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Gus SinnisPRC-US Workshop, Beijing June 2006
Synoptic VHE Gamma-Ray Telescopes
Gus Sinnis
Los Alamos National Laboratory
Gus SinnisPRC-US Workshop, Beijing June 2006
Outline
• Physics reach of gamma-ray astrophysics
• Description of current instruments
• New results from Milagro
• Sketch of future plans
Gus SinnisPRC-US Workshop, Beijing June 2006
Vela Jr.TeV &x-ray
HESS TeV image of Supernova Remnant
High Energy Particle AstrophysicsWhat do we know?• Nature accelerates
particles to >1020 eV• Gamma-ray sources
accelerate particles to >1014 eV– Galactic sources
• Pulsar winds• Supernova Remnants• Stellar Mass Black Holes
– Extragalactic sources• Supermassive Black
Holes in active galactic nuclei
HST Image of M87 (1994)
Black Hole producing relativistic jet
Pulsar powering a relativistic wind
Crab nebula x-ray
Gus SinnisPRC-US Workshop, Beijing June 2006
What Do We Want to Learn?• What are the origins of cosmic rays?
– Are the accelerators of hadrons different from electrons?– How high in energy can galactic sources produce particles?– What are the sources of the UHECRs?
• How do astrophysical sources accelerate particles?– What is the role of the extreme gravitational an magnetic
fields surrounding black holes and neutron stars?– How are particles accelerated within relativistic jets?
• Fundamental physics & cosmology– What is the EBL and how did it evolve?– What is the dark matter?– What are the tightest constraints on Lorentz invariance?– Are there primordial black holes?
Gus SinnisPRC-US Workshop, Beijing June 2006
What Measurements Required?
• Measure -ray flux due to cosmic-ray interactions• Observe multiple -ray sources of different classes of
astrophysical sources• Detect hadronic vs. leptonic signatures in energy spectra • Determine the highest energy particles accelerated in
different types of sources• Observe rapid variability to probe the closest regions to
the black hole in active galactic nuclei• Compare -ray images with images at other wavelengths
Gus SinnisPRC-US Workshop, Beijing June 2006
What Tools Do We Use?• Auger and HiRes measure the
highest energy cosmic ray flux, spectrum, and anisotropy
• ICECube searches for TeV neutrino sources – the most direct signature of hadronic accelerators
• GLAST will detect thousands of new GeV sources
• VERITAS, HESS, MAGIC, and CANGAROO image and measure spectra and variability of TeV sources
• Milagro, As, and ARGO image large-scale structures and searches for new and transient TeV sources
Gus SinnisPRC-US Workshop, Beijing June 2006
Active Galactic Nuclei ~108 Msun black hole Relativistic particle jets 1048 ergs/sec TeV emission is along jet Highly variable Open questions
– what is being accelerated?– how large is the bulk Lorentz factor
of shock?– B-field in shock?
Need multi-wavelength observations
– many objects– many flares– long-term monitoring
Gus SinnisPRC-US Workshop, Beijing June 2006
AGN Modeling
Relative sizes oflow and high energypeaks changes withjet axis orientation withrespect to us
Low energy peak dueto synchrotron.
High energy peak due to inverse Compton scattering of synchrotron photons (SSC) or external (ECR) sources (disk, clouds)AND/OR proton interactions with thesephotons
Gus SinnisPRC-US Workshop, Beijing June 2006
Gamma Ray Bursts• Most energetic objects in
universe ~1051 ergs• Rapid Variability• Unpredictable Direction• ~ 1 /day/ 4 sr
Gus SinnisPRC-US Workshop, Beijing June 2006
High Energy Component in GRBsCombined EGRET-BATSE observation shows a new high energy component with hard spectrum and more fluence. (Gonzalez, 2003 Nature 424, 749)
The highest energy gamma-ray detected by EGRET from a GRB was ~20 GeV and was over an hour late. (Hurley, 1994 Nature 372, 652)
Milagrito’s > 650 GeV observation implies a new mechanism with greater fluence than synchrotron. (Atkins, 2003, Ap J 583 824)
GRB940217
GRB970417
GRB941017
Gus SinnisPRC-US Workshop, Beijing June 2006
Gamma Ray Bursts ModelsCentral Engine:
hypernovaeneutron star - neutron star mergerblack hole - neutron star mergers
Emission Spectra:fireball - internal or external shocks convert energy into electromagnetic radiation.
Gus SinnisPRC-US Workshop, Beijing June 2006
Detectors in Gamma-Ray Astrophysics
High SensitivityHESS, MAGIC, CANGAROO, VERITAS
Large Aperture/High Duty CycleMilagro, Tibet, ARGO, miniHAWC, HAWC?
