Identifying and Simulating Hydrogen in the Galactic Center Outflow

The existence of galactic nuclear wind, both in neighboring galaxies and our own Milky Way, has been discussed since the early 2000s (e.g., 1, 2, 3). We have been analyzing both new and previously published 21cm HI data from the Green Bank Telescope (GBT) that have revealed a population of neutral clouds entrained in the wind from the Milky Way nucleus. So far, over 200 hydrogen clouds have been discovered, with recent data revealing hydrogen clouds with particularly high velocities that do not fit previous kinematic models(4, 5, 6). To solve this issue, we found that the outflow must be accelerating for longer and is much older than previously predicted. Furthermore, a noticeable gap in the velocities of clouds at high latitudes could be attributed to an episodic outflow, although the same outcome could be due to clouds evaporating in the winds and becoming too faint to observe. Other important work includes analyzing cloud morphology, as well as finding clouds exhibiting “comet”-like features that may be fundamental to understanding how the nuclear winds develop. We will discuss the distribution and kinematics of the additional cloud sample, along with its implications for cloud lifetimes and evolution of the wind. The Green Bank Telescope is a facility of the National Science Foundation, operated by Associated Universities, Inc. Thank you to the Green Bank Observatory REU program for providing the opportunity and funding for me to embark on this research. References: (1) Bland-Hawthorn, J., + 2003, ApJ, 582, 246 (2) Veilleux, S.+ J. 2005, ARAA, 43, 769 (3) Keeney, B. A.+ 2006, ApJ, 646, 951 (4) Lockman, F. J.+ 2020, ApJ, 888, 51 (5) Di Teodoro + 2018, ApJ, 855, 33 (6) McClure-Griffiths + 2013, ApJL, 770, L4