The Tidal Tails of the Ultra-Faint Globular Cluster Palomar 1

TL;DR

This study reveals extended tidal tails of Palomar 1, an ultra-faint globular cluster, suggesting recent accretion from a disrupted dwarf galaxy and highlighting the role of relaxation-driven evaporation in tail formation.

Contribution

First detection of extensive tidal tails around Palomar 1 using SDSS data and analysis of its possible origin from a disrupted dwarf galaxy.

Findings

Tails extend about 1 degree from the cluster.

Tails contain as many stars as the cluster itself.

Isophotes twist in an S-shape indicating tidal disruption.

Abstract

Using the Optimal Filter Technique applied to Sloan Digital Sky Survey photometry, we have found extended tails stretching about 1 degree (or several tens of half-light radii) from either side of the ultra-faint globular cluster Palomar 1. The tails contain roughly as many stars as does the cluster itself. Using deeper Hubble Space Telescope data, we see that the isophotes twist in a chacteristic S-shape on moving outwards from the cluster centre to the tails. We argue that the main mechanism forming the tails may be relaxation driven evaporation and that Pal 1 may have been accreted from a now disrupted dwarf galaxy ~500 Myr ago.