Very hot gases, with temperatures of a few million degrees, are also observed in a variety of galaxies; we are beginning to understand how these hot gases may be produced and evolve in different galaxies.
These hot gases are important for the ecology of the universe, because hot winds may spread the metals formed in stars (the ‘elements of life’) outside of the parent galaxy, to be recycled in future episodes of star formation. Hot gaseous halos are trapped by the gravitation potential in some galaxies or groups of galaxies, thus providing the means for measuring the mass of the dark matter in these systems.
Hot gases interact with the super-massive black holes at the nuclei of galaxies and are important for the creation and evolution of Active Galactic Nuclei (AGN) and quasars.
X-ray image from the ROSAT All-Sky Survey. This X-ray image is from the ROSAT All-Sky Survey. It shows X-rays at energies of .75 keV. This image is dominated by the radiation from the north polar spur and from the large-scale central region of our Galaxy, which contains hot interstellar matter and tens of thousands of unresolved point sources. Near the equator in the left half of the image, the Cygnus superbubble becomes visible as a broken yellow and red ring. The Vela supernova remnant is an isolated red spot towards the right side of the image. 1
- The Mulitwavelength Milkyway - The RXTE Learning Center, Astrophysics Science Division at NASA-Goddard Space Flight Center.
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"Hot Gas Halo Detected Around Galaxy NGC 4631" – The central region of the spiral galaxy NGC 4631 as seen edge-on from NASA's Chandra X-ray Observatory and the Hubble Space Telescope. The Chandra data shows a halo of hot gas surrounding a galaxy that is very similar to our Milky Way. The Hubble data shows the galaxy's ridge of gas and stars, and bright giant bursting bubbles created by clusters of massive stars. (Source/Credit: NASA/UMass/HST/D. Wang et al.)