Introducing a new, robust galaxy-finder algorithm for simulations

Rodrigo Canas, Pascal J. Elahi, Charlotte Welker, Claudia del P. Lagos, Chris Power, Yohan Dubois, Christophe Pichon

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

Identifying galaxies in hydrodynamical simulations is a difficult task, particularly in regions of high density such as galaxy groups and clusters. We present a new scale-free, shape-independent algorithm to robustly and accurately identify galaxies in simulations, implemented within the phase-space halo-finder code VELOCIRAPTOR. This is achieved by using the full phase-space dispersion tensor for particle assignment and an iterative adjustment of search parameters, which help us overcome common structure-finding problems. We apply our improved method to the Horizon-AGN simulation and compare galaxy stellar masses (M-*), star formation rates (SFRs), and sizes with the elaborate configuration-space halo-finder HALOMAKER. Galaxies living in haloes with > 1 galaxy are the most affected by the shortcomings of real-space finders, with their mass, SFR, and size being > 2 times larger (smaller) in the case of host (satellite) galaxies. Thus, our ability to measure minor/major merger rates and disentangle environmental effects in simulations can be generally hindered if the identification of galaxies is not treated carefully. Though large systematic differences are obtained on a one-to-one basis, the overall galaxy stellar mass function, the SFR function, and the mass-size relations are not greatly affected. This is due to isolated galaxies being the most abundant population, dominating broad statistics.

Original languageEnglish
Pages (from-to)2039-2064
Number of pages26
JournalMonthly Notices of the Royal Astronomical Society
Volume482
Issue number2
DOIs
Publication statusPublished - Jan 2019

Cite this

Canas, Rodrigo ; Elahi, Pascal J. ; Welker, Charlotte ; Lagos, Claudia del P. ; Power, Chris ; Dubois, Yohan ; Pichon, Christophe. / Introducing a new, robust galaxy-finder algorithm for simulations. In: Monthly Notices of the Royal Astronomical Society. 2019 ; Vol. 482, No. 2. pp. 2039-2064.
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Introducing a new, robust galaxy-finder algorithm for simulations. / Canas, Rodrigo; Elahi, Pascal J.; Welker, Charlotte; Lagos, Claudia del P.; Power, Chris; Dubois, Yohan; Pichon, Christophe.

In: Monthly Notices of the Royal Astronomical Society, Vol. 482, No. 2, 01.2019, p. 2039-2064.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Introducing a new, robust galaxy-finder algorithm for simulations

AU - Canas, Rodrigo

AU - Elahi, Pascal J.

AU - Welker, Charlotte

AU - Lagos, Claudia del P.

AU - Power, Chris

AU - Dubois, Yohan

AU - Pichon, Christophe

PY - 2019/1

Y1 - 2019/1

N2 - Identifying galaxies in hydrodynamical simulations is a difficult task, particularly in regions of high density such as galaxy groups and clusters. We present a new scale-free, shape-independent algorithm to robustly and accurately identify galaxies in simulations, implemented within the phase-space halo-finder code VELOCIRAPTOR. This is achieved by using the full phase-space dispersion tensor for particle assignment and an iterative adjustment of search parameters, which help us overcome common structure-finding problems. We apply our improved method to the Horizon-AGN simulation and compare galaxy stellar masses (M-*), star formation rates (SFRs), and sizes with the elaborate configuration-space halo-finder HALOMAKER. Galaxies living in haloes with > 1 galaxy are the most affected by the shortcomings of real-space finders, with their mass, SFR, and size being > 2 times larger (smaller) in the case of host (satellite) galaxies. Thus, our ability to measure minor/major merger rates and disentangle environmental effects in simulations can be generally hindered if the identification of galaxies is not treated carefully. Though large systematic differences are obtained on a one-to-one basis, the overall galaxy stellar mass function, the SFR function, and the mass-size relations are not greatly affected. This is due to isolated galaxies being the most abundant population, dominating broad statistics.

AB - Identifying galaxies in hydrodynamical simulations is a difficult task, particularly in regions of high density such as galaxy groups and clusters. We present a new scale-free, shape-independent algorithm to robustly and accurately identify galaxies in simulations, implemented within the phase-space halo-finder code VELOCIRAPTOR. This is achieved by using the full phase-space dispersion tensor for particle assignment and an iterative adjustment of search parameters, which help us overcome common structure-finding problems. We apply our improved method to the Horizon-AGN simulation and compare galaxy stellar masses (M-*), star formation rates (SFRs), and sizes with the elaborate configuration-space halo-finder HALOMAKER. Galaxies living in haloes with > 1 galaxy are the most affected by the shortcomings of real-space finders, with their mass, SFR, and size being > 2 times larger (smaller) in the case of host (satellite) galaxies. Thus, our ability to measure minor/major merger rates and disentangle environmental effects in simulations can be generally hindered if the identification of galaxies is not treated carefully. Though large systematic differences are obtained on a one-to-one basis, the overall galaxy stellar mass function, the SFR function, and the mass-size relations are not greatly affected. This is due to isolated galaxies being the most abundant population, dominating broad statistics.

KW - methods: numerical

KW - galaxies: evolution

KW - dark matter

KW - cosmology: theory

KW - SUSSING MERGER TREES

KW - MASS ASSEMBLY GAMA

KW - DARK-MATTER

KW - STAR-FORMATION

KW - CLUSTER SIMULATIONS

KW - COSMOLOGICAL HYDRODYNAMICS

KW - ILLUSTRIS SIMULATION

KW - COMPARISON PROJECT

KW - EAGLE SIMULATIONS

KW - ANGULAR-MOMENTUM

U2 - 10.1093/mnras/sty2725

DO - 10.1093/mnras/sty2725

M3 - Article

VL - 482

SP - 2039

EP - 2064

JO - Monthly Notices of the Royal Astronomical Society

JF - Monthly Notices of the Royal Astronomical Society

SN - 0035-8711

IS - 2

ER -