Post on 29-Jan-2016
description
TeVPA, SLAC, 2009
Pratik MajumdarPratik MajumdarDESY, ZeuthenDESY, Zeuthen
(for the MAGIC Collaboration)(for the MAGIC Collaboration)
Outline: MAGIC Telescope Observations of High
redshift AGNs Conclusions
MAGIC Observations of High Redshift AGNs
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
TeVPA, SLAC, 2009
The MAGIC telescope
• Largest single dish Cherenkov Telescope: 17 m Ø mirror dish, mirror surface (241 m2 )
• 3.5° FoV Camera with 577 enhanced QE PMT’s
• Fast repositioning for GRBs: average < 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 > 500 GeV )• Energy resolution: 20 - 30%
Canary Island La Palma 2200 m asl
First telescope in regular observation mode since fall 2004 Extended observations during Moon
TeVPA, SLAC, 2009
MAGIC AGN Physics Program Strategy
MWL campaigns on known TeV sources to MWL campaigns on known TeV sources to make precision studies of spectrum, make precision studies of spectrum, variability variability
Discover new sources at high redshifts, Discover new sources at high redshifts, test EBL test EBL
(extragalactic background light) models (extragalactic background light) models Vigorously pursued owing to its low Vigorously pursued owing to its low
threshold threshold
Long term monitoring of TeV blazarsLong term monitoring of TeV blazars
Why do we see high z objects
at all? Is the universe more transparent to VHE -rays than assumed?
Limits on EBL ?
Can VHE data give vital inputs to distinuish
between different models ?
TeVPA, SLAC, 2009
VHE detections using Optical Triggers
Regular optical monitoring of candidate sources by KVA optical telescope at LaPalma Continuing the success stories of Mrk180 and 1ES1011+496
S5 0716+714Trigger in April
2008
Preliminary
Optical trigger on S50716+714: MAGIC observations in 2008 April
→ 2.6h of data, clear signal (6.8 σ): 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 discovery Apr 23-25F(>400 GeV) ≈ 10-11 ph/cm²/s (≈25% Crab) : (paper in prep.)
Host Galaxy detected Z=0.31+/-0.08
(Nilson 08), 2nd farthest VHE emitter
Host Galaxy detected Z=0.31+/-0.08
(Nilson 08), 2nd farthest VHE emitter
3rd low-peaked
VHE Blazarafter BL Lac
&W Comae
3rd low-peaked
VHE Blazarafter BL Lac
&W Comae
arXiv:0907.2386
TeVPA, SLAC, 2009
S50716+714 ( Contd.)
Collecting all data from 2007 to 2008
SSC model predicts a huge GeV flux
Structured jet model could be an interesting alternative
( Ghisellini et al (2005) )
Preliminary
Preliminary
Preliminary
10.3 good hrs in 2007, 2.8 in 2009 (Zd ~ 42 to 55 deg )
TeVPA, SLAC, 2009
3C 279 (z = 0.536)Wehrle et al. 1998
x100
• EGRET brightest AGN ( Wehrle et. al 1998)EGRET brightest AGN ( Wehrle et. al 1998)• Gamma-ray flares in 1991 and 1996 Gamma-ray flares in 1991 and 1996 • Apparent luminosity ~ 10Apparent luminosity ~ 10erg/serg/s• Fast time variation T ~ 6hr in 1996 flareFast time variation T ~ 6hr in 1996 flare
• 9.7 hours, 10 nights from 9.7 hours, 10 nights from January to April January to April
• Clear detection on 23Clear detection on 23rdrd Feb Feb
(5.8(5.8 after trial), after trial), marginal on 22marginal on 22ndnd. .
• No short scale variability in No short scale variability in opticaloptical
• VHE distance champion !!!VHE distance champion !!!
