Extremely Large Telescope

Abstract:

Conducting resolved spectroscopy on large samples of very faint objects is a strong requirement for the Next Generation Space Telescope (NGST). We are presenting the IFMOS concept, a 1 to 5 microns integral field spectrograph developed under contract with ESA. Image slicers are feeding compact spectrograph modules with very few moving parts. The wide field survey mode has low spatial - low spectral resolution over a field similar to 46 x 40 arcsec(2) (0.19 arcsec per resolved element). The high spatial -high spectral resolution mode covers a field 3.8 x 2.6 arcsec(2) sampled at 0.05 arcsec, a pointed object mode at the diffraction limit of the telescope. A detailed opto-mechanical design has been produced, meeting the environmental requirements for the NGST payload.

Abstract:

The results from the IFMOS ESA 1-5 microns integral field multiobject spectrograph study are presented. A review of the science requirements indicates that integral field 2D spectroscopy is a powerful concept of great value for the NGST. We present the opto-mechanical design of the instrument, based on image slicers. A low resolution and a high resolution channels are working in parallel, with only one mechanical motion. The low resolution channel covers a field 40 x 46 arcsec(2) at R similar to 150, while the high resolution channel covers 2.6 x 3.8 arcsec at R = 3000. We show that the performances on single sources is equal or better than classical dispersive spectrographs, and yet very efficient on large galaxy surveys, and conclude that IFMOS is both scientifically attractive and technically feasible.