Shapes and Alignments of Galaxy Cluster Halos

By S. Kasun, August E. Evrard. 2004

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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 ΛCDM 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 × 1014 h-1 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 minor-axis ratio in position follows ⟨c/a⟩(M,z) = c15,0[1 - α ln(M/1015 h-1 M☉)](1 + z)-ϵ, with c15,0 = 0.631 ± 0.001, α = 0.023 ± 0.002, and ϵ = 0.086 ± 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-1 Mpc, while a filamentary statistic exhibits nonrandom alignment extending to scales ~200 h-1 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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/e224998b570a5ef19007380efdfbf39bc9d40c60

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Citations in the corpus

The spin and shape of dark matter haloes in the Millennium simulation of a Λ cold dark matter universe (2006, background): “Again, this is in qualitative agreement with previous results, such as those of Warren et al. (1992), Bullock (2002), Kasun & Evrard (2005), Shaw et al. (2006), Gottlöber & Turchaninov (2006), Allgood et al. (2006), and Macciò et al. (2006).”
Statistics of Physical Properties of Dark Matter Clusters (2005, background): “Again, these values agree quite well with the axis ratios found by Warren et al. (1992), Cole & Lacey (1996), and Kasun & Evrard (2005).”
Concentration, spin and shape of dark matter haloes: Scatter and the dependence on mass and environment (2006, result): “We find that more massive haloes are on average more flattened (more prolate), in qualitative agreement with previous studies (Jing & Suto 2002; Bailin & Steinmetz 2005; Kasun & Evrard 2005; Allgood et al. 2006).”
Formation of Galaxy Clusters (2012, background): “Triaxiality of halos decreases with decreasing mass and redshift (Allgoodet al. 2006, Kasun & Evrard 2005) in a way that again can be parameterized in a universal form as a function of peak height (Allgood et al. 2006).”
Structure finding in cosmological simulations: the state of affairs (2013, methodology): “Note that the simplest method determines the shape and orientation of a halo using all particles within a spherical volume or shell at a given radius (e.g. Frenk et al. 1988; Bailin & Steinmetz 2005; Hopkins, Bahcall & Bode 2005; Kasun & Evrard 2005).”
ON THE ACCURACY OF WEAK-LENSING CLUSTER MASS RECONSTRUCTIONS (2010, background): “First, the triaxial shapes of Cold Dark Matter (CDM) halos (e.g., Warren et al. 1992; Jing & Suto 2002; Bailin & Steinmetz 2005; Kasun & Evrard 2005; Allgood et al. 2006; Shaw et al. 2006; Bett et al. 2007; Macciò et al. 2007, 2008) can bias a spherically-symmetric model fit of the reduced…”
The shape of dark matter haloes : dependence on mass, redshift, radius and formation (2005, methodology): “More recent studies of haloes’ shape were performed by Bullock (2002), Jing & Suto (2002) (JS), Springel, White & Hernquist (2004), Bailin & Steinmetz (2005), Kasun & Evrard (2005) and Hopkins, Bahcall & Bode (2005).”
The shape of dark matter haloes in the Aquarius simulations: evolution and memory (2011, methodology): “15 66 v2 [ as tr oph have yielded similar conclusions (Jing & Suto 2002; Bailin & Steinmetz 2005; Kasun & Evrard 2005; Hopkins et al. 2005; Bett et al. 2007; Hayashi et al. 2007; Kuhlen et al. 2007; Stadel et al. 2009; Diemand & Moore 2011).”
The alignment between the distribution of satellites and the orientation of their central galaxy (2006, background): “…dark matter haloes is also consistent with our finding that the alignment strength increases with halo mass; after all, numerical simulations have shown that more massive haloes are less spherical (Warren et al. 1992; Bullock 2002; Jing & Suto 2002; Bailin & Steinmetz 2005; Kasun & Evrard 2005).”
ON THE CLUSTER PHYSICS OF SUNYAEV–ZEL'DOVICH AND X-RAY SURVEYS. I. THE INFLUENCE OF FEEDBACK, NON-THERMAL PRESSURE, AND CLUSTER SHAPES ON Y–M SCALING RELATIONS (2011, background): “The axis ratios that we find for the DM mass dependence and redshift evolution have slopes consistent with Kasun & Evrard (2005), but as an overall trend, our axis ratios are more spherical than theirs.”