La tesis consiste en un trabajo bien completo, empezando de una parte puramente observacional, donde imágenes de galaxias obtenidas por el tensinando en el Observatorio del Roque de los Muchachos se reducen y se presentan de forma fotométrica calibrada. Después el autor aplica unas técnicas cuya base estaba desarrollada por colegas, pero que nunca

The results of Hα photometry of a sample of early-type galaxies belonging to nearby compact groups are presented. Over 75% of the galaxies in the sample were detected in Hα, a result that we have interpreted as proof of the presence of a warm interstellar medium within them. Comparing the Hα luminosities of the galaxies in our sample with those of

Spectral synthesis calculations in stellar (magnetized) atmospheres are based on the solution of the radiative transfer equation (RTE) for polarized light. The thermodynamic and magnetic properties of the atmospheres, along with the radiation field, completely specify the basic ingredients of the RTE, after which numerical methods have to be

IAUC 7022 available at Central Bureau for Astronomical Telegrams.

Time series of two-dimensional spectra were taken with the Göttingen 2D spectrometer at the VTT on Tenerife in 1996. They were investigated for Doppler velocities and velocity oscillations in small spots and pores of rapidly evolving sunspot groups. For the present measurements the magnetically insensitive lines Fe i 557.6 nm and Fe i 709.0 nm were