Executive Summary

SWIFT is an adaptive optics assisted integral field spectrograph covering the I and z astronomical bands (0.65 -- 1.0 microns) . It builds on two recent developments (i) the improved ability of second generation adaptive optics systems to correct for atmospheric turbulence at wavelengths <1micron, and (ii) the availability of CCD array detectors with high quantum efficiency at very red wavelengths (close to the silicon band edge cut-off). Combining these with a state-of-the-art integral field unit design using an all-glass image slicer, SWIFT's design provides very high throughput and low scattered light. It is a dedicated integral field spectrograph, specifically built to address a range of interesting astrophysical questions.

One of the highlights of SWIFT's scientific capabilities will be the study of galaxies, proto-galaxies, and their active nuclei at very high redshifts (5 < z < 7), through observations of the morphology, kinematics and dynamics of their Ly-alpha emission, red-shifted into the SWIFT wavelength range. The recent discovery of QSOs at z > 6 by SDSS, with follow-up spectroscopic studies indicating that the epoch of reionization occurs at higher redshifts than previously expected, highlights the importance of studies in this redshift range. Furthermore, studying the kinematics of the large, spatially extended, Ly-alpha haloes surrounding QSOs at high redshift will help establish the crucial connection between the visible and dark matter, thus providing constraints to theoretical models of structure formation in the early Universe.

Another area of research where SWIFT will excel is the measurement of dynamical masses of galaxies at moderate redshifts (1 < z < 1.7), in the range termed as the redshift desert. Although multi-object spectrographs at large telescopes also target this problem, the measurement of masses of galaxies that are spatially marginally resolved with a single long slit is fraught with peril. SWIFT data cubes, providing a complete 2D map of the kinematics at high spatial resolution, will lead to robust and secure mass estimates. These, in turn, will determine the evolution of the Tully-Fischer and Faber-Jackson relations with redshift.,

The super-massive black holes thought to lurk in the nuclei of every galaxy in the local Universe form another topic where SWIFT can make an impact. Its unique combination of high sensitivity and good angular resolution will allow SWIFT to carry out a census of stellar dynamical mass determinations of super-massive black holes in nearby galaxies. Comparable instruments, working at infrared wavelengths, are limited to studying a few prototypical objects due to the higher night-sky background limiting their sensitivity.

SWIFT's uniqueness stems from three improvements over existing instruments of a similar nature: (1) a state-of-the-art image slicer design for the integral field unit (IFU), made of sets of flat glass mirrors using conventional polishing techniques, that provides high throughput and very low scattering (critical at these short wavelengths). Coupled with a compact spectrograph design with few moving parts, it boosts the sensitivity of SWIFT by a factor of 2 over current fibre-coupled IFUs (which are often add-ons to long-slit/multi-object spectrographs), whilst maintaining a substantial field of view (4000 spatial elements, arranged in a 44x89 format), (2) a second generation adaptive optics system that provides substantial improvements over the atmospheric seeing at these short wavelengths (not a part of SWIFT). SWIFT is optimized to take full advantage of the gain in image quality and encircled energy, with 0.15" pixels providing a 6.6"x13.4" field of view (a second pixel scale with 0.1" per pixel, and 4.4" 8.9" FoV is also provided), and (3) a large format CCD detector with very high quantum efficiency (60% at 950 nm) and low fringing, suitable for moderate resolution spectroscopy (R ~ 3500) covering the 0.65 -- 1.0 micron window.

SWIFT is funded through a Marie Curie Excellence Grant from the European Commission, and via supporting funds from the University of Oxford. A compact, light-weight spectrograph built by a dedicated team of researchers from the Oxford University Astrophysics Instrumentation group, it is expected to see first light in early 2008.