The impact of bar origin and morphology on stellar migration

Abstract

Different mechanisms driving bar structure formation indicate that bar origins should be distinguishable in the stellar populations of galaxies. To study how these origins affect different bar morphologies and impact stellar orbits and migration, we analyse three simulated discs which are representative of bar formation under isolated evolution motivated by disc instability, and interaction-driven tidal development. The first isolated disc and the tidally driven disc produce similar bar structure, while the second isolated disc, generated by the tidal initial condition without the companion, is visibly dissimilar. Changes to radial and vertical positions, angular momentum in the disc-plane, orbital eccentricity, and the subsequent disc metallicities are assessed, as is the dependence on stellar age and formation radii. Bar origin is distinguishable, with the tidal disc displaying larger migration overall, higher metallicity difference between the inner and outer disc, and a population of inner disc stars displaced to large radii and below the disc-plane. The effect of closest approach on populations of stars formed before, after, and during this period is evident. However, bar morphology is also found to be a significant factor in the evolution of disc stellar properties, with similar bars producing similar traits in migration tendency with radius, particularly in vertical stellar motion and in the evolution of central metallicity features.

Effects of Halo Spin on the Formation and Evolution of Bars in Disk Galaxies

“…Nearly two-thirds of disk galaxies in the local Universe possess a weak or strong bar in optical and near-infrared images (de Vaucouleurs 1963; Whyte et al 2002;Laurikainen et al 2004;Marinova & Jogee 2007;Menéndez-Delmestre et al 2007;Aguerri et al 2009;Méndez-Abreu et al 2012;Buta et al 2015;Díaz-García et al 2016, 2019. Bars are one of the main drivers of the dynamical and secular evolution of disk galaxies, and are responsible for stellar migration (Di Matteo et al 2013;Kawata et al 2017;Halle et al 2018;Iles et al 2024), angular momentum transport from disk to halo (Saha & Naab 2013;Petersen et al 2016;Collier et al 2018;Collier & Madigan 2021), and the formation of pseudo-bulges (Combes & Sanders 1981;Combes et al 1990;Athanassoula 2005;Debattista et al 2006;Gadotti 2011). Despite the importance of bars, however, there has been no clear answer as to why some galaxies are barred or nonbarred and what controls the physical properties of bars.…”