Constraining DM scenarios with CMB

Fabio IoccoInstitut d’Astrophysique de Paris

Institut de Physique Theorique, CEA/Saclay

In collaboration with: G. Bertone, M. Cirelli, S. Galli, A. Melchiorri, P. Panci

RPP, Lyon, 26/01/10

The Pamela(/Fermi/ATIC) saga(or “buzz”, see talk by J. Lavalle)

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

DM annihilation and the IGM

e

p

W

primary HE shower

heating and ionization

Courtesy of T. Slatyer

GeV scale

keVscale

Self-annihilating DM and the IGM

The smooth DM componentannihilates with a rate (per volume)

depositing energy in the gas (IGM) at a rate

more about “ f ” later

Main effect ofinjected energy:

heating and ionizationof the IGM

Evolution of free electron fraction, xe

The only DM parameter is

[Galli, FI, Bertone, Melchiorri `09]

Self-annihilating DM and the CMB

DM annihilationindirect,

SZ by “additional” e-

z>1000 there are many e- no effects

Energy injection is small

Letting pann free parameter [Galli, FI et al. `09]

Modifying TT, TE, EE withadditional e- (by DM annih)

A little more about “ f ”(coupling DM induced shower to IGM)

“ f ” is DM model-dependent:type of secondaries is important!

Photoionization, IC scattering, pair production (on CMB and matter),

scattering

[Slatyer et al. `09]

“Opacity window” of the Universe

Evaluating “ f ”

All channels,all secondaries,redshift dependence

[Slatyer et al. 09]

leptons quarks

XDM => e XDM =>

Branching ratio ofDM annihilation

essential fordetermining absorption

Little reminder:Pamela is leptophilic

Structure formation “boosts” DM annihilation

Structure formation starts at z ~ 150with minihalos of Earth mass 10-6 Msun

Smooth component

Structure component

Structure formation history(Press-Schechter / Sheth-Tormen)

DM density halo profile Burkert / Einasto / NFW

Structure boost: parameter dependence

Mmin=Mfs(?)

Cvir(M) = ?

[Huetzi et al. 09] [Pieri et al 08]

[Cirelli, FI, Panci `09]

Transparency of the Universe& structure formation

HE shower gets absorbed at high z

Structure formation takes place in a late Universe

[Slatyer, et al..`09]

[Cirelli, FI, Panci `09]

Neutral:Ly- absorber

z

Ionized:Ly- free to pass by

z ~ 6

A quick view on “Reionization”

= free electrons

Electron optical depth

Measured with CMB polarization

WMAP 5 value

Integrated quantity!

constraints(annihilation from structures can overproduce free e-)

To be integrated!

[CIP `09]

[CIP `09]

In this models:

no astrophysical sources (z > 6)

Extra-conservative bounds!

Constraining DM with CMB

[Galli et al. 09]+ [Slatyer et al. 09]

Constraining SE with CMB

[Galli et al. 09]

zr=1000, 10-8

Sommerfeld saturated

Yukawa potentiala benchmark model

Sommerfeld enhancement

Temperature constraints!

[CIP 09]

“Exotic heating”:DM, after coupled f

1/3 heat, 1/3 ioniz. 1/3 Ly-

Watching negative: gammas

[Profumo & Jeltema 09]

Mainly IC photons

z band breakup:locally dominated

e+ e-

boost IC

Combining the constraints

[Hurtzi et al 09]

channel NFW profile

[CIP 09]

gammas + + IGM temperature

Down to thermalcross-section!

z[CIP `09]

[Galli, FI et al. `09]

conservative bounds,no astrophysics z > 6

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 DM density field(can get rid of structure formation uncertainties!)

<sv> ≤ 10-21cm3/s5.1x10-4 ≤ Z ≤ 2x106

[McDonald, Scherrer, Walker ‘02]

[Zavala, Volgersberger, White ‘09]

Looser constraint than from anisotropies