21cm Constraints on Reionization

1. 21cm Constraints on Reionization Benedetta Ciardi MPA T. Di Matteo (CMU), A. Ferrara (SISSA), I. Iliev (CITA), P. Madau (UCSC), A. Maselli (MPA), F. Miniati (ETH), R. Salvaterra (UInsubria), E. Scannapieco (UCSB), P. Shapiro (UAustin), F. Stoehr (IAU), M. Valdes (SISSA), S. White (MPA)

2. Cooling function (no metals!) 3-σ (Barkana & Loeb 2001) Atomic H cooling 2-σ Temperature [K] Λ/n² [erg cm³/s] 1-σ H2 cooling Redshift Temperature [K] The first sites of ionizing radiation DM halos virial temperature H2 is a key species in the early universe The gas needs to cool to be available for star formation HD cooling Atomic hydrogen cooling Molecular hydrogen cooling

3. (Shapiro et al. 2003) (Gnedin 2000) Feedback effects on primordial objects H2 photodissociation (L-W photons, 11.2-13.6 eV) Radiative feedback Mechanical feedback Chemical feedback Radiative feedback Photoheating The first generation of stars affects the subsequent star formation process Photoevaporation

4. Blow-out Blow-away (Mac Low & Ferrara 99) Feedback effects on primordial objects Blowout/blowaway Radiative feedback Mechanical feedback Chemical feedback Mechanical feedback

5. ~ 100 Msun ~ 1 Msun ~ 0.1 Msun Fraction of metals depleted onto dust grains (Schneider et al) Metallicity / Solar Metallicity Feedback effects on primordial objects Radiative feedback Mechanical feedback Chemical feedback Chemical feedback Change in fragmentation mode due to Z (Bromm et al, Schneider et al)

6. Feedback effects on primordial objects Radiative feedback Mechanical feedback Chemical feedback IGM reionization See Ciardi & Ferrara 2005 for a review

7. Constraints on the epoch of reionization High-z QSOs  latest stages of reionization at z~6 Which are the first sources of ionizing radiation? How did the reionization process evolve? Which is its interplay with the galaxy formation process? CMB  global amount of electrons

8. 21 cm line diagnostic u 21 cm l HI ground state • CMB photons are absorbed by HI thermal equilibrium Ideal probe of neutral H at high-z different observed frqs.  different z (ν~150,120,80 MHz  z~8,11,18) Scattering with Lyalpha photons emitted by the same stars that reionize DECOUPLING

9. 30<z<200  absorption IGM CMB z_ion<z<30  emission (Loeb & Zaldarriaga 2004) 1 10 100 1000 (1+z) Absorption or emission? Differential brightness temperature: absorption emission Heating by Lyalpha or X-ray photons, shock heating (Madau, Meiksin & Rees 1997; Giroux & Shull 2001; Glover & Brand 2002; Chen & Miralda-Escude’ 2003; Gnedin & Shaver 2004)

10. Modeling of cosmic reionization: ingredients • Simulations of galaxy formation (feedback effects) Galaxies Quasars • Properties of the sources of ionizing radiation • Radiative transfer of ionizing radiation computationally demanding

11. Tsu3: cosmological radiative transfer codes comparison Dense clump Cosmological field Stromgren sphere (Iliev, BC et al. 2006) www.mpa-garching.mpg.de/tsu3

12. Modeling of cosmic reionization: ingredients • Simulations of galaxy formation (feedback effects) Galaxies Quasars • Properties of the sources of ionizing radiation • Radiative transfer of ionizing radiation computationally demanding

13. Modeling of cosmic reionization: parameters Spectral Energy Distribution ?Source emission properties: ?IMF and spectrum: Salpeter or Larson IMF? Zero or higher metallicity? ?Escape Fraction: Fesc <20% but there is a big variation in the number both theoretically & observationally

14. Simulations of reionization • Simulations of galaxy formation  gas & galaxy properties (Springel et al. ‘00; Stoehr ‘04) • Stellar type sources  emission properties •  propagation of ionizing photons (BC et al. ’01; Maselli, Ferrara & BC ’03) Simulation properties Source properties - - metal-free stars - L=20/h Mpc com. - Salpeter/Larson IMF - Fesc=5-20%

