Περίληψη :
The concept of the Galactic Habitable Zone (GHZ) is a foundational framework for assessing where and when life might emerge on galactic scales. However, this picture is typically based on static annular boundaries, defined primarily by metallicity, and increasingly struggles to capture the full complexity of galaxy evolution. In this talk, I will present my completed and ongoing work, which progressively challenges and enriches the classical GHZ paradigm.
I begin with N-body simulations of the Milky Way-like galaxy, demonstrating that stellar radial migrations are non-negligible even in the simplest axisymmetric model. The GHZ is not a fixed ring but a broad zone of radial mixing extending from roughly 3 to 12 kpc, through which stars (and their potential planetary systems) continuously redistribute. Turning to the cosmological scale, I revisit earlier claims of a bimodality in galactic habitability, specifically the proposition that a population of small, metal-rich dwarf galaxies (the "Cloudlet") forms a second peak of habitable potential. Applying rigorous filtering to IllustrisTNG, it becomes clear that this population is overwhelmingly composed of non-cosmological structures. Finally, I present recent work identifying a substantial population of massive galaxies undergoing chemical decoupling: systems in which the stellar metallicity significantly exceeds the gas-phase metallicity (due to recent merger-driven dilution) and show signs of partial quenching. These non-equilibrium galaxies dominate the high end of standard habitability proxies at the present epoch, yet their suppressed star formation and diluted gas reservoirs simultaneously constrain future terrestrial planet formation. This reveals an intrinsic habitability trade-off: the conditions that maximize the present-day habitable potential of a galaxy are precisely those that limit its capacity to generate new, potentially habitable, planets. Therefore, galactic habitability is not a static property; it is a transient phase of cosmic evolution. Ongoing and future work focuses on a few questions, but most importantly, it argues for a fundamentally dynamic, multi-scale, and time-dependent understanding of galactic habitability, with direct implications for how we target exoplanet searches and technosignature surveys across the nearby universe.
