1. HAWC: A Next Generation All-Sky VHE Gamma-Ray Telescope

3. Physics Goals Gamma-Ray Burst Studies –Detect GRBs > 25 GeV –Detect GRBs to z~1 –Quantum Gravity Probe AGN Studies –Monitor all AGN in fov –Detect AGN to z > 0.3 –Sensitivity to ~15 minute flares Discovery –Time domain astronomy at VH energies –New sources unseen at other wavelengths

4. VHE Astrophysics Energy range 10 GeV – 10 TeV Non thermal processes in the universe Particle acceleration Physics of extreme objects –Supernova remnants –Active galactic nuclei –Gamma ray bursts Fundamental Physics –Quantum gravity –Extragalactic background light –Dark Matter Unexplored energy range –Discoveries likely –New types of sources revealed

5. Active Galactic Nuclei Particle Jet Accretion Disk/torus  Supermassive Black Hole 10 8-10 M sun  Rotating magnetic field converts rotational energy of hole into kinetic energy.  Shocks propagate along jets and accelerate particles.  ~50  10 48 ergs/sec  Highly variable in VHE band

6. Mrk 501 Longterm Variability

7. Doppler Boosting: II  Energy is Boosted  Time is Contracted    e + e - suppressed

8. AGN Spectra

9. Gamma-Ray Bursts Discovered in 1960’s – VELA spy satellites at Los Alamos Intense bursts of  -rays coming from seemingly random directions Last from milliseconds to 100’s of seconds Over >2500 observed to date Cosmological origin Most energetic phenomena known 10 ~54 ergs! Counterparts in other wavelengths (optical, radio, GeV, TeV?)

10. Gamma-Ray Burst Properties GRB Positions in Galactic Coordinates Spatial Distribution Duration Distribution

11. GRB Profiles 156040 2015020 8055 100400.5 Counts/second Seconds

12. GRBs: High Energy Emission BATSE is sensitive to 20 keV- 2 MeV photons EGRET is sensitive to 30 MeV – 30 GeV photons EGRET observed 6 GRBs with spark chambers 18 GeV photon

13. GRB Models Central Engine: hypernovae (death of a very massive star) neutron star -- neutron star merger black hole -- neutron star mergers Emission Spectra: fireball -- internal or external shocks convert energy into electromagnetic radiation.

14. Absorption of TeV Photons e+e+ e-e- ~eV  ~TeV 

15. The First Unidentified TeV Source HEGRA: Deep observation 113 hours of observation (3 years) 4.6  significance 30 mCrab strength Centered on Cygnus OB2 (dense region of young, massive stars) Possibly an extended source

16. TeV Catalog NameSourceTypeDiscovery Date/Group EGRET 3 rd. Catalog Grade TeV 0047−2518NGC 253Starburst2003/CangaroonoB TeV 0219+42483C66ABlazar1998/CrimeayesC- TeV 0535+2200Crab NebulaSNR1989/WhippleyesA (Milagro) TeV 0834−4500VelaSNR1997/CangaroonoC TeV 1121−6037Cen X-3Binary1999/DurhamyesC TeV 1104+3813Mrk 421Blazar1992/WhippleyesA (Milagro) TeV 1231+1224M87Radio Galaxy2003/HEGRAnoC TeV 1429+4240H1426+428Blazar2002/WhipplenoA TeV 1503−4157SN1006SNR1997/CangaroonoB TeV 1654+3946Mrk 501Blazar1995/WhipplenoA (Milagro) TeV 1710−4429PSR 1706−44SNR1995/CangaroonoA TeV 1712−3932RXJ1713.7−39SNR1999/CangaroonoB+ TeV 2000+65091ES1959+650Blazar1999/TAnoA TeV 2032+4131CygOB2OB assoc.2002/HEGRAyes†B TeV 2159−3014PKS2155−304Blazar1999/DurhamyesA TeV 2203+4217BL LacertaeBlazar2001/CrimeayesC TeV 2323+5849Cas ASNR1999/HEGRAnoB TeV 2347+51421ES2344+514Blazar1997/WhipplenoA Galactic PlaneMilky WayDiffuse2004/MilagroyesB (Milagro) † CygOB2 lies within the 95% error ellipse of the EGRET source 3EG J0233+4118 8 verified (A) sources, 5 B sources, 5 C sources 10 extragalactic source, 8 galactic Horan & Weekes 2003

