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

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

Quasar Absorption lines Lyman  forest DLA Metal lines Wavelength (Angstroms) N >2x10 cm HI

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

…bathe HI cloud in photoionizing radiation… Photons  E > 13.6 eV

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

…bathe HI cloud in photoionizing radiation… optical depth  > 1 for  E ~ 13.6 eV photons N >3x10 cm HI note:  < 1 … transparent… hard to heat!

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

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

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

Quasar Absorption lines Lyman  forest DLA Metal lines Wavelength (Angstroms)

Quasar Absorption lines Lyman  forest DLA Metal lines LL

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

C IV M gII / Lyman limit (CII, FeII, SiII, …) Relative interception cross sections … Z=3 Ly break galaxyDLA

HI Column density distribution function Petijean etal 1993 Log f (N HI ) Log N HI Number of interceptions in range: N to N+dN f (N) dN per unit z N HI = N H (n HI / n H ) Ionization fraction ~10 -3 ? Ly  forest IGM DLA C IV  LL > 1

M ~ N f (N)dN HI f (N)dN ~ N dN /unit Z -3/ HI Column density distribution function Petijean etal 1993 Log f (N HI ) Log N HI DLA M / Log Interv ~ N f (N) HI 2 ~ N~ N +1/2

C IV M gII / Lyman limit (CII, FeII, SiII, …) Relative interception cross sections … What are these things??? Z=3 Ly break galaxyDLA (tough to image)pin

nearby Neutral gas disks analogs to high Z DLAs ??? Optical + Radio

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

Square Kilometre Array

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

D Sensivity depends on collecting area Angular resolution ~ /D

D Sensivity depends on collecting area Angular resolution ~ /D

VLA ALMA ESO VLTI

6 th ATNF Synthesis Imaging Workshop “Synthesis Imaging from Centimetre to Millimetre Wavelengths” May 2003 at Narrabri NSW

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

SKA Design “Magic Carpet”

Eggs on Legs

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

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

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

new GMRT Kanekar & Chengalur 988 MHz

high redshift radio galaxies TNR J TNR J

Radio galaxy spectra No UV continuum No DLA absorption lines

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

CosmicEvolutionIndicators Redshift co-moving number density of bright Quasars Cosmic Star Formation Rate history: the Madau Plot extent of metal-rich gaseous halos cosmic density  g of Neutral Gas

Violent accretion accretion Passive relaxation relaxation CosmicEvolutionIndicators Redshift MHz frequency

Cut off from view of optical wavelengths !!! n HI n HI +n HII  If neutral fraction >

Gnedin’s simulation of Reionization: log(Neutral fraction) log(density) log T log(mean intensity of ionizing flux)

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

MAP

Z = 17  ??? Rules out WDM MAP Result

70 MHz ………………..180 MHz

Global Signal… 20 mK

“The Z=20 Expt” JR, FB, et al

Passband filters (from load scan) and RFI (from sky scan)

10 arcmin LOFAR and SKA … Quasar distributed star formation

SUMMARY: still plenty to do !