Mathieu de Naurois: TeV Observations of GC and Starburst Systems

TeV observations
  • scintillation in air (Cherenkov)
  • Hadron detection
  • watching for light showers
  • HESS camera is huge: 1.5m across (fast photometers)
  • HESS, VERITAS, MAGIC dominate
Galactic Center
  • high energy density (100 eV cm^-3)
  • dense GMCs & starburst activity
  • HESS CMZ good...
  • VERITAS CMZ 18-sigma in 46h
  • HESS, mol clds trace similar areas
  • Local excess of 10 TeV -> requires local source of CRs
  • Correlation between mol clds great in Sgr B, Sgr A, but poor in Sgr D + no TeV emission at |l|>1 degree + Propagation from central source? not enough propagation time + Maybe CRs directly accelerated?
Central Source
  • Could be Sgr A*, Sgr A East SNR, or other
  • best fit position is 6"rms around Sgr A* + Sgr A East ruled out with CCD-guiding based observations
  • No variability detected
  • in general, only middle part of SED variable
  • Pulsar Wind Nebula ruled out with Chandra?
Dark Matter search
  • exclude central region with diffuse CR-driven emission
  • search at |b|>0.5
  • no positive detection; see Friday talks
Testing SFR
  • TeV detections of M82 (Veritas), NGC 253 (HESS)
  • NGC 253 approximately pointlike + 0.5% crab + Linear from gamma ray to TeV + hard spectrum + 3 orders of magnitude more luminous than CMZ + 2x10^38 vs 10^35
  • M82 VERITAS + 0.9% crab + more luminous: 2x10^39 ergs
  • Why brighter? + Higher B-field? Higher CR density?
  • Starburst could be calorimetric; Sgr A cannot be + [Unclear - does that mean CRs escape in the Galaxy?]
HESS II
  • bigger telescopes
  • lower energy threshold
  • better res & sens
  • 10m+ optical dish
Sgr A* with HESS II
  • 3 hrs so far...
  • lines up with Fermi spectrum
Questions
  • Can you model with no pulsar wind nebula (all emission in black hole)?
  • A: PWN can explain GeV but not TeV. PWN not needed for TeV. But, PWN could still account for some GeV emission.
  • GeV and TeV could be different. Which has worse resolution?
  • Similar resolution. Fermi around 200 MeV ~ HESS 100 GeV. Both have better resolution at higher energy.
  • Consistent with Sgr A*...
  • Fermi problem is the diffuse background; HESS doesn't have that problem
  • Q Farhad: What is the energy density of CRs for diffuse TeV emission?
  • about 100 eV cm^-3, maybe
  • Q Stocke: How much loss is there between us and CMZ due to electron/positron? For TeV rays?
  • <10%. Main absorber is CMB?
  • Maybe more photons from CMZ -> greater absorption than CMZ
  • ~5% loss at highest energy only

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