Do galaxies age 'gracefully'?


This article in Space.com, Nature vs. Nurture in the Cosmos, there seems to be evidence of a gradual evolution of galaxies. It says: Now, if this analysis of galaxy star formation is correct (see pix in article for examples), where a galaxy at 7 million light years has many blue stars, while one at 33 million light years has only a peripheral remnant, and at 62 million light years nearly no blue stars, then it seems there is a natural progressions tied into time and distance for galaxy evolution.

The first ATM question is: Can a galaxy evolve to full maturity in such a short time, of only about 50 to 60 million years?

The second question is: What are we actually observing? Do we actually know this analysis of galaxy evolution based on blue stars observation is correct?

Consider this possibility: (1) that beyond a certain distance, blue stars are no longer observable, if their light shift turns towards the red; and (2) if it takes only about 60 million years for a galaxy to reach full maturity, shouldn't there be some evidence of 'star formation' beyond the 62 million light years 'horizon'? Or (3) if there are blue stars observable beyond 62+ million light years horizon, then what does it mean in terms of galaxy evolution, if these galaxies are creating new stars at any time scale? What about billions of light years away? In fact, shouldn't it all be in reverse, that older (farther away, farther back in time) galaxies show more star formations, if the universe is expanding from a Big Bang (so called) origin?

I propose, from #3, that the above article has either not given us enough information to come to a necessary conclusion about galaxy evolution, or because older (farther away) galaxies are not showing more star formations, that the observation is flawed. Furthermore, is about 60 million years enough time to complete a full cycle of galaxy evolution from youngster to old age, gracefully?

What we are actually seeing, in effect, is that over great distances the blue stars simply are not observable, not even at the ultraviolet wavelength. The above hypothesis is therefore flawed because of an observational limit, that older blue stars are not observable. In fact, we should be seeing more blue stars at billions of light years, in my opinion, if galaxies formation was more common then, closer to the Big Bang 'origin' of the universe.

What do you think? Here's the conundrum: Looking back farther in time into the early universe, we should be seeing more star formation, not less! ATM here?

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We see more starburst galaxies at high z than low z. That is not necessarily revealing, but useful.

Thanatos, the conundrum here is that we should see a progression of star formation in reverse, where older galaxies (father away) should show more star formation (more blue stars), with closer galaxies (more recent) maturing into less blue stars, if the article's premise is to be take face value. However, that is not how it was presented, where the newer galaxies with more star formations were more recent (closer to us) while the older more mature galaxies were further away (older) had fewer blue stars. I think this presents a problem, because if age of the universe is a factor, it should be in reverse order, as you point out. There are more starburst (new stars) galaxies at high Z than low z. The only solution to this, if there is a solution here, is that blue star formation is not indicative of the age of any given galaxy. In fact, it may be indicative of our inability to observe blue light stars over great distances instead. Isn't this the problem?

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1) full maturity in 50 Myr?

doubt it. While that would get out alot of the really blue O and B stars, I think the A stars can last longer. If I remember right, you prolly want upwards of a billion to get to maturity. Even then, there will still be alot of white and yellow.

2) I think you are observing the summed color spectra of all the galaxy. The blue drains out first. As to how much is correct, 100 years of observation of billion year timescale effects means there is still alot of if and maybe.

3) I know blue galaxies are common in the hubble deep field, so there are some waaaay out there. I also know that there are effects that can make galaxies very blue. Collision seems to be one of the big ones. I think that the current thought is that galaxies start mostly spiral, then collide with their neighbors, which tends to make them very blue for a while, and also tends to change the spiral to an elliptical, then they end up being an evolved mature elliptical.

Why is this in ATM? It looks like reasonable questions and answers stuff.

Let's get the chronology straight, at least as I understand it according to the most up to date theory.

The galaxies have been around for some billions of years. We see the nearby ones as they were very recently, and the more distant ones as they were in earlier stages of their evolution.

Star formation rates were generally higher in the earliest stages, and massive, brilliant blue stars of types O and B are believed to have been more abundant. Thus I would expect to see more blue light in the most distant ones. It will be redshifted, but the spectral lines will identify it as intrinsically blue. Redshift alone should not make the blue light unobservable.

If the opening round of star formation had been all there was, there would be no remaining blue stars to be seen in nearby galaxies. The fact that some galaxies, including our own, have an impressive sprinkling of them indicates that episodes of star formation have occurred in recent times. Collisions and mergers can provide the necessary perturbations to start new episodes in previously quiescent interstellar gas and dust.

Other galaxies, which have insufficient remaining gas for such star formation, will have only "later" type main sequence stars, red giants, and the dim or dark remnants of the primordial blue stars. These are the ones that are described as old and red.

