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Data analysis with Cherenkov Telescopes: MAGIC

Problematiche astrofisica VHE

Antonio StamerraUniversità di Siena & INFN Pisa

JC - 10 febbraio 2010 Pisa

[email protected]

Istituto Nazionaledi Fisica Nucleare


Perugia, 22 ottobre 2009 MAPS school a.Stamerra 2

IACT detector

IACT Imaging Atmospheric Cherenkov Telescope

Atmosphere is opaque to γ-rays

IACT detector IACT detector = =

Atmosphere + telescopeAtmosphere + telescope

Satellite: direct detection of γ-ray

Ground-based: indirect detection



Electromagnetic atmospheric shower

pair-production

Bremsstrahlung

R~9/7 X0~45g/cm2

(in air, 20oC)



MAGIC17 m diameter reflecting surface (240 m2 )

Analog signal transport via optical fibers 2-level trigger

system& 300 MHz FADC system

Active mirror control

high reflective diamond milled aluminum mirrors

Light weight Carbon fiber structure for

fast repositioning



Stereoscopic mode: Improved sensitivity Better angular and energy

resolution New technologies:

Camera: Photo-detectors with higher QE (HPDs in near future)

Faster Digitalization: 4 GHz Analogue to Digital Converts (Domino)

MAGIC-IIFlorian Goebel

Telescopes



QuickTimeï¾ª e undecompressore

sono necessari per visualizzare quest'immagine.

Imaging Air Cherenkov Telescopes

Direction reconstruction Particle-id Energy reconstruction

Showertop

Showertail

×

γ -ray direction

A telescope placed inside the Cherenkov light A telescope placed inside the Cherenkov light pool can obtain an image of the development pool can obtain an image of the development of the shower above the night sky background of the shower above the night sky background (NSB) fluctuations(NSB) fluctuations

Distances in camera

= Angular Distances

on sky

Shower top

N1 ,θ C1

Shower tail

n2>n1 ⇒ θC2> θC1



Background

Cosmic-ray background γ-rays have a definite direction

(source position on sky) CR are isotropically distributed

ON-OFF selection? CR flux overwhelms γ-ray flux…

Night-Sky background (NSB, LONS)

Field stars



Gamma/hadron separationgamma proton

300 GeV gamma 1 TeV proton



Modelli emissione adronica



Cosmic rays

“All-particle” spectrum Power law spectrum (~E-

2.7) Particles decrease with

energy

Two breaks in the power law Knee ~3 PeV (3x1015 eV) Ankle ~1 EeV (1018 eV)

Underlying physical processes?

Acceleration mechanism?

Acceleration sites?



Cascade showerCascade shower

100GeV gamma ray 300GeV Proton

By M. Hayashida



EAS simulation - uncertainties

Reliability of simulation of hadronic interactions (extrapolation of accelerator data and/or theoretical assumptions) - partially solved by IACTs using real hadrons…

Forward physics unexplored (LHC? E.g. TOTEM)Physical Intrinsic shower fluctuations

Enviromental Weather condition (Calima, high clouds,…) Night sky light (Bright stars, Moon, city, …)

Instrumental Calibration (absolute QE, mirror aging, …) Background estimation (inhomogeneity, …) Telescopes condition (dead pixels, misspointing, …)

Analysis Simulation (atmospheric model, trigger, …) Analyzer choices (optimizations, binning, …)

Generally, IACTs claim 20% systematics !



Sensitivity in 50h5σ & 10 evts

For 5σ: Sensitivity ∝ 1/sqrt(time)

For 10 evt: Sensitivity ∝ 1/time

Sensitivity

Depends on the Effective area and CR Background rejection (and background uncertainty)



MAGIC-II

Overall sensitivity will be Overall sensitivity will be improved by a factor of 2-3improved by a factor of 2-3

Energy resolutionEnergy resolution ~25% ~25% 15-20% 15-20%

Angular resolutionAngular resolution Substantial improvementSubstantial improvement



Sites of particle acceleration

Hillas plot

Compact sites and high B Diffuse objects and low B

The acceleration site environment plays a key role…

A deeper (astrophysical) knowledge of candidate sites is mandatory



Exploring extreme accelerators with gamma-rays

VHEγ-astronomy address diversity of topics related to the nonthermal Universe:

acceleration, propagation and radiation of ultrarelativistic protons/nuclei and electrons

generally under extreme physical conditions in environments characterized with

huge gravitational, magnetic and electric fields, highly excited media, shock waves

and very often associated with relativistic bulk motions linked, in particular, to

jets in black holes (AGN, Microquasars, GRBs) and cold ultrarelativistic pulsar winds



Goal 0: Detection!

