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Cosmic Rays, Gamma Rays and Multi Messenger Astronomy. Part 2. Jacques Paul. CEA IRFU , Service d’Astrophysique, Saclay. 7 July 2012. International School of Astronomy and Astrophysics Multi-Messenger Approach in High Energy Astrophysics. APCParis. Space gamma-ray astronomy.

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  1. Cosmic Rays, Gamma Rays and Multi Messenger Astronomy Part 2 Jacques Paul CEA IRFU, Service d’Astrophysique, Saclay 7 July 2012 International School of Astronomy and Astrophysics Multi-Messenger Approach in High Energy Astrophysics APCParis

  2. Space gamma-ray astronomy For a complete review on space activities, please refer to the lecture on “Astroparticles in space" to be given next week by Olivier La Marle. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 2

  3. Guiseppe (Beppo) Occhialini (1907-1993) Prominent particle physicist Founding Father of the European space research One of the first to understand the importance of gamma-ray astronomy J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 3

  4. The beginnings of gamma-ray astronomy Up to the end of the 1960s, gamma-ray astronomy was solely based on theoretical considerations, whose overly optimistic predictions proved to be rather accurate as concerned the nature of the gamma-ray sources. During the 1950s, such predictions took advantage of the discoveries reported by radio astronomers, as e.g. the detection of huge amounts of atomic hydrogen in the Galaxy thanks to the first 21 cm observations. McGee, Murray (1961), Australian Journal of Phys, vol. 14, pp. 260-278. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 4

  5. A long expectation 1952 Prediction of the high-energy gamma-ray emission of the Galactic disk via p-p interactions Hayakawa (1952), Prog. Theor. Phys., vol. 8, p. 571. 1958 Inventory of the cosmic sites expected to radiate gamma rays: It include the Crab Nebula, Cyg A and the Sun Morrison (1958), NuovoCimento, vol. 7, p. 858. 1958 First detection of cosmic gamma rays during a solar flare Peterson, Winckler (1958), Phys. Rev. Let., vol. 1, p. 205. 1967 First exhaustive revue devoted to gamma-ray astronomy “Ten years after the launch of Sputnik 1, one had not succeeded in definitely detecting any gamma rays from cosmic sites localized beyond the solar system” Fazio (1967), ARA&A, vol. 5, p. 481. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 5

  6. First detection of cosmic gamma rays 1968 Discovery of the high-energy (> 100 MeV) galactic gamma-ray emission with a pair-production detector aboard OSO III Clark et al. (1968), ApJ, vol. 153, p. L203. 3 2 Rate (×10-4 s-1) 1 -90 -60 -30 0 30 60 90 Galactic latitude (deg.) OSO III (1967-1969) Galactic emission latitude profile J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 6

  7. First detection of gamma-ray bursts 1973 Report on the detection of gamma-ray bursts by the Vela satellites Klebesadel et al. (1973), ApJvol. 182, p. L85. Vela 5A 103 102 101 103 Vela 6A Detector count rate (counts s-1) 102 101 103 Vela 6B 102 101 -40 0 0.1 1 10 100 Time (mn) Lin. scale Time (s) Log. scale Artist view of a Vela satellite Light curve of GRB 700822 J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 7

  8. Nov. 1972-June 1973 Aug. 1975-April 1982 High-energy observatories of the 1970’s 1972 Launch of SAS-2, interruption of the data taking after 8 months due to the failure of a low-voltage power supply 1975 Launch of COS-B, the first European Space Agency satellite J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 8

  9. +20 Galactic latitude (degrees) +20 150 120 90 60 30 0 330 300 270 240 210 180 Galactic longitude (degrees) COS-B major outcomes Mayer-Hasselwander et al. (1982), A&A, vol. 107, p. 390. Swanenburg et al. (1981), ApJ, vol. 243, p. 69. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 9

  10. GRANAT CGRO Gamma-ray observatories of the 1990’s 1990 Following a period of little activity (Challenger disaster), the 1990s were a golden decade for space gamma-ray astronomy owing to a new generation of gamma telescopes aboard GRANAT and CGRO. In operation from 1990 until 1997 In operation from 1991 until 2000 J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 10

