Evidence for UHECR Acceleration from Fermi Observations of AGNs and GRBs

1. Evidence for UHECR Acceleration from Fermi Observations of AGNs and GRBs Evidence for UHECR Acceleration from Fermi Observations of AGNs and GRBs Chuck Dermer Space Science Division US Naval Research Laboratory, Washington, DC charles.dermer@nrl.navy.mil TeV Particle Astrophysics 2009 SLAC, July 13-17, 2009

2. Outline • Requirements for UHECR sources: • Extragalactic (but within the GZK radius) • Emissivity (>1044 erg Mpc-3 yr-1) • Apparent IsotropicPower (> few×1045 erg s-1) (for Fermi acceleration) • Extragalactic Gamma Ray Sources from Fermi • Radio Galaxies and Blazars as Sources of the UHECRs • Gamma-Ray Bursts as Sources of the UHECRs Dermer, Razzaque, Finke, Atoyan (New Journal of Physics, 2009) Razzaque, Dermer, Finke (Nature Physics, submitted, 2009) Dermer and Menon, “High Energy Radiation from Black Holes: Gamma Rays, Cosmic Rays, and Neutrinos” (Princeton University Press, 2009)

3. Black-Hole Jet Sources of UHECRs Nonthermal g rays  relativistic particles + intense photon fields • Leptonic jet model: radio/optical/ X-rays: nonthermal lepton synchrotron radiation • Hadronic jet model: • Photomeson production second g-ray component • pg→ p→ g, n, n • Neutrons escape to decay and become UHECR protons (Neutral beam model: Atoyan & Dermer 2003) Large Doppler factors required for g rays to escape Photopair/photopion vs. ion synchrotron

4. Horizon distance vs. MFP: Linear distance where proton with measured energy E had energy eE GZK Horizon Distance for Protons CMBR only: Auger limits: GZK cutoff consistent with UHECR protons For model-dependent definition: Harari, Mollerach, and Roulet 2006

5. UHECR Emissivity knee ankle (Waxman 1995)

6. UHECR Acceleration by Relativistic Jets Proper frame (´) energy density of relativistic wind with apparent luminosity L x Maximum particle energy G Lorentz contraction DR´= G DR R´= R/ G What extragalactic sources have (apparent isotropic) L /G2 >> 1045 ergs s-1? Those with (apparent isotropic) Lg > 1044 ergs s-1

7. UHECRs from Blazars • LAT Bright AGN Sample (LBAS): Abdo et al. arXiv:0902.1559(ApJ, 2009) 0FGL: 205 LAT Bright Sources Test Statistic > 100 Significance > 10s 132 |b|>10 sources 114 associated with AGNs Compare EGRET: 31 >10s sources (total) (10 at |b|>10) 3 month catalog:August 4 – October 30, 2008 11 mo. Source List! Fermi AGNs reviewed by Jim Chiang, Greg Madejski, D. Paneque

8. Luminosity Distribution vs. Redshift GZK horizon For sources within GZK radius, need > 103persistentsourcesper Gpc3 Abdo et al., ApJS (2009) (Cen A (>100 MeV) few×1041 erg/s)

9. Luminosity Density of g-ray Blazars • Minimum luminosity density of Radio Galaxies from LBAS (5×1040 erg/s w/i 3.5 Mpc) 1044 ergs Mpc-3 yr-1

10. Centaurus A ~100 kpc × 500 kpc lobes Need >> 1045 erg s-1 apparent power to accelerate UHECR protons by Fermi processes Cen A power: Bolometric radio luminosity: 4×1042 erg s-1 Gamma-ray power (from Fermi): few ×1041 erg s-1 Hard X-ray/soft g-ray power: 5×1042 erg s-1 UHECR power: few ×1040 erg s-1

11. What is Average Absolute Jet Power of Cen A? Total energy and lifetime: Cocoon dynamics (Begelman and Cioffi 1989 for Cyg A) Use synchrotron theory to determine minimumenergy B field, absolute jet power Pj. Jet/counter-jet asymmetry gives outflow speed: Dermer, Razzaque, Finke, Atoyan, NJP 09 Hardcastle et al. 2009 Celotti and Fabian 93

12. Mean B-field and Average Absolute Jet Power in Cen A Hardcastle et al. 2009 Pj(Cen A)  1044 erg s-1 Apparent jet power 20 x larger?

13. Search for UHECRs Enhancements from Radio Galaxies and Blazars Blue: Auger, > 56 EeV (1◦) Red: HiRes > 56 EeV (1◦) Magenta: AGASA, > 56 EeV (1.8◦) Orange: AGASA, 40-56 EeV (1.8◦) Pinkand purple circles: angular deflections of UHECRs with 40 EeV and 20 EeV from source AGN, respectively, in the galactic disk magnetic field. Green circles represent angular deflections in assumed 0.1 nG intergalactic magnetic field, assuming no magnetic-field reversals. GC GC MW magnetic deflection UHECR protons If blazars accelerate UHECR protons, then mean IGM field

14. UHECRs from Gamma Ray Bursts Luminosity density of GRBs GRB fluence: > 20 keV fluence distribution of 1,973 BATSE GRBs (477 short GRBs and 1,496 long GRBs). 670 BATSE GRBs/yr (full sky) Vietri 1995; Waxman 1995 (independent of beaming) Baryon loading (Band 2001)

