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Spectro-photometric analysis of galaxy merger remnants with tidal features
Get PDF1 online resource (xvi, 68 pages) : illustrations (chiefly colour)Includes abstract and appendix.Includes bibliographical references (pages 65-68).We use 21 208 galaxies at redshifts 0.05 < z < 0.45 with images from the Hyper Suprime-Cam Subaru Strategic Program (HSC-SSP) and accompanying spectroscopic observations from the Sloan Digital Sky Survey (SDSS) to study the properties of systems that host features of past mergers: streams and shells. We detect 251 shells and 774 streams through visual classification of the original and filtered galaxy images. We retrieve measurements of stellar mass and stellar population age for 16 936 galaxies from our sample. Galaxies with shells are more massive and older than both featureless galaxies and stream hosts, suggesting that they may be a result of major mergers. We analyse the star formation rates (SFR) for 6738 of our galaxies, derived from reliable measurements of Hα available from the SDSS Legacy Survey. Shell hosts are predominantly among quiescent galaxies while stream hosts span the full range of SFR measurements. We construct diagnostic diagrams for 6778 galaxies to separate star forming galaxies from those that are dominated by Active Galactic Nuclei (AGN). A fraction (10%) of galaxies with streams show evidence of strong AGN activity, which may be a result of material being funnelled into the central region of the host galaxy. In contrast, almost no shell hosts show the presence of strong nuclear activity. We measure the local density in the vicinity of our tidal feature hosts using data from the New York University Value-Added Galaxy Catalog (NYU-VAGC). We find that galaxies with features are, as expected, neither in isolated regions nor in clusters since these environments suppress mergers. We also observe that galaxies with shells tend to be in regions with slightly higher densities than the general population of galaxies. Based on sheer numbers and the distribution of the basic properties of the galaxies, we find that streams can occur in a vast range of galaxy mergers, while the formation of shells needs specific sets of conditions
Screening scale for primary hebephilic interests
Get PDF1 online resource (vi, 104 pages)Includes abstract and appendices.Includes bibliographical references (pages 58-74).This thesis sought to create a behavioural measure to assess for primary hebephilia (i.e., a primary sexual interest in pubescent children between the ages of 11 and 14) in male perpetrators of child sexual abuse, and to examine the measure’s ability to predict sexual recidivism. In Study 1, two victim characteristics were associated with primary hebephilia (i.e., boy victims under 15 and offences for child pornography), and a behavioural measure of primary hebephilia was not able to be created. Since a measure was not developed in Study 1, Study 2 instead examined the predictive validity of the SSPI-2 and whether the SSPI-2 contributed additional variance beyond the Static-99R in predicting sexual recidivism. Results revealed that total SSPI-2 scores were positively associated with an increased likelihood of sexual recidivism. Challenges of assessing hebephilia and the implications of the association between pedohebephilia and sexual recidivism are discussed
Reproductive isolating mechanisms influencing the direction of Banded Killifish (Fundulus diaphanus) x Common Killifish (F. heteroclitus) hybridization in Porter’s Lake, Nova Scotia
Get PDF1 online resource (vii, 92 pages) : illustrations (chiefly colour), colour maps, charts, graphsIncludes abstract.includes bibliographical references (pages 73-80).Hybridization events provide opportunities to examine the mechanisms influencing
interspecific reproductive isolation. In Porter’s Lake, Nova Scotia, hybridization between
two killifish species (Fundulus heteroclitus and Fundulus diaphanus) predominantly
occurs with F. diaphanus mothers and F. heteroclitus fathers. To test if pre-zygotic
isolating barriers contributes to this cross-direction bias, breeding behaviour was studied
in the lab. Fundulus heteroclitus females preferred conspecific males while F. diaphanus
females showed no preference. Additionally, all possible pairwise crosses were made in
vitro and incubated at four salinities to test reproductive barriers related to fertilization
and hybrid development. Fundulus heteroclitus x F. diaphanus (female x male) hybrids
had lower fertilization and longer development times than other cross types. Together,
these results suggest that both pre- and post-zygotic mechanisms contribute to the absence
of F. heteroclitus x F. diaphanus hybrids in the wild, and that additional, un-measured
reproductive isolating mechanisms are also likely to be quite important
Spectroscopic analysis of stars in the outskirts of NGC 1851
