Please use this identifier to cite or link to this item: http://dlib.scu.ac.ir/handle/2123/13603
Title: The survival and evolution of the smallest galaxies
subject: astronomy;astrophysics;dwarf galaxies;galactic archaeology;Supernovae
Publisher: University of Sydney
School of Physics
Sydney Institute for Astronomy
Description: The newly discovered low-luminosity galaxies known as ultrafaint dwarfs show little chemical evolution and may therefore retain the signatures of the first stars. This thesis models these galaxies as intrinsically very low-mass systems that formed only a few thousand stars in the early universe. The first part uses hydrodynamical models to determine the lower mass limit for a dwarf galaxy in the face of feedback from its own star formation. Dark matter halos with virial masses greater than 10^6 solar masses are found to retain a large percentage of their baryons following a single supernova event under favourable assumptions regarding radiative cooling, inhomogeneity of the interstellar medium, and position of the supernova. The inclusion of the ionising radiation from a 25 solar mass star prior to the supernova raises this limit to 10^6.5 solar masses. The second part of the thesis uses the first part as a template for the effect of a supernova on 10^7 solar mass systems, allowing extension of the model beyond the first supernova. The model can reproduce the observed chemical abundances of ultrafaint dwarfs (UFDs). Two possible star formation histories are modelled, with continuous star formation fitting the observed abundances better than two-single age bursts. Very metal-poor Damped Lyman-alpha systems (DLAs) at redshifts z = 2-3 are also studied as they may be the precursors to systems similar to the UFDs, but in isolation rather than part of the Milky Way system. However, there are discrepancies in chemical abundances between the DLAs and both the UFDs and the models in this thesis. The 20-metre telescopes to commence operations in the next decade will revolutionise the study of the smallest galaxies, providing chemical abundances for many more stars and a wider range of elements.
URI: https://ses.library.usyd.edu.au/handle/2123/13603
More Information: http://hdl.handle.net/2123/13603
Appears in Collections:Postgraduate Theses

Files in This Item:
Click on the URI links for accessing contents.
Title: The survival and evolution of the smallest galaxies
subject: astronomy;astrophysics;dwarf galaxies;galactic archaeology;Supernovae
Publisher: University of Sydney
School of Physics
Sydney Institute for Astronomy
Description: The newly discovered low-luminosity galaxies known as ultrafaint dwarfs show little chemical evolution and may therefore retain the signatures of the first stars. This thesis models these galaxies as intrinsically very low-mass systems that formed only a few thousand stars in the early universe. The first part uses hydrodynamical models to determine the lower mass limit for a dwarf galaxy in the face of feedback from its own star formation. Dark matter halos with virial masses greater than 10^6 solar masses are found to retain a large percentage of their baryons following a single supernova event under favourable assumptions regarding radiative cooling, inhomogeneity of the interstellar medium, and position of the supernova. The inclusion of the ionising radiation from a 25 solar mass star prior to the supernova raises this limit to 10^6.5 solar masses. The second part of the thesis uses the first part as a template for the effect of a supernova on 10^7 solar mass systems, allowing extension of the model beyond the first supernova. The model can reproduce the observed chemical abundances of ultrafaint dwarfs (UFDs). Two possible star formation histories are modelled, with continuous star formation fitting the observed abundances better than two-single age bursts. Very metal-poor Damped Lyman-alpha systems (DLAs) at redshifts z = 2-3 are also studied as they may be the precursors to systems similar to the UFDs, but in isolation rather than part of the Milky Way system. However, there are discrepancies in chemical abundances between the DLAs and both the UFDs and the models in this thesis. The 20-metre telescopes to commence operations in the next decade will revolutionise the study of the smallest galaxies, providing chemical abundances for many more stars and a wider range of elements.
URI: https://ses.library.usyd.edu.au/handle/2123/13603
More Information: http://hdl.handle.net/2123/13603
Appears in Collections:Postgraduate Theses

Files in This Item:
Click on the URI links for accessing contents.
Title: The survival and evolution of the smallest galaxies
subject: astronomy;astrophysics;dwarf galaxies;galactic archaeology;Supernovae
Publisher: University of Sydney
School of Physics
Sydney Institute for Astronomy
Description: The newly discovered low-luminosity galaxies known as ultrafaint dwarfs show little chemical evolution and may therefore retain the signatures of the first stars. This thesis models these galaxies as intrinsically very low-mass systems that formed only a few thousand stars in the early universe. The first part uses hydrodynamical models to determine the lower mass limit for a dwarf galaxy in the face of feedback from its own star formation. Dark matter halos with virial masses greater than 10^6 solar masses are found to retain a large percentage of their baryons following a single supernova event under favourable assumptions regarding radiative cooling, inhomogeneity of the interstellar medium, and position of the supernova. The inclusion of the ionising radiation from a 25 solar mass star prior to the supernova raises this limit to 10^6.5 solar masses. The second part of the thesis uses the first part as a template for the effect of a supernova on 10^7 solar mass systems, allowing extension of the model beyond the first supernova. The model can reproduce the observed chemical abundances of ultrafaint dwarfs (UFDs). Two possible star formation histories are modelled, with continuous star formation fitting the observed abundances better than two-single age bursts. Very metal-poor Damped Lyman-alpha systems (DLAs) at redshifts z = 2-3 are also studied as they may be the precursors to systems similar to the UFDs, but in isolation rather than part of the Milky Way system. However, there are discrepancies in chemical abundances between the DLAs and both the UFDs and the models in this thesis. The 20-metre telescopes to commence operations in the next decade will revolutionise the study of the smallest galaxies, providing chemical abundances for many more stars and a wider range of elements.
URI: https://ses.library.usyd.edu.au/handle/2123/13603
More Information: http://hdl.handle.net/2123/13603
Appears in Collections:Postgraduate Theses

Files in This Item:
Click on the URI links for accessing contents.