Speaker: Callie Clontz (Galactic Nuclei research group at MPIA)

Title: Combining Nuclear Star Cluster Assembly Probes to Study Our Nearest Galactic Center: 𝜔 Centauri

Abstract: An understanding of the assembly history of the complex star cluster Omega Centauri has long been sought after, with many studies separating the stars on the color-magnitude diagram into multiple groupings across small magnitude ranges. Utilizing the oMEGACat combined astro-photometric and spectroscopic dataset we parse 14 subpopulations from the upper red-giant branch to below the main-sequence turnoff. We combine our results with previous works to estimate the age and age spread of each population. We find that the chemically enhanced (P2) populations are all ~1 Gyr younger (~11.6 Gyr old) and have significantly higher intrinsic age spreads (0.6 Gyr) than the primordial (P1) populations (~12.6 Gyr old, 0.3 Gyr spread), with the intermediate (Im) populations falling in between the two. Additionally, we connect for the first time the chromosome diagram to the two-stream age-metallicity relation, allowing us to link the P1 and P2 stars to distinct star formation tracks, proposed to be in-situ and ex-situ contributions to the cluster’s assembly. Our results are consistent with some suggested formation models and rule out others but no current model can explain all observed features of the subpopulations.

Note: Let me and Ivan know if you want to meet with Callie. She will be visiting on 20 and 21 of November. We will also go for dinner with her on Thursday evening.

• Date:
  Nov. 20, 2025, 2 p.m. – 3 p.m.
  
  
• Location:

  AIP; Leibnizhaus, Seminar room

  
  
• Contact:
  nkacharov@aip.de