We analyse spectral images across the full emission line in H_α of the discs of M100 and M101, extracting for each HII region its spectrum, and for the more luminous and extended, spectra over a range of circular apertures. The principal components of these spectra are presented in log-log plots of luminosity vs. turbulent line-width. These plots

We use the catalogue of HII regions obtained from a high quality continuum-subtracted H_α image of the grand-design spiral galaxy NGC 7479, to construct the luminosity function (LF) for the HII regions (over 1000) of the whole galaxy. Although its slope is within the published range for spirals of the same morphological type, the unusually strong

We are currently performing a new analysis of the close environment of star-forming dwarf galaxies and its effects on their star-forming activity. For a sample of 142 thoroughly studied objects, we search the NASA Extragalactic Database for possible companion galaxies of any apparent luminosity and angular size. From a first analysis of a part of

The isophotal profiles and colour maps of a sample of 12 spiral galaxies allowed us to analyse the different structural components that compose them. These components were parameterized by performing a decomposition of the galaxy brightness profiles. Inferring the geometry for each component, we have obtained the spatial mass distribution and the

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)