The development of WIFIS: a wide integral field infrared spectrograph

Abstract

We present the current results from the development of a wide integral field infrared spectrograph (WIFIS). WIFIS offers an unprecedented combination of etendue and spectral resolving power for seeing-limited, integral field observations in the 0.9 − 1.8 µm range and is most sensitive in the 0.9 − 1.35 µm range. Its optical design consists of front-end re-imaging optics, an all-reflective image slicer-type, integral field unit (IFU) called FISICA, and a long-slit grating spectrograph back-end that is coupled with a HAWAII 2RG focal plane array. The full wavelength range is achieved by selecting between two different gratings. By virtue of its re-imaging optics, the spectrograph is quite versatile and can be used at multiple telescopes. The size of its field-of-view is unrivalled by other similar spectrographs, offering a 4.5 × 12 integral field at a 10-meter class telescope (or 20 × 50 at a 2.3-meter telescope). The use of WIFIS will be crucial in astronomical problems which require wide-field, two-dimensional spectroscopy such as the study of merging galaxies at moderate redshift and nearby star/planet-forming regions and supernova remnants. We discuss the final optical design of WIFIS, and its predicted on-sky performance on two reference telescope platforms: the 2.3-m Steward Bok telescope and the 10.4-m Gran Telescopio Canarias. We also present the results from our laboratory characterization of FISICA. IFU properties such as magnification, field-mapping, and slit width along the entire slit length were measured by our tests. The construction and testing of WIFIS is expected to be completed by early 2013. We plan to commission the instrument at the 2.3-m Steward Bok telescope at Kitt Peak, USA in Spring 2013.

The wide integral field infrared spectrograph: commissioning results and on-sky performance

“…The critical aspects of WIFIS's optical and mechanical design details are discussed elsewhere. [8][9][10] For reference, we show the overall optical and mechanical layout of WIFIS in Figure 1. Tables 1 and 2 provide the details of the integral field spectrograph and the AGC respectively.…”

“…A mapping of the slices is shown in the right panel, which is discussed in greater detail in an earlier paper. 8 The data have been flatfielded, background subtracted and placed on a uniform wavelength and spatial grid after wavelength and spatial calibrations. The dispersion axis is along the x-axis with the shortest wavelength on the left.…”

“…This instrument, called the Wide Integral Field Infrared Spectrograph (WIFIS) * , is the widest field infrared IFS that currently exists, which allows spectroscopy at moderate spectral resolving power (R ∼ 3, 000). It is also the largest etendue (AΩ product) infrared IFS, 8 allowing efficient observations of very extended objects. The original concept and design details for this instrument can be found in previous work.…”

“…The original concept and design details for this instrument can be found in previous work. [8][9][10] This powerful new instrument will be able to image large sections of nearby galaxies in a single shot and complement current visible-light IFS surveys of nearby galaxies. We organize the paper as follows: in Section 2, we discuss the scientific drivers for the instrument; in Section 3, we outline the overall design and measured parameters for the instrument; in Section 4, we highlight the calibration and observation techniques we have developed for WIFIS; in Section 5, we summarize the features of the WIFIS data reduction pipeline; in Section 6, we present the overall performance of the instrument and example results and outstanding performance issues; and finally in Section 7, we summarize our findings.…”

“…The central slice is the first slice, and the slices alternate as one moves further from the centre of WIFIS's field. A mapping of the slices is shown in the right panel, which is discussed in greater detail in an earlier paper 8. The data have been flatfielded, background subtracted and placed on a uniform wavelength and spatial grid after wavelength and spatial calibrations.…”