Press Releases
Aug. 11, 2009

The 1m telescope at the Atacama Observatory has Started Scientific Operation, detecting the Hydrogen Emission Line from the Galactic Center in the Infrared Light

  • Yuzuru Yoshii (Professor, Director of Institute of Astronomy, School of Science, The University of Tokyo)
  • Kentaro Motohara (Assistant Professor, Institute of Astronomy, School of Science, The University of Tokyo)
  • Takashi Miyata (Associate Professor, Institute of Astronomy, School of Science, The University of Tokyo)
  • Natsuko Mitani (Technical Staff, Institute of Astronomy, School of Science, The University of Tokyo)

The TAO group (PI ; Prof. Y. Yoshii) at Institute of Astronomy has started scientific observation in the near infrared wavelength at a 1m infrared telescope on the summit of Mt. Chajnantor in northern Chile, called the University of Tokyo Atacama Observatory (TAO) project. The altitude of the observatory is 5640m, which makes it the world's highest telescope. Here, the atmospheric absorption, especially by water vapor, is far smaller than that at the sea level and we can observe infrared light which was difficult to obtain at the existing facilities. This project is also a pathfinder for the planned 6.5m telescope project.

After the successful engineering first light of the 1m telescope with an optical CCD camera in March 2009, we have started scientific observation installing a near infrared imaging camera having high sensitivity at wavelength of 1 to 2.5 micrometer in June 2009. This camera is optimized for the observation of the Paschen-alpha emission line at 1.875 micrometer radiated from the ionized Hydrogen gas, which is very strong and little attenuated by interstellar dust particles, meaning that we can look through far into our Galaxy. The problem is that, the atmospheric absorption by water vapor prevents us from observing it from the ground. However, the miniTAO telescope at the altitude of 5600m enables us to carry out such observation.

In the first observation in the Paschen-alpha emission line carried out on June 9 2009, we have successfully obtained the images of the Galactic center regions. This is the first time ever that we have obtained the Paschen-alpha image of the Galactic object from the ground. Obtained images show interesting features, such as extended Paschen-alpha structure which matches to the radio continuum image well, suggesting clearly that this is the ionized hydrogen gas cloud. However, some radio structures is not seen in Paschen-alpha, meaning that there exist several type of structures at the Galactic center. Such a comparison is necessary to understand what is going on at the Galactic center.

We will start the wide-field imaging survey of the Galactic center in the Paschen-alpha emission line to probe the distribution of hydrogen gas clouds, which will finally reveal the real structure of our Milky Way Galaxy.

Figure 1 Figure 2

The miniTAO 1m telescope installed at the altitude of 5640m in the Atacama desert of northern Chile.

Figure 1 (top) : Overall view of the TAO observatory. The white dome on the right contains the telescope.

Figure 2 (bottom) : The 1m telscope and the near-infrared camera. The black structure is the telescope, and the silver part below the red circular plate is the camera.

Figure 3 Figure 4

The images of the Galactic center region obtained by the miniTAO 1m telescope. The Galactic center is seen on the right side of the image as a dense stellar cluster with orange color. A super-massive blackhole is located at the center of the cluster.

Figure 3 (top) : Pesudo-color image of the Galactic center, where red is assigned to Paschen-alpha (1.875 micrometer) and 2.07 micrometer continuum light, green to 1.87 micrometer light, and blue to 1.91 micrometer light. The extended structure seen in the red corresopnds to the region emitting Paschen-alpha emission line.

Figure 4 (bottom) : Same as Figure 3, overlapped with the position of Galactic center and the direction of Galactic plane.