Simulating non-axisymmetric flows in disk galaxies

Abstract

Context. We present a two-step method to simulate and study non-circular motions in strongly barred galaxies. The first step is to constrain the initial parameters using a Bayesian analysis of each galaxy's azimuthally averaged rotation curve, the 3.6 µm surface brightness, and the gas surface density. The second step is to generate equilibrium models using the GalactICS code and evolve them via GADGET-2. Aims. The bar strengths and mock velocity maps of the resulting snapshots are compared to observations in order to determine the best representation of the galaxy. Methods. We test our method on the unbarred galaxy NGC 3621 and the barred galaxies NGC 1300 and NGC 1530. NGC 3621 provides a validation of our method of generating initial conditions. NGC 1530 has an intermediate bar orientation that allows for a comparison to DiskFit. Finally NGC 1300 has a bar oriented parallel to the galaxy's major axis, where other algorithms tend to fail. Results. Our models for NGC 3621 and NGC 1530 are comparable to those obtained using commonly available algorithms. Moreover, we have produced one of the first mass distribution models for NGC 1300.

galactics with gas

“…The inclusion of a gas disc opens up new and exciting possibilities that we are eager to explore in future work. Indeed, the models have already been used to study the rotation curves of barred spiral galaxies (Randriamampandry et al 2018). Many stan-dard algorithms for galaxy modelling fail for particular bar orientations.…”

“…Not only are these processes interesting in and of themselves, they also provide additional constraints on the models. For example, an equilibrium model that satisfies observational constraints but is nevertheless unstable to the formation of a strong bar is not a suitable model for a galaxy that has a weak bar or no bar at all (Sellwood 1985;Widrow et al 2008;Randriamampandry et al 2018).…”

Connection among environment, cloud-cloud collision speed, and star formation activity in the strongly barred galaxy NGC1300

“…A bisymmetric model expresses the non-circular motion driven by barlike distortion using the 𝑚 = 2 term in the Fourier expansion of 𝑉 𝑡 and 𝑉 𝑟 . However, it is known that application of this model fails when the galactic bar is almost parallel to the major axis of the disc due to the degeneracy of the velocity components (Sellwood & Sánchez 2010;Randriamampandry et al 2015Randriamampandry et al , 2018. Since the PA of the bar in NGC 1300 is close to that of the line of node (see Table 1), it is inappropriate to use the bisymmetric mode.…”