Synoptic VHE Gamma-Ray Telescopes

1. Synoptic VHE Gamma-Ray Telescopes Gus Sinnis Los Alamos National Laboratory Gus Sinnis PRC-US Workshop, Beijing June 2006

2. Outline • Physics reach of gamma-ray astrophysics • Description of current instruments • New results from Milagro • Sketch of future plans Gus Sinnis PRC-US Workshop, Beijing June 2006

3. HESS TeV image of Supernova Remnant Pulsar powering a relativistic wind Vela Jr. TeV & x-ray HST Image of M87 (1994) Crab nebula x-ray Black Hole producing relativistic jet High Energy Particle Astrophysics What do we know? • Nature accelerates particles to >1020 eV • Gamma-ray sources accelerate particles to >1014 eV • Galactic sources • Pulsar winds • Supernova Remnants • Stellar Mass Black Holes • Extragalactic sources • Supermassive Black Holes in active galactic nuclei Gus Sinnis PRC-US Workshop, Beijing June 2006

4. What Do We Want to Learn? • What are the origins of cosmic rays? • Are the accelerators of hadrons different from electrons? • How high in energy can galactic sources produce particles? • What are the sources of the UHECRs? • How do astrophysical sources accelerate particles? • What is the role of the extreme gravitational an magnetic fields surrounding black holes and neutron stars? • How are particles accelerated within relativistic jets? • Fundamental physics & cosmology • What is the EBL and how did it evolve? • What is the dark matter? • What are the tightest constraints on Lorentz invariance? • Are there primordial black holes? Gus Sinnis PRC-US Workshop, Beijing June 2006

5. What Measurements Required? • Measure g-ray flux due to cosmic-ray interactions • Observe multiple g-ray sources of different classes of astrophysical sources • Detect hadronic vs. leptonic signatures in energy spectra • Determine the highest energy particles accelerated in different types of sources • Observe rapid variability to probe the closest regions to the black hole in active galactic nuclei • Compare g-ray images with images at other wavelengths Gus Sinnis PRC-US Workshop, Beijing June 2006

6. What Tools Do We Use? • Auger and HiRes measure the highest energy cosmic ray flux, spectrum, and anisotropy • ICECube searches for TeV neutrino sources – the most direct signature of hadronic accelerators • GLAST will detect thousands of new GeV sources • VERITAS, HESS, MAGIC, and CANGAROO image and measure spectra and variability of TeV sources • Milagro, As, and ARGO image large-scale structures and searches for new and transient TeV sources Gus Sinnis PRC-US Workshop, Beijing June 2006

7. Active Galactic Nuclei • ~108 Msun black hole • Relativistic particle jets • 1048 ergs/sec • TeV emission is along jet • Highly variable • Open questions • what is being accelerated? • how large is the bulk Lorentz factor of shock? • B-field in shock? • Need multi-wavelength observations • many objects • many flares • long-term monitoring Gus Sinnis PRC-US Workshop, Beijing June 2006

8. AGN Modeling High energy peak due to inverse Compton scattering of synchrotron photons (SSC) or external (ECR) sources (disk, clouds) AND/OR proton interactions with these photons Relative sizes of low and high energy peaks changes with jet axis orientation with respect to us Low energy peak due to synchrotron. Gus Sinnis PRC-US Workshop, Beijing June 2006

9. Gamma Ray Bursts • Most energetic objects in universe ~1051 ergs • Rapid Variability • Unpredictable Direction • ~ 1 /day/ 4p sr Gus Sinnis PRC-US Workshop, Beijing June 2006

10. High Energy Component in GRBs Combined EGRET-BATSE observation shows a new high energy component with hard spectrum and more fluence. (Gonzalez, 2003 Nature 424, 749) GRB940217 GRB941017 The highest energy gamma-ray detected by EGRET from a GRB was ~20 GeV and was over an hour late. (Hurley, 1994 Nature 372, 652) Milagrito’s > 650 GeV observation implies a new mechanism with greater fluence than synchrotron. (Atkins, 2003, Ap J 583 824) GRB970417 Gus Sinnis PRC-US Workshop, Beijing June 2006

11. Gamma Ray Bursts Models Central Engine: hypernovae neutron star - neutron star merger black hole - neutron star mergers Emission Spectra: fireball - internal or external shocks convert energy into electromagnetic radiation. Gus Sinnis PRC-US Workshop, Beijing June 2006

