The SAMI galaxy survey: linking tidal features and orbit populations using Schwarzschild modelling
Year: 2026
Type: article
Abstract: ABSTRACT The evolution of angular momentum in galaxies is shaped by a combination of internal secular processes and external mechanisms such as mergers. Orbit-superposition based dynamical modelling provides a powerful means of linking the intrinsic orbital structures of galaxies to their global properties and merger histories. We construct Schwarzschild orbit-superposition models of massive ($\log _{10}\!\left(\rm {M}_*/\rm {M}_\odot \right)$>10) SAMI galaxies using the DYNAMITE code, utilising deep Kilo-Degree Survey photometry to accurately reproduce each galaxy’s luminosity distribution. We find that the fractions of hot, cold, warm, and counter-rotating orbits all show significant correlations with the spin parameter proxy $\lambda _{R_{\rm {e}}}$, with the strongest correlation arising from the combined hot plus counter-rotating fraction. When controlling for stellar mass and environment, we find that the fraction of hot and cold orbits show significant correlations with stellar age, whereas warm orbits do not. We further find that the lower values of $\lambda _{R_{\rm {e}}}$ for young galaxies with shell merger features as compared to the full sample is driven by an excess of hot orbits and a deficit of cold orbits, with no dependence on warm orbits. We suggest that the kinematic transformation in this SAMI sample proceeds through stars transitioning directly from cold to hot orbits. As warm orbits are expected to arise from secular heating processes, these findings indicate that merger-driven heating is the dominant mechanism governing the redistribution of angular momentum and the reduction of rotational support in massive galaxies.
Institutions: The University of Sydney, ASTRO-3D, ARC Centre of Excellence for All-sky Astrophysics, UNSW Sydney, European Southern Observatory, Commonwealth Scientific and Industrial Research Organisation, University of Vienna, The University of Queensland, Australian Astronomical Optics, Macquarie University
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $3,046
Funders: National Science Foundation, Smithsonian Institution, National Aeronautics and Space Administration, Princeton University, Johns Hopkins University, Space Telescope Science Institute, Queen's University Belfast, Durham University, Deutsche Forschungsgemeinschaft, Ministry of Education, Culture, Sports, Science and Technology, Academia Sinica, Cabinet Office, Government of Japan, Nederlandse Organisatie voor Wetenschappelijk Onderzoek, Queen's University, Università degli Studi di Padova, National Central University, National Astronomical Observatory of Japan, High Energy Accelerator Research Organization, Eötvös Loránd Tudományegyetem, ARC Centre of Excellence for All-Sky Astrophysics, Max-Planck-Institut für Astronomie, Toray Science Foundation, Smithsonian Astrophysical Observatory, Science Mission Directorate, Australian Research Council, Japan Society for the Promotion of Science, Japan Science and Technology Agency, Australian Astronomical Optics-Macquarie, Planetary Science Division, Division of Arctic Sciences, Los Alamos National Laboratory
Awards: Understanding diversity: chemical and kinematic tracers of galaxy evolution, How do galaxies get their gas?, G1773674019, G3612552936, G426156348, G4474636675, ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions, G4856916410, G4974873094, G5202711728, G618131832, G6586185420, A NEO SEARCH PROGRAM USING THE PAN-STARRS PS1 TELESCOPETHE GOAL OF THE PROPOSED RESEARCH IS TO USE T, G7187964967, Pan-STARRS1: Operations; Public Data Release; Education and Outreach, G833430883
OpenAlex ID: W7203639656
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