Pratik%20Majumdar

1
MAGIC Observations of High Redshift AGNs

• Outline
• MAGIC Telescope
• Observations of High redshift AGNs
• Conclusions

Pratik Majumdar DESY, Zeuthen (for the MAGIC
Collaboration)
Instituto de Astrofisica, Andalucia, Barcelona
IFAE, UA Barcelona, U. Barcelona, HU Berlin,
Instituto Astrofisica Canarias, R.B. Inst.,
Croatia, U.C. Davis, U. Dortmund, DESY Zeuthen,
IEEC-CSIC, Spain, U. Lodz, UCM Madrid, MPI
München, INFN/ U. Padua, INAF, INFN/ U. Siena,
INR Sofia, Tuorla Observatory, Yerevan Phys.
Institute, INFN/ U. Udine, U. Würzburg, ETH Zürich
2
The MAGIC telescope
First telescope in regular observation mode since
fall 2004 Extended observations during Moon

• Largest single dish Cherenkov Telescope 17 m Ø
  mirror dish, mirror surface (241 m2 )
• 3.5 FoV Camera with 577 enhanced QE PMTs
• Fast repositioning for GRBs average lt 40 s
• Low energy trigger threshold
• 50 - 60 GeV
• Sensitivity 1.6 Crab / 50 h
• (improvement with 2 GHz sampling
• and timing parameters in g/h separation)
• ?-PSF 0.1 ( E gt 500 GeV )
• Energy resolution 20 - 30

3
MAGIC AGN Physics Program Strategy

• MWL campaigns on known TeV sources to make
  precision studies of spectrum, variability
• Discover new sources at high redshifts, test
  EBL
• (extragalactic background light) models
• Vigorously pursued owing to its low threshold
• Long term monitoring of TeV blazars

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VHE detections using Optical Triggers
Regular optical monitoring of candidate sources
by KVA optical telescope at LaPalma Continuing
the success stories of Mrk180 and 1ES1011496
Preliminary
S5 0716714 Trigger in April 2008
Host Galaxy detected Z0.31/-0.08 (Nilson 08),
2nd farthest VHE emitter
3rd low-peaked VHE Blazar after BL Lac W Comae
Optical trigger on S50716714 MAGIC
observations in 2008 April? 2.6h of data, clear
signal (6.8 s) DISCOVERY

• April 28 Swift reports F(0.3-10 keV) 4x10-11
  erg/cm²/s,
• about 50 larger than that observed in 2007
• Apr 29 ATel 1500, MAGIC reports 6.8 s discovery
  Apr 23-25
• F(gt400 GeV) 10-11 ph/cm²/s (25 Crab) (paper
  in prep.)

arXiv0907.2386
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S50716714 ( Contd.)
Preliminary
Preliminary
Preliminary
Collecting all data from 2007 to 2008
10.3 good hrs in 2007, 2.8 in 2009 (Zd 42 to 55
deg )
SSC model predicts a huge GeV flux Structured jet
model could be an interesting alternative (
Ghisellini et al (2005) )
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3C 279 (z 0.536)

• EGRET brightest AGN ( Wehrle et. al 1998)
• Gamma-ray flares in 1991 and 1996
• Apparent luminosity 1048 erg/s
• Fast time variation T 6hr in 1996 flare

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Implications on Extragalactic Background Light

• Powerlaw G- 4.11/-0.68
• Spectrum sensitive to 0.2 to 2 mm
• Deabsorption using Low
• density model ( Primack ) and high one (
  Stecker fast evolution)
• Assuming a gt 1.5, model parameters based on
  Kneiske et.al can be tuned to give EBL upper limit

No internal absorption taken into account
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Caveats and Open Issues

• Alternative emission models can produce spectra
  a lt 1.5
• Internal absorption by photon fields
• can produce hard spectra (Bednarek
• 1997, Aharonian et.al 2008,Tavecchio
• and Mazin 2008 )
• SSC model with narrow electron distribution can
  produce
• spectra 0.7
• Intrinsic absorption is redshift
• dependent and can mimic EBL evolution
• ( Reimer 2007 )
• Position of the emitting region crucial for
  internal absorption studies ( Liu, Bai etal 2009)
• Presence of ALP ? ( Roncadelli et al )
• ( see D. Paneques talk )

arXiv0905.1447v1
Rg rBLRout
Rg rBLRin
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Implications on SED

