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Pré-Publication, Document De Travail Année : 2023

Micro galaxies as a falsifiable prediction of LCDM cosmology

Raphaël Errani
  • Fonction : Auteur
Julio F Navarro
  • Fonction : Auteur
Jorge Peñarrubia
  • Fonction : Auteur
Matthew G Walker
  • Fonction : Auteur

Résumé

A fundamental prediction of the Lambda Cold Dark Matter (LCDM) cosmology are the centrally-divergent cuspy density profiles of dark matter haloes. These density cusps render CDM haloes resilient to tides, and protect dwarf galaxies embedded in them from full tidal disruption. The hierarchical assembly history of the Milky Way may therefore give rise to a population of "micro galaxies"; i.e., heavily-stripped remnants of early accreted satellites which may reach arbitrarily low luminosity. Assuming that the progenitor systems are dark matter dominated, we use an empirical formalism for tidal stripping to predict the evolution of the luminosity, size and velocity dispersion of such remnants, tracing their tidal evolution across multiple orders of magnitude in mass and size. The evolutionary tracks depend sensitively on the progenitor distribution of stellar binding energies. We explore two cases that likely bracket most realistic models of dwarf galaxies: one where the energy distribution of the most tightly bound stars follows that of the dark matter, and another where stars are less tightly bound and have a well-defined finite density core. The tidal evolution in the size-velocity dispersion plane is quite similar for these two models, although their remnants may differ widely in luminosity. Micro galaxies are therefore best distinguished from globular clusters by the presence of dark matter; either directly, by measuring their velocity dispersion, or indirectly, by examining their tidal resilience. Our work highlights the need for further theoretical and observational constraints on the stellar energy distribution in dwarf galaxies.

Dates et versions

hal-04329360 , version 1 (07-12-2023)

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Raphaël Errani, Rodrigo Ibata, Julio F Navarro, Jorge Peñarrubia, Matthew G Walker. Micro galaxies as a falsifiable prediction of LCDM cosmology. 2023. ⟨hal-04329360⟩
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