We analyse the evolution with redshift of the radial gradient of oxygen abundances in spiral disks resulting from our MULCHEM chemical evolution models, computed for galaxies of different sizes or masses, studying the relationships between the gradients and galaxy characteristics as the stellar mass, the size, the gas fraction or the star formation rate for z < 4.

We describe the challenges inherent to low surface brightness imaging and present some early results from the Dragonfly Nearby Galaxies survey. Wide field, ultra-low surface brightness imaging (μg > 31 mag arcsec−2) of the first eight galaxies in the survey reveals a rich variety in the distribution of stars in the outskirts of luminous nearby galaxies. The mean stellar halo mass fraction is 0.009 ± 0.005 with a peak-to-peak scatter of a factor of > 100. Some galaxies in the sample feature strongly structured halos resembling that of M31, but three of the eight galaxies have halos that are completely undetected in our data. We conclude that spiral galaxies as a class exhibit a rich variety in stellar halo properties, implying that their assembly histories have been highly non-uniform. While the outskirts of some galaxies are dominated by halos with the rich substructures predicted by numerical simulations, in other cases the outermost parts of galaxies are simply the extrapolated smooth starlight from enormous stellar disks that closely trace neutral gas morphology out to around 20 scale lengths.

We show observations obtained with the integral field spectrometer OASIS for the centers of a sample of barred galaxies. The high spatial resolution of the instrument allows to distinguish spatially some structures within these regions as defined by stellar populations of different ages and metallicities. From these data we deduce important clues about the star formation history. But we advise that, in order to obtain adequately the evolutionary sequence, a combination of chemical and synthesis models might be necessary.

The growth and the evolution of the bar instability in stellar-gaseous disks embedded in a dark matter halo evolving in a cosmological framework is explored. We point out the impact of different gas fractions on the bar formation, inside disks of different disk-to-halo mass ratio.