Astronomers discover that galaxies are either asleep or awake

Jun 21, 2011
Bluer galaxies are actively “awake” and forming stars, while redder galaxies have shut down and are “asleep.” (Image: NASA, ESA, S. Beckwith (STScI) and the HUDF team)

(PhysOrg.com) -- Astronomers have probed into the distant universe and discovered that galaxies display one of two distinct behaviors: they are either awake or asleep, actively forming stars or are not forming any new stars at all.

Scientists have known for several years that galaxies in the nearby universe seem to fall into one of these two states. But a new survey of the distant universe shows that even very young galaxies as far away as 12 billion are either awake or asleep as well, meaning galaxies have behaved this way for more than 85 percent of the history of the universe. (Looking at galaxies farther away is like looking back in time when they were much younger, because of how long it takes the light they emit to reach us here on .)

“The fact that we see such young galaxies in the distant universe that have already shut off is remarkable,” said Kate Whitaker, a Yale University graduate student and lead author of the paper, which is published in the June 20 online edition of the Astrophysical Journal.

In order to determine whether the galaxies were asleep or awake, Whitaker and her colleagues fabricated a new set of filters, each one sensitive to different wavelengths of light, which they used on a 4-meter Kitt Peak telescope in Arizona. They spent 75 nights peering into the and collecting light from 40,000 galaxies ranging in distance from the out to 12 billion light years away. The resulting survey is the deepest and most complete ever made at those distances and wavelengths of light.

The team deciphered the galaxies’ dual behavior based on the color of the light they emit. Because of the physics of star formation, active, wakeful galaxies appear bluer, while the light emitted by passive, sleepy galaxies tends toward the redder end of the spectrum.

The researchers found that there are many more active galaxies than passive ones, which agrees with the current thinking that galaxies start out actively forming stars before eventually shutting down.

“We don’t see many galaxies in the in-between state,” said Pieter van Dokkum, a Yale astronomer and another author of the paper. “This discovery shows how quickly galaxies go from one state to the other, from actively forming stars to shutting off.”

Whether the sleeping galaxies have completely shut down remains an open question, Whitaker said. However, the new study suggests the active galaxies are forming stars at rates about 50 times greater than their sleepy counterparts.

“Next, we hope to determine whether galaxies go back and forth between waking and sleeping or whether they fall asleep and never wake up again,” van Dokkum said. “We’re also interested in how long it takes to fall asleep, and whether we can catch one in the act of dozing off.”

Explore further: First potentially habitable Earth-sized planet confirmed: It may have liquid water

More information: Citation: arXiv:1105.4609v1

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User comments : 18

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Decimatus
4.7 / 5 (12) Jun 21, 2011
And Neutron Repulsion in 3...2....1....
omatumr
1.3 / 5 (7) Jun 21, 2011
Thanks for the story.

I personally doubt most "either/or" conclusions, but that is a good place to start!

Thanks, also to Decimatus for looking ahead.

With kind regards,
Oliver K. Manuel
Former NASA Principal
Investigator for Apollo
Decimatus
4.5 / 5 (4) Jun 21, 2011
I don't like either/or conclusions either. Especially with something as complicated as star formation in galaxies.

Statements such as "X Galaxy ALREADY shut off star formation is too final in it's wording.

The universe is quite a dynamic place. A galaxy that is shut off today may not be a billion years from now.

I wonder how much effect intergalactic dust has on things such as star formation in these galaxies. A million lightyears of "low density" dust and debris adds to to be a phenomenal amount of matter in reality.

Seems like all you would need is for a galaxy to enter a higher density area of dust for a string of supernova's and star formation to follow.
Tuxford
1.6 / 5 (7) Jun 21, 2011
Once again this observation supports LaViolette's inside-out growth model, and also hints that his predicted superwave phenomenon may be valid. Last year it was shown that galactic core ejections can shut off rapidly.
http://www.physor...ead.html
This year it was shown that galactic cores can turn on in an instant.
http://www.physor...ent.html
Generally, the active state is a small percentage in the life of a galaxy. No doubt there are exceptions. Currently, our galaxy is in a quiescent state, though the Fermi bubbles indicate this is not always the case. The Crab nebula is currently illuminated by a passing superwave, which triggered the last ice age.
http://www.spaced...999.html
http://nanobionex...e-earth/

yyz
3.7 / 5 (6) Jun 21, 2011
"I don't like either/or conclusions either. Especially with something as complicated as star formation in galaxies."

I think that's just a strawman argument by Oliver. Notice the comment by coauthor van Dokkum: We dont see many galaxies in the in-between state.....This discovery shows how quickly galaxies go from one state to the other, from actively forming stars to shutting off.

Clearly, not all galaxies are "quiescent" or "star-forming"; some intermediate types ARE observed.

The current study looked at 13,000 galaxies with redshifts between z=1.5 & z=3. Accurate photometry of this sample revealed a "a clear bimodal color distribution between quiescent and star-forming galaxies that persists to z~3, a higher redshift than has been probed so far." (from the abstract): http://arxiv.org/abs/1105.4609

con't
yyz
4.3 / 5 (6) Jun 21, 2011
"Statements such as "X Galaxy ALREADY shut off star formation is too final in it's wording.

The universe is quite a dynamic place. A galaxy that is shut off today may not be a billion years from now."

Note van Dokkum's comments above: Next, we hope to determine whether galaxies go back and forth between waking and sleeping or whether they fall asleep and never wake up again, van Dokkum said. Were also interested in how long it takes galaxies to fall asleep, and whether we can catch one in the act of dozing off.