I don't think the nearby blue galaxies are younger overall. They just have a greater abundance of star-forming capability. I think the SPACE.com writer used some poor choices of words. I am skeptical when a writer uses gussied up figurative language such as "sexy" in such a context. I would rather hear more from Mr. Martin directly concerning the intermediate stages of galactic evolution.

Yes, and that is exactly what we see, as the article you linked to indicates ...
The cosmic star formation rate is seen to peak about a redshift of 3, about 11,500,000,000 years ago, when the universe was about 2,200,000,000 years old. It has fallen off by about a factor of 10 since then. See, for instance, Hopkins & Beacom, 2006.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

The conclusion that all observational evidence is consistent with the standard model framework is simply not true.


One of the outstanding features of the ‘early’ universe is that galaxies out to redshift 7 appear to have normal stellar populations (Richard S. Ellis, Caltech, 2004).

Using data obtained with the Frederick C. Gillett Gemini North Telescope on Mauna Kea, Gemini Deep Deep Survey took the deepest spectra ever of very distant galaxies. The galaxy populations encountered look identical to local groups, with astoundingly no sign of evolution during this important era that was believed to be one of most significant change.

"It is quite obvious from the Gemini spectra that these are indeed very mature galaxies, and we are not seeing the effects of obscuring dust. Obviously there are some major aspects about the early lives of galaxies that we just don’t understand.” Said Patrick McCarthy (Observatories of the Carnegie Institution).

“Studying the chemical composition of the interstellar gas, we discovered that the galaxies in our survey are more metal-rich than expected." Sandra Savaglio (Johns Hopkins University).

Hold on, there’s more: Isobel Hook (see Hook et al, c2004), head of the UK Gemini Support Group, (Oxford University) is part of the Gemini Deep Deep Survey (GDDS) team whose objective is to capture the faintest galactic light ever detected. Three hundred galaxies were scrutinized. “These highly developed galaxies, whose star-forming youth is in fact long gone, just shouldn’t be there, but are," said Co-Principal Investigator Karl Glazebrook (Johns Hopkins University).

Others too have found that distant red galaxies in the Hubble Ultra Deep Field (Toft et al 2005) present morphological properties that suggest “complex stellar populations, consisting of both evolved populations that dominate the mass and the restframe optical light, and younger populations, which show up as patches of star formation in the restframe UV light; in many ways resembling the properties of normal local galaxies."

The supposition that the morphology of galaxies in the Hubble Deep Fields is very different in the past than in the present is not a confirmed observational fact, when redshift and surface brightness are taken into account (Buta & Block 2001, Thompson, R.I, 2000, Ellis 1997, Takamiya 1999).


Coldcreation

Short lived 'baby boom' star clusters last only a few dozen million years, per this Hubble article: http://hubblesite.org/newscenter/arc.../2007/05/full/

However, note these are very specific stars (per korjick), B stars that burn out quickly and not indicative of other globular clusters of A stars last much longer. Also, star clusters are not uniformly the same, since some of the may give 'star birthing' in several generations: http://hubblesite.org/newscenter/arc.../2007/18/full/ There's the dilemma, to find evidence for what we see in the very early universe at high Z~6 in the Z<~1 universe, much closer to home.

The way this OP article was written, with its illustrations of (reverse) order of star birthing and maturing from 7 MLY to 62 MLY gives one the impression that there should be (within a few dozen million years) a marked evolution from birthing to maturing galaxies. However, this is in reverse order, because we should be looking (from galaxies reference frame) as older galaxies (newer in their reference frame) being where the birthing is more pronounced, not more recently. The trouble with this idea (where it is ATM) is that if we do not find local evidence of such birthing and maturing, then how are we to interpret it in the very ancient (billions of light years) universal star formations, where they 'appear' to have been very much more active than today (by factor of 10?), since we do not see such activity here? (Except for when galaxies collide?) Either that, or something was truly fundamentally different billions of light years ago versus what the universe looks like today; or our instruments looking back 13 BLY make it 'look like' it was very different. The only problem with this (ATM) is that when they look back to 13 BLY, they find already fully formed galaxies.

Can the universe birth itself within a mere <~1 billion years? Or, as ColdCreation said: The idea is that what happened in the very early universe, some 13 Billion years ago, where fully formed galaxies already existed, should not be contrary to what is happening today, where new stars are birthing, if the universe is the same today as it was 13 billion years ago (where fully formed galaxies already existed). The problem (ATM) is that the order of birthing seems to be reversed, whereby older galaxies (newer from galaxy reference frame) show more mature star formations, and new galaxies (older from galaxy reference frame) show newer star formations. Shouldn't this actually show up in reverse (from galaxy frame reference)? It looks right from our frame reference, but wrong from galaxy frame reference, unless we find evidence in total reverse: Older galaxies have newer star formations (Z~<1) and newer galaxies (z<~1) have more mature stars.

