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ToSeek
2005-Mar-02, 08:35 PM
Young Universe Was Surprisingly Structured (http://www.universetoday.com/am/publish/young_universe_structure.html?232005)


A team of European astronomers have discovered a highly structured cluster of thousands of galaxies at an incredible 9 billion light-years away. In other words, this structure was highly evolved only a few billion years after the Big Bang; a situation that should be impossible, according to current theories. Incredibly, some of the galaxies in the cluster are red and elliptical, which would indicate that they were already quite old at only a few billion years old.

Spaceman Spiff
2005-Mar-02, 09:50 PM
Young Universe Was Surprisingly Structured (http://www.universetoday.com/am/publish/young_universe_structure.html?232005)


A team of European astronomers have discovered a highly structured cluster of thousands of galaxies at an incredible 9 billion light-years away. In other words, this structure was highly evolved only a few billion years after the Big Bang; a situation that should be impossible, according to current theories. Incredibly, some of the galaxies in the cluster are red and elliptical, which would indicate that they were already quite old at only a few billion years old.

The above summary quote of the linked article isn't very accurate in describing our current (if rapidly changing) understandings or even of the rest of the article. This quote, snipped a bit lower does a better job.


The discovery of such a complex and mature structure so early in the history of the Universe is highly surprising. Indeed, until recently it would even have been deemed impossible.
(my emphasis)

dgruss23
2005-Mar-02, 10:25 PM
The above summary quote of the linked article isn't very accurate in describing our current (if rapidly changing) understandings or even of the rest of the article. This quote, snipped a bit lower does a better job.


The discovery of such a complex and mature structure so early in the history of the Universe is highly surprising. Indeed, until recently it would even have been deemed impossible.
(my emphasis)

Which theoretical developments now make this observational result possible that was previously thought to be impossible on theoretical grounds?

Van Rijn
2005-Mar-02, 11:37 PM
Observation doesn't appear to be the issue, it was what they found - surprisingly mature structures. I suspect, though, that most scientists, rather than story writers, would shy away from "impossible" in this context.

dgruss23
2005-Mar-03, 12:02 AM
Observation doesn't appear to be the issue, it was what they found - surprisingly mature structures. I suspect, though, that most scientists, rather than story writers, would shy away from "impossible" in this context.

The point of my question is that whether we say this is "impossible" or "surprising" - it is - as you say - the observational result. I'm not disputing that.

But what I'd like to know from Spaceman(or anyone) is which new developments in current BBT parameters allow this observation - which formerly would have been considered impossible (within BBT context) to now be compatible with the BBT.

I think for clarity we should know which of two possible reasons is responsible for this no longer being as surprising to astronomers. Is it because of theoretical developments that allow for it - or is it because these types of structures are being discovered at ever higher redshift and therefore to find yet another is not surprising? Or is it both?

Ari Jokimaki
2005-Mar-03, 07:18 AM
Could someone explain to me why this is considered as a problem?

Early universe was quite dense and I think that galaxies would form close to each other, and so we would get ready made clusters. But clearly there is something that I'm missing here, what is it?

crosscountry
2005-Mar-03, 02:45 PM
Could someone explain to me why this is considered as a problem?

Early universe was quite dense and I think that galaxies would form close to each other, and so we would get ready made clusters. But clearly there is something that I'm missing here, what is it?


yea, but many galaxies in the cluster are red and elipsoidal, meaning they were already old 9,000,000,000 years ago when the light left to come this way.

correct me if I'm wrong, but doesn't red also mean heavy elements? if that's the case then the galaxies are made of 1st, 2nd, and 3rd, generation stars, where they should just be made of 1st and 2nd gens.

I could be wrong about that of course

John Kierein
2005-Mar-03, 02:47 PM
It's a problem for the big bang. If there are "old" galaxies (like 10 billion year old?) 9 billion light years away, then it means these galaxies were formed before the big bang (like 19 billion years ago?). Most think the big bang was about 13 to 14 billion years ago and there some that say only about 10 billion years ago.

dgruss23
2005-Mar-03, 03:03 PM
Could someone explain to me why this is considered as a problem?

