Dark Matter in the Dark Age Constraints on Dark Matter Decay and Annihilation from Cosmic Ionization

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Dark Matter in the Dark AgeConstraints on Dark
Matter Decay and Annihilation from Cosmic
Ionization History

• Xuelei Chen
• National Astronomical Observatories of China

3rd Irvine Cosmology Workshop March 24, 2007,
Irvine
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Cosmic Ionization History
CMB
reionization
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Active Dark Matters
DM annihilation is physically motivated
neutralino

• DM decay is physically plausible

active neutrino, sterile neutrino, gravitino,
stop, super heavy dark matter SuperWIMP,
Q-ball, topological defects ...
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Active Dark Matter and its Impact on ionization
Decay/Annihilation

• produce gamma-ray, cosmic ray, anti-matter
  release energy, ionize/heat up baryonic gas
• Energy released enormous, 1 GeV energy is
  sufficient to ionize 7 x 107 hydrogen, only a
  tiny fraction of DM decay/annihilate is enough to
  affect ionization history
• constrain decays with lifetime gt 3 x 105 year
  1013 sec, before that, decay products thermalize
  with CMB

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WMAP First Year Result on Reionization
large TE polarization at large angle (low l)
produced by free electron re-scattering after
reionization
t 0.17, z 17 -5
Kogut et al 2003
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active dark matter in light of WMAP 1st year
result

• Rephaeli Szalay 1981 Salati Wallet 1984
  Sciama 1982
• reionization could be due to DM decay
• Doroshkevich Naselsky 2002
• decaying super heavy particle produce shower,
  CMB details
• Hansen Haiman, 2003
• a decaying sterile neutrino which decays at z
  20, ???0 e-
• Bean, Melchiorri, Silk 2003
• effect on recombination process

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• Kasuya, Kawasaki, Sugiyama, 2003
• X? ? ?, detailed investigation on CMB
  photon background
• Pierpaoli, 2003 detailed investigation on CMB
  for HH model
• Chen Kamionkowski, 2003 detailed
  investigation on CMB photo background, and
  energy deposition mechanism

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WMAP3 TE correlation
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EE spectrum
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CMB spectra
TT
TE
EE
BB
lensing
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Reionization back to normal
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ionizational evolution during dark age
recombination (slowed by expansion)
ionization by CMB photons (z1000) ionization
by star photons (z10) ionization by dark
matter decay/annihilation?
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thermal evolution during dark age
adiabatic cooling heating from CMB heating from
star light heating from decaying/annihilating
dark matter
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Energy Deposition

• rest mass of decay products
• weakly interacting particles escape (e.g.
  neutrino, neutralino, etc)
• electrons and photons-- Main Energy Source for
  Ionization
• hadrons

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Energy loss mechanism for high energy electrons
and photons

• Photon
• photoionization
• Compton scattering
• pair production
• scattering with CMB photons
• pair production with CMB photons
• redshift

• Electron
• ionization loss
• synchrotron emission
• inverse-Compton scattering
• pair production
• redshift

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Transparency window
Photon transparency window photon loose most
energy by redshift in this energy range (assume
neutral gas and CMB only).
Electron transparency window electron loose
most energy by scattering CMB photons into the
transparency window.
In transparency window
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Absorption of Energy into IGM
The fudge factor flt1 In most optimistic case,
all rest mass converted in decay (low mass
leptonic decay), in situ absorption (not in the
transprant window), but still For some typical
low energy decaying DM, calculate the amount of
energy absorbed by the IGM is f0.3-0.5
(Ripamonti, Mapelli Ferrara MNRAS 375,
1399(2007)
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Thermal evolution with a long lived decaying
particle
Findings

• extended partial ionization (gradual
  increase)
• also affect recombination
• raise of temperature
• slow increase of optical depth ? ln (1z)

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How Reionization affect CMB
free electrons re-scatter CMB photons

• small scale anisotropy damped by a factor of
  exp(-2?)
• generate small scale anisotropy (kSZ effect)
• Effects on polarization

Zaldarriaga 1997
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renormalized spectrum
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Short Lived Particle

• broad peaks of ionization
• no hidden reionization peaks at high redshift
• strongly affect recombination

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Fit on CMB
low l
whole range
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distortion of blackbody spectrum induced by free
electrons
COBE y lt 10-5
models considered here y lt 10-8
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Constraint with WMAP 1yr
For photons outside transparency window WMAP
TTTE data of 1403 d.o.f., 1? bound ??250
e.g., if ?0.1, fX 5, then
?-1 ? 1024 sec
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Limits on DM decay from X-ray and ?-ray
backgrounds
For photons in transparency window
Assuming monochromatic photons produced in
decays, then each energy corresponding to one
redshift
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diffuse photon background
?-ray background (EGRET)
X-ray background (ASCA)
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Diffuse Background Constraint
Note This applies for photons within
transparency window, while reionization
constraint applies to different situation.
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Degeneracy with cosmological parameters
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Constraint with WMAP 3yr LSS
parameter space explored with MCMC
L. Zhang et al., in preparation
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Current CMB Constraint on DM decay
If tlt1025 sec, must have very small ?
L. Zhang et al, in prep
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(No Transcript)
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Dark matter annihilation
positron annihilation (511 keV photon) observed
by INTEGRAL SPI (Weidenspointner et al,
astro-ph/0702621)
If dark matter mass is 1-100 MeV instead of 100
GeV (neutralino), then the number density is much
higher. Annihilation rate n2, can produce such
excess positrons
Boehm, Hooper Silk 2003
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Impact on recombination
L. Zhang, X. Chen, Y. Lei, Z. Si., PRD 74
,103519(2006)
Annihilation effect larger at higher redshift,
can affect recombination
impact depends on cross section/mass
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Ionization History CMB
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CMB constraint
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Correlation with parameters
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Constraint on MeV dark matter
Knodlseder et al 2005 observed 0.511 keV flux
1.05 x 10-3 cm-2 s-1
P. Jean et al 2006
Adopting J 231.8 (NFW, 8 deg)
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Constraint on MeV Dark matter
for 0.1ltflt1
SN Fayet, Hooper, Sigl (2006) ? Sizun, Casse,
Schanne (2006) see also Beacom Yuksel (2006),
Ahn Komatsu (2006)
To produce the galactic positrons and also
satisfy CMB constraint m lt 7 MeV
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Prospects
21cm observation of dark age fluctuations in the
redshift range 50-200 can in principle be
detected (radio telescope on the moon?) DM decay
life time up to 10-27 sec
Impact on first star formation free-electron
enhance H2 formation cool DM halos to form stars,
but heating increase critical mass for star
formation in DM halos, and suppress gas infall to
DM halos, so overall effect is complicated and
not too large (Ripamonti, Mapelli, Ferrara, 375.
1099 (2007).
Furlanetto, Oh, Pierpaoli, PRD 74, 103502 (2006)