A stellar census in globular clusters with MUSE. Metallicity spread and dispersion among first-population stars

Abstract

Multiple populations are ubiquitous in the old massive globular clusters (GCs) of the Milky Way. It is still unclear how they arose during the formation of a GC. The topic of iron and metallicity variations has recently attracted attention with the measurement of iron variations among the primordial population (P1) stars of Galactic GCs. We use the spectra of more than 8000 RGB stars in 21 Galactic GCs observed with MUSE to derive individual stellar metallicities [M/H]. For each cluster, we use the HST photometric catalogs to separate the stars into two main populations (P1 and P2). We measure the metallicity spread within the primordial population of each cluster by combining our metallicity measurements with the stars ${\Delta }_{F275W,F814W}$ pseudo-color. We also derive metallicity dispersions (${\sigma }_{[M/H]}$) for the P1 and P2 stars of each GC. In all but three GCs, we measure a significant correlation between the metallicity and the ${\Delta }_{F275W,F814W}$ pseudo-color of the P1 stars such that stars with larger ${\Delta }_{F275W,F814W}$ have higher metallicities. We measure metallicity spreads that range from 0.03 to 0.24 dex and correlate with the GC masses. As for the intrinsic metallicity dispersions, when combining the P1 and P2 stars, we measure values ranging from 0.02 dex to 0.08 dex that correlate very well with the GC masses. We compared the metallicity dispersion among the P1 and P2 stars and found that the P2 stars have metallicity dispersions that are smaller or equal to that of the P1 stars. We find that both the metallicity spreads of the P1 stars (from the ${\Delta }_{F275W,F814W}$ spread in the chromosome maps) and the metallicity dispersions (${\sigma }_{[M/H]}$) correlate with the GC masses, as predicted by some theoretical self-enrichment models presented in the literature.

Accepted for publication in Astronomy and Astrophysics

References in corpus (32)

• The ACS Survey of Galactic Globular Clusters. I. Overview and Clusters Without Previous HST Photometry
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. I. Overview of the Project and Detection of Multiple Stellar Populations
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. IX. The Atlas of Multiple Stellar Populations
• The Data Processing Pipeline for the MUSE Instrument
• What is a globular cluster? An observational perspective
• A stellar census in globular clusters with MUSE: The contribution of rotation to cluster dynamics studied with 200 000 stars
• Iron and s-elements abundance variations in NGC5286: comparison with anomalous globular clusters and Milky Way satellites
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XIX. A Chemical Tagging of the Multiple Stellar Populations Over the Chromosome Maps
• ALMA Observations of the Antennae Galaxies: I. A New Window on a Prototypical Merger
• The Hubble Space Telescope UV Legacy Survey of Galactic Globular Clusters. XXIII. Proper-motion catalogs and internal kinematics
• The Accreted Nuclear Clusters of the Milky Way
• A deep view into the nucleus of the Sagittarius Dwarf Spheroidal Galaxy with MUSE. I. Data and stellar population characterization
• Atomic Diffusion and Mixing in Old Stars. III. Analysis of NGC 6397 Stars under New Constraints
• Constraining globular cluster formation through studies of young massive clusters - V. ALMA observations of clusters in the Antennae
• On The Origin of the Blue Tilt in Extragalactic Globular Cluster Systems
• Atomic Diffusion and Mixing in Old Stars V: A deeper look into the Globular Cluster NGC 6752
• The origin of the spurious iron spread in the globular cluster NGC 3201
• Chemical abundances along the 1G sequence of the chromosome maps: The Globular Cluster NGC 3201
• Differential reddening in the direction of 56 Galactic globular clusters
• oMEGACat I: MUSE spectroscopy of 300,000 stars within the half-light radius of $\omega$ Centauri
• Is helium the key parameter in the extended color spread of the first generation stars in M3?
• Star clusters forming in a low metallicity starburst -- rapid self-enrichment by (very) massive stars
• Kinematic differences between multiple populations in Galactic globular clusters
• Constant light element abundances suggest that the extended P1 in NGC 2808 is not a consequence of CNO-cycle nucleosynthesis
• Peeking beneath the precision floor I: metallicity spreads and multiple elemental dispersions in the globular clusters NGC 288 and NGC 362
• Chemistry of multiple stellar populations in the mono-metallic, in situ, bulge globular cluster NGC 6388
• Simulations of globular clusters within their parent galaxies: Metallicity spreads and anomalous precursor populations
• How many explosions does one need? -- Quantifying supernovae in globular clusters from iron abundance spreads
• Central kinematics of the Galactic globular cluster M80
• Variability in NGC 3201 giant stars and its impact on their spectroscopic [Fe/H] determination
• Investigating a predicted metallicity [Fe/H] variation in the Type II Globular Cluster NGC 362
• Prospects of measuring a metallicity trend and spread in globular clusters from low-resolution spectroscopy