17. VHE Sky Map Horan & Weekes 2003

18. EGRET Sky Map 270 sources (150 unidentified)

19. Current Status of VHE Astronomy Only 8 confirmed sources (89, 92, 2x95, 97, 2x99, 2002) Lack of sources due to: –Small field of view of ACTs –Low sensitivity of all-sky instruments Small source counts lead to poor understanding of VHE sources VHE GRBs inconclusive (Milagrito) HAWC – high sensitivity over entire sky –Detect many sources –Monitor transient sources –Discover VHE emission from GRBs –Limit/Measure effects of quantum gravity

20. HAWC: High Altitude Water Cherenkov Telescope

21. HAWC Performance Requirements Energy Threshold ~20 GeV GRBs visible to redshift ~1 Near known GRB energy AGN to redshift ~0.3 Large fov (~2 sr) / High duty cycle (~100%) GRBs prompt emission AGN transients Large Area / Good Background Rejection –High signal rate –Ability to detect Crab Nebula in single transit Moderate Energy Resolution (~40%) –Measure GRB spectra –Measure AGN flaring spectra

22. Effect of Altitude Approximation B Low Energy Threshold Requires High Altitude

23. EAS Particle Content Ngammas Nelectrons Primary Energy (GeV) Low Energy Threshold Requires Detection of Gamma Rays in EAS

24. HAWC Strawman Configuration 200m x 200m water Cherenkov detector Two layers of 8” PMTs on a 3 meter grid –Top layer under 1.5m water (trigger & angle) –Bottom layer under 6m water (energy & nature) Two altitudes investigated –4500 m (Tibet, China) –5200 m (Altacama desert Chile)

25. Effective Area vs. Energy

26. Event Reconstruction

28. Angular Resolution

29. CORSIKA: Energy Resolution

32. Energy Distribution of Fit Events Median Energy 180 GeV (Milagro ~3 TeV)

33. Gammas Protons Background Rejection Bottom Layer 30 GeV70 GeV230 GeV 20 GeV70 GeV 270 GeV

34. Background Rejection Uniformity Parameter nTop/cxPE > 4.3 Reject 70% of protons Accept 87% of gammas 1.6x improvement in sensitivity Gammas Protons

35. D.C. Sensitivity: Galactic Sources Crab Spectrum: dN/dE = 3.2x10 -7 E -2.49 –Milagro 0.002 (0.001) Hz raw (cut) rate –HAWC 0.220 (0.19) Hz raw (cut) rate –Whipple 0.025 Hz –Veritas 0.5 (.12) Hz raw (cut) rate Background rate 80 (24) Hz raw (cut) 4  /sqrt(day) raw data 6  /sqrt(day) cut data –120  /sqrt(year) 40 mCrab sensitivity (all sky) in one year –Whipple: 140 mCrab per source –VERITAS: 7 mCrab per source (15 sources/year)

36. Transient Sensitivity Mrk flares

37. Effect of IR Absorption on Distant Sources z = 0.03 z = 0.1 z = 0.2 z = 0.3 z = 0.0

38. Energy Distribution of Fit Events

39. AGN Sensitivity 1 Year

40. Gamma Ray Burst Sensitivity 50 events

41. Point Source Sensitivity

42. Survey Mode Sensitivity

43. Conclusions A large area, high altitude all sky VHE detector will: –Detect the Crab in a single transit –Detect AGN to z = 0.3 –Observe 15 minute flaring from AGN –Detect GRB emission at ~50 GeV –Detect GRBs at a redshift of ~1 –Detect 6-10 GRBs/year (EGRET 6 in 9 years) –Have excellent discovery potential Continuing work –Improve background rejection & event reconstruction Increase sensitivity by ~50% - 100%? Develop energy estimator –Detailed detector design (electronics, DAQ, infrastructure) –Reliable cost estimate needed (~$30M???) –Site survey