The Expanded Very Large Array
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Transcript of The Expanded Very Large Array
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Atacama Large Millimeter/submillimeter ArrayExpanded Very Large Array
Robert C. Byrd Green Bank TelescopeVery Long Baseline Array
The Expanded Very Large Array
Rick Perley1 and Sean Dougherty21 NRAO, Socorro, NM2 DRAO/HIA/NRC, Penticton BC
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EVLAThe Expanded Very Large Array• The Expanded Very Large Array is a $90M
upgrade of the Very Large Array.– Project began in 2001, will be completed in 2012 – on
time, on spec, on budget.• The EVLA will multiply by orders of magnitude
the observational capabilities of the VLA. • Key goals are:
– Full frequency coverage from 1 to 50 GHz.– Up to 8 GHz instantaneous bandwidth, per polarization– New correlator with unprecedented capabilities– ~3 mJy (1-s, 1-Hr) point-source continuum sensitivity at
most bands.– ~1 mJy (1-s, 1 km/sec, 1 Hr) line sensitivity at most
bands.
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EVLA
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Overall EVLA Performance Goals• Providing orders of magnitude improvements in
performance!Parameter VLA EVLA Factor
Continuum Sensitivity (1-s, 1 hr.) 30 mJy 3 mJy 10
Maximum BW in each polarization 0.1 GHz 8 GHz 80
# of frequency channels at max. BW 16 16,384 1024
Maximum number of freq. channels 512 4,194,304 8192
Coarsest frequency resolution 50 MHz 2 MHz 40
Finest frequency resolution 381 Hz 0.12 Hz 3180
# of full-polarization spectral windows 2 64 32
(Log) Frequency Coverage (1 – 50 GHz) 22% 100% 5
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EVLAMajor EVLA Milestones• All 28 antennas now converted to EVLA
standards. • VLA correlator was shut down on January 11. • New EVLA correlator turned on March 2.
• Wideband Interferometric Digital ARchitecture (WIDAR) correlator contributed by Canada
• EVLA ‘early science’ OSRO and RSRO programs began March 2010 and continue through end of 2011.
• 2 GHz bandwidth available by June 2010.• Correlator installation complete July 2010.• Full bandwidth (8 GHz) available on all antennas
late-2011. • Receiver implementation will be completed end of
2012. 4
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EVLAThe ‘WIDAR’ Correlator• A 10 petaflop special-purpose computer.
– Designed and built by Canadian HIA/DRAO.• Major capabilities:
– 8 GHz maximum instantaneous bandwidth, with full polarization.
– 16384 minimum, 4.2 million maximum frequency channels
– 64 independently tunable full polarization ‘spectral windows’, each of which effectively forms an independent ‘sub-correlator’.
– Extensive special modes: pulsar gating/binning, phased array, VLBI-ready, burst modes, and more.
• Most of this correlator now in place at the VLA site.
• Fundamental capabilities will be developed first, with specialty modes later. 5
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EVLAEarly EVLA Results• Results shown from:
– A 12-antenna sub-array used to test WIDAR-0 prototype.
• 8192 channel, Full polarization, Eight adjacent spectral windows
– The full WIDAR, with all antennas.• Eight tunable spectral windows
• For more early results, see posters:– WIDAR – the High-Performance Heart of the EVLA (DRAO
WIDAR team)– EVLA and Early Galaxies: Current Status (Carilli et al.) – Zeeman Effect at 36 and 44 GHz from Class I Methanol
Masers (Momjian and Sarma)
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EVLA3C147 Deep Field @ 1440 MHz• 12 antennas, 110 MHz
bandwidth, 6 hours integration
• Fidelity ~ 400,000:1• Peak/rms ~ 850,000:1 • The highest fidelity image
ever made with the VLA – using only a fraction of the full capability!
• The artifacts are due to non-azimuthal symmetry in the antenna primary beams. – Illustrates the need for
advanced calibration/imaging software.
