Realistic ab-initio 3D, radiative-hydrodynamical convection simulations of the solar granulation have been applied to Fe i and Fe ii line formation. In contrast to classical analyses based on hydrostatic 1D model atmospheres the procedure contains no adjustable free parameters but the treatment of the numerical viscosity in the construction of the

We limit the contribution of the hot intracluster gas, by means of the Sunyaev-Zeldovich effect, to the temperature anisotropies measured by the Tenerife experiment. The data are cross-correlated with maps generated from the ACO cluster catalog, the ROSAT PSPC catalog of clusters of galaxies, a catalog of superclusters and the HEAO 1 A-1 map of X

Various radial velocity surveys have now produced a number of candidates Very Low Mass Stars, Brown Dwarfs and Giant Extrasolar Planets to nearby G, K and M dwarfs. Building upon our experience in High Angular Resolution imaging, radial velocities measurements and atmosphere modeling, we discuss the detectability of Brown Dwarfs and Extrasolar

We have obtained NIR broad-band images in the J, H and K bands of 12 barred galaxies that make up our sample, during three observing runs with the 3.6 m Canada-France-Hawaii Telescope on Hawaii. We used the Montreal NIR camera (MONICA) equipped with a 256 x 256 pixel HgCdTe array detector with a projected size of 0.248 arcsec. One of the main data

Modern Acquisition and Guiding systems provide a range of services with the aim of optimizing telescope performance. These include wavefront sensing for active optics, fast guiding and measurement of seeing. On a segmented-mirror telescope, the Acquisition and Guiding system may also be expected to provide measurements of the piston errors between

El estudio de las galaxias enanas, especialmente de las compactas azules, ha sido de especial interés en las últimas décadas despues del exceso observado de estos objetos a z intermedios, lo cual puede ser interpretado como evidencia de la existencia de enanas con formación estelar alta en otra época y que actualmente han desaparecido. Especial