Accretion of Galaxy Groups into Galaxy Clusters. (arXiv:2005.05344v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Benavides_J/0/1/0/all/0/1">José. A. Benavides</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sales_L/0/1/0/all/0/1">Laura. V. Sales</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Abadi_M/0/1/0/all/0/1">Mario. G. Abadi</a>
We study the role of group infall in the assembly and dynamics of galaxy
clusters in $Lambda$CDM. We select $10$ clusters with virial mass $M_{rm 200}
sim 10^{14} , M_{odot}$ from the cosmological hydrodynamical simulation
Illustris and follow their galaxies with stellar mass $M_{star} geq 1.5
times 10^8 , M_{odot}$. A median of $sim 38%$ of surviving galaxies at
$z=0$ are accreted as part of groups and did not infall directly from the
field, albeit with significant cluster-to-cluster scatter. The evolution of
these galaxy associations is quick, with observational signatures of their
common origin eroding rapidly in $1$-$3$ Gyr after infall. Substructure plays a
dominant role in fostering the conditions for galaxy mergers to happen, even
within the cluster environment. Integrated over time, we identify (per cluster)
an average of $17 pm 6$ mergers that occur in infalling galaxy associations,
of which $7 pm 3$ occur well within the virial radius of their cluster hosts.
The number of mergers show large dispersion from cluster to cluster, with our
most massive system having $42$ mergers above our mass cut-off. These mergers,
which are typically gas rich for dwarfs and a combination of gas rich and gas
poor for $M_{star} sim 10^{11} , M_{odot}$, may contribute significantly
within $Lambda$CDM to the formation of specific morphologies, such as
lenticulars (S0) and blue compact dwarfs in groups and clusters.
We study the role of group infall in the assembly and dynamics of galaxy
clusters in $Lambda$CDM. We select $10$ clusters with virial mass $M_{rm 200}
sim 10^{14} , M_{odot}$ from the cosmological hydrodynamical simulation
Illustris and follow their galaxies with stellar mass $M_{star} geq 1.5
times 10^8 , M_{odot}$. A median of $sim 38%$ of surviving galaxies at
$z=0$ are accreted as part of groups and did not infall directly from the
field, albeit with significant cluster-to-cluster scatter. The evolution of
these galaxy associations is quick, with observational signatures of their
common origin eroding rapidly in $1$-$3$ Gyr after infall. Substructure plays a
dominant role in fostering the conditions for galaxy mergers to happen, even
within the cluster environment. Integrated over time, we identify (per cluster)
an average of $17 pm 6$ mergers that occur in infalling galaxy associations,
of which $7 pm 3$ occur well within the virial radius of their cluster hosts.
The number of mergers show large dispersion from cluster to cluster, with our
most massive system having $42$ mergers above our mass cut-off. These mergers,
which are typically gas rich for dwarfs and a combination of gas rich and gas
poor for $M_{star} sim 10^{11} , M_{odot}$, may contribute significantly
within $Lambda$CDM to the formation of specific morphologies, such as
lenticulars (S0) and blue compact dwarfs in groups and clusters.
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