A spectroscopic study of the Trapezium Cluster stars in the Orion Nebula is presented. We determine the stellar parameters of the two B0.5V stars theta(1}_{) Ori A and D. The variable spectral features of theta(1}_{) Ori C are studied, and some consequences on the modeling of the stellar atmosphere are considered.

The redshift distribution of flat-spectrum radio sources with 5 GHz flux densities S5>~5 mJy is a key component in using current radio lens surveys to probe the cosmological model. We have constructed the first flat-spectrum radio sample in the flux density range 3-20 mJy. Our new sample has 33 sources; we have determined the redshifts of 14 of

Only less than 150 Wolf-Rayet galaxies are actually known. Many of them are dwarf or irregular galaxies, and some show close companion objects. Peculiar morphological features, like mergers or tidal tails connecting small stellar aggregates, are found in many cases. Therefore, we think that interaction could be an important mechanism that triggers

We have imaged the planetary nebula (PN) NGC 246 in the near-ultraviolet wavelengths [Ne V] 342.6 nm, the Bowen fluorescence line of O III at 344.4 nm, and a nearby line-free region centered on 338.6 nm, as well as Hα, [O III] 500.7 nm, and [S II] 673.0 and 671.5 nm. Imaging in the 344.4 nm line is necessary to deconvolve contamination of the [Ne V

The Century Survey Galactic Halo Project is a photometric and spectroscopic survey from which we select relatively blue stars (V-R

Here we stress some of the major differences between supergalactic winds and giant superbubbles evolving into the giant low density haloes of galaxies. Both events are the result of massive bursts of star formation within the densest regions of the host galaxies. However, supergalactic winds are able to channel the metals produced by the recent