Refiloe edited subsection_Black_holes_and_Active__.tex  over 8 years ago

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It was in the late 1940s when the connection between cosmic radio waves and synchrotron emission was established. In AGN, Bremsstrahlung, Synchrotron and Compton emission processes are most common. Synchrotron radiation accounts for much of the radio emissions in AGN. The jets of an AGN produce synchrotron radiation due to near-relativistic electrons spiraling around magnetic field lines.  This process produces polarized radiation in the direction of propagation of the emitting electron. The torus emits unpolarized thermal radiation. radiation - refer to Figure 3.  It has been theorized that the ionized disk associated with the torus produces a varying magnetic field across its surface. The varying magnetic field then induces a large electric field which accelerates particles to relativistic speeds. These particles spiral along the magnetic field lines and produce synchrotron radiation. Within AGN the radiation is emitted by a variety of sources, where some of the sources are thermal and others non-thermal. \cite{Burke_1997} states that the relative strength of these sources depends on the orientation of the AGN. The overall spectrum however, can be represented by a simple power law. It is widely held that radio sources in the Universe emit by the synchrotron process at lower radio frequencies in the meter and centimeter wavelength range.\cite{Wielebinski_2006} The radio core of an AGN emits synchrotron radiation emitted through particle acceleration and collimation into a double lobed structure. These are typical traits of radio galaxies. AGN also have a pair of jets of material ejected from their core. The structure of a radio source is also determined by the interaction of its energetic jets with ionized gas which surround the host galaxy. \cite{Krawczynski_2013} also observe that the black holes in AGN accrete matter and convert the gravitational energy of the accreted matter (and possibly also the rotational energy of the black hole) into mechanical and electromagnetic energy. We also have that inside the accretion disk, a fraction of the gravitational energy of the accreted material is converted to heat and electromagnetic radiation which is then radiated away by the accretion disk. The jets are formed from a portion of the material processed through the accretion disk which escapes the accretion system as collimated and uncollimated outflows. Jet plasma velocity can be denoted by v where $v = \beta_{jet}*c \approx c $ ,and c represents the speed of light. $\Gamma_{jet}$ , the bulk Lorentz factor of the plasma is given by $ \Gamma_{jet} = (1 - (\beta_{jet})^2 )^{-1/2}$ . Emissions from the jets can be red or blue-shifted as a result of the relativistic Doppler factor $\delta_{jet} = \frac{1}{\Gamma_{jet} \times (1- \beta_{jet}\times\cos{\theta})}$