The WiggleZ Dark Energy survey is currently being carried out using the AAOmega instrument on the AAT. It is measuring redshifts for 240,000 emission line galaxies with high star-formation rates over 1,000 sq. degrees of sky. These galaxies are selected for spectroscopic observation from a combination of optical and ultraviolet imaging. The target selection criterion applied to these datasets is highly optimised to select high redshift emission line galaxies. The redshift distribution of these galaxies peaks at z

It has become clear that the global star formation rate in the Universe has been decreasing since at least z~1, and blue, star-forming galaxies are transformed into red, passive galaxies through one or more processes. The origin of this decline and transformation remains unclear. The role environment plays in all this is especially uncertain. Despite the observed domination of a passive population in the cores of clusters, in contrast to the more actively star-forming field population, whether or not, and how environment affects the properties of galaxies when they fall into clusters is an unsettled question. In this thesis, we look into these issues by examining both the passive and star-forming galaxies, from the cores out to the infall regions, in a large sample of clusters at 0.15<z<0.36 we detected from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We find that in the cores of clusters, the red-sequence galaxies are a mixture of two populations, indicated by the inflexion in their luminosity function. There is no strong evolution in the shape of the red-sequence between z~0.4 and z~0.2; however, from z~0.2 to today, there is a rapid increase in the number of faint galaxies on the red-sequence relative to the bright ones, suggesting a rapid quenching of the faint galaxies in cluster cores within the last few billion years. At z~0.2, we find that the red fraction (star-forming fraction), at all stellar mass explored (9.0<log10(M*/M_solar)<11.5), shows no dependence on the distance from cluster centres, in the range 3<r<7Mpc; but within the inner 3 Mpc, we see a clear increase (decrease) in the red fraction (star-forming fraction). Also, for the lowest stellar mass galaxies, their red fraction has increased by a factor of 2 from z~0.3 to z~0.2 (over 1 Gyr), and yet we do not detect any difference between the star formation properties of the star-forming galaxies in clusters at all radii and that in the field. This suggests that for the low mass galaxies, it is likely that a mechanism that truncates star formation rapidly (within 1 Gyr) is at work. In the outskirts of the clusters, despite the low density contrast with the field, the red fraction is still higher than that in the field, suggesting that those galaxies have had their star formation quenched relative to the field population, supporting the pre-processing scenario.

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Dense cluster environment influences the properties of galaxies and their evolution. In order to understand this environmental effect and how it evolves with time, we study the infrared (IR) properties of galaxies in three rich clusters. The IR luminosities provide us with extinction-free measurements of the star formation rates (SFRs) of these cluster galaxies. We find a strong evolution in the IR luminosity function (LF) of two z ∼ 0:8 clusters when compared to two local clusters. The evolution rate of the IR LF found in these clusters is consistent with the evolution in field IR LFs. The similar evolution rate found in very different environments favors some internal mechanism, e.g., the gradual consumption of the gas fuel in galaxies, as being responsible for much of the star formation evolution. The mass-normalized integrated SFRs within 0.5R₂₀₀ of these clusters also shows an evolution trend, ∝ (1 + z)5. But this evolution has large scatter and may be affected by the mass selection effect of the sample. In the dense cluster core regions (r < 0.3 Mpc), we find evidence for enhanced SFR suppression. A substantial fraction of members in MS 1054-03 (z ∼ 0.8) are still forming stars actively. This cannot be explained by the scenario where the cluster is only passively accreting star-forming galaxies from the surrounding field, after which their star formation is quenched quickly. We also study the extended IR emission from the intracluster dust (ICD) in A2029. We only find weak signals at 24 and 70 μm and obtain upper limits for the ICD emission.