  11. 1E 1740.7-2942 SIGMA/GRANAT major outcomes Low-energy gamma-ray studies of the Galactic Center region Goldwurm et al. (1994), Nat, vol. 371, p. 589. Contribution to the discovery of microquasars Mirabel et al. (1992), Nat, vol. 358, p. 215. 6 4 Galactic latitude (degrees) 2 0 4 2 0 358 356 354 Galactic longitude (degrees) J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 11

  12. EGRET/CGRO major outcomes EGRET High-energy gamma-ray survey revealing tens of blazars Hartman et al. (1999), ApJS, vol. 123, p. 79. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 12

  13. 4 kpc Galactic gamma-ray emission 100-300 MeVlongitude profile of the Gamma-rayemission measured by EGRET in the –2° < b < 2° latitude interval (point sources subtracted) The gamma-ray emission from the Galactic disk originate mainly from the 4 kpc molecular ring as revealed by mm observations Hunter et al. (1997), ApJ, vol. 481, p. 205. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 13

  14. BATS/CGRO major outcomes 1000 100 N (> Φ) 10 1 1 10 100 Fluence Φ (cm-2 s-1) The 2704 GRBs detected by BATSE are uniformly distributed on the celestial sphere Deficit of weak bursts in case of a population uniformly distributed in an Euclidean space J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 14

  15. The gamma-ray domain Upper bound no limit… …except those implied by detection processes At ~ 10 PeV, one expects only few photons km-2 day-1 Lower bound endless – but instructive – debate on the boundary between X rays and gamma rays Question: at which energy begins the gamma-ray domain? J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 15

  16. Possible answers From the literature 100 keV Fazio (1967), ARA&A, vol. 5, p. 480. 50 keV Macomb, Gehrels (1999), ApJS, vol. 120, p. 335. From the nature of the emission processes Continuum emissions: no clear indication Line emissions:conflicting indications A plausible answer: 20 keV… Although arbitrary, this limit refers to significant facts Astrophysical facts Experimental facts J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 16

  17. Astrophysical facts Most stars radiate thermal emission ± similar to that of a blackbody Two conditions to sustain blackbody emission: 1 The luminosity cannot exceed the Eddington limit 4 πR2σT 4 1.3 × 10 38 (M/ M) erg s -1 2 The radius must exceed the Schwarzschild radius R> 2 M G / c 2 The radius upper limit is then: R< 475 (T / 10 7)- 4 km Beyond 20 keV, thermal processes give way to non-thermal J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 17

  18. Experimental facts photons of energy > 20 keV Photons of energy < 20 keV J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 18

  19. Why gamma-ray astronomy? The specific character of the emission processes Interactions of HE particles with matter, magnetic & photons fields Decay of unstable particles induced by p-p interactions Matter-antimatter annihilation Nuclear de-excitation The diversity of the emission sites High-temperature plasmas confined by compact objects (NS, BH) Relativistic plasmas Diluted media crossed by accelerated particles Media “contaminated” by radioactive species The extreme luminosity of gamma-ray sources High-z Universe The penetrating power of HE radiation J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 19

  20. Transient source Host galaxy SN 1994d GRB 011121 Messier 87 1E 1740.7-2942 Compact (point like) gamma-ray sources Sites where extreme physical conditions prevail: intense gravity fields, very high temperatures, strong magnetic and electric fields An apparently ill-assorted gallery of cosmic sites, but ... All sites give way to the fatal attraction of gravity Many sites produce copious outflows of relativistic matter Privileged messengers: gamma-ray photons, neutrinos, cosmic rays, gravitational waves J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 20

  21. All sky surveys Gamma rays (Eγ > 100 MeV) Gamma rays (Eγ = 1.8 MeV) Gamma rays (Eγ = 511 keV) J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 21

  22. 100 Atmospheric transmission reduced by 50% 80 Altitude (km) 60 40 20 radio IR V UV X gamma The atmospheric screen J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 22

  23. 10 TeV 10 GeV 1 GeV 10 MeV 1 MeV 1 TeV 1 PeV 100 TeV 100 GeV 100 keV 100 MeV Exploring the gamma-ray domain From space From ground From space HESS INTEGRAL Fermi J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 23

