Observation of the Crab Nebula with the MAGIC Telescope

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Observation of the Observation of the Crab Nebula with the Crab Nebula with the

MAGIC TelescopeMAGIC Telescope

M. López-MoyaM. López-MoyaUniv. Complutense de Madrid,Univ. Complutense de Madrid,

on behalf of the MAGIC Collaborationon behalf of the MAGIC Collaboration

XXXXth Rencontres de Moriond

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OutlineOutline

IntroductionIntroduction

AnalysisAnalysis

Data SetData Set

First ResultsFirst Results


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Crab Nebula: the standard Crab Nebula: the standard candle (I)candle (I)

Remnant of a supernova explosion, occurred in 1054.

Pulsar injecting relativistic electrons into the nebula.

Emission predominantly by non-thermal processes, covering a huge energy range (radio to TeV).

First TeV source (Whipple Telescope, 1989).

Very strong and stable at TeV → our standard candle


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Crab Nebula: the standard candle Crab Nebula: the standard candle (II)(II)

SSC model SSC model fits the fits the observed observed spectrum.spectrum.

Inverse Inverse Compton Compton peak peak expected expected below 100 below 100 GeV.GeV.

Inverse-Compton Emission

SynchrotronEmission

MAGIC should MAGIC should see the IC-peak.see the IC-peak.

577 pixels, 3.5 deg 577 pixels, 3.5 deg

FOV cameraFOV camera

Fast pulse sampling: 300MHzFast pulse sampling: 300MHz

Optical signal transportOptical signal transport

17 m diameter dish17 m diameter dish Active mirror controlActive mirror control

The The MAGICMAGIC Telescope Telescope

Located at 2220m at La Palma Located at 2220m at La Palma

(Canary islands) (Canary islands)

Threshold: Threshold: 30 GeV30 GeV

Characteristics:Characteristics:


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Imaging Cherenkov Technique Imaging Cherenkov Technique (I)(I)

-like-like hadron-likehadron-like -arc-arc


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Imaging Cherenkov Technique Imaging Cherenkov Technique (II)(II)

Alpha


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Background reduction (I)Background reduction (I) Down to Down to ~~150 GeV, the traditional techniques 150 GeV, the traditional techniques

based on based on simple image parameter cutssimple image parameter cuts, still , still work well.work well.

E>180 GeVE>180 GeV


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Background reduction (II)Background reduction (II) At lower energies the traditional At lower energies the traditional

techniques start to be not so effective. techniques start to be not so effective.


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Background reduction (III)Background reduction (III)

A new approach has been used for the A new approach has been used for the gamma/hadron separation: gamma/hadron separation:

Random ForestRandom Forest

Train in the parameters: Train in the parameters: SIZE, DISTANCE, LENGTH, SIZE, DISTANCE, LENGTH, WIDTH, CONC, ASYM WIDTH, CONC, ASYM (no ALPHA used).(no ALPHA used).

No a priori No a priori parameterization needed.parameterization needed.

For each shower we get For each shower we get its “hadronness”.its “hadronness”.


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Background reduction (IV)Background reduction (IV)

For each energy bin we cut in different For each energy bin we cut in different Hadronness and AlphaHadronness and Alpha

All EnergiesAll Energies E>200 GeVE>200 GeV

GammasGammas

HadronsHadrons


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Energy EstimationEnergy Estimation Basic principle:Basic principle: Energy Energy light content of the shower (SIZE). light content of the shower (SIZE).

We use a Taylor expansion on the more relevant image We use a Taylor expansion on the more relevant image parameters:parameters:

Coefficients obtained by minimizing:Coefficients obtained by minimizing:

Resolution ~30%Resolution ~30% Bias at very low energies, since very low size events are Bias at very low energies, since very low size events are

rejected (by trigger and analysis cuts).rejected (by trigger and analysis cuts).

),,,,( ZENITHWIDTHLENGTHDISTSIZEEE

estestMC EEEE /)(


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Energy EstimationEnergy Estimation


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Energy EstimationEnergy Estimation Basic principle:Basic principle: Energy Energy light content of the shower (SIZE). light content of the shower (SIZE).

We use a Taylor expansion on the more relevant image We use a Taylor expansion on the more relevant image parameters:parameters:

Coefficients obtained by minimizing:Coefficients obtained by minimizing:

Resolution ~30%Resolution ~30% Bias at very low energies, since very low size events are Bias at very low energies, since very low size events are

discarded (by trigger and analysis cuts).discarded (by trigger and analysis cuts).

),,,,( ZENITHWIDTHLENGTHDISTSIZEEE

estestMC EEEE /)(

Currently applying new methods, like Random Forest energy Currently applying new methods, like Random Forest energy estimation, giving similar results. estimation, giving similar results.


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Data SetData Set

datedate Zd. [Zd. [00]]Nº Nº

events events [·10[·1033]]

TTobsobs [min][min]

ONON 13,14,213,14,222

14-3014-30 12221222 110110

OFFOFF 18,2118,21 11-3011-30 885885 7070

First data set after full mirror First data set after full mirror installation: Sept. 2004installation: Sept. 2004

Background rate Background rate ~~200 Hz200 Hz


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Collection Area & Expected Collection Area & Expected RatesRates


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Alpha plots vs. EnergyAlpha plots vs. Energy

ON

OFF


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SpectrumSpectrum


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ConclusionsConclusions

MAGIC already operational and taking its MAGIC already operational and taking its first data since 2004.first data since 2004.

Crab Nebula spectrum measured by Crab Nebula spectrum measured by MAGIC consistent with previous MAGIC consistent with previous experiments, and compatible with SSC experiments, and compatible with SSC emission model.emission model.

First signals obtained well below 100 GeV First signals obtained well below 100 GeV with a Cherenkov telescope. with a Cherenkov telescope.

Analysis still can improve to push down Analysis still can improve to push down more the analysis threshold.more the analysis threshold.

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Observation of the Crab Nebula with the MAGIC Telescope