Stellar populations in central cluster galaxies: the influence of cooling flows

We present detailed, high spatial and spectral resolution, long-slit observations of four central cluster galaxies (Abell 0085, 0133, 0644 and Ophiuchus) recently obtained on the Southern African Large Telescope (SALT). Our sample consists of central cluster galaxies (CCGs) with previously-observed H\alpha-filaments, and have existing data from the X-ray to radio wavelength regimes available. Here, we present the detailed optical data over a broad wavelength range to probe the spatially-resolved kinematics and stellar populations of the stars. We use the Pegase.HR model with the ELODIE v3.1 stellar library to determine the star formation histories of the galaxies using full spectrum fitting. We perform single stellar population (SSP) as well as composite stellar population (CSP) fits to account for more complex star formation histories. Monte-Carlo simulations and \chi 2-maps are used to check the reliability of the solutions. This, combined with the other multiwavelength data, will form a complete view of the different phases (hot and cold gas and stars) and how they interact in the processes of star formation and feedback detected in central galaxies in cooling flow clusters, as well as the influence of the host cluster. We find small, young stellar components in at least three of the four galaxies, even though two of the three host clusters have zero spectrally-derived mass deposition rates from X-ray observations.Comment: Based on observations made with the Southern African Large Telescope (SALT). Accepted for publication in MNRA

The detailed nature of active central cluster galaxies

We present detailed integral field unit (IFU) observations of the central few kiloparsecs of the ionised nebulae surrounding four active central cluster galaxies (CCGs) in cooling flow clusters (Abell 0496, 0780, 1644 and 2052). Our sample consists of CCGs with H{\alpha} filaments, and have existing data from the X-ray regime available. Here, we present the detailed optical emission-line (and simultaneous absorption line) data over a broad wavelength range to probe the dominant ionisation processes, excitation sources, morphology and kinematics of the hot gas (as well as the morphology and kinematics of the stars). This, combined with the other multiwavelength data, will form a complete view of the different phases (hot and cold gas and stars) and how they interact in the processes of star formation and feedback detected in central galaxies in cooling flow clusters, as well as the influence of the host cluster. We derive the optical dust extinction maps of the four nebulae. We also derive a range of different kinematic properties, given the small sample size. For Abell 0496 and 0780, we find that the stars and gas are kinematically decoupled, and in the case of Abell 1644 we find that these components are aligned. For Abell 2052, we find that the gaseous components show rotation even though no rotation is apparent in the stellar components. To the degree that our spatial resolution reveals, it appears that all the optical forbidden and hydrogen recombination lines originate in the same gas for all the galaxies. Based on optical diagnostic ratios ([OIII]{\lambda}5007/H{\beta} against [NII]{\lambda}6584/H{\alpha}, [SII]{\lambda}{\lambda}6717,6731/H{\alpha}, and [OI]{\lambda}6300/H{\alpha}), all galaxies show extended LINER emission, but that at least one has significant Seyfert emission areas, and at least one other has significant HII like emission line ratios for many pixels. ABRIDGED.Comment: 30 pages, accepted for publication in MNRAS. High resolution version, with spaced figures available from autho

The UV-upturn in brightest cluster galaxies

This paper is part of a series devoted to the investigation of a large sample of brightest cluster galaxies (BCGs), their properties and the relationships between these and the properties of the host clusters. In this paper, we compare the stellar population properties derived from high signal-to-noise, optical long-slit spectra with the GALEX ultraviolet (UV) colour measurements for 36 nearby BCGs to understand the diversity in the most rapidly evolving feature in old stellar systems, the UV-upturn. We investigate: (1) the possible differences between the UV-upturn of BCGs and those of a control sample of ordinary ellipticals in the same mass range, as well as possible correlations between the UV-upturn and other general properties of the galaxies; (2) possible correlations between the UV-upturn and the properties of the host clusters; (3) recently proposed scenarios where helium-sedimentation in the cluster centre can produce an enhanced UV-upturn. We find systematic differences between the UV-colours of BCGs and ordinary ellipticals, but we do not find correlations between these colours and the properties of the host clusters. Furthermore, the observations do not support the predictions made by the helium-sedimentation model as an enhancer of the UV-upturn.Comment: 12 pages, accepted for publication in MNRA

