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Milagro a TeV Gamma-Ray Observatory

Milagro a TeV Gamma-Ray Observatory. Gus Sinnis Los Alamos National Laboratory. Milagro: A Summary of Results. 1991 Milagro proposal submitted to NSF & DOE Funding started in 1994 (ended in 1998 for central reservoir) 1997 (Milagrito) Evidence for TeV emission from a gamma-ray burst (3  )

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Milagro a TeV Gamma-Ray Observatory

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  1. Milagro a TeV Gamma-Ray Observatory Gus Sinnis Los Alamos National Laboratory Gus Sinnis HAWC Review December 2007

  2. Milagro: A Summary of Results • 1991 Milagro proposal submitted to NSF & DOE • Funding started in 1994 (ended in 1998 for central reservoir) • 1997 (Milagrito) Evidence for TeV emission from a gamma-ray burst (3) • 1997 (Milagrito) Detection of Mrk 501 • 2000 Milagro begins physics operation • 2002 Detection of Crab Nebula • 2003 Detection of Mrk 421 • 2004 Outriggers installed (funding from 2002-2004) • 2005 Discovery of Galactic diffuse emission • 2007 Discovery of TeV emission from Cygnus • 2007 Galactic Survey: 3 new sources 4 candidates • 2007 Cosmic-ray anisotropy: anomalous spectrum Gus Sinnis HAWC Review December 2007

  3. Imaging Air Cherenkov Telescopes Extensive Air Shower Arrays Complementarity of TeV Gamma-Ray Detectors Energy Range .05-50 TeV Area > 104 m2 Background Rejection > 99% Angular Resolution 0.05o Energy Resolution ~15% Aperture 0.003 sr Duty Cycle 10% Energy Range 0.1-100 TeV Area > 104 m2 Background Rejection > 95% Angular Resolution 0.3o - 0.7o Energy Resolution ~50% Aperture > 2 sr Duty Cycle > 90% Unbiased Complete Sky Survey Extended Sources Transient Objects (GRB’s & AGN) Multi-Wavelength/Messenger Observations High Resolution Energy Spectra Precision Study of Known Sources Source Location & Morphology Deep Surveys of Limited Regions of Sky Gus Sinnis HAWC Review December 2007

  4. Current Generation EAS Arrays Tibet AS Milagro Gus Sinnis HAWC Review December 2007

  5. Gus Sinnis HAWC Review December 2007

  6. Gus Sinnis HAWC Review December 2007

  7. 25 Northern Hemisphere Sources Whipple 4 (1969 - 2006) HEGRA 4 (1992 - 2002) Milagro 4 (+3*)(2000 - present) HESS 6 (2004 - present) MAGIC 7 (2005 - present) VERITAS (coming soon!) Gus Sinnis HAWC Review December 2007

  8. e m g 8 meters 50 meters 80 meters Milagro • Water Cherenkov Detector • 2600m asl • 898 detectors • 450(t)/273(b) in pond • 175 water tanks • 4000 m2 / 4.0x104 m2 • 2-12 TeV median energy • 1700 Hz trigger rate • 0.5o-1.4o resolution • 95% background rejection Gus Sinnis HAWC Review December 2007

  9. Event Reconstruction Time (ns) Measure time to <1 ns Direction reconstruction 0.5o to 1.4o (size dependent) Gus Sinnis HAWC Review December 2007

  10. Proton MC Proton MC g MC g MC Data Data Background Rejection in Milagro • Hadronic showers contain penetrating component: ’s & hadrons • Cosmic-ray showers lead to clumpier bottom layer hit distributions • Gamma-ray showers give smooth hit distributions Gus Sinnis HAWC Review December 2007

  11. Apply a cut on A4 to reject hadrons:A4 > 3 rejects 99% of Hadrons retains 18% of Gammas S/B increases with increasing A4 Background Rejection (Cont’d) Background Rejection Parameter mxPE: maximum # PEs in bottom layer PMT fTop: fraction of hit PMTs in Top layer fOut: fraction of hit PMTs in Outriggers nFit: # PMTs used in the angle reconstruction Gus Sinnis HAWC Review December 2007

  12. Distribution of Excesses in the Galactic Plane cut level • 6.5 year data set (July 2000-January 2007) • Weighted analysis using A4 parameter • Crab nebula 15  • Galactic plane clearly visible Cygnus Region Crab Nebula Mrk 421 Gus Sinnis HAWC Review December 2007

