FUEGOS: Multi-Objects and 2-D Spectrograph for the VLT

FUEGOS, a multi-object spectrograph is built by a consortium of the following institutes: Observatoire de Paris-Meudon, Observatoire de Toulouse, Observatoire de Geneve, Osservatorio Astronomico di Bologna. Its goal is to provide the European community with a first class equipment allowing high and low resolution spectroscopy, in a large field, for stellar and extragalactic observations. This large field of view, 26 arcmin, provided by the VLT, is quite unique on 8m class telescopes and it is fully exploited by the use of optical fibres. The multi-object spectrograph, fibre fed, will be implemented on the Nasmyth platform of one 8m telescope. FUEGOS is made of two parts: a fibre positioner attached to the Nasmyth rotator and a spectrograph sitting on the Nasmyth platform. The two components are linked together with optical fibres. For the MEDUSA mode, the positioner is of the robot type, made of two heads travelling simultaneously, on a X-Y carriage. It locks magnetically 86 independent optical fibre bundles at object coordinates, on a metallic focal surface. 2-D or integral field spectroscopy is provided through a 600 fibres anamorphoser, called the ARGUS mode. An atmospheric dispersion corrector is supplied for this mode. The spectrograph is of classical type, based on a catadioptric design, with spherical optical correctors. It uses a premonochromator as orders selector. Spectral resolutions are ranging from 2 500 to 45000 and the detector is equivalent to a 4k × 4K CCD. The spectral range extends from 370 nm to 900 nm. Examples of applications of this instrument to Early Universe investigations as well in stellar as in extragalactic research are presented. The first light is expected at the dawn of the third millennium.