Wide-Field Gamma-Ray Instruments Milagro Results Plans for HAWC

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					    Wide-Field Gamma-Ray Instruments:
              Milagro Results
              Plans for HAWC

Scientific Goals
Experimental Techniques
Recent Results
                                 Gus Sinnis
Future Plans
                          Los Alamos National Lab
                            TeVPA 2008 Beijing
Modern Gamma-Ray Telescopes
    Low Energy Threshold               High Sensitivity               Large Aperture/High Duty Cycle
       EGRET/FERMI                  HESS, MAGIC, VERITAS,                  Milagro, Tibet, ARGO

   Space-based (Small Area)                 Large Area                          Large Area
      “Background Free”           Excellent Background Rejection        Good Background Rejection
   Good Angular Resolution         Excellent Angular Resolution          Good Angular Resolution
Large Duty Cycle/Large Aperture   Low Duty Cycle/Small Aperture       Large Duty Cycle/Large Aperture

Sky Survey 100 MeV - 10 GeV       Surveys of limited regions of sky        Unbiased Sky Survey
        AGN Physics               High Resolution Energy Spectra            Extended sources
Transients (GRBs) < 100 GeV             Source morphology                    Highest energies
                                                                            Transients (GRB’s)
Science Goals of Ground-Based
 • Cosmic-ray origins
    – High-energyW and high resolutionA spectra of Galactic sources
    – Galactic diffuse emissionW
    – Discover Galactic cosmic-ray acceleratorsA
 • Particle acceleration
    – Transient phenomena (AGN flares and GRBs)
        • prompt emissionW & delayedA
        • orphan flaresW, TeV duty factorsW, fastest phenomenaA
    – Multi-wavelength (GLAST, x-ray, optical, radio) WA, multi-messengerA
    – Source morphologyA
    – PulsarsA
 • Fundamental Physics
    – Lorentz invariance (GRBW, AGNA)
    – Dark matter detectorA (annihilation gammas from neutralinos)
 • Discovery
    – Unbiased sky survey (2.6 sr) to 2% of Crab NebulaW
    – Deep Galactic survey to 0.1% of CrabA                           W   Wide field instrument
                                                                      A   Air Cherenkov Array
  The Milagro Collaboration

Abdo, Allen, Berley, DeYoung, Dingus, Ellsworth, Gonzalez, Goodman,
Hoffman, Huentemeyer, Kolterman, Linnemann, McEnery, Mincer, Nemethy,
Pretz, Ryan, Saz Parkinson, Shoup, Sinnis, Smith, Williams, Vasileiou, Yodh
Water Cherenkov Technology

    • gammas                     Provides fully active area
    • electrons   TeV gamma      Converts  to electrons
                  at 2600m asl    : electron ~ 6:1


Milagro Gamma-Ray Observatory
• 2600m above sea level           • Angular resolution~0.5o
• 2 sr field-of-view              • 1700 Hz trigger rate
• 95% duty factor

  8’ dia. x 3’ deep

A. Abdo, B. Allen, D. Berley, T. DeYoung,B.L. Dingus, R.W. Ellsworth, M.M. Gonzalez,
J.A. Goodman, C.M. Hoffman,P. Huentemeyer, B. Kolterman, J.T. Linnemann, J.E.
McEnery, A.I. Mincer, P. Nemethy, J. Pretz, J.M. Ryan, P.M. Saz Parkinson, A. Shoup,
G. Sinnis, A.J. Smith, D.A. Williams, V. Vasileiou, G.B. Yodh
How Milagro Works

 • Direction via timing (~1 ns)
 • Background rejection via muons

 • Energy via shower size


                                         e          m   

                                                            8 meters

                             50 meters
                             80 meters
Background Rejection in Milagro
                                          Proton MC   Proton MC
Bottom layer (6 mwe overburden) detects
penetrating component of hadronic EAS

Reject 95% of background
Retain 50% of gammas
Rejection is highly energy dependent!

          MC                  MC             Data        Data
Milagro Wide Field View of Galaxy (10-50 TeV)
                                             Tibet AS

                                                                Confirmed by
                             Cygnus Region

                   Geminga                      Sources are extended
                                                Correlated with EGRET GeV catalog
                                                Hard spectra (-2.3 connects to EGRET)
                                                Clearly visible diffuse component
Galactic Diffuse Emission
      Cygnus Region with Matter Density
         Contours overlaying Milagro

 component due to CR-matter interactions
Inverse Compton to e-  (~CMB) interactions
                           GALPROP (Strong et al.)
                                                                  GALPROP (Strong et al.)
        EGRET data             30o < l < 65o
                                                                   Cygnus Region
                                                     EGRET data
                                                                    65o < l < 85o


Large-Scale Cosmic-Ray Anisotropy
  New analysis technique – forward backward asymmetry
  Milagro results consistent with Tibet AS discovery
  Modulation amplitude ~5x10-3 with deficit at RA=180o
Large-Scale Cosmic-Ray Anisotropy:
Time Dependence
   Amplitude of anisotropy has been increasing over past
  6 years (solar max to solar min)
   Error bars include systematic errors

     Solar Max

                                                         Solar Min


Intermediate-Scale Cosmic-Ray Anisotropy
               at ~10 TeV
•   Excesses are hadronic particles not gamma rays
•   Anisotropy ~6x10-4 (~10% of the large-scale anisotropy)
•   Larmor radius of 10 TeV proton in 1 mG is .01pc
•   Lifetime of 10 TeV neutron is 0.1 pc
•   Explanations difficult: requires ordered B-field (Drury & Aharonian 2008)

