1. The Murchison Wide Field Array (MWA)

2. @ Murchison, ~300 km from Geraldton

3. The Partnership  MIT Haystack Observatory (Project Office)  MIT Kavli Institute  Harvard Smithsonian Center for Astrophysics  UMelbourne, Curtin Uni, Aus Nat Uni  USydney, UTasmania, Uni Western Aus  ATNF CSIRO (via synergy with ASKAP)  Raman Research Institute, India 3

4. MWA Science Goals  Epoch of Reionization  Power spectrum  Strömgren spheres  Solar/Heliospheric/Ionospheric Science (SHI)  Solar imaging  Faraday rotation – B field of CME’s and heliosphere  Interplanetary Scintillation  Small scale ionospheric structure  Transients  Deep blind survey  Light curves (field and targeted)  Synoptic surveys  …  Other  Galactic and Extra-galactic astronomy  Pulsars  ISM survey  Recombination lines ...

5. Epoch of Reionisation (EOR)  After ~300,000 years electrons and protons combine to form hydrogen  After ~1 billion years stars and quasars ignite, radiation splits hydrogen into protons and electrons.  In between are the Dark Ages

6. Solar and Heliospheric science

7. MWA Science Goals  Epoch of Reionization  Power spectrum  Strömgren spheres  Solar/Heliospheric/Ionospheric Science (SHI)  Solar imaging  Faraday rotation – B field of CME’s and heliosphere  Interplanetary Scintillation  Small scale ionospheric structure  Transients  Deep blind survey  Light curves (field and targeted)  Synoptic surveys  …  Other  Galactic and Extra-galactic astronomy  Pulsars  ISM survey  Recombination lines ...

8. Murchison Widefield Array: Design 8

9. Murchison Widefield Array: Specs Frequency range 80-300 MHz Number of receptors 8192 dual polarization dipoles Number of tiles 512 Collecting area ~8000 m 2 (at 200 MHz) Field of View ~15°-50° (1000 deg 2 at 200 MHz) Configuration Core array ~1.5 km diameter (95%, 3.4’) + extended array ~3 km diameter (5%, 1.7’) Bandwidth 220 MHz (Sampled); 31 MHz (Processed) # Spectral channels 1024 Temporal resolution 8 sec Polarization Full Stokes Point source sensitivity 20mJy in 1 sec (32 MHz, 200 MHz) 0.34mJy in 1 hr Multi-beam capability 32, single polarization Number of baselines 130,816 (VLA: 351, GMRT: 435, ATA: 861 )

10. 1.5 km Array Configuration 500 m 1.5 km 120 m

11. Data Flow Diagram

12. RFI Environment

13. Early Deployment: 3 Tile System

14. Galaxy (single tile)

15. Solar (Type 3) Burst

16. Crab giant pulse detections with the ED system Bhat, Wayth, Knight, et al. (2007), ApJ, 665, 618 System: 3 tiles - G ~ 0.01 K/Jy Tsys ~ 200 + 180 K BW ~ 0.75 x 8 MHz Freq = 200 MHz # GPs ( > 9 kJy) = 31

17. Giant pulse and (fast) transient detection prospects with MWA Bhat et al. (2008)

18. 32 Tile Prototype  Motivation  Engineering test bed  End to end signal/data path and system performance testing  Training data sets for calibration system  Learning to operate in the site conditions  Early Science

19. 32 Tile system: Specs Aperture plane uv plane 32 tiles, 4 nodes∆t = 50 ms A eff = 550 m 2 (~6% of MWA)  0 ~15’ @ 200 MHz Bandwidth = 31 MHz496 physical baselines ∆ = 10 kHz Max data rate ~12.7 Mvis/s (1TByte in ~2h45min)

20. 6 Tile system  6 tiles from the 32 available  First field testing of the prototype receiver  Bandwidth – 1.28 MHz  Offline software correlation  Essentially arbitrary spectral and time resolution – Extremely well suited for imaging of solar bursts

21. Early 6T results uv coverage Closure Phase Phase (deg) Time (4 hrs) Amplitude band shapes 1.28 MHz Phase band shapes

22. Some Images

23. Real time system for calibration and imaging: signal processing challenges  Data volume - 19 GB/s Raw visibility cannot be stored Dedicated hardware for correlation and data processing  Large FOV Wide FOV requires new approach to integrating, imaging (and deconvolution) Gain and polarisation responses are direction dependent  Calibration Must be real time, since visibilities are not stored Ionosphere shifts source positions by ~arcminutes Ionosphere should be a phase ramp over array Ionospheric faraday rotation

24. The MWA Real Time System (RTS)

25. Calibration and measurement loop

26. MWA RTS - The Imaging pipeline Mitchell, Greenhill, Wayth, et al. (2008), IEEE

27. Real time system: Computational costs  Parameters (8 second cadence): 40 peel sources, 400 iono sources 1125^2 image size (primary beam) 768 frequency channels, 130000 visibilities  Calibration:3.3 Tflop  Grid and image:1.8 Tflop  Stokes conv:4.3 Tflop  Regridding:? (0.05 to 28 Tflops)  Approx total:10 Tflop (efficient regrid) (over 8 seconds)

28. User access to the MWA  Not an open facility - as originally proposed  Some partners have proposed a “user facility”  Current policy - Interested pulsar users are welcome to join the collaboration  Pulsar science - part of the transient science collaboration - coordinators: Roger Cappallo (MIT) and Shami Chatterjee (Univ. Syd)  Current (pulsar) members: Bhat, Bailes, Deshpande

29. Concluding Remarks  MWA - a major low frequency instrument in the southern hemisphere  Status: 32T system by Q4 2008, full system by 2009  Primary science: EOR, transients, solar  A great instrument for pulsars (G ~ 3 K/Jy)  Early pulsar science - Crab giants @200 MHz  Interested users are welcome to join the collaboration (transients + pulsars)