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Gigabyte
2009-May-24, 12:42 PM
Some Massive Galaxies May Be Relatively New

http://www.sciencedaily.com/releases/2009/04/090410123510.htm

IU astronomer's discovery poses challenge to galaxy formation theories

http://esciencenews.com/articles/2009/04/10/iu.astronomers.discovery.poses.challenge.galaxy.fo rmation.theories

Gigabyte
2010-Feb-07, 10:57 AM
The HUDF09 team also combined the new Hubble data with observations from NASA's Spitzer Space Telescope to estimate the ages and masses of these primordial galaxies. "The masses are just 1 percent of those of the Milky Way," explains team member Ivo Labbe of the Carnegie Institute of Washington, leader of two papers on the data from the combined NASA Great Observatories. He further noted that "to our surprise, the results show that these galaxies at 700 million years after the Big Bang must have started forming stars hundreds of millions of years earlier, pushing back the time of the earliest star formation in the universe."


The existence of these newly found galaxies pushes back the time when galaxies began to form to before 500-600 million years after the Big Bang.
http://hubblesite.org/newscenter/archive/releases/2010/02/full/

This is just so awesome. These galaxies long ago ceased to exist. It's like a time machine.


The deeper Hubble looks into space, the farther back in time it looks, because light takes billions of years to cross the observable universe. This makes Hubble a powerful "time machine" that allows astronomers to see galaxies as they were 13 billion years ago, just 600 million to 800 million years after the Big Bang.

I can remember back long into the past. The theories about how galaxies form have changed a lot just in my lifetime. It used to be thought that instabilities in the early universe led to the first galaxies forming.

But if the first galaxies formed as early as 500 million years after the big bang, the wasn't enough time for the tiny primordial instabilities to grow sufficiently. What? Huh?

Then there is the black holes, dark matter and other theories about modern galaxies. None of these seem to be evident in the early ones. Or are they?

Of course this is all early on, but it is just delightful to see that far back.



Several teams are finding that the number of detected galaxies per unit of volume of space drops off smoothly towards earlier times, and that there may be too few of them to ionize the universe. On the other hand, the early galaxies were possibly extraordinarily efficient at emitting ionizing radiation, or perhaps other more exotic phenomena may need to be invoked.
http://www.ciw.edu/news/astronomers_detect_earliest_galaxies

It always amazes me that astronomers look at new data like this, and immediately start speculating about how it effects their theories, theories that I usually didn't even know about. In this case, the early ionization of the entire universe.

Who are these people? Can you just imagine them, sitting around a table saying things like "more exotic phenomena may need to be invoked" to each other?

It's like watching Spock discuss something with other Vulcans. It's awesome.

Xelebes
2010-Feb-08, 09:50 PM
Or maybe it suggests that the universe is expanding like a bubble (simple expansion of space and matter) instead of an explosion (expansion of space and matter from a source material). Who knows?

Jerry
2010-Feb-10, 12:55 AM
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Who are these people? Can you just imagine them, sitting around a table saying things like "more exotic phenomena may need to be invoked" to each other?

It's like watching Spock discuss something with other Vulcans. It's awesome.

We already have Dark Matter and Dark Energy creeping into the canons. Dark gelatin?

kzb
2010-Feb-25, 12:57 PM
Hi Robinson
It's like watching Spock discuss something with other Vulcans. It's awesome.

You're right but IMHO it's not awesome in a good way. I tend to agree with Jerry's comment. I wonder if astronomers have watched too much Star Trek, specially the more recent series, where every other problem is sorted by producing some new exotic particle to spray out the deflector emitter.

On Google Scholar, search out some articles by R Schild and C Gibson. Fascinating stuff about the early universe and how current theories are hopeless oversimplifications of fluid dynamics.

noncryptic
2010-Mar-01, 02:42 PM
Hi Robinson
It's like watching Spock discuss something with other Vulcans. It's awesome.

You're right but IMHO it's not awesome in a good way. I tend to agree with Jerry's comment. I wonder if astronomers have watched too much Star Trek, specially the more recent series, where every other problem is sorted by producing some new exotic particle to spray out the deflector emitter.

On Google Scholar, search out some articles by R Schild and C Gibson. Fascinating stuff about the early universe and how current theories are hopeless oversimplifications of fluid dynamics.

I think it's not correct to say that "the problem is sorted" by invoking dark matter and dark energy.
It's astronomer's way of saying they know something/some phenomena is there but they don't yet know what it is.
It's bad only insofar that it means they don't know, but then again science would be boring if we'd never not know.
At any rate, it's not "sorted", not by a long shot.

Personally i think it is awesome every time science stumbles on something that they have trouble understanding. After all, science is about figuring out the unknown, it's not a contest about who's the smartest guy.

It may or may not be that Schild and Gibson do know, but if they do then the process of science will cause their theory to float to the surface. Saying that other astronomers are stupid (watched too much Star Trek) does not contribute to that.

Gigabyte
2011-Jul-03, 12:56 PM
Who are these people? Can you just imagine them, sitting around a table saying things like "more exotic phenomena may need to be invoked" to each other?


Once again a new discovery (the brightest distant object) brings up the "reionization of the early universe" issue discussed in the OP.


The energy radiating from it would have contributed to the last phase of reionization of the early universe, the process that helped clear away the hydrogen fog shrouding the infant cosmos.
http://news.sciencemag.org/sciencenow/2011/06/scienceshot-distant-quasar-is-ea.html

Cougar
2011-Jul-05, 01:06 PM
The theories about how galaxies form have changed a lot just in my lifetime.

This puts you at about 5 years old, because more than 5 years ago, early structure formation ("how galaxies form") was admittedly one of the unsolved problems in astrophysics. This seems to be coming into sharper focus, but even now I believe many questions remain.



It used to be thought that instabilities in the early universe led to the first galaxies forming.

Well, this leaves out quite a few steps between the one and the other. AFAIK, it is still thought that the inflation of quantum fluctuations provided sightly over-dense regions (100,000-1) for gravity and the high radiation to "fight over," ultimately leaving the acoustic oscillations.

Gigabyte
2012-May-26, 04:17 PM
Baby Galaxies Grew Up Quickly

ScienceDaily (May 16, 2012) — Baby galaxies from the young Universe more than 12 billion years ago evolved faster than previously thought, shows new research from the Niels Bohr Institute.

Up until now, researchers thought that it had taken billions of years for stars to form and with that, galaxies with a high content of elements heavier than hydrogen and helium. But new research from the Niels Bohr Institute shows that this process went surprisingly quickly in some galaxies. http://www.sciencedaily.com/releases/2012/05/120516120256.htm#.T8AFyyvcnSQ.reddit

Like I said before, theories about Galaxy formation have changed a lot in my lifetime. Now they are starting on star formation? It's hard to know what is or isn't mainstream sometimes.


ScienceDaily (Aug. 16, 2006) — A heavy form of hydrogen created just moments after the Big Bang has been found to exist in larger quantities than expected in the Milky Way, a finding that could radically alter theories about star and galaxy formation, says a new international study led by the University of Colorado at Boulder.http://www.sciencedaily.com/releases/2006/08/060816013315.htm


A research paper by experts at the Tufts University proposes that the most massive galaxies which developed in the early Universe are, or were, in fact billions of years older than first calculated.

The conclusion the group arrived at goes against current scientific models that predict how galaxies appear and evolve, and also against models showing how the early Universe looked like. http://news.softpedia.com/news/New-Theory-on-Galaxy-Formation-Goes-Against-Models-168640.shtml


A team led by an Indiana University astronomer has found a sample of massive galaxies with properties that suggest that they may have formed relatively recently. This would run counter to the widely-held belief that massive, luminous galaxies (like our own Milky Way Galaxy) began their formation and evolution shortly after the Big Bang, some 13 billion years ago.http://phys.org/news158585134.html and http://www.astronomy.com/en/News-Observing/News/2009/04/New%20discovery%20challenges%20galaxy-formation%20theories.aspx

TooMany
2012-May-26, 09:01 PM
http://www.sciencedaily.com/releases/2012/05/120516120256.htm#.T8AFyyvcnSQ.reddit

Like I said before, theories about Galaxy formation have changed a lot in my lifetime. Now they are starting on star formation? It's hard to know what is or isn't mainstream sometimes.

http://www.sciencedaily.com/releases/2006/08/060816013315.htm

http://news.softpedia.com/news/New-Theory-on-Galaxy-Formation-Goes-Against-Models-168640.shtml

http://phys.org/news158585134.html and http://www.astronomy.com/en/News-Observing/News/2009/04/New%20discovery%20challenges%20galaxy-formation%20theories.aspx

I believe all of this evidence tends to conflict LCDM which the current mainstream "concordance" model. The mainstream has some explaining to do.

antoniseb
2012-May-26, 09:27 PM
I believe all of this evidence tends to conflict LCDM which the current mainstream "concordance" model. The mainstream has some explaining to do.
OK, you have earned an infraction... and I'm telling you here in public, since you clearly are bent on continuing this kind of behavior no matter what we say. IF you have something specific to say against the mainstream, bring it up in a new thread in the ATM section, and prepare to defend your position. If not, then do not post these snide information-free posts that simply say you have doubts, and think the burden of proof is on someone else.

Cougar
2012-May-27, 12:05 AM
A research paper by experts at the Tufts University proposes....

Really? A research paper by experts? I'm sorry, but that softpedia article looked even less reliable than wikipedia.

Gigabyte
2012-May-27, 03:11 PM
Really? A research paper by experts? I'm sorry, but that softpedia article looked even less reliable than wikipedia.

http://news.tufts.edu/releases/release.php?id=215

tusenfem
2012-May-27, 06:28 PM
http://news.tufts.edu/releases/release.php?id=215

So, why discuss a press release, when the actual paper was published November/December 2010?!?!
Here is the published paper (http://esoads.eso.org/abs/2010ApJ...725.1277M) (including a link to arxiv, but the pdf is free downloadable).

Doing "science" with press release interpretations is such a bad thing.

Cougar
2012-May-27, 07:32 PM
http://news.tufts.edu/releases/release.php?id=215

Yes, it's easy to find the press release for this story, and news stories from every conceivable news outlet and blog, but I found it wasn't that easy to find the actual paper. But I persevered. :)



The Most Massive Galaxies at 3.0<z<4.0 in the NEWFIRM Medium-Band Survey: Properties and Improved Constraints on the Stellar Mass Function (http://arxiv.org/abs/1009.0269) -
Danilo Marchesini, Katherine E. Whitaker, Gabriel Brammer, Pieter G. van Dokkum, Ivo Labbe, Adam Muzzin, Ryan F. Quadri, Mariska Kriek, Kyoung-Soo Lee, Gregory Rudnick, Marijn Franx, Garth D. Illingworth, David Wake
(Submitted on 1 Sep 2010 (v1), last revised 30 Sep 2010 (this version, v2))


All of the news reports of the linked paper make large of the claim that this finding is really inconsistent with all the existing models. But an object seen with z=3.5 has had roughly 1.8 billion years to form. Marchesini, et al., are saying they have found some high luminosities in the infrared, reportedly at z between 3 and 4. That's great. This area of early cosmic evolution has never been well understood. So what do we take from this paper, assuming it is accurate? That some of the earliest galaxies are considerably larger than we would have thought? OR they also offer the alternantive that they're detecting very early quasars and active galactic nuclei surrounded by infrared-glowing dusty clouds and accretion disks.

Perhaps contrary to your desires, this finding may support the proposition that a non-baryonic dark matter is therefore necessary to get an earlier start on the gravitational wells that came to define the diversity of structures in the Universe.

While I was looking for the above paper, I noticed a different paper, actually older than the one mentioned above, reporting on a search for such "massive galaxies" at z>4. There weren't any in their sample.

Gigabyte
2012-May-27, 08:29 PM
A formula that astronomers have long used to determine how much mass galaxies had at their birth may not be as dependable as scientists once thought, a new study suggests.

