Large Scale Simulations of Reionization Garrelt Mellema Stockholm Observatory Collaborators: Ilian Iliev, Paul Shapiro, Marcelo Alvarez, Ue-Li Pen, Hugh Merz, LOFAR EoR Key Project team

Contents Reionization Reionization Simulations Simulations Some results Some results WMAP1 versus WMAP3 WMAP1 versus WMAP3 Secondary CMB Anisotropies Secondary CMB Anisotropies Iliev et al. 2006, astro-ph/ Iliev et al. 2006, astro-ph/ GM et al. 2006, astro-ph/ GM et al. 2006, astro-ph/

Reionization A view of the epoch when the first galaxies formed. A view of the epoch when the first galaxies formed. Current observational data: WMAP Thomson optical depth, SDSS QSOs, T IGM from Lyα forest Current observational data: WMAP Thomson optical depth, SDSS QSOs, T IGM from Lyα forest Future observational data: redshifted 21cm radiation (21CMA, LOFAR, MWA, SKA); direct view of HII regions (nature of sources) and IGM density field. Future observational data: redshifted 21cm radiation (21CMA, LOFAR, MWA, SKA); direct view of HII regions (nature of sources) and IGM density field.

Simulations: Pro and Cons Limited ranges Limited ranges –mass resolution –spatial resolution –number of sources Expensive Expensive –Possible saves: No temperature No temperature No helium No helium Simple source prescription Simple source prescription Reionization process is complex: Reionization process is complex: –Source clustering –HII region overlap –Recombinations (n 2 ) –Temperature effects Analytical models cannot capture all of these effects, numerical models can. Analytical models cannot capture all of these effects, numerical models can.

Simulations: How? Our motivation: large scalesimulations. Our motivation: large scale simulations. –Observationally needed (~degree fields of view). –Theoretically needed (cosmic variance, size of HII regions, >>10 Mpc). Approach: Approach: –PMFAST (Merz, Pen, Trac 2005) simulations (4.3 billion particles): Evolving density field Evolving density field Collapsed halo list Collapsed halo list 100/h and 35/h Mpc volumes (minimum halo masses 2.5x10 9 and 10 8 M , respectively). 100/h and 35/h Mpc volumes (minimum halo masses 2.5x10 9 and 10 8 M , respectively). –C 2 -Ray (GM et al. 2006) postprocessing (203 3, ): Ionized hydrogen fraction Ionized hydrogen fraction ΛCDM (WMAP)

Simulations: Sources We have been working with stars as our sources of ionizing radiation. We have been working with stars as our sources of ionizing radiation. Assumptions: Assumptions: –M/L=const. –only atomically cooling halos contribute (M>10 8 M  ). –halos with M<10 9 M  can be suppressed. –fixed photons/atom escaping (Iliev, Scannapieco & Shapiro 2005): f = f SF x f esc x N photon. 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: evolution Movie of density field and HII regions Movie of density field and HII regions Green: neutral Green: neutral Red: Ionized Red: Ionized Note: clustering & overlap. Note: clustering & overlap. From z=20 to 10 (WMAP3 parameters). Overlap expected at z~7. From z=20 to 10 (WMAP3 parameters). Overlap expected at z~7. 35/h Mpc

Importance of Large Scales From our (100/h Mpc) 3 volume we can analyze the reionization history of subvolumes. From our (100/h Mpc) 3 volume we can analyze the reionization history of subvolumes. Large variations found, need at least volume of (30/h Mpc) 3. Large variations found, need at least volume of (30/h Mpc) 3. Reionization is mostly inside-out. Reionization is mostly inside-out. Reionization histories for subvolumes

Statistics 3D powerspectra: 3D powerspectra: –Poisson noise at largest scales –Clear peak at some (time- dependent) characteristic scale. –Resemble analytical work (Furlanetto et al. 2004a,b) The signal is strongly non-gaussian: The signal is strongly non-gaussian: –Numerical results do not resemble analytical inside- out, nor outside-in results (Furlanetto et al. 2004a,b) Furlanetto et al. 2004a Full density HII density HI density

