We present a detailed, comparative study of low angular degree solar p-mode variations extracted by analyses of two sets of observational data. These were collected by the ground-based Birmingham Solar-Oscillations Network (BiSON) and the Global Oscillations at Low Frequency (GOLF) instrument on board the ESA/NASA SOHO satellite. The ~5.5 yr period

We investigate the possibility of measuring magnetic field strength in G-band bright points through the analysis of Zeeman polarization in molecular CH lines. To this end we solve the equations of polarized radiative transfer in the G band through a standard plane-parallel model of the solar atmosphere with an imposed magnetic field and through a

The luminosity-size and mass-size distributions of galaxies out to z~3 are presented. We use very deep near-infrared images of the Hubble Deep Field-South in the Js, H, and Ks bands, taken as part of FIRES at the VLT, to follow the evolution of the optical rest-frame sizes of galaxies. For a total of 168 galaxies with Ks,AB~2×1010 h-2 Lsolar) at 2

We estimate the dust extinction laws in two intermediate-redshift galaxies. The dust in the lens galaxy of LBQS 1009-0252, which has an estimated lens redshift of zl~=0.88, appears to be similar to that of the SMC, with no significant feature at 2175 Å. Only if the lens galaxy is at a redshift of zl~=0.3, which is completely inconsistent with the

We present the results of a near-infrared imaging study of the host galaxies of 17 quasars in the redshift range 1 RLQ(host)=-27.55+/-0.12 and K>RLQ(host)=-26.83+/-0.25]. Comparison with other samples of quasar hosts at similar and lower redshift indicates that the difference in the host luminosity between RLQs and RQQs remains the same from z=2 to

Esta tesis presenta los análisis cuantitativos de espectros ópticos y UV de una muestra de estrellas supergigantes de tipo B en la Vía Láctea, M33 y NGC300, con objeto de determinar los parámetros fundamentales, así como sus composiciones químicas y comparar los resultados obtenidos con las predicciones de los modelos de evolución estelar y