The Tidal Tails of 47 Tucanae

TL;DR

This paper models the tidal tails of the globular cluster 47 Tucanae, predicting their locations and densities, which can help in detecting these features and refining the cluster's distance measurement.

Contribution

The study introduces a streakline method to predict tidal tail features of 47 Tuc without complex N-body simulations, aiding observational detection and distance estimation.

Findings

Overdensities are 3-4% above background, detectable with matched filtering.

The Heliocentric distance significantly influences tail features.

The method allows shape and extent determination of tidal tails efficiently.

Abstract

The Galactic globular cluster 47 Tucanae (47 Tuc) shows a rare increase in its velocity dispersion profile at large radii, indicative of energetic, yet bound, stars at large radii dominating the velocity dispersion and, potentially, of ongoing evaporation. Escaping stars will form tidal tails, as seen with several Galactic globular clusters, however, the tidal tails of 47 Tuc are yet to be uncovered. We model these tails of 47 Tuc using the most accurate input data available, with the specific aim of determining their locations, as well as the densities of the epicyclic overdensities within the tails. The overdensities from our models show an increase of 3-4% above the Galactic background and, therefore, should be easily detectable using matched filtering techniques. We find that the most influential parameter with regard to both the locations and densities of the epicyclic overdensities is the Heliocentric distance to the cluster. Hence, uncovering these tidal features observationally will contribute greatly to the ongoing problem of determining the distance to 47 Tuc, tightly constraining the distance of the cluster independent of other methods. Using our streakline method for determining the locations of the tidal tails and their overdensities, we show how, in principle, the shape and extent of the tidal tails of any Galactic globular cluster can be determined without resorting to computationally expensive N-body simulations.