Physics Insights from Recent MAGIC AGN Observations

Transcription

1 Physics Insights from Recent MAGIC AGN Observations R. M. Wagner on behalf of the MAGIC Collaboration Max-Planck-Institut für Physik & Excellence Cluster Universe München Introduction: MAGIC Recent Multiwavelength Campaigns Delay in Mkn 501 Flare ToO Detections on Optical High States Dissecting the Blazar Phenomenon: M87 New VHE emitters: MAGIC J (3C 66B/A), 3C 279 Cosmological γ-rays as Test Beams: Extragalactic Background Light, Lorenz Invariance Tests

2 The Imaging Air Cherenkov Technique Extended Air Shower initiated in atmosphere Detect the Cherenkov radiation from charged particles in EAS A mirror reflects and concentrates the light An image of the shower formed in the camera Gamma event Hadron event 15 km Ch er en ko vl igh t ~ 1o ~ 120 m Hadrons (background) dominate over gammas (signal). They must be rejected statistically in the analysis Works excellent > 0 GeV but very difficult < 0 GeV

3 The MAGIC Telescope(s) Currently a single-dish Cherenkov telescope, 17 m diameter Located at the European Northern Observatory, Instituto Astrofísica de Canarias on the Canary Island of La Palma, Spain In operation since fall 2004 (AO-5 in spring 2009) Substantially lower energy threshold than other installations: 55 GeV nominal 25 GeV pulsar ( sum ) trigger Sensitivity: 1.6% Crab in 50 h Angular resolution: 0.1 Energy resolution: ~ 20% Enhanced duty cycle (by 50%) thanks to moonlight & twilight observations Fast repositioning (<40 sec!) 2 nd telescope (MAGIC-II) first light this winter 150 physicists 23 institutes MPI leading institute MAGIC-1 Roque de los Muchachos observatory, 2200 m a.s.l. MAGIC-2 Details: Lorenz 04, Cortina 05, Goebel 07

4 AGNs & the Blazar Phenomenon Small fraction of observed galaxies Supermassive black holes of 6 solar masses Rotating accretion disk Emission of collimated, relativistic jets Blazars: Factories of violent, broad-band (up to high energy) non-thermal radiation Jets viewed under small angle Relativistic boosting, high Doppler factors High variability at all wavelengths Radio galaxies: Misaligned blazars? Other Blazar mechanisms? FSRQs External photon fields important/ dominant p + ( TeV) matter π + π 0 π - γ γ e (TeV) B γ (ev) synchrotron γ (ev kev) Urry+Padovani 95 γ-rays are messenger particles, may allow to probe properties of: leptonic acceleration hadronic acceleration inverse Compton γ (TeV)

5 Particle Acceleration in Blazars Distinguish hadronic vs. leptonic acceleration: Shape of spectrum, correlations, multi-wavelength leptonic models favored due to: X-ray/TeV correlation found in some objects (Mkn 501, PKS ) Recent review: RMW 08 (arxiv: ) Fast flaring: down to minutes! e.g., Ghisellini+08 (arxiv: ) We still do not know: Variability scales? Other correlations (optical, radio)? successful MAGIC ToOs! E.g., Lindfors+08 Open questions: Origin of γ-rays? Physical conditions in the jet? Reason for the variability? Buckley 99 synchrotron peak hadronic model Inverse Compton peak

6 MAGIC: AGNs in TeV γ-rays Recent overview: RMW, arxiv:08.68 MAGIC has discovered 8 new extragalactic sources: 1ES , Mkn 180, BL Lacertae, PG ES , S C 279 MAGIC J (=3C 66B/A region) 5 known extragalactic sources detected and studied: Mkn 421, Mkn 501, 1ES , 1ES Messier 87 Upper limits on emission from various BL Lac objects, 3C 454.3, Arp 220 Astrophysics: extragalactic background light Fundamental physics: e.g., Lorentz invariance

7 Our Old Friends : Bright Blazars, MWL Campaigns Mkn 501, Mkn 421, 1ES , Click to editpg Master title style

8 Northern Blazar Multi-Wavelength Campaigns Simultaneous Multifrequency Observations SEDs spanning over > 15 orders of magnitude VHE: HESS, MAGIC, VERITAS X-ray: Suzaku, Swift, Chandra, INTEGRAL Optical: KVA, GASP-WEBT Radio: Metsahövi,... Some recent Multi-Wavelength Campaigns: Mkn 421 April 06: clear detection in all instruments Mkn 501 July 06: lowest VHE state ever in MWL (MAGIC, Suzaku, KVA) Hayashida+07, MAGIC+ in prep. 1ES , 1H : significant X-ray variability, VHE still under study PG July 06: No significant variability, first MWL campaign with VHE, VHE compatible with earlier measurements MAGIC 09, Reimer+08 Mkn 421 June 08: clear detection during a flare (AGILE, WEBT, MAGIC, VERITAS) Donnarumma+09 Further campaigns completed, under progress, organized 8

