100 research outputs found
On the phase-space structure of galaxy clusters from cosmological simulations
Cosmological N-body simulations represent an excellent tool to study the formation and evolution of dark matter (DM) haloes and the mechanisms that have originated the universal profile at the largest mass scales in the Universe. In particular, the combination of the velocity dispersion \u3c3v with the density p can be used to define the pseudo-entropy S(r) = \u3c32 v /p 2/3, whose profile is well described by a simple power law S 1e r \u3b1. We analyse a set of cosmological hydrodynamical re-simulations of massive galaxy clusters and study the pseudo-entropy profiles as traced by different collisionless components in simulated galaxy clusters: DM, stars, and substructures. We analyse four sets of simulations, exploring different resolution and physics (N-body and full hydrodynamical simulations) to investigate convergence and the impact of baryons. We find that baryons significantly affect the inner region of pseudo-entropy profiles as traced by substructures, while DM particles profiles are characterized by an almost universal behaviour, thus suggesting that the level of pseudo-entropy could represent a potential low-scatter mass-proxy. We compare observed and simulated pseudo-entropy profiles and find good agreement in both normalization and slope. We demonstrate, however, that the method used to derive observed pseudo-entropy profiles could introduce biases and underestimate the impact of mergers. Finally, we investigate the pseudo-entropy traced by the stars focusing our interest in the dynamical distinction between intracluster light and the stars bound to the brightest cluster galaxy: The combination of these two pseudo-entropy profiles is well described by a single power law out to almost the entire cluster virial radius
Guinada conservadora e mudanças polĂticas de acesso Ă terra no Brasil: uma análise do perĂodo entre 2015 e 2020
O presente artigo se propõe a contribuir com o atual panorama de reflexões acerca das polĂticas de acesso Ă terra no Brasil, tendo como foco principal a guinada conservadora na qual a polĂtica brasileira tem se deparado nos Ăşltimos anos. Para isso foram realizadas pesquisas bibliográficas e documentais, sendo de base qualitativa e com caráter indutivo. Os resultados se dĂŁo atravĂ©s de análise em trĂŞs diferentes nĂveis. No primeiro foi feito o levantamento da temperatura da controvĂ©rsia; em um segundo nĂvel, destaca-se a mudança de termos nos Ăşltimos anos: a escolha pelo termo “regularização fundiária” em detrimento de “reforma agrária”; e por Ăşltimo, no terceiro nĂvel, foi possĂvel observar a formação de uma eventual aliança entre setores heterogĂŞneos, que nem sempre se articulam em coalizões, e que se colocaram contra a MP 910 em manifestações virtuais organizadas. Nossos achados demonstram que o avanço do paradigma neoliberal nas polĂticas de acesso Ă terra gerou impactos nas legislações do tema, bem como possibilitaram uma maior privatização das terras, ampliando a visĂŁo desta como mercadoria.Palavras-Chave: Conservadorismo; Regularização fundiária; Reforma agrária
Populações de Pratylenchus brachyurus em raĂzes de soja cultivada apĂłs adensamento de Brachiaria ruziziensis.
