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Evolution and application of the 21 cm signal throughout cosmic history

Evolution and application of the 21 cm signal throughout cosmic history. Jonathan Pritchard (CfA-HCO). Collaborators: Steve Furlanetto (UCLA) Avi Loeb (Harvard) Mario Santos ( CENTRA - IST) Alex Amblard (UCI) Hy Trac (CfA) Renyue Cen (Princeton)

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Evolution and application of the 21 cm signal throughout cosmic history

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  1. Evolution and application of the 21 cm signal throughout cosmic history Jonathan Pritchard (CfA-HCO) Collaborators: Steve Furlanetto (UCLA) Avi Loeb (Harvard) Mario Santos (CENTRA - IST) Alex Amblard (UCI) Hy Trac (CfA) Renyue Cen (Princeton) Asantha Cooray (UCI)

  2. Overview • 21 cm as probe of high-z radiation backgrounds • Fluctuations in Lya andX-ray backgrounds lead to 21 cm fluctuations • What might 21 cm observations tell usabout first sources? • Reionization • Experimental prospects z~30 z~12 z~7

  3. Use CMB backlight to probe 21cm transition • HI hyperfine structure TS Tb Tg n1 11S1/2 HI l=21cm TK 10S1/2 n0 z=0 z=13 n1/n0=3 exp(-hn21cm/kTs) fobs=100 MHz f21cm=1.4 GHz 21 cm basics • 3D mapping of HI possible - angles + frequency • 21 cm brightness temperature • 21 cm spin temperature • Coupling mechanisms: • Radiative transitions (CMB) • Collisions • Wouthuysen-Field

  4. Wouthuysen-Field effect Hyperfine structure of HI 22P1/2 21P1/2 Effective for Ja>10-21erg/s/cm2/Hz/sr Ts~Ta~Tk 21P1/2 20P1/2 W-F recoils Field 1959 nFLJ Lymana 11S1/2 Selection rules: DF= 0,1 (Not F=0F=0) l~21 cm 10S1/2

  5. Thermal History e.g. Furlanetto 2006

  6. 21 cm fluctuations W-FCoupling Velocitygradient BaryonDensity Neutralfraction Gas Temperature Brightnesstemperature b Cosmology Reionization X-raysources Lyasources Cosmology Amount ofneutral hydrogen Spin temperature Velocity(Mass)

  7. Angular separation? W-FCoupling Velocitygradient BaryonDensity Neutralfraction Gas Temperature b • In linear theory, peculiar velocities correlate with overdensities Bharadwaj & Ali 2004 • Anisotropy of velocity gradient term allows angular separation Barkana & Loeb 2005 • Initial observations will average over angle to improve S/N

  8. Temporal separation? W-FCoupling Velocitygradient BaryonDensity Neutralfraction Gas Temperature Brightnesstemperature b Cosmology Reionization X-raysources Lyasources Cosmology Twilight Dark Ages

  9. d dV continuum injected Fluctuations from the first stars • Fluctuations in flux from source clustering, 1/r2 law, optical depth,… • Relate fluctuations in Lya and X-ray fluxes to overdensities • Start with Lya... Barkana & Loeb 2005 • Three contributions to Lya flux: continuum & injected from stars + x-ray Chen & Miralde-Escude 2006, Chuzhoy & Shapiro 2006, Pritchard & Furlanetto 2006,2007

  10. Determining the first sources da dominates source properties density bias Chuzhoy,Alvarez, & Shapiro 2006 Sources Ja,* vs Ja,X Pritchard & Furlanetto 2007 Spectra aS z=20

  11. X-ray heating • Soft X-rays heat closer to source, hard X-rays have long m.f.p. • X-ray flux -> heating rate -> temperature evolution • Integrated effect - so whole SF history contributes Pritchard & Furlanetto 2007

  12. TK<Tg TK>Tg Indications of TK • Learn about source bias and spectrum in same way as Lya • Constrain heating transition dT dominates

  13. dx dT da ? X-ray background? • To avoid giving the idea of certainty… Extrapolating low-z X-ray:IR correlation gives: Glover & Brand 2003

  14. Reionization Santos, Amblard, JRP, Trac, Cen, Cooray 2008 (100 Mpc/h)3 cube, 18803 particle N-body + UV photon ray tracing X-ray heating and coupling included via simple model

