system VHE: ≈100 GeV - 100 TeV ‣ 1 TeV = 1.602 erg = h •2.4x1026 Hz Explore: ‣ non-thermal processes in the universe ‣ acceleration mechanisms ‣ origin of cosmic rays Tuesday, June 28, 2011
have very few “features” ‣ No lines at these energies* ‣ Only get: ★ Flux, Spectral slope ★ Cutoff energy (sometimes) ★ Peak energy (rarely) Multi-wavelength data are crucial for understanding the sources! *unless we detect dark matter, e.g. annihilating Neutralinos Tuesday, June 28, 2011
—› gamma] and hadronic [p + target —› π0 —› gamma] production processes exhibit a 2-humped spectrum with different characteristics. VHE Gamma E dN dEdAdt E2 • Radio X-ray GeV Gamma Ray TeV Gamma Ray Tuesday, June 28, 2011
—› gamma] and hadronic [p + target —› π0 —› gamma] production processes exhibit a 2-humped spectrum with different characteristics. VHE Gamma E dN dEdAdt E2 • Radio X-ray GeV Gamma Ray TeV Gamma Ray Tuesday, June 28, 2011
—› gamma] and hadronic [p + target —› π0 —› gamma] production processes exhibit a 2-humped spectrum with different characteristics. VHE Gamma E dN dEdAdt E2 • Radio X-ray GeV Gamma Ray TeV Gamma Ray Fermi Tuesday, June 28, 2011
Resolved supernova remnant shells Galaxy is full of VHE pulsar-wind-nebulae Pulsed VHE emission in Pulsars Galactic Center Source: possible accreting SMBH Binary Systems: VHE modulation, Outbursts Diffuse gamma rays from interacting molecular clouds and star-forming regions Starburst Galaxies Dark Accelerators and other unidentified objects Extra-galactic background light constraints Cosmic Ray Electron and Iron spectra Tuesday, June 28, 2011
Berlin Ruhr-Univ. Bochum Univ. Erlangen-Nürnberg Univ. Hamburg Landessternwarte Heidelberg Univ. Tübingen Ecole Polytechnique, Palaiseau APC Paris Univ. Paris VI-VII Paris Observatory, Meudon LAPP Annecy LAOG Grenoble LPTA Montpellier CEA Saclay CESR Toulouse Durham Univ. Univ. Leeds Dublin Inst. for Adv. Studies Polish Academy of Sciences, Warsaw Polish Academy of Sciences, Cracow Jagiellonian Univ., Cracow Universität Innsbruck Stockholm University, Sweden Royal Institute of Technology (KTH), Stockholm, Sweden Charles Univ., Prague Yerewan Physics Inst. Univ. Adelaide North-West Univ., Potchefstroom Univ. of Namibia, Windhoek GERMANY FRANCE ENGLAND IRELAND POLAND AUSTRIA SWEDEN CZECH REPUBLIC ARMENIA AUSTRALIA SOUTH AFRICA NAMIBIA Tuesday, June 28, 2011
no radiation. H owever, when a charged ity greater than the speed of light in the m edium ( v > cm edium ), ted by the oscillation interfere constructively and satisfy the conditions tion at a specific angle from the particle’s trajectory. The em itted radiation nown as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle ( θc) can be derived classically from the sim ple interference diagram shown in Figure 2.5, as: θc = cos − 1 cm t vt = cos − 1 1 βn , (2.4) e speed of light in the m edium ( c/n), and n is the index of refraction of ysical interpretation of this diagram is that along the wave potential is such that the dipoles created by th e in phase at θc (Jelley, 1958). In ∼ 1 .0003 (at sea-level), t for ˇ Cerenkov r 2.1 A t field and thus no radiation. greater than the speed of light in the m d by the oscillation interfere constructively and satisfy on at a specific angle from the particle’s trajectory. The em itted own as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle (θ c ) can be derived c from the sim ple interference diagram shown in Figure 2.5, as: θ c = cos − 1 c m t vt = cos − 1 1 βn , the speed of light in the m edium (c/n ), an e physical interpretation of this ded potential is such diate in Cherenkov Radiation ~ 100 m ≈10km Energy ∝ total signal (Calorimeter) Interaction in atmosphere generates an Air Shower (e+ , e-) VHE Gamma-ray Tuesday, June 28, 2011
