Dark Matter tested with satellites

TL;DR

This paper compares dark matter models and modified gravity theories against satellite velocity dispersion data around isolated galaxies, highlighting the challenges in distinguishing models due to parameter degeneracies.

Contribution

It demonstrates that current observational data can be fitted by multiple dark matter and modified gravity models, emphasizing the need for additional constraints.

Findings

All models can fit the data with appropriate parameters.

Parameter degeneracies prevent clear discrimination between models.

Realistic velocity anisotropy variations are essential for accurate modeling.

Abstract

Recently, the distribution of velocity dispersion as far as 400kpc around red isolated galaxies was derived from statistical studies of satellites in the SDSS (Klypin & Prada 2009). This could help to constrain dark matter models at intermediate scales. We compare the predictions of different DM distributions, LCDM with NFW or cored profiles, and also modified gravity models, with observations. It is shown how the freedom in the various parameters (radial distribution of satellites, velocity anisotropy, external field effect), prevents to disentangle the models, which all can give pretty good fits to the data. In all cases, realistic radial variations of velocity anisotropy are used for the satellites, and a constant stellar-mass to light ratio for the host galaxies.