Primordial Resonant Lines in the early universe
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Primordial Resonant Lines in the early universe
Roberto MaoliUniv. di Roma "La Sapienza" – IAP Paris
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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
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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
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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
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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
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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
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3,,0 1
7
5zn
mzn jvmol
N
crBi
obs
jiz ,1
horanis
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Redshift condition
25obs GHz
, ( ) 444.3i j LiH n GHz
,1 i j
obs
z
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Angular condition
obs zres z=1000
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Molecular contribution to the optical depth
Damping is frequency dependent
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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
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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
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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
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Primordial Resonant Lines
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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
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Summary of PRL features
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Observational summary• Frequency: 10 - 800 GHz• Angular scale: 5" – 2'• Spectral resolution: 72 1010
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Observational results
• IRAM 30m: few spots with a narrow band
upper limits and a (false) detection
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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
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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