Low Energy ThresholdEGRET/GLAST
Large Effective Area
Good Background Rejection (~95%)
Excellent Angular Resolution (~0.07o)
Low Duty Cycle/Small Aperture
High Resolution Energy Spectra
Studies of known sources
Surveys of limited regions of sky
Space-based (small area)
“Background Free”
Good angular resolution (~0.4o)
Large Duty Cycle/Large Aperture
Sky Survey (<10 GeV)
AGN Physics
Transients (GRBs) <100 GeV
Moderate Area/Large Area (HAWC)
Good Background Rejection (~95%)
Good Angular Resolution (~0.5o)
Large Duty Cycle/Large Aperture
Unbiased Sky Survey (~1 TeV)
Extended sources
Transients (AGN, GRB’s)
Solar physics/space weather
Gus SinnisPRC-US Workshop, Beijing June 2006
First Generation EAS ArraysT
ibet
III
Mila
gro
Gus SinnisPRC-US Workshop, Beijing June 2006
Milagro
• 2600m asl• Water Cherenkov Detector• 898 detectors
– 450(t)/273(b) in pond– 175 water tanks
• 3.4x104 m2 (phys. area)• 1700 Hz trigger rate• 0.5o resolution• 95% proton rejection
10 m
Gus SinnisPRC-US Workshop, Beijing June 2006
Milagro Detector
175 Outrigger tanks (Tyvek lined – water filled)2.4m diameter, 1m deep1 PMT looking down
Gus SinnisPRC-US Workshop, Beijing June 2006
Event Reconstructione
Tim
e Pond only
w/outriggersMilagro PSF
Degrees
Gus SinnisPRC-US Workshop, Beijing June 2006
• Cosmic-ray induced air showers contain penetrating ’s & hadrons– Cosmic-ray showers lead to
clumpier bottom layer hit distributions
– Gamma-ray showers gives smoother hit distribution
Background Rejection in MilagroProton MC Proton MC
Data Data MC MC
Gus SinnisPRC-US Workshop, Beijing June 2006
Background Rejection (Cont’d)
• Parameterize “clumpiness” of the bottom layer hits– Compactness ( nb2/mxPE > 2.5)
• 50% gammas & 10% hadrons• Sensitivity improved by 1.6
– A4 ((nOut+nTop)*nFit/mxPE > 1600)• 20% gammas & 1% hadrons• Sensitivity further improved by 1.4
mxPE: maximum # PEs in bottom layer PMT
nb2: # bottom layer PMTs with 2 PEs or more
nTop: # hit PMTs in Top layer
nOut: # hit PMTs in Outriggers
nFit: # PMTs used in the angle reconstruction
Gus SinnisPRC-US Workshop, Beijing June 2006
Spectral Determination
A4 is related to energy2-20 TeV useful range
S/N increases with A4
No loss of statistical accuracy!
Sensitivity
improvement
Gus SinnisPRC-US Workshop, Beijing June 2006
Sky Survey (Milagro today)Crab Nebula ~14
Galactic Ridge clearly visible
Cygnus Region discovery ~12
Prelim
inary
Gus SinnisPRC-US Workshop, Beijing June 2006
Diffuse Emission from the Galactic Plane
EGRET data
• Diffuse emission from the Galaxy is due to– Proton matter interactions (
component)– Inverse Compton scattering of
high-energy electrons from CMB, IR, optical photons (ISRF)
• EGRET observations to 20 GeV– Indicate a GeV excess– Stronger IC component?– Unresolved point sources– Dark matter?
• Higher energy observations critical for understanding GeV excess
Gus SinnisPRC-US Workshop, Beijing June 2006
The Galactic Plane a TeV energies
Sig
nific
ance
Gus SinnisPRC-US Workshop, Beijing June 2006
Galactic Plane Analysis
• Strong & Moskalenko optimized model– Fit to EGRET– Increase 0 (2x) and IC
(5x) component throughout Galaxy
• TeV flux can not be fit with a pure component
• Requires large inverse Compton component
• Work in progress
EGRET
From A. Strong
Milagro
Gus SinnisPRC-US Workshop, Beijing June 2006
The Cygnus Region
• Complex region of Galaxy
• But simpler than Galactic Center
• 9 SNRs• >20 Wolf-Rayet stars• 6 OB associations• Shocked gas• Excellent Cosmic Ray
Laboratory
Canadian Galactic Plane Survey - Far IR
Gus SinnisPRC-US Workshop, Beijing June 2006
Cygnus Region Morphology
Contours are EGRET diffuse model
Crosses are EGRET sources TeV/matter correlation good Brightest TeV Region
– Coincident with 2 EGRET sources (unidentified)
– Possible Pulsar wind nebula (similar to Crab)
– Possible blazar (unlikely TeV counterpart)
– TeV extended ~0.35 degrees Diffuse region Energy Analysis in progress
Prelim
inary
Gus SinnisPRC-US Workshop, Beijing June 2006
Diffuse Emission from Cygnus Region
• Strong & Moskalenko optimized model– Fit to EGRET– Increase 0 and IC
component throughout Galaxy
– Milagro ~2x above prediction
– Unresolved sources?– Proton accelerators?
