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The chemodinamical evolution of elliptical galaxies

Grant number: 06/01025-3
Support type:Scholarships abroad - Research
Effective date (Start): January 16, 2007
Effective date (End): June 15, 2007
Field of knowledge:Physical Sciences and Mathematics - Astronomy
Principal Investigator:Thais Eunice Pires Idiart
Grantee:Thais Eunice Pires Idiart
Host: Joseph I. Silk
Home Institution: Instituto de Astronomia, Geofísica e Ciências Atmosféricas (IAG). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Local de pesquisa : New College Oxford, England  

Abstract

The objective of my stay at the University of Oxford is to develop collaboration with the cosmology group associated to the Professor Joseph Silk, aiming to understand better the formation and the chemical evolution of galaxies. I will work with the development of a chemodynamical evolution model for the study of the variations or gradients of metallicity and colors observed in elliptical galaxies. The already elaborated analytical two-phase multi-population model (Idiart 2006) gives the key elements to be followed in time with the chemodynamical model: the hot and cold gas mixing, the star formation efficiency, the chemical enrichment of interstellar medium and how the abundance gradients can be formed. To build the chemodynamical model, I plan to use the cosmological simulation code GADGET-2 (Springel 2005). This code is originally more appropriate to see the large-scale structure formation in a maximum spatial resolution of approximately 50 kpc (Springel 2005). I intent to adapt this cosmological code in a spatial resolution suitably to analyze abundance gradients in elliptical galaxies. The working plan will be divided in three main parts: 1)In this first stage, global star formation rate and the chemical enrichment of intergalactic medium in high redshifts will be investigated. We will use the GADJET-2 including stellar and AGN feedbacks and the evolution yields from massive stars (metals, winds) developed in the analytic model (Idiart 2006). The problems of initial conditions of intergalactic medium, such as the need of an extra amount of momentum, energy or heating to reproduce the observed physical properties (White & Frank 1991, Springel 2004) will also be tackled. 2) Given the initial conditions to the proto-galaxy formation, we can investigate the star formation rate in lower redshifts. In this stage the aim is to study in detail the LOCAL feedback mechanism. The local feedback of the interstellar medium in a galaxy originates basically from normal stars through ionizing photons and supernova events that contribute with mechanical energy and metallic enrichment. The mechanisms of ionization and metals enrichment act as potential delayers of the local stellar formation. This work is in low/medium spatial resolution yet, only investigating the global star formation including all morphological galaxy types.3) The introduction of a zooming procedure gets a more detailed view of a given region in the analyzed local universe. The aim is to achieve a maximum spatial resolution of dozens of kpc, enabling the study not only of total integrated properties but also the abundances and colors variations along a giant ellipticals. The origin of radial abundances and colors gradients in giant ellipticals will be explored from the point of view of the two formation scenarios of accretion and merging (Thorsten et al. 2005). The dynamical evolution of gas and stars will be followed, trying to understand how the apparently high star formation rates observed in ellipticals can produce well defined radial gradients. (AU)