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Sensitivity of High Energy Telescopes

Sensitivity of High Energy Telescopes. Chandra. fov, psf, exposure, systematics, value-added science. Goal: 10 -6 ph/cm 2 /s. Sources. Extragalactic Science with an MeV Telescope. 1. Gamma-ray galaxies/AGNs: (RQ) Seyferts; Buried Seyferts; FSRQs and BL Lacs; radio galaxies; others

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Sensitivity of High Energy Telescopes

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  1. Sensitivity of High Energy Telescopes Chandra fov, psf, exposure, systematics, value-added science Goal: 10-6 ph/cm2/s

  2. Sources Extragalactic Science with an MeV Telescope 1. Gamma-ray galaxies/AGNs: (RQ) Seyferts; Buried Seyferts; FSRQs and BL Lacs; radio galaxies; others black-hole powered: 1e48 erg/s at z~1 => 1e-10 erg/cm^2-s lobe emission in radio galaxies/Cen A/M87/NGC 1275/ 2. Gamma-ray galaxies/normal (LMC), star-forming, starburst, IR luminous cosmic-ray powered (MW luminosity ~few x 10^39 erg/s) ~1e39 erg/s at 1 Mpc => 1e-10 erg/cm^2 s depends on gas density and star formation rate 3. Gamma-ray bursts: long-duration (long-soft), short hard, LLGRBs, XRFs, SGRs 4. Clusters of galaxies/Diffuse extragalactic 5. Galaxies bright in MeV lines/dark matter annihilation/evaporating black holes Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  3. Astrophysics Extragalactic Science with an MeV Telescope Relativistic flows: Compactness arguments: Elliott-Shapiro relation for Eddington-limited accretion, DL/D t arguments,Gmin Spectral Modeling of relativistic jets: Synchrotron/SSC model; EC model; hadronic models 2. Statistics of GRBs and blazars/selection biases/contributions to the background 3. Cosmic-ray theory for cosmic-ray galaxies Secondary nuclear production, transport and escape, diffusion (LMC) 4. Pair features in gamma-ray spectra/ annihilation line physics 5. Compton-scattered CMB/EBL Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  4. Gamma Ray AGNs McNaron-Brown et al. (1995) Dermer and Gehrels (1995) Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  5. Multiwavelength Spectra of AGNs Largest energy release of FSRQs/LSP blazars Fill in SED at energies where nFn is greatest Blazars at MeV – GeV energies 3C 279 Mrk 421 Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  6. Non-power law spectra • First definitive evidence of a spectral break above 100 MeV • General feature in FSRQs and many BLLac-LPBs • Absent in BLLac-HPBs • Broken power law model seems to be favored • ~1.0 > 0.5  not from radiative cooling • Favored explanation: feature in the underlying particle distribution • Implications for EBL studies and blazar contribution to extragalactic diffuse emission (Benoit Lott’s talk) Preliminary Challenge for modelers to account for the break and the relative constancy of spectral index with time FSRQs BLLac-IPBs BLLac-HPBs BLLac-LPBs Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  7. Blazar Main Sequence Extreme blazars 1 GeV Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  8. Black Hole Evolution FSRQ BL Lac Evolution from FSRQ to BL Lac Objects in terms of a reduction of fuel from surrounding gas and dust Böttcher and Dermer (2000) Cavaliere and d’Elia (2000) Sambruna et al. (1996); Fossati et al. (1998) Ghisellini et al. (1998) BL Lac objects are late stages of FSRQs (1) Blazar main sequence valid? (2) BL Lac BH Masses > FSRQ BH masses? Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  9. Centaurus A and Radio Galaxies Compton-scattered CMB from lobes bright at MeV energies Cen A power: Bolometric radio power: 4×1042 erg s-1 Gamma-ray power: 5×1041 erg s-1 Hard X-ray/soft g-ray power: 5×1042 erg s-1 UHECR power: few ×1040 erg s-1 Cen A power: Bolometric radio power: 4×1042 erg s-1 Fermi gamma-ray power: 5×1041 erg s-1 Hard X-ray/soft g-ray power: 5×1042 erg s-1 UHECR power: few ×1040 erg s-1 Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  10. Cen A SED Origin of Cen A MeV emission? Simultaneous Swift-XRT Swift-BAT Suzaku HESS data does not smoothly extrapolate to LAT g-rays. Internal gg absorption also makes fitting HESS emission difficult. Green: var. timescale ~ 1 day Purple: var. timescale ~1 day Blue: decel. jet model (Georganopoulos & Kazanas 2003) Model by J. Finke Brown: var. timescale ~ 1 day, fits HESS Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  11. GRB Spectra and Peak Energy Distributions Mallozzi et al. (1997)   Epk Epk Schaefer et al. (1998) Spectra Epk Distribution Epk = Peak energy of nFn Distribution Origin of MeV radiation in GRBs: Line of death: photosphere vs. synchrotron vs. SSC Temporal variaibility Epk distribution Dermer/Fermi Splinter Session: Soft Gamma ray Astronomy 05/11/2009

