a hot topic: the 21cm line iii

A hot topic:

the 21cm line

III

Benedetta CiardiMPA

o Differential brightness temperature

o Maps are difficult to obtain statistical quantities

o Power spectrum:

o Angular power spectrum:

Some terminology & quantities

bT

221 |)(~|)( kk21P

221 || lmalC


xde)(δπ)(

)(δ

Tδ

TδδT)(δ

i/

b

bb

3212321

21

2

1~ kxxk

x

221 |)(~|)( kk21P

o Differential brightness temperature

o Maps are difficult to obtain statistical quantities

o Power spectrum:

o Angular power spectrum:


bT

221 |)(~|)( kk21P

221 || lmalC

depends on e.g.:- underlying density distribution- ionized fraction- Lyalpha distribution- …

bT

(Loeb

& Z

ald

arria

ga 2

00

4)

Absorption of CMB flux prior to structure formation density structure

Absorption prior to reionization

(Loeb & Zaldarriaga 2004; Ali, Bharadwaj & Panday 2005; Barkana & Loeb 2005a; Pillepich, Porciani & Matarrese 2007; Lewis & Challinor 2007)

Angular power spectrum

(Loeb

& Z

ald

arria

ga 2

00

4)


Pb. Observations atfrequencies <50MHz are extremely challenging



Atmospheric visibility

T. Wilson

Spitzer

Hubble

ChandraCompton GRO

(Loeb

& Z

ald

arria

ga 2

00

4)


Pb. Observations atfrequencies <50MHz are extremely challenging



If density fluctuations dominate 21cm fluctuations cosmological parameters

Determination of cosmological parameters

McQuinn et al. 2006

Errors on cosmological parameter estimates at z=8

If density fluctuations dominate 21cm fluctuations cosmological parameters

Determination of cosmological parameters

McQuinn et al. 2006

Errors on cosmological parameter estimates at z=10, 12

Baryonic Acoustic Oscillations

o Cosmological perturbations excite sound waves acoustic peaks in CMB

o Imprints also on the power spectrum of non relativistic matter BAO

Mao &

Wu

20

07

Pure baryons

Pure CDMCMD + baryons

z=6

Linear power spectrum

Eistenstein & Hu 1998Cooray & Sheth 2002




Mao &

Wu

20

07

Pure baryons

Pure CDMCMD + baryons

z=6

Linear power spectrum




o BAO has been observed in large galaxy surveys as SDSS and 2dF

BAO detection: galaxy surveys

SDSS


SDSS

Eisentein et al. 2005Cole et al. 2005

Ωm h²=0.12

0.130.14

no baryons


2dF




o BAO has been observed in large galaxy surveys as SDSS and 2dF

o Measurements of BAO information on cosmological parameters

BAO detection: 21cm observations

Mao &

Wu

20

07

21cmA LOFAR

o BAO signature on matter power spectrum 21cm power spectrum Mao & Wu 2007;

Wyithe, Loeb & Geil 2007

BAO detection: 21cm observations o BAO signature on matter power spectrum 21cm power spectrum

o 21cm galaxy survey

Gravitational lensing o Mass deflect light multiple images, magnification, de-magnification, distortion


Turner 2002


NASA


o If distortions very small statistical analysis

o Measurement of distortion reconstruction of the foreground mass


o If distortions very small statistical analysis

o Measurement of distortion reconstruction of the foreground mass

o Measurements of LSS weak lensing done with galaxies as background sources

o Use NIRB, CMB or 21cm as background sources (Cooray 04; Pen 04; Zhan & Zaldarraiga 06; Lu & Pen 07)

o Advantage of 21cm: many more sources, many more z

Gravitational lensing

Metcalf & White 2007


Metcalf & White 2008


Hilbert, Metcalf & White 200720'

HI sources at z=12 Spaced based gal. survey zmed=1.23 Redshifts and virial masses

Hilbert, Metcalf & White 2007

No n

ois

e N

ois

e

HI sources Spaced based galaxy survey Ground based galaxy survey

Redshift Evolution of HI density

z=18 z=16 z=14

z=12

z=13

z=11.5 z=10.5

z=9.5 z=9

z=10

z=8.5 z=8

0.0

0.015

(BC

, Sto

ehr &

White

20

03

)

Maps of brightness temperature

13.5

8.79.3

9.910.611.3

12.012.8

8.1

K

/K)Tlog( bDistribution of bT

(BC

& M

adau 2

00

3)

• Instrument sampling

• Instrument sensitivity

• Convolution with a Gaussian beam (=3 arcmin)

