Large Scale Simulations Large Scale Simulations of Reionizationof ReionizationGarrelt MellemaGarrelt MellemaStockholm Observatory Stockholm Observatory

Collaborators:Collaborators:Ilian Iliev, Paul Shapiro, Marcelo Alvarez, Ue-Li Pen, Hugh Merz, LOFAR EoR Key Ilian Iliev, Paul Shapiro, Marcelo Alvarez, Ue-Li Pen, Hugh Merz, LOFAR EoR Key

Project teamProject team

ContentsContents

ReionizationReionization SimulationsSimulations Some resultsSome results WMAP1 versus WMAP3WMAP1 versus WMAP3 Secondary CMB AnisotropiesSecondary CMB Anisotropies

Iliev et al. 2006, astro-ph/0512187Iliev et al. 2006, astro-ph/0512187 GM et al. 2006, GM et al. 2006, astro-ph/0603518 astro-ph/0603518

ReionizationReionization A view of the epoch when A view of the epoch when

the first galaxies formed.the first galaxies formed. CurrentCurrent observational observational

data: WMAP Thomson data: WMAP Thomson optical depth, SDSS QSOs, optical depth, SDSS QSOs, TTIGMIGM from Ly from Lyαα forest forest

FutureFuture observational data: observational data: redshifted 21cm radiation redshifted 21cm radiation (21CMA, LOFAR, MWA, (21CMA, LOFAR, MWA, SKA); SKA); directdirect view of HII view of HII regions (nature of sources) regions (nature of sources) and IGM density field.and IGM density field.

Simulations: Pro and Simulations: Pro and ConsCons

Limited rangesLimited ranges– mass resolutionmass resolution– spatial resolutionspatial resolution– number of sourcesnumber of sources

ExpensiveExpensive– Possible saves:Possible saves:

No temperatureNo temperature No heliumNo helium Simple source Simple source

prescriptionprescription

Reionization process Reionization process is complex: is complex: – Source clusteringSource clustering– HII region overlapHII region overlap– Recombinations (nRecombinations (n22))– Temperature effectsTemperature effects

Analytical models Analytical models cannot capture all of cannot capture all of these effects, these effects, numerical models numerical models can.can.

Simulations: How?Simulations: How?

Our motivation: Our motivation: large large scalescale simulations.simulations.– Observationally needed (~degree fields of view).Observationally needed (~degree fields of view).– Theoretically needed (cosmic variance, size of HII regions, Theoretically needed (cosmic variance, size of HII regions,

>>10 Mpc).>>10 Mpc). Approach:Approach:

– PMFASTPMFAST (Merz, Pen, Trac(Merz, Pen, Trac 2005)2005) simulations (4.3 billion particles): simulations (4.3 billion particles): Evolving density fieldEvolving density field Collapsed halo listCollapsed halo list 100/h and 35/h Mpc volumes (minimum halo masses 100/h and 35/h Mpc volumes (minimum halo masses

2.5x102.5x109 9 and 10 and 1088 M M, respectively)., respectively).– CC22-Ray-Ray (GM et al. 2006)(GM et al. 2006) postprocessing (203 postprocessing (20333, 406, 40633):):

Ionized hydrogen fractionIonized hydrogen fraction

ΛCDM (WMAP)

Simulations: SourcesSimulations: Sources

We have been working with stars as our sources We have been working with stars as our sources of ionizing radiation.of ionizing radiation.

Assumptions: Assumptions: – M/L=const.M/L=const.– only atomically cooling halos contribute (M>10only atomically cooling halos contribute (M>108 8 MM).).– halos with halos with M<10M<109 9 MM can be suppressed. can be suppressed.– fixed photons/atom escaping (Iliev, Scannapieco & fixed photons/atom escaping (Iliev, Scannapieco &

Shapiro 2005): f = fShapiro 2005): f = fSF SF x fx fesc esc xx NNphotonphoton.. Choices used: f=2000 and 250.Choices used: f=2000 and 250. Other source models to be explored in the future.Other source models to be explored in the future.

Results: evolutionResults: evolution

Movie of density field Movie of density field and HII regionsand HII regions

Green: neutralGreen: neutral Red: IonizedRed: Ionized

Note: clustering & Note: clustering & overlap.overlap.

From z=20 to 10 From z=20 to 10 (WMAP3 parameters). (WMAP3 parameters). Overlap expected at Overlap expected at z~7.z~7.

35/h Mpc

Importance of Large Importance of Large Scales Scales From our (100/h From our (100/h

Mpc)Mpc)33 volume we can volume we can analyze the analyze the reionization history of reionization history of subvolumes.subvolumes.

Large variations Large variations found, need at least found, need at least volume of (30/h volume of (30/h Mpc)Mpc)33..

Reionization is mostly Reionization is mostly inside-out.inside-out. Reionization histories for subvolumes

StatisticsStatistics 3D powerspectra:3D powerspectra:

– Poisson noise at largest Poisson noise at largest scalesscales

– Clear peak at some Clear peak at some (time-dependent) (time-dependent) characteristic scale.characteristic scale.

