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This article explores the field of TeV gamma ray astrophysics, including techniques, experiments, and scientific questions pertaining to the detection and study of high-energy gamma rays. It discusses atmospheric transmission, detection of shower particles, Cherenkov radiation, ground-based experiments, particle acceleration, and more.
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TeV Gamma Ray Astrophysics Wei Cui Department of Physics Purdue University
Atmospheric Transmission Nanchang, China
Atmospheric Showers Nanchang, China
Detection of Shower Particles Courtesy of HongboHu Nanchang, China
Cosmic Ray Physics Wang et al. 2010 Nanchang, China
Detection of Shower Particles Courtesy of HongboHu 2000平米MUON：100TeV,10倍改进！ Nanchang, China 中日方将投入的设备和灵敏度
g-ray 1 radiation length atmosphere superluminal particles Emit Cherenkov radiation Cherenkov light pool ~6 nsec ~130m Detection of Cherenkov Radiation Nanchang, China
laterally broader less compact Cosmic Rejection Looking for needles in a haystack! Nanchang, China
orientation distance length width Imaging Atmospheric Cherenkov Technique Nanchang, China
Cosmic Ray Event Nanchang, China
Single MuonEvent Below about 250 GeV singlemevents become the dominant background Nanchang, China
Stereoscopic View • Array: • reduce background • improve angular resolution • improve energy resolution Cherenkov light pool Nanchang, China
Ground-Based Gamma Ray Experiments • Narrow-field imaging • Wide-field surveying VERITAS MAGIC CANGAROO H.E.S.S. Nanchang, China
Complementarities: Technique • Wide-Field Survey • Full-sky coverage • Long duty cycle • Narrow-Field Imaging • High sensitivity • Low energy threshold • Superior energy resolution • Good spatial resolution Nanchang, China
Complementarities: Science • Wide-field survey • Discovery • Transient phenomena • Variable sources • Large-scale emission • Narrow-field imaging • Detailed studies: morphology, spectral energy distribution, source identification, … Nanchang, China
Scientific Questions • Properties of radiating particles • Leptonic vs hadronic • Radiation mechanisms • Inverse Compton scattering, 0 decay, synchrotron, • Particle acceleration processes • Shock, magnetic reconnection • Origin of cosmic rays • SNR? GRB? AGN? • Cosmic background radiation • Absorption of gamma rays • Nature of dark matter Nanchang, China
Laboratories in the Sky http://tevcat.uchicago.edu/ Nanchang, China
Messy Laboratories Nanchang, China
Particle Acceleration Near Black Holes Cui 2005 Science, Perspective Article Nanchang, China
Leptonic Jet vs Hadronic Jet Nanchang, China
Rapid Variability of Supermassive BHs MRK 421 PKS 2155-304 HESS Collaboration Cui 2004 Nanchang, China
Variability Constraints Cui 2004 Size of flaring region: Also: Nanchang, China
Opacity Constraints Optical depth: e- gt In terms of observables: e+ g For Mrk 421: 1 0 1 2 v F ( v ) 1 0 e r g s c m - - - ~ t t and x 1 5 a t v 6 1 0 H z ~ t Nanchang, China
Multiwavelength Observations Mrk 421 Blazejowski et al. 2005 Nanchang, China
Optical/IR 2.7 K CMBR Cosmic X-ray Ressel & Turner 1989 Cosmic Background Radio 10 GeV – 1 TeV Nanchang, China
Reference shape HESS limits More Transparent Universe measure- ments upper limits lower limits from galaxy counts Hoffman 2005 Nanchang, China
Particle Acceleration Near Neutron stars Aharonian et al. 2005 Nanchang, China
Chandra X-ray image PSR B1509-58 Contours: ROSAT Particle Acceleration Near Neutron Stars Aharonian et al. 2005 Ph. index 2.27 Nanchang, China
Particle Acceleration in Supernova Remnants Leptonic Aharonian et al. 2006 Aharonian et al. 2004 Hadronic Nanchang, China
Other Topics in Fundamental Physics • Dark matter annihilation • e.g., Dwarf galaxies • Lorentz invariance • Strong transient signals • Evaporation of primordial black holes • Bursts of gamma rays • … … Nanchang, China
Common Dilemma • What to observe? • Theorist’s guesses (aka predictions) • Observer’s guesses • Politics • How to distribute time among hot targets? • Well, each gets an hour • My targets are better than yours! • Shall we go after that GRB? • … … Nanchang, China
Solution • Full-sky coverage at the sensitivity of the current narrow-field imaging experiments • Ideally, one experiment in each hemisphere • Complete sampling of the sky at a proven flux limit • Easy maintenance and thus long lifetime, reaching even lower fluxes • Upgradability Nanchang, China
Microwave Visible Light Surveys at Longer Wavelengths Nanchang, China
Development X-ray astronomy TeV gamma-ray astronomy Cherenkov and particle detectors Crab Nebula More sources detected Milagro HESS, VERITAS, MAGIC, CANGAROO HAWC? LHAASO? CTA? AGIS? HAWC? LHAASO? LHAASO? CTA? AGIS? Sounding rockets, balloons Sco X-1 More sources detected Uhuru survey Einstein satellite Ariel 5, Ginga, ROSAT, ASCA ROSAT all-sky survey RXTE, Swift Chandra, XMM-Newton First detection First detection Nanchang, China
Comparison of Surveys Nanchang, China
ARGO-YBJ: A Path Finder Courtesy of Zhen Cao Nanchang, China
Concluding Remarks • TeV gamma ray astronomy has matured. • Thanks to state-of-the-art imaging experiments • Sensitive surveying experiments are required to move the field to the next level. • discovering more sources • catching new transient phenomena • increasing statistics on known sources • facilitating multiwavelength observations Nanchang, China
