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arXiv · 1112.3207

Principal Component Analysis on Chemical Abundances Spaces

Yuan-Sen Ting·Kenneth C. Freeman·Chiaki Kobayashi·Gayandhi M. De Silva·Joss Bland-Hawthorn
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Abstract

In preparation for the HERMES chemical tagging survey of about a million Galactic FGK stars, we estimate the number of independent dimensions of the space defined by the stellar chemical element abundances [X/Fe]. [...] We explore abundances in several environments, including solar neighbourhood thin/thick disk stars, halo metal-poor stars, globular clusters, open clusters, the Large Magellanic Cloud and the Fornax dwarf spheroidal galaxy. [...] We find that, especially at low metallicity, the production of r-process elements is likely to be associated with the production of alpha-elements. This may support the core-collapse supernovae as the r-process site. We also verify the over-abundances of light s-process elements at low metallicity, and find that the relative contribution decreases at higher metallicity, which suggests that this lighter elements primary process may be associated with massive stars. [...] Our analysis reveals two types of core-collapse supernovae: one produces mainly alpha-elements, the other produces both alpha-elements and Fe-peak elements with a large enhancement of heavy Fe-peak elements which may be the contribution from hypernovae. [...] The extra contribution from low mass AGB stars at high metallicity compensates the dimension loss due to the homogenization of the core-collapse supernovae ejecta. [...] the number of independent dimensions of the [X/Fe]+[Fe/H] chemical space in the solar neighbourhood for HERMES is about 8 to 9. Comparing fainter galaxies and the solar neighbourhood, we find that the chemical space for fainter galaxies such as Fornax and the Large Magellanic Cloud has a higher dimensionality. This is consistent with the slower star formation history of fainter galaxies. [...]

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Yuan-Sen Ting, Kenneth C. Freeman, Chiaki Kobayashi, Gayandhi M. De Silva, Joss Bland-Hawthorn. 2011-12-14. Principal Component Analysis on Chemical Abundances Spaces. https://doi.org/10.1111/j.1365-2966.2011.20387.x

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