Multiwavelength observations of the gamma-ray blazars detected by AGILE Filippo D’Ammando INAF - Istituto di Astrofisica Spaziale e Fisica Cosmica Roma Università degli Studi di Roma “Tor Vergata” Ph.D in Astronomy - Cycle XXII Roman Young Researchers Meeting 2009 Active Galactic Nuclei - Unification Model • central Black Hole (106 -109 Mʘ) • accretion disk rotating around the SMBH • clouds of gas gravitational attracted by the black hole and illuminated by the disk radiation • optically thick torus of molecular gas and dust • two collimated relativistic jets Urry and Padovani 1995 RYRM 2009 Filippo D’Ammando 21 July 2009 Almost all galaxies contains a massive black hole but 99% of them are silent and 1% is active (mostly radio-quiet AGNs)... and only 0.1% is radio-loud AGNs Blazar characteristics: - compact radio inverted spectrum core, flat or - apparent superluminal motion - irregular, rapid and often very large variability at all frequencies - high and variable polarization at optical and radio frequencies RYRM 2009 Filippo D’Ammando 21 July 2009 Emission mechanisms in blazars Leptonic processes: - synchrotron emission - inverse Compton where seed photons came from the internal synchrotron radiation - inverse Compton where seed photons came from external radiation (accretion disk, BLR and/or torus) Hadronic processes: - synchrotron emission - proton-initiated cascades - proton-synchrotron emission RYRM 2009 Filippo D’Ammando 21 July 2009 Synchrotron Self-Compton (SSC) Electrons in a magnetic field can work twice: first producing synchrotron radiation, and then Comptonizing it (SSC) Synchrotron RYRM 2009 Filippo D’Ammando SSC 21 July 2009 Sikora, Begelman and Rees 1994 In External Compton model the seed photons come from outside to the jet RYRM 2009 Filippo D’Ammando 21 July 2009 The blazar (spectral) sequence Epk of synchrotron and Compton components inversely correlated with L FSRQ L BL Lac Fossati et al. 1998 Donato et al. 2001 npeak RYRM 2009 Filippo D’Ammando 21 July 2009 Low power slow cooling large ɣpeak Big power fast cooling small ɣpeak Ghisellini et al. 1998, 2002 RYRM 2009 Filippo D’Ammando 21 July 2009 First AGILE multi-λ campaign: 3C 279 Giuliani, D’Ammando, Vercellone, et al. 2009, A&A, 494, 509 First extragalactic source detected in gamma-ray by AGILE-GRID, monitored simultaneously in optical band by REM telescope and in X-rays by Swift <Fɣ> = (210 38) 10-8 ph cm-2 s-1 E > 100 MeV Gamma-ray flux similar to the EGRET high state but soft spectrum The soft spectrum during a flaring episode could be an indication of a dominant contribution of EDC emission compared to ECC emission model 9 - 13 July 2007 ECC ECD RYRM 2009 Filippo D’Ammando 21 July 2009 R-band light curve between December 2006 and December 2007: a strong minimum occurred about 2 months before the AGILE observation This optical minimum might be correlated with a low accretion state of the disk and then with a ECC component deficit, delayed of about two months Hartman et al. 2001 RYRM 2009 Filippo D’Ammando 21 July 2009 PKS 1510-089 Pucella, Vittorini, D’Ammando, et al. 2008, A&A, 491, L21 <Fɣ> = (195 30) 10-8 ph cm-2 s-1 E >100 MeV Possible correlation between optical and gamma-ray bands: contemporaneous decrease in fluxes The IC contribution from the BLR can explain the observed hard gamma-ray spectrum 23 August - 1 September 2007 RYRM 2009 Filippo D’Ammando 21 July 2009 PKS 1510-089: a rapid gamma-ray flare in March 2008 17 - 21 March 2008 D’Ammando, Pucella, Raiteri, et al., submitted to A&A Serendipitous detection during an AGILE pointing towards the Galactic Center 3 ToO by Swift/XRT: the spectrum becomes harder when the source is brighter GASP-WEBT observed intense optical activity between January and April 2008 RYRM 2009 Filippo D’Ammando 21 July 2009 Between January and April 2008, the blazar PKS 1510-089 showed intense optical activity with several episodes of fast variability detected by GASP - WEBT Peaks was detected in the optical band on 15 February, 29 March and 11 April 2008 After two episodes of medium intensity the source was not detected for some days in gamma-ray band and suddenly a rapid flare was observed by AGILE on 18-19 March 2008 RYRM 2009 Filippo D’Ammando 21 July 2009 Radio-to-optical behaviour The light curve at 230-345 GHz suggests that the mechanism producing the flaring event observed in optical in the second half of February and in late March-April 2008 also interested the millimetric emitting zone, with some delay At 22-43 GHz a hint of flux increase is visible in the second part of the light curve, while the radio flux at 5-15 GHz shows no trend RYRM 2009 Filippo D’Ammando 21 July 2009 Spectral Energy Distribution - March 2008 Likely signatures of the little and big blue bumps RYRM 2009 hard X-ray spectrum: soft X-ray excess? Filippo D’Ammando 21 July 2009 PKS 1510-089 March 2009 PKS 1510-089 showed an extraordinary gamma-ray activity during March 2009, with several flaring episodes D’Ammando et al., in preparation RYRM 2009 Filippo D’Ammando 21 July 2009 GASP observations of PKS 1510-089 During March 2009 the optical activity of PKS 1510-089 is greatly increased with a peak on 26 March 2009 D’Ammando et al., in preparation