On the accuracy of dark matter halo merger trees and the consequences for semi-analytic models of galaxy formation

Abstract

Galaxy formation and evolution models, such as semi-analytic models, are powerful theoretical tools for predicting how galaxies evolve across cosmic time. These models follow the evolution of galaxies based on the halo assembly histories inferred from large $N$-body cosmological simulations. This process requires codes to identify halos ("halo finder") and to track their time evolution ("tree builder"). While these codes generally perform well, they encounter numerical issues when handling dense environments. In this paper, we present how relevant these issues are in state-of-the-art cosmological simulations. We characterize two major numerical artefacts in halo assembly histories: (i) the non-physical swapping of large amounts of mass between subhalos, and (ii) the sudden formation of already massive subhalos at late cosmic times. We quantify these artefacts for different combinations of halo finder (SUBFIND, VELOCIRAPTOR, HBT-HERONS) and tree builder codes (D-TRESS+DHALO, TREEFROG, HBT-HERONS), finding that in general more than $50\%$ ($80\%$) of the more massive subhalos with $>10^3$ ($>10^4$) particles at $z=0$ inherit them in most cases. However, HBT-HERONS, which explicitly incorporates temporal information, effectively reduces the occurrence of these artefacts to $5\%$ ($10\%$). We then use the semi-analytic models SHARK and GALFORM to explore how these artefacts impact galaxy formation predictions. We demonstrate that the issues above lead to non-physical predictions in galaxies hosted by affected halos, particularly in SHARK where the modelling of baryons relies on subhalo information. Finally, we propose and implement fixes for the numerical artefacts at the semi-analytic model level, and use SHARK to show the improvements, especially at the high-mass end, after applying them.

Accepted for publication in MNRAS (a new section 3.3.3 discussing results in the context of other galaxy formation models and other minor changes). 32 pages (26 of main body and 6 of appendices)

References in corpus (38)

• The EAGLE project: Simulating the evolution and assembly of galaxies and their environments
• 3D-HST+CANDELS: The Evolution of the Galaxy Size-Mass Distribution since $z=3$
• The Role of Pressure in GMC Formation II: The H_2 - Pressure Relation
• A population of red candidate massive galaxies ~600 Myr after the Big Bang
• Direct cosmological simulations of the growth of black holes and galaxies
• A primer on hierarchical galaxy formation: the semi-analytical approach
• The Main Sequence of star-forming galaxies across cosmic times
• Stress Testing $\Lambda$CDM with High-redshift Galaxy Candidates
• Disruption of Dark Matter Substructure: Fact or Fiction?
• The FLAMINGO project: cosmological hydrodynamical simulations for large-scale structure and galaxy cluster surveys
• Building Merger Trees from Cosmological N-body Simulations
• Galaxy And Mass Assembly (GAMA): Data Release 4 and the z < 0.1 total and z < 0.08 morphological galaxy stellar mass functions
• WALLABY -- An SKA Pathfinder HI Survey
• SubHaloes going Notts: The SubHalo-Finder Comparison Project
• A surprising abundance of massive quiescent galaxies at 3 < z < 5 in the first data from JWST CEERS
• Effects of AGN feedback on LCDM galaxies
• HBT+: an improved code for finding subhalos and building merger trees in cosmological simulations
• Galaxy And Mass Assembly (GAMA): ${\mathcal{M}}_{\star }-R_{\mathrm{e}}$ relations of $z=0$ bulges, discs and spheroids
• A massive galaxy that formed its stars at $z\sim 11$
• Metal Enrichment of the ICM: a 3-D Picture of Chemical and Dynamical Properties
• SWIFT: A modern highly-parallel gravity and smoothed particle hydrodynamics solver for astrophysical and cosmological applications
• Galaxy And Mass Assembly (GAMA): A forensic SED reconstruction of the cosmic star formation history and metallicity evolution by galaxy type
• Hunting for Galaxies and Halos in simulations with VELOCIraptor
• Elemental Abundances in Milky Way-like Galaxies from a Hierarchical Galaxy Formation Model
• Supermassive black holes as the regulators of star formation in central galaxies
• The host dark matter halos of [OII] emitters at 0.5< z< 1.5
• Disruption of satellite galaxies in simulated groups and clusters: the roles of accretion time, baryons, and pre-processing
• Galaxy formation with L-GALAXIES: Modelling the environmental dependency of galaxy evolution and comparing with observations
• Testing the predictions of the cold dark matter model for the sizes, colours, morphologies and luminosities of galaxies with the SDSS
• SURFS: Riding the waves with Synthetic UniveRses For Surveys
• A Comparison of Galaxy Merger History Observations and Predictions from Semi-Analytic Models
• Flybys, orbits, splashback: subhalos and the importance of the halo boundary
• Subhaloes gone Notts: Spin across subhaloes and finders
• Convergence properties of halo merger trees; halo and substructure merger rates across cosmic history
• Sussing Merger Trees : The Impact of Halo Merger Trees on Galaxy Properties in a Semi-Analytic Model
• Insights on the origin of ORCs from cosmological simulations
• Constructing high-fidelity halo merger trees in AbacusSummit
• Extracting Galaxy Merger Timescales II: A new fitting formula

Cited by in corpus (7)

• Modelling the evolution and influence of dust in cosmological simulations that include the cold phase of the interstellar medium
• Simulations of the accreted stellar halos of low-mass field galaxies
• The role of gas stripping in the quenching of satellite galaxies using SHARK v2.0
• Kennicutt-Schmidt relation of galaxies over 13 billion years in the COLIBRE hydrodynamical simulations
• On the Origin of Intracluster Light based on the High-resolution Simulation, NewCluster
• The DORCHA suite: nature, nurture, and the phase space distribution of the Milky Way's high redshift progenitors today
• CWTHF: Subhalo Identification with Continuous Wavelet Transform