Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear...

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Probing Dark Energy with RSD around voids Ixandra Achitouv

Transcript of Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear...

Page 1: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

ProbingDarkEnergywithRSDaroundvoids

Ixandra Achitouv

Page 2: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

Howtodistinguish between Dynamical vs.Λ vs.MGtheories? DEUSSSIM

• Besides globalexpansionoftheUniverse,DEimpactstheformationofthecosmic web

• Cosmic Structuresformationcan helpusbreakthedegeneracies between different DEinterpretations

• Growth rateofcosmic structures:

Linear regime +GR:

DependsongravitationalforcesSensitivetothebackgroundexpansion

Credit:Y.Rasera

Page 3: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

Howtodistinguish between Dynamical vs.Λ vs.MGtheories? DEUSSSIM

• NLscales can helpusbreakthedegeneracies betweendifferent DEinterpretations

• Besides globalexpansionoftheUniverse,DEimpactstheformationofthecosmic web

• Growth rateofcosmic structures:

DependsongravitationalforcesSensitivetothebackgroundexpansion

Credit:Y.Rasera

Thegrowth rateasafunction oftime/scale is very sensitivetothenatureofDE

Page 4: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

Why probing RSDaround voids?

∆=0

∆ 𝑅 >0

∆ 𝑅 <0

Illustrationoftwo environments

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• Environmental effectsàtestfin Non-linear regime àmoreinformation

• PertinenttestofMGtheories (screeningmechanism)

• Different systematic errors (void evolution is less NLthan haloevolution)

Why probing RSDaround voids?

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TAIPANVoids Analysis

• Voids cataloguesinmocks since June 2018(Achitouv 16)

• Other voids finder arebeeing develop aswell forthemocks

• RSDanalysis inprogress (summer break!)

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Outline

I. Overview ofGrowth ratemeasurement inunderdense regions

II. Dowe expect thegrowth rateinunderdense regions tobe thesame asthegrowth rateinoverdense regions orinaveraged regions oftheUniverse?

III. Howtoprobethegrowth rateinthehighly non-linear regime?

Page 8: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

WhyareRSDsensitivetothelineargrowthrate?

RealSpace: coherentinflow/outflow ofthePV

Random motionwithinvirialized halo:

NLatsmall scales

RSDpatterns

Page 9: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

RealSpace: coherentinflow/outflow ofthePV

Random motionwithinvirialized halo:

NLatsmall scales

I.Achitouv,C.Blake,P.Carter,J.Koda&F.Beutler,Phys.Rev.D,(2017)

WhyareRSDsensitivetothelineargrowthrate?

Low zsurvey parentofTAIPAN,~100Kgalaxies

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NLalsoimpactRSDaroundVoids…

Assumptions&Model:- Gausian StreamingModel(e.g.

Peebles93;Fisher94)

I.Achitouv,Phys.Rev.D(2017)F.Beutler etal.,MNRAS(2012)

𝜒' 𝑅()* = ,(𝜉/0*0 𝑅1 − 𝜉*345(𝑅1))'

𝜎1'

89:8;<=

89:>

Keepinmindthatstandardproceduresthrowawaydataat

smallscales

Page 11: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

Wefoundfor6dFGSaconsistencybetweenthelineargrowthratesinthetwoenvironments:

fσ8 =0.36±0.06forgal-galRSDfσ8 =0.39±0.11forthegal-voidRSD

Assumptions&Model:- Gausian StreamingModel- LCDMcosmology- Linearbias- Constantvelocitydispersion(nuisanceparameter)- Weconsidervoidsofsize~20Mpc.h-1

Resultswith6dFGS

I.Achitouv,C.Blake,P.Carter,J.Koda&F.Beutler,Phys.Rev.D,(2017)

Page 12: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

Wefoundfor6dFGSaconsistencybetweenthelineargrowthratesinthetwoenvironments:

fσ8 =0.36±0.06forgal-galRSDfσ8 =0.39±0.11forthegal-voidRSD

Assumptions&Model:- Gausian StreamingModel- LCDMcosmology- Linearbias- Constantvelocitydispersion(nuisanceparameter)- Weconsidervoidsofsize~20Mpc.h-1

Resultswith6dFGS

Hawkenetal.,A&A(2017)

Hamaus etal.,PRL(2016)

3independant analysis forthegal-void RSD,using GSMbutcovering 3different redshifts &

having different void selection.

I.Achitouv,C.Blake,P.Carter,J.Koda&F.Beutler,Phys.Rev.D,(2017)

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WhyperformmultipoleanalysisoftheRSDaroundvoids?

Hamaus etal,JCAP(2017)

Questions:• Isit newphysic?• Isit abad estimationofthequadrupole – bad

approximationoftheerrorbars?• Failure ofthemodelatsmall scales?

• Different treatment ofthedata

• Easier totestforsystematic errors

• Inprinciple we can infer thegrowthratesimply from thedata(nomodeling oftherealspacecorrelation function )

• Easier tocompute Covariancematrices…

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MultipoleanalysisoftheRSDaroundvoidsinLowZsample

MyPreliminaryresults

Rcut Rcut

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MultipoleanalysisoftheRSDaroundvoidsinLowZsample

MyPreliminaryresults

Correlation Matrixfortheresidual using 500mocks

Consistency with expected LCDMcosmology 𝛃=0.37LZSouthBF0.47+- 0.1LZNorth BF0.32+-0.08

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Going onestep further:Theanalysis ofthegrowth ratein

thenon-linear regime

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• Standard2-ptRSDanalysesdonotgenerally recover thelinear growthrateexpectationbelow acertainscale.

