Ultra-fast outflows help monster black holes shape their galaxies

Feb 27, 2012 by Francis Reddy
The supermassive black holes in active galaxies can produce narrow particle jets (orange) and wider streams of gas (blue-gray) known as ultra-fast outflows, which are powerful enough to regulate both star formation in the wider galaxy and the growth of the black hole. Inset: A close-up of the black hole and its accretion disk. Artist concept credit: ESA/AOES Medialab

(PhysOrg.com) -- A curious correlation between the mass of a galaxy's central black hole and the velocity of stars in a vast, roughly spherical structure known as its bulge has puzzled astronomers for years. An international team led by Francesco Tombesi at NASA's Goddard Space Flight Center in Greenbelt, Md., now has identified a new type of black-hole-driven outflow that appears to be both powerful enough and common enough to explain this link.

Most big galaxies contain a central black hole weighing millions of times the sun's mass, but galaxies hosting more massive also possess bulges that contain, on average, faster-moving stars. This link suggested some sort of between a galaxy's black hole and its star-formation processes. Yet there was no adequate explanation for how a monster black hole's activity, which strongly affects a region several times larger than our solar system, could influence a galaxy's bulge, which encompasses regions roughly a million times larger.

"This was a real conundrum. Everything was pointing to supermassive black holes as somehow driving this connection, but only now are we beginning to understand how they do it," Tombesi said.

Active black holes acquire their power by gradually accreting -- or "feeding" on -- million-degree gas stored in a vast surrounding disk. This hot disk lies within a corona of , and while both are strong X-ray sources, this emission cannot account for galaxy-wide properties. Near the inner edge of the disk, a fraction of the matter orbiting a black hole often is redirected into an outward particle jet. Although these jets can hurl matter at half the speed of light, computer simulations show that they remain narrow and deposit most of their energy far beyond the galaxy's star-forming regions.

Astronomers suspected they were missing something. Over the last decade, evidence for a new type of black-hole-driven outflow has emerged. At the centers of some active galaxies, X-ray observations at wavelengths corresponding to those of fluorescent iron show that this radiation is being absorbed. This means that clouds of cooler gas must lie in front of the X-ray source. What's more, these absorbed spectral lines are displaced from their normal positions to shorter wavelengths -- that is, blueshifted, which indicates that the clouds are moving toward us.

In two previously published studies, Tombesi and his colleagues showed that these clouds represented a distinct type of outflow. In the latest study, which appears in the Feb. 27 issue of Monthly Notices of the Royal Astronomical Society, the researchers targeted 42 nearby active galaxies using the European Space Agency's XMM-Newton satellite to hone in on the location and properties of these so-called "ultra-fast outflows" -- or UFOs, for short. The galaxies, which were selected from the All-Sky Slew Survey Catalog produced by NASA's Rossi X-ray Timing Explorer satellite, were all located less than 1.3 billion light-years away.

The outflows turned up in 40 percent of the sample, which suggests that they're common features of black-hole-powered galaxies. On average, the distance between the clouds and the central black hole is less than one-tenth of a light-year. Their average velocity is about 14 percent the speed of light, or about 94 million mph, and the team estimates that the amount of matter required to sustain the outflow is close to one solar mass per year -- comparable to the accretion rate of these black holes.

"Although slower than particle jets, UFOs possess much faster speeds than other types of galactic outflows, which makes them much more powerful," Tombesi explained.

"They have the potential to play a major role in transmitting feedback effects from a black hole into the galaxy at large."

By removing mass that would otherwise fall into a supermassive black hole, ultra-fast outflows may put the brakes on its growth. At the same time, UFOs may strip gas from star-forming regions in the galaxy's bulge, slowing or even shutting down star formation there by sweeping away the gas clouds that represent the raw material for new stars. Such a scenario would naturally explain the observed connection between an active galaxy's black hole and its bulge stars.

Tombesi and his team anticipate significant improvement in understanding the role of ultra-fast outflows with the launch of the Japan-led Astro-H X-ray telescope, currently scheduled for 2014. In the meantime, he intends to focus on determining the detailed physical mechanisms that give rise to UFOs, an important element in understanding the bigger picture of how active galaxies form, develop and grow.

