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

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

3. Gus Sinnis PRC-US Workshop, Beijing June 2006 Vela Jr. TeV & x-ray HESS TeV image of Supernova Remnant High Energy Particle Astrophysics What do we know? Nature accelerates particles to >10 20 eV Gamma-ray sources accelerate particles to >10 14 eV –Galactic sources Pulsar winds Supernova Remnants Stellar Mass Black Holes –Extragalactic sources Supermassive Black Holes in active galactic nuclei HST Image of M87 (1994) Black Hole producing relativistic jet Pulsar powering a relativistic wind Crab nebula x-ray

4. Gus Sinnis PRC-US Workshop, Beijing June 2006 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?

5. Gus Sinnis PRC-US Workshop, Beijing June 2006 What Measurements Required? Measure  -ray flux due to cosmic-ray interactions Observe multiple  -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  -ray images with images at other wavelengths

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

7. Gus Sinnis PRC-US Workshop, Beijing June 2006 Active Galactic Nuclei  ~10 8 M sun black hole  Relativistic particle jets  10 48 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

8. Gus Sinnis PRC-US Workshop, Beijing June 2006 AGN Modeling Relative sizes of low and high energy peaks changes with jet axis orientation with respect to us Low energy peak due to synchrotron. 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

9. Gus Sinnis PRC-US Workshop, Beijing June 2006 Gamma Ray Bursts Most energetic objects in universe ~10 51 ergs Rapid Variability Unpredictable Direction ~ 1 /day/ 4  sr

10. Gus Sinnis PRC-US Workshop, Beijing June 2006 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) 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) GRB940217 GRB970417 GRB941017

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

12. Gus Sinnis PRC-US Workshop, Beijing June 2006 Detectors in Gamma-Ray Astrophysics High Sensitivity HESS, MAGIC, CANGAROO, VERITAS Large Aperture/High Duty Cycle Milagro, Tibet, ARGO, miniHAWC, HAWC? Low Energy Threshold EGRET/GLAST Large Effective Area Good Background Rejection (~95%) Excellent Angular Resolution (~0.07 o ) 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 (~0.4 o ) 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 (~0.5 o ) Large Duty Cycle/Large Aperture Unbiased Sky Survey (~1 TeV) Extended sources Transients (AGN, GRB’s) Solar physics/space weather

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

14. Gus Sinnis PRC-US Workshop, Beijing June 2006 Milagro 2600m asl Water Cherenkov Detector 898 detectors –450(t)/273(b) in pond –175 water tanks 3.4x10 4 m 2 (phys. area) 1700 Hz trigger rate 0.5 o resolution 95% proton rejection 10 m

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

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

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

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

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

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

21. Gus Sinnis PRC-US Workshop, Beijing June 2006 Diffuse Emission from the Galactic Plane EGRET data Diffuse emission from the Galaxy is due to –Proton matter interactions (  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

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

23. Gus Sinnis PRC-US Workshop, Beijing June 2006 Profile of the Galaxy at 10 TeV Galactic longitude 20-100 1 degree bins in latitude (independent bins) Galactic latitude -5 to 5 2 degree bins in longitude (independent bins)

24. Gus Sinnis PRC-US Workshop, Beijing June 2006 Galactic Plane Analysis 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  component Requires large inverse Compton component Work in progress EGRET From A. Strong Milagro

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

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

27. Gus Sinnis PRC-US Workshop, Beijing June 2006 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? Milagro preliminary

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

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

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

31. Gus Sinnis PRC-US Workshop, Beijing June 2006 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 e   150 meters 4 meters ~$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)

32. Gus Sinnis PRC-US Workshop, Beijing June 2006 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 m 2 ) –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) e   300 meters 6 meters

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

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

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

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

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

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

39. Gus Sinnis PRC-US Workshop, Beijing June 2006 Gamma Ray Bursts Isotropic Distribution Duration Distribution Discovered in 1960’s (Los Alamos/VELA spy satellites) Cosmological distances ~10 51 ergs - most energetic phenomena known

40. Gus Sinnis PRC-US Workshop, Beijing June 2006 Gamma Ray Bursts Profiles 156040 2015020 8055 100400.5 Counts/second Seconds

