Upcoming Instruments to Probe Reionization… Frank Briggs ANU

Upcoming Instruments to Probe Reionization… in the 21cm line Frank Briggs ANU Complementarity with WMAP/Planck/SPT HST JWST Already taught us that 21cm observations will be harder than originally thought…

Science, Vol no. 5948, pp – 1619, 25 September 2009, +supplements Cosmic Reionisation Australia Experiment (CORE) (India) Giant Metrewave Radio Telescope India km ----

Science, Vol no. 5948, pp – 1619, 25 September 2009, +supplements Cosmic Reionisation Australia Experiment (CORE) (India) Giant Metrewave Radio Telescope India km ---- Radio Astronomy “Facilities” multi-purpose

Science, Vol no. 5948, pp – 1619, 25 September 2009, +supplements Cosmic Reionisation Australia Experiment (CORE) (India) Giant Metrewave Radio Telescope India km ---- “Campaign style” Experiments

Science, Vol no. 5948, pp – 1619, 25 September 2009, +supplements Cosmic Reionisation Australia Experiment (CORE) (India) Giant Metrewave Radio Telescope India km ---- “Campaign style” Experiments

Summary of Main Points : in a period of exploration and creativity - for hardware and design of observational methods present generation of EoR Experiments are becoming novel “testbeds” antenna technologies array concepts signal processing: hardware, firmware, software for imaging, RFI rejection, … analysis: learn about foregrounds, high-dynamic range wide-field imaging

The new instruments… Contrast Contrast with traditional techniques What’s driving us to new approaches …? …cost…++

“Protected” Radio Frequency Bands versus Frequencies dictated by current science… … has been adequate ! redshifted spectral lines other new science requirements technical advances permit “wideband studies”

Murchison [Beresford & Chippendale] Z

ITU-R Rec.RA769 “Harmful” Threshold -260 Murchison ARRAYS “Harmful Threshold” x10 7 Large qso bubble

LEO satellites around 147 MHz Dynamic Spectra: Netherlands 256 channels over 156 kHz Very intense ‘pager signals’ at MHz and MHz 10 8 dynamic range 1 Hour LOFAR STRATEGY: use good time and frequency ranges - in between the Interference

LEO satellites around 147 MHz Dynamic Spectra: Netherlands 256 channels over 156 kHz Very intense ‘pager signals’ at MHz and MHz 10 8 dynamic range 1 Hour LOFAR STRATEGY: use good time and frequency ranges - in between the Interference MWA strategy = “Murchison”  Low frequency resolution  Only 8 bit ADC PAPER strategy: Radio quiet zone in South Africa

Traditional Radio Astronomy: => Discrete HighSB Objects against benign LSB Sky 21cm Emission from Recombination: => Diffuse LSB Structure against HSB Sky + structure Radio Imaging

Deep GMRT “L Band Image” ( 21cm rest freq ) Size: 12’x12’ Resol: 3” Sens: ~10  Jy [courtesy P. Lah] T B (sources) ~ K T B (sky) ~ 3 K

T B (source) ~ K T B (sky) ~ 3 K T B (EoR “sources”) ~ 23 mK [(1+Z)/7] 1/2 x […] (maybe -150 mK absorption) T B (“cold sky”) ~ 180 K ( F /180 MHz ) -2.6 ~ 133 K [(1+Z)/7] 2.6 Low Freq Sky Need Dynamic Range ~10 5 [(1+Z)/7] 2

Imaging Implications: “UV coverage” Fourier Transform Discrete Sources + Bland Sky Structure on all scales + Complex foreground sky FT.need “complete” UV sampling

LOFAR24 core RED DOTS  High Band Stations 2 km

LOFAR - HBA - Core 25x2 stations 4 h +45 o Core layout U-V Coverage

Ultimately…. 500 Tiles… MWA: 512 Tiles Layout in field instantaneous UV coverage Distance [km] 1 km 130,816 Interferometer Baselines !

