3D-NTT: A New Instrument for the NTT Based on Versatile Tunable Filter Technology

Summary

The 3D-NTT will be a visitor instrument for the NTT, built by GEPI (Paris) and LAM (Marseille) with the collaboration of LAE (Montréal, Canada) and AAO (Australia). It is a spectro-imager offering two modes: a low resolution mode (100-5000) with a Tunable Filter, and a high resolution mode (5000 - 40 000) with a standard scanning Fabry-Perot. A large variety of programmes may be led with such an instrument as has been shown recently (1997-2003) with the Taurus Tunable Filter on the AAT and WHT. In the frame of a large scientific coollaboration, gathering European teams as well as collaborators from other countries, we propose a Large Programme (IOGA) dedicated to the study of ionized gas in galaxies, at low and high z, to be undertaken with the 3D-NTT. Nearby IR galaxies (IRGs) are the key to understanding the formation and evolution of galaxies, as they are believed to be the local counter-part of the numerous luminous starburst galaxies at high z. To understand the nature, origin and evolution of IRGs, we propose to map the star formation and kinematics in 500 galaxies and obtain dust extinction, metal abundances and electron density maps in 50 of them for obtaining a reference sample with high spectral and spatial resolution (sub-kpc) to be compared with distant objects being observed on the VLT (GIRAFFE, SINFONI). We will take advantage of both modes proposed by the instrument: high resolution mode with scanning Fabry Perot (FOV 5.5’ or 11’), and low resolution mode with Tunable Filter and larger field (FOV 20’). This mode will be used at high z to look for star forming galaxies around quasars with a range of intrinsic UV luminosity. Star forming galaxies exist in significant numbers around low power quasars and we want to check if this remains true around more distant and luminous quasars. This may be the first evidence that powerful UV fields can suppress or delay widespread star formation in galaxies and, as such, may provide important constraints on cosmological models.