Have we seen this? I searched, and all I found was references to 'distant star bursts': http://www.spaceref.com/news/viewpr.html?pid=12569 , which observed 12 BLY back (UK ATC), but no evidence that this (reverse order) had been observed. What are we missing here?

What Hornblower says makes sense, that type O and B stars were eliminated early on, but there should be some evidence of this happening now too. And if the evidence is found, then it means the universe is still evolving just as it was evolving 13 billion years ago, without any change whatsoever. In fact, to extrapolate back a bit, it may not have changed at all over its 13 BLY history (all we can see), except that our ability of observation has changed. In effect, the universe might even be much older than what we think (ATM). But to prove this idea, that the universe is the same now as it ever was, we need to find the correct progressions of type O and B stars within our local reference frame (reverse order for local galaxy reference frame), but which the OP article seems to contradict.

And that's the crux of the matter: we should be seeing star birthing from the galaxy reference frames, which is reverse of what we see from ours. Or as Tim Thompson's refered (abstract) says: Should we be seeing the same rate of star birthing in Z<~1 as much farther back in time, then there is no compelling argument for the early universe being different from the present one, barring any meaningful adjustments with 'normalization and analytical formalisms'. What are we actually observing, if we do not find evidence of greater star birthing in the time sequences of Z<~1 in reverse order (from galaxy reference frame) than what had been observed (from our reference frame)? Rather, it appears we find the opposite effect (from our reference frame) of more birthing closer in, rather than farther out. This begs the question (ATM) as to what is it we are seeing with our instruments at the blue light spectrum? Are our readings true, or are they obscured by space dust, or otherwise, to let us see blue star formations closer in (not farther out)?

Or, in effect, are our instruments not up to par at the blue light/ultraviolent range, because of all the space dust in between here and there? So what we get in merely a skewed picture, where older stars (in there reference frames) or galaxies appear younger to us? But that's opposite of what it should be!

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I cannot find anything in your long list which is inconsistent with big bang cosmology. How do you know, or on the basis of what physics do you argue, that galaxies cannot form rapidly in big bang cosmology? How, exactly does the presence of a few evolved galaxies in the early universe actually contradict big bang cosmology?

The references you cite are incomplete, and none are linked back to papers or abstracts. I cannot easily find where you are getting your quotes. Can you be more complete in providing references?

What about the paper I linked to before: On the Normalization of the Cosmic Star Formation History, Hopkins & Beacom, Astrophysical Journal 651(1): 142-154, November 2006. I specifically reference figure 1 (you can download the PDF from the arXiv link). This figure explicitly shows the rapid decline in star formation rate since redshift 3, and the increase in star formation rate prior to that, from about redshift 6.6 to redshift 3. Is this figure in error, and if so, why?

And what about this: Evidence for strong evolution of the cosmic star formation density at high redshifts, Mannucci, et al., Astronomy and Astrophysics 461(2): 423-431, January II 2007. They find that no galaxies with redshifts as high as ~7 are visible in the GOODS-south field, in deep HST/ACS & VLT/ISSAC images. The non-detection is significant. In the abstract they reach this conclusion: "Our non detection of galaxies at z ~7 provides clear evidence for a strong evolution of the luminosity function between z=6 and z=7, i.e. over a time interval of only ~170 Myr. Our constraints also provide evidence of a significant decline in the total star formation rate at z=7, which must be less than 40% of that at z=3 and 40-80% of that at z=6." Strong evolution of the star formation rate is consistent with the results reported by Hopkins & Beacom.

The example of only a few evolved galaxies at high redshift is not contrary to these results. They are also not contrary to big bang cosmology, until & unless you are able to enforce your implied conclusion that galaxies cannot evolve as quickly as observed by Mannucci, et al., or quickly enough to be massive at redshifts as high as 6-7.

I can't follow the point you are trying to make, especially what you mean by "reverse" order. And I don't know what this is supposed to mean: "It looks right from our frame reference, but wrong from galaxy frame reference ...". So let me ask a couple of questions to clear my own vision.

Without reference to "reverse" order, and keeping in mind that larger redshifts are farther back in time, what do you think the cosmic star formation rate should look like to us in the Milky Way, here & now, if big bang cosmology is valid? Is the above referenced figure 1 from Hopkins & Beacom consistent with the way you think it should look?

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

I had those links in another computer.

Here you will find most, if not all, of the quotes from my previous post.



