neutral hydrogen

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 !