The shapes and alignments of dark matter halos

被引:120
作者
Schneider, Michael D. [1 ,2 ]
Frenk, Carlos S. [2 ]
Cole, Shaun [2 ]
机构
[1] Lawrence Livermore Natl Lab, Livermore, CA 94551 USA
[2] Univ Durham, Dept Phys, Inst Computat Cosmol, Durham DH1 3LE, England
关键词
dark matter simulations; galaxy clusters; cosmic web; weak gravitational lensing; INTRINSIC ELLIPTICITY CORRELATION; ELLIPSOIDAL GALAXY CLUSTERS; PROBE WMAP OBSERVATIONS; LUMINOUS RED GALAXIES; X-RAY; SUNYAEV-ZELDOVICH; DENSITY PROFILES; ANGULAR MOMENTA; ASSEMBLY BIAS; COSMIC SHEAR;
D O I
10.1088/1475-7516/2012/05/030
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
We present measurements of the triaxial dark matter halo shapes and alignment correlation functions in the Millennium and Millennium-2 dark matter N-body simulations. These two simulations allow us to measure the distributions of halo shapes down to 10% of the virial radius over a halo mass range of 6 x 10(9)-2 x 10(14) h(-1)M(circle dot). We largely confirm previous results on the distributions of halo axis ratios as a function of halo mass, but we find that the median angle between halo major axes at different halo radii can vary by a factor of 2 between the Millennium-1 and 2 simulations because of the different mass resolution. Thus, error in the shape determinations from limited resolution is potentially degenerate with the misalignment of halo inner and outer shapes used to constrain Brightest Cluster Galaxy alignments in previous works. We also present simplifying parameterizations for the 3-D halo-mass alignment correlation functions that are necessary ingredients for triaxial halo models of large-scale structure and models of galaxy intrinsic alignments as contaminants for cosmic shear surveys. We measure strong alignments between halos of all masses and the surrounding dark matter overdensities out to several tens of h(-1) Mpc, in agreement with observed shear-galaxy and cluster shape correlations. We use these measurements to forecast the contribution to the weak lensing signal around galaxy clusters from correlated mass along the line-of-sight. For prolate clusters with major axes aligned with the line-of-sight the fraction of the weak lensing signal from mass external to the cluster can be twice that predicted if the excess halo alignment correlation is assumed to be zero.
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页数:45
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