Predicting accreted satellite galaxy masses and accretion redshifts based on globular cluster orbits in the E-MOSAICS simulations. (arXiv:2003.00076v2 [astro-ph.GA] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Pfeffer_J/0/1/0/all/0/1">Joel L. Pfeffer</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Trujillo_Gomez_S/0/1/0/all/0/1">Sebastian Trujillo-Gomez</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Kruijssen_J/0/1/0/all/0/1">J. M. Diederik Kruijssen</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Crain_R/0/1/0/all/0/1">Robert A. Crain</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hughes_M/0/1/0/all/0/1">Meghan E. Hughes</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Reina_Campos_M/0/1/0/all/0/1">Marta Reina-Campos</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bastian_N/0/1/0/all/0/1">Nate Bastian</a>
The ages and metallicities of globular clusters (GCs) are known to be
powerful tracers of the properties of their progenitor galaxies, enabling their
use in determining the merger histories of galaxies. However, while useful in
separating GCs into individual accretion events, the orbits of GC groups
themselves have received less attention as probes of their progenitor galaxy
properties. In this work, we use simulations of galaxies and their GC systems
from the E-MOSAICS project to explore how the present-day orbital properties of
GCs are related to the properties of their progenitor galaxies. We find that
the orbits of GCs deposited by accretion events are sensitive to the mass and
merger redshift of the satellite galaxy. Earlier mergers and larger galaxy
masses deposit GCs at smaller median apocentres and lower total orbital energy.
The orbital properties of accreted groups of GCs can therefore be used to infer
the properties of their progenitor galaxy, though there exists a degeneracy
between galaxy mass and accretion time. Combining GC orbits with other tracers
(GC ages, metallicities) will help to break the galaxy mass/accretion time
degeneracy, enabling stronger constraints on the properties of their progenitor
galaxy. In situ GCs generally orbit at lower energies (small apocentres) than
accreted GCs, however they exhibit a large tail to high energies and even
retrograde orbits (relative to the present-day disc), showing significant
overlap with accreted GCs. Applying the results to Milky Way GCs groups
suggests a merger redshift $z sim 1.5$ for the Gaia Sausage/Enceladus and
$z>2$ for the `low-energy’/Kraken group, adding further evidence that the Milky
Way had two significant mergers in its past.
The ages and metallicities of globular clusters (GCs) are known to be
powerful tracers of the properties of their progenitor galaxies, enabling their
use in determining the merger histories of galaxies. However, while useful in
separating GCs into individual accretion events, the orbits of GC groups
themselves have received less attention as probes of their progenitor galaxy
properties. In this work, we use simulations of galaxies and their GC systems
from the E-MOSAICS project to explore how the present-day orbital properties of
GCs are related to the properties of their progenitor galaxies. We find that
the orbits of GCs deposited by accretion events are sensitive to the mass and
merger redshift of the satellite galaxy. Earlier mergers and larger galaxy
masses deposit GCs at smaller median apocentres and lower total orbital energy.
The orbital properties of accreted groups of GCs can therefore be used to infer
the properties of their progenitor galaxy, though there exists a degeneracy
between galaxy mass and accretion time. Combining GC orbits with other tracers
(GC ages, metallicities) will help to break the galaxy mass/accretion time
degeneracy, enabling stronger constraints on the properties of their progenitor
galaxy. In situ GCs generally orbit at lower energies (small apocentres) than
accreted GCs, however they exhibit a large tail to high energies and even
retrograde orbits (relative to the present-day disc), showing significant
overlap with accreted GCs. Applying the results to Milky Way GCs groups
suggests a merger redshift $z sim 1.5$ for the Gaia Sausage/Enceladus and
$z>2$ for the `low-energy’/Kraken group, adding further evidence that the Milky
Way had two significant mergers in its past.
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