Abundance and phase-space distribution of subhalos in cosmological N-body simulations: testing numerical convergence and correction methods

Abstract

Subhalos play a crucial role in accurately modeling galaxy formation and galaxy-based cosmological probes within the highly nonlinear, virialized regime. However, numerical convergence of subhalo evolution is difficult to achieve, especially in the inner regions of host halos where tidal forces are strongest. I investigate the numerical convergence and correction methods for the abundance, spatial, and velocity distributions of subhalos using two $6144^3$-particle cosmological N-body simulations with different mass resolutions -- Jiutian-300 ($1.0\times 10^7{h}^{-1}{M}_{\odot }$) and Jiutian-1G ($3.7\times 10^8{h}^{-1}{M}_{\odot }$) -- with subhalos identified by HBT+. My study shows that the Surviving subhalo Peak Mass Function (SPMF) converges only for subhalos with $m_{\mathrm{peak}}$ above $5000$ particles but can be accurately recovered by including orphan subhalos that survive according to the merger timescale model of Jiang et al., which outperforms other models. Including orphan subhalos also enables recovery of the real-space spatial and velocity distributions to $5$--$10\%$ accuracy down to scales of $0.1$--$0.2h^{-1}\mathrm{Mpc}$. The remaining differences are likely due to cosmic variance and finite-box effects in the smaller Jiutian-300 simulation. Convergence below $0.1h^{-1}\mathrm{Mpc}$ remains challenging and requires more sophisticated modeling of orphan subhalos. I further highlight that redshift-space multipoles are more difficult to recover even at larger scales because unreliable small-scale pairs at $r_{\mathrm{p}}<0.1h^{-1}\mathrm{Mpc}$ in real space affect scales of tens of $\mathrm{Mpc}$ in redshift space due to elongated Fingers-of-God effects. Therefore, for redshift-space statistics, I recommend using modified or alternative measures that reduce sensitivity to small projected separations in subhalo-based studies.

24 pages, 15 figures. Published in JCAP

References in corpus (16)

• Rotation-Dependent Catastrophic Disruption of Gravitational Aggregates
• Simulating cosmic structure formation with the GADGET-4 code
• Dark matter and cosmic structure
• Dark Matter Substructure in Numerical Simulations: A Tale of Discreteness Noise, Runaway Instabilities, and Artificial Disruption
• A fitting formula for the merger timescale of galaxies in hierarchical clustering
• An excess of small-scale gravitational lenses observed in galaxy clusters
• ELUCID - Exploring the Local Universe with reConstructed Initial Density field I: Hamiltonian Markov Chain Monte Carlo Method with Particle Mesh Dynamics
• HBT+: an improved code for finding subhalos and building merger trees in cosmological simulations
• The Preferential Tidal Stripping of Dark Matter versus Stars in Galaxies
• Orbital parameters of infalling satellite haloes in the hierarchical $\Lambda$CDM model
• Constraining Extended Gamma-ray Emission from Galaxy Clusters
• The Aemulus Project V: Cosmological constraint from small-scale clustering of BOSS galaxies
• CSST Cosmological Emulator I: Matter Power Spectrum Emulation with one percent accuracy to k = 10 h/Mpc
• The Universal Specific Merger Rate of Dark Matter Halos
• Tracking the orbit of unresolved subhalos for semi-analytic models
• Describing the Nonuniversal Galaxy Merger Timescales in IllustrisTNG: Effects of Host Halo Mass, Baryons, and Sample Selection