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

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

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

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

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

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

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

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

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)

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

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

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

EVLA

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Full-Bandwidth Availability Timescale• During transition, L, C, and X band receivers are on all

antennas.

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