Analogues of the Milky Way–Sagittarius interaction in the TNG50: Effect on the Milky Way
5 affiliations
- 1Departament de Física Quàntica i Astrofísica (FQA), Universitat de Barcelona (UB)
- 2Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona (UB)
- 3Institut d’Estudis Espacials de Catalunya (IEEC), Edifici RDIT, Campus UPC
- 4LIRA, Observatoire de Paris, Université PSL, Sorbonne Université, Université Paris Cité, CY Cergy Paris Université, CNRS
- 5Kavli IPMU (WPI), UTIAS, The University of Tokyo, Kashiwa
Abstract
Context. The Sagittarius dwarf galaxy is often invoked as a key driver of vertical perturbations in the Milky Way stellar disc and possible star formation enhancements in the solar neighbourhood, though most prior work assumes an initially near-equilibrium disc.
Aims. We analyse how satellite passages analogous to Sagittarius perturb Milky Way-like discs in cosmological simulations that place such interactions within a realistic environment, focusing on vertical stellar kinematics and star formation.
Methods. Using the TNG50 simulation, we identified 105 interactions approximately analogous to the Milky Way–Sagittarius one between z = 1 and 0 occurring to 52 MW/M31-like discs which interact with satellites more massive than 10 ¹⁰ M ⊙ on polar orbits with pericenters below 50 kpc and isolated in time from other similar interactions. We measured the response to the pericentric passages through the Fourier amplitudes of the m = 1 mode of the stellar vertical velocity, the stellar vertical velocity dispersions, and the specific star formation rates (sSFRs) before and after the interactions, and we compared the results against a non-interacting control sample.
Results. We find that the after-to-before ratios of the m = 1 vertical velocity Fourier amplitudes, velocity dispersions, and sSFR peak near or below unity, with approximately equal number of hosts exhibiting increases and decreases. Moreover, these ratios follow nearly identical distributions in both the interacting and control samples, suggesting that Sagittarius-like interactions do not systematically drive vertical perturbations or enhancements in the sSFR.
Conclusions. Cosmologically evolved discs are rarely in the near-equilibrium state assumed by idealized models. Within this realistic framework, Sagittarius-like passages produce no detectable population-wide effect on vertical kinematics or star formation. Our results weaken the case for Sagittarius being the sole driver of the Milky Way’s vertically perturbed state. They do not, however, exclude it: individual systems in our sample do respond strongly to their encounters, and the Milky Way may be such a case.
Related
- Kinematic analysis of the TNG50 Milky Way and Andromeda analogues
- Impact of Gaia-Sausage-Enceladus Debris on Milky Way Escape-velocity Estimates in TNG50
- Impact of Gaia–Sausage–Enceladus Debris on Milky Way Escape-velocity Estimates in TNG50
- Dust in cold and warm dark matter in a suite of zoom-in simulations of Milky Way analogues
- Environmental Dependence of Satellite Planarity and Orbital-Pole Coherence around Milky Way Analogues in a Hydrodynamical Cosmological Simulation
BibTeX
@article{semczuk2026analogues,
title = {{Analogues of the Milky Way–Sagittarius interaction in the TNG50: Effect on the Milky Way}},
author = {Marcin Semczuk and Teresa Antoja and Alexandra Girón-Soto and Chervin F. P. Laporte},
journal = {Astronomy \& Astrophysics},
year = {2026},
month = nov,
doi = {10.1051/0004-6361/202556714},
url = {https://www.aanda.org/10.1051/0004-6361/202556714},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Analogues of the Milky Way–Sagittarius interaction in the TNG50: Effect on the Milky Way
AU - Marcin Semczuk
AU - Teresa Antoja
AU - Alexandra Girón-Soto
AU - Chervin F. P. Laporte
PY - 2026
DA - 2026/11/05
JO - Astronomy & Astrophysics
DO - 10.1051/0004-6361/202556714
UR - https://www.aanda.org/10.1051/0004-6361/202556714
AB - Context. The Sagittarius dwarf galaxy is often invoked as a key driver of vertical perturbations in the Milky Way stellar disc and possible star formation enhancements in the solar neighbourhood, though most prior work assumes an initially near-equilibrium disc. Aims. We analyse how satellite passages analogous to Sagittarius perturb Milky Way-like discs in cosmological simulations that place such interactions within a realistic environment, focusing on vertical stellar kinematics and star formation. Methods. Using the TNG50 simulation, we identified 105 interactions approximately analogous to the Milky Way–Sagittarius one between z = 1 and 0 occurring to 52 MW/M31-like discs which interact with satellites more massive than 10 ¹⁰ M ⊙ on polar orbits with pericenters below 50 kpc and isolated in time from other similar interactions. We measured the response to the pericentric passages through the Fourier amplitudes of the m = 1 mode of the stellar vertical velocity, the stellar vertical velocity dispersions, and the specific star formation rates (sSFRs) before and after the interactions, and we compared the results against a non-interacting control sample. Results. We find that the after-to-before ratios of the m = 1 vertical velocity Fourier amplitudes, velocity dispersions, and sSFR peak near or below unity, with approximately equal number of hosts exhibiting increases and decreases. Moreover, these ratios follow nearly identical distributions in both the interacting and control samples, suggesting that Sagittarius-like interactions do not systematically drive vertical perturbations or enhancements in the sSFR. Conclusions. Cosmologically evolved discs are rarely in the near-equilibrium state assumed by idealized models. Within this realistic framework, Sagittarius-like passages produce no detectable population-wide effect on vertical kinematics or star formation. Our results weaken the case for Sagittarius being the sole driver of the Milky Way’s vertically perturbed state. They do not, however, exclude it: individual systems in our sample do respond strongly to their encounters, and the Milky Way may be such a case.
SN - 0004-6361
SN - 1432-0746
ER -