The study, which took a close look at 260 early galaxies, found that the distribution of stars in early galaxies is actually different from galaxies that formed at a later time in the universe — a finding that could change our understanding of how galaxies evolve.
http://www.msnbc.msn.com/id/47180433/ns/technology_and_science-space/t/strange-evolution-early-galaxies-revealed/#.T8KN9rBYs3U


They discovered not only that the galaxies from the very early Universe had a surprisingly large quantity of heavier elements, but also that one of the galaxies in particular was especially interesting.
"For one of the galaxies, we observed the outer regions and here there was also a high element content. This suggests that large parts of the galaxy are enriched with a high content of heavier elements and that means that already in the early history of the Universe there was potential for planet formation and life," says Johan Fynbo. http://www.sciencedaily.com/releases/2012/05/120516120256.htm

"
We have found a relatively large number of very massive, highly luminous galaxies that existed almost 12 billion years ago when the universe was still very young, about 1.5 billion years old. These results appear to disagree with the latest predictions from models of galaxy formation and evolution," said Tufts astrophysicist Danilo Marchesini, lead author on the paper and assistant professor of physics and astronomy at the Tufts School of Arts and Sciences. http://www.news-about-space.org/astronomy-news/cluster7252818/

Interesting times.

Tensor
2012-May-27, 10:48 PM
http://www.msnbc.msn.com/id/47180433/ns/technology_and_science-space/t/strange-evolution-early-galaxies-revealed/#.T8KN9rBYs3U

Press release + No paper = useless information. Do you have a link to the actual paper? If not, there really isn't anything useful here, as demonstrated by comparing the press release from Tufts and the actual paper.


http://www.sciencedaily.com/releases/2012/05/120516120256.htm

So? Do you have a problem with astronomers and astrophysicists looking for new information to adjust current theories?


" http://www.news-about-space.org/astronomy-news/cluster7252818/

You presented this before, and the paper doesn't quite match the hype of the press release. Care to explain to us what the paper itself (http://de.arxiv.org/PS_cache/arxiv/pdf/1009/1009.0269v2.pdf) means?


Interesting times.

It was interesting times in 1998, when the supernova data, indicating accelerating expansion was found. It was interesting times in 1967, when Jocelyn Bell and Antony Hewish first detected pulsars. It was interesting times in the late 1950s-early 1960s when quasars were first found and then the nature of their spectra was explained by Maarten Schmidt. It was interesting times in the 1920s, when the nature of M31 was debated. It was interesting times in 1912 when Vesto Slipher discovered the redshift of galaxies. (note the inversion of the discovery of the recession was before the objects were know to be galaxies).

This is nothing more than the normal operating procedure, so I'm not quite sure why you are just dropping these press releases into the thread, without actually making some kind of point.

To quote tusenfem "Doing "science" with press release interpretations is such a bad thing."

Gigabyte
2012-May-28, 03:17 AM
30 June 2011: An international team of astronomers, including Dr Chris Simpson of Liverpool John Moores University's (LJMU) Astrophysics Research Institute (ARI), have used the Liverpool Telescope, owned and operated by the ARI, to help discover a black hole more than a billion times the mass of our Sun, seen when the Universe was only 770 million years old.
http://www.ljmu.ac.uk/NewsUpdate/index_119824.htm

The headline reads, "Liverpool Telescope challenges galaxy formation theory". If I could find an explanation (http://www.bautforum.com/showthread.php/34960-Galaxy-formation-current-status) of what the "galaxy formation theory" actually is, I might have a chance of knowing how the Liverpool Telescope is challenging it.

Gigabyte
2012-May-28, 03:24 AM
Astrophysicists at the Hebrew University of Jerusalem have formulated a novel theory that takes issue with the prevailing view on the origin of galaxies. Their research, which was recently published in the journal Nature, concludes that the galaxies primarily formed as a result of intensive cosmic streams of cold gas (mostly hydrogen) and not as a result of galactic mergers. In fact, the scientists say that these mergers “had only limited influence on the cosmological makeup of the universe as we know it.”http://thefutureofthings.com/news/6534/new-galaxy-formation-theory-proposed.html


While their luminosities are characteristic of other massive galaxies, their chemical signatures display relatively low abundances of heavy elements, or metals. Taking some basic assumptions relating stellar evolution to chemical enrichment, the galaxies may be as young as just three or four billion years old, placing them outside the bracket for when massive galaxies are expected to form.http://www.astronomynow.com/090417Galaxyformationtheorychallengedbynewdiscover y.html

It seems there are several discoveries that are challenging galaxy formation theory. (whatever that actually is)

Obviously the size is one issue, the metal content another, and then there are the ones that are too young. All of them seem to involve time.

Tensor
2012-May-28, 05:21 AM
http://thefutureofthings.com/news/6534/new-galaxy-formation-theory-proposed.html

http://www.astronomynow.com/090417Galaxyformationtheorychallengedbynewdiscover y.html

It seems there are several discoveries that are challenging galaxy formation theory.

Actually, no. They challenge parts of galactic formation theory. See the link below. Or are you saying those press releases challenge all the sections of that paper. If so, can you specify what parts of each section those press releases invalidate?


(whatever that actually is)

It took me all of 30 seconds to find this paper (http://arxiv.org/pdf/1006.5394v2.pdf) which provides the current theory of galactic formation. Note it is a paper, not a press release.


Obviously the size is one issue, the metal content another, and then there are the ones that are too young. All of them seem to involve time.

And you know these are a problem, how? From the abstract of the paper:


Throughout, we highlight successes and failures of current galaxy formation theory.

What part of that paper says we are absolutely sure about galactic formation? Since you seem to think current theory is in error, you should have no problem pointing out specifically where in that galactic formation paper size, metallicity, and age problems are and exactly what those problems are, ACCORDING TO YOU. Along with why you think time is a problem. And, just to let you know, I want your explanations, since you are claiming the problems. Or, the explanation of problems in another actual paper, with a comparison of the appropriate section in the theory paper. Don't bother with a press release, which can't be compared with the actual paper.

Tensor
2012-May-28, 05:26 AM
http://www.ljmu.ac.uk/NewsUpdate/index_119824.htm

The headline reads, "Liverpool Telescope challenges galaxy formation theory". If I could find an explanation (http://www.bautforum.com/showthread.php/34960-Galaxy-formation-current-status) of what the "galaxy formation theory" actually is, I might have a chance of knowing how the Liverpool Telescope is challenging it.

I noticed you didn't bother to answer the questions I asked in Post #17. Is it because you can't, or you simply won't?

Do you have a link to the actual paper?
Do you have a problem with astronomers and astrophysicists looking for new information to adjust current theories?
Care to explain to us what the paper itself (http://de.arxiv.org/PS_cache/arxiv/pdf/1009/1009.0269v2.pdf) means?

tusenfem
2012-May-28, 08:15 AM
Gigabyte, it might be useful if you actually joined the discussion, instead of dumping a multitude of links to (sometimes very) old press releases.
You might want to start to look at actual papers as many a press release will give its own "twist" to the results that were (or were not) in the published paper.

Gigabyte
2012-May-28, 06:16 PM
The astronomy.com page makes it pretty clear, and is right from the mouth of the lead researcher. (if we can believe astronomy.com that is)
http://www.astronomy.com/en/News-Observing/News/2009/04/New%20discovery%20challenges%20galaxy-formation%20theories.aspx
April 16, 2009
A team led by an Indiana University astronomer has found a sample of massive galaxies with properties that suggest they may have formed recently. This would run counter to the widely held belief that massive, luminous galaxies (like our own Milky Way Galaxy) began their formation and evolution shortly after the Big Bang, some 13 billion years ago. Further research into the nature of these objects could open new windows into the study of the origin and early evolution of galaxies.

John Salzer, principal investigator for the study, said the 15 galaxies in the sample exhibit luminosities — a measure of their total light output — indicating that they are massive systems like the Milky Way and other giant galaxies. However, these particular galaxies are unusual because they have chemical abundances that suggest very little stellar evolution has taken place within them. Their relatively low abundances of "heavy" elements — elements heavier than helium, called "metals" by astronomers — imply the galaxies are cosmologically young and may have formed recently

Certainly the idea is interesting enough.


While the hypothesis that these galaxies are young is provocative, it is not the only possible explanation for these enigmatic systems. An alternative explanation proposes that the galaxies are the result of a recent merger between two smaller galaxies. Such a model might explain these objects, since the two-fold result of such a merger might be the reduction of metal abundances due to dilution from unprocessed gas and a brief but large increase in luminosity caused by rampant star formation. As a way to distinguish between these two scenarios, Salzer and his team intend to request observing time on NASA's Hubble Space Telescope to use high-resolution imaging to determine whether or not the systems might be products of merging.

The http://www.sciencedaily.com/releases/2012/05/120516120256.htm seems to be a completly different kettle of fish.


Up until now, researchers thought that it had taken billions of years for stars to form and with that, galaxies with a high content of elements heavier than hydrogen and helium. But new research from the Niels Bohr Institute shows that this process went surprisingly quickly in some galaxies. So, this is the other end of the spectrum. It seems. The first says metal poor giant galaxies formed too recently. The other says metal rich galaxies formed too early, or rather star formation seems to have happened too quickly.

And while looking into this, what do I find?

As well as wrapping up several problems in galaxy formation, their theory makes clear predictions that will be tested rapidly. One such prediction is that isolated dwarf and satellite galaxies will be found to have companions. Since their theory was first circulated, the dwarf galaxy Leo IV was found to have another little Leo V companion in July. The existence of nearby dwarf associations also supports this new theory.
http://www.astronomy.com/en/News-Observing/News/2008/10/New%20theory%20improves%20understanding%20of%20gal axy%20formation.aspx

Now they are challenging the dwarf galaxies as well? In any case, I find it most interesting. Like the following.
Ask most astronomers where to find the oldest stars in the galaxy and they’ll tell you to look at globular clusters, dense knots of stars that hover above and below the plane of the Milky Way. But Young-Wook Lee of Yonsei University Observatory in Seoul, South Korea, says most astronomers have been looking in the wrong place. Some stars in globular clusters may be 15 billion years old, he says, but the great bulge at the center of the Milky Way--a younger part of the galaxy, according to conventional wisdom--actually holds stars that are 1 or 2 billion years older. That difference matters, because the age of the oldest stars sets a lower limit on the age of the universe. What’s more, having the oldest stars at the center of the galaxy would contradict the conventional model of how our galaxy formed.

I find that sort of theorizing interesting, even when I can't follow the reasoning, it is still interesting. Like the basic dispute, over the location of the oldest stars.


But if the oldest stars are at the center of the galaxy rather than in the halo, then something is wrong with the standard picture.

Lee thinks the galaxy probably formed not from the cataclysmic collapse of one big gas cloud but from the mergers of many smaller ones. (This alternative theory is not new; in fact, Lee’s mentor, Yale astronomer Robert Zinn, helped develop it about 15 years ago.) Stars would have appeared first where the clouds collided, in what became the dense center of the primordial galaxy, and only later in the more tenuous halo. Basically the textbook picture of galaxy formation is kind of an outside-in picture, says Lee. Mine is an inside-out picture. It’s exactly the opposite view.
http://discovermagazine.com/1993/may/thecenterisancie219/?searchterm=%20galaxy%20formation

Since that is from 1993, the alternative theory is almost 34 years old now. In the paper linked to http://arxiv.org/pdf/1006.5394v2.pdf the phrase "oldest stars" doesn't appear anywhere in the paper. Neither does the word "youngest", so it's not very helpful in regards to this.

Gigabyte
2012-May-28, 06:24 PM
This is just so awesome. No, it really is if you think about it.

The "farther" we look into space, the farther back in time it looks, because light takes billions of years to cross the observable universe. This makes Hubble a powerful "time machine" that allows astronomers to see galaxies as they were 13 billion years ago, just 600 million to 800 million years after the Big Bang.

I can remember back long into the past. The theories about how galaxies form have changed a lot just in my lifetime.
It used to be thought that instabilities in the early universe led to the first galaxies forming. (which is a very simplified description of course)

But if the first galaxies formed as early as 500 million years after the big bang, the wasn't enough time for the tiny primordial instabilities to grow sufficiently. What? Huh? (at this point it all seems quite theoretical, so it's pure speculation of course)

Then there is the black holes, dark matter and other theories about modern galaxies. None of these seem to be evident in the early ones. Or are they? The question is clearly undecided.

