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Carbon Abundance in the Milky Way Galaxy

Kvernes Macpherson, Calum LU (2021) In Lund Observatory Examensarbeten ASTK02 20211
Lund Observatory
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... (More)
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. (Less)
Popular Abstract
The question of the origin of carbon in the Milky Way is widely debated and notcompletely settled. Carbon is the fourth most abundant element after hydrogen, heliumand oxygen respectively, yet we still struggle to conclude the main source of carbon in theMilky Way.It is important to study carbon, since it is a by-product of galactic nucleosynthesis inwhich carbon is made from the process of nuclear fusion in stars. Finding the origins of theabundance of carbon for stars in the Milky Way will help in understanding the evolution ofthe universe and will help facilitate further research in the field of astrobiology, since carbonis known as a strong indicator for organic life. The main question up for debate is thenwhether the main contributor... (More)
The question of the origin of carbon in the Milky Way is widely debated and notcompletely settled. Carbon is the fourth most abundant element after hydrogen, heliumand oxygen respectively, yet we still struggle to conclude the main source of carbon in theMilky Way.It is important to study carbon, since it is a by-product of galactic nucleosynthesis inwhich carbon is made from the process of nuclear fusion in stars. Finding the origins of theabundance of carbon for stars in the Milky Way will help in understanding the evolution ofthe universe and will help facilitate further research in the field of astrobiology, since carbonis known as a strong indicator for organic life. The main question up for debate is thenwhether the main contributor of carbon in the Milky Way is from one of two categoriesof stars. The first category, known as the low/intermediate mass stars, are thought tocontribute carbon by stellar winds stripping the carbon in their atmosphere out in to theinterstellar medium. This is much like how a tornado would strip away anything in itspath out into the open. These low/intermediate mass stars are relatively cold and live forbillions of years, some as long as the universe itself; their atmospheres act as time capsulesthat can be analysed, as they remain unchanged since their birth. The other category ofstars are the high mass stars. These types of stars are a lot hotter; more heat means theyrun out of fuel a lot faster than colder stars, which in turn means they live in the timescale of millions of years rather than billions. Such hot stars build up an onion-like layer ofelements through nucleosynthesis over millions of years of nuclear fusion. This is possibledue to extraordinary temperatures well above 100,000,000 K (which is around 17,500 timeshotter than the surface of the sun) that cannot be reached by low/intermediate mass stars.Hot stars then contribute carbon by supernovae explosions, the enriched metallic guts ofthe star are ejected into the interstellar medium when the star reaches the final stages ofits life.Since many different papers indicate a different form of contribution of carbon in theMilky Way, the results of this project hopes to bring us closer to the true origin of carbonin the Milk Way. We do this by generating artificial spectras of different carbon lines usinga specialised programming software, one can then find the different carbon abundances ofseveral stars. The results are then plotted in order to visualise different trends. (Less)
Please use this url to cite or link to this publication:
author
Kvernes Macpherson, Calum LU
supervisor
organization
course
ASTK02 20211
year
type
M2 - Bachelor Degree
subject
keywords
Carbon, Abundance, Milky Way, Chemical Evolution
publication/series
Lund Observatory Examensarbeten
report number
2021-EXA180
language
English
id
9051659
date added to LUP
2021-06-16 12:33:36
date last changed
2021-06-16 12:33:36
@misc{9051659,
  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.}},
  author       = {{Kvernes Macpherson, Calum}},
  language     = {{eng}},
  note         = {{Student Paper}},
  series       = {{Lund Observatory Examensarbeten}},
  title        = {{Carbon Abundance in the Milky Way Galaxy}},
  year         = {{2021}},
}