On the Nature of Galaxy Clusters as Archaeological Records

Dr. Thomas Connor (JPL)
Tuesday, February 9, 2021 - 11:00am

Among certain astronomers, galaxy clusters are known as the Universe’s largest trash bins—galaxies get dumped in and never come out, and these galaxies stop changing and evolving once they are discarded. While this framing is a tad dismissive, it is not wholly inaccurate. Yet, as archaeologists will attest, garbage dumps are fantastic tools for investigation, concentrating and mostly preserving the physical relics of multiple eras into one location. Here I describe a broad research program in that framework: of galaxy clusters as garbage dumps, preserving their history and the history of the universe in a way unparalleled among other astronomical objects. I will focus on four specific questions whose answers are needed to utilize clusters for this purpose: how gas and galaxies enter into a cluster, how we can derive temporal information for individual galaxies, how galaxies change during their time in a cluster, and what is the earliest extent we can probe with these measures. Combining data from Chandra, HST, and the telescopes of Las Campanas, I will discuss the cosmic web connections of a nearby cluster, the techniques needed to attain meaningful insight from galaxy populations, and the births of clusters as traced by quasars in the first billion years of the Universe.

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