Examinando por Autor "Pedrosa, Susana E."

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  • Miniatura
    Ítem
    Angular momentum evolution for galaxies in a Λ-CDM scenario
    (EDP Sciences, 2015-12) Pedrosa, Susana E.; Tissera, Patricia B.
    Galaxy formation in the current cosmological paradigm is a very complex process in which inflows, outflows, interactions, and mergers are common events. These processes can redistribute the angular momentum content of baryons. Recent observational results suggest that disc formed conserving angular momentum while elliptical galaxies, although they lose angular momentum, determine a correlation between the specific angular momentum of the galaxy and the stellar mass. These observations provide stringent constraints for galaxy formation models in a hierarchical clustering scenario. Aims. We aim to analyse the specific angular momentum content of the disc and bulge components as a function of virial mass, stellar mass, and redshift. We also estimate the size of the simulated galaxies and compare them with observations. Methods. We use cosmological hydrodynamical simulations that include an effective, physically motivated supernova feedback which is able to regulate the star formation in haloes of different masses. We analyse the morphology and formation history of a sample of galaxies in a cosmological simulation by performing a bulge-disc decomposition of the analysed systems and their progenitors. We estimate the angular momentum content of the stellar and gaseous discs, stellar bulges, and total baryons. Results. In agreement with recent observational findings, our simulated galaxies have disc and spheroid components whose specific angular momentum content determine correlations with the stellar and dark matter masses with the same slope, although the spheroidal components are offset by a fixed fraction. The average angular momentum efficiency for the simulated discs is η ~ 1, while for bulges it is η ~ 0.10-0.20. For the simulated sample, the correlations found for the specific angular momentum content as a function of virial mass or stellar mass are found not to evolve significantly with redshift (up to z ~ 2). Both dynamical components seem to move along the correlations as they evolve. The total specific angular momentum of galaxies occupy different positions filling the gap between pure rotational-dominated and dispersion-dominated systems. The scaling relations derived from the simulated galaxies determine a similar relation with the virial radius, which is in agreement with recent observations. © 2015 ESO.
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    Ítem
    Mild evolution of the stellar metallicity gradients of disc galaxies
    (EDP Sciences, 2017-08) Tissera, Patricia; MacHado, Rubens E. G.; Vilchez, José M.; Pedrosa, Susana E.; Sanchez-Blazquez, Patricia; Varela, Silvio
    Context. The metallicity gradients of the stellar populations in disc galaxies and their evolution store relevant information on the disc formation history and on those processes which could mix stars a posteriori, such as migration, bars and/or galaxy-galaxy interactions. Aims. We aim to investigate the evolution of the metallicity gradients of the whole stellar populations in disc components of simulated galaxies in a cosmological context. Methods. We analyse simulated disc galaxies selected from a cosmological hydrodynamical simulation that includes chemical evolution and a physically motivated supernova feedback capable of driving mass-loaded galactic winds. Results. We detect a mild evolution with redshift in the metallicity slopes of-0.02 ± 0.01 dex kpc-1 from z ∼ 1. If the metallicity profiles are normalised by the effective radius of the stellar disc, the slopes show no clear evolution for z< 1, with a median value of approximately-0.23 dex reff-1. As a function of stellar mass, we find that metallicity gradients steepen for stellar masses smaller than ∼1010.3M· while the trend reverses for higher stellar masses, in the redshift range z = [0,1]. Galaxies with small stellar masses have discs with larger reff and flatter metallicity gradients than expected. We detect migration albeit weaker than in previous works. Conclusions. Our stellar discs show a mild evolution of the stellar metallicity slopes up to z ∼ 1, which is well-matched by the evolution calculated archeologically from the abundance distributions of mono-age stellar populations at z ∼ 0. The dispersion in the relations allows for stronger individual evolutions. Overall, supernova feedback could explain the trends but an impact of migration can not be totally discarded. Galaxy-galaxy interactions or small satellite accretions can also contribute to modify the metallicity profiles in the outer parts. Disentangling the effects of these processes for individual galaxies is still a challenge in a cosmological context. © 2017 ESO.
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    Ítem
    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.