THE MAGIC TELESCOPES Observatorio del Roque de los Muchachos, La Palma (2200 m a.s.l.) System of two 17 m Cherenkov Telescopes for VHE γ-ray astronomy MAGIC-I operational since 2004, Stereo system since fall 2009 Main characteristics: Field of view: 3.5 Energy threshold: ~50 GeV Sensitivity (5σ in 50 h, E > 250 GeV) ~0.8% Crab Nebula flux Major Atmospheric Gamma Imaging Cherenkov Telescopes Energy resolution: 15% - 25% Angular resolution: 0.04-0.15 Slewing: < 20 s / 180 Saverio Lombardi, 32nd ICRC, Beijing 2011 2
GALAXY CLUSTERS Largest gravitationally bound systems in the Universe with masses of 10 14 10 15 M and radii of few Mpc PERSEUS CLUSTER Actively evolving objects Cosmic Energy reservoirs Expected to contain substantial populations of Cosmic Rays (CR) About 80% of their mass is in form of Dark Matter (DM) non-thermal emission from radio to γ-rays 3
γ-ray EMISSION FROM CR INTERACTIONS CRs distribution γ-ray flux Pinzke, A. & Pfrommer, C. 2010, MNRAS, 409, 449 Energy [GeV] Cluster cosmological simulations reproduce the observed synchrotron radio (mini-)halo emission and predict a γ-ray emission which mainly depends on CR spatial and spectral distribution and ICM gas distribution γ-ray observations can give clues on: CR population spectral indexes CR acceleration efficiency CR-to-thermal pressure CR transport properties Magnetic field (+radio emission) At energies of interest for MAGIC (100 10000 GeV) the γ-ray spectrum is well approximated by a power-law with spectral index -2.2 4
γ-ray EMISSION FROM DM About 80% of mass in clusters is expected to be in form of DM In many models, DM particles are expected to annihilate or decay and to produce γ-rays as final states Particle Physics factor Astrophysical factor (source dependent) DM spectral shape is very different from that expected from CR related emissions, but typically with much smaller flux DM substructures in clusters can flatten the DM profiles due to boosts in flux in the outer regions up to 10 3 Sanchez-Conde et al., arxiv:1104.3530 Pinzke et al., arxiv:1105.3240 Gao et al., arxiv:1107.1916 Monochromatic lines, IB, cut-off Universal spectrum 5
PERSEUS CLUSTER Radio mini-halo VHE simulated emission Distance: 77.7 Mpc (z = 0.018) Mass: 7.7 10 14 M Brightest X-ray cluster Massive central cooling flow Radio mini-halo (~200 kpc) (diffuse synchrotron emission) Central radio galaxy NGC 1275 One of the most promising targets for the detection of γ-rays from π 0 decays result of the hadronic CR interactions with ICM Pinzke et al., arxiv:1105.3240 6
PERSEUS OBSERVATIONS WITH MAGIC Deepest survey of any cluster ever made so far at VHE MAGIC-I observation ~25 h (Nov - Dec 2008) Flux upper limits above 100 GeV (MAGIC Coll., APJ 710, 634, 2010) STEREO observation ~40 h (Oct 2009 - Feb 2010) Discovery at VHE of IC 310 (MAGIC Coll., APJ 723, 207, 2010) STEREO observation ~45 h (Aug 2010 - Feb 2011) Discovery at VHE of NGC 1275 (Atel#2916; MAGIC Coll., in preparation) Overall stereo observation + E > 150 GeV (see talk by Hildebrand et al.: id1221) + 7
MAGIC-I RESULTS ~25 h (Nov Dec 2008) No excesses found above 100 GeV Upper Limits (ULs) on the flux compared to γ-ray expected flux from simulations of Pinzke & Pfrommer, 2010, MNRAS, 409, 449 APJ 710, 634, 2010 + APJ 710, 634, 2010 MAGIC-I flux ULs (95% CL) are a factor ~2 higher than the CR emission model Constraints on the CR-to-thermal pressure to < 4% (center) - 8% (whole cluster) Flux boosts of the order of 10 4 for typical msugra DM models 8
MAGIC STEREO RESULTS (MAGIC Coll., in preparation) ~40 h (Oct 2009 Feb 2010) ~45 h (Aug 2010 Feb 2011) Overall Stereo observation: ~85 h CR and DM studies above ~600 GeV (where NGC 1275 is no longer detected) E > 630 GeV PRELIMINARY PRELIMINARY MAGIC flux ULs (95% CL) are below theoretical expectations: Constraints on maximum CR acceleration efficiency in simulations Tighten the constraints on the CR-to-thermal pressure to < 2% (center) - 4% (whole cluster) DM interpretation challenging 9
SUMMARY AND CONCLUSIONS MAGIC performed the deepest survey of the Perseus cluster ever made so far at VHE. Detection at VHE of NGC 1275 and IC 310 (see talk by Hildebrand et al.: id1221). MAGIC-I constraints on CR model improved by MAGIC Stereo results. First time that VHE ULs are below theoretical expectations. Paper in preparation. DM related studies are challenging due to the presence at VHE of NGC 1275 emission, to an expected flux typically much smaller than that coming from CR interactions, and to the possible very extended DM profile of the Perseus cluster (related to substructures). Detection of VHE γ-ray emission from CR hadronic interactions in the Perseus cluster may be close at hand. MAGIC will continue to collect data. 10
COSMIC RAYS IN CLUSTERS NON THERMAL PROCESS & EMISSION
γ-ray EMISSIONS FROM PERSEUS CENTRAL REGION Colafrancesco et al. 2010, A&A 519, A82 MAGIC Coll., APJ 710, 634, 2010