Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear...
Transcript of Probing Dark Energy with RSD around voids · We found for 6dFGS a consistency between the linear...
ProbingDarkEnergywithRSDaroundvoids
Ixandra Achitouv
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
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
Why probing RSDaround voids?
∆=0
∆ 𝑅 >0
∆ 𝑅 <0
Illustrationoftwo environments
• Environmental effectsàtestfin Non-linear regime àmoreinformation
• PertinenttestofMGtheories (screeningmechanism)
• Different systematic errors (void evolution is less NLthan haloevolution)
Why probing RSDaround voids?
TAIPANVoids Analysis
• Voids cataloguesinmocks since June 2018(Achitouv 16)
• Other voids finder arebeeing develop aswell forthemocks
• RSDanalysis inprogress (summer break!)
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?
WhyareRSDsensitivetothelineargrowthrate?
RealSpace: coherentinflow/outflow ofthePV
Random motionwithinvirialized halo:
NLatsmall scales
RSDpatterns
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
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
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)
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)
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…
MultipoleanalysisoftheRSDaroundvoidsinLowZsample
MyPreliminaryresults
Rcut Rcut
MultipoleanalysisoftheRSDaroundvoidsinLowZsample
MyPreliminaryresults
Correlation Matrixfortheresidual using 500mocks
Consistency with expected LCDMcosmology 𝛃=0.37LZSouthBF0.47+- 0.1LZNorth BF0.32+-0.08
Going onestep further:Theanalysis ofthegrowth ratein
thenon-linear regime
• Standard2-ptRSDanalysesdonotgenerally recover thelinear growthrateexpectationbelow acertainscale.
• Canwe usethedatabelow thatscale:is there moreinformationtogain?
Canweusetheenvironmentalgrowthratetotestcosmology onhighlyNLscales?
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?
What is thevalueofthegrowth rateinsmallunder/overdense regions ofdensity contrast ∆(𝑅)?
Achitouv &Cai2018,arXiv1806.04684
𝑓 =𝑑𝑙𝑛∆(𝑅)𝑑𝑙𝑛𝑎
Canweusetheenvironmentalgrowthratetotestcosmology onhighlyNLscales?
What is thevalueofthegrowth rateinsmallunder/overdense regions ofdensity contrast ∆(𝑅)?
Achitouv &Cai2018,arXiv1806.04684
𝑓 =𝑑𝑙𝑛∆(𝑅)𝑑𝑙𝑛𝑎
Canweusetheenvironmentalgrowthratetotestcosmology onhighlyNLscales?
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
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?
Anewapproach topredicts evolution ofdensity profiles&Linkwith observational
properties
LognormalMonteCarloRandomWalks
randomwalksfor3differentinitialconditions
a void?
I.Achitouv,Phys.Rev.D94,(2016)
• Evolutionofthesmoothedlineardensityfield:
<δ(k’)δ(k)>=Plin(k)
• Today,the1-pointdistributionofmatteriswell-describedbyalog-normalPDF:
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
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
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:
Testingfortheenvironmentaldependenceofthegrowthrate Ixandra Achitouv
Other slides
Testingfortheenvironmentaldependenceofthegrowthrate Ixandra Achitouv
LognormalMonteCarloRandomWalks
I.Achitouv,Phys.Rev.D94,(2016)
• Evolutionofthesmoothedlineardensityfield:
<δ(k’)δ(k)>=Plin(k)
• Today,the1-pointdistributionofmatteriswell-describedbyalog-normalPDF: