Scalelengths in Dark Matter Halos

Abstract

We investigate a hypothesis regarding the origin of the scalelength in halos formed in cosmological N-body simulations. This hypothesis can be viewed as an extension of an earlier idea put forth by Merritt and Aguilar. Our findings suggest that a phenomenon related to the radial orbit instability is present in such halos and is responsible for density profile shapes. This instability sets a scalelength at which the velocity dispersion distribution changes rapidly from isotropic to radially anisotropic. This scalelength is reflected in the density distribution as the radius at which the density profile changes slope. We have tested the idea that radially dependent velocity dispersion anisotropy leads to a break in density profile shape by manipulating the input of a semi-analytic model to imitate the velocity structure imposed by the radial orbit instability. Without such manipulation, halos formed are approximated by single power-law density profiles and isotropic velocity distributions. Halos formed with altered inputs display density distributions featuring scalelengths and anisotropy profiles similar to those seen in cosmological N-body simulations.

accepted for publication in ApJ

References in corpus (19)

• A Universal Density Profile from Hierarchical Clustering
• The Structure of Cold Dark Matter Halos
• Cold collapse and the core catastrophe
• The Inner Structure of LambdaCDM Halos III: Universality and Asymptotic Slopes
• The Inner Structure of LambdaCDM Halos I: A Numerical Convergence Study
• A universal angular momentum profile for galactic halos
• Resolving the Structure of Cold Dark Matter Halos
• The Structure of Dark Matter Haloes in Hierarchical Clustering Models
• The Phase-Space Density Profiles of Cold Dark Matter Halos
• The Average Mass Profile of Galaxy Clusters
• Generating Equilibrium Dark Matter Halos: Inadequacies of the Local Maxwellian Approximation
• A Universal Density Profile for Dark and Luminous Matter?
• On Formation and Evolution of Disk Galaxies: Cosmological Initial Conditions and the Gravitational Collapse
• Halo Cores and Phase Space Densities: Observational Constraints on Dark Matter Physics and Structure Formation
• How universal are the density profiles of dark halos?
• Investigating the Origins of Dark Matter Halo Density Profiles
• Self-similar spherical collapse with non-radial motions
• A family of models of partially relaxed stellar systems II. Comparison with the products of collisionless collapse
• Universal profile of dark matter halos and the spherical infall model

Cited by in corpus (23)

• CLASH-VLT: The mass, velocity-anisotropy, and pseudo-phase-space density profiles of the z=0.44 galaxy cluster MACS 1206.2-0847
• On the origin of cold dark matter halo density profiles
• Semi-analytical dark matter halos and the Jeans equation
• On Universal Halos and the Radial Orbit Instability
• The Role of the Radial Orbit Instability in Dark Matter Halo Formation and Structure
• The Radial Orbit Instability in Collisionless N-Body Simulations
• Two strong-lensing clusters confront universal dark-matter profiles
• Nonspherical similarity solutions for dark halo formation
• Density Profiles of Collisionless Equilibria. I. Spherical Isotropic Systems
• Radial orbit instability: review and perspectives
• Density Profiles of Collisionless Equilibria. II. Anisotropic Spherical Systems
• A Counterpart to the Radial Orbit Instability in Triaxial Stellar Systems
• Lopsidedness of self-consistent galaxies by the external field effect of clusters
• Power-laws and Non-Power-laws in Dark Matter Halos
• Testing DARKexp against energy and density distributions of Millennium-II halos
• Stirring N-body systems: Universality of end states
• On the Apparent Power Law in CDM Halo Pseudo Phase Space Density Profiles
• Velocity Distributions from Nonextensive Thermodynamics
• Radially anisotropic systems with $r^{-\alpha }$ forces. II: radial-orbit instability
• Detecting Triaxiality in the Galactic Dark Matter halo through Stellar Kinematics
• The kinematics of star clusters undergoing gas expulsion in Newtonian and Milgromian dynamics
• Triaxiality Inhibitors in N-Body Simulations
• Stirring N-body systems II: Necessary conditions for the dark matter attractor