Kenshi Yanagisawa

Kiso observatory near-infrared camera with a large format array

We have constructed a near-infrared camera with a 1040 by 1040 PtSi CSD array for astronomical use. The camera is attached to the prime focus (f/3.1) of the 105 cm Schmidt telescope at Kiso observatory. The field of view is 18.4 by 18.4 arcmin2 and the spatial resolution is 1.06 by 1.06 arcsec2/pixel. The camera can be used mainly in J ((lambda) eff equals 1.25 micrometer), H (1.65 micrometer), and K (2.15 micrometer) bands. Since thermal emissions from the atmosphere and room-temperature bodies are main background noise sources in the near-infrared, we designed a cold baffle inside the camera to minimize the effect of the thermal radiation from the telescope. Both the charge transfer efficiency and the dark current of PtSi arrays are sensitive to the array temperature. Therefore we carefully control the temperature at 60 +/- 0.05 K by using a refrigerator and a temperature controller. The readout noise was reduced to 70 e by adopting a correlated multiple sampling technique. The array response was linear within 0.7% accuracy below 25% of the full well capacity (< 4.0 X 105 e).

Evaluation of the 1040 x 1040 PtSi CSD for astronomical use

We present the performance of the 1040 by 1040 PtSi CSD manufactured by Mitsubishi Electric Co. for an application of astronomical imaging. The sensor was evaluated both in laboratory and in real observing conditions. The results of noise, quantum efficiency, linearity, dark current and photometric accuracy are presented.

Multi-Color Surface Photometry of Nearby Galaxies

Near-infrared (NIR) emission in galaxies is mainly radiated by old population low temperature stars, which construct the basic stellar structure and keep the trails of past galaxy evolution. On the other hand, optical observations show recent star formation activity, especially in spiral galaxies. Therefore multi-color observations from optical to near-infrared wavelengths are very important to understand the past and recent star-formation history. Nearby large galaxies are well studied not only in optical but also in mid- and far-infrared by IRAS, CO and HI radio observations. However, the study in the near-infrared is still limited because large format arrays are not common. Here we show a wide-field, near-infrared imaging of nearby elliptical and spiral galaxies and discuss their star-formation history.

Mosaic near-infrared focal plane array

To built a 3K X 3K pixel near-IR FPA, we have made a package and a multi-chip module for Mitsubishi 1040 X 1040 PtSi CSD, which is one of the largest SWIR FPAs. Mosaicing demands smallest gaps between chips to achieve a large fill-factor and controlled flatness to fit a camera focal plane. The package of 52-pin half-pitch PGA has been designed to be smaller than the bear chip. After the chip is glued on the package and wire-bonded, nine packages with the chip are arrayed in three by three on a multi chip module (MCM) of 6 cm X 6 cm area. The fill-factor of the imaging area is 89 percent. The package and MCM are made of AlN ceramic of high thermal conductivity. MCM, therefore, plays a role of an efficient heat sink. The surface of the package, with which the chip is in contact, has been polished with accurate flatness as well as MCM. As the result, the height of nine chips built on MCM are uniform within approximately 20 micrometers in 6 cm X 6 cm area. The mosaic array will be equipped in a near-IR camera for astronomical observations of a wide field view.

Astronomical wide-field imaging with the Mitsubishi PtSi 1040 x 1040 CSD

A new infrared camera equipped with a 1040 by 1040 PtSi CSD array is in operation as a common-use instrument at Kiso Observatory of the University of Tokyo. The camera attached to the prime focus (F/3.1) of the 105 cm Schmidt telescope gives a field of view of 18.4 by 18.4 with a spatial resolution f 1.1 per pixel. The image resolution, detection limit, and other performances in an astronomical application are presented. Based on the observations of nearby galaxies and Galactic objects, we demonstrate that the camera is very powerful for wide-field imaging in astronomy.

Wide-Field Imaging of Nearby Galaxies in Near-Infrared Bands

We present the results of wide-field imaging of nearby galaxies observed in the near-infrared using a large format array. The total magnitudes and mass-to-luminosity ratios of NGC 253, M 82, NGC 891, and some cluster members are discussed.

Near-Infrared Imaging with a Schmidt Telescope

We have carned out wide field imaging observations in the near-infrared (J, H and K’ band) with a large format array camera attached to the prime focus of the 105 cm Schmidt telescope at Kiso Observatory. The image resolution, limiting magnitudes and the effect of thermal radiation are discussed.

Imaging Observations of Nearby Galaxies with a 512 × 256 PtSi Camera

Near-infrared imaging observations were made of nearby galaxies using a 512 × 256 PtSi camera attached to the 105cm Schmidt telescope. The large format array having a field of view of 14′ × 11′ with a scale 1.6″ × 2.5″/pixels allows us to observe nearby large galaxies without mosaicking. We report the images of NGC 891 and M82. The structure of the bulge and disk as well as the dust distribution are discussed.