The multiple roles of hla in hiv immunity and treatment

South Africa has a national HIV-1 prevalence of 12.2% and due to the large population size of 52.9 million, this equates to a 6.5 million people living with HIV-1. The high HIV-1 prevalence has warranted the scaling up of the national antiretroviral treatment program with over 2 million people accessing treatment since 2012. The population of South Africa is genetically diverse and consists of South African Black (SAB), South African Mixed ancestry (SAM), South African Caucasian (SAC) and South African Indian (SAI) populations that constitute 79.8%, 9.0%, 8.7% and 2.5% of the total population. The reasons for the disproportionate HIV-1 prevalence rates estimated for the different populations (15.0%, 3.1%, 0.3% and 0.8% for the SAB, SAM, SAC and SAI populations, respectively) are unknown; however, host genetic differences may be a contributory factor. Human leukocyte antigen (HLA) class I genes play a crucial role in the antiviral innate and adaptive immune response, since HLA class I proteins present antigenic peptides to CD8+ Cytotoxic T cells (CTLs) of the adaptive immune system and are also involved in the innate immune response via interaction with killer-cell immunoglobulin-like receptors (KIRs) expressed by Natural Killer cells (NK cells)

Analyzing the potential demand for mobility as a service in a developing country

Abstract: The transport system with the private car as the main mode of transport is unsustainable. Mobility-as-a-Service (MaaS) is a system that can improve the efficiency and sustainability of the transport system. MaaS in developing countries needs to be adjusted from the MaaS operations in developed countries for it to be successful. The objective of this research is to evaluate the potential userbase of different MaaS configurations in a developing country. This is achieved by first characterizing the characteristics of a potential global MaaS user from literature. The typical global MaaS user can be described as a young, educated and employed with a high income, who values reliability and quality service in the mode of transport. The potential userbase of MaaS is evaluated based on two perspectives, the perspective of the population and the perspective of the travel mode. Secondary data sources such as the National Household Travel Survey (NHTS) and the Community Survey (CS) was used to evaluate the potential userbase of different MaaS configurations in Gauteng. The penetration rate of MaaS was determined to be between 4% - 5.36% of the general population, depending on which perspective was used. The results also showed that the penetration rate of social night trips was the highest, while workers contributed the majority of the trips and potential userbase. This research can assist potential operators, public entities and researchers with for marketing, policies, knowledge of transport in developing countries and analyzing the potential demand for MaaS in other countries.M.Ing. (Engineering Management

The influence of buildings on ground level wind conditions

Changes in the morphology of modern cities with the increasing incidence of high rise construction, have signifi­cantly altered the built environment and its microclimate. In fact in many cases the presence of tall buildings has created what may be regarded as inhospitable micro-environments and even at times dangerous ground level wind conditions. As a result an accep­table wind environment in outdoor public areas, has become a major consideration for new building com­plexes, as too remedial steps which may also become necessary in existing problem areas. The aim of this study was to examine those situations which led to severe amplification of ground level wind speeds in a built environment. A case study conducted in Cape Town is used to illustrate how buildings may alter wind conditions and create severe wind problems for pedestrians. Guide­lines and some practical steps are given for controlling the flow of air near the ground to within acceptable levels, in terms of pedestrian comfort and safety, are finally noted

