2
a
π/k[comovingscale]
1kpc 10kpc 100kpc 1Mpc 10Mpc 100Mpc 1Gpc 10Gpc
1
0.1
10−2
10−3
10−4
10−5
10−6
10−7
recombination
matter-radiationequality
• Nocausalcommunicationpossible• Relativisticanalysisnecessary
• DMperturbationsgrowlogarithmically• Acousticoscillationsinbaryon-photonplasma
IGMreheating• Baryonssmoothlydistributed
• BaryonandDMperturbationsgrow~G(a)
matter-Λequality
• DMswitchestogrowthδ~a
Nonlineartransition,Δ~1
Scalesofinterest
Transferfunction:results
0.001
0.01
0.1
1
0.001 0.01 0.1 1
CDM
all
3
k(Mpc−1)
T(k)
Eisenstein&Hu(1998)formulae
MajorTechniques
1. Higher-orderperturbationtheory– Usefulforweaklynonlinearevolution,e.g.largescale
structureat~10Mpcscales– Butwillneverunderstandgalaxyformationbydoingthis!
2. N-bodysimulations– “Exact”solutionofDM-onlyevolutionevenwhenδ>>1– Understandformation/structureofgalaxyhaloes,merger
history,…
3. Analytictreatmentsofhaloformation– Usefulforgainingintuition– ButnotasaccurateasfullN-bodyapproaches
4
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