Katsumi Imi

Subaru Prime Focus Camera — Suprime-Cam

We have built an 80-mega pixels (10240 ×8192) mosaic CCD camera, called Suprime-Cam, for the wide-field prime focus of the 8.2m Subaru telescope. Suprime-Cam covers a field of view 34 � ×27 � , a unique facility among the 8-10m class telescopes, with a resolution of 0. �� 202 per pixel. The focal plane consists of ten high-resistivity 2k ×4k CCDs developed by MIT Lincoln Laboratory, which are cooled by a large Stirling-cycle cooler. The CCD readout electronics was designed to be scalable, which allows the multiple read-out of tens of CCDs. It takes 50 seconds to readout entire arrays. We designed a filter-exchange mechanism of the jukebox type that can hold up to ten large filters (205 ×170 ×15mm 3 ). The wide-field corrector is basically a three-lens Wynne-type, but has a new type of atmospheric dispersion corrector. The corrector provides a flat focal plane and an un-vignetted field of view of 30 � in diameter. The achieved co-planarity of the focal array mosaic is smaller than 30 µm peak-to-peak, which realizes mostly the seeing limited image over the entire field. The median seeing in the Ic-band, measured over one year and ah alf, is 0. 61. The PSF anisotropy in Suprime-Cam images, estimated by stellar ellipticities, is about 2% under this median seeing condition. At the time of commissioning, Suprime-Cam had the largest survey speed, which is defined as the field of view multiplied by the primary mirror area of the telescope, among those cameras built for

Characterization and mosaicking of CCDs and the applications to the Subaru wide-field camera (Suprime-Cam)

We are building an 8192 X 10240 CCD mosaic camera for 8 m Japanese Telescope (Subaru). The mosaic will consist of 2 X 5 arrays of 3-edge buttable 4096 X 2048 15 micrometer pixel imagers. Although several vendors have just started supplying the type of large format CCD, it is still in the development phase. Therefore, careful characterization and optimizations of individual CCD are critical. We describe the system used to evaluate several kinds of the CCDs. In addition to the CCD characterization, we also present the mechanical design of the mosaic focal plane which is an another issue to realize the large mosaic.

High-Resolution Near-Infrared Imaging of the Powerful Radio Galaxy 3C 324 at z = 1.21 with the Subaru Telescope

We have obtained high-resolution K ′ -band images of the powerful z = 1.206 radio galaxy 3C 324 with the Subaru telescope under seeing conditions of 0 ′′ .3–0 ′′ .4. We clearly resolved the galaxy and directly compared it to the optical images obtained with the Hubble Space Telescope. The host galaxy of 3C 324 is revealed to be a moderately luminous elliptical galaxy with a smooth light profile. The effective radius of the galaxy, as determined by profile fitting, is 1.3± 0 ′′ .1 (1.2 kpc), which is significantly smaller than the value of 2 ′′ .2 published in Best et al. (1998, MNRAS, 292, 758). The peak of the K ′ -band light coincides with the position of the radio core, which implies that the powerful AGN lies at the nucleus of the host galaxy. The peak also coincides with the gap in the optical knotty structures which may be a dust lane hiding the UV-optical emission of the AGN from our line of sight; it is very likely that we are seeing the obscuring structure almost edge-on. We clearly detected the ‘aligned component’ in the K ′ -band image by subtracting a model elliptical galaxy from the observed image. The red RF702W K color of the outer region of the galaxy avoiding the aligned component indicates that the near infrared light of the host galaxy is dominated by an old stellar population.

Coating and cleaning of the Subaru Telescope mirrors

After the initial coating of the 8.3-m primary mirror of the Subaru Telescope in November 1998, we have conducted the first re-aluminization in August 1999. The primary mirror washing fixture worked efficiently for stripping the old coating and for washing the surface. Dry process is still to be improved. Suite of secondary and tertiary mirrors are being tested at the telescope, two of which were coated in- house, one in silver for the infrared observations and the other in aluminum for the optical observations, respectively. Evaluation of the coating film is conducted in two methods. Using a portable microScan, the reflectivity and the BRDF numbers of the primary mirror is monitored. Reflectivity over a wide range of the wavelength is measured in the witness mirrors. The preliminary data shows reasonably good number for the telescope optics. The in-situ cleaning of the primary mirror with solid and gaseous CO2 sprinkle arms is operating once every month. Next step for the coating chamber commissioning is to improve the heating capacity for silver coating of the infrared secondary and tertiary mirrors, and the experiment for silver coating is going.