报告摘要：Galaxy clusters are the most massive gravitationally bound objects in the Universe today. Their alluring beauty so prominently on display in the present-day Universe - mega-parsec-sized structures containing up to thousands of galaxies residing in massive dark matter halos - belies what is a complex and prolonged evolutionary history. This seminar delves into fundamental questions about the early stages of galaxy cluster formation, specifically examining protoclusters during the Cosmic Dawn Era at redshifts greater than 6. Our recent investigation, based on the COSMOS2020 catalogue featuring ultra-deep photometry of approximately 10^6 sources across the ~2 square degree COSMOS area, reveals promising protocluster candidates at redshifts between 6 and 8. We derive their dark matter halo masses, and compare their abundances with expectations from current models of hierarchical structure formation. Utilizing Keck, we spectroscopically confirm two of our z=6 protocluster candidates, and find that they are indeed very massive and rich structures that most likely will end up as Coma-like clusters at the present day. Notably, these structures appear embedded at the intersection of large-scale filaments, supporting the hypothesis that protoclusters form at the nodes of such filaments. Studies such as this will soon be possible on a much larger scale through coordinated surveys with Euclid and ground-based telescopes. Combined with follow-up efforts with JWST and ALMA, and numerical simulations of increasing scope and complexity, we are now for the first time in a position to answer the most fundamental questions regarding the formation and evolution of galaxy clusters.
主讲人简介：My research deals with the formation and evolution of galaxies and the clusters they live in. I led some of the first extragalactic blank field surveys at 1mm, which established the presence of dusty starburst galaxies at high redshifts. I also conducted the first systematic interferometric CO survey of high-z starburst showing them to be rich in molecular gas. An important aspect of my research is interfacing observations with numerical simulations and my group developed the SIGAME (SImulator of GAlaxy Millimeter Emission) as part of this effort. I led or am part of a number of international collaborations. E.g., I am PI of the JCMT Large Program RAGERS (RAdio Galaxy Environment Reference Survey), and I am the Danish co-PI on the European JWST/MIRI consortium, and part of the MIRI Dep Imaging Survey (MIDIS) of the Hubble Ultra Deep Field. Beyond research, I enjoy teaching, supervising and mentoring students, and engaging in public outreach. Employment Professor of Astronomy and Co-Director of the Cosmic Dawn Center (DAWN) at the Technical University of Denmark since 2019. Associate Professor (tenured) at University College London, 2012-2019 Associate Professor, Dark Cosmology Center, Copenhagen University, 2010-2012 Postdoctoral researcher, Max-Planck Institute for Astronomie, Heidelberg, 2007-2010 Postdoctoral Scholar of Physics, California Institute of Technology, 2005-2007 PhD, University of Edinburg ,2005.
