1. Selected topics & results
OUTLINE:
The telescope
Dark Matter searches
Extragalactic sources
Gamma Ray Bursts
Barbara De Lotto INFN and Univ. of Udine – Italy on behalf of the MAGIC collaboration
C2CR07 – Lake Tahoe

2. Current generation Cherenkov telescopes
MAGIC
De Lotto - C2CR07 Lake Tahoe
HESS
VERITAS
CANGAROO-III

3. The MAGIC site La Palma, IAC 28° North, 18° West 2200 m asl
De Lotto - C2CR07 Lake Tahoe
MAGIC
MAGIC and its Control House
La Palma, IAC
28° North, 18° West
2200 m asl

4. The MAGIC -ray telescope
Barcelona IFAE, UA Barcelona, U. Barcelona, HU Berlin, Instituto Astrofisica Canarias, U.C. Davis, U. Dortmund, U. Lodz, UCM Madrid, MPI München, INFN/ U. Padua, INFN/ U. Siena, INR Sofia, Tuorla Observatory, Yerevan Phys. Institute, INFN/ U. Udine, U. Würzburg, ETH Zürich
De Lotto - C2CR07 Lake Tahoe
Largest Cherenkov Telescope: 17 m Ø mirror dish
3.5° FoV Camera with 576 enhanced QE PMT’s
Fast repositioning for GRBs: average < 40 s
Trigger threshold: 50 GeV
Sensitivity: 2.5% Crab / 50 h
-PSF: ~ 0.1°
Energy resolution: %

5. VHE -ray physics overview
pulsar
-quasar
shelltype
SNR
galactic
center
pulsar wind nebula
GRBs
AGN
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cold dark matter
quantum gravity effects
origin of cosmic rays
cosmological
-ray horizon
> 30 sources above 100 GeV, rapid growth in recent years

6. -ray emission from Dark Matter
Standard Cosmological scenario of Cold Dark Matter
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Neutralino (lightest SUSY particle) attractive candidate
g-line Eg = mc
g-line Eg = mc- mZ2/4 mc
g continuum
Particle physics: 
Z,H q
CDM density:
g-ray flux ~ r2 => search for CDM clumps
observe: galactic center (high diffuse g bkg), other dense objects
g-flux from c annihilations:
g-continuum with E << m
dominates
g-lines suppressed
signature for IACTs:

7. Past observations: the Galactic Center
ApJ L638 (2006) 101
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Clear VHE signal:
UNCUT power law spectrum up to > 10 TeV: spectral slope: -2.2 ± 0.2
(in good agreement with HESS)
steady signal over 2 years no significant variability
The high cutoff required by the data (> 10 TeV)  most SUSY DM scenarios rather unlikely
 signal associated to astrophysical source
(emission mechanism still unknown)
HESS, PRL 97 (2006)

8. Proposals of candidates for observations (> June 2006)
“Mini-spike” model
[Bertone, Zentner, Silk, Phys. Rev. D72 (2005) ]
Possible formation of high r DM regions in association with Intermediate-Mass Black Holes in the galactic halo
Unidentified EGRET sources (>100):
high galactic latitude (more clean signal)
stable flux
no counterpart at large wavelengths
Look for identical cut-offs (DM mass) and similar spectra
Nearby galaxies with:
high mass, low luminosity (M/L)
 possible large DM content
low stellar gas, dust content
reduced background
northern hemisphere  low Zd
High M/L dwarf spheroid galaxies
Draco
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~20 h Draco and ~30 h 3EG_J observed up to now

