ASTRO-ARCHAEOLOGY IN THE TRIANGULUM GALAXY: STUDYING GALAXY FORMATION AND EVOLUTION WITH THE GLOBULAR CLUSTERS AND STELLAR HALO IN M33

The currently-favoured cosmological paradigm, Lamda-CDM, predicts that galaxies are built up from smaller galaxies in a bottom-up process known as hierarchical merging. Lambda-CDM is extremely successful for large-scale structures, but is less so for the detailed features of individual galaxies. We can study these features - the galaxies’ foundations and the remnants of the smaller components that built them - only in the closest galaxies in which we can resolve individual stars. In this thesis, we use data from the Canada-France-Hawaii Telescope (CFHT)/MegaCam as part of the Pan-Andromeda Archaeological Survey (PAndAS) to observe M33 (the Triangulum Galaxy) and the detailed features of its old stellar population. The study of these details is vital for our understanding of galaxy formation and evolution. We search for two types of components within the old stellar population: globular star clusters and the faint, diffuse stellar halo. We find only one new unambiguous outer halo star cluster, in addition to the five previously known in the M33 outer halo (r=10-50 kpc). A further 2440 cluster candidates are identified, which we analyse using two different types of simulated clusters. We are able to describe the type of clusters that are likely to remain hidden from our searches. Our study of a population of red giant branch (RGB) stars far from the M33 disk reveals a low-luminosity, centrally concentrated component which we interpret as the discovery of M33’s halo. It is everywhere in our data fainter than mu_V ~ 33 mag arcsec^−2, with scale length r_exp ~ 20 kpc, an overall luminosity not more than a few percent of the total luminosity of M33, and is possibly also not azimuthally symmetric. For M33 to have so few outer halo clusters compared to M31 and to have such a low-luminosity halo, with the possible asymmetry that we see, suggests tidal stripping of M33’s halo components by M31 - a view that is also favoured by the morphology of the disk substructure and recent modelling.Doctor of Philosophy (PhD

Furthering decolonization and reconciliation via a portable planetarium

The William J. McCallion Planetarium at McMaster University, Hamilton, Canada (established 1949), is pleased to share details of the first year of outreach initiatives and statistics from its new small (6m diameter) portable planetarium. The portable planetarium, purchased with funding from the Faculty of Science, was launched in June 2022, and has the primary goal of extending astronomy-based education and outreach initiatives to underserved and underrepresented communities off campus (to supplement the fixed planetarium on campus). The portable planetarium has also allowed us to continue our reconciliation efforts and astronomy collaborations with local Indigenous communities, resulting in the co-creation of one show and further shows in development. This presentation will highlight the co-creation process, successes and challenges we have experienced during our first months of operation, and will welcome conversations from communities we may be able to visit and/or from other institutes who currently have or are seeking to set up similar programs

Further Definition of the Mass-Metallicity Relation in Globular Cluster Systems Around Brightest Cluster Galaxies

We combine the globular cluster data for fifteen Brightest Cluster Galaxies and use this material to trace the mass-metallicity relations (MMR) in their globular cluster systems (GCSs). This work extends previous studies which correlate the properties of the MMR with those of the host galaxy. Our combined data sets show a mean trend for the metal-poor (MP) subpopulation which corresponds to a scaling of heavy-element abundance with cluster mass Z ~ M^(0.30+/-0.05). No trend is seen for the metal-rich (MR) subpopulation which has a scaling relation that is consistent with zero. We also find that the scaling exponent is independent of the GCS specific frequency and host galaxy luminosity, except perhaps for dwarf galaxies. We present new photometry in (g',i') obtained with Gemini/GMOS for the globular cluster populations around the southern giant ellipticals NGC 5193 and IC 4329. Both galaxies have rich cluster populations which show up as normal, bimodal sequences in the colour-magnitude diagram. We test the observed MMRs and argue that they are statistically real, and not an artifact caused by the method we used. We also argue against asymmetric contamination causing the observed MMR as our mean results are no different from other contamination-free studies. Finally, we compare our method to the standard bimodal fitting method (KMM or RMIX) and find our results are consistent. Interpretation of these results is consistent with recent models for globular cluster formation in which the MMR is determined by GC self-enrichment during their brief formation period.Comment: 35 pages, 20 figures. Accepted by Astronomical Journal. Complete preprint including high resolution figures available at http://www.physics.mcmaster.ca/~cockcroft/MMRpape

The M33 Globular Cluster System with PAndAS Data: The Last Outer Halo Cluster?