Gammas are not for free…

Signal reconstruction Background rejection Sensitivity

Minimum flux detectable Shortest time variation Observation time

In the following we assume we are lucky and we always get gammas.

We focus on goals 1, 2, 3. We’ll tackle goal 0 later on (slide 35 ff).

S s Â»Rate

g

RateB

T



Standard candle: Crab Nebula

Crab broad-band spectrum



UVUV

OpticalOptical

RadioRadio

X-RayX-Ray

MWMW

γγ -ray-ray

VHEVHE

Energy Energy

Flu

x

Flu

x

sincrotrone

IC

100Mev-10GeV

>100GeV

BBe-

γ

e-

e- γ

γ



Goals summary

Spectrum #ph in ∆E

Energy reconstruction

E’ energy resolution

Skymap #ph in ∆Ω

Angular resolution - PSF

F.o.V.

Lightcurve #ph in ∆ t

Time resolution

Pulsar ⇒ ms AGN ⇒ min.



Gamma/Neutrino astronomy

Fermi acceleration processes create secondary particles, among them neutral particles

γ and ν bring direct information on the acceleration site

But…. Their emission, and

propagation depends on the environment and source details

A deep (astrophysical) knowledge of the source is mandatory!

Chargedparticles

Acceleratedparticles

Bpp

HeHeIonsIonsππnnµµee

γγνν



γ-ray production

Synchrotron radiation

Bremstrahlung

Inverse Compton

Annihiliation

p/nuclei interaction with ISM (proton induced cascade)

Proton-synchrotron

ISM

e-

γ

BBe-

γ

e-

e- γγ

e+

γ

γ

e-

P (RC)π +

π0

γ

γHadro

nic

pro

ces s

es

Lep

toni

c pr

oces

ses



Hadronic or leptonic?

Emissione γ ray emission from π0 decay and interaction with molecular clouds

Signature: π0 decay spectrum



Hadronic or leptonic?

modelli leptonici modelli leptonici (IC)(IC)modelli

adronici Yet no “smoking gun” evidence of γ-rays stemmed from hadronic acceleration and π0 decay!

But many hints….



WHAT DO WE LEARN FROM GAMMA RAYS?

courtesy P. Blasi



WHY IS IT INTERESTING:II. Large B observed?

TYPICAL THICKNESS OF FILAMENTS: 10-2 pc

The synchrotron limited thickness is:

Dx 4 D E tsyn

E Â»4 pc Bm3/2

BÂ»100 m Gauss courtesy P. Blasi



RXJ1713

EFFICIENT ACCELERATION – LARGE B FIELDS

PROBLEMS: 1. LARGE THERMAL X-RAYS (BUT…) 2. VERY LOW RATIO OF ELECTRONS AND PROTONS



INEFFICIENT ACCELERATION – LOW B FIELDS

PROBLEMS: 1. VERY HIGH PHOTON DENSITY FOR ICS 2. LOW B FIELDS (IGNORES X-RAY OBSERVATIONS) 3. BAD FIT TO HIGHEST-E HESS DATA POINTScourtesy P. Blasi



Kep~0.01

Kep~0.1



AGN - blazars

Intense and variable emission up to ~10 TeVObserved structures: accretion disk; obscuring thorus Relativistic Jet Broad/Narrow line regions (NLR, BLR)

TeV emitting zone: jet with high relativistic bulk motion Particle acceleration at shock

boundaries bundled in a magnetic field (Fermi acceleration processes)

Gamma-ray emission from accelerated electrons (synchrotron and inverse-Compton scattering) or hadronic interactions

Unified AGN model: different AGN classes depending on viewing angle FRI, FR-II, Radio quasars, BL-Lac

(HBL-LBL)

FR-I, FR-II Radio quasars

BL-Lac



γ-ray emission from AGN: SSC a (minimal)

standard model

Blazar: collimated emission from jet (relativistic amplification) Environment: B, δ, R

