Following the Metals in the Intergalactic and Circumgalactic Medium over Cosmic Time

Nicolas Lehner, Joseph N. Burchett, J. Christopher Howk, John M. O'Meara, Molly S. Peeples, Marc Rafelski, Joseph Ribaudo, Sarah Tuttle

Published 2019-03-18Version 1

The circumgalactic medium (CGM) of galaxies serves as a record of the influences of outflows and accretion that drive the evolution of galaxies. Feedback from star formation drives outflows that carry mass and metals away from galaxies to the CGM, while infall from the intergalactic medium (IGM) is thought to bring in fresh gas to fuel star formation. Such exchanges of matter between IGM-CGM-galaxies have proven critical to producing galaxy scaling relations in cosmological simulations that match observations. However, the nature of these processes, of the physics that drives outflows and accretion, and their evolution with cosmic time are not fully characterized. One approach to constraining these processes is to characterize the metal enrichment of gas around and beyond galaxies. Measurements of the metallicity distribution functions of CGM/IGM gas over cosmic time provide independent tests of cosmological simulations. We have made great progress over the last decade as direct result of a very sensitive, high-resolution space-based UV spectrograph and the rise of ground-based spectroscopic archives. We argue the next transformative leap to track CGM/IGM metals during the epoch of galaxy formation and transformation into quiescent galaxies will require 1) a larger space telescope with an even more sensitive high-resolution spectrograph covering both the far- and near-UV (1,000-3,000 \AA); and 2) ground-based archives housing science-ready data.