15. UHECR Spectrum from Long-Duration GRBs • Inject -2.2 spectrum of UHECR protons to E > 1020 eV • Injection rate density determined by birth rate of GRBs early in the history of the universe • High-energy (GZK) cutoff from photopion interactions with cosmic microwave radiation photons • Ankle formed by pair production effects (Berezinskii, Gazizov, Grigoreva) Wick, Dermer, and Atoyan 2004 Test UHECR origin hypothesis by detailed fits to measured cosmic-ray spectrum

16. Effects of Different Star Formation Rates g-ray and n signatures of UHECRs at source tests GRB source hypothesis Hopkins & Beacom 2006

17. Light Curves of GRBs 080825C, 081024B Preliminary • First LAT GRB. Note: • delayed onset of high-energy emission • extended (“long-lived”) high-energy g rays First short GRB with >1 GeV photon detected (Fermi GRBs reviewed by H. Tajima)

18. 8 keV – 260 keV 260 keV – 5 MeV LAT raw LAT > 100 MeV LAT > 1 GeV T0 Light Curves of GRB 080916C • Again, two notable features: • Delayed onset of high-energy emission • Extended (“long-lived”) high-energy g rays • seen in both long duration and short hard GRBs

19. Interpretation of Delayed Onset of >100 MeV Emission • Random collisions between plasma shells  Separate emission regions from forward/reverse shock systems  Second pair of colliding shells produce, by chance, a harder spectrum  Expect no time delays for >100 MeV in some GRBs, yet to be detected • Opacity effects  Expansion of compact cloud, becoming optically thin to >100 MeV photons  Expect spectral softening break evolve to higher energy in time, not observed GRB 080916C • Up-scattered cocoon emission Synchrotron-self-Compton for < MeV External Compton of cocoon photons, arriving late from high-latitude, to >100 MeV Toma, Wu, Meszaros (2009) • Proton synchrotron radiation Inherent delay to build-up proton synchrotron flux which sweeps into LAT energy range from high-energy end Razzaque, Dermer and Finke (2009)

20. Synchotron Radiation from UHE Protons Instantaneous energy flux F (erg cm-2 s-1); variability time tv, redshift z Implies a jet magnetic field rb is baryon loading-parameter (particle vs. g-ray energy density) xB gives relative energy density in magnetic field vs. particles G > Gmin 103G3 from gg opacity arguments

21. Fermi Acceleration of Protons in GRB Blast Waves Protons gain energy on timescales exceeding Larmor timescale, implying acceleration rate f is acceleration efficiency Saturation Lorentz factor: Proton saturation frequency (in mec2 units): Observer measures a time for protons to reach

22. Time for Proton Synchrotron Radiation to Brighten gg processes induce second generation electron synchotron spectrum at i.e., ~ 500 MeV for standard parameters Time for proton synchrotron radiation to reach esat,e:

23. Long GRBs as the Sources of UHECRs • Maximum energy of escaping protons • Long GRB rate 2fb Gpc-3 yr-1 at the typical redshift z 1–2 • 10 smaller at 100d100 Mpc due to the star formation • fb > 200 larger due to a beaming factor • 60E60 EeV UHECR deflected by an angle • IGM field with mean strength BnGnG coherence length of l1 Mpc • Number of GRB sources within 100 Mpc with jets pointing within 4 of our line-of-sight is •  If typical long duration GRBs have a narrow core accelerating UHECRs, then GRBs could account for Auger events within GZK radius.

24. Extended High Energy Emission GRB 080916C • LAT detected GRBs show significant high energy emission extending after the GBM emissionreturns to background (discovered originally with EGRET on Compton Observatory; Hurley et al. 1994) • Could be due to … • Delayed arrival of SSC • Long-lived hadronic emissions (Böttcher and Dermer 1998) Abdo et al., Science (2009) Greiner et al., A&A (2009) • Injection problem • Internal shells • External shock • extended (> 1016 cm) wind/shell

25. Auger UHECR arrival directions correlated with matter within 100 Mpc UHECR Origin Galactic sources young neutron stars or pulsars, black holes, GRBs in the Galaxy Particle physics sources superheavy dark matter particles in galactic halo top-down models Clusters of galaxies Ruled out: Viable: Jets of AGNs: radio-loud or radio-quiet? Cen A!, M87?  nG IGM magnetic field (long) GRBs: Requires nano-Gauss intergalactic magnetic field UHECRs accelerated by black-hole jets

26. Unresolved g-Ray Background BL Lacs: ~2 - 4% (at 1 GeV) FSRQs: ~ 10 - 15% Star-forming galaxies (Pavlidou & Fields 2002)Starburst galaxies(Thompson et al. 2006) Galaxy cluster shocks (Keshet et al. 2003, Blasi Gabici & Brunetti 2007) Thermal black holes (accretion) Dermer (2007) Nonthermal black holes (jet) Data: Sreekumar et al. (1998) Strong, Moskalenko, & Reimer (2000)

27. Fermi LAT GRBs as of 090510 192 GBM GRBs ~30 short GRBs 8 LAT GRBs (reviewed by H. Tajima, this conference) (distinguish long vs. short GBM GRBs)