LOFAR-type telescope could be able to map the IGM reionization history &

distinguish between reionization sources

Expected response

/k)Tlog( b

Simulated Synthetic

z=10.6, ν=122 MHz

z=9.89, ν=130 MHz

z=9.26, ν=138 MHz

-1

-1

-2

-2

-2

-3

-3

-3

-4

-4

-4

-5

-5

-5

-1-1.4

-1.6

-1.8

-2.0

-2.2-1.6

-1.8

-2.0

-2.2

-2.4

-1.6

-1.8

-2.0

-2.2

-2.4

-2.6

-2.8

Valdes et al. 2006

Observation of HII regions of high-z QSOs

Wyith

e, Lo

eb

& B

arn

es 2

00

5

Additional tool to study the IGM at z~6; estimate of nHI

(Zaroubi & Silk 2005; Chen & Miralda-Escude' 2006; Cen 2006; Rhook & Haehnelt 2007; Liu et al. 2007)

Late Early

T/T)(

CMB anisotropies are produced by free electrons 21cm line is emitted by neutral hydrogen

CMB/21cm line correlation

Late Early

Characteristic angular scale of the cross-correlation function

Late

Early

Mpc/h

The characteristic angular scale of the cross-correlation function gives an estimate

of the typical dimension of the HII regions at redshift of the 21cm emission line.

CMB/21cm line correlation

We find an anti-correlation below a characteristic angular scale, θ0, when the correlation function becomes < 0.

(Salvaterra et al. 2005; Alvarez et al. 2006; Holder et al. 2006; Adshead & Furlanetto 2007)

Also correlation with galaxies?

Late

Early

(BC

& M

ad

au

20

03

)

Fluctuations of brightness temp.

Late/Early reionization show similar behaviour

The peak of the emission is ~10 mK

Early reion. peaks @ 90MHz, late reion. peaks @ 115MHz

Planned radio telescopes should be able to detect such signal

(Madau et al. 1997; Ciardi & Madau 2003; Furlanetto et al. 2004; Zaldarriaga et al. 2004; Mellema et al. 2006; Santos et al. 2007)

Absorption features in high-z radio sources

o Luminous radio source 21cm absorption features



o DLAs


DLAs



o DLAs



o DLAs

o Proto-galactic disks and mini-halos


Proto-galactic disks & mini-halos

Furla

netto

& Lo

eb

20

02



o DLAs




o DLAs


o IGM 21cm forest


21cm forest

forest 21cm forest Lyalpha

IGM absorption from high-z radio source

(Carilli, Gnedin & Owen 2002; Carilli et al. 2004)

10z@mJy20S120MHz

8z@mJy35S120MHz

Additional information HI in the IGM

(GRB's afterglow, Ioka & Meszaros 2004)



o DLAs


o IGM 21cm forest

Pb. Are there brightenough sources of radioradiation at high-z?

High-z radio sources

smin 1/T )(0.002/ mJy 1S

Masers

o Population inversion masers

)/TT3exp()T/kexp(-h/gg/nnssB0101

statistical weight spin temperatureK0.068T

Masers


o A maser can boost the 21cm signal by order of magnitudes

12)0()( 2121

221

2121

e

kTeIrI s

00:1

2121 ss

TT

I(r) grows exponentially with r !!!

Masers



o works!maserTTand0Tif :T~T radiation Ly With k s

kCMB

s T~T~y1

TyTT

α

α

Masers




1

)(

1~

J

JT

If there are more photons with than with maser! Ly Ly

(Madau, Meiksin & Rees 1997)

Masers




Dijkstra

& Lo

eb

20

07

Frequency shift:

Doppler frequency width:

Velocity dispersion:

D

Lyx

LythD cV /)/(

2/1/2 HBth mTkV

eVHzLy 28.1010466.2 15

K -160~T

K -230~T

Masers



o

o

works!maserTTand0Tif :T~T radiation Ly With k s

k45

Ly TTbringsLsucherg/s;10L:Pb. αα

SETI: Search for Extraterrestrial Intelligence

o SETI program started in the '60s

o Typically radio frequencies are scanned

o Big Ear Observatory, Arecibo, Jodrell Bank…

o Current programs could detect:

- powerful beacons

- transmissions with more typical power levels at distances < 1pc

no star within 1pc from the Sun no detection!

Signals detectableby SKA

Tarter (2001); Lazio et al. (2004)

o Power spectrum & cosmological parameters (BAOs, WL, 21cm from very high z…)

o Map the evolution of HI in the IGM reionization history & sources

o Absorption studies of high-z radio sources

Future 21cm observations

a hot topic: the 21cm line iii

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