We have analyzed archival Hubble Space Telescope Advanced Camera for Surveys images in g and z of the globular cluster (GC) systems of 53 ellipticals in the Virgo Cluster, spanning massive galaxies to dwarf ellipticals (dEs). Several new results emerged. (1) In the giant ellipticals (gEs) M87 and NGC 4649, there is a correlation between luminosity

We have modelled, for the cases of Milky Way and M31, the effects on the galactic discs, of the arrival at high velocity (≥150 km s-1) of giant HI clouds, with masses of up to 108M&sun;. Predictions are compared with the detailed structure of the observed rotation curves for these two galaxies. The model explains the rises and falls observed at

En esta tesis presentamos un estudio morfológico, fotométrico y espectroscópico detallado de una muestra de 20 galaxias Wolf-Rayet (WR). Las galaxias WR son un subtipo de las galaxias H II cuyo espectro integrado muestra líneas de emisión propias de estrellas WR, indicando la presencia de una población importante de estrellas masivas y la juventud

The atmosphere of the Sun is being stirred and reshaped continuously through the emergence of magnetized plasma from the convection zone. Magnetic elements coming from the solar interior produce structures in the photosphere, chromosphere and corona in a bewildering range of length and time scales, from the smallest magnetic tubes to the largest

To model the emergence of magnetic fields at the photosphere, we carried out 3D magneto-hydrodynamics (MHD) simulations using the MURaM code. Our simulations take into account the effects of compressibility, energy exchange via radiative transfer and partial ionization in the equation of state. All these physical ingredients are essential for a

The radiative transfer equation (RTE) gives us information about how the light streams through the medium. It must be inverted in order to obtain the properties of the medium that generated the observation. While there are a number of well discussed methods to approach the solution of the inversion, none of them is suitable for the real-time