The origin and implications of dark matter anisotropic cosmic infall on ~L * haloes

By Dominique Aubert, C. Pichon, Stéphane Colombi. 2004

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We measure the anisotropy of dark matter flows on small scales (∼500 kpc) in the near environment of haloes using a large set of simulations. We rely on two different approaches to quantify the anisotropy of the cosmic infall: we measure the flows at the virial radius of the haloes while describing the infalling matter via fluxes through a spherical shell; and we measure the spatial and kinematical distributions of satellites and substructures around haloes detected by the subclump finder adaptahop described for the first time in the appendix. The two methods are found to be in agreement both qualitatively and quantitatively via one- and two-point statistics. The peripheral and advected momenta are correlated with the spin of the embedded halo at levels of 30 and 50 per cent. The infall takes place preferentially in the plane perpendicular to the direction defined by the spin of the halo. We computed the excess of equatorial accretion both through rings and via a harmonic expansion of the infall. The level of anisotropy of infalling matter is found to be ∼15 per cent. The substructures have their spin orthogonal to their velocity vector in the rest frame of the halo at a level of about 5 per cent, suggestive of an image of a flow along filamentary structures, which provides an explanation for the measured anisotropy. Using a ‘synthetic’ stacked halo, it is shown that the positions and orientations of satellites relative to the direction of spin of the halo are not random even in projection. The average ellipticity of stacked haloes is 10 per cent, while the alignment excess in projection reaches 2 per cent. All measured correlations are fitted by a simple three-parameter model. We conclude that a halo does not see its environment as an isotropic perturbation, we investigate how the anisotropy is propagated inwards using perturbation theory, and we discuss briefly the implications for weak lensing, warps and the thickness of galactic discs.

Subfields: Astronomy and Astrophysics, Instrumentation, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/3af867af37597b306983c44c783140050f3a2360

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Citations in the corpus

Bimodal gas accretion in the Horizon–MareNostrum galaxy formation simulation (2008, unknown): “We then define the local accretion rate ṁ as (see e.g. Aubert et al. (2004), Aubert & Pichon (2007)) ṁ(r,Ω) = ∂Ṁ ∂Ω = ρv · n r2 , (2) where the solid angle is defined by dΩ = sin θdθdφ in the direction Ω = (θ, φ), and n is the vector normal to the sphere and of norm 1.”
Extended Lyman-alpha emission from cold accretion streams (2011, methodology): “We identify halos in our simulation outputs with the AdaptaHOP algorithm from Aubert et al. (2004) and Tweed et al. (2009), where the virial radius of a halo, Rvir, is defined as the radius where the average density is 200 times the critical density of the Universe, and the halo center corresponds…”
Euclid preparation (2021, methodology): “Laigle et al. (2019) extracted a galaxy catalogue from the stellar particle distribution using the AdaptaHOP halo finder (Aubert et al. 2004), where galaxy identification is based exclusively on the local stellar particle density.”
The Great disk of Milky Way satellites and cosmological sub-structures (2004, background): “The theoretical sub-structure distribution of MW-type hosts must therefore be essentially isotropic (Ghigna et al. 1998; Zentner & Bullock 2003; Diemand et al. 2004; Kravtsov et al. 2004; Aubert et al. 2004).”
Spin alignments within the cosmic web: a theory of constrained tidal torques near filaments (2015, background): “Given that they locally reflect the large-scale geometry, will the gas continue to flow-in along preferred directions (as does the dark matter, see e.g. Aubert et al. 2004), or does the hot phase erase any anisotropy?”
Building merger trees from cosmological N-body simulations. Towards improving galaxy formation model (2009, methodology): “…inner structure of the haloes and detect subhaloes within them (e.g. IsoDen, Pfitzner & Salmon (1996); SKID, Ghigna et al. (1998); HFOF, Klypin et al. (1999); SUBFIND, Springel et al. (2001); AdaptaHOP, Aubert et al. (2004); MHF, Gill et al. (2004) and its successor AHF, Knollmann & Knebe (2009)).”
Connecting the cosmic web to the spin of dark haloes: implications for galaxy formation (2012, background): “Given that they locally reflect the large-scale geometry, will the gas continue to flow-in along preferred directions (as does the dark matter, see e.g. Aubert et al. 2004), or does the hot phase erase any anisotropy?”
A DIRECT MEASUREMENT OF THE BARYONIC MASS FUNCTION OF GALAXIES AND IMPLICATIONS FOR THE GALACTIC BARYON FRACTION (2012, methodology): “The identification of DM haloes and sub-haloes was done with the adaptaHOP algorithm presented in Aubert et al. (2004).”
The Intrinsic Alignment of Galaxies and its Impact on Weak Gravitational Lensing in an Era of Precision Cosmology (2014, methodology): “The high-mass galaxy misalignment is due to the merger of galaxies and was suggested by Aubert et al. (2004); Bailin and Steinmetz (2005).”
Dancing in the dark: galactic properties trace spin swings along the cosmic web (2014, background): “Galaxies are identified with the AdaptaHOP finder (Aubert et al. 2004, updated to its recent version by Tweed et al. 2009 for building merger trees) which directly operates on the distribution of star particles.”
CONNECTING ANGULAR MOMENTUM AND GALACTIC DYNAMICS: THE COMPLEX INTERPLAY BETWEEN SPIN, MASS, AND MORPHOLOGY (2015, background): “Aubert et al. (2004) investigated the alignment between the inner spin of halos and the angular momentum of the outer halo and also the alignment between the inner spin and the angular momentum of the inflowing material.”