9 PG Northern Blazar MW Campaigns First VHE MW campaign July 2006 Exposures: MAGIC 8.5h, HESS h, Suzaku 11.4 h MAGIC Collab., A&A 493 in press Reimer et al. ApJ 682 (2008) 775. Suzaku MAGIC No significant variability HESS MAGIC KVA Combined MAGIC-HESS VHE spectrum Click to edit Master title Reimer+08 extends from 75 GeV to 600 GeV style combined spectral slope α= 4.1±0.2 z>0.7 requires Γ<1.0 z 0.3: Sy & IC power about equal X spectral form extraordinarily stable Measurements 2001, 2003 (RXTE 5x lower), this campaign Reimer+08 9

10 1ES Multi-Wavelength campaign in May 2006: Suzaku, Swift, MAGIC Swift-XRT nights, Suzaku 2 nights Suzaku/Swift in good agreement Relatively high X-ray/optical flux, X-ray peak: shifts with increasing flux 14.3h VHE data: among lowest VHE flux (60% of low flux measured by MAGIC 2004) Highest/lowest XRT state (factor 2) Northern Blazar MW Campaigns One-zone SSC Suzaku/MAGIC w.r.t SED: similar parameters source slightly more compact (7.3 x 15 cm), magnetic field slightly lower (0.25 G) Doppler factor identical (D=18) no variability decay timescale d Tagliaferri et al. + MAGIC ApJ 679 (2008) 29 γ-ray light curve VHE monitors above Compton peak would expect high variability! X-ray decay d=2.7pc cannot be 1 blob standing shock?

11 Mkn 421 Northern Blazar MW Campaigns Donnarumma et al., ApJ Lett. in press (AGILE, MAGIC, VERITAS, GASP-WEBT) Hard X-ray flare 2008 June triggered MWL campaign kev flux 30 mcrab, order of magnitude larger than in quiescent state WEBT, Swift, MAGIC, VERITAS, AGILE participation Time variability: R<cTδ 5 16 (δ/20)cm SSC modeling: B=0.1 G Cause for variability? Spectral slope of electrons? TeV variability comparable to X-ray variab. Change of comoving particle density? (Injection of additional particles) TeV variability 2 larger than X-ray variab. Optical decay, no X-ray decay More complex scenarios, e.g. inner jet produces X-rays, partially transparent for VIS; Outer jet only VIS Variations of the order of % on a time-scale of few days, over-imposed to a long decay for the entire period Optical GASP-WEBT optical R-band Individual peaks: flux increase by factor!2.5. Individual peaks: flux increase by factor!5. BAT Swift-BAT kev MAGIC & VERITAS >400 GeV >400 GeV period 1 period 2 moon time ASM RXTE-ASM 2-12 kev Swift-XRT 2- kev Swift SuperAGILE kev AGILE >0 MeV Follow-up interpretative publication in preparation MAGIC & VERITAS Crab nebula

12 Bright Blazar Monitoring Statistical study of blazar emission states: regular & unbiased observations Flare hunting, orphan flares Goebel et al., arxiv: Satalecka et al., ASP Conf. Ser. in press Tluczykont+06 Ground state? Instrumental effect? Bright TeV Blazars: Mkn 501, Mkn 421 (very active VHE blazar), 1ES (famous for orphan VHE-only flare 2002), 1ES (MAGIC detection at rather low flux level 2005) 14-yr flux statistics Mkn 421 ( ) Up to 40 short observations per source evenly distributed over observable time during period Heavily rely on MAGIC s moon observation capabilities Possibility to extend observations, issue alert on high states Online analysis and multilateral IACT/satellite ToO alerts Frequent & successful alerts among facilites, e.g., for Mkn 421 Successful test of neutrino-triggered alerts Ackermann+07, arxiv: Galante 08 12

13 Bright Blazar Monitoring Satelecka et al. (MAGIC Collab.), ASP Conf. Ser. in press r=0.74± σ from zero preliminary X/VHE Mkn 421 preliminary Click O/VHE to edit Master title style 0.4 s -1 ] [cm -2 F E>300 GeV Mrk421 Optical/TeV Correlation preliminary Two Crab One Crab Mkn 501 preliminary R-band flux F O [Jy] 13

