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Astronomy Tea Talk

Tuesday, July 28, 2026
4:00pm to 5:00pm
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Cahill 370
From Metal-Enriched Halos to Growing Black Holes: Gas and dust Across Scales in the High-Redshift Universe
Siwei Zou, Research Professor, Chinese Academy of Sciences South America Center for Astronomy,

Abstract: The growth of galaxies and their central supermassive black holes is governed by the circulation of multiphase gas across a wide range of physical scales, from the circumgalactic medium to star-forming regions and the dense gas in the immediate vicinity of the black hole. This gas carries metals, dust, and angular momentum, regulating how galaxies form stars, how black holes accrete, and how feedback redistributes baryons into the surrounding halos.

In this talk, I will present a multiwavelength view of this baryon cycle using observations from JWST, ALMA, and VLT. I will first discuss how metal enrichment and dust in the circumgalactic medium reveal the exchange of material between galaxies and their environments, providing insight into possible chemical fossils preserved in CGM gas during the Epoch of Reionization. I will then discuss the possible AGN contribution in the dusty star-forming galaxies at z = 4-6. Finally, I will move inward to the nuclear region, where dense and ionized gas shapes black hole accretion, obscuration, outflows, and the co-evolution of the SMBH and its host galaxy.

Together, these results build a unified picture in which multiphase gas acts as the physical link between galaxy assembly, chemical enrichment, star formation, and black hole growth. By connecting the CGM, the star-forming interstellar medium, and the circumnuclear environment, this talk highlights how gas flows across scales drive the evolution of galaxies and their central black holes across cosmic time.

For more information, please contact Kaitlyn Shin by email at [email protected].

Event Series
Astronomy Tea Talks