In this paper we make a quantitative study of the hypothesis that the diffuse Hα emitted from the discs of spiral galaxies owes its origin to the ionizing photons escaping from H SHAPE II regions. The basis of the models is the assumption that a fraction of the Lyman continuum (Lyc) luminosity from the OB stars within each H SHAPE II region escapes

Five planetary nebulae (PNe) have been discovered in the nearby dwarf irregular galaxy. Emission line images were obtained using the Wide Field Camera of the 2.5 m Isaac Newton Telescope (INT) at La Palma (Spain). The candidate PNe were identified by their point-like appearance and relatively strong [O III] emission-line fluxes. They are located

We present the results of a new spectroscopic and photometric survey of the hot X-ray cluster 1E0657-56, at z=0.296. We determine the presence of a low velocity dispersion subcluster, which is offset from the main cluster position by 0.7 Mpc and =~ 600 km s-1. We determine the virial masses and total luminosities of the cluster and its subcluster

We present deep L- (3.8 μm) and M- (4.7 μm) band imaging with the Infrared Spectrometer and Array Camera (ISAAC) on the ESO Very Large Telescope (VLT) with unprecedented spatial resolution of the nearby Seyfert 2 galaxies NGC 7496 and NGC 7582 and the Seyfert 1 galaxy NGC 7213, all at a comparable distance. The unresolved nuclear component

Planet accretion onto solar type stars may significantly change the stellar atmospheric abundances of 6Li and 7Li if it takes place after the star has arrived at the main sequence. Ingestion of planets at an earlier phase will not affect theses abundances because of extensive pre-main sequence mixing and burning. We present quantitative estimates

The optical morphological and photometric properties of 79 low redshift radio galaxies are discussed. It is found that most radio galaxies are luminous bulge dominated systems similar to normal non-radio giant ellipticals. The average absolute magnitude of the sample is =-23.98, with a clear trend for FR I sources to be /~0.5 mag brighter than FR