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Future directions in Ground-Based Gamma-Ray Astronomy

Future directions in Ground-Based Gamma-Ray Astronomy. Simon Swordy - TeV Particle Astro II, UW Madison, 2006. Discuss. Future of ground-based gamma-rays, postulate: "Where there's a will there's a way..". Will. Way. Some History. The Crab in early x-rays from a rocket flight. Also.

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Future directions in Ground-Based Gamma-Ray Astronomy

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  1. Future directions in Ground-Based Gamma-Ray Astronomy Simon Swordy - TeV Particle Astro II, UW Madison, 2006

  2. Discuss.. Future of ground-based gamma-rays, postulate: "Where there's a will there's a way.."

  3. Will Way

  4. Some History........

  5. The Crab in early x-rays from a rocket flight....

  6. Also....

  7. Balloon "sky survey"......

  8. Catalog of objects, mostly not there...

  9. What happened next? Then Now Balloon/ x-rays >20keV still awaiting NuSTAR NASA/Explorer Rocket/ x-rays<10keV etc....

  10. WHY did <10keV do so much better? The technology of x-ray mirrors as focusing optics could be used <10keV, (now also possible >20keV, hence NuSTAR) Low energy x-ray detectors could be built from silicon -> CCDs Low energy single photon resolution became sub arcsec The energy window ~20-100keV is only being more fully explored recently because modern detector technology in SWIFT has angular resolution ~17arcmin. (Coded mask and CdZnTe).

  11. Ground-based gamma-ray astronomy will not be able get much better than ~5arcmin (for single gamma), so several objects will always seem close to point-like (e.g. Cass A, Tycho, Crab..) It cannot compete with optical, radio, soft x-ray in the detailed morphology of sources..... but it can provide a clear outline of the extreme non-thermal pieces of our Galaxy and beyond. So..... Will Way

  12. So what "ways" are there and where might they go?

  13. "Easy" ways to go.. Make 'em bigger (increase to an array size of sqkm) Make 'em higher (go up a bigger mountain) "Tricky" ways to go... Lower energy threshold (going up a mountain helps, high QE devices help) Increase FOV for air cherenkov (some optical limits to this) Seemingly impossible stuff... Get better single photon angular resolution Increase live-time for air cherenkov

  14. Some examples: S. Fegan, V. Vassiliev, UCLA "HE-ASTRO" concept • Array • 217 telescopes • 8 hexagonal rings + 1 • 80m separation • Telescope and Detector • ø10m equivalent • QE = 0.25 (Bialkali) • 15º field of view • Facts and Figures • Outer radius: 640m • Single cell area: 5543m2 • Total area: 1.06km2 Distance From Center Of Array [m] Distance From Center Of Array [m]

  15. Observation Modes Current IACTAs Narrow field of view <0.01 km2 @ 40 GeV 0.05-0.1 km2 @ 100 GeV 0.2-0.3 km2 @ 10 TeV Field of view [πsr] Field of view [deg] Square KM Array Continuum of modes Trade area for solid angle Parallel mode Narrow field of view 1 km2 @ 40 GeV 2 km2 @ 100 GeV 4-5 km2 @ 10 TeV “Fly’s Eye” mode Wide field of view 0.02-0.03 km2 @ 40 GeV 0.1-0.2 km2 @ 100 GeV 3-4 km2 @ 10 TeV Collecting Area [km2]

  16. New Info… HAWC or miniHAWC? (300m versus 150m baseline)

  17. Milagro group + collaborators

  18. CTA - European Initiative (HESS+MAGIC) Hofmann: Array layout: 2-3 Zones High-energy section ~0.05% area coverage Medium-energy section ~1% area coverage Low-energy section ~10% area coverage FoV increasing to 8-10 degr. in outer sections 70 m 250 m few 1000 m Eth ~ 10-20 GeV Eth ~ 50-100 GeV Eth ~ 1-2 TeV

  19. Option: Mix of telescope types Not to scale !

  20.  Sensitivity on Crab: Whipple 5/√hr Milagro ~8/√yr (wide angle) VERITAS-4, etc 23/√hr HAWC 7/√hr (wide angle) HE-ASTRO 23 /√hr (wide angle) HE-ASTRO 166 /√hr (sees Crab in 3s!)

  21. Ground Gamma-Ray Timeline Whipple, HEGRA, CANGAROOII, Milagrito HESS, MAGIC VERITAS, CANGAROOIII, Milagro HESS2, MAGIC2 VERITAS2, CANGAROOIII+?, MiniHAWC CTA, HE-ASTRO, HAWC, +….

  22. Some Ways Forward: • In principle, collection area can be increased ad infinitum. The collection area of present ACTs is defined by the light pool size. The detector becomes larger than the light pool above ~105m2. Future ACT arrays head toward >1km2 • Higher altitude sites help ACTs and ground arrays, probably >3000m (presently ~2000m). • Coverage of full sky is highly desirable -> north and south facilities. • Given expected world-wide resources (<$500M?) this will probably be a limit -> two observatories • All-sky monitoring capability at <0.1 Crab level seems essential. Possibly with a co-located HAWC-type detector, or with a single HE-ASTRO-type detector, or maybe something new. • The interested science community will probably grow significantly - we need to get our world-wide act together

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