Distant Red Galaxies in the Hubble Ultra Deep Field (Toft et al) arXiv:astro-ph/0503454 v1 21 March 2005

Ellis, R.S., 2004 Seeing the Very First Galaxies

Gemini Observatory, Faintest Spectra Ever Raise Glaring Question: Why do Galaxies in the Young Universe Appear so Mature?

and/or http://www.gemini.edu/project/announ...ss/2004-1.html

and/or Why do Galaxies in the Young Universe Appear so Mature?


Massive Distant Galaxy Calls Theory into Question

The Metallicity of 0.5 < z < 1 Field Galaxies




PS. I'll be back to respond to the rest of your post later.


Coldcreation

The time line of new blue stars in distant galaxies shows (per OP article) a time line going from more recent to older (7 MLY to 62 MLY) where blue stars progressively disappear. My term "reverse order" means that from the perspective of the light coming to us from the galaxies (light from their reference frames) should show newer blue stars formation (within the galaxies) happening in older (farther away) galaxies, and progressively disappear in newer (closer in) galaxies. Try to visualize this, because it is a relativistic phenomenon, by putting yourself in the point of view 'as if' you were looking at this from the other direction, that of the stars sending light towards us.

About your other question, "...what do you think the cosmic star formation rate should look like to us in the Milky Way, here & now, if big bang cosmology is valid?" I am not sure how to answer that, in part because I don't know if any sequence of star formation in our own galaxy has any identifiable pattern to work with. If the galaxy formed at some period of time, one would assume the stars within it evolved within a relatively short time to gather together into a galaxy around a central gravity 'black hole'. If I were observing this from a distant vantage point way beyond our galaxy, perhaps some pattern vis-a-vis other nearby galaxies (in line of sight) could show the pattern of blue star formation over time (distance), but I don't know if that answers you question. My opinion is that within a galaxy, no such progression is visible. Once an aggregate of stars forms into a galaxy, it is now its own internal phenomenon. The difference between this, one galaxy, and the star formation development from multiple galaxies (line of sight) is that the latter may show a progression with time of blue star formation. I think this is what the OP article was trying to show, but it did it in "reverse" given how the time line was presented. Can you see that? That's the main issue.

I can't do more now, must run out the door, but will study this some more and get back if find new stuff. I also have to read Coldcreation's links before going deeper.

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The author showed a blue galaxy at 7 million light years and a red galaxy at 62 million. She just as easily could have shown a blue one that is farther away. From that, along with her loose use of young and old as if she thinks they apply to the entire galaxy, you appear to have made a great-leap inference of the evolutionary time lines of those galaxies. Beyond that, I cannot follow your line of thought. Your expressions "older (farther away) galaxies" and "newer (closer) galaxies" make no sense to me. You appear to be inferring things that the author never said and never quoted anyone else as saying.

For all we know, both galaxies may be over 10 billion years old, and for whatever reason the red one has long since exhausted its supply of gas while the blue one has not. I see nothing in the article which implies otherwise. The 55 million year difference in the lookback times is a twinkling in comparison.

From this article and others on similar topics, I would guess that the red one is the result of past mergers in which the interactions accelerated the star-forming process and in the process exhausted the supply of gas. Computer simulations indicate that such mergers also scramble the original spirals and yield a large elliptical galaxy. Given enough time, the blue components of the other one will disappear and leave it similarly red. If it does not merge with another large galaxy I would expect it to remain a disk rather than become an elliptical blob.

Yes, this is exactly right. If she had shown the reverse order I would not have questioned it. Oversight on her part? Or is this simply 'not there' that in the time progression of an (expanding) universe the opposite does not exist? Or possibity that we are simply unable to register such blue stars further out? These are the unresolved questions.

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In terms of star colors, that is exactly what we should, and actually do see. But that's because our ability to see red stars falls off rapidly with distance. The red stars are invisible in the older galaxies, we can see only the blue stars, because they are hotter & brighter, and their light therefore carries over larger distance. So if you look only at the star colors, you will get a very skewed picture of the evolution of galaxies, because most stars are too red to see. Blue stars do not mean young galaxies, they mean young stars. Star formation is episodic, so that a very old galaxy could easily undergo a burst of star formation, pump up its blue star population, and make you think it is young when it is really very old.

It is better to look at the global star formation rate as a function of time (redshift). That's why I linked to the Hopkins & Beacom paper where you can see the history you expect to see. At high redshift the star formation rate is low, simply because things haven't got started yet, except in a few places. But the star formation rate goes up dramatically as star formation really gets going, peaking about redshift 3 (about 11.5 billion years ago). Since then the global star formation rate has fallen off by about a factor of 10.

