Slicer based integral-field spectroscopy at the diffraction limit
University of Oxford
Integral-field spectroscopy (IFS) measures the spectra of all field points in a two-dimensional field-of-view simultaneously and hence makes very efficient use of telescope time. Over the last 20 years it has evolved from a niche instrumental technique in to a mainstream astronomical tool. IFS has a wide range of astronomical applications from solar system science, high contrast imaging of exoplanets to studying the properties of galaxies at any redshift out to first light. This versatility has led to almost all ground-based telescopes, as well as some space-borne observatories, having IFS capability and IFS’ are the natural choice for first light instruments on future extremely large telescopes. Only few IFSs are fed by adaptive optics and can take advantage of diffraction limited performance. I describe current and forthcoming instruments that will make use of the diffraction limit, in particular I focus on IFS in operation on-sky that are slicer-based, a technology that has been thought to limit the image quality at the diffraction limit because of differential aberrations between slices originating in the spectrograph. I will describe the SINFONI and SWIFT instruments that have demonstrated that slicer-based IFS not only deliver very good image quality at the diffraction limit, but that they also have the advantages of a more efficient use of detector real estate while providing a larger simultaneous wavelength coverage compared to lenslet based IFS. As such they are the ideal instruments to exploit the high angular resolution and high sensitivity of future ELTs.