MAGIC observations
TeVPA, SLAC, 2009
Implications on Extragalactic Background Light
• Powerlaw Powerlaw =- 4.11+/-0.68=- 4.11+/-0.68• Spectrum sensitive to 0.2 to 2 Spectrum sensitive to 0.2 to 2 mm• Deabsorption using Low Deabsorption using Low
density model ( Primack ) and high density model ( Primack ) and high one ( Stecker fast evolution)one ( Stecker fast evolution)
• Assuming Assuming model model parameters based on Kneiske parameters based on Kneiske et.al can be tuned to give EBL et.al can be tuned to give EBL upper limitupper limit No internal absorption taken into No internal absorption taken into
accountaccount
TeVPA, SLAC, 2009
Caveats and Open Issues
• Alternative emission models can produce spectra Alternative emission models can produce spectra
• Internal absorption by photon fieldsInternal absorption by photon fields can produce hard spectra can produce hard spectra (Bednarek(Bednarek
1997, Aharonian et.al 2008,Tavecchio1997, Aharonian et.al 2008,Tavecchio
and Mazin 2008and Mazin 2008 ) )
• SSC model with narrow electron distribution can SSC model with narrow electron distribution can
produce produce
spectra ~ 0.7 spectra ~ 0.7
Intrinsic absorption is redshift Intrinsic absorption is redshift
dependent and can mimic EBL evolution dependent and can mimic EBL evolution ( Reimer 2007 )( Reimer 2007 )
Position of the emitting region crucial for internal absorption studies ( Liu, Bai etal 2009)
Presence of ALP ? ( Roncadelli et al ) ( see D. Paneque’s talk )
R = rBLRin
R = rBLRout
arXiv:0905.1447v1
TeVPA, SLAC, 2009
Implications on SED
• Optical (BVRI) and X-ray (RXTE) Optical (BVRI) and X-ray (RXTE) data available , X-ray flare follows data available , X-ray flare follows VHE flare by about 5-7 VHE flare by about 5-7 days,optical state high, but little days,optical state high, but little variabilityvariability
• One zone EC model : steep One zone EC model : steep optical spectrum, soft X-ray optical spectrum, soft X-ray spectrum spectrum unusually low B ( ~ unusually low B ( ~ 0.03 G)0.03 G)
or high or high factors , X-ray flux factors , X-ray flux cannot be reproduced. cannot be reproduced.
• Multizone emission regionMultizone emission region• Hadronic model seems to Hadronic model seems to
describe the data well with or describe the data well with or without external radiation field as without external radiation field as target for ptarget for p interactions interactions
• Future MWL campaigns will be key to constrain emission models
arXiv:0810.4864
TeVPA, SLAC, 2009
3c279 Observations in 2007
• New observations after an optical New observations after an optical outburst in January 2007outburst in January 2007
• 9 nights from 149 nights from 14thth till 22 till 22ndnd January January• Only 16Only 16thth shows significant signal shows significant signal
at 5.6 sigma ( 150 mins of data )at 5.6 sigma ( 150 mins of data )
( not corrected for trials ) ( not corrected for trials )
Preliminary
• No significant emission on other No significant emission on other nightsnights
TeVPA, SLAC, 2009
3c279 Observations in 2007
• Extensive MWL campaign Extensive MWL campaign organised in 2009organised in 2009
Data analysis close to finish, Data analysis close to finish,
stay tuned…… stay tuned……
Preliminary
• Spectrum hard as in 2006Spectrum hard as in 2006• SED and physics SED and physics
interpretetion sooninterpretetion soon
Gamma ray flare seems to come Gamma ray flare seems to come
during optical decay !!!during optical decay !!!
X-ray data sparseX-ray data sparse
• Challenge for conventional Challenge for conventional modelsmodels
Preliminary
MAGIC
RXTE
Optical, KVA
Chatterjee et al
TeVPA, SLAC, 2009
Upper Limits on 3C454.3• Well known AGN ( z =0.859), many observations Well known AGN ( z =0.859), many observations
by EGRET, highly variable emissionby EGRET, highly variable emission• in 2007 intense flaring observed in 2007 intense flaring observed
in opticalin optical, triggerred observations , triggerred observations
in X-rays (Swift), in X-rays (Swift),
AGILE : intense emission in summer 2007 AGILE : intense emission in summer 2007
and in November-December 2007and in November-December 2007• Triggerred by these observations, Triggerred by these observations,
MAGIC observations : MAGIC observations :
9.6 hours (July to August),9.6 hours (July to August),
6.8 hours ( Nov-Dec)6.8 hours ( Nov-Dec)
No emission seen, UL derived.No emission seen, UL derived.