We use CFHT/MegaCam data to search for outer halo star clusters in M33 as part of the Pan-Andromeda Archaeological Survey (PAndAS). This work extends previous studies out to a projected radius of 50 kpc and covers over 40 square degrees. We find only one new unambiguous star cluster in addition to the five previously known in the M33 outer halo (10 kpc <= r <= 50 kpc). Although we identify 2440 cluster candidates of various degrees of confidence from our objective image search procedure, almost all of these are likely background contaminants, mostly faint unresolved galaxies. We measure the luminosity, color and structural parameters of the new cluster in addition to the five previously-known outer halo clusters. At a projected radius of 22 kpc, the new cluster is slightly smaller, fainter and redder than all but one of the other outer halo clusters, and has g' ~ 19.9, (g'-i') ~ 0.6, concentration parameter c ~ 1.0, a core radius r_c ~ 3.5 pc, and a half-light radius r_h ~ 5.5 pc. For M33 to have so few outer halo clusters compared to M31 suggests either tidal stripping of M33's outer halo clusters by M31, or a very different, much calmer accretion history of M33.Comment: 37 pages, 9 figures. Accepted by the Astrophysical Journa

Prosthetics services in Uganda : a series of studies to inform the design of a low cost, but fit-for-purpose, body-powered prosthesis

The majority of people with upper limb absence (PWULA) live in lower, or middle-income countries (LMICs). However, efforts to develop improved prostheses have largely focused on electrically powered devices, sustainable deployment of which, in LMICs, is difficult. In the ‘Fit-for-purpose, affordable body-powered prostheses’ project, teams from the UK, Uganda and Jordan are developing mechanically-operated prostheses, optimised for LMICs, and establishing local methods for fabrication, fitting and evaluation. Here we first report on preliminary studies aimed at grounding the project in the reality of current prosthetics services and the experiences of people with limb absence in Uganda. Finally, we outline our ongoing work in the context of our findings. In our first two studies we reviewed current prosthetics and associated repair services. An issue which came up repeatedly was the difficulty faced by orthopaedic technologists in accessing componentry/materials. All specialised prosthetics components and materials are imported, often at a high cost. Purchasing does not appear to be well coordinated between centres, meaning potential economies of scale are not being fully exploited. Although there is supposed to be government funding for prosthetics, in practice budgets are often inadequate and a reliance on donations is common. The resource limitations mean Orthopaedic Technologists often resort to ad-hoc solutions; unsurprisingly perhaps, failures in prostheses were reported. In particular, lamination-based socket manufacture is very difficult, given the complexity (and cost) of the processes involved. Repair services are also limited, in part also due to problems accessing materials/components. Despite (or in part, as a result of) these challenges, the orthopaedic technologists are generally an extremely resourceful and multi-skilled group and there is genuine enthusiasm to see services improve. Further, there is a growth in interest and capabilities in the area of medical device innovation. In the third of our studies, we interviewed 17 PWULA and present preliminary results from the analysis of a subset of five participants. Firstly, we found that only 2 of the participants reported experience with using an upper limb prosthesis, again supporting the picture which emerged from the other studies. The findings illustrate the emergence of four key themes: a) attitude towards disability; b) barriers to prosthesis use; c) coping without a prosthesis; and d) communication with other PWULA. Although attitudes to those with limb loss varied, participants reported impacts in terms of social isolation and a mixed experience of emotions that appeared predominantly negative; barriers to prosthesis use were broader than just cost and functionality, and included a lack of training and psychological support; given that it is difficult to access an upper limb prosthesis, PWULA have found ways to perform daily life activities without relying on one; finally, most PWULA find the suggestion of communicating with other people with the same experience appealing. In our project we are addressing some of the issues found in the preliminary studies. To make socket manufacture less dependent on access to imported materials and specialised equipment, we are investigating the development of lattice-style, adjustable sockets, made from locally available materials. We are also investigating alternatives to the traditional harness-controlled, body-powered prosthetic hands. Given that clinicians have no objective means of evaluating the value of the prosthesis to their clients, we are testing the use of low-cost digital monitoring tools. We are also exploring the potential value of using mobile-phones to reduce the isolation of PWULA. Finally, we are exploring how these innovations may be translated into the Ugandan health setting

Hybrid Organic-Inorganic Coordination Complexes as Tunable Optical Response Materials.