9. Extragalactic VHE -ray sources
15 blazars & 1 radio galaxy
MAGIC observations:
Mrk 421 z= astro-ph / Mrk 501 z= astro-ph
1ES z= astro-ph /
Mrk 180 z= ApJL 648 (2006) 105
1ES z= ApJ 639 (2006) 761
1ES z= ApJL 642 (2006) 119
PG z> ApJL 654 (2007) 119
3 more in pipeline
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redshift
AGN with relativistic jet aligned with observer’s line of sight
non-thermal emission, highly variable
Blazars:
observer
AGN are supermassive Black Holes in the center of mostly elliptical galaxies with a strong accretion of mass and jets emerging perpendicular to the accretion disk from the BH. Nearly half of all discovered cosmic VHE  sources are AGNs. Most of them show intense flaring at the highest  energy while there is no or very little variation in visible light emission.
VHE -rays: leptonic or hadronic origin?
Fast flares can be used for tests on light propagation
Gamma Ray Horizon
 cosmological parameters

10. Focus on particular features
Light curves
g-ray fluxes as a function of time
Differential energy spectra
most follow a pure power law
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2 min bin
1ES
slope:
± ± 0.2

11. Attenuation of VHE -raysx
gVHEgEBL  e+e-
Red shifted
stellar light
dust light
2.7K
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Absorption leads to cutoff in spectrum
Measurement of spectral features allows to constrain EBL models

12. known VHE sources new effects, increased knowledge
Mkn 421 (z=0.030)
Slope: -2.20±0.08 (hardens with intensity)
cutoff TeV
TeV-Xray correlation
Mkn 501 (z=0.034)
23.1 h in June/July ’05
14k excess events
High variability
Spectrum hardens with intensity
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1ES (z=0.044)
Slope ± 0.12
1ES (z=0.047)
Slope: ± 0.14
Inverse Compton clearly observed
in high-flux nights

13. High time-resolution study of Mkn 501 flare
TeV
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Unprecedented fast variations
Doubling time < 5 min
Spectrum shape changes within minutes:
implications on the dispersion relation for light
TeV
TeV
Fuer QG limits: Tau limitiert auf 50sec+/- 50%, alle 3 symmetrisch
TeV
Time (min)

14. Dispersion of light in vacuo
In some QG approaches [Amelino-Camelia 1998] :
Dv/c ~ E / EQG, EQG~EP ~ GeV
At 1st order, the arrival delay of g-rays emitted simultaneously from a distant source should be proportional to their energy difference and the path L to the source:
The expected delay is very small and to make it measurable one needs to observe very high energy g-rays coming from sources at cosmological distances.
=> new, stronger constraints on emission mechanism and light-speed dispersion relations could come from high time-resolution studies of AGN flares.
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Caveat: blazars physical mechanisms (gradual e- acceleration in the emitting plasma) could explain the time delays
Mkn 501 flare: assuming all g produced at the same moment
EQG = (0.6 ± 0.2) 1017 GeV

15. new VHE sources PG1553+113 (z>0.09)
MAGIC DISCOVERIES!
PG1553
PG (z>0.09)
HESS: 4.0 hint (A&A 448L (2006))
MAGIC: 8.8 from 19h observation in
Steepest observed g-ray spectrum:
Mkn 180 (z=0.045) slope: ± 0.7
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New Sources
1ES (z=0.182)
Upper limits from HEGRA, WHIPPLE
Jan 2005, 8.2 h, 6.4 
slope: ± 0.4
slope: ± 0.3
Upper limit of z < 0.42 using MAGIC+HESS spectra
[Mazin & Goebel ApJL 655 (2007) 13]

16. The g-ray horizon at 10 GeV the universe becomes transparent
Spectra affected by EBL absorption
optical depth t
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Fazio-Stecker relation: (E,z) = 1
Distance estimator based on the
absorption over g-ray path
If model assumptions on EBL
possibility of accessing cosmological parameters
[ Blanch & Martinez, Astropart.Phys.23 (2005) 598]
old generation IACTs
MAGIC, HESS
future IACTs
at 10 GeV the universe becomes transparent