  24. Specificities of space gamma-ray astronomy Space gamma-ray astronomers face a threefold handicap: Gamma rays cannot be reflected and need dense detection material Detection area = collecting area Large and massive detectors At equal luminosity, gamma-ray sources radiate much less photons Very long observing time (days, weeks) Necessity of wide fields of view Space devices are exposed to huge fluxes of charged particles that… …produce detection effects similar to those of cosmic gamma rays …produce secondary gamma in the detector and surrounding material The resulting background makes gamma observations as prohibitive as observations in the visible performed in broad daylight! J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 24

  25. E0 E1 = ––––––––––––––– E0 (1 – cosθ) 1– –––––––––––– me c2 Detection processes Photoelectric effect Absorption of a photon of energy E0 with ejection of a bound electron: E = E0–EBINDING Compton scattering The energy E1 (E1 < E0) of the scattered photon is related to its energy E0 and to the scattering angle θ according to: Pair creation A photon of energy E0 > 2mec2 creates in the intense electric field of a nucleus an electron-positron pair such as: E0 = E1+ E2+ 2mec2 J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 25

  26. 103 102 Photoelectric 10 Mass attenuation coefficient (cm2 g-1) 1 10-1 10-2 Compton Pair 1 10 102 103 104 Energy (keV) Diffusive material: aluminum J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 26

  27. 104 103 Photoelectric 102 Mass attenuation coefficient (cm2 g-1) 10 1 10-1 Compton 10-2 Pair 1 10 102 103 104 Energy (keV) Absorbing material: lead J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 27

  28. Imaging technique in gamma-ray astronomy Cosmic-ray sources (sites where cosmic rays are accelerated to relativistic energies) are likely to be also sources of copious gamma-ray radiation… BUT The gamma-ray radiation cannot be reflected since its wavelength is much below the inter-atomic distances in solids. Then to localize sources, gamma-ray telescopes cannot features classical arrangements of mirrors and specific imaging techniques have to be worked out. Straightforward imaging techniques are based on the modulation of the incident radiation, such as collimators and coded apertures. More sophisticated techniques take advantage of the properties of the interaction processes (Compton diffusion/pair production) to estimate the arrival direction of incident photons. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 28

  29. collimator detector Collimators The simplest optical device to determine gamma-ray incident direction Main issues are: Induced background Opacity vs mass On-Off technique J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 29

  30. Coded aperture J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 30

  31. Coded aperture imaging matrix algebra Sγ (sky) The distribution of the source intensities in the field of view M (mask) The distribution of opaque and transparent mask elements D = M Sγ D (detector) If  is the cyclic convolution operator W (sky image) Can be constructed in a unique way if M is invertible G  M = δ This condition holds if it exists G such as: W = G  D In such a case, the sky image is: W = G M Sγ W =Sγ G  M = δ Implying: since The Uniformly Redundant Array (URA), meets the above conditions while minimizing the background contribution Fenimore, Cannon (1978), Applied Optics, vol. 17, p. 337. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 31

  32. SIGMA: the precursor First space coded mask gamma-ray telescope to operate in space Energy band: 35 keV to 1.3 MeV; angular resolution: 13 arc minutes Paul et al. (1991), Adv. in Sp. Res., vol. 11, p. (8)289. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 32

  33. transmission It works! observation decoding J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 33

  34. A basic Compton telescope features two Telescope axis Φ layer of position sensitive detectors Layer 1: made of diffusive material to scatter the incident gamma ray Ψ θ Layer 2: made of absorbing material to absorb the scattered photon Both incoming photon incidence angle Φ and energy E0 can be derived from the energy deposits E1in layer 1 and E2 in layer 2 and from the angle Ψof the scattered photon Compton telescope J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 34

  35. Gamma-ray polarimetry incident photon electric vector scattered photon α Photon fairly scattered in a plane perpendicular to its electric vector Azimuthal distribution of scattered photons (α angle) around the source direction allows an estimate of the degree of linear polarization Method successfully tested in the case of INTEGRAL Forot et al. (2008), ApJ, vol. 688, p. L29. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 35

  36. Incident photon whose energy Eγ> 2mec2 (Eγ> 1.022 MeV) can induce charged particle anticoincidence shield an e--e+ pair in the intense electric field close to an atomic nucleus pair conversion foils Particle trajectories do not markedly deviate from the photon particle tracking detectors direction as soon as the photon energy Eγ >> 2mec2 calorimeter e+ e- The mean electron pair deviation θ is given by: Pair production telescope In case of Eγ = 100 MeV, the mean deviation θ ~ 1.5° J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 36

