Xavier Isidro Pereira Hernandez

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We use recent HST colour-magnitude diagrams of the resolved stellar populations of a sample of local dSph galaxies (Carina, LeoI, LeoII, Ursa Minor and Draco) to infer the star formation histories of these systems, SFR(t). Applying a new variational calculus maximum likelihood method which includes a full Bayesian analysis and allows a non-parametric(More)
We explore the predictions of the standard hierarchical clustering scenario of galaxy formation, regarding the numbers and metallicities of PopIII stars likely to be found within our Galaxy today. By PopIII we shall be referring to stars formed at large redshift (z > 4), with low metallicities ([Z/Z⊙] < −2.5) and in small systems (total mass < ∼ 2×10 8M⊙)(More)
We examine isothermal dark matter halos in hydrostatic equilibrium with a“Λ– field”, or cosmological constant Λ = ΩΛ ρcrit c , where ΩΛ ≃ 0.7, and ρcrit is the present value of the critical density with h ≃ 0.65. Modeling cold dark matter as a self–gravitating Maxwell-Boltzmann gas, the Newtonian limit of General Relativity yields equilibrium equations that(More)
We obtain the characteristic numbers of the variety of non degenerate cuspidal plane cubics in P3, namely, the non-zero intersection numbers which arise from considering 10 (possibly repeated) conditions from among the following: P , that the cuspidal cubic go through a point; ν, that the cuspidal cubic intersect a line; and ρ, that the cuspidal cubic be(More)
We calculate chemical evolution models for 4 dwarf spheroidal satellites of the Milky Way (Carina, Ursa Minor, Leo I and Leo II) for which reliable non-parametric star formation histories have been derived. In this way, the independently obtained star formation histories are used to constrain the evolution of the systems we are treating. This allows us to(More)
The formation and evolution of disk galaxies in the cosmo-logical context is studied. We consider the observable properties of disk galaxies and treat the disk formation and galactic evolutionary processes in a self-consistent fashion. We find the matter accretion regime to be the dominant ingredient in establishing the Hubble sequence. The accretion regime(More)
Objective determination of a star formation history from a colourmagnitude diagram, independently of assumed parametric descriptions, is necessary to determine the evolutionary history of a galaxy. We introduce a new method for solving maximum likelihood problems through variational calculus, and apply it to the case of recovering an unknown star formation(More)
Late accretion models for formation of the Galactic halo require that many Galactic satellite galaxies have been cannibalised into the halo field. Comparison of the metallicity and age distribution function of stars in the surviving satellites with the apparently exclusively old stars in the field halo can constrain the importance of any such process. We(More)
We estimate the timescales for orbital decay of wide binaries embedded within dark matter halos, due to dynamical friction against the dark matter particles. We derive analytical scalings for this decay and calibrate and test them through the extensive use of N-body simulations, which accurately confirm the predicted temporal evolution. For density and(More)