Observed emission (SED) well described by leptonic models, such as SSC and EC. Expected X-ray / Tev time

correlation Synchrotron peak: IR to x-ray IC peak: UV to γ-rays LBL, IBL, HBL Outbursts of e.m. radiation

Synchrotron IC Em

itte

d po

wer

Energy

BBe-

γ

e-

e- γγγ min γbr γmax γ br γmaxKN

Relativistic electrons injection/acceleration/cooling



Blazar Multiwavelength campaigns

ExtremeExtreme (~>1 order of magnitude in flux) and (~>1 order of magnitude in flux) and fast fast (~hours, minutes) (~hours, minutes)

vvaarriiaabbiilliittyy Simultaneous Multifreq. Observations covering 15 decades in photon

energy:VHE: H.E.S.S., MAGIC, VERITASHE: Agile, FermiX-ray: Suzaku, Swift, Chandra, IntegralOptical: KVARadio: Metsahövi, VLBI…

Methods: Monitoring (optical, x-ray, radio) Intensive planned campaigns Target of Opportunity (ToO): react to alerts (internal/external)

• MAGIC Monitoring program of bright blazars (Mrk421, Mrk501, 1ES1959, 1ES2344+514….)

Some recent MWL campaigns: • Mrk 421, Mrk 501, OJ287, PG 1553+113, 1ES 1218+304, 1H 1426+428, M87• …and other campaigns organized…



Mrk 421 2008 activity

MWL campaigns on Mrk421 in flaring stateoptical to TeV energies

Simultaneous data strong SSC model constraints time evolution of the SEDs

New 2009 campaign on Mrk421 and Mrk501

Bonnoli G. et al. (MAGIC Coll.) arXiV:0907.0831Bonnoli G. et al. (MAGIC Coll.) arXiV:0907.0831Publication in preparationPublication in preparation

preliminary



Mrk421 - 2009 campaign

4.5 months Jan 20th - June 1st

~20 instruments

2-day sampling

Complete coverage 0.1 GeV-10 TeV

preliminary

Fermi

MAGIC

Swift/XRT

D.Paneque, Fermi symposium



S5 0716+714IBL z=0.31(?)

Bright in optical ⇒ trigger MWL campaign (opt-X-γ) Clear signal in 2.6 h: 6.9σ

1st VHE detection F(>400 GeV) =7.5x10-12 ph/cm²/s (≈9% Crab)

Significance 6.8 σ

ApJ - accepted arXiv:0907.2386MAGIC collab. 2008, Atel #1500

SSC model predicts an unplausible IC γ -ray flux⇒ Spine-layer model Ghisellini et al. 2005, A&A, 432, 401

High redshift Nilsson,A&A 487(2008)L29 reports the detection of the host galaxy: z=0.31±0.08

2008



S5 0716+714IBL z=0.31

Rotation of positional angle of polarization (EVPA) during maximum (60deg/day) Larionov et al.,ATel #1502

propagation of a polarized knot spiraling down the jet, following helical magnetic field (e.g. BLLac, Marscher et al., 2008, Nature, 452, 966)

Similar behavior (degree of polarization) during Fermi campaign on 3C279: polarization degree a good precursor of γ-flares?

X-ray spectrum shows synchrotron component: transition between LBL-HBL states? E.g. reported on PKS2155-304

Y.H.Zhang, ApJ,682(2008)789

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BL Lacertae

MAGIC detection in 2005-2006flare end October 2005 ~MJD 53670

MAGIC Coll., ApJL 666 (2007) L17MAGIC Coll., ApJL 666 (2007) L17

A. Marscher et al., Nature 452 (2008) 966A. Marscher et al., Nature 452 (2008) 966



M87 RG z=0.0043, 16.7 Mpc

RadioVLBA 8 GHz

X-raysChandra

nucleus

HST-1

knot Dknot A

Harris+07

“misaligned blazar” (15-25o); 17 Mpc HEGRA hint; HESS/VERITAS detection

Candidate nearby CR site (hadronic emission?)

Variability?Site for TeV emission (core/HST-1)?



