We have recently commissioned a novel infrared (0.9 1.7 pm) integral field spectrograph
(IFS) called the Wide Integral Field Infrared Spectrograph (WIFIS). WIFIS is a unique
instrument that offers a very large field-of-view (50" x 20") on the 2.3-meter Bok
telescope at Kitt Peak, USA for seeing-limited observations at moderate spectral resolving
power. The measured spatial sampling scale is 1 x 1" and its spectral resolving power
is R 2, 500 and 3, 000 in the zJ (0.9 1.35 pm) and Hshort (1.5 1.7 pm) modes, respectively.
WIFIS's corresponding etendue is larger than existing near-infrared (NIR) IFSes, which
are mostly designed to work with adaptive optics systems and therefore have very narrow
fields. For this reason, this instrument is specifically suited for studying very
extended objects in the near-infrared such as supernovae remnants, galactic star forming
regions, and nearby galaxies, which are not easily accessible by other NIR IFSes.
This enables scientific programs that were not originally possible, such as detailed
surveys of a large number of nearby galaxies or a full accounting of nucleosynthetic
yields of Milky Way supernova remnants. WIFIS is also designed to be easily adaptable
to be used with larger telescopes. In this paper, we report on the overall performance
characteristics of the instrument, which were measured during our commissioning runs
in the second half of 2017. We present measurements of spectral resolving power, image
quality, instrumental background, and overall efficiency and sensitivity of WIFIS
and compare them with our design expectations. Finally, we present a few example observations
that demonstrate WIFIS's full capability to carry out infrared imaging spectroscopy
of extended objects, which is enabled by our custom data reduction pipeline.
