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.

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

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

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

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

= 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

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

=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

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

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