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: )
TPCSF cosmology workshop

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. How cold is dark matter: matter power spectrum
WDM
CDM
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. Simulations
NT-WDM
1 keV WDM
Lin et al. (2001)
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