Congratulations to Michelle Lochner! From the 14th of April, we are thrilled to be welcoming her at the department. She did her undergraduate in physics and maths at Rhodes University and moved on to do her honours with NASSP at UCT in 2010. She stayed at UCT for a masters in cosmology, later upgrading to a Ph.D. supervised by Prof. Bruce Bassett which she finished in 2014. After that she took up a postdoc at University College London with Prof. Hiranya Peiris, working on supernova classification with machine learning. In 2016 she returned to South Africa with a joint research position between the African Institute for Mathematical Sciences and the South African Radio Astronomy Observatory, focusing on the development of statistical and machine learning algorithms for astronomy. See https://astro.uwc.ac.za/michelle-lochner/ for more details on research interests and activities.
Massive stars are primary sources of chemical yields and mechanical and ionization luminosity budgets. Therefore, understanding massive stars’ evolution is crucial to have a complete understanding of the chemical and ionization evolution of galaxies. Moreover, with the advent of instruments like MUSE, JWST (upcoming), HST, etc., we have (/are going to have) a comprehensive picture of the impact of dust-masked massive stars in the evolution of galaxies for the wide range of wavebands starting from IR to optical to UV. The evolutionary paths taken by very massive stars, M > 60MSun, remain substantially uncertain: they begin their lives as main sequence O stars, but, depending on their masses, rotation rates, and metallicities, can then pass through a wide range of evolutionary states, yielding an equally broad set of possible surface compositions and spectral classifications. The surface enrichment of He and N is quite common in rotating WNL stars, but the WNL-like surface elemental abundances in slow rotators, as observed by Herrero et al. 2000, Vink et al. 2017, etc., puzzled astronomers for almost two decades. Meynet & Maeder (2000) hypothesised that an exotic scenario of stellar spin-down needs to be invoked in order to explain the origin of these unusually high surface enriched slow rotators. Contrary to this hypothesis, I discovered that these nonrotating metal-rich stars reveal the products of nucleosynthesis on their surfaces because even modest amounts of mass loss expose their “fossil”-convective cores: regions that are no longer convective, but which were part of the convective core at an early stage in the star’s evolution. This mechanism provides a natural explanation for the origin of metal-rich ([Fe/H] ≥ -1.0) slowly-rotating WNL stars without any need for exotic spin-downs. These stars have a huge impact on determining the chemical evolution of galaxies at high redshift. I will also discuss the impact of these stars on determining the ionisation budgets in different wavebands.
Alice Allen (Editor of the Astrophysics Source Code Library – ASCL ascl.net)
Journal articles detail the general logic behind new results and ideas, but often the source codes that enable these results remain hidden from public view and those who author these computational methods have not always received credit for their work. This presentation will cover recent changes in astronomy, and indeed, in many other disciplines, that include new journals, policy changes for existing journals, community resources such as the Astrophysics Source Code Library, changes to infrastructure, and availability of new workflows that make recognizing the contributions of software authors easier. This talk will include steps coders can take to increase the probability of having their software cited correctly and steps researchers can take to improve their articles by including citations for the computational methods that enabled their research. For those interested, please email firstname.lastname@example.org to receive the Zoom link.
Girls from Grades 1 & 2 from the Molo Mhlaba School (www.molomhlaba.org) in Khayelitsha visited the South African Astronomical Observatory today to celebrate International Women’s Day. The trip was made possible by the Astro UWC department, which covered the costs of the visit.
The school, in partnership with Astro UWC and the Office of Astronomy for Development, coordinates Astro Molo Mhlaba (www.astromolomhlaba.org), an award-winning programme that brings astronomy to girls of all ages in Khayelitsha and Philippi (www.astromolomhlaba.org).
Paolo Molaro (Astronomical Observatory of Trieste)
Abstract: Li is the element with the largest number of astrophysical nucleosynthetic processes. Although a primordial element, it is also produced by spallation processes in the interstellar medium, in a slow process lasting billions of years. The Li abundance in the old halo population of the Galaxy, however, is lower by a factor 3 than predicted by Big Bang models. This well known issue is known as the Cosmological Lithium problem. In this talk, I will present a tentative stellar fix to the problem, dealing with pre-main sequence depletion. One or more Galactic sources of Li are still to be identified in order to reach the Li abundance observed in the pre-solar nebula. Only recently, after decades of unsuccessful Li search, its parent nuclei Be-7 has been detected in novae outburst. Observations of Be-7 in few recent novae will be presented. The Li yields obtained from novae overproduce the meteoritic Li abundance by several orders of magnitude, and are therefore candidates for “the” source of Galactic lithium. Within this framework, the different Li evolution of the disk stars could be explained. The Li abundance in some Gaia – Enceladus candidate stars will be also presented and discussed.
Matteo Martinelli (Instituto de Fisica Teorica UAM/CSIC)
Abstract: In recent years, measurements of cosmological parameters coming from different observables have shown tensions between each other, the most striking the approximately 4.5 sigma tension on the Hubble constant between CMB and local measurements. In this talk I will briefly review the status of these tensions and some attempts to solve them modifying the late time evolution of the Universe. I will focus on a specific model, where Vacuum energy and Dark Matter interact with each other, and I will investigate the possibility that unaccounted systematic effects in Supernovae observations might help to reduce these tensions.
All Framework and Funding and Application Guide documents are available on the NRF website at https://www.nrf.ac.za/funding/framework-documents. These documents should also be consulted for the relevant contact persons for each Funding Instrument.
“The cosmos is within us. We are made of star-stuff. We are a way for the universe to know itself.”― Carl Sagan
On January 29th, the UWC Astro group was delighted to host Prof. Ewine F. van Dishoeck from the Leiden Observatory. Prof van Dishoeck is a world-leading expert in the realm of molecular astrophysics, a field which brings chemistry, astronomy and physics together. The talk showcased the ingredients and recipes for the formation of celestial objects at a molecular level.
Apart from being a prestigious academic, Prof. Ewine F. van Dishoeck is also president of the International Astronomical Union (IAU) which oversees the global astronomical community in areas of professional research and education in astronomy. In her role as President, she also visited the Khayelitsha-based Molo Mhlaba school which, in collaboration with UWC Astro, coordinates the IAU-OAD funded Astro Molo Mhlaba project.
The UWC Astrophysics group is playing host to two visitors from the Missouri University of Science and Technology; Prof. Shun Saito and Dr Sid Gurung Lopez. With over 30 years of partnership between the two universities, strengthening the ties between the two astrophysics groups would aide in improving international collaboration.
Our guests also presented their research which covered, theoretical cosmology and computational cosmology. Prof. Saito talk covered ‘Towards a robust analysis of the redshift-space bispectrum’ which sees to trace the large-scale structure of the Universe in 3D with galaxy clustering and/or with intensity mapping. Dr Lopez presented ‘Modeling Lyman alpha emitters in the epoch of reionization’ which looks at detecting galaxies in the early Universe.
Students and staff from the UWC Astro Group attended the South African Radio Astronomical Observatory (SARAO) Postgraduate Bursary conference in Durban from the 2nd – 6th December. The conference is held for those funded by the SARAO in order to showcase their work as well as to network with the South African radio astronomy community. The UWC group which attended consisted of 11 MSc and 7 PhD candidates, 8 Post-Doctoral and 2 staff members as well as a few of our international collaborators.
The week-long conference comprised of talks and a poster session for all to see. The topics varied from the science that SARAO can do with MeerKAT to the engineering aspect and issues facing MeerKAT.
18 students and 8 postdocs from the UWC Astro Group presented their research works on the conference.