Direct and Indirect Searches For Particle Dark Matter[直接和间接搜索粒子暗物质](-49)

《Direct and Indirect Searches For Particle Dark Matter[直接和间接搜索粒子暗物质](-49)》由会员分享，可在线阅读，更多相关《Direct and Indirect Searches For Particle Dark Matter[直接和间接搜索粒子暗物质](-49)（49页珍藏版）》请在文档大全上搜索。

1、Did Dark Matter Annihilations Reionize The Universe?Dan HooperFermilabTheoretical Astrophysics GroupFNAL Particle Astrophysics SeminarJune 1, 2009(Based on recent work with Alexander Belikov, arXiv:0904.1210)The Ionization History Of Our UniverseThe atoms in our universe have undergone two major pha

2、se transitionsDan Hooper - Did Dark Matter Annihilations Reionize The Universe?The Ionization History Of Our Universe370,000 years after the big bang, electrons and protons combine to form neutral atoms, and release the cosmic microwave backgroundDan Hooper - Did Dark Matter Annihilations Reionize T

3、he Universe?M a c in to s h P IC Tim a g e fo r m a tis n o t s u p p o r te dM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dThe Ionization History Of Our Universe 370,000 years after the big bang, electrons and protons combine to form neutral atoms, and release the cosmic microwave

4、 background Between z6-20, our universes gas once again became ionizedDan Hooper - Did Dark Matter Annihilations Reionize The Universe?M a c in to s h P IC Tim a g e fo r m a tis n o t s u p p o r te dM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dM a c in to s h P IC Tim a g e fo r

5、m a tis n o t s u p p o rte dEmpirical Handles On Reionization1) The Gunn-Peterson TroughNeutral hydrogen absorbs light very efficiently via the Lyman-alpha transition The lack of strong Lyman-alpha absorption in the spectra of very distant quasars demonstrates that the vast majority of hydrogen sin

6、ce z6 was ionized2) CMB Anisotropies Thompson scattering of the CMB photons with free electrons can produce observable anisotropiesWMAP has reported a Thompson optical depth of the universe of =0.017 (about 0.04 of which corresponds to full ionization at z 6, UV radiation from star forming galaxies

7、dominated reionization; at z 4, non-thermal emission from quasars became significant, enabling the double ionization of helium (Madau, Haardt, Rees, 1999)* Not to be confused with “Consensus”What Caused Reionization?Dan Hooper - Did Dark Matter Annihilations Reionize The Universe?The convention scen

8、ario, however, does not automatically lead to the full reionization of the universe by z6M a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dVolonteri and GnedinWhat Caused Reionization?Dan Hooper - Did Dark Matter Annihilat

9、ions Reionize The Universe?The convention scenario, however, does not automatically lead to the full reionization of the universe by z6This can be accommodated by reasonable (1) shifts in cosmological parameters (8, s)Volonteri and GnedinM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte

10、 dM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dM a c in to s h P IC Tim a g e fo rm a tis n o t s u p p o rte dDan Hooper - Did Dark MatterAnnihilations Reionize The Universe?Current StatusMacintosh PICTimage formatis

11、 not supportedDark Matter As An Alternative Source Of Ionizing Radiation?Over the first billion years, dark matter had begun to form clumps and annihilate efficientlyDark matter annihilation products include gamma rays, which can scatter with electrons, causing gas to become ionizedIf one in 109 dar