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First Null Primary BeamHalf Power
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EVLA
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Orion-KL Spectrum – 3 GHz Wide• Three short obs. of Orion, each 1024 MHz wide, with ~1.5
km/sec velocity resolution and 2.5” spatial resolution, show 31 strong lines. • From ammonia (NH3):
• 8 lowest meta-stable inversion transitions (J,K) = (1,1) to (8.8)
• (6,6) line from 15NH3 isotopologue, • the 4(1,4)-4(0,4) line from NH2D.• meta-stable (9,8) & (10,9) lines,• Two E/A doublets of methyl
formate: CH3CHO• OCS 2-1• Three lines from SO2
• Ten strong methanol maser lines from E-type series (J=2 – 11).
• One unidentified line• Numerous weak lines.
24072 channels
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EVLAOrion-KL: Zooming in …
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• Left Side: The lowest 1.0 GHz, showing identifications.• Right Side: The two lowest meta-stable transitions,
showing blended hyperfine structure.
Two SO2 lines
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EVLASpectra from the 128 x 128 x 24012 data cube
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Moment-0 ImageEnd to end processing done in CASA by Steve
Myers
Data Cube available at: http://science.nrao.edu/evla/projectstatus/inde
x.shtml
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EVLAEVLA K-band Observations of massive young stellar objects in NGC6334-I• 8 x 8 MHz subbands with 256 channels, 0.4 km/sec; 10 minutes on source!!!!• Test for RSRO project AB1346 (PI Crystal Brogan): “A Diagnostic K-band Survey of
Massive Young Protostellar Objects” which will use 16 subbands
NGC6334-I
masers
NH3 (3,3)
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EVLACrystal’s ‘RSRO’ Project : A Diagnostic K-band Survey of 30 Massive Protostellar Objects
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• In the “best case” scenario we will use 32 subbands (solid and dotted lines above) which includes a number of rare and deuterated species
• In the “great case” scenario we will use 16 subbands (solid lines above)• Current tests uses 8 of the subbands above
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EVLAEarly Science Programs• Two early science programs: March 2010 through
December 2011. • Open Shared Risk Observing (OSRO):
– A ‘business as usual’ observing protocol. – Observers will access EVLA in same manner as current for
VLA. – Initial configuration provides 512 spectral channels with one
or two spectral windows of 128 MHz (maximum) each.• Resident Shared Risk Observing (RSRO):
– Must be resident in Socorro for at least 3 months.– Participants will have access to more extensive observing
capabilities. – Participants will assist NRAO staff in expanding capabilities– Observing time proportional to length of residency. – 27 proposals received on first call, 13 have been accepted.
• For details, see: – http://science.nrao.edu/evla/earlyscience/osro.shtml– http://science.nrao.edu/evla/earlyscience/osro.shtml
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EVLA
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WIDAR Growth: 2010+• Observational capabilities will grow rapidly through 2010 -
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homogeneous correlator setup’– All spectral windows adjacent, with same width &
channelization, arranged to maximize total bandwidth (BW) coverage
• Resident observers (RSRO Program) should have access to:– 2 GHz/polarization BW (all antennas) by mid-2010– 8 GHz/polarization BW (all antennas) by end of 2011. – Recirculation (increased spectral resolution) by late 2010– Independent spectral window tuning by early 2011– Flexible resource allocation (trading spectral windows for
more spectral resolution) by mid 2011
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EVLASummary• EVLA is now conducting science observations with all
antennas and unprecedented new capabilities• Wide-band (full tuning range) receivers available on all
antennas– Highest frequency bands (18 – 50 GHz): mid 2010– 4 – 8 GHz: end 2010– Remaining four bands: 2012
• Ever Increasing Science opportunities: Mar 2010 - Dec 2011 – Basic modes via OSRO Program:
• 256 MHz max BW, and you stay home– Advanced modes via RSRO Program:
• 2 – 8 GHz max BW, and you come to Socorro– Specialty modes as implemented, guided by user
interest• Full Regular Observing begins Jan 2012 15
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EVLA
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Full-Bandwidth Availability Timescale• During transition, L, C, and X band receivers are on all
antennas.
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EVLASpectral Windows Continuity
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•Eight continuous subbands, each of 128 MHz, spanning 1 – 2 GHz band.
1.024 GHz
Satellites
AircraftNavigation
Cellphones
• Single baseline, ampscalar average, showing RFI, but also extensive ‘empty space’. These are raw data, with no bandpass correction.
• Same data, vector average, showing how RFI is decohered over a few minutes integration.
GPS