Aside from the selection effects involving star color, there is also the small numbers problem. You cannot hope to learn anything at all about star formation in the universe by looking only at 2 or 3 galaxies, as there are always exceptions. You need to look at thousands of galaxies, more if you can. That's how the star formation history studies work. So, even though we know that the global star formation rate is low at high redshifts, that does not exclude the local star formation rate from being quite high in some places (i.e, HUDF-JD2, if it is really as far as redshift 6.5; Chary, et al., 2007 argue that it is actually much closer, about redshift 2; this also serves to show the difficulty of determing the redshift for distant galaxies).

Consider the galaxies featured in the OP story. The "blue" galaxy at 7 million light years is NGC 300. But is it "blue", or do we only see blue stars slectively? And remember that the GALEX instrument looks only in UV, so it would not efficiently see red stars even if they were nearby. See Butler, Martinez-Delgado & Brandner, 2004. They conclude that "The main disk stellar population is predominantly old, consisting of red giant branch (RGB) and asymptotic giant branch (AGB) stars ..." and "Taken at face value, this finding would agree with the Davidge report of suppressed star formation there during the past 10⁹ yr ...". We expect blue star to be in the minority in any galaxy, and so we see here. The point is that the stellar population of the galaxy is peculiar to that galaxy and its own specific star formation history (not all galaxies have the same distribution of gas from which stars form).

The "red" galaxy at 62 million light years is the giant elliptical galaxy NGC 1316, also known as the bright radio source Fornax A. But this galaxy is a merger remnant (Horellou, et al., 2001). The merger event(s) trigger short term bursts in star formation activity. What we see now is a galaxy that was very blue, due to active star formation, about 100,000,000 years ago, but star formation activity has dropped off since then. So you look at the "red" color, as far as GALEX is concerned, and think perhaps that the galaxy is far older than it really is (about 3 billion years since the major mergers that formed it; Kaneda, Onaka & Sakon, 2007). The appearance of this galaxy, as with NGC 300, is dominated by its own peculiar history, not by cosmic evolution.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

Coldcreation provided the link to the Astrophysical Journal, which cannot be read without a subscription, and the arXiv link, which can be read by anyone. The NASA/ADS link includes links to citing papers, and the arXiv link: Distant Red Galaxies in the Hubble Ultra Deep Field, Toft, et al., The Astrophysical Journal Letters 624(1): L9-L12, May 2005. I note only that this paper studies 5 galaxies in the Hubble Ultra-Deep Field (HUDF, Beckwith, et al., 2006) which range in redshift from 1.2 to 3.4, which translates into distances 8.5 billion to 11.8 billion light years. Assuming an age for the universe roughly 13.7 billion years (just to make all you WMAP fans happy) redshift 1.2 is a universe that is 5.2 billion years old, and redshift 3.2 translates into a universe that is 1.9 billion years old (I get my numbers from Ned Wright's Cosmology Calculator). I see nothing about this which is contrary to, or even difficult for big bang cosmology. I also note that, as I indicated elsewhere, the Hopkins & Beacom paper illustrates the observational determination that the global cosmic star formation rate peaked about redshift 3, which pits the Toft, et al., galaxies mostly on the down sloping side of the cosmic star formation curve. They live in a universe old enough to be no problem for big bang cosmology.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

The link provided by Coldcreation leads back to an article in Sky & Telescope which talks about work by one group headed by Ellis, and another by Malhotra. Unfortunately, the article does not reference any original publication, so I can only go by the quote give here. The quote is misleading at best.

It is not true that all galaxies at redshift 7 appear to have normal stellar populations, although one might think so from the way the quote is presented. There are, or more appropriately "may be" galaxies with that high a redshift with "normal" stellar populations (i.e., as mentioned before, Chary, et al., 2007 dispute the high redshift given to HUDF-JD2, lowering it from ~7 to ~2).

"Normal stellar colors" means that the galaxies appear to have evolved stellar populations. Why should the presence of a few evolved galaxies, even at redshift 7, when the universe ws about 780 million years old, be a problem for big bang cosmology? Do we know (does anyone know) that galaxies cannot form & evolve in that much time? I also note that while the galaxies may have normal stellar colors, they are neither as large nor as massive as are galaxies in the current universe. There is a great deal of evidence to show that galaxies grow in size & mass over time (i.e., NASA's Hubble Finds Hundreds of Young Galaxies in Early Universe, Tracing the Evolution of the First Galaxies in the Universe, The Secret Lives of Galaxies Unveiled in Deep Survey, Ravindranath, et al., 2004, Pirzkal, et al., 2006, Trujillo, et al., 2006, Sargent, et al., 2007). Stellar colors only reveal the evolutionary state of the visible stars, but say nothing about the bulk properties of the host galaxies.

