The SLUGGS survey: chromo-dynamical modelling of the lenticular galaxy NGC 1023

TL;DR

This study presents a detailed analysis of globular cluster kinematics in NGC 1023, revealing their association with galaxy components and providing insights into the galaxy's formation history using a novel decomposition method.

Contribution

Introduces a new photometric and kinematic method to assign globular clusters to galaxy components, enhancing understanding of galaxy assembly processes.

Findings

Red GCs are likely associated with the disk, indicating disk formation at z ~ 2.

Most blue GCs are associated with the spheroidal component.

Identifies GCs that are not in equilibrium, linked to a companion galaxy.

Abstract

Globular clusters (GCs) can be considered discrete, long-lived, dynamical tracers that retain crucial information about the assembly history of their parent galaxy. In this paper, we present a new catalogue of GC velocities and colours for the lenticular galaxy NGC 1023, we study their kinematics and spatial distribution, in comparison with the underlying stellar kinematics and surface brightness profile, and we test a new method for studying GC properties. Specifically, we decompose the galaxy light into its spheroid (assumed to represent the bulge + halo components) and disk components and use it to assign to each GC a probability of belonging to one of the two components. Then we model the galaxy kinematics, assuming a disk and spheroidal component, using planetary nebulae (PNe) and integrated stellar light. We use this kinematic model and the probability previously obtained from the photometry to recalculate for each GC its likelihood of being associated with the disk, the spheroid, or neither. We find that the reddest GCs are likely to be associated with the disk, as found for faint fuzzies in this same galaxy, suggesting that the disk of this S0 galaxy originated at z ~ 2. The majority of blue GCs are found likely to be associated with the spheroidal (hot) component. The method also allows us to identify objects that are unlikely to be in equilibrium with the system. In NGC1023 some of the rejected GCs form a substructure in phase space that is connected with NGC 1023 companion galaxy.