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Science with TAO

Advantages of TAO

Since astronomy is the study of various phenomena in the Universe, observations with wide wavelength range is essentially important. Infrared astronomy has second longest history after optical astronomy and is very useful. However observations in the infrared wavelength are not easy because the infrared light is strongly absorbed by the earth atmosphere. The TAO telescope is planned to be built at the world highest site (5640m) at which the atmosphere is exceptionally transparent even in the infrared. In near infrared wavelength range discrete atmospheric gwindowsh of J, H, K-bands coalesces into one continuous window at the TAO site. In addition a new window from 25 to 40 micron appears in the mid infrared wavelength. Accessibility of these wavelengths is the most unique capability and the strongest advantage of the TAO telescope.

(Upper) Atmospheric transmittance at the Chajnantor TAO site (model) (Lower) Atmospheric transmittance at the Paranal site of the VLT 8m telescopes. The TAO site has a continuous window in the near infrared and a new window above 25 micron.

To utilize the best observing environment, the TAO telescope has two state-of-art instruments called SWIMS and MIMIZUKU. SWIMS (Simultaneous-color Wide-field In- frared Multi-object Spectrograph) is an instrument optimized for near infrared observations. It has a unique spectroscopic capability covering 0.9-2.5 micron continuously. This is very useful for line observations of red shifted galaxies. Its ability of simultaneous observations in two different wavelength bands, as well as the wide field-of-view of 9.6f, enables us to carry out surveys with high efficiency which is a key for studying galaxy evolution, cosmology, and searching rare objects.

NIR survey power of current and near future projects. X-axis indicates limiting magnitude of the survey, and y-axis indicates survey area. TAO covers relatively wide and moderately deep area in this figure.

Longer mid-infrared is observed by a MIMIZUKU (Mid-Infrared Multi-mode Imager for gaZing at the UnKnown Universe) instrument. It covers a very wide wavelength range from 2 to 38 micron. Especially longer mid infrared from 26 to 38 micron is accessible only by TAO/MIMIZUKU. Thanks to its higher spatial resolution than satellite telescopes in this wavelength range, MIMIZUKU is a very powerful tool for studying planet formation and origin of materials. Furthermore MIMIZUKU has a unique function of simultaneous observations of two discrete fields of view, which enable us to carry out accurate monitoring in the mid infrared.

Spatial resolution of space/groundbased mid-infrared facilities. TAO achieves the highest spatial resolution among current and near-future projects around 30 micron.

Science Cases with TAO

There are many kinds of scientific case with the TAO telescope. The most important two are gOrigin of Galaxies and the Universeh and gOrigin of Planets and Materialsh.

gOrigin of Galaxies and the Universeh

When were galaxies born? How did they form the current structure? To answer these questions it is essentially important to understand growth process of stellar mass in each period of the evolutional history. Wide and deep survey of galaxies in the near infrared wavelength is a key observation to reveal the process statistically and investigate environment effect for the evolution.
Galaxies born in the early Universe (protogalaxies) are located extremely far away and moving away from us according to the cosmic expansion. Light from these galaxies goes longer, i.e., redder wavelengths (red shift) and normal optical light comes into the infrared wavelength. Transparent atmosphere in the near of the site and the wide field of view of TAO/SWIMS enable us to carry out near-infrared survey with high sensitivity and wide sky coverage. Main topics of research are followings: acquisition process of gas in protogalaxies, star forming history, galaxy population found only in the early universe including infrared galaxies and sub-mm galaxies. Observations of Pa-alpha emission line of nearby galaxies are another important subject since it is only accessible from the TAO site.

An optical image of the distant universe seen by the Subaru telescope. Most of bright spots correspond to distant galaxies. TAO will be able to obtain similar image of distant universe in the infrared wavelength, and reveals their distance and characteristics by spectroscopic observations.

Simulation of spectroscopic observations of high redshift quasars by TAO. A black curve shows the limiting magnitude with R=5,000 and the exposure time of 10,000 sec. Blue, green, and red curves indicates simulated spectra of quasars with z=3, 6, and 10, respectively. The shadowed range is the wavelength coverage of the TAO spectroscopy.

gOrigin of Planets and Materialsh

Recently a lot of planets outside the Solar system (so called exoplanets) are detected and studied intensively by many astronomers. Total number of the detected planets reaches 500 at the time writing in August 2011. Investigations of the details of the exoplanets including orbit, size, composition, and their atmosphere are a key for understanding formation of the (exo)planets and begging of life eventually. These planets are thought to be formed in dust disks around young stars which called pre-main-sequence stars. Therefore the dust disks are important targets for observational astronomy as well as the exoplanets themselves. The dust disks do not shine in the optical wavelength, but are very bright in mid infrared wavelength. The capability of 30 micron imaging of TAO is expected to reveal the formation process of planets for the first time.
Dust grains are one of major constituents of the Universe. They contain most of metal elements in the interstellar medium, and play important parts on physical and chemical processes in both interstellar and circumstellar environments. Studying the formation and the evolution process of the dust grains is essentially important to understand the cycle of matter in the Universe.
TAO is a quite powerful faculty for observational studies of the dust grains. Mid infrared images of dust supplying stars with high spatial resolution obtained by TAO provide us precious information about the dust forming process. Spectroscopy of stars in various evolutional stages is useful to carry out mineralogical and chemical studies of the dust grains as well as detailed studies of stellar physics.



A cold and massive torus in the planetary nebula NGC6302 detected by miniTAO. Red (left) and green (right) contours show mid-infrared images obtained by miniTAO/MAX38 at 18 and 31 micron, respectively. The image at the 31 micron has a relatively elongated shape, indicating the colder dust torus exists at the central region of the nebula. Background is a narrow band image at Pa-beta obtained by miniTAO/ANIR.

(Upper) Near infrared spectra of Mira variables obtained by ISO/SWS. A red curve shows a spectrum of omi Cet, and a green and blue show spectra of T Cep at the variable phase of 0.38 and 1.61, respectively. (Lower) Atmospheric transmittance at the alititude of 2600m(Paranal; blue), 4200m(Quimal; green), and 5640m (Chajnantor; red). In the upper panel, complex features corresponding to various molecules around stars are seen. In order to carry out observational studies of these molecules wide and continuous spectral coverage is absolutely needed.