The Dynamics and History of the Milky Way

This thesis uses a combination of observations, simulations, and dynamical analysis to study the dark matter (DM) halo and accretion history of the Milky Way (MW). Chapter 2 presents and applies a method to infer the mass of the MW by comparing the dynamics of observed satellites to those in the EAGLE cosmological hydrodynamics simulations. The method is robustly calibrated on mock EAGLE systems and then validated on the independent AURIGA high-resolution simulation suite of 30 MW-like galaxies. The method is shown to recover a galaxy's true mass and associated uncertainties accurately. Using ten classical satellites with 6D phase-space measurements, including updated proper motions from the Gaia satellite, the method is applied to the MW. The mass of the MW is estimated to 15 percent error. This is then combined with recent mass estimates in the inner regions of the Galaxy to infer an NFW halo concentration. Chapter 3 models the effect of baryonic contraction in DM haloes by first studying the orbital phase-space of DM haloes in the AURIGA simulation suite of MW analogues. The haloes are characterised by their spherical action distribution of the DM particles, allowing a comparison between the dynamical descriptions of DM-only and hydrodynamical simulations of the same haloes. By applying an iterative algorithm, the AURIGA DM haloes are adiabatically contracted to a given baryon density profile and halo mass. Using this algorithm, the AURIGA haloes are contracted to the baryon profile of the MW, inferring the total mass profile and the dynamics of the MW's contracted DM halo. These models allow the derivation of updated values for the key astrophysical inputs to DM direct detection experiments: the DM density and velocity distribution in the Solar neighbourhood. Chapter 4 introduces a multi-component chemo-dynamical model for decomposing the Galactic population of Globular Clusters (GCs) into bulge, disc, and stellar halo components. The halo GCs are further split into the major Galactic accretion events, GES, Kraken, Sequoia, Sag, and Helmi streams. The modelling approach is extensively tested using mock GCs built using the AURIGA suite of hydrodynamical simulations. The method is applied to the Galactic GCs data to infer, in a statistically robust and easily quantifiable way, the GCs associated to each MW accretion event. The MW sample contains 170 GCs, including previously uncategorized clusters from Gaia EDR3 observations. The number of GCs if each accretion group is then used to infer properties, such as halo and stellar masses, of these defunct satellites of the MW

The Extragalactic Sky at Low Radio Frequencies: A Study of Peaked-Spectrum Sources

We have entered a new era of radio astronomy where the low radio frequency sky is accessible to astronomers at a level of detail never before attainable. In particular, radio surveys are now being completed with incredibly wide fractional bandwidths, which can be exploited to study the unique radio spectra of gigahertz-peaked spectrum sources (GPS) and compact-steep spectrum (CSS) sources. GPS and CSS sources have been hypothesised to be an early stage of radio galaxy evolution due to their small scale morphologies. However, such an interpretation is contentious as there is evidence that these sources are not young but are confined to small spatial scales due to a high density circum-nuclear medium. One of the reasons that there has not been a resolution between these two competing hypotheses is because the absorption mechanism responsible for the turnover in their radio spectra remains ambiguous. In this thesis we produce high quality, low frequency spectra of GPS and CSS sources to test the dominant absorption mechanism in the population. We first study PKS B0008-421, which has the steepest known spectral slope below the turnover and the smallest known spectral width of any GPS source. We find that free-free absorption is responsible for the turnover in the spectrum. This thesis then describes the empirical modelling of the primary beam of the Murchison Widefield Array (MWA) and the production of the GaLactic and Extragalactic All-sky MWA (GLEAM) catalogue. The GLEAM survey represents the widest fractional bandwidth radio survey to date, with the derived extragalactic catalogue constituting an unprecedented database of high quality low frequency spectra. We then use the GLEAM catalogue to double the number of GPS and CSS sources known. We discuss the inconsistency of the standard radio galaxy evolutionary model with the presence of sources with high power and low intrinsic peak frequencies, suggesting that current evolutionary models are deficient

From research to practice: The case of mathematical reasoning

Mathematical proficiency is a key goal of the Australian Mathematics curriculum. However, international assessments of mathematical literacy suggest that mathematical reasoning and problem solving are areas of difficulty for Australian students. Given the efficacy of teaching informed by quality assessment data, a recent study focused on the development of evidence-based Learning Progressions for Algebraic, Spatial and Statistical Reasoning that can be used to identify where students are in their learning and where they need to go to next. Importantly, they can also be used to generate targeted teaching advice and activities to help teachers progress student learning. This paper explores the processes involved in taking the research to practice

Muscle fibrils: Solubilization and gel electrophoresis

In a three-year longitudinal intervention study developing an understanding of statisticalliteracy with a cohort of students from Years 4 to 6, teachers delivered lessons fromprovided materials, including scripts and prompts. Besides completing seven majorinvestigations, workbooks, and several in-class assessments, the students undertook foursurveys, from which their overall progress was determined, as well as individual learningprogressions. Findings indicated that despite experiencing the same lessons delivered insimilar ways, students had very different learning progressions. The implications of thesefindings are explored

Explaining student achievement: the influence of teachers' pedagogical content knowledge in statistics

Statistics is an increasingly important component of the mathematics curriculum. StatSmart was a project intended to influence middle-years students’ learning outcomes in statistics through the provision of appropriate professional learning opportunities and technology to teachers. Participating students in grade 5/6 to grade 9 undertook three tests, a pre-test, a post-test and a longitudinal retention test over a period of 2 years. Their teachers completed a survey that included items measuring pedagogical content knowledge (PCK) for teaching statistics. Despite the development of valid instruments to measure both student and teacher content knowledge and teachers’ PCK, linking teachers’ knowledge directly to students’ learning outcomes has proved elusive. Multilevel modelling of results from 789 students for whom there were 3 completed tests and measures from their teachers indicated that students’ outcomes were influenced positively by their initial teacher’s PCK. Extended participation of teachers in the project also appeared to reduce negative effects of changing teachers

Working with practitioners and learning trajectories: Sharpening the focus on mathematical reasoning in grades 5-9

This paper will report on the role of practitioners in a recent Australian study that developed empirically based learning and assessment frameworks (i.e. learning trajectories) for algebraic, geometrical, and statistical reasoning in the middle years of schooling. To understand the nature of the teachers’ role, the paper begins with a description of what is meant by ‘curriculum’ in Australia and the implications of this for teacher decision making and planning. We then provide a rationale for the study and a brief description of the methodology before illustrating how teachers were involved in the iterative research design through task development and the trial and refinement of partial credit scoring rubrics. The paper concludes by describing the development of targeted teaching advice and considering some of the challenges involved in dissemination