Press Release

Wide Field Color Image with Suprime-Cam

November 14, 2000

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High Res. (2.48 MB)

Object Name:
Wide Field Color Image with Suprime-Cam
Telescope: Subaru Telescope / Prime Focus
Instrument: Suprime-Cam
Filter: B (0.45 micron) , V (0.55 micron) , R (0.65 micron)
Color: Blue (B), Green (V) , Red (R)
Date: UT2000 August 3 (B), June 8 (V), August 2 (R)
Exposure: 40 min (B) , 25 min (V), 30 min (R)
Field of View: 24 arcmins
Orientation: North up, east left
Position: Hercules

Suprime-Cam (Subaru Prime Focus Camera) is a wide field camera for visible light, installed at the prime focus of Subaru Telescope. It can currently produce a 24 x 24 arcminute square image with each exposure, an area almost equal to the size of the full moon (about 31 arcminutes in diameter, see supplement). At present, Subaru is the only large telescope in the world (primary mirror larger than 4 meters in diameter) that can take such a large-scale image. The combination of large field coverage and large light-gathering power makes the Subaru Telescope / Suprime-Cam combination the most powerful tool available for studying faint celestial objects spread out over extended regions of the sky.

The builders of Suprime-Cam have been researching the large-scale structure in the universe through the "weak lensing" method while adjusting the instrument. The weak lensing method estimates the mass of nearer galaxies by measuring distortion in shapes of the more distant galaxies caused by gravitational lensing (the phenomenon where light from a farther object is bent by the gravity of a nearer object). The aim of the research is to determine the mass distribution over a wide area in the universe.

The image shown here is a good example of what Suprime-Cam can achieve in terms of detail and faintest objects visible. Even though the field-of-view is large, there is no compromise in the finest details that can be imaged by Suprime-Cam. The limit is set by the Earth's atmosphere, which, from Mauna Kea, is exceptionally steady. Suprime-Cam has already demonstrated its ability to resolve details as small as 0.3 arcseconds in diameter, about one six-thousandths the size of the full moon. The image shown here has a resolution of about 0.6 arcseconds. The peak efficiency of Suprime-Cam is also very good, with better than 70% of the light entering the telescope being detected. The faintest details visible in the color image are about 100 million times fainter than what can be seen with the unaided eye.

The image contains more than 30,000 objects within approximately 10 billion light years of the Earth. The brightest features in the image are faint stars belonging to our own Milky Way Galaxy. The streaks running vertically from these stars are artifacts created when the electronic detectors (CCDs) are over exposed. Many stars are visible in this image; but most of the objects seen are actually other galaxies many tens of thousands of times further than the furthest stars in our galaxy. This image with its tremendous number of galaxies shown in good detail is exactly what's required for doing the weak lensing analysis.

In the course of their research, the Suprime-Cam group discovered a previously unknown cluster of galaxies (*) within this image (see supplement). The distance between the Earth and the cluster is estimated to be approximately 5 billion light years. It is expected that many such serendipitous discoveries will occur as a matter of course for researchers using Suprime-Cam on Subaru Telescope.

Open use of Subaru Telescope will start in December of this year. For the first semester, "S00", running from December 2000 to March 2001, two of Subaru's seven first-phase observational instruments were deemed ready for general use: Suprime-Cam; and the Infrared Camera and Spectrograph (IRCS). The 36 available nights will be used for 26 research projects. The remainder of time will be assigned for engineering work on the telescope and its instruments.

(*) A cluster of galaxies is defined as a group of more than 50 galaxies within a region approximately 10 million light years across.

Supplementary Image: Low Res. (187 KB) / High Res. (1.44 MB)



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