Old galaxies stick together in the young universe

Apr 04, 2008

UK astronomers have developed the most sensitive infrared map of the distant universe ever produced, revealing the origins of the most massive galaxies in the cosmos.

Using images obtained with the United Kingdom Infra-Red Telescope (UKIRT), astronomers combined data over a period of three years. This produced a map encompassing more than 100,000 galaxies over an area of sky four times the size of the full moon.

As light from the far reaches of the universe takes so long to reach observers on Earth, UKIRT allows astronomers to look back in time — more than ten billion years — producing images of the galaxies' infancy. The image is so large and so deep that thousands of galaxies can be studied at these early epochs for the first time.

By observing these galaxies at the infrared wavelength, astronomers can now peer even further back in time — as light is shifted towards the redder wavelength as it travels through the expanding universe.

Researchers at The University of Nottingham led the study, which also produced convincing evidence that galaxies which look old early in the history of the Universe reside in enormous clouds of invisible dark matter and will eventually evolve into the most massive galaxies that exist in the present day.

The distant galaxies identified are considered elderly because they are rich in old, red stars. But because the light from these systems has taken up to 10 billion years to reach Earth, they are seen as they appeared in the very early Universe, just four billion years after the Big Bang. The presence of such fully-evolved galaxies so early in the life of the cosmos is hard to explain and has been a major puzzle to astronomers studying how galaxies form and evolve.

The team used the deep UKIRT images to estimate the mass of the dark matter surrounding the old galaxies by measuring how strongly the galaxies cluster together. All galaxies are thought to form within massive halos of dark matter which collapse under their own gravity from a smooth distribution of matter after the Big Bang.

These halos are invisible to normal telescopes but their mass can be estimated through analysis of galaxy clustering.

“Luckily, even if we don't know what dark matter is, we can understand how gravity will affect it and make it clump together. We can see that the old, red galaxies clump together far more strongly than the young, blue galaxies, so we know that their invisible dark matter halos must be more massive,” said Will Hartley, PhD student at the University of Nottingham, who led the work into the clustering of old galaxies.

The halos surrounding the old galaxies in the early Universe are found to be extremely massive, containing material which is up to one hundred thousand billion times the mass of our Sun. In the nearby Universe, halos of this size are known to contain giant elliptical galaxies, the largest galaxies known.

“This provides a direct link to the present day Universe,” says Hartley, "and tells us that these distant old galaxies must evolve into the most massive but more familiar elliptical-shaped galaxies we see around us today. Understanding how these enormous elliptical galaxies formed is one of the biggest open questions in modern astronomy and this is an important step in comprehending their history.”

“I would compare these observations to the ice cores drilled deep into the Antarctic,” said Dr Sebastien Foucaud, who led the building of the new images into a map. “Just as they allow us to peer back in time, our ultra-deep image allows us to look back and observe galaxies evolving at different stages in cosmic history, all the way back to just one billion years after the big bang.

“We see galaxies ten times the mass of the Milky Way already in place at very early epochs. Now, for the first time, we are sampling a large enough volume of the distant universe to be able to see them in sufficient numbers and really pin down when they were formed.”

Will Hartley and Dr Foucaud presented their work at this week's National Astronomy Meeting held by the Royal Astronomical Society. They were joined by Dr Omar Almaini, Reader in Astronomy at the University and overall leader of the survey team.

Dr Almaini said: “We are leading the world with this project, and there is much more to come. We will continue taking data over the next few years, which will detect galaxies in the ever more distant Universe.”

The old galaxies were identified from images taken as part of the Ultra-Deep Survey (UDS), one element of a five-part project, the UKIRT Infrared Deep Sky Survey (UKIDSS), which commenced in 2005. UKIRT is the world's largest telescope dedicated solely to infrared astronomy, sited near the summit of Mauna Kea, Hawaii, at an altitude of 4194 metres (13760 feet) above sea level.

Source: University of Nottingham

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not rated yet May 06, 2008
Galaxy Clusters Evolved By Dispersion, Not By Accretion

A. Compact Galaxies In Early Universe Pack A Big Punch


Again, repeating an old posting of mine:

"Singularity and D-Infinity (max expansion/ cosmic energy dilution) are the two cosmic stable states. Their in-between is a metastable state, which is an everyday commonsense observation. Likewise is the observation that the denser the compacting goal of material the more energy is required, and vice versa the more thorough the disintegration of material the higher the amount of energy released. It seems that E=mC^2 is a specific case of the cosmic (and universal) process
E=Total[m(1 plus D)] where D is the Distance from Big Bang point and the sum is of all spatial values of D from D=0 to D=selected value.

BTW, following Newton (1) gravity is decreased when mass is decreased and (2) acceleration of a body is given by dividing the force acting upon it by its mass. By plain common sense, best scientific approach, the combination of those two 'laws' may explain the accelerating cosmic expansion of galaxy clusters, based on the above E/ m/ D suggested relationship. "

Thus the young "condensed galaxies" are, in fact, what later evolved into galactic clusters.

B. Galaxy Clusters Evolved By Dispersion, Not By Buildup


1. Genesis


Extrapolation of the expansion of the universe backwards in time to the early hot dense "Big Bang" phase, using general relativity, yields an infinite density and temperature at a finite time in the past.

At age 10^-35 seconds the Universe begins with a cataclysm that generates space and time, as well as all the matter and energy the Universe will ever hold.

2. How did galaxy clusters evolve

1. http://herschel.j...es.shtml

"Among the stranger objects that appear to have populated the early universe are active galactic nuclei (AGNs)."

3. http://imagine.gs...ion.html

"How did the Universe evolve after the Big Bang?" and "How did galaxies form?" These are big questions, and they are not easy to answer: after all, these things occurred billions of years ago. Galaxy clusters provide one window into the very early Universe. They are the largest gravitationally bound objects in the Universe, and the properties of clusters can be used to place strong limits on cosmological theories of structure formation and evolution.

4. http://www.scienc...2543.htm

The process of galaxy formation largely is a mystery. Current theory is that large galaxies formed over time from the interaction and merging of smaller galaxies. This process began more than 12 billion years ago, shortly after the Big Bang. Scientists have observed galaxies merging over a large range of distances and time, providing hard evidence to reinforce the theory. However, using current technology, it is difficult to detect this process at the most extreme distances, when galaxy formation was in its infancy.

Scientists believe galaxy clusters form in a similar manner. As galaxies congregate and interact in large, dense regions of space, the cluster grows with time. Witnessing this process first-hand helps scientists confirm their theory and deepen their understanding of the universe. Galaxy clusters can be detected at extreme distances with current technology because they are bright, but they are difficult to find.

C. Galaxy Clusters evolved by Dispersion of "condensed packs",

not by accretion of smaller matter. The dispersion/breakdown of the "condensed packs"
followed the relationship E=Total[m(1 plus D)] , i.e. it was accompanied by an overall decrease of mass. Accretion possibly and probably took place, too, in this and other cosmic evolutions, but the GC evolved as D, dispersion, increased accompanied by m decreased.


Dov Henis

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