17. GRB Positions in Galactic Coordinates, BATSE
Gamma Ray Bursts
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Brightest, most violent known phenomena
Origin still unclear
Short (0.1 – 100 s)
Need fast repositioning after GRB alert
Origin at cosmological distances
=> High energy -rays will be absorbed by EBL
=> Need low energy threshold
GRB Positions in Galactic Coordinates, BATSE
Only to be seen by all sky
monitor detectors
Acc. by MAGIC
DURATION OF GRBs

18. GRBs and MAGIC
MAGIC is the right instrument, due to its fast movement & low threshold
MAGIC is in the GCN Network
GRB alert active since Apr 2005
De Lotto - C2CR07 Lake Tahoe 13

19. GRB observation with MAGIC
GRB050713a
ApJ L641 (2006) 9
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MAGIC data-taking
GRB-alarm from SWIFT
No VHE g emission from GRB positively detected yet...
(all other observed GRB very short or at very high z)
We are on the track!

20. Conclusions Conclusions MAGIC is delivering very good physics results
detected ~15 sources (galactic sources not covered in this talk)
discovered 4 new VHE -ray sources
17 scientific publications (printed or submitted)
Cycle2 almost completed: important commitment to test fundamental physics (DM, Lorentz violation, …)
A second telescope will see
the first light soon (end 2007)
2 x better sensitivity 
no. of sources may increase up to ~50
De Lotto - C2CR07 Lake Tahoe

21. De Lotto - C2CR07 Lake Tahoe
BACKUP

22. Observational Technique
Incoming
g-ray
~ 10 km
Particle
shower
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Hadron
Gamma
~ 1o
Cherenkov light
~ 120 m

23. The threshold  We are publishing with a threshold of 70 GV
We detect significant signal above 40 GeV
Understanding our efficiency towards the goal of 40 GeV. A special task force (UHU) has been set up; preliminary physics results at 50 GeV.
Substantial improvement on DM studies and determination of cosmological constants
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Secret 

24. TeV blazars Active Galactic Nuclei: • Extragalactic sources
• Small fraction of observed galaxies harbor active nuclei
• Supermassive black hole ole of 106 – 1010 solar masses
• Relativistically rotating accretion disk
Emission of collimated relativistic jets
Blazars:
• Strong nonthermal radiation
• High variability at all wavelenghts
• Jets viewed under small angle
• High Doppler factors expected: Jets may
attain high luminosities Lobs~L d4
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g-rays are messenger particles particles,
revealing properties of:
• Leptonic acceleration
• Hadronic acceleration in the jets

25. Absorption of extragalactic  - rays
Any  that crosses cosmological distances through the universe interacts with the EBL
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Attenuated flux function of g-energy and redshift z.
For the energy range of IACTs (10 GeV-10 TeV), the interaction takes place with the infrared (0.01 eV-3 eV, 100 m-1 m) Star formation, Radiation of stars, Absorption and reemission by ISM
EBL
By measuring the cutoffs in the spectra of AGNs, any suitable type of detector can help in determining the IR background-> needs good energy resolution
Acc. by new detectors

26. De Lotto - C2CR07 Lake Tahoe

27. AGN at a glance
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At least a handle on EBL but also the possibility of accessing cosmological constants (Martinez et al.) could become reality soon (maybe including X-ray obs.)

28. Constraining the EBL density (and paving the way to a measurement of cosmological parameters)
Simulated
measurements
Mkn 421
Mkn 501
1ES
PKS
1ES
1ES H
PKS H
GRH/GRH(WM=0.3,WL=0.0)
De Lotto - C2CR07 Lake Tahoe
Blanch & Martinez 2004
Different
EBL models
Simulated
measurements
Mkn 421
Mkn 501
1ES
PKS
PKS H
1ES
1ES H

29. Energy spectrum
The absence of a spectral feature between 10 and 100 keV goes against an accretion scenario
Contemporaneous multiwavelength observations are needed to understand the nature of the object
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Albert et al. 2006

30. De Lotto - C2CR07 Lake Tahoe