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User comments : 10

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rain_atherstone
3 / 5 (2) Feb 27, 2012
Um, no, you said it in plain English. If Magnetism is a constant (which it is,) and Gravity is it's scaler, (Time, a scaler as well) and so will it's perpetuating power-source (black hole). The bigger the solar system/tesseract, the bigger the gravitational forcefield, or quantum...yada yada....lol It's ALL relative!
Callippo
1.7 / 5 (7) Feb 27, 2012
In dense aether model the young black holes are gigantic fountains, which are emanating photons and neutrinos via polar jets. These particles recombine mutually and fall back again into center of galaxy along spiral. This forms the flat shape of galaxies at their mature state. The flow of neutrinos continues a long after the central black hole evaporated its excessive matter.
Lurker2358
not rated yet Feb 27, 2012
In dense aether model the young black holes are gigantic fountains, which are emanating photons and neutrinos via polar jets. These particles recombine mutually and fall back again into center of galaxy along spiral.


Pssssst...

I did the calculation for this a few hours ago.

Gravity only slows the winds by a few tens of kilometers per second by the time they reach the radius of a Milky Way sized galaxy. thus the winds are still moving about 13.9% of the speed of light by the time they exit a typical galaxy, regardless of which direction they were moving in initially, which is about 75 to 100 times greater than galactic escape velocity at that distance.

any other bright ideas?

Yeah, intuitively, you think it should get caught, but it doesn't. It's just too much energy involved. The expanding winds will pretty much never be stopped by anything in the universe, except a head-on collision with massive objects or perhaps opposing winds from other galaxies...
MorituriMax
4.2 / 5 (5) Feb 27, 2012
blah blah aether voodoo ---> then a miracle happened <--- explains anything.
Deesky
3.4 / 5 (5) Feb 27, 2012
"Although slower than particle jets, UFOs possess much faster speeds than other types of galactic outflows, which makes them much more powerful," Tombesi explained.

I would suggest that Tombesi stops using the unfortunate acronym 'UFO'. There are enough whackos around here without baiting them! :)
Graeme
5 / 5 (1) Feb 27, 2012
Lurker2358 - your wind is stoppable, as the front edge of it hits a gas cloud it will be slowed down, and the the wind behind will catch up. Clumpiness in the gas feeding the backhole will make a variation in wind blowing out, which will turn into clumps. Another feature is that the alignment of the jet will depend on the average flow of material entering the accretion disk. This may not match the blackhole spin, and this will cause the jet to precess or change in direction. This will reduce the cahnce of your jet firing its way half way accross the universe.
Lurker2358
1 / 5 (1) Feb 27, 2012
Graeme:

It IS stoppable, but it takes a head-on collision of the particles.

Also, if you work out kinetic energy for the mass of particles, you find just how much energy there is.

Each particle from the wind has enough kinetic energy to ideally accelerate about 3100 times it's own mass to galactic escape velocity through collisions.

so it can stop, but it needs to hit something massive, like a planet, a star, or a very, very dense nebula.
Tuxford
1 / 5 (3) Feb 29, 2012
Astronomers must acknowledge these recent observations of massive outflows in all directions with no reasonable explanation of an external source for this material. Such outflows would disrupt the formation of any accretion disk. Rather than providing negative feedback, shutting off the star formation process, recent observations of hot young stars are detected in clusters and galactic centers. These young stars are linked to these outflows as well.

http://www.physor...ars.html

In LaViolettes model, these internally-generated outflows provide positive feedback, enhancing the conditions for new matter generation and core star instability. The gas is likely ejected in all directions, which explains the link between the galactic bulge formation and the supermassive core star. As uncomfortable as this explanation seems, it seems to fit.
Tuxford
1 / 5 (2) Feb 29, 2012
Under some circumstances where the gas clouds remain close to the core star, accelerated positive feedback can grow the core into an ultra-luminous galaxy, as likely in Arp 220.

http://www.physor...arp.html
jsdarkdestruction
5 / 5 (1) Feb 29, 2012
you seem to have forgotten to include the important points of laviolettes theory that their is a secret code hidden in the location of stars warning us of an impending galactic superwave hidden their during the last ice age to be rediscovered by laviolette now as we approach 2012 and the disaster is imminent. the code laviolette found also somehow reveals how matter is created from the centers of stars/galaxies. the worldwide scientific community is just engaging in a conspiracy to supress laviolettes great discovery. Thats right, he says he found a code hidden in the stars of the night sky and astrology/studying the zodiac should be a mainstream scientific field and philosophy should be re-united with science. you always forget that part tuxford.

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