Status and Future of the HESS experiment

Transcription

1 Status and Future of the HESS experiment Martin Tluczykont for the HESS Collaboration LLR Ecole Polytechnique Joint Symposium on GeV-TeV Astrophysics in the GLAST Era Stanford, September 2004 HESS Phase 1 Status Performance Operation and Observations HESS Phase 2 Concept Expectations Collaboration with GLAST

2 HESS 1: Stereoscopic System of 4 Cherenkov Telescopes Namibia, Khomas Highlands (23 S, 15 E) Altitude 1800 m 380 mirrors 12 m relectors (4 107 m2 ) 960 PMT cameras (0.16 ) Fast trigger coincidence Electronics integrated in Cameras 5.3 FoV Energy threshold 100 GeV Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 2/26

3 HESS I Phase 1 Completed First light telescope 1 : June 2002 Two telescopes : March 2003 Stereoscopy : July 2003 Three telescopes : September 2003 Four telescopes : December 2003 Phase 1 completed and operational! Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 3/26

4 The Mirror Alignment Data PSF 2.3 off axis MC Individual mirror facets steerable Alignment of facets using stars PSF well within specifications Martin Tluczykont for the HESS Collaboration 4/26

5 The Mirror Alignment Data PSF 2.3 off axis MC Individual mirror facets steerable Alignment of facets using stars PSF well within specifications Martin Tluczykont for the HESS Collaboration 5/26

6 The Mirror Alignment Data PSF 2.3 off axis MC Individual mirror facets steerable Alignment of facets using stars PSF well within specifications Martin Tluczykont for the HESS Collaboration 6/26

7 Simulation, Calibration & Analysis Monte Carlo simulations CORSIKA + sim hessarray KASKADE + smash 2 Calibration chains Heidelberg Paris Background subtraction Geometric models Template-model Likelihood-based model Different Calibration methods Laser System Single ph.e. Muon rings Shower reconstruction methods Standard Hillas reconstruction Semi-analytical model 3D-Model Redundance gives confidence: Robust results Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 7/26

8 HESS 1 Performance: The Crab Nebula (preliminary) HESS: Crab Nebula Preliminary High zenith angle (E thr 325 GeV) Independent analyses give consistent results Spectral index: α = 2.59 ± 0.04 Compatible with previous results Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 8/26

9 HESS 1 Performance: Sensitivity 0.01 Crab in 25 h 0.05 Crab in 1 h Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 9/26

10 HESS 1 Performance: Angular resolution Standard analysis: Angular resolution < HESS Preliminary Crab Nebula 2 χ / ndf 216 / 23 p ± p ± events squared angular distance θ [deg ] Improving with more sophisticated models (Semi-Analytical model & 3D-Model) Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 10/26

11 HESS 1 Performance: Extended objects / Images Skymaps of Field of View HESS: 1 st ever VHE image 5 deg Field of View Independent Background estimations: Ring-background Template-model Likelihood-based Angular resolution < 0.1 Pointing error 20 Optimum conditions for extended sources and surveys Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 11/26

12 HESS 1 Performance: Energy Reconstruction MC Energy resolution: % Reconstruction bias < 10 % Crab Nebula Spectrum α = 2.59 ± 0.04 stat Whipple: α = 2.49 ± 0.07 HEGRA: α = 2.62 ± 0.05 CAT: α = 2.76 ± 0.04 Flux (E>1 TeV): 2.16 ± m 2 s 1 Whipple: 2.15 ± m 2 s 1 HEGRA: 1.75 ± m 2 s 1 CAT: 1.78 ± m 2 s 1 Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 12/26

13 HESS Observations Object Significance Flux [σ] [Crab] Crab Nebula > PSR B /SS2823 > HESS J RXJ Galactic Center Mrk 421 > PKS st source of new HESS catalogue!! Most efficient shift so far : 90 % η 70% Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 13/26

