Integral field spectroscopy with the Gemini Multiobject Spectrographs

Abstract

The most innovative feature of the Gemini multiobject spectrographs (GMOS) is the capability for integral field spectroscopy. This will allow the Gemini telescopes to obtain spectra over a contiguous rectangular field of area 50 arcsec2 with a sampling of 0.2 arcsec. The field will be reformatted into two long slits so that each element in the field is dispersed into a long spectrum containing up to 900 resolution elements at spectral resolutions up to 10,000. Background subtraction will be carried out via a separate field with identical optical characteristics. This will support a number of background-subtraction techniques including beam-switching. The integral field unit will be loaded into the focal plane in the same way as a slit mask to allow a rapid changeover between integral field and aperture spectroscopy. The design employs a combination of optical fibers and microlens arrays with enlarging fore-optics. The fibers give the desired reformatting ability to maximize the length of the spectrum while the microlenses provide both contiguous field coverage and optimal matching to the slow telescope and spectrograph optics. The integral field capability may be augmented and upgraded by adding different units. Of particular interest are options for finer spatial sampling (0.1 arcsec) and for operation in the near-infrared. Show more