u n c l a s s i f i e d high-energy astrophysics probing the extreme universe gus sinnis p-23
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U N C L A S S I F I E D
U N C L A S S I F I E D
High-Energy Astrophysics
Probing the Extreme Universe
Gus Sinnis
P-23
U N C L A S S I F I E D
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Outline
Milagro Tera-Volt Gamma-Ray Telescope• Physics Goals• The Milagro Detector• Recent results
Future Directions
Milagro at TA-57
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The Milagro Collaboration
LANL• Sinnis (PI/co-spokesman), Dingus (TSM), Walker, Casanova, Spaulding (UGS)
U. Maryland• Goodman (PI/co-spokesman), Smith, Lansdell (at LANL), Vasilios (GRA), Noyes (GRA)
U.C. Irvine• Yodh, Shoup, Allen (GRA), Amarotto (UGS), Delay (tech at LANL)
U.C. Santa Cruz• Williams, Saz-Parkinson, Schneider (tech)
Michigan State University• Jim Linnemann, Aous Abdo (GRA), Iris Gebauer (GRA)
New York University• Nemethy, Mincer
George Mason University• Ellsworth
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Milagro: A Tera-Volt Astrophysical Observatory
Physics Goals• Particle acceleration • Astrophysical shocks• Black hole environments• Neutron star environments• Gamma-ray bursts• Solar physics• Space weather
Open aperture/continuous observation • Monitoring of variable sources• Study large-scale structure of
sources• Discovery potential
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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
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Water Cherenkov Technology
e T
ime
Top layer detects 50% of particles that enters the pond (,e+,e-)
Measure relative timing across pond (~1ns)
Reconstruct direction ~0.5o
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Background Rejection in Milagro
Pro
ton
sG
am
ma
s
Reject 90% of proton background
Retain 50% of -ray signal
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Galactic Plane in TeV Gamma Rays
Cosmic rays interacting with matter in Galaxy produce ’s that decay into rays
Gamma ray spectrum is sensitive to cosmic ray source models
• inverse Compton component• point sources
EGRET observations up to 20 GeV indicated an excess > 1 GeV
Higher energy observations have proven elusive despite 20 years of effort
Milagro has made the first detection of TeV gamma rays from the Galactic plane
S/B level ~3:10-4 – a very difficult analysis
Submitted to PRL
EGRET data
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Galactic Plane in TeV Gamma Rays
Demonstrates the strength of Milagro in finding diffuse and extended sources• Due to good “inherent”
background rejection• ACTs get most of their rejection
from angular resolution• Large observation time• Large field of view
Our flux measurement is ~1/10 of previous upper limits
E-2.51±0.05
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TeV Point-Source Survey of the Northern Hemisphere
Crab Nebula and active galaxy Mrk421 detected
9 regions of interest identified (>4) – 3 coincident with “roi’s” from Tibet array (Walker et al. ApJ)
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Extended Source Survey
Two of the regions of interest are actually extended sources
~6 degree source in Cygnus arm of Galaxy
~3 degree source near the Crab Nebula
HESS telescope now performing follow-up observations
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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
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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
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Milagro Status and Future
Milagro is running in stable mode
We are discovering new source of TeV gamma rays• Galactic plane• Extended sources (not anticipated)
Online GRB analysis continuing• Tied into global alert network (GCN)
Several exciting solar events detected
NSF anticipates 2 more years of operations
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Future Plans: miniHAWC
Reuse Milagro PMTs and electronics
Build pond at extreme altitude (Tibet – 4300m asl)
Incorporate new design• Optical isolation between PMTs• Larger PMT spacing• Deeper PMT depth (in top layer)
Increase collaboration• Added IHEP (Beijing), MSU, UNM, and Utah
$2-3M for complete detector
>15x sensitivity of Milagro• Crab Nebula in 2-3 days (now 1 year)• GRBs to redshift of >1 (now 0.4)
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miniHAWC Sensitivity: Galactic Emission
Extrapolate from Milagro detection of Galactic plane
Use neutral H map to predict TeV intensity
Maps on left show 1-year of data from Milagro, miniHAWC and HAWC
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Conclusion
Milagro has made several discoveries• TeV emission from the Galactic plane• 2 extended sources of TeV gamma rays
Milagro is a completely new technique and we are still learning. The best days lie ahead.
Design of next generation instrument in progress
For modest cost (~$2-3M) we can build an instrument >15x more sensitive than Milagro
Needed for monitoring of GLAST sources, ICECUBE sources, and discovery of new phenomena
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HAWC Sensitivity: Active Galaxies
Assume theoretical model of 27 AGN
Account for IR absorption
Add in 5 known TeV sources
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Forbush Decreases – The interplanetary field
3800
3600
3400
3200
3000
2800
10/18/03 10/23/03 10/28/03 11/2/03
UT
1.35
1.30
1.25
1.20 2003 October/November
Climax Milagro
1.5%
6%
3.2%/day
4.3%/day
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The High Resolution Fly’s Eye
Studying the most energetic particles in the universe
• E=1018 eV to 1021 eV
Outstanding Issues• The shape of the spectrum (is there an
endpoint to the spectrum?)• The composition of these particles
(protons, gammas, Fe, ?)• Are there any anisotropies in their
arrival directions?
LANL’s role in HiRes• Post 9/11 Dugway closed to non-
cleared personnel• LANL “rescued” HiRes – operated
HiRes with Q-cleared personnel• 2004 Dugway allowed US citizen’s on
base – LANL no longer operates• LANL receives ~100k/year from NSF
for a postdoc (starting now)
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The HiRes Detector
The fluorescence yield is proportional to the number of electrons
We directly measure the development of the extensive air shower and the energy of the primary particle
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The Ultra-High-Energy Cosmic Ray Spectrum
Griesen, Zatsepin, and Kuzmin (GZK) predicted an endpoint to the UHECR spectrum at 1019.6 eV
• protons interacting with the 3K CMBR lose energy via pion production
AGASA measures a continuing spectrum
HiRes mono consistent with endpoint
HiRes stereo in progress
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Anisotropy of Ultra-High Energy Cosmic Rays
Outstanding questions• Are there point sources of UHECRs?• Is there large-scale structure to the UHECR arrival directions?
Motivated by results from the AGASA array• Found event clusters (2 or more events from same direction)• Claimed strong evidence for neutral particles from the Galactic plane
LANL work• Hoffman working with Westerhoff (Columbia) developed maximum
likelihood analysis to search for point sources (paper accepted)• Sinnis searched for enhancement from Galactic plane (paper in
progress)
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Point Source Search
Combining data from AGASA and HiRes > 4x1019 eV
Most likely “point source” position consists of 3 AGASA events and 1 HiRes event
Chance probability is 24% - no evidence for point sources of UHECRs
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Galactic Plane Enhancement
AGASALong-standing claim of excess from Galaxy between 1018eV and 1018.4 eV – interpreted as neutral particles
HiRes4 years of stereo data No evidence of Galactic enhancement. 90% CL upper limit ~ to AGASA signal level
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HiRes Status and Future
Operations will continue until ~March 2006
Stereo data analysis is our major effort
Spectrum – Utah and Nevis
Anisotropy – LANL and Columbia• Galactic plane• Point sources• Correlations with known objects
Expect 1-2 more years of analysis than effort shifting