So I maintain that the comment by Ellis, taken out of scientific context by a news story, is no problem for big bang cosmology. The observational evidence clearly shows strong evolution in size & mass with time, as expected by the heirarchical model of galaxy evolution in big bang cosmology.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

I have already presented evidence to falsify this assertion in my previous mesages. Here I will address the specific references give here, as best I can.

Takamiya 1999: Takamiya did not look at any galaxies with a redshift higher than 1, which is already well past the star formation peak at redshift ~3, and well past the time that most of the major galaxy formation would be expectd to have finished. Therefore this too is no real critique of big bang cosmology (i.e., Morphological Evolution of Galaxies, Marianne Takamiya, Astrophysics and Space Science 269/270: 339-344 (1999), Galaxy Structural Parameters: Star Formation Rate and Evolution with Redshift, M. Takamiya, The Astrophysical Journal Supplement Series 122(1): 109-150, May 1999)

Ellis 1997: I can find only one likely reference: HDF: Introduction and Motivation, Richard S. Ellis, August 1997. Ellis does not discuss redshifts greater than 3. And in any case, I do not see any comment consistent with the claim made about morphology of galaxies in the HDF. But this may be the wrong reference in any case, so feel free to point me in the right direction.

Thomson, R.I., 2000: That should be Thompson, R.I. The only source I can find is an abstract (Thompson, Weymann & Storrie-Lombardi, 2000) which is uninformative. Corbin, et al., 2000, which includes Thompson as a co-author, looks at high redshift galaxies in the NICMOS parallel fields (fields next to the Hubble deep fields). But they too are limited to galaxies with a redshift less than 3.

Buta & Block, 2001: There are only 4 references to papers by Buta & Block, 2001, and none of them appear to be relevant to me. A wider search is equally unrevealing, so I cannot comment since I cannot find the reference.

So the bottom line on this for me is that we expect galaxies with redshifts less than about 3 (when the universe was already about 2.2 billion years old) to be similar to the galaxies in our present universe. The fact that they look as one would expect is hardly much of a criticism, but it seems to be the underlying theme of the critiques offered by Coldcreation.

If you are going to criticize big bang cosmology in this manner, you need to do a better job. First, you need really high redshifts, at least greater than 3 to get past the cosmic star formation peak. Furthermore, you need to show that many, or even most of the galaxies at such a high redshift are similar to the massive galaxies of today (in mass, size & morphology, not just color). And finally, you need to present some kind of reason to believe that galaxies simply cannot become what we see in the time allocated to them by cosmological evolution. Pull that off, and you may have something. Otherwise, you are going nowhere, and doing it effectively.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

Thanks Tim, I looked for this effect, but had been unable to locate any sources: Would you know of a link where I can find this explained, that blue stars show up further back in time (distance) but less so nearby? I'd be curious to read up on it, and increase my knowledge. Obviously, the article showed it 'backwards'.

BTW, I did print out and read the Hopkins & Beacom paper, but it did not answer this question, since the paper was not clear on what you described, that "star formation goes up dramatically" at about 11.5 billion years ago. I suspect the real culprit is our inability to see blue band at great distances, but maybe I misunderstood. (I thought that red light traveled further in the 'dirty' dust of space than blue light!) And I agree that a sample of three galaxies is meaningless in and of itself, we need to see a pattern over hundreds if not thousands of galaxies. Thanks for your other references, will read up.

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I still do not understand how you are inferring unobservability of blue galaxies at vast distances from any statements in this article. The author just happened to choose a showy, easily observed one that happens to be relatively nearby.

I do not see anything being presented "backward" in the article. Please highlight the words or phrases which lead you to disagree with my opinion. As I and others have pointed out, those three pictures do not show the overall trend.

If the Big Bang really happened and we were close to the center, then the effect you are talking about would happen. You would of course see something entirely different depending on were you are. 10 billion light years in either direction and you will see the expanding edge of the universe.

Now if you went 10 billion light years in either direction and there was still redshift as far as you could see, you could rule out expanding universe and posit something like the micro electric field from the plasma we are embeded in.

There are different color galaxies at both near and far distances, I would not rely on the color scheme as the last word in galaxy evolution.

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"Only those who attempt the absurd will achieve the impossible." - M. C. Escher

"Freedom is popular." -Ron Paul

I think you misundersand. Starlight, like any other light, will carry farther when it is brighter. Since blue stars are generally brighter than red stars, we can see blue stars from farther away. It has nothing to do with the color, it is an effect only of brightness. That's why we can see blue stars farther out than we can see red stars. So, the farther back in time we look (i.e., the higher the redshift), the more likely we are to sample only the bright, blue stars in a galaxy, and the less likely we are to sample dim red stars. This kind of selection effect is common in astronomy.