                                                               Galactic Plane


HAWC: High Altitude Water Cherenkov

 10-15x more sensitive than Milagro
    1 Crab in 5 hrs, 10 Crab in 3 minutes
 Located at base of volcán Sierra Negra
 • latitude : 18º 59’
 • altitude : 4100m
 Inside Parque Nacional Pico de Orizaba
 2 hours from Puebla (INAOE)
The HAWC Collaboration
   Los Alamos National Laboratory                Instituto Nacional de Astrofísica Óptica y Electrónica
        B. Dingus, J. Pretz, G. Sinnis                  Alberto Carramiñana, L. Carasco, E. Mendoza,
          Uniersity of Maryland                                      S. Silich, G. T. Tagle
D. Berley, R. Ellsworth, J. Goodman, A. Smith,        Universidad Nacional Autónoma de México
            G. Sullivan, V. Vasileiou               R. Alfaro, E. Belmont, M. Carrillo, M. González, A. Lara,
       University of New Mexico                        Lukas Nellin, D. Page, V. A. Reese, A. Sandoval,
                 J. Matthews                                G. Medina Tanco,O. Valenzuela, W. Lee
            University of Utah                      Benemérita Universidad Autónoma de Puebla
          D. Kieda, P. Huentemeyer                     C. Alvarez, A. Fernandez, O. Martinez, H. Salazar
       Pennsylvania State University             Universidad Michoacana de San Nicolás de Hidalgo
                Ty DeYoung                                                L. Villasenor
             NASA Goddard                                         Universidad de Guanajuato
                 J. McEnery                            David Delepine, Victor Migenes, Gerardo Moreno,
      Naval Research Laboratory                                   Marco Reyes, Luis Ureña
                   A.Abdo                                                 UC Irvine
             U.C. Santa Cruz                                                G. Yodh
                M. Schneider                                  University of New Hampshire
                                                                            J. Ryan
HAWC Design
                                • ~1000 large tanks (~4m dia x ~4m height)
                                   – 1 PMT/tank (looking up)
                                   – Non-reflective interior
                                • 22,000 m2 enclosed area
                                • 4100 m above sea level

100 MeV   photons shown

100 MeV  1/50 photons shown
HAWC Performance: Effective Area
•   At low energies (<1 TeV), HAWC has ~30x the effective area of Milagro
    • larger dense sampling area (5x)
    • higher altitude
    • Larger muon detection area (10x)

                                                         HAWC w/reconstruction
                                                         HAWC w/Rejection
                                                         Milagro w/reconstruction
                                                         Milagro w/Rejection
HAWC Performance: Angular Resolution
•   At similar energies, HAWC’s angular resolution is ~1.5x better than Milagro.
    • larger area
    • higher altitude
    • optical isolation
•   Resolution defined as sigma of a 2-d Gaussian.

           Resolution at 10 TeV   Angular Resolution (degrees)
HAWC Background Rejection
 •   10x better hadron rejection than Milagro above 10 TeV
     • larger muon detection area (10x)
     • optical isolation
 •   2.5x higher gamma efficiency at lower energies (< 10 TeV)

Size of HAWC

Size of Milagro
  deep layer
HAWC Performance: Energy Resolution I
                                                   Fixed first interaction elevation: 30km

 Energy Resolution in an EAS is
dominated by the fluctuations in the

                                                                                                 10 TeV gamma-ray shower Longitudinal Profile
depth of first interaction

                       Distribution of height of
                       1st interaction

                                                                HAWC elevation
HAWC Performance: Energy Resolution II

•  EAS arrays can measure shower
  size very well (<20% resolution)
• Shower fluctuations (depth of 1st
  interaction) dominate energy
  resolution of array.
• Because of increased altitude
  HAWC will have much better energy
  resolution than Milagro
Point Source Sensitivity
            IACTs 50 hrs (~0.06 sr/yr)

                                         EAS 5 yrs (~2 sr)
High-Energy Spectra with HAWC

   HESS J1616-508
 0.2 Crab @ 1 TeV
 dN/dE  -2.3
 Highest energy
 ~20 TeV

Simulated HAWC data
   1 year TeV cutoff
 1 year 40no cutoff
Transient Phenomena: AGN and GRB
         PKS J2155-304 (z=0.117) 50x quiescent (1 hr) dN/dE=kE-3.5
                                6 s in HAWC

                                                         GLAST and HAWC
                       <1 MeV
                                                         sensitivity for a

                                                         source of spectrum

                                                         z=0     no E cutoff
                    TeV AGN                              z=0.1   Eexp~700GeV
                     flares                              z=0.3   Eexp~260GeV

                                                         z=0.5   Eexp~170GeV
Transient Phenomena: AGN Flares
• HAWC will obtain TeV duty factors, search for orphan flares, & notify other
 observers in real time.
• All sources within ~2  sr would be observed every day for ~ 5 hrs.
• HAWC sensitivity: 10 Crab in 3 min and 1 Crab in 5 hrs

           Worldwide Dataset of TeV Observations of Mrk421

                   3 min

5 hr
       Gus Sinnis
       AGIS Collaboration

• The role of wide-field instruments now established
• Large sensitivity gain (>10x) is achievable
• Strong Scientific Motivation
   –   Highest energies (>5-10 TeV)
   –   Extended sources
   –   Galactic diffuse emission
   –   Unique TeV transient detector (GRBs and AGN flares)
        • 4x Crab in 15 minutes
• HAWC Status
   – Fall 2007 Full proposal submitted to NSF and CONyCT
   – July 2008 NSF funds $1M MRI grant for HAWC
      • Develop site infrastructure (roads, power, water, internet)
      • R&D for large tank
   – US funding decision awaits Particle Astrophysics SAG (early 2009)
"Confirming an idea is always gratifying. But finding
 what you don't expect opens new vistas on the nature of
 reality. And that's what humans, including those of us
 who happen to be physicists, live for.”
-Brian Greene NYT 9/12/2008

                              Thank You!