Talk Title and Abstract:
Quenching Star Formation in Massive Galaxies: Insights from X-ray Observations of their Gas Halos
Not long ago, cosmological simulations including dark matter and baryons could approximately reproduce the properties of the most massive systems in the universe, the clusters of galaxies, by preventing the gas from cooling. But in order to self-consistently predict the stellar contents of galaxies, the simulations had to let gas cool (radiate) and discovered that such hypothetical systems were far too efficient at converting gas to stars. Even after incorporating the suppressive side-effects of forming stars, explosion from supernovae and winds from stars, the most massive simulated galaxies not only overproduced stars, but make them over a longer time than allowed by observations. The most suspicious culprit is still the Active Galactic Nuclei, or AGN Feedback. AGN Feedback includes many different aspects of accretion onto a central supermassive black hole, but also likely works together with stellar-scale processes like supernova-driven winds in galaxies. This talk will identify some of the observational clues that came from unexpected corners of astronomy — high resolution X-ray astronomy — and explore what we have learned so far from studying the gaseous atmospheres of clusters of galaxies, massive galaxies, and the observable phenomena associated with the supermassive black holes. The talk will also suggest why a mission like the Lynx Observatory, proposed to the Astro2020 US decadal review process, is the optimal way to make progress in understanding the baryon cycles in galaxies and their dark matter halos.
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