what good are low frequencies?

• HI, neutral hydrogen, H0, atomic hydrogen

• high redshifts and early times…. USS, GPS, …

• “enabling technologies” …multi-beaming, all-sky transients,…, the highest energy cosmic rays…

FREQ. GHz

FREQ MHz 50 100 200 1000 50 100 200 1000

Z = 4

Gigahertz Peak Sources: young radio sources ???

.….

ion

ized

…… re-re-ionized

re-ionized

Big Bang Nucleosynthesis

HI HI HI HI HI

70 MHz ………………..180 MHz

dampedLyman-abs-lines

21cm Line Studies (HIPASS)

CosmicCosmicEvolutionEvolutionIndicatorsIndicators

Redshift

0 1 2 3 4 5

co-moving number density of bright Quasars

Cosmic Star Formation Rate history: the Madau Plot

0 1 2 3 4 5

extent of metal-rich gaseous haloscosmic density g of Neutral Gas

0 1 2 3 4 5

ViolentViolent accretionaccretion

PassivePassive relaxationrelaxation

CosmicCosmicEvolutionEvolutionIndicatorsIndicators

Redshift1420 500 250 MHzfrequency

3C196-G1 z = 0.437

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 J2254+1857

TNR J1402-1510

Radio galaxy spectra

No UV continuum No DLA absorption lines

Molonglo Telescope: SKAMP III• frequency coverage• sensitivity• RFI rejection

VLBI to resolve source

the Molonglo challenges:

• broadband line feeds

• 96 station correlator

• Defence HQ 3 km away ?!?!