2023/07/24 by Katy L. Proctor, Claudia del P. Lagos, Proctor, Katy L. +5
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysics of Galaxies (astro-ph.GA) #FOS: Physical sciences #Galaxies: Formation, Evolution, Phenomena #Stellar, planetary, and galactic studies
paper · pdf · doi:10.48550/arxiv.2307.12584
openalex publication_date 2023/07/24 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
We perform a structural decomposition of galaxies identified in three cosmological hydrodynamical simulations by applying Gaussian Mixture Models (GMMs) to the kinematics of their stellar particles. We study the resulting disc, bulge, and intra-halo light (IHL) components of galaxies whose host dark matter haloes have virial masses in the range M200=1011-- 1015 \rm M_\odot. Our decomposition technique isolates galactic discs whose mass fractions, f\rm disc, correlate strongly with common alternative morphology indicators; for example, f\rm disc is approximately equal to κ\rm co, the fraction of stellar kinetic energy in co-rotation. The primary aim of our study, however, is to characterise the IHL of galaxies in a consistent manner and over a broad mass range, and to analyse its properties from the scale of galactic stellar haloes up to the intra-cluster light. Our results imply that the IHL fraction, f\rm IHL, has appreciable scatter and is strongly correlated with galaxy morphology: at fixed stellar mass, the IHL of disc galaxies is typically older and less massive than that of spheroids. Above M200≈ 1013 \rm M_\odot, we find, on average, f\rm IHL≈ 0.45, albeit with considerable scatter. The transition radius beyond which the IHL dominates the stellar mass of a galaxy is roughly 30 \rm kpc for M200\lesssim 1012.8 \rm M_\odot, but increases strongly towards higher masses. However, we find that no alternative IHL definitions -- whether based on the ex-situ stellar mass, or the stellar mass outside a spherical aperture -- reproduce our dynamically-defined IHL masses.