Speaker
Description
The Circumgalactic Medium (CGM), as a key interface connecting galaxies to the cosmic web, has its metal distribution and evolution directly reflecting the dynamical processes of halo boundaries. Using early data from the Dark Energy Spectroscopic Instrument (DESI), we analyze the equivalent widths (W) of 33 metal absorption lines to reveal the spatiotemporal evolution of the CGM and its implications for the definition of halo boundaries. This work covers a redshift range of 0.3 < z < 5.5 and a projected distance of D < 6.5 Mpc for galaxies (and QSOs), with a focus on absorption lines from elements such as Mg II, Fe II, and C IV. Result shows that the distribution of Mg exhibits a radial break at 100–200 kpc (depending on stellar mass), which can serve as a method for defining the Edge Radius. Additionally, we observe that star formation influences Mg II absorption primarily within 50 kpc,whcih could partially reflect the size of the outflows. Furthermore, This size may decrease with increasing stellar mass, as we find a significant reduction in absorption along the minor axis in more massive galaxies, suggesting that outflows are confined within deeper gravitational potential wells.