12. Detectors in Gamma-Ray Astrophysics Large Aperture/High Duty Cycle Milagro, Tibet, ARGO, miniHAWC, HAWC? Low Energy Threshold EGRET/GLAST High Sensitivity HESS, MAGIC, CANGAROO, VERITAS Large Effective Area Good Background Rejection (~95%) Excellent Angular Resolution (~0.07o) Low Duty Cycle/Small Aperture High Resolution Energy Spectra Studies of known sources Surveys of limited regions of sky Space-based (small area) “Background Free” Good angular resolution (~0.4o) Large Duty Cycle/Large Aperture Sky Survey (<10 GeV) AGN Physics Transients (GRBs) <100 GeV Moderate Area/Large Area (HAWC) Good Background Rejection (~95%) Good Angular Resolution (~0.5o) Large Duty Cycle/Large Aperture Unbiased Sky Survey (~1 TeV) Extended sources Transients (AGN, GRB’s) Solar physics/space weather Gus Sinnis PRC-US Workshop, Beijing June 2006

13. First Generation EAS Arrays Tibet III Milagro Gus Sinnis PRC-US Workshop, Beijing June 2006

14. 10 m Milagro • 2600m asl • Water Cherenkov Detector • 898 detectors • 450(t)/273(b) in pond • 175 water tanks • 3.4x104 m2 (phys. area) • 1700 Hz trigger rate • 0.5o resolution • 95% proton rejection Gus Sinnis PRC-US Workshop, Beijing June 2006

15. Milagro Detector 175 Outrigger tanks (Tyvek lined – water filled) 2.4m diameter, 1m deep 1 PMT looking down Gus Sinnis PRC-US Workshop, Beijing June 2006

16. e m g Milagro PSF w/outriggers Pond only Time Degrees Event Reconstruction Gus Sinnis PRC-US Workshop, Beijing June 2006

17. Proton MC Proton MC g MC g MC Data Data Background Rejection in Milagro • Cosmic-ray induced air showers contain penetrating m’s & hadrons • Cosmic-ray showers lead to clumpier bottom layer hit distributions • Gamma-ray showers gives smoother hit distribution Gus Sinnis PRC-US Workshop, Beijing June 2006

18. Background Rejection (Cont’d) • Parameterize “clumpiness” of the bottom layer hits • Compactness ( nb2/mxPE > 2.5) • 50% gammas & 10% hadrons • Sensitivity improved by 1.6 • A4  ((nOut+nTop)*nFit/mxPE > 1600) • 20% gammas & 1% hadrons • Sensitivity further improved by 1.4 mxPE: maximum # PEs in bottom layer PMT nb2: # bottom layer PMTs with 2 PEs or more nTop: # hit PMTs in Top layer nOut: # hit PMTs in Outriggers nFit: # PMTs used in the angle reconstruction Gus Sinnis PRC-US Workshop, Beijing June 2006

19. Spectral Determination S/N increases with A4 No loss of statistical accuracy! A4 is related to energy 2-20 TeV useful range Sensitivity improvement Gus Sinnis PRC-US Workshop, Beijing June 2006

20. Sky Survey (Milagro today) Crab Nebula ~14 s Galactic Ridge clearly visible Cygnus Region discovery ~12 s Preliminary Gus Sinnis PRC-US Workshop, Beijing June 2006

21. EGRET data Diffuse Emission from the Galactic Plane • Diffuse emission from the Galaxy is due to • Proton matter interactions (p component) • Inverse Compton scattering of high-energy electrons from CMB, IR, optical photons (ISRF) • EGRET observations to 20 GeV • Indicate a GeV excess • Stronger IC component? • Unresolved point sources • Dark matter? • Higher energy observations critical for understanding GeV excess Gus Sinnis PRC-US Workshop, Beijing June 2006

22. The Galactic Plane a TeV energies Significance Gus Sinnis PRC-US Workshop, Beijing June 2006

23. Galactic Plane Analysis From A. Strong • Strong & Moskalenko optimized model • Fit to EGRET • Increase 0 (2x) and IC (5x) component throughout Galaxy • TeV flux can not be fit with a pure p component • Requires large inverse Compton component • Work in progress EGRET Milagro Gus Sinnis PRC-US Workshop, Beijing June 2006

24. The Cygnus Region • Complex region of Galaxy • But simpler than Galactic Center • 9 SNRs • >20 Wolf-Rayet stars • 6 OB associations • Shocked gas • Excellent Cosmic Ray Laboratory Canadian Galactic Plane Survey - Far IR Gus Sinnis PRC-US Workshop, Beijing June 2006

