Design Overview and Performance of the WIYN11The WIYN Observatory is a joint facility of the University of Wisconsin-Madison, Indiana University, Yale University, and the National Optical Astronomy Observatories. High Resolution Infrared Camera (WHIRC)

Abstract

ABSTRACTWe present the design overview and on-telescope performance of the WIYN High Resolution Infrared Camera (WHIRC). As a dedicated near-infrared (0.8–2.5 μm) camera on the WIYN Tip-Tilt Module (WTTM) port, WHIRC can provide near-diffraction-limited imaging with an FWHM of ∼0.25′′ at Ks with active WTTM correction and does deliver typical imaging with an FWHM of ∼0.6′′ without WTTM. WHIRC uses a 2048 × 2048 HgCdTe array from Raytheon’s VIRGO line, which has been developed for the VISTA project. The WHIRC filter complement includes J, H, Ks, and 10 narrowband filters. WHIRC’s compact design makes it the smallest near-infrared camera with this capability. We determine a gain of 3.3 ± 0.2 e- ADU-1 via a photon transfer analysis and a readout noise of ∼19 e-. A measured dark current of 0.13 e- s-1 indicates that the cryostat is extremely light tight. A plate scale of 0.099′′ × 0.10′′ pixel-1 results in a field of view (FOV) of 3.3′ × 3.4′, which is a compromise between the highest angular resolution achievable and the largest FOV correctable by WTTM. Measured throughput values (∼0.27 ± 0.02 in H band) are consistent with those predicted for WHIRC based on an analysis of individual optical elements and detector quantum efficiency (QE). WHIRC’s photometric quality is better than ∼0.02 magnitudes in all bands. WHIRC is a general use instrument at the WIYN telescope enabling high-definition near-infrared imaging studies of a wide range of astronomical phenomena including star formation regions, stellar populations, and interstellar medium in nearby galaxies, high- z galaxies, and transient phenomena.