Title: Learning about galaxy mergers through tidal features in LSST: Characterizing extragalactic tidal features in cosmological simulations
Abstract:
Λ-Cold Dark Matter cosmological simulations of the Universe predict that major (mass ratio > 1/4) and minor mergers (mass ratio < 1/4) both play a significant role in shaping the galaxies that populate our Universe today. Due to the long timescales of galaxy mergers, we must infer their occurrence and properties in observations through merger features, such as the tidal debris around a galaxy. Tidal features form from stars that have been pulled into specific orbits during mergers, creating low-surface-brightness structures around galaxies (e.g., streams, tails, and shells). The properties of the tidal feature can provide insights into the merger that created it. With the upcoming Legacy Survey of Space and Time (LSST) on the Rubin Observatory, we will have an unprecedented sample of these low-surface-brightness features, enabling us to use tidal features to test how mergers transform galaxies.
To make a like-for-like comparison with LSST, we have produced a sample of idealized mock observations from four cosmological simulations: EAGLE, IllustrisTNG, Magneticum Pathfinder, and NewHorizon. Using different simulations, we probe the influence of subgrid physics models and simulation resolution on the occurrence and characteristics of tidal features. We have studied the properties of galaxies with and without tidal features in an observationally motivated manner and examined how the occurrence of tidal features around galaxies varies as a function of galaxy colour, stellar mass, group/cluster halo mass and distance from the group/cluster center in the velocity-radius phase space, therefore probing whether the occurrence of tidal features around galaxies reflects the trends regarding the occurrence of mergers as a function of galaxy stellar mass and environment.
A natural continuation is to leverage the opportunity to directly connect mergers in simulated galaxies to the tidal features characterized in previous work. This will provide a valuable test, quantifying the extent to which the role of mergers in transforming galaxies varies across different simulations with varying subgrid physics prescriptions and resolutions. Furthermore, we aim to quantify the lifetimes of the visible tidal features and potentially probe the morphological properties of the progenitor galaxies through the photometric properties of tidal features, providing a framework to interpret tidal features in the LSST survey.
