early science specification and expected array evolution masao saito ea alma project scientist ea ps...
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Early Science Specification and Expected Array Evolution
Masao Saito
EA ALMA Project Scientist
EA PS Report 12nd ALMA Users Meeting 2011/1/13
Contents
• Early Science Specification– Minimum Requirement– Stretch
• Galleries
• Summary
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ALMA 5 antennas at AOS (2010.6)
2nd ALMA Users Meeting 2011/1/13
9 operational antennas at AOS as of 2011.1
Early Science Concept
• ALMA Early Science Cycle 0 – is expected to span 9 months. – is anticipated that 500-700 hours of array time will
be available for Early Science projects.– Any astronomer may submit a proposal in
response to the ALMA Early Science Cycle 0 Call for Proposals.
– Proposals that best demonstrate and exploit the advertised ALMA Early Science Cycle 0 capabilities, producing scientifically worthwhile results from relatively short observations (averaging a few hours), will be given preference.
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Important to understand capability in writing a proposal
Cycle 0 Minimum Spec
• 16 x 12m antenna array • 18 - 250m baselines, 2 configurations• Single field imaging• Frontend
– Band 3 (2SB: 84GHz - 116GHz)– Band 6 (2SB: 211GHz - 275GHz)– Band 7 (2SB: 275GHz - 373GHz)– Band 9 (DSB: 602GHz – 720GHz)
• Set of ~21 spectral modes (see later)• No subarrays, no special modes• Amp Calibration good to 5% (band 3) and less
accurate at high frequencies – 15% at band 9?
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Cycle 0 Capabilities - Stretch
To be decided by ~ mid-March 2011• Polarization: Full Stokes parameters on compact
sources: Q, U and V accurate to 1% of I. • Pointed Mosaics – up to 25 points
• Zero-spacing (single-dish rasters maps) – to cover same area as mosaics – Spectral Line only.
• Baselines up to 500m, 3 configurations (or perhaps some other scheme to give us longer baselines late in the first cycle).
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Spectral modes for Cycle 0
TDM modes Point Spacing1 (MHz) →
Band- MHz 7.8 15.6 31.3
width2 1800 13 23 43
“ASAC” modes in red
FDM modes Spacing of spectral points1 (kHz)→
Band- MHz 7.6 15.3 30.5 61 122 244 488 977
width2 1800 13 23 43
↓ 938 1 2 4
469 1 2 4
234 1 2 4
117 1 2 4
58.6 1 2 4
FDM: Digitization efficiency is ~85% TDM: Digitization efficiency is ~88%.Same mode for 4 basebands
with 122 kHz 1.77 times worse ~ 0.3 mJy /hr at 345 GHz
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1) Spatial Resolution and Field of View
Resolution
Field of View 2) Sensitivity
ES cycle0 Resolution
Early Science
)GH(
GH345
)(
250"72.0
z
z
L m m
)GH(
GH345"15
z
z
)(345@2sec3600
sec23.01
2
1
2
1
polaridualGHzGHz
GHztmJy
• Spatial Resolution Max baseline of SMA ~ 600m ALMA ES (cycle0) ~ 250m
• 感度 ( 2GHz Bandwidth 1 3.2mJy @ 345GHz) SMA integ time(WV 2.50mm) τ=4.0hr ALMA integ time(WV 1.26mm) τ=18.4sec
※ (SMA http://sma1.sma.hawaii.edu/beamcalc.html , ALMA OT IT3)
ALMA needs1/780 integtimeof SMA
Similar to SMA extended Configuration
Cycle0 Sensitivity (Comparison with SMA)
SMA
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SMA 6hr(on source 4hr)Extended configuration
ALMA 5min integ time250m configuration
Contour every 5 %
20% level
SMA サイト http://sma1.sma.hawaii.edu/beamcalc.html で計算
Contour every 10 %
Similar beam sizewith similar sidelobe level
Cycle0 PSF(Comparison with SMA)
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Example
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Early Science 1hr integ 5sigma detection limit
JCMT Disk Survey in Taurus by Andrews+05
Cycle 0: UV coverage and PSF
https://safe.nrao.edu/wiki/bin/view/ALMA/EarlyScienceSims
UV coverage and PSF by CASA image simulator with 5 min and 8 hr integrationALMA site: latitude = -23 degrees16 12m antennasMax Baseline 250mTentative Array Configuration
Antennas (Blue dots) and Pads (pink dots) 120 baseline UV Plane
FOV ~14.9 arcsec @ 345GHz
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Taurus(04h30m,25d00m) の PSF@345GHz
コントアは 0.05(5%) 刻み
5 minutes integration 8 hours integration
