Searching for tidal tails around $\omega$ Centauri using RR Lyrae Stars

TL;DR

This study surveyed RR Lyrae stars around $$ Centauri to detect potential tidal debris, finding no significant evidence of such debris despite previous claims elsewhere, thus supporting the idea that the cluster's surroundings are largely intact.

Contribution

The paper provides a comprehensive analysis of RR Lyrae stars around $$ Centauri, using multiple methods to assess tidal debris, and concludes that there is no significant debris, challenging previous claims.

Findings

No significant tidal debris detected around $$ Centauri.

Most RR Lyrae stars outside the tidal radius are consistent with halo/thick disk populations.

Radial velocities and orbital analyses do not support debris origin for the outer RR Lyrae stars.

Abstract

We present a survey for RR Lyrae stars in an area of 50 deg$^2$ around the globular cluster $\omega$ Centauri, aimed to detect debris material from the alleged progenitor galaxy of the cluster. We detected 48 RR Lyrae stars of which only 11 have been previously reported. Ten among the eleven previously known stars were found inside the tidal radius of the cluster. The rest were located outside the tidal radius up to distances of $\sim 6$ degrees from the center of the cluster. Several of those stars are located at distances similar to that of $\omega$ Centauri. We investigated the probability that those stars may have been stripped off the cluster by studying their properties (mean periods), calculating the expected halo/thick disk population of RR Lyrae stars in this part of the sky, analyzing the radial velocity of a sub-sample of the RR Lyrae stars, and finally, studying the probable orbits of this sub-sample around the Galaxy. None of these investigations support the scenario that there is significant tidal debris around $\omega$ Centauri, confirming previous studies in the region. It is puzzling that tidal debris have been found elsewhere but not near the cluster itself.