This thesis investigates the abundance and properties of extremely red galaxies (EROs). Although the existence of such conspicuous galaxies has been known for some time, there are numerous open questions regarding their nature, formation, and evolution. One reason is the number of different colour criteria applied to select EROs. Hence, different

Using spectroscopic data presented in Magrini et al. (cite{m03}), we have analyzed with the photoionization code CLOUDY 94.00 (Ferland et al. cite{ferland}) 11 Planetary Nebulae belonging to the spiral galaxy M 33. Central star temperatures and nebular parameters have been determined. In particular the chemical abundances of He/H, O/H, N/H, Ar/H

We present a detailed and uniform study of C, S, Zn and Cu abundances in a large set of planet host stars, as well as in a homogeneous comparison sample of solar-type dwarfs with no known planetary-mass companions. Carbon abundances were derived by EW measurement of two C I optical lines, while spectral syntheses were performed for S, Zn and Cu. We

Basaltic asteroids, classified as V-type in all taxonomies, are quite rare among the asteroid population. They are spectrally similar to 4 Vesta and to the basaltic achondrite meteorites, specifically the Eucrites, the Diogenites and the Howardites, known as HED meteorites. It has been suggested that all these objects, V-type asteroids and HED

One-third of present-day spirals host optically visible strong bars that drive their dynamical evolution. However, the fundamental question of how bars evolve over cosmological times has yet to be resolved, and even the frequency of bars at intermediate redshifts remains controversial. We investigate the frequency of bars out to z ~ 1 drawing on a

We present the discovery of an L0 companion to the nearby M1.5 dwarf G 239-25, at a projected distance of 31 AU. It is the faintest companion discovered so far in our adaptive optics survey of all known M dwarfs within 12 pc, and it lies at the stellar/substellar limit. Given the assumed age of the primary star, the companion is likely an extremely