Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons +...

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Modeling galaxy redshift space distortions for WFIRST Nick Hand UC Berkeley March 3, 2016 with Uros Seljak, Yu Feng, and Grigor Aslanyan

Transcript of Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons +...

Page 1: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

ModelinggalaxyredshiftspacedistortionsforWFIRST

NickHandUCBerkeleyMarch3,2016

withUrosSeljak,YuFeng,andGrigorAslanyan

Page 2: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

GalaxyclusteringwithWFIRST

theul'mategoal:measureexpansionhistoryandgrowthratewithsub-percentlevelprecision

Andersonetal.2014 PlanckCollabora'onXIII2015

BAOasstandardruler redshiHspacedistor'ons

Page 3: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

UncertaintiesintheforecastingofRSDconstraints

•smallscalescontaminatedbynon-lineareffects,buthavegreatersta's'calprecision

•theore'calsystema'csimplicitlyforecastedthroughvalueofkmax

source:Weinbergetal.2013

Page 4: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

RSDconstraintshavegreatpotential

source:Wangetal.2010

•needfullP(k)analysistofullycaptureinforma'on

•factorof~3improvementindarkenergyFOMwhenusingfullP(k)shapemeasurements(assumingGR)

•fullshapeanalysisprovidesinforma'ononneutrinomassesandexpansionthroughAPtest

Page 5: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

AnewschemeformodelingRSD

1.ApproximateN-bodysolverwithhaloforma'onmodelthatisbothsufficientlyfastandaccurateenoughtoextractgalaxysta's'cs

2.Physicalmodelforgalaxy-haloconnec'onthatisgeneralenoughtoavoidthemanyunknownaspectsofgalaxyforma'on

3.Simultaneouslysampletheposteriordistribu'onandemulatetheslowevalua'onofthedatalikelihood

Page 6: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

FastPM:fastsimulationsofhalos

•anapproximatepar'clemeshN-bodysolverthatenforcesthecorrectlarge-scalelineargrowthateach'mestep

•wriXenfromscratchtoexhibitstrong-scaling—nearlylinearscalingwiththenumberofCPUsallowsforfastsimula'ons

•benchmarkswith10'mestepsproducehalocatalogsthatareveryclosetotheexact(N-body)solu'on

•simula'onsledbyYuFengatUCBerkeley,withpublica'oncomingsoon

findtheprojectongithub:hXps://github.com/rainwoodman/fastpm

Page 7: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

preferredconfigura'ontakes~100CPU-hours—>typicallyO(1min)

Fengetal.2016(inprep.)

FastPM:fastsimulationsofhalos

Page 8: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

FastPM:benchmarksforhalocatalogs

transfer(P

1/P 2)1/2

Fengetal.2016(inprep.)

atz=0

Page 9: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

thegalaxy-haloconnection:HODformalism

•flexibleenoughtoimmunizeconstraintsagainstgalaxyforma'onuncertain'es:

1. velocitybiasforcentrals/satellites2. centralgalaxyincompleteness3. satelliteprofileuncertain'es4. assemblybias—>decoratedHODs(seeHearinetal.2015,

1512.03050)5. others?

•simplifiedHOD-modelingalreadysuccessfulinextendingRSDconstraintstosmallerscales:Reidetal.2014,Guoetal.2014.

•populateFastPMhalocatalogsusingasmanyfeaturesasneededusingHalotools soHware(ledbyAndrewHearin)

Halotools:hXps://github.com/astropy/halotools

Page 10: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

0.2 0.4 0.6 0.8 1.0k (h/Mpc)

−0.5

0.0

0.5

1.0

1.5

2.0

Pgg ℓ)(,2/PEH

ℓ)((k)

satellitefrac'on

fromsimulationtoclusteringobservables

•fastpowerspectrummeasurementsviaFFTsvianbodykit• popula'on+powerspectrumstepstakeO(seconds)

nbodykit:hXps://github.com/bccp/nbodykit

monopole

quadrupole

todo:tailortoWFIRSTvolume,HODmasses,observa'onaleffects,etc

Page 11: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

CombiningthepieceswithCosmo++ emulator

•acombinedsamplerandemulatorfordatalikelihoodusingtrainingsetofexactresultsproducedduringsamplingprocedure

•robusterrorcontrolofemula'onerrorsthatarepropagatedtoposteriorprobabilitydistribu'on

•exactsolu'oncomputediferrormodelpredictsanunacceptableemula'onerror

•“learn-as-you-go”:updateserrormodelandtrainingsetgivennew,exactsolu'ons

Aslanyanetal.2015,1506.01079hXps://github.com/aslanyan/cosmopp

Page 12: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

ledbyGrigorAslanyanatUCBerkeley

appliedtoCMBlikelihoodsin1506.01079

Aslanyanetal.2015

CombiningthepieceswithCosmo++ emulator

Page 13: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

Conclusions

• RSDanalysescanprovidepowerfulconstraintsondarkenergyandGeneralRela'vitytestswithWFIRST,iftheore'caluncertain'escanbecontrolled

• keychallenge:accuratemodelingofnon-lineareffectsandgalaxyforma'onphysicsonsmall-scales

• developingasimula'on-basedRSDmodelthatisbothcomputa'onallytractableandsufficientlyaccurate

1. FastPMsimula'onsproducehalocatalogsinO(minutes)2. HODpopula'onandpowerspectrumes'ma'onin

O(seconds)3. Combinethesestepsinlearn-as-you-goemulatorto

simultaneouslysampletheposteriorandemulatethenon-lineargalaxypowerspectrum

Page 14: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

FastPM:benchmarksforhalocatalogsstochas'city

Fengetal.2016(inprep.)

~0.18dexscaXerinhalomasscorrespondsto:stochas'city~0.10,0.18,0.22in1012,1013,1014Msun/hhalos

Page 15: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

ModelingassemblybiaswithdecoratedHODs

Page 16: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

thecurrentstatusofgrowthrateresults

bestuncertaintyonfσ8(z=0.57)is~8%,fipngtokmax=0.24h/Mpc

Gil-Marinetal.2015

Page 17: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

BAOsystematicsarewell-controlled

simula'onsindicatereconstruc'oneliminatessystema'cstothe~0.1%level

BAOsh

i1

source:Mehtaetal.2011

Page 18: Modeling galaxy redshift space distortions for WFIRST · • python tools for N-body simula’ons + LSS surveys • parallelized with MPI and designed to run on super-computers •

NickHand,UCBerkeley March3,2016

nbodykitsoftwaretools

•pythontoolsforN-bodysimula'ons+LSSsurveys

•parallelizedwithMPIanddesignedtorunonsuper-computers

•availabletools/features:

•periodicandwindowedpowerspectra

•correla'onfunc'ons

•FOFhalofinder

•sub-halofinder

•runningabovealgorithmsinparallelacrossnodesinbatchmode

availableatgithub.com/bccp/nbodykit