The structure of galaxy clusters in various cosmologies

Thomas, P.; Colberg, J. M.; Couchman, H. M. P.; Efstathiou, G.; Frenk, Carlos S.; Jenkins, Adrian; Nelson, A. H.; Hutchings, R.; Peacock, J. A.; Pearce, Frazer R.; White, Simon D. M.

doi:10.1046/j.1365-8711.1998.01491.x

Cited by 190 publications

(175 citation statements)

References 27 publications

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“…Warren et al (1992) applied this technique to ground-breaking, massively parallel simulations and found a distribution of minor-axis ratios for galactic-scale halos that peaked atc ' 0:6, with dispersion $0.1. Thomas et al (1998) analyze four Virgo simulations, including the two used here, and find a mean minor-axis ratio of 0.50 with dispersion $0.15 for a sample of 300 halos with mass limit 2 ; 10 14 h À1 M in low-m cosmologies. This shape result is significantly more ellipsoidal than our mean value of 0.64.…”

Section: Comparisons To Previous Workmentioning

confidence: 99%

Shapes and Alignments of Galaxy Cluster Halos

Kasun

Evrard

2005

ApJ

188

244

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We present distribution functions and mark correlations of the shapes of massive dark matter halos derived from Hubble volume simulations of a ÃCDM universe. We measure both position and velocity shapes within spheres that encompass a mean density 200 times the critical value and calibrate small-N systematic errors using Poisson realizations of isothermal spheres and higher resolution simulations. For halos more massive than 3 ; 10 14 h À1 M , the shape distribution function peaks at (minor/major, intermediate/major) axial ratios of (0.64, 0.76) in position and is rounder in velocity, peaking at (0.72, 0.82). Halo shapes are rounder at lower mass and/or redshift; the mean minoraxis ratio in position follows hc/ai(M ; z) ¼ c 15;0 ½1 À ln (M/10 15 h À1 M ) (1 þ z) À , with c 15;0 ¼ 0:631 AE 0:001, ¼ 0:023 AE 0:002, and ¼ 0:086 AE 0:004. Position and velocity principal axes are well aligned in direction, with median alignment angle 22 , and the axial ratios in these spaces are correlated in magnitude. We investigate mark correlations of halo pair orientations using two measures: a simple scalar product shows !1% alignment extending to 30 h À1 Mpc, while a filamentary statistic exhibits nonrandom alignment extending to scales $200 h À1 Mpc, 10 times the sample two-point correlation length and well into the regime of negative two-point correlation. Shapes of cluster halos are little affected by the large-scale environment; the distribution of supercluster member minor-axis ratios differs from that of the general population at only the few percent level.

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Section: Comparisons To Previous Workmentioning

confidence: 99%

Shapes and Alignments of Galaxy Cluster Halos

Kasun

Evrard

2005

ApJ

188

244

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“…Probes of the Milky Way halo indicate that it should be rather spherical with f 0.2 and that an oblate structure of f ∼ 0.2 might be preferable (see, e.g., [47] and references therein). Milky Way sized halos formed in dissipationless simulations are usually predicted to be considerably more triaxial and prolate, although a large scatter is expected [48,49,50,51,52,53,54]. Including dissipational baryons into the numerical simulation, and thereby converting the halo prolateness into a slightly oblate halo, might turn out to be essential to produce good agreement with observations.…”

Section: Nonsphericitymentioning

confidence: 99%

Baryonic pinching of galactic dark matter halos

2006

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High resolution cosmological N-body simulations of four galaxy-scale dark matter halos are compared to corresponding N-body/hydrodynamical simulations containing dark matter, stars and gas. The simulations without baryons share features with others described in the literature in that the dark matter density slope continuously decreases towards the center, with a density ρDM ∝ r −1.3±0.2 , at about 1% of the virial radius for our Milky Way sized galaxies. The central cusps in the simulations which also contain baryons steepen significantly, to ρDM ∝ r −1.9±0.2 , with an indication of the inner logarithmic slope converging. Models of adiabatic contraction of dark matter halos due to the central build-up of stellar/gaseous galaxies are examined. The simplest and most commonly used model, by Blumenthal et al., is shown to overestimate the central dark matter density considerably. A modified model proposed by Gnedin et al. is tested and it is shown that while it is a considerable improvement it is not perfect. Moreover it is found that the contraction parameters in their model not only depend on the orbital structure of the dark-matter-only halos but also on the stellar feedback prescription which is most relevant for the baryonic distribution. Implications for dark matter annihilation at the galactic center are discussed and it is found that although our simulations show a considerable reduced halo contraction as compared to the Blumenthal et al. model, the fluxes from dark matter annihilation is still expected to be enhanced by at least a factor of a hundred as compared to dark-matter-only halos. Finally, it is shown that while dark-matter-only halos are typically prolate, the dark matter halos containing baryons are mildly oblate with minor-to-major axis ratios of c/a = 0.73 ± 0.11, with their flattening aligned with the central baryonic disks.

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“…The formation and evolution of clusters depends sensitively on cosmological parameters like the mean matter density in the universe Ω m (Thomas et al 1998;Jenkins et al 1998;Beisbart et al 2001). Therefore it is important to determine the dynamical state of clusters at different redshifts, i.e.…”

Section: Introductionmentioning

confidence: 99%

XMM observation of the dynamically young galaxy cluster CL 0939+4713

Filippis

Schindler

Castillo-Morales

2003

A&A

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Abstract. We present an XMM observation of the distant galaxy cluster CL 0939+4713. The X-ray image shows pronounced substructure, with two main subclusters which have even some internal structure. This is an indication that the cluster is a dynamically young system. This conclusion is supported by the temperature distribution: a hot region is found between the two main subclusters indicating that they are at the beginning of a major merger, and that they will probably collide in a few hundreds of Myr. The intra-cluster gas of CL 0939+4713 shows inhomogeneities in the metal distribution, with the optically richer subcluster having a higher metallicity.

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The structure of galaxy clusters in various cosmologies

Cited by 190 publications

References 27 publications

Shapes and Alignments of Galaxy Cluster Halos

Shapes and Alignments of Galaxy Cluster Halos

Baryonic pinching of galactic dark matter halos

XMM observation of the dynamically young galaxy cluster CL 0939+4713

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