The Circumgalactic Medium at Cosmic Noon with KCWI

Wednesday 28 Apr 2021 @ 12 p.m., David Caro building, Level 2, Hercus Theatre (+Zoom)
Dr Nikole M. Nielsen, Swinburne University; Email: nikolenielsen[at]


The star formation history of the universe reveals that galaxies most actively build their stellar mass at “cosmic noon” (z=1-3). The gas accreting onto galaxies to drive their construction and the resulting metal-enriched material ejected from these galaxies due to feedback must pass through the circumgalactic medium (CGM). The CGM is a massive reservoir of diffuse, multiphase gas out to ~200 kpc and is the interface between the intergalactic medium and the galaxy. While the CGM is well-studied at z<1, little attention has been paid to the reservoir when star formation is most active, due to the difficulty in identifying host galaxies at cosmic noon. The installation of the Keck Cosmic Web Imager (KCWI), a sensitive integral field spectrograph, on Keck II has opened a new window to quickly identify galaxies via their Lyman alpha emission at cosmic noon as well as to directly image the CGM in emission. I will introduce two new surveys with KCWI aiming to study the CGM in (1) absorpti
on around galaxies at z=2-3 and (2) emission around local starbursting galaxies (cosmic noon analogues). These surveys are still in progress, but first results reveal strong outflows at cosmic noon and tantalising sub-kiloparsec structure in the CGM.