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The fraction of dark matter within galaxies from the IllustrisTNG simulations

The fraction of dark matter within galaxies from the IllustrisTNG simulations

Title: The fraction of dark matter within galaxies from the IllustrisTNG simulations
Author: Lovell, Mark   orcid.org/0000-0001-5609-514X
Pillepich, Annalisa
Genel, Shy
Nelson, Dylan
Springel, Volker
Pakmor, Rüdiger
Marinacci, Federico
Weinberger, Rainer
Torrey, Paul
Vogelsberger, Mark
... 2 more authors Show all authors
Date: 2018-08-25
Language: English
Scope: 1950-1975
University/Institute: Háskóli Íslands
University of Iceland
School: Verkfræði- og náttúruvísindasvið (HÍ)
School of Engineering and Natural Sciences (UI)
Department: Raunvísindastofnun (HÍ)
Science Institute (UI)
Series: Monthly Notices of the Royal Astronomical Society;481(2)
ISSN: 0035-8711
1365-2966 (eISSN)
DOI: 10.1093/mnras/sty2339
Subject: Galaxy: kinematics and dynamics; Galaxy: structure; Cosmology: dark matter; Vetrarbrautir; Heimsfræði; Stjarneðlisfræði
URI: https://hdl.handle.net/20.500.11815/1213

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Mark R Lovell, Annalisa Pillepich, Shy Genel, Dylan Nelson, Volker Springel, Rüdiger Pakmor, Federico Marinacci, Rainer Weinberger, Paul Torrey, Mark Vogelsberger, Adebusola Alabi, Lars Hernquist, The fraction of dark matter within galaxies from the IllustrisTNG simulations, Monthly Notices of the Royal Astronomical Society, Volume 481, Issue 2, December 2018, Pages 1950–1975, https://doi.org/10.1093/mnras/sty2339


We use the IllustrisTNG (TNG) cosmological simulations to provide theoretical expectations for the dark matter mass fractions (DMFs) and circular velocity profiles of galaxies. TNG predicts flat circular velocity curves for z = 0 Milky Way (MW)-like galaxies beyond a few kpc from the galaxy centre, in better agreement with observational constraints than its predecessor, Illustris. TNG also predicts an enhancement of the dark matter mass within the 3D stellar half-mass radius (⁠rhalf⁠; M200c=1010−1013M⊙⁠, z ≤ 2) compared to its dark matter only and Illustris counterparts. This enhancement leads TNG present-day galaxies to be dominated by dark matter within their inner regions, with fDM(<rhalf)≳0.5 at all masses and with a minimum for MW-mass galaxies. The 1σ scatter is ≲10 per cent at all apertures, which is smaller than that inferred by some observational data sets, e.g. 40 per cent from the SLUGGS survey. TNG agrees with the majority of the observationally inferred values for elliptical galaxies once a consistent initial mass function is adopted (Chabrier) and the DMFs are measured within the same apertures. The DMFs measured within rhalf increase towards lower redshifts: this evolution is dominated by the increase in galaxy size with time. At z ∼ 2, the DMF in disc-like TNG galaxies decreases with increasing galaxy mass, with fDM(<rhalf)∼0.10--0.65 for 1010 ≲ Mstars/M⊙ ≲ 1012, and are two times higher than if TNG galaxies resided in Navarro–Frenk–White dark matter haloes unaffected by baryonic physics. It remains to be properly assessed whether recent observational estimates of the DMFs at z ∼ 2 rule out the contraction of the dark matter haloes predicted by the TNG model.


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