Probing the Hot Gaseous Halos of Milky Way-like Galaxies in the TNG50 simulation

Original Abstract

The origin and structure of the hot ($T\gtrsim10^6$ K) gaseous halo around Milky Way (MW)-mass galaxies provide a critical test for galaxy formation models. We perform a comprehensive comparison for a sample of MW analogues from the TNG50 cosmological simulation by generating synthetic soft X-ray emission and O VII/O VIII absorption lines. The simulated halos successfully reproduce the observed global soft X-ray luminosity and key inner-halo properties, including X-ray surface brightness, emission measure, and O VII absorption strength. However, two critical discrepancies are identified: (i) the simulated X-ray surface brightness profiles decline too steeply at large radii compared to extended eROSITA stacking emission, and (ii) the halos systematically underproduce O VIII absorption, indicating a deficit of hotter-phase gas at $T\sim(1.6-3.2)\times10^{6}$ K. These findings indicate that the simulated halos are spatially too compact and lack the hotter gas phase observed in real galaxies. This suggests that the feedback model in TNG50, while generating hot gas, may deposit its energy too centrally and too vigorously to sustain a gently extended, multi-phase corona.