1 / 15

MPI Kernphysik, Heidelberg Humboldt Univ. Berlin Ruhr-Univ. Bochum Univ. Hamburg

Ground-Based Gamma Ray Astronomy at Energies > 10 TeV (H.E.S.S. et al. & beyond......) Gavin Rowell (MPIK Heidelberg). MPI Kernphysik, Heidelberg Humboldt Univ. Berlin Ruhr-Univ. Bochum Univ. Hamburg Landessternwarte Heidelberg Univ. Kiel Ecole Polytechnique, Palaiseau

bethan
Download Presentation

MPI Kernphysik, Heidelberg Humboldt Univ. Berlin Ruhr-Univ. Bochum Univ. Hamburg

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Ground-Based Gamma Ray Astronomyat Energies > 10 TeV(H.E.S.S. et al. & beyond......)Gavin Rowell (MPIK Heidelberg) MPI Kernphysik, Heidelberg Humboldt Univ. Berlin Ruhr-Univ. Bochum Univ. Hamburg Landessternwarte Heidelberg Univ. Kiel Ecole Polytechnique, Palaiseau College de France, Paris Univ. Paris VI-VII Univ. Montpellier II MPI Kernphysik, Heidelberg Humboldt Univ. Berlin Ruhr-Univ. Bochum Univ. Hamburg Landessternwarte Heidelberg Univ. Kiel Ecole Polytechnique, Palaiseau College de France, Paris Univ. Paris VI-VII Univ. Montpellier II

  2. Lessons from H.E.S.S. data of 2003/2004 - Hard spectra for most new TeV sources. - Most skymaps (of galactic sources) are produced using Hard cuts (Q < 0.1°, image SIZE > 200 pe., >= 2 tels) --> improved CR bkg rejection --> improved angular resolution (high E events trigger >2 tels) - Hard spectra motivates further efforts for E > 10 TeV detection (Astrophysical motivations are clear and discussed this week) Investigate - HESS performance at E > 10 TeV at high zenith angles - New dedicated telescopes for E > 10 TeV astronomy

  3. E < 0.6 TeV 0.6 < E < 1.4 E > 1.4 TeV Morphology of Gamma-Ray Sources eg. the hard spectrum of RXJ1713 permits good statistics well above HESS threshold. Images below have the same gamma excess (overall) RX J1713.7-3946 HESS Preliminary

  4. The Crab Pulsar Wind Nebula Strong, steady source at all wavelengths - Standard candle - Spectrum measured up to ~ 70 TeV (HEGRA) --> Particle accel to E > 100 TeV (GeV sync + IC) Aharonian et al. 2004 (HEGRA) Inverse Compton (various seed photons)

  5. H.E.S.S. Crab: HESS & HEGRA Results HESS ~ 30 hrs data E>250 GeV 7-10 gammas/min ~ 30 sigma/sqrt(hr) ZA>40° --> spectrum consistent with HEGRA dN/dE ~ E -2.6 paper in preparation HEGRA (1997 - 2002) - Over 300 hrs data E > 500 GeV 1-2 gammas/min ~ 10 sigma/sqrt(hr) Aharonian et al. 2004 (HEGRA)

  6. HESS Collection Area: After 'Standard' Cuts (Q < 0.112°, Image SIZE > 80 pe., >= 2 tels) Energy & Zenith Angle Aeff approaches 1 km2 ZA >= 60° Use increasing atm. thickness with ZA: --> EAS/Cerenkov more spread out --> EAS can trigger further away > 1000m ! Sommers & Elbert (1987) Zenith angle (ZA)

  7. HESS Crab: Compare Med/High ZA for E > 10 TeV Use runs with 4 telescopes & Crab <= 1.0° off-axis Q < 0.112° + 'standard' shape cuts, >= 2 tels ZA <= 40° (medium zenith) 4.10.6 gam/hr 7.0 sigma 5.9 hrs 3.2 sigma/sqrt(hr) ZA >= 60° (high zenith) 8.11.6 gam/hr 4.9 sigma 2.2 hrs 3.3 sigma/sqrt(hr) --> High ZA observation definitely viable. Improved evt rate, similar sigma/sqrt(hr)..... Improved angular res for High ZA expected --> even better! --> Crab has a rather steep spectrum: Better for hard spectra.

