Large Latin American Millimeter Array

Large Latin American Millimeter Array

Large Latin American Millimeter Array (LLAMA)
LLAMA logo
Organisation Argentina, Brazil
Location Alto de Chorrillos, near San Antonio de los Cobres
Salta, Argentina
Coordinates
Altitude 4,825 m
Wavelength From 8 mm to 0.3 mm
Telescope style Single dish with Nasmyth optics antenna provided by Vertex Antennentechnik, GmbH
Diameter 12 m
Focal length 4.8 m
Mounting Altazimuth mount
Website Official LLAMA site

The Large Latin American Millimeter Array (LLAMA) is a single-dish 12 m Nasmyth optics antenna with VLBI capability which is under construction in the Puna de Atacama desert in the Province of Salta (Argentina). The primary mirror accuracy will allow to observe from 40 GHz up to 900 GHz. It is also planned to install a bolometer camera at millimeter wavelengths. After installation it will be able to join other similar instruments to do Very Large Base Line Interferometry or to work in stand alone mode. Finnancial support is provided by the Argentinian Government through its Science Ministry, and from Brazil through a FAPESP grant. The total cost of construction (around US$20 million) and operation as well as the telescope time use will be 50% shared by both countries. The construction started on July 2014, after the formal signature of an agreement between the main Institutions involved. It should see the first light in 24 to 30 months.

Overview

LLAMA is a joint project between Argentinian and Brazilian Astronomers to build and operate a radio telescope at submillimeter wavelengths, that can work in stand alone mode or join a VLBI network. It is similar to the APEX antenna, also build by the German firm Vertex Antennentechnik, GmbH (the same firm provided 25 of the ALMA antennae). The main scientific Institutions involved in the project are the Instituto Argentino de Radio Astronomía (IAR), and the Núcleo para o Apoio da Rádio Astronomia (NARA), from the Universidade de São Paulo (Brazil). The telescope is located at a very high altitude (4,825 m) where the atmospheric absorption (mostly due to water vapor) allows the observation at the very short wavelengths of less than 1 mm. It is a multipurpose instrument that will have cryogenic receivers with very high sensitivity in order to observe very faint sources, and filters to observe the Sun. This large receivers input range is quite a big challenge (although is not the first time that it was achieved since ALMA 12 m atennas have the same capacity.)

History

The history of the instrument can be traced back to 2007, during the XII Latin American Regional IAU Metting (LARIM)[1] held in Isla de Margarita (Venezuela). Argentinian Radioastronomers discussed the idea with colleagues from South America.[2] The search for the best place for a submillimeter (less than 1 mm wavelengths) telescope started in Argentina well before, in 2003, with a 210 GHz tipper which was installed in different places to investigate the Atmospheric Opacity.[3][4] During the XXVII General Assembly[5] in Rio de Janeiro, the project gained a name in a document authored by the leading scientists of the project.[6] In the same document, it was also proposed the science, initial budget, strategies for construction, site, etc. The formal presentation before the Argentinian Science Ministry (MinCyT) was in 2010, while a meeting held at the offices of FAPESP in August 2011, was the kick off in Brazil. In 2011 MinCyT ranked LLAMA as its astronomical project and in 2012 FAPESP approved a €7 M grant. The final agreement, between MinCyT, FAPESP and USP was signed in June 2014, and in July 9, it was formally presented to the public.[7]

A group of llamas near San Antonio de los Cobres shot from a car in movement.

The word llama has different meanings in Spanish. Llama means flame. However, the origin of the observatory acronym comes from the Quechuan word llama that designates the South American camelid that lives in the region where the telescope is being installed. There is some confusion with the word array, since LLAMA will consist of a single dish antenna. The justification goes with the fact that the instrument will have VLBI technology, therefore it can be part of an antenna array with telescopes of other observatories. Moreover, the LLAMA observatory can be expanded in the future by installing other antennas in different sites.

In different official documents the acronym LLAMA may be found expanded as Long Latin American Millimeter Array and not as Large. It is also possible to read Millimetric (instead of Millimeter). After some debate, the LLAMA Executive Committee stated that Large Latin American Millimeter Array is the right expansion for the LLAMA acronym.[8]

The observatory logo has as symbols the Southern Cross (upper right), a telescope sketch (bottom right), the acronym (upper left) and a llama profile (bottom left). Although it changed with time, these symbols are present since the beginning. The image illustrating this page is the official logo since August 2014.

Science

LLAMA is a multipurpose instrument, with the capacity to both observe strong sources (the Sun) and very weak very far sources from Earth. The following is a list of different subjects that will be addressed with LLAMA observations.

