Broken degeneracies: the rotation curve and velocity anisotropy of the Milky Way halo

Monthly Notices of the Royal Astronomical Society (Impact Factor: 5.23). 04/2012; 424(1). DOI: 10.1111/j.1745-3933.2012.01283.x
Source: arXiv

ABSTRACT We use distant Blue Horizontal Branch stars with Galactocentric distances 16
< r/kpc < 48 as kinematic tracers of the Milky Way dark halo. We model the
tracer density as an oblate, power-law embedded within a spherical power-law
potential. Using a distribution function method, we estimate the overall
power-law potential and the velocity anisotropy of the halo tracers. We measure
the slope of the potential to be gamma ~ 0.4 and the overall mass within 50 kpc
is ~ 4 x 10^11 M_sol. The tracer velocity anisotropy is radially biased with
beta ~ 0.5, which is in good agreement with local solar neighbourhood studies.
Our results provide an accurate outer circular velocity profile for the Milky
Way and suggest a relatively high concentration dark matter halo (c_vir ~ 20).

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: A suite of vast stellar surveys mapping the Milky Way, culminating in the Gaia mission, is revolutionizing the empirical information about the distribution and properties of stars in the Galactic stellar disk. We review and lay out what analysis and modeling machinery needs to be in place to test mechanism of disk galaxy evolution and to stringently constrain the Galactic gravitational potential, using such Galactic star-by-star measurements. We stress the crucial role of stellar survey selection functions in any such modeling; and we advocate the utility of viewing the Galactic stellar disk as made up of ‘mono-abundance populations’ (MAPs), both for dynamical modeling and for constraining the Milky Way’s evolutionary processes. We review recent work on the spatial and kinematical distribution of MAPs, and point out how further study of MAPs in the Gaia era should lead to a decisively clearer picture of the Milky Way’s dark-matter distribution and formation history.
    Astronomy and Astrophysics Review 01/2013; 21(1). · 13.31 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: A fermion triplet of SU(2)_L - a wino - is a well-motivated dark matter candidate. This work shows that present-day wino annihilations are constrained by indirect detection experiments, with the strongest limits coming from H.E.S.S. and Fermi. The bounds on wino dark matter are presented as a function of mass for two scenarios: thermal (winos constitute a subdominant component of the dark matter for masses less than 3.1 TeV) and non-thermal (winos comprise all the dark matter). Assuming the NFW halo model, the H.E.S.S. search for gamma-ray lines excludes the 3.1 TeV thermal wino; the combined H.E.S.S. and Fermi results completely exclude the non-thermal scenario. Uncertainties in the exclusions are explored. Indirect detection may provide the only probe for models of anomaly plus gravity mediation where the wino is the lightest superpartner and scalars reside at the 100 TeV scale.
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: From the archaeological point of view, the local dwarf galaxies are unique objects in which the imprint of the conditions that shaped the early structure formation can be studied today at high resolution. Over the last decade, this new window into the high redshift Universe has started to be exploited using deep wide-field imaging, high resolution spectroscopy and cutting edge N-body and hydro-dynamical simulations. We review the recent advances in the observational studies of the Milky Way dwarf galaxies, with the aim to understand the properties of the population as a whole and to assist an objective comparison between the models and the data.
    New Astronomy Reviews 06/2013; · 6.72 Impact Factor


1 Download
Available from