The Extended Tidal Tails of NGC 7089 (M2)

TL;DR

This paper reports the discovery of a 45-degree-long stellar stream associated with globular cluster NGC 7089 using Gaia EDR3 data, and models its orbit considering the influence of the Large Magellanic Cloud.

Contribution

It presents the first detection of an extended stellar stream from NGC 7089 and models its orbit including the LMC's gravitational influence.

Findings

The stream is about 100 pc wide and dynamically cold.

The leading tail detection is uncertain due to distance and proper motion issues.

Including the LMC improves the orbital model's fit to observations.

Abstract

Using photometry and proper motions from Gaia Early Data Release 3, we detect a 45 degree-long trailing stellar debris stream associated with the old, metal-poor globular cluster NGC 7089. With a width on the order of 100 pc, the extended stream appears to be as dynamically cold as the coldest known streams found to date. There is some evidence for an extended leading tail extending between 28 and 37 degrees from the cluster, though the greater distance of this tail, combined with proper motions that are virtually indistinguishable from those of foreground stars, make the detection much less certain. The proper motion profile and the path on the sky of the trailing tail are not well matched using a simple Galactic potential comprised purely of a disk, bulge, and spherical halo. However, the addition of a moving, massive (M = 1.88 x 10^(11) solar masses) Large Magellanic Cloud brings the model predictions into much better agreement with the observables. We provide tables of the most highly ranked candidate stream stars for follow-up by ongoing and future spectroscopic surveys.