measuring the density parameters of the...

MeasuringtheDensityParametersoftheUniverse(WITHEMPHASISONBARYONICACOUSTICOSCILLATIONS)ANDREWYIDEPARTMENTOFPHYSICS, KAIST

TableofContentsTheObjective

TheOtherTwoMethods◦ CosmicMicrowaveBackground(CMB)◦ TypeIa Supernova(SNIa)

BaryonicAcousticOscillations(BAO)◦ Whattheyare◦ Whatwecanlearnfromthem

PuttingEverythingTogether

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TheObjective

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Howdoestheuniversework?

Weneedausefulcosmologicalmodel!

TheΛCDMCosmologicalModelBigBang+Inflation+GravitationalInstability+ColdDarkMatter+CosmologicalConstant

Fourcomponentsmakeuptheuniverse:matter,darkenergy,radiation,curvature

Wecanrelatetheexpansionratewithredshift

Ourquestion:Howmuchofeachcomponentisthereintheuniverse?

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Ω",Ω#

TheDensityParametersandMethods

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CosmicMicrowaveBackgroundTheBasis

TypeIa SupernovaeTheStandardCandle

BaryonicAcousticOscillationsTheStandardRuler

CosmicMicrowaveBackground(CMB)

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http://www.esa.int/var/esa/storage/images/esa_multimedia/images/2013/03/planck_cmb/12583930-4-eng-GB/Planck_CMB.jpg

AnisotropiesinCMBAnisotropiesinCMBcanbestudiedusingthepowerspectrum

Duetothelocationofthefirstpeak,theuniverseisflat.

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P.Ade,etal.,(PlanckCollaboration),A&A594,A13(2016).arXiv:1502.01589.

𝑙% =220Ω)

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CosmicMicrowaveBackgroundTheuniverseisflatΩ" + Ω# ≈ 1

Ω"

Ω#0

0.2

0.4

0.6

1.0

0.8

1.2

1.4

00.2 0.4

0.6

0.8 1.0

NoBigBang

TypeIa Supernovae(SNIa)

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http://sci.esa.int/science-e-media/img/68/Gaia_SNIa_Artist_Impression.jpg

SNIa asstandardcandlesAftersufficientcorrection,theluminositycurveofallSNIa arethesame

Validtobeusedasstandardcandles

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http://burro.astr.cwru.edu/Academics/Astr328/Notes/Tests/stretch_hamuy1.gif http://burro.astr.cwru.edu/Academics/Astr328/Notes/Tests/stretch_hamuy2.gif

DarkEnergyBecomesNecessaryItturnsoutthatsupernovaexplosionsarefainterthanweexpectedinveryfarregions

Anacceleratinguniverseneedsdarkenergy

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A.Riess,etal.,AJ,116,1009(1998)

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TypeIa SupernovaeThereshouldbemoredark

energythanmatter

Ω"

Ω#0

0.2

0.4

0.6

1.0

0.8

1.2

1.4

00.2 0.4

0.6

0.8 1.0

NoBigBang

SNIa

BaryonicAcousticOscillationsBeforerecombination:Freeelectronspreventphotonsfrompropagatinginonedirection(Thomsonscattering)

Pressureandgravitytrytobalanceeachother,producingacousticwavesintheprocess

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Pressure:Expansion

Gravity:Collapsehttp://background.uchicago.edu/~whu/intermediate/gravity.html

BAO:AfterrecombinationNeutralatomsareformed.Photonspropagatefreelyandpressureisrelieved

Baryonsanddarkmatter formseparateoverdensity regions

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http://galaxies-cosmology-2015.wikidot.com/baryon-acoustic-oscillations D.J.Eisenstein,H.J.Seo,andM.White,ApJ.664,660(2007)

TheSoundHorizonBaryonicacousticwaveswillpropagateatthespeedofsound,whichisrelatedtothedensityofbaryonsandphotons

Thiswillformasoundhorizonwherematterisdistributedsphericallyaroundonedensepoint

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GalaxyFormationfromBAOsBaryonswillendupforminggalaxiesalongthecircumferenceofthesoundhorizon

BAObecomesa“statistical”standardruler

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http://galaxies-cosmology-2015.wikidot.com/baryon-acoustic-oscillations B.A.BassettandR.Hlozek,DarkEnergy,Ed.P.Ruiz-Lapuente.(2010)

TheCorrelationFunctionA preferredscaleforgalaxyformationcanbefoundusingthecorrelationfunction

Thereisapeakat100h-1 Mpc ~150Mpc,whichisinterpretedasthescaleofthesoundhorizon

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D.J.Eisenstein,etal.,ApJ,633,560(2005)

MatchingObservationsWiththeModelThesizeofthesoundhorizoncanbecalculatedusingtheangulardiameterdistance 𝑑/

Meanwhile,𝑑/ and𝐻(𝑧) canbeobserveddirectly

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1 + 𝑧 𝑑/ 𝑧 𝜃

𝑐𝑑𝑧𝐻(𝑧)

𝜃

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Ω"

Ω#0

0.2

0.4

0.6

1.0

0.8

1.2

1.4

00.2 0.4

0.6

0.8 1.0

NoBigBang

BAO

BaryonicAcousticOscillationsTheremustbeacertainamount

ofmatterintheuniverse

SUMMARY

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BaryonicAcousticOscillationsTheremustbeacertainamount

ofmatterintheuniverse

CosmicMicrowaveBackgroundTheuniverseisflatΩ" + Ω# ≈ 1

TypeIa SupernovaeThereshouldbemoredark

energythanmatter

R.Amanullah,etal.,ApJ,716,712,2010

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SummaryPuttingEverythingTogether

http://planck.cf.ac.uk/files/Planck-only_Cosmic%20recipe%20pie%20chart.jpg

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Q&ASession

AdditionalSlide1:ThewCDMModelThedarkenergydoesnotnecessarilyneedtobeconstant,andmaydependonredshift.

Currentobservationresultspointtoa𝑤) = −1,𝑤8 = 0 solution,meaningthatdarkenergyisindeedthecosmologicalconstant.

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Forsomespecificpointontheprojected(𝜃, 𝜑) planeforCMB,wecandefinetheanisotropyas

Sphericalharmonicsanddefiningthepowerspectrum

AdditionalSlide2:SpecificsofCMB

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AdditionalSlide3:SpecificsofCMB2Fordarkenergydominantuniverses,thelocationofthefirstmultipolepeakisaffected.

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A.MelchiorriandL.M.Griths,NewAstron.Rev.45,321(2001)

AdditionalSlide4:SpecificsofSNIaSNIa measurementsusetheluminositydistance.

Byusingthedistancemodulusrelationship,wecancalculatetheluminositydistanceanduseittofindthechangeinluminositydistanceasafunctionofredshift.

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