The strange case of NGC2419: stellar populations, chemical composition, dynamics

TL;DR

This study of NGC2419 combines spectroscopic and photometric data to reveal multiple stellar populations, peculiar chemical abundance patterns, and spatial distributions, providing insights into its complex formation history.

Contribution

It presents new evidence of multiple populations and chemical peculiarities in NGC2419 using deep photometry and spectroscopic analysis, advancing understanding of its stellar composition and structure.

Findings

Detection of a larger-than-error color spread on the Red Giant Branch

Blue RGB stars are more centrally concentrated

Observed peculiar abundance patterns in cluster giants

Abstract

A few years ago we started an observational campaign aimed at the thorough study of the massive and remote globular cluster NGC2419. We have used the collected data, e.g., to test alternative theories of gravitation, to constrain the stellar M/L ratio by direct analysis of the observed luminosity function, and to search for Dark Matter within the cluster. Here we present some recent results about (a) the peculiar abundance pattern that we observed in a sample of cluster giants, and (b) newly found photometric evidence for the presence of multiple populations in the cluster. In particular, from new deep and accurate uVI LBT photometry, we find that the color spread on the Red Giant Branch is significantly larger than the observational errors both in V-I and u-V, and that the stars lying to the blue of the RGB ridge line are more concentrated toward the center of the cluster than those lying to the red of the ridge line.