ALMA Atacama Large Millimetre Array

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ALMA Atacama Large Millimetre Array

• Presentation by Tiffany Fung

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ATACAMA LARGE MILLIMETRE ARRAY

• The Worlds largest and most sensitive radio
  telescope operating at millimetre and
  submillimetre wavelengths!

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ALMA an international telescope
T

• merging MMA (from the NSF), and LSA (from the
  ESO) projects to be one global project
  
• includes countries such as France, Germany,
  Spain, Sweden, Canada, USA and the Netherlands
  
• possibly merging the LMSA project, Japans
  contribution

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Why do we need ALMA?

• Counterpart to HST and in the future JWST
• Better angular resolution and sensitivity than
  the other 4 millimetre arrays (Berkeley-Illinois-M
  aryland Array, Owens Valley Radio Array, Nobeyama
  Radio Observatory and Plateau de Bure
  Interferometer)
• Sub-mm window

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The Altiplano of Chajnantor, Chile

• Atacama Desert dry
• 5000 m above sea level great atmosphere
• Altiplano flat good array interferometry

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Antennas and the Array Configuration

• Small antennas higher precision, higher FOV, and
  more antennas lead to higher image quality
  
• Large antennas larger collecting area, better
  angular resolution, and less antennas leads to
  less money spent
  
• 64 antennas, each 12m in diameter
• Parabolic telescope with cassegrain focus
• Surface accuracy - 20µm RMS
• Fast switch 1/sec
• Angular resolution from 0.1 to 0.01 arcsec
• Atmospheric window of 0.3-10 mm, or 30-950 GHz

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Sensitivity and angular resolution comparison
with other major facilities
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Currently, at ALMAs test facility in Socorro,
New Mexico, at the VLA, these prototypes are
being tested and evaluated.
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• 220 antenna stations
• Array configurations
• Compact (filled) 150 m
• Continuous zoom 200-5000 m
• Highest resolution 14.0 km

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Front End Electronics

• Coherent detectors 10 bands, but initially, the
  four highest priority bands will be
  provided84-119 GHz SIS
  
• 211-275 GHz SIS
• 275-370 GHz SIS
• 602-720 GHz SIS
• Two orthogonal receivers to measure dual
  polarization state of radiation
  
• Receivers in single cryogenic dewar below 4 K
• Water Vapor Radiometer 183 GHz

signal
Intermediate frequency
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Back End Electronics

• 8 GHz bandwidth
• intermediate frequency is subdivided and digitized

2 GHz 2 GHz 2 GHz 2 GHz
Correlator
8GHz
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Correlator

• Combines digital signals from all the antennas
  pair wise
  
• (64 C 2)64!/(62!2!)6463/22016 pairs

2016 pairs of phase and amplitude info
Image!
Fourier inversion
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Technical requirements for great scientific goals

• High fidelity imaging
• To image spatial structure within galactic disks
• To image chemical structure within molecular
  clouds
  
• To image protostars in star forming regions

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Technical requirements for great scientific goals

• Submillimetre receiving system frequency range
  best suited for transitions of simple molecules
  
• To measure the spectral energy distribution of
  high z galaxies
  
• To determine CII and NII abundance in galaxies as
  a function of cosmological epoch
  
• To image the dust continuum emission from
  cosmologically distant galaxies

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Technical requirements for great scientific goals

• High Spectral Sensitivity sensitivity best
  suited to detect thermal emissions in cold
  objects
  
• To get spectroscopic probes of protostellar and
  galactic strucure kinematics
  
• To get a spectroscopic chemical analysis of
  protostars, protoplanetary systems and galactic
  nuclei
  

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Technical requirements for great scientific goals

• Full polarization capabilities
• To measure the magnetic field direction from
  polarized emission of dust
  
• To measure magnetic field structure in solar
  active regions

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What an astronomer wants ALMA can help you study
lots

• Galaxies and Cosmology
• Star and planet formation
• Stars and their evolution, including the Sun
• Solar System

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Galaxies and Cosmology

• High resolving power allows for higher redshifts,
  up to z 10
  
• THE EARLY UNIVERSE
• Locating high z galaxies through their submm
  emission lines
  
• Finding a galaxys Spectral Energy Distribution
  to determine z, internal structure, rotation
  curves and mass distribution using spectral
  lines
• Structure formation using chemical and
  structural imaging, and measuring the magnetic
  field structure
  

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Galaxies and Cosmology

• Hot young stars emit optical and UV radiation
  that is absorbed by interstellar dust and
  re-radiates the light at longer wavelengths,
  peaking at 100µm.
• -Antennae from the HST and CO contour lines from
  ISO
  

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850 µm SCUBA image superimposed on Hale telescope
image submm sources are faint in the optical
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Star and Planet Formation

• Star formation hidden by visual extinction in the
  cold, dense molecular clouds
  
• Measure chemical composition and kinematics of a
  molecular cloud, even non-star forming clouds
  
• Measuring the magnetic field structure

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Simulation of magnetic field polarized by
protostar at 850-micron
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HII region massive star formation
Image taken by VLA at the continuum at 3.6cm
Countour of the continuum at 1.3mm emission line
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Serpens molecular cloud Dense cluster of young st
ars emerging from the cloud
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Model of protostellar accretion disk with giant
protoplanet forming in gap
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Simulation of image received by ALMA of
protoplanet in gap
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Stars and their Evolution

• Understand physical structure of bipolar jets
• Understand dust and gas distribution
• Measure chemistry of envelope
• Measure the magnetic field structure and
  polarization

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Bipolar jets HH211 molecular outflow from excess
angular momentum during star formation in 2.12
micron emmission line, while white contours show
CO emissions, and red countours show 1.33 mm
emmissions
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Solar Flare
Magnetic field lines
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Our own Solar System

• Detect winds on Mars
• Rates of gas evaporation and mapping chemical
  composition on Giants
  
• Images of volcanoes on Io

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Winds on Mars
CO emmission lines provides temperature profile
and contours of winds 50km above atmosphere
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TIMELINE

• June 1998 Phase 1 (Research and Development)
• June 1999 European/American cooperation
• January 2002 North American Prototype Antenna
  Testing at VLA Site
  
• July 2003 European Prototype Antenna Testing at
  VLA Site
  
• 2004 Tests of the Prototype System
• 2007 First observations made with ALMA
• 2011 Final construction of the array for full
  observations

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THE FUTURE JWST and ALMA

• The two telescopes that will detect and study the
  first luminous objects in our UNIVERSE
  
• JWST - optical and near- and mid-infrared
• ALMA mm and submm

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Thanks for listening!

• http//www.alma.nrao.edu/
• http//www.eso.org/projects/alma
• http//hia-iha.nrc-cnrc.gc.ca/projects/alma_e.html