A method to resolve the nuclear activity in galaxies, as applied to NGC1358

TL;DR

This paper presents a method to disentangle complex nuclear structures in galaxies by analyzing emission line data, applied specifically to NGC1358, revealing a detailed model of its nuclear activity.

Contribution

It introduces a novel approach combining spectral line analysis, modeling, and PSF knowledge to resolve nuclear components in galaxies from long slit spectra.

Findings

Identified a nuclear point source and outflow in NGC1358.

Reconstructed the velocity and excitation structure of the galaxy's nucleus.

Proposed extension of the method to two-dimensional spectroscopy for more accurate results.

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 Seyfert2 galaxy NGC1358, 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, 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 NGC1358 is obtained, involving a nuclear point source and an emerging outflow of high excitation with a post shock cloud, as well as a nuclear emission line disk rotating in the potential of a stellar bulge and expressing a radial exitation gradient. The method results in a likely scenario for the nuclear structure of NGC1358. For definitive results an extrapolation of the method to two dimensions combined with the use of integral field spectroscopy will generally be necessary.