The feeding habits of teenage galaxies

March 14, 2012
This deep view of a tiny patch of sky in the constellation of Cetus (the Sea Monster) shows a selection of galaxies, marked with red crosses, that were used in a new survey of the feeding habits of young galaxies as they grew through cosmic time. Each of the tiny blobs, galaxies seen as they were between three and five billion years after the Big Bang, has been studied in detail using ESO's VLT and the SINFONI instrument. Credit: ESO/CFHT

( -- New observations made with ESO’s Very Large Telescope are making a major contribution to understanding the growth of adolescent galaxies. In the biggest survey of its kind astronomers have found that galaxies changed their eating habits during their teenage years - the period from about 3 to 5 billion years after the Big Bang. At the start of this phase smooth gas flow was the preferred snack, but later, galaxies mostly grew by cannibalising other smaller galaxies.

Astronomers have known for some time that the earliest were much smaller than the impressive spiral and elliptical galaxies that now fill the Universe. Over the lifetime of the cosmos galaxies have put on a great deal of weight but their food, and eating habits, are still mysterious. A new survey of carefully selected galaxies has focussed on their teenage years — roughly the period from about 3 to 5 billion years after the Big Bang.

By employing the state-of-the-art instruments on ESO's Very Large Telescope an international team is unravelling what really happened. In more than one hundred hours of observations the team has collected the biggest ever set of detailed observations of gas-rich galaxies at this early stage of their development.

"Two different ways of growing galaxies are competing: violent merging events when larger galaxies eat smaller ones, or a smoother and continuous flow of gas onto galaxies. Both can lead to lots of new stars being created," explains Thierry Contini (IRAP, Toulouse, France), who leads the work.

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This zoom sequence starts with a view of the faint constellation of Cetus (The Sea Monster). We then close in on a region of sky close to the famous red variable star Mira. This region contains a selection of galaxies that were used in a new survey of the feeding habits of young galaxies as they grew through cosmic time. Each of the tiny blobs, marked with red crosses, are galaxies seen as they were between three and five billion years after the Big Bang. They have been studied in detail using ESO’s VLT and the SINFONI instrument. The colour maps at the end of the video show the motions of the gas in the galaxies. Blue indicates that the gas is moving towards us, compared to the galaxy as a whole, and red that the gas is receding. These colours allow astronomers to see if the galaxies is rotating like a disc or has some other behaviour. Credit: ESO/A. Fujii/Digitized Sky Survey 2/CFHT. Music: John Dyson (from the album Moonwind).

The new results point toward a big change in the cosmic evolution of galaxies, when the Universe was between 3 and 5 billion years old. Smooth gas flow (eso1040) seems to have been a big factor in the building of galaxies in the very young Universe, whereas mergers became more important later.

"To understand how galaxies grew and evolved we need to look at them in the greatest possible detail. The SINFONI instrument on ESO's VLT is one of the most powerful tools in the world to dissect young and distant galaxies. It plays the same role that a microscope does for a biologist," adds Thierry Contini.

Distant galaxies like the ones in the survey are just tiny faint blobs in the sky, but the high image quality from the VLT used with the SINFONI instrument means that the astronomers can make maps of how different parts of the galaxies are moving and what they are made of. There were some surprises.

"For me, the biggest surprise was the discovery of many galaxies with no rotation of their gas. Such galaxies are not observed in the nearby Universe. None of the current theories predict these objects," says Benoit Epinat, another member of the team.

"We also didn't expect that so many of the young galaxies in the survey would have heavier elements concentrated in their outer parts — this is the exact opposite of what we see in galaxies today," adds Thierry Contini.

The team are only just starting to explore their rich set of observations. They plan to also observe the galaxies with future instruments on the VLT as well as using ALMA to study the cold gas in these galaxies. Looking further into the future the European Extremely Large Telescope will be ideally equipped to extend this type of study deeper into the early Universe.

Explore further: Gamma-ray burst reveals surprising ingredients of early galaxies

More information: This research was presented in four papers describing the MASSIV survey that will appear in the journal Astronomy & Astrophysics.

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1.6 / 5 (7) Mar 14, 2012
No surprise here. Galaxies have never been shown to be rotating by optical displacement of their stars; only inferred by Doppler 'interpretation'. And most stars within our own galaxy have a radial velocity component directed toward the galactic anti-center. With the massive outflows now observed from the galactic core of so many galaxies, it is time to reconsider galactic evolution.

Galaxies grow like snowflakes from the inside out, not the reverse, in general. Thus, the older stars with higher metallicity would likely be concentrated in the outer regions. See LaViolette's 'continuous creation' model. Astronomers: there is no need to remain confused. Physicists have led you astray into the fantasyland of the Big Bang.
4.5 / 5 (2) Mar 14, 2012
Are you now saying that line-of-sight velocities can't be measured by the doppler shift of electromagnetic radiation? Try that one in traffic court and tell us how that works out for you.
1 / 5 (2) Mar 14, 2012
Galaxies grow like snowflakes from the inside out, not the reverse, in general

I do support the steady state model too, but IMO both ways are possible, the large galaxies grow inside out, the small ones rather with accretion. After all, the same duality - just at smaller scale - we can observe at the case of growth of planetesimals from protoplanetary disk: at the dense central areas of this disk the planets grow from bottom up, at the sparse areas the classical models is more preferred. We discussed it just recently. http://www.physor...ion.html
1.5 / 5 (10) Mar 14, 2012
No doubt accretion plays a role, as likely in this example, where there is not central core.

In this case, LaViolette's model might suggest that over long periods of time, new matter nucleated in deep space forming vast gas clouds, which slowly condensed to form this sparsely distributed structure through accretion.

And no doubt Doppler effect remains a major component of the red shift, just not the sole cause on galactic scales, the effect of which may not be measureable in an Earthbound laboratory. Just because we cannot measure the secondary cause does not mean it does not exist. It may be our limitation. We should not formulate another 'law', unless we live in Texas. Nature need not obey our 'human' laws.
3 / 5 (6) Mar 14, 2012
Tuxford, why not mention how laviolette came up with this theory.....he says he found a coded message in the stars left warning us of an galactic superwave disaster in 2012 that also told him about how new matter is created from nothing. You always seem to forget that part. seems to be a big part of the theory....
1.8 / 5 (20) Mar 15, 2012
Doesn't LaViolette also claim that teenage galaxies grow by consuming protoplanetary chips and soda?

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