Broadband Emission of Blazars 2

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1 D X D G S Prototypical xample: 3 273, The kpc-scale jet of seen at λ = 198 cm with (onway et al., 1993) Broadband mission of Blazars 3 D X D G S Prototypical xample: 3 273, The kpc-scale jet of seen at λ = 73 cm with (onway et al., 1993) Broadband mission of Blazars 4 D X D G S ntroduction Blazars are broadband emitters and the most natural targets for multiwavelength astronomy! The expression Blazar was first used in 1978 to express that optically violently variable quasars (Os) and B ac objects share their extreme variability characteristics. lthough been first detected in the optical and radio, a large portion of their total energy output is at high energies: hard X-rays, γ-rays, and up to the very high energy (H) regime. The ompton Gamma-ay Observatory (GO) with its main detector GT revolutionized blazar research by the finding that blazars are the dominant population of extragalactic gamma-ray sources. The short variability time scales (days!) indicated that the gamma-ray emission comes from beamed plasma (jets) to avoid photon-photon pair production in otherwise too dense gamma photon fields. Broadband mission of Blazars 1 D X D G S Prototypical xample: 3 273, 3 273: irst detected and brightest (and probably best studied) quasar Bright throughout the whole electromagnetic spectrum Prominent big blue bump Huge public database: Türler et al. (1999); Soldi et al. (2008) (Türler et al., 1999) Broadband mission of Blazars 2

2 D X D G S Broadband mission odels, General agreement that the low-energy component is jet-synchrotron emission. High-energy photons are produced in eptonic models through scattering of soft seed photons by the same relativistic electrons responsible for the synchrotron emission. Seed photons are the synchrotron photons themselves (SS, e.g. Tavecchio, araschi & Ghisellini, 1998), or external, e.g., from the accretion disk or the B (, e.g. Sikora, Begelman & ees, 1994) Hadronic models through reactions involving high-energy protons (hadron-hadron or photon-hadron collisions, pair production and subsequent e + e cascades (e.g. annheim, 1993)) Geometry in leptonic models (Sikora, Hadronic models are attractive because they can explain the observed ultra-high energetic (UH) cosmic rays but they have problems explaining the observed blazar X-ray spectra. Begelman & ees, 1994) Broadband mission of Blazars 7 D X D G S Broadband mission odels, odeling the broadband SD: onsider primary components: synchrotron, disk, scattered B emission nverse-ompton components from SS and (of the dominating external photon fields) Pucella et al. (2008) This is an SD of PKS B ; see below Broadband mission of Blazars 8 D X D G S Prototypical xample: 3 273, ontribution of largescale jet negligible above 5 GHz. The kpc-scale jet of seen at λ = 2 cm with the (onway et al., 1993) Broadband mission of Blazars 5 D X D G S Prototypical xample: 3 273, adio: low-frequency emission from large-scale jet; high-frequencies from compact jet (flat spectrum in ν) up to : synchrotron emission from compact jet (possibly plus dust component (dusty torus?)) big blue bump in the optical: accretion disk (?) X-rays and up: inverse ompton emission (possibly from multiple seed photon fields) Broadband mission of Blazars 6

3 D X D G S Prototypical xample: (continued), ractional variability amplitude: S 2 ε 2 (3.50) x 2 var = with the sample variance of the light curve S 2, the average flux x, and the mean of the squared measurement uncertainties ε 2 = 1 i ε 2 i. (Soldi et al., 2008) The fractional variability amplitude strongly depends on frequency, rising towards the high-energy end of the synchrotron and components. ess-variable emission (from dust?). Broadband mission of Blazars 11 D X D G S Prototypical xample: (continued), lmost 40 years of multiwavelength observations of (Soldi et al., 2008) Broadband mission of Blazars 12 D X D G S Prototypical xample: (continued), lmost 40 years of multiwavelength observations of (Soldi et al., 2008) Broadband mission of Blazars 9 D X D G S Prototypical xample: (continued), (Türler et al., 1999) ariability at all wavelengths but with different time scales and amplitudes multiple emission components and/or mechanisms (Soldi et al., 2008) Broadband mission of Blazars

D X D G S Pathological xample: O 0235+16, B: always unresolved even with sub-milliarcsecond resolution Broadband mission of Blazars 15 D X D G S Pathological xample: O 0235+16, ightcurves: extremely

4 D X D G S Pathological xample: O , B: always unresolved even with sub-milliarcsecond resolution Broadband mission of Blazars 15 D X D G S Pathological xample: O , ightcurves: extremely variable with repeated multiwavelength outbursts Shown here: Optical -band (top), adio 37/22/15/8/5 GHz (2nd from top to bottom) aiteri et al. (2001) claimed a 5 6 year periodicity (aiteri et al., 2001) Broadband mission of Blazars 16 D X D G S Prototypical xample: (continued), historic jet-emission minimum (Türler et al., 2006) Broadband mission of Blazars 13 D X D G S Prototypical xample: (continued), historic jet-emission minimum (Türler et al., 2006) When the jet is weak, Seyfert-like features appear: Thermal dust, iron line; blue bump not directly coupled to jet emission Broadband mission of Blazars 14

