21cm Constraints on Reionization Benedetta Ciardi MPA T. Di Matteo (CMU), A. Ferrara (SISSA), I....

The gas needs to cool to beavailable for star formation

The first sites of ionizing radiation

KTvir410

KTvir410

Atomic hydrogen cooling

Molecular hydrogen cooling

DM halos virial temperature Cooling function (no metals!)

Temperature [K]

Λ/n

² [e

rg c

m³/

s]

H2 cooling

Atomic H cooling

HD coolingTem

pera

ture

[K

]

1-σ

2-σ

3-σ

(Barka

na &

Loeb

20

01

)

Redshift

H2 is a key species in the early universe

Feedback effects on primordial objects

The first generation of stars affects the subsequent star formation process

Radiative feedback

Mechanical feedback

Chemical feedback

H2 photodissociation(L-W photons, 11.2-13.6 eV)

Radiative feedback

Photoheating

(Gn

ed

in 2

00

0)

Photoevaporation

(Sh

ap

iro e

t al. 2

00

3)


Blowout/blowaway

Blow-awayBlow-out

(Mac Lo

w &

Ferra

ra 9

9)

Radiative feedback

Mechanical feedback

Chemical feedback

Mechanical feedback


Change in fragmentation mode due to ZRadiative feedback

Mechanical feedback

Chemical feedbackChemical feedback~ 100 Msun

~ 1 Msun

~ 0.1 Msun

F rac t

ion

of

meta

ls d

ep

lete

d o

nto

du

s t g

r ain

s

Metallicity / Solar Metallicity

(Sch

neid

er e

t al)

(Bromm et al, Schneider et al)


Radiative feedback

Mechanical feedback

Chemical feedback

IGM reionization

See Ciardi & Ferrara 2005 for a review

Constraints on the epoch of reionization

High-z QSOs latest stages of reionization at z~6

CMB global amount of electrons

Which are the first sources of ionizing radiation?How did the reionization process evolve?

Which is its interplay with the galaxy formation process?

21 cm line diagnostic

21 cm

T S CMBT

Ideal probe of neutral H at high-zdifferent observed frqs. different z

(ν~150,120,80 MHz z~8,11,18)

DECOUPLING

HI ground state

)s0.07K/T3exp(l/nun

• CMB photons are absorbed by HI thermal equilibrium

u

l

Scattering with Lyalpha photons emitted by the same stars that reionize

Absorption or emission?

Differential brightness temperature:

)/TT-(1z1

T-TT sCMB

CMBsb

CMBs TT

sCMB TT absorption

emission

30<z<200 absorption

z_ion<z<30 emission

Heating by Lyalpha or X-ray photons, shock heating (Madau, Meiksin & Rees 1997; Giroux & Shull 2001; Glover & Brand 2002; Chen & Miralda-Escude’ 2003; Gnedin & Shaver 2004)

(1+z)

(Loeb

& Z

ald

arria

ga 2

00

4)

1 10 100 1000

IGM

CMB

Simulations of galaxy formation (feedback effects)

Galaxies Quasars

Properties of the sources of ionizing radiation

Radiative transfer of ionizing radiation

Modeling of cosmic reionization: ingredients

computationallydemanding

Tsu3: cosmological radiative transfer codes comparison

(Iliev, BC et al. 2006)

Stromgren sphere Dense clump Cosmological field

ww

w.m

pa-g

arch

ing.m

pg.d

e/tsu

3

Simulations of galaxy formation (feedback effects)

Galaxies Quasars

Properties of the sources of ionizing radiation

Radiative transfer of ionizing radiation

Modeling of cosmic reionization: ingredients

computationallydemanding

Spectral Energy Distribution

? Source emission properties:

? Escape Fraction:

Modeling of cosmic reionization: parameters

Zero or higher metallicity?

Salpeter or Larson IMF?

