neutral hydrogen
DESCRIPTION
NEUTRAL HYDROGEN. Frank Briggs RSAA and ATNF. z = 8. z = 0. damped Lyman- a abs-lines. 21cm Line Studies (HIPASS). 20. -2. N >2x10 cm. Lyman a forest. Metal lines. HI. DLA. Quasar Absorption lines. Wavelength (Angstroms). HI D.L.A. - PowerPoint PPT PresentationTRANSCRIPT
NEUTRAL HYDROGENNEUTRAL HYDROGENFrank Briggs
RSAA and ATNF
z = 8 z = 0
dampedLyman-abs-lines
21cm Line Studies (HIPASS)
QuasarAbsorption lines
Lyman forest
DLA
Metal lines
Wavelength (Angstroms)
N >2x10 cm-220HI
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-217HI
note: < 1 … transparent… hard to heat!
Energy Levels in Hydrogen
E = 0
Ground State
Ener
gyOptically thick at the Lyman limitOptically thick in the Lyman
continuum
Photons E > 13.6 eV are absorbed
transitions from groundstate are absorbed
Energy Levels in Hydrogen
E = 0
Ground State
Ener
gyOptically thick in the Lyman continuum
BUT HI layer is transparent to all other wavelengths shorter than the Lyman limit
E = 0
Ground State
Ener
gy
H He C N O Na Mg Al Si Ca Ti Cr Mn Fe Zn
Ionization by ambient starlight with > 912 Angstrom
QuasarAbsorption lines
Lyman forest
DLA
Metal lines
Wavelength (Angstroms)
QuasarAbsorption lines
Lyman forest
DLA
Metal lines
LL
QuasarAbsorption lines
thoroughly developed statistics !!! for Lyman and metal lines…
(whatever is common… is most likely to intervene by chance)(ordinary Galaxies
CIV MgII/ Lyman limit(CII, FeII, SiII, …)
Relative interception cross sections …
Z=3Ly break galaxy
DLADLA
12 14 18 20 22
HI Column density distribution function Petijean etal 1993
Log f(NHI)
-10
-15
-20
Log NHI
Number of interceptions in range: N to N+dN
f(N) dN per unit zNHI = NH (nHI / nH)
Ionization fraction ~10-3 ?
LyforestIGM DLA
CIV
LL > 1
M ~ N f(N)dN HI
f(N)dN ~ N dN /unit Z-3/2
12 14 18 20 22
HI Column density distribution function Petijean etal 1993
Log f(NHI)
-10
-15
-20
Log NHI
DLAM /Log Interv ~ N f(N)
HI2
~ N+1/2
CIV MgII/ Lyman limit(CII, FeII, SiII, …)
Relative interception cross sections … What are these things???
Z=3Ly break galaxy
DLADLA
(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 thelower densitymaterial ??
SquareKilometreArray
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
ALMAESO VLTI
6th ATNF Synthesis Imaging Workshop“Synthesis Imaging from Centimetre to Millimetre Wavelengths”
12-16 May 2003 at Narrabri NSW
www.atnf.csiro.au/synthesis
ARRAY
Simple antenna“elements” “Station” “Array”
SKA Design“Magic Carpet”
Eggs on Legs
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 GMRTKanekar & 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
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
Cut off fromview of opticalwavelengths !!!
nHInHI +nHII
10-3
If neutral fraction>
Gnedin’s simulation of Reionization:
log(Neutral fraction)
log(density)log T
log(mean intensity of ionizing flux)
http://casa.colorado.edu/~gnedin/GALLERY/
.…. i
oniz
ed…
… re-re-ionizedre-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 …
QuasarQuasardistributeddistributedstar formationstar formation
SUMMARY: still plenty to do !
