The redshifted 21 cm background and particle decays

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The redshifted 21 cm background and particle
decays

• Evgenii O. Vasiliev Yuri A. Shchekinov
• Tartu Observatory, Estonia
• South Federal University, Russia

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21 cm line of neutal hydrogen
21 cm line van de Hulst (1945) possibility
Shklovsky (1949) observations e.g. Muller Oort
(1951) exitation in the neutral IGM Wouthuysen
(1952), Field (1958,1959)
dark ages epoch of interest
21 cm and dark ages Hogan Rees 1979, Madau
et al 1997
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Reionization and unstable particles (Sciama 1982,
1990) LSS and unstable particles (Doroshkevich
Khlopov 1984 ) Nucleosynthesis and unstable
particles (Scherer 1984)
WMAP 1 year, large optical depth strong
requirements to UV photon production from first
stellar and QSO objects complementary sources
of reionization decaying dark matter ultra high
energy cosmic rays (UHECRs)
possible solution partial ionization due to
extra sources
Doroshkevich et al 2003Hansen Haiman 2004
Chen Kamionkowski 2004 Kasuya et al 2004
Kasuya Kawasaki 2004 Pierpaoli 2004Mapelli
et al 2006 Biermann Kusenko 2006Ripamonti et
al 2006
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Extra ionization sources

• decaying dark matter
• cold and warm DM, e.g. axino, neutralino,
  sterile neutrino
• (Dolgov 2002, Hansen Haiman 2004, Chen
  Kamionkowski 2004,
• Mapelli et al 2006, Ripamonti et al 2006)
• decay rate
• long lifetime Hubble time gt
• short lifetime Hubble time lt
• UHECRs
• origin from Super Heavy Dark Matter particles
  (gt1012 GeV)
• (Berezinsky et al 1997, Kuzmin Rubakov 1998,
  Birkel Sarkar 1998)
• SHDM UHECRs (electromagnetic cascades) UV
  photons (Ly-c Ly-alpha)

Peebles et al 2000Doroshkevich Naselsky 2002
production rate
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The model
Ionization and temperature evolution (similar to
Chen Kamionkowski 2004)
Peebles et al 2000Doroshkevich Naselsky 2002
UHECRs
Decaying particles
Chen Kamionkowski 2004
Heating rate
Chen Kamionkowski 2004
Modified version of the code RECFAST (Seager et
al 1999)
Smooth or global signal evolution
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Basics of 21 cm physics
brightness temperature (or specific
inrensity) spin temperature (or exitation
temperature)
T 0.068 K energy splitting TSgtgtT in
astrophysical applications 3 of 4 atoms in the
exited state

• spin temperature
• absorption of CMB photons
• collisions with hydrogen atoms, protons, free
  electrons
• scattering of Ly? - Lyc photons (Wouthuysen-Field
  effect)

Observable parameters global signal
fluctuations
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Ionization, spin and kinetic temperatures
CMB temperatureBlack standard
recombinationRed UHECRsGreen long living
particlesBlue short living
heating vs spin temperature
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UHE cosmic rays
standard recombination

• weak extra ionization
• negligible heating

• Ly-alpha and Ly-c photons
• Wouthuysen-Field effect

e 0 e 0.3 e 1 e 3
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Decaying dark matter particles
long living particles (heating rate)
short living particles (decay rate, density)
3x10-25 s-1
10-15 s-1 , 5
6x10-26 s-1
10-15 s-1 , 1
3x10-26 s-1
5x10-15 s-1 , 1
6x10-27 s-1
10-14 s-1 , 0.5
density in units 10-8 ?d at zeq
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Major impact collisions or photons?
long living particles
short living particles
UHECRs
solid collisions dash photons
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Major impact collisions or photons?
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Power spectrum of 21 cm fluctuations
Barkana Loeb (2005), Hirata Sigurdson (2006)
power spectrum
baryon density fluctuations density-velocity
cross spectrum velocity fluctuations
cos(angle between line of sight and wavevector)
brightness temperature fluctuations
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standard recombination
UHECRs
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?Tb 21 cm brightness temperature fluctuations
(in mK)
standard recombination
UHECRs
long living particles
short living particles
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Discrimination between sources observations
observations at three redshift three wave-band
observations

• z1 z2 z3
• 20 40

2 central redshift
open emissionfilled absorption half-filled
emission/absorption standard
recombination UHECRs
long living particles short living
particles
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Discrimination between sources observations
observations at three redshift three wave-band
observations

• z1 z2 z3
• 20 4010
  30 50

2 central redshift
open emissionfilled absorption half-filled
emission/absorption standard
recombination UHECRs
long living particles short living
particles
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Discrimination between sources observations
observations at three redshift three wave-band
observations

• z1 z2 z3
• 20 4010
  30 5020
  40 50

standard recombination
2 central redshift
open emissionfilled absorption half-filled
emission/absorption standard
recombination UHECRs
long living particles short living
particles
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z1 zc z3
dz 0.. dzm dz dz
m
m
m
Black standard
recombinationGreen UHECRsRed long living
particlesBlue short living
m
Minimum background flux 10 weeks integration
time 10 mJy z 20-40 LOFAR 1-3 mJy z 20-40
SKA/LWA
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Conclusions

• long living and short living unstable dark matter
  particles and UHECRs produce distinguishable
  dependences of brightness temperature on redshift
• future radio telescopes (such as LOFAR, LWA and
  SKA) seem to have sufficient flux sensitivity for
  detection the signal in 21 cm influenced by
  decaying particles and UHECRs (three wave-band
  observations)

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