Spitzer finds distant galaxies grazed on gas

Jun 30, 2011
This split view shows how a normal spiral galaxy around our local universe (left) might have looked back in the distant universe, when astronomers think galaxies would have been filled with larger populations of hot, bright stars (right). Image credit: NASA/JPL-Caltech/STScI

(PhysOrg.com) -- Galaxies once thought of as voracious tigers are more like grazing cows, according to a new study using NASA's Spitzer Space Telescope.

Astronomers have discovered that galaxies in the distant, continuously ingested their star-making fuel over long periods of time. This goes against previous theories that the galaxies devoured their fuel in quick bursts after run-ins with other galaxies.

"Our study shows the merging of was not the dominant method of galaxy growth in the ," said Ranga-Ram Chary of NASA's Spitzer Science Center at the California Institute of Technology in Pasadena, Calif. "We're finding this type of galactic cannibalism was rare. Instead, we are seeing evidence for a mechanism of galaxy growth in which a typical galaxy fed itself through a steady stream of gas, making stars at a much faster rate than previously thought."

Chary is the principal investigator of the research, appearing in the Aug. 1 issue of the . According to his findings, these grazing galaxies fed steadily over periods of hundreds of millions of years and created an unusual amount of plump stars, up to 100 times the mass of our sun.

"This is the first time that we have identified galaxies that supersized themselves by grazing," said Hyunjin Shim, also of the Spitzer Science Center and lead author of the paper. "They have many more than our ."

Galaxies like our Milky Way are giant collections of stars, gas and dust. They grow in size by feeding off gas and converting it to . A long-standing question in astronomy is: Where did distant galaxies that formed billions of years ago acquire this stellar fuel? The most favored theory was that galaxies grew by merging with other galaxies, feeding off gas stirred up in the collisions.

Chary and his team addressed this question by using Spitzer to survey more than 70 remote galaxies that existed 1 to 2 billion years after the Big Bang (our universe is approximately 13.7 billion years old). To their surprise, these galaxies were blazing with what is called H alpha, which is radiation from hydrogen gas that has been hit with ultraviolet light from stars. High levels of H alpha indicate stars are forming vigorously. Seventy percent of the surveyed galaxies show strong signs of H alpha. By contrast, only 0.1 percent of galaxies in our local universe possess this signature.

Previous studies using ultraviolet-light telescopes found about six times less star formation than Spitzer, which sees infrared light. Scientists think this may be due to large amounts of obscuring dust, through which infrared light can sneak. Spitzer opened a new window onto the galaxies by taking very long-exposure infrared images of a patch of sky called the GOODS fields, for Great Observatories Origins Deep Survey.

Further analyses showed that these galaxies furiously formed stars up to 100 times faster than the current star-formation rate of our Milky Way. What's more, the star formation took place over a long period of time, hundreds of millions of years. This tells astronomers that the galaxies did not grow due to mergers, or collisions, which happen on shorter timescales. While such smash-ups are common in the universe -- for example, our Milky Way will merge with the Andromeda galaxy in about 5 billion years -- the new study shows that large mergers were not the main cause of galaxy growth. Instead, the results show that distant, giant galaxies bulked up by feeding off a steady supply of gas that probably streamed in from filaments of dark matter.

Chary said, "If you could visit a planet in one of these , the sky would be a crazy place, with tons of bright stars, and fairly frequent supernova explosions."

Explore further: Quest for extraterrestrial life not over, experts say

Related Stories

'Big baby' galaxy found in newborn Universe

Sep 28, 2005

The NASA/ESA Hubble Space Telescope and NASA’s Spitzer Space Telescope have teamed up to 'weigh' the stars in distant galaxies. One of these galaxies is not only one of the most distant ever seen, but it appears to be unusually ...

Antennae Galaxies

May 19, 2008

This image of the Antennae galaxies is the sharpest yet of this merging pair of galaxies. During the course of the collision, billions of stars will be formed. The brightest and most compact of these star ...

Colliding galaxies make love, not war

Oct 17, 2006

A new Hubble image of the Antennae galaxies is the sharpest yet of this merging pair of galaxies. As the two galaxies smash together, billions of stars are born, mostly in groups and clusters of stars. The ...

