We discuss the effects of collisional enhancement of Balmer lines on the determination of the primordial helium abundance. To this aim, we present a...

We compute photoionization models for the giant extragalactic H II region NGC 2363, and compare them with optical observational data. We show that models...

We have compared direct estimates of the ionizing photon flux from the stars observed within the H II region NGC 346 in the Small Magellanic Cloud with its...

The existence of an extended component of diffuse ionized gas (DIG) is a well-known property of spiral galaxies. The integrated ensuremath {{H}alpha }...

We analyze the physical conditions (density and temperature), chemical abundances, dynamics and kinematics of gas in HH529II, HH529III and HH204, photoionized...

Using the Ultraviolet Visual Echelle Spectrograph (UVES) at the Very Large Telescope (VLT), we study the photoionized Herbig-Haro object HH529 in two associated...

We carried out a photometric analysis of a sample of early-type galaxies in Abell~1689 at z = 0.183, using HST/ACS archive images in the rest-frame V band. We...

We present results of photometry and photopolarimetry of the Wolf-Rayet eclipsing binary system HD 5980 in the Small Magellanic Cloud, which underwent an...

This project presents the principal conclusions of a long series of infrared and visible observations of blazars taken from 1987-92. The data fall broadly into...