Coronagraph Imager with Adaptive Optics (CIAO): Description and first results

We describe a near-infrared coronagraphic camera built for use with the Subaru 8.2-m telescope and its adaptive optics system. The purpose of this instrument CIAO (Coronagraph Imager with Adaptive Optics) is to obtain high-resolution (0.06 arcsec at 2 micron) images of faint objects in close vicinity of bright objects at infrared wavelengths. Such a desire is strong in astronomy, especially in the study of companion brown dwarfs and extra-solar planets, circumstellar disks around both young stellar objects and main-sequence stars, jets and outflows from both young stars and evolved stars, circumnuclear regions around AGNs, and host galaxies of QSOs. CIAO is a 1-5 micron camera with two focal plate scales: 22 milli-arcsec/pixel and 11 milli-arcsec/pixel. The camera is equipped with the standard broad-band filters (zJHKKsL'M') as well as a number of narrow-band filters. Choice of masks, filters and camera lenses and optical alignment with collimator and detector are made with cryogenic motors. CIAO utilizes one ALLADIN II (1024x1024 InSb) "science"-grade detector array manufactured by SBRC. Occulting masks whose diameter ranges from 0.1 to 3 arcsec and several types of pupil masks are selectable, all cooled down to about 60 K and the detector is cooled to about 30 K. Also available are a R less than or similar to 1000 grism with coronagraphic slits and a polarimetric module. We also present preliminary results from the first commissioning run (without the adaptive optics system) at the Subaru telescope.