A Gemini/GMOS Study of Intermediate Luminosity Early-Type Virgo Cluster Galaxies. I. Globular Cluster and Stellar Kinematics

TL;DR

This study analyzes the kinematics of globular clusters and stellar light in four intermediate luminosity Virgo cluster galaxies, revealing diverse and complex kinematic behaviors beyond the inner regions, highlighting the importance of wide-field observations.

Contribution

It provides new wide-field kinematic data for globular clusters and stars in fainter galaxies, showing diverse kinematic structures and differences between stellar and GC systems.

Findings

Outer galaxy regions show diverse kinematic behaviors.

Globular cluster systems can have different kinematics from stars.

Wide-field data reveals complex kinematic structures.

Abstract

We present a kinematic analysis of the globular cluster systems and diffuse stellar light of four intermediate luminosity (sub-$L^{\ast}$) early-type galaxies in the Virgo cluster based on Gemini/GMOS data. Our galaxy sample is fainter ($-23.8<M_K<-22.7$) than most previous studies, nearly doubling the number of galaxies in this magnitude range that now have GC kinematics. The data for the diffuse light extends to $4R_e$, and the data for the globular clusters reaches 8--$12R_e$. We find that the kinematics in these outer regions are all different despite the fact that these four galaxies have similar photometric properties, and are uniformly classified as "fast rotators" from their stellar kinematics within $1R_e$. The globular cluster systems exhibit a wide range of kinematic morphology. The rotation axis and amplitude can change between the inner and outer regions, including a case of counter-rotation. This difference shows the importance of wide-field kinematic studies, and shows that stellar and GC kinematics can change significantly as one moves beyond the inner regions of galaxies. Moreover, the kinematics of the globular cluster systems can differ from that of the stars, suggesting that the formation of the two populations are also distinct.