A deep view of cool gas entrained in the Fermi Bubbles at high latitude

A massive multiphase nuclear outflow is emanating from the Galactic Center and can be seen in wavelength ranges covering gamma rays, microwaves, X-rays, radio and ultra-violet in both absorption and emission. Together these observations suggest that a violent nuclear event that happened a few Myrs ago in the center of our Galaxy gives rise to the Fermi Bubbles. In this work, we take a detailed look at a galactic latitude of ~28 degrees in the Northern Fermi Bubble with a deep 21 cm GBT survey. This region is also probed by a background quasar sightline with HST/COS UV spectroscopic observation. We report the discovery of a new population of high velocity (v_LSR ~ -172 kms^-1) cool HI gas clouds that resides at these high latitudes and present detailed morphology and mass budgets of these gas clouds entrained in a nuclear wind. These cool gas clouds co-exist with warm (10⁵ K) gas detected via HST/COS spectroscopy in the same field and suggest that they are all dense gas clouds entrained in a biconical nuclear wind. These estimates can be used to constrain the mass of cool gas entrained in the Fermi Bubbles.