Early universe was quite dense and I think that galaxies would form close to each other, and so we would get ready made clusters. But clearly there is something that I'm missing here, what is it?

The reason is that the CMB indicates a very smooth start to the universe. It takes time to grow large scale structures and this structure would be formed only ~ 2billion years after the BB. This is why I'm asking Spaceman for clarification. Previously such rapid growth was not considered possible. I'm wondering if the change of view on that is coming from the fact that it has been observed or some theoretical advancement that allows for the rapid growth.

ngc3314
2005-Mar-03, 03:05 PM
It's a problem for the big bang. If there are "old" galaxies (like 10 billion year old?) 9 billion light years away, then it means these galaxies were formed before the big bang (like 19 billion years ago?). Most think the big bang was about 13 to 14 billion years ago and there some that say only about 10 billion years ago.

I'll be quite interested to see the formal report. In particular, the press release is vague about how red "red" is, and about the ages to be inferred from this (and it's always possible that the error range is large or complex and they don't want to get into that for a press report). If that is based on the observed optical (i.e. emitted ultraviolet) range, stellar populations redden and fade very rapidly in that range because the dominant stars don't last long, so that could mean ages of only 0.5 Gyr and no particular problem with timescales in itself. If they in fact mean red in the emitted optical (observed near-IR), that's a whole different kettle of fish, because the options for explaining galaxies which are at once young and red are limited - either very dusty, which a detailed enough spectrum can test for because individual spectral features wouldn't be affected by the dust reddening, or star formation weighted to lower-mass stars than we're used to seeing locally. The latter would be shocking just because all the evidence has, if anything, pointed to violent star formation (the best analogs to early galaxies, we think) being weighted the other way.

Doodler
2005-Mar-03, 03:22 PM
Is the problem truly the structured nature of that cluster or the fact that we're not allowing for the possibility of first generation stars forming much earlier than previously believed?

http://www.universetoday.com/am/publish/young_star_grown_quickly.html

If the early universe acted like a supersized star forming nebula where stars formed with the help of these magnetic fields, then the possibility of fast forming galaxies shouldn't be that much of a leap. If its more than just gravity acting on the formation of stars, we're simply not assuming a fast enough time frame for their formation, and these early advanced structures might not seem so unusual.

Also, they're calling these 'older' stars, my question is, older relative to what? Are they older in terms of modern gen 2 and gen 3 stars, or old relative to gen 1 stars?

dgruss23
2005-Mar-03, 03:24 PM
It's a problem for the big bang. If there are "old" galaxies (like 10 billion year old?) 9 billion light years away, then it means these galaxies were formed before the big bang (like 19 billion years ago?). Most think the big bang was about 13 to 14 billion years ago and there some that say only about 10 billion years ago.

I'll be quite interested to see the formal report. In particular, the press release is vague about how red "red" is, and about the ages to be inferred from this (and it's always possible that the error range is large or complex and they don't want to get into that for a press report).

The research article came out yesterday on astro-ph (http://xxx.lanl.gov/abs/astro-ph/0503004). I haven't had a chance to read it yet, but it may answer your question.

dgruss23
2005-Mar-03, 03:27 PM
Is the problem truly the structured nature of that cluster or the fact that we're not allowing for the possibility of first generation stars forming much earlier than previously believed?

No. That would be an issue of "seeing" the mass. The problem with this structure is the accumulation of so much mass into such a large structure in only ~ 2 billion years. Even if no stars formed within this cluster, to accumulate that much mass so rapidly from the initial very uniform state of the universe (as indicated by the CMB) is still a problem unless someone has identified the theoretical advancement that allows it to happen.

ngc3314
2005-Mar-03, 04:41 PM
Is the problem truly the structured nature of that cluster or the fact that we're not allowing for the possibility of first generation stars forming much earlier than previously believed?

No. That would be an issue of "seeing" the mass. The problem with this structure is the accumulation of so much mass into such a large structure in only ~ 2 billion years. Even if no stars formed within this cluster, to accumulate that much mass so rapidly from the initial very uniform state of the universe (as indicated by the CMB) is still a problem unless someone has identified the theoretical advancement that allows it to happen.