  12. Positron Production from GRBs • Massive star h Carinae: most likely progenitor of GRB in the Milky Way. Wiegelt blobs: Thomson-thick clouds < 1016 cm from central star • Photon front photoionizes and Compton-scatters ambient electron. Back-scattered photons pair-produce with successive waves of photons • Make pair plasma which expands and cools. Pair efficiency of 0.1% of 2.6 x 1039 ergs/s can produce 1042 annihilation 0.511 MeV photons per second in Galaxy Dermer and Böttcher (2000)

  13. Broad Annihilation Lines from GRBs • Thermalized positrons • Direct annihilation • e+ + e- 2g

  14. Annihilation Galaxies g  • N*  N + b+ Novae, SNe, WR stars few • N + p  p+ e+ CRs in diffuse ISM, flares > 60 • N + N'  N*  N + b+ CRs, Sun, Accreting NSs and BHs > few • eB  gB  e+ e- Pulsar electromagnetic cascades ~106-108 • gg e+ e- AGN, Galactic Center, GRBs > few • higher order processes, e.g., e + N, g + N  e+ e- N >102 (compare recent detection of LMC and starburst galaxies at GeV/TeV energies)

  15. 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) Pulsar contribution Galaxy cluster shocks (Keshet et al. 2003, Blasi Gabici & Brunetti 2007) Sreekumar et al. (1998) Strong, Moskalenko, & Reimer (2000) Contribution to the background at MeV enegies

  16. Summary • Gamma-ray AGNs often very luminous at MeV energies • Radio-quiet AGN/Seyferts • Buried AGNs / (EXIST) • Radio-loud AGNs • Statistics and black hole evolution • Energetics • Annihilation galaxies • Relativistic flows • Unresolved gamma-ray background

  17. Back-up Slides

  18. Positron Production from 26Al • Total observed 1.809 MeV 26Al  line flux of 3.1(0.9)10-4 cm-2 s-1   21042 e+ s-1 •  W-R stars and novae (and possibly other sources) make important contributions to 26Al and positron production in the Galaxy (Diehl et al. 1995)

  19. Positron Annihilation Processes Ps ground state • 2g and 3g annihilation • Direct annihilation • 2g • Positronium formation • 2g and 3g • Slowing down, thermalization, and formation of Ps in flight • e+ + e- e+ + e- Coulomb energy loss • e+ + H  e+ + H* excitation • e+ + H  e+ + H+ + e- ionization energy loss • competes with Ps formation through charge exchange (direct annihilation is small) • e+ + H  Ps + H+ charge exchange in flight 1S0 ( - )/2 t2g = 1.25 10-10 s  (  )/2   3S1 t3g = 1.4 10-7 s

  20. Positron Annihilation Processes • Thermalized positrons • Direct annihilation • e+ + e- 2g • e+ + H  2g + H* • Positronium formation • e+ + e- Ps • Radiative recombination • e+ + H  Ps + H+ • Charge exchange (6.8 eV threshold) • Annihilation on dust • quenches Ps (requires n > 1013 cm-3 ) • Positronium quenching at high temperatures Guessoum, Ramaty, and Lingenfelter (1991)

  21. Flux of 0.511 MeV Annihilation Radiation • Measured flux of 2g annihilation radiation correlated with detector FOV • Total 2g flux • f2g = 26 (3)10-4g cm-2 s-1 (SMM) • f2g = 28 (4)10-4g cm-2 s-1 (OSSE) • Total Galactic annihilation rate: • 4p (8 kpc)2f2g 21043 g s-1 • 1 positron produces 2[(1-f)+ (f/4)] 0.511 MeV photons; f is fraction that decay via positronium. (Purcell et al.1999) For f  0.9,  positron sources are producing  31043 e+ s-1in the Milky Way d < 0.5 Mpc (31043 e+ s-1/4p10-6 ph/cm2/s)1/2 for detection—at the level of Milky Way

  22. Sites of annihilation radiation in galaxies • GRB remnants in nearby galaxies or Milky Way (e.g. luminous X-ray sources in M101; Wang 1999) • remnant ages < 106 yrs • total energies > 1052-1053 ergs • HI shells, stellar arcs Diffuse extragalactic annihilation background radiation • Combined spectral, intensity, imaging, and temporal study of annihilation radiation with soft gamma-ray telescope: • novae/old stellar bulge population • annihilation from star forming regions (disk/high-latitude enhancement) • gamma ray bursts/cosmic-ray hadron sources • compact objects

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