2 km LOFAR Core MWA

Ultimately…. 500 Tiles… 512 Tiles Layout in field instantaneous UV coverage Distance [km] 1 km 130,816 Interferometer Baselines ! (VLA => 351, but earth rotation synthesis) Having many interferometer baselines buys 1.Complete uv coverage … 2.Over-determined Calibration, every 10 sec Changing antenna gains Changing ionospheric refraction Having many interferometer baselines costs 1.Extravagant Data Rate 2.Requires Real-Time Calibration, every 10 sec 3.Data compression, loss of flexibility, large storage requirements NOVEL Developments

PAPER : Precision Array to Probe the Epoch of Reionization (Backer et al) Layout of 64 element array Density of U-V coverage

Physical Area: 50544m 2 Effective Area: m 2 at 150 MHz 21 Centimeter Array (21CMA) x6 km arms

E W SN control room 21CMA Layout 81 pods along two perpendicular arms (6km+4km) 1 pod=127 antennas Baselines: 3240 Freq channels: 4096 Working Band: MHz Sampling rate 5s Total data size: 4 terabytes / day 6km 4km

0. Global signature …………………. 1.Imaging … 2.21cm absorption line forest …………….. 3.Power spectrum analysis ………… 4.Cross-correlation with … Five Types of Observation :

0. Global Signature (Ravi Subrahmanyhan, later talk) CORE EDGES Chippendale, Subrahmanyhan & Ekers Bowman & Rogers

Bowman et al Bowman & Rogers: EDGES status Feb 2010 February 2009August 2009September 2009 yellow: 68% gray: 95% reionization barrier Concluded 3 month deployment in MRO – “Noise Level”: 5 mK rms – Instantaneous reionization ruled out: 21 cm rapid step constrained to <30 mK between 6<z<13

1.Imaging … 3. Power spectrum analysis 4. Cross-correlation with … Antenna Array Elements MWA PAPER LOFAR “station” 130 m

LBA antenna station (48 dipoles, Feb 2007) LBA-antenna (4 wires, 2 pol) + ground plane

HBA initial test configuration Tile with 4x4 dipoles (5x5 meter) with Styrofoam backing structure 2x3 tiles

HBA tiles: what is inside…. But to keep parallel dipoles antenna rotation within styrofoam HBA-tile structure is required.

ARRAY DESIGN STRATEGIES: Single Dipole as element in Array Antenna “Tile” of 4x4 Dipoles “Station” built of many Tiles

ARRAY DESIGN STRATEGIES: Simple Pattern with nearly all sky beam, Takes many dipoles to attain sensitivity… Complex to build and control, with deg beam Narrow beam ~5deg, Reduces data rate, Better out-of-beam rejection…

Restricted Choice of Survey Fields Decl. R.A. need for Array Elements to form beams to reject Galaxy EoR expts will NOT be all sky… “selected regions”

2 km LOFAR Core MWA Compact is Good for EoR; why have any long baselines?

3C MHz WSRT-LFFE 2.7 km Array (de Bruyn) Need longer baselines for: 1.Calibration using unresolved sources 2. Tracking Ionospheric wobble 3.Discrete source identification and subtraction (4. Other scientific applications - such as identifying High Z radio sources)

LBA (10) MHz HBA MHz isolated dipoles tiles (4x4 dipoles) Core 2 km 18+ stations NL 80 km 18+ stations Europe >1000 km 8+ stations A station will have antennas / tiles: FOV: dipole ~100 o, tile ~20 o, station ~5 o Resolution: 60 MHz150 MHz Core 9’ 3.4’ NL 13’’ 5’’ Europe 1’’ 0.4’’ The LOFAR observatory

The ‘superstation’: on a 350 m diameter ‘island’ Sep 2008

MWA ( no digging for environmental and cultural heritage issues, until recently)

Aerial Photo of 32 Tile Prototype Array: 512 Tiles in 2011 !

MWA Pic A field 18 minute integration Continuum: MHz (FM radio and aircraft comms) 25’ resolution

ForA PicA > 20 degrees

Pic A U-V coverage

60 hours 173 Mhz 9.7x9.4” resol 20 HBA Stations LOFAR 173 MHz VLA 74 MHz LOFAR 173 Mhz VLA 1500 MHz WSRT 325 MHz LOFAR 173 Mhz

Summary of Main Points : in a period of exploration and creativity - for hardware and design of observational methods present generation of EoR Experiments are becoming novel “testbeds” antenna technologies array concepts signal processing: hardware, firmware, software for imaging, RFI rejection, … analysis: learn about foregrounds, high-dynamic range wide-field imaging

Science, Vol no. 5948, pp – 1619, 25 September 2009, +supplements Cosmic Reionisation Australia Experiment (CORE) (India) Giant Metrewave Radio Telescope India km ---- * * South Africa