It always amazes me that astronomers look at new data like this, and immediately start speculating about how it effects their theories, theories that I usually didn't even know about. In this case, the early ionization of the entire universe.

Who are these people? Can you just imagine them, sitting around a table saying things like "more exotic phenomena may need to be invoked" to each other?

It's like watching Spock discuss something with other Vulcans. It's awesome.

Then one of the aliens notices me and demands I join in. And I am like, "No way man! I don't even understand half of what you are saying"

Gigabyte
2012-Jun-05, 04:47 AM
Well that certainly didn't work.


30 June 2011: An international team of astronomers, including Dr Chris Simpson of Liverpool John Moores University's (LJMU) Astrophysics Research Institute (ARI), have used the Liverpool Telescope, owned and operated by the ARI, to help discover a black hole more than a billion times the mass of our Sun, seen when the Universe was only 770 million years old.

Although no light is emitted by the black hole itself, its strong gravity pulls in surrounding gas that is heated up and shines as what astronomers call a quasar. The existence of such a massive black hole so soon after the Big Bang presents a challenge to theories that attempt to describe the formation of galaxies. http://www.ljmu.ac.uk/NewsUpdate/index_119824.htm

Even I can understand why that discovery challenges the timeline of things. Black holes, that massive, and how long they take to form, and their role in Galaxy formation, it certainly looks like things may be a bit different than we thought. Looking at the paper on Galaxy formation we read
Before supermassive black holes can grow via accretion or merging, there must be some pre-existing (probably
not supermassive) seed black holes. Most plausibly, these seeds form at high redshifts as the remnants of the earliest
generation of Population III stars which have reached the end of their stellar lifetimes. Details of the formation of
these first stars remain incompletely understood, but hydrodynamical simulations suggest that they have masses in
the range of a few hundred Solar masses (Abel et al. 2002; Bromm et al. 2002), leaving intermediate mass black hole
remnants. (thanks to Tensor)
It took me all of 30 seconds to find this paper which provides the current theory of galactic formation. Note it is a paper, not a press release.

Now I'm no expert on Galaxy formation theory, but the timeline doesn't fit at all there. I checked Wikipedia http://en.wikipedia.org/wiki/Galaxy_formation_and_evolution#Formation_of_the_fi rst_galaxies but people keep adding the new discoveries to the page, making it hard to understand just what the current theory actually is at this point.

Tensor
2012-Jun-05, 05:34 AM
Well that certainly didn't work.

http://www.ljmu.ac.uk/NewsUpdate/index_119824.htm

Even I can understand why that discovery challenges the timeline of things. Black holes, that massive, and how long they take to form, and their role in Galaxy formation, it certainly looks like things may be a bit different than we thought.

Yeah, according to the press release. What does the paper itself claim? What does the paper itself show? What data does the paper itself provide for support? Unless you produce that, all you have is some hyped up press article. Which is useless for any actual analysis.



Looking at the paper on Galaxy formation we read (thanks to Tensor)

Now I'm no expert on Galaxy formation theory, but the timeline doesn't fit at all there.

You're not an expert, but you're going to pontificate on how the press release claims the timeline doesn't fit, right? Perhaps you can explain how a non-expert, as you claim to be, can tell from the press release exactly what the paper itself specifically claims to be able to state that the timeline doesn't fit. What part of the galaxy formation paper and the paper the press release (not the press release only) comes from are incompatible?

You do know there are other ways to form black holes (http://arxiv.org/pdf/astro-ph/0602363v2.pdf), right? It's called direct collapse (http://arxiv.org/pdf/0709.0545v1.pdf).



I checked Wikipedia http://en.wikipedia.org/wiki/Galaxy_formation_and_evolution#Formation_of_the_fi rst_galaxies but people keep adding the new discoveries to the page, making it hard to understand just what the current theory actually is at this point.

Yeah, your best bet is to stay away from Wikipedia. If you want something specific, use the paper and look it up. So how about you explain to us exactly what you're looking for? You seem to keep bringing in old press releases and Wikipedia links with old claims that there is something wrong with galactic formation theory. Yet, you haven't presented anything concrete, just some press release puffing up of discoveries. You can't even provide us with the actual papers and don't seem to be acquainted with current research, or even older research. So what exactly do you think is wrong with galactic formation theory? Specifically.

Gigabyte
2012-Jul-03, 04:52 AM
http://blogs.discovermagazine.com/badastronomy/2012/06/27/the-galaxy-that-shouldnt-be-there/

I feel so vindicated.

Tensor
2012-Jul-03, 05:10 AM
http://blogs.discovermagazine.com/badastronomy/2012/06/27/the-galaxy-that-shouldnt-be-there/

I feel so vindicated.

Why? What specifically in that link agrees with what else you've linked to in this thread? What in that link specifically vindicates what you've claimed in this thread. Mostly, all you've done is link to a press release or Wikipedia, without specifically stating what you are talking about. How about some specifics?

Gigabyte
2012-Jul-03, 07:33 AM
Maybe galaxies formed more vigorously than we thought in the early Universe, so there are more than we might suppose.

I thought it was obvious.


If you get one weird thing happening, you might be able to shrug it off as coincidence. But two? In this case the existence of the arc at all coupled with the huge mass of this galaxy and cluster make me think there’s more going on here than we see.

Which pretty much sums up what I've said for years now.

Cougar
2012-Jul-03, 11:47 AM
...there’s more going on here than we see.

Gee, that's kind of vague. Can you be more specific?

Cougar
2012-Jul-03, 12:34 PM
I feel so vindicated.

I would also question why you feel vindicated. It appears you are not understanding these articles. The lensed galaxy in your newest link is estimated at z=3. That's pretty far away (and fairly young), but nowhere near as far away and young as ULAS J1120+0641, the quasar discussed in your earlier links, which is at z=7.085.

Please note that, as earlier mentioned, you are falling for the hyperbole in press releases and popsci mags. The actual paper on ULAS J1120+0641 says nothing about challenging or tossing out galaxy formation theories. Here is all they say:



The existence of 109 MSun black holes at z ~ 6 already placed strong limits on the possible models of black hole seed formation, accretion mechanisms and merger histories; the discovery that a 2*109 MSun black hole existed just 0.77 Gyr after the Big Bang makes these restrictions even more severe.


I guess sciencedaily could report that this finding "further restricts our models," but with such straightforward reporting, they'd probably go out of business.

Gigabyte
2012-Jul-03, 08:57 PM
Gee, that's kind of vague. Can you be more specific?

Me? I didn't write the article. I didn't publish or discover anything. Just talking about what other scientists are saying.

Gigabyte
2012-Jul-03, 09:40 PM
Maybe galaxies formed more vigorously than we thought in the early Universe, so there are more than we might suppose.

I find that sort of musing interesting, as well as all the other ramifications of new research and discoveries. It's just a conversation. About what happened a long time ago.

Tensor
2012-Jul-04, 03:15 AM
Me? I didn't write the article. I didn't publish or discover anything. Just talking about what other scientists are saying.

How is providing a link to a article (not the paper itself, mind you, just the article) then claiming you've been vindicated talking about what other scientists are saying?

Gigabyte
2012-Jul-04, 07:03 PM
http://arxiv.org/pdf/1205.3788.pdf

It's fairly obvious what they are saying in their conclusions.

speedfreek
2012-Jul-04, 08:37 PM
Yes, they are saying we have found a surprisingly large galaxy that existed around 2 billion years after the Big-Bang. It looks like there are galaxies out there that are larger than previously predicted for the early universe. It means we still don't really understand how galaxies formed in the early universe.

Gigabyte
2012-Jul-04, 09:05 PM
Actually the huge galaxy cluster is pretty surprising by itself. The multiple findings of unexpected things leads to the inevitable challenge of existing theory. Science has always progressed in this way.

Early metal rich galaxies, early giant galaxies, huge galaxy clusters, and even earlier huge galaxies beyond them, it's all quite surprising.

Gigabyte
2012-Jul-04, 09:07 PM
Baby Galaxies Grew Up Quickly


ScienceDaily (May 16, 2012) — Baby galaxies from the young Universe more than 12 billion years ago evolved faster than previously thought, shows new research from the Niels Bohr Institute.

Up until now, researchers thought that it had taken billions of years for stars to form and with that, galaxies with a high content of elements heavier than hydrogen and helium. But new research from the Niels Bohr Institute shows that this process went surprisingly quickly in some galaxies.http://www.sciencedaily.com/releases/2012/05/120516120256.htm#.T8AFyyvcnSQ.reddit

If that is to be believed, galaxy formation theory has changed just this year. It's hard to say.

antoniseb
2012-Jul-04, 09:34 PM
... If that is to be believed, galaxy formation theory has changed just this year. It's hard to say.

Galaxy formation is one of the hotbeds of astronomy right now. I hesitate to use the word theory in the same way that General Relativity is a theory. It is a collection of models, some of which might be close to what actually happened. We are applying increasing amount of detail to our computational models, and increasing the detail of our observation. This is science, and the scientific method. It isn't as though all this is already worked out perfectly, and one stray observation blows the whole thing apart. There isn't just one model, and none of the models are detailed down to the atom by atom level. We will be learning more and refining our understanding of galaxy formation for several decades at least.

Cougar
2012-Jul-04, 10:59 PM
ScienceDaily (May 16, 2012) — Baby galaxies from the young Universe more than 12 billion years ago evolved faster than previously thought, shows new research from the Niels Bohr Institute... Up until now, researchers thought that it had taken billions of years for stars to form and with that, galaxies with a high content of elements heavier than hydrogen and helium. But new research from the Niels Bohr Institute shows that this process went surprisingly quickly in some galaxies.
If that is to be believed, galaxy formation theory has changed just this year. It's hard to say.

I don't believe there are many researchers who think it took two or more billion years for stars to form.

Nevertheless, early structure formation does indeed appear to have developed quite early, maybe surprisingly early, but as antoniseb mentioned, there really was no single existing "theory" that these new observations are coming in confict with. These observations should be surprising because they are new and previously unknown, and they're adding to our understanding of early structure formation, not because they're overthrowing the Standard Model of Cosmology. :naughty:

Tensor
2012-Jul-05, 05:09 PM
Baby Galaxies Grew Up Quickly


ScienceDaily (May 16, 2012) — Baby galaxies from the young Universe more than 12 billion years ago evolved faster than previously thought, shows new research from the Niels Bohr Institute.

Up until now, researchers thought that it had taken billions of years for stars to form and with that, galaxies with a high content of elements heavier than hydrogen and helium. But new research from the Niels Bohr Institute shows that this process went surprisingly quickly in some galaxies.

http://www.sciencedaily.com/releases/2012/05/120516120256.htm#.T8AFyyvcnSQ.reddit

If that is to be believed, galaxy formation theory has changed just this year. It's hard to say.

I gave you a link to the paper on Galaxy Formation Theory(GFT). Did you bother to read it? From this last comment, it doesn't appear that you did. There is a list of 19 papers, prior to 2010 that talks about early galaxy formation, and doesn't even count the papers posted since then.

Anyway, from the actual paper that the article is taken from:


An important point to note is that four of the data points have specifically been chosen to have high metallicity.

If it was thought, up until now, the high content of heavier elements took billions of years, then why where they looking for high metallicity galaxies?


Møller et al. in 2004 made the prediction, based on a hint of a luminosity-metallicity relation for DLA(Damped Lyman alpha absorbers), that HI size should increase with increasing metallicity. In this paper we investigate the distribution of impact parameter and metallicity that would result from the correlation between galaxy size and metallicity. We compare our observations with simulated data sets given the relation of size and metallicity. The observed sample presented here supports the metallicity-size prediction: The present sample of DLA galaxies is consistent with the model distribution.

Not to mention that a prediction on the high metallicity was made in 2004 was found to hold in this recent paper. The observations matched the model. So, it doesn't appear that it's changed all that much, if it matches model predictions from 2004.

Continuing:


The correlation of [M/H] and halo mass suggests that the metal poor systems are to be found in smaller haloes and therefore at smaller impact parameters. The opposite is true for metal rich DLAs. This agrees well with the data presented here in Fig. 3.

