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

21 cm and “dark ages” Hogan & Rees 1979, Madau et al 1997 “dark ages” epoch of interest 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)

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) Doroshkevich et al 2003 Hansen & Haiman 2004 Chen & Kamionkowski 2004 Kasuya et al 2004 Kasuya & Kawasaki 2004 Pierpaoli 2004 Mapelli et al 2006 Biermann & Kusenko 2006 Ripamonti et al 2006 … possible solution: partial ionization due to extra sources Tõravere '07: Astrophysics and particle physics

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 > short lifetime – Hubble time <  UHECRs origin from Super Heavy Dark Matter particles (>10 12 GeV) (Berezinsky et al 1997, Kuzmin & Rubakov 1998, Birkel & Sarkar 1998) SHDM – UHECRs – (electromagnetic cascades) – UV photons (Ly-c & Ly-alpha) – production rate Peebles et al 2000 Doroshkevich & Naselsky 2002 Tõravere '07: Astrophysics and particle physics

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

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

Ionization, spin and kinetic temperatures CMB temperature Black – standard recombination Red – UHECRs Green – long living particles Blue – short living heating vs spin temperature Tõravere '07: Astrophysics and particle physics

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

long living particles (heating rate) short living particles (decay rate, density) Decaying dark matter particles 6x s -1 3x s -1 6x s -1 3x s s -1, 0.5 5x s -1, s -1, s -1, 5 Tõravere '07: Astrophysics and particle physics density in units  d at z eq

Major impact: collisions or photons? long living particlesshort living particlesUHECRs solid – collisions dash – photons

Major impact: collisions or photons?

Power spectrum of 21 cm fluctuations Tõravere '07: Astrophysics and particle physics 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 standard recombinationUHECRs

Tõravere '07: Astrophysics and particle physics long living particlesshort living particles standard recombinationUHECRs  T b – 21 cm brightness temperature fluctuations (in mK)

Discrimination between sources & observations observations at three redshift – three wave-band observations 2 – “central” redshift open – emission filled – absorption half-filled – emission/absorption – standard recombination – UHECRs – long living particles – short living particles z 1 z 2 z Tõravere '07: Astrophysics and particle physics

Discrimination between sources & observations observations at three redshift – three wave-band observations 2 – “central” redshift open – emission filled – absorption half-filled – emission/absorption – standard recombination – UHECRs – long living particles – short living particles z 1 z 2 z Tõravere '07: Astrophysics and particle physics

Discrimination between sources & observations observations at three redshift – three wave-band observations 2 – “central” redshift open – emission filled – absorption half-filled – emission/absorption – standard recombination – UHECRs – long living particles – short living particles standard recombination z 1 z 2 z Tõravere '07: Astrophysics and particle physics

Minimum background flux 10 weeks – integration time ~10 mJy z = LOFAR ~1-3 mJy z = SKA/LWA Black – standard recombination Green – UHECRs Red – long living particles Blue – short living z 1 z c z 3 δz = 0.. δz m δz δz m mm m Tõravere '07: Astrophysics and particle physics

✔ long living 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) Conclusions Tõravere '07: Astrophysics and particle physics