Summary of Scientific Results – 2000
This year concentrated on finalizing the commissioning of the Subaru Telescope
to provide the highest performance in the astronomical world. Performanceverification tests were conducted and First Light events occurred on a wide-arrayof instruments. The adaptive optics system came on-line and Suprime-Cam
demonstrated capabilities close to its theoretical maximum sharpness. To end
the year, Subaru began Open Use operation and welcomed astronomers fromaround the world. Subaru has already left its mark on the new millennium.
During the second year of operation, the four focal units on Subaru were set up
and calibrated, and the observational instruments went through test observations
and tireless engineering to maximize their capabilities. The first-generation
instruments, consisting of innovative cameras and spectrographs (FOCAS,CIAO, OHS, IRCS, and HDS) operating in optical or infrared light, all commenced
observations. A brief description of each instrument system follows.
Four instruments (FOCAS, CIAO, OHS, and IRCS) experienced First Light inFebruary 2000. One of these, the two-ton Faint Object Camera andSpectrograph, FOCAS, detects visible light in one of two modes (imaging andspectroscopically), and can automatically switch between modes via computercontrol. FOCAS can image directly or can obtain spectra of faint galaxies inorder to estimate their physical parameters, such as temperature and density.
On its first night of operation, FOCAS imaged the Cigar Galaxy M82, a mere 12
million light years from Earth.
Another instrument “seeing” for the first time in February was CIAO, a large
Coronagraphic Imager with Adaptive Optics. CIAO observes near-infrared
radiation of wavelength 0.9 to 5.5 microns, which is between visible light andmiddle-infrared. What makes this instrument unique from the two other nearinfrared instruments (IRCS and OHS) is that CIAO has a mechanism called acoronagraph that is able to hide a star (and its brightness) under a circular blackmask so that dim objects near that star may be imaged. The aims of CIAO are toobserve star-formation regions and directly discover a planet around a nearbystar.
Two weeks after CIAO received its first photons of radiation, the OH-AirglowSuppression Spectrograph (OHS) experienced First Light. OHS, a large
instrument installed at the infrared Nasmyth focus, is designed to work with nearinfrared radiation between 1 and 2 microns. OHS helps the detection of faintastronomical objects by removing background light caused by OH (hydroxyl)
molecules in the Earth’s upper atmosphere. It is particularly useful for studying
dim celestial objects at all other wavelengths, such as distant galaxies and browndwarfs. The OH-suppressed light is fed from OHS into another instrument,typically near-infrared camera and spectrograph CISCO, which then acts as thedetector.
A brief three days later saw the Infrared Camera and Spectrograph (IRCS)
achieve First Light. Mounted at the Cassegrain focus, IRCS can take both
images and spectra in the wavelength range of 1 to 5 microns, commonly known
as the “thermal infrared”. What makes IRCS unique is that it can image at longer
wavelengths than OHS, over a wider field of view than CIAO, and offers higher
resolution spectroscopy than both instruments. Among other projects, IRCS is
used to search for brown dwarfs, investigate chemical reactions around stars,and study the dynamics of distant galaxies.
Mid-year at Subaru brought First Light for a large and heavy instrument mounted
at the optical nasmyth focus, High Dispersion Spectrograph (HDS). As the namesuggests, HDS observes objects in visible light between 0.3 and 1 microns anddisperses/splits their light into 100,000 separate colors. With these qualities,
HDS is used to study the chemical compositions of old stars in our Galaxy anddistant clouds of gas to better understand their evolution. Its high precision also
allows for the indirect detection of planets around other stars. A few days afterFirst Light, HDS made observations of nearby comet LINEAR (C/1999S4),
confirming Subaru’s ability to perform non-sidereal tracking and clearing the way
for studying objects within our Solar System.
The end of 2000 brought two momentous events: First Light for the adaptive
optics (AO) system and Open Use operations. The AO system allows for
sharper imaging of celestial objects by monitoring atmospheric turbulence andcompensating for the distortion. The AO system essentially removes
atmospheric blur and provides image quality and clarity close to Subaru’s
theoretical limit. With the telescope and instruments having completed theirpreliminary set-up and testing, Subaru began accepting applications andproposals from non-Japanese astronomers. The world-wide demand to conduct
research at Subaru was overwhelming; the number of nights requested outbid
the number of nights available by a factor of 6.2. Subaru was the new telescopewith the best new instruments and everyone wanted to experience thewonderment; a lucky few were privileged to experience.