Again, matching the model. However, there is the problem with having only 10 data points. That can introduce some rather high bias in the sample. There is also the the deliberate choice of high metallicity galaxies.

Interestingly, considering your original quote talked about billions of years to form high metal content galaxies:


The nature of the metal poor population of DLA galaxies is, however, still unknown, as these DLA counterparts are much more difficult to observe. Furthermore, this sample of spectroscopically confirmed DLA galaxies serves as constraints for future simulations that include modeling of DLAs.

Meaning there are still unknowns, which will have to discovered and investigated. But the written article doesn't seem to match the actual paper. Which is why tusenfem advised against using science articles.

Gigabyte
2012-Jul-05, 05:44 PM
“We have studied 10 galaxies in the early Universe and analysed their light spectra. We are observing light from the galaxies that has been on a 10-12 billion year journey to Earth, so we see the galaxies as they were then. Our expectation was that they would be relatively primitive and poor in heavier elements, but we discovered somewhat to our surprise that the gas in some of the galaxies and thus the stars in them had a very high content of heavier elements. The gas was just as enriched as our own Sun,” explains Professor Johan Fynbo from the Dark Cosmology Centre at the Niels Bohr Institute, University of Copenhagen. http://news.ku.dk/all_news/2012/2012.5/baby_galaxies_grew_up_quickly/

It's pretty clear what they are saying.

KABOOM
2012-Jul-05, 05:54 PM
If we can now detect light from galaxies that was emitted ~ 12 billion years ago from stars with similar metalicity as our own sun, what does this mean to the time line of initial star and galaxy formation?

Conentional wisdom is: Population 3 stars were the earliest stars formed and were almost all hydrogen and helium. These very large early stars then went SN and the next geneartion of stars (Population 2) had heavier elements and formed galaxies.

tusenfem
2012-Jul-05, 05:55 PM
http://news.ku.dk/all_news/2012/2012.5/baby_galaxies_grew_up_quickly/

It's pretty clear what they are saying.

Interesting though that in the abstract of the paper in MNRAS (link at the bottom of the news link) there is no mention whatsoever about "surprise" but for that that the measurements agree with the model of H I size vs. metalicity.

Ahh, the pitfalls of doing science by press release.

antoniseb
2012-Jul-05, 06:03 PM
If we can now detect light from galaxies that was emitted ~ 12 billion years ago from stars with similar metalicity as our own sun, what does this mean to the time line of initial star and galaxy formation?

Conentional wisdom is: Population 3 stars were the earliest stars formed and were almost all hydrogen and helium. These very large early stars then went SN and the next geneartion of stars (Population 2) had heavier elements and formed galaxies.

What it means is that the brightest light is coming from places that have formed big stars. If the lifetime of a large star is 10 million years, and you are looking at a time 1.7 billion years after the big bang, how many generations of large stars might have formed in your bright area. The answer is enough. It was probably enough 13.1 billion years ago.

Cougar
2012-Jul-05, 07:35 PM
It's pretty clear what they are saying.

However, this says nothing about what you are saying, if anything... or even what you think they are saying. Please tell us what you think. I don't come here to read ScienceDaily articles.

TooMany
2012-Jul-05, 08:29 PM
However, this says nothing about what you are saying, if anything... or even what you think they are saying. Please tell us what you think. I don't come here to read ScienceDaily articles.

Cougar, we can all read what an author of the paper was quoted as saying. The meaning of his statement seems clear enough. If you believe that quote is not representative of their own conclusions, then you are simply in a state of denial.

Things are changing very quickly as deeper and deeper analysis has become possible in recent years. There are unexpected surprises. You cannot rewrite history to say "we expected that all along".

AFAIK there has been no detection of a decline in metallicity in distant sources. This was indeed unexpected.

TooMany
2012-Jul-05, 08:48 PM
What it means is that the brightest light is coming from places that have formed big stars. If the lifetime of a large star is 10 million years, and you are looking at a time 1.7 billion years after the big bang, how many generations of large stars might have formed in your bright area. The answer is enough. It was probably enough 13.1 billion years ago.

But was there 1.7 billion years available for star formation? When did the Universe reach a temperature at which pure hydrogen/helium stars could form? When did the quantum fluctuations become amplified enough to enable the formation of such stars? I.e., how much time was really available? Why would the first stars be so massive when matter in the Universe has had the least amount of time to cool and collect into dense clouds. I've read talk about early stars with masses around 300 M_solar. How could the gas be concentrated enough? Stars so heavy very rarely form now, right? Does decreased metallicity cause larger stars to form? The oldest stars in the MW are small in comparison and formed very early, didn't they? Of course such large stars would blow up in a few millions years as you suggest.

I don't know what the rates of metal formation would be and exactly how many generations would be required to reach solar levels. Do you? It would be interesting to know what assumptions theorist are making about the early universe now in light of these recent discoveries. Or is it your contention that it is just hype and theorist expected this all along?

TooMany
2012-Jul-05, 09:46 PM
I did a little research and the most distance galaxy detected so far is 12.9 Gly away, or 800 millions years after t0. The first stars are supposed to have formed anywhere from 200 My to 500 My after t0. Thus the age of this galaxy is at most between 300 and 600 million years. You can get 30 to 60 generations of stars that live to 10 My. That seems like a lot, but I don't know the expected enrichment rate. Also it's unlikely that all stars were so massive so that has to be factored in.

antoniseb
2012-Jul-05, 10:20 PM
... When did the quantum fluctuations become amplified enough to enable the formation of such stars? ...
This is an active area of research, and observation is playing a big role. There is no fragile glass theory to break here, only models and simulations... so as you noted in your next post, looking it up yields consistent answers within a range... but nothing exact. (BTW, not quantum fluctuations.... but density fluctuations.)

Cougar
2012-Jul-05, 10:29 PM
Cougar, we can all read what an author of the paper was quoted as saying. The meaning of his statement seems clear enough.

As does the meaning of my statement, which seems to have escaped your understanding.

Tensor
2012-Jul-06, 03:39 AM
http://news.ku.dk/all_news/2012/2012.5/baby_galaxies_grew_up_quickly/

It's pretty clear what they are saying.

Actually, no, it's not. How primitive is relatively primitive? How much, in actual numbers, is poor in heavier elements? It says some of the galaxies, how many? How unusual is that number? Specifics, specifics, specifics. See, none of those specifics are in there, because that is not what the paper is about. The specifics that are in the paper are what the paper is about. Are current theories still able to account for that amount of heavier elements? After all, about 10 years ago, researchers were surprised at the number of massive clusters at .5 < z <1. But, they found that theory could account for them.

It's also interesting that you're pulling one paragraph out of the paper, and that paragraph is not the even the point of the paper, and you're ignoring the rest of it. If all this is so surprising, then perhaps you can explain to us why you think galaxy formation theory must have changed this year, when the paper shows that a prediction from 2004 was verified by the paper. Because the high metallicity was first found in the years prior to that (2002 and 2003 to be exact).

TooMany
2012-Jul-06, 11:18 PM
This is an active area of research, and observation is playing a big role. There is no fragile glass theory to break here, only models and simulations... so as you noted in your next post, looking it up yields consistent answers within a range... but nothing exact. (BTW, not quantum fluctuations.... but density fluctuations.)

Aren't the density fluctuations thought to be caused by quantum fluctuations in the extremely early universe? Or are the quantum fluctuations supposed to be on some other scale? Is there some other cause for density fluctuations (e.g. are they spontaneous since nothing is in perfect balance)?

TooMany
2012-Jul-06, 11:40 PM
As does the meaning of my statement, which seems to have escaped your understanding.

Sorry if I misinterpreted your statement. I agree with Gigabyte that the meaning of the author's statement is pretty clear. No, the author doesn't cite exact numbers as demanded by Tensor, he just expresses his opinion in the quote which I've condensed to this sentence to be specific:



Our expectation was that they [distant galaxies] would be relatively primitive and poor in heavier elements, but we discovered somewhat to our surprise that the gas in some of the galaxies and thus the stars in them had a very high content of heavier elements [solar levels similar to galaxies 12 Gys older].


They expected one thing but discovered another and therefore they were somewhat surprised. If they were somewhat surprised, then maybe they didn't know this was already expected back in 2002-2003 or 2004. One might conclude that theory led to the original expectation but they didn't say anything about that so it would only be speculation.

Many papers are written in a formal, profession tone. You don't see "surprised" all that much in papers. You are more likely to see that sort of comment when a professional is interviewed and asked for his opinion, as in this case apparently. Sometimes the important conclusion in papers are expressed so technically that it is difficult for the layman to appreciate what the significance is. You can often blame the press (which attempts to interpret for the laymen) for sensationalism. However, in this case you have a direct quote from an author that expresses something about their conclusions.

If you review Gigabyte's posts in this thread I think you will find they are quite innocuous. He is simply citing some articles he has read that indicate some changes relative to previous expectations.

I don't see the harm in Gigabyte's posts or any reason to challenge him personally about their contents. He has only acted as a messenger.

antoniseb
2012-Jul-07, 12:34 AM
... (e.g. are they spontaneous since nothing is in perfect balance)?
I wasn't there, but if you look up "baryonic acoustic oscillations" you'll find why there were density fluctuations, and these existed in part because, as you noted, nothing was in particle-by-particle perfect balance.

Tensor
2012-Jul-07, 02:13 AM
Sorry if I misinterpreted your statement. I agree with Gigabyte that the meaning of the author's statement is pretty clear. No, the author doesn't cite exact numbers as demanded by Tensor, he just expresses his opinion in the quote which I've condensed to this sentence to be specific:.

They expected one thing but discovered another and therefore they were somewhat surprised. If they were somewhat surprised, then maybe they didn't know this was already expected back in 2002-2003 or 2004. One might conclude that theory led to the original expectation but they didn't say anything about that so it would only be speculation.

If they didn't know it was expected in 2002-2004, then why is the main thrust of the paper confirmation of the high metallicity-large size prediction? After all, they state in the paper that the prediction in 2004 was based on prediction prior to that. Now, maybe it was a surprise back in 2002-2004, but that would hardly be news now.


Many papers are written in a formal, profession tone. You don't see "surprised" all that much in papers. You are more likely to see that sort of comment when a professional is interviewed and asked for his opinion, as in this case apparently. Sometimes the important conclusion in papers are expressed so technically that it is difficult for the layman to appreciate what the significance is. You can often blame the press (which attempts to interpret for the laymen) for sensationalism.

That is exactly what tusenfem and I have pointed out several times, that what is in an article, may not be exactly what is in the paper, and in fact, as in this case, may have nothing to do with the paper.


However, in this case you have a direct quote from an author that expresses something about their conclusions.

The direct quote has nothing to do with the paper. In fact, it wasn't even about the paper. See below.


If you review Gigabyte's posts in this thread I think you will find they are quite innocuous. He is simply citing some articles he has read that indicate some changes relative to previous expectations.

I don't see the harm in Gigabyte's posts or any reason to challenge him personally about their contents. He has only acted as a messenger.

And I pointed out where the articles may not have been correct. He then asked for information on Galaxy Formation Theory. I provided a link to a paper that covered it. Several of his next posts indicated things he though were changes that weren't changes. It's as if he didn't bother reading the paper.


He is simply citing some articles he has read that indicate some changes relative to previous expectations.

If that was all it was, I would agree with you. Linking to an article, posting "I feel vindicated", when the article has nothing to do with the listed paper and even the paper(s) it does have connections to don't indicate any big changes is simply citing something that is wrong. Vindicated about what, seems to be a fair question.

TooMany
2012-Jul-07, 03:59 PM
I wasn't there, but if you look up "baryonic acoustic oscillations" you'll find why there were density fluctuations, and these existed in part because, as you noted, nothing was in particle-by-particle perfect balance.

Where do the quantum fluctuations come into play? Large scale structure? parejkoj suggested that the BAO fluctuations are larger (150 Mpc?) than the more obvious void pattern seen in the SDSS plots which are about 20-50 Mpc, I think.

Do you know what accounts for the smaller pattern of fluctuations? Is the BAO "visible" when you look at the SDSS plots? (I'll try to read up on this.)

