Chris Orban (OSU Physics) with David Weinberg (OSU Astronomy)
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Transcript of Chris Orban (OSU Physics) with David Weinberg (OSU Astronomy)
Self-similar Bumps and Wiggles: Isolating the Evolution of the BAO Peak with
Power-law Initial Conditions
Chris Orban (OSU Physics) with
David Weinberg (OSU Astronomy)
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BackgroundEarly Universe Late Universe
credit: SDSScredit: WMAP
Eisenstein et al. 2005
Problem:
How does the BAO signature change over cosmic time?
How “standard” is this standard ruler?Opportunity:
Largest “ruler” ever discovered – very useful for distance scale, dark energy
Anchored to CMB (not LMC!)Challenge:
Need to observe large cosmological volumes!
Need sub-percent accurate theory for any w(z)!
Initial Conditions
FourierTransform
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Linear regime
Strongly non-linear regime
Chris Orban – Self-similar Bumps and Wiggles
Self-similar Bumps!
rbao / Lbox = 1 / 10
rbao / np1/3 = 100/8
rbao / Lbox = 1 / 20
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!!!
• Because of self-similarity the bump evolution should be exactly the same as a scaling of the previous results
• Comparing results from rbao x2 simulations (e.g. rbao = 200 h-1Mpc) to previous results
• Numerical effects may break self-similarity – a test more powerful and more general than convergence testing
• Can’t do this with CDM initial conditions!
Fourier-space phenomenology
PNL(k) = exp(-2k2/2) PL(k/) + A(k)
DampingNon-linear spectrum
Small-scale model
Initial spectrum shift!
Beyond linear-order
1-loop SPT predictions!
PT valid
PT breaks down•Many groups developing beyond-linear-order perturbation theory methods to describe BAO evolution
•If successful BAO evolution for arbitrary w(z) can be computed without N-body simulations
•Powerlaw setup is problematic for many of these methods – may point to better schemes
Chris Orban – Self-similar Bumps and Wiggles
1-loop SPT predictions from publically-available code:http://mwhite.berkeley.edu/Copter/
(Carlson, White, & Padmanabhan 2009)
Future Plans
• Run “powerlaw” setup with 0• Explore the broadening of the BAO feature in
the halo clustering• Run simulations with a different N-body code
(PKDGRAV instead of Gadget2)• Compare and develop phenomenological
models to describe non-linear evolution
Chris Orban – Self-similar Bumps and Wiggles