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Surface-brightness profiles for early-type (S0-Sb) disks exhibit three main classes (Type I, II, and III). Type II profiles are more common in barred galaxies, and most of the time appear to be related to the bars Outer Lindblad Resonance. Roughly half of barred galaxies in the field have Type II profiles, but almost none in the Virgo Cluster do; this might be related to ram-pressure stripping in clusters. A strong textit{anti}correlation is found between Type III profiles (antitruncations) and bars: Type III profiles are most common when there is no bar, and least common when there is a strong bar.
Observations suggest that the structural parameters of disk galaxies have not changed greatly since redshift 1. We examine whether these observations are consistent with a cosmology in which structures form hierarchically. We use SPH/N-body galaxy-sc
Context. The structure of the inner parts of Be star disks (20 stellar radii) is well explained by the viscous decretion disk (VDD) model, which is able to reproduce the observable properties of most of the objects studied so far. The outer parts, on
By studying the stellar population properties along the radius in 15 nearby S0 galaxies, I have found that the outer stellar disks are mostly old, with the SSP-equivalent ages of 8-15 Gyr, being often older than the bulges. This fact puts into doubt
Evolutionary models of fast-rotating stars show that the stellar rotational velocity may approach the critical speed. Critically rotating stars cannot spin up more, therefore they lose their excess angular momentum through an equatorial outflowing di
In a hierarchical merging scenario, the outer parts of a galaxy are a fossil record of the galaxys early history. Observations of the outer disks and halos of galaxies thus provide a tool to study individual galaxy histories and test formation theori