no radiation. H owever, when a charged ity greater than the speed of light in the m edium ( v > cm edium ), ted by the oscillation interfere constructively and satisfy the conditions tion at a specific angle from the particle’s trajectory. The em itted radiation nown as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle ( θc) can be derived classically from the sim ple interference diagram shown in Figure 2.5, as: θc = cos − 1 cm t vt = cos − 1 1 βn , (2.4) e speed of light in the m edium ( c/n), and n is the index of refraction of ysical interpretation of this diagram is that along the wave potential is such that the dipoles created by th e in phase at θc (Jelley, 1958). In ∼ 1 .0003 (at sea-level), t for ˇ Cerenkov r 2.1 A t field and thus no radiation. greater than the speed of light in the m d by the oscillation interfere constructively and satisfy on at a specific angle from the particle’s trajectory. The em itted own as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle (θ c ) can be derived c from the sim ple interference diagram shown in Figure 2.5, as: θ c = cos − 1 c m t vt = cos − 1 1 βn , the speed of light in the m edium (c/n ), an e physical interpretation of this ded potential is such diate in Cherenkov Radiation ~ 100 m ≈10km Energy ∝ total signal (Calorimeter) Cherenkov Camera Interaction in atmosphere generates an Air Shower (e+ , e-) VHE Gamma-ray Tuesday, June 28, 2011
no radiation. H owever, when a charged ity greater than the speed of light in the m edium ( v > cm edium ), ted by the oscillation interfere constructively and satisfy the conditions tion at a specific angle from the particle’s trajectory. The em itted radiation nown as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle ( θc) can be derived classically from the sim ple interference diagram shown in Figure 2.5, as: θc = cos − 1 cm t vt = cos − 1 1 βn , (2.4) e speed of light in the m edium ( c/n), and n is the index of refraction of ysical interpretation of this diagram is that along the wave potential is such that the dipoles created by th e in phase at θc (Jelley, 1958). In ∼ 1 .0003 (at sea-level), t for ˇ Cerenkov r 2.1 A t field and thus no radiation. greater than the speed of light in the m d by the oscillation interfere constructively and satisfy on at a specific angle from the particle’s trajectory. The em itted own as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle (θ c ) can be derived c from the sim ple interference diagram shown in Figure 2.5, as: θ c = cos − 1 c m t vt = cos − 1 1 βn , the speed of light in the m edium (c/n ), an e physical interpretation of this ded potential is such diate in Cherenkov Radiation ~ 100 m ≈10km Energy ∝ total signal (Calorimeter) Cherenkov Camera Interaction in atmosphere generates an Air Shower (e+ , e-) VHE Gamma-ray Tuesday, June 28, 2011
no radiation. H owever, when a charged ity greater than the speed of light in the m edium ( v > cm edium ), ted by the oscillation interfere constructively and satisfy the conditions tion at a specific angle from the particle’s trajectory. The em itted radiation nown as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle ( θc) can be derived classically from the sim ple interference diagram shown in Figure 2.5, as: θc = cos − 1 cm t vt = cos − 1 1 βn , (2.4) e speed of light in the m edium ( c/n), and n is the index of refraction of ysical interpretation of this diagram is that along the wave potential is such that the dipoles created by th e in phase at θc (Jelley, 1958). In ∼ 1 .0003 (at sea-level), t for ˇ Cerenkov r 2.1 A t field and thus no radiation. greater than the speed of light in the m d by the oscillation interfere constructively and satisfy on at a specific angle from the particle’s trajectory. The em itted own as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle (θ c ) can be derived c from the sim ple interference diagram shown in Figure 2.5, as: θ c = cos − 1 c m t vt = cos − 1 1 βn , the speed of light in the m edium (c/n ), an e physical interpretation of this ded potential is such diate in Cherenkov Radiation ~ 100 m ≈10km Energy ∝ total signal (Calorimeter) Cherenkov Camera Interaction in atmosphere generates an Air Shower (e+ , e-) VHE Gamma-ray Tuesday, June 28, 2011