RYRM 2009 Filippo D’Ammando 21 July 2009 S5 0716+714 in September - October 2007 Chen, D’Ammando, Villata, et al. 2008, A&A, 489, L37 <Fɣ> = (97 15) 10-8 ph cm-2 s-1 E >100 MeV with a peak level of (193 42) 10-8 ph cm-2 s-1 z = 0.31 0.08 (Nilsson et al., 2008) Total power transported in the jet is extremely high ( Ltot > 3 x 1045 erg s-1) , at the limit of the maximum power generated by a spinning black hole of 109 Mʘ 4 - 23 September 2007 RYRM 2009 Filippo D’Ammando 21 July 2009 The Discrete Correlation Function (DCF) displays a significant peak for a time-lag of -1 day Possible delay in the gamma-ray flux variations with respect to optical variations of the order of 1 day To fit the SED we use 2 different SSC components: - the first component reproduces the ground state - the second components dominates the optical and gamma-ray bands RYRM 2009 Filippo D’Ammando 21 July 2009 Swift and AGILE simultaneous obs. in October - November 2007 23 October - 13 November 2007 Giommi, Colafrancesco, Cutini, et al., 2008, A&A, 487, L49 <Fɣ> = (47 ± 11) 10-8 ph cm-2 s-1 E >100 MeV The gamma-ray flux is about a factor of 2 lower than in September Strong variability in soft X-ray, moderate variability at optical/UV and approximately constant behavior in hard X-rays The SED is consistent with a two-components SSC model RYRM 2009 Filippo D’Ammando 21 July 2009 3C 273: simultaneous detection by GRID & SA Pacciani, Donnarumma, Vittorini, et al. 2009, A&A, 494, 49 <Fɣ> = (22 6) 10-8 ph cm-2 s-1 E >100 MeV Fɣ [peak] = (33 11) 10-8 ph cm-2s-1 E >100 MeV Multi-wavelength campaign: REM, Swift, RXTE, INTEGRAL and AGILE No optical variability during the entire campaign. Hint of a possible anti-correlated variability between X-rays and gamma-rays SSC + EC: spectral variability consistent with an acceleration episode of the electron population 16 December 2007 – 8 January 2008 RYRM 2009 Filippo D’Ammando 21 July 2009 3C 454.3: July 2007 24 - 30 July 2007 Vercellone, Chen, Giuliani, et al. 2008, ApJL, 676, 13 AGILE repointing the source during a period of strongly enhanced optical emission <Fɣ> = (280 ± 40) 10-8 ph cm-2 s-1 E >100 MeV Highest gamma-ray flux from this source in the last 15 years but see Fermi obs. RYRM 2009 Filippo D’Ammando 21 July 2009 MW Observations of 3C 454.3 in November 2007 Vercellone, Chen, Vittorini, Giuliani, D’Ammando et al. 2009, ApJ, 690, 1018 <Fɣ> = (170 13) 10-8 ph cm-2 s-1, with a peak of ~400 x 10-8 ph cm-2 s-1 E >100 MeV Rapid variability in the optical band Emission in the optical range appears to be correlated with that at gamma-ray energies 10 November - 1 December 2007 The DCF indicate a moderate correlation with no lag between gamma-ray and optical flux variations RYRM 2009 Filippo D’Ammando 21 July 2009 ECC ECD The contribution of ECD radiation alone cannot account for the hardness of the spectrum. The gamma-ray emission seems to be dominated by IC scattering of the external photons from the broad line region clouds ECC ECD RYRM 2009 Filippo D’Ammando 21 July 2009 MW Observations of 3C 454.3 in December 2007 Donnarumma et al., 2009, submitted to ApJ Simultaneous multi-wavelength campaign with the contribution of Spitzer, REM, GASPWEBT, MITSuME, Swift, Suzaku and AGILE <Fɣ> = ~ 250 x 10-8 ph cm-2 s-1 E >100 MeV A leptonic EC model is considered, with also a contribution of EC on a hot corona (T=106 K), to account for the hard ɣ-ray spectrum RYRM 2009 Filippo D’Ammando 21 July 2009 DCF analysis shows a (possible) delay of the gamma-ray flux variations with respect to the optical ones of about 10 hours Vercellone et al., in preparation The longest monitor so far of a blazar in the gamma-ray band A factor of about 10 in dynamic range in about 2 years with a possible spectral trend (harder when brighter) RYRM 2009 Filippo D’Ammando 21 July 2009 Mrk 421: WEBT + AGILE + VERITAS + MAGIC = … RYRM 2009 Filippo D’Ammando 21 July 2009 Mrk 421 from optical to TeV energies Donnarumma, Vittorini, Vercellone et al., 2009, ApJ 691, L13 <Fɣ> = (42 ± 13) 10-8 ph cm-2 s-1 E >100 MeV Swift/XRT: Flux (2 - 10 keV) = 2.6 x 10-9 ph cm-2 s-1 Possible correlated variability between optical, X-rays and high-energy parts of the spectrum SSC model: hardening/softening of electron energy distribution caused by particle acceleration process Summary and remarks • Gamma-ray astronomy is still a largely unexplored territory, in particular for the class of blazars • AGILE (and EGRET) detected only few objects with flux greater than 100 x 10-8 ph cm-2 s-1? Why? Selection effects or there is a subclass of blazar with peculiar characteristics? • SSC vs EC vs more complex models? How to distinguish? • AGILE observations has brought to light a more complex behaviour of blazars with respect to the standard models: - the presence of two emission components in any BL Lacs - the possible contributions of an hot corona as source of seed photons for the EC in FSRQs • The study of multi-wavelength correlations is the key to understanding the structure of the inner jet and the origin of the seed photons for the IC process • The study of sources in different activity states, not only during flaring states, could provide new informations Thanks for your attention!!!