Get PDF1 online resource (vi, 38 pages) : colour illustrationsIncludes abstract.Includes bibliographical references (page 38).NGC 1851 is a peculiar globular cluster with hints of a bimodal populations of stars (possibly two different episodes of formation of stars that resulted in a small spread in the metallicity in the centre of the cluster). It is suggested that it might have been part of a progenitor dwarf galaxy. Spectroscopic analysis of stars in the outskirts of this cluster can indicate its origin by looking at the metallicity distribution. The stars closer to the core of the cluster have a metallicity of [Fe/H]=-1.18 ± 0.2 and the stars studied here are cluster members of NGC 1851 which are obtained based on Gaia DR2 parallaxes and proper motions and for which we have spectroscopic data from the FLAMES instrument on the Very Large Telescope covering a bigger area of the cluster, all the way to the Jacobi radius. The calcium infrared triplet lines, which are strong absorption lines in the range of 8400 Å to 9000 Å are investigated by looking at their equivalent width. The equivalent width, which is related to the metallicity of a star, is studied for 89 stars which are located in the outer regions of the cluster. Indication of a small spread in [Fe/H] is found which might suggest that the cluster has not been part of a progenitor dwarf galaxy
The nature, environments, and origin of post-starburst galaxies at [zeta] [less than or equal to] 0.6
Get PDF1 online resource (xix, 132 pages) : charts (some colour), graphs (some colour)Includes abstract.Includes bibliographical references (pages 122-135).Post-starburst galaxies represent a transitional stage between star-forming and quiescent galaxies and thus studying their nature, environments and origin mechanisms is fundamental to understanding galaxy evolution. In this thesis, we select a sample of 48 post-starburst galaxies from SHELS F2 spectroscopic sample using the width of Hδ absorption line combined with visual inspection. We construct galaxy stellar mass density field for the mass-limited SHELS F2 sample within 0.2 < ζ < 0.55 to investigate the environments of post-starburst galaxies with respect to general galaxy population. We find that similar fractions of post-starburst galaxies reside in underdense, average dense and overdense regions, i.e., that these galaxies do not prefer special environments. Based on HSC ι− band images, we find that ram-pressure stripping, if present, is not strong enough to disturb the morphology of stellar light in cluster post-starburst galaxies and that merger/galaxy interactions drive the formation of post-starburst galaxies in average dense and underdense regions
Native plant mixtures for Atlantic Canada green roofs: compatibility with sedums, propagation techniques and soil design
Get PDF1 online resource (128 pages) : illustrations (chiefly colour), chartsIncludes abstract and appendix.Includes bibliographical references (pages 107-119).In Atlantic Canada, there has been a significant amount of research on green roofs
including ecosystem services and native plant selection. This project examines a few
remaining gaps in the research: lack of locally available growth media, the feasibility of
combining native plants with Sedum in the same system, and optimal propagation
techniques for native species. Plant growth and performance of ecosystem functions were
examined with the combinations in a replicated modular green roof system. The most
beneficial treatment was a mixture of native plants/Sedums planted as plugs in the
commercially available growth medium. Moreover, plug planting was the most effective
way to quickly establish plant canopy density in this green roof system. This project is
expected to facilitate the use of native plants on green roofs to diversify the plant selection
available while also outlining the most effective techniques and growth media at a cheaper
cost
Dependents as signals of mate value in an online dating context
Get PDF1 online resource (83 pages) : illustrationsIncludes abstract and appendix.Includes bibliographical references (pages 50-70).Sexual strategies theory indicates that humans can adopt short- and long-term mating strategies, producing sex- and strategy-specific mating behaviours due to asymmetries in obligate parental investment into children. Consequently, demonstrating an ability and willingness to invest in a mate and offspring is highly desired under long-term mating contexts – especially by women. Investment may be financial and/or based on social status, as well as the ability to care for a mate and any resulting offspring. While male carers of dependents (i.e., pets and children) have typically been perceived as high-quality mates by women, no studies have examined how dependents are associated with short- and long term mating strategies. I selected profiles from the online dating platform Plenty of Fish to test the predictions that men seeking a long-term mate will be more likely to display a dependent on their profile, and those who display a dependent will do so more frequently than men seeking short-term mates and women seeking long-term ones. The results show that men seeking long-term mates were more likely to show a dependent and did so more frequently when compared to men seeking short-term mates; however, men and women seeking a long-term mate displayed dependents in a similar fashion. These patterns were driven mainly by the displays of high-investment dependents (children and canines). These findings indicate that men adopting long-term mating strategies are more likely to advertise their investment capabilities compared to those seeking a short-term mate in a modern dating context, which may be used to signal their mate value
