Orbital decay of Globular Clusters in the galaxy with little dark matter

TL;DR

This paper investigates the orbital decay of globular clusters in a dark matter-deficient galaxy, using simulations to understand their dynamics and implications for the galaxy's mass profile.

Contribution

It provides the first analysis of globular cluster orbital decay in a galaxy with little dark matter, combining analytic estimates and N-body simulations.

Findings

Massive GCs should have decayed orbitally within a few Gyrs.

Orbital decay constrains the galaxy's mass distribution.

Results inform galaxy formation scenarios with low dark matter.

Abstract

Recently, \cite{vanDokkum2018} have presented an important discovery of an ultra diffuse galaxy, NGC1052-DF2, with a dark matter content significantly less than predicted from its stellar mass alone. The analysis relies on measured radial velocities of 10 Globular Clusters (GCs), of estimated individual masses of a few $ \times 10^6 M_\odot$. This is about $1\%$ of the inferred mass of NGC1052-DF2 of $2\times 10^8 M_\odot$ within a half-light radius, $R_\mathrm{e}=2.2\, \mathrm{kpc}$. The large relative mass and the old age of these objects imply that they might be susceptible to orbital decay by dynamical friction. Using analytic estimates and N-body simulations of an isolated system matching the inferred mass profile of NGC1052-DF2, we show that orbits of the most massive GCs should already have decayed on a time scale of a few Gyrs. These findings should help in constraining mass profile and formation scenarios of NGC1052-DF2.