The Hot Stars of Galaxies: Who Are They and What Do They Reveal?

Star-forming galaxies are like stellar gyms where massive, hot stars are born. These stars not only shine brightly but also emit ionizing radiation that influences the evolution of the galaxies themselves. The stellar winds they produce are so powerful that they shape the interstellar environment, enriching it with chemical elements. But there's more: in metal-poor environments, these stars become even more extreme. Thanks to telescopes like the HST and JWST, we can observe these young stellar populations and study their properties. Stellar population synthesis is a key tool for understanding these cosmic giants better. New evolutionary and atmospheric models allow us to explore new frontiers of research, characterizing both nearby and distant stellar populations.

Massive stars, with masses over 8 times that of the Sun, have short but intense lives. In galaxies with low metallicity, these stars are even more massive and luminous. Stellar winds, which can reach speeds of thousands of kilometers per second, expel large amounts of material, influencing star formation and the structure of the galaxy. Stellar population synthesis allows us to model the evolution of these stars and better understand their impact on the surrounding environment. New atmospheric and evolutionary models, which take into account parameters such as rotation and mass loss, give us a more complete picture of the properties of these stars. Additionally, observations with the JWST allow us to study distant galaxies, providing valuable information on how massive stars influence galaxy evolution over time.