| Resumo: |
In this work we present a semi-analytical Chemical Evolution Model in the Cosmological Framework for 11 elements, taking into account the evolution of Population III and II stars and the transition between metallicities Z = 0 and 10$^{−6}$, 10$^{−4}$, 10$^{−3}$, 4.10$^{−3}$, 8.10$^{−3}$ and 2.10$^{−2}$ Z$_{\odot}$. We calculate the star formation rate in the framework of hierarchical structure formation (PEREIRA; MIRANDA, 2010) coupled with chemical evolution equations for Oxygen (\emph{O}), Iron (\emph{Fe}), Zinc (\emph{Zn}), Nickel (\emph{Ni}), Silicon (\emph{Si}), Magnesium (\emph{Mg}), Aluminum (\emph{Al}), Carbon (\emph{C}), Nitrogen (\emph{N}), Phosphorus (\emph{P}) and Sulphur (\emph{S}). The best results are reached when considering a Press-Schechter-like formalism, a Salpeter IMF (x = 1.35) and \emph{T}$_{s}$ = 2Gyr as time-scale for star formation (VITTI, 2012). We compare data generated by the model with chemical abundances in the gas-phase from Damped Lyman-$\alpha$ Systems (DLAs). Zn is underabundant probably due to the lack of Hypernovae (HNe) yields in the code, while P and Ni are underabundant probably because Supernovae type Ia (SNe Ia) yields are not taken into account. Al and Mg are discussed to be underabundant because of chemical abundances measurement problems in DLAs (such as blending with the Ly-$\alpha$ Forest) while \emph{Fe} and \emph{Si} are thought to be overabundant because of dust depletion effects on these systems. \emph{C}, \emph{N} and \emph{O} are unexpectedly overabundant and although \emph{C} and \emph{O} are used as fuel in SNe Ia, this mechanism is probably not enough to remove significant amount of these elements from the Intergalactic Medium (IGM), leaving the possibility for further studies on the influence of Carbon-enhanced Metal-Poor stars (CEMPs), Carbon planets formation in the early Universe and the appearance of life on the Chemical Cosmic Evolution (LOEB, 2016). |
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