An ontological exploration of change and constancy

The history of philosophy presents a variety of viewpoints regarding the ontological primacy of either change or constancy. Some views regard change as foundational, to the point where constancy is denied (e.g. Heraclitus). Other views regard constancy as so important, that change becomes unthinkable (e.g. Parmenides). The apparent dialectical tension between the different conceptions demands an ontological clarification of these issues. This study illustrates and evaluates the relationship between change and constancy in the viewpoints of various philosophers and scientists throughout history. This is done by appropriating a reformational insight that change and constancy exist in cohesion. The study finds that the relationship between change and constancy is not dialectical, but rather one of integration, seated in irreducible primitive domains (modalities). The purpose of the article is twofold (1) to show that change and constancy cannot be reduced to one another but can only exist in a relationship of coherence and (2) to contribute a systematic clarification of framework change in terms of the relationship between change and onstancy on the ontological level

Afrikaner identity in the born-free generation: Voortrekkers, farmers and Fokofpolisiekar

A research report submitted to the Faculty of Humanities, University of the Witwatersrand, in fulfilment of the requirements for the degree of Masters of Arts in Journalism and Media Studies. Johannesburg, September 2014The broad aim of this project is to examine the attitudes and opinions of the younger generation of Afrikaners born in or after 1994 at the birth of democracy in South Africa, also referred to as the ‘born-free’ generation, through the medium of long-form journalism. The project consists of two parts. The first is a theoretical and scholarly exploration of Afrikaner identity, including its history and how it is positioned in South Africa today. This is to highlight the baggage that the younger generation could be inheriting from the older generations, which have been described as suffering from a profound identity crisis since the advent of democracy in 1994. The research also examines some of the debates around Afrikaner identity that has played out in the media, as well as some of the writing about it. This includes debates around the Afrikaans language, as the language has been closely associated with Afrikaner identity from the outset. The second part of the project is a long-form article based on interviews with young Afrikaners. They were asked questions to probe how they see themselves in relation to the concept of an Afrikaner identity and how they see their place and future in South Africa. The article also contains elements of my own experiences as an Afrikaner and the issues around identity pertaining to that. While most of the research is not repeated in the long-form article, the article was informed by the theoretical and scholarly piece

A case study analysis of the impact of the Davis Tax Committee's First Interim Report on Estate Duty on certain trust and estate planning structures used by South African residents

A research report submitted to the Faculty of Commerce, Law and Management, University of the Witwatersrand, Johannesburg, in partial fulfilment of the requirements for the degree of Master of Commerce (specialising in Taxation) Johannesburg, 2016The Davis Tax Committee released their First Interim Report on Estate Duty on 13 July 2015 which contained certain recommendations concerning the way trusts should be taxed which were to act as a deterrent against aggressive estate planning. This report also contained suggested changes to current estate duty legislation. Changes to these recommendations, yet to be published in a second report, were discussed in a webinar by Judge Dennis Davis in December 2015 and the 2016 Budget Review contained additional suggestions with regard to the taxation of trusts. This study constructs case studies to compare the effect of the various recommendations on total taxation and capital preservation in a scenario where assets are held in a South African trust over a period of time, with a scenario where such assets are kept in a South African tax resident’s personal estate. The case studies focus only on high-net-worth trusts and personal estates. The possible double taxation which may occur as a result of levying both estate duty and capital gains tax on death is also briefly considered. The case study results show the punitive effects of the proposed repeal of the s 4(q) estate duty deduction for inter-spousal bequests on the personal estate scenarios and show how several of the new proposals could result in effective capital tax rates in excess of the deemed maximum capital tax benchmark of 15%. This may result in more aggressive estate planning strategies being employed should such proposals be enacted. The report also concludes that the double taxation effect of both estate duty and capital gains tax levied on death is likely to be small on average, although individual high-net-worth estates may be subject to such double taxation in certain cases. Key words: Davis Tax Committee’s First Interim Report on Estate Duty, taxation of South African trusts, South African trusts, South African estate duty, estate planning, double taxation on death, estimate for total capital gains tax collected on death, high-net-worth individuals, inequality in South Africa, wealth tax in South Africa, total taxation in South African trusts, income-splitting in South African trusts, capital preservation in South African trusts, South African trust case study, South African estate duty case study, South African estate planning case studyMT201

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