The spin and shape of dark matter haloes in the Millennium simulation of a LambdaCDM universe

Abstract

We investigate the spins and shapes of over a million dark matter haloes identified at z=0 in the Millennium simulation. Our sample spans halo masses ranging from dwarf galaxies to rich galaxy clusters. The very large dynamic range of this simulation enables the distribution of spins and shapes and their variation with halo mass and environment to be characterised with unprecedented precision. We compare results for haloes identified using different algorithms, including a novel one based on the branches of the halo merger trees. We investigate (and remove) biases in the estimate of angular momentum introduced by both the algorithms themselves and by numerical effects. We find that for this many objects, the traditional lognormal function is no longer an adequate description of the distribution of the dimensionless spin parameter lambda, and we provide a different function that gives a better fit. The variation of spin with halo mass is weak but detectable, although the trend depends strongly on the halo definition used. The haloes exhibit a range of shapes, with a preference for prolateness over oblateness. More massive haloes tend to be less spherical and more prolate. We find that the more spherical haloes have spin in the median, and those closest to spherical have a spin independent of mass. The most massive have a spin independent of shape. The majority of haloes have their angular momentum vector aligned with their minor axis and perpendicular to their major axis. We find that higher tend to be more clustered, with a stronger effect for more massive haloes. (abridged)

24 pages, 25 figures. Final version accepted for publication in MNRAS. Significant re-arranging and clarification of text from previous versions, science content unchanged. Final five figures at reduced resolution; full resolution version available at http://star-www.dur.ac.uk/~dph3peb1/spindistro_web

Cited by in corpus (42)

• From rings to bulges: evidence for rapid secular galaxy evolution at z~2 from integral field spectroscopy in the SINS survey
• Formation of the first nuclear clusters and massive black holes at high redshift
• The Evolution of Dark Matter Halo Properties in Clusters, Filaments, Sheets and Voids
• Baryonic Pinching of Galactic Dark Matter Halos
• The spin and orientation of dark matter halos within cosmic filaments
• The Shape of the Gravitational Potential in Cold Dark Matter Halos
• The shapes, orientation, and alignment of Galactic dark matter subhalos
• Environmental Dependence of Dark Matter Halo Growth I: Halo Merger Rates
• A Statistical Study of Weak Lensing by Triaxial Dark Matter Halos: Consequences for Parameter Estimation
• Angular momentum-Large-scale structure alignments in LCDM models and the SDSS
• The formation of compact massive self-gravitating discs in metal-free haloes with virial temperatures of ~ 13000-30000 K
• A New Look at Massive Clusters: weak lensing constraints on the triaxial dark matter halos of Abell 1689, Abell 1835, & Abell 2204
• Shape, spin and baryon fraction of clusters in the MareNostrum Universe
• The assembly bias of dark matter haloes to higher orders
• The Self-Regulated Growth of Supermassive Black Holes
• Satellite Galaxies and Fossil Groups in the Millennium Simulation
• Environmental dependence in the ellipsoidal collapse model
• The Alignment between Satellites and Central Galaxies: Theory vs. Observations
• The Graininess of Dark Matter Haloes
• Do Mergers Spin up Dark Matter Halos?
• LensPerfect: Gravitational Lens Massmap Reconstructions Yielding Exact Reproduction of All Multiple Images
• Testing the predictions of the cold dark matter model for the sizes, colours, morphologies and luminosities of galaxies with the SDSS
• On the Correlation between Spin Parameter and Halo Mass
• The Flattened Dark Matter Halo of M31 as Deduced from the Observed HI Scale Heights
• The merger-driven evolution of warm infrared luminous galaxies
• The Near-IR Luminosity Function and Bimodal Surface Brightness Distribution of Virgo Cluster Galaxies
• The Effects of Halo Assembly Bias on Self-Calibration in Galaxy Cluster Surveys
• Why does the clustering of haloes depend on their formation history
• On the relation between radial alignment of dark matter subhalos and host mass in cosmological simulations
• Angular momentum and clustering properties of early dark matter halos
• The role of spin in the formation and evolution of galaxies
• The Origin of Extended Disk Galaxies at z=2
• An MCMC Fitting Method for Triaxial Dark Matter Haloes
• The radial alignment of dark matter subhalos: from simulations to observations
• Environment and mass dependencies of galactic $\lambda$ spin parameter: cosmological simulations and observed galaxies compared
• Richness Dependence of the Recent Evolution of Clusters of Galaxies
• Star formation and bar instability in cosmological haloes
• Kinematic effect in gravitational lensing by clusters of galaxies
• Two-component, ideal, self-gravitating fluids: the fractional virial potential energy
• The Hubble constant from galaxy lenses: impacts of triaxiality and model degeneracies
• Holes within galaxies: the egg or the hen?
• R fluids