M87 MWL campaign jan-feb 2008

(triggered by MAGIC detection on 1st February flare)

9.9σ detection; 8.0σ single night 1st-feb First spectrum at E>100 GeV

Marginal hint of spectral hardening

Clear <~daily variability at E>350GeV Chandra observations ⇒ core/HST-1

contribution (core active / HST1 dim)

Science, 325 (2009) 444

Joint paper MAGIC-VERITAS-HESS-VLBI-Chandra MAGIC coll. ApJL, 685 (2008)

Apr07 Jul07 Oct07 Jan08 Apr08

VHE

HST-1

nucleus

X-ray

radio

jet

Nucleus ~100Rs

Nucleus radiobrightening



Goal 2: lightcurve

AGN, µQSO ⇒ days, minutes

Pulsar ⇒ ms

#ph / ∆T Time resolution

X-ray

TeV

Crab pulsar

33 ms

26 days

LS I+61 303

0.15-0.25 TeV

0.25-0.6 TeV

0.6-1.2 TeV

1.2-10 TeV 4 min lag

Mrk 501

20 minutes



Crab pulsar Cutoff depends on the acceleration

and radiation process (outer gap/polar cap) Absorption in magnetosphere

(magnetic/photon pair production) Maximum acceleration energy

First hint at E~>60 GeV

Albert et al. 2008, ApJ, 674, 1037



Crab pulsar

Lower trigger threshold: new trigger system (sum-trigger)

M. Teshima et al. 2008, Atel #1421MAGIC coll., Science 322 (2008) 1221



LS I +61 303o High Mass X-ray Binary (2kpc)

o Be star orbiting unknown object (NS-BH)

o P=26.5d; e=0.72

o X-ray emission at

o Φ~0.5

o GeV-emitter (3EG 0241+6103)

⇒ Candidate for TeV emission

Mirabel 2006

Relativistic electrons from accretion powered jet

Relativistic electrons from rotational energy of pulsar

Relativistic Jet radio structures: µ-QSO nature? (Massi et al. 2004)

Cometarylike radio structure: interaction of pulsar/jet wind Massi et al 2004

M. Massi et al., A&A 414, L1 (2004) J.Albert et al., ApJ, 684, 1351 (2008)

10 mas100 mas



LS I +61 303

MAGIC observations 2005-2006 (54 hrs, 6 orbits)

8.7 sigma; point-like; max at Φ~0.6-0.7

MAGIC Coll. 2006, Science, 312, 1771



F

(E

> 4

00 G

eV)

LS I +61 303

2nd campaign - sep-dec 2006; 112 hrs

Hint of X-ray/TeV emission correlation

No time correlation with radio Highest emission at Φ=0.65 Periodicity: 26.8±0.2 days No significant spectral changes

with phase

Swift/XRT0.3-10 keV

P.Esposito et al 2007

MAGICE>400GeV

æ 1stcampaignPhase 0.6 - 0.7Phase 0.5 - 0.6Phase 0.4 - 0.7 (1st campaign)

Periastron

MAGIC coll. 2009, ApJ, 693, 303



LS I+61 303

Simultaneous MWL campaign, single period

XMM, Swift, MAGIC - sep 2007; Clear X-ray/TeV emission

correlation No radio-TeV(X-ray) correlation Highest emission at Φ=0.65 No significant spectral changes

with phase X-ray

TeV

MAGIC coll. 2009, ApJ Lett. 706, L27



⇒⇒ Interaction with Extragalactic Background Interaction with Extragalactic Background Light (EBL)Light (EBL)

⇒ energy dependent energy dependent γγ -ray absorption -ray absorption

⇒ modification of original spectrummodification of original spectrum

Î ¦Î ³o b s e r v e d E Î ¦

Î ³u n a b s o r b e dE e

Ï„ EÎ ³

, z

ττ (E,z): Optical Depth(E,z): Optical DepthGamma Ray Horizon (GRH): Gamma Ray Horizon (GRH):

ττ=1=1

EBLEBL

EHEε EBL=3.6(mec2)2

Emitted spectrum

observed spect.

High absorption

Low absorption

Energy

Energ

y flux

Energy

Energy

Î» 1 .2 4m mE

g

1 T e V1 z2



Cosmic backgrounds



CIB: modelli

Primack (2005)



http://wwwmagic.mppmu.mpg.de/[email protected]@pi.infn.ithttp://www.pi.infn.it/magic/http://www.pi.infn.it/magic/

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