Super-GIRAFFE: The Next Generation High Multiplex Optical Spectrograph with d-IFUs

Abstract

We propose to build super-GIRAFFE, a high multiplex (several hundred or more fibers), very efficient (total throughput >20%) spectrograph with deployable IFUs (20–30) that simultaneously covers the full optical band (0.35–1.0 μm) at two spectral resolutions (R∼5000 and 15 000–20 000). The total field of view of the instrument would be like that of the current FLAMES/GIRAFFE (25′). Our focus with such an instrument is to make it highly efficient, with a throughput similar to that of a simple multi-slit spectrometer, and high multiplex. Such a spectrograph could be build cheaply and quickly by upgrading the fiber positioner of FLAMES/GIRAFFE. By building it quickly, we believe the VLT will have a unique capability for tackling such important issues as the growth of large scale structure, the tomography of the inter-galactic medium, the spatially-resolved dynamics and emission/absorption line distributions of high redshift galaxies, stellar populations in the halo of the MW and in other nearby galaxies, etc., before anyone else. Also, “keeping it simple” has the advantage that several copies could be built, allowing for truly significant surveys to start within a few years, rather than within a decade. We also discuss possible enhancements to this baseline design.