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 M200β=1011--
1015Mββ. Our decomposition technique isolates galactic discs
whose mass fractions, fdiscβ, correlate strongly with common
alternative morphology indicators; for example, fdiscβ is approximately
equal to ΞΊcoβ, 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, fIHLβ,
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 M200ββ1013Mββ,
we find, on average, fIHLββ0.45, albeit with considerable
scatter. The transition radius beyond which the IHL dominates the stellar mass
of a galaxy is roughly 30kpc for M200ββ²1012.8Mββ, but increases strongly towards higher masses. However, we find that
no alternative IHL definitions -- whether based on the ex-situ stellar
fraction, or the stellar mass outside a spherical aperture -- reproduce our
dynamically-defined IHL fractions.Comment: 17 pages, 12 figures, submitted to MNRA