works equally well, although with larger systematic uncertainties. It gives an estimated virial mass for the Milky Way of $2.43 \times
    10^{12}{\rm \,M_{\odot}}$ with a 95% lower confidence limit of $0.80 \times
    10^{12}{\rm \,M_{\odot}}$.
author:
- |
    Yang-Shyang Li$^{1}$[^1] and Simon D. M. White$^{2}$[^2]\
    $^{1}$Kapteyn Astronomical Institute, PO Box 800, 9700 AV, Groningen, The Netherlands\
    $^{2}$Max–Planck–Institut für Astrophysik, Karl-Schwarzschild-Str. 1, D-85748 Garching, Germany
date: 'Accepted. Received ; in original form '
title: Masses for the Local Group and the Milky Way
---

\[firstpage\]

Galaxy: formation – galaxies: Local Group – galaxies: kinematics and dynamics – dark matter.

Introduction {#intro_section}
============

During the 1970’s it became generally accepted that most, perhaps all, galaxies are surrounded by extended distributions of dark matter, so-called dark halos [@eks74; @opy74]. These were soon understood to play an essential role in driving the formation and clustering of galaxies [@wr78]. With the introduction of the Cold Dark Matter (CDM) paradigm, these ideas took more concrete form, allowing quantitative predictions to be made both for the population properties [@blumenthal84] and for the large-scale clustering [@davis85] of galaxies.

Measurements of the fluctuation spectrum of the Cosmic Microwave Background [@smoot92; @spergel03] and of the apparent acceleration of the cosmic expansion 