25. Cygnus Region Morphology • Contours are EGRET diffuse model • Crosses are EGRET sources • TeV/matter correlation good • Brightest TeV Region • Coincident with 2 EGRET sources (unidentified) • Possible Pulsar wind nebula (similar to Crab) • Possible blazar (unlikely TeV counterpart) • TeV extended ~0.35 degrees • Diffuse region • Energy Analysis in progress Preliminary Gus Sinnis PRC-US Workshop, Beijing June 2006

26. Diffuse Emission from Cygnus Region • Strong & Moskalenko optimized model • Fit to EGRET • Increase 0 and IC component throughout Galaxy • Milagro ~2x above prediction • Unresolved sources? • Proton accelerators? preliminary Milagro Gus Sinnis PRC-US Workshop, Beijing June 2006

27. Solar Physics • Coronal mass ejections are an ideal laboratory to study particle acceleration in the cosmos • By monitoring the singles rates in all PMTs we are sensitive to “low”-energy particles (>10 GeV) • Milagro has detected 4 events from the Sun with >10 GeV particles Gus Sinnis PRC-US Workshop, Beijing June 2006

28. X7-Class flare Jan. 20, 2005 • GOES proton data • >10 MeV • >50 MeV • >100 MeV • Milagro scaler data • > 10 GeV protons • ~1 min rise-time • ~5 min duration Gus Sinnis PRC-US Workshop, Beijing June 2006

29. Future Instruments: ARGO-YBJ Gus Sinnis PRC-US Workshop, Beijing June 2006

30. g e m 4 meters 150 meters Farther Future: miniHAWC • Build pond at extreme altitude (Tibet 4300m, Bolivia 5200m, Mexico 4030m) • Incorporate new design • Optical isolation between PMTs • Larger PMT spacing • Deeper PMT depth (in top layer) • Reuse Milagro PMTs and electronics ~$4-5M for complete detector ~10-15x sensitivity of Milagro Crab Nebula in 1 day (4 hours) [Milagro 3-4 months] GRBs to z < 0.8 (now 0.4) Gus Sinnis PRC-US Workshop, Beijing June 2006

31. g e m 6 meters 300 meters Farther Future: HAWC • Build pond at extreme altitude (Tibet 4300m, Bolivia 5200m, Mexico 4030m) • Incorporate new design • Optical isolation between PMTs • Much larger area (90,000 m2) • Two layer design (2 m and 6 m below water surface) • Advanced electronics and DAQ (~200MBytes/sec) ~$40-50M for complete detector ~60x sensitivity of Milagro Crab Nebula in 30 minutes [Milagro 3-4 months] GRBs to z >1 (now 0.4) Gus Sinnis PRC-US Workshop, Beijing June 2006

32. Effective Areas: Future Detectors Gus Sinnis PRC-US Workshop, Beijing June 2006

33. EGRET Crab Nebula GLAST Current synoptic instruments Whipple VERITAS/HESS miniHAWC HAWC Detector Sensitivity (Single Location) Gus Sinnis PRC-US Workshop, Beijing June 2006

34. 1500 hrs/fov 7 min/fov 4 min/fov 1500 hrs/fov Survey Sensitivity Gus Sinnis PRC-US Workshop, Beijing June 2006

35. Conclusions • EAS arrays have achieved sufficient sensitivity to detect known TeV sources and discover new sources! • All-sky view has lead to significant discoveries • Diffuse g-ray emission from the Galactic plane • Diffuse emission from Cygnus region • Extended source coincident with 2 EGRET unidentified objects • Some evidence for VHE emission from GRBs • Constraints now VHE fluence < ~keV fluence • Solar physics results study particle acceleration in well known environment • We are still understanding the performance of EAS arrays • Significant improvement possible for low cost • miniHAWC <$5M ~10x Milagro sensitivity • HAWC ~$50M ~60x Milagro sensitivity Gus Sinnis PRC-US Workshop, Beijing June 2006

36. Gus Sinnis PRC-US Workshop, Beijing June 2006

37. HAWC: Simulated Sky Map • C&G AGN • Hartmann IR model • known TeV sources • Milagro extended sources • 1-year observation Gus Sinnis PRC-US Workshop, Beijing June 2006

38. Air Cherenkov Telescope Extensive Air Shower Array 100 GeV gamma ray 1 TeV gamma ray Detecting TeV Gamma Rays Moderate energy threshold (1 TeV) Good angular resolution (0.5o) Good background rejection (95%) Large field of view (~2 sr) High duty cycle (>90%) Low energy threshold (300 GeV) Excellent angular resolution (0.07o) Good background rejection (95%) Small field of view (2 msr) Small duty cycle (< 10 %) Gus Sinnis PRC-US Workshop, Beijing June 2006