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Globular Clusters in M33 and the Kinematics of the Halo

Presentation #407.02 in the session “Star Clusters: Galactic & Extragalactic”.

Published onJan 11, 2021
Globular Clusters in M33 and the Kinematics of the Halo

The warping of the stellar and gas disks of the Triangulum galaxy (M33) is typically explained as the result of a mild tidal disruption by its host M31. Further evidence can be seen in faint stellar features along the north-south direction, populated mostly by old, metal-poor stars. This scenario could explain the apparent lack of an outer halo population in M33, and also offers the tantalizing possibility that the outermost star clusters in M31 may have originated in M33. However, the existence of an outer M33 halo has not been settled, and more recent proper motion studies have cast doubt on the viability of this scenario, motivating a fuller accounting of the kinematics of M33 and its component populations. Globular clusters (GCs) are ideal for testing these ideas, as they are good tracers of the formation processes and assembly history of a galaxy. Furthermore, the spatial distribution of the known GCs in M33 is broadly aligned with the (metal-poor) faint stellar features, hinting at their ability to trace potential tidal interactions. I will present an updated catalog of precision radial velocities for ~230 GC candidates in M33, nearly one-third of which are newly determined by the Apache Point Observatory Galactic Evolution Experiment (APOGEE) survey. This catalog represents the largest collection of radial velocity measurements for GCs in M33 to date. I will discuss the construction of the catalog, taking care to highlight removal of Milky Way contamination, as well as a preliminary kinematic analysis. Future work will incorporate results from an ongoing analysis of high-resolution LBT imaging of M33, as well as new APOGEE-derived ages and metallicities.

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