THE MURCHISON WIDEFIELD ARRAY: FROM COMMISSIONING TO OBSERVING D. Oberoi 1,2, I. H. Cairns 3, L. D. Matthews 2 and L. Benkevitch 2 on behalf of the MWA Collaboration 1 National Centre for Radio Astrophysics, TIFR, India 2 MIT Haystack Observatory, USA 3 School of Physics, Univ. of Sydney, Australia

Outline Murchison Widefield Array – An introduction Current status and near term plans Some recent results from the MWA

The Murchison Widefield Array Low radio frequency interferometer ( MHz) Key Design Considerations Exploit the advances in Digital Signal Processing and affordability of computing. Emphasis on quality calibration Optimize the design for carefully chosen science targets Simplify the problem to the extent possible Key Design Features Large N (no. of interferometer elements) Compact footprint (max baseline ~3 km) Operation at higher end of the ‘low radio frequency‘ range Radio quiet location - Western Australian Outback  Humans ~ 4x10 -3 humans km -2

MWA: Key Science Projects Epoch of Reionization 21cm hyperfine transition line of neutral hydrogen, red-shifted to frequencies below 200 MHz Flagship science application, but very challenging Galactic and Extra-galactic Science Confusion limited all-sky survey with full polarimetry and good spectral resolution Time domain astrophysics Known and not yet known transients Solar, Heliospheric and Ionospheric Science Spectroscopic solar imaging IPS and Faraday rotation studies of the Heliosphere Ionospheric propagation effects AOGS, Brisbane, June 2013

X Axis spans MHz (~ MHz); Y Axis spans ~10 min

MWA: uv coverage Very Large Array NM, USA 351 baselines 27 elements 8128 baselines128 elements

MWA: Current Status Instrument re-scoped to 128 tiles (~early 2011) Status as of June 2012 Site infrastructure  Site survey for marking tile locations and trench paths  Trenching  Laying power and optical fiber cables  Building receiver pads Hardware installation  Tiles - all 128  Beamformers – all 128 AOGS-AGU Joint Assembly, Singapore August 2012 Aug. 2012, AOGS

MWA: Current Status Commissioning Period (June 2012 – June 2013)  Test and commission the array in 5 groups of 32 tiles each (June 12 – Dec 12)  Install the 128T correlator to run the entire array as a single instrument  Commission the 128T as a single instrument  Commissioning report accepted on June 20, 2013 at MWA Project meeting in Seattle, WA. Formal end of the commissioning period One year period of ‘shared risk observing’ starts Jul 2013 Jul-Dec 2013 – Open only to MWA Project members Jan-Jun 2014 – Significant amount of ‘Open Skies’ observing time AOGS, Brisbane, June 2012

MWA: Solar Observations Proposal Lead by Cairns and Oberoi Unbiased solar observing In-depth investigations concentrate disproportionately on what is deemed to be ‘interesting’. Exploring new phase space – discovery potential – avoid application of any a-priori bias 30 hours (19 TB) 1 hr/day for a month, at the same UT slot Same observing mode (12 chunks of 2.56 MHz distributed from 80 to 300 MHz); 1s, 40 kHz resolution Observations for Interplanetary Scintillation (IPS), Ionospheric Scintillation, satellite radio beacons – all require high time resolution data (~20ms) – voltage beamformer to provide this is currently under development – expect to conduct proof-of- principle observations using Director’s Discretionary Time GRANTED

Andrea Offringa (ANU) and the MWA Commissioning Team

Commissioning Highlights Southern Galactic Plane Mosaic Ben McKinley (ANU), Natasha Hurley-Walker (Curtin), Randall Wayth (Curtin) and the MWA Science Commissioning Team

Commissioning Highlights: Solar Imaging 16 May, :15:02 UT 0 = MHz  =640 kHz  t=1 second Imaging Dynamic Range ~1500

Radio Movie 16 May, :11:04 – 04:16:00 UT 0 = MHz  =640 kHz  t=1 second Imaging Dynamic Range ~1500

Spatial Variability of Radio Emission 20% 70% 250% 600%

Conclusions Commissioning successfully completed on schedule. Shared risk observing commences next month. MWA is exceptionally well suited for solar imaging - represents the state-of-the-art for the high dynamic range, high fidelity imaging at low radio frequencies. ‘Open Skies’ policy - observing proposals from the community are invited for period starting Jan Visit for more informationhttp:// If you would like to get involved – (Divya

Baselines and u-v plane The u-v plane, except that units on the axes should have been, not length N Baselines = N(N-1)/2 (u ij, v ij ) (-u ij,-v ij ) u ( ) v ( )

25 Sep, :08:50 – 04:18:47 UT 0 =152.3 MHz  =80 kHz  t=1 second Imaging Dynamic Range ~5500