• Canwe usethedatabelow thatscale:is there moreinformationtogain?

Canweusetheenvironmentalgrowthratetotestcosmology onhighlyNLscales?

Page 18: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

Naive ‘’island Universe’’picture can be helpful

SeparateUniversepredictionmaynotworkforislandradiusR~10Mpc/h

e.g.non-linearcouplingoflargeperturbationsonsmallscalesmodes,althoughseeChiangetal.PRD2017

• Standard2-ptRSDanalysesdonotgenerally recover thelinear growthrateexpectationbelow acertainscale.

• Canwe usethedatabelow thatscale:is there moreinformationtogain?

Canweusetheenvironmentalgrowthratetotestcosmology onhighlyNLscales?

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What is thevalueofthegrowth rateinsmallunder/overdense regions ofdensity contrast ∆(𝑅)?

Achitouv &Cai2018,arXiv1806.04684

𝑓 =𝑑𝑙𝑛∆(𝑅)𝑑𝑙𝑛𝑎

Canweusetheenvironmentalgrowthratetotestcosmology onhighlyNLscales?

Page 20: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

What is thevalueofthegrowth rateinsmallunder/overdense regions ofdensity contrast ∆(𝑅)?

Achitouv &Cai2018,arXiv1806.04684

𝑓 =𝑑𝑙𝑛∆(𝑅)𝑑𝑙𝑛𝑎

Canweusetheenvironmentalgrowthratetotestcosmology onhighlyNLscales?

Page 21: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

What is thevalueofthegrowth rateinsmallunder/overdense regions ofdensity contrast ∆(𝑅)?

Achitouv &Cai2018,arXiv1806.04684

𝑓 =𝑑𝑙𝑛∆(𝑅)𝑑𝑙𝑛𝑎

Whydowe want tomeasure f(∆)instead off(<R)?• f(∆) :different scales can contribute to∆à access theNL

scales• Probing f(∆)should contain moreinformationthan 2-pt

RSDàDoestheslope f(∆)changesforMG?

Canweusetheenvironmentalgrowthratetotestcosmology onhighlyNLscales?

Linear information

Page 22: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

What is thevalueofthegrowth rateinsmallunder/overdense regions ofdensity contrast ∆(𝑅)?

Achitouv &Cai2018,arXiv1806.04684

𝑓 =𝑑𝑙𝑛∆(𝑅)𝑑𝑙𝑛𝑎

Linkwith observation?• We need density profileindifferent zbinse.g.Lensing,counting galaxies• We could uselinear RSDmodeltoinfer NLgrowth

Canweusetheenvironmentalgrowthratetotestcosmology onhighlyNLscales?

Whydowe want tomeasure f(∆)instead off(<R)?• f(∆) :allscales can contribute totheperturbationà

access thehighly NLscales• Probing f(∆)should contain moreinformationthan 2-pt

RSDàDoes theslope f(∆)changesforMG?

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Anewapproach topredicts evolution ofdensity profiles&Linkwith observational

properties

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LognormalMonteCarloRandomWalks

randomwalksfor3differentinitialconditions

a void?

I.Achitouv,Phys.Rev.D94,(2016)

• Evolutionofthesmoothedlineardensityfield:

<δ(k’)δ(k)>=Plin(k)

• Today,the1-pointdistributionofmatteriswell-describedbyalog-normalPDF:

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Whatcanwedonow?

1/Generate 1Mlog-normalMCRWatz=0:acoupleofhours…

2/Compute these walks athigher z:2minsonmy laptop

3/Compute thegrowth rateaswe doinN-bodysimulationasf(∆):2mins

𝑓 =𝑑𝑙𝑛∆(𝑅)𝑑𝑙𝑛𝑎

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Whatcanwedonow?

• Generateanestimateofnon-standardgravityimpactondensityfluctuationstatistics

e.g.quickestimateofhowvoidprofileschangeforMGtheories

• Followevolutionoftheprofilesasafunctionofzwithnoneedtostartfromzini (asweneedforobservations).

V.Demchenko,Y.Cai,I,Achitouv inprep

I.Achitouv,M.Baldi,E.Pushwein&J.Weller2015

I.Achitouv PRD2016

• Otherapplications:voidabundance, Nonlineargrowthrateasafunctionoftheenvironment

SphericalVs MCRW

MCRW

N-body

Bias studiesongoing

Bias predicition inprep

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Conclusion:

• Testing mutlipole analysis with:• SDSS• TAIPAN• EUCLID

• Applyting thef(D)approach toMGsimulationsandobservations

• Cosmic voids could play acentralrole intesting MGtheories BUTstillsome effortrequired toadress systematic errors….

• Growth ratemeasurement:Potentially newinformationbeyond thelinear regime that require newapproaches e.g.f(D)

Prospects&ongoing work:

Page 28: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

Testingfortheenvironmentaldependenceofthegrowthrate Ixandra Achitouv

Other slides

Page 29: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11

Testingfortheenvironmentaldependenceofthegrowthrate Ixandra Achitouv

LognormalMonteCarloRandomWalks

I.Achitouv,Phys.Rev.D94,(2016)

• Evolutionofthesmoothedlineardensityfield:

<δ(k’)δ(k)>=Plin(k)

• Today,the1-pointdistributionofmatteriswell-describedbyalog-normalPDF:

Page 30: Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear growth rates in the two environments: fσ 8= 0.36±0.06 for gal-gal RSD fσ 8= 0.39±0.11