Barbara De Lotto INFN and Univ. of Udine – Italy on behalf of the MAGIC collaboration
C2CR07 – Lake Tahoe
Selected topics & resultsOUTLINE:
• The telescope • Dark Matter searches• Extragalactic sources• Gamma Ray Bursts
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Current generation Cherenkov telescopes
MAGIC
VERITAS
CANGAROO-III
HESS
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MAGIC and its Control House
MAGIC
La Palma, IAC28° North, 18° West
The MAGIC site
2200 m asl
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The MAGIC -ray telescope
•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: 20 - 30%
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
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VHE -ray physics overview
GRBs
AGN
cold dark
matter
quantum gravity effects
origin of cosmic rays
cosmologicacosmologicall
-ray -ray horizonhorizon
pulsar
--quasarquasar
shelltypeSNR
galacticcenter
pulsar windnebula
> 30 sources above 100 GeV, rapid growth in recent years
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-ray emission from Dark Matter
NeutralinoNeutralino (lightest SUSY particle) attractive candidate (lightest SUSY particle) attractive candidate
-flux from -flux from annihilations: annihilations:
)()(v
)( 2
2dll
M
NDM
Z
-line E-line E = m = m
--line Eline E = m = mmm22mm
continuumcontinuum
Particle physics:
Z,H
q
q)1100( TeVmGeV
Standard Cosmological scenario of Standard Cosmological scenario of Cold Dark MatterCold Dark Matter
-continuum with E << m-continuum with E << m
dominatesdominates
--lines suppressed
signature for IACTs:CDM density:
-ray flux ~ -ray flux ~ 22 => => search for CDM clumpssearch for CDM clumps
observe: galactic center (high diffuse galactic center (high diffuse bkg),bkg), other dense objectsother dense objects
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Past observations: the Galactic CenterApJ L638 (2006) 101
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) 221102
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Proposals of candidates for observations (> June 2006)
“Mini-spike” model [Bertone, Zentner, Silk, Phys. Rev. D72 (2005) 103517]
Possible formation of high 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
~20 h Draco and ~30 h 3EG_J1835+5918 observed up to now
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Extragalactic VHE -ray sources15 blazars & 1 radio galaxy15 blazars & 1 radio galaxy
• VHE -rays: leptonic or hadronic origin?
• Fast flares can be used for tests on light propagation • Gamma Ray Horizon cosmological parameters
MAGIC observations:
Mrk 421 z=0.030 astro-
ph /0603478 Mrk 501 z=0.034 astro-ph 0702008
1ES2344+514 z=0.044 astro-ph /0612383
Mrk 180 z=0.045 ApJL 648 (2006) 105
1ES1959+650 z=0.047 ApJ 639 (2006) 761
1ES1218+308 z=0.182 ApJL 642 (2006) 119
PG1553+113 z>0.09 ApJL 654 (2007) 119
• 3 more in pipeline
redshift
• AGN with relativistic jet aligned with observer’s line of sight
• non-thermal emission, highly variable
Blazars:observerobserver
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Focus on particular features• Light curves-ray fluxes as a function of time
• Differential energy spectramost follow a pure power law
slope: - 2.72 ± 0.14 - 3.2 ± 0.2
slope spectral
EdE
dN
1ES1959+6502 min bin
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Attenuation of VHE -raysx
xx
VHEEBL e+e-
Red shifted stellar light
Red shifted dust light
2.7K
• Absorption leads to cutoff in Absorption leads to cutoff in spectrumspectrum• Measurement of spectral Measurement of spectral features allows to features allows to constrain EBLconstrain EBL modelsmodels
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Mkn 501 (z=0.034) • 23.1 h in June/July ’05• 14k excess events• High variability• Spectrum hardens with
intensity
• Inverse Compton clearly observed in high-flux nights
Mkn 421 (z=0.030) • Slope: -2.20±0.08 (hardens with intensity) cutoff 1.1 -1.6 TeV• TeV-Xray correlation
1ES2344+514 (z=0.044)
1ES1959+650 (z=0.047) Slope: - 2.72 ± 0.14
known VHE sourcesnew effects, increased knowledge
Slope - 2.95 ± 0.12
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High time-resolution study of Mkn 501 flare
•Unprecedented fast variations Doubling time < 5 min
• Spectrum shape changes within minutes:implications on the dispersion relation for light
Time (min)
0.15-0.25 TeV
0.25-0.6 TeV
0.6-1.2 TeV
1.2-10 TeV
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• In some QG approaches [Amelino-Camelia 1998] :
v/c ~ E / EQG, EQG~EP ~ 1019 GeV• At 1st order, the arrival delay of -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 -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.
