The stellar content and stellar age distribution of the Pegasus Dwarf Irregular Galaxy are discussed in the light of deep CM diagrams for (V - R) and (V - I) color indices, complemented by Hα data. The CM diagrams of Pegasus show two structures-red tail and red tangle-which denote the presence of intermediate-age and old stars in the galaxy. After

Optical spectroscopy of three recently discovered BL Lacs (PG 1246+586, PG 1424+240 and PG 1437+398) in the Palomar-Green optical survey is presented. The three sources have featureless spectra and the continuum is well represented by a power law model with slopes typical of BL Lac objects. The observations together with data at other frequencies

SE HAN REALIZADO OBSERVACIONES ESPECTROSCOPICAS CON RESOLUCION ESPACIAL Y RESOLUCION ESPECTRAL INTERMEDIA PARA UNA MUESTRA DE NEBULOSAS PLANETARIAS (NP) EXTENSAS REPRESENTATIVAS DE DIFERENTES CLASES. SE HAN INCLUIDO NP CON MULTIPLES CAPAS (M 1-46, NGC 2438, NGC 5882 Y NGC 6720), BIPOLARES (K 4-55, M 1-75, NGC 2440 Y NGC 2818) Y DEFICITARIAS EN

We present the results of Thuan & Gunn r CCD imaging observations of the Universidad Complutense de Madrid (UCM) sample of emission-line galaxies (ELGs), selected by the presence of Hα emission in low-resolution objective prism spectra. In this work we characterize photometrically and morphologically a total of 212 objects from the UCM survey. This

This thesis is made of three main parts. In the first one a sample of 55 galaxies with an active nucleus (Seyfert 1, Seyfert2 and LINERs) is analysed; these were observed with the 4.2m WHT and 1m JKT in CCD narrow band H-alpha +[NII] and [OIII] to map the distribution of HII regions and the morphology of the circumnuclear extended emission

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