Kinematics of Milky Way Satellites in a Lambda Cold Dark Matter Universe

TL;DR

This study tests if the dark matter subhalos in Lambda-CDM simulations can explain the observed properties of Milky Way satellites, finding good agreement with cusped dark matter profiles and specific velocity ranges.

Contribution

It demonstrates that simple spherical models within Lambda-CDM subhalos can accurately reproduce the observed kinematic and photometric data of several Milky Way satellites.

Findings

Models fit observed star counts and velocity dispersions well

Most satellites are consistent with cusped dark matter profiles

Satellites likely hosted by subhalos with maximum circular velocities of 10-30 km/s

Abstract

We investigate whether the subhalos of Lambda-CDM galaxy halos have potentials consistent with the observed properties of Milky Way satellites, particularly those with high-quality photometric and kinematic data: Fornax, Leo I, Sculptor, Sextans, and Carina. We compare spherical models with isotropic velocity dispersion tensors to the observed, circularly averaged star counts, line-of-sight velocity dispersion profiles and line-of-sight velocity distributions. We identify subhalos within the six high-resolution dark matter halos of the Aquarius Project for which the spherically averaged potentials result in excellent fits to each of the five galaxies. In particular, our simple one-integral models reproduce the observations in the inner regions, proving that these data are fully consistent with Lambda-CDM expectations and do not require cored dark matter distributions. For four of the five satellites the fits require moderately cusped {\it stellar} density profiles. The star count data for Leo I, however, do require a cored distribution of star counts. Current data suggest that these five satellites may be hosted by Lambda-CDM subhalos with maximum circular velocities in the range 10 to 30 km/s.