Nikki Nielsen

Research Fellow

Swinburne University of Technology

Biography

I aim to understand how galaxies form and evolve by examining the properties and motions of gas in the circumgalactic medium (CGM), a massive and diffuse reservoir of gas surrounding galaxies. I study the baryon cycle, or the flow of gas into and out of galaxies, as cosmological simulations have shown it is vital in regulating galaxy evolution and building up the CGM. To study the gas in the CGM, I use background quasars whose light pierces the halos surrounding foreground galaxies and those galaxies imprint absorption signatures on the quasar's light. By comparing the properties of the absorbing gas and the host galaxy, I can determine whether the gas is accreting onto, outflowing from, or orbiting around galaxies. My current work is focused on "Cosmic Noon" (z~2) when galaxies are most actively building up their mass and at lower redshift (z~0.02) where we can now image the CGM directly in emission.