TeV Gamma-ray Astronomy and UHECR-1

1. TeV Gamma-ray Astronomyand UHECR-1 Trevor C. Weekes, Whipple Observatory, Harvard-Smithsonian Center for Astrophysics

2. Outline Relevance to UHECR’s Atmospheric Cherenkov Imaging Technique Status of TeV Observations Extragalactic TeV Sources Observations of the UHECR Sources Next Generation Telescopes Trevor Weekes Watson Fest

3. Relevance of TeV Astronomy to Studies of UHE Cosmic Rays • Historical Precedent • Similar Techniques • Understanding of discrete Source (e.g. UHECR-1) demands study at other wavelengths; TeV Band is the Highest Energy Band in which Cosmic Sources have been reliably detected • Existence of Extragalactic Sources of Relativistic Particles has been established • New Generation of TeV Telescopes have the sensitivity for detection of TeV component of UHECR sources Trevor Weekes Watson Fest

4. Why study TeV Gamma rays? Why do we study elephants when mosquitoes are easier to find and more plentiful? TeV gamma-rays, like elephants, are bigger, more difficult to produce, and stretch the the production models to their limits! Trevor Weekes Watson Fest

5. Simple Technique, Simple Detectors, Small Budgets Trevor Weekes Watson Fest

6. Early Expectations of TeV Gamma-ray Astronomy We would find the Origin of the Cosmic Radiation which would entail: * Single source or class of sources * Unambiguous detection of the 70 MeV bump in the spectrum * Source(s) would be in the Galaxy In short: locate the “Smoking Gun” of Cosmic Ray Origins! Trevor Weekes Watson Fest

7. Atmospheric Cherenkov Imaging 20 km p g Cherenkov Imaging gives the ability to distinguish compact images of gamma-ray showers from more irregular images from hadronic showers Arrival Directions also determined with high accuracy Atmospheric height 5o e_ e+ m_ m+ To record the Cherenkov light images of gamma-ray initiated air showers, a large camera, consisting of an array of PMTs in the focal plane of a large optical reflector, is used. Trevor Weekes Watson Fest

8. Types of images seen by atmospheric Cherenkov camera Hadron Gamma Gamma ray Muon Ring Sky Noise Trevor Weekes Watson Fest

9. The First TeV Sources *Imaging systems came into operation 1984 - *First Galactic Source detected (Crab Nebula/ Whipple Observatory) 1989 *First Extragalactic Source detected (Mrk 421/Whipple Observatory) 1992 Trevor Weekes Watson Fest

10. Tev Gamma-ray Sky Status c.2003 18 Sources reported in refereed literature; 10 are Extragalactic, 8 are Galactic Trevor Weekes Watson Fest

11. Trevor Weekes Watson Fest

12. + New Sources ~ 2004 • Galactic Center • PSR1259-63 at periastron • Others? See following papers on results from HESS and MAGIC • (also credibility of some southern sources has been questioned) But no source (Galactic or Extragalactic) has yet been unambiguously identified as a source of Hadronic Cosmic Rays; all the TeV gamma rays could have Electron Progenitors. Trevor Weekes Watson Fest

13. TeV Catalog of AGN HBL = High frequency BL Lac All confirmed sources Spectra measured Light-curves determined Multi-wavelength Correlations Only two in EGRET Catalog Horan, Weekes, 2003 Trevor Weekes Watson Fest

14. Time Variability: AGN Light Curves Variation in Nightly Rates from Markarian 421 Whipple Observatory 1995 Buckley et al. 1996 Trevor Weekes Watson Fest

15. Variations Seen on Many Time-scales Markarian 421 Whipple Observatory Hours - minutes Markarian 501 HEGRA Days-months Trevor Weekes Watson Fest

16. TeV Results: Correlations with X-rays Trevor Weekes Watson Fest

17. Mrk421 Spectral Variability Exponent of Power Law Changes with Total Intensity. Cutoff Term Remains the Same Power Law Cutoff Term Krennrich et al. 2003 Trevor Weekes Watson Fest

18. Multiwavelength Results: Power Spectra Mrk 501 Compton Synchrotron Similar double peaked Power Spectra seen in other AGN Trevor Weekes Watson Fest

19. AGN Jet Emission Mechanisms CosmicCannon: Looking down the Barrel of the Cannon Electron Progenitors: Synchrotron Self Compton External Compton Proton Progenitors: Proton Cascades Proton Synchrotron (Buckley, Science, 1998) Trevor Weekes Watson Fest

20. Detection of Radio Galaxy, M87 Nearby Radio Galaxy (Virgo A) Off axis jet source HEGRA Group 4.1 sigma detection Weak source but important Aharonian et al. 2003 Trevor Weekes Watson Fest