5 D X D G S Pathological xample: O , SD (measured in 2003/04 campaign): 24 optical/ telescopes and 4 radio telescopes plus X-ewton were waiting for the outburst that never happened Blazar SD with a primary (synchrotron) component in the radio optical, secondary () rising in the X-ray regime and an additional bump in the U (aiteri et al., 2005). Broadband mission of Blazars 19 D X D G S Pathological xample: O , ong-term SD analysis: aiteri et al. (2006) Broadband mission of Blazars 20 D X D G S Pathological xample: O , SD (as known in 2003): essy! Well studied radio optical spectrum onfusing X-ray situation Bright gamma-ray spectrum Yellow spectral regions targeted by a large observing campaign in 2003/04 (poch of the next predicted outburst) Broadband mission of Blazars 17 D X D G S Pathological xample: O , O in 2003/04: o outburst! Still: ampaign collected a wealth of multiwavelength data (aiteri et al., 2005) Broadband mission of Blazars 18

D D SG X D Pathological xample: O 0235+16, D O D SG X D Broadband mission of Blazars

ow renemed to ermi Gamma-ay Space Telescope and in routine all-sky monitoring mode. http://agile.

The elusive gamma-ray regime is much better covered than ever before: The ermi and gile ra,

the end of the optical visibility season.

6 D D SG X D Pathological xample: O , D O D SG X D Broadband mission of Blazars GST (Gamma ay arge rea Space Telescope) launched in June ow renemed to ermi Gamma-ay Space Telescope and in routine all-sky monitoring mode. nr.it/ gile launched in pril ow in routine pointed observations mode. The elusive gamma-ray regime is much better covered than ever before: The ermi and gile ra, Broadband mission of Blazars The next big flare of O occured in ebruary 2007, close to the end of the optical visibility season... O High galactic-latitude gamma-ray point sources are flat-spectrum radio quasars and B ac objects 1st-ight mage of the ermi Gamma-ray Space Telescope (one week of data in ugust 2008)

7 D X D D X D G S The Blazar Sequence, onstruction of average blazar SDs binned according to radio luminosity (ossati et al., 1998; Donato et al., 2001) or all luminosity classes, two broad peaks High-luminosity sources peak at lower frequencies ( and e range): B objects ow-luminosity sources peak at higher frequencies (U/X-rays and up to Te energies): HB objects (Donato et al., 2001, based on ossati et al. (1998)) Broadband mission of Blazars 27 D X D G S The Blazar Sequence, nalytic parametrization: Peak frequencies are inversely proportional to luminosity onstant ratio of the two peak frequencies Strength of the second peak proportional to luminosity ttention: GT detected preferentiall blazars during outbursts Bias in high-energy data. Ongoing debate about the validity of the blazar sequence. (small) number of sources does not fit in. (Donato et al., 2001, based on ossati et al. (1998)) Broadband mission of Blazars 28 G S The ermi and gile ra, Quasar PKS B : 0 e to 1 Ge spectrum: P with Γ 2 SD modeled with a synchrotron+ss+ model (external photon field from the disk and from B) for a jet with orentz factor γ = 20 observed at the critical angle 1/γ. gile+gsp observation of PKS B15-089: Pucella et al. (2008) GSP: GST-gile Support Program OJ speed for : 20c! aybe even faster at 43 GHz (46 c) Broadband mission of Blazars 25 D X D G S The ermi and gile ra, Bright flare of detected by ermi in September 2008 (Tramacere, 2008) nalysis of follow-up multiwavelength observations going on T still in calibration phase only photons/cm 2 /s are published Photons/cm^2/s The T detector onboard ermi operates in all-sky scanning mode [JD] With ermi it is now much easier to detect source flares and compare flaring and non-flaring SDs. ermi light curve of PKS B (shown are weekly data points starting in late ugust 2007, about 1 year after the gile pointed observation.) Broadband mission of Blazars 26

D X D G S The Only Te Galaxy: 87 87 established as a Te source by H..S.S. (haronian et al., 2006) Te γ-ray excess events 200 87 (H..S.S.) Previous 4-σ tentative detection by HG; non-detection by Whipple 12.

