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Identifier

000457414

Title

Theoretical model fits to the optical/UV spectral energy distributions of AGN

Alternative Title

Προσαρμογή θεωρητικών μοντέλων στο οπτικό/υπεριώδες φάσμα ενεργών γαλαξιακών πυρήνων

Author

Παπουτσής, Μάριος Χ.

Thesis advisor

Παπαδάκης, Ιωσήφ

Reviewer

Παυλίδου, Βασιλική
Κυλάφης, Νικόλαος

Abstract

In this work, we aim to study simple theoretical models of the accretion disk in AGN, compute the resulting model SED, and then compare it with observed SEDs. We consider the Novikov-Thorne (1973) model and we take into account the effects of electron opacity, i.e. Thomson scattering and free-free absorption, as well as Compton scattering. Regarding the first two processes, we consider the case of a modified blackbody spectrum, while regarding the latter process we consider the case of a colour correction to the blackbody emission formula. We then create model accretion disk spectra for a wide range of AGN parameters (i.e. black hole mass, accretion rate, spin, and inclination) and fit their average to the observed mean SED of 119,652 SDSS quasars (taken from Krawczyk et al. 2013). In this way, we can investigate whether the current accretion disk models are consistent with the observed AGN SED, and at the same time determine the bet-fit black hole mass, accretion rate, spin, and inclination distribution for a large sample of AGN. The sample size is one of the main differences between our modeling and previous works. In addition, we use a rather innovative way of accounting for the electron opacity effects and also include the relativistic effects of photon propagation from the disk to the observer at infinity as computed by Dovciak (2004). We conclude that the accretion disk models we consider cannot fit the observed quasar SEDs well. Therefore, models that include the intrinsic reddening of AGN or the illumination of the disk from the AGN X-ray source might be required.

Language

English

Subject

Accretion disks

Galaxies: active

Δίσκοι προσαύξησης

Ενεργοί γαλαξίες

Issue date

2023-07-28

Collection

School/Department--School of Sciences and Engineering--Department of Physics--Post-graduate theses

Type of Work--Post-graduate theses