1. Brenda Dingus HAWC Review - December 2007 Scientific Objectives of HAWC Brenda L. Dingus Los Alamos National Lab

2. Brenda Dingus HAWC Review - December 2007 HAWC Scientific Goals Constrain the origin of cosmic rays via HAWC’s observations of  -rays up to 100 TeV from discrete sources and the Galactic plane.Constrain the origin of cosmic rays via HAWC’s observations of  -rays up to 100 TeV from discrete sources and the Galactic plane. Probe particle acceleration in extreme magnetic and gravitational fields via HAWC’s observations of transient TeV sources, such as gamma ray bursts and supermassive black holes.Probe particle acceleration in extreme magnetic and gravitational fields via HAWC’s observations of transient TeV sources, such as gamma ray bursts and supermassive black holes. Explore new TeV physics via HAWC’s unbiased sky survey with a detection threshold of ~30 mCrab in two years.Explore new TeV physics via HAWC’s unbiased sky survey with a detection threshold of ~30 mCrab in two years.

3. Brenda Dingus HAWC Review - December 2007 Galactic Sources of Cosmic Rays Galactic Cosmic Rays extend to >1000 TeV (at least to the knee).Galactic Cosmic Rays extend to >1000 TeV (at least to the knee). Gamma rays will be produced up to >100 TeV by these cosmic rays.Gamma rays will be produced up to >100 TeV by these cosmic rays. Gamma rays produced by Inverse Compton scattering of electrons will be suppressed by K-N effects.Gamma rays produced by Inverse Compton scattering of electrons will be suppressed by K-N effects. HESS observes hard spectra sources, but are these the accelerators of cosmic rays? If so, their spectra should extend to > 100 TeV.HESS observes hard spectra sources, but are these the accelerators of cosmic rays? If so, their spectra should extend to > 100 TeV. HAWC has the sensitivity to measure spectra to the highest energies.HAWC has the sensitivity to measure spectra to the highest energies. HESS Survey of the Inner Galaxy Reveals Extended Sources with average spectra of dN/dE=kE -2.3

4. Brenda Dingus HAWC Review - December 2007 Shower Fluctuations Dominate Energy ResolutionShower Fluctuations Dominate Energy Resolution Higher Altitude of HAWC increases # of particles by ~6xHigher Altitude of HAWC increases # of particles by ~6x Ability to measure a high energy cut off is a combination of the energy resolution AND the statistical error in the fluxAbility to measure a high energy cut off is a combination of the energy resolution AND the statistical error in the flux HAWC Energy Resolution

5. Brenda Dingus HAWC Review - December 2007 HESS J1616-508 0.2 Crab @ 1 TeV  =-2.3 Highest energy ~20 TeV

6. Brenda Dingus HAWC Review - December 2007 HESS J1616-508 0.2 Crab @ 1 TeV  =-2.3 Highest energy ~20 TeV Simulated HAWC data for 1 year with no cutoff

7. Brenda Dingus HAWC Review - December 2007 HESS J1616-508 0.2 Crab @ 1 TeV  =-2.3 Highest energy ~20 TeV Simulated HAWC data for 1 year with 40 TeV exponential cutoff

8. Brenda Dingus HAWC Review - December 2007 Galactic Sources are Extended  EAS ~0.5 o  IACT ~0.1 o HAWC’s large fov of 2 sr: Entire source & background are simultaneously observable Background is well measured

9. Brenda Dingus HAWC Review - December 2007 Galactic Diffuse Emission Hadrons are correlated with matter density and the flux of hadrons is strongly constrained by direct cosmic ray observationsHadrons are correlated with matter density and the flux of hadrons is strongly constrained by direct cosmic ray observations Flux from electrons is less constrained, but must decrease at highest energies due to K-N effectsFlux from electrons is less constrained, but must decrease at highest energies due to K-N effects HAWC + IACTs will detect additional localized sources to extract true diffuse emissionHAWC + IACTs will detect additional localized sources to extract true diffuse emission HAWC will measure the spectrum and spatial distribution to constrain the electronic and hadronic flux of cosmic rays outside the solar neighborhoodHAWC will measure the spectrum and spatial distribution to constrain the electronic and hadronic flux of cosmic rays outside the solar neighborhood Hadronic Pion Decay Electron Inverse Compton Scattering GALPROP Conventional (solid) and Optimized (dashed) Models Milagro Observation

