Introduction

SWIFT is an adaptive optics fed integral field spectrograph currently being built at the University of Oxford. Operating in the I/ z band, SWIFT will take R~4000 spectra over an AO-corrected 10x20" field of view. SWIFT will be commissioned as a facility instrument on the 200-inch Hale telescope in mid-2008.

The main characteristics of the SWIFT instrument are:


Motivation

Galaxies are spatially extended sources, and as our understanding of their structure, kinematics and dynamics has improved, treating them as such has become increasingly important. At the same time the inadequacy of long-slit spectroscopy for extended sources has become increasingly apparent. Conventional long-slit (or aperture) spectroscopy limits the observer to obtaining information in only one (or zero) dimension on the sky (i.e. along the slit). The technique therefore throws away most of the spatial information about the source. Spatial information can be reconstructed from a sequence of observations, scanning across the slit, but with a commensurate loss in observing efficiency. In addition, constructing a homogenous two-dimensional dataset from a sequence of one-dimensional spectra is fraught with difficulties due to changing meteorologic and astrophysical conditions. Integral field spectroscopy (IFS) solves this problem by obtaining simultaneous spectra at every spatial element over a two-dimensional field in a single exposure. Current large diameter telescopes provide the enhanced sensitivity needed to spectroscopically study distant galaxies in a spatially resolved way. But telescope time is becoming increasingly precious, placing a premium on instruments to use it efficiently. Integral field spectroscopy provides high efficiency by reduced constraints on aligning faint objects within a narrow slit, and by providing spectra of extended sources in a single exposure.