Transcript Fairbairn et al. 08

WIMP dark matter & stars
Fabio Iocco
Institut de Physique Theorique, CEA/Saclay
Institut d’Astrophysique de Paris
GDR Terascale, Grenoble 31/3/09
Outline
 WIMP DM and stars: general mechanism and effects
 The local Universe:
 Compact Objects in Globular Clusters
 Stars at the Galactic Center
 The Early Universe
 Proto-stellar phase and DM, which effects?
 How long can DM burning PopIII survive?
Scattering and capture
Halo WIMPs are captured
Captured WIMPs accumulate
inside the star, thermalize
and “sink” to the center
by scattering off the gas of the star
DM and stars: scattering and
capture
Capture rate C
“Dark Luminosity” inside the star
WIMPs thermally relaxed within the star:
Distribution
WIMP annihilation
 point-source
RX<<Rc
Equilibrium timescales are short
At equilibrium
Virtually no dependence on
self-annihilation rate
<v>
Seminal literature by:
Gould, Griest, Press,
Raffelt,Salati, Seckel,
Spergel
The Sun: HE s from DM
Icecube Collaboration
arXiv:0902.2460
Wikstrom & Edsjo
arXiv:0903.2986
Probing the cold disk?
(DM distribution in the solar system)
Cold dark disk in gas+DM simulations
Read et al. arXiv:0902.009
Bruch et al. arXiv:0902.4001
White dwarfs in Globular Clusters
White dwarfs
DENSE and with
no intrinsic energy production
WD, blackbody approx
T*, L*  r*  C*
DM profile reconstructed
from baryons/stars
(sample stars from the innermost field)
Bertone & Fairbairn 08
(WD at the Galactic Center by Moskalenko & Wai07)
Going cool: WIMP burning
(stars
have negative specific
heat)
Fairbairn et al. 08
Fairbairn et al. 08
Iocco et al. 08
Taoso et al.08
DM burning at the Galactic Center
At the limit of effectiveness
With current upper limits on cross section
Scott, Fairbairn & Edsjo 2009
The first stars (Population III)
Form in halos of Mh106Msun at z20 (Tvir< 104K)
First Stars  primordial chemical composition
(BBN: no C,N,O -- A > 7)
Weak cooling: H2 vs CO  big masses
Smooth collapse, at the center of the halo
No fragmentation, one star per halo
Live fast, die young (30-300Msun go SNe)
Hot: first engines for IGM Reionization
(possibly) seed BH, correlated to quasars
As of now, we have
(very likely) not seen one yet
Simulations!
By courtesy of M. J. Turk
Building the DM cusp
Gas (collisional) cooling
and collapsing to the center
(gravitationally)“pulling in”
embedded DM
Spolyar, Freese & Gondolo 07
(PRL 100, 2008)
(modeled through adiabatic contraction)
Iocco et al. 08
(also Freese+ 08)
Powering the structure (with DM)
Energy production
DM profile critical!
+
Energy deposition
Gas profile critical!
Energy repartition for
WIMP annihilation:
1/3 electrons
1/3 photons
1/3 neutrinos (lost)
Spolyar, Freese & Gondolo 07
(PRL 100, 2008)
At ngas1012 #/cm3
structure opaque
to annihilation products
Feedback effects
DM annihilation
induces heating : T up
Central shell
DM annihil. induces ionization
Ionization catalizes H2 formation
H2 is a coolant : T down
T = ??
Jeans mass unchanged
E. Ripamonti, FI et al 09; arXiv:0902.0346
Evolving “Dark Stars”
Proto-stellar stages
(or early pre-MS)
at T 5000 K
Lasting ≈ 104 years
Adopted
fiducial values:
(mX=200GeV, shorter times)
DM burning: prolonging lifetimes
DM powered
stars are “frozen”
as long as environmental
DM stays supecritical
frozen
evolving
Taoso et al 08
Iocco et al 08
SD0=10-38 cm2
Why should you care?
(astrophysical signatures)
z
(not actual size)
Halo merger
DM cusp erosion
(baryons + self-annihilation)
Bertone & Merritt 05
Wechsler + 02
Concluding
We can learn something from
interactions of WIMPs with stars
In the local Universe:
The Sun & the Earth (neutrinos!)
Compact Objects (observe them in dense
environments)
In the early Universe:
PopIII are very likely most affected
Observables yet to be modeled