TeV Gamma-ray Astronomy and UHECR-1

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TeV Gamma-ray Astronomyand UHECR-1

• Trevor C. Weekes,
• Whipple Observatory,
• Harvard-Smithsonian Center for Astrophysics

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Outline

• Relevance to UHECRs
• Atmospheric Cherenkov Imaging Technique
• Status of TeV Observations
• Extragalactic TeV Sources
• Observations of the UHECR Sources
• Next Generation Telescopes

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Relevance of TeV Astronomy to Studies of UHE
Cosmic Rays

• Historical Precedent
• Similar Techniques
• Understanding of discrete Source (e.g. UHECR-1)
  demands study at other wavelengths TeV Band is
  the Highest Energy Band in which Cosmic Sources
  have been reliably detected
• Existence of Extragalactic Sources of
  Relativistic Particles has been established
• New Generation of TeV Telescopes have the
  sensitivity for detection of TeV component of
  UHECR sources

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Why study TeV Gamma rays?

• Why do we study elephants when mosquitoes are
  easier to find and more plentiful?

TeV gamma-rays, like elephants, are bigger, more
difficult to produce, and stretch the the
production models to their limits!
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Simple Technique, Simple Detectors, Small Budgets
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Early Expectations of TeV Gamma-ray Astronomy

• We would find the Origin of the Cosmic Radiation
• which would entail
• Single source or class of sources
• Unambiguous detection of the 70 MeV bump in
  the spectrum
• Source(s) would be in the Galaxy
• In short locate the Smoking Gun of Cosmic Ray
  Origins!

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Atmospheric Cherenkov Imaging

• Cherenkov Imaging gives the ability to
  distinguish compact images of gamma-ray showers
  from more irregular images from hadronic showers
• Arrival Directions also determined with high
  accuracy

20 km
g
p
Atmospheric height
5o
m_
m
e
e_
To record the Cherenkov light images of gamma-ray
initiated air showers, a large camera,
consisting of an array of PMTs in the focal plane
of a large optical reflector, is used.
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Types of images seen by atmospheric Cherenkov
camera
Hadron
Gamma
Gamma ray
Muon Ring
Sky Noise
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The First TeV Sources
Imaging systems came into operation 1984
- First Galactic Source detected (Crab
Nebula/ Whipple Observatory) 1989 First
Extragalactic Source detected (Mrk 421/Whipple
Observatory) 1992
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Tev Gamma-ray Sky Status c.2003
18 Sources reported in refereed
literature 10 are Extragalactic, 8
are Galactic
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Catalog Name Source Type Date/Group EGRET Grade
TeV 0047-2518 NGC 253 Starburst 2003/CANG. no B
TeV 02194248 3C66A Blazar 1998/Crimea yes C-
TeV 05352200 Crab Nebula SNR 1989/Whipple yes A
TeV 0834-4500 Vela SNR 1997/CANG. yes C
TeV 1121-6037 Cen X-3 Binary 1999/Durham yes C
TeV 11043813 Mrk 421 Blazar 1992/Whipple yes A
TeV 12311224 M87 Radio Gal. 2003/HEGRA no C
TeV 14294240 H1426428 Blazar 2002/Whipple no A
TeV 1503-4157 SN1006 SNR 1997/CANG. no B
TeV 16543946 Mrk 501 Blazar 1995/Whipple no A
TeV 1710-2229 PSR 1706-44 SNR 1995/CANG. no A
TeV 1712-3932 RXJ1713-39 SNR 1999/CANG. no B
TeV 20006509 1ES1959650 Blazar 1999/TA no A
TeV 20324131 CygOB2? OB Assoc. 2002/HEGRA no C
TeV 2159-3014 PKS2155-304 Blazar 1999/Durham yes A
TeV 22034217 BL Lacertae Blazar 2001/Crimea yes C
TeV 23235849 Cas A SNR 1999/HEGRA no B
TeV 23475142 1ES2344514 Blazar 1997/Whipple no C

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New Sources 2004

• Galactic Center
• PSR1259-63 at periastron
• Others? See following papers on results from HESS
  and MAGIC
• (also credibility of some southern sources has
  been questioned)

But no source (Galactic or Extragalactic) has yet
been unambiguously identified as a source of
Hadronic Cosmic Rays all the TeV gamma
rays could have Electron Progenitors.
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TeV Catalog of AGN
Catalog Name Source Date/Group Type Redshift
TeV 11043813 Mrk 421 1992/Whipple HBL 0.031
TeV 14294240 H1426428 2002/Whipple HBL 0.129
TeV 16543946 Mrk 501 1995/Whipple HBL 0.033
TeV 20006509 1ES1959650 1999/TA HBL 0.048
TeV 2159-3014 PKS2155-304 1999/Durham HBL 0.116
TeV 23475142 1ES2344514 1997/Whipple HBL 0.044
HBL High frequency BL Lac All confirmed
sources Spectra measured Light-curves
determined Multi-wavelength Correlations Only two
in EGRET Catalog
Horan, Weekes, 2003
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Time Variability AGN Light Curves
Variation in Nightly Rates from Markarian
421 Whipple Observatory 1995
Buckley et al. 1996
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Variations Seen on Many Time-scales
Markarian 421 Whipple Observatory Hours - minutes
Markarian 501 HEGRA Days-months
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TeV Results Correlations with X-rays
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Mrk421 Spectral Variability
Exponent of Power Law Changes with Total
Intensity. Cutoff Term Remains the Same
Power Law
Cutoff Term
Krennrich et al. 2003
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Multiwavelength Results Power Spectra
Mrk 501
Compton
Synchrotron
Similar double peaked Power Spectra seen in other
AGN
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AGN Jet Emission Mechanisms
Cosmic Cannon Looking down the Barrel of the
Cannon

