On a Method to Resolve the Nuclear Activity in Galaxies as Applied to the Seyfert 2 Galaxy NGC 1358

Nuclear regions of galaxies generally host a mixture of components with different excitations, compositions, and kinematics. Derivation of emission line ratios and kinematics could then be misleading if due correction is not made for the limited spatial and spectral resolutions of the observations. The aim of this paper is to demonstrate, with application to a long-slit spectrum of the Seyfert 2 galaxy NGC 1358, how line intensities and velocities, together with modeling and knowledge of the point-spread function, may be used to resolve the differing structures. In the situation outlined above, the observed kinematics differs for different spectral lines. From the observed intensity and velocity distributions of a number of spectral lines, and with some reasonable assumptions about the structure of different subcomponents to diminish the number of free parameters, the true line ratios and velocity structures may be deduced. A preliminary solution for the nuclear structure of NGC 1358 is obtained, involving a nuclear point source and an emerging outflow of high excitation, ending with shock and postshock cloud as revealed by the velocities, as well as a nuclear emission-line disk rotating in the potential of a stellar bulge and expressing a radial excitation gradient. The method results in a likely scenario for the nuclear structure of the Seyfert 2 galaxy NGC 1358. For definitive results, an extrapolation of the method to two dimensions combined with the use of integral field spectroscopy will be necessary