1. Markus B ӧ ttcher Ohio University Athens, OH VHE Gamma-Ray Induced Pair Cascades in Blazars and Radio Galaxies

2. Leptonic Blazar Models Relativistic jet outflow with  ≈ 10 Injection, acceleration of ultrarelativistic electrons Q e ( ,t)  Synchrotron emission F Compton emission F    -q Radiative cooling ↔ escape => Seed photons: Synchrotron (within same region [SSC] or slower/faster earlier/later emission regions [decel. jet]), Accr. Disk, BLR, dust torus (EC) Q e ( ,t)     -(q+1) bb  -q or  -2  bb 11  b :  cool (  b ) =  esc

3. Spectral modeling results along the Blazar Sequence: Leptonic Models High-frequency peaked BL Lac (HBL): No dense circumnuclear material → No strong external photon field Synchrotron SSC Low B fields (~ 0.1 G); High electron energies (up to TeV); Large bulk Lorentz factors (  > 10) The “classical” picture

4. Spectral modeling results along the Blazar Sequence: Leptonic Models Radio Quasar (FSRQ) Plenty of circumnuclear material → Strong external photon field Synchrotron External Compton High magnetic fields (~ a few G); Lower electron energies (up to GeV); Lower bulk Lorentz factors (  ~ 10)

5. Spectral modeling with pure SSC would require extreme parameters (far sub-equipartition B-field) 3C66A October 2008 Intermediate BL Lac Objects Including External-Compton on an IR radiation field allows for more natural parameters and near-equipartition B-fields (Abdo et al. 2011) (Acciari et al. 2009)

6.  -Absorption Features? Şentürk et al., in prep. Absorption trough from Ly  expected at E abs ~ 25/(1+z) GeV. CAVEAT: Non-simultaneous data Vastly different integration times

7.  -Absorption Features? M. Errando - Şentürk et al., in prep.

8.  -Absorption Features? M. Errando - Şentürk et al., in prep.

9. VHE  -ray production within dense external radiation fields HE  -ray Detections of Radio Galaxies: M 87, NGC 1275, 3C 120, 3C 270, 3C 380 3C 111, NGC 6251, Cen A Fermi EGRET + Fermi VHE Gamma-Ray Induced Pair Cascades   absorption  Pair cascades  Deflection by B-fields

10. The trajectories of the particles are followed in full three-dimensional geometry. Power-law spectrum of HE – VHE  -rays from the inner jet Arbitrary ext. photon spectrum a)Monoenergetic optical/UV (BLR) b)Thermal IR (torus) Model Setup

11. In AGN env.: Inverse Compton Scattering dominates Deflection, isotropization Compton supported cascades Compton vs. Synchrotron

12. General Considerations Electron/positron escape: Energy-dependent Isotropization -> High-energy spectral turnover:  defl ( IC ) =  obs  esc (  ) =  cool (  ) -> E esc ~ E s  2

13. Viewing Angle B = 1 mG  B = 5 o u ext = 10 -5 erg cm -3 R ext = 10 18 cm T BB = 1000 K  = cos  obs

14. External Radiation Field, u ext

15. Magnetic Field B  ~ 60 o B = 1  G For moderate/large inclination angles, isotropization becomes very efficient!

16. U ext = 5* 10 -2 erg/cm -3 R ext = 10 16 cm B= 1 mG,     30 0 <   D = 74 MpcL BLR = 1.6x10 42 erg/s  ≈ 30 o – 55 o L BLR = 4  R 2 ext c u ext Incident (forward)  -ray spectrum normalized to a moderately bright Fermi blazar Application to NGC 1275 (Roustazadeh & B ӧ ttcher 2010)

17. D = 3.7 Mpc Viewing angle ~ 50 o – 80 o T = 2300 K → peak frequency at K-band Fit to the broad-band SED (Boettcher & Chiang 2002) Cascade Emission Sum of both contributions U ext = 1.5* 10 -3 erg/cm -3 R ext =3* 10 16 cm B= 1 mG,     67 0 <   L BLR = 4  R 2 ext c u ext    ergs -1 L ~ 6X10 41 erg/s R ~ 6x10 17 cm Leptonic fit by Abdo et al. (2010) required  max = 10 8 ! Application to Cen A (Roustazadeh & B ӧ ttcher 2011)

18. 1- Leptonic models prefer external-Compton over SSC in non- HBL blazars -> VHE  -ray emission in intense external radiation fields ->  absorption (detectable by Fermi+CTA)-> Compton supported pair cascades. 2 - VHE gamma-ray induced cascades are effectively isotropized even in weak perpendicular (B y ) magnetic fields (B y ~  G) -> MeV- GeV gamma-ray flux in directions misaligned with respect to the jet axis. 3 - Fermi detections of radio galaxies (NGC 1275, Cen A) can be modeled as off-axis VHE gamma-ray induced pair cascade emission. Summary

20. Blazar Classification Quasars: Low-frequency component from radio to optical/UV, sy ≤ 10 14 Hz High-frequency component from X-rays to  -rays, often dominating total power (Hartman et al. 2000) High-frequency peaked BL Lacs (HBLs): Low-frequency component from radio to UV/X-rays, sy > 10 15 Hz often dominating the total power High-frequency component from hard X-rays to high-energy gamma-rays Low-frequency peaked / Intermediate BL Lacs (LBLs/IBLs): Peak frequencies at IR/Optical and GeV gamma-rays, 10 14 Hz < sy ≤ 10 15 Hz Intermediate overall luminosity Sometimes  -ray dominated (Abdo et al. 2011) 3C66A (Acciari et al. 2009)

21. TeV  -Ray Blazars NameClasszDate Mrk421HBL0.03108/1992 Mrk501HBL0.03401/1996 1ES 2344+514HBL0.04407/1998 Mrk 180HBL0.04509/2006 1ES1959+650HBL0.04808/1999 AP LibLBL0.04907/2010 PKS 0548-322HBL0.06907/2007 BL LacertaeLBL0.06905/2005 PKS 2005-489HBL0.07106/2005 RGBJ0152+017HBL0.0802/2008 SHBL J001355.9…HBL0.09509/2010 W ComaeIBL0.10208/2008 1ES 1312-423HBL0.10812/2010 PKS 2155-304HBL0.11606/1999 RGB J0710+591HBL0.12503/2009 1H 1426+428HBL0.12902/2002 1ES 1215+303LBL0.1301/2011 NameClasszDate 1ES 0806+524HBL0.13802/2008 1ES 0229+200HBL0.1402/2006 1RXS J101015.9…HBL0.14212/2010 1H 2356-309HBL0.16504/2006 1ES 1218+304HBL0.18205/2006 1ES 1101-232HBL0.18604/2006 1ES 0347-121HBL0.18808/2007 RBS 0413HBL0.1910/2009 PKS 0447+439HBL0.2012/2009 1ES 1011+496HBL0.21209/2007 1ES 0414+009HBL0.28711/2009 S5 0716+714LBL0.31804/2008 1ES 0502+675HBL0.34111/2009 PG1553+114HBL0.3503/2006 PKS 1510-089FSRQ0.3603/2010 4C+21.35FSRQ0.43206/2010 3C66AIBL0.444 ?03/2008 3C279FSRQ0.53606/2008 PKS1424+240IBL???06/2009