On the Orbital Decay of Globular Clusters in NGC1052-DF2: Testing a Baryon-Only Mass Model. (arXiv:1902.05959v1 [astro-ph.GA])
<a href="http://arxiv.org/find/astro-ph/1/au:+Chowdhury_D/0/1/0/all/0/1">Dhruba Dutta Chowdhury</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bosch_F/0/1/0/all/0/1">Frank C. van den Bosch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dokkum_P/0/1/0/all/0/1">Pieter van Dokkum</a>
The dark matter content of the ultra diffuse galaxy NGC1052-DF2, as inferred
from globular cluster (GC) and stellar kinematics, carries a considerable
amount of uncertainty, with current constraints also allowing for the complete
absence of dark matter. We test the viability of such a scenario by examining
whether in a `baryon-only’ mass model, the observed GC population experiences
rapid orbital decay due to dynamical friction. Using a suite of 50 multi-GC
$N$-body simulations that match observational constraints on both the stellar
component of NGC1052-DF2 and its GC population but differ in the initial
line-of-sight positions and the tangential velocities of the GCs, we show that
there is a substantial amount of realization-to-realization variance in the
evolution of the GCs. Nevertheless, over 10 Gyr, some of the GCs experience
significant orbital evolution. Others evolve less. A combination of reduced
dynamical friction in the galaxy core and GC-GC scattering keeps the GCs
afloat, preventing them from sinking all the way to the galaxy center. While
the current phase-space coordinates of the GCs are not unlikely for a
baryon-only mass model, the GC system does evolve over time. Therefore, if
NGC1052-DF2 has no dark matter, some of its GCs must have formed further out,
and the GC system must have been somewhat more extended in the past. The
presence of a low mass cuspy halo, while allowed by the kinematics, seems
improbable as significantly shorter inspiral timescales in the central region
would quickly lead to the formation of a nuclear star cluster.
The dark matter content of the ultra diffuse galaxy NGC1052-DF2, as inferred
from globular cluster (GC) and stellar kinematics, carries a considerable
amount of uncertainty, with current constraints also allowing for the complete
absence of dark matter. We test the viability of such a scenario by examining
whether in a `baryon-only’ mass model, the observed GC population experiences
rapid orbital decay due to dynamical friction. Using a suite of 50 multi-GC
$N$-body simulations that match observational constraints on both the stellar
component of NGC1052-DF2 and its GC population but differ in the initial
line-of-sight positions and the tangential velocities of the GCs, we show that
there is a substantial amount of realization-to-realization variance in the
evolution of the GCs. Nevertheless, over 10 Gyr, some of the GCs experience
significant orbital evolution. Others evolve less. A combination of reduced
dynamical friction in the galaxy core and GC-GC scattering keeps the GCs
afloat, preventing them from sinking all the way to the galaxy center. While
the current phase-space coordinates of the GCs are not unlikely for a
baryon-only mass model, the GC system does evolve over time. Therefore, if
NGC1052-DF2 has no dark matter, some of its GCs must have formed further out,
and the GC system must have been somewhat more extended in the past. The
presence of a low mass cuspy halo, while allowed by the kinematics, seems
improbable as significantly shorter inspiral timescales in the central region
would quickly lead to the formation of a nuclear star cluster.
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