A Systematic Study of The Optical to X-ray Spectral Properties of Active Galactic Nuclei

Abstract

In this thesis I present a detailed study of the optical to X-ray spectral properties of Active Galactic Nuclei (AGN). We propose a new broadband SED model which combines the standard accretion disc emission, low and high temperature Comptonisation components by introducing a corona radius. Applying the new models to broadband spectral data, we found that RX J0136.9-3510 and RE J0134+396 have similar spectra and broadband SEDs, representing a distinct spectral state which can only be attained by super Eddington flows.


A detailed optical and X-ray spectral analysis is then carried out for a big sample of 51 unobscured nearby type 1 AGNs. We find that NLS1s tend to have softer 2-10 keV spectra, lower black hole mass, higher Eddington ratio, higher index and smaller coronal radius. The edge of Balmer continuum is shifted redwards and smoothed by more than predicted by the FWHM of the Balmer emission lines. A new method called `Correlation Spectra Technique (CST)' is proposed, which is powerful for multi-waveband spectral analysis. We find that among the three Balmer line components, the broad component has the best correlation with hard X-ray emission. Optical oxygen forbidden lines all well correlate with the hard X-ray emission.


We conducted a systematic cross-correlation among the 9 key SED parameters: , , , , FWHM, M, , L and L, and found the driven parameters to be M, and L (or equivalently ). AGN's intrinsic SEDs exhibit strong diversity and changes similarly with , , , , FWHM and M. However, the SED shape is not sensitive to L.