Of course, there are bright red stars, the supergiants like Betelgeuse come to mind. But they are outnumbered by the blue supergiants like Rigel, or younger blue stars like Sirius. The vast majority of the stars in any galaxy are red dwarf stars like Proxima Centauri, which is 21,000 times dimmer than the sun.

How can you say that the paper does not answer your question, if you did not read it? The paper directly addresses the question you say it is unclear about, and explicitly shows exactly what you say it does not. So I suggest you read it. In particular, see figure 1, which explicitly plots the star formation rate as a function of redshift.

Red light will penetrate further than blue light, but not enough to compensate for the enormous difference in brightness. It is infrared that really penetrates through dust, as opposed to red starlight (which is still eyeball light). That's one of the things that makes the Spitzer Space Telescope so valuable, it can see sources embedded in the dust; Globular Cluster GLIMPSE-C01 was discovered behind 150 magnitudes of dust extinction!

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

Here is what the OP article says, in part: I don't know if this answers your question Hornblower, but it put up a 'red flag' for me, that "blue young'uns running out of star-making material and maturing into passive red galaxies" implies an 'evolution' that is time dependent upon the age of the universe. Now, perhaps we should establish some ground rules here:

1. Do you agree that the further away we look the farther we are looking back in time?

2. Do you agree the universe has a natural age progression whereby the further away (distance and time) we look, the earlier in its evolutionary stage we are seeing?

3. Do you agree that in the 'earlier' universe there should be a pattern of more blue star population (star birth) vis-a-vis the 'later' universe (i.e., earlier is farther away, later is closer in) if there is a natural aging progression for galaxies?

Now, though the author never specifically stated that this is the case, she is making a case for #3 even if she is not aware that she is. This is the point of my OP here, and as far as I can tell, it is ATM since some are having trouble with this. Therefore, two possibilities may explain this phenomenon:

A. There is a progression of older bluer stars being more populous in the early universe vis-a-vis the later universe (meaning more further back and fewer closer in distance), or

B. We are observationally limited in seeing blue stars are very great distances (earlier universe) so no such pattern has been observed, though it should be.

Therefore, if I may condense all this into one sentense:


What obsersational evidence do we have that there were more blue stars in the 'early' universe than in the later universe, from our observations?


If we can establish that there were MORE blue stars in the earlier (more distant) universe than later, at any span in time (from earlier to later, at any distance), then the progression of evolution, as implied by OP article, is confirmed. (She had it 'backwards' in her article's picture illustrations, though perhaps unaware of this, where she showed blue stars closer in.) But if no such evidence exists, then what are we actually seeing? That is the point, and I personally as yet do not know the answer to this? Perhaps you do? And if so, from what source?

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Tim, I'm looking at Fig. 1, Hopkins & Beacom, right now, but all I see is a high concentration of 'blue' stars within the 0-1 Z, which fall off prgressively towards 6 Z. What am I missing? Is this an observational problem, where blue is harder to read further back? I notice a much higher concentration closer in at just above 0 Z than further out at 2 Z, for example.

I will read the paper again to see what I'm missing here. Thanks.

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Without adding to the list of publications, it is clear from many that there is an apparent 'bulge' in the blue population that is consistent with an increase and then a decrease in star formation.

What is not clear, is at what redshift this peak occurs, or if and how blue galaxies transition to red ones. The population of 'blue' galaxies in the recent past is too high in metallicity to state that they are the precursors to galaxies like our own.

There is also the issue of whether or not the bulge is real, or the result of selection effects as NG has argued. Each time we have cranked open the extinction-limited window, the peak in the bulge has been pushed further back in time. It is reasonable to ask if this trend will continue through the next generation of scopes. Current statistics say it will not, but if it does, it means at least one more basic assumption about star formation environments is wrong. Watch for this 'evolving' trend: the peak star formation period moving backward in time with increasing optical depth penetration.

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jwj

It's a big universe out there...is it really unwinding, really burning out?

So as not to take the quotes by Ellis out of context, see Seeing the Very First Galaxies.





If you look for example at this article, ASTRONOMERS FIND MOST DISTANT KNOWN GALAXIES, you will read:

This too is interesting: Keck observatory sees universe's infancy



And if you look here, Old Stars Seen in the Early Universe: British and US Astronomers use new Spitzer Space Telescope to see light from old stars in the most distant galaxies yet, you will read:



It would appear, then, at this time in the history of cosmology, it is too early to determine for sure the extent to which galaxy evolution (along with their stellar components) is taking place in the look-back time.

