29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 1

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 2

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 3 The End Of the ‘Dark Ages’ : new telescopes shedding new light Rachel Webster University of Melbourne

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 4 Outline Brief History of Hydrogen What is Reionisation? New Telescopes: MWA (& others)

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 5 Outline Brief History of Hydrogen What is Reionisation? New Telescopes: MWA (& others) Acknowledgements to a long list of collaborators, including: David Barnes, Frank Briggs, Jackie Hewitt, Colin Lonsdale, Miguel Morales, Stuart Wyithe

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 6 History of the universe: Miralda-Escude 2003

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 7 History of the universe JWST

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 8 History of the universe JWST & MWA

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 9 Primordial Fluctuations First Stars Galaxies and Clusters

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 10 Evolution of structure Z=28.6 Andrey Kravtsov

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 11 Structure at z=10

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 12 Local Cosmic Web: HICAT, Meyer atal 2004

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 13 What is Reionisation? Ly-  Low z: long mean free path for Ly-  (1216Å) and photo-ionizing photons (<912Å) High z: short mean free path for Ly-  (1216Å) and photo-ionizing photons (<912Å) HI HII

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 14 Spin Temperature: absorption or emission? Definition of spin temperature: Given the number of atoms in each of the hyperfine transition levels of HI, Spin temp and CMB temp equal at early times Later kinetic temp T k of gas increases; spin temp coupled to T k by scattering of Ly  photons; 21cm emission

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 15 Z = cold H I H II   < 1 (Gunn-Peterson Effect) 70 MHz 90 MHz MHz Lowest possible redshift for reionisation

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 16 Quasars Before Reionisation HI absorbs photons near Ly-  resonance

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 17 Quasars Before Reionisation HI absorbs photons near Ly-  resonance

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 18 Gunn-Peterson troughs give the overlap redshift for HII at 6<z reion <6.4 The IGM has a neutral fraction x HI >0.001 at z~6 Fan et al. (2001) Becker et al. (2001) The data Gunn-Peterson Trough (total absorption)

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 19 Z = cold H I H II 70 MHz 90 MHz MHz Highest likely redshift for reionisation warm HI WMAP  z=15-20 Correlation between polarisation and temperature on large angular scales due to Thomson scattering by electrons

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 20 Detection Expt I: ‘the step’ Shaver etal 1999 Plenty of signal; can the feature be separated from the bandpass?

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 21 Experiment II: ‘Strömgren Spheres’ HI at IGM temperature HI warmed by X-rays HII (no contrast)

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 22 CMB+quasar +foreground IGM Or ∆z along the line of sight  z along the line-of-sight Contrast measures x HI Wyithe & Loeb 2003

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 23 Measuring the size of ‘Strömgren spheres’ Ly-  at z=6.28 White et al. (ApJ 2003) source HI HII

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 24 Detection Expt III: ‘power spectrum’ Morales & Hewitt 2004 also Zaldarriaga etal 2004

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 25 Neutral hydrogen is opaque Theoretical Simulation: Nick Gnedin 2005

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 26 Early structure was simple Theorist’s heaven: excellent progress Modelling of Stromgren spheres provides new limits on neutral fraction at z~6:  >0.1 t q ~10 6 yr t q ~10 7 yr Wyithe, Loeb, Carilli 2004

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 27 But it was never going to be easy…. **Foreground radio emission (noise ~ xsignal) »Synchrotron and free-free emission from MW (Shaver etal 1999) »Low frequency radio point sources (Di Matteo etal 2004) »Free-free emission from IGM electrons (Oh 1999)

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 28 ‘Noise’ spectra smooth in frequency  robust removal Santos, Cooray & Knox 2005 Power spectrum noise bias x ionisation fraction

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 29 New Telescopes: history Clarke Lake Radio Obs Bill Erikson and his students

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 30 New Experiments LOFAR – Holland »(Partially) funded, lots of momentum PaST - China (Mongolia) »On the ground, collecting data LWA - SW USA »Still planning; below 90MHz spread over 400km MWA- Western Australia »US-Australian collab, seeking funding

