The detection of spatially extended line emission in multiply imaged QSOs offers a new possibility to study the properties (kinematics and structure) of the ionized gas in the host galaxies of high-redshift QSOs. We have studied the arc of extended emission detected in Q2237+0305, finding that it arises from the core of the C III] λ1909 emission

This paper shows the different design concepts and techniques employed in the structural and thermal analysis of EMIR (Espectrografo Multiobjeto Infrarrojo), nowadays under development at the Instituto de Astrofisica de Canarias.

EMIR is a multiobject intermediate resolution near infrared (1.0 - 2.5 microns) spectrograph with imaging capabilities, to be mounted on the Gran Telescopio Canarias. After the successful results of the preliminary design review, EMIR optical system is being fixed. Detailed status of the solutions adopted for the optical system as well as the

ELMER is an instrument for the GTC designed to observe between 365 and 1000 nm. The observing modes for the instrument at Day One shall be: Imaging, Long Slit and Mask-Multi-object Spectroscopy, Slit-less multi-object spectroscopy, Fast Photometry and Fast short-slit spectroscopy, over a FOV of 4.2 arcmin diameter. Spectral resolutions of 250, 1000

We investigate the formation of polarization profiles induced by a magnetic field in the He I multiplet at 10830 Å. Our analysis considers the Zeeman splitting in the incomplete Paschen-Back regime. The effects turn out to be important and produce measurable signatures on the profiles, even for fields significantly weaker than the level-crossing

The accepted explanation of the observed dichotomy of two orders of magnitude between in situ measurements of electron density in H II regions, derived from emission line ratios, and average measurements based on integrated emission measure, is the inhomogeneity of the ionized medium. This is expressed as a ``filling factor", the volume ratio of