  13. C4 J2226+60 EGRET MGRO 1908+06 E. Ona-Wilhelmi, et al., ICRC 2007 106 108 C3 J0634+17 Geminga • Milagro has discovered3 new sources & 4 candidate sources in the Galaxy. • 5/7 of these TeV sources have GeV counterparts (only 13 GeV counterparts in this region - excluding Crab) • Probability = 3x10-6 Abdo, et al. ApJ 2007 Gus Sinnis HAWC Review December 2007

  14. H.E.S.S. A&A 2006 ~-2.0 Ec ~20 TeV The Highest Energy Gamma Rays: HESS RX J1713.7-3946 HESS Observations 3 years of data 2003-2005 4.8 above 30 TeV Gus Sinnis HAWC Review December 2007

  15. MGRO 1908+06 60 90 1908+06 The Highest Energy Gamma Rays Preliminary Milagro detection with median energy of 90 TeV. Strong indicator of proton acceleration in this source. Milagro data 20 TeV cutoff 6.4 x 10-11 E-2.05 7.6 @ 90 TeV Gus Sinnis HAWC Review December 2007

  16. MGRO J2019+37 MGRO J2031+41 3.8  5.8  C2 J2031+33 4.5  C1 J2044+36 The Cygnus Region • MGRO J2019+37: 10.9σ • Extended source 1.1o ± 0.5o (top hat dia.) • Possible Counterparts • GeV J2020+3658, PWN G75.2+0.1 • MGRO J2031+41: 6.9σ (5.0σ post-trials) • Possible Counterparts: • 3EG J2033+4118, GEV J2035+4214 • TEV J2032+413 (⅓ of Milagro flux) • 3.0o ± 0.9o (top hat dia.) • C1 J2044+36: 5.5σ pre-trials • no counterparts • < 2.0o • C2 J2031+33: 5.3σ pre-trials • no counterparts • possible extension of MGRO J2019+37 • possible fluctuation of MGRO J2019 tail & diffuse emission & background • Tibet AS preliminary detections of 3 sources Abdo, et al. ApJ 2007 Wang, et al. ICRC 2007 Gus Sinnis HAWC Review December 2007

  17. TeV Galactic Diffuse Emission pion component IC component Cygnus Region: Matter Density Contours overlaying Milagro Obs. 20 TeV profile in Cygnus Region w/GALPROP model TeV excess possibly due to: a. Unresolved sources? b. CR accelerators? Gus Sinnis HAWC Review December 2007

  18. 1/1/2000 1/1/2001 1/1/2002 1/1/2003 1/1/2004 1/1/2005 1/1/2006 1/1/2007 Mrk 421: 7 Year Multi-Wavelength Campaign 7 year data set July 2000 - May 2007 No gamma/hadron cut (low energy) 64 day averaging period Average flux is 67% of the Crab May-July 2005 5  excess during x-ray quiescent period Smith et al. ICRC 2007 ASM Flux cts/s Milagro - Events/day MJD - 50000 Gus Sinnis HAWC Review December 2007

  19. Significance B A Fractional Excess x103 B A Walker, et al. ICRC 2007 Anisotropy of TeV Sky Gus Sinnis HAWC Review December 2007

  20. Anisotropy: What is it? • Excess is not gamma rays • Region A has a hard spectrum & a cutoff • Points to a nearby cosmic-ray accelerator Gus Sinnis HAWC Review December 2007

  21. Future Synoptic TeV Telescopes HAWC ARGO China-Japan collaboration 4300m asl (YBJ, Tibet) Tibet w/buried water tanks Emphasis 10-1000 TeV Complete summer 2007 Chinese-Italian collaboration 4300m asl (YBJ, Tibet) RPC carpet 10-15 /√year on Crab US-Mexico collaboration 4100m asl (Mexico) Water Cherenkov >100  /√year on Crab Tibet w/Muon Detectors Gus Sinnis HAWC Review December 2007

  22. Conclusions • Milagro has made large advances in TeV survey technology • Discovery of diffuse TeV gamma rays from the Galactic plane & Cygnus • Discovery of at least 3 Galactic TeV sources (point and extended) • Highest energy gamma rays detected > 100 TeV • Anomalous cosmic-ray anisotropy observed • Demonstration of long-term AGN monitoring (enabling multi- observations) • Others are beginning to propose similar detectors • Tibet w/muon • IHEP and Chinese Academy of Sciences proposing HAWC-like detector (105 m2) for 2013 construction date • Lessons Learned from Milagro • Optical isolation is important (angular resolution & energy resolution) • Altitude is critical for low-energy response • Larger area needed (bkgd rejection, angular res., & HE response) • We are uniquely qualified to extend this technology to the next phase Gus Sinnis HAWC Review December 2007

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