Cosmic phylogeny: reconstructing the chemical history of the solar neighbourhood with an evolutionary tree

Abstract

Using 17 chemical elements as a proxy for stellar DNA, we present a full phylogenetic study of stars in the solar neighbourhood. This entails applying a clustering technique that is widely used in molecular biology to construct an evolutionary tree from which three branches emerge. These are interpreted as stellar populations which separate in age and kinematics and can be thus attributed to the thin disk, the thick disk, and an intermediate population of probable distinct origin. We further find six lone stars of intermediate age that could not be assigned to any population with enough statistical significance. Combining the ages of the stars with their position on the tree, we are able to quantify the mean rate of chemical enrichment of each of the populations, and thus show in a purely empirical way that the star formation rate in the thick disk is much higher than in the thin disk. We are also able to estimate the relative contribution of dynamical processes such as radial migration and disk heating to the distribution of chemical elements in the solar neighbourhood. Our method offers an alternative approach to chemical tagging methods with the advantage of visualising the behaviour of chemical elements in evolutionary trees. This offers a new way to search for `common ancestors' that can reveal the origin of solar neighbourhood stars.

MNRAS in press

References in corpus (14)

• The GALAH Survey: Scientific Motivation
• High-precision abundances of elements in solar twin stars: Trends with stellar age and elemental condensation temperature
• Tracing chemical evolution over the extent of the Milky Way's Disk with APOGEE Red Clump Stars
• Constraining the Galaxy's dark halo with RAVE stars
• On the Formation of Galactic Thick Disks
• The Gaia-ESO Survey: the chemical structure of the Galactic discs from the first internal data release
• Early turbulent mixing as the origin of chemical homogeneity in open star clusters
• High-precision abundances of Sc, Mn, Cu, and Ba in solar twins. Trends of element ratios with stellar age
• Testing the chemical tagging technique with open clusters
• HD 98618: A Star Closely Resembling our Sun
• The Gaia-ESO Survey: a quiescent Milky Way with no significant dark/stellar accreted disc
• The environment of formation as a second parameter for globular cluster classification
• Towards a Phylogenetic Analysis of Galaxy Evolution : a Case Study with the Dwarf Galaxies of the Local Group
• Stellar populations in $\omega$ Centauri: a multivariate analysis

Cited by in corpus (4)

• The AMBRE project: The thick thin disk and thin thick disk of the Milky Way
• The GALAH survey: Chemical Tagging of Star Clusters and New Members in the Pleiades
• Blind chemical tagging with DBSCAN: prospects for spectroscopic surveys
• Phylogenetic Analyses of Quasars and Galaxies