Carbon Abundance in the Milky Way Galaxy

University essay from Lunds universitet/Astronomi

Abstract: Carbon is the fourth most abundant element after hydrogen, helium and oxygen. It is a product of stellar nucleosynthesis as well as it being an important bio signature for life; this makes the analysis of carbon very fundamental. The origin of carbon and the relative contributions from massive and low-to-intermediate mass stars in producing it is still under debate. The principal focus of this thesis is to analyse the carbon abundance in the Milky Way. Through the synthetic spectral analysis of five carbon lines of 5052.1 ̊A, 5380.3 ̊A, 6587.6 ̊A, 7111.5 ̊A, and 7113.2 ̊A in tandem with high resolution (R = 40000 - 110 000) and high signal to noise ratio (S/N = 150 - 300) observed spectra, we can determine the carbon abundances of the stars in the sample. In this thesis, the trends of[C/H], [C/Fe], and [C/Mg] versus [Fe/H] as well as, [C/O] versus [O/H] for 502 type F and G dwarf and subgiant stars will have their carbon abundances analysed. By distinguishing between the galactic thin and thick disks we are able to contrast and compare the galactic evolution of carbon. It was found that for [C/H], [C/Fe], and [C/Mg] versus [Fe/H] there was a distinctive overlap in thin and thick disks. For [C/O] versus [O/H] there was a major disparity in the trends of the thin and thick disks. The interpretation of these results leads us to believe the origin of carbon and its contribution is a combination of both low-to-intermediate mass stars and massive stars. Massive stars are believed to contribute more carbon at earlier ages in the universe where as low to intermediate mass stars contribute more in later stages. This interpretation of the results is in line with other recent findings of carbon abundances; typically, it has been found that there is a combination of contributions from massive and low-to-intermediate mass stars but these relative contributions are still disputed.

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