Colloquium: Nikole Nielsen (Host: Chris Churchill)

September 18, 2020 @ 3:00 pm – 4:00 pm

The Circumgalactic Medium at Cosmic Noon with KCWI

Nikole Nielsen, Swinburne University of Technology

The star formation history of the universe reveals that galaxies most actively build their stellar mass at cosmic noon (z=1-3), roughly 10 billion years ago, with a decrease toward present-day. The resulting metal-enriched material ejected from these galaxies due to supernovae and stellar feedback is deposited into the circumgalactic medium (CGM), which is a massive reservoir of diffuse, multiphase gas out to radii of 200 kpc. The CGM is the interface between the intergalactic medium and the galaxy, through which accreting filaments of near-pristine gas must pass to contribute new star formation material to the galaxy and outflowing gas is later recycled. Simulating these baryon cycle flows is crucial for accurately modeling galaxy evolution. 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 the host galaxies. The installation of the Keck Cosmic Web Imager (KCWI), an integral field spectrograph, on Keck II has opened a new window to quickly identify galaxies via their Lyman alpha emission at this redshift. I will introduce a new survey to build a catalog of absorber-galaxy pairs at z=2-3 with KCWI. With the combination of HST images, high-resolution quasar spectra, and the cutting-edge KCWI data, this survey aims to examine CGM kinematics and metallicities and relate them to the host galaxy star formation rates and orientations to reveal the baryon cycle at cosmic noon.

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