Black hole winds pull the plug on star formation

Posted on 15 April 2015
Observations of winds from a black hole that are capable of blowing gas out of a host galaxy reinforce the idea that black holes can control star formation in galaxies. The findings, reported in Nature this week by Dr James Reeves, astrophysics at Keele, as part of a study led by Dr Francesco Tombesi at NASA Goddard Space Flight Centre, USA, may help us to learn more about galaxy evolution.
The study looked at observations made with ESA's Herschel space telescope and the Japanese Suzaku X-ray satellite at the dust enshrouded galaxy, IRAS F11119+3257. The Suzaku telescope observed a very fast and energetic wind from the centre of this galaxy, which contains a super massive black hole thought to contain 16 millions times the mass of the Sun. The energetic radiation emitted from the hot X-ray emitting gas from around the black hole is capable of expelling matter at one quarter of the speed of light, producing this initial wind from the black hole. The Herschel observations then observed the effect this fast energetic wind has on the rest of the galaxy, finding nearly 1000 Solar masses of material being pushed out through the galaxy, in the form of hydroxyl (or OH) molecules.
"While we have already known about the existence of fast winds produced from other super-massive black holes, this is the first time we have been able to directly see its effect on the rest of the galaxy at the same time" explained James Reeves. "The wind from the black hole is acting like a snowplough, sweeping the gas and dust up in its wake. This is likely to stop new stars from forming and can limit how big both the galaxy and the black hole can become."
Large-scale winds have been seen before, but what makes this study remarkable is that the authors have linked the small-scale wind coming off the accretion disk around the black hole to the outflow of molecular gas detected in the same galaxy, notes James Geach in an accompanying News & Views article in Nature.