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The Effect of Baryons and Dissipation on the Matter Power Spectrum

The Effect of Baryons and Dissipation on the Matter Power Spectrum. Douglas Rudd (KICP, U. Chicago) Andrew Zentner & Andrey Kravtsov. astro-ph/0703741. Baryons vs Dark Matter. 1E 0657-56, Bullet cluster. Gravity dominates at large scales and baryons trace dark matter

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The Effect of Baryons and Dissipation on the Matter Power Spectrum

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  1. The Effect of Baryons and Dissipation on the Matter Power Spectrum Douglas Rudd (KICP, U. Chicago) Andrew Zentner & Andrey Kravtsov astro-ph/0703741

  2. Baryons vs Dark Matter 1E 0657-56, Bullet cluster Gravity dominates at large scales and baryons trace dark matter At some scale this will change Dynamics of baryons different than dark matter (shocks, pressure, dissipation) 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.

  3. Growth of Structure with Baryons 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

  4. Effect on Matter Power Spectrum Simulation with cooling Weak lensing 2-d power spectrum relative to simulation without baryons 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! Scale dominated by large clusters Simulation without cooling

  5. Effect of Cooling on Halo Profiles Mass distribution altered beyond virial radius Limited resolution leads to “overcooling” “Adiabatic Contraction” Blumenthal et al (1986), Gnedin et al (2004) Cooling of baryons Cumulative mass profile for most massive cluster

  6. Dark Matter Halo Concentrations cvir = Rvir / rs NFW fits to DM halo density profiles excluding inner 0.05 Rvir ~10% increase in non-radiative simulation See also Lin et al 2006 Rasia et al 2004 ~40% increase in cooling simulation Halo Mass

  7. Effect on parameter estimation Simple Model Now normalized to simulation with cooling, aka “reality” • 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

  8. Conclusions • 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

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