The ISSI International Team led by Dr Céline Péroux from the European Southern Observatory (ESO) is an international collaboration focused on uncovering the mysterious 90% of baryons—the building blocks of regular matter—that reside in intergalactic gas. By combining extensive Hubble Space Telescope observations with multi-wavelength datasets and cutting-edge hydrodynamical simulations, the project aims to explore how gas moves into, through, and out of galaxies, a process known as the cosmic baryon cycle.
A key aspect of this research involves multi-facility observational campaigns using VLT/MUSE, ALMA, and HST. By analysing the properties of HI (neutral atomic hydrogen) gas reservoirs, which act as absorbers of Ly-alpha photons from background quasars, the team has detected 79 associated galaxies, revealing that these absorbers often connect with multiple galaxies. This allows researchers to statistically map the gas and metal distribution in the circumgalactic medium, shedding light on the crucial role of the baryon cycle in galaxy evolution and star formation.
Significantly, the findings show that most absorption-selected galaxies align with the star formation main sequence, among which higher-mass galaxies are less likely to harbour large amounts of neutral hydrogen gas within 120 kpc. Additionally, the illustris TNG simulations suggest that a portion of the absorbers represent quasi-static gas, rather than gas in motion. Together, these insights offer a comprehensive view of the neutral atomic gas, molecular gas, and stars, advancing our understanding of the complex structures within galaxies and contributing to a more complete baryon census in the universe.
For more information and a publication list, see the ISSI International Team #564 Webpage.