  37. Grazing incidence telescope using Wolter I optics are governed by: EM (keV) = k F / D EM is the spectral upper bound D is the mirror diameter F is the telescope focal length k is a coefficient depending of the reflecting surface (for gold, k = 1) One simple way to operate beyond 20 keV is to markedly increase the focal length Absolute necessity of bringing into operation two satellites in close formation Towards a grazing incidence telescope Focal distance = 7.5 m Focal plane J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 37

  38. Multi-wavelength astronomy J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 38

  39. 1031 X rays visible soft gamma rays 1030 hard from space radio 1029 from ground νFν (W) 1028 10 GeV 300 GeV 10 TeV 100 TeV 1027 Crab Nebula 1026 1010 1015 1020 1025 1030 Frequency ν (Hz) Usefulness of multi-wavelength observations X rays soft gamma rays hard from space from ground 10 TeV 100 TeV Crab Nebula Thanks to the non-thermal nature of the emission processes gamma-ray sources can be profitably observed at longer wavelengths J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 39

  40. Multi-wavelength view of the galactic disk J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 40

  41. Multi-wavelength observations and cosmic rays Studies combining data on the distribution of the gas (atomic and molecular)… …as well as radio waves and gamma-ray observations of the Galactic disk provided reliable information on the distribution of cosmic rays throughout the Galactic disk and on the sources of cosmic rays within the Galaxy Paul, Cassé, Cesarsky (1976), ApJ, vol. 207, pp. 62-77. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 41

  42. 1E 1740.7-2942 Multi-wavelength discovery of microquasars In 1990, the first accurate images of GC region obtained with the SIGMA coded-mask telescope aboard GRANAT prompted a multi-wavelength campaign to investigate the newly discovered hard source 1E 1740-2942. 6 4 Galactic latitude (degrees) 2 0 4 2 0 358 356 354 Galactic longitude (degrees) J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 42

  43. Multi-wavelength discovery of microquasars The multi-wavelength campaign included the VLA, a radio interferometer designed to perform observations with a very high angular resolution J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 43

  44. Multi-wavelength discovery of microquasars Mirabel et al. (1992), Nat, vol. 358, p. 215. J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 44

  45. Multi-wavelength study of microquasars In 1992, the SIGMA observation of a long outburst of GRS 1915+105 prompted a similar multi-wavelength campaign to monitor the source. In 1994, the VLA enabled the detection of superluminal motion similar to that observed in AGN, a new justification of the name microquasar. Mirabel, Rodriguez (1994) Nat, vol. 371, pp. 46-48 J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 45

  46. Multi-wavelength study of microquasars Separation (106 km) 0 200 400 600 800 1.0 X rays infrared radio Luminosity (arbitrary unit) 0.5 disk emptying ejection 0.0 7.9 8.0 8.1 8.2 8.3 8.4 8.5 8.6 8.7 8.8 8.9 Time (hours) Detailed evolution of the matter ejection from GRS 1915+105 J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 46

  47. Polarized gamma rays from Cygnus X-1 Comptonization spectrum adjusted to the 20-150 keV data points Exposure: 5×106 s (58 days) 10-2 10-3 10-4 power-law fitto the 400-2000 keV data points (photon index 1.6) Photon cm-2 s-1 keV-1 10-5 10-6 Two spectral components 100 1000 Energy (keV) Polarization fraction < 20% (250-400 keV) 67±30% (400-2000 keV) Laurent et al. (2011), Science, vol. 332, p. 438 J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 47

  48. A jet origin for gamma rays at E>400 keV High degree of polarization implies that the magnetic field is coherent over the emission site jet origin strongly favored The photon spectrum >400 keV is a power law of index α=1.6 Electron spectrum is also a power law of index p=2.2 consistent with the canonical value p=2 for shock-accelerated particles For B ~10 mG, electron energy would be around a few TeV J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 48

  49. The case of gamma-ray burst J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 49

  50. An unexpected consequence of the Cold War J. Paul ISAPP 2012 – Cosmic Rays, Gamma Rays and Multi Messenger Astronomy – APC Paris – 7 July 2012 Slide 50

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