1. Astronomy at 100 MHz HI-z vs ZZ Top

3. damped Lyman-  abs-lines 21cm Line Studies (HIPASS)

4. Cut off from view of optical wavelengths !!! n HI n HI +n HII  10 -3 If neutral fraction >

5. Pre-WMAP 6.2 alter

6. Gnedin’s simulation of Reionization: log(Neutral fraction) log(density) log T log(mean intensity of ionizing flux) http://casa.colorado.edu/~gnedin/GALLERY/

7. MAP

8. Z = 17  ??? Rules out WDM MAP Result 6.2 alter

9. .…. ionized…… re-re-ionized re-ionized

10. Time scales for Recombination … t = n /R recomb e # Electrons /cm 3 # Recombinations /sec /cm 3 = n /(n n  ) eep recomb

11. Time scales for Recombination in IGM… t = n /R recomb e = n /(n n  ) eep recomb = 1 /( n  ) p recomb = T /( n 2 x 10  ) sec p 1/2 -11 but, n ~ n proportional ~ (1+z) 3 p baryon t proportional T /(1+z) recomb 3 1/2

12. Time scales for Recombination … t = n /R recomb e = n /(n n  ) eep recomb t proportional T /(1+z) recomb 3 1/2 at z=9 t ~ 10 yrs recomb 8 at z=0 t ~ 10 yrs recomb 11

13. 70 MHz ………………..180 MHz

15. Z = 20 15 10 8 7 6 cold H I warm H I R. Cen: 2 Reionisations Pop III stars: @ 500 Solar mass H II

16. 10 arcmin LOFAR and SKA … Quasar distributed star formation

19. log T B log Frequency 180 MHz 180 K T B ~ f -2.6 Foregrounds: - Galactic synchrotron - Discrete sources - R.F.I. 3000K Galactic Center

20. 74 MHz x 6

21. WMAP result

23. Galactic / CMB separation…

24. TE Spectrum at low l

25. “The Z=20 Expt” JR, FB, et al

26. FM band in NRQZ Green Bank, WV Nominal NRQZ Limit Barnbaum & Bradley 1998 3x10 -11 w/m 2 VLBI Total Power 10 -19

27. Mileura Station – min/median/max 10 hrs @ 1 min intervals Azimuth :– 30 deg 3kHz bandpass average A. Chippendale 3 feb 2003 Nominal NRQZ Limit VLBI Total Power

28. RFI Subtraction with a reference horn… origins in Int-Mit group at CSIRO – ATNF illustrations from Parkes Telescope… (Jon Bell et al.)

29. RxRx gASgAS S I + g 1 I I g3Ig3I - g 1 I Signal Processing  gASgAS g1g1 g3g3 X Cross Correlation

30. R F I

31. Reference Antenna I I(t) =   h  (t) * i o (t    Impulse Response h(t) for each path  Convolution operator Signal radiated by transmitter … with DELAY  

32. = G(f) I o (f) I (f) = (   G  (f) e - i 2    f ) I o (f) Reference Antenna I Time Domain Frequency Domain I(t) =   h  (t) * i o (t    

33. Cross correlation: single polarization feed with 2 reference signals 1. Pol A 3. Ref 1 4. Ref 2 …G 1 G 4 * | I o 2 | G 3 G 4 * | I o 2 | ?? G1G1 G3G3 = G 1 G 4 * | I o 2 | G 3 G 4 * | I o 2 | G1G1 G3G3

34. Cross correlation: single polarization feed with 2 reference signals 1. Pol A 3. Ref 1 4. Ref 2 …G 1 G 4 * | I o 2 | G 3 G 4 * | I o 2 | G1G1 G3G3 = G 1 G 4 * | I o 2 | G 3 G 4 * | I o 2 | = C 14 (f) C 34 (f) = C 14 = C 34

35. Practical Application: Auto-Correlation Spectrometer |gA2||S2||gA2||S2| S I A/C spectrometer + | g 1 2 | |I 2 | | g 1 2 | |I 2 | = Power Spectrum P(f) g 1 g 3 * |I 2 | g 4 g 1 * |I 2 | g 4 g 3 * |I 2 | = C 13 (f) C 14 * (f) C 34 * (f) Advantage: Cross Correlation Spectra  NO BIAS due to NOISE power

