Séminaire/Seminar Galaxies |
| « The Ashes of the First Stars: A Transition at z ~ 9 » |
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Denis Burgarella |
| Recent observations with JWST and ALMA reveal a sudden break in the dust content of galaxies at z~9. Dust attenuation and dust-to-stellar mass ratios drop sharply, implying that early galaxies contain far less dust than expected. Why does dust seemingly disappear so early? I argue that we are not seeing a lack of dust production, but a regime where dust is rapidly destroyed. In this picture, grains formed in supernovae are efficiently processed by reverse shocks, leaving behind intrinsically dust-poor, metal-poor systems. This naturally produces a population of galaxies with extremely low dust attenuation (GELDAs), where the transparency is driven by a true deficit of surviving grains, not by outflows or geometry. When implemented in galaxy models, this mechanism suppresses the brightest systems and reconciles theory with JWST observation, without invoking extreme star formation or dust-free galaxies. If correct, the break at z~9 marks a transition: we may be witnessing galaxies whose dust is shaped, and largely destroyed, by the first generations of supernovae, potentially carrying the imprint of Population III stars. I will conclude by presenting the PRIMA project, and its main characteristics, highlighting how it will probe the origin and evolution of dust in galaxies. |
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lundi 18 mai 2026 - 11:30 Salle Entresol Daniel Chalonge Institut d'Astrophysique de Paris |
| Page web du séminaire / Seminar's webpage |