15. Redshift Evolution of HI density 0.015 0.5 z=18 z=12 0.0 0.0 z=10 z=16 z=8 z=14 (BC, Stoehr & White 2003) The environment affects the reionization process ‘Field’: 20/h Mpc ‘Proto-Cluster’: 10/h Mpc

16. 68% CL (Kogut et al. 2003) (BC, Ferrara & White 2003) Early/Late Reionization Source properties: S5: Salpeter IMF+fesc=5% (late reion. case) S20: Salpeter IMF+fesc=20% L20: Larson IMF+fesc=20% (early reion. case) The simulations are consistent with the WMAP results

17. cell sub-grid physics Effect of mini-halos - MHs are sinks of UV photons - MHs photoevaporation has been studied in hydro-simulation and implemented in semi-analytic models (e.g. Shapiro, Iliev & Raga 2004; Iliev, Scannapieco & Shapiro 2005) • Fraction of gas collapsed in MHs • UV photons needed to photoevaporate the MHs 1. No MHs re-formation allowed once they are evaporated 2. MHs are allowed to form again

18. Ionization fraction no MHs MHs, re-formation MHs, no re-formation Effect of mini-halos (BC et al 2006) With no MHs re-formation there is no substantial difference form the no-MHs case If MHs are allowed to re-form, reionization can be delayed by Δz~2

19. 0 The 21cm line is observed in emission if: -2 -4 -6 (BC & Madau 2003) 21 cm line diagnostic

20. L20 S5 Fluctuations of brightness temp. The fluctuations are due to variations in HI distribution (density distrib. + ionized regions) • Late/Early reionization show similar behaviour • The peak of the emission is ~10 mK • Early reion. peaks @ 90MHz, late reion. peaks @ 115MHz Future radio telescopes should be able to detect such signal

21. LOw Frequency ARray

22. Simulated Synthetic -1.4 -1 -1.6 -2 -3 -1.8 -4 -2.0 z=10.6, ν=122 MHz -5 -2.2 -1 -1.6 -1.8 -2 -3 -2.0 -2.2 -4 z=9.89, ν=130 MHz -2.4 -5 -1.6 -1 -1.8 -2 -2.0 -2.2 -3 -2.4 -4 -2.6 z=9.26, ν=138 MHz -5 -2.8 LOFAR expected response (late reion.) • Instrument sampling • Instrument sensitivity • Convolution with a Gaussian • beam (s=3 arcmin) LOFAR will be able to map the reionization history, especially its latest stages (Valdes, BC et al. , 2006)

23. CMB secondary anisotropies L20 The power spectrum is dominated by the secondary anis. at l > 4000 (θ < 3’). They reach a peak of ~ which could be detected by e.g. ALMA, ACT S5 L20 S5 CMB/21cm line correlation (Salvaterra, BC, Ferrara & Baccigalupi 2005) • CMB anisotropies are produced by free electrons • 21cm line is emitted by neutral hydrogen

24. Characteristic angular scale of the cross-correlation function L20 Mpc/h S5 CMB/21cm line correlation We find an anti-correlation below a characteristic angular scale, θ0, when the correlation function becomes < 0. The characteristic angular scale of the cross-correlation function gives an estimate of the typical dimension of the HII regions at redshift of the 21cm emission line.

25. Extra-galactic foreground contamination (Di Matteo, BC& Miniati 2004) • Point Sources: • - Free-free emission from IS HII regions • - Low-z radio galaxies • Extended Sources: • - Free-free emission from IG HII regions • - Syncrotron emission from cluster radio halos • & relics Late reionization case @115 MHz F>0.1 mJy

26. After removal of bright sources (F>0.1 mJy), at scales >1 arcmin 21cm emission line is free from extra-galactic foreground contamination Extra-galactic foreground contamination Radio galaxies Radio halos

27. Conclusions • Simulations of cosmic reionization • 21cm line emission from neutral IGM (from reionization simulations) • CMB/21cm line cross-correlation • Extra-galactic foreground contamination calculated self-consistently • with emission signal • LOFAR should be able to map the reionization process, at least • its latest stages • More detailed information will be acquired implementing the above • observations with CMB anisotropies measurements • Observations of 21cm line at angles > 1 arcmin could be free from • extra-galactic foreground contamination