We analyse the results of an Eulerian AMR cosmological simulation in order to quantify the mass growth of galaxy clusters, exploring the differences between dark matter and baryons. We have determined the mass assembly histories (MAHs) of each of the mass components and computed several proxies for the instantaneous mass accretion rate (MAR). The mass growth of both components is clearly dominated by the contribution of major mergers, but high MARs can also occur during smooth accretion periods. We explored the correlations between MARs, merger events and clusters’ environments, finding the mean densities in 1 ≤ r/R200m ≤ 1.5 to correlate strongly with Γ200m in massive clusters which undergo major mergers through their MAH. From the study of the dark matter velocity profiles, we find a strong anticorrelation between the MAR proxies Γ200m and α200m. Last, we present a novel approach to study the angularly-resolved distribution of gas accretion flows in simulations, which allows to extract and interpret the main contributions to the accretion picture and to assess systematic differences between the thermodynamical properties of each of these contributions using multipolar analysis. We have preliminarily applied the method to the best numerically-resolved cluster in our simulation. Amongst the most remarkable results, we find that the gas infalling through the cosmic filaments has systematically lower entropy compared to the isotropic component, but we do not find a clear distinction in temperature.

Both simulations and observations have shown that turbulence is a pervasive phenomenon in cosmic scenarios, yet it is particularly difficult to model numerically due to its intrinsically multiscale character which demands high resolutions. Additionally, turbulence is tightly connected to the dynamical state and the formation history of galaxies and galaxy clusters, producing a diverse phenomenlogy which requires large samples of such structures to attain robust conclusions. In this work, we use an adaptive mesh refinement (AMR) cosmological simulation to explore the generation and dissipation of turbulence in galaxy clusters, in connection to its assembly history. We find that major mergers, and more generally accretion of gas, is the main process driving turbulence in the ICM. We have especially focused on solenoidal turbulence, which can be quantified through enstrophy. Our results seem to confirm a scenario for its generation which involves baroclinicity and compression at the external (accretion) and internal (merger) shocks, followed by vortex stretching downstream of them. We have also looked at the infall of mass to the cluster beyond its virial boundary, finding that gas follows trajectories with some degree of helicity, as it has already developed some vorticity in the external shocks.

Context. New-generation cosmological simulations are providing huge amounts of data, whose analysis becomes itself a pressing computational problem. In particular, the identification of gravitationally bound structures, known as halo finding, is one of the main analyses. Several codes that were developed for this task have been presented during the past years. Aims. We present a deep revision of the code ASOHF. The algorithm was thoroughly redesigned in order to improve its capabilities of finding bound structures and substructures using both dark matter particles and stars, its parallel performance, and its abilities of handling simulation outputs with vast amounts of particles. This upgraded version of ASOHF is conceived to be a publicly available tool. Methods. A battery of idealised and realistic tests are presented in order to assess the performance of the new version of the halo finder.Results. In the idealised tests, ASOHF produces excellent results. It is able to find virtually all the structures and substructures that we placed within the computational domain. When the code is applied to realistic data from simulations, the performance of our finder is fully consistent with the results from other commonly used halo finders. The performance in substructure detection is remarkable. In addition, ASOHF is extremely efficient in terms of computational cost. Conclusions. We present a publicly available deeply revised version of the ASOHF halo finder. The new version of the code produces remarkable results in terms of halo and subhalo finding capabilities, parallel performance, and low computational cost. Key words. large-scale structure of the Universe -dark matter -galaxies: clusters: general -galaxies: halos -methods: numerical 1 Friends of friends. 2 Spherical overdensity. 3 Bound density maxima. 4 Amiga halo finder. 5 Adaptive spherical overdensity halo finder. 6 Hierarchical bound tracing.

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Cosmic voids are underdense regions filling up most of the volume in the universe. They are expected to emerge in regions comprising negative initial density fluctuations, and subsequently expand as the matter around them collapses and forms walls, filaments, and clusters. We report results from the analysis of a cosmological simulation specially designed to accurately describe low-density regions, such as cosmic voids. Contrary to the common expectation, we find that voids also experience significant mass inflows over cosmic history. On average, 10% of the mass of voids in the sample at z ∼ 0 is accreted from overdense regions, reaching values beyond 35% for a significant fraction of voids. More than half of the mass entering the voids lingers on periods of time ∼10 Gyr well inside them, reaching inner radii. This would imply that part of the gas lying inside voids at a given time proceeds from overdense regions (e.g., clusters or filaments), where it could have been preprocessed, thus challenging the scenario of galaxy formation in voids, and dissenting from the idea of them being pristine environments.