– Resemble analytical work Resemble analytical work (Furlanetto et al. (Furlanetto et al. 2004a,b)2004a,b)

The signal is strongly The signal is strongly non-gaussian:non-gaussian:– Numerical results do not Numerical results do not

resemble analytical resemble analytical inside-out, nor outside-in inside-out, nor outside-in results (Furlanetto et al. results (Furlanetto et al. 2004a,b)2004a,b)

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Full densityHII densityHI density

StatisticsStatistics 3D powerspectra:3D powerspectra:

– Poisson noise at largest Poisson noise at largest scalesscales

– Clear peak at some Clear peak at some (time-dependent) (time-dependent) characteristic scale.characteristic scale.

– Resemble analytical work Resemble analytical work (Furlanetto et al. (Furlanetto et al. 2004a,b)2004a,b)

The signal is strongly The signal is strongly non-gaussian:non-gaussian:– Numerical results do not Numerical results do not

resemble analytical resemble analytical inside-out, nor outside-in inside-out, nor outside-in results (Furlanetto et al. results (Furlanetto et al. 2004a,b)2004a,b)

20/h Mpc10/h Mpc 5/h Mpc

z=11.9 z=10.8

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LOS Reionization LOS Reionization HistoriesHistories From the From the

simulations we simulations we can construct can construct reionization reionization histories along histories along the line of sight.the line of sight.

Will be used to Will be used to prepare for the prepare for the analysis of the analysis of the LOFAR LOFAR observations observations (2009)(2009)

What Cosmology?What Cosmology?

11st st year WMAP versus 3 year WMAP:year WMAP versus 3 year WMAP:– ττ: 0.17: to 0.09 (if instantanious, z: 0.17: to 0.09 (if instantanious, zreionreion: 16 to 11): 16 to 11)– nnss: 1.0 to 0.95, : 1.0 to 0.95, σσ88: 0.9 to 0.74.: 0.9 to 0.74.

Reionization happened later (good!), but Reionization happened later (good!), but structure formation also took longer.structure formation also took longer.

Alvarez et al. (2006): approximate scaling for Alvarez et al. (2006): approximate scaling for simulations with similar types of sources: simulations with similar types of sources: (1+z(1+z11)/(1+z)/(1+z33)≈1.4. Confirmed by new )≈1.4. Confirmed by new simulations.simulations.

WMAP1 versus WMAP3WMAP1 versus WMAP3 Identical simulations (100/h Mpc, f=250), Identical simulations (100/h Mpc, f=250),

differing only in cosmological parameters:differing only in cosmological parameters:

WMAP1

WMAP3

FM Band

FM Band

Secondary CMB Secondary CMB AnisotropiesAnisotropies Patchy reionization is expected to imprint Patchy reionization is expected to imprint

small scale anisotropies on the CMB signal small scale anisotropies on the CMB signal through the kinetic Sunyaev-Zel’dovich effect.through the kinetic Sunyaev-Zel’dovich effect.

Several analytical estimates exist (Several analytical estimates exist (Hu & Gruzinov 98, McQuinn et al. 2005, Santos et McQuinn et al. 2005, Santos et al. 2006, Zahn et al. 2006), with large al. 2006, Zahn et al. 2006), with large variation in strength and scales. Now the first variation in strength and scales. Now the first numerical ones.numerical ones.

Temperature variations given by LOS integral:Temperature variations given by LOS integral:

Sample kSZ map from Sample kSZ map from patchy reionizationpatchy reionization Sample kSZ map Sample kSZ map

(100/h Mpc, (100/h Mpc, f=250).f=250).

Range of pixel Range of pixel values is values is T/T=-10T/T=-10-5-5 to 10to 10-5-5 , i.e. , i.e. T T max/min are in the max/min are in the tens of tens of K at K at ~arcmin scales. ~arcmin scales.

~1°

~1°

kSZ Power SpectrakSZ Power Spectra Power spectra peak Power spectra peak

at l~3000-5000, with at l~3000-5000, with a peak value ~1 a peak value ~1 μμK.K.

InstantInstant reionization reionization has order of has order of magnitude less magnitude less power for l~2000-power for l~2000-8000, but same 8000, but same large-l behaviour.large-l behaviour.

UniformUniform reionization reionization has much less power has much less power on all scales. on all scales.

ConclusionsConclusions

Large scale simulations needed for useful Large scale simulations needed for useful results.results.

Reionization produces a clear signature in Reionization produces a clear signature in the nthe nHIHI power spectra. power spectra.

WMAP3 results do not require different types WMAP3 results do not require different types of sources, but move reionization by a factor of sources, but move reionization by a factor ~1.4 in (1+z).~1.4 in (1+z).

kSZ due to patchy reionization produces a kSZ due to patchy reionization produces a signal of ~signal of ~μμK at K at l~3000-5000.l~3000-5000.