galaxies Probing
with radio telescopes and supercomputers
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alaxies are the basic structural element of the Universe. It is the job of astrophysicists to generate theories that can be compared to observations in order to understand how these structures form and evolve with time. Hydrogen is the most abundant element in the Universe – a product of the Big Bang. Our current standard model of cosmological structure formation is one in which dark matter collapses under the influence of gravity to form large conglomerations known as dark matter haloes. Within these haloes, hydrogen collects. When the hydrogen is sufficiently pressurised, it begins to form stars. Hence, hydrogen is the raw fuel for star formation. In addition to the starlight we see from galaxies, there is also emission of radio waves from their hydrogen content. Radio telescopes are used to observe the hydrogen emission. Doing so allows astronomers to study many important galaxy processes. With the advent of telescopes such as MeerKAT, and in the near future the Square Kilometre Array, astronomy is entering a golden era of innovation and discovery. UWC astronomers are already leading some of the important efforts that will ultimately lead to vastly improved understanding of galaxies, which will unlock many secrets of our marvellous Universe.
Observing galaxies with MeerKAT Hydrogen emission very faint. Historically, we’ve been limited to studying galaxies within the Milky Way neighbourhood. However, all of this is changing thanks to the MeerkAT telescope. The powerful imaging capabilities of MeerKAT allow South African astronomers to study the hydrogen properties of very distant galaxies. Because of the finite travel speed of light and radio waves, we see distant galaxies as they were billions of years ago. In this sense, MeerKAT is like a time machine that allows us to unlock the secrets of galaxies in the ancient Universe. MeerKAT is also shedding new light on the properties of nearby galaxies. In 2019, UWC researchers used MeerKAT to observe a nearby pair of galaxies, NGC1512/1510. When using only an optical or infrared telescope to observe the starlight from these two galaxies, there is no evidence of them being influenced by one another. But the new MeerKAT image reveals the two galaxies to be completely embedded within a large reservoir of hydrogen. This complex hydrogen environment is probably a result of the ways in which the two galaxies have actually interacted with one another over billions of years. As they orbit their common centre of mass, they remove material from one another. The MeerKAT image is therefore a map of the interaction history of this system. In the near future, numerical simulations will be used to link features seen in the MeerKAT
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image to the interaction processes that have occurred. In the Department of Physics and Astronomy, Dr Ed Elson leads a group of talented researchers working on a variety of galaxy-related projects. The most recent member is Thando Mothogoane. For her MSc, Thando is studying the neutral hydrogen content of a nearby galaxy, IC4710. The hydrogen properties of this galaxy have never before been studied in detail. Thando has already investigated the ways in which the huge amount of energy pumped out by stars near the centre of the galaxy is shaping the overall structure of the system (as traced by its hydrogen content). Soon, Thando will generate the first measure of the galaxy’s rotation curve – a probe of how fast the galaxy is rotating. This will allow her to constrain the dark matter properties of the galaxy. After completing her MSc in 2020, Narusha Isaacs has recently started her PhD. Her project will focus on studying the hydrogen maps of a large sample of nearby galaxies in order to generate a quantitative, statistically significant understanding of their evolutionary processes. Narusha’s project will include components of coding, data mining, data analysis, and theoretical (mathematical) calculations. Nandrianina Randriamiarinarivo started his PhD in 2019. Nandri has been using supercomputer simulations of cosmological structure formation to understand some of the important processes related to galaxy evolution. A main aim for his project is to generate theoretical predictions of the results that will be produced from MeerKAT data acquired as part of various large galaxy surveys. Given that MeerKAT will allow us to probe new regions of parameter space, it is very important to compare the results to what we know from numerical simulations. Soon, Nandri will start searching MeerKAT data sets for galaxies – some of which will be new discoveries. Nicole Thomas is currently in the process of submitting her PhD, supervised by Prof Romeel Dave of the University of Edinburgh, UK, and Dr Elson. (Prof Dave was at UWC before moving to Edinburgh, and remains affiliated to UWC.) Nicole has used supercomputer simulations to study the ways in which supermassive black holes at the centres of large galaxies affect the properties and evolution of their host galaxies. Nicole’s research has already resulted in three publications in peer-reviewed international journals. Soon, Nicole will start a position as a postdoctoral research fellow at a prestigious European university. Marc Harris recently submitted his PhD, under the supervision of Dr Michelle Cluver of Swinburne University, Australia (who is formerly from UWC, and remains affiliated with UWC), and Prof Mario Santos. Marc used a multiwavelength approach
