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The Effect of Baryons and The Effect of Baryons and Dissipation on the Matter Dissipation on the Matter Power SpectrumPower Spectrum
Douglas Rudd (KICP, U. Chicago)Andrew Zentner & Andrey Kravtsov
astro-ph/0703741
Baryons vs Dark MatterBaryons vs Dark Matter
Credit: X-ray: NASA/CXC/CfA/M.Markevitch et al.; Optical: NASA/STScI; Magellan/U.Arizona/D.Clowe et al.; Lensing Map: NASA/STScI; ESO WFI; Magellan/U.Arizona/D.Clowe et al.
Dynamics of baryons
different than dark matter
(shocks, pressure,
dissipation)
1E 0657-56, Bullet cluster
Gravity dominates at large scales and baryons trace dark
matter
At some scale this will change
Growth of Structure with Growth of Structure with BaryonsBaryons
Dark Matter only
Non-radiative Gas & DM
Cooling and Starformation
3 simulations with the same initial conditions
60 h-1 Mpc box, 2563 particles, 1 billion cells
Effect on Matter Power Effect on Matter Power SpectrumSpectrum
Simulation with cooling
Simulation without cooling
Scale dominated by large clusters
Huterer & Takada 2005
must theoretically predict nonlinear power spectrum P(k) to ~2% at k~1 h/Mpc to measure (σ8, Ωm, w)
See next talk by Charles Shapiro!
Weak lensing 2-d power spectrum relative to simulation without baryons
Effect of Cooling on Halo Effect of Cooling on Halo ProfilesProfiles
“Adiabatic Contraction”
Blumenthal et al (1986), Gnedin et al (2004)
Cumulative mass profile
for most massive cluster
Mass distribution
altered beyond virial radius
Limited resolution leads to
“overcooling”
Cooling of baryons
Dark Matter Halo Dark Matter Halo ConcentrationsConcentrations
NFW fits to DM halo density profiles excluding inner 0.05 Rvir
~40% increase in cooling simulation
cvir = Rvir / rs
Halo Mass
~10% increase in non-radiative simulation
See also
Lin et al 2006 Rasia et al 2004
Effect on parameter Effect on parameter estimationestimation
Now normalize
d to simulation
with cooling,
aka “reality”
2
DMDM
CSFCSFDM ),/(
),/()()(P
ccRk
ccRkkPk
Simple Model
•λ – “one-halo” contribution to power spectrum (Fourier-transform of NFW profile)
•R – size of typical halo ~Mpc
•cDM,cCSF – concentration of typical halo in DM simulation vs simulation with cooling
ConclusionsConclusions
Baryons change structure of dark halos even when baryons can’t cool (not just adiabatic contraction!)
Can model the effect of baryons as a shift in concentration relative to dissipationless simulations
Current simulations unable to predict absolute magnitude of effect, but non-radiative simulation demonstrates robust lower limit
Next step: see how adding additional parameters affects cosmological parameter constraints
astro-ph/0703741