• beamFWHM(0.62”,0.92”)PA ~ -20deg
• side-lobe-2% ~ 20%
• 1σ sensitivity (2GHz BW)0.86mJy (17.2mK)
• beamFWHM(0.69”,0.85”)PA ~ 40deg
• side-lobe-4% ~ 6%
• 1σ sensitivity (2GHz BW)0.088mJy (1.71mK)
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Orion(05h35m,-5d00m) の PSF@345GHz
コントアは 0.05(5%) 刻み
5 minutes integration 8 hours integration
• beamFWHM(0.58”,0.69”)PA ~ -40deg
• side-lobe-6% ~ 20%
• 1σ sensitivity (2GHz BW)0.79mJy (22.3mK)
• beamFWHM(0.62”,0.73”)PA ~ -60deg
• side-lobe-6% ~ 8%
• 1σ sensitivity (2GHz BW)0.080mJy (2.03mK)
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-Oph. (16h25m,-25d00m) の PSF@345GHz
コントアは 0.05(5%) 刻み
5 minutes integration 8 hours integration
• beamFWHM(0.58”,0.65”)PA ~ -40deg
• side-lobe-6% ~ 20%
• 1σ sensitivity (2GHz BW)0.78mJy (23.3mK)
• beamFWHM(0.58”,0.73”)PA ~ -75deg
• side-lobe-6% ~ 8%
• 1σ sensitivity (2GHz BW)0.079mJy (2.70mK)
EA PS Report 152nd ALMA Users Meeting 2011/1/13
Lupus (15h40m,-35d00m) の PSF@345GHz
コントアは 0.05(5%) 刻み
5 minutes integration 8 hours integration
• beamFWHM(0.58”,0.65”)PA ~ -40deg
• side-lobe-6% ~ 20%
• 1σ sensitivity (2GHz BW)0.78mJy (23.5mK)
• beamFWHM(0.58”,0.73”)PA ~ -75deg
• side-lobe-6% ~ 6%
• 1σ sensitivity (2GHz BW)0.080mJy (2.14mK)
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Chameleon (15h40m,-70d00m) の PSF@345GHz
コントアは 0.05(5%) 刻み
5 minutes integration 8 hours integration
• beamFWHM(0.62”,0.88”)PA ~ -30deg
• side-lobe-6% ~ 20%
• 1σ sensitivity (2GHz BW)0.86mJy (17.9mK)
• beamFWHM(0.73”,0.73”)PA ~ -75deg
• side-lobe-4% ~ 4%
• 1σ sensitivity (2GHz BW)0.088mJy (1.86mK)
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Gallery1
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This is an object in our own galaxy. It is a young star which is still surrounded by a disc of gas. Here we are observing the carbon monoxide J = 3-2 line at 345 GHz in the disc. (The star itself is not visible here.) The integrated flux is shown as contours on the left, while the spectrum at the peak of the emission is on the right, showing, via the Doppler effect, that the gas is moving at different speeds. In the middle is the average velocity of the gas at each point in the image, indicated by the colour. This shows a characteristic pattern created by the rotation of the disc around the star.
Gallery2
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As a test of ALMA’s ability to observe broad spectral lines, we observed the quasar BRI 0952-0115, which is at a red-shift of z = 4.43. The object is again unresolved on short baselines, but the 158 micron line from ionized carbon is clearly detected in the spectrum, which is impressive given that this observation took only one hour in total.
Summary
• ALMA Early Science Cycle0 is coming soon with unprecedented sensitivity.
• Prepare for your proposal with understanding ALMA Cycle0 capability.
• Cycle0 final spec will be decided by Mid March.
• Join us in the ALMA special session on Mar 16th in the ASJ annual meeting in Tsukuba.
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2nd ALMA Users Meeting 2011/1/13 2121
www.almaobservatory.org
The Atacama Large Millimeter/submillimeter Array (ALMA), an international astronomy facility, is a partnership among Europe, North America and East Asia in cooperation with the Republic of Chile. ALMA is funded in Europe by the European Organization for Astronomical Research in the Southern Hemisphere (ESO), in North America by the U.S. National Science Foundation (NSF) in cooperation with the National Research Council of Canada (NRC) and the National Science Council of Taiwan (NSC) and in Japan by the National Institutes of Natural Sciences (NINS) in cooperation with the Academia Sinica (AS) in Taiwan. ALMA construction and operations are led on behalf of Europe by ESO, on behalf of North America by the National Radio Astronomy Observatory (NRAO), which is managed by Associated Universities, Inc. (AUI) and on behalf of East Asia by the National Astronomical Observatory of Japan (NAOJ). The Joint ALMA Observatory (JAO) provides the unified leadership and management of the construction, commissioning and operation of ALMA..
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