Metal Abundance and Kinematical Properties of M81 Globular Cluster System

TL;DR

This study analyzes the metallicity and kinematic properties of 144 globular clusters in M81, revealing bimodal metallicity distribution, differential spatial concentration, and distinct rotational behaviors linked to galaxy structure.

Contribution

It provides the largest sample analysis of M81 globular clusters, highlighting their metallicity bimodality, spatial distribution differences, and rotation patterns, especially in relation to galaxy components.

Findings

Metallicity distribution is bimodal with peaks at [Fe/H]~-1.51 and -0.58.

Metal-rich clusters are less spatially concentrated than metal-poor ones.

Strong rotation observed in metal-rich clusters, absent in metal-poor clusters.

Abstract

In this paper, we presented metal abundance properties of 144 M81 globular clusters. These globulars consist of the largest globular cluster sample in M81 till now. Our main results are: the distribution of metallicities are bimodal, with metallicity peaks at [Fe/H]\sim-1.51 and -0.58, and the metal-poor globular clusters tend to be less spatially concentrated than the metal-rich ones; the metal-rich globular clusters in M81 do not demonstrate a centrally concentrated spatial distribution as the metal-rich ones in M31 do; like our Galaxy and M31, the globular clusters in M81 have a small radial metallicity gradient. These results are consistent with those obtained based on a small sample of M81 globular clusters. In addition, this paper showed that there is evidence that a strong rotation of the M81 globular cluster system around the minor axis exists, and that rotation is present in the metal-rich globular cluster subsample, while the metal-poor globular cluster subsample shows no evidence for rotation. The most significant difference between the rotation of the metal-rich and metal-poor globular clusters occurs at intermediate projected galactocentric radii. The results of this paper confirm the conclusion of Schroder et al. that M81's metal-rich globular clusters at intermediate projected radii were associated with a thick disk of M81.