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SALT’s Latest Addition: The Near Infrared Integral Field Spectrograph — Marsha Wolf
Jun 23 @ 11:00 am - 12:00 pm
SALT’s Latest Addition: The Near Infrared Integral Field Spectrograph
Dr Marsha Wolf (Senior Scientist, University of Wisconsin-Madison)
Washburn Astronomical Laboratories of the University of Wisconsin-Madison Astronomy Department has developed a near infrared (NIR) integral field spectrograph for the 11-meter Southern African Large Telescope (SALT). This instrument will be the first to extend SALT’s capabilities into the NIR, providing medium resolution spectroscopy at R = 2000-6000 over the wavelength range of 0.8 to 1.7 microns. Its integral field unit (IFU) is an elongated hexagonal bundle of 212 fibers, each of which subtends 1.3 arcsec on the sky, approximately matching the median site seeing. The IFU has on-sky dimensions of 29 x 18 arcsec, ideally suited for resolving nearby galaxies. A separate 38-fiber bundle simultaneously samples the sky. It can be adjusted to distances ranging from 48 to 159 arcsec from the object IFU with a gimbaled jaw in the Fiber Instrument Feed (FIF) that maintains telecentricity and common field angles for the object and sky bundles. Sky fibers are interleaved with object fibers along the 8-arcmin long spectrograph slit for optimizing sky subtraction. The spectrograph is cooled to -40 C in an enclosure beneath the telescope, with the cryogenic dewar inside this enclosure operating at 120 K via a separate closed cycle cooler. The spectrograph uses volume phase holographic gratings with an articulated camera, similar to RSS, for setup versatility. The spectrograph has been fully tested in the laboratory and is currently being installed and commissioned on SALT. I will present an overview of the instrument capabilities, some design highlights, performance results from laboratory characterization in Wisconsin, and the status and timeline of commissioning on the telescope.