Survey Reveals Building Block Process For Biggest Galaxies

Apr 12, 2006

A new study of the universe's most massive galaxy clusters shows how mergers play a critical role in their evolution. Astronomers used the twin Gemini Observatory instruments in Hawaii and Chile, and the Hubble Space Telescope ...

Recommended for you

Quest for extraterrestrial life not over, experts say

Apr 18, 2014

The discovery of an Earth-sized planet in the "habitable" zone of a distant star, though exciting, is still a long way from pointing to the existence of extraterrestrial life, experts said Friday. ...

Continents may be a key feature of Super-Earths

Apr 18, 2014

Huge Earth-like planets that have both continents and oceans may be better at harboring extraterrestrial life than those that are water-only worlds. A new study gives hope for the possibility that many super-Earth ...

Exoplanets soon to gleam in the eye of NESSI

Apr 18, 2014

(Phys.org) —The New Mexico Exoplanet Spectroscopic Survey Instrument (NESSI) will soon get its first "taste" of exoplanets, helping astronomers decipher their chemical composition. Exoplanets are planets ...

User comments : 5

Adjust slider to filter visible comments by rank

Display comments: newest first

kevinrtrs
2 / 5 (8) Jul 01, 2011
Further analyses showed that these galaxies furiously formed stars up to 100 times faster than the current star-formation rate of our Milky Way. What's more, the star formation took place over a long period of time, hundreds of millions of years.

So is this now the explanation for why there are OLD looking galaxies far out in space, instead of the expected youngish looking ones that the Big Bang predicts? Or is there now a strange correlation of distance from us to speed of galaxy formation?

Also, where are the remnants of the super novas that should have accumulated over these supposed hundreds of millions of years? There is far, far fewer than the expected number that is supposed to have occurred.
Tuxford
1 / 5 (3) Jul 01, 2011
Would not the galaxies sampled consist generally of the largest brightest most actively forming galaxies at such distances? In LaViolette's core ejection model, the larger galaxies with the more massive cores which nucleate and eject new gas much more rapidly as seed material than in smaller galaxies. These bigger galaxies would naturally experience much more rapid growth. I suspect the conclusions reached are based somewhat on natural data selection effects.

And how did these massive galaxies condense slowly so soon after the BB 'non'-event? Accepted cosmological 'conclusions' and a few physics 'laws' need to be re-visited. Nature, please obey the law!
TheRedComet
3 / 5 (2) Jul 01, 2011

So is this now the explanation for why there are OLD looking galaxies far out in space, instead of the expected youngish looking ones that the Big Bang predicts? Or is there now a strange correlation of distance from us to speed of galaxy formation?

Also, where are the remnants of the super novas that should have accumulated over these supposed hundreds of millions of years? There is far, far fewer than the expected number that is supposed to have occurred.

Read about Einsteins theory of general relativity if you want to explore that thought further.

Super novas created a large percentage of the atoms above oxygen through nucleosynthesis.
frajo
1 / 5 (3) Jul 01, 2011
Instead, the results show that distant, giant galaxies bulked up by feeding off a steady supply of gas that probably streamed in from filaments of dark matter.
Sometimes I'm wondering whether there's any cosmological question which will not immediately be answerable by that magical ingredient called "dark matter".
omatumr
1 / 5 (4) Jul 01, 2011
Galaxies once thought of as voracious tigers are more like grazing cows


Thanks, Ranga-Ram Chary and associates of NASA's Spitzer Science Center at the California Institute of Technology, for backing away from the story that galaxies "voraciously" consume hydrogen.

They do not.

Galaxies of neutron stars (future stellar cores) produced by fragmentation generate and gravitationally retain a cloud of decay products (mostly H and He) that emits photons and glows brightly as stellar photosphere, thus hiding the neutron star from view.

See: "Neutron Repulsion", The APEIRON Journal, in press, 19 pages (2011)

http://arxiv.org/...2.1499v1

With kind regards,
Oliver K. Manuel

More news stories

Easter morning delivery for space station

Space station astronauts got a special Easter treat: a cargo ship full of supplies. The shipment arrived Sunday morning via the SpaceX company's Dragon cargo capsule.

Making graphene in your kitchen

Graphene has been touted as a wonder material—the world's thinnest substance, but super-strong. Now scientists say it is so easy to make you could produce some in your kitchen.