The High Velocity Gas toward Messier 5: Tracing Feedback Flows in the Inner Galaxy
Abstract
We present Far Ultraviolet Spectroscopic Explorer (FUSE) and Space Telescope Imaging Spectrograph (STIS E140M) observations of the post-asymptotic giant branch star ZNG 1 in the globular cluster Messier 5 (l=3.9, b=+47.7; d=7.5 kpc, z=+5.3 kpc). High velocity absorption is seen in C IV, Si IV, O VI, and lower ionization species at LSR velocities of -140 and -110 km/s. 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]=+0.22\pm0.10, 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 circulation in the inner regions of the Milky Way.
Cite
@article{arxiv.0802.0286,
title = {The High Velocity Gas toward Messier 5: Tracing Feedback Flows in the Inner Galaxy},
author = {William F. Zech and Nicolas Lehner and J. Christopher Howk and W. Van Dyke Dixon and Thomas M. Brown},
journal= {arXiv preprint arXiv:0802.0286},
year = {2009}
}
Comments
23 pages, 11 figures, 7 tables