library. II. Exploring Chemical Bimodalities in Disk Galaxies with GSE-like Mergers and Massive Star-forming Clumps}},
author = {João Amarante and Chervin Laporte and Victor Debattista and Leandro Beraldo E Silva and Guilherme Limberg and Hélio Perottoni and Zhao-Yu Li and Lais Borbolato and Karl Fiteni and Chengye Cao and Nathan Deg and Tigran Khachaturyants and Xiaojie Liao},
journal = {The Astrophysical Journal},
year = {2026},
month = jun,
doi = {10.3847/1538-4357/ae70fe},
eprint = {2512.01293},
archivePrefix = {arXiv},
url = {https://hal.science/hal-05855817v1},
note = {CC BY},
}
RIS
TY - JOUR
TI - GASTRO Library. II. Exploring Chemical Bimodalities in Disk Galaxies with GSE-like Mergers and Massive Star-forming Clumps
AU - João Amarante
AU - Chervin Laporte
AU - Victor Debattista
AU - Leandro Beraldo E Silva
AU - Guilherme Limberg
AU - Hélio Perottoni
AU - Zhao-Yu Li
AU - Lais Borbolato
AU - Karl Fiteni
AU - Chengye Cao
AU - Nathan Deg
AU - Tigran Khachaturyants
AU - Xiaojie Liao
PY - 2026
DA - 2026/06/17
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/ae70fe
UR - https://hal.science/hal-05855817v1
AB - We use several smoothed particle hydrodynamics+ N -body models as part of the GASTRO library to study the role of high-density star-forming clumpy regions and a single merger on the formation of the α -rich and α -poor populations in the disk galaxies. These experiments are tailored to mimic what is expected to be the Gaia-Sausage/Enceladus (GSE) accretion event, which occurred circa 10 Gyr ago in the Milky Way (MW). We find that either an early clumpy phase or a retrograde merger significantly reduces the star formation rate (SFR) of the disk, giving rise to a chemical bimodality qualitatively similar to the MW’s. The decrease of the SFR as the cause of the chemical bimodality is consistent with previous idealized and cosmological simulations. On the other hand, a prograde radial merger does not significantly modify the SFR of the disk, resulting in no clear chemical bimodality. We further show that stars originating from the inner regions ( R form < 4 kpc) do not create the disk’s chemical bimodality, although they can enhance it. Finally, only the models with an early clumpy phase can produce a significant fraction of old, age >11 Gyr, α- poor stars with disk-like orbits, similar to what has been recently observed in the MW. Our results strengthen the case of clumpy disky galaxies observed at redshift z ≈ 1–2 as likely progenitors of our Galaxy.
SN - 0004-637X
SN - 1538-4357
ER -