14 Energy-delayed flare: Mkn July 9: Delayed observation of high energies in the flare Quantification of the delay: Measured delay: (0.030±0.012) s GeV 1 Zero-delay probability P=0.026, effect marginal Interpretation of the observed delay: 1. Gradual acceleration of electrons 2. Gradually-accelerated blob model clear prediction for Fermi+IACT MWL 3. Brief episode of enhanced particle injection within SSC model 4. If extrinsic propagation effect attributed to Lorentz invariance violation c = c z=0.034 (D=146 Mpc) ( 1 + ξ E (Bednarek+RMW 08) (Mastichiadis+Moraitis 08) E Pl + χ E2 E 2 Pl > 0.25!0.60 TeV light curve 0.60!1.2 TeV >1.2 TeV light curve delay implies LIV: ξ 30, but marginal: ξ <60, ζ < probing the Planck mass scale, M QG > 0.21 x 18 GeV ) light curve 14 MAGIC Coll., ApJ 669 (2007) 892 Phys. Lett. B 668 (2008) 253 Quiescence In-Flare 21:50 22:00 22: 22:20 22:30 review: Scineghe 08, to appear in AIP Conf. Ser.

15 M87: A Unique Astrophysical Laboratory A. Marscher Hubble Heritage Team STScI/AURA and NASA/ESA 15

16 Giant Radio Galaxy M87 Radio VLBA 8 GHz X-rays: HST-1 sometimes brighter than nucleus Nature of the TeV emission? HST-1 core knot D Harris+07 knot A X-rays Chandra Beilicke, Mazin, Raue, RMW et al Colin et al., TODAY, right after lunch Leptonic or hadronic acceleration? Proton-induced cascades (Mannheim 93) Synchrotron proton radiation (Mücke+Protheroe 01; Aharonian 00) Might also account for parts of the UHECR? (Protheroe+03) Location of TeV emission? Core, HST-1, Knot A? close to the core (Georganopoulos+05; Ghisellini+05; Lenain+08; Tavecchio+Ghisellini+08) large-scale jet (Stawarz+03; Honda07) in the vicinity of BH (Neronov+Aharonian 07; Rieger+Aharonian 08) Collaborative VERITAS/MAGIC/H.E.S.S. monitoring aiming at good TeV coverage, Organized schedule, data exchange, Chandra & Swift coverage, 120 h in

17 Strong Flaring in M87 Beginning of 2008: Nucleus bright in X-rays (at all-time high), while HST-1 rather dim Strong signal: 8 σ on 2008 February 1: 9.9 σ in overall sample (22.8 h) 2008 January 30 February 11 TeV flux variable 3% 15% Crab, Apparent & high variability >350 GeV Day-scale variability (5.6 σ) -5 HST-1 core x knot D Harris+07 knot A X-rays Chandra Fast variability Knot A as VHE γ-ray source unlikely s -1 ) -2 integral flux, F (>350 GeV, cm ! s -1 ) -2 F (>350 GeV, cm -12! MAGIC Coll., ApJ 685 (2008) L23 Mazin, Tescaro, RMW et al. HDGS :00 06:00 07:00 08:00 time (hours:minutes) 17 (Harris, Cheung, Stawarz in prep.) M87, nightly flux % of Crab Nebula flux 29/01 30/01 31/01 01/02 02/02 03/02 04/02 05/02 06/02 07/02 08/02 09/02 /02 11/02 12/02 time (day/month) ) -1 TeV s -1-2 df/de (cm fit function: df = f de 0 2 M87-12 ph cm 2 s TeV f 0 = 2.89 ± 0.37 = ± / ndf = 1.42 / 4 E 1 TeV Crab Hard spectrum compatible with previous observations 3 M87 spectrum fit function Crab Nebula spectrum Energy (GeV) 4

18 New Discoveries, New TeV-AGN Subclasses LBLs, FSRQs, Radio Galaxies 3C 279 EGRET Skymap 18

19 Do Optical Triggers Work? Regular optical monitoring of candidate sources Mkn 180 ToO trigger MAGIC Collab., ApJ 648 (2006) L5, ApJ 667 (2007) L21 March h S=5.5 σ Flux [mjy] Optical light curves: KVA telescope, La Palma 1ES ToO trigger MAGIC 2006 MAGIC h S=6.2 σ March-May 07 Soft spectrum: Γ=3.3 after EBL deabsorption % Crab at 200 GeV No significant variability 3 σ in 2006 data. If 2006 signal genuine, then 50% lower flux than in ES From the optical spectrum we determined the redshift to be z = ± 0.02 Third-most distant VHE γ-ray source 19

