Mullard Space Science Laboratory

N. J. Salvi
Central engines of AGN
2003 (supervisor: K. O. Mason)

Active Galactic Nuclei (AGN) are luminous objects thought to be powered by accretion of material onto a super-massive black hole. They emit radiation across a wide frequency range from the gamma-rays to the radio. X-ray emission, relativistic jets and superluminal motion are phenomena which originate close to the central power source and can be used to study conditions in the innermost regions around a black hole. To understand the central engines in these sources, I have used the high sensitivity and signal to noise XMM-Newton data to study the X-ray emission in three observationally very different AGN. III Zw2 is a luminous (L_2-10 ~ 10^45 erg s^-1) radio-intermediate (i.e. intrinsically radio weak but with relativistic jets pointed straight at the observer) quasar and I have studied its radio to X-ray emission over a period of 25 years. The X-ray data for a bright (L_2-10 ~ 10^44 erg s^-1) radio quiet Seyfert 1 galaxy MCG-2-58-22 is compared with advanced reflection models incorporating Compton reflection and re-processing of X-rays in an accretion disc in a self consistent manner. I have also studied the rapidly variable X-ray emission in a low luminosity (L_2-10 ~ 10^40-41 erg s^-1) narrow line Seyfert 1 galaxy NGC 4051. Time resolved spectra are used to better understand the properties of various components in the X-ray emission of this source. To help discriminate between theoretical models that explain energy generation close to the central source and to obtain clues to the dominant emission mechanisms within the source I have also studied the multiwavelength emission and the broad band spectrum (radio to X-rays) of these AGN.


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