Clearly they are planning future observations of this sample of galaxies to study how galaxies may swing between quiescent and star-forming modes.

Also note - some galaxies may have nearby reservoirs of gas to fuel star formation; gravitational encounters with other galaxies might be enough to induce SF. Mergers with gas-rich galaxies may also induce SF, while some galaxies have been observed accreting gas directly from the intergalactic medium (leading to SF).

Tuxford
1.6 / 5 (7) Jun 21, 2011
Let's not forget another recent observation: that galaxies grow from a 'seed' from the inside-out. This active/quiescent state change is likely part of this process. The study concludes incorrectly in my view, that the collapsed gas seed then accumulates stars from other galaxies. I believe if that were indeed the case, we would see far more colliding and evenly distributed galaxies in the universe.

http://www.physor...ace.html
omatumr
1 / 5 (5) Jun 21, 2011
Let's not forget another recent observation: that galaxies grow from a 'seed' from the inside-out.

http://www.physor...ace.html


I agree.

Many others have noticed the dominance of fragmentation patterns in the cosmos.

See: "On the cosmic nuclear cycle and the similarity of nuclei
and stars", Journal of Fusion Energy 25, 107-114 (2006);

http://xxx.lanl.g.../0511051

Decimatus points out the energy source that causes fragmentation in the first comment posted here.
SemiNerd
4.2 / 5 (5) Jun 21, 2011
omatumr - I suspect that Decimatus was gently poking fun at you. You seem to believe that neutron repulsion accounts for every cosmological phenomena presented.

Given some shred of evidence that there is a repulsive force between neutrons under ANY conditions would help bolster your credibility. Since real measurements could only be made at the big labs, would it be too much to ask for actual peer reviewed articles in established physics publications?

If not, then we are left with speculation and phenomena that have far simpler theories to explain them than neutron repulsion.
HannesAlfven
1.3 / 5 (7) Jun 22, 2011
This is an interesting observation, because within the plasma universe model, blue stars represent higher electrical stress than red stars. Within that view, the blue galaxies are electrically stimulated.

They are also, within that view, electrically connected with filamentary plasma cables. This observation presents a fascinating opportunity to try to understand something about the power source -- which, within the electrical framework, is something we know nothing about. It is akin to the conventional model's CMB.

I wonder if there is a message in the bottle.
kevinrtrs
1.3 / 5 (12) Jun 22, 2011
The fact that we see such young galaxies in the distant universe that have already shut off is remarkable,

So now we have another conundrum for the big bang theory. First its blue stars everywhere even in the milky way and as far out as 13 billion light years away, then we have fully formed galaxies at vast distances instead of all new ones and now this. When do we chuck out the big bang theory? WHEN?
Deesky
4.5 / 5 (8) Jun 22, 2011
When do we chuck out the big bang theory? WHEN?

When a better theory comes along. So far, it's easily the best.
RobertKarlStonjek
1 / 5 (1) Jun 22, 2011
Oh dear, the BBT predicted that early galaxies were prodigious star generators, older ones are quiet. Now it seems that there is no difference between local and distant galaxies: active and quiescent galaxies are found everywhere.
dutchman
not rated yet Jun 22, 2011
Oh dear, the BBT predicted that early galaxies were prodigious star generators, older ones are quiet. Now it seems that there is no difference between local and distant galaxies: active and quiescent galaxies are found everywhere.


I don't think that invalidates the basic principle of the BBT. My main issue with "the theory" has been the apparent violation of the principle of entropy. With this I do not intend to open the door for the creationist - puleaze NO!

I understand some (real) scientists are trying to solve that issue. It's just that whatever I've read so far, has been a bit too esoteric. Too abstract.
Deesky
5 / 5 (1) Jun 22, 2011
Oh dear, the BBT predicted...

Oh dear, what do you propose is better than BBT?
RobertKarlStonjek
1 / 5 (1) Jun 23, 2011
A weak theory and no viable alternative does not bode well for the cosmological community. It would be prudent, for the long term health of cosmology (health=funding) if they had an alternative up their sleeve.

As much as I'd like to propose some half baked idea as an alternative, viable alternative models must come from within the scientific community ~ patching a model up after the fact is not a good look eg dark energy pops up after the Universe is found to be misbehaving with regard to its contractual obligations (expansion accelerating).
Deesky
5 / 5 (3) Jun 23, 2011
A weak theory and no viable alternative does not bode well for the cosmological community.

There is no viable alternative because the current theory far surpasses anything else. That you think it's 'weak' is your problem, not the scientific community's.
RobertKarlStonjek
1 / 5 (1) Jun 30, 2011
Science is an adversarial system and while there are contrary positions within the BB community on particular points, no-one is strength testing the main assumptions and that is not healthy considering the vast discoveries waiting to be made. Further adjustments, some major ones, will have to be made upon those discoveries.

With a more serious challenge, the BBT would have to cover the bases with a wider theoretical spread than it currently has and so will be less likely to be caught short, such as when the expansion of the universe was discovered to be accelerating and before that when the ripples in the CMBR were 1,000 times smaller than the nearest estimate by any of the then current models.

Scientists get lazy when they don't have to prove some part of a theory or model due to lack of opposition requiring that proof. This is how science has progressed throughout last two centuries, and the consensus on the BBT after Hoyle has seen the biggest surprises totally unanticipated.

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