10. Brenda Dingus HAWC Review - December 2007 Extragalactic Science: HAWC & Transients Active Galactic Nuclei (AGN) and Gamma Ray Bursts (GRBs)Active Galactic Nuclei (AGN) and Gamma Ray Bursts (GRBs) – Bright Flares – Rare Events Large Field of View, High Duty Factor Observatories are requiredLarge Field of View, High Duty Factor Observatories are required EXAMPLE: PKS J2155-304 (z=0.117) flared to 50x quiescent flux in one hour with dN/dE=kE -3.5 which would be detectable by HAWC (6  ) as well as the moderate state observed in prior weeks HESS Obs of 2155-304

11. Brenda Dingus HAWC Review - December 2007 HAWC & GLAST Transient Sensitivity GLAST and HAWC sensitivity for a source of spectrum dN/dE=KE -2 z=0no E cutoff z=0.1E exp ~700GeV z=0.3E exp ~260GeV z=0.5E exp ~170GeV 10 - 12 10 - 10 10 -8 10 -6 TeV AGN flares GRB <1 MeV

12. Brenda Dingus HAWC Review - December 2007 HAWC example GRB lightcurve High Energy cut off could occur due to absorption in GRB or in transit via EBL interaction.High Energy cut off could occur due to absorption in GRB or in transit via EBL interaction. Measurements of lightcurve reveal information about progenitor, such as bulk Lorentz factor of the ejecta.Measurements of lightcurve reveal information about progenitor, such as bulk Lorentz factor of the ejecta. Best constraints on Lorentz invariance from initial peak of the lightcurve.Best constraints on Lorentz invariance from initial peak of the lightcurve. HAWC lightcurve of a bright GRB (1e-4 ergs/cm2 fluence). Weaker burst counts scale with fluence.

13. Brenda Dingus HAWC Review - December 2007 GRBs Milagro searches data within few seconds for short duration transients and sends alerts to GCN, but has found no significant emissionMilagro searches data within few seconds for short duration transients and sends alerts to GCN, but has found no significant emission HAWC’s low energy response allows dimmer GRBs at more distant redshifts to be observedHAWC’s low energy response allows dimmer GRBs at more distant redshifts to be observed

14. Brenda Dingus HAWC Review - December 2007 TeV Emission From Short & Long GRBs Short Bursts 2 sec Neutron Star Binaries CoalescenceSupernova of Massive Star ~1/2 with z<0.5Few % with z<0.5 Not Observable by IACTsObservable by IACTS after >50 sec z z F(z)

15. Brenda Dingus HAWC Review - December 2007 Active Galactic Nuclei Open questionsOpen questions –Protons or electrons? –Plasma Bulk Lorentz factor? –B-field? –Location of  -ray production? –Acceleration mechanism? HAWC observationsHAWC observations –Many flares from known TeV AGN –New TeV AGN –Spectra > 1 TeV –Multiwavelength Observations with other wide field observatories & by rapid notification HAWC scienceHAWC science –Average Flux & Spectra –Duty Cycle –Unbiased Survey –Constraints on Extragalactic Background Light (EBL)

16. Brenda Dingus HAWC Review - December 2007 AGN Monitoring HAWC will obtain duty factors and notify multiwavelength observers of flaring AGN in real time. All sources within ~2  sr would be observed every day for ~ 5 hrs. HAWC’s continuous observations would not have gaps due to weather, moon, or solar constraints. HAWC’s 5  sensitivity is (10,1,0.1) Crab in (3 min, 5 hrs, 1/3 yr) Worldwide Dataset of TeV Observations by IACTs of Mrk421 1 month

17. Brenda Dingus HAWC Review - December 2007 Mrk 421 with Milagro Milagro has observed 7yr lightcurve of Mrk 421 HAWC’s increased sensitivity would result in ~10x smaller error bars and have similar error bars on hour time scale rather than 64 days Milagro - Events/day ASM Flux cts/s MJD - 50000 1/1/20001/1/20011/1/2002 1/1/2003 1/1/2004 1/1/2005 1/1/2006 1/1/2007 Milagro and XTE ASM 7 yr lightcurve of Mrk 421 (Smith et al. ICRC 2007) Crab Flux