What is clear form the latest data, at this premature stage in their interpretation, is that there are many galaxies at distances where according to the standard model there should be none, or few.

Prognosis and prediction: With higher resolution imaging more well-formed metal-rich galaxies will be seen at the greatest distances visible - meaning that the galaxies at those early times are much older that expected. Proof of this should come in 2013 after NASA and ESA launch the James Webb Space Telescope.

Indeed, The JWST observations may very well be the stumbling block that will lead scientists to reconsider the various schemes lumped under the umbrella name of big bang driven cosmology.



Coldcreation

I think that is a valid conclusion. We have been able to make these observations, of very high redshift galaxies, for only a few years. We have a lot to learn about galaxy formation, which is a topic that has still to be developed both observationally & theoretically.

But this is not a valid conclusion. It is not true that "according to the standard model there should be none, or few", because the standard model is not yet strong enough to make any such concusion. The statements being quoted are the intuitive opinions of scientists working in the field, and not definitive conclusions based on science. All cosmological models have to be calibrated against observation. We can predict when & how galaxies should form, but the predictions in all cases are based on arbitrary choices of model parameters, and are therefore strictly model dependent. And the arbitrary choices depend on the scientists who make them; different scientists make different choices, and often argue about it quite vigorously. You are mistaking these arbitrary choices for necessary conclusions from big bang cosmology.

The fact is that the era when galaxies form, and the universe reionizes, cannot be uniquely predicted from any cosmological model. It can be determined only by observation. It will then remain to be seen if a model can be constructed which is consistent with observations.

Indeed, the JWST will be a major advance. But it's not because of higher resolution imaging, its because JWST is a bigger light bucket. After all, the Spitzer Space Telescope is only 0.85 meters (33 inches) in aperture, whereas the JWST will be 6.5 meters (256 inches) in aperture. Multiband photometry is used to determine the band to band color differences, which are in turn used to determine the nature of the stellar population of the galaxy, its current star formation rate, and its star formation history.

But it may also be the case that the observations are not a problem for big bang cosmology. Its really a matter of how one astrophysically constructs a galaxy out of the raw material laying around. And that has a lot more to do with mundane astrophysical topics than it does with cosmology. That's why I repeat that you seriously overestimate the value of the observations you cite, as to their effectiveness in falsifying current cosmological models.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

The plot is explained at the beginning of the "Results" section, from the bottom of page 5 to the top of page 6. The piecewise linear fit peaks about redshift 1. But see that the data points, and the smooth fit peak about redshift 2.5

I think you are reading the plot wrong. It looks like you are assuming that where there are more points, there are more blue stars. The points represent observations, so where there are more points, there are more observations. The number of blue stars is not represented directly on the plot, as it is quite impossible to do more than guess at it anyway. The vertical axis is the star formation rate, and the horizontal axis is redshift. A higher star formation rate indicates more blue stars, since blue stars are younger. So you can see the relative abundance of blue stars indirectly from the star formation rate.

It is partly an observational problem, but that has nothing to do with the color. It is simply harder to see anything at very high redshift, so naturally there are more observations, and therefore more points on the plot, at lower redshift. Also the intrinsic uncertainties are higher at higher redshifts. You can see from the both the vertical & horizontal error bars are larger at higher redshift.

The grey points tend to remain distributed flatly across the plot, while the blue points tend to fall down at very high redshift. So both the location (because of the large redshift uncertainties) and the reality (the difference between blue & grey) of the peak at about redshift 2.5 are still debatable. But the reality of the rapid decline since about redshift 2.5 is unquestionable.

You are way too fixated on color, and I don't know how to better explain that it just makes no physical sense at all to insist that there is a problem seeing blue stars, as compared to red stars, over long distance. The selection is due to brightness, not color. It should be obvious and I don't know why you think it isn't.

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The point of philosophy is to start with something so simple as not to seem worth stating, and to end with something so paradoxical that no one will believe it. -- Bertrand Russell

Thanks Tim, for helping me understand the rather technical paper. I think I found the answer to the OP question on 'blue star' formation in your earlier referenced non-technical paper: NASA's Hubble Finds Hundreds of Young Galaxies in Early Uni, where it says (my bold):
I don't know about the 'reheating' the cold early universe, but there seems to be a clear pattern of more distant 'blue stars' than later, nearer galaxies, if this is correct. It would be great to find more evidence of this sort, where 'furious star births' show up in blue further back in time and space vis-a-vis more recent space. However, it still leaves puzzling that looking back into the Desert-zone of the early universe so many galaxies already appear fully formed within the first billion years, or less. But that would be for another thread.

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