Close galaxy flybys, interactions during which two galaxies inter-penetrate, are frequent and can significantly affect the evolution of individual galaxies. Equal-mass flybys are extremely rare and almost exclusively distant, while frequent flybys have mass ratios 0.1 or lower, with a secondary galaxy penetrating deep into the primary. This can result in comparable strengths of interaction S between the two classes of flybys and lead to essentially the same effects. To demonstrate this, emphasize and explore the role of the impact parameter $b$, we performed a series of N-body simulations of flybys with varying relative $b$ ranging from 0.114 to 0.272 of the virial radius of the primary. Two-armed spirals form during flybys, with radii of origin correlated with $b$ and strengths well approximated with an inverted S-curve. The impact parameter does not affect the shape of induced spirals, and the lifetimes of a distinguished spiral structure appear to be constant, 2 Gyr. Bars, with strengths anti-correlated with $b$, form after the encounter is over in simulations with interaction strengths $S\geq0.076$, but they are short-lived except for the stronger ones with $S\geq0.129$. We showcase an occurrence of double bar that survives for a long time in one of the simulations. Effects on the pre-existing bar instability are diverse. There is no uniform correlation between these effects and $b$, as they are secondary effects, happening later in a post-flyby stage. Bulges are resilient to flybys, while dark matter halos can significantly spin up in the amount anti-correlated with $b$. There is an offset angle between the angular momentum vector of the dark matter halo and that of a disc, and it correlates linearly with b. Flybys remain an important pathway for structural evolution within galaxies in the local Universe.
How Mergers and Flybys Shape Azimuthal Age Patterns in Spiral Galaxies
Research School of Astronomy and Astrophysics, Australian National University（澳大利亚国立大学天体物理与天文学研究学院）；ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D)（ARC三维全天空天体物理学卓越中心）；Department of Astronomy, University of Virginia（弗吉尼亚大学天文学系）；Centre for Extragalactic Astronomy, Department of Physics, Durham University（杜伦大学物理系河外天文中心）；Universitäts-Sternwarte München, Fakultät für Physik, LMU München（慕尼黑大学天文台，慕尼黑大学物理学院）；International Centre for Radio Astronomy Research, University of Western Australia（西澳大学国际射电天文研究中心）
Discovery of an Unbound Flyby Companion of UBC 63: In the Immediate Aftermath of a Close Encounter
Gauhati University（古哈提大学）；INAF—Catania Astrophysical Observatory（意大利国家天体物理研究所卡塔尼亚天文台）；Shanghai Normal University（上海师范大学）；Dali University（大理大学）；Shanghai Astronomical Observatory, Chinese Academy of Sciences（中国科学院上海天文台）；University of Chinese Academy of Sciences（中国科学院大学）；Institut de Ciències del Cosmos, Universitat de Barcelona (ICCUB)（巴塞罗那大学宇宙科学研究所）；Cotton University（科顿大学）；Assam University（阿萨姆大学）
