Normal spiral galaxies such as our own Milky Way contain immense
volumes of very hot gas, with temperatures of millions of degrees. We
are beginning to understand the sources and life cycle of this gas,
heated by supernova explosions and the winds from young, hot stars.
It is still not clear, for example, how this gas, rich in newly
synthesized elements such as carbon, oxygen, and iron, cools and is
recycled into future generations of stars and planets (e.g. in starbursts
and galaxy mergers). Gas at these
temperatures is a potent source of x-rays, smoothly distributed over
large areas of the sky.
We have used Chandra and other x-ray observatories to survey our own
and other galaxies for bubbles of hot gas. Teasing apart the foreground
heliospheric x-ray emission from
Galactic hot gas, and from extragalactic x-ray sources, is tricky, but
can be approached due to the superb angular resolution of the Chandra
This hot gas fills voids in cooler gas, which can be seen in absorption
with satellites such as HST and FUSE. Five-times ionized Oxygen in the
boundaries of hot regions can be studied with FUSE, and combined with
x-ray observations of six- and seven-times ionized oxygen to provide a
more complete picture of the hot interstellar medium.
Jonathan Slavin, Terrance Gaetz, Paul Plucinsky, Mike Juda, Richard
Edgar, Maxim Markevich, Ryan Hickox, Joy Nichols, John Raymond (SSP), Brad Wargelin, Ralph Tuellmann
Caption: A map of the sky produced by Rosat (the Roentgen
Sattelit, which was operated by the Max Planck Institut für
Extraterrestrische Physik in Germany) in the 3/4 keV band. This figure
shows broad diffuse features of gas with temperatures of a few million
degrees.Snowden et al (1995) ApJ, 454, 643.
Snowden et al (1995) ApJ, 485, 125.