The objective of this dissertation is twofold. Firstly an extensive yet concise literature
review on the state-of-the-art of near infrared barred spiral galaxy classi cation is presented.
Secondly, two quantitative approaches to galaxy classi cation at near infrared
wavelengths, the relative gravitational torque method and the isophotal ellipse tting
method, are applied for the rst time to a sample of selected Spitzer IRAC nearby
barred galaxies. Maximum relative gravitational torques are derived for a sample of 40
nearby bright barred disk galaxies at 3.6 m and 4.5 m. These torques are compared
between galaxy pairs at these passbands and we nd an excellent agreement between
the 3.6 m and 4.5 m morphology. The sample used incorporates a wide range of
inclination and bar strength values. The tight coupling of 3.6 m and 4.5 m morphology
provides an opportunity to classify intermediate redshift galaxies that have their
near-infrared rest frame emissions shifted red-ward to 4.5 m; i.e.: out to z = 0:25.
We nd a greater frequency of higher maximum relative torques in our sample compared
with either Block et al. (2002) or Buta et al. (2004) due to sample bias, as
this dissertation is aimed at understanding quantitative methods in classifying barred
galaxies. Furthermore, we compare results from applying an isophotal ellipse tting
technique and a gravitational torque analysis to a common sample of 28 nearby barred
S4G/Spitzer galaxies imaged at 3.6 m. These two quantitative bar strength methods
are applied to images that have identical orientation and deprojection parameters
for an objective comparison. We nd a strong correlation between the gravitational
torque and isophotal ellipse tting methods which in principle supports a method for
estimating bar potentials out to intermediate redshifts by using an isophotal ellipse tting
approach. This has important implications for bar-fraction estimates and galaxy
accretion/evolution scenarios.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:wits/oai:wiredspace.wits.ac.za:10539/11934 |
| Date | 12 September 2012 |
| Creators | Tailor, Asha |
| Source Sets | South African National ETD Portal |
| Language | English |
| Detected Language | English |
| Type | Thesis |
| Format | application/pdf, application/pdf |
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