A Revised Velocity for the Globular Cluster GC-98 in the Ultra Diffuse Galaxy NGC1052-DF2

TL;DR

This paper revises the velocity measurements of a globular cluster in galaxy NGC1052-DF2, affecting the inferred galaxy velocity dispersion and implications for its dark matter content.

Contribution

It provides updated velocity data and dispersion measurements for GC-98 and NGC1052-DF2, refining previous estimates and addressing recent critiques.

Findings

Revised velocity for GC-98

Updated galaxy velocity dispersion (~5.6-7.8 km/s)

Galaxy's dispersion consistent with stellar mass alone

Abstract

We recently published velocity measurements of luminous globular clusters in the galaxy NGC1052-DF2, concluding that it lies far off the canonical stellar mass - halo mass relation. Here we present a revised velocity for one of the globular clusters, GC-98, and a revised velocity dispersion measurement for the galaxy. We find that the intrinsic dispersion $\sigma=5.6^{+5.2}_{-3.8}$ km/s using Approximate Bayesian Computation, or $\sigma=7.8^{+5.2}_{-2.2}$ km/s using the likelihood. The expected dispersion from the stars alone is ~7 km/s. Responding to a request from the Editors of ApJ Letters and RNAAS, we also briefly comment on the recent analysis of our measurements by Martin et al. (2018).