  15. Ionization history WMAP1 WMAP3 Zreion=10.8±1.4 (instant) WMAP5 Zreion~9 ±1.4 (extended) Xi>0.1 zR~7t~0.07

  16. Theory vs Simulation Furlanetto, Zaldarriaga, Hernquist 2004 • Bubbles imprint “knee” on large scales • Limited agreement at end of reionizationon large scales

  17. Experimental efforts MWA: Australia Freq: 80-300 MHz Baselines: 10m- 1.5km PAST/21CMA: China Freq: 70-200 MHz LOFAR: Netherlands Freq: 120-240 MHz Baselines: 100m- 100km Foregrounds are thebig problem! SKA: S. Africa/Australia ??? Freq: 60 MHz-35 GHz Baselines: 20m- 3000km More from Judd next

  18. Temporal evolution Post-reionization Reionization Dark ages Signal from denseneutral clumps at low z Pritchard & Loeb 2008

  19. x  T SKA ? MWA Temporal evolution

  20. High-z Observations poor angular resolution foregrounds • Need SKA to probe these brightnessfluctuations • Observe scalesk=0.025-2 Mpc-1 • Easily distinguishtwo models • Optimistic foregroundremoval • B~12MHz ->Dz~1.5

  21. Low-z Observations LOFAR MWA SKA • Low k cutofffrom antennaesize • Sensitivity ofLOFAR and MWA drops off by z=12 McQuinn et al. 2006

  22. MWA SKA LARC Angular Separation Astrophysics Cosmology

  23. Conclusions • Today told a simple story - lots of uncertainty in all attempts at modeling this period • Can use 21 cm to learn about the first luminous sources via the Lya background • Temperature fluctuations should give insight into thermalevolution of IGM • If X-ray heating important, then can learn about early X-ray sources • Map out reionization topology and evolution • Detailed measurements will require SKA and luck • Beginnings of full theoretical framework coming into being • Early days for 21 cm and still unclear what will and will not be possible - foregrounds will be determining factor

  24. Bonus material

  25. Redshift slices: Lya z=19-20 • Pure Lya fluctuations

  26. Redshift slices: Lya/T z=17-18 • Growing T fluctuationslead first to dip inDTb then to double peak structure • Double peak requiresT and Lya fluctuationsto have different scaledependence

  27. Redshift slices: T z=15-16 • T fluctuations dominate over Lya • Clear peak-trough structure visible • Dm2 <0 on largescales indicates TK<Tg

  28. Redshift slices: T/d z=13-14 • After TK>Tg , thetrough disappears • As heating continuesT fluctuations die out

  29. Redshift slices: d/x z=8-12 • Bubbles imprint featureon power spectra once xi>0.2 • Non-linearities in density fieldbecome important (TK fluc. not included)

  30. Thermal history • Lya forest Zaldarriaga, Hui, & Tegmark 2001 Hui & Haiman 2003 ?? • IGM retains short term memory of reionization - suggests zR<10 • Photoionization heating erases memory of thermal history beforereionization • CMB temperature • Knowing TCMB=2.726 K and assuming thermal coupling byCompton scattering followed by adiabatic expansion allows informed guess of high z temperature evolution

  31. Ionization history • Gunn-Peterson Trough Becker et al. 2005 • Universe ionized below z~6, some neutral HIat higher z • black is black • WMAP3 measurement oft~0.09 (down from t~0.17) Page et al. 2006 • Integral constraint on ionization history • Better TE measurements+ EE observations

  32. When did things start?

  33. Foregrounds • Many foregrounds • Galactic synchrotron (especially polarized component) • Radio Frequency Interference (RFI) e.g. radio, cell phones, digital radio • Radio recombination lines • Radio point sources • Foregrounds dwarf signal: foregrounds ~1000s K vs 10s mK signal • Strong frequency dependence Tskyn-2.6 • Foreground removal exploits smoothness in frequency and spatial symmetries • Cross-correlation with galaxies also important

  34. Reionization? =0.06 =0.09 =0.12 WMAP1 WMAP3 Zreion~11±1 (instant) WMAP5 Zreion~9 ±1 (model)

  35. Global history Furlanetto 2006 Adiabaticexpansion X-rayheating + + Comptonheating Heating expansion UV ionization + recombination HII regions X-ray ionization + recombination IGM Lya flux continuum injected • Sources: Pop. II & Pop. III stars (UV+Lya) Starburst galaxies, SNR, mini-quasar (X-ray) • Parameters: fstar, X, N, Nion (+ spectra + bias +…)

  36. Angular Separation

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