New observations from the Spitzer Space Telescope indicate that supermassive black holes at the heart of elliptical galaxies might keep temperatures so high that gas can’t cool down. And without large clouds of cool gas, new stars can’t form. As long as the black hole is raging, star formation in the galaxy is put on hold.
Thanks to the Spitzer observations, astronomers have detected dust grains mingling with blazing hot gas at temperatures of 10 million degrees Celsius in an area surrounding the elliptical galaxy NGC 5044. Astronomers have seen this kind of situation before, where hot gas surrounding galaxies blaze hot in the X-ray spectrum.
There are many kinds of galaxies. Spiral galaxies like our own Milky Way have active regions of star formation. The older, larger, redder elliptical galaxies are different. They’re found at the centres of galaxy clusters, and have large quantities of hot gas that never seems to cool down enough to begin star formation.
Researchers from UC Santa Cruz think that this hot gas is being heated by the supermassive black holes through a process called feedback heating. They believe that material ejected by dying stars gravitates towards the centre of the galaxy. As it approaches the black hole, a large amount of energy is released, heating the gas up. This makes it buoyant, sort of like how smoke and embers float away from a fire. These plumes then mix with other, more distant gas, and heat it up as well. Each time the supermassive black hole feeds, it creates a feedback effect that travels outward, heating up gas across the galaxy.
And this is what kills star formation. Stars can only form when dust is cool enough to condense together, like water makes steam – you only get rain when it cools down. With all this heated gas, material never comes together to create stars.
Original Source: Spitzer News Release