Intermediate Seyfert: optical spectroscopic characteristics

Active Galactic Nuclei (AGN) are a particular class of galaxies characterized by a pretty luminous central region produced by an accreting disk. According to the Unified Model (UM) around this central structure we can recognize three regions: the Broad-Line Region (BLR) characterized by high velocity clouds, the Narrow-Line Region (NLR) with small velocity clouds, and the obscuring torus (Antonucci, 1993). The last component is fundamental in explaining the differences between AGN. According to the angle between the orientation of the torus and the observer we can find Seyfert 1 (Sy1), Seyfert 1.2/1.5/1.8/1.9 (IS), and Seyfert 2 (Sy2) galaxies (Khachikian & Weedman, 1974; Osterbrock, 1981). The second group defines what are called Intermediate Seyfert galaxies, in which both the NLR and the BLR can be seen due to the inclination. This work is focused on this kind of AGN, often ignored and never extensively studied as a class. Indeed, most of the studies tend to include them in the type 1/2 classification, causing a clear pollution of the analyzed samples. In addition, in some cases IS can be confused with Narrow-Line Seyfert 1 (NLS1). Obviously this is an effect of the composite profile of the Balmer lines, that makes difficult to easily or automatically separate IS from the other types. The aim of this work is to explore the spectroscopic characteristics of IS that could allow to define criteria to isolate them in a generic sample fo AGN. In addition, studying their properties could confirm the UM or on the contrary give new insights in the AGN structure, suggesting for example the existence of irregular emission from the accretion disk. The study is divided in: Chapter 1 introduction on AGN and Seyfert galaxies; Chapter 2 presentation of the sample, data analysis, fitting procedure, and physical outcomes; Chapter 3 conclusions and future work.

Active Galactic Nuclei (AGN) are a particular class of galaxies characterized by a pretty luminous central region produced by an accreting disk. According to the Unified Model (UM) around this central structure we can recognize three regions: the Broad-Line Region (BLR) characterized by high velocity clouds, the Narrow-Line Region (NLR) with small velocity clouds, and the obscuring torus (Antonucci, 1993). The last component is fundamental in explaining the differences between AGN. According to the angle between the orientation of the torus and the observer we can find Seyfert 1 (Sy1), Seyfert 1.2/1.5/1.8/1.9 (IS), and Seyfert 2 (Sy2) galaxies (Khachikian & Weedman, 1974; Osterbrock, 1981). The second group defines what are called Intermediate Seyfert galaxies, in which both the NLR and the BLR can be seen due to the inclination. This work is focused on this kind of AGN, often ignored and never extensively studied as a class. Indeed, most of the studies tend to include them in the type 1/2 classification, causing a clear pollution of the analyzed samples. In addition, in some cases IS can be confused with Narrow-Line Seyfert 1 (NLS1). Obviously this is an effect of the composite profile of the Balmer lines, that makes difficult to easily or automatically separate IS from the other types. The aim of this work is to explore the spectroscopic characteristics of IS that could allow to define criteria to isolate them in a generic sample fo AGN. In addition, studying their properties could confirm the UM or on the contrary give new insights in the AGN structure, suggesting for example the existence of irregular emission from the accretion disk. The study is divided in: Chapter 1 introduction on AGN and Seyfert galaxies; Chapter 2 presentation of the sample, data analysis, fitting procedure, and physical outcomes; Chapter 3 conclusions and future work.The aim of this work is to obtain some optical characteristics of intermediates galaxies in order to distinguish them from NLS1 or to include them in the samples without polluting the scientific analysis. The work is divided as follow: Chapter 1 with an introduction on AGNs and Seyfert properties in the different bands, Chapter 2 a presentation of the selected sample and some general characteristics, Chapter 3 with the data analysis, in particular fittings and line ratios, Chapter 4 with the classification and discussion.