Reionizing the Universe with Dark Matter : constraints on self-annihilation cross sections Fabio Iocco Marie Curie fellow at Institut d’Astrophysique de Paris IDM 2010 Montpellier, 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

Constraining with multimessenger [Pato et al. `09] = 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 keV scale

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  =  = 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 IGM The 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 of injected energy: ionization of the IGM free electron fraction, x e The only DM parameter is [Galli, FI, Bertone, Melchiorri `09]

Self-annihilating DM and the CMB DM annihilation causes indirect effects, SZ by “additional” e - [Galli, FI et al. `09] Modifying TT, TE, EE with additional e - (by DM z >1000, many e - no effects energy 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 of DM annihilation essential for determining 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] z r =1000,  Sommerfeld saturated A toy-Yukawa potential Sommerfeld enhancement f = 0.5 cold DM !!!!

Constraints on decaying DM Same 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 [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]

≤ cm 3 /s 5.1x10 -4 ≤ Z ≤ 2x10 6 [McDonald, Scherrer, Walker ‘02] [Zavala, Volgersberger, White ‘09] Looser constraint than from anisotropies

The equation to Solve-I Energy deposition rate Gas (IGM) Opacity Annihilation rates

The equation to Solve-II Evolution 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 ~ cm 3 /s Forget about thermal decoupling WIMP miracle Unless = (v) DM decoupling:  ~1 Recombination:  ~10 -8 Small halos:   Milky Way:  ~10 -4 By courtesy of M. Cirelli “Sommerfeld” enhancement fulfills the requirements (higher masses preferred) E [GeV] e - + e + e + fraction

Electron optical depth  Measured with CMB polarization WMAP 5 value Integrated quantity!