Design and development of SWIMS: a near-infrared multi-object spectrograph for the University of Tokyo Atacama Observatory

Abstract

SWIMS (Simultaneous-color Wide-field Infrared Multi-object Spectrograph) is one of the first-generation instruments for the University of Tokyo Atacama Observatory (TAO; P.I.: Yuzuru Yoshii) 6.5-m telescope which is planned to be constructed at the world's highest site, the summit of Cerro Chajnantor (an altitude of 5,640 m or 18,500 ft) in northern Chile. By placing a dichroic mirror into the collimated beam, SWIMS is capable of wide-field (φ 9^'.6 with 0^".126 pixel^-1) two-color simultaneous imaging as well as multi-object spectroscopy (MOS) using cooled multi-slit masks covering the entire near-infrared spectra between 0.9 and 2.5 μm in a single exposure with low-to-medium spectral resolutions. Up to 20 user-defined slit masks as well as long slit masks are available. The field of view is covered with four 2048 x 2048 pixel HgCdTe focal plane arrays (HAWAII-2RG). Tests of the MOS slit mask exchanger motions have been completed successfully without any trouble under cryogenic environment. Further MOS tests will be performed at various tilt and rotation angles of the instrument using a telescope simulator. Also, a conceptual study of a compact and cryogenic wide-field integral field spectroscopy unit handled by the slit mask exchanger is now being carried out. The part of the current designs is optimized for installation on the Subaru Telescope for performance verification and early scientific observations prior to the construction of the TAO 6.5-m telescope. In this paper, we present the design and development status of the instrument.