Chemodynamic subpopulations of the Carina dwarf galaxy

TL;DR

This study reveals three distinct chemodynamical subpopulations in the Carina dwarf galaxy, showing complex spatial, kinematic, and metallicity distributions that challenge simple gradient models.

Contribution

It provides a detailed chemodynamical analysis of Carina, identifying multiple subpopulations with unique properties and uncovering unexpected inversions in their spatial and chemical ordering.

Findings

Three chemodynamical subpopulations identified

Low-metallicity population is more extended and kinematically hotter

An inversion in metallicity and kinematic ordering in metal-rich populations

Abstract

We study the chemodynamical properties of the Carina dwarf spheroidal by combining an intermediate spectroscopic resolution dataset of more than 900 red giant and red clump stars, with high-precision photometry to derive the atmospheric parameters, metallicities and age estimates for our targets. Within the red giant branch population, we find evidence for the presence of three distinct stellar sub-populations with different metallicities, spatial distributions, kinematics and ages. As in the Fornax and Sculptor dwarf spheroidals, the subpopulation with the lowest average metallicity is more extended and kinematically hotter than all other populations. However, we identify an inversion in the parallel ordering of metallicity, kinematics and characteristic length scale in the two most metal rich subpopulations, which therefore do not contribute to a global negative chemical gradient. Contrary to common trends in the chemical properties with radius, the metal richest population is more extended and mildly kinematically hotter than the main component of intermediate metallicity. More investigations are required to ascertain the nature of this inversion, but we comment on the mechanisms that might have caused it.