TooMany
2012-Jul-07, 04:16 PM
Now, maybe it was a surprise back in 2002-2004, but that would hardly be news now.


Right, so the quote doesn't seem to make sense, unless maybe the author meant that they were surprised to confirm the finding?



That is exactly what tusenfem and I have pointed out several times, that what is in an article, may not be exactly what is in the paper, and in fact, as in this case, may have nothing to do with the paper.
The direct quote has nothing to do with the paper. In fact, it wasn't even about the paper. See below.


Did you read the paper? (I haven't yet.) Maybe the quote is completely out of context which would not speak well for the reporter.



And I pointed out where the articles may not have been correct. He then asked for information on Galaxy Formation Theory. I provided a link to a paper that covered it. Several of his next posts indicated things he though were changes that weren't changes. It's as if he didn't bother reading the paper.

If that was all it was, I would agree with you. Linking to an article, posting "I feel vindicated", when the article has nothing to do with the listed paper and even the paper(s) it does have connections to don't indicate any big changes is simply citing something that is wrong. Vindicated about what, seems to be a fair question.

Gigabyte will have to speak for himself, but I suppose he thinks that this supports his notion that recent observations were not expected from galaxy formation theory.

Do you think that in the late 90's such findings concerning metallicity would have been a surprise?

antoniseb
2012-Jul-07, 04:18 PM
Where do the quantum fluctuations come into play?...
First, let me say that the phrase "Quantum fluctuations" is a catch-all for things we don't know, and what it might mean would depend a lot on which m-theory/string-theory/LQG-theory/etc you subscribe to. But more importantly to your question, quantum fluctuations can only come to play in a meaningful way at a time when the universe is very small (before or at the beginning of inflation). Once inflation has finished (however it happened), how could something at the quantum scale have a wide impact?

tusenfem
2012-Jul-07, 04:44 PM
Where do the quantum fluctuations come into play? Large scale structure? parejkoj suggested that the BAO fluctuations are larger (150 Mpc?) than the more obvious void pattern seen in the SDSS plots which are about 20-50 Mpc, I think.

Do you know what accounts for the smaller pattern of fluctuations? Is the BAO "visible" when you look at the SDSS plots? (I'll try to read up on this.)


And this is exactly the thing I was PMing you about, You just make claims without even knowing if they apply or not.
If you don't know whether some effect happens or not THEN DO NOT MAKE THE CLAIM THAT THIS EFFECT WILL HAPPEN.
This is not jus "hypothesizing" with science jumping ahead by thinking outside of the box, this is just showing off ignorace,

TooMany
2012-Jul-07, 04:49 PM
First, let me say that the phrase "Quantum fluctuations" is a catch-all for things we don't know, and what it might mean would depend a lot on which m-theory/string-theory/LQG-theory/etc you subscribe to. But more importantly to your question, quantum fluctuations can only come to play in a meaningful way at a time when the universe is very small (before or at the beginning of inflation). Once inflation has finished (however it happened), how could something at the quantum scale have a wide impact?

I don't know but I thought they were supposed to set the pattern for some structure scale. Here's a quote from the wiki "Big Bang" article:



Heisenberg's uncertainty principle predicts that during the inflationary phase there would be quantum thermal fluctuations, which would be magnified to cosmic scale. These fluctuations serve as the seeds of all current structure in the Universe. Inflation predicts that the primordial fluctuations are nearly scale invariant and Gaussian, which has been accurately confirmed by measurements of the CMB.


So if they are scale invariant then should fluctuations in cosmic density also be? Perhaps there is an upper limit on the scale of 50 Mpc or so?

Sorry if this is off topic, maybe it should be another thread.

antoniseb
2012-Jul-07, 04:58 PM
... Here's a quote from the wiki "Big Bang" article. ...

This article includes a lot of speculation about times when we don't have one specific model... and it includes handwaving for the public.
People ask where the structure came from. The reality is that we are still working that out... as you can tell by the rather conditional language around the phrase "quantum thermal fluctuations".
Don't ask for details about this era, unless you specifically ask about one particular model with one specific theory about the nature of particles in the quantum realm, and one specific theory of gravity. Nothing absolute can be said, and that will probably be true for many decades or even centuries.

TooMany
2012-Jul-07, 05:02 PM
This article includes a lot of speculation about times when we don't have one specific model... and it includes handwaving for the public.
People ask where the structure came from. The reality is that we are still working that out... as you can tell by the rather conditional language around the phrase "quantum thermal fluctuations".
Don't ask for details about this era, unless you specifically ask about one particular model with one specific theory about the nature of particles in the quantum realm, and one specific theory of gravity. Nothing absolute can be said, and that will probably be true for many decades or even centuries.

OK, thanks.

Gigabyte
2012-Jul-08, 08:52 AM
Getting back to the latest example of discoveries that challenge accepted ideas about galaxy formation, which is sort of like the topic actually, I was wondering exactly what Phil Plait means when he writes:
It would take a lot more than just a few odd examples before we’d be ready to dump an idea like dark matter that goes a long, long way to explaining so many other things.

But therein lies the beauty of all this! Old models do get overthrown, and we’re willing to do it once the evidence is strong enough. This gravitational lens observation is not enough to do it, but it may be part of a bigger picture that will. Or, more likely, there’s a simpler explanation that we just don’t know yet.

After all, this is science! If we knew everything already, we wouldn’t be doing research. There’s a lot about the Universe we have yet to understand. That’s why this is so much fun. http://blogs.discovermagazine.com/badastronomy/2012/06/27/the-galaxy-that-shouldnt-be-there/

I guess looking at it as fun might annoy some people, but if it's not fun, why do it? By it, I mean post on a forum. Or on his blog.

Shaula
2012-Jul-08, 09:25 AM
Of course it is fun. It is like solving a crossword puzzle. But the problem is that there is a tendency for people to see a clue like "Household pet, 3 letters", see that another clue means it has to fit into -Z- and scream! OMGOMGOMGOMG! DOG Doesn't fit! We have to throw out all our other answers, rip everything up and start again! In fact we could just change one of our answers, making the word -A- and then realise that DOG was not the answer after all, it was CAT.

If something doesn't immediately fit the correct way to go about it is to try changing the current models, see if they fit. If they are not doing a good job then consider other models previously rejected because they do a worse job fitting other observations and tweak them. If they don't work then try some brand new ideas. It is fun but requires patience, an awareness of the current models that goes deeper than a few pop-sci quotes and most importantly neutrality.

Gigabyte
2012-Jul-08, 09:40 AM
I've never seen that tendency in real astronomers. They seem cautious and careful, especially when describing new evidence they discover. OK sometimes they get all excited and surprised, but I don't see anyone trying to overthrow all of science.

Nereid
2012-Jul-08, 11:03 AM
I've never seen that tendency in real astronomers. They seem cautious and careful, especially when describing new evidence they discover. OK sometimes they get all excited and surprised, but I don't see anyone trying to overthrow all of science.(bold added)

Well, they wouldn't be astronomers if they were trying to overthrow all of science, would they?

But, to overthrow all of science is actually very simple (in principle): since all of science is built on just two theories - General Relativity (GR) and the Standard Model (of particle physics, the SM) - all you need to do is overthrow them both. And thousands of physicists are trying the very best to do exactly that! And the best they've come up with so far is called "String Theory" (the second-best might be "Loop Quantum Gravity").

Or not.

Something which overthrows both GR and the SM won't overthrow the neo-Darwinian synthesis, to take one example, nor Arrwo-Debreu type general equilibrium theory (in economics), to take another.

And it may not overthrow any galaxy formation theory either.

Oops.

Shaula
2012-Jul-08, 01:47 PM
I've never seen that tendency in real astronomers. They seem cautious and careful, especially when describing new evidence they discover. OK sometimes they get all excited and surprised, but I don't see anyone trying to overthrow all of science.
You rarely see actual scientists trying to overthrow everything, no. That is because they tend to have a good grasp of how inter-related things are and how small changes can have profound effects. If you are about to change everything then you need to have a very, very strong set of evidence and be able to prove that the predictions match earlier observations. That does not stop a fair few people out there from claiming that everything we know is wrong.

Tensor
2012-Jul-08, 02:20 PM
First off, my apologies, I gave you a "see below" and then there isn't an explanation for the "see below". Honest, it was in there, and I must have deleted it during my edit prior to uploading.



Did you read the paper? (I haven't yet.)

Yes, I read the paper. I always read a paper before using it as a source. We've had quite a few people here present a paper supporting their pet idea, when, in fact, the presented paper, completely refutes their idea. This usually happens when they only use the title or parts of the abstract, or only the abstract, without providing a link to the paper. I can usually find a link to the actual paper, which doesn't always actually show what someone might claim from the abstract. So, to make sure that doesn't happen to me, I always make sure any paper I present as support, actually supports my contentions.


Maybe the quote is completely out of context which would not speak well for the reporter.

Here's the part that somehow got deleted in edit before getting uploaded. The author quoted, Johan Fynbo wrote a paper in 2011, that discusses the the very thing that was in the article. Again, though, surprise is not in the actual paper. It's more of a report of what they found, reflection on why it maybe shouldn't have been a surprise, and a couple of possible explanations within current cosmological parameters and galactic formation theories. So, yes, the original find was a surprise,(presented, as you said, as previous studies showed xxx but we found yyy) but it really shouldn't have been as current theories and recent simulations indicate that it was entirely possible. So, yes, the reporter kind of blew it as far as linking the quote with the paper, the quote doesn't go with the linked paper. He also went to sensationalism, by highlighting the surprise part, and ignoring the parts where the explanations about why it shouldn't have been a surprise were located(of the paper that he was actually referring to). Which is why tusenfem and I pointed out the dangers of doing science by press release.


Do you think that in the late 90's such findings concerning metallicity would have been a surprise?

Hard to say. Recent observations indicate that the star formation rate peaked around 5 billion years ago. Compared to the previously thought 8 billion. If star formation peaked at 8 billion years ago, there would be quite a bit of metallicty around. However, the recent observation show that while the currently thought peak was later, the rate of star formation wasn't all that much less than the previous peak. The previous peak was more steeply curved on both sides of the peak (high rate for ~5 billion years). The current peak is more flat prior to and after the peak and the rate remains rather high for ~9 billion years. The rate of Star Formation is about the same in both at early epochs, so the metallicity should be about the same.

antoniseb
2012-Jul-08, 03:07 PM
... Recent observations indicate that the star formation rate peaked around 5 billion years ago. Compared to the previously thought 8 billion. If star formation peaked at 8 billion years ago, there would be quite a bit of metallicty around. ...

An important point that usually escapes conscious thought is that no matter when star-forming peaked, for distant galaxies, the light we see largely only comes from areas of active star forming where metallicity will almost always be close to mature levels. We aren't looking at spectra from the parts of the galaxy that haven't formed.

Tensor
2012-Jul-08, 03:28 PM
An important point that usually escapes conscious thought is that no matter when star-forming peaked, for distant galaxies, the light we see largely only comes from areas of active star forming where metallicity will almost always be close to mature levels. We aren't looking at spectra from the parts of the galaxy that haven't formed.

That's a good point, for emission lines. Although the paper by Johan Fynbo found metallicity by finding absorption lines by observing quasars through the observed galaxies, away from the star forming regions. As these galaxies are near the current Star Forming peak, the metallicity was and should have been near mature levels, even away from the star forming regions. At least, they said, once they thought about it a bit.

TooMany
2012-Jul-09, 12:08 AM
One of the problems with current galaxy formation theory is the bottom-up growth by mergers to form spiral galaxies. Spiral galaxies have a thin, "delicate" and highly ordered structure. The Milk Way disk is about 100 times wider than it is thick. How could random mergers of massive components result in these beautiful spiral structures, unless the mergers occurred very early allowing time for the spiral structure to form after major mergers ceased? The Milky Way, at it's current rotation rate, could have revolved (at the solar radius) only about 50 times in it's entire history .

Back in 60's and perhaps much later as well, the top-down theory was popular. That is, a spiral galaxy forms from a single, accreted, large cloud of gas and not primarily through mergers. Thinking about this, I'm wondering why astronomers changed their minds about the formation theory over the decades.

