TeVPA, SLAC, 2009 Pratik Majumdar DESY, Zeuthen (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 m 2 ) 3.5° FoV Camera with 577 enhanced QE PMT’s Fast repositioning for GRBs: average < 40 s Low energy trigger threshold: 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: % 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 make precision studies of spectrum, variability MWL campaigns on known TeV sources to make precision studies of spectrum, variability Discover new sources at high redshifts, test EBL Discover new sources at high redshifts, test EBL (extragalactic background light) models Vigorously pursued owing to its low threshold Vigorously pursued owing to its low threshold Long term monitoring of TeV blazars Long 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 1ES S Trigger in April 2008 Preliminary Optical trigger on S : MAGIC observations in 2008 April → 2.6h of data, clear signal (6.8 σ): DISCOVERY ‣ April 28: Swift reports F( keV) = 4x erg/cm²/s, about 50% larger than that observed in 2007 ‣ Apr 29: ATel #1500, MAGIC reports 6.8  discovery Apr F(>400 GeV) ≈ ph/cm²/s (≈25% Crab) : (paper in prep.) Host Galaxy detected Z=0.31+/-0.08 (Nilson 08), 2 nd farthest VHE emitter Host Galaxy detected Z=0.31+/-0.08 (Nilson 08), 2 nd farthest VHE emitter 3rd low- peaked VHE Blazar after BL Lac & W Comae 3rd low- peaked VHE Blazar after BL Lac & W Comae arXiv:

TeVPA, SLAC, 2009 S ( 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 10.3 good hrs in 2007, 2.8 in 2009 (Zd ~ 42 to 55 deg )

TeVPA, SLAC, C 279 (z = 0.536) Wehrle et al 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 ~ 10  erg/s Apparent luminosity ~ 10  erg/s Fast time variation T ~ 6hr in 1996 flare Fast time variation T ~ 6hr in 1996 flare 9.7 hours, 10 nights from January to April 9.7 hours, 10 nights from January to April Clear detection on 23 rd Feb Clear detection on 23 rd Feb (5.8  after trial), marginal on 22 nd. (5.8  after trial), marginal on 22 nd. No short scale variability in optical No short scale variability in optical VHE distance champion !!! VHE distance champion !!! MAGIC observations

TeVPA, SLAC, 2009 Implications on Extragalactic Background Light Powerlaw  = /-0.68 Powerlaw  = /-0.68 Spectrum sensitive to 0.2 to 2  m Spectrum sensitive to 0.2 to 2  m Deabsorption using Low Deabsorption using Low density model ( Primack ) and high one ( Stecker fast evolution) density model ( Primack ) and high one ( Stecker fast evolution) Assuming    model parameters based on Kneiske et.al can be tuned to give EBL upper limit Assuming    model parameters based on Kneiske et.al can be tuned to give EBL upper limit No internal absorption taken into account

TeVPA, SLAC, 2009 Caveats and Open Issues Alternative emission models can produce spectra    Alternative emission models can produce spectra    Internal absorption by photon fields Internal absorption by photon fields can produce hard spectra (Bednarek can produce hard spectra (Bednarek 1997, Aharonian et.al 2008,Tavecchio 1997, Aharonian et.al 2008,Tavecchio and Mazin 2008 ) and Mazin 2008 ) SSC model with narrow electron distribution can produce SSC model with narrow electron distribution can 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  = r BLRin R  = r BLRout arXiv: v1

TeVPA, SLAC, 2009 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 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) One zone EC model : steep optical spectrum, soft X-ray spectrum  unusually low B ( ~ 0.03 G) or high  factors, X-ray flux cannot be reproduced. or high  factors, X-ray flux cannot be reproduced. Multizone emission region Multizone emission region Hadronic model seems to describe the data well with or without external radiation field as target for p  interactions Hadronic model seems to describe the data well with or without external radiation field as target for p  interactions Future MWL campaigns will be key to constrain emission models arXiv:

TeVPA, SLAC, c279 Observations in 2007 New observations after an optical outburst in January 2007 New observations after an optical outburst in January nights from 14 th till 22 nd January 9 nights from 14 th till 22 nd January Only 16 th shows significant signal at 5.6 sigma ( 150 mins of data ) Only 16 th shows significant signal at 5.6 sigma ( 150 mins of data ) ( not corrected for trials ) ( not corrected for trials ) Preliminary No significant emission on other nights No significant emission on other nights

TeVPA, SLAC, c279 Observations in 2007 Extensive MWL campaign organised in 2009 Extensive MWL campaign organised in 2009 Data analysis close to finish, Data analysis close to finish, stay tuned…… stay tuned…… Preliminary Spectrum hard as in 2006 Spectrum hard as in 2006 SED and physics SED and physics interpretetion soon interpretetion soon Gamma ray flare seems to come Gamma ray flare seems to come during optical decay !!! X-ray data sparse Challenge for conventional models Challenge for conventional models 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 emission by EGRET, highly variable emission in 2007 intense flaring observed in 2007 intense flaring observed in optical, triggerred observations in optical, 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 2007 and 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 EC models, cutoff at GeV EC models, cutoff at GeV ( Maraschi & Tavecchio, 2003) ( Maraschi & Tavecchio, 2003) arXiv: v1

TeVPA, SLAC, 2009 Conclusions Highly successful AGN program, discovered Highly successful AGN program, discovered few high redshift objects few high redshift objects 15 detections under Extragalactic source 15 detections under Extragalactic source program, 8 discoveries, Active monitoring and MWL campaigns organised on known sources to study them deeply. program, 8 discoveries, Active monitoring and MWL campaigns organised on known sources to study them deeply. 2 nd MAGIC telescope almost end of commissioning phase => will improve sensitivity of the MAGIC system. Preliminary Mrk421 in June 2009 First Stereo Signal

TeVPA, SLAC, 2009 Backup

TeVPA, SLAC, 2009 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 Red shifted stellar light Red shifted dust light Dwek&Krennrich 05, Kneiske et al K

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

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: Source Redshift z type Mrk HBL Mrk HBL 1ES HBL Mrk HBL 1ES HBL BL Lac 0.069LBL PKS HBL 1ES HBL 1ES HBL 3C FSRQ PG > 0.09HBL Jet Black Hole Obscuring Torus Narrow Line Region Broad Line Region Accretion Disk Urry & Padovani (1995) blazar E 2 dF/dE energy E  0 decay 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 (controversial ) 3C66A blazar at z = 0.44 (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’ away from 3C66A ( z = ) 3C66B : a large FRI radio galaxy, 6’ away from 3C66A ( z = ) MAGIC observations after an optical outburst in August MAGIC observations after an optical outburst in August Total time : 54.2 hrs, 6  signal ( 5.4  after trial correction ), 2.2% Crab > at 150 GeV, Spectrum : -3.1+/-0.31 Total time : 54.2 hrs, 6  signal ( 5.4  after trial correction ), 2.2% Crab > at 150 GeV, Spectrum : -3.1+/-0.31 Excess 6.1’ away from 3C66A Excess 6.1’ away from 3C66A MAGIC J From simulations of skymaps, exclusion probability from 3C66A is 85.4% ( including systematics in pointing accuracy ) From simulations of skymaps, exclusion probability from 3C66A is 85.4% ( including systematics in pointing accuracy ) Published in ApJL