We describe the design, construction, and expected performance of two new fiber integral field units (IFUs) -
HexPak and GradPak - for the WIYN 3.5m Telescope Nasmyth focus and Bench Spectrograph. These are the
first IFUs to provide formatted fiber integral field spectroscopy with simultaneous sampling of varying angular
scales. HexPak and GradPak are in a single cable with a dual-head design, permitting easy switching between
the two different IFU heads on the telescope without changing the spectrograph feed: the two heads feed a
variable-width double-slit. Each IFU head is comprised of a fixed arrangement of fibers with a range of fiber
diameters. The layout and diameters of the fibers within each array are scientifically-driven for observations
of galaxies: HexPak is designed to observe face-on spiral or spheroidal galaxies while GradPak is optimized
for edge-on studies of galaxy disks. HexPak is a hexagonal array of 2.9 arcsec fibers subtending a 40.9 arcsec
diameter, with a high-resolution circular core of 0.94 arcsec fibers subtending 6 arcsec diameter. GradPak is a
39 by 55 arcsec rectangular array with rows of fibers of increasing diameter from angular scales of 1.9 arcsec to
5.6 arcsec across the array. The variable pitch of these IFU heads allows for adequate sampling of light profile
gradients while maintaining the photon limit at different scales.
© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
Corey M. Wood ; Matthew A. Bershady ; Arthur D. Eigenbrot ; Scott A. Buckley ; John S. Gallagher, et al.
HexPak and GradPak: variable-pitch dual-head IFUs for the WIYN 3.5m Telescope Bench Spectrograph
", Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 84462W (September 24, 2012); doi:10.1117/12.926580; http://dx.doi.org/10.1117/12.926580