The Atacama Telescope Project

1. The Atacama Telescope Project The propagation of far infrared radiation through the atmosphere is inhibited by water vapor. Thus, far infrared Astronomy requires the driest possible atmosphere. Why not outer space? A variety of reasons, mainly cost. A telescope’s ability to see fine details is dictated by its size. Large size translates into high weight, which limits what can be shuttled to space. For example, the Hubble Space Telescope has a diameter of 2.4 m and the Infrared Spitzer Space Telescope has a diameter of 1/3 that. The Atacama telescope will be 25 m in diameter. To make its cost affordable, it must be ground-based. To minimize atmospheric effects, it will be built at a site as high as we can drive a truck in the highest, driest desert on Earth: ATACAMA. Overview In February 2004, Cornell University and the California Institute of Technology signed an agreement that will lead to the construction and operation of a 25 meter class, Far Infrared/Submillimeter telescope to be located at very high altitude in the Andean highlands of the Atacama Desert, in northern Chile. Scheduled for completion by the beginning of the next decade, this telescope will be the highest altitude astronomical facility, as well as the largest and most sensitive of its type on Earth. Science Case: Evolution of Structure and The Assembly of Galaxies How did the Universe evolve from this:  Map of the sky obtained by the Wilkinson MAP satellite. It displays fluctuations in the Cosmic Microwave Background Radiation, which originated when the Universe was a mere few 100,000 years old. Those fluctuations are thought to be The precursors of present day galaxies, clusters and superclusters. The main driver of cosmic evolution is gravity: density fluctuations in the early Universe were amplified by gravity, leading to the formation of the first stars and galaxies. Galaxies merged to form larger units, clusters and even larger structures. To the right  an image of western South America (cred: D. Vuille). The Atacama region is outlined by the small square. Peru Bolivia . . . to this: The first episodes of star formation produced elements heavier than Helium. Some of those atoms formed dust grains (Carbon and Silica compounds mixed with ices). Dust absorbs optical radiation and re-emits in the far infared. The expansion of the Universe shifts that radiation to even longer wavelengths. Thus, the detection and study of primeval galaxies relies on our ability to build sensitive far infrared telescopes and detectors. • Satellite image (credit: Jen Wu) of the Atacama region. The Salar (salt flat) is the white/greenish region to the left, at 8500 ft elevn. The highest parts • In the digital elevation map exceed 16,000 ft. Computer  generated rendition of the filamentary nature of the large-scale distribution of galaxies in the Universe at the present time, 13 billion years after the Big Bang. (credit: MPIfAp) Chile Argentina The Atacama region is rich in history, as well as in physical beauty. The church  of San Pedro, the largest village in the Salar dates back to the colonial period. Probably through many events like this: Image of two nearby colliding galaxies (credit: B. Whitmore), on their way to  merge into a single system. Galaxy mergers are thought to have been far more frequent in the early Universe than they are today. As a result, star formation activity – stimulated by the merger process – was most likely many times more intense billions of years ago than it is today. Salar (salt flat) floor, at 8500 ft elevation. Science Case: Planetary Disks (Above) View of the Chajnantor Plateau (16,000 ft) from the summit of Cerro Toco (18,000 ft). The view is towards the Southwest. Cerro Negro (a view from its summit is shown to the left) is the peak on the right side of this image. Interacting galaxies are known to stimulate prodigious episodes of star forming activity, known as starbursts. It is thought that they may be precursor events to the formation of supermassive black holes. Starburst activity takes place in very dusty environments, the inspection and full understanding of which requires infrared observations. In the image below (credit: J. Hibbard), a sequence of merger stages is shown. Planets form within the dense dust cocoons which surround young stars. The dusty material settles into flattened disks, and the accretion of particles leads to the formation of seeds that will turn into planets. This  image, taken at 870 micron with the currently largest submm telescope (JCMT) shows the disk around Vega. View to the North, of distant peaks (Licancabur and Juriques) from the summit of Cerro Negro (17,000 ft), a candidate site for the Atacama telescope. The Atacama telescope will be located at an elevation higher than 17,000 ft. A few candidate sites are under close scrutiny, through survey campaigns that measure meteo parameters, water vapor content and infrared transparency. The artistic rendition below shows what the Vega disk would look like as seen with a resolution similar to that of the Atacama telescope at 200 mm. A view to the North, with the summits of Licancabur, Toco and Chajnantor. A view of the summits of Licancabur (19,500 ft) and Juriques  (18,800 ft), from the desert floor. The computer generated image above shows the effect on a circumstellar disk produced by the formation of a giant planet within it, i.e. the partial evacuation of a ring region (credit: GSMT team) A long exposure taken at 2 a.m., in moonlight, towards the South Celestial  Pole.