Boldrin, Michele
Clustering and Lensing properties of Dark Matter haloes in Euclid era [Tesi di dottorato]

Following the most accredited cosmological model, the LCDM model, only 4% of the Universe is formed by baryonic matter, while about 26% is made up of Cold Dark Matter (CDM) and the remaining 70% is given by the component responsable of the cosmic accelerated expansion, called dark energy. Primordial perturbations in the CDM distribution that oppose to cosmic expansion and begin to collapse origin the potential wells where baryonic matter condense to form galaxies and stars. Observed on scales minor than some Mpc, the Universe is far from being homogeneous: galaxies are embedded by collapsed dark matter haloes. Therefore, the study of the substratum of dark matter in which the baryonic matter lies is fundamental to understand the formation and evolution of cosmic structures. Every object we observe come from an aggregation history of dark matter haloes, which generally enter in a host halo and orbit around the center of mass, becoming satellites. During this motion, several dynamical phenomenons may cause partial or total satellite mass-loss, or they can brake it through loss of angular momentum, so the satellite fall in the center of the host halo. In any case, the evolution of the satellite mass is very different from the evolution of a single halo. In this work we analyse the average relations between the satellite mass at the time of accretion and the mass at a given later observation moment. In particular, we wonder how can we estimate the former by the latter and viceversa. Using the new set of cosmological simulations LE SBARBINE, developed in the Physics and Astronomy Department of the University of Padova, we test the law that regulates the average mass-loss rate of satellites and we develop a new relation between the mass observed at a certain redshift and the average mass it could have at the accretion time. Furthermore, we discuss some factors that originate anomallies in the satellite mass evolution with respect to the average law we found, with particular attention to major mergers. In the context of the structure formation, galaxy clusters represent the last phase of the aggregation process of dark matter haloes. Being the largest and more recent objects in the Universe, every their feature or behaviour is a probe for the reference cosmological model. This is even more important in this epoch of technological progress, as the statistical study of these objects requires large and deep observations. An optimal example of those future innovative instruments is given by the spatial telescope Euclid (ESO), which will be launched in 2019-2020 and will observe a main 15000 square degrees of extragalactic sky, collecting images and spectra with excellent resolution and quality in optical and NIR bands. One of the research field that will be mostly improved by future observations is arc statistics, that is the cosmological research through the observation of giant gravitational arcs, the most magnificent effects of strong gravitational lensing. In the last decades, the study and the observations of gravitational lensing phenomenons has increased, following the rate of technological development. In particular, giant gravitational arcs, which are mainly created by galaxy clusters, need detailed and deep observations to be identified and used in statistical investigations. Because of the strong dependence of the number of those objects in the sky on the cosmology, we study as the number of arcs visible in the main survey of Euclid is dependent on the cosmological parameters Omega matter and sigma8, the two that mostly determine the structure formation process. Moreover, we analise the effect of the survey size and of the application of a selection function on our estimates.

In relazione con
FIS/05 - Astronomia e astrofisica

Tesi di dottorato. | Lingua: | Paese: | BID: TD18055681