Presentation Transcript

1. Where will supersymmetric dark matter first be seen? Liang Gao National observatories of China, CAS
2. Cold dark matter ? Dark matter discovery possible in several ways: Fermi Direct detection UK DM search (Boulbymine) Annihilation radiation Evidence for SUSY
3. Intensity of annihilation radiation at x depends on: I(x) a∫ r2(x) ‹sv› dV halo density at x cross-section Indirect CDM detection through annihilation radiation Supersymmetric particles annihilation lead to production of g-rays which may be observable by FERMI  Theoretical expectation requires knowing r(x)  Accurate high resolution N-body simulations of halo formation from CDM initial conditions
4. Dwarf galaxies around the Milky Way Fermi Fornax
5. The Phoenix programme of cluster halo simulations China, UK, Germany, Netherlands, Canadacollaboration Gao Liang Adrian Jenkins Julio Navarro Volker Springel, Carlos Frenk Simon White
6. Simulation overview 9 clusters (Ph-[A-I]) with masses great than 5e14 Msun randomly selected from the MS 9 clusters have been simulated with 10^8 particles inside their R200. Per DM particles ~5e6 Msun/h , force resolution 320 pc/h The PhA halo has been simulated with 4 different resolutions. The PhA-1 has 10^9 particles inside its viral radius. Mass resolution 5e-5 Msun/h, softenning=150pc/h
7. z = 0.0
8. Phoenix clusterhalos
9. The main halo and the substructures all contribute to the annihilation radiation
10. The Density Profile of Cold Dark Matter Halos Halo density profiles are independent of halo mass & cosmological parameters There is no obvious density plateau or `core’ near the centre. (Navarro, Frenk & White ‘97) Galaxy clusters Dwarf galaxies Log density (1010 Mo kpc3) More massive halos and halos that form earlier have higher densities (bigger d) Log radius (kpc)
11. Density profile r(r) z=0 Orignal NFW simulations resolved down to 5% of rvir NFW
12. (r-rNFW)/rNFW R [kpc] Deviations from NFW Aq-A-2 Aq-A-3 Aq-A-4 The density profile is fit by the NFW form to ~10-20%. In detail, the shape of the profile is slightly different.
13. An improved fitting formula A profile whose slope is a power-law of r fits all halos to <5% Log density Has extra param: a residuals (similar to stellar distribution in ellipticals - Einasto) Navarro et al 04 Log radius (kpc) Log radius (kpc)
14. Deviations from NFW & Einasto forms NFW Einasto Aquarius (r-rNFW)/rNFW (r-rEisna)/rEinas Phoenix Galactic and cluster halos deviate from NFW to ~10-20% and from Einasto to <~ 7% Gao, Frenk, Jenkins, Springel & White ‘11
15. The structure of the cusp NFW slope slope Aquarius Phoenix
16. The structure of the cusp slope Scatter in the inner slope Aquarius g = dlogr/dlnr Asymptotic slope ≤1 Phoenix r/r-2 Gao, Frenk, Jenkins, Springel & White ‘11
17. Cluster dark halos seem to have cusps
18. Substructures Important for annhilation radiation Intensity a∫ r2(x) ‹sv› dV
19. Large number of substructures survive, mostly in outer parts
20. The mass function of substructures Aquarius N(M)  Ma a = -1.90 The subhalo mass function is shallower than M-2 dN/dMsub [ Mo] Most of the substructure mass is in the few mostmassive halos The total mass in substructures converges well even for moderate resolution Msub [Mo] 300,000 subhalos within virialized region in Aq-A-1 Springel, Wang, Vogelsberger, Ludlow, Jenkins, Helmi, Navarro, Frenk & White ‘08 Virgo consortium Springel et al 08
21. The specific mass function of substructures Subhalo mass function steeper for galaxies than clusters clusters: N(>m)~M0.97galaxies: N(>m)~M0.90 Phoenix N(msub)/M200 Aquarius ~20% more subs per unit mass in clusters msub/M200 Virgo consortium Gao et al 2011
22. Large number of substructures survive, mostly in outer parts
23. The cold dark matter linear power spectrum k3 P(k) z~1000 10-6 Mo for 100 GeV wimp lcutα mx-1 Galaxies Clusters Fluctuation amplitude n=1 Superclusters CMB k [h Mpc-1] Small scales Large scales
24. Substructures Important for annhilation radiation Intensity a∫ r2(x) ‹sv› dV Need to extrapolate to Earth mass  gravitational physics
25. Extrapolation to Earth mass Annihilation luminosity of subs. per unit mass Annihilation luminosity of subhalos field halo mass function Subhalo L (per halo mass) similar to L of field halo mass fn. Aquarius Phoenix Extrapolate using halo mass function (x1.5) + mass-concentration reln Gao, Frenk, Jenkins, Springel & White ‘11
26. Substructures M>10-12 Mo Annihilation radiation from cluster halos Substructures M>10-6 Mo Smooth main halo Surface brightness Resolved substructures M<5x107 Mo Gao, Frenk, Jenkins, Springel & White ‘11 R [kpc]
27. Substructure boost Extrapolating luminosity down to 10-6Mo (e.g. for 100 Gev WIMP) For dwarf galaxy b~few For galactic halos b=97 For cluster halos b~1300 (Gao et al. ‘11)
28. M31 galaxy Annihilation radiation Coma cluster Surface brightness Surface brightness UMII dwarf Gao, Frenk, Jenkins, Springel & White ‘11 R [arcmin]
29. Coma cluster M31 galaxy Annihilation radiation UMII dwarf Signal-to-noise signal-to-noise Gao, Frenk, Jenkins, Springel & White ‘11 R [arcmin]
30. Properties of nearby galaxy clusters, satellites of the Milky Way and M31
31. Conclusions Halos have nearlyuniversal “cuspy" densityprofiles ~10% of halo mass is in substructures, primarily in outer parts Annihilation radiation Emission from galaxies and clusters is extended boost factor is about one thousand for clusters, one hundred for galaxy and few for dwarfs Comacluster has 10 × (S/N) of UMAII, thus offer the best place to detect dark matter annihilation