The 2023-2024 WCA Student Paper Prize was jointly awarded to Andrew M. M. Reeves for his paper "How many stars form in galaxy mergers?", and to Chloe M. Cheng for her paper "Initial mass function variability from the integrated light of diverse stellar systems". Honourable mention was given to Alan B. H. Nguyen ("Self-calibrating BAO measurements in the presence of Small Displacement Interlopers") and Kiana Salehi ("Photon Rings and Shadow Size for General Integrable Spacetimes").
Here Andrew summarises his prize-winning paper.
What did Andrew do?
We used a new dataset of recently merged galaxies (like the Antennae Galaxies, right) observed in the Sloan Digital Sky Survey (SDSS) that had been identified with machine learning and visually verified by astronomers. We wanted to measure how much of a galaxy’s stars form when galaxies merge, something that is not well understood. When galaxies merge, everything gets chaotically mixed together, especially their fuel for star formation: cold gas.
How was it done?
We used simulated galaxies’ star formation histories and added in an extra burst of star formation to see how that changes the average age of their star populations. We then compared this to the estimated average ages of the stars in the galaxies (modeled based on how much light they emit in each different color).
What were the results?
We found 20% of the mass of all stars present in recently merged galaxies were formed in a “short” burst, possibly 120 to 250 million years long (short compared to the 13.7 billion year age of the universe!). The amount of stars formed is compatible with the typical amount of cold gas other astronomers have measured in pre-merger and post-merger galaxies.