c
L
E
Et
QG
Dispersion of light in vacuo
Mkn 501 flare: assuming all produced at the same moment
EQG = (0.6 ± 0.2) 1017 GeV
Caveat: blazars physical mechanisms (gradual e- acceleration in the emitting plasma) could explain the time delays
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new VHE sources
Mkn 180 (z=0.045)slope: - 3.3 ± 0.7
1ES1218+304 (z=0.182)Upper limits from HEGRA, WHIPPLE
Jan 2005, 8.2 h, 6.4
PG1553+113 (z>0.09) HESS: 4.0 hint (A&A 448L (2006))• MAGIC: 8.8 from 19h observation in 2005-06• Steepest observed -ray spectrum:
• Upper limit of z < 0.42 using MAGIC+HESS spectra[Mazin & Goebel ApJL 655 (2007) 13]
MAGIC DISCOVERIES!
slope: - 3.0 ± 0.4slope: - 4.2 ± 0.3
BL Lac objects
1.5
2.0
2.5
3.0
3.5
4.0
4.5
0 0.1 0.2 0.3 0.4
Redshift Parameter z
Spec
tral I
ndex
PG1553
New Sources
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The -ray horizonSpectra affected by EBL
absorption),( zE
oe
old generation IACTs
MAGIC, HESS
future IACTs
• at 10 GeV the universe becomes transparent
Fazio-Stecker relation: (E,z) = 1(E,z) = 1
If model assumptions on EBL
• possibility of accessing cosmological parameters[ Blanch & Martinez, Astropart.Phys.23 (2005) 598]
optical depth
Distance estimator based on theabsorption over -ray path
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GRB Positions in Galactic Coordinates, BATSE
Acc. by MAGIC
Only to be seen by all sky monitor detectors
DURATION OF GRBs
Gamma Ray Bursts
• 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
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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
13
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GRB-alarm from SWIFTGRB-alarm from SWIFTGRB-alarm from SWIFTGRB-alarm from SWIFTMAGIC data-MAGIC data-takingtakingMAGIC data-MAGIC data-takingtaking
We are on the track!
GRB observation with MAGIC ApJ L641 (2006) 9ApJ L641 (2006) 9
• No VHE No VHE emission from GRB positively detected yet... emission from GRB positively detected yet... (all other observed GRB very short or at very high z)(all other observed GRB very short or at very high z)
GRB050713a
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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
Conclusions
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BACKUP
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Incoming
-ray
~ 10 kmParticleshower
~ 1o
Che
renk
ov li
ght
~ 120 m
Observational Technique eep
ee
Hadron
Gamma
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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
Secret
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TeV blazarsActive 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 mayattain high luminosities Lobs~L 4
-rays are messenger particles particles, revealing properties of:• Leptonic acceleration• Hadronic acceleration in the jets
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Any that crosses cosmological distances through the universe interacts with the EBL
Absorption of extragalactic - rays
eeEBLHE
E 1 cos 2 mec2 2
Attenuated flux function of -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
Acc. by new detectorsBy measuring the cutoffs in the spectra of AGNs, any suitable type of detector can help in determining the IR background-> needs good energy resolution
EBL
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oE
z
ndddz
dtcdzzE
)(sin),(
:depth optical2
00
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AGN at a glanceSource Redshift Spectral Index Type Detection (>5) Confimation
M87 0.004 2.9 FR I HESS
Mkn 421 0.031 2.2 BL Lac Whipple Many
Mkn 501 0.034 2.4 BL Lac Whipple Many
1ES 2344+514 0.044 2.9 BL Lac Whipple HEGRA,MAGIC
1ES 1959+650 0.047 2.4 BL Lac Tel. Array Many
PKS 2005-489 0.071 4.0 BL Lac HESS
PKS 2155-304 0.116 3.3 BL Lac Mark VI HESS
H1426+428 0.129 3.3 BL Lac Whipple Many
H2356-309 0.165 3.1 BL Lac HESS
1ES 1218+304 0.182 3.0 BL Lac MAGIC
1ES 1101-232 0.186 2.9 BL Lac HESS
PG 1553 >0.25 4.0 BL Lac MAGIC
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.)
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Constraining the EBL density (and paving the way to a measurement of cosmological parameters)
Blanch & Martinez 2004
Simulatedmeasurements
Different EBL models
Mkn 421Mkn 501
1ES1959+650
PKS 2155-304H1426+428
PKS2005-489
1ES1218+3041ES1101-232H2356-309
Simulatedmeasurements
Mkn 421Mkn 501
1ES1959+650PKS2005-489 1ES1218+304
1ES1101-232
H2356-309PKS 2155-304H1426+428
GR
H/G
RH
(M=
0.3,
L=
0.0)
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Energy spectrum
Albert et al. 2006
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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