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

The spiral galaxy NGC 3521 exhibits apparently normal kinematic properties of gas and stars along its major axis. However, the analysis of the LOSVD reveals strong asymmetries. A decomposition of the LOSVD data with a two-Gaussian component model shows two counter-rotating stellar components. The observed kinematic decoupling is interpreted as a