1. TeV Gamma Ray Astrophysics Wei Cui Department of Physics Purdue University

2. Atmospheric Transmission Nanchang, ChinaApril 17-20, 20102

3. Atmospheric Showers Nanchang, ChinaApril 17-20, 20103

4. Detection of Shower Particles Courtesy of Hongbo Hu Nanchang, ChinaApril 17-20, 20104

5. Cosmic Ray Physics Wang et al. 2010 Nanchang, ChinaApril 17-20, 20105

6. 中日方将投入的设备和灵敏度 2000 平米 MUON ： 100TeV,10 倍改进！ Detection of Shower Particles Courtesy of Hongbo Hu Nanchang, ChinaApril 17-20, 20106

7. atmosphere 1 radiation length ~6 nsec ~130 m  -ray superluminal particles Emit Cherenkov radiation Cherenkov light pool Detection of Cherenkov Radiation Nanchang, ChinaApril 17-20, 20107

8. laterally broader Looking for needles in a haystack! Cosmic Rejection less compact Nanchang, ChinaApril 17-20, 20108

9. length distance width Imaging Atmospheric Cherenkov Technique orientation Nanchang, ChinaApril 17-20, 20109

10. Cosmic Ray Event Nanchang, ChinaApril 17-20, 201010

11. Below about 250 GeV single  events become the dominant background Single Muon Event Nanchang, ChinaApril 17-20, 201011

12. Cherenkov light pool Array: ✴ reduce background ✴ improve angular resolution ✴ improve energy resolution Stereoscopic View Nanchang, ChinaApril 17-20, 201012

13. Nanchang, ChinaApril 17-20, 201013

14. Ground-Based Gamma Ray Experiments  Narrow-field imaging  Wide-field surveying H.E.S.S. MAGIC CANGAROO VERITAS Nanchang, ChinaApril 17-20, 201014

15. 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, ChinaApril 17-20, 201015

16. 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, ChinaApril 17-20, 201016

17. 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, ChinaApril 17-20, 201017

18. Laboratories in the Sky http://tevcat.uchicago.edu/ Nanchang, ChinaApril 17-20, 201018

19. Nanchang, China Messy Laboratories April 17-20, 201019

20. Particle Acceleration Near Black Holes Cui 2005 Science, Perspective Article Nanchang, ChinaApril 17-20, 201020

21. Leptonic Jet vs Hadronic Jet Nanchang, ChinaApril 17-20, 201021

22. Rapid Variability of Supermassive BHs PKS 2155-304 MRK 421 HESS Collaboration Cui 2004 Nanchang, ChinaApril 17-20, 201022

23. Variability Constraints Size of flaring region: Also: Cui 2004 Nanchang, ChinaApril 17-20, 201023

24. Opacity Constraints 1012 15 ()10 610 tt t vFvergscm atvHz  ~ ~ gtgt g e+e+ e-e- In terms of observables: Optical depth: and For Mrk 421: x Nanchang, ChinaApril 17-20, 201024

25. Multiwavelength Observations Blazejowski et al. 2005 Mrk 421 Nanchang, ChinaApril 17-20, 201025

26. Ressel & Turner 1989 2.7 K CMBR Cosmic X-ray Optical/IR Radio 10 GeV – 1 TeV Cosmic Background Nanchang, ChinaApril 17-20, 201026

27. More Transparent Universe lower limits from galaxy counts measure- ments upper limits Reference shape HESS limits Hoffman 2005 Nanchang, ChinaApril 17-20, 201027

28. Particle Acceleration Near Neutron stars Aharonian et al. 2005 Nanchang, ChinaApril 17-20, 201028

29. Chandra X-ray image Particle Acceleration Near Neutron Stars Contours: ROSAT PSR B1509-58 Ph. index 2.27 Aharonian et al. 2005 Nanchang, ChinaApril 17-20, 201029

30. Particle Acceleration in Supernova Remnants Aharonian et al. 2004 Leptonic Hadronic Aharonian et al. 2006 Nanchang, ChinaApril 17-20, 201030

31. 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, ChinaApril 17-20, 201031

32. 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, ChinaApril 17-20, 201032

33. 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, ChinaApril 17-20, 201033

34. Surveys at Longer Wavelengths Visible Light Microwave Nanchang, ChinaApril 17-20, 201034

35. Development X-ray astronomy TeV gamma-ray astronomy 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 Cherenkov and particle detectors Crab Nebula More sources detected Milagro HESS, VERITAS, MAGIC, CANGAROO HAWC? LHAASO? CTA? AGIS? HAWC? LHAASO? LHAASO? CTA? AGIS? First detection Nanchang, ChinaApril 17-20, 201035

36. Comparison of Surveys Nanchang, ChinaApril 17-20, 201036

37. ARGO-YBJ: A Path Finder April 17-20, 2010Nanchang, China37 Courtesy of Zhen Cao

38. 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, ChinaApril 17-20, 201038