no radiation. H owever, when a charged ity greater than the speed of light in the m edium ( v > cm edium ), ted by the oscillation interfere constructively and satisfy the conditions tion at a specific angle from the particle’s trajectory. The em itted radiation nown as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle ( θc) can be derived classically from the sim ple interference diagram shown in Figure 2.5, as: θc = cos − 1 cm t vt = cos − 1 1 βn , (2.4) e speed of light in the m edium ( c/n), and n is the index of refraction of ysical interpretation of this diagram is that along the wave potential is such that the dipoles created by th e in phase at θc (Jelley, 1958). In ∼ 1 .0003 (at sea-level), t for ˇ Cerenkov r 2.1 A t field and thus no radiation. greater than the speed of light in the m d by the oscillation interfere constructively and satisfy on at a specific angle from the particle’s trajectory. The em itted own as ˇ Cerenkov light 2 , and the ˇ Cerenkov angle (θ c ) can be derived c from the sim ple interference diagram shown in Figure 2.5, as: θ c = cos − 1 c m t vt = cos − 1 1 βn , the speed of light in the m edium (c/n ), an e physical interpretation of this ded potential is such diate in Cherenkov Radiation ~ 100 m ≈10km Energy ∝ total signal (Calorimeter) Cherenkov Camera Interaction in atmosphere generates an Air Shower (e+ , e-) VHE Gamma-ray Tuesday, June 28, 2011
‣ Large collection area = lower energy threshold ‣ Good overlap with Fermi (Energies down to a few GeV) ‣ Operate in stand-alone or hybrid mode (with other HESS telescopes) Data from the beginning of next year Tuesday, June 28, 2011
extended TeV source! Correspondance with X-Ray morphology: implies gamma/X- ray production mechanism linked Aharonian et al., 2004, Nature, 432, 75 RX J1713 Tuesday, June 28, 2011
extended TeV source! Correspondance with X-Ray morphology: implies gamma/X- ray production mechanism linked Aharonian et al., 2004, Nature, 432, 75 RX J1713 Tuesday, June 28, 2011
extended TeV source! Correspondance with X-Ray morphology: implies gamma/X- ray production mechanism linked Aharonian et al., 2004, Nature, 432, 75 RX J1713 Tuesday, June 28, 2011
+ few non-blazar AGNs) ‣ EBL absorption: only see Z < 0.3-0.5 We monitor several interesting AGN periodically to check for flares React on alerts from e.g. Fermi, VERITAS, Magic Tuesday, June 28, 2011
et al ApJL 664, 2007 First major AGN flare for Southern hemisphere source ‣ 15x Crab Nebula flux! Variability on 200s timescales! (fastest ever in the field) ★ Spectra on same timescales! ‣ Very small emission region or very high Lorentz factor! Tuesday, June 28, 2011
et al ApJL 664, 2007 First major AGN flare for Southern hemisphere source ‣ 15x Crab Nebula flux! Variability on 200s timescales! (fastest ever in the field) ★ Spectra on same timescales! ‣ Very small emission region or very high Lorentz factor! Tuesday, June 28, 2011
FOV (<5°) ‣ Not particularly fast slewing time (few minutes required) ‣ There is no wide-field VHE instrument (Fermi helps though) We often need long exposures! ‣ Not many photons to detect at high energies (steep power law spectrum) ‣ Heavily background-dominated at lower energies (need long integration) ‣ fairly large PSF (≈0.1°) ‣ absorption by extragalactic background light for extra-galactic objects Tuesday, June 28, 2011
observations (lowest energy threshold, E>100GeV) At larger ZA, the overlap is larger, but with E>1TeV (dec ≈ -23 ± 50°) HESS (low zenith angle) VERITAS/MAGIC (low zenith angle) Image courtesy of tevcat.uchicago.edu Image courtesy of tevcat.uchicago.edu Tuesday, June 28, 2011
Moonless nights + good weather required HESS Observation Committee ‣ Leaders of each science working group + multi-wavelength coordinators + Postdoc representative ‣ Plan the long-term schedule, meet multiple times throughout year ‣ Continuously monitor data taking and update schedule as needed (hard work is done by an autoscheduler program) Tuesday, June 28, 2011