20 A Continuing Success Story... MAGIC Collab., ATel 1500; Lindfors et HDGS08 Optical light curve: KVA telescope, La Palma S MAGIC PRELIMINARY KVA R-band optical Significance 6.8 σ Known Click blazar to with edit (then) unknown Master redshift title style October/November 2007: X-ray outburst, detected by Swift 3rd low-peaked April 17, 2008: Optical flux doubled within three nights VHE Blazar April 22, 2008: MAGIC observations commence after BL Lac & W Comae Optical trigger on S : MAGIC observations in 2008 April 2.6h of data, clear signal (6.8 σ): discovery! Host galaxy detected: April 28: Swift reports F(0.3- kev) = 4x -11 erg cm - ² s -1, z=0.31±0.08 Nilsson+08 about 50% larger than that observed in 2007 Apr 29: ATel #1500, MAGIC reports 6.8σ discovery Apr F(>400 GeV) 25% Crab 20

21 The 3C 66A/B region MAGIC Collab., ApJ in press arxiv: C 66A/B: just separated by 6 in the sky 3C 66B large FR-I radio galaxy, similar to M87, z=0.o215 3C 66A blazar with uncertain redshift, z=0.444 single emission line, host: z=0.321? Miller+78 3C 66A: VHE candidate source EGRET: 3EG J associated with 3C 66a Hartman+99 EGRET error box also covers 3C 66B and PSR J Detections by Crimea group, yet only HEGRA & Whipple U.L. Sept 2008: Clear VERITAS detection above 0 % Crab Swordy 08, ATel 1753 Shortly after: Fermi GRT reports high state > 20 MeV Tosti 08, ATel 1759 Wurtz+96 Optical outburst in August 2007 triggered MAGIC observations, 54.2 h in total August to December 2007 Another Optical ToO Varying PSF due to mirror replacements in that period Varying mispointing during different observation epochs Separate analysis for different PSF periods (2 systematic uncertainty) Bretz+08 21

22 The 3C 66A/B region Smoothed significance map for 150 GeV to 1 TeV γ-rays 6 MAGIC γ PSF CoG from 2-dim Gaussian fit: MAGIC J away from 3C66A 1.1 away from 3C66B Statistical study: 3C66A excluded 95.6% 2 systematic uncertainty: events / % 95.4% 99.7% Click 3C66A excluded to edit 85.4% Master title style N exc = N bkd = On/Off normalization = 0.33 Significance = 6.0! Alpha (deg) ATel 1753 Sept 08 VERITAS preliminary Scineghe08 MAGIC J C 66B > 150 GeV Significance of detection: 6.0 σ pre-trial for MAGIC J MAGIC Collab., ApJ in press 3C 66A MAGIC Aug-Dec 07 arxiv: σ / 30 trials: search region where >50% acceptance 22

23 Light Curve & Spectrum Cannot exclude contribution of 3C 66A at lowest energies Flux >150 GeV: (7.3±1.5) -12 cm -2 s -1 (2.2% Crab) lowest ever detected by MAGIC ] -1 s -1 TeV -2 / de da dt [cm dn! Click to edit Master L 2-8x title that of style Combined spectrum M for observed region Fit Function: " dn/de = f 0 (E / 0.3TeV) f [cm s -1 0 = (1.74 ± 0.28) TeV ] " = -3. ± 0.31 # 2 / ndf = 1. / 2 Γ= 3.±0.31 extends >2 TeV Energy [GeV] If 3C66A (unlikely): distance cannot be z > 0.23 (no > 1 TeV γ-rays, EBL) Mazin+Raue 08, Aharonian+06 Hard spectra possible, but require unusual blazar energetics (L> 47 erg s -1!) Aharonian+08, Wagner 08, Persic+De Angelis 08 s -1 ] -2 Flux (E>150 GeV) [cm R-band flux [mjy] 20-3C66B: intrinsic jet angle 45 vs C66B as TeV radio galaxy structured jet Tavecchio & Ghisellini MAGIC Collab., ApJ in press arxiv: MAGIC J no significant variability in VHE 3C 66A (KVA) time [MJD]

