Untangling stellar components of galaxies: Evaluation of dynamical decomposition methods in simulated galaxies with GalaxyChop

¹ Instituto de Astronomía Teórica y Experimental – Observatorio Astronómico de Córdoba (IATE, UNC–CONICET), Córdoba, Argentina
² Observatorio Astronómico de Córdoba, Universidad Nacional de Córdoba, Laprida 854, X5000BGR Córdoba, Argentina
³ Facultad de Matemática, Astronomía y Física, Universidad Nacional de Córdoba (FaMAF–UNC), Bvd. Medina Allende s/n, Ciudad Universitaria, X5000HUA Córdoba, Argentina
⁴ Gerencia De Vinculación Tecnológica Comisión Nacional de Actividades Espaciales (CONAE), Falda del Cañete, Córdoba, Argentina
⁵ Instituto de Investigación y Desarrollo en Ingeniería de Procesos y Química Aplicada (IPQA, CONICET-UNC), Av. Velez Sarsfield 1611, CP. 5016, Córdoba, Argentina
⁶ Facultad de Ciencias Exactas, Físicas y Naturales, Universidad Nacional de Córdoba (FCEFyN-UNC), Av. Velez Sarsfield 1611, CP. 5016, Córdoba, Argentina
⁷ Aix Marseille Univ., CNRS/IN2P3, CPPM, Marseille, France
⁸ Instituto de Astronomia, Universidad Nacional Autonoma de Mexico, Apdo. Postal 106, Ensenada, 22800 B.C., Mexico

^⋆ Corresponding author; valeria.cristiani@unc.edu.ar

Received: 21 June 2024
Accepted: 24 September 2024

Abstract

Galaxy formation is intrinsically connected to the distinct evolutionary processes of disk and spheroidal systems, which are the fundamental stellar components of galaxies. Understanding the mutual, dynamical interplay and co-evolution of these components requires a detailed dynamical analysis to allow for disentanglement of these systems. We introduce JEHistogram, a new method for the dynamical decomposition of simulated galaxies into disk and spheroidal stellar components that utilizes the angular momentum and energy of star particles. We evaluate its performance against five previously established methods using a sample of equilibrium galaxies with stellar masses in the range 10¹⁰ ≤ M_gal/M_⊙ ≤ 10¹². Our assessment involves several metrics, including the completeness and purity of stellar particle classification, scale lengths, mass density profiles, velocity dispersion, and rotational velocity profiles. While all methods approximate the properties of the original components, such as mass fractions and density or velocity profiles, JEHistogram demonstrates a better accuracy, particularly in the inner regions of galaxies where component overlap complicates separation. Additionally, we apply JEHistogram to a Milky Way-like galaxy from the IllustrisTNG cosmological simulations, showcasing its capability to derive properties such as the size, mass, velocity, color, and age of dynamically defined disk and spheroidal components. All the dynamical decomposition methods we analyzed are publicly accessible through the Python package GalaxyChop.