emission to the bubbles’ gamma-ray emission. All of these origin scenarios can reproduce the bubbles’ morphology, but they imply significantly different input energetics and timescales required to inflate the bubbles ($\dot{E} \gtrsim 10^{41}$ erg s$^{-1}$, $t \lesssim 5$ Myr for black hole accretion compared to $\dot{E} \lesssim 5 \times 10^{40}$ erg s$^{-1}$, $t \gtrsim 50$ Myr for star formation). This variation in the feedback rate is a significant uncertainty in how the bubbles impact the Galaxy, but there are additional factors that can constrain the characteristic bubble energetics.

Constraining the bubbles’ thermal gas distribution is a promising avenue to solve this problem, since the characteristic densities and temperatures should be significantly different depending on the bubble energetics. In the framework of expanding galactic outflows and shocks [e.g., @veilleux_etal05], a higher energy input rate leads to a higher plasma temperature and a larger expansion rate for a fixed bubble size and ambient density. Thus, the plasma temperature at the interface between the bubbles and surrounding medium encodes information on the bubbles’ shock strength, expansion properties, and overall energy input rate. A generic prediction from simulations and observations of galactic outflows is that the bubbles are overpressurized and hotter than the surrounding 