Metallicity Gradients in Local Star-Forming Galaxies
The gas-phase metallicity is one of the most fundamental properties of a galaxy. Measuring the gas-phase metallicity distribution allows us to gauge the age of the gas and hence how the galaxy has formed over time. By combining the gas-phase metallicity with galaxy evolution simulations, we can gain...
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| Format: | Doctoral or Postdoctoral Thesis |
| Language: | English |
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| Online Access: | http://hdl.handle.net/1885/202038 https://doi.org/10.25911/ZYKM-SZ81 https://openresearch-repository.anu.edu.au/bitstream/1885/202038/3/Poetrodjojo%20Thesis%202021.pdf.jpg |
| Summary: | The gas-phase metallicity is one of the most fundamental properties of a galaxy. Measuring the gas-phase metallicity distribution allows us to gauge the age of the gas and hence how the galaxy has formed over time. By combining the gas-phase metallicity with galaxy evolution simulations, we can gain insight into dynamical processes which may have affected its formation process in the past. In this thesis, we use spatially resolved spectra from the SAMI galaxy survey and TYPHOON survey to explore the gas-phase metallicity of galaxies as a function of stellar mass, environment and star-formation rate. We also investigate the systematic errors and reliability of measuring gas-phase metallicity through popular strong emission line diagnostics. In the second chapter of this thesis, we present gas-phase metallicity and ionization parameter maps of 25 star-forming face-on spiral galaxies from the SAMI galaxy survey. We measure the metallicity gradients of each galaxy and find a weak mass dependence of the metallicity gradients ranging from -0.20 to -0.03 dex/Re. No significant trends were found in the ionization parameter distribution with the ionization parameter typically ranging between 7.0 < log(q) < 7.8. Ionization parameter variations of this magnitude may lead to systematic deviations of up to 0.3 dex when using the O3N2 metallicity diagnostic. It is known that metallicity gradients are significantly flattened when undergoing merger activities. This is due to the mixing of gas through tidal forces as well as inflows of pristine gas. In the third chapter, we compare the metallicity gradients of galaxies in isolated environments to those in denser environments and find no significant trends with any of the three environment density metrics tested (fifth nearest neighbour, number of galaxies within a cylinder and the average Gaussian ellipsoid density parameter). In the fourth chapter, we discuss the reliability of measuring gas-phase metallicity using strong emission line diagnostics and analyse the large ... |
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