Haloes at the ragged edge: The importance of the splashback radius

Abstract

We have explored the outskirts of dark matter haloes out to 2.5 times the virial radius using a large sample of halos drawn from Illustris, along with a set of zoom simulations (MUGS). Using these, we make a systematic exploration of the shape profile beyond R${}_{vir}$. In the mean sphericity profile of Illustris halos we identify a dip close to the virial radius, which is robust across a broad range of masses and infall rates. The inner edge of this feature may be related to the virial radius and the outer edge with the splashback radius. Due to the high halo-to-halo variation this result is visible only on average. However, in four individual halos in the MUGS sample, a decrease in the sphericity and a subsequent recovery is evident close to the splashback radius. We find that this feature persists for several Gyr, growing with the halo. This feature appears at the interface between the spherical halo density distribution and the filamentary structure in the environment. The shape feature is strongest when there is a high rate of infall, implying that the effect is due to the mixing of accreting and virializing material. The filamentary velocity field becomes rapidly mixed in the halo region inside the virial radius, with the area between this and the splashback radius serving as the transition region. We also identify a long-lasting and smoothly evolving splashback region in the radial density gradient in many of the MUGS halos.

arXiv comment22 pages, 15 figures, Accepted for publication in MNRAS

References in corpus (58)

• The NumPy array: a structure for efficient numerical computation
• A Universal Density Profile from Hierarchical Clustering
• The Structure of Cold Dark Matter Halos
• Wilkinson Microwave Anisotropy Probe (WMAP) Three Year Results: Implications for Cosmology
• The Global Schmidt Law in Star Forming Galaxies
• Nine-Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Cosmological Parameter Results
• Populating a cluster of galaxies - I. Results at z=0
• E pur si muove: Galiliean-invariant cosmological hydrodynamical simulations on a moving mesh
• Statistical Properties of X-ray Clusters: Analytic and Numerical Comparisons
• Introducing the Illustris Project: Simulating the coevolution of dark and visible matter in the Universe
• Mass function of dark matter halos
• Properties of galaxies reproduced by a hydrodynamic simulation
• Radiative transfer in a clumpy universe: IV. New synthesis models of the cosmic UV/X-ray background
• Introducing the Illustris Project: the evolution of galaxy populations across cosmic time
• Ahf: Amiga's Halo Finder
• Formation of Galaxy Clusters
• Triaxial Modeling of Halo Density Profiles with High-resolution N-body Simulations
• The merger rate of galaxies in the Illustris Simulation: a comparison with observations and semi-empirical models
• Star Formation and Feedback in Smoothed Particle Hydrodynamic Simulations--I. Isolated Galaxies
• Merger rates in hierarchical models of galaxy formation. II: Comparison with N-body simulations
• Gasoline: An adaptable implementation of TreeSPH
• The Shape of Dark Matter Halos: Dependence on Mass, Redshift, Radius, and Formation
• Formation and evolution of galaxy dark matter halos and their substructure
• Precision Determination of the Mass Function of Dark Matter Halos
• The Illustris Simulation: Public Data Release
• The evolution substructure I: a new identification method
• Making Galaxies in a Cosmological Context: The Need for Early Stellar Feedback
• Rotation-Dependent Catastrophic Disruption of Gravitational Aggregates
• Dependence of the outer density profiles of halos on their mass accretion rate
• The Enrichment of the Intergalactic Medium with Adiabatic Feedback I: Metal Cooling and Metal Diffusion
• Haloes gone MAD: The Halo-Finder Comparison Project
• Internal and External Alignment of the Shapes and Angular Momenta of LCDM Halos
• Metallicity Gradients in Disks: Do Galaxies Form Inside-Out?
• Splashback in accreting dark matter halos
• The pseudo-evolution of halo mass
• The Redshift Evolution of LCDM Halo Parameters: Concentration, Spin, and Shape
• Structure Finding in Cosmological Simulations: The State of Affairs
• Internal Alignment of the Halos of Disk Galaxies in Cosmological Hydrodynamic Simulations
• Cosmological Galaxy Formation Simulations Using SPH
• How far do they go? The outer structure of dark matter halos
• Anisotropy in the Distribution of Satellite Galaxy Orbits
• The virialized mass of dark matter haloes
• The preferred direction of infalling satellite galaxies in the Local Group
• On determining the shape of matter distributions
• The splashback radius of halos from particle dynamics. II. Dependence on mass, accretion rate, redshift, and cosmology
• Shape, spin and baryon fraction of clusters in the MareNostrum Universe
• The universal nature of subhalo accretion
• The splashback radius of halos from particle dynamics. I. The SPARTA algorithm
• The Structure of Halos: Implications for Group and Cluster Cosmology
• Splashback Shells of Cold Dark Matter Halos
• The correlation structure of dark matter halo properties
• Dark Matter Halo Structure in CDM Hydrodynamical Simulations
• Mechanisms of Baryon Loss for Dark Satellites in Cosmological SPH Simulations
• The stellar metallicity distribution of disc galaxies and bulges in cosmological simulations
• Evolution and Statistics of Non-Sphericity of Dark Matter Halos from Cosmological N-Body Simulation
• The history of stellar metallicity in a simulated disc galaxy
• The Role of Feedback in Shaping the Structure of the Interstellar Medium
• The luminosity function of diverse satellite galaxy systems

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