Astronomers locate protogalaxy linked to the cosmic web

SAN DIEGO, Aug. 6 (UPI) -- Astronomers at Caltech have identified a protogalaxy 10 billion light-years from Earth -- a still-forming galaxy accreting primordial gas sourced directly from the streams of cosmic material produced by the Big Bang.

Researchers say the protogalaxy -- which was observed using the Palomar Observatory's Cosmic Web Imager -- is linked to what they call the cosmic web.

Cosmologists have a variety of explanations for how the universe began to take shape post-Big Bang. One explanatory model, called the cold-flow model, posits that streams of cold gas spread through the early universe forming a web that distributed star-forming materials to young galaxies.

Scientists were able to build a map of the protogalaxy by studying the varying wavelengths of the light emanating from protogalactic disk. The imaging revealed a swirling disk of gas 400,000 light-years across -- half the light moving away from Earth and half moving toward. Also imaged was a filament or stream of gas, which was also moving toward Earth at the same speed -- suggesting the filament is a feeder stream for the forming galaxy.

"This is the first smoking-gun evidence for how galaxies form," Christopher Martin, professor of physics at Caltech and principal investigator on Cosmic Web Imager project, said in a press release. "Even as simulations and theoretical work have increasingly stressed the importance of cold flows, observational evidence of their role in galaxy formation has been lacking."

Martin is the lead author of a new paper on the game-changing discovery, published this week in the journal Nature.

"The images plainly show that there is a rotating disk -- you can see that one side is moving closer to us and the other is moving away," Martin added. "And you can also see that there's a filament that extends beyond the disk."

The new findings -- and the cold-flow model scientists say they support -- stand in contrast to the standard model of galaxy formation, which credits the expansion of star-forming gas and matter to the large scale collapse of dark matter halos.

While the findings may shift the conversation, few things in science arrive with complete certainty.

"Overall, it's hard to say with certainty that they're definitely seeing a cold-flow disk -- as opposed to some other phenomenon that just happens to look like a cold-flow disk," Kyle Stewart, a researcher at California Baptist University who simulates cold-flow disks, told Sky & Telescope. "But when you look at all the observable properties of cold-flow disks from the simulations to determine what they should look like in the real universe, in my opinion, it's amazingly similar to what these authors have just observed."

But Martin says furthers proof is coming. He and his colleagues have already identified protogalactic disks being fed by similar filaments.