Is it because the distant galaxies observed are much smaller than today's spirals? I found this quote in the wiki Galaxy Formation article:


Known as a top-down formation scenario, this theory is quite simple yet no longer widely accepted because observations of the early universe strongly suggest that objects grow from bottom-up (i.e. smaller objects merging to form larger ones).

Cougar
2012-Jul-09, 12:31 AM
One of the problems with current galaxy formation theory is the bottom-up growth by mergers to form spiral galaxies. Spiral galaxies have a thin, "delicate" and highly ordered structure. The Milk Way disk is about 100 times wider than it is thick. How could random mergers of massive components result in these beautiful spiral structures, unless the mergers occurred very early allowing time for the spiral structure to form after major mergers ceased?

Hmm. Perhaps many were the result of a single merger, which would produce a thin disk....


Back in 60's and perhaps much later as well, the top-down theory was popular. That is, a spiral galaxy forms from a single, accreted, large cloud of gas and not primarily through mergers. Thinking about this, I'm wondering why astronomers changed their minds about the formation theory over the decades.... Is it because the distant galaxies observed are much smaller than today's spirals?

Yes, I expect deep surveys and analysis of the Hubble ultra deep field have pretty much cinched the bottom-up scenario, more or less. :whistle:


As these galaxies are near the current Star Forming peak, the metallicity was and should have been near mature levels, even away from the star forming regions. At least, they said, once they thought about it a bit.

:doh:

TooMany
2012-Jul-09, 01:06 AM
Hmm. Perhaps many were the result of a single merger, which would produce a thin disk....


Why would a single merger produce a disk? Is a single merger sufficient?



Yes, I expect deep surveys and analysis of the Hubble ultra deep field have pretty much cinched the bottom-up scenario, more or less. :whistle:


How have these surveys clinched the bottom-up scenario?

Tensor
2012-Jul-09, 01:55 AM
One of the problems with current galaxy formation theory is the bottom-up growth by mergers to form spiral galaxies. Spiral galaxies have a thin, "delicate" and highly ordered structure. The Milk Way disk is about 100 times wider than it is thick. How could random mergers of massive components result in these beautiful spiral structures, unless the mergers occurred very early allowing time for the spiral structure to form after major mergers ceased? The Milky Way, at it's current rotation rate, could have revolved (at the solar radius) only about 50 times in it's entire history .

Actually, a spiral swallowing a smaller irregular galaxy can provide the impetus to form the arms. For example, NGC 5907 (http://en.wikipedia.org/wiki/File:NGC_5907.jpg) is an edge on spiral. It merged (http://arxiv.org/pdf/0805.1137v2.pdf) with a smaller dwarf galaxy and the results can be seen. It's one of the few loop or tidal streams that can be seen outside of the local group. About all it has done to NGC 5907 is to warp one edge of the disk. (the images are all the way at the end of the paper). This paper (http://arxiv.org/pdf/1109.2918v1.pdf) describes the evolution of the Milky Way disk and spiral structures, with the merger of the Sagittarius Dwarf Galaxy. And shows that it doesn't really effect the spiral structures all that much.


Back in 60's and perhaps much later as well, the top-down theory was popular. That is, a spiral galaxy forms from a single, accreted, large cloud of gas and not primarily through mergers. Thinking about this, I'm wondering why astronomers changed their minds about the formation theory over the decades.

Part of it has to do with the stellar streams and loops that have been found in both the Milky Way and M31. Wikipedia (http://en.wikipedia.org/wiki/List_of_stellar_streams) has a pretty good list of the different tidal streams. With so many different dwarfs becoming part of the Milky Way, there are reasons for leaning that way. Don't quote me on this one, as it's off the top of my head, but I seem to remember the Hubble Ultra Deep Field shows more highly irregular and smaller galaxies the further back they went. I'll have to do some looking, but it may not be until tomorrow before I can get to it.


Is it because the distant galaxies observed are much smaller than today's spirals? I found this quote in the wiki Galaxy Formation article:

I'll pass the following along to you this paper (http://arxiv.org/pdf/1006.5394v2.pdf) was the paper I mentioned earlier that discusses Galactic Formation Theory. This paper (http://arxiv.org/pdf/1001.5430.pdf) discusses some developments in Spiral Galaxy formation and this one (http://arxiv.org/pdf/1008.2737.pdf) talks about the spiral patterns and their lifetimes in spiral galaxies.

I know I'm dropping a lot of information and reading on you, and for that I somewhat apologize. But there is a lot of information associated with galactic formation, merger, and evolution.

TooMany
2012-Jul-09, 03:19 AM
Actually, a spiral swallowing a smaller irregular galaxy can provide the impetus to form the arms.


But how would you explain the symmetry often seen in the spiral arms if they were created by swallowing a galaxy? One might expect some asymmetric structure to form. Oh well, complex systems can do strange things (e.g. violent relaxation).



For example, NGC 5907 (http://en.wikipedia.org/wiki/File:NGC_5907.jpg) is an edge on spiral. It merged (http://arxiv.org/pdf/0805.1137v2.pdf) with a smaller dwarf galaxy and the results can be seen. It's one of the few loop or tidal streams that can be seen outside of the local group. About all it has done to NGC 5907 is to warp one edge of the disk. (the images are all the way at the end of the paper).

That's pretty wild. I've never seen that one. Seems like the edge-on is much more massive and almost unaffected. Whatever hit it looks like it got stretched into a couple of loop-the-loops.



Don't quote me on this one, as it's off the top of my head, but I seem to remember the Hubble Ultra Deep Field shows more highly irregular and smaller galaxies the further back they went. I'll have to do some looking, but it may not be until tomorrow before I can get to it.


I've seen references to this as well, but I think that story may have came out before the camera upgrade. I'm not sure whether the assertion of highly irregular galaxies stuck, but I do think that smaller galaxies is a consensus.



I'll pass the following along to you [url=http://arxiv.org/pdf/1006.5394v2.pdf] this paper (http://arxiv.org/pdf/1109.2918v1.pdf) was the paper I mentioned earlier that discusses Galactic Formation Theory. This paper (http://arxiv.org/pdf/1001.5430.pdf) discusses some developments in Spiral Galaxy formation and this one (http://arxiv.org/pdf/1008.2737.pdf) talks about the spiral patterns and their lifetimes in spiral galaxies.

I know I'm dropping a lot of information and reading on you, and for that I somewhat apologize. But there is a lot of information associated with galactic formation, merger, and evolution.

No need to apologize. Yes it will take some time to digest. Thanks for the links.

Tensor
2012-Jul-10, 05:05 AM
OK, here is the result of my search.


That's pretty wild. I've never seen that one. Seems like the edge-on is much more massive and almost unaffected. Whatever hit it looks like it got stretched into a couple of loop-the-loops.

If you look at the paper I gave for the Sagittarius Dwarf galaxy, you'll see that one has also been stretched into a loop. Not quite as bad as the debris around NGC 5907, but still, somewhat of a loop


I've seen references to this as well, but I think that story may have came out before the camera upgrade. I'm not sure whether the assertion of highly irregular galaxies stuck, but I do think that smaller galaxies is a consensus.

The original HUDF was taken from Sep. 2003 to Jan. 2004 in Visible bands. The upgrade of the camera (to the WCS3) had more to do with adding a better IR capability. The 2009 HUDF was about adding IR frequencies to the optical data. The IR data was captured over 192 orbits, compared to the 400 orbits for the visual data, but could capture higher z galaxies. Good thing I told you not to quote me, you were right. The galaxies were smaller, but not highly irregular. They were more irregular and not as symmetric, but not highly irregular.


No need to apologize. Yes it will take some time to digest. Thanks for the links.

Well, here's a few more. This paper (http://arxiv.org/pdf/astro-ph/0607632v1.pdf) is the overall paper on the HUDF. Prior to the overall data being released, there was some other data released earlier. The next four papers probably contributed to the changeover to the merging galaxy scenario. This paper (http://arxiv.org/pdf/astro-ph/0408031.pdf) looks at a specific galaxy, UDF 5225, at z ~ 5.4. They determine it was a galactic merger, with active star forming regions. The second paper (http://hubblesite.org/pubinfo/pdf/2006/04/pdf1.pdf) deals with a class of object (of which the first galaxy belongs) called "tadpole galaxies". These are galaxies with a "core" component, with a "tail". Both components can have active star forming regions and the tail is thought to result from tidal actions during galactic interactions. This paper looks at 70 "tadpole galaxies" found in the HUDF. Then, there is this paper (http://hubblesite.org/pubinfo/pdf/2006/04/pdf2.pdf), which looks at 45 variable objects that are clear cut enough to consider point sources, without various detection defects. These are Active Galactic Nucleus (AGN) objects. Models show that tadpole galaxies appear ~700 million years after the merger starts, but ~1 billion years before the AGN stage starts. The delay is due to the large amount of gas and dust that hides the SMBH until it starts accreting most of its mass ~1 billion years after the tadpole stage. When the age of these 45 objects are compared to the age of the 70 "tadpole galaxies", it is found that there is no overlap, in age, among the objects. Which leads us to the last paper (http://arxiv.org/pdf/astro-ph/0503369v2.pdf). This paper details the new (for then) idea of galactic mergers building up disk galaxies. The one thing this needs, however, are gas dominated mergers. Which, according to the previous two papers, tadpole galaxies have.

I want to point out that there are still unanswered questions about galaxy formation, and merger scenarios. Nothing is absolutely, cut and dried this is how it is. However, I don't think there has been any complete overturn of the ideas of formation. Incremental changes, yes. New information that will lead to more incremental changes, definitely. Which is why I gave you those three papers on galaxy formation and these papers here. You will more than likely find some contradictions among the papers. Just remember that the three I gave you yesterday are from 2010 and these are from 2004-2006, so there may have been some changes since.

antoniseb
2012-Jul-10, 01:44 PM
But how would you explain the symmetry often seen in the spiral arms if they were created by swallowing a galaxy?...
This kind of symmetry often happens in systems involving gravity and loose parts. Look at the propeller-shaped things in Saturn's rings. Look at the tides on Earth, which are high twice a day because they are raised on both the Moon facing side and the opposite side. Look at the streams of stars pulled from small galaxies after interacting with large ones (they go in both directions). This kind of symmetry is common. The specifics of how it arises in galaxies to form arms is beyond my hand-waving explanation, but not hard to visualize after seeing the other examples. Computer simulations bear this out.

TooMany
2012-Jul-10, 04:50 PM
This kind of symmetry often happens in systems involving gravity and loose parts. Look at the propeller-shaped things in Saturn's rings. Look at the tides on Earth, which are high twice a day because they are raised on both the Moon facing side and the opposite side. Look at the streams of stars pulled from small galaxies after interacting with large ones (they go in both directions). This kind of symmetry is common. The specifics of how it arises in galaxies to form arms is beyond my hand-waving explanation, but not hard to visualize after seeing the other examples. Computer simulations bear this out.

Perhaps, but I don't see much evidence of galactic interactions perserving symmetry here (https://www.google.com/search?q=galaxy+interactions&hl=en&rlz=1C1CHKD_enUS418&prmd=imvns&source=lnms&tbm=isch&sa=X&ei=Vlr8T5OkEano2gWK9LThBg&ved=0CEkQ_AUoAQ&biw=1680&bih=935). Do you have some examples?

TooMany
2012-Jul-10, 04:55 PM
OK, here is the result of my search.



If you look at the paper I gave for the Sagittarius Dwarf galaxy, you'll see that one has also been stretched into a loop. Not quite as bad as the debris around NGC 5907, but still, somewhat of a loop



The original HUDF was taken from Sep. 2003 to Jan. 2004 in Visible bands. The upgrade of the camera (to the WCS3) had more to do with adding a better IR capability. The 2009 HUDF was about adding IR frequencies to the optical data. The IR data was captured over 192 orbits, compared to the 400 orbits for the visual data, but could capture higher z galaxies. Good thing I told you not to quote me, you were right. The galaxies were smaller, but not highly irregular. They were more irregular and not as symmetric, but not highly irregular.



