摘要：Context. The stellar metallicity gradients of disc galaxies provide
information on disc assembly, star formation processes, and chemical evolution. They also
might store information on dynamical processes that could affect the distribution of
chemical elements in the gas phase and the stellar components. Understanding their joint
effects within a hierarchical clustering scenario is of paramount importance.
Aims. We studied the stellar metallicity gradients of simulated discs in
a cosmological simulation. We explored the dependence of the stellar metallicity gradients
on stellar age and on the size and mass of the stellar discs.
Methods. We used a catalogue of galaxies with disc components selected
from a cosmological hydrodynamical simulation performed including a physically motivated
supernova feedback and chemical evolution. Disc components were defined based on angular
momentum and binding energy criteria. The metallicity profiles were estimated for stars
with different ages. We confront our numerical findings with results from the Calar Alto
Legacy Integral Field Area (CALIFA) Survey.
Results. The simulated stellar discs are found to have metallicity
profiles with slopes in global agreement with observations. Low stellar mass galaxies tend
to have a larger variety of metallicity slopes. When normalized by the half-mass radius,
the stellar metallicity gradients do not show any dependence and the dispersion increases
significantly, regardless of the galaxy mass. Galaxies with stellar masses o f around
1010M⊙ show steeper negative
metallicity gradients. The stellar metallicity gradients correlate with the half-mass
radius. However, the correlation signal is not present when they are normalized by the
half-mass radius. Stellar discs with positive age gradients are detected to have negative
and positive metallicity gradients, depending on the relative importance of recent star
formation activity in the central regions.
Conclusions. Our results suggest that inside-out formation is the main
process responsible for the metallicity and age profiles. The large dispersions in the
metallicity gradients as a function of stellar mass could be ascribed to the effects of
dynamical processes such as mergers, interactions and/or migration as well as those
regulating the conversion of gas into stars. The fingerprints of the inside-out formation
seem better preserved by the stellar metallicity gradients as a function of the half-mass
radius.
关键词：galaxies: abundances;galaxies: formation;galaxies: fundamental parameters
