Title：Growing in the Shadows: Tracing Obscured Black Hole Accretion Across Cosmic Time

Speaker：Dr. Ezequiel Treister ( University of Tarapaca)

Time：3:00 pm Jan.29th (Thursday)

Tencent Meeting：46822606747 password: 6360

Location: Lecture Hall, 3rd floor

Abstract：

How do supermassive black holes grow, and where do their seeds come from? The cosmic X-ray background provides a luminosity-weighted census of black hole accretion over cosmic time, and its successful modeling might suggest that we now understand the full history of supermassive black hole growth. However, Soltan's argument leaves significant room for additional accretion still unaccounted for — growth that remains consistent with current constraints yet hidden from our view. This missing growth likely occurs in heavily obscured phases that are invisible to X-ray surveys, spanning the entirety of cosmic history.

I will present new methods using sub-millimeter and millimeter continuum emission to identify obscured AGN that X-rays miss, revealing that merging black holes are surprisingly "picky eaters." Regarding the formation of the first supermassive black holes, JWST observations of Little Red Dots at z > 4 may provide important clues: rather than breaking our current understanding, these sources likely represent the most obscured extreme of the high-redshift AGN population. Together, these results suggest that critical phases of black hole assembly happen in the shadows — and we are only now learning to see them.

CV：

Dr. Ezequiel Treister is a Full Professor at the Institute for Advanced Research at the University of Tarapaca in Chile. He got his Ph.D. in Astronomy in the joint Universidad de Chile/Yale program in 2005, working under the supervision of Prof. Meg Urry. Afterward, he was an ESO postdoctoral fellow with duties at the VLT from 2006 to 2008 and a Chandra/Einstein postdoctoral fellow at the Institute for Astrophysics of the University of Hawaii from 2008 to 2011. He was then appointed as an Associate Professor at the Universidad de Concepción in Chile, a position he held until March 2016, and subsequently at the Universidad Católica until March 2025. Prof. Treister's research focuses on studying the formation and growth of supermassive black holes, the triggering mechanisms that drive their growth, and their connection to galaxy evolution.