21. Galactic Center: TeV Source Whipple 10 m telescope Observations 1995-2003 Southern Source E > 2.5 TeV 40 % of Crab 3.7 sigma Kosack et al. ApJL (2004) CANGAROO-III E > 250 GeV 10% 0f Crab Detection: strong Steep spectrum: -4.6+/-0.5 Tsuchiya et al., ApJL (2004) Can HESS Definitive results See next talk! Trevor Weekes Watson Fest

22. TeV Gamma-ray Astronomy:A Legitimate New Astronomical Discipline Essential Features of an Astronomical Discipline: • Location of Sources • Measurement of Spectrum • Time Variability • Correlation with other wavelengths Ready to be used to aid in the Exploration of UHECR Sources Trevor Weekes Watson Fest

23. Study of Arrival Directions of Ultra High Energy Cosmic Rays • UHECRs may be diffuse…or they may come from discrete sources • Since these must be nearby, they should be easily recognizable at long wavelengths • If not, and if the production of UHECRs is their unique property, they should still be source of TeV gamma rays • Detection of coincident TeV source would confirm existence of UHECR source and give better location Trevor Weekes Watson Fest

24. Possible Sources of UHECR’s: New Challenge for TeV Astronomy Possible Clustering into discrete sources of 92 cosmic rays with E > 4 x 10^19 eV (results from AGASA, Havarah Park, Yakutsk, Volcano Ranch) Marginally statistically significant correlation of Doublets and Triplets with Supergalactic Plane Uchihori et al. 2000 Trevor Weekes Watson Fest

25. TeV Counterpart to UHECR Source: Extragalactic Cascade Ferrigno, Blasi, Marco astro-ph/0404352 Electromagnetic Cascades initiated by photopion production of UHECR on extragalactic radio and microwave background may give detectable flux of TeV photons. Trevor Weekes Watson Fest

26. Whipple Search for TeV Emission in Error box of Fly’s Eye 3 x 10^20 eV UHECR The Most Important Direction in the Universe Akerlof et al. 2003 Search made at 12 positions within the Error Box; no evidence for TeV emission Trevor Weekes Watson Fest

27. TeV maps from six of the twelve fields surveyed; no evidence of an excess. Field includes quasar 3C147 of historical interest….but too distant to be a candidate. Akerlof et al. 2003 Trevor Weekes Watson Fest

28. Next GENERATION TELESCOPES Arrays of Imaging Telescopes Philosophy • Improve Flux Sensitivity • Reduce Energy Threshold • Multiple > “10 m” telescopes • New Technology where appropriate. Now on line: CANGAROO III - 2004 HESS - 2004 MAGIC - 2004 (VERITAS to come - 2006) Trevor Weekes Watson Fest

29. VERITAS, 2004 1 tel. 2006 4 tel. MAGIC, 1 tel., 2004 2 tel., 2006 CANGAROO III, 4 tel., 2004 HESS, 4 tel., 2004 World Picture of sub-TeV Observatories Four Major Observatories ideally distributed to give maximum coverage Trevor Weekes Watson Fest

30. p Chicago Airport Display Trevor Weekes Watson Fest

31. VERITAS • Four telescope system • 12 m aperture • 80m separation • Filled triangle configuration • 499 pixel camera (0.15º/ pixel, 3.5º FOV) • Kitt Peak, Tucson (32ºN, 36ºW, 1800m a.s.l.) • Current status • Prototype telescope operating at Whipple basecamp • Funded • Sources detected • VERITAS-4 in 2006 Trevor Weekes Watson Fest

32. 1 GeV 100 GeV Whipple 10 m (3s in 50 hrs) GLAST (2 Years) VERITAS-4(3s in 50 hrs) Trevor Weekes Watson Fest

33. VERITAS Movie Cameras: Advanced technology cameras; 500 Mhz FADCs 2 ns slices through shower images (Leeds group has played major role in their design and construction) Prototype VERITAS Telescope Trevor Weekes Watson Fest

34. Typical Event: Prototype Trevor Weekes Watson Fest

35. Results: Markarian 421 Alpha<8 gives: ON =1570 OFF=635.8 Sigma=19.9 Total Exposure=18.7 hours Mean rate=0.83 gammas/min Trevor Weekes Watson Fest

36. Summary Not one source but many Extragalactic Sources in profusion No Smoking Gun YET for Cosmic Ray Origins A New Astronomical Discipline is Established Foundations are laid for Major Advances with next Generation Systems working with auger, GLAST, icecube, etc. THESE MAY BE THE important PROBES OF UHECR SOURCES Trevor Weekes Watson Fest

37. VERITAS Movie Camera You have read the book: now watch the movie! (in 2 ns slices) Trevor Weekes Watson Fest