The abundance of satellite galaxies is a critical small-scale test of the standard cosmological model. From comparing the predictions of structure formation in simulations with observations of Local Group dwarf galaxies there is a clear mismatch in the abundance, leading to the so-called “missing satellites” problem. The comparison between simulation and observation have, however, suffered from a limited sample of satellite galaxies, with the only reasonably complete sample being from the most local galaxy groups. It is unknown whether the observed abundance of dwarf satellite galaxies of the nearest groups is statistically representative of the abundance of dwarf satellites in the greater universe. We construct a volume-limited sample of galaxies down to a well-defined stellar mass limit (M★ ≥ 6 × 109 Msun ) using the Atlas3D parent sample of spiral and ellipsoidal galaxies by Cappellari et al. 2011. In order to statistically identify bound satellites around galaxies in our primary catalogue, we apply cuts on the background based on the properties of known dwarf satellites of the Local Group using both the Sloan Digital Sky Survey Data Release 8 (SDSS DR8) (http://www.sdss3.org/dr8/) spectroscopic and photometric galaxy catalogues. We detect an over-density of faint objects at projected separations of < 500 kpc at S/N ∼ 8, corresponding to an average of 4.8 ± 0.65 satellite detections per primary after stacking these systems and subtracting the background. We further find that the over-density of faint objects strongly depends on primary morphology and magnitude. While the Milky Way seems to be unusual in its number of bright satellites, our faint end satellite abundances are in agreement from the ∆m luminosity function for primaries in our sample as bright as the Milky Way. Our work has extended the work of previous authors by several magnitudes further down the faint end of the luminosity function.

Thesis (Ph. D.)--University of Adelaide, Dept. of Plant Science, 1998. / Includes bibliographical references (15 leaves ).

Strigolactones (SLs) are a novel class of phytohormones that shape shoot and root architecture. Carlactone, the precursor of SLs, is synthesized from all-trans-β-carotene by the sequential action of three enzymes: the all-trans/9-cis-β-carotene isomerase DWARF27 (D27) that reversibly converts all-trans-β-carotene into 9-cis-β-carotene (shown only for the rice D27) and the carotenoid cleavage dioxygenases 7 and 8 (CCD7 and CCD8). Genomes of higher plants encode two D27 homologs (D27-like 1 and D27-like 2) with unknown function. Rice and Arabidopsis d27 mutants show less pronounced high tillering/more branching phenotype, compared to ccd7 or ccd8 mutants. This difference might be the result of functional redundancy caused by the presence of D27-like 1 and D27-like 2. In this study, we investigated the enzymatic and biological activity of the Arabidopsis D27 and the rice and Arabidopsis D27-like 1, using both in vivo and in vitro studies. Our results show that AtD27 is a true ortholog of the rice D27. Like SLs, the biosynthesis of ABA requires an all-trans/9-cis-isomerization reaction. However, the enzyme postulated for this activity is still elusive. Our enzymatic activity tests exclude a direct involvement of AtD27 in ABA biosynthesis. Nevertheless, Atd27 mutant shows low level of ABA, and analysis of AtD27 promoter

Fatty acid composition of five dwarf mistletoe species was analysed by Gas Liquid Chromatography. Because of the limitations of available equipment, only aerial shoots were analysed. Palmitic, oleic, linoleic and arachidic acids were the major components of total lipids. The sum of these acids accounted for 85-95 percent of total lipids present in the tissue. There was no apparent difference between species. The ratio of saturated acids to unsaturated acids in summer collections was higher than that of fall collections. Temperature may play an important role in controlling of these ratios. Lipid content varied from 3.25% to 8.5% on a dry weight basis depending on species.

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The results of a study of the neutral hydrogen (HI) content and distribution within a sample of 18 blue compact dwarf galaxies (BCDs) are presented. An investigation of the behaviour of the gas-to-dust ratio (GDR) as a function of metallicity (Z) is also presented. Observations of these BCDs was performed using the Very Large Array (VLA) in 2009, a year in which the array was undergoing a technological upgrade to the the Karl G. Jansky VLA (JVLA). The observations were reduced and images processed using the Astronomical Image Processing Software (AIPS), and data cubes for each galaxy were produced. The results include detections of eleven HI lines (two new detections) and ten background continuum sources (two new discoveries). All detections are at a higher resolution and/or sensitivity than previous measurements. These detections spanned a large range of line widths and HI masses; some masses comparable to those in normal galaxies. Of particular interest was the discovery of a compact absorption feature in the dwarf galaxy Haro 11. A paper submitted to the Monthly Notices of the Royal Astronomical Society (MNRAS) Letters on this discovery is presented. Another significant result was the discovery of a highly extended and massive HI region in the dwarf galaxy CGCG 297-017. For those galaxies with no detected HI line or radio continuum, an upper limit to the flux density was computed, which was used to derive upper limits to the HI mass or star-formation rate (SFR) respectively. Three HI flux density upper limits are new results, and seven continuum flux density upper limits are also new. The GDR-Z relation at low metallicities shows a potential power law or broken power law relation with a turning point at Z=7.96 or Z=8.05. To within error, these turning points and power law indices of the broken power law fits are consistent with other work. / Thesis (Master, Physics, Engineering Physics and Astronomy) -- Queen's University, 2013-09-30 20:21:20.045

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