Statistics 3D powerspectra: 3D powerspectra: –Poisson noise at largest scales –Clear peak at some (time- dependent) characteristic scale. –Resemble analytical work (Furlanetto et al. 2004a,b) The signal is strongly non-gaussian: The signal is strongly non-gaussian: –Numerical results do not resemble analytical inside- out, nor outside-in results (Furlanetto et al. 2004a,b) 20/h Mpc 10/h Mpc 5/h Mpc z=11.9 z=10.8 Furlanetto et al. 2004b

LOS Reionization Histories From the simulations we can construct reionization histories along the line of sight. From the simulations we can construct reionization histories along the line of sight. Will be used to prepare for the analysis of the LOFAR observations (2009) Will be used to prepare for the analysis of the LOFAR observations (2009)

What Cosmology? 1 st year WMAP versus 3 year WMAP: 1 st year WMAP versus 3 year WMAP: –τ : 0.17: to 0.09 (if instantanious, z reion : 16 to 11) –n s : 1.0 to 0.95, σ 8 : 0.9 to Reionization happened later (good!), but structure formation also took longer. Reionization happened later (good!), but structure formation also took longer. Alvarez et al. (2006): approximate scaling for simulations with similar types of sources: (1+z 1 )/(1+z 3 )≈1.4. Confirmed by new simulations. Alvarez et al. (2006): approximate scaling for simulations with similar types of sources: (1+z 1 )/(1+z 3 )≈1.4. Confirmed by new simulations.

WMAP1 versus WMAP3 Identical simulations (100/h Mpc, f=250), differing only in cosmological parameters: Identical simulations (100/h Mpc, f=250), differing only in cosmological parameters: WMAP1 WMAP3 FM Band

Secondary CMB Anisotropies Patchy reionization is expected to imprint small scale anisotropies on the CMB signal through the kinetic Sunyaev-Zel’dovich effect. Patchy reionization is expected to imprint small scale anisotropies on the CMB signal through the kinetic Sunyaev-Zel’dovich effect. Several analytical estimates exist ( McQuinn et al. 2005, Santos et al. 2006, Zahn et al. 2006), with large variation in strength and scales. Now the first numerical ones. Several analytical estimates exist (Hu & Gruzinov 98, McQuinn et al. 2005, Santos et al. 2006, Zahn et al. 2006), with large variation in strength and scales. Now the first numerical ones. Temperature variations given by LOS integral: Temperature variations given by LOS integral:

Sample kSZ map from patchy reionization Sample kSZ map (100/h Mpc, f=250). Sample kSZ map (100/h Mpc, f=250). Range of pixel values is  T/T= to 10 -5, i.e.  T max/min are in the tens of  K at ~arcmin scales. Range of pixel values is  T/T= to 10 -5, i.e.  T max/min are in the tens of  K at ~arcmin scales. ~1°

kSZ Power Spectra Power spectra peak at l~ , with a peak value ~1 μK. Power spectra peak at l~ , with a peak value ~1 μK. Instant reionization has order of magnitude less power for l~ , but same large-l behaviour. Instant reionization has order of magnitude less power for l~ , but same large-l behaviour. Uniform reionization has much less power on all scales. Uniform reionization has much less power on all scales.

Conclusions Large scale simulations needed for useful results. Large scale simulations needed for useful results. Reionization produces a clear signature in the n HI power spectra. Reionization produces a clear signature in the n HI power spectra. WMAP3 results do not require different types of sources, but move reionization by a factor ~1.4 in (1+z). WMAP3 results do not require different types of sources, but move reionization by a factor ~1.4 in (1+z). kSZ due to patchy reionization produces a signal of ~μK at l~ kSZ due to patchy reionization produces a signal of ~μK at l~