# On the Orbital Decay of Globular Clusters in NGC1052-DF2: Testing a Baryon-Only Mass Model

## TL;DR

This study uses N-body simulations to test if globular clusters in NGC1052-DF2 could survive orbital decay without dark matter, finding that some GCs can remain stable over 10 Gyr due to reduced dynamical friction and scattering.

## Contribution

The paper provides the first detailed N-body simulation analysis of GC orbital evolution in a baryon-only model of NGC1052-DF2, highlighting the variance and potential for GC survival without dark matter.

## Key findings

- Some GCs experience significant orbital decay over 10 Gyr.
- Reduced dynamical friction and GC-GC scattering prevent all GCs from sinking.
- GCs likely formed further out and the system was more extended in the past.

## Abstract

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.