Ω Centauri

Omega Centauri (ω Cen, NGC5139) is the brightest, most massive globular cluster in the Milky Way and it has complex stellar populations. More specifically it shows multiple sequences in its color-magnitude diagram, large spread in metallicity and possibly also ages. Due to this, it has long be suspected to be a stripped of nuclei of a dwarf galaxy that has merged with the Milky Way a long time ago.

Image Credit: ESO/INAF-VST/OmegaCAM. Acknowledgement: A. Grado, L. Limatola/INAF-Capodimonte Observatory

MUSE Catalog

We present an unprecedented MUSE spectroscopic dataset out to its half-light radius and stars ranging from the main sequence to the tip of the red giant branch. We extract spectra of more than 300,000 stars (using PampelMUSE, Kamann et al., 2013) reaching more than two magnitudes below the main sequence turn-off and we use these spectra to derive metallicity and line-of-sight velocity measurements (with spexxy). This massive spectroscopic dataset will allow future studies that will transform our understanding of ω Cen, allowing us to investigate the stellar populations, ages, kinematics, and formation history in great detail.

This work has been accepted for publication in ApJ and it is on arXiv , see Publication List

Image Credit: Nitschai et al., 2023

Spatially Well-mixed Populations

We use new Multi-Unit Spectroscopic Explorer spectroscopic and Hubble Space Telescope photometric catalogs to investigate the underlying metallicity distributions as well as the spatial variations of the populations within the cluster up to its half-light radius. Based on 11,050 member stars, the [M/H] distribution has a median of (−1.614 ± 0.003) dex and a large spread of ∼1.37 dex, reaching from −0.67 to −2.04 dex for 99.7% of the stars. In addition, we show the chromosome map of the cluster, which separates the red giant branch stars into different subpopulations, and analyze the subpopulations of the most metal-poor component. Finally, we do not find any metallicity gradient within the half-light radius, and the different subpopulations are well mixed.

This work has been accepted for publication in ApJ and it is on arXiv , see Publication List

Image Credit: Nitschai et al., 2024