8 D X D G S The Only Te Galaxy: established as a Te source by H..S.S. (haronian et al., 2006) Te γ-ray excess events (H..S.S.) Previous 4-σ tentative detection by HG; non-detection by Whipple Hard spectrum (Γ 2.2) detected up to 20 Te (H..S.S.) 1 ) Te 2 s 2005 Declination (deg) d/d (cm PS m 30 h 12 m 31 h 12 m 32 h nergy (Te) ight scension (hours) (haronian et al., 2006) Broadband mission of Blazars 31 D X D G S The Only Te Galaxy: 87 2 ay 2005 pril 2005 arch 2005 eb Te flux variable on time scales from years down to days s ) mission region must be compact Φ(>730Ge) (cm 0 Highest measured fluxes coincide with Date 04/ay 11/ay 30/ar 06/pr 09/ar 16/ar 09/eb 16/eb 2 2 B ) s a flare of the HST- 1 knot in the H..S.S. 1.5 f(0.2-6 ke) (erg cm s ) 40 average -2 HG jet as measured by handra (Harris handra (HST) 20 handra (nucleus) 0.5 Φ(>730Ge) (cm et al., 2006) (at this epoch brighter than the nucleus!) 12/ / / / /2006 Date (haronian et al., 2006) Broadband mission of Blazars 32 D X D G S Blazars at ery High nergies, The blazar sequence predicts a dominance of HB objects at very high energies. This is confirmed by recent blazar detections of Te telescopes (H..S.S., G, TS, GOO): urrently 17 HB objects detected and only two B objects (W omae and B ac; ØØÔ»»Ø Ú ØºÙ Óº Ù» check for updated lists) Only non-blazar Te source: 87 Broadband mission of Blazars 29 D X D G S Blazars at ery High nergies, Te blazars are weak radio sources, because the cm-range is so far left of their synchrotron peak and because they are low-luminosity objects.similarly, they are bright X-ray sources and relatively weak in the e/ge range. Despite their variability and SDs require very high Doppler factors, B measures slow jets (barely superluminal Piner, Pant & dwards, 2008, and references therein) 1) extremely small angles or 2) jet deceleration from the blazar scale to the B scale, or 3) another sign of jet-stratification (spine-sheath structure). (Piner, Pant & dwards, 2008) Broadband mission of Blazars 30

D X D G S The Only Te Galaxy: 87 new Te flare of 87 has been seen in early 2008 by G (lbert et al., 2008). The 87 jet was under intense B monitoring at the time of the flare. To be continued.

, 685, 23 Biretta, J.., Sparks, W. B., & acchetto,., 1999, pj, 520, 621 heung,.., Harris, D.., & Stawarz, Ł., 2007, strophys. J., ett., 663, 65 onway,. G., Garrington, S. T., Perley,.., & Biretta, J.

9 D X D G S The Only Te Galaxy: 87 new Te flare of 87 has been seen in early 2008 by G (lbert et al., 2008). The 87 jet was under intense B monitoring at the time of the flare. To be continued... Broadband mission of Blazars haronian,., khperjanian,. G., Bazer-Bachi,.., Beilicke,., Benbow, W., & et al. 2006, Science, 314, 1424 lbert, J., et al., 2008, strophys. J., ett., 685, 23 Biretta, J.., Sparks, W. B., & acchetto,., 1999, pj, 520, 621 heung,.., Harris, D.., & Stawarz, Ł., 2007, strophys. J., ett., 663, 65 onway,. G., Garrington, S. T., Perley,.., & Biretta, J.., 1993, &, 267, 347 Donato, D., Ghisellini, G., Tagliaferri, G., & ossati, G., 2001, &, 375, 739 ossati, G., araschi,., elotti,., omastri,., & Ghisellini, G., 1998, S, 299, 433 Harris, D.., heung,.., Biretta, J.., Sparks, W. B., Junor, W., Perlman,. S., & Wilson,. S., 2006, pj, 640, 211 annheim, K., 1993, &, 269, 67 Piner, B. G., Pant,., & dwards, P. G., 2008, pj, 678, 64 Pucella, G., et al., 2008, &, 491, 21 aiteri,.., et al., 2001, &, 377, 396 aiteri,.., et al., 2005, &, 438, 39 aiteri,.., et al., 2006, &, 459, 731 Sikora,., Begelman,.., & ees,. J., 1994, pj, 421, 153 Soldi, S., et al., 2008, &, 486, 411 Tavecchio,., araschi,., & Ghisellini, G., 1998, pj, 509, 608 Tramacere,., 2008, The stronomer s Telegram, 1743, 1 Türler,., et al., 2006, &, 451, 1 Türler,., et al., 1999, &S, 134, 89 D X D G S The Only Te Galaxy: 87 HST resolved by B, but still compact sub-structure (heung, Harris & Stawarz, 2007) Broadband mission of Blazars 33 D X D G S The Only Te Galaxy: 87 HST has moving sub-components with superluminal speeds up to 4c in agreement with optical measurements by Biretta, Sparks & acchetto (1999). elativistic bulk motion > 120 pc downstream from the central engine and coinciding with the flaring putative Te emission region (heung, Harris & Stawarz, 2007) Broadband mission of Blazars 34

The Extragalactic Gamma-Ray View of AGILE and Fermi

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