This thesis examines emissions from the interstellar medium (ISM) of the Small Magellanic Cloud (SMC) and reports the detection of planetary nebulae in the radio continuum (RC) from both Magellanic Clouds (MCs). New RC measurements of the planetary nebulae are used to calibrate a statistical distance scale based on the surface brightness""diameter relation (I£""D) (defined as I£ = A × D-I²). The correlation between far-infrared (FIR) and RC emissions from the ISM of the SMC was investigated over scales from 3 kpc to 0.01 kpc. Good far-infrared/radio continuum (FIR/RC) correlation down to 15 pc was seen. The reciprocal slope of the FIR/RC emission correlation, RC/FIR, in the SMC was shown to be greatest in the most active star""forming regions with a power law slope of 1.14 indicating that the RC emission increases faster than the FIR emission. The slope of the other regions and the entire SMC are much flatter and in the range of 0.63""0.85. The slopes tend to follow the thermal fractions of the regions with a range of 0.5"" 0.95. It was found that the thermal fraction of the RC emission alone can provide the expected FIR/RC correlation. This result was consistent with a common source for ultraviolet (UV) photons which heat dust and which ionise Hi to produce thermal electrons leading to freefree (FF) radiation. The UV photons, which ionise the ISM and heat the dust, come from hot young stars, the largest of which will eventually become supernovae. Non-thermal emission, in the form of synchrotron radio emission, is from ultra-relativistic electrons accelerated by supernovae. These ultra-relativistic electrons interact with the galactic magnetic field and the acceleration produces the synchrotron radiation observed. The SMC results with minimal nonthermal contributions may not provide support for coupling between the local gas density and the magnetic field intensity. Planetary nebulae detected in the RC are frequently referred to by the shorthand "radio planetary nebulae". A search for radio planetary nebulae in the SMC resulted in ten new RC detections reported here from the 105 catalogued planetary nebula positions in the SMC (SMP S6, LIN41, LIN142, SMPS13, SMP S14, SMP S16, J 18, SMP S18, SMPS19, and SMPS22). Six SMC radio planetary nebulae previously detected (LIN45, SMPS11, SMP S17, LIN321, LIN339, and SMP S24) were re-observed. These sixteen radio detections represent 15% of the total catalogued planetary nebula population in the SMC. Six of these objects, however, were shown to have characteristics that suggest they are likely planetary nebula mimics (LIN41, LIN45, SMPS11, LIN142, LIN321, and LIN339). The SMC radio planetary nebula population was also used in a (I£""D) relation study. The results of this study were consistent with previous SMC and Large Magellanic Cloud (LMC) planetary nebula measurements of the (I£""D) relation. This study contributed twenty-one new radio detections of planetary nebulae to the total of thirty-one radio planetary nebulae that have been detected in the LMC. The search for these radio planetary nebulae in the LMC began with the exploration of all 629 validated planetary nebula positions. All presently available data from the ATOA at 3, 6, 13, and 20 cm were examined at these positions. The newly detected planetary nebulae were: SMP L13, SMPL15, SMPL21, SMP L23, SMPL29, SMPL37, SMP L38, SMPL45, SMPL50, SMP L52, SMPL53, SMPL58, SMPL63, SMP L66, SMPL73, SMPL75, SMP L76, SMPL78, RP 659, SMPL85, and SMPL92. Seven previously detected radio planetary nebulae (Filipovic et al., 2009) were also detected: SMP L47, SMP L48, SMPL62, SMPL74, SMP L83, SMP L84, and SMP L89. An additional three planetary nebulae from the study by Filipovic et al. (2009): SMPL25, SMPL33, and SMPL39 were not detected in this study but were included in the complete catalogue compilation of radio planetary nebulae presented here. One of the previous detections from that study, SMP L8, had been reclassified as a planetary nebula mimic, a compact Hii region. With the available planetary nebula 6 cm surface brightness measurements and the corresponding planetary nebula diameter data, a bootstrap resampled sample was constructed from twenty-eight LMC radio planetary nebulae and nine SMC radio planetary nebulae which revealed that Magellanic Cloud (MC) planetary nebulae were not likely to follow linear evolutionary paths. The best fitting parameters from this resampled sample were comparable to previous results from the MCs and the Galactic planetary nebulae. A value of I² = 2.9 ± 0.4 was obtained for MC planetary nebulae compared to I² = 3.1 ± 0.4 for the Galaxy. The MC planetary nebula resampled sample was used to calibrate a planetary nebula (I£""D) statistical distance model which resulted in a predicted statistical distance error of 17%. Since a value of I£ = 2.9±0.4 was found for the MC sample which is just below the minimum predicted theoretical value of I² = 3, sensitivity selection effects were examined. To estimate the significance of the sensitivity selection effects, a Monte Carlo bootstrap resampled sample was created which included various sensitivity bias parameters. The best fitting parameters from the bias effects on the bootstrap resampled sample created in this way indicated that selection effects were significant for I² values larger than I² 2.6. The selection effect was shown to produce a measured value of I² = 2.9 when the unbiased sample had a value of I² 3.4. A continuous probability density function (PDF) was also constructed using a Monte Carlo bootstrap resampled sample with more advanced techniques. This approach resulted in an enhanced accuracy for the statistical distance calculation with a distance error of 16%. This error was comparable to a study by Frew et al. (2016b) which used the (SHI±-r) relation and reported a distance measurement error of 18% with a calibration sample of 1100 planetary nebulae.
| Date of Award | 2018 |
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| Original language | English |
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