18. Brenda Dingus HAWC Review - December 2007 Nearby AGN M87 is a known, variable source of TeV  -raysM87 is a known, variable source of TeV  -rays –HAWC will detect average flux at 5.8  extending spectra to highest energies & monitoring variability Auger’s evidence for a correlation of UHECR with AGN point to other nearby particle acceleratorsAuger’s evidence for a correlation of UHECR with AGN point to other nearby particle accelerators –UHECR directions are deflected by several degrees, so individual sources can’t be determined –However, UHECR will produce TeV gamma-rays near the sources due to interactions with the CMB & infrared –HAWC can search the 100s of nearby AGN to find UHECR emitters Auger’s 27 UHECRs (black circles) > 6e19eV & nearby, z<0.018, AGN (red *) plotted in Galactic coordinates with the SuperGalactic plane indicated by the dashed line

19. Brenda Dingus HAWC Review - December 2007 Cosmology from EBL Absorption e+e+ e-e- ~eV  ~TeV  HESS & MAGIC constraints on the EBL require the intrinsic spectrum of AGN is very hard  =-1.5)HESS & MAGIC constraints on the EBL require the intrinsic spectrum of AGN is very hard  =-1.5) –HAWC will increase the # of sources & the # of flares from the same source to decouple source dependent effects Highest Energy Spectra constrains longest wavelength EBLHighest Energy Spectra constrains longest wavelength EBL –HAWC’s Spectra to > 10 TeV measures the dust temperature & impacts Galaxy Formation theories Pair Halos around AGN probes EBL at different ages of UniversePair Halos around AGN probes EBL at different ages of Universe –HAWC’s all sky survey of extended objects is required to find these halos GLAST IACT HAWC

20. Brenda Dingus HAWC Review - December 2007 Surveying the TeV Sky Discovery PotentialDiscovery Potential Many Classes of Potential TeV SourcesMany Classes of Potential TeV Sources –Extended Sources Dark Matter, Galaxy clusters, AGN Pair Halos, Molecular Clouds,... –Variable Sources Compact Binaries, Microquasar Flares, Solar Energetic Particles,...

21. Brenda Dingus HAWC Review - December 2007 Astrophysical Sources Known TeV sources such as x-ray binaries and microquasarsKnown TeV sources such as x-ray binaries and microquasars –HAWC will monitor for flares and for periods difficult for IACTs (such as the 3.4 year period of PSR B1959-63 in which periastron aligned with the full moon) Postulated TeV sources such as Galaxy Clusters & GLAST sourcesPostulated TeV sources such as Galaxy Clusters & GLAST sources –HAWC’s field of view contains 100s of Galaxy Clusters within z<0.1 and will constrain the TeV flux of Galaxy Clusters as a class of TeV emiters –>1/2 of GLAST sources will be within HAWC’s field of view HESS x-ray binary obs. & HAWC’s sensitivity

22. Brenda Dingus HAWC Review - December 2007 Particle-Antiparticle Annihilation Particle-Antiparticle Annihilation WIMP neutralino,  is postulated by SUSY 50 GeV< m  < ~ TeV HAWC can survey >2  sr for potential dark matter sources— nearby clumps, dwarf galaxies, clusters HAWC will monitor Galactic center for variability (a definite indication that the source is not dark matter) Primordial Black Hole EvaporationPrimordial Black Hole Evaporation As mass decreases due to Hawking radiation, temperature increases causing the mass to evaporate faster Eventually temperature is high enough to create a quark-gluon plasma and hence a flash of gamma-rays HAWC’s continuous observation of >2  sr is necessary to find these transients Exotic Sources q q or  or Z  lines?  

23. Brenda Dingus HAWC Review - December 2007 Summary HAWC’s sensitivity will allow new observations leading to new understanding of the high energy UniverseHAWC’s sensitivity will allow new observations leading to new understanding of the high energy Universe –Highest Energy HAWC Observations constrain origin of cosmic rays –Wide field of view, High Duty Cycle probes the transient TeV sky –Unbiased survey of >2  sr has discovery potential for new TeV physics HAWC’s scientific investigations are complementary and enhance the scientific return of other current and planned particle astrophysics observatoriesHAWC’s scientific investigations are complementary and enhance the scientific return of other current and planned particle astrophysics observatories