# Galactoseismology in cosmological simulations: Vertical perturbations by dark matter, satellite galaxies and gas

**Authors:** B. García-Conde, T. Antoja, S. Roca-Fàbrega, F. Gómez, P. Ramos, N. Garavito-Camargo, MA. Gómez-Flechoso  
**arXiv:** [2311.07137](https://arxiv.org/abs/2311.07137)  
**Date:** 2023-11-13  
**Summary page:** https://www.summarizepaper.com/en/paper/2311.07137v1/

## Key points

- Significant advancements in the study of disk galaxies, such as the Milky Way (MW)
- Complex models incorporating factors like dwarf satellite galaxies, dark matter halo structure, gas infalls, and stellar disk
- Utilization of high-resolution hydrodynamical cosmological simulation called GARROTXA
- Investigation of relationship between vertical disturbances in MW model's galactic disk and perturbations from sources like dark matter halo, satellite galaxies, and gas
- Calculation of bending modes in galactic disk over 6 billion years to understand contributions from dark matter and gas
- Complex bending patterns at different radii and times within the galactic disk
- Inner retrograde mode with high frequency and outer slower retrograde mode excited at different times
- Highest amplitudes of bending modes during early stages of thin disk formation reaching up to 8.5 km/s in later stages of evolution
- Infall of satellite galaxies causing tilt in the disk and anisotropic gas accretion leading to star formation events and supernovae
- Misalignment between disk and inner stellar/dark matter triaxial structure resulting in strong vertical acceleration on stars
- Multiple agents triggering bending of stellar disk including satellite galaxies, dark sub-halos, misaligned gaseous structures, and inner dark matter profiles
- Importance of holistic approach to studying disk dynamics and consideration of often overlooked factors in simplistic models
- Challenges when incorporating cosmological simulations into studies on disk dynamics but potential for more realistic results by analyzing coexisting perturbative processes

## Summary

In recent years, there have been significant advancements in the study of the dynamics of disk galaxies, such as the Milky Way (MW). Complex models that incorporate various factors, including dwarf satellite galaxies, dark matter halo structure, gas infalls, and stellar disk, have become available for studying these dynamics in a cosmological context. In this study, the researchers utilized a high-resolution hydrodynamical cosmological simulation called GARROTXA to investigate the relationship between vertical disturbances observed in the galactic disk of the MW model and multiple perturbations from sources such as the dark matter halo, satellite galaxies, and gas. The bending modes in the galactic disk were calculated over a period of 6 billion years to understand how dark matter and gas contribute to these disturbances. The researchers compared the vertical acceleration exerted by these components onto the disk with Fourier analysis of the bending behavior. The findings revealed complex bending patterns at different radii and times within the galactic disk. These included an inner retrograde mode with high frequency and an outer slower retrograde mode excited at different times. The amplitudes of these bending modes were highest during the early stages of thin disk formation and reached up to 8.5 km/s in later stages of disk evolution. The study also highlighted how various factors contribute to these bending modes. The infall of satellite galaxies was found to cause a tilt in the disk and create anisotropic gas accretion leading to star formation events and supernovae. Additionally, misalignment between the disk and inner stellar/dark matter triaxial structure formed during ancient galaxy assembly resulted in strong vertical acceleration on stars. Overall, it was concluded that multiple agents play a role in triggering bending of the stellar disk and phase spirals within this simulation. These agents include satellite galaxies, dark sub-halos, misaligned gaseous structures, and inner dark matter profiles which coexist and influence each other making it challenging to establish direct causality. The researchers emphasized the importance of a holistic approach to studying disk dynamics and highlighted the need to consider factors often overlooked in simplistic models. They also acknowledged challenges when incorporating cosmological simulations into studies on disk dynamics but noted that analyzing coexisting perturbative processes will lead to more realistic galactoseismology results. It is worth noting that while this model's number of satellites aligns with predictions for Milky Way's mass; lack of interaction with massive satellites equivalent to Large Magellanic Cloud (LMC) or Small Magellanic Cloud (SMC) makes direct comparison with present-day Milky Way challenging yet provides valuable insights into how past interactions can have long-lasting impacts on stellar disks morphology & kinematics.