KRATOS: A large suite of N-body simulations to interpret the stellar kinematics of LMC-like discs^⋆

¹ Departament de Física Quàntica i Astrofísica (FQA), Universitat de Barcelona (UB), C Martí i Franquès, 1, 08028 Barcelona, Spain
e-mail: ojimenez@icc.ub.edu
² Institut de Ciències del Cosmos (ICCUB), Universitat de Barcelona, Martí i Franquès 1, 08028 Barcelona, Spain
³ Institut d’Estudis Espacials de Catalunya (IEEC), c. Esteve Terradas 1, 08860 Castelldefels (Barcelona), Spain
⁴ Lund Observatory, Division of Astrophysics, Lund University, Box 43 221 00 Lund, Sweden
⁵ Departamento de Física de la Tierra y Astrofísica, UCM, and IPARCOS, Facultad de Ciencias Físicas, Plaza Ciencias, 1, Madrid 28040, Spain
⁶ School of Physics & Astronomy, University of Leicester, University Road, Leicester LE1 7RH, UK
⁷ Instituto de Astrofísica, Universidad Andres Bello, Fernandez Concha 700, Las Condes, Santiago RM, Chile

Received: 21 December 2023
Accepted: 22 March 2024

Abstract

Context. The Large and Small Magellanic Clouds (LMC and SMC, respectively) are the brightest satellites of the Milky Way (MW), and for the last thousand million years they have been interacting with one another. As observations only provide a static picture of the entire process, numerical simulations are used to interpret the present-day observational properties of these kinds of systems, and most of them have been focused on attempting to recreate the neutral gas distribution and characteristics through hydrodynamical simulations.

Aims. We present KRATOS, a comprehensive suite of 28 open-access pure N-body simulations of isolated and interacting LMC-like galaxies designed for studying the formation of substructures in their discs after interaction with an SMC-mass galaxy. The primary objective of this paper is to provide theoretical models that help us to interpret the formation of general structures in an LMC-like galaxy under various tidal interaction scenarios. This is the first paper of a series dedicated to the analysis of this complex interaction.

Methods. Simulations are grouped into 11 sets of up to three configurations, with each set containing (1) a control model of an isolated LMC-like galaxy; (2) a model that contains the interaction with an SMC-mass galaxy, and (3) a model where both an SMC-mass and a MW-mass galaxy may interact with the LMC-like galaxy (the most realistic model). In each simulation, we analysed the orbital history between the three galaxies and examined the morphological and kinematic features of the LMC-like disc galaxy throughout the interaction. This includes investigating the disc scale height and velocity maps. When a bar was found to develop, we characterised its strength, length, off-centredness, and pattern speed.

Results. The diverse outcomes found in the KRATOS simulations, including the presence of bars, warped discs, and various spiral arm shapes, demonstrate the opportunities they offer to explore a range of LMC-like galaxy morphologies. These morphologies directly correspond to distinct disc kinematic maps, making them well-suited for a first-order interpretation of the LMC’s kinematic maps. From the simulations, we note that tidal interactions can: boost the disc scale height; both destroy and create bars; and naturally explain the off-centre stellar bars. The bar length and pattern speed of long-lived bars are not appreciably altered by the interaction.

Conclusions. The high spatial, temporal, and mass resolution used in the KRATOS simulations has been shown to be appropriate for the purpose of interpreting the internal kinematics of LMC-like discs, as evidenced by the first scientific results presented in this work.