The spectroscopic parallaxes in the Hipparcos catalogue can be used to translate absolute stellar fluxes observed at Earth to the fluxes emerging at the stellar surface for nearby stars. The comparison of these fluxes with the predictions of theoretical model atmospheres allows us to determine the effective temperature and the metallicity of the

We report the detection of a bisymmetric nuclear spiral structure in the spiral galaxy NGC 5248. The two red spiral arms can be followed for about 3 arcsec, before they appear to end inside the radius of the circumnuclear starburst `ring' at about 5.5 arcsec or 400 pc distance from the nucleus. We combine our near-infrared Canada-France-Hawaii

We present an objective and automated procedure for detecting clusters of galaxies in imaging galaxy surveys. Our Voronoi Galaxy Cluster Finder (VGCF) uses galaxy positions and magnitudes to find clusters and determine their main features: size, richness and contrast above the background. The VGCF uses the Voronoi tessellation to evaluate the local

We have digitally coadded APM scans of 13 Kodak TechPan films of the SE region of the Virgo Cluster of galaxies. The ~6.2°×6.2° field of the R-band films combined with the resolution of ~2 arcsec pixel^- results in data-file sizes of about 222 MBytes. The 13 scanned films have been aligned, coadded, corrected for vignetting effects and cleaned of

I present an evolutionary stellar population synthesis model which predicts spectral energy distributions, SEDs, for simple old single-metallicity stellar populations, SSPs, in the wavelength intervals λλ 3856-4476Å and 4795-5465Å at a resolution of FWHM$equals;1.8 $Aring;, on the basis of an extensive empirical spectral library composed of ~550

We quantify the energy radiated through all the collisional lines in a photoionized nebula in the presence of temperature fluctuations in the form of hot spots caused by an unknown heating process. The excess energy radiated in the lines as a result of the fluctuations is found to scale linearly with their mean-square amplitude t2. We find that the