Consistent with leptonic Consistent with leptonic
EC models, cutoff at 20-30 GeVEC models, cutoff at 20-30 GeV
( Maraschi & Tavecchio , 2003)( Maraschi & Tavecchio , 2003)
arXiv:0809.1737v1
TeVPA, SLAC, 2009
Conclusions Highly successful AGN program, discovered Highly successful AGN program, discovered
few high redshift objectsfew high redshift objects
1515 detections under detections under Extragalactic sourceExtragalactic source
program, program, 8 discoveries8 discoveries, Active monitoring and MWL , Active monitoring and MWL campaigns organised on known sources to study campaigns organised on known sources to study them deeply. them deeply.
22ndnd MAGIC telescope almost end of commissioning MAGIC telescope almost end of commissioning phase => will improve sensitivity of the MAGIC phase => will improve sensitivity of the MAGIC system. system.
Preliminary
Mrk421 in June 2009
First Stereo Signal
TeVPA, SLAC, 2009
Backup
TeVPA, SLAC, 2009
What is EBL?
• Unique imprint of the Unique imprint of the history of the history of the universeuniverse
• Test of star Test of star formation and galaxy formation and galaxy evolution modelsevolution models
• Cosmological Cosmological evolution models evolution models have to explain have to explain current EBLcurrent EBL
• Opacity source of Opacity source of GeV-TeV photonsGeV-TeV photonsRed shifted stellar
light Red shifted dust light
Dwek&Krennrich 05, Kneiske et al. 04
2.7K
TeVPA, SLAC, 2009
EBL Absorption
e-e+
EBL
VH
E
blazarIACT
TeVPA, SLAC, 2009
Extragalactic VHE -ray sources:
• AGN with relativistic jet aligned with observer’s line of sight
(exception M87, Cen A, 3c66B…)• non-thermal emission, highly variable• High Doppler factors, jets may attain
high luminosities
Blazars:
Jet
Black
Hole
Obscuring
Torus
NarrowLineRegion
BroadLineRegion
AccretionDisk
Urry & Padovani (1995)
blazar
E2 d
F/d
E
energy E
0decay
IC
• discriminate hadronic vs leptonic acceleration
• leptonic models (SSC or EC) favoured due to X-ray/TeV correaltions in some objects
• Still not well known : - Variability scales - correlations with other
wavelengths : optical/radio
TeVPA, SLAC, 2009
Observations in the vicinity of 3c66A• 3C66A blazar at z = 0.44 3C66A blazar at z = 0.44
(controversial )(controversial )• In September 2008, In September 2008,
VERITAS reported detection VERITAS reported detection
at > 100 GeV (see ATEL # 1753 )at > 100 GeV (see ATEL # 1753 )• 3C66B : a large FRI radio galaxy, 6’ 3C66B : a large FRI radio galaxy, 6’
away from 3C66A ( z = 0.0215 ) away from 3C66A ( z = 0.0215 ) • MAGIC observations after an MAGIC observations after an
optical outburst in Augustoptical outburst in August• Total time : 54.2 hrs, 6Total time : 54.2 hrs, 6 signal signal
( 5.4( 5.4 after trial correction ), 2.2% after trial correction ), 2.2% Crab > at 150 GeV , Spectrum : -Crab > at 150 GeV , Spectrum : -3.1+/-0.313.1+/-0.31
• Excess 6.1’ away from 3C66A Excess 6.1’ away from 3C66A
MAGIC J0233+430• From simulations of skymaps, From simulations of skymaps,
exclusion probability from 3C66A is exclusion probability from 3C66A is 85.4% ( including systematics in 85.4% ( including systematics in pointing accuracy ) pointing accuracy )
Published in ApJL