Unveiling the Thermal Structure and Super-Solar Nitrogen Abundance in the Milky Way's Circumgalactic Medium
The circumgalactic medium (CGM) plays a pivotal role in galaxy formation, primarily characterized by its hot, diffuse nature, which necessitates X-ray observations for detailed study. As inhabitants of the Milky Way, we are uniquely positioned to examine the CGM of our own spiral galaxy. Recent discoveries have overturned traditional views of the CGM's thermal structure, unveiling a complex model of X-ray emissions that includes temperatures near the galaxy’s virial temperature (~0.18 keV), as well as a super-virial range (0.4–1.2 keV). Even more striking is the newfound evidence of significantly enhanced abundances of nitrogen, neon, and magnesium in the Milky Way’s CGM—particularly an abundance of nitrogen detected throughout the sky.
This super-solar nitrogen abundance, along with the super-virial temperature gas, is likely shaped by hot outflows driven by ongoing star formation across the Galactic disk. Notably, the CGM in the direction of the Galactic center interacts with the X-ray Galactic bubbles, providing clear evidence of Galactic Center feedback that injects both energy and momentum into the extended CGM.
In my presentation, I will explore these latest findings on the thermal structure of the extended Milky Way CGM, focusing on the surprising nitrogen abundance and its implications for Galactic evolution.