24 Limits on 3C Internal absorption, decreasing IC cross section: FSRQs cannot be strong VHE emitters Rather high redshifts: significant EBL absorption (Liu+Bai06, Reimer07; Tavecchio+Ghisellini08) 3C well known z=0.86 Detected several times by EGRET, average photon index of 2.2 Activity during summer 2007; intense emission detected by AGILE; also Nov-Dec 07 July & August: 9.6 h, December: 6.8 h Upper limits above 0 GeV, 4% in July, 186 GeV in August, 235 GeV in December AGILE spectrum rather hard (1.7) MAGIC limits imply cutoff above 0 GeV Leptonic model, BLR radiation included Cutoff at tens of GeV: Decrease of scattering cross section Absorption by pair production Absorption of γ-rays can also be relevant in hadronic models emission neglecting absorption MAGIC Collab., A&A submitted SSC arxiv: July Log ν [Hz]

25 3C 279: A Famous EGRET Blazar MAGIC Coll., Science 320 (2008) 1752 Flat Spectrum Radio Quasar at z=0.536 Apparent luminosity 48 erg s -1 Brightest EGRET AGN (Wehrle+97,98) Gamma-ray flares in 1991 and 1996: High dynamical range in EGRET data Rapid variability: ΔT ~ 6hr in 1996 flare (Wehrle+98) s -1 ] -2 Integral flux (0-500 GeV) [cm MAGIC observations: 2006 January April during WEBT campaign (Böttcher+08) Feb σ MAGIC Skymap MAGIC: E>0 GeV 23 Feb σ Flux incompatible with const.: 5.04 σ Time (Julian Date ) 25

26 3C 279: What s the Relevance? z=0.536! Major jump in redshift of VHE sources First FSRQ in TeV gamma-rays: All source classes of the blazar sequence detected in VHE Modeling of 3C 279 non-trivial: FSRQ bright emission lines: External photon fields important (Dermer+93, Sikora+94) External-Inverse Compton Modeling required, more free parameters VHE provides vital input! Follow-up models & papers... Böttcher 08, Chatterjee+08, Marscher+08, Tavecchio+Mazin 08 Sitarek+Bednarek08... MAGIC Coll., Science 320 (2008) 1752 MAGIC And finally... Why do we see it at all? Is the universe more transparent to VHE γ-rays than assumed? Extragalactic Background Light 26

27 νi Measuring the EBL Reconstruct intrinsic spectrum using state-of-the-art EBL models: Stecker fast-evol. α*=0.5±1.2 Primack: α*=2.9±0.9 Generic acceleration mechanism arguments, e.g. Aharonian+06: Assume α*<1.5 unreasonable Formation of hard spectra possible Aharonian+08, Sitarek+Bednarek 08, Liu+08 2 Internal absorption in 3C279 does not produce important hardening Tavecchio+Mazin 08 Infer maximum tolerable EBL Gamma-ray horizon s -1 ] cm -2-1 differential flux, dn/de [TeV ) -1 sr -2 (nw m ν MAGIC Coll., Science 320 (2008) 1752 fit to measured spectrum: -α dn/de = N E 0 200GeV - = (5.2 ± 1.7) [TeV N 0 α = 4.11 ± Energy, E [GeV] EBL spectrum: probing 0.2-2µm λ (µ m) 27 3c279, measured systematic error band EBL-corrected, Primack, α* = 2.94 ± 0.91 EBL-corrected, Stecker (fast), α* = 0.49 ± 1.19 Energy spectrum of 3C 279 α=4.1 excluded excluded -1 cm -2 s -1 ] Stecker et al., 2006, (fast evolution) max-ebl (this work) Primack et al., 2005 Cosmic Microwave Background Mazin & Raue, upper limit 2007 HESS upper limit, 2006 still allowed 2 3

28 Summary There are now 23 AGNs observed in E>0 GeV γ-rays, mostly high-peaked BL Lac objects Studied known HBLs in various MWL campaigns Blazar monitoring ongoing for bright blazars Successful optical triggers lead to discovery of Mkn 180 (2006), and far-away 1ES (z=0.212, 2007) & S (z=0.31±0.08, 2008) Now reaching much further in redshift: 3C 279 & S Non-HBLs: BL Lac, S (MAGIC), W Comae (VERITAS), 3C 279 (FSRQ, MAGIC 2006) ClickFirst tofsrq edit Master title style in TeV gamma-rays: All source classes of the blazar sequence detected in VHE very distant, important input for EBL! and M87 (2008 MAGIC detection, shared HESS/VERITAS/MAGIC campaign) day-scale variability on the way to identifying the TeV engine in M87 3C 66B/A region: MAGIC (2007, B) and VERITAS (2008, A) detections