Incontri di Fisica delle Alte Energie IFAE 2006 Pavia Vincenzo Vitale Recent Results in Gamma Ray Astronomy with IACTs

Introduction Instruments and techniques Scientific highlights and observations Summary Outline

Introduction Cosmic gamma-ray observation: - directly from satellites (HE) < O(10 GeV) and - indirectly from ground-based installations (VHE) > O(100 GeV) Satellites: EGRET -> HE gamma-ray astronomy already consolidated. EGRET: Around 350 sources (250 unidentified)

Ground based vs satellite Satellite : primary detection small effective area ~1m 2 lower sensitivity large angular opening large duty-cycle large cost lower energy low bkg IACT/ground based Secondary detection huge effective area ~10 4 m 2 Higher sensitivity small angular opening small duty-cycle low cost high energy high bkg

Sensitivity of γ detectors High galactic latitudes  b =  cm -2 s -1 sr -1 (100 MeV/E) 1.1 ). Cerenkov telescopes sensitivities (Veritas, MAGIC, Whipple, Hess, Celeste, Stacee, Hegra) are for 50 hours of observations.Large field of view detectors sensitivities (AGILE, GLAST, Milagro, ARGO, AMS) are for 1 year of observation.

STACEE CACTUS MILAGRO TIBET ARGO-YBJ PACT GRAPES TACTIC VERITAS MAGIC HESS CANGAROO TIBET MILAGRO STACEE TACTIC VHE γ detectors

Observation tecnique ~ 10 km Particle shower Detection of TeV gamma rays using Cherenkov telescopes ~ 1 o Cherenkov light ~ 120 m

Image intensity  Shower energy Image orientation  Shower direction Image shape  Primary particle

Better bkgd reduction Better angular resolution Better energy resolution Slide fro Pr W. Hofmann

Galactic Sources  Acceleration of Galactic cosmic rays in SNR  Galactic center emissions  New type of sources

HESS galactic plane survey 330° Sources > 6 sigma: 9 new, 11 total Sources > 4 sigma: 7 new Most sources: Shell-type SNR Pulsar-Wind- Nebulae Unidentified New objects

RX J  Unambiguous evidence for particle acceleration in an SNR shell  Resolved shell in VHE g-rays  Close correlation between X-rays and g-rays

RX J Preliminary Index ~ 2.1 – 2.2 Little variation across SNR No evidence of cutoff or break at high energy  Acceleration of primary particles in SNR shock to well beyond 100 TeV

Galactic Center Sgr A Diffuse emission Nature, Feb. 9th 2006

Galactic Center Unbroken power law, index 2.3 Good agreement between HESS and MAGIC (large zenith angle observation ).

PSR B  Binary system  Strong stellar wind  Shock at wind- pulsar interaction

Extragalactic Sources  Physics of AGN jets  Cosmological extragalactic background light (EBL)

AGN summary SourceRedshiftType First Detection Confimation M FR I HEGRAHESS Mkn BL Lac WhippleMany Mkn BL Lac WhippleMany 1ES BL Lac WhippleHEGRA 1ES BL Lac Tel. Array Many PKS BL Lac HESS PKS BL Lac Mark VI HESS H BL Lac WhippleMany H HESS 1ES BL Lac MAGIC 1ES BL Lac HESS

Extrag. Background Light  Cosmological radiation from star formation and evolution.  Spectral signature from gg absorption for Eg ~ GeV.  Use measured AGN spectra to constrain EBL. 1ES (HESS col.) Gamma ray horizon Martinez et al 2005

AGN with orphan flares  Source observed already by Whipple and HEGRA in flaring state.  Orphan flares (hadronic origin ?)  MAGIC observation: low threshold and low flux (low state).  Two neutrinos in AMANDA data ?.  Two HiRes stereo events ?.  => Connection btw. Gamma-ray astronomy and neutrino/UHECR astronomy ?.

High resolution flare study Huge Mkn 501 flare on 1st July > 4 Crab intensity. Intensity variation in 2 minute bins -> new, much stronger, constraints on emission mechanism and light-speed dispersion relations (effective quantum gravity scale). Preliminary 2 minutes time bins Preliminary Crab

GRBs observation with MAGIC # GRB Event Satellite Onset [UTC] Dt alert [sec] Dt obs. [sec]q[deg]z1GRB050408HETE16:22: GRB050421SWIFT04:11: GRB050502SWIFT02:14: GRB050505SWIFT23:22: GRB050509ASWIFT01:46: GRB050509BSWIFT04:00: GRB050528SWIFT04:06: GRB050713ASWIFT04:29: On 13 July 2005 MAGIC has observed a GRB with only 40 s delay Preliminary analysis shows no signal Constrain models on prompt emission

Mrk421 Mrk501 Crab Pulsar AGN The VHE γ ray sky + some additional sources in galactic plane

Source Counts Source Type* Pulsar Wind Nebula (e.g. Crab, MSH …) 16 Supernova Remnants (e.g. Cas-A, RXJ 1713 …) 26 Binary Pulsar (B ) 01 Micro-quasar (LS 5039) 01 Diffuse (GC clouds) 01 AGN (e.g. Mkn 421, PKS 2155 …) 711 Unidentified26 TOTAL1232  Explosion in the number of VHE sources.

Summary  Galactic Plane rich in number and type of VHE emitters.  PWN and SNRs firmly established as TeV sources.  Unprecedented spectrum and morphology studies.  Discovery of VHE gamma-ray emission from a binary Pulsar and from a Microquasar.  Wide-range spectrum of gamma-ray emission from GC. No hint for DM annihilation signals.  Increased number of TeV blazars at large redshift. Constraints in cosmological EBL.  2 minutes-resolution light-curve of a fast flare. Constraints in emission models and light-speed dispersion relations.  First GRB follow-up in coincidence with X-ray observation. Constraints in GRB models.

γ /hadron separation  CR (2) Shape:  –rays are narrower than cosmic rays.

γ /hadron separation Proton shower Gamma shower Crab Nebula

New Cherenkov Telescopes HESS-II New 28m telescope pixel camera. Lower energy GeV First light in MAGIC-II Improved 17m telescope. Faster FADCs and a high-QE camera. First light in MAGIC-I MAGIC-II 85m VERITAS 4x 12m telescopes at Kitt-Peak in 2006.