Observation of Acceleration of HI Clouds Within the Fermi Bubbles

Abstract

The ~200 HI clouds observed to be entrained in the Fermi Bubble wind show a trend of increasing maximum |VLSR| with Galactic latitude. We analyze previous observations and present new data from the Green Bank Telescope that rule out systematic effects as the source of this phenomenon. Instead, it is likely evidence for acceleration of the clouds. The data suggest that clouds in the lower 2 kpc of the Fermi Bubbles, within the Bubble boundaries established from X-ray studies, have an outflow velocity that rises from ~150 - 200 km/s close to the Galactic Center and reaches ~330 km/s at a distance of 2.5 - 3.5 kpc. These parameters are also consistent with the kinematics of UV absorption lines from highly ionized species observed against two targets behind the Fermi Bubbles at $b=-6.6^{\circ }$, and $b=+11.2^{\circ }$. The implied neutral cloud lifetime is 4 - 10 Myr.

Accepted for publication in the Astrophysical Journal

References in corpus (11)

• Giant Gamma-ray Bubbles from Fermi-LAT: AGN Activity or Bipolar Galactic Wind?
• Extended Anomalous Foreground Emission in the WMAP 3-Year Data
• Magnetized Gas Clouds can Survive Acceleration by a Hot Wind
• Giant Magnetized Outflows from the Centre of the Milky Way
• The Launching of Cold Clouds by Galaxy Outflows I: Hydrodynamic Interactions with Radiative Cooling
• Hydrodynamical Coupling of Mass and Momentum in Multiphase Galactic Winds
• Probing the Fermi Bubbles in Ultraviolet Absorption: A Spectroscopic Signature of the Milky Way's Biconical Nuclear Outflow
• Nuclear Outflow of the Milky Way: Studying the Kinematics and Spatial Extent of the Northern Fermi Bubble
• The Interaction of the Fermi Bubbles with the Milky Way's Hot Gas Halo
• Does the Milky Way Produce a Nuclear Galactic Wind?
• The large-scale ionization cones in the Galaxy

Cited by in corpus (4)

• Cold gas in the Milky Way's nuclear wind
• Shock-multicloud interactions in galactic outflows -- I. Cloud layers with log-normal density distributions
• Mapping Outflowing Gas in the Fermi Bubbles: a UV Absorption Survey of the Galactic Nuclear Wind
• The turbulent gas structure in the centers of NGC253 and the Milky Way