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

qq

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

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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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