On February 23rd, 2024, the A&A Board finalised their selection for this year's A&A Awards, recognising exceptional work of early-career researchers in the field.

A&A Best PhD Thesis Award

Dr Mohammad Farhat of the Observatoire de Paris was awarded the A&A Best PhD Thesis Award for his research on resolving the discrepancies in the Earth-Moon system's tidal and geological ages through advanced tidal dissipation models. Soon after the Apollo space mission placed retroreflectors on the Moon, laser ranging measurements started showing that our natural satellite drifts away from Earth at "too fast" a rate: extrapolating this rate back in time through models of tidal dissipation, has the two bodies merging at most 1.6 billion years ago. This is less than half the well-constrained age of the Moon, 4.425 ± 0.025 Ga, and demonstrates that the Earth currently dissipates its rotational energy much faster than it typically has over its history. More elaborate models, taking into account oceanic tidal dissipation in addition to solid tides, had until now failed to solve this long-standing conundrum. Farhat et al. demonstrate that it stems from the changes in oceanic tidal dissipation which the evolving configuration of the Earth's continents triggers. Accounting for these changes in a simplified way, they show that the Earth-Moon system crossed multiple tidal resonances which are associated with rapid variations in the length of an Earth day, the lunar orbital distance, and the Earth’s obliquity, and finally reconcile the tidal and geological ages of the Moon.

A&A Early Career Award

Dr Michael Romano from the National Centre for Nuclear Research in Warsaw was awarded the A&A Early Career Award for his contributions to our understanding of galaxy formation. Galaxy mergers are one of the main contributors to the mass assembly of galaxies, but are observationally poorly constrained beyond z ~ 4. Recent work suggests that major mergers were more frequent in the early universe, but leaves unclear whether their contribution to the mass assembly dominates over star formation in accreted gas. One major reason for that uncertainty is that securely identifying major mergers from purely morphological information becomes increasingly difficult as the redshift increases. Romano et al. take advantage of the morpho-kinematic information available for the 75 z> 4.4 star-forming galaxies of the ALPINE survey, observed with ALMA in the [CII] 158 micrometer line and with extensive multiwavelength archival information, and obtain a much cleaner measurement of the major merger fraction than hitherto possible. Combining their result with lower readshift measurements, they show that the merger fraction increases rapidly, peaks at z ~ 3, and slowly decreases at earlier epochs. Whether these mergers contribute significantly to the galaxy mass assembly depends strongly on the assumed merger timescale, which is needed to convert merger numbers to merger rates, but adopting scalings of the merger timescale with redshift inferred from cosmological simulations suggests a considerable role of mergers in the early build-up of galaxies.

We extend our sincere congratulations to the winners of these A&A awards, whose work underscores the vital contributions of emerging scholars to the advancement of knowledge in astronomy and astrophysics. The A&A Awards continue to highlight the importance of innovative research and the role of young scientists in shaping the future of the field.