Well, here's a few more. This paper (http://arxiv.org/pdf/astro-ph/0607632v1.pdf) is the overall paper on the HUDF. Prior to the overall data being released, there was some other data released earlier. The next four papers probably contributed to the changeover to the merging galaxy scenario. This paper (http://arxiv.org/pdf/astro-ph/0408031.pdf) looks at a specific galaxy, UDF 5225, at z ~ 5.4. They determine it was a galactic merger, with active star forming regions. The second paper (http://hubblesite.org/pubinfo/pdf/2006/04/pdf1.pdf) deals with a class of object (of which the first galaxy belongs) called "tadpole galaxies". These are galaxies with a "core" component, with a "tail". Both components can have active star forming regions and the tail is thought to result from tidal actions during galactic interactions. This paper looks at 70 "tadpole galaxies" found in the HUDF. Then, there is this paper (http://hubblesite.org/pubinfo/pdf/2006/04/pdf2.pdf), which looks at 45 variable objects that are clear cut enough to consider point sources, without various detection defects. These are Active Galactic Nucleus (AGN) objects. Models show that tadpole galaxies appear ~700 million years after the merger starts, but ~1 billion years before the AGN stage starts. The delay is due to the large amount of gas and dust that hides the SMBH until it starts accreting most of its mass ~1 billion years after the tadpole stage. When the age of these 45 objects are compared to the age of the 70 "tadpole galaxies", it is found that there is no overlap, in age, among the objects. Which leads us to the last paper (http://arxiv.org/pdf/astro-ph/0503369v2.pdf). This paper details the new (for then) idea of galactic mergers building up disk galaxies. The one thing this needs, however, are gas dominated mergers. Which, according to the previous two papers, tadpole galaxies have.

I want to point out that there are still unanswered questions about galaxy formation, and merger scenarios. Nothing is absolutely, cut and dried this is how it is. However, I don't think there has been any complete overturn of the ideas of formation. Incremental changes, yes. New information that will lead to more incremental changes, definitely. Which is why I gave you those three papers on galaxy formation and these papers here. You will more than likely find some contradictions among the papers. Just remember that the three I gave you yesterday are from 2010 and these are from 2004-2006, so there may have been some changes since.

Looks interesting. I'll read the papers.

antoniseb
2012-Jul-10, 05:26 PM
Perhaps, but I don't see much evidence of galactic interactions perserving symmetry here (https://www.google.com/search?q=galaxy+interactions&hl=en&rlz=1C1CHKD_enUS418&prmd=imvns&source=lnms&tbm=isch&sa=X&ei=Vlr8T5OkEano2gWK9LThBg&ved=0CEkQ_AUoAQ&biw=1680&bih=935). Do you have some examples?
I saw lots of examples in those images with tails going both ways. It's not like spiral galaxies are perfectly radially symmetric. They have arms, and the number of arms varies from galaxy to galaxy and the number of forks in the arms vary from arm to arm. Do you have any examples of perfect symmetry in a spiral galaxy?

TooMany
2012-Jul-10, 09:13 PM
I saw lots of examples in those images with tails going both ways. It's not like spiral galaxies are perfectly radially symmetric. They have arms, and the number of arms varies from galaxy to galaxy and the number of forks in the arms vary from arm to arm. Do you have any examples of perfect symmetry in a spiral galaxy?

I showed you examples of interactions. Almost all result in a noticeable loss of symmetry (at least temporarily). No galaxy has perfect symmetry of course. They are natural objects without a plan (unlike a flower). However, it does not take a great deal of expertise to distinguish an unperturbed spiral from one which has interacted with another galaxy of significant mass. It may be unrealistic to assume that mergers of galaxies with comparable masses (say up to 3:1 ratio) will result in today's spirals that appear to be insignificantly disturbed, especially considering that a number of such mergers are needed to make the small distant galaxies grow into today's spirals. Mainstream astronomers are aware of this issue. Some have suggested that spirals grow from gas in-fall or from digestion of small satellite galaxies rather than from major mergers. Of course there could be some mechanism through which merged galaxies can quickly reform to appear as undisturbed spirals. Do you know whether such a mechanism has been proposed?

It used to be believed (as I recall from way back) that elliptical galaxies were formed by mergers of spirals. I think some issues have been raised with that as well. It's seems unlikely that major mergers of spirals can result in either another nice spiral or an elliptical since the morphologies are so different.

antoniseb
2012-Jul-10, 09:29 PM
... Do you know whether such a mechanism has been proposed? ...
Mechanisms? I don't know of one. Mostly what we see is simulations demonstrating that certain shapes can happen, and using those sims to try and constrain the initial masses of the contributors. No mechanism (TMK) that you might name has been proposed.

TooMany
2012-Jul-17, 02:32 AM
Here's a new paper relevant to this thread: The Current Status of Galaxy Formation (http://arxiv.org/abs/1207.3080). Towards the end of the paper is a substantial and interesting list of current problems with theory versus observations.

This new paper Evolution of Massive Galaxy Structural Properties and Sizes via Star Formation In the GOODS NICMOS Survey (http://arxiv.org/abs/1207.3084) discusses one of the important problems which is how galaxies got so much larger since z = 2 (3 to 5 times in radius). It argues that star formation cannot be the answer. Various star formation scenarios analyzed can account for only a small part of the growth. Also, there don't appear to be enough major mergers to account for the growth. (Maybe they haven't really grown?)

TaylorS
2012-Jul-17, 05:08 AM
I suspect that spirals have retained their flat disks because they have only grown by "eating" galaxies too small to destroy the disk. the globular cluster Omega Centauri, IIRC, is the remnant core of a small galaxy eaten by the Milky Way eons ago. The MW is consuming the Sagittarius Dwarf right now, and will eventually consume the Magellanic Clouds. The stars from the consumed galaxy end up as halo stars, the gas and dust from the consumed galaxy will eventually be absorbed into the disk. If a galaxy that is being eaten is very rich in gas and dust (like the Magellanic Clouds) it may trigger a burst of star formation, turning the host galaxy into a "starburst" galaxy.

Gigabyte
2012-Jul-17, 06:12 AM
Here's a new paper relevant to this thread: The Current Status of Galaxy Formation (http://arxiv.org/abs/1207.3080). Towards the end of the paper is a substantial and interesting list of current problems with theory versus observations.

This new paper Evolution of Massive Galaxy Structural Properties and Sizes via Star Formation In the GOODS NICMOS Survey (http://arxiv.org/abs/1207.3084) discusses one of the important problems ...

After reading those papers I feel way over my head again. What are they trying to say? I need a sciencedaily article to explain it for me.

TooMany
2012-Jul-17, 05:36 PM
I suspect that spirals have retained their flat disks because they have only grown by "eating" galaxies too small to destroy the disk. the globular cluster Omega Centauri, IIRC, is the remnant core of a small galaxy eaten by the Milky Way eons ago. The MW is consuming the Sagittarius Dwarf right now, and will eventually consume the Magellanic Clouds. The stars from the consumed galaxy end up as halo stars, the gas and dust from the consumed galaxy will eventually be absorbed into the disk. If a galaxy that is being eaten is very rich in gas and dust (like the Magellanic Clouds) it may trigger a burst of star formation, turning the host galaxy into a "starburst" galaxy.

I suppose that is a possibility, but I wonder if it is realistic. The question is can the rate of such satellite consumption account for the growth. Does anyone know whether this is a seriously considered possibility and what the issues might be?

The Sagittarius Dwarf may not be a good example of what is required to maintain a disk. It's orbit is nearly polar which means that a merger will tend to disrupt the disk. Most of the MW satellite galaxies are in polar orbits. Kroupa has published a paper suggesting that the MW satellites are the remnants of a very early merger of the MW with another galaxy.

Another problem with growth seems to be that at z~2, galaxies are already massive so that they need to get larger in size without accumulating a proportional amount of mass. A simplistic calculation would say that to grow by a factor of 3 in radius (keeping the same overall shape and density), the mass would need to grow by 3^3 or a factor of 27. Galaxies at z~2 are thought to be massive but very compact. I suppose it's possible that they could somehow spread out and become less dense through minor mergers.

TooMany
2012-Jul-17, 06:00 PM
After reading those papers I feel way over my head again. What are they trying to say? I need a sciencedaily article to explain it for me.

I can't pretend to truly understand it, but the gist seems to be that no matter how you juggle the pieces they don't fit well.

trinitree88
2012-Jul-17, 07:07 PM
Mechanisms? I don't know of one. Mostly what we see is simulations demonstrating that certain shapes can happen, and using those sims to try and constrain the initial masses of the contributors. No mechanism (TMK) that you might name has been proposed.

antoniseb. There might be one. The effect proposed by Catherine Braiding in star formation cannot be excluded from being used for more extended sources...galaxies.
SEE:http://arxiv.org/pdf/1110.2168v1.pdf
SEE:http://arxiv.org/abs/1109.1370

pete

TooMany
2012-Jul-17, 10:37 PM
antoniseb. There might be one. The effect proposed by Catherine Braiding in star formation cannot be excluded from being used for more extended sources...galaxies.
SEE:http://arxiv.org/pdf/1110.2168v1.pdf
SEE:http://arxiv.org/abs/1109.1370

pete

Wow, that's complicated stuff. The complexity of baryonic matter is just amazing. Even though we have studied it for centuries and we know the physical principles that govern it's behavior in some detail, we are still without certainty about it's behavior on these scales. We have to more or less guess what processes may dominate and then attempt to quantify the effects and compare them with observation. Who knew that the Hall effect would end up being so important in star formation? It's remarkable that EM fields dominate the dynamics of star formation rather than gravity. I suppose we shouldn't be too surprised since gravity is such a weak force in comparison.

Haven't magnetic fields and currents been largely discounted as having importance on galactic scales? As far as I know such effects aren't even considered in computational models of galaxies or their formation. Can galactic fields act significantly on mass concentrations like stars? It hardly seems plausible. Has the charge of the sun been measured to be very close to neutral? Some amount of positive charge could be speculated based on the much lower mass of electrons versus nuclei. But how far could the lost electrons go? On the other hand it's certainly plausible (to me) that weak fields can induce currents in the interstellar plasma.

Reality Check
2012-Jul-18, 01:30 AM
Here's a new paper relevant to this thread: The Current Status of Galaxy Formation (http://arxiv.org/abs/1207.3080). Towards the end of the paper is a substantial and interesting list of current problems with theory versus observations.

This new paper Evolution of Massive Galaxy Structural Properties and Sizes via Star Formation In the GOODS NICMOS Survey (http://arxiv.org/abs/1207.3084) discusses one of the important problems which is how galaxies got so much larger since z = 2 (3 to 5 times in radius). It argues that star formation cannot be the answer. Various star formation scenarios analyzed can account for only a small part of the growth. Also, there don't appear to be enough major mergers to account for the growth. (Maybe they haven't really grown?)
Two very interesting papers though your summary of the second paper is not quite correct. That paper presents evidence that star formation cannot be the full answer for the observed increase in effective radius for massive galaxies. They then suggest that mergers may supply the rest of the answer.

We conclude that due to the lack of sufficient size growth and Sérsic evolution by star formation and stellar migration other mechanisms must contribute a large proportion to account for the observed structural evolution from z > 1 to the present day. Recent studies by Bluck et al. (2011) have found that minor and major mergers have a large influence on the size of massive galaxies possibly contributing the remaining 80% of size growth needed to explain the observed trends.

Reality Check
2012-Jul-18, 01:47 AM
antoniseb. There might be one. The effect proposed by Catherine Braiding in star formation cannot be excluded from being used for more extended sources...galaxies.
SEE:http://arxiv.org/pdf/1110.2168v1.pdf
SEE:http://arxiv.org/abs/1109.1370

pete
Hi pete - I suspect that the Hall effect in the formation of stars may not be applicable to galaxies. This effect dominates at intermediate densities during star formaiton. At low densities, ambipolar diffusion (http://en.wikipedia.org/wiki/Ambipolar_diffusion) dominates. Galaxies have relatively low densities and during their formation are are mostly neutral hydrogen (it is the formation of stars in the galaxies that ionize hydrogen).

Cougar
2012-Jul-18, 02:40 AM
I can't pretend to truly understand it, but the gist seems to be that no matter how you juggle the pieces they don't fit well.

