Dark Matter Limits From The Galactic Halo With H.E.S.S. Daniil Nekrassov, MPI Heidelberg Emrah Birsin, Humbold University Berlin Gerrit Spengler, Humbold University Berlin

Overview DM searches with Cherenkov Telescopes Galactic center region Wobble Observations Reflected pixel method On-Off Observation Summary & Outlook

H.E.S.S. Array of 4 Imaging Cherenkov Telescopes, located in Namibia Energy range 0.1 – 100 TeV (!) Angular resolution ~ 0.1° (!) Energy resolution ~ 15 – 20% 1 % crab flux (2¢10-13 cm-2 s-1 TeV-1 at 1 TeV) in 25h (!)

DM Searches With IACTs Astrophysical Factor S  +  ! ¼0 ! ° + ° Tasitsiomi spectrum  +  ! ¼0 ! ° + ° Depends on model, assumed measured Astrophysical Factor S Depends on target, assumed Calculate limit

Possible Targets Regions of high DM density specifically important for the annihilation case, signal ~ ½2 Centers of DM halos Supergalactic scales: galaxy clusters Galactic scales: (dwarf) galaxies Subgalactic scales: subhaloes, globular clusters, Intermediate Mass Black Holes (IMBHs) Today: Galactic halo

The Galactic Center Region >100h of observation Strong sources Galactic centre(PWN, SMBH) G0.9+0.1(PWN) Also there: HESS J1745-303(UnId) Diffuse emission (CR-MCs) G 0.9 + 0.1 Sgr A* Diffuse Emission HESS J 1745-303

The Galactic Center Halo Avoid sources and diffuse emission Choose source region close to center Find region for background estimation far away from center Diffuse Emission HESS J 1745-303

Wobble Observations Standard observations Dataset >100h “Only” 5° FoV

Background Estimation Standard: Reflected regions around observation position DM halo search: Reflected pixels No DM detection  upper limit on <¾v> Most limiting HESS result so far! standard Abramowski et. al. Phys.Rev.Lett.106 arXiv:1103.3266

On-Off Observations Each observation is a standard observation Huge differences in astrophysical factor Off observations maybe “uninteresting” Systematics under investigation

Reflected Pixel Vs. On-Off On-Off expected to be ~25% more sensitive then Reflected Pixel method in same time Limits for ~100h of observation D. Nekrassov G. Spengler Would need ~10000 h

The Future Cherenkov Telescope Array (CTA) Studies on the way Sensitivity at 1TeV: 10×H.E.S.S. Energy threshold: ~10GeV Studies on the way

Summary And Outlook GC region is a promising target Limits derived from the GC region are the most limiting from H.E.S.S. Dependent on density profile in center region On-Off observations are expected to be more sensitive Systematics under investigation Off observations maybe empty For DM detection a more sensitive instrument will be needed  CTA

Thanks for listening!

Is The GC Source A DM Source? Spectrum well described by power law with exponential cut off No indication for DM annihilation A&A 503, 817-825 (2009)