There is one obvious mechanism - nonbaryonic dark matter. The smoothness of the CMB tells us about ordinary matter, which remained smooth until it decoupled from radiation (after which it was free to follow the dictates of gravity without radiation pressure pushing back towart uniformity). Depending on its spectrum of clumping, dark matter could have started falling together toward denser regions earlier, providing prefabricated potential wells for ordinary matter to slide into after recombination. One fairly recent development has been in exploring what the constraints are on the dark-matter density field at this epoch (in science, one does prefer a game with some rules to a game without...).

Doodler
2005-Mar-03, 04:44 PM
Is the problem truly the structured nature of that cluster or the fact that we're not allowing for the possibility of first generation stars forming much earlier than previously believed?

No. That would be an issue of "seeing" the mass. The problem with this structure is the accumulation of so much mass into such a large structure in only ~ 2 billion years. Even if no stars formed within this cluster, to accumulate that much mass so rapidly from the initial very uniform state of the universe (as indicated by the CMB) is still a problem unless someone has identified the theoretical advancement that allows it to happen.

I suppose magnetic entanglements in the early days wouldn't cover it? I'm leaping here but even uniform structures like the sun have incredibly chaotic magnetic fields. Could the early universe have behaved similarly, with a uniform physical structure, but chaotic magnetic fields causing matter to clump as it scattered?

Spaceman Spiff
2005-Mar-03, 05:49 PM
Ok, sports fans. Two issues have arisen here.

First, is whether the stellar populations representing the bulk of the emitted light in the galaxies within this z = 1.393 cluster are older than the universe was then, assuming the so-called "concordance cosmological model". In that model the age of the universe at that redshift is about 4.6 billion years old. In section 3 of the science article (http://xxx.lanl.gov/abs/astro-ph/0503004) it says:


The central cluster galaxies clearly delineate the bright end of the cluster red sequence at a color of R − z ≃ 2.1. Given a realistic galaxy model, we can use the location of the red sequence as a reliable distance indicator (e.g., Kodama & Arimoto 1997; Gladders & Yee 2000). Assuming cluster ellipticals form via monolithic collapse at z ≈ 3 and then passively evolve to the observed redshift (e.g., Daddi, Cimatti, & Renzini 2000), we derive a color-redshift transformation indicated on the right-side ordinate of the color-magnitude diagram. Thus the observed red sequence color of XMMUJ2235.32557 corresponds to a redshift of z ∼ 1.4.

Note that the first appearance of "z" in the above quote refers to a broad band filter called 'z'. In any case, even if these galaxies formed at a redshift of 3 when the universe was about 2.2 billion years old, their expected colors are consistent with the actual observed ones. I note that the cluster redshift derived from the spectra, confirming their original analysis based on color alone, is 1.393. As a rule of thumb, "old", with regards to stellar populations in galaxy evolution, means older than 1 billion years.

The second and more interesting issue is whether such a massive galaxy cluster is to be expected at this redshift, given our present knowledge of the parameters governing the expansion of the universe. I don't have a post for dgruss23 at the moment to address this, though there was an excellent article in December's Sky & Telescope, called Cosmology with Clusters, by Megan Donahue, that might address this (I've already forgotten #-o). I also note that nowhere in the science article prompting this discussion do I see the word "impossible" or anything of the kind regarding current models for the evolution of large scale structure. However, I believe it is true, as mentioned by ngc3314, that the earlier clumping of dark matter is required. That is, the models require the presence of substantial cold dark matter (because cdm doesn't interact with light, it naturally begins clumping much earlier than normal baryonic matter). And as the authors do say


It is important to recognize that the leverage on both the derived cosmological parameters and the efficacy of evolutionary studies is greatly enhanced as we probe to higher redshifts.

{edited: fixed second sentence, and fixed up sentence that begins with "In any case..."}

Ari Jokimaki
2005-Mar-04, 06:23 AM
The reason is that the CMB indicates a very smooth start to the universe. It takes time to grow large scale structures and this structure would be formed only ~ 2billion years after the BB.

This is what I was asking, thank you!