I guess that's one way of looking at it. That recent paper, The Current Status of Galaxy Formation (http://arxiv.org/abs/1207.3080) by Joe Silk and Gary Mamon, submitted on 12 Jul 2012, was quite the literature review on the topic. I thought the gist was that there's still a lot we don't know about early structure formation and evolution. A field ripe for discovery.

TooMany
2012-Jul-18, 05:28 PM
Two very interesting papers though your summary of the second paper is not quite correct. That paper presents evidence that star formation cannot be the full answer for the observed increase in effective radius for massive galaxies. They then suggest that mergers may supply the rest of the answer.

Maybe but there are issues. Here's one of the merger assumptions listed on page 11 of the paper:


While the gas settles into disks, major mergers of galaxies cause disks to transform into ellipticals, and after subsequent disk build-up, the merger remnant is identified to a bulge inside a spiral galaxy.
The bulge can also be built-up by repeated minor mergers, as well as starbursts and secular evolution of the disk.

So in order to explain disk galaxies, major mergers occur first building an elliptical which becomes the core of a neat spiral no longer damaged by major mergers because there are only minor mergers subsequently? Well maybe, but on the other hand, they also attribute very massive galaxies (presumably ellipticals) to major mergers too. How do they explain disk galaxies without bulges?

Here's another assumption in the same list:


Satellite galaxies trajectories are assumed to be those of the subhalos they belong to, and when they
are no longer resolved in the cosmological simulation, or if one is only using a halo merger tree, the
galaxies are merged with the central galaxy on a dynamical friction time.

LCDM theory predicates large numbers of satellite galaxies (some much larger than any observed) in a random distribution. There are several difficulties with that. One is that our galaxy has no such distribution of satellites (nor does M31). The few satellites that we have orbit in a plane roughly perpendicular to the disk. If the disk was built up by mergers of such satellites over time, it's hard to explain the thin disk. If the satellites are gone due to mergers, that needs explanation. How is it that so few survive? Shouldn't there be some in more distant orbits which cannot fall in the allowed time?

That's the sort of thing I'm getting at with the puzzle parts not fitting. It's hard to invent a hypothesis for this growth that is consistent with all of the galaxies and observations. Perhaps these merger hypotheses can be conjectured without substantiation because we are as yet unable to simulate the details?

In case you missed it, the paper ends with a long list of problems (15) introduced by this sentence:


Here is a summary of some of the key reasons why CDM does not yet provide a robust explanation of the observations: we list below several examples that represent challenges for theorists.

This is a bit of an understatement since many of the problems listed indicate that the LCDM model contradicts observation. Then in the final paragraph the hope is presented that some current misunderstanding will eventually solve the problems, presumably in the context of LCDM.

We can only wait and see. In the meantime since astronomers have no alternative theory, they will continue to approach the puzzle by trying to understand why observations don't match theory and look for explanations that bring observations back into line with existing theory. This approach is evident in papers recently published that try to explain the lack of cusps and the BTF relation. Theorist are looking to explain away the apparent problems with the theory. They are not considering alternative explanations, because they are deeply committed to the theory they have (undoubtedly for some good reasons). One way to put it is that thinking is still within the box. Perhaps out of the box thinking will become necessary if more serious difficulties arise.

Gigabyte
2012-Jul-18, 06:42 PM
Since we can observe many different kinds of galaxies, shouldn't there be multiple theories to explain the different kinds?

In keeping with the topic, I just found the following article about an article from Nature. (I wish I had found it years ago now)


Astrophysicists have long been trying to understand the way in which these two types of galaxies are formed. Some experts say this question is the primary challenge facing modern cosmological researchers today, as galaxies formation is “an essential stage in the cosmological process that leads to the formation of life.” Until now, the standard model explained galaxy formations by spherical gas infall into a central disk, followed by mergers between disks. Stars were assumed to form slowly within the gaseous disks, which converted into globes as they merged. In such a “merger” the colliding gas clouds produce a big burst of new stars at a rate of hundreds of solar masses per year.


Recent astronomical observations, however, put the accepted theory to question as new data was collected using advanced telescopes, which allowed scientists to examine the galaxies as they were about three billion years after the Big Bang. “The large galaxies, as they appear in this early stage, indeed created stars at a very rapid rate, but this does not appear to be at all a result of galactic mergers” - said Avishai Dekel, professor of theoretical physics at the Racah Institute of Physics in the Hebrew University. The observations led researchers to ask the natural question – “How is it that these galaxies were able to form stars so quickly and in large quantities at such an early stage without massive galactic mergers?”
http://thefutureofthings.com/news/6534/new-galaxy-formation-theory-proposed.html

Now it may be possible the author of that piece is some kind of an idiot, but he does write, "Recent astronomical observations, however, put the accepted theory to question as new data was collected using advanced telescopes, which allowed scientists to examine the galaxies as they were about three billion years after the Big Bang."

I'm going to use that to feel all vindicated again.

TooMany
2012-Jul-18, 10:29 PM
Since we can observe many different kinds of galaxies, shouldn't there be multiple theories to explain the different kinds?

In keeping with the topic, I just found the following article about an article from Nature. (I wish I had found it years ago now)


http://thefutureofthings.com/news/6534/new-galaxy-formation-theory-proposed.html

Now it may be possible the author of that piece is some kind of an idiot, but he does write, "Recent astronomical observations, however, put the accepted theory to question as new data was collected using advanced telescopes, which allowed scientists to examine the galaxies as they were about three billion years after the Big Bang."

I'm going to use that to feel all vindicated again.

One of the researchers mentioned (Avishai Dekel) goes on to propose a growth mechanism that is not based on mergers but rather cosmic cold filaments of gas (and DM?) that galaxies seem to form along. The galaxies grow as gas from the filaments falls through the halo and clumps into molecular clouds. I think these would be the same filaments seen in structure formation simulations. This gets interesting because then you have to ask what is the behavior of filaments which presumably contain both baryonic and collisionless non baryonic matter. If somehow a filament of both baryonic and DM were falling into a galaxy, one might expect the baryonic matter to pile up into clumps while the non-baryonic matter sails right through.

The paper behind the article could be this one:

Formation of Massive Galaxies at High Redshift: Cold Streams, Clumpy Disks and Compact Spheroids (http://arxiv.org/abs/0901.2458)

There are some papers published lately in which it is suspected that the merger theory is wrong. It seems fair to say that it's all up in the air at present.

Cougar
2012-Jul-19, 12:36 AM
Since we can observe many different kinds of galaxies, shouldn't there be multiple theories to explain the different kinds?

Well, no. You'd want a single theory to be able to explain them all. The general theory of relativity and the standard model of particle physics are currently doing a pretty good job at the overall explanation. Apparently many scientists are not even satisfied with that :), and they think there ought to be some kind of unification of the two, the realization of which has so far eluded them.

Reality Check
2012-Jul-19, 01:48 AM
Maybe but there are issues. Here's one of the merger assumptions listed on page 11 of the paper:

Wrong paper. The second paper whose summary you do not quite get right is: Evolution of Massive Galaxy Structural Properties and Sizes via Star Formation In the GOODS NICMOS Survey.



So in order to explain disk galaxies, major mergers occur ...

Yes - that is an ingredient of the galaxy formation simulations.


Here's another assumption in the same list:

And another ingredient of the galaxy formation simulations.

So what?
You need to include some kind of physics in computer simulations.

You seem to be concentrating on a rather trivial aspect of science - there are nearly always "puzzle parts not fitting" in scientific models.
Scientists know this which is why they are always trying to improve models.



It's hard to invent a hypothesis for this growth that is consistent with all of the galaxies and observations.

In fact it is easy to explain the growth of galaxies as in the second paper: stellar evolution + migration + mergers = growth in effective radius.


In case you missed it, the paper ends with a long list of problems (15) introduced by this sentence:

In case you missed it, this long list of problems (15) includes solutions for many of the probelms.

The LCDM model does have several problems on small scales. That has not much impact on the validity of the LCDM model because it works at larger scales as the paper's introduction states.
The authors think that the small scale problems will be resolved with better physics and models (see page 2):

However, the naıve assumption that stellar mass follows halo mass, leads to too many small galaxies, too many big galaxies in the nearby universe, too few massive galaxies at high redshift, and too
many baryons within the galaxy halos. In addition there are structural problems: for example, massive galaxies with thin disks and/or without bulges are missing, and the concentration and cuspiness of cold
dark matter is found to be excessive in barred galaxies and in dwarfs. The resolution to all of these difficulties must lie in feedback. There are various flavours of feedback that span the range of processes
including reionisation at very high redshift, supernova (SN) explosions, tidal stripping and input from active galactic nuclei. All of these effects no doubt have a role, but we shall see that what is missing
is a robust theory of star formation as well as adequate numerical resolution to properly model the interactions between baryons, dynamics and dark matter.

So we can only wait and see: Are the problems at small scales a result of incorrect physics in the computer simulations? Or are the properrties of DM even stranger than we think? Or it is something else?

Gigabyte
2012-Jul-19, 01:57 AM
Meanwhile

http://www.msnbc.msn.com/id/48229023/ns/technology_and_science-space/#.UAdnlmGe6dw

Tensor
2012-Jul-19, 04:01 AM
Meanwhile

http://www.msnbc.msn.com/id/48229023/ns/technology_and_science-space/#.UAdnlmGe6dw

LOL, I've been waiting for you to post this since this afternoon, when I saw it in various different outlets. The problem is the articles don't include the important stuff in the actual paper. You know, like the merging galaxy that causes the formation of the spiral structures has to be of a certain size and orientation, or the spiral structures won't form. That the spiral structures, unlike nearby spirals, are unstable and are short term features ( < 100 Myr). That the spiral structures can't form, unless the large galaxy is of a certain minimum size. Or that they have to be oriented to near face-on and be observed within the short time frame of for us to see them. I figured you would get all excited about it, but you wouldn't bother running down the paper to actually read it to find all the caveats that aren't usually listed in "Science by Popular Science article". Go over to "Fun Papers in Arxiv", the link to the actual paper is the first paper listed.

Gigabyte
2012-Jul-19, 11:33 AM
The problem is the articles don't include the important stuff in the actual paper.

It's not a problem, because they quoted the lead researcher.


"The fact that this galaxy exists is astounding," study lead author David Law, of the University of Toronto, said in a statement. "Current wisdom holds that such ‘grand-design’ spiral galaxies simply didn’t exist at such an early time in the history of the universe."

Tensor
2012-Jul-19, 02:03 PM
It's not a problem, because they quoted the lead researcher.


"The fact that this galaxy exists is astounding," study lead author David Law, of the University of Toronto, said in a statement. "Current wisdom holds that such ‘grand-design’ spiral galaxies simply didn’t exist at such an early time in the history of the universe."

Like I said, the paper explains why the spiral structures are not permanent, so the galaxy is not really a "grand design" spiral at such an early time in the history of the universe. The lead researcher had all that put in the paper. Science by quote doesn't work too well, as the quotes in an article and the actual science in the paper may not always match. It also has a tendency to make people feel like they are in over their head, when confronted with the actual science.

Cougar
2012-Jul-19, 05:26 PM
It's not a problem, because they quoted the lead researcher.

You seem to be quote mining, Gigabyte. Your linked MSNBC article (an outfit not known for scientific rigor) also says:


The Hubble and Keck observations also revealed a companion dwarf galaxy residing near BX442. The scientists think the gravitational interaction between the two galaxies may be creating BX442's spiral shape, possibly explaining how it became so different than its galactic contemporaries.

Did you have a particular comment about this finding?

TooMany
2012-Jul-19, 05:50 PM
You seem to be quote mining, Gigabyte. Your linked MSNBC article (an outfit not known for scientific rigor) also says:


The Hubble and Keck observations also revealed a companion dwarf galaxy residing near BX442. The scientists think the gravitational interaction between the two galaxies may be creating BX442's spiral shape, possibly explaining how it became so different than its galactic contemporaries.

Did you have a particular comment about this finding?

Well, I've just got to mine my favorite quote from the abstract:



Alternatively, current instrumentation may simply not be sensitive enough to detect spiral structures comparable to