Tremaine-Weinberg integrals for gas flows in double bars

TL;DR

This paper investigates the application of the Tremaine-Weinberg method to doubly barred galaxies, demonstrating conditions under which pattern speeds can be accurately measured despite complexities.

Contribution

It explores the effects of different tracer distributions on the reliability of Tremaine-Weinberg integrals in measuring pattern speeds in doubly barred galaxies.

Findings

Signatures of two rotating patterns are often detectable.

Direct fitting may yield incorrect pattern speeds without proper tracer distribution.

Certain tracer distributions allow reliable retrieval of pattern speeds.

Abstract

We report on our attempts to achieve a nearly steady-state gas flow in hydrodynamical simulations of doubly barred galaxies. After exploring the parameter space, we construct two models, for which we evaluate the photometric and the kinematic integrals, present in the Tremaine-Weinberg method, in search of observational signatures of two rotating patterns. We show that such signatures are often present, but a direct fit to data points is likely to return incorrect pattern speeds. However, for a particular distribution of the tracer, presented here, the values of the pattern speeds can be retrieved reliably even with the direct fit.