The Dynamical Structure of Dark Matter Halos With Universal Properties

Hese, E. Van; Baes, M.; Dejonghe, Herwig

doi:10.1088/0004-637x/690/2/1280

Cited by 22 publications

(20 citation statements)

References 47 publications

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“…fainter than BHB stars. We replaced this fraction of stars in each bin with R GC > 40 kpc, with blue stragglers at the appropriate distance, with velocities sampled from a Gaussian random deviate with σ(r) from van Hese et al (2009), at the appropriate r for a contaminating blue straggler. The results of this exercise are shown in Figure 7.…”

Section: Also Arguesmentioning

confidence: 99%

Mapping the Galactic Halo With Blue Horizontal Branch Stars From the Two-Degree Field Quasar Redshift Survey

Propris

Harrison

Mares

2010

ApJ

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We use 666 blue horizontal branch (BHB) stars from the 2Qz redshift survey to map the Galactic halo in four dimensions (position, distance and velocity). We find that the halo extends to at least 100 kpc in Galactocentric distance, and obeys a single power-law density profile of index ∼ −2.5 in two different directions separated by about 150 • on the sky. This suggests that the halo is spherical. Our map shows no large kinematically coherent structures (streams, clouds or plumes) and appears homogeneous. However, we find that at least 20% of the stars in the halo reside in substructures and that these substructures are dynamically young. The velocity dispersion profile of the halo appears to increase towards large radii while the stellar velocity distribution is non Gaussian beyond 60 kpc. We argue that the outer halo consists of a multitude of low luminosity overlapping tidal streams from recently accreted objects.

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Section: Also Arguesmentioning

confidence: 99%

Mapping the Galactic Halo With Blue Horizontal Branch Stars From the Two-Degree Field Quasar Redshift Survey

Propris

Harrison

Mares

2010

ApJ

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“…Although some recent models of the distribution function offer a little more flexible parametrization of the anisotropy profile (e.g. Baes & Van Hese 2007; Van Hese et al 2009), we find that our choice is quite suitable for the purpose of this work, given that we wish to reproduce the variability of β( r ) with as few parameters as possible.…”

Section: The Phase‐space Densitymentioning

confidence: 99%

“…Quite recently, several models satisfying this requirement have been proposed. The anisotropy profile is specified by a proper parametrization of the angular momentum part of the distribution function (Wojtak et al 2008) or the augmented density (Van Hese, Baes & Dejonghe 2009). The purpose of the present work was to adopt the approach of Wojtak et al (2008) to the Bayesian analysis of kinematic data and to test on mock data sets how well the mass and anisotropy profiles are reproduced.…”

Section: Introductionmentioning

confidence: 99%

The mass and anisotropy profiles of galaxy clusters from the projected phase-space density: testing the method on simulated data

Wojtak

Łokas

Mamon

et al. 2009

Monthly Notices of the Royal Astronomical Society

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We present a new method of constraining the mass and velocity anisotropy profiles of galaxy clusters from kinematic data. The method is based on a model of the phase‐space density, which allows the anisotropy to vary with radius between two asymptotic values. The characteristic scale of transition between these asymptotes is fixed and tuned to a typical anisotropy profile resulting from cosmological simulations. The model is parametrized by two values of anisotropy, at the centre of the cluster and at infinity, and two parameters of the NFW density profile, the scale radius and the scale mass. In order to test the performance of the method in reconstructing the true cluster parameters, we analyse mock kinematic data for 20 relaxed galaxy clusters generated from a cosmological simulation of the standard Λ cold dark matter model. We use Bayesian methods of inference and the analysis is carried out following the Markov Chain Monte Carlo approach. The parameters of the mass profile are reproduced quite well, but we note that the mass is typically underestimated by 15 per cent, probably due to the presence of small velocity substructures. The constraints on the anisotropy profile for a single cluster are in general barely conclusive. Although the central asymptotic value is determined accurately, the outer one is subject to significant systematic errors caused by substructures at large clustercentric distance. The anisotropy profile is much better constrained if one performs joint analysis of at least a few clusters. In this case, it is possible to reproduce the radial variation of the anisotropy over two decades in radius inside the virial sphere.

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“…Dehnen & McLaughlin (2005, hereafter DM05) also solved the Jeans equation under this assumption, and demonstrated explicitly that one can thus derive analytically all relevant profiles for the DM structure. Many other authors have considered similar pseudo phase-space densities, e.g., Hansen et al (2006), Knebe & Wießner (2006), Stadel et al (2008), Knollmann et al (2008), Ascasibar & Gottloeber (2008), Zait et al (2008), Van Hese et al (2008), Navarro et al (2008), and Lapi & Cavaliere (2008).…”

Section: Introductionmentioning

confidence: 99%

Alas, the Dark Matter Structures Were Not That Trivial

Schmidt

Hansen

Macciò

2008

ApJ

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The radial density profile of dark matter structures has been observed to have an almost universal behavior in numerical simulations; however, the physical reason for this behavior remains unclear. It has previously been shown that if the pseudo phase-space density, , is a beautifully simple power law in radius, with the "golden e r/j d values" and (i.e., the phase-space density is only dependent on the radial component of the velocity e p 3 d p r dispersion), then one can analytically derive the radial variation of the mass profile, dispersion profile, etc. That would imply, if correct, that we just have to explain why , and then we would understand everything 3 Ϫa r/j ∼ r r about equilibrated DM structures. Here we use a set of simulated galaxies and clusters of galaxies to demonstrate that there are no such golden values, but that each structure instead has its own set of values. Considering the same structure at different redshifts shows no evolution of the phase-space parameters toward fixed points. There is also no clear connection between the halo virialized mass and these parameters. This implies that we still do not understand the origin of the profiles of dark matter structures.

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The Dynamical Structure of Dark Matter Halos With Universal Properties

Cited by 22 publications

References 47 publications

Mapping the Galactic Halo With Blue Horizontal Branch Stars From the Two-Degree Field Quasar Redshift Survey

Mapping the Galactic Halo With Blue Horizontal Branch Stars From the Two-Degree Field Quasar Redshift Survey

The mass and anisotropy profiles of galaxy clusters from the projected phase-space density: testing the method on simulated data

Alas, the Dark Matter Structures Were Not That Trivial

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