Outer Stellar Halos of Galaxies from Field to Cluster Environment
Outer halos of galaxies are known to store essential information about
the formation history and merger-induced evolution of their central
galaxies, since the relaxation timescales in these outer regions are
much larger than in the inner parts and thus the memory of the
events is conserved over a long period.
The merger history provides fundamental insights into the processes of
morphological changes and the importance of gas dynamics in changing
the appearance of galaxies, broadening our understanding of the
different mechanisms of structure formation.
Observations of outer stellar halos extend from the interstellar light
within galaxy clusters down to Milky-Way-mass galaxies, reaching
unprecedented depth in magnitudes.
However, simulations to accompany these observations to help
decipher the information hidden in these observations need to be
provided, and this is one of the aims of the work done by my students and me.
This work covers a broad range of topics, starting from the diffuse
stellar component in galaxy clusters (see
Remus et al., 2017),
where the velocity and density distributions of the BCGs and the
diffuse component were analyzed, over global radial stellar halo
properties (see
Remus et al., 2016
for a study about the shape of the global outer stellar halos
featuring Einasto density profiles and
Forbes & Remus 2018
for a comparison of the metallicity gradients of observed globular cluster systems and simulated accreted
galaxy components) to outer stellar halo kinematics (see
Schulze et al., 2020).
These studies were performed using the
Magneticum Pathfinder
simulation set, as this provides large enough statistics from galaxy
clusters down to galaxy scales.
Additionally, we used isolated merger simulations to understand where the mass
from different progenitor galaxies is deposited (
Karademir et al., 2019)
, and to trace the origin of different features
like streams, umbrellas and shells back to their original merger
configurations.
These isolated merger simulations also provided an opportunity to
search for signatures of major merger events which can be observed,
for example the σ-bump (see
Schauer et al., 2014).
These features can then be observed using tracer populations at
large radii, for example globular clusters, as is done with the
SLUGGS survey.
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