Introduction to ALMA Al Wootten ALMA Project Scientist/North America

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Introduction to ALMA Al WoottenALMA Project
Scientist/North America
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The Millimeter Spectrum
COBE observations

• Millimeter/submillimeter photons are the most
  abundant photons in the spectrum of the Milky Way
  and most spiral galaxies, and in the cosmic
  background.
• After the 3K cosmic background radiation,
  millimeter/submillimeter photons carry most of
  the visible energy in the Universe, and 40 of
  that in for instance the Milky Way Galaxy.
• ALMA range--wavelengths from 1cm to 0.3 mm.

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Northern Chile
Site must be high to make the best use of
the atmospheric windows. Site should also be
accessible, supported by reasonably close
support facilities. Site should be dry for
transparency. Chajnantor lies relatively close to
the ancient town of San Pedro de Atacama,
inhabited for more than two millennia. San Pedro
is relatively near the Calama airport, and not
far from the ESO site at Paranal. Chajnantor lies
astride the paved Pasa de Jama road to
Argentina major gas pipelines from Argentina
traverse it.
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Chajnantor
AUI/NRAO S. Radford
SW from Cerro Chajnantor, 1994 May
Photo S. Radford
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Complete Frequency Access
Construction Project Bands 3, 6, 7 9.
Proposed by Japan 4, 8 10. Post-construction
1, 2 5
N.B. Band 1 31.3-45 GHz not shown
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ALMA Specifications
Antennae 64 12 m collecting area gt 7000
m2 Configurations 150 m 14 km resolution
(300 GHz) 1.4 0.015" Frequency 31 950
GHz wavelength 10 0.3 mm Receiver
sensitivity close to quantum limit Correlator
16 GHz / 4096 chan. Site excellent Result
A leap of over two orders of magnitude in both
spatial resolution and sensitivity
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ALMA Test Facility
Prototyping and testing ALMA Antennas and other
equipment at the VLA site in preparation for
Chilean Operations.
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Mercury3mm95 GHzVertexRSI Antenna
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SaturnVertexRSI Antenna265 GHz
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ALMA Median Sensitivity(1 minute AM1.3
75Quartile opacities lgt1mm, 25 l lt1mm)ALMA
Sensitivity Calculator http//www.eso.org/projec
ts/alma/science/bin/sensitivity.html
Frequency (GHz) Continuum (mJy) Line 1 km s-1 (mJy) Line 25 km s-1 (mJy)
110 0.05 7.0 1.4
230 0.10 10. 2.1
345 0.2 16. 3.3
675 1.0 61. 12.
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ALMA Brightness Temperature Sensitivity(1
minute AM1.3 1 Beam 75Quartile opacities
lgt1mm, 25 l lt1mm)ALMA Sensitivity Calculator
http//www.eso.org/projects/alma/science/bin/sensi
tivity.html
Frequency (GHz) Continuum (K) Line 1 km s-1 (K) Line 25 km s-1 (K)
110 0.005 0.70 0.14
230 0.002 0.24 0.5
345 0.002 0.18 0.03
675 0.003 0.17 0.03
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The ALMA Design Reference Science Plan

• To provide a prototype suite of high-priority
  ALMA projects that could be carried out in 3 yr
  of full ALMA operations gt quantitative reference
  for
• Science operations plan
• Imaging simulations
• Software design
• Data rates and dataset sizes
• Any other application within ALMA project
• URL http//www.alma.nrao.edu/science/

Goal
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How the DRSP was made

• Start from ALMA science case
• Washington Meeting October 1999
• ESO council proposal 2000 gt translate each
  chapter into one or more observing progams
• Identify Science IPT members as leaders for
  various topics add ASAC, ESAC, ANASAC members
  where needed
• Leaders free to involve other experts from the
  community
• Spontaneous, unsolicited contributions from
  community (no open call was made)

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DRSP status

• Started planning late April 03 outline teams
  complete early July submitted December 03
• 128 submissions received involving 75
  astronomers
• Review by ASAC members completed comments
  included
• Living document, with periodic updates
• Current version of DRSP on Website at
• http//www.alma.nrao.edu/science/

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Some initial conclusions

• Overall distribution over receiver bands
  reasonably consistent with weather statistics
• Fraction of continuum-only programs varies per
  receiver band and theme Band 6 pre-dominantly
  line Band 7 and 9 large fraction continuum
• Fraction of proposals which require total power
  continuum of order 10
• Fraction of proposals which require baselines of
  at least 1 km 50-60 (with peak around 0.1-0.2)
• Data rate consistent with plans.
• Image rate to visibility rate 1/30.
• 7 of projects result in images of size gt100GB.

