Examinando por Autor "Sillero, Emanuel"

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    The evolution of the metallicity gradient and the star formation efficiency in disc galaxies
    (Oxford University Press, 2017-12) Sillero, Emanuel; Tissera, Patricia B.; Lambas, Diego G.; Michel-Dansac, Leo
    We study the oxygen abundance profiles of the gas-phase components in hydrodynamical simulations of pre-prepared disc galaxies including major mergers, close encounters and isolated configurations. We analyse the evolution of the slope of oxygen abundance profiles and the specific star formation rate (sSFR) along their evolution. We find that galaxy-galaxy interactions could generate either positive or negative gas-phase oxygen profiles, depending on the state of evolution. Along the interaction, galaxies are found to have metallicity gradients and sSFR consistent with observations, on average. Strong gas inflows produced during galaxy- galaxy interactions or as a result of strong local instabilities in gas-rich discs are able to produce both a quick dilution of the central gas-phase metallicity and a sudden increase of the sSFR. Our simulations show that, during these events, a correlation between the metallicity gradients and the sSFR can be set up if strong gas inflows are triggered in the central regions in short time-scales. Simulated galaxies without experiencing strong disturbances evolve smoothly without modifying the metallicity gradients. Gas-rich systems show large dispersion along the correlation. The dispersion in the observed relation could be interpreted as produced by the combination of galaxies with different gas-richness and/or experiencing different types of interactions. Hence, our findings suggest that the observed relation might be the smoking gun of galaxies forming in a hierarchical clustering scenario. © 2017 The Authors.
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    The gas metallicity gradient and the star formation activity of disc galaxies
    (Oxford University Press, 2016-03) Tissera, Patricia B.; Pedrosa, Susana E.; Sillero, Emanuel; Vilchez, Jose M.
    We study oxygen abundance profiles of the gaseous disc components in simulated galaxies in a hierarchical universe. We analyse the disc metallicity gradients in relation to the stellar masses and star formation rates of the simulated galaxies. We find a trend that galaxies with low stellar masses have steeper metallicity gradients than galaxies with high stellar masses at z ∼ 0. We also detect that the gas-phase metallicity slopes and the specific star formation rate (sSFR) of our simulated disc galaxies are consistent with recently reported observations at z ∼ 0. Simulated galaxies with high stellar masses reproduce the observed relationship at all analysed red shifts and have an increasing contribution of discs with positive metallicity slopes with increasing red shift. Simulated galaxies with low stellar masses have a larger fraction of negative metallicity gradients with increasing red shift. Simulated galaxies with positive or very negative metallicity slopes exhibit disturbed morphologies and/or have a close neighbour. We analyse the evolution of the slope of the oxygen profile and sSFR for a gas rich galaxy–galaxy encounter, finding that this kind of event could generate either positive or negative gas-phase oxygen profiles depending on their state of evolution. Our results support claims that the determination of reliable metallicity gradients as a function of red shift is a key piece of information in understanding galaxy formation and setting constraints on the subgrid physics.