It has become clear that the global star formation rate in the Universe has been decreasing since at least z~1, and blue, star-forming galaxies are transformed into red, passive galaxies through one or more processes. The origin of this decline and transformation remains unclear. The role environment plays in all this is especially uncertain. Despite the observed domination of a passive population in the cores of clusters, in contrast to the more actively star-forming field population, whether or not, and how environment affects the properties of galaxies when they fall into clusters is an unsettled question. In this thesis, we look into these issues by examining both the passive and star-forming galaxies, from the cores out to the infall regions, in a large sample of clusters at 0.15<z<0.36 we detected from the Canada-France-Hawaii Telescope Legacy Survey (CFHTLS). We find that in the cores of clusters, the red-sequence galaxies are a mixture of two populations, indicated by the inflexion in their luminosity function. There is no strong evolution in the shape of the red-sequence between z~0.4 and z~0.2; however, from z~0.2 to today, there is a rapid increase in the number of faint galaxies on the red-sequence relative to the bright ones, suggesting a rapid quenching of the faint galaxies in cluster cores within the last few billion years. At z~0.2, we find that the red fraction (star-forming fraction), at all stellar mass explored (9.0<log10(M*/M_solar)<11.5), shows no dependence on the distance from cluster centres, in the range 3<r<7Mpc; but within the inner 3 Mpc, we see a clear increase (decrease) in the red fraction (star-forming fraction). Also, for the lowest stellar mass galaxies, their red fraction has increased by a factor of 2 from z~0.3 to z~0.2 (over 1 Gyr), and yet we do not detect any difference between the star formation properties of the star-forming galaxies in clusters at all radii and that in the field. This suggests that for the low mass galaxies, it is likely that a mechanism that truncates star formation rapidly (within 1 Gyr) is at work. In the outskirts of the clusters, despite the low density contrast with the field, the red fraction is still higher than that in the field, suggesting that those galaxies have had their star formation quenched relative to the field population, supporting the pre-processing scenario.

Study determined if 2MASS photometric data are reliable for luminosity classification using JHK plots of Reid and Hawley (2001). Effects of interstellar reddening on the placement of giant and dwarf data on the JIIK plot were analyzed. Dwarfs (N=54) were selected from Hipparchos and the 2MASS data reduced to an H-K range of 0.14-0.40. A disk dwarf region was identified using linear regression on the low space velocity stars. Giants selected from Volume 5 of the Michigan Catalogue of HD stars and SAG stars classified at Ball State University. They yielded 304 individual giants and 13 matches in the 0.14-0.40 H-K range respectively. The 2MASS data was reliable for luminosity classification of the SAGBSU giants. The classification of the Michigan giants was not possible due to interstellar reddening and the likely presence of faint giant companions. / Department of Physics and Astronomy

This paper presents the photometric luminosity classification of M dwarfs in Kaptyn’s Selected Area 124 (SA124). This project is part of an ongoing program at Ball State University to use R, I, and CaH photometry in an attempt to probe low luminosity star contributions to the luminosity function. Data is taken at the Southeastern Association for Research in Astronomy (SARA) telescope located at Kitt Peak, Arizona. With a limiting magnitude of R=15.0, we have observed ~75% of a full square degree in SA124 and have detected 19 M dwarf candidates, which are then confirmed using matched 2MASS J, H, and K magnitudes. We present the detections of 19 ±4.4 M dwarfs observed in SA124. The current estimates of our luminosity function are consistent with those previously determined for the galactic plane. / Department of Physics and Astronomy

This investigation in the 24 Kapteyn Selected Areas along the celestial equator examined 21 red dwarf stars identified in an objective-prism survey. These stars were classified as red dwarf stars using light at wavelengths between 5800 A and 6800 A. Using calcium-hydride-based luminosity classification, this study found 13 of these stars to be red giant stars, and only 6 stars were found to be red dwarfs. One star was determined to be warm star. One star was not clearly distinguishable as a dwarf or giant. Distance calculations for the red dwarf stars found that these stars lie within 40 parsecs of the sun. / Department of Physics and Astronomy

This thesis is an investigation into some properties of brown dwarfs using medium-resolution spectroscopy. In the first part of the thesis, I address the issue of parameter degeneracy in brown dwarfs. In the course of my analysis, I derive a gravity-sensitive spectral index which can be used, statistically at least, to differentiate populations of young objects from field dwarfs. The index is also capable of finding the difference between a population of ~1 Myr objects and a population of ~10 Myr objects and may be used to separate low-mass members from foreground and background objects in young clusters and associations. The second part of my thesis is an investigation into the major opacity sources in the atmospheres of late T dwarfs. I look particularly at CH4 and NH3 absorption features in the near-infrared spectra of these objects. In my analysis, I identify new absorption features produced by these molecules. I also correct features which had previously been wrongly identified. This has been made possible by the use of high quality data, together with a new CH4 synthetic line list, which is more complete at these temperatures than any previously available list.