We have characterized the physical properties (electron temperature, density and metallicity) of the ionized gas and the ionizing population (age, metallicity and presence of Wolf-Rayet stars) in the Lynx arc, an HII galaxy at z= 3.36. The ultraviolet doublets (i.e. CIII], SiIII] and NIV) imply the existence of a density gradient in this object

The unprecedented spatial resolution of Chandra is allowing reliable identifications of the counterparts of M31 X-ray sources at other wavelengths. Comparisons with Hubble Space Telescope data, recent ground-based Local Group Survey data, and Very Large Array radio data reveal many interesting objects. These include newly-resolved X-ray/optical

The analysis of the light distribution of galaxy is a crucial step in studying their structural components and therefore it plays a key role in understanding the processes that led to galaxy formation and evolution. For example, this allows to investigate the 3D shape of bulges and disks or when combined with kinematic data to derive the mass

In this thesis, we investigate the emergence of kinetic processes in finite quantum systems. We first generalize the Redfield theory to describe the dynamics of a small quantum system weakly interacting with an environment of finite heat capacity. We then study in detail the spin-GORM model, a model made of a two-level system interacting with a

We present the first results of intermediate resolution spectral observations in the CaII triplet region obtained with VLT/FLAMES for 3 dwarf spheroidal galaxies in the Local Group: Sculptor, Fornax and Sextans. For each galaxy, we obtained accurate velocity and metallicity measurements for hundreds of stars out to and beyond the tidal radius: this

H-alpha emission both traces diffuse ionised nebulae and is commonly prominent in the spectra of pre- and post-main-sequence stars and interacting binaries. Since these are mostly relatively short-lived phases of evolution, they represent a minority of objects in a mature galaxy like our own at any one time. In the case of interacting binaries