Examinando por Autor "Schaller, Matthieu"

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    Baryon effects on void statistics in the EAGLE simulation
    (Oxford University Press, 2017-10) Paillas, Enrique; Lagos, Claudia D.P.; Padilla, Nelson; Tissera, Patricia; Helly, John; Schaller, Matthieu
    Cosmic voids are promising tools for cosmological tests due to their sensitivity to dark energy, modified gravity and alternative cosmological scenarios. Most previous studies in the literature of void properties use cosmological N-body simulations of dark matter (DM) particles that ignore the potential effect of baryonic physics. Using a spherical underdensity finder, we analyse voids using the mass field and subhalo tracers in the Evolution and Assembly of Galaxies and their Environment (EAGLE) simulations, which follow the evolution of galaxies in a Λ cold dark matter universe with state-of-the-art subgrid models for baryonic processes in a (100 cMpc)3 volume. We study the effect of baryons on void statistics by comparing results with DM-only simulations that use the same initial conditions as EAGLE. When identifying voids in the mass field, we find that a DM-only simulation produces 24 per cent more voids than a hydrodynamical one due to the action of galaxy feedback polluting void regions with hot gas, specially for small voids with rvoid ≤ 10 Mpc. We find that the way in which galaxy tracers are selected has a strong impact on the inferred void properties. Voids identified using galaxies selected by their stellar mass are larger and have cuspier density profiles than those identified by galaxies selected by their total mass. Overall, baryons have minimal effects on void statistics, as void properties are well captured by DM-only simulations, but it is important to account for howgalaxies populateDMhaloes to estimate the observational effect of different cosmological models on the statistics of voids. © 2017 The Authors.
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    The oxygen abundance gradients in the gas discs of galaxies in the EAGLE simulation
    (Oxford University Press, 2019) Tissera, Patricia B.; Rosas-Guevara, Yetli; Bower, Richard G.; Crain, Robert A.; Lagos, Claudia del P.; Schaller, Matthieu; Schaye, Joop; Theuns, Tom
    We use the EAGLE simulations to study the oxygen abundance gradients of gas discs in galaxies within the stellar mass range [109.5, 1010.8] ∼M at z = 0. The estimated median oxygen gradient is -0.011 ± 0.002 dex kpc-1, which is shallower than observed. No clear trend between simulated disc oxygen gradient and galaxy stellar mass is found when all galaxies are considered. However, the oxygen gradient shows a clear correlation with gas disc size so that shallower abundance slopes are found for increasing gas disc sizes. Positive oxygen gradients are detected for ∼40 per cent of the analysed gas discs, with a slight higher frequency in low-mass galaxies. Galaxies that have quiet merger histories show a positive correlation between oxygen gradient and stellar mass, so that more massive galaxies tend to have shallowermetallicity gradients. At high stellarmass, there is a larger fraction of rotationaldominated galaxies in low-density regions. At low stellar mass, non-merger galaxies show a large variety of oxygen gradients and morphologies. The normalization of the disc oxygen gradients in non-merger galaxies by the effective radius removes the trend with stellar mass. Conversely, galaxies that experienced mergers show a weak relation between oxygen gradient and stellar mass. Additionally, the analysed EAGLE discs show no clear dependence of the oxygen gradients on local environment, in agreement with current observational findings.