Milagro
preliminary
Gus SinnisPRC-US Workshop, Beijing June 2006
Solar Physics
Coronal mass ejections are an ideal laboratory to study particle acceleration in the cosmos
By monitoring the singles rates in all PMTs we are sensitive to “low”-energy particles (>10 GeV)
Milagro has detected 4 events from the Sun with >10 GeV particles
Gus SinnisPRC-US Workshop, Beijing June 2006
X7-Class flare Jan. 20, 2005
GOES proton data– >10 MeV– >50 MeV– >100 MeV
Milagro scaler data– > 10 GeV protons– ~1 min rise-time– ~5 min duration
1.45E+07
1.47E+07
1.49E+07
1.51E+07
1.53E+07
1.55E+07
1.57E+07
1.59E+07
1.61E+07
1.63E+07
1.65E+07
45.0 47.0 49.0 51.0 53.0 55.0 57.0 59.0 61.0 63.0 65.0
Minutes after 18:00 UT
Counts/Sec in Muon layer
Gus SinnisPRC-US Workshop, Beijing June 2006
Future Instruments: ARGO-YBJ
Gus SinnisPRC-US Workshop, Beijing June 2006
Farther Future: miniHAWC Build pond at extreme altitude (Tibet 4300m, Bolivia 5200m, Mexico 4030m) Incorporate new design
– Optical isolation between PMTs– Larger PMT spacing– Deeper PMT depth (in top layer)
Reuse Milagro PMTs and electronics
e
150 meters
4 meters
~$4-5M for complete detector~10-15x sensitivity of Milagro
Crab Nebula in 1 day (4 hours) [Milagro 3-4 months]GRBs to z < 0.8 (now 0.4)
Gus SinnisPRC-US Workshop, Beijing June 2006
Farther Future: HAWC Build pond at extreme altitude (Tibet 4300m, Bolivia 5200m, Mexico 4030m) Incorporate new design
– Optical isolation between PMTs– Much larger area (90,000 m2)– Two layer design (2 m and 6 m below water surface)
Advanced electronics and DAQ (~200MBytes/sec)
~$40-50M for complete detector~60x sensitivity of Milagro
Crab Nebula in 30 minutes [Milagro 3-4 months]GRBs to z >1 (now 0.4)
e
300 meters
6 meters
Gus SinnisPRC-US Workshop, Beijing June 2006
Effective Areas: Future Detectors
Gus SinnisPRC-US Workshop, Beijing June 2006
Detector Sensitivity (Single Location)
miniHAWCHAWC
GLAST
EGRET
Crab Nebula
WhippleVERITAS/HESS
Current synoptic instruments
Gus SinnisPRC-US Workshop, Beijing June 2006
Survey Sensitivity
4 m
in/fo
v
7 m
in/fo
v1500 hrs/fov1500 hrs/fov
Gus SinnisPRC-US Workshop, Beijing June 2006
Conclusions EAS arrays have achieved sufficient sensitivity to detect known
TeV sources and discover new sources! All-sky view has lead to significant discoveries
– Diffuse g-ray emission from the Galactic plane – Diffuse emission from Cygnus region– Extended source coincident with 2 EGRET unidentified
objects• Some evidence for VHE emission from GRBs
– Constraints now VHE fluence < ~keV fluence Solar physics results study particle acceleration in well known
environment We are still understanding the performance of EAS arrays
– Significant improvement possible for low cost– miniHAWC <$5M ~10x Milagro sensitivity– HAWC ~$50M ~60x Milagro sensitivity
Gus SinnisPRC-US Workshop, Beijing June 2006
Gus SinnisPRC-US Workshop, Beijing June 2006
HAWC: Simulated Sky Map
C&G AGN
Hartmann IR model
known TeV sources
Milagro extended sources
1-year observation
Gus SinnisPRC-US Workshop, Beijing June 2006
Low energy threshold (300 GeV)Excellent angular resolution (0.07o)Good background rejection (95%)Small field of view (2 msr)Small duty cycle (< 10 %)
Moderate energy threshold (1 TeV)Good angular resolution (0.5o)Good background rejection (95%)Large field of view (~2 sr)High duty cycle (>90%)
Detecting TeV Gamma RaysAir Cherenkov Telescope Extensive Air Shower Array
100 GeV gamma ray 1 TeV gamma ray
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