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We present age estimates for over 8100 sub-giant branch (SGB) stars in Omega Centauri ($\omega$ Cen) to study its star formation history. Our large data set, which combines multi-wavelength HST photometry with MUSE metallicities, provides an unprecedented opportunity to measure individual stellar ages. We do this by fitting each star's photometry and metallicity with theoretical isochrones, that are embedded with an empirical [C+N+O]-[Fe/H] relation specifically for $\omega$ Cen. The bulk of the stars have ages between 13 and 10 Gyr, with the mean stellar age being 12.08$\pm$0.01 Gyrs and the median age uncertainty being 0.68 Gyrs. From these ages we construct the most complete age-metallicity relation (AMR) for $\omega$ Cen to date. We find that the mean age of stars decreases with increasing metallicity and find two distinct streams in the age-metallicity plane, hinting at different star formation pathways. We derive an intrinsic spread in the ages of 0.75$\pm$0.01 Gyr for the whole cluster, with the age spread showing a clear increase with metallicity. We verify the robustness of our age estimations by varying isochrone parameters and constraining our systematics. We find the C+N+O relation to be the most critical consideration for constraining the AMR. We also present the SGB chromosome map with age information. In the future, these stellar ages could be combined with chemical abundances to study age differences in subpopulations, and uncover the chemical evolution history of this massive nuclear star cluster., Comment: 23 pages, 11 figures

Star formation rates (SFRs), gas-phase metallicities, and stellar masses are crucial for studying galaxy evolution. The different relations resulting from these properties give insights into the complex interplay of gas inside galaxies and their evolutionary trajectory and current characteristics. We aim to characterize these relations at $z\sim 0.3$, corresponding to a 3-4 Gyr lookback time. We utilized optical integral field spectroscopy of 65 emission-line galaxies from the MAGPI survey at a redshift of $0.28

$\omega$ Centauri, the most massive globular cluster in the Milky Way, has long been suspected to be the stripped nucleus of a dwarf galaxy that fell into the Galaxy a long time ago. There is considerable evidence for this scenario including a large spread in metallicity and an unusually large number of distinct sub-populations seen in photometric studies. In this work, we use new MUSE spectroscopic and HST 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 \pm 0.003)$ dex and a large spread of $\sim$ 1.37 dex reaching from $ -0.67$ dex 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 sub-populations, and analyze the sub-populations of the metal-poorest component. Finally, we do not find any metallicity gradient within the half-light radius, and the different sub-populations are well mixed., Comment: 22 pages, 18 figures, and 3 tables. Accepted for publication in ApJ

The kinematics and chemical composition of stellar populations of different ages provide crucial information about the evolution of a galaxy. We aim to provide such information for IC 1613, an isolated, gas-rich, star-forming dwarf galaxy in the Local Group. We present here the results of a new spectroscopic study performed with MUSE, an integral-field spectrograph on the Very Large Telescope. We extracted from the data cubes more than 2000 sources from which we separated stellar objects for further spectroscopic analysis. The quality of the data set allowed us to obtain accurate classifications and line-of-sight velocities for about 800 stars. Our sample includes not only Red Giant Branch (RGB) and Main Sequence (MS) stars, but also a number of probable Be and C stars. We also obtained reliable metallicities for about 300 RGB stars. The kinematic analysis revealed for the first time the presence of stellar rotation with high significance. We found general agreement with the rotation velocity of the neutral gas component. Examining the kinematics of stars as a function of broad age ranges, we find that the velocity dispersion increases as a function of age, with the behaviour being very clear in the outermost pointings, while the rotation-to-velocity dispersion support decreases. On timescales shorter than a Gyr, the stellar kinematics still follow very closely that of the neutral gas, while the two components decouple on longer timescales. The chemical analysis of the RGB stars revealed average properties comparable to other Local Group dwarf galaxies. We also provide a new estimation of the inclination angle using only independent stellar tracers. Our work provides the largest spectroscopic sample of an isolated LG dwarf galaxy. The results obtained seem to support the scenario in which the stars of a dwarf galaxy are born from a less turbulent gas over time., Comment: Accepted for publication in A&A. Changes from previous version include: a more structured text, updated figures and the addition of a discussion section (incl. a new figure). Previous results remain unchanged, but are now contextualised with respect to similar dwarf galaxies. A new estimate of the inclination angle has been added. References updated. 18 pages (10 figures, 5 tables) + appendices