A palhada de Brachiaria ruziziensis tem sido empregada para o manejo do mofo branco (Sclerotinia sclerotiorum). Contudo, esta forrageira Ă© hospedeira de Praylenchus brachyurus, e nĂŁo há informações em campo sobre este patossistema forrageira x nematĂłide. Para verificar esta relação, foi conduzido um experimento em JataĂ, GO, na safra 2008/2009
Euclid preparation TBD. The effect of baryons on the Halo Mass Function
The Euclid photometric survey of galaxy clusters stands as a powerful cosmological tool, with the capacity to significantly propel our understanding of the Universe. Despite being sub-dominant to dark matter and dark energy, the baryonic component in our Universe holds substantial influence over the structure and mass of galaxy clusters. This paper presents a novel model to precisely quantify the impact of baryons on galaxy cluster virial halo masses, using the baryon fraction within a cluster as proxy for their effect. Constructed on the premise of quasi-adiabaticity, the model includes two parameters calibrated using non-radiative cosmological hydrodynamical simulations and a single large-scale simulation from the Magneticum set, which includes the physical processes driving galaxy formation. As a main result of our analysis, we demonstrate that this model delivers a remarkable one percent relative accuracy in determining the virial dark matter-only equivalent mass of galaxy clusters, starting from the corresponding total cluster mass and baryon fraction measured in hydrodynamical simulations. Furthermore, we demonstrate that this result is robust against changes in cosmological parameters and against varying the numerical implementation of the sub-resolution physical processes included in the simulations. Our work substantiates previous claims about the impact of baryons on cluster cosmology studies. In particular, we show how neglecting these effects would lead to biased cosmological constraints for a Euclid-like cluster abundance analysis. Importantly, we demonstrate that uncertainties associated with our model, arising from baryonic corrections to cluster masses, are sub-dominant when compared to the precision with which mass-observable relations will be calibrated using Euclid, as well as our current understanding of the baryon fraction within galaxy clusters
Euclid preparation: XXIV. Calibration of the halo mass function in (?)CDM cosmologies
Euclid s photometric galaxy cluster survey has the potential to be a very competitive cosmological probe. The main cosmological probe with observations of clusters is their number count, within which the halo mass function (HMF) is a key theoretical quantity. We present a new calibration of the analytic HMF, at the level of accuracy and precision required for the uncertainty in this quantity to be subdominant with respect to other sources of uncertainty in recovering cosmological parameters from Euclid cluster counts. Our model is calibrated against a suite of N-body simulations using a Bayesian approach taking into account systematic errors arising from numerical effects in the simulation. First, we test the convergence of HMF predictions from different N-body codes, by using initial conditions generated with different orders of Lagrangian Perturbation theory, and adopting different simulation box sizes and mass resolution. Then, we quantify the effect of using different halo finder algorithms, and how the resulting differences propagate to the cosmological constraints. In order to trace the violation of universality in the HMF, we also analyse simulations based on initial conditions characterised by scale-free power spectra with different spectral indexes, assuming both Einsteinde Sitter and standard CDM expansion histories. Based on these results, we construct a fitting function for the HMF that we demonstrate to be sub-percent accurate in reproducing results from 9 different variants of the CDM model including massive neutrinos cosmologies. The calibration systematic uncertainty is largely sub-dominant with respect to the expected precision of future massobservation relations; with the only notable exception of the effect due to the halo finder, that could lead to biased cosmological inference
Euclid preparation. XXIV. Calibration of the halo mass function in CDM cosmologies
Euclid's photometric galaxy cluster survey has the potential to be a very
competitive cosmological probe. The main cosmological probe with observations
of clusters is their number count, within which the halo mass function (HMF) is
a key theoretical quantity. We present a new calibration of the analytic HMF,
at the level of accuracy and precision required for the uncertainty in this
quantity to be subdominant with respect to other sources of uncertainty in
recovering cosmological parameters from Euclid cluster counts. Our model is
calibrated against a suite of N-body simulations using a Bayesian approach
taking into account systematic errors arising from numerical effects in the
simulation. First, we test the convergence of HMF predictions from different
N-body codes, by using initial conditions generated with different orders of
Lagrangian Perturbation theory, and adopting different simulation box sizes and
mass resolution. Then, we quantify the effect of using different halo-finder
algorithms, and how the resulting differences propagate to the cosmological
constraints. In order to trace the violation of universality in the HMF, we
also analyse simulations based on initial conditions characterised by
scale-free power spectra with different spectral indexes, assuming both
Einstein--de Sitter and standard CDM expansion histories. Based on
these results, we construct a fitting function for the HMF that we demonstrate
to be sub-percent accurate in reproducing results from 9 different variants of
the CDM model including massive neutrinos cosmologies. The calibration
systematic uncertainty is largely sub-dominant with respect to the expected
precision of future mass-observation relations; with the only notable exception
of the effect due to the halo finder, that could lead to biased cosmological
inference.Comment: 24 pages, 21 figures, 5 tables, 3 appendixes
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