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

We have analysed short-exposure high-resolution images obtained on the William Herschel Telescope (WHT), Big Telescope Azimuthal (BTA) and Canada-France-Hawaii Telescope (CFHT) in order to investigate mechanical vibrations that are capable of reducing the high angular resolution allowed by speckle-interferometric methods. After filtering the photon

Searching for subtle dips in brightness is all the rage among astronomers seeking Earthlike planets beyond the solar system.