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Pratik Majumdar DESY, Zeuthen (for the MAGIC Collaboration)

MAGIC Observations of High Redshift AGNs. Outline: MAGIC Telescope Observations of High redshift AGNs Conclusions. Pratik Majumdar DESY, Zeuthen (for the MAGIC Collaboration).

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Pratik Majumdar DESY, Zeuthen (for the MAGIC Collaboration)

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  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 TeVPA, SLAC, 2009

  2. Canary IslandLa Palma 2200 m asl The MAGICtelescope 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 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% TeVPA, SLAC, 2009

  3. Why do we see high z objects at all? Is the universe more transparent to VHE g-rays than assumed? Limits on EBL ? Can VHE data give vital inputs to distinuish between different models ? 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 TeVPA, SLAC, 2009

  4. 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 Preliminary S5 0716+714 Trigger in April 2008 Host Galaxy detected Z=0.31+/-0.08 (Nilson 08), 2nd farthest VHE emitter 3rd low-peaked VHE Blazar after BL Lac & W Comae 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 s discovery Apr 23-25 • F(>400 GeV) ≈10-11 ph/cm²/s (≈25% Crab) : (paper in prep.) arXiv:0907.2386 TeVPA, SLAC, 2009

  5. S50716+714 ( 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) ) TeVPA, SLAC, 2009

  6. Wehrle et al. 1998 x100 MAGIC observations • 9.7 hours, 10 nights from January to April • Clear detection on 23rd Feb (5.8s after trial), marginal on 22nd. • No short scale variability in optical • VHE distance champion !!! 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 TeVPA, SLAC, 2009

  7. 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* > 1.5, model parameters based on Kneiske et.al can be tuned to give EBL upper limit No internal absorption taken into account TeVPA, SLAC, 2009

  8. Caveats and Open Issues • Alternative emission models can produce spectra a* < 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. Paneque’s talk ) arXiv:0905.1447v1 Rg = rBLRout Rg = rBLRin TeVPA, SLAC, 2009

  9. 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 arXiv:0810.4864 • Future MWL campaigns will be key to constrain emission models TeVPA, SLAC, 2009

  10. 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 TeVPA, SLAC, 2009

  11. 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 TeVPA, SLAC, 2009

  12. Upper Limits on 3C454.3 arXiv:0809.1737v1 • 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) TeVPA, SLAC, 2009

  13. 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 => will improve sensitivity of the MAGIC system. Preliminary First Stereo Signal Mrk421 in June 2009 TeVPA, SLAC, 2009

  14. Backup TeVPA, SLAC, 2009

  15. What is EBL? • 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 Dwek&Krennrich 05, Kneiske et al. 04 2.7K Red shifted stellar light Red shifteddust light TeVPA, SLAC, 2009

  16. EBL Absorption blazar IACT VHE EBL e+ e- TeVPA, SLAC, 2009

  17. IC E2 dF/dE 0decay energy E Extragalactic VHE -raysources: Narrow Line Region Jet 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 observer’s line of sight (exception M87, Cen A, 3c66B…) • non-thermal emission, highly variable • High Doppler factors, jets may attain high luminosities TeVPA, SLAC, 2009

  18. Observations in the vicinity of 3c66A • 3C66A blazar at z = 0.44 (controversial ) • In September 2008, VERITAS reported detection at > 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 > at 150 GeV , Spectrum : -3.1+/-0.31 • Excess 6.1’ away from 3C66A MAGIC J0233+430 • From simulations of skymaps, exclusion probability from 3C66A is 85.4% ( including systematics in pointing accuracy ) Published in ApJL TeVPA, SLAC, 2009

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