The redshifted 21 cm background and particle decays

1. Evgenii O. Vasiliev & Yuri A. Shchekinov Tartu Observatory, Estonia South Federal University, Russia The redshifted 21 cm background and particle decays Tõravere '07: Astrophysics and particle physics

2. 21 cm line of neutal hydrogen 21 cm line: van de Hulst (1945) possibility: Shklovsky (1949) observations: e.g. Muller & Oort (1951) exitation in the neutral IGM: Wouthuysen (1952), Field (1958,1959) “dark ages” epoch of interest 21 cm and “dark ages” Hogan & Rees 1979, Madau et al 1997 Tõravere '07: Astrophysics and particle physics

3. Reionization and unstable particles (Sciama 1982, 1990) LSS and unstable particles (Doroshkevich & Khlopov 1984 – ) Nucleosynthesis and unstable particles (Scherer 1984) • WMAP 1 year, large optical depth –strong requirements to UV photon production from first stellar and QSO objects • complementary sources of reionization • decaying dark matter • ultra high energy cosmic rays (UHECRs) possible solution:partial ionization due to extra sources • Doroshkevich et al 2003Hansen & Haiman 2004 Chen & Kamionkowski 2004 Kasuya et al 2004 Kasuya & Kawasaki 2004 Pierpaoli 2004Mapelli et al 2006 Biermann & Kusenko 2006Ripamonti et al 2006… Tõravere '07: Astrophysics and particle physics

4. Extra ionization sources • decaying dark matter cold and warm DM, e.g. axino, neutralino, sterile neutrino (Dolgov 2002,Hansen & Haiman 2004, Chen & Kamionkowski 2004, Mapelli et al 2006, Ripamonti et al 2006) – decay rate long lifetime – Hubble time > shortlifetime – Hubble time < • UHECRs origin from Super Heavy Dark Matter particles (>1012 GeV) (Berezinsky et al 1997, Kuzmin & Rubakov 1998, Birkel & Sarkar 1998) • SHDM – UHECRs – (electromagnetic cascades) – UV photons (Ly-c & Ly-alpha) Peebles et al 2000Doroshkevich & Naselsky 2002 – production rate Tõravere '07: Astrophysics and particle physics

5. The model Ionization and temperature evolution (similar to Chen & Kamionkowski 2004): Peebles et al 2000Doroshkevich & Naselsky 2002 UHECRs Decaying particles Chen & Kamionkowski 2004 Heating rate Chen & Kamionkowski 2004 Modified version of the codeRECFAST (Seager et al 1999) “Smooth” or global signal evolution Tõravere '07: Astrophysics and particle physics

6. Basics of 21 cm physics brightness temperature (or specific inrensity) spin temperature (or exitation temperature) T* = 0.068 K – energy splitting TS>>T* in astrophysical applications ~3 of 4 atoms in the exited state • spin temperature: • absorption of CMB photons • collisions with hydrogen atoms, protons, free electrons • scattering of Ly - Lyc photons (Wouthuysen-Field effect) Observable parameters: global signal & fluctuations Tõravere '07: Astrophysics and particle physics

7. Ionization, spin and kinetic temperatures CMB temperatureBlack – standard recombinationRed – UHECRsGreen – long living particlesBlue – short living heating vs spin temperature Tõravere '07: Astrophysics and particle physics

8. UHE cosmic rays standard recombination • weak extra ionization • negligible heating Ly-alpha and Ly-c photons Wouthuysen-Field effect ε= 0ε= 0.3ε= 1ε= 3 Tõravere '07: Astrophysics and particle physics

9. Decaying dark matter particles short living particles (decay rate, density) long living particles (heating rate) 3x10-25 s-1 10-15 s-1 , 5 6x10-26 s-1 10-15 s-1 , 1 3x10-26 s-1 5x10-15 s-1 , 1 6x10-27 s-1 10-14 s-1 , 0.5 density in units 10-8d at zeq Tõravere '07: Astrophysics and particle physics

10. Major impact: collisions or photons? UHECRs long living particles short living particles solid – collisions dash – photons

11. Major impact: collisions or photons?

12. Power spectrum of 21 cm fluctuations Barkana & Loeb (2005), Hirata & Sigurdson (2006) – power spectrum – baryon density fluctuations – density-velocity cross spectrum – velocity fluctuations – cos(angle between line of sight and wavevector) – brightness temperature fluctuations Tõravere '07: Astrophysics and particle physics

13. standard recombination UHECRs Tõravere '07: Astrophysics and particle physics

14. Tb – 21 cm brightness temperature fluctuations (in mK) standard recombination UHECRs long living particles short living particles Tõravere '07: Astrophysics and particle physics

15. Discrimination between sources & observations observations at three redshift – three wave-band observations z1 z2 z3 20 40 2 – “central” redshift open – emissionfilled – absorption half-filled – emission/absorption – standard recombination – UHECRs – long living particles – short living particles Tõravere '07: Astrophysics and particle physics

16. Discrimination between sources & observations observations at three redshift – three wave-band observations z1 z2 z3 20 4010 30 50 2 – “central” redshift open – emissionfilled – absorption half-filled – emission/absorption – standard recombination – UHECRs – long living particles – short living particles Tõravere '07: Astrophysics and particle physics

17. Discrimination between sources & observations observations at three redshift – three wave-band observations z1 z2 z3 20 4010 30 5020 40 50 standard recombination 2 – “central” redshift open – emissionfilled – absorption half-filled – emission/absorption – standard recombination – UHECRs – long living particles – short living particles Tõravere '07: Astrophysics and particle physics

18. z1 zc z3 δz = 0.. δzm δz δz m m m Black – standard recombinationGreen – UHECRsRed – long living particlesBlue – short living m Minimum background flux 10 weeks – integration time ~10 mJy z = 20-40 LOFAR ~1-3 mJy z = 20-40 SKA/LWA Tõravere '07: Astrophysics and particle physics

19. Conclusions • longliving and short living unstable dark matter particles and UHECRs produce distinguishable dependences of brightness temperature on redshift • future radio telescopes (such as LOFAR, LWA and SKA) seem to have sufficient flux sensitivity for detection the signal in 21 cm influenced by decaying particles and UHECRs (three wave-band observations) Tõravere '07: Astrophysics and particle physics