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Xibelly Eliseth Mosquera Escobra

Numerical convergence in the dark matter halos properties using cosmological simulations

Nowadays, the accepted cosmological model is the so called Λ-Cold Dark Matter (ΛCDM). In such model, the universe is considered to be homogeneous and isotropic, composed by diverse components as the dark matter and dark energy, where the latter is the most abundant one. Dark matter plays an important role because it is responsible to the generation of gravitational potential wells, commonly called dark matter halos, objects that form the large-scale structures in the universe and host galaxies. These halos can be studied through cosmological simulations that allow us to study the formation and evolution process and also to obtain the structural parameters of these objects. To study the halos properties in different dynamical states is important modelling the hierarchical formation processes, to this end, is necessary follow the coalescence history of the halos. In this work we use cosmological simulations to find in what extent the numerical parameters of the simulations, such as gravitational softhening, integration time step and force calculation accuracy affect the physical properties of the dark matter halos. These parameters were varied in a systematic way, first a referential value was taken the common value used in different studies of dark matter halos- then variations above and below of this referential value was done, such that each ensemble of these parameters values constituted a new simulation to be analyzed. In general results of the simulations and specifically significant findings, of how the numerical parameters affect the halo structure (its dynamical state, density profile, etc) are presented. As a principal result, we show that the numerical parameters variations affect the structural parameters of dark matter halos, such as concentration, virial radius, and radius scale. These modifications emerged in nonlinear regimens to redshift ~2, such that these variations affected the formation and evolution structure to low redshifts. As a quantitative result, we propose which would be the most appropriate values for the numerical parameters of the simulations, such that they do not affect the halos properties that are formed. For force calculation accuracy we suggest to be equal to 0. 0001, integration time step equal to 0. 005 and for gravitational softhening equal to 1. 3, these values, correspond to the smaller values in the numerical parameters variations.

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Maria Emilia De Rossi

Fundamental metallicity relations in the EAGLE simulation

The study of the chemical enrichment of galaxies and its relation with
other global properties of these systems, such as total stellar mass or star formation rate, can provide important constraints on galaxy formation models. In particular, over the last decades, different research projects have focused on the analysis of the mass-metallicity relation (MZR) and its evolution with redshift. In this work, we analyse the MZR since redshift z=3 by using the EAGLE (Evolution and Assembly of GaLaxies and their Environments) simulations. These results are compared with previous findings obtained by using GIMIC (Galaxies-Intergalactic Medium Interaction Calculation) suite of cosmological simulations (De Rossi et al. 2015).