SDSS-IV MaNGA: the ‘G-dwarf problem’ revisited

Michael J Greener,Alfonso Aragón-Salamanca,Richard R Lane,Thomas Peterken,Michael Merrifield,Brett Andrews

doi:10.1093/mnrasl/slab012

Abstract

ABSTRACT The levels of heavy elements in stars are the product of enhancement by previous stellar generations, and the distribution of this metallicity among the population contains clues to the process by which a galaxy formed. Most famously, the ‘G-dwarf problem’ highlighted the small number of low-metallicity G-dwarf stars in the Milky Way, which is inconsistent with the simplest picture of a galaxy formed from a ‘closed box’ of gas. It can be resolved by treating the Galaxy as an open system that accretes gas throughout its life. This observation has classically only been made in the Milky Way, but the availability of high-quality spectral data from SDSS-IV MaNGA and the development of new analysis techniques mean that we can now make equivalent measurements for a large sample of spiral galaxies. Our analysis shows that high-mass spirals generically show a similar deficit of low-metallicity stars, implying that the Milky Way’s history of gas accretion is common. By contrast, low-mass spirals show little sign of a G-dwarf problem, presenting the metallicity distribution that would be expected if such systems evolved as pretty much closed boxes. This distinction can be understood from the differing timescales for star formation in galaxies of differing masses.

Highlights

A low-mass spirals show little sign of a G-dwarf problem, presenting the metallicity distribution that M would be expected if such systems evolved as pretty much closed boxes
D objects incorporate matter recycled from previous stellar E generations, with stars born early on containing less of this
U tory of the Galaxy encoded in the distribution of the metallicity that we find in its stars (Talbot & Arnett 1971). This phenomenon can be most quantified by the cumulative metallicity distribution function (CMDF), which is just

Summary

INTRODUCTION

Almost all of the elements heavier than helium that we find in our galaxy’s stars, the “metals”, are there because these. U tory of the Galaxy encoded in the distribution of the metallicity that we find in its stars (Talbot & Arnett 1971). This phenomenon can be most quantified by the cumulative metallicity distribution function (CMDF), which is just. The problem is that by the time a closed box has built up sufficient heavy elements to make stars with high metallicity, there is very little gas left to make new. I While the quality of the reconstructed CMDFs may not be R as high as for our own galaxy, it should be more than adequate to distinguish between the very different functions of Figure 1, providing an overview of the metallicity evolution.

Sample Selection

Spectral Fitting The stellar evolution histories of the sample galaxies were

RESULTS AND DISCUSSION