Studying size and physical properties of the narrow-line region in active galaxies

We explore the size and physical properties of the narrow-line region (NLR) in active galaxies via imaging and spectroscopy. From HST [OIII] images, we find striking correlations between the size and the luminosity of the NLR with different slopes for type-1 and type-2 AGNs. We show that the influence of the observers viewing angle with respect to the NLR cone axis as well as the effects of a receding torus can explain the different slopes. Using high-sensitivity VLT longslit spectra of the nearby Seyfert-2 galaxy NGC 1386, we improve methods to derive pure AGN emission-line spectra using the outer galaxy itself as template to correct for the stellar contribution. From spatially resolved spectral diagnostics, we find a clear transition between the AGN-excited NLR and the surrounding star-forming areas, enabling us to determine the NLR size independent of stellar contamination. We find a decreasing electron density and ionization parameter, indicating that the NLR is photoionized by the central source only. The comparison of gaseous and stellar velocity curves reveals signs of rotational motion and no break in velocities from the NLR towards the HII regions, suggesting that the ionization cone lies within the galactic disk.