Functional difference in plant communities as a driver of green roof ecosystem services
Get PDF1 online resource (v, 33 pages) : colour illustrationsIncludes abstract.Includes bibliographical references (pages 31-33).Green roofs provide ecosystem services that help humans in urban environments. Ecosystem services provided by green roofs include reducing storm water run-off, better regulation of building temperatures, reduced heat flux and urban heat island effect and providing a place for wildlife to inhabit. This study aims to expand the knowledge of how plant species functional traits and the plant community's functional diversity determine the ecosystem services green roofs provide. The experimental design compared seven species mixture treatments that differed in functional diversity, comprised of 11 plant species, with monoculture treatments. Nine replicates of each treatment were planted in trays and established on a roof in Halifax, NS, in a block design accounting for shading from an adjacent building. This study examined 10 response variables that indicate ecosystem services and used regression to assess the ability of functional diversity in the mixtures to predict ecosystem services. There was a very weak negative relationship between functional diversity and two response variables: canopy density and floral abundance. Position on the roof relative to shade showed that areas more sheltered by an adjacent building had greater stability in summer soil temperature regardless of functional diversity. While functional diversity was not positively related to any of the ecosystem services, several of the species mixture treatments outperformed the best monoculture treatments. Additional research on functional divergence as a predictor for green roof ecosystem services needs to be conducted
Entering the workforce in Halifax : strategies and coping mechanisms among the African migrant community
Get PDF1 online resource (vii, 114 pages)Includes abstract and appendices.Includes bibliographical references (pages 92-102).This study investigates the experiences of Sub-Saharan African migrants entering the job market in Halifax, Nova Scotia, Canada. Informed by Bourdieu’s concept of habitus and the Labour Market Segmentation theory, this study examines the experiences, strategies used, challenges and barriers faced, available support, and coping mechanisms of the migrants. An online survey of 30 respondents and a key informant interview were used. Findings from the study showed that they use strategies such as volunteering, multiple applications, course certification, networking and using job fairs and job search engines, and sometimes settling with the jobs with lesser qualifications and language competence. The barriers identified were systemic discrimination and
racism, cultural/social differences, and individual limitations. The available
support for them was found to be inadequate due to growing numbers of migrants and reducing job opportunities in the province. They drew on the support of the black communities, their social networks, and native born Canadians as coping mechanisms. The study highlights how interconnected relationships between the individual, group, and systematic factors shape the experiences of labour market integration of Sub-Saharan African migrants in Halifax
Spatial and temporal variations in sediment composition within newly restored salt marshes
Get PDF1 online resource (viii, 91 pages) : colour illustrations, colour maps, graphsIncludes abstract and appendices.Includes bibliographical references (pages 73-79).Salt marsh ecosystems are highly vulnerable to climate change and sea-level rise. Adaptation
strategies such as managed realignment, or dyke realignment, allow for the growth of new salt
marsh in areas where one had been previously destroyed through dyking by historical settlers.
Two newly restored salt marshes in the Bay of Fundy were monitored through this study. The
spatial and temporal variations in water content, organic matter content, organic carbon content
and sediment grain size were examined across the salt marsh surfaces. This study found that
newly restored salt marshes in the Bay of Fundy can sequester carbon immediately after
restoration. Carbon sequestration values resemble those in previously restored marshes in the
surrounding areas. This study determined that there is a spatial variation in sediment
characteristics across the salt marsh surface. This spatial variation is tied to varying elevation
within the tidal frame. Spatial variations of sediment characteristics are not exclusively consistent
over time but do tend to follow the same patterns. The sediment characteristics measured at both
newly restored salt marshes used in this study were compared to previously restored salt marshes
in Nova Scotia. All sediment characteristics data falls within similar ranges, creating a better
understanding of what sediment characteristics to expect when restoring a salt marsh in the Bay of Fundy