Using ESA’s XMM-Newton and NASA’s Nuclear Spectroscopic Telescope Array (NuSTAR) X-ray telescopes, astronomers have discovered that the super-fast winds from supermassive black holes at the core of galaxies blow in a nearly spherical fashion, emanating in every direction. The finding rules out the possibility that the winds blow in narrow beams.
Supermassive black holes at the cores of galaxies blast radiation and ultra-fast winds outward, as illustrated in this artist’s conception, based on an image of the Pinwheel galaxy from Hubble. Image credit: NASA / JPL-Caltech.
At the core of every massive galaxy in the Universe, including our own Milky Way, sits a supermassive black hole, with a mass some millions or billions of times that of our Sun.
Some of these black holes are active, meaning that their intense gravitational pull causes matter to spiral inward, and at the same time part of that matter is cast away through powerful winds.
“We know that black holes in the centers of galaxies can feed on matter, and this process can produce winds. This is thought to regulate the growth of the galaxies,” said Dr Fiona Harrison of the California Institute of Technology, a co-author of the paper published online in the journal Science.
“Knowing the speed, shape and size of the winds, we can figure out how powerful they are.”
Dr Emanuele Nardini of Keele University, UK, who is the first author on the study, added: “black holes are powerful objects, but their gravitational influence does not extend much beyond the very inner parts of a galaxy.”
“If black holes are really to influence the star-forming activity of an entire galaxy, there must be a feedback mechanism connecting the two on a global scale.”
In the new study, Dr Nardini, Dr Harrison and their colleagues determined that PDS 456 – an extremely luminous black hole (quasar) located more than 2 billion light-years away – has winds that carry more energy every second than what is emitted by more than 1 trillion suns. That’s enough of a punch to affect the entire galaxy and its ability to make stars.
“By looking at this huge spherical outflow, we can now see a mechanism to explain the correlation between black hole and galaxy formation,” said co-author Dr Bill Craig of Lawrence Livermore National Laboratory and the Space Science Laboratory at University of California, Berkeley.
NuSTAR and XMM-Newton simultaneously observed PDS 456 on five separate occasions in 2013 and 2014.
“This is a great example of the synergy between XMM-Newton and NuSTAR,” said Dr Norbert Schartel, XMM-Newton project scientist at ESA, who was not involved in the study.
The telescopes complement each other by observing different parts of the X-ray light spectrum: XMM-Newton views low-energy and NuSTAR views high-energy.
Their goal was to look for iron, which is blown from the PDS 456’s winds along with other matter.
“The complementarity of these two X-ray observatories is enabling us to unveil previously hidden details about the powerful side of the Universe,” Dr Schartel added.
The X-ray data from NuSTAR, when combined with observations from XMM-Newton, provided the key information, proving that the winds emanate not in a beam but in a nearly spherical fashion.
Scientists think supermassive black holes and their home galaxies evolve together and regulate each other’s growth. Evidence for this comes in part from observations of the central bulges of galaxies – the more massive the central bulge, the larger the supermassive black hole. This latest report demonstrates a supermassive black hole and its high-speed winds greatly affect the host galaxy.
As the black hole bulks up in size, its winds push vast amounts of matter outward through the galaxy, which ultimately stops new stars from forming.
Because PDS 456 is relatively close, by cosmic standards, it is bright and can be studied in detail.
This black hole gives astronomers a unique look into a distant era of our Universe, around 10 billion years ago, when supermassive black holes and their raging winds were more common and possibly shaped galaxies as we see them today.
“For an astronomer, studying PDS 456 is like a paleontologist being given a living dinosaur to study. We are able to investigate the physics of these important systems with a level of detail not possible for those found at more typical distances, during the Age of Quasars,” said study co-author Dr Daniel Stern of NASA’s Jet Propulsion Laboratory in Pasadena.
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E. Nardini et al. 2015. Black hole feedback in the luminous quasar PDS 456. Science, vol. 347, no. 6224, pp. 860-863; doi: 10.1126/science.1259202