Fesc <20% but there is a big variation in the number both theoretically & observationally

? IMF and spectrum:

Simulations of reionization

M~M 910

Simulation properties Source properties

- - metal-free stars - L=20/h Mpc com. - Salpeter/Larson IMF - Fesc=5-20%

Simulations of galaxy formation gas & galaxy properties (Springel et al. ‘00; Stoehr ‘04)

Stellar type sources emission properties

propagation of ionizing photons (BC et al. ’01; Maselli, Ferrara & BC ’03)

(BC

, Sto

ehr &

White

20

03

) Redshift Evolution of HI density

‘Proto-Cluster’: 10/h Mpc‘Field’: 20/h Mpc

z=18

z=16

z=14

z=12

z=10

z=8

0.0

0.015 0.5

0.0

The environment affects the reionization process

S5: Salpeter IMF+fesc=5% (late reion.

case)

S20: Salpeter IMF+fesc=20%

L20: Larson IMF+fesc=20% (early reion.

case)

Early/Late Reionization

0.040.16e 68% CL (Kogut et al. 2003)

(BC

, Ferra

ra &

White

20

03

)

The simulations are consistentwith the WMAP results

Source properties:

- MHs are sinks of UV photons

- MHs photoevaporation has been studied in hydro-simulation

and implemented in semi-analytic models (e.g. Shapiro, Iliev & Raga

2004;

Iliev, Scannapieco & Shapiro

2005)

Effect of mini-halos

cell

sub-gridphysics

• Fraction of gas collapsed in MHs • UV photons needed to photoevaporate the MHs

1. No MHs re-formation allowed once they are evaporated

2. MHs are allowed to form again

Effect of mini-halosIonization fraction

no MHs

MHs, re-formation

MHs, no re-formation

With no MHs re-formation there is nosubstantial difference form the no-MHs caseIf MHs are allowed to re-form, reionization

can be delayed by Δz~2

(BC

et a

l 20

06

)

-6

0

-4

-2

/k)Tlog( b

21 cm line diagnostic

(BC & Madau 2003)

The 21cm line is observed in emission if:

HIsCMBCMBs

b n)/TT-(1z1

T-TT

CMBs TT

Fluctuations of brightness temp.The fluctuations are due to variations in HI distribution (density distrib. + ionized regions)

Late/Early reionization show similar behaviour

The peak of the emission is ~10 mK

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

S5 L20

Future radio telescopes should be able to detect such signal

LOw Frequency ARray

(Valdes, BC et al. , 2006)

• Instrument sampling

• Instrument sensitivity

• Convolution with a Gaussian beam (=3 arcmin)

LOFAR will be able to map the reionization history,

especially its latest stages

LOFAR expected response (late reion.)

/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

S5 L20

T/T)(

1

040 ),(ˆ),()ˆ(

xvxd

T

THII

CMB

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

The power spectrum is dominated by the secondary anis. at l > 4000 (θ < 3’). They reach a peak of ~

which could be detected by e.g. ALMA, ACT

2K][ 1

CMB secondary anisotropies CMB/21cm line correlation(Salvaterra, BC, Ferrara & Baccigalupi 2005)

S5 L20

Characteristic angular scale of the cross-correlation function

S5

L20

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.

Extra-galactic foreground contamination (Di Matteo, BC & Miniati 2004)

Point Sources:

- Free-free emission from IS HII regions

- Low-z radio galaxies

Extended Sources:

- Free-free emission from IG HII regions

- Syncrotron emission from cluster radio halos

& relics

Late reionization case @115 MHz

F>0.1 mJy

Extra-galactic foreground contamination

Radio galaxies

Radio halos

After removal of bright sources (F>0.1 mJy), at scales >1 arcmin 21cm emission line is free from

extra-galactic foreground contamination

Conclusions

• Simulations of cosmic reionization

• 21cm line emission from neutral IGM (from reionization simulations)

• CMB/21cm line cross-correlation

• Extra-galactic foreground contamination calculated self-consistently with emission signal

LOFAR should be able to map the reionization process, at least its latest stages

More detailed information will be acquired implementing the above observations with CMB anisotropies measurements

Observations of 21cm line at angles > 1 arcmin could be free from extra-galactic foreground contamination

21cm Constraints on Reionization Benedetta Ciardi MPA T. Di Matteo (CMU), A. Ferrara (SISSA), I....

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