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Abstract:
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Active Galactic Nuclei (AGN) are galaxy cores in which a supermassive black hole
is being surrounded with an accretion disk, which emits powerful continuum emission. This
continuum ionizes the surrounding gas which than emits the broad lines, detected in the optical
band. The aim of this thesis is to model complex optical spectra of large numbers of type 1
AGNs (AGNs with broad emission lines) and study physical properties of the emitting gas,
so-called broad line region. Understanding the physics of the broad line region, as well as the
physics of AGN as a whole is important for understanding the galaxy formation and evolution.
This thesis investigate a large sample of type 1 AGNs taken from the SDSS spectral database.
In total, over 1500 spectra were analyzed, for which a completely new software for modeling
of optical AGN spectra (named FANTASY) was developed. Automated simultaneous modeling
of all emission components in the optical spectrum enables reliable measurement of spectral
parameters, which can have significant application in future investigation of large AGN samples,
collected within the upcoming large spectroscopic sky surveys.
The physical properties in the broad line region were studied through the analysis of a still
unexplained (anti)correlation between the equivalent width of the emission lines and the conti-
nuum flux (the so-called Baldwin effect). It has been confirmed that the intrinsic Baldwin effect
exists in the Balmer hydrogen lines in type 1 AGNs, and that a potential physical explanati-
on for this effect might be presence of an additional non-ionizing optical continuum emission,
which originates from the broad line region. Finally, the significant outcome of this thesis is is
the new publicly available software package FANTASY, which can be widely used in the future
spectral analysis of AGN. |