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 31 New Experiments LOFAR – Holland »(Partially) funded, lots of momentum PaST - China (Mongolia) »On the ground, collecting data LWA - SW USA »Still planning; below 90MHz spread over 400km MWA- Western AustraliaMWA- Western Australia »US-Australian collab, seeking funding

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 32 MWA Collaboration Project leaders: MIT & MIT-Haystack (technical and scientific) Harvard/CFA (scientific) ATNF(technical) Melbourne (early deployment & scientific) ANU-RSAA, Tasmania (scientific) Curtin, UWA, OSI (local infrastructure & scientific)

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 33 Experiments with MWA EoR –Stromgren spheres –Power spectrum Transients Coronal Mass Ejections

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 34 Simulated Stromgren Spheres: LFD 100 Hours 1000 Hours z=6.5, R=4Mpc Stu Wyithe, Loeb, Barnes astro-ph/

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 35 Full Array ie 10xLFD 100 Hours 1000 Hours There are 10’s of Stromgren Spheres in the field-of-view larger than 4Mpc

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 36 Detecting the Power Spectrum with MWA (Bowman & Morales 2005) Ionized frac. = 0.6 =0

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 37 The SUN Coronal Mass Ejections: measure interplanetary scintillation and Faraday rotation to describe the behaviour of the solar wind from near the sun to the earth’s location

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 38 Effect of space weather

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 39 Why Western Australia? FORTE satellite 131 MHZ

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 40 Mileura Homestead

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 41 The road to Mileura

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 42 Early Deployment Site

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 43 Tile assembly

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 44 Tile 1 from the air

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 45 RFI Environment minute integrations over full bandpass

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 46 Sun at 96 MHz Yes, that is the FM band …

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 47 Interferometry on an AGN time

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 48

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 49 Galactic Centre at 108MHz

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 50 Specs for MWA-LFD Frequency range: MHz, 32MHz bandwidth [3.8<z(21cm)<16.9] 500 tiles 4x4 dipoles in ‘phased array’, 8000m 2 Field-of-view: ~25deg fully steerable, multibeam Area: 1.5km giving MHz 125,000 baselines, 4x10 9 visibilities/0.5sec, full stokes polarisation [FPGA-based massively parallel digital hardware]

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 51 Finally…… Tomography of the earliest structures in universe Novel `technology telescope’ cheap array design huge, fast data network huge collecting area stunning radio-quiet location

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 52

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 53

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 54 Strömgren Spheres Expand Faster into Partially Reionised IGM High neutral fraction: Slow expansion Low neutral fraction: Fast expansion neutral IGMionised IGM

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 55 ground based radio techniques 10 MHz 350  MWA-LFD

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 56

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 57 furlanetto

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 58 ciardi

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 59 ciardi

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 60 NASA

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 61 The Surface of Bubble Overlap There is a surface on the sky corresponding to the redshifts along different lines of sight where the IGM was most recently partially neutral Contribution from HII regions Morales & Hewitt (2004)

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 62

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 63

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 64 Numerical Simulations of Reionization (Gnedin et al. 2000) neutral H fraction ionizing intensity 4Mpc << 60Mpc

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 65 Structure on Angular Scales in Emission from the Cosmic Web The temperature map, and the size of fluctuations on different scales reveal the topology of reionisation Tozzi et al. (ApJ 2002)

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 66 Numerical Simulations of Reionization (Gnedin et al. 2000) neutral H fraction ionizing intensity neutral H fraction ionizing intensity 4Mpc << 60Mpc

29 June 2005 Caroline Herschel Distinguished Lecture Rachel Webster 67 What is Reionisation? After recombination the universe comprised mostly neutral hydrogen Today, little hydrogen remains between galaxies Most of the hydrogen was re-ionised at z>6.5 The first sources must have been responsible: predominantly PopIII stars