Energy equipartition between stellar and dark matter particles in cosmological simulations results in spurious growth of galaxy sizes

Abstract

The impact of 2-body scattering on the innermost density profiles of dark matter haloes is well established. We use a suite of cosmological simulations and idealised numerical experiments to show that 2-body scattering is exacerbated in situations where there are two species of unequal mass. This is a consequence of mass segregation and reflects a flow of kinetic energy from the more to less massive particles. This has important implications for the interpretation of galaxy sizes in cosmological hydrodynamic simulations, which nearly always model stars with less massive particles than are used for the dark matter. We compare idealised models as well as simulations from the EAGLE project that differ only in the mass resolution of the dark matter component, but keep sub-grid physics, baryonic mass resolution and gravitational force softening fixed. If the dark matter particle mass exceeds the mass of stellar particles, then galaxy sizes--quantified by their projected half-mass radii, ${\mathrm{R}}_{50}$--increase systematically with time until ${\mathrm{R}}_{50}$ exceeds a small fraction of the redshift-dependent mean inter-particle separation, $l$ (${\mathrm{R}}_{50}\ge 0.05\times l$). Our conclusions should also apply to simulations that adopt different hydrodynamic solvers, subgrid physics or adaptive softening, but in that case may need quantitative revision. Any simulation employing a stellar-to-dark matter particle mass ratio greater than unity will escalate spurious energy transfer from dark matter to baryons on small scales.

arXiv comment6 pages, 3 figures; replaced by MNRAS accepted version

References in corpus (20)

• Planck 2013 results. XVI. Cosmological parameters
• The cosmological simulation code GADGET-2
• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• Populating a cluster of galaxies - I. Results at z=0
• The Average Star Formation Histories of Galaxies in Dark Matter Halos from z=0-8
• The size distribution of galaxies in the Sloan Digital Sky Survey
• The Inner Structure of LambdaCDM Halos I: A Numerical Convergence Study
• Dancing in the dark: galactic properties trace spin swings along the cosmic web
• The Diversity and Similarity of Simulated Cold Dark Matter Halos
• The APOSTLE simulations: solutions to the Local Group's cosmic puzzles
• The optical morphologies of galaxies in the IllustrisTNG simulation: a comparison to Pan-STARRS observations
• Quantifying the heart of darkness with GHALO - a multi-billion particle simulation of our galactic halo
• The Size Evolution of Star-forming and Quenched Galaxies in the IllustrisTNG simulation
• Galaxy And Mass Assembly (GAMA): mass-size relations of z$<$0.1 galaxies subdivided by Sérsic index, colour and morphology
• Size evolution of normal and compact galaxies in the EAGLE simulation
• Pushing back the limits: detailed properties of dwarf galaxies in a LCDM universe
• Two--body heating in numerical galaxy formation experiments
• An iterative method for the construction of N-body galaxy models in collisionless equilibrium
• Knowing the unknowns: uncertainties in simple estimators of galactic dynamical masses
• Two-Body Relaxation in Cosmological Simulations

Cited by in corpus (69)

