We have obtained a new, deep, wide-field optical imaging survey of the young Alpha Persei cluster which reveals a well-populated lower main sequence extending into the substellar mass regime. Subsequent infrared photometry confirms that most of the candidate brown dwarfs are indeed likely to be cluster members, with a predicted minimum mass of

We revise the physical conditions in the O++ zone of the planetary nebula NGC 6543, obtaining two different estimates of the electron temperature (Te) and one estimate of the electron density (Ne). The electron temperature is computed by means of two independent methods, the nebular-to-auroral ratio [O III] λ5007/λ4363 and the diagnostic diagram

This paper presents the results of a high-resolution imaging survey, using both ground-based and Hubble Space Telescope images, of a complete sample of nearby barred S0-Sa galaxies in the field, with a particular emphasis on identifying and measuring central structures within the bars: secondary bars, inner disks, nuclear rings and spirals, and off

We present the power spectrum of the fluctuations in the cosmic microwave background detected by the Very Small Array (VSA) in its first season of observations in its compact configuration. We find clear detections of first and second acoustic peaks at l~ 200 and ~550, plus detection of power on scales up to l= 800. The VSA power spectrum is in

We present new deep color-magnitude diagrams at different galactocentric distances of the Local Group dwarf spheroidal galaxy Fornax, and preliminary results on metallicities of individual stars, obtained from Ca II triplet spectroscopy. These data will be used to reliably derive the star formation and chemical enrichment histories of this galaxy

We constrain the basic cosmological parameters using the first observations by the Very Small Array (VSA) in its extended configuration, together with existing cosmic microwave background data and other cosmological observations. We estimate cosmological parameters for four different models of increasing complexity. In each case, careful