36. Cross correlation: single polarization feed with 2 reference signals 1. Pol A 3. Ref 1 4. Ref 2 G 1 G 3 * | I o 2 | G 1 G 4 * | I o 2 | G 3 G 4 * | I o 2 | = C 14 = C 34 | g 1 2 | |I 2 | = C 13 (f) C 14 * (f) C 34 * (f) = C 13 A/C Spectrum Contamination

37. Cross correlation: dual polarization feed with 2 reference signals 1. Pol A 2. Pol B 3. Ref 1 4. Ref 2 G 1 G 3 * | I o 2 | G 1 G 4 * | I o 2 | G 2 G 3 * | I o 2 | G 2 G 4 * | I o 2 | G 3 G 4 * | I o 2 | = C 13 = C 34 = C 14 = C 23 = C 24

38. Duration 56 s with 0.1 s steps Bandwidth 5 MHz Raw Dynamic Spectra: Time Pol A Pol B frequency

39. Pol A Pol B frequency Canceled Dynamic Spectra: Time RFI not in reference horn NOT is NOT subtracted ! Non-Toxic to celestial signals

40. VOLTAGE Spectral Domain Contamination: the VOLTAGE spectrum Estimate { g 1 (f) I (f) } = X 13 (f) g 3 (f) I (f) C 14 (f) C 34 (f) stable on 0.1 second time scale Update every second 1  f Time Domain Contamination: Estimate { g  I(t) } =  x  (t) * g  I (t  Ref Horn FIR filter Effectively… FIR filter coefficients

41. Time 0.1 sec steps FIR Coefficients + Delay 0.1  s steps

42. Pol APol B using Ref. “3” using Ref. “4”

44. Phase Dynamic Pulsar Spectra Pol. A Pol. B Average Spectra Frequency

45. Phase Dynamic Pulsar Spectra Pol. A Pol. B Frequency Average Spectra Cancellation Applied

46. Time Domain Contamination: Estimate { g  I(t) } =  x  (t) * g  I (t  Ref Horn Pol A FIR filter Effectively… FIR filter coefficients Estimate { g  I(t) } =  x  (t) * g  I (t  Ref Horn Pol B { P(t) } = | g  2 | | I(t) 2 | = { g  I(t) }  { g  I(t) }  *

47. Time Domain Contamination: Estimate { g  I(t) } =  x  (t) * (g  I (t  N  ) Estimate { g  I(t) } =  x  (t) * (g  I (t  N  ) { P  (t) } = | g  2 | | I(t) 2 | = { g  I(t) }  { g  I(t) }  * = … + ( x  (t) * N  ) ( x  (t) * N  ) * Uncorrelated NoiseUnbiased Power

49. Phase Dynamic Pulsar Spectra Pol. A Pol. B Frequency Average Spectra Passband Normalization Applied

50. Bell’s Bucket Rx

51. Total Power Spectra Ref A Ref B

52. Raw Cross- correlation Spectra Ref B

53. Corrected Cross- correlation Spectra Ref B

54. Steve Ellingson: 17 Dec 1999 A Variation on the Ekers-Sault Correlation Idea Cross- correlation matrix Eigen decomposition Partition

55. Frequency Channels Twelve Eigenvalue Spectra plus, reference crosspower spectrum !

56. Frequency Channels Twelve Eigenvalue Spectra plus, reference crosspower spectrum 2 nd RFI source

57. Frequency Channels Eigenvector Spectra for one channel (amplitudes of complex coefficients) …

58. Conclusions complications of multi-path are contained in complex gains G(f) adaptive filtering with correlation functions preserves phase information…. … equivalent to subtraction of the voltage waveform

59. Applied RFI ID and subtraction… 1. New 50cm Rx 2. 74 MHz … (Courtesy Mal Smith)

60. ZZ Top: “… when yer movin’ down the road, … in yer V-8 foad, … a shine on yer boots, … and yer sideburns low…”