• Electron Progenitors
• Synchrotron Self Compton
• External Compton
• Proton Progenitors
• Proton Cascades
• Proton Synchrotron

(Buckley, Science, 1998)
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Detection of Radio Galaxy, M87
HEGRA Group 4.1 sigma detection Weak source but
important
Nearby Radio Galaxy (Virgo A) Off axis jet source
Aharonian et al. 2003
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Galactic Center TeV Source
Whipple 10 m telescope Observations
1995-2003 Southern Source E gt 2.5 TeV 40 of
Crab 3.7 sigma Kosack et al. ApJL (2004)
CANGAROO-III E gt 250 GeV 10 0f Crab Detection
strong Steep spectrum -4.6/-0.5 Tsuchiya et
al., ApJL (2004)
Can
HESS Definitive
results See next talk!
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TeV Gamma-ray AstronomyA Legitimate New
Astronomical Discipline

• Essential Features of an Astronomical Discipline
• Location of Sources
• Measurement of Spectrum
• Time Variability
• Correlation with other wavelengths

Ready to be used to aid in the Exploration
of UHECR Sources
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Study of Arrival Directions of Ultra High Energy
Cosmic Rays

• UHECRs may be diffuseor they may come from
  discrete sources
• Since these must be nearby, they should be easily
  recognizable at long wavelengths
• If not, and if the production of UHECRs is their
  unique property, they should still be source of
  TeV gamma rays
• Detection of coincident TeV source would confirm
  existence of UHECR source and give better
  location

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Possible Sources of UHECRs New Challenge for
TeV Astronomy
Possible Clustering into discrete sources of 92
cosmic rays with E gt 4 x 1019 eV
(results from AGASA, Havarah Park, Yakutsk,
Volcano Ranch)
Marginally statistically significant correlation
of Doublets and Triplets with
Supergalactic Plane
Uchihori et al. 2000
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TeV Counterpart to UHECR Source Extragalactic
Cascade
Ferrigno, Blasi, Marco astro-ph/0404352
Electromagnetic Cascades initiated by photopion
production of UHECR on extragalactic radio and
microwave background may give detectable flux of
TeV photons.
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Whipple Search for TeV Emission in Error box of
Flys Eye 3 x 1020 eV UHECR
The Most Important Direction in the Universe
Akerlof et al. 2003
Search made at 12 positions within the Error
Box no evidence for TeV emission
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TeV maps from six of the twelve fields surveyed
no evidence of an excess. Field includes quasar
3C147 of historical interest.but too distant
to be a candidate.
Akerlof et al. 2003
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Next GENERATION TELESCOPES
Arrays of Imaging Telescopes

• Philosophy
• Improve Flux Sensitivity
• Reduce Energy Threshold
• Multiple gt 10 m telescopes
• New Technology where appropriate.

Now on line CANGAROO III - 2004 HESS
- 2004 MAGIC -
2004 (VERITAS to come - 2006)
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World Picture of sub-TeV Observatories

• Four Major Observatories ideally distributed to
  give maximum coverage

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p
Chicago Airport Display
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VERITAS

• Four telescope system
• 12 m aperture
• 80m separation
• Filled triangle configuration
• 499 pixel camera (0.15º/
• pixel, 3.5º FOV)
• Kitt Peak, Tucson (32ºN, 36ºW, 1800m a.s.l.)
• Current status
• Prototype telescope operating at Whipple basecamp
• Funded
• Sources detected
• VERITAS-4 in 2006

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VERITAS Movie Cameras Advanced technology
cameras 500 Mhz FADCs 2 ns slices through
shower images (Leeds group has played major role
in their design and construction)
Prototype VERITAS Telescope
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Typical Event Prototype
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Results Markarian 421
Alphalt8 gives ON 1570 OFF635.8 Sigma19.9
Total Exposure18.7 hours Mean rate0.83
gammas/min
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Summary
Not one source but many Extragalactic Sources in
profusion No Smoking Gun YET for Cosmic Ray
Origins A New Astronomical Discipline is
Established Foundations are laid for Major
Advances with next Generation Systems working
with auger, GLAST, icecube, etc. THESE MAY BE
THE important PROBES OF UHECR SOURCES
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VERITAS Movie Camera
You have read the book now watch the movie!
(in 2 ns slices)