1 / 17

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.

midori
Télécharger la présentation

The Expanded Very Large Array

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related