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In order to form stars, one first requires a supply of cold gas

What first seems to be a fairly trivial statement is wrapped up in many other complex and sometimes interrelated physical processes which govern the supply of gas. I am working towards understanding the efficiency with which a galaxy can convert the hot, ionised hydrogen from its surroundings into the dense clouds of molecular hydrogen that birth the stars whose light shines across the Universe and into our telescopes.

The Universe is a tremendously chaotic place. Galaxies are continuously colliding with one another, shredding plumes of debris into space and inciting intense bursts of star formation. These ‘Cosmic Car Crashes’, known as mergers, are one of the primary mechanisms through which galaxies evolve over time.

The Advanced Camera for Surveys (ACS), the newest camera on NASA/ESA Hubble Space Telescope, has captured a spectacular pair of galaxies engaged in a celestial dance of cat and mouse or, in this case, mouse and mouse. Located 300 million light-years away in the constellation Coma Berenices, the colliding galaxies have been nicknamed "The Mice" because of the long tails of stars and gas emanating from each galaxy. Otherwise known as NGC 4676, the pair will eventually merge into a single giant galaxy.

NASA, H. Ford (JHU), G. Illingworth (UCSC/LO), M.Clampin (STScI), G. Hartig (STScI), the ACS Science Team, and ESA.

A key prediction of the current cosmological model is that smaller subunits of galaxies combine to form larger systems, which themselves merge into the colossal giants observed today. Alongside the birth of new stars, galaxy merging is the key process by which material is being redistributed in the Universe. Therefore, understanding this process is necessary in order to reveal how the current population of galaxies formed — including our own Milky Way and its eventual fate.

However, surprisingly little observational agreement of the impact of mergers exists outside of the local Universe. This will dramatically change with the Deep Extragalactic VIsible Legacy Survey (DEVILS; led from ICRAR/UWA by Dr Luke Davies), which is building a state-of-the-art spectroscopic sample of ~50,000 galaxies (the largest of its kind) spanning the last ~8 billion years of galaxy evolution. The DEVILS campaign bridges the currently dissociated near and distant Universe, making it the only survey suited to explore the impact of mergers across cosmic timescales.

I am working closely with the The MeerKAT International GHz Tiered Extragalactic Exploration (MIGHTEE) Survey to bridge the gap between the unprecedented depth of cold gas observations in galaxies with the richness of environmental metrics providing by DEVILS.

ICRAR Statement

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