Novel lead and bismuth dipyrido complexes have been synthesized and characterized by single-crystal X-ray diffraction, which shows their structures to be directed by highly oriented π-stacking of planar fully conjugated organic ligands. Optical band gaps are influenced by the identity of both the organic and inorganic component. Density functional theory calculations show optical excitation leads to exciton separation between inorganic and organic components. Using UV-vis, photoluminescence, and X-ray photoemission spectroscopies, we have determined the materials' frontier energy levels and show their suitability for photovoltaic device fabrication by use of electron- and hole-transport materials such as TiO2 and spiro-OMeTAD respectively. Such organic/inorganic hybrid materials promise greater electronic tunability than the inflexible methylammonium lead iodide structure through variation of both the metal and organic components

Globular Cluster Systems in Brightest Cluster Galaxies: Further Definition of the Mass-Metallicity Relation

Globular clusters (GCs) can be divided into two subpopulations when plotted on a colour-magnitude diagram: one red and metal-rich (MR), and the other blue and metal-poor (MP). For each subpopulation, any correlation between colour and luminosity can then be converted into mass-metallicity relations (MMRs). Tracing the MMRs for fifteen GC systems (GCSs) - all around Brightest Cluster Galaxies - we see a nonzero trend for the MP subpopulation but not the MR. This trend is characterised by p in the relation Z=M^p. We find p ~ 0.35 for the MP GCs, and a relation for the MR GCs that is consistent with zero. When we look at how this trend varies with the host galaxy luminosity, we extend previous studies (e.g., Mieske et al, 2006b) into the bright end of the host galaxy sample. In addition to previously presented (B-I) photometry for eight GCSs obtained with ACS/WFC on the HST, we present seven more GCSs. Four of these are newly analysed from HST data, one is previously presented (g-i) photometry obtained with GMOS on Gemini South, and two are the author's newly reduced and analysed (g-i) photometry also obtained with GMOS on Gemini South. Interpretation of these results is important for further understanding the formation and evolution of galaxies within the hierarchical-merging picture, and what process enables the production of two subpopulations.ThesisMaster of Science (MSc

Diabetes, pulse pressure and cardiovascular mortality: the Hoorn Study

Objective: Type 2 diabetic patients have an increased arterial stiffness and a very high risk of cardiovascular death. The present study investigated the relationship between pulse pressure, an indicator of vascular stiffness, and risk of cardiovascular mortality among type 2 diabetic and non-diabetic individuals. Second, we determined the relationship between pulse pressure and its main determinant (i.e. age), and the influence of diabetes and mean arterial pressure on this relationship. Design and methods: We studied a cohort of 2484 individuals including 208 type 2 diabetic patients. Mean age and median follow-up for non-diabetic and diabetic individuals, respectively, were 61 and 66 years, and 8.8 and 8.6 years. One-hundred and sixteen non-diabetic and 34 diabetic individuals died of cardiovascular causes. Relative risks of cardiovascular mortality were estimated by Cox proportional hazards regression adjusted for age, gender and mean arterial pressure. Results: Pulse pressure was associated with cardiovascular mortality among the diabetic, but not among the non-diabetic individuals [adjusted relative risk (95% confidence interval) per 10 mmHg increase, 1.27 (1.00-1.61) and 0.98 (0.85-1.13), P interaction = 0.07]. Further adjustment for other risk factors gave similar results. The association, at baseline, between age and pulse pressure was dependent on the presence of diabetes (P interaction = 0.03) and on the mean arterial pressure (P interaction < 0.001) (i.e. there was a stronger association when diabetes was present and when mean arterial pressure was higher). Conclusions: We conclude that, in type 2 diabetes, pulse pressure is positively associated with cardiovascular mortality. The association between age and pulse pressure is influenced by the presence of type 2 diabetes and by the height of the mean arterial pressure. These findings support the concept of accelerated vascular aging in type 2 diabetes. © 2002 Lippincott Williams & Wilkins

The remnants of galaxy formation from a panoramic survey of the region around M31

In hierarchical cosmological models, galaxies grow in mass through the continual accretion of smaller ones. The tidal disruption of these systems is expected to result in loosely bound stars surrounding the galaxy, at distances that reach $10 - 100$ times the radius of the central disk. The number, luminosity and morphology of the relics of this process provide significant clues to galaxy formation history, but obtaining a comprehensive survey of these components is difficult because of their intrinsic faintness and vast extent. Here we report a panoramic survey of the Andromeda galaxy (M31). We detect stars and coherent structures that are almost certainly remnants of dwarf galaxies destroyed by the tidal field of M31. An improved census of their surviving counterparts implies that three-quarters of M31's satellites brighter than $M_V < -6$ await discovery. The brightest companion, Triangulum (M33), is surrounded by a stellar structure that provides persuasive evidence for a recent encounter with M31. This panorama of galaxy structure directly confirms the basic tenets of the hierarchical galaxy formation model and reveals the shared history of M31 and M33 in the unceasing build-up of galaxies.Comment: Published in Nature. Supplementary movie available at https://www.astrosci.ca/users/alan/PANDAS/Latest%20news%3A%20movie%20of%20orbit.htm