Press Release

Europe Agrees on Common Strategy to Initiate Study of LSA/MMA

Council Specifies ESO's Role in Planning

15 September 1998

In an extraordinary meeting at the ESO Headquarters, the ESO Council today endorsed ESO's involvement in the planning of a major new astronomical facility in the southern hemisphere. Some years from now, the Large Southern Array/Millimetre Array (LSA/MMA) may become the world's prime sub-mm/mm radio observatory [1] at a pristine site at 5000 m altitude in the Chilean Andes, not very far from the VLT Paranal Observatory.

Background

One of the highest-priority items in astronomy today is a large millimetre-wavelength array. This would be a millimetre counterpart to the ESO VLT and the NASA/ESA Hubble Space Telescope (HST), with similar scientific objectives and comparable high angular resolution and sensitivity.

An antenna array with about 10,000 m 2 area would provide very high sensitivity and angular resolution, compatible with that of the VLT and HST. Such a large collecting area implies an array with many antennas and baselines, which give the added advantage of fast, high-quality images. The site must be high, dry, large, and flat - a high plateau in the Atacama desert is ideal, and has the great advantage of being in the southern hemisphere, important for compatibility with the VLT. Thus, discussions in Europe have focussed on a "Large Southern Array" (LSA) .

The scientific case for such a telescope is overwhelming. It would be able to study the origins of galaxies and stars: the epoch of first galaxy formation and the evolution of galaxies at later stages, including the dust-obscured star-forming galaxies that the HST and VLT cannot see, and all phases of star formation hidden away in dusty molecular clouds. But the LSA will go far beyond these main science drivers - it will have a major impact on virtually all areas of astronomy, and make millimetre astronomy accessible to all astronomers. It may well have as big a user community as the VLT itself.

European involvement in millimetre astronomy

Europe already has a strong involvement in millimetre astronomy: the 5 x 15-m IRAM array on Plateau de Bure (France), the 30-m IRAM antenna (Spain), the 20-m at Onsala (Sweden), the 15-m Swedish-ESO Submillimetre Telescope (SEST, La Silla), the 15-m JCMT (Mauna Kea, Hawaii), the 10-m HHT (Arizona), and others. Over 60 research institutes around Europe use these facilities. Many of them have developed technical expertise and leadership in this area together with European industry, so it is natural that a European collaboration should be looking to the future.

The idea of a large European southern millimetre array has been discussed since 1991. In 1995, an LSA Project collaboration was established between ESO, the Institut de Radio Astronomie Millimetrique (IRAM), the Onsala Space Observatory, and the Netherlands Foundation for Research in Astronomy (NFRA). This consortium of observatories agreed to pool resources to study critical technical areas and conduct site surveys in Chile. Details are available in a Messenger article (March 98).

Possibilities of intercontinental collaboration

An important step was taken in June 1997. A similar project is under study in the United States of America (the "Millimeter Array", MMA ). An agreement was entered into between ESO and the U.S. National Radio Astronomy Observatory (NRAO) to explore the possibility of merging the two projects into one. Until then the emphasis in Europe had been on the large collecting area provided by 16-m antennas operating at purely millimetre wavelengths, while in the U.S. the concept was a smaller array of 8-m antennas with good submillimetre performance. However, as there is also considerable interest in Europe in submillimetre observations, and in the U.S. in a larger collecting area, a compromise seemed feasible.

Several joint working groups formed under the ESO-NRAO agreement were set up to explore the possibility of a collaborative project. It was concluded that a homogeneous array of 64 x 12-m antennas, providing submillimetre performance with a total collecting area of 7,000 m 2, could be built at the high (5000 m) Chajnantor site , an hour from the array control center at the town of San Pedro de Atacama. It is this collaborative facility that is presently referred to as the Large Southern Array/Millimetre Array (LSA/MMA) .

The decision by the ESO Council

The ESO Council today passed a resolution that emphasizes the great potential of this proposed astronomical facility for scientific discoveries. It will operate in a relatively unexplored waveband region and with imaging and spectral resolution vastly better than anything now available.

The ESO Council requests the ESO Executive to develop a proposal for ESO's role in the design and development phase of the new facility to be submitted to Council in its December 1998 meeting. This phase (Phase I) will cover the technical, financial, human resources, scheduling and organizational aspects for the development, construction, commissioning and operation of the LSA/MMA.

The ESO Council supports the intention to create a European Coordinating Committee with participation of ESO that will discuss related policy and technical matters. A European Negotiating Team will then be established that will discuss with the U.S. and other interested nations the conditions of the union of the LSA and MMA as a single common enterprise.

Notes

[1] The corresponding wavelength interval is about 0.3 to 10 mm.

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