41. Gus Sinnis PRC-US Workshop, Beijing June 2006 GRBs with Milagro  Milagrito saw evidence for VHE emission from GRBs –54 BATSE GRBs in our fov –1 had 10 -7 probability (pretrial) –10 -3 post trial (large BATSE error box)  What does Milagro see? –Even w/out satellite trigger Milagro could see GRB of same TeV fluence as “Grito” GRB  Performed SWIFT triggered and untriggered searches –Nothing seen to date

42. Gus Sinnis PRC-US Workshop, Beijing June 2006 VHE Emission - Theory  Shape of high energy component applies tight constraints to ambient densities and magnetic fields  Milagro has the sensitivity to observe the predicted emission or rule out the model  More GRBs with low redshift are needed Pe’er & Waxman (ApJL 603,1, L1-L4, 2004) constrain source parameters for Inverse Compton emission of GRB941017 z=0.2 z=0.02 z=0.5

43. Gus Sinnis PRC-US Workshop, Beijing June 2006 Milagro Untriggered Search Probability histograms GRB alerts No significant emission detected The number of trials is optimized to achieve the best sensitivity with the available computing power. 0.0398s 0.158s0.1s 0.0251s -20 -10 log(P)

44. Gus Sinnis PRC-US Workshop, Beijing June 2006 Constraining GRB models  Redshift dependence  EBL model dependence  Fluence dependence Conclusion Milagro can set model-dependent upper limits on the VHE emission from GRBs TeV fluence < keV fluence redshiftT 90 E iso

45. Gus Sinnis PRC-US Workshop, Beijing June 2006 GRB Detection Difficult > 100GeV Primack et al. 04 20% of GRBs z<0.5 >100 GeV photons absorbed by interactions with IR field

46. Gus Sinnis PRC-US Workshop, Beijing June 2006 VHE Emission - Theory Shape of high energy component applies tight constraints to ambient densities and magnetic fields Milagro has the sensitivity to observe the predicted emission or rule out the model More GRBs with low redshift are needed Pe’er & Waxman (ApJL 603,1, L1-L4, 2004) constrain source parameters for Inverse Compton emission of GRB941017 z=0.2 z=0.02 z=0.5

47. Gus Sinnis PRC-US Workshop, Beijing June 2006 Milagro Untriggered Search Probability histograms GRB alerts No significant emission detected The number of trials is optimized to achieve the best sensitivity with the available computing power. 0.0398s 0.158s0.1s 0.0251s -20 -10 log(P)

48. Gus Sinnis PRC-US Workshop, Beijing June 2006 Constraining GRB models Redshift dependence EBL model dependence Fluence dependence Conclusion Milagro can set model-dependent upper limits on the VHE emission from GRBs. redshiftT 90 E iso

49. Gus Sinnis PRC-US Workshop, Beijing June 2006 Triggered Search GRB 010921 Relatively close z=0.45 10 degrees zenith E iso (TeV)/E iso (keV) < 0.3 – 7 ApJ, Sept 2005 GRB 041219 A long burst 520s Bright 1x10 -4 erg cm- 2 Z = 0.1-0.5 E iso (TeV)/E iso (keV) < 0.3 – 7 GRB 050509b z=0.225? GCN Circular 3411 E iso (keV) = 2x10 -8 erg cm -2 E iso (TeV)/Eiso(keV) < 10 – 20 GRB010921, z=0.45 E iso (TeV)/E iso (keV) < 1-4

50. Gus Sinnis PRC-US Workshop, Beijing June 2006 GRBs in Milagro in the ‘Swift’ Era Good zenith angle. GCN Circular 4265 11 November 2005 First detected afterglow from short burst. GCN Circular 3411 5 May 2005 Short IPN burst possibly associated with M81 GCN Circular 4249 11 November 2005 (15-350 keV = 2.3x10 -8 ) (0.02-10 MeV = 2.3x10 -5 ) (20-500 keV = 4.0x10 -6 )

51. Gus Sinnis PRC-US Workshop, Beijing June 2006 Milagro GRB Sensitivity

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