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Scientific Objectives of HAWC

Scientific Objectives of HAWC. Brenda L. Dingus Los Alamos National Lab. HAWC Scientific Goals. Constrain the origin of cosmic rays via HAWC’s observations of g -rays up to 100 TeV from discrete sources and the Galactic plane.

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Scientific Objectives of HAWC

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

  2. HAWC Scientific Goals • Constrain the origin of cosmic rays via HAWC’s observations of g-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. • Explore new TeV physics via HAWC’s unbiased sky survey with a detection threshold of ~30 mCrab in two years. Brenda Dingus HAWC Review - December 2007

  3. Galactic Sources of Cosmic Rays • 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 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. • 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 Brenda Dingus HAWC Review - December 2007

  4. HAWC Energy Resolution • Shower Fluctuations Dominate Energy Resolution • Higher 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 flux Brenda Dingus HAWC Review - December 2007

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

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

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

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

  9. Galactic Diffuse Emission GALPROP Conventional (solid) and Optimized (dashed) Models • Hadrons 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 effects • HAWC + 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 neighborhood Hadronic Pion Decay Electron Inverse Compton Scattering Milagro Observation Brenda Dingus HAWC Review - December 2007

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

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

  12. HAWC example GRB lightcurve HAWC lightcurve of a bright GRB (1e-4 ergs/cm2 fluence). Weaker burst counts scale with fluence. • 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. • Best constraints on Lorentz invariance from initial peak of the lightcurve. Brenda Dingus HAWC Review - December 2007

  13. GRBs • Milagro 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 observed Brenda Dingus HAWC Review - December 2007

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

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

  16. AGN Monitoring • HAWC will obtain duty factors and notify multiwavelength observers of flaring AGN in real time. • All sources within ~2 p 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 s 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 Brenda Dingus HAWC Review - December 2007

  17. 1/1/2000 1/1/2001 1/1/2002 1/1/2003 1/1/2004 1/1/2005 1/1/2006 1/1/2007 Crab Flux 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 and XTE ASM 7 yr lightcurve of Mrk 421 (Smith et al. ICRC 2007) ASM Flux cts/s Milagro - Events/day MJD - 50000 Brenda Dingus HAWC Review - December 2007

  18. Nearby AGN • M87 is a known, variable source of TeV g-rays • HAWC will detect average flux at 5.8s extending spectra to highest energies & monitoring variability • Auger’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 Brenda Dingus HAWC Review - December 2007

  19. e- ~TeV g e+ ~eV g Cosmology from EBL Absorption • HESS & MAGIC constraints on the EBL require the intrinsic spectrum of AGN is very hard (G=-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 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 Universe • HAWC’s all sky survey of extended objects is required to find these halos Brenda Dingus HAWC Review - December 2007 HAWC IACT GLAST

  20. Surveying the TeV Sky • Discovery Potential • Many 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, . . . Brenda Dingus HAWC Review - December 2007

  21. Astrophysical Sources • Known 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 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 Brenda Dingus HAWC Review - December 2007

  22. c q or gg or Zg q lines? c Exotic Sources • Particle-Antiparticle Annihilation • WIMP neutralino, c, is postulated by SUSY • 50 GeV< mc< ~ TeV • HAWC can survey >2p 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 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 >2p sr is necessary to find these transients Brenda Dingus HAWC Review - December 2007

  23. Summary • HAWC’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 >2p 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 observatories Brenda Dingus HAWC Review - December 2007

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