The stellar metallicity gradients in galaxy discs in a cosmological scenario

TISSERA, P. B.; MACHADO, R. E.; SÁNCHEZ-BLÁZQUEZ, P.; PEDROSA, S.E.; SÁNCHEZ, S.; SNAITH, O. N.; VILCHEZ,J. M.

ASTRONOMY AND ASTROPHYSICS

EDP SCIENCES S A

Lugar: Paris; Año: 2016

0004-6361

Context. The stellar metallicity gradients of disc galaxies provide information on the disc assembly, star formation processes andchemical evolution. They also might store information on dynamical processes which could affect the distribution of chemical elementsin the gas-phase and the stellar components. Understanding their joint effects within a hierarchical clustering scenario is ofparamount importance.Aims. We studied the stellar metallicity gradients of simulated discs in a cosmological simulation. We explored the dependence of thestellar metallicity gradients on stellar age and the size and mass of the stellar discs.Methods. We used a catalogue of galaxies with disc components selected from a cosmological hydrodynamical simulation performedincluding a physically-motivated Supernova feedback and chemical evolution. Disc components were defined based on angular momentumand binding energy criteria. The metallicity profiles were estimated for stars with different ages. We confront our numericalfindings with results from the CALIFA Survey.Results. The simulated stellar discs are found to have metallicity profiles with slopes in global agreement with observations. Lowstellar-mass galaxies tend to have a larger variety of metallicity slopes. When normalized by the half-mass radius, the stellar metallicitygradients do not show any dependence and the dispersion increases significantly, regardless of the galaxy mass. Galaxies with stellarmasses around 1010M⊙ show steeper negative metallicity gradients. The stellar metallicity gradients correlate with the half-massradius. However, the correlation signal is not present when they are normalized by the half-mass radius. Stellar discs with positiveage gradients are detected to have negative and positive metallicity gradients, depending on the relative importance of the recent starformation activity in the central regions.Conclusions. Our results suggest that the inside-out formation is the main process reponsible for the metallicity and age profiles. Thelarge dispersions in the metallicity gradients as a function of stellar mass could be ascribed to the effects of dynamical processes suchas mergers/interactions and/or migration as well as those regulating the conversion of gas into stars. The fingerprints of the inside-outformation seem better preserved by the stellar metallicity gradients as a function of the half-mass radius.