Assessing the Association between the Globular Cluster NGC 4147 and the Sagittarius Dwarf Galaxy

TL;DR

This study investigates whether globular cluster NGC 4147 is associated with the Sagittarius dwarf galaxy, using new data and analysis of its parameters, tidal structures, and kinematics, and finds no evidence supporting a connection.

Contribution

The paper provides updated fundamental parameters for NGC 4147 and demonstrates that its morphology and dynamics are inconsistent with an origin from the Sagittarius dwarf galaxy.

Findings

NGC 4147 is 11.0 Gyr old with metallicity Z=0.0006.

Tidal structures around NGC 4147 do not align with Sgr's orbit.

Kinematic analysis shows NGC 4147 is not associated with Sgr.

Abstract

The potential association of the globular cluster (GC) NGC 4147 with the Sagittarius (Sgr) dwarf spheroidal galaxy has been proposed due to their comparable locations and radial velocities. However, there are still debates about this connection. In this study, we use data from the Dark Energy Spectroscopic Instrument Legacy Imaging Surveys to assess their association. We redetermine thefundamental parameters of NGC 4147 and find that the cluster is 11.0 Gyr old, has a metallicity of Z=0.0006, and is located 18.5 kpc from the Sun. We utilize the matched filter algorithm to identify extratidal structures in the surrounding sky of NGC 4147. The multiarmed tidal structures we find align more closely with the result of internal two-body relaxation processes within the cluster itself. The orientations of the dispersed tidal structures, the orbital direction of the cluster, and the mean orbital direction of Sgr do not show any apparent connection to each other. It seems to challenge the hypothesis of a common origin between the cluster and Sgr. To further investigate the association, we study the kinematics of NGC 4147 with the newly determined fundamental parameters. We find that the orbit, orbital energy, and angular momentum of NGC 4147 are not compatible with those of Sgr or its streams. This suggests that the cluster is not dynamically associated with Sgr. The morphology and dynamics of NGC 4147 are more consistent with it being a GC that formed with other origin rather than being accreted from the Sgr dwarf galaxy.