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Statistics
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ALMA Data Product Complexity

• Primary data product is a calibrated image.
• Sensitivity increase of two orders of magnitude
  over previous millimeter arrays
• Resolution increase of up to an order of
  magnitude
• Total flux images include total power data
• Natural mode mosaicing large images
• All data in spectroscopic mode multiplane
  images
• Excellent site weather downtime minimized
• 24/7 Operation instrument productivity
  maximized
• High image content suggest that the science
  content per image is high
• High data rate suggests high potential science
  volume
• N.B. compare 500 GB/day to 20 GB/yr typical
  twenty years ago!
• This is ALMA average data rate peak is 10x
  higher potential much higher still.
• North American ALMA Science Center provides the
  resources to enable the potentially high volume
  of science ALMA can produce.
• Achieving ALMAs potential requires appropriate
  resourcing of individual ALMA researchers
• Questionnairehave the right resources been
  identified?

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Early Science Observing2007-2011

• Follows Commissioning and Science Verification
• Open to community through call for proposals
• Should demonstrate unique ALMA capabilities to
  all astronomers
• Provides feedback to ALMA operations

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ASAC Capabilities of Early Science Observing

• Sensitivity gain over existing facilities
• once gt6 antennas
• Long baselines gt high angular resolution
• High frequencies
• Southern sky
• Polarization capabilities

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ALMA Workshop
Purpose Consider DRSP and similar projects to
assess community needs for full realization of
the potential of ALMA datasets. As ALMA reaches
its Early Science milestone, what are the most
important ALMA features to incorporate into the
Early Science array? What are priorities of the
NA community for future ALMA instrumentation
initiatives?
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Operations Stages

• Early Pre-Operations
• Prior to 3-antenna interferometer
• Late Pre-Operations
• Prior to 6-antenna interferometer
• Early Operations 2007 Q3
• 6-antenna interferometer, Band 3 one other
• Baselines up to one (1) km
• Basic user tools commissioned
• Etc, etc, etc
• Full Operations 2011 Q4

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Early Science Operations Concepts
In 2007

• Staff hired into/trained by Integration and
  Commissioning teams
• Not 24/7 science operations
• Limited array configurations
• No breakpoints, limited eavesdropping
• Limited pipeline
• Central archive at OSF
• Only two (2) proposal calls in first 24 months
• Other issues, see Operations Plan

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Early Science Operations Time-Line
Relative time-line analysis on-going
Note the compressed timeframe, which calls for a
simple set of modes for Early Science
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Simplicity

• With fringes expected around Jan 2005, ATF
  Interferometer offers more time for debugging
  modes BUT
• Some ATF equipment will not be production ALMA
  equipment (including the antennas!)
• Hence, an appealing philosophy is to offer only
  those modes which can be demonstrated at the ATF,
  augmented by a very few additional modes.
• We explore modes possible under this philosophy

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What is a mode?

• What is a mode anyway?
• A mode is an element of an observational setup,
  including
• Configurations
• Receivers
• Correlator setups
• Calibration strategy
• Reduction strategy
• A description of all modes, or combinations of
  them, would be difficult

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Configurations

• First Science Array Configurations
• Defined in ALMA-90.02.00.00-004-A-SPE (John
  Conway)
• Encompass the spacings available from 172 inner
  pads
• Assumes 6 antennas available
• Resolution steps of about a factor of 3
• 3 moves at a time 15 baselines of which 3 are
  sequentially shared
• Provide a range of spatial frequencies
• Six configurations
• C1 Closest spacing, high brightness sensitivity
  but poor sidelobes
• C2 Slightly larger, still a 15m baseline, better
  sidelobes. T2.7_at_345 GHz
• C3-6 Resolution increases to T0.033_at_345 GHz
• Recommend Begin with C2

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Proposed Early Science Configurations
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Early Science Configuration Properties
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Receivers

• Current schedule forsees B3, B6, B7 and B9
  available
• Only B3 and B6 reasonably usable at ATF B7
  marginal
• Target having these available for Early Science
• Augment as commissioning and science verification
  allows
• WVRs available

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Correlator

• ATF prototype one baseline correlator modes.
• Four basebands available in correlator unclear
  if hardware support will exists
• ALMA correlator could support additional
  modese.g. four bits?

