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Throughout the last decades a number of correlations between the proper- ties of the supermassive black holes (SMBH) in the center of galaxies and their hosting galaxies have been found. This suggests that these compo- nents influence each other in their evolution. Especially the SMBHs, which accrete matter and reveal themselves as Active Galactic Nuclei (AGN), are suspected to have a major impact on the host galaxy. The so-called ‘pos- itive feedback’ of an AGN triggers star formation locally by outflows and jets. The ‘negative feedback’ manifests itself in the galaxy-wide quench- ing of star formation e.g. by the accretion of almost all the galaxy’s gas onto the SMBH. The ‘feeding’ of the SMBH is also considered to be re- sponsible for the degree of activity of the nucleus. The transport of matter from large distances to the direct vicinity of the nucleus, where the SMBH can accrete it on its own, requires the removal of almost all the matter’s angular momentum (∼ 99.9 %). How is the energy taken away from the mass? On large scales (kpc-scale) bars, spirals and other asymmetries in density are invoked, leading to the dissipation of energy and forcing the gas to lower its orbit. At the order of 100 pc nested bars and nuclear spi- rals take over. Eventually, at ∼ 10 pc, viscuous processes are suspected to bridge the final gap to the SMBH. However, these mechanisms are poorly understood, particularly on very small scales. To improve the understand- ing of different feeding mechanisms more observations are necessary. The Nuclei-of-Galaxies (NuGA) survey targets nearby low-luminosity galaxies using 12CO to pursue the topic of AGN feeding. In this thesis, complemen- tary optical integral field spectroscopic (IFS) data for three NuGA galaxies (NGC 5850, NGC 3626 and NGC 3627) is analysed. Though not selected for this property, they all show signs of interaction with other galaxies. Interactions provide a natural way to perturb the regmotion of gas in galaxies in such a way that they create mechanisms capable of transporting gas to the center. Indeed two out of three galaxies I present here have at least one bar. The data focuses on the circumnuclear area, showing the diverse kinematics of the gas. NGC 5850 shows a smaller bar surrounded by a ring and nested in the large scale bar. Deviations from circular motion can be found also found in NGC 3626. NGC 3627 displays signs of oval gas orbits combined with the influence of a nuclear bar and shocks. Additionally to the feeding topic, the special role of low-ionisation nuclear emission regions (LINERs) and their role in the AGN paradigm is studied exemplary with the observed galaxies. LINERs are often considered to be low-luminosity AGNs and have a characteristic spectrum. In this thesis I point out that other physical mechanisms exist which can produce a similar spectrum. Not every nucleus classed as a LINER is an AGN. With the here used observations, I emphasise the importance of carefully disentangling the dominant ionisation mechanisms and show how helpful spatially resolved spectroscopy (i.e. IFS) is. Indeed, at least in NGC 5850, but possibly also in NGC 3626, the influence of an AGN is likely to be negligible, although they are both considered as LINERs. There is a chance that these two galaxies are not active at all.

The cross-correlation of the Sloan Digital Sky Survey Data Release 7 with the Faint Images of the Radio Sky at Twenty-Centimeters survey allows for a multiwavelength statistical study of radio-optical galaxy properties on a very large number of sources. The correlation we find between $L_{[20 cm]}/L_{[H\alpha]}$ and optical emission line ratios suggests that the origin of the emission in powerful radio-galaxies is of nuclear rather than of stellar origin. In particular, the spectroscopic classification in Seyferts, Low Ionization Narrow Emission Regions (LINERs) and star-forming galaxies provided by emission-line diagnostic diagrams peaks on the AGN region for higher $L_{[20 cm]}/L_{[H\alpha]}$ values. The trend differs from Seyferts to LINERs. The [NII]/H$\alpha$ vs. equivalent width of the H$\alpha$ line diagram confirms the LINER classification for most of those that have been identified with the traditional diagnostic diagrams. A small fraction of sources seem to be powered by post-AGB stars instead., Comment: 8 pages, 4 figures, Proceedings of Nuclei of Seyfert galaxies and QSOs - Central engine \& conditions of star formation