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Gamma-ray emission from warm WIMP annihilation

Gamma-ray emission from warm WIMP annihilation. Qiang Yuan Institute of High Energy Physics Collaborated with Xiaojun Bi, Yixian Cao, Jie Liu, Liang Gao, Pengfei Yin & Xinmin Zhang (arXiv:1203.5636) TPCSF cosmology workshop 2012-05-23. Outline. Introduction of cold/warm dark matter

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Gamma-ray emission from warm WIMP annihilation

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  1. Gamma-ray emission from warm WIMP annihilation Qiang Yuan Institute of High Energy Physics Collaborated with Xiaojun Bi, Yixian Cao, Jie Liu, Liang Gao, Pengfei Yin & Xinmin Zhang (arXiv:1203.5636) TPCSF cosmology workshop 2012-05-23

  2. Outline • Introduction of cold/warm dark matter • Gamma-ray emission of warm WIMP based on numerical simulations • Conclusion

  3. Structure evolution: cold dark matter Bottom-up structure formation pattern instead of top-down pattern (fragmentation): cold dark matter Springel et al. (2006) Nature CDM simulation vs. galaxy survey

  4. How cold is dark matter? The coldness of dark matter depends on the free-streaming scale during the formation of structures • Hot dark matter (eV neutrinos) that washes out fluctuations on cluster scale (10 Mpc/h) • Warm dark matter (sterile neutrinos) that washes out fluctuations on galaxy scale (1 Mpc/h) • Cold dark matter that has effectively zero thermal velocity From Jing’s Nanjing talk (2012)

  5. CDM WDM How cold is dark matter: matter power spectrum Tegmark et al. (2004)

  6. How cold is dark matter: number of satellites Jing (2001)

  7. How cold is dark matter: circular velocity of Milky Way satellites Lovell et al. (2012)

  8. How cold is dark matter: velocity width function of galaxies (ALFALFA survey) Papastergis et al. (2011)

  9. How cold is dark matter: central density of dwarf galaxies Burkert (1995) From Shi Shao (2012)

  10. Observational summary • Large scale structures are very close to CDM • At (sub-)galactic scales, many discrepancies between observations and CDM expected (abundance, density profile, velocity profile) • WDM can better explain the observations

  11. If it is conventional WDM (like sterile neutrino), it is fatal for DM detection • However, the non-thermal production can make WIMPs warm (Jeannerot et al. 1999; Lin et al. 2001; Bi et al. 2009)

  12. Outline • Introduction of cold/warm dark matter • Gamma-ray emission of warm WIMP based on numerical simulations • Conclusion

  13. 1 keV WDM NT-WDM Lin et al. (2001) Simulations Lovell et al. (2012)

  14. Subhalo statistics M vs. L≡∫2dV M vs. F≡L/d2

  15. Spatial skymaps: CDM

  16. Spatial skymaps: WDM

  17. Two supersymmetric benchmark models Total skymaps with diffuse background (E>10 GeV)

  18. Detectability comparison

  19. Conclusion • Subhalos are less abundant for WDM, resulting a very flat subhalo luminosity function • It is currently difficult to detect either the cold or warm WIMPs, but the detectability of warm WIMP can be in principle better than cold WIMP due to a potentially larger cross section • For DM indirect search strategy, the Galactic center may be prior to dwarf galaxies for warm WIMP scenario (different from that for cold WIMPs)

  20. Thank you

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