EMBARGOED FOR 2:00 pAstronomers have peered through gas, dust and general chaos to get an unprecedented look at the vicinity of a hefty black hole at the heart of one of the earliest galaxies in the universe.
And they've seen just what they expected: lots of baby stars and more on the way.
The finding provides important direct evidence for an emerging theory of galaxy formation, termed co-evolution, which holds that black holes and galaxies evolved together and that neither could have alone managed to mastermind the rapid star birth known to take place in the early universe.
"This unique look into a very distant, young galaxy gives us unprecedented insight into the process that produced both tremendous numbers of stars and supermassive black holes in forming galaxies," said Chris Carilli, of the National Radio Astronomy Observatory (NRAO) in Socorro, NM, leader of the research team. "This work strongly supports the idea that the stars and the black holes formed simultaneously."
Astronomers had already made a similar connection in more nearby galaxies -- those of the more modern universe. But they could only infer that the process went on in the early universe.
There was a time when competing theories suggested perhaps black holes came first, then galaxies formed around them, or that galaxies and stars formed, followed by the evolution of central, supermassive black holes. Over the past three years or so almost all experts have come to believe that the two processes feed off each other: The cloud of gas that becomes food for a black hole also fuels the formation of new stars as the gas moves toward the center of a fledgling galaxy.
The new study examined a bright galaxy known as a quasar, called PSS J2322+1944. It is about 12 billion light-years from Earth, seen when the universe was less than 2 billion years old, about 15 percent of its current age.
The intense radiation pouring from a quasar is thought to be created by both rapid star birth and intense activity around a central, voracious black hole that can weigh billions of times more than our Sun. Matter spiraling into the black hole approaches the speed of light and is superheated in a process that unleashes much radiation.
The intrinsic brightness makes quasars hard to study. It's much like trying to see the filament of a 100-watt light bulb. Worse, the radiation from so distant an object is severely reduced by the time it makes it to Earth.
Fortuitously an intervening galaxy served as a natural "gravitational lens" in this case, magnifying the radiation coming from the more distant quasar.
The observations were made with National Science Foundation's Very Large Array (VLA) radio telescope. The gravitational lens not only magnified the radio waves but distorted them into what's called an Einstein Ring. Most important, the magnification made it possible to detect carbon monoxide (CO), an important component of the gas that forms stars.
| How a Gravitational Lens Works | | 
Light rays (the gray arrows) from a distant galaxy or galaxies (to the right in the image) are bent by gravity when passing another galaxy or cluster of galaxies (symbolized by the ball with blue glow in the center). When the light finally arrives at the Earth (to the left), it can be magnified. The distant object is often depicted more than once, because the light appears to come from multiple directions (the red arrows). The targeted object can also appear distorted.
Illustration: Martin Kornmesser &
Lars Lindberg Christensen, ST-ECF | | | |
"The gravitational lens provides that extra telescopic effect to 'blow-up' the inner regions of the galaxy, and the images reveal in a direct way a very active star forming disk," Carilli said in an e-mail interview.
The observations, reported today in the online version of the journal Science, show that while gas is falling into the central black hole of the quasar, stars are also forming around that black hole, at the rate of hundreds every year.
"This new observation gives strong support to the idea that large numbers of stars were forming in young galaxies at the same time that their central black holes were pulling in additional mass," said Pierre Cox, of the Institute for Space Astrophysics of the University of Paris.
The rate of star birth calculated by the new study means a large, normal elliptical galaxy could form in just 100 million years or so. That is important, because other observations have shown that this must be the case, though astronomers have never seen the rapid rate of star formation in action until now.
advertisement
