THE HIGH-VELOCITY GAS TOWARD MESSIER 5: TRACING FEEDBACK FLOWS IN THE INNER GALAXY

We present FUSE and STIS E140M observations of the post-AGB star ZNG 1 in the globular cluster Messier 5 (l 3:9", b þ47:7"; d 7:5 kpc, z þ5:3 kpc). High-velocity absorption is seen in C iv, Si iv, O vi, and lower ionization species at LSR velocities of roughly$140 and$110 km s$1.We conclude that this gas is not circumstellar on the basis of photoionization models and path length arguments. Thus, the high-velocity gas along the ZNG 1 sight line is the first evidence that highly ionized HVCs can be found near the Galactic disk. We measure the metallicity of these HVCs to be O/H& þ0:22 ' 0:10, the highest of any known HVC. Given the clouds ’ metallicity and distance constraints, we conclude that these HVCs have a Galactic origin. This sight line probes gas toward the inner Galaxy, and we discuss the possibility that these HVCs may be related to a Galactic nuclear wind or Galactic fountain circu-lation in the inner regions of the Milky Way