• Optical (BVRI) and X-ray (RXTE) data available ,
  X-ray flare follows VHE flare by about 5-7
  days,optical state high, but little variability
• One zone EC model steep optical spectrum, soft
  X-ray spectrum ? unusually low B ( 0.03 G)
• or high G factors , X-ray flux cannot be
  reproduced.
• Multizone emission region
• Hadronic model seems to describe the data well
  with or without external radiation field as
  target for pg interactions

arXiv0810.4864

• Future MWL campaigns will be key to constrain
  emission models

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3c279 Observations in 2007

• New observations after an optical outburst in
  January 2007
• 9 nights from 14th till 22nd January
• Only 16th shows significant signal at 5.6 sigma
  ( 150 mins of data )
• ( not corrected for trials )

Preliminary

• No significant emission on other nights

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3c279 Observations in 2007

• Spectrum hard as in 2006
• SED and physics
• interpretetion soon
• Gamma ray flare seems to come
• during optical decay !!!
• X-ray data sparse

Preliminary
MAGIC
RXTE
Chatterjee et al

• Challenge for conventional models

Optical, KVA

• Extensive MWL campaign organised in 2009
• Data analysis close to finish,
• stay tuned

Preliminary
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Upper Limits on 3C454.3
arXiv0809.1737v1

• Well known AGN ( z 0.859), many observations
• by EGRET, highly variable emission
• in 2007 intense flaring observed
• in optical, triggerred observations
• in X-rays (Swift),
• AGILE intense emission in summer 2007
• and in November-December 2007
• Triggerred by these observations,
• MAGIC observations
• 9.6 hours (July to August),
• 6.8 hours ( Nov-Dec)
• No emission seen, UL derived.
• Consistent with leptonic
• EC models, cutoff at 20-30 GeV
• ( Maraschi Tavecchio , 2003)

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Conclusions
Highly successful AGN program, discovered few
high redshift objects 15 detections under
Extragalactic source program, 8 discoveries,
Active monitoring and MWL campaigns organised on
known sources to study them deeply. 2nd MAGIC
telescope almost end of commissioning phase gt
will improve sensitivity of the MAGIC system.

Preliminary
First Stereo Signal
Mrk421 in June 2009
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Backup
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What is EBL?
DwekKrennrich 05, Kneiske et al. 04

• Unique imprint of the history of the universe
• Test of star formation and galaxy evolution
  models
• Cosmological evolution models have to explain
  current EBL
• Opacity source of GeV-TeV photons

2.7K
Red shifted stellar light
Red shifted dust light
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EBL Absorption
blazar
IACT
?VHE
?EBL
e
e-
17
Extragalactic VHE ?-ray sources
Narrow Line Region
Jet
Source Redshift z type
Mrk 421 0.030 HBL
Mrk 501 0.034 HBL
1ES 2344514 0.044 HBL
Mrk 180 0.045 HBL
1ES 1959650 0.047 HBL
BL Lac 0.069 LBL
PKS 2155-304 0.117 HBL
1ES 1218308 0.182 HBL
1ES 1011496 0.212 HBL
3C 279 0.536 FSRQ
PG 1553113 gt 0.09 HBL
Broad Line Region
Black Hole
Accretion Disk

• discriminate hadronic vs leptonic acceleration
• leptonic models (SSC or EC) favoured due to
  X-ray/TeV correaltions in some objects

Obscuring Torus
Urry Padovani (1995)
blazar
Blazars

• Still not well known
• - Variability scales
• - correlations with other wavelengths
  optical/radio

• AGN with relativistic jet aligned with observers
  line of sight
• (exception M87, Cen A, 3c66B)
• non-thermal emission, highly variable
• High Doppler factors, jets may attain high
  luminosities

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Observations in the vicinity of 3c66A

• 3C66A blazar at z 0.44 (controversial )
• In September 2008,
• VERITAS reported detection
• at gt 100 GeV (see ATEL 1753 )
• 3C66B a large FRI radio galaxy, 6 away from
  3C66A ( z 0.0215 )
• MAGIC observations after an optical outburst in
  August
• Total time 54.2 hrs, 6s signal ( 5.4s after
  trial correction ), 2.2 Crab gt at 150 GeV ,
  Spectrum -3.1/-0.31
• Excess 6.1 away from 3C66A MAGIC J0233430
• From simulations of skymaps, exclusion
  probability from 3C66A is 85.4 ( including
  systematics in pointing accuracy )

Published in ApJL