A search for star-forming objects belonging to tidal tails has been carried out in a sample of deep Hα images of 16 compact groups of galaxies. A total of 36 objects with Hα luminosities greater than 1038 ergs s-1 has been detected in five groups. The fraction of the total Hα luminosity of their respective parent galaxies shown by the tidal objects

Based on the best observations of extragalactic H II regions of low metallicity available in the literature we redetermine the primordial helium abundance, Y[p], taking into account all the observed He I line intensities with the exception of those strongly affected by underlying absorption. We derive He/H, N[e](He II), T[e](He II), and τ (3889)

We have used photometric images of ten barred galaxies in the B and I bands to infer the geometrical and dynamical parameters of their bars: Their length, (R_bar), their strengths, (S_b), and their corotation radii, (R_CR). These parameters have been obtained studying azimuthal profiles from the B and I band images of the galaxies. We find that R

We are currently analysing image data for a large sample of blue compact dwarf galaxies (BCDs), obtained in multiple optical broad- and narrow-band filters. We present preliminary results of a multi-band analysis of two typical BCDs, Mrk 5 and I Zw 123, for which surface-brightness profiles, colour profiles, colour maps and H_α equivalent-width

We investigate a one-zone chemo-photometric evolutionary model of truncated spiral galaxies with and without starbursts in order to explore the origin of the spectrophotometric properties of S0s. First, we show that 1) the tight U-V colour-magnitude (CM) relation cannot reject the model with a starburst and 2) the model with a starburst can explain

In recent years, a lot of effort has been put into better understanding the physical processes which lead a sunlike star, at the end of its evolution, to lose its gaseous envelope and die as a slowly cooling white dwarf. The most spectacular phase of this late evolution is the one in which the ejected envelope is made fluorescent by the energetic