The work presented in this thesis studies the role that accretion
events play in the evolution of galaxies in dense environments, such as
galaxy clusters. Cosmological simulations allow us to study in detail
the evolution of galaxies' halos in cluster environments and have shown
that the formation of extended halos around central cluster
galaxies and intracluster light (ICL) is closely correlated to the
morphological transformation of galaxies in clusters. However, the
extremely low surface brightness of these components makes it
difficult to gather observational constraints.
This thesis studies the light and stellar motion in the halo of the
giant elliptical galaxy M87 and its surrounding IC component at the
centre of the Virgo cluster. Virgo is the nearest (∼15~Mpc away)
large scale structure, a young cluster characterised by both spatial
and kinematic substructures. M87 has one of the oldest stellar
populations in the local Universe and a stellar halo that contains
∼ 70\% of the galaxy light down to μV=27magarcsec−2. Moreover, deep images of the Virgo cluster core have
revealed an extended network of tidal features suggesting that
accretion events characterise its mass assembly. Thus, M87 and its host
environment are prime targets to shed light on the hierarchical
assembly of structure in the Universe.
This work uses new Suprime-Cam@Subaru photometry and FLAMES@VLT
spectroscopy to study a ∼0.5deg2 area around
M87, in the transition region between galaxy halo and ICL. We use
planetary nebulas (PNs) as tracers, whose strong [OIII] λ5007
\AA\ emission line makes them excellent photometric and kinematic
probes, also at large distances from the galaxy's centre.
The photometric analysis of the PN sample shows the superposition of
two stellar populations, both halo and ICL. This is confirmed by
spectroscopically detected PNs, whose velocity phase-space also
reveals that halo and ICL split into two different kinematic
components. They have very different spatial distributions and parent
stars, as indicated by the properties of the PN populations they are
associated with, such as the α-parameter and the slope of the
planetary nebula luminosity function (PNLF).
In this thesis I give the observational proof that in Virgo
the central galaxy and the ICL both evolve through the
ongoing accretion of smaller systems. However, stellar halo and ICL
are dynamically distinct components with different velocity and
density distributions, and parent stellar populations. Whether or not
these conclusions are true for different galaxies in different Virgo
subclusters is still an open question and the topic of one of
my planned future studies