ALMA

What is ALMA?

The Atacama Large Millimeter/submillimeter Array (ALMA), will be a single research instrument composed of up to 80 high-precision antennas, located on the Chajnantor plain of the Chilean Andes in the District of San Pedro de Atacama, 5000 m above sea level. ALMA will enable transformational research into the physics of the cold Universe, regions that are optically dark but shine brightly in the millimeter portion of the electromagnetic spectrum. Providing astronomers a new window on celestial origins, ALMA will probe the first stars and galaxies, and directly image the formation of planets.

ALMA will operate at wavelengths of 0.3 to 9.6 millimeters, where the Earths atmosphere above a high, dry site is largely transparent, and will provide astronomers unprecedented sensitivity and resolution. The up to sixty-four antennas of the 12 m Array will have reconfigurable baselines ranging from 150 m to 18 km. Resolutions as fine as 0.005" will be achieved at the highest frequencies, a factor of ten better than the Hubble Space Telescope.

ALMA will be a complete astronomical imaging and spectroscopic instrument for the millimeter/sub millimeter, providing scientists with capabilities and wavelength coverage that complement those of other research facilities of its era, such as the Expanded Very Large Array (EVLA), the Thirty Metre Telescope (TMT ), the European Extremely Large Telescope (E-ELT), and the James Webb Space Telescope (JWST).

ALMA is an international astronomy facility. It is a partnership of Europe, Japan, and North America in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organisation for Astronomical Research in the Southern Hemisphere (ESO) and Spain, in Japan by the National Institutes of Natural Sciences (NINS) in cooperation with the Academia Sinica in Taiwan, and in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC). ALMA construction and operations are led on behalf of Europe by ESO, on behalf of Japan by the National Astronomical Observatory of Japan (NAOJ) and on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI).

Some of ALMA’s capabilities will include:

• Up to sixty-four 12-meter antennas located at an elevation of 16,400 feet in Llano de Chajnantor, Chile

• Imaging instrument in all atmospheric windows between 10 mm and 350 microns

• Array configurations from approximately 150 meters to 10 km

• Spatial resolution of 10 milliarcseconds, 10 times better than the VLA and the Hubble Space Telescope

• Able to image sources arcminutes to degrees across at one arcsecond resolution

• Velocity resolution under 0.05 km/s

• Faster and more flexible imaging instrument than the VLA

• Largest and most sensitive instrument in the world at millimeter and sub millimeter wavelengths

• Point source detection sensitivity 20 times better than the VLA

Location

Unlike most radio telescopes, the ALMA antennas will be at a very high altitude of 5000m on the Llano de Chajnantor in northern Chile. This is more than 750 meters higher than Mauna Kea and more than 2300 meters higher than Cerro Paranal. The U.S. National Radio Astronomy Observatory (NRAO), the European Organisation for Astronomical Research in the Southern Hemisphere (ESO), and the National Astronomical Observatory of Japan (NAOJ) have collected atmospheric and meteorological data at this site since 1995. These studies show the sky above the site has the dryness and stability essential for ALMA. The site is large and open, allowing easy re-positioning of the antennas over an area 18 km in extent. ALMA Chilean operations will be the responsibility of the Joint ALMA Observatory (JAO). The telescope array itself is located at the Array Operations Site (AOS). Because of the limited oxygen at 5000 m, the array will be operated from the Operations Support Facility (OSF) at an elevation of 2900 m, with trips to the AOS to install, reinstall, or retrieve equipment or antennas. The JAO has a central office in Santiago. Interim OSF site facilities have been completed with offices, sleeping facilities, and a contractor camp. More permanent facilities are under construction to handle the ongoing operations, maintenance, and repairs of ALMA antennas and receivers, and will include a public Visitor Center.

University of Calgary's Role in the ALMA Project

Apart from their scientific interests in using ALMA, astronomers at the Institute for Space Imaging Science are playing a key role in its development. Led by Dr.'s Russ Taylor and René Plume, the ISIS Radio Astronomy division received a grant from the Canada Foundation for Innovation to provide Canada's "site access" fee to the ALMA project, and also to assist in the ALMA software development. ISIS currently supports two software engineers who are contributing vital components to the ALMA control and data reduction software. McMaster University will be hosting a workshop in June 2009, to teach astronomers how to plan for and reduce ALMA observations.

ALMA Links

i) Sensitivity Calculator: http://www.eso.org/projects/alma/science/bin/sensitivity.html

ii) CASA (ALMA data reduction software): https://wikio.nrao.edu/bin/view/Software/ObtainingCASA

iii) ALMA Simulator: http://www.iram.fr/IRAMFR/ARN/may01/node7.html

iv) Main ALMA website: www.alma.info

v) Receiver development by the National Research Council of Canada: http://www.hia-iha.nrc-cnrc.gc.ca/atrgv/alma_e.html

vi) 2009 ALMA Workshop: www.almatelescope.ca/Workshop/Home.html