The Milky Way’s Circular Velocity Curve to 60 kpc and an Estimate of the Dark Matter Halo Mass from the Kinematics of ∼2400 SDSS Blue Horizontal‐Branch Stars
Year: 2008
Type: article
Abstract: We derive new constraints on the mass of the Milky Way's dark matter halo, based on 2401 rigorously selected blue horizontal-branch halo stars from SDSS DR6. This sample enables construction of the full line-of-sight velocity distribution at different galactocentric radii. To interpret these distributions, we compare them to matched mock observations drawn from two different cosmological galaxy formation simulations designed to resemble the Milky Way. This procedure results in an estimate of the Milky Way's circular velocity curve to ~60 kpc, which is found to be slightly falling from the adopted value of 220 km s −1 at the Sun's location, and implies M (< 60 kpc) = (4.0 ± 0.7) × 10 11 M ☉ . The radial dependence of V cir ( r ) , derived in statistically independent bins, is found to be consistent with the expectations from an NFW dark matter halo with the established stellar mass components at its center. If we assume that an NFW halo profile of characteristic concentration holds, we can use the observations to estimate the virial mass of the Milky Way's dark matter halo, M vir = 1.0 + 0.3 −0.2 × 10 12 M ☉ , which is lower than many previous estimates. We have checked that the particulars of the cosmological simulations are unlikely to introduce systematics larger than the statistical uncertainties. This estimate implies that nearly 40% of the baryons within the virial radius of the Milky Way's dark matter halo reside in the stellar components of our Galaxy. A value for M vir of only ~1 × 10 12 M ☉ also (re)opens the question of whether all of the Milky Way's satellite galaxies are on bound orbits.
Source: The Astrophysical Journal
DOI: 10.1086/589500
Institutions: Chinese Academy of Sciences, Max Planck Institute for Astronomy, National Astronomical Observatories, University of Chinese Academy of Sciences, University of Ljubljana, Leibniz Institute for Astrophysics Potsdam, Joint Institute for Nuclear Astrophysics, Michigan State University, University of California, Santa Cruz, Fermi National Accelerator Laboratory, Rensselaer Polytechnic Institute, Texas Tech University, University of Cambridge, Pennsylvania State University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, U.S. Department of Energy, National Aeronautics and Space Administration, Alfred P. Sloan Foundation, Princeton University, Ohio State University, University of Chicago, University of Washington, Johns Hopkins University, University of Pittsburgh, Case Western Reserve University, Drexel University, Universität Basel, University of Portsmouth, New Mexico State University, National Natural Science Foundation of China, Chinese Academy of Sciences, Max-Planck-Gesellschaft, Max-Planck-Institut für Astronomie, Science and Technology Facilities Council, U.S. Naval Observatory, Fermilab, Los Alamos National Laboratory
OpenAlex ID: W2118239294