MOIRCS - Subaru’s new “infrared eye” now open
February 22, 2006
Subaru Telescope opened its door to astronomers from all over the world in December, 2000. In the past five years, the telescope’s capabilities have been further advanced through ongoing development of new observational instruments. Leading the change, we now have MOIRCS, the Multi-Object Infrared Camera and Spectrograph which became available for general use in February, 2006.
Figure 1: MOIRCS mounted on Subaru
Telescope’s Cassegrain Focus. This
giant instrument measures about two
meters in height, width and length, and
weighs about two tons (Larger Image).
The Widest Field of View for Infrared Imaging and Spectroscopy
Co-developed by Tohoku University and the National Astronomical Observatory of Japan (NAOJ), MOIRCS has two giant four-million pixel detectors. With a field of view of 4 arcmin x 7 arcmin (Note 1), MOIRCS has the widest view of all the infrared instruments in the world amoung 8 to 10 meter telescopes. This field of view is 8.6 times wider than that of CISCO, our Cooled Infrared Spectrograph and Camera. In conjunction with a large primary mirror, such as that of Subaru, a wide field of view is key to the exploration of objects at the far reaches of the Universe.
MOIRCS’ First Light Images
Figure 2 was taken in 2004, in conjunction with the first engineering test of the instrument. The entire Orion Nebula (Messier 42) fit in just two MOIRCS images. It would require as many as 17 shots to capture an image like this with the narrow field of view of CISCO. Compare the image taken with MOIRCS to a composite of 9 images taken with CISCO in the Image of Orion Nebula (Subaru First Light Image: January, 1999). This really gives you a feel for the size of the MOIRCS field of view.
Figure 2: Orion Nebula taken with MOIRCS (Entire Image)
Figure 3 is an image of the center of our Galaxy. The many stars in our Galaxy and nearby dark clouds create a complex and memorable mix of light and dark. Infrared light is able to penetrate dark clouds better than optical light. MOIRCS is thus able to image stars right into the Galaxy’s center. If you compare an optical and infrared image of the Galactic Center, you can see that many stars do not show up in the optical image. (A comparison of optical and infrared images of the Galactic Center)
Figure 3: Galactic center of our galaxy taken with MOIRCS (Entire Image)
Powerful Infrared Multi-Object Spectrograph
Not only does MOIRCS have a wonderfully large field of view, it also has the capability to obtain multiple spectra of astronomical objects at the same time (Note 2). MOIRCS is the first instrument to provide this capability in the infrared for an 8 to 10 meter class telescope. Earlier infrared spectrographic instruments such as IRCS and OHS are only able to analyze the light from one celestial object at a time. MOIRCS dramatically increases observation efficiency with the ability to perform spectroscopy with light coming from many objects at the same time.
Overcoming Design Challenges
Anything warm, including an observational instrument, emits light in the infrared. To observe infrared light coming from celestial objects, the interior of the instrument must be cooled to minus 150 degrees or below, including the mask that selects light from objects of interest for any specific observation. (Note 3) For MOIRCS to be successful, the design team had to overcome several challenges, such as developing a drive mechanism for the mask which could withstand cryogenic conditions. Fortunately, the team was able to overcome all the design challenges and MOIRCS’s spectroscopy function worked flawlessly during its first observational test in January, 2005. Since then performance testing is ongoing and preparations for opening for general use in August, 2006 are on track.
This multi object spectroscopy original data is from a single observation with MOIRCS (H+K band). Each barcode-like strip of light in the left and right side of this image is the spectrum of an individual object. This image shows the spectra of 31 different objects, one of the largest numbers of infrared spectra in a single observation. The barcode-like pattern is actually the spectrum of Earths atmosphere. The spectrum of the astronomical object is the faint line of light running horizontally through the middle of the barcode pattern. The thick, bright, continuous lines that run across either the left or right side of the image are from holes in the mask for aligning the mask with the position of stars. (Click here for a diagram of the Multi Object Spectrograph.)
Figure 4: MOIRCS multi object spectroscopic data (Larger Image)
Built by Graduate Students
Graduate students from Tohoku University were the main work force on the MOICS development team. The students moved from Japan to Hawaii and worked with Subaru Telescope staff for over five years. Ryuji Suzuki, the graduate student who has been involved the longest, explains, “The development of a large instrument like MOIRCS includes a great many different tasks, so it was very important for each individual involved to take full responsibility for performing their part of the work.”Dr. Takashi Ichikawa, associate professor of Tohoku University who oversaw the graduate students while directing the development reflects, “The fact that they could go from having zero expertise to this great achievement has led me to raise my expectations for the potential and capabilities of young researchers.”
A Handcrafted Instrument
Many astronomical instruments are special ordered from manufacturers. MOIRCS, however, was built up part by part from individually procured high performance parts, each carefully tested as the team built the instrument. Koji Omata, MOIRCS project manager at Subaru Telescope, explains, “the significance of MOIRCS’s development is that we set a precedent for instrument development at observatories - our challenge was to carry out the project “Quickly” (i.e. on a deadline), “Cheaply” (i.e. on a budget) and “Well” (i.e. with high performance). I expect that much of the difficulties we overcame and the experience we gained will prove highly valuable to future instrument development.”
A Dream Come True
As the universe expands, all the visible light emitted by the galaxy shifts to the infrared region (red shift). Therefore, to study the current frontier of the distant universe, large-scale telescopes have awaited the development of multi-object infrared spectroscopic instruments. Tadayuki Kodama, an associate professor at NAOJ and one of the first users of MOIRCS, says, “with this revolutionary instrument, we are going to be able to study the properties of stars in galaxies that existed when the Universe was only one tenth of its current age. I’m really excited that we can now study the formation and evolution of galaxies beginning at such early times.”
Since it saw First Light back in September year before last, MOIRCS has had over a year of continued efficiency upgrades and improvements. What view into the Universe will be unveiled with this new “infrared eye” that so dramatically increases the capabilities of the Subaru telescope? Look for more MOIRCS news to find out.
Note 1: 1arcminute equals one sixtieth of one degree. Note 2: Spectroscopy is the process of resolving light all wavelengths of light coming from a celestial object and analyzing in detail the physical properties of that object. Note 3: Click here for more about the multi-object spectroscopic observation of FOCAS, the Faint Object Camera And Spectrograph for visible light observation, and the mask.
MOIRCS Group: Director: Takashi Ichikawa (Astronomical Institute, Tohoku University); Previous Director: Testuo Nishimura (Subaru Telescope, National Astronomical Observatory of Japan); Project Manager: Koji Omata (Subaru Telescope, National Astronomical Observatory of Japan); Development Members (in alphabetical order): Yuka Katsuno (Subaru Telescope, National Astronomical Observatory of Japan); Masahiro Konishi (Tohoku University); Ryuji Suzuki / Ichi Tanaka / Chihiro Tokoku (Subaru Telescope, National Astronomical Observatory of Japan), Toru Yamada (Mitaka Campus, National Astronomical Observatory of Japan), TomohiroYoshikawa (Tohoku University).
Direct inquiries to: Takashi Ichikawa at ichikawa at astr.tohoku.ac.jp