# IAUS379: Dynamical Masses of Local Group Galaxies

20-24 March 2023
Haus H, Telegrafenberg
Europe/Berlin timezone

## The Formation of Planes of Satellite Galaxies in the Local Group

22 Mar 2023, 12:48
2m
Haus H, Telegrafenberg

#### Haus H, Telegrafenberg

Potsdam, Germany
Poster SESSION 3 : Dwarf galaxies: dwarf spheroidal, ultra-faint dwarfs, dwarf irregulars

### Description

Numerous observations in recent years have shown that the satellite galaxies orbiting our local galaxies tend to align their orbits in one or two thin planes around the host galaxy. This has been observed in local galaxies, Andromeda and Centaurus A, and our own Milky Way. Numerical simulations in a cosmological context find these planes to be rare or short-lived leading to tension between observation and theory. This leads to considerable debate on whether observations are compatible with the standard, Lambda Cold Dark Matter, model of cosmology. We argue that on large scales, these simulations did not sufficiently resolve the nearby large-scale structure, cosmic filaments, which we believe to be responsible for the anisotropic infall of satellites forming planar alignments, and on smaller scales, they did not sufficiently resolve dwarf satellite galaxies. We use the high precision, hydrodynamic, cosmological zoom simulation, New Horizon, which has both the large volume, (16 Mpc)$^3$ and the small-scale resolution, ~ 35 pc, required to study the interplay between cosmic web dynamics and the formation, funneling, and eventually the anisotropic distribution of satellites around local galaxies. Our results indicate that these planes exist in New Horizon in ~ 30% of Milky Way-type systems. The identified planes are comparable to observation in both physical extent and kinematic coherence. We also find that the distribution of dwarf satellites within their host dark matter haloes is more anisotropic than previously understood.

Do you plan to attend the symposium in-person or virtually? in-person

### Co-authors

Dr Charlotte Welker (Johns Hopkins University) Dr Susan Kassin (Space Telescope Science Institute) Dr Yohan Dubois (Institut d'Astrophysique de Paris) Dr Christophe Pichon (Institut d'Astrophysique de Paris)