On the Evolution of the Globular Cluster System in NGC 1052-DF2: Dynamical Friction, Globular–Globular Interactions, and Galactic Tides

Abstract

The ultradiffuse galaxy NGC 1052-DF2 has an overabundance of luminous globular clusters (GCs), and its kinematics is consistent with the presence of little to no dark matter. As the velocity dispersion among the GCs is comparable to the expected internal dispersions of the individual GCs, the galaxy might be highly conducive to GC–GC merging. If true, this could explain the puzzling luminosity function of its GCs. Here we examine this possibility by resimulating three of our earlier simulations of the GC system, where the GCs were modeled as single particles, with live GCs. Somewhat surprisingly, we infer a low merger rate of ∼0.03 Gyr−1. The main reason is that the GCs are too dense for tidal shock capture, caused by impulsive encounters among them, to operate efficiently (we infer a tidal capture rate of only ∼0.002 Gyr−1). Therefore, whatever mergers occur are driven by other mechanisms, which we find to be captures induced by dynamical friction and compressive tides from other GCs. The low merger rate inferred here makes it unlikely that the unusually large luminosities of the GCs can be explained as a result of past GC–GC mergers. Our simulations also indicate that, if NGC 1052-DF2 is indeed largely devoid of dark matter, its tidal field is too weak to induce any significant mass loss from the GCs. Therefore, in such a scenario, we predict that it is improbable for the GCs to reveal tidal features, something that can be tested with future deep observations.

Dynamical friction in globular cluster-rich ultra-diffuse galaxies: the case of NGC5846-UDG1

“…For some dwarf galaxies and UDGs, τ DF 10 Gyr, meaning that DF should be effective over the life of the galaxy. This was noticed long ago for the Fornax dwarf spheroidal satellite galaxy (Tremaine 1976) and more recently for NGC1052-DF2 (Nusser 2018;Dutta Chowdhury et al 2019) 2 .…”

Evolution of globular-cluster systems of ultra-diffuse galaxies due to dynamical friction in MOND gravity

“…is the dynamical time at the half-mass radius of the cluster of the mass M. In order to decide whether the gain of energy of a GC by the encounters can cause a substantial evaporation of GCs or a creation of tidal tails, we compared ∆E enc to the Newtonian gravitational binding energy of a Plummer sphere, 3πGM 2 /(32r h ). The effective radius of GCs of DF2 is around 8 pc (Dutta Chowdhury et al 2020), while the MOND transitional radius, where deviations from Newtonian gravity become important, is 34 pc. If a GC became that big, it would not be classified as a GC, and this is why we consider the Newtonian binding energy.…”

“…For the simulation with the DF2-like GC masses, it is suitable to accept the characteristic radius for the GCs as the typical radius of the GCs of DF2, 8 pc (Dutta Chowdhury et al 2020). For this value we got a total relative change of internal energy greater than (0.1,0.5,1) for (66,61,57) GCs out of the total 100 in the whole ensemble of our 10 simulations with the DF2-like GC masses.…”

Ultra-Diffuse Galaxies in the Perseus Cluster: Comparing Galaxy Properties with Globular Cluster System Richness

“…Large cosmological simulations of galaxy formation do not (yet) have the resolution to properly resolve GC formation. Probing galaxy GC formation requires either the implementation of specialised simulations for single galaxies (e.g., Dutta Chowdhury et al 2020) or additional sub-grid/semi-analytic modelling within the simulation (e.g., Carleton et al 2021;Doppel et al 2021). To date, only one work has applied such semi-analytic models to a cosmological simulation to investigate GC formation in UDGs.…”