1. NEUTRAL HYDROGEN Frank Briggs RSAA and ATNF z = 8 z = 0

2. damped Lyman-a abs-lines 21cm Line Studies (HIPASS)

3. 20 -2 N >2x10 cm Lyman a forest Metal lines HI DLA Quasar Absorption lines Wavelength (Angstroms)

4. HI D.L.A. SiII CII SiII FeII AlII OI/SiII SiIV CIV Quasar (all DLAs have metal lines)

5. …bathe HI cloud in photoionizing radiation… Photons DE > 13.6 eV

6. …bathe HI cloud in photoionizing radiation… ?? minimum thickness of skin before becomes self-shielding ??

7. 17 -2 N >3x10 cm HI …bathe HI cloud in photoionizing radiation… optical depth t > 1 for DE ~ 13.6 eV photons note: t< 1 … transparent… hard to heat!

8. transitions from ground state are absorbed Photons DE > 13.6 eV are absorbed Energy Levels in Hydrogen Optically thick at the Lyman limit Optically thick in the Lyman continuum E = 0 Energy Ground State

9. Energy Levels in Hydrogen Optically thick in the Lyman continuum E = 0 BUT HI layer is transparent to all other wavelengths shorter than the Lyman limit Energy Ground State

10. Ionization by ambient starlight with l > 912 Angstrom E = 0 Energy Ground State H He C N O Na Mg Al Si Ca Ti Cr Mn Fe Zn

11. Lyman a forest Metal lines DLA Quasar Absorption lines Wavelength (Angstroms)

12. Metal lines LL Quasar Absorption lines Lyman a forest DLA

13. Quasar Absorption lines • thoroughly developed statistics !!! for Lyman a and metal lines… (ordinary Galaxies (whatever is common… is most likely to intervene by chance)

14. DLA CIV MgII/ Lyman limit (CII, FeII, SiII, …) Relative interception cross sections … Z=3 Ly break galaxy

15. HI Column density distribution function Number of interceptions in range: N to N+dN NHI = NH (nHI / nH) f(N) dN per unit z Ionization fraction ~10-3 ? tLL > 1 Lya forest IGM DLA CIV Petijean etal 1993 -10 -15 Log f(NHI) -20 12 14 18 20 22 Log NHI

16. HI Column density distribution function -3/2 f(N)dN ~ N dN /unit Z M~Nf(N)dN HI DLA M/Log Interv~N f(N) 2 HI +1/2 ~N Petijean etal 1993 -10 -15 Log f(NHI) -20 12 14 18 20 22 Log NHI

17. DLA CIV MgII/ Lyman limit (CII, FeII, SiII, …) Relative interception cross sections … What are these things??? Z=3 Ly break galaxy (tough to image)pin

18. nearby Neutral gas disksanalogs to high Z DLAs ??? Optical + Radio

19. Extended, low-column density gas = analog of LymanLimit/MgII CIV is the lower density material ??

20. Square Kilometre Array

21. ARRAY Simple antenna “elements” “Array” “Station”

22. Sensivity depends on collecting area Angular resolution ~ l/D D

23. Sensivity depends on collecting area Angular resolution ~ l/D D

24. ESO VLTI ALMA VLA

25. 6th ATNF Synthesis Imaging Workshop “Synthesis Imaging from Centimetre to Millimetre Wavelengths” 12-16 May 2003 at Narrabri NSW www.atnf.csiro.au/synthesis

26. ARRAY Simple antenna “elements” “Array” “Station”

27. SKA Design “Magic Carpet”

28. Eggs on Legs

29. Cohen et al 3” 3C196-G1 z = 0.437 HST image (Ridgway & Stockton)

30. Radio spectrum at 988 MHz Westerbork (Briggs, deBruyn, Vermeulen) Double Lobed Radio Source 300 km/s

31. source centroid as fnct of Frequency SKA map emission ? map absorption ?

32. new GMRT Kanekar & Chengalur 988 MHz

33. high redshift radio galaxies TNR J2254+1857 TNR J1402-1510

34. Radio galaxy spectra No DLA absorption lines No UV continuum

35. VLBI to resolve source Molonglo Telescope: SKAMP III • frequency coverage • sensitivity • RFI rejection

36. cosmic density Wg of Neutral Gas extent of metal-rich gaseous halos co-moving number density of bright Quasars Cosmic Star Formation Rate history: the Madau Plot 0 1 2 3 4 5 0 1 2 3 4 5 0 1 2 3 4 5 Cosmic Evolution Indicators Redshift

37. frequency 1420 500 250 MHz Passive relaxation Violent accretion Cosmic Evolution Indicators Redshift

41. If neutral fraction nHI > ~10-3 nHI +nHII Cut off from view of optical wavelengths !!!

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

44. re-ionized re-re-ionized .…. ionized……

45. MAP

46. MAP Result Z = 17 + 4 ??? Rules out WDM

47. 70 MHz ………………..180 MHz

49. 20 mK Global Signal…

50. “The Z=20 Expt” JR, FB, et al