Sagittarius, a dwarf spheroidal galaxy without dark matter?

TL;DR

This study explores whether the Sagittarius dwarf galaxy can be explained without dark matter by simulating different models and comparing their observational consistency, suggesting it may be in the process of disruption.

Contribution

The paper introduces alternative N-body models for Sagittarius, showing that low or negligible dark matter models can better match observations than dark matter-rich models.

Findings

Low dark matter models fit observational data better.

Sagittarius is likely undergoing disruption.

Dark matter may not be necessary to explain its properties.

Abstract

The existence of dwarf spheroidal galaxies with high internal velocity dispersions orbiting in the Milky Way raises questions about their dark matter content and lifetime. In this paper, we present an alternative solution to the dark matter dominated satellites proposed by Ibata & Lewis (1998) for the Sagittarius dwarf galaxy. We performed simulations of two kinds of N-body satellites: the first models (f-models) could correspond to satellites with high dark matter content and they represent initially isolated models. The second models (s-models) have either low or negligible dark matter content and they are constructed in a tidal field. In spite of being on the same orbits, the s-models are able to produce a better agreement with some observational constraints concerning Sagittarius. From our simulations, we can also infer that Sagittarius is in the process of being disrupted.