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Radiation backgrounds from the first sources and the redshifted 21 cm signal

Radiation backgrounds from the first sources and the redshifted 21 cm signal. Jonathan Pritchard (Caltech). Collaborators: Steve Furlanetto (Yale). Overview. 21 cm as probe of high-z radiation backgrounds Fluctuations in Ly a and X-ray backgrounds lead to 21 cm fluctuations

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Radiation backgrounds from the first sources and the redshifted 21 cm signal

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  1. Radiation backgrounds from the first sources and the redshifted 21 cm signal Jonathan Pritchard (Caltech) Collaborators: Steve Furlanetto (Yale)

  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? • Experimental prospects (SKA) z~30 z~12

  3. TS Tb Tg HI TK 21 cm basics • Use CMB backlight to probe 21cm transition z=0 z=13 fobs=100 MHz f21cm=1.4 GHz • 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. ZR ZT Za Z* Z30 Z~150 No 21 cm signal Collisionallycoupled regime Density Ly X-ray UV 21 cm fluctuations W-FCoupling Velocitygradient BaryonDensity Neutralfraction Gas Temperature Cosmology Reionization X-raysources Lyasources Cosmology Twilight Dark Ages Reionization TS~Tg

  7. 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 2005,2006

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

  9. 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 2006

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

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

  12. Experimental efforts MWA: Australia Freq: 80-300 MHz Baselines: 10m- 1.5km PAST: 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 See Bowman poster + Hewitt talk tomorrow

  13. Observations poor angular resolution foregrounds • Need SKA to probe these brightnessfluctuations • Observe scalesk=0.025-3 Mpc-1 • Can distinguishdifferent models

  14. 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 • Measurements discussed will require SKA and luck • Early days for 21 cm and still unclear what will and will not be possible - foregrounds will be determining factor • For more details: astro-ph/0607234 + astro-ph/0508381

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