what good are low frequencies?
DESCRIPTION
what good are low frequencies?. HI, neutral hydrogen, H 0 , atomic hydrogen high redshifts and early times…. USS, GPS, … “enabling technologies” …multi-beaming, all-sky transients,…, the highest energy cosmic rays…. Z = 4. FREQ MHz. 50 100 200 1000. - PowerPoint PPT PresentationTRANSCRIPT
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 ?!?!