On a method to resolve the nuclear activity in galaxies as applied to the Seyfert 2 galaxy NGC1358

TL;DR

This paper presents a method to resolve complex nuclear structures in galaxies by analyzing emission lines and velocities, demonstrated on NGC 1358, revealing a nuclear point source, outflow, and rotating disk.

Contribution

It introduces a novel approach combining spectral data, modeling, and PSF knowledge to disentangle nuclear components in galaxies, applicable to long slit spectra.

Findings

Identified a nuclear point source and high-excitation outflow in NGC 1358.

Revealed a rotating emission line disk with a radial excitation gradient.

Provided a preliminary model of the galaxy's nuclear structure.

Abstract

Nuclear regions of galaxies generally host a mixture of components with different exitation, composition, 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 modelling 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 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 exitation, 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 generally be necessary.