Sensitivity of a Ground‐based Infrared Interferometer for Aperture Synthesis Imaging

Abstract

ABSTRACTSensitivity limits of ground‐based infrared interferometers using aperture synthesis are presented. The motivation for this analysis is to compare interferometers composed of multiple large telescopes and a single giant telescope with adaptive optics. In deriving these limits, perfect wave front correction by adaptive optics and perfect cophasing by fringe tracking are assumed. We consider the case in which n beams are pairwise combined at n(n - 1)/2 detectors (nC2 interferometer) and the case in which all the n beams are combined at a single detector (nCn interferometer). Our analysis covers broadband observations by considering spectral dispersion of interference fringes. In the read‐noise limit, the nCn interferometer with one‐dimensional baseline configuration is superior to the nC2 interferometer, while in the background limit, the advantage of the one‐dimensional nCn interferometer is small. As a case study, we compare the point‐source sensitivities of interferometers composed of nine 10 m diameter telescopes and a 30 m diameter single telescope with adaptive optics between 1 and 10 μm for 10 σ detection in 1 hr. At J and H, the sensitivities of the interferometers are limited to 25–24 mag by read noise and OH airglow background, while that of the single telescope is limited to 28–26 mag by OH airglow background. Longward of 2 μm, the sensitivities of the interferometers and the single telescope are all limited by instrumental thermal background. At K, the sensitivities of the interferometers are around 23 mag, while that of the single telescope is 27 mag. At N, the sensitivities of the interferometers are around 10.7 mag, while that of the single telescope is 14.4 mag.