# Gaia EDR3 proper motions, energies, angular momenta of Milky Way dwarf galaxies: a recent infall to the Milky Way halo

**Authors:** Yang Y., Hammer F., Li H., Pawlowski M. S., Wang J. L., Babusiaux C., Mamon G. A., Bonifacio P., Jiao Y., Wang H.  
**arXiv:** [2306.17208](https://arxiv.org/abs/2306.17208)  
**Date:** 2023-06-29  
**Summary page:** https://www.summarizepaper.com/en/paper/2306.17208v1/

## Key points

- Gaia EDR3 provides highly accurate proper motions of Milky Way (MW) dwarf galaxies
- Total energy and angular momentum of MW dwarf galaxies exceed those of MW K-giant stars, Sagittarius stream stars, and globular clusters
- Suggests that many MW dwarf galaxies have recently fallen into the MW halo
- MW dwarf galaxies are located near their pericenters, indicating they do not behave like satellite systems from cosmological simulations
- Implications on estimating the mass of these dwarf galaxies will be discussed in the study
- Findings shed light on dynamics and formation history of MW dwarf galaxies
- Prompt further exploration into their origins and interactions within the larger galactic system

## Summary

Gaia EDR3 has provided us with highly accurate proper motions of Milky Way (MW) dwarf galaxies, allowing us to delve into their orbital properties. In our investigation, we have discovered that the total energy and angular momentum of MW dwarf galaxies far exceed those of MW K-giant stars, Sagittarius stream stars, and globular clusters. This finding strongly suggests that many MW dwarf galaxies have recently fallen into the MW halo. Furthermore, our research confirms that MW dwarf galaxies are located near their pericenters, indicating that they do not behave like satellite systems derived from Lambda-Cold-Dark-Matter cosmological simulations. These intriguing new results call for a reevaluation of the origin of MW dwarf galaxies. If they indeed arrived in the MW halo relatively recently, it is likely that they experienced gas removal due to ram pressure induced by the hot gas in the Milky Way and were influenced by tidal forces exerted by the MW. The implications of these processes on estimating the mass of these dwarf galaxies will be thoroughly discussed in our study. Our findings shed light on the complex dynamics and formation history of MW dwarf galaxies and prompt further exploration into their origins and interactions within the larger galactic system. Authors: Yang Y., Observatoire de Paris, Paris Sciences et Lettres, CNRS France; Hammer F., Observatoire de Paris, Paris Sciences et Lettres, CNRS France; Li H., School of Physical Sciences, University of Chinese Academy of Sciences, Beijing China; Pawlowski M. S., Leibniz-Institut fuer Astrophysik Potsdam Germany; Wang J. L., CAS Key Laboratory of Optical Astronomy National Astronomical Observatories Beijing 100101 China; Babusiaux C., Université de Grenoble-Alpes CNRS IPAG F-38000 Grenoble France; Mamon G. A., Institut d'Astrophysique de Paris CNRS France; Bonifacio P., Observatoire de Paris Paris Sciences et Lettres CNRS France; Jiao Y., Observatoire de Paris Paris Sciences et Lettres CNRS France; Wang H., Centro ...