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The Expanded Very Large Array

The Expanded Very Large Array. Rick Perley 1 and Sean Dougherty 2. 1 NRAO, Socorro, NM 2 DRAO/HIA/NRC, Penticton BC. The Expanded Very Large Array. The Expanded Very Large Array is a $90M upgrade of the Very Large Array.

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The Expanded Very Large Array

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  1. The Expanded Very Large Array • Rick Perley1 and Sean Dougherty2 • 1 NRAO, Socorro, NM • 2 DRAO/HIA/NRC, Penticton BC

  2. The 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.

  3. Overall EVLA Performance Goals • Providing orders of magnitude improvements in performance!

  4. Major 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 InterferometricDigital 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.

  5. The ‘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.

  6. Early 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)

  7. 3C147 Deep Field @ 1440 MHz Primary Beam Half Power First Null • 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.

  8. 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 15NH3isotopologue, • the 4(1,4)-4(0,4) line from NH2D. • meta-stable (9,8) & (10,9) lines, 24072 channels • 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.

  9. Orion-KL: Zooming in … • Left Side: The lowest 1.0 GHz, showing identifications. • Right Side: The two lowest meta-stable transitions, showing blended hyperfine structure. Two SO2 lines

  10. Spectra from the 128 x 128 x 24012 data cube End to end processing done in CASA by Steve Myers Moment-0 Image Data Cube available at: http://science.nrao.edu/evla/projectstatus/index.shtml

  11. EVLA 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 NH3 (3,3) masers

  12. Crystal’s ‘RSRO’ Project : A Diagnostic K-band Survey of 30 Massive Protostellar Objects • 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

  13. Early 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

  14. WIDAR Growth: 2010+ • Observational capabilities will grow rapidly through 2010 - 11 • All earlyobservations will be with the ‘fundamental 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

  15. Summary • 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

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

  17. Spectral Windows Continuity • Eight continuous subbands, each of 128 MHz, spanning 1 – 2 GHz band. Aircraft Navigation • Single baseline, ampscalar average, showing RFI, but also extensive ‘empty space’. These are raw data, with no bandpass correction. Satellites Cellphones GPS • Same data, vector average, showing how RFI is decohered over a few minutes integration. 1.024 GHz

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