Nonthermal radiative processes

This lecture is part of the course "physics of active galactic nuclei" offered to graduate students in astrophysics by Rodrigo Nemmen and Joao Steiner at IAG USP.

https://rodrigonemmen.com/teaching/active-galactic-nuclei/

Transcript

1. Rodrigo Nemmen Non thermal Radiative Processes AGA5727 - Active Galactic Nuclei Credit: ESO
2. Ghisellini Black body intensity compared to Raleigh-Jeans and Wien laws 2 Bremsstrahlung and Black Body
3. Main applications of blackbodies to AGNs Dusty torus . 1 pc Accretion disks 10 5 pc . l . 0.1 pc T~100 K T~104-105 K
4. Synchrotron radiation: Single electron in a uniform magnetic field
5. Synchrotron radiation: Single electron in a uniform magnetic field
6. Synchrotron spectrum of single electron in a uniform magnetic field m Emitted by the Single Electron 53 panel: The /νc) describing on spectrum e single electron. : F(ν/νc) is h some g formulae, as ave defined Ghisellini
7. Extended radio lobes in AGNs Hercules A
8. Radio jets M87
9. Synchrotron spectrum of self-absorbed source Beckmann 2.2 Synchrotron Emission 31 optically thick optically thin 0 1 1 1 . 0 0.1 1
10. Synchrotron spectrum of self-absorbed source in log space and physical units Ghisellini sorption: Electrons 59 tron ally ld tions of electron
11. Synchrotron spectrum of self-absorbed source vs blackbody Netzer Nonthermal radiation processes 1013 1014 1015 1016 1017 .0001 .001 .01 .1 1 10 frequency normalized L ν T=105 K ν5/2 ν2 Figure 2.1. A comparison of a synchrotron source with p = 2.5 (solid line) and a 5
12. Polarization of synchrotron sources Blandford f Linear B Polarisation Fig. 2.3. a) Polarisation of cyClotron radiation from a non-relativistic electron. b) Polarisa- tion of synchrotron radiation from a relativistic electron. usually polarised to a degree that ranges from '" a few per cent to '" 60 per cent. Partly for this reason, it is thought to be synchrotron radiation. 2.2.3 Emission by a power-law electron distribution function. The electrons in
13. Polarization of synchrotron sources Blandford f Linear B Polarisation Fig. 2.3. a) Polarisation of cyClotron radiation from a non-relativistic electron. b) Polarisa- tion of synchrotron radiation from a relativistic electron. usually polarised to a degree that ranges from '" a few per cent to '" 60 per cent. Partly for this reason, it is thought to be synchrotron radiation. 2.2.3 Emission by a power-law electron distribution function. The electrons in
14. Some sites of synchrotron radiation in AGNs Blandford radiation is 100 per cent circular polarised. Now let the electron move with a relativistic speed and beam this radiation in the direction of motion. The two components of circular polarisation will effectively cancel, whereas the linear polarisation will largely survive. The net effect is a typical degree of polarisa- tion of '" 70 per cent. The radio emission from extragalactic radio sources is Table (2.1). Possible synchrotron radiation sites and characteristic physical parameters. Location B 1/ , tcool tdyn Pmin Umin G Hz yr yr dyne cm-2 erg Extended Radio Source 10-5 109 104 107 108 10-11 1059 Radio Jet 10-3 109 103 104 104 10-7 1057 Compact Radio Source 10-1 109 102 10 10 10-3 1054 Outer Accretion Disk 10 1014 103.5 10-4 1 10 1049 Inner Accretion Disk 103 1016 103.5 10-8 1 105 1047 Black Hole Magnetosphere 104 1018 104 10-10 10-3 107 1047 169
15. Fig. 8.—Same as Fig. 1, but for 3C 272.1 (LX = 6.8 ; 10À8LEdd). The emis- Edd). The total WU, YUAN, & CAO Vol. 669 Wu et al. 2007, ApJ Applications of synchrotron to AGNs: radio galaxy spectral energy distributions
16. Thin disk model Nemmen & Brotherton (2010) Radio-loud Radio-quiet Quasar spectral energy distributions log (radiation flux) log (frequency / Hz) Shang, …, Nemmen et al. (2011)
17. Second Series May, lying Vol. zI, Po. 5 THE P HYSICA: REVIEW A QUANTUM THEORY OF THE SCATTERING OF X— RAYS BY LIGHT ELEMENTS BY ARTHUR H. CoMPToN ABSTRACT A quantum theory of the scattering of X-rays and p-rays by light elements. — The hypothesis is suggested that when an X-ray quantum is scattered it spends all of its energy and momentum upon some particular electron. This electron in turn scatters the ray in some definite direction. The change in momentum of the X-ray quantum due to the change in its direction of propaga- tion results in a recoil of the scattering electron. The energy in the scattered quantum is thus less than the energy in the primary quantum by the kinetic energy of recoil of the scattering electron. The correspondingincrease in the wave-length of the scattered beam is Xg — Xp = (2h/mc) sin'-,'9 = o.o484 sin'-', 8, where h is the Planck constant, m is the mass of the scattering electron, c is 1927
18. Squaring these equations, we obtain (po — pi cos 0)2 =p2 cos2 (p and pi sin2 B = p2 sin2 cp Photon E0,P0 V ^ X Electron K,p Before After Figure 2-7 Compton's interpretation. A photon of wavelength 2 is incident o electron at rest. On collision, the photon is scattered at an angle B with increas length 2', while the electron moves o ff at angle 'p. ⌫ ⌫0 Eisberg & Resnick Compton scattering
19. hot electrons photon source Inverse Compton scattering
20. S⌫ ⌫ ⌫ ↵ ⌫0 hot electrons photon source Inverse Compton scattering
21. S⌫ ⌫ ⌫ ↵ ⌫0 hot electrons photon source Inverse Compton scattering
22. Blandford Spectrum of monochromatic source embedded within a hot electron scattering region Fig. 2.6. Spectrum produced by a monochromatic pho ded within a hot electron scattering region. The slope Comptonisation parameter y, given by equation(2.38}. acceleration rate to the escape rate. The spectrum e ⌫0
23. Blandford Synchrotron self-Compton spectrum: synchrotron photons are inverse Compton scattered by rel. electrons are related by equation(2.15)and the limits of integration are exhib- cally in Fig.(2.8). The spectral index of the synchrotron radiation is ely preserved in the inverse Compton emission. Synchrotron I V-a( £I 6max2c.> G lJ' d"max2 WG i 2if _ 2fT 2TT)) Limits of integration for equation(2.42). The electron distribution function is xtend as a power law from "Ymin to "Ymax. Combinations of synchrotron pho- and electron energy radiating a given Compton frequency are shown. b) The ctrum extends as a rough power law (ignoring weakly-varying logarithmic fac- "Y!.inwa/21r to '" "Y:"axwa/21r. synchrotron IC
24. Application of pair production: Fermi Gamma Ray Telescope, 20 MeV - 300 GeV Fermi 2-year all sky
25. Bremsstrahlung radiation is emitted when electrons collide with ions or positrons
26. 2 Bremsstrahlung and Black Body ung ity y for of n if is ung Ghisellini Bremsstrahlung intensity for a spherical source with different temperatures R = 1015 cm ne = np = 1010 cm 3