/Liverpool’s Sky At Night … Alex Hill

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Date: 18th January 2019

Liverpool’s Sky At Night … Alex Hill

In our newest 'Liverpool's Sky At Night' edition, we caught up with Alex Hill from LJMU's Astrophysics Research Institute. The ARI are based out of iC2 and are setting the pace of astrophysics research globally. Their research interests are as varied as they are, and so we are delighted to introduced the human faces behind the science.

Alexander Hill is a PhD student at LJMU’s Astrophysics Research Institute, where he researches galaxy formation and evolution as part of the High Performance Computing group. He is also part of the LIV.DAT collaboration with the University of Liverpool, a Centre for Doctoral Training aimed at improving the Data Science skills and employability of UK postgraduates. Originally from Leeds, he obtained a master’s degree in Physics with Astronomy at Durham University. His webpage can be found here.

I work at the Astrophysics Research Institute as part of the High-Performance Computing group (HPC), where we use simulations to understand how the universe formed and evolved. Contemporary astronomy involves a marriage between conventional observations and supercomputer simulations of astronomical phenomena. These simulations are used to interpret the physical origins of observations, test theories and make predictions of future discoveries.

The astronomer is at a disadvantage to most of her fellow scientists, as she cannot answer questions by designing an experiment that isolates exactly what interests her. She must sift through the deluge of information one receives when studying the universe, separating the billions of stars and the billions of galaxies from the precise object of her curiosity. On the largest scales, the universe is apparently eternal and unchanging. All we see are photographs of the universe at a given age. With simulations, we can turn these photographs into videos.  We can ‘turn the knobs’ of the universe, testing how significant various phenomena are. We can see what lies behind our observations, for instance most of the universe’s mass is in the form of dark matter, which we cannot directly observe, but plays a critical role in the formation of galaxies. Simulations allow us to ‘observe’ the dark matter, and how it interacts with the stars and gas that we can see. They have led to the current paradigm: galaxies form and reside within extended blobs of dark matter, named ‘haloes’.





My current research is focussed on the shapes and alignments of galaxies in the EAGLE simulation. There are many reasons that one may do this, including whether galaxies align with their host dark matter haloes, and whether the alignment of neighbouring galaxies depend on the observed frequency. The chief motivation for my work lies in some upcoming observations of ‘gravitational weak lensing’, which is where the images of distant galaxies are minutely distorted into apparently-aligned shapes by some foreground object, usually a large concentration of dark matter around a cluster of galaxies or a filament. By understanding the distortion, one understands the dark matter. A systematic error of such studies lies in the intrinsic alignment of galaxies, where neighbouring objects are in fact naturally aligned before any distortion. I use simulations to understand the degree of this intrinsic alignment, so that observers may better understand its impact on weak lensing measurements.

The Astrophysics Research Institute (ARI) is part of Liverpool John Moores University and based in the IC2 building at the Liverpool Science Park. Comprised of nearly seventy research staff and forty graduate students, the work of the ARI encompasses a range of observational and theoretical research: Star Formation and Stellar Populations, Time Domain Astrophysics (focussing on rapidly changing astrophysical phenomena such as supernovae), Galaxy Formation and Evolution, Astronomical Instrumentation, and Computational Cosmology.
Additionally, the ARI works with the University of Liverpool to deliver Bachelor and Master’s courses in astronomy, and also provides a range of distance learning courses. Through its operation of the world’s largest robotic telescope, the National Schools’ Observatory provides data and telescope time to schools around the UK, helping to make professional astronomy accessible to the next generation