Galaxy population identification with a phylogenetic approach.
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Date
2020
Authors
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Journal ISSN
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Publisher
Universidad de Concepción.
Abstract
We propose a phylogenetic approach as a novel and robust tool capable of detecting galaxy
populations (GPs) based on their chemical composition. This method clusters galaxies into
the hierarchical structure of a phylogenetic tree that connects galaxies through features
we call "nodes". The branches of the tree are interpreted as different GPs and the length
between nodes (NodeLength) as the internal chemical variation along a branch. The
NodeLength works as a chemical index, thus relating galaxy stellar populations with
other structural and local environmental properties of galaxies. We apply the phylogenetic
approach using 30 abundance indices from the Sloan Digital Sky Survey to 475 galaxies
in the Coma cluster (0,015 < z < 0,033) and 438 galaxies in the field (0,035 < z < 0,054).
We find that Coma is a complex system with multiple populations. It has three main GPs
that can readily be identified in color-magnitude space, and several minor structures in its
red sequence. On the other hand, the field is more homogeneous, presenting one main GP.
This phylogenetic analysis of cluster and field galaxies, shows a contrast in terms of how
chemically related galaxies are within different environments. We also find that, regardless
of their morphology, galaxies can have a similar chemical composition. Therefore, this
new approach to study galaxy properties and their evolution makes it possible to perform
robust analyses and interpretations without introducing biases by first selecting samples
based on a specific characteristic like stellar mass, morphology, sSFR or metallicity, as
done with more traditional techniques.
Description
Tesis para optar al grado académico de Magíster en Astronomía.
Keywords
Galaxias, Evolución, Galaxias, Cúmulos, Abundancia Cósmica, Filogenia