The Sun

In the unperturbed solar Atmosphere, the shorter the wavelength the deeper the observation. Frequencies near the submillimeter range are produced in the lower Chromosphere or even the Photosphere.[9][10] Therefore, LLAMA observations will bring new information about the structure of the lower Solar Atmosphere, the active and quiescent filaments and the dynamics of the Chromosphere and its Magnetic Field. The possibility to observe Solar Flares at high frequencies with a high sensitive instrument will give clues about the acceleration of the high energetic particles in the Sun, complementing results obtained with the Solar Submillimeter Telescope. In particular the still unexplained spectral reversion above ≈ 100 GHz.[11] A very challenging experiment would be to make VLBI solar observations. For example, in a joint observation between LLAMA and some of the ALMA antennas, a spatial resolution of 0.001" will be achieved for λ ≈ 1 mm, i.e. 700 m over the solar surface, never attained before at any wavelength.

Planets

  • Extra-solar planetary systems around stars near the Sun.
  • Proto-planetary disks in star located in the Solar neighborhood.
  • Near-Earth objects.

Stellar objects

  • Star forming regions, young stellar objects, and mechanisms of the star formation.
  • Non-thermal processes in stellar magnetospheres.
  • Interaction of stars and remnants of supernova with the interstellar medium.

Astrophysical jets and maser emission

  • Astrophysical jets.
  • Maser phenomena of the recombination lines of the hydrogen atom.
  • Maser emission in star-forming regions.
  • Maser emission in late stars stellar envelopes.

Galactic and Intergalactic interstellar medium

  • Continuum radiation from extragalactic cold dust.
  • Molecular material in the direction of different stellar objects.
  • Intergalactic Medium using the detection of molecular absorption lines in the direction of quasars.
  • Cosmic background radiation.

Galaxies

  • Search for CO in galaxies with high redshift.
  • Molecular abundance.
  • Active Galactic Nuclei (AGN).
  • Variation of the fundamental constants by the observation of gravitational lensing.
  • High redshifts of regions with very high rate of star formation.
  • Proto-clusters of galaxies.
  • Space-time distortion produced by massive black holes.

High energies

Optics, Receivers

The Nasmyth optics will allow to install as many as 6 different heterodyne receivers. There is a consensus about the frequency for these receivers to adopt the same spectral bands used in ALMA.[12] With this scheme the Nasmyth cabins will allocate receivers for the bands
# Frequency Band [GHz] Wavelength Band [mm]
1 35 - 50 8.6 - 6.0
3 84 - 116 3.6 - 2.6
5 162 - 211 1.9 - 1.4
6 211 - 275 1.4 - 1.1
7 275 - 373 1.1 - 0.8
9 602 - 720 0.5 - 0.4

It is intended to install in the Cassegrain focus a bolometer multi-wavelength camera, or even a camera plus a small heterodyne array.

Pictures

References

  1. ^ 12th LARIM, 2007
  2. ^ Mirabel, I.F, Arnal, M.E., Morras, R., Romero, G, Proyecto Latinoamericano de Astronomía en Argentina, 2008, presented during the Annual Meeting of the Astronomical Argentinian Association
  3. ^ Arnal,E.M, Morras, R., García Lambas, D.G., Recabarren P., ¿Dónde instalamos el telescopio?, Revista Ciencia Hoy, 19, 110, Abril-Mayo, 2009
  4. ^ Bareilles, F., Opacidad al cénit a 210 GHz (tipper)
  5. ^ XVII IAU GA, Rio de Janeiro, 3-14 Aug 2009
  6. ^ Mirabel, I.F, Arnal, E.M., Morras, R., Romero, G., Lepine, J.R.D., Abraham, Z., de Gouveia Dal Pino, E., Long Latin American Millimeter Array,pdf)
  7. ^ Jesús Rodríguez, Diario Clarín, Buenos Aires, 9 July 2014, accessed on 15 August 2014
  8. ^ LLAMA Executive Committee Meeting, May 2014, La Plata (personal communication)
  9. ^ De la Luz, V, Lara, A., Raulin, J.-P., Synthetic spectra of radio, millimeter, sub-millimeter, and infrared regimes with non-local thermodynamic equilibrium approximation, Astrophys. J., 737, 1 (2011)
  10. ^ Silva, A. V. et al., Diffuse Component Spectra of Solar Active Regions at Submillimeter Wavelengths, Solar Phys., 227,261 (2005)
  11. ^ Kaufmann, P et al. , A new solar burst spectral component emitting only in the Terahertz range, Astrophys. J. 603, L121 (2004)
  12. ^ ALMA frequency bands

See also