Bandwidth Single Polzn Dual Polzn Full Polzn
2GHz 256 128 64
128MHz 2048 1024 512
31.25MHz 8192 4096 2048
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Calibration Strategy

• Phase correction
• Fast switching useful for larger baselines.
• WVR usage after some testing of prototype devices
  at ATF.
• Amplitude calibration
• As with final array
• Total Power
• Single ACA 12m antenna, continuum and spectral
  line
• All antennas, spectral line

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Imaging Strategy

• Pipeline rudimentary or unavailable
• Mosaics supported
• Combination of total power plus interferometric
  data
• Data rate limited, brought on line to scale with
  number of available baselines
• Implications for ARC support appreciated

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ALMA Early Science Median Sensitivity(6
antennas 1 minute AM1.3 75Quartile opacities
lgt1mm, 25 l lt1mm)
Frequency (GHz) Continuum (mJy) Line 1 km s-1 (mJy) Line 25 km s-1 (mJy)
110 0.4 60. 12.
230 0.85 80. 16.
345 1.2 92. 19.
675 12. 685. 137.
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Comparison
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Animation
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Example Dataset final ALMA
M82 from ISO, Beelen and Cox, in preparation

• As galaxies get redshifted into the ALMA bands,
  dimming due to distance is offset by the brighter
  part of the spectrum being redshifted in. Hence,
  galaxies remain at relatively similar brightness
  out to high distances.

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ALMA Deep FieldPoor in Nearby Galaxies, Rich in
Distant Galaxies
Source Wootten and Gallimore, NRAO
Nearby galaxies in ALMA Deep Field
Distant galaxies in ALMA Deep Field
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Hubble Deep Field Rich in Nearby Galaxies, Poor
in Distant Galaxies
Source K. Lanzetta, SUNY-SB
Nearby galaxies in HDF
Distant galaxies in HDF
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An ALMA Redshift Survey in a 44 Field
Step 1 A continuum survey at 300 GHz, down
to 0.1 mJy (5s). This requires 140 pointings,
each with 30 minutes of observation, for a total
of 3 days. Such a survey should find about
100-300 sources, of which 30-100 sources will be
brighter than 0.4 mJy. This field is twice the
size of the HDF. Image 3000x3000 pixels x 1024
frequencies.
Step 2 A continuum and line survey in
the 3 mm band down to a sensitivity of 7.5 mJy
(at 5s). This requires 16 pointings, each with 12
hours of observation, so a total of 8 days. The
survey is done with 4 tunings covering the 84-116
GHz frequency range. Image 1000 x 1000 pixels x
4096 frequencies. The 300 to 100 GHz flux
density ratio gives the photometric redshift
distribution for redshifts z gt 3-4. For expected
line widths of 300 km/s, the line sensitivity of
this survey is 0.02 Jy.km/s at 5s. Using the
typical SED presented earlier this should detect
CO lines in all sources detected in Step 1.
At least one CO line would be detected for all
sources above z 2, and two for all sources
above z 6. The only blind'' redshift regions
are 0.4-1.0 and 1.7-2.0.
Step 3 A continuum and
line survey in the 210-274 GHz band down to a
sensitivity of 50 mJy (at 5s). 8 adjacent
frequency tunings would be required. On average,
90 pointings would be required, each with 1.5
hours, giving a total of 6 days. Together with
Step 2, this would allow detection of at least
one CO line for all redshifts, and two lines for
redshifts greater than 2. 2000x2000 pixels by
8192 frequencies. N.B. Three data products of
substantial complexity to assimilate.
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Example Early Science

• Unbiased line surveys of high mass star forming
  regions (Design Reference Science Plan project
  2.3.4)
• 64X64 pixels x 100,000 channels in four bands
• Spectral confusion limited, hence does not need
  full ALMA sensitivity (100 baselines sufficient)
• Example of complex data product from Early
  Science