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Why Circumgalactic Matter Matters for Galaxy Evolution

PAA 102

Carolyn Porco (Space Science Institute)

May 24 @ 4:00 PM - 5:00 PM

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The circumgalactic medium (CGM; non-ISM gas within a galaxy virial radius) regulates the gas flows that shape galaxies. Owing to the vastly improved capabilities in space-based UV spectroscopy with the installation of HST/COS in 2009, observations and simulations of the CGM have emerged as the new frontier of galaxy evolution studies. In the last decade, we have learned that the CGM of Milky Way mass galaxies likely contains enough material to harbor most of the metals lost in galaxy winds and to sustain star-formation for billions of years. Remarkably, this implies that most of the heavy elements on earth cycled back and forth multiple times through the Milky Way’s own CGM before the formation of the solar system. I will describe constraints we have placed on the origin and fate of this material by studying the gas kinematics, metallicity and ionization state. I will conclude by posing several unanswered questions about the CGM that will be addressed with future survey data and hydrodynamic simulations in a cosmological context.