Reionizing the Universe with Dark Matter : constraints on self-annihilation cross sections
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Transcript of Reionizing the Universe with Dark Matter : constraints on self-annihilation cross sections
Reionizing the Universe with Dark Matter :
constraints on self-annihilation cross sections
Fabio IoccoMarie Curie fellow at
Institut d’Astrophysique de Paris
IDM 2010Montpellier, 27/07/10
Indirect local DM searches
Courtesy of P. Salati
, ‘ s: straight messengers
e+, p, e- …subject to magnetic fields,diffusion, energy losses
Astrophysical uncertainties: CR propagation, DM halo density profile, boost factor
( r ) = smooth + clumps
Indirect searches of annihilating DM
The SA DM signal (easily re-writable for decaying DM)
Which line of sight?
Particle physics astrophysics(structures)
with substructures <2> ≥ <>2
Constraining with multimessenger
[Pato et al. `09]
<v>=<v>e+
Via Lactea Aquarius
Courtesy of NASA (through Google, Wikipedia, etc etc etc.)
Going early Universe
DM annihilation and the IGM
e
p
W
primary HE shower
heating and ionization
Courtesy of T. Slatyer
GeV -TeV scale
keVscale
Smooth component
Structure component
Structure formation history(Press-Schechter / Sheth-Tormen)
DM density halo profile Burkert / Einasto / NFW
Only after structure formation z ≤ ≈ 100
Isotropically averaged cosmological DM annihilation(easily re-writable for decaying DM)
…and its absorption by the surrounding gas(coupling DM induced shower to IGM)
Photoionization, IC scattering, pair production (on CMB and matter),
scattering
[Slatyer et al. `09]
“Opacity window” of the Universe
Neutral:Ly- absorber
z
Ionized:Ly- free to pass by
z ~ 6
“Reionization”: a history of free electrons
Completely ionized IGM
= 0.084
= neutral gas
Electron optical depth
Integrated quantity
Known contribution
Sources z > 6: known unknowns
constraints(DM annihilations can overproduce free e-)
To be integrated!
[Cirelli, FI, Panci `09]
In this models:
no astrophysical sources (z > 6)
Extra-conservative bounds!
Transparency of the Universe& structure formation
HE shower gets efficiently absorbed
at high z
Structure formation takes place in a late Universe (z < 60)
[Slatyer et al.`09]
[Cirelli, FI, Panci `09]
Self-annihilating DM and the IGMThe smooth DM component
annihilates with a rate (per volume)(easily re-writable for decaying DM)
depositing energy in the gas (IGM) at a rate
Main effect ofinjected energy:
ionization of the IGM
fre
e e
lect
ron
fra
ctio
n, x
e
The only DM parameter is
[Galli, FI, Bertone, Melchiorri `09]
Self-annihilating DM and the CMB
DM annihilationcauses indirect effects,
SZ by “additional” e-[Galli, FI et al. `09]
Modifying TT, TE, EE withadditional e- (by DM annih)
@ z >1000 , many e- no effectsenergy injection is small
Constraining DM with CMB
[Galli, FI et al. `09]
Evaluating “ f ”
All channels,all secondaries,redshift dependence
[Slatyer et al. 09]
leptons quarks
XDM => e XDM =>
Branching ratio ofDM annihilation
essential fordetermining absorption
Constraining DM with CMB
Thermal WIMP
[Galli, FI et al. + Slatyer et al `09]
Constraining Sommerfeld Enh. with CMB
[Galli, FI et al. 09]
zr=1000, 10-8
Sommerfeld saturated
A toy-Yukawa potentialSommerfeld enhancement
f = 0.5
cold DM !!!!
Constraints on decaying DMSame principle, same physics,
different “time dependence” of energy injection
DM Cirelli, FI, Ibarra, Panci, Tran:
preliminary results!
Constraints are not so strong:if the particles decay today, they did
less decay in the past…
[Catena et al. `10]
Comparing constraints
Concluding
It is possible to use Early Universe astrophysical observables to constrain DM properties
Self-annihilating DM can inject enough energy (free electrons)to modify the cross correlation CMB spectra!
The detectability of a DM annihilation in the CMB signal is DM model dependent (annihilation channel)
Would you ever believe we have found DM if I told you there is an (even strong) anomaly in the TE CMB spectrum?
Signal comes from smooth, cold DM density field(can get rid of structure formation uncertainties!
And it rocks with SE)
Observing Reionization:electrons and CMB
z
Damping of spectra
low(er) l polarization signal
Temperature constraints!
[CIP 09]
“Exotic heating”:DM, after coupled f
1/3 heat, 1/3 ioniz. 1/3 Ly-
Pamela saga: the e+ excess
[Delahaye et al. `09]Evidence for e+ excess: primary positrons
Combining the constraints on self-annihilating
[Hurtzi et al 09]
channel NFW profile
[CIP 09]
gammas + + IGM temperature
Einasto
NFW
Burkert
ee
ee
ee
[CIP `09]
Galactic bounds and their uncertainties
Radio constraints from GC (B=10 mG) [Bertone et al. `09]
IC gamma constraints (from GC)[Cirelli & Panci `09]
<sv> ≤ 10-21cm3/s5.1x10-4 ≤ Z ≤ 2x106
[McDonald, Scherrer, Walker ‘02]
[Zavala, Volgersberger, White ‘09]
Looser constraint than from anisotropies
The equation to Solve-IEnergy deposition rate
Gas (IGM) Opacity
Annihilation rates
The equation to Solve-IIEvolution of ionization fraction
Recombination rates
Ionization rates
Watching negative: gammas
[Profumo & Jeltema 09]
Mainly IC photons
z band breakup:locally dominated
e+ e-
boost IC
The Pamela(/Fermi/ATIC) saga
IF intepreted as DM:
High annih cross-section<v> ~10-24-10-21cm3/s
Forget about thermal decoupling
WIMP miracle
Unless<v> = <v>(v)
DM decoupling: ~1
Recombination: ~10-8
Small halos: 10-4
Milky Way: ~10-4
By courtesy of M. Cirelli
“Sommerfeld” enhancementfulfills the requirements(higher masses preferred)
E [GeV]
e- + e+
e+ fraction
Electron optical depth
Measured with CMB polarization
WMAP 5 value
Integrated quantity!