Exploring the stellar streams and satellites around the giant low surface brightness galaxy Malin 1

Abstract

Context. Giant Low Surface Brightness galaxies (gLSBGs), such as Malin 1, host extended stellar and gaseous discs exceeding 100 kpc in radius. Their formation and evolution remain debated, with interactions with satellite galaxies and accretion streams proposed as key contributors. Malin 1 presents multiple nearby and distant satellites. Additionally, it exhibits two giant stellar streams, the largest extending 200 kpc in projection, likely related to past interactions. Aims. We investigate the orbital dynamics of Malin 1's satellites and their possible connections with the observed stellar streams, testing their nature with different formation scenarios. Methods. We constructed gravitational potentials for Malin 1 using optical and HI rotation curve data, incorporating stellar, gaseous, and dark matter components. We explored a wide orbital parameter space to determine whether the candidate progenitors of the stellar streams could have originated from past interactions, testing both Navarro-Frenk-White (NFW) and the pseudo-isothermal (ISO) halo profiles. Results. Among several explored scenarios, some produced bound orbital solutions. The ISO halo model, with mass of Mvirial ≈ 2.6 × 1012 M⊙, favours bound satellite orbits more than the NFW model, that has a lower mass of Mvirial ≈ 1.4 × 1012 M⊙. These orbital models show that the giant stellar streams could be substructures of some satellites galaxies located along their leading and trailing orbital trajectories. Furthermore, our analysis indicates that the most distant Malin 1 satellite (eM1) could have reached its orbital pericentre ~1.6 Gyr ago, while the nearest companions could have interacted as early as ~100 Myr ago. At the same time, one of the closest companions would still be under a strong interaction. Another close companion displays both leading and trailing arms in a radial orbit, although it also shows a polar orbit. Furthermore, we identify some unbound orbital solutions that could link some satellites with streams. Conclusions. The observed alignment of satellites and streams indicates that past interactions likely shaped aspects of Malin 1's morphology. Our orbital modelling constrains possible progenitors of the observed stellar streams and their orbital histories, providing new insights into the dynamical evolution of gLSBGs. Our findings are consistent with results reported very recently by other studies using Malin 1 kinematic data.