Description:

The nucleus of many galaxies is the source of a massive outflow of gas that can shape the future evolution of the galaxy. In the Milky Way we have evidence of a such a phenomenon. The Fermi Bubbles are regions of hot gas that extend many thousands of light years above and below the Galactic center, formed through energetic events associated with star formation or the nuclear black hole. The Bubbles are traced by very faint emission across the electromagnetic spectrum implying that they contain relativistic particles as well as hot, ~10^7 K thermal gas. The origin of the bubbles, as well as their energetics and lifetime, is uncertain. In observations of neutral atomic hydrogen from the 21cm hyperfine transition, the Bubbles appear as voids in the extended Hydrogen layer, but within these voids is a population of neutral Hydrogen clouds apparently entrained in the outflowing nuclear wind. The Green Bank Telescope was recently used to survey the inner Galaxy for neutral clouds entrained in the nuclear wind, and has detected more than 100 such objects. A picture emerges which implies an outflow luminosity > 3 x 10^40 ergs/sec over the last 10 Myr, and a cold-gas mass flow into the Bubbles of ~0.1 solar masses per year.

Felix Lockman, NRAO

Host: Zadeh

Keywords: Physics, Astronomy, Radio Astronomy