Studies of AGN populations with XMM-Newton

This thesis presents an X-ray and optical analysis of the Subaru XMM-Newton Deep Survey (SXDS), focusing on the analysis of the combined XMM-Newton and INT-WFC data. The SXDS has an unprecedented combination of depth and area coverage, covering 1.3 square degrees, making this survey the largest ultra-deep survey to date. The vast majority of the ≈ 1000 X-ray sources within the survey are found to be active galactic nuclei (AGN), making this an excellent resources for investigating the distribution of unobscured and obscured sources.;Concentrating on the AGN population, cross-correlation of X-ray, optical and spectroscopic data have enabled investigation into optical and X-ray colours, optical morphologies, redshift distribution and X-ray and optical obscuration. This thesis, utilizing underlying X-ray and optical properties of AGN such as central nucleus luminosity and obscuration also introduces a simple toy model with the aim of understanding the SXDS AGN X-ray-to-optical flux ratio distribution.;XMM-Newton's large field of view and SXDS field depth has also enabled investigations into the X-ray spectral properties of the brightest 130 sources (> 300 total EPIC counts) within the SXDS. These sources are shown to mainly comprise of unobscured and obscured AGN with a range of intrinsic absorptions and best filling photon indices of ? ≈ 1.8 -- 2.0, consistent with other X-ray surveys.;To illustrate the capabilities of XMM-Newton the X-ray source properties of two powerful, high redshift (z = 2.48) narrow line radio-loud type-2 quasars B3 0731+438 and 3C 257, observed separately from the SXDS are also presented.;The combined optical and X-ray analysis presented in this thesis reveals the SXDS AGN population comprise of a large population of unobscured and obscured AGN. These sources have a range of absorption columns, redshifts and luminosities, encompassing low luminosity AGN through to luminous quasars and demonstrate a strong relationship between optical and X-ray obscuration.