NGC 1300 Dynamics: I. The gravitational potential as a tool for detailed stellar dynamics

TL;DR

This paper estimates the gravitational potential of galaxy NGC 1300 from near-infrared data using three models, revealing a highly nonlinear gravitational field and analyzing the stability of Lagrangian points across different pattern speeds.

Contribution

It introduces a method to estimate the galaxy's gravitational potential directly from observations, considering multiple geometries and asymmetries for detailed stellar dynamics analysis.

Findings

Potential is highly nonlinear, with force perturbations up to 0.8 of the axisymmetric background.

Multiple stationary points exist, with stability depending on pattern speed.

Potential models include contributions from central mass and dark halo.

Abstract

In a series of papers we study the stellar dynamics of the grand design barred-spiral galaxy NGC~1300. In the first paper of this series we estimate the gravitational potential and we give it in a form suitable to be used in dynamical studies. The estimation is done directly from near-infrared observations. Since the 3D distribution of the luminous matter is unknown, we construct three different general models for the potential corresponding to three different assumptions for the geometry of the system, representing limiting cases. A pure 2D disc, a cylindrical geometry (thick disc) and a third case, where a spherical geometry is assumed to apply for the major part of the bar. For the potential of the disc component on the galactic plane a Fourier decomposition method is used, that allows us to express it as a sum of trigonometric terms. Both even and odd components are considered, so that the estimated potential accounts also for the observed asymmetries in the morphology. For the amplitudes of the trigonometric terms a smoothed cubic interpolation scheme is used. The total potential in each model may include two additional terms (Plummer spheres) representing a central mass concentration and a dark halo component, respectively. In all examined models, the relative force perturbation points to a strongly nonlinear gravitational field, which ranges from 0.45 to 0.8 of the axisymmetric background with the pure 2D being the most nonlinear one. We present the topological distributions of the stable and unstable Lagrangian points as a function of the pattern speed $(\Omega_p)$. In all three models there is a range of $\Omega_p$ values, where we find multiple stationary points whose stability affects the overall dynamics of the system.