  8. Horns et al. (2004), Aharonian et al. (2005) Night of MJD 53113 CR rate Gam rate dN/dE ~ E-2.1+-0.1 exp(-E/3.1+-0.5) H.E.S.S. Obs. Of Mkn 421 at High ZA - Apr – May 2004 (9 nights, 10 hours) - ZA ~ 61° to 65° - Eth ~ 1.5 TeV - Aeff ~ 2 km2 (> 10 TeV) - <rate> ~ 8 gam/min peak 14 gam/min (4 Crab) - ~7000 gam >100 sigma - flux change factor 4 to 5 internight. - also intranight variability - Good stability of atm. CR rate constant ~ few % (after run selection)

  9. L L A Dedicated Cerenkov Imaging System for E > 10 TeV Astronomy Consider an array of Telescopes (we want stereo!): - Telescope mirror area A - Camera FoV & pixel size - Array size/dimension L Results based on earlier MC simulation study: Plyasheshnikov et al. (2000) J. Phys. G: Nucl. Part. Phys. v. 26, p183 - employed ALTAI shower simulation code 0.7 to 200 TeV gammas, 1.5 to 300 TeV protons --> use these results to suggest the fundamental design.......

  10. Lateral Distribution Cerenkov Image pe. 'Size' vs. Impact Param 'R' Mirror area A x QE = 1 m2 ie. A = 10 m2 QE = 0.1 Infinite FoV camera --> 10 m2 perfectly adequate for E > 10 TeV --> sufficient Cerenkov pe. R > 500m Gamma (solid) Protons (dashed) 100 pe.

  11. FoV Dist Image First Look at Cerenkov Image Centroid 'Dist' vs. Impact Param 'R' Single Telescope Gamma EAS (on-axis) FoV = 9.3° Pixel Trigger q = 15 pe. --> Need large FoV ~ 9° – 10°

  12. Array Dimension & FoV of each Telescope Detection Efficiency vs. FoV (Cell of 4 telescopes) Gamma EAS (on axis) L L L = 333 m L = 500 m --> FoV ~9° – 10° recommended ...esp. for extended srcs!

  13. Array Data Analysis Cerenkov Image Parameters: Hillas (1985) moment approach width, length, major-axes etc + image cleaning (tailcuts) Stereo gamma/hadron separation: Mean-scaled-width (MSW) MSW =  wi / wexpected,i sum over tels Stereo direction reconstruction: Intersecting pairs of image major axes (Hofmann et al. 1999)  ang. res ~0.15° is achieved --> apply MSW + direction cuts (CR bkg rejection) same as for HEGRA, HESS, VERITAS .....

  14. Array Performance (E > 8-10 TeV) Array: 4 telescopes L = 500m, q=10 pe., pixel size 0.3°, FoV = 9.3° Crab-like flux & spectrum (vertical) Ethres ~ 8 - 10 TeV before after direction + shape cuts Rgamma 3.4 1.7 evts/hr Rprotons 702 0.2 --> sig/bkg ~ 9 compare to: HESS ~5 gam/hr sig/bkg ~ 20 (ZA>40deg!) (E > 8 TeV) HEGRA ~2 sig/bkg ~4 • -> A modest 4-tel array ~ HESS performance • (sims used conservative QE, mirror area..)

  15. Summary High Zenith Angle Obs for E>10 TeV: Already verified with HEGRA & HESS! (VERITAS...in future) Aeff >= few km2 Interesting Consequence: High ZA Obs. of Southern sources by VERITAS v. useful! (such sources available 2-4 hrs/night) Vice versa for HESS obs of Northern sources. Dedicated Array of Cerenkov Imaging Telescopes for E>10 TeV Require modest mirror area ~10 m2 Large FoV ~ 9 to 10° Telescope spacing large > 300 m Good sensitivity for a modest 4-tel array - extend to many more telescopes & optimise detector parameters....further work

More Related