14 The Future: HESS Phase 2 Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 14/26

15 HESS Phase 2 = HESS 1 + Very Large Telescope HESS Phase II : additional very large central telescope Event Classes : 1. Mono : VLCT 2. Stereo : VLCT+ LCT or LCT+ LCT HESS I (4 x LCT) Very Large Cherenkov Telescope Very Large Cherenkov Telescope: Reflector : 28 m ( 600 m 2 ) Focal distance 35 m Camera: diam. 2.5 m ( 2000 kg) 2048 PMTs (0.07 /pixel) FoV : 3.5 Trigger rate khz Faster memories needed ( 500 khz) Minimize data flow: 2 nd level trigger Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 15/26

16 HESS Phase 2 = HESS 1 + Very Large Telescope HESS Phase II : additional very large central telescope Event Classes : 1. Mono : VLCT 2. Stereo : VLCT+ LCT or LCT+ LCT HESS I (4 x LCT) Very Large Cherenkov Telescope MC Simulation: 30 GeV γ-ray Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 16/26

17 HESS Phase 2 in Namibia Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 17/26

18 HESS Phase 2 : Expectations Energy threshold Sensitivity: Stereoscopic mode New HESS event class: E GeV Increase sensitivity for E GeV Improve resolution for E > 100 GeV Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 18/26

19 HESS: Summary HESS Phase I completed and fully operational Planned performance achieved (E thr = 100 GeV, Sensitivity 0.05 Crab in 1 h) Outstanding new results Potential for more HESS Phase II is being planned: Objective: close the gap to GLAST Method: additional Very Large Central Telescope Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 19/26

20 Connecting HESS with GLAST

21 Future collaboration with GLAST Overlapping energy regime : Observations of the same particle population GLAST trigger for HESS-observations HESS will produce sensitive variability studies Simultaneous observations of a steady source Intercalibration Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 21/26

22 Future collaboration with GLAST : Intercalibration Flux Intercalibration in the GeV regime HESS II : Systematics GLAST : Systematics schematical, steady state source GLAST : Statistics < 50 GeV approx. 300 GeV HESS II : Statistics MeV GeV TeV Energy Simultaneous observations of steady source estimation of the systematic error of HESS estimation of the statistical error of GLAST Work underway (Pol d Avezac & Martin Tluczykont) Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 22/26

23 Backup Transparencies Martin Tluczykont for the HESS Collaboration 23/26

24 Stereoscopic Observation Technique Hofmann algorithm nr. 3 events Crab Nebula signal region (N on ) background region (N off ) tracking direction θ reconstructed shower direction 1000 CT System squared angular distance θ, [deg ] 2 images superposition:... in the camera direction (θ)... at observation level core impact position Hadron rejection: core + amplitude + zenith angle mean scaled width (mscw) frequency Crab Nebula θ 2 <0.05 deg 2 photons / 11 Constant Mean E-02 Sigma E E-02 signal region (photons + hadrons) background region (hadronen) signal - background = photonen Gauß fit to photons hadrons mscw Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 24/26

25 What kind of objects to observe for inter calibration? Steady state source: simplifies a lot Hadronic Naive: straight power law More efficient acceleration at GeV energies? Leptonic? dn/de, [photons cm s MeV ] EGRET data 3EG J GLAST? HEGRA data TeV J HESS? energy, [MeV] ], arb. units -1 TeV -1-2 m flux [ph. s energy spectrum index: Γ = 2.2 R± 0.2 stat (H.E.S.S., preliminary) Possible Candidate: HESS Power law: α = 2.2 Flux: 0.1 Crab (E>1 TeV) 10-3 GLAST-detection: O(days) energy [TeV] Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 25/26

26 Calibration LED system: Single photo electron spectrum Determination of conversion factors Laser Flatfielding: relative PMT amplitudes Single ph.-electron: conversion factor (gain) Muon Calibration: verification Entries χ /dof Norm P 27.31± σ P ±0.19 γ e ± σ γe 0.46 ±0.01 µ 1.11 ± Pedestal Single photo electron peak ADC counts (arbitrary offsets) Muon Ring Calibration Data Simulation Corrected Simulation N. Leroy, 2004 collection efficiency Martin Tluczykont for the HESS Collaboration Martin.Tluczykont@poly.in2p3.fr 26/26