analysis tools Most proposals internal to collaboration, but some time is reserved for external proposals ‣ see http://www.hess-experient.eu and click the “External proposals” link ‣ Data must be analyzed with a HESS collaboration member ‣ Author list on publication will contain full HESS collaboration + external proposers ‣ Data rights for 1 year Tuesday, June 28, 2011
analysis tools Most proposals internal to collaboration, but some time is reserved for external proposals ‣ see http://www.hess-experient.eu and click the “External proposals” link ‣ Data must be analyzed with a HESS collaboration member ‣ Author list on publication will contain full HESS collaboration + external proposers ‣ Data rights for 1 year Tuesday, June 28, 2011
analysis tools Most proposals internal to collaboration, but some time is reserved for external proposals ‣ see http://www.hess-experient.eu and click the “External proposals” link ‣ Data must be analyzed with a HESS collaboration member ‣ Author list on publication will contain full HESS collaboration + external proposers ‣ Data rights for 1 year Tuesday, June 28, 2011
the Observation Committee ‣ some are easy: proposal contains strict trigger criteria ‣ Others may come up unexpectedly: (no formal proposal, but something interesting happening) ‣ Usually we can react within 1 day and schedule observations Special case: GRBs ‣ Telescope integrated with GCN, shift crew immediately alerted to bursts matching specific criteria ‣ Telescopes slew as quickly as possible Tuesday, June 28, 2011
others Large array of Cherenkov telescopes ‣ 3 telescope sizes, optimized for different energy ranges 2 Sites: CTA-north and CTA- South ‣ optimized for extra-galactic and galactic science, respectively Tuesday, June 28, 2011
domain Low-energy section energy threshold of some 10 GeV High-energy section 10 km2 area at multi-TeV energies put in Werner’s latest image from the last CTA meeting... Tuesday, June 28, 2011
light typical pool (200m) ‣ cost increases with number of telescopes ‣ can’t be too far apart or no stereo! Denser Telescope Spacing: ‣ Higher angular resolution ‣ More telescopes = more money Bigger telescopes: ‣ lower energy threshold ‣ Expensive to build! Wider FOVs ‣ Cameras become more expensive, or optics more complex Tuesday, June 28, 2011
light typical pool (200m) ‣ cost increases with number of telescopes ‣ can’t be too far apart or no stereo! Denser Telescope Spacing: ‣ Higher angular resolution ‣ More telescopes = more money Bigger telescopes: ‣ lower energy threshold ‣ Expensive to build! Wider FOVs ‣ Cameras become more expensive, or optics more complex Tuesday, June 28, 2011
with performance! Large Array Size ‣ >> size of light typical pool (200m) ‣ cost increases with number of telescopes ‣ can’t be too far apart or no stereo! Denser Telescope Spacing: ‣ Higher angular resolution ‣ More telescopes = more money Bigger telescopes: ‣ lower energy threshold ‣ Expensive to build! Wider FOVs ‣ Cameras become more expensive, or optics more complex Tuesday, June 28, 2011
Analysis frameworks (mostly based on particle physics) ‣ Data formats (e.g. custom ROOT-based object-oriented databases) ‣ data and observations! (no true external propsals) The future will be open to the public! ‣ Astronomy standards followed and extended to support VHE needs ‣ Open observing programs ‣ Full data access Tuesday, June 28, 2011
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![Some Unidentified Sources Aharonian et al 2008, A&A [K. Kosack]](https://files.speakerdeck.com/presentations/4fde42fadbe56c001f011151/slide_51.jpg){kind=link}
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![Some Unidentified Sources Aharonian et al 2008, A&A [K. Kosack]](https://files.speakerdeck.com/presentations/4fde42fadbe56c001f011151/slide_53.jpg){kind=link}
