INAF, Osservatorio Astronomico di Capodimonte 22 February 2012 The Extragalactic Gamma-Ray View of AGILE and Fermi Elena Pian INAF, Trieste Astronomical Observatory & Scuola Normale Superiore di Pisa
UNIFIED SCHEME OF AGN (Urry & Padovani 1995) 10% of all AGNs are radio-loud, and a small fraction of these are blazars
Extragalactic Jets: radiogalaxies and blazars Lorentz factors Γ~ 10-20 Cen A d = 4 Mpc Virgo A (M87) d = 20 Mpc VLA z = 0.056
UNIFIED SCHEME: Blazars are radiogalaxies with their jets pointing at a small angle with respect to the observer line of sight: 1) Superluminal motions 2) Radio spectra are not self-absorbed despite the small emitting region 3) Gamma-rays at MeV and higher energies are observed!
VLBI monitoring of radio structures and blobs ~5c Radio-blobs emitted at different epochs may have different apparent velocities, vapp = βappc 43 GHz; Jorstad et al. 2005 ~20c " = " app " app cos# + sen# BL Lac 5-10.6 GHz; Mutel et al. 1990
VLBA observations at 7 mm (43 GHz) of BL Lac 5c Marscher et al. 2008 Lorentz factor: " = 1 1# $ 2 " = 1 Doppler factor: #(1$ %cos&) If we assume that θ = 5 deg: βapp = 5 β = 0.9866 Γ = 6 δ = 9.5 βapp = 20 β = 0.9994 Γ = 30 δ = 7.6
Brightness Temperature argument T B = c 2 F " 2k" 2 # 2 For observed radio fluxes and angular sizes (directy measured with VLBI or inferred from radio variability), TB ~ e11 K The GHz spectra of blazars are flat (α < 0.7, where F ~ ν^-α), but not self-absorbed " 2.5 Torniainen et al. 2007
Compactness Argument Compactness: l = L" T Rm e c 3 Optical depth for photon-photon collision: " ## $ l 60 x% x x = h" mc 2 For an energy of 5 GeV (x = 10000), luminosity L = e48 erg/s, size of the emitting region R = 2 light days, and X-ray spectral slope α = 0.5, τ is about 100, therefore no gamma-rays should escape Solution of the paradox: L int r = " #3 L obs R int r = ct var 1+ z " $ int r = $ obs " By imposing that τ < 1, one has δ 6 McBreen 1979; Maraschi et al. 1992
The Fermi GST mission: 11 June 2008 LAT, 0.1-300 GeV Glast Burst Monitor Energy Range: 10 kev - 30 MeV 12 Sodium Iodide (NaI) Scintillation detectors Burst trigger Coverage of the typical GRB spectrum (10 kev 1 MeV) 2 Bismuth Germanate (BGO) Scintillation detectors Spectral overlap with the LAT (150 kev-30 MeV) Courtesy: N. Omodei
Second Fermi LAT Catalog (2FGL): 1873 sources (576; 187 of these already identified as blazars thru comparison with WISE Catalog, Massaro et al. 2012) (~1000, compare with 66 CGRO-EGRET blazars!) http://www.nasa.gov/mission_pages/glast/news/gamma-ray-census.html
Blazars in the Fermi-LAT sky (FSRQ) (FSRQ) (FSRQ) (BL Lac)
First Fermi-LAT observation of the FSRQ 3C454.3 (z = 0.859) 2008 Jul 7 - Aug 2 Abdo et al. 2009
AGILE-GRID observation of the FSRQ 3C454.3 (z = 0.859): 24-30 Jun 2007 (30 MeV - 50 GeV) 2008 Jul 7 - Aug 2 Vercellone et al. 2008
3C454.3 E-06 ph/s/cm2 AGILE-GRID and MWL observations of 3C454.3, 15-25 November 2010: the very high gamma-ray state can be reproduced by external Compton scattering off variable seed photons mjy INTEGRAL Jy Leptonic model of synchrotron Plus SSC and external Compton Vercellone et al. 2011
Fermi-LAT discovery of FSRQ PKS1502+106 (z = 1.839) Variable parameters: accelerating power of electrons and Magnetic field Aug 2008 INTEGRAL Position circles Seyfert 1 galaxy 1 The blazar target was not detected by INTEGRAL, but we detected serendipitously a Seyfert 1! Corona and Accretion disk Pian et al. 2011
Simultaneous AGILE and VERITAS observations of the BL Lac object Mkn421 (z = 0.031), 2008 May 24 - Jun 23 Donnarumma et al. 2009
Fermi-LAT and MWL campaign of Mkn421 (2009 Jan 19 - Jun 1) Abdo et al. 2011
Spectral energy distribution of blazars and spectral sequence
Is the blazar sequence an exhaustive representation? z > 1.2 Padovani & Giommi 2012
Spectral Energy Distribution of Flat Spectrum Radio Quasars HBL: High synchrotron peak frequency Accretion disk Ghisellini et al. 2011
Fundamental properties of gamma-ray Blazars accretion must play a key role in producing the jet Ghisellini et al. 2011
Optical polarimetry of FSRQ PKS1510-089 (z = 0.36) in January - June 2009, during an outburst Marscher et al. 2010
X-ray polarimetry to study geometry of jets S5 2007+777 (Z = 0.342) Sambruna et al. 2008 GEMS, to be launched in 2014 Gas Pixel Detector (PI: Enrico Costa) Both based on photoelectric effect
NuSTAR: Nuclear Spectroscopic Telescope Array The NuSTAR mission will deploy the first focusing telescopes to image the sky in the high energy X-rays (6-79 kev)
Summary Blazars extreme luminosities and variability at all wavelengths depend on the kinematic conditions and orientation of their powerful jets Blazars constitute the majority of the detected MeV-GeV extragalactic persistent emitters Blazar spectra are predominantly non-thermal (syncrotron and Inverse Compton), but their accretion disks are occasionally observed, especially in FSRQs, and allow the measurement of the central BH mass The accretion on this black hole plays a fundamental role in producing the jet power
Swift J164449.3+573451 = a relativistic jet from a tidal disruption flare (GRB110328A) Swif BAT, XRT z = 0.35 15-50 kev 0.3-10 kev Chandra 1 WSRT MBH = 1-20 e6 M masses (based on X-ray variability time-scale and MBH vs Mbulge Relationship) super-eddington accretion regime beaming along observing direction Levan et al. 2011; Zauderer et al. 2011; Burrows et al. 2011; Bloom et al. 2011