The study of the IR emission from Seyfert galaxies is of key importance for understanding the origin of the extraordinary nuclear activity seen in these objects as well as the differences between the various Seyfert types. Two important problems remain unresolved. For instance, whether the IR radiation from Seyfert galaxies is of mostly thermal or

We have digitally co-added APM scans of 13 Kodak TechPan films of the SE region of the Virgo cluster of galaxies. The ~ 6.2degr x 6.2degr field of the R-band films combined with the resolution of ~ 2 arcsec pixel(-1) results in data file sizes of about 222 MBytes. The 13 scanned films have been aligned, co-added, corrected for vignetting effects

We report the first reliable measurement of the nebular [OI] 5577AA emission line in the Orion nebula. The use of diagnostic diagrams using the nebular [OI] and [NI] lines and the comparison with available photoionization models, indicate that the bulk of the nebular emission of the neutral ionic species in the Orion nebula is produced in regions

We have performed a detailed oxygen abundance analysis of 23 metal-poor (-3.0 [Fe/H] -0.3) unevolved halo stars and one giant through the OH bands in the near UV, using high-resolution echelle spectra. Oxygen is found to be overabundant with respect to iron in these stars, with the [O/Fe] ratio increasing from 0.6 to 1 between [Fe/H] = -1.5 and

We present spatially resolved echelle spectroscopy, obtained at high spectral resolution, for 15 multiple-shell planetary nebulae. Most exhibit faint detached halos (IC 1295, MA 3, M 2-2, M 2-40, NGC 6804, NGC 6826, NGC 6884, NGC 6891, NGC 7662, PM 1-295, and Vy 2-3). Furthermore, we have included some with attached shells (IC 1454, K 1-20, K 3-73

The Cometary Knots in the Helix Nebula have shown themselves to be formed of a head which is a photoionized surface, optically thick to Lyman continuum radiation, on the central star facing sides of neutral clumps and a cometary tails photionized by the diffuse radiation field. In this study we will present the results of a photoionization model of