the redshifted 21 cm background and particle decays

The redshifted 21 cm background The redshifted 21 cm background and particle decaysand 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 2003Hansen & Haiman 2004 Chen & Kamionkowski 2004 Kasuya et al 2004 Kasuya & Kawasaki 2004 Pierpaoli 2004Mapelli et al 2006 Biermann & Kusenko 2006Ripamonti et al 2006

…

possible solution: partial ionization due to extra sources


Extra ionization sourcesExtra 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 <

UHECRsorigin 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)

– production rate Peebles et al 2000Doroshkevich & Naselsky 2002


The modelThe modelIonization and temperature evolution (similar to Chen & Kamionkowski 2004):

UHECRs

Decaying particles

Heating rate

Peebles et al 2000Doroshkevich & Naselsky 2002

Modified version of the code RECFAST (Seager et al 1999)

“Smooth” or global signal evolution

Chen & Kamionkowski 2004

Chen & Kamionkowski 2004


Basics of 21 cm physicsBasics of 21 cm 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* = 0.068 K – energy splitting

TS>>T

* in astrophysical applications

~3 of 4 atoms in the exited state

Ionization, spin and kinetic temperaturesIonization, spin and kinetic temperatures

CMB temperatureBlack – standard recombinationRed – UHECRsGreen – long living particlesBlue – short living

heating vs spin temperature


UHE cosmic raysUHE 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


long living particles (heating rate) short living particles (decay rate, density)

Decaying dark matter particlesDecaying dark matter particles

6x10-27 s-1

3x10-25 s-1

6x10-26 s-1

3x10-26 s-1

10-14 s-1 , 0.5

5x10-15 s-1 , 1

10-15 s-1 , 1

10-15 s-1 , 5


density in units 10-8 d at z

eq

Major impact: collisions or photons?Major impact: collisions or photons?

long living particles short living particles UHECRs

solid – collisions

dash – photons

Major impact: collisions or photons?Major impact: collisions or photons?

Power spectrum of 21 cm fluctuationsPower 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


standard recombination UHECRs


long living particles short living particles

standard recombination UHECRs

TTbb – – 21 cm brightness temperature fluctuations 21 cm brightness temperature fluctuations (in (in

mK)mK)

Discrimination between sources & Discrimination between sources & observationsobservationsobservations at three redshift – three wave-band observations

2 – “central” redshift

open – emissionfilled – absorption half-filled – emission/absorption

– standard recombination

– UHECRs

– long living particles

– short living particles

z1 z2 z3

1 20 40






– UHECRs



z1 z2 z3

1 20 4010 30 50






– UHECRs



standard recombination

z1 z2 z3

1 20 4010 30 5020 40 50


Minimum background flux

10 weeks – integration time

~10 mJy z = 20-40 LOFAR

~1-3 mJy z = 20-40 SKA/LWA

Black – standard recombinationGreen – UHECRsRed – long living particlesBlue – short living

z1 zc z3 δz = 0.. δzm

δz δz

m mm

m


✔ 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)

ConclusionsConclusions


the redshifted 21 cm background and particle decays

Documents

kasuya et

ripamonti et

mapelli et

gevberezinsky et

madau et

particle physicstravere

particle decaysevgenii

particle physics21