• The Milky Way total mass profile as inferred from Gaia DR2
• Introducing the THESAN project: radiation-magnetohydrodynamic simulations of the epoch of reionization
• Ultra-faint dwarfs in a Milky Way context: Introducing the Mint Condition DC Justice League Simulations
• Hydrodynamical simulations of the galaxy population: enduring successes and outstanding challenges
• The Formation of Ultra-Diffuse Galaxies in Clusters
• The Formation of Ultra-Diffuse Galaxies in the RomulusC Galaxy Cluster Simulation
• The Formation of Isolated Ultra-Diffuse Galaxies in Romulus25
• The THESAN project: Lyman-alpha emission and transmission during the Epoch of Reionization
• Spurious heating of stellar motions in simulated galactic disks by dark matter halo particles
• An EAGLE's View of Ex-situ Galaxy Growth
• The importance of black hole repositioning for galaxy formation simulations
• The impact of quenching on galaxy profiles in the Simba simulation
• To beta or not to beta: can higher-order Jeans analysis break the mass-anisotropy degeneracy in simulated dwarfs?
• Numerical convergence of hydrodynamical simulations of galaxy formation: the abundance and internal structure of galaxies and their cold dark matter haloes
• Recovering ${\lambda }_R$ and $V/\sigma$ from seeing-dominated IFS data
• Streams on FIRE: Populations of Detectable Stellar Streams in the Milky Way and FIRE
• The impact of spurious collisional heating on the morphological evolution of simulated galactic discs
• The impact of early massive mergers on the chemical evolution of Milky Way-like galaxies: insights from NIHAO-UHD simulations
• Molecular hydrogen in IllustrisTNG galaxies: carefully comparing signatures of environment with local CO & SFR data
• Accreted or Not Accreted? The Fraction of Accreted Mass in Galaxies from Simulations and Observations
• An ever-present $Gaia$ snail shell triggered by a dark matter wake
• What's in a name? Quantifying the interplay between the Definition, Orientation, and Shape of Ultra-diffuse Galaxies Using the Romulus Simulations
• The effect of gas accretion on the radial gas metallicity profile of simulated galaxies
• Characterising the intra-cluster light in The Three Hundred simulations
• VINTERGATAN-GM: The cosmological imprints of early mergers on Milky-Way-mass galaxies
• How cosmological merger histories shape the diversity of stellar haloes
• The lensing properties of subhaloes in massive elliptical galaxies in sterile neutrino cosmologies
• The galaxy size to halo spin relation of disk galaxies in cosmological hydrodynamical simulations
• The galaxy morphology-density relation in the EAGLE simulation
• Mapping Accreted Stars in Early-Type Galaxies Across the Mass-Size Plane
• The survival of globular clusters in a cuspy Fornax
• A high-resolution cosmological simulation of a strong gravitational lens
• Real and counterfeit cores: how feedback expands halos and disrupts tracers of inner gravitational potential in dwarf galaxies
• The volume density of giant low surface brightness galaxies
• Deprojecting Sersic Profiles for Arbitrary Triaxial Shapes: Robust Measures of Intrinsic and Projected Galaxy Sizes
• Mass accretion rates of clusters of galaxies: CIRS and HeCS
• There and back again: understanding the critical properties of backsplash galaxies
• The stellar mass function and evolution of the density profile of galaxy clusters from the Hydrangea simulations at $0<z<1.5$
• Testable predictions of outside-in age gradients in dwarf galaxies of all types
• Novel Conservative Methods for Adaptive Force Softening in Collisionless and Multi-Species N-Body Simulations
• Quenching, Mergers and Age Profiles for z=2 Galaxies in IllustrisTNG
• Drivers of asymmetry in synthetic H I emission-line profiles of galaxies in the EAGLE simulation
• Dwarf Galaxies and the Black-Hole Scaling Relations
• Exploiting flux ratio anomalies to probe warm dark matter in future large scale surveys
• The age gradients of galaxies in EAGLE: outside-in quenching as the origin of young bulges in cluster galaxies
• A common origin for the Fundamental Plane of quiescent and star-forming galaxies in the EAGLE simulations
• Auriga Streams I: disrupting satellites surrounding Milky Way-mass haloes at multiple resolutions
• Resolution criteria to avoid artificial clumping in Lagrangian hydrodynamic simulations with a multi-phase interstellar medium
• The morphology of star-forming gas and its alignment with galaxies and dark matter haloes in the EAGLE simulations
• The survival of stellar discs in Fornax-like environments, from TNG50 to real galaxies
• EDEN: Exploring Disks Embedded in N-body simulations of Milky-Way-mass halos from Symphony
• Numerical Discreteness Errors in Multi-Species Cosmological N-body Simulations
• Premature supermassive black hole mergers in cosmological simulations of structure formation
• The fragility of thin discs in galaxies -- I. Building tailored N-body galaxy models
• Intrinsic alignments of the extended radio continuum emission of galaxies in the EAGLE simulations
• N-body simulations of dark matter-baryon interactions
• Understanding Stellar Mass-Metallicity and Size Relations in Simulated Ultra-Faint Dwarf Galaxies
• Auriga Streams II: orbital properties of tidally disrupting satellites of Milky Way-mass galaxies
• Numerical effects on the stripping of dark matter and stars in IllustrisTNG galaxy groups and clusters
• Kennicutt-Schmidt relation of galaxies over 13 billion years in the COLIBRE hydrodynamical simulations
• The FLAMINGO simulations data release
• Dynamical disequilibrium in dwarf galaxies: rethinking gas dynamics, rotation curves, and dark matter inference
• Galaxy 3D Shape Recovery using Mixture Density Network
• The Role of Mass and Environment on Satellite distributions around Milky Way analogs in the Romulus25 simulation
• Particle loads for cosmological simulations with equal-mass dark matter and baryonic particles
• Observed structural parameters of EAGLE galaxies: reconciling the mass-size relation in simulations with local observations
• Broken Expectations: The Effects of Modelling Assumptions on the Inferred Dark Matter Distribution in the Milky Way's Satellites
• CASCO: Cosmological and AStrophysical parameters from Cosmological simulations and Observations IV. Testing warm dark matter cosmologies with galaxy scaling relations: A joint simulation-observation study using DREAMS simulations
• CROCODILE-DWARF: Assembly and Kinematics of Field Dwarf Galaxies with GADGET4-OSAKA