Primordial Resonant Lines in the early universe

Roberto MaoliUniv. di Roma "La Sapienza" – IAP Paris

Direct observation of the universe

z=5-10: first quasars

Dark ages ReionizationStructure formation

z=1100: CMB anisotropies

z=0: today universe

Pre-reionizationDark Ages

Post-reionizationDark Ages

Secondary anisotropies of the CMB• Rees-Sciama effectvariation of the gravitational potential during the non linear evolution of

the perturbation

• Vishniac effectnon linear second order effect produced by the coupling between the

velocity and the density fluctuation

• kinetic Sunyaev-Zel'dovich effectThomson scattering by the electrons of a cluster with peculiar velocity

• reionization at z=20 (WMAP) damping of CMB primary anisotropiesThomson scattering by the electrons of the cosmic medium

Components of the cosmic medium

• Electrons

• Molecules from primordial elementsH2, H2

+, HD, HD+, HeH+, LiH, LiH,

• Atoms and ions of heavy elementsCI, OI, SiI, SI, FeI

CII, NII, NIII, SiII, FeII, FeIII, OIII

Interaction process

• Thermal emission and absorption are negligible

• Elastic resonant scattering is the most promising process

σT=6.652·10-25 cm2

ijijijij

i

jres d

c

A

g

g 2191037.3

4

Damping of primary anisotropies

• Optical depth:

• Molecular density:

• Cross section:

• Redshift condition:

• Angular condition:

i i obsobs , cdttn resiii obs ,,

ijijijij

i

jres d

c

A

g

g 2191037.3

4

3,,0 1

7

5zn

mzn jvmol

N

crBi

obs

jiz ,1

horanis

Redshift condition

25obs GHz

, ( ) 444.3i j LiH n GHz

,1 i j

obs

z

Angular condition

obs zres z=1000

Molecular contribution to the optical depth

Damping is frequency dependent

Observations with Planck

Foregrounds contamination

An observational frequency without resonant scattering

Basu et al. 2004

100 GHz

144 GHz – 100 GHz

63μ OI line at z=32

How to observe Dark Ages

• Lyman-α absorbers

distant point source (QSO) + absorption by HI

depends on the optical depth and not on the distance

How to observe Dark Ages• CMB: diffuse source + scattering

depends on the optical depth and not on the distance

need of a peculiar velocity for the scattering source

all sky background source

CMB(z=1100)

νobs= ν0(1+βpcosθ)

Prim. cloud(z=zres)

ν0

3cos12cos1 pNpCMB

eeI

I

p

Primordial Resonant Lines

Line width and line shape of the PRL

• linear evolution:

• turn-around:

• spherical collapse: max,2 c

T71054.2

zmz

z

11077.5 31

124

Summary of PRL features

Observational summary• Frequency: 10 - 800 GHz• Angular scale: 5" – 2'• Spectral resolution: 72 1010

Observational results

• IRAM 30m: few spots with a narrow band

upper limits and a (false) detection

Observational results

• ODIN: few spots with a large band (see Hjalmarson talk)

31 GHz survey in 300 orbits

upper limits 65 mK with 1 MHz resolution

test of pattern recognition tools for future experiments

• HERSCHEL-HiFi: many spots with a large band

Conclusions

• PRLs are the most promising tool to observe Dark Ages and test the structure formation models

• very large bandwidth needed (satellites)• easy to test cosmological origin (observation of two lines,

search for main molecular lines at z=0)• no foregrounds contamination• richness of information:

– frequency → chemical composition, redshift of the scattering source, abundance– line shape → dynamical environment– two lines → temperature– diffuse background source → size of the scattering source