M.Sc Thesis

M.Sc StudentCohen Fishel
SubjectThe Origin of Radio Emission in Radio Quit Active Galaxies
DepartmentDepartment of Physics
Supervisor PROF. Ari Laor
Full Thesis textFull thesis text - English Version


The origin of radio emission in radio quiet quasars (RQQs) is not established yet. One possibility is that the radio emission in RQQ originates in coronal activity. If it is correct, then RQQ should generally display compact flat cores at a few GHz due to synchrotron self absorption.

X - ray emission is known to be significantly variable in AGN. Radio observation also shows some variability. These led us to examine how the synchrotron radiation from coronal emission may change over time.

We assume that a disturbance in the X - ray emission presumably following a coronal mass ejection causes a change in the electron distribution function and in the magnetic field.

Our main goal is to examine the following change in the synchrotron emission. This can be used as a tool to derive the radio source properties in RQ AGN based on observations of radio variability in different band.

In our work, we calculate the spectrum for slab and sphere geometries for different gradients in the electron distribution and in the magnetic field.

In the optically thin limit the slope of the spectrum remains constant at the value -0.5.

In the optically thick limit the slope of the spectrum is dependent upon the gradient of the electron distribution and the magnetic field. Combinations of different gradients produce slopes in the range between -0.5 to -2.5.

We also calculate the luminosity versus time at different frequencies and different gradients and derive the evolution of the spectrum in the radio as a function of time.

We find that steeper gradients in the magnetic field and in the energy density of the electrons cause the time delay between the radio and the X - ray variability and between different bands in the radio to decrease.

These results can be used, together with future radio and X - ray monitoring, to probe the nature of the radio emission in RQQs.