1. Searches for dark matter subhaloes with wide field Cherenkov telescope surveys
J-F. Glicenstein, P.Brun, E.Moulin (IRFU-Saclay)
J.Diemand (ITP-Zurich)
Phys Rev D,83, (2011)
Image courtesy of Via Lactea Project:

2. Searches for DM subhaloes with Cherenkov telescopes surveys
Outline
HESS flux sensitivity map (Galactic plane)
Search for clumps in HESS galactic plane survey
CTA flux sensitivity map (Galactic plane)
predictions for clumps in CTA galactic plane survey
conclusion
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

3. Indirect dark matter search strategy
WIMP annihilation flux into rays observed in solid angle :
fAP: dark halo model
particle model
Astrophysical factor:
dN/dE given by a particle model neutralinos
DW: assumes point source search 3

4. Signal boosts astrophysics: particle physics: unresolved sub-clumps
Sommerfeld effect:
effective low velocity dispersions
resonances at:
Internal Brehmstrahlung
annihilation to W+W-,ff
(c heavy higgsino-like)
relative velocity b
FSR IB

5. The H.E.S.S. survey of the Galactic plane
F.A. Aharonian et al (HESS) , ApJ. 636, 777 (2006)
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

6. Galactic plane sensitivity map
in each bin (b,l) of the map, get Ng (g candidates)/ Nhadr
outside sources, Ng is dominated by fake gammas
background B estimated by the « template method »
Ng compared to B  90% C.L. upper limit on signal S90
F90 obtained from S90 by
Assumes dN/dE from ccbb (not sensitive to this assumption)
Mc = 500 GeV
(from Berge et al 2007) _

7. Galactic plane flux sensitivity map (HESS)
from HESS galactic survey ( )
|b| ≤3o, -30o ≤l≤ 60o
map divided into 0.02o x 0.02o bin
smoothed to a 0.1o x 0.1o resolution (HESS)
F.Aharonian et al (HESS)+Bertone,PRD 78 (2008),
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

8. Searches for DM subhaloes with Cherenkov telescopes surveys
Dark matter clumps
HESS
sensitivity
clumps from ViaLacteaII (Diemand, Kuhlen, Madau, 2008)
~104 resolved halos in MW (M>105Msol)
103 random realizations (rotate the observer kpc)
168±44 clumps inside HESS galactic survey
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

9. Searches for DM subhaloes with Cherenkov telescopes surveys
HESS clump limits
use the HESS Galactic plane sensitivity map
find <sv> so that 2.3 subhalos are seen on average
90% C.L. limits comparable to Sgr dwarf, Galactic Center (point source)
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

10. Expectations for Galactic plane survey
Funk,Hinton,Hermann,Digel, arXiV
HESS map of the Gal.plane, total exp ~500 hours
simulated CTA map, flat exposure ~ 5 hours/field
assumes
x 2 improvement in hadron rejection
x 2 gain in angular resolution
x 10 gain in effective area
 overall increase in sensitivity of ~ 9
expect ~ 300 sources in -30 deg≤ l ≤ 30 deg
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

11. Galactic plane sensitivity (CTA)
~400 hours total
10 hours each bin
assume Emin = 50 GeV
500 GeV WIMP annihilating to bb
x10 gain in effective area, x2 gain in hadron rejection
reaches cm-2 s-1 sensitivity, except on new sources
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

12. CTA clump limits (Galactic plane)
90% C.L. limits improved by an order of mag/ HESS
interesting <sv>s not reached
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

13. CTA clump limits (1/4 sky)
1/4 survey in ~6 years
assume cm-2s-1 sensitivity (5 hour/bin)
number of subhalos: 3907±324
thermal WIMPs region reachable
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

14. Searches for DM subhaloes with Cherenkov telescopes surveys
Conclusions
168 DM clumps (estimated from Via Lactea II) expected in
field of view of the HESS galactic plane survey
Visibility of clumps depends on <sv>  90% CL limits on <sv> equivalent to HESS galactic center limits.
Limits improved with CTA, however <sv> typical of thermally produced WIMPs not accessible.
Contraints at the level of <sv> ~ cm3/s can be obtained by a 6-year survey of ¼ of the sky with CTA.
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

15. Searches for DM subhaloes with Cherenkov telescopes surveys
Back-up slides
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

16. Dark matter annihilation around IMBH
200 MC
realisations
NIMBH inside
galactic survey
HESS
sensitivity
« scenario B » of Bertone, Zentner, Silk 2005
collapse of a primordial cloud of gas ~105 Msol
into ~4 104 Msol Intermediate Mass Black Hole
101±22 IMBH in MW (4.3±2.3 in Hess galactic survey)
very luminous (due to the DM spike around BH)
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys

17. HESS IMBH limits (scenario B)
for each mDM, decrease <s v> until NIMBH < 2.3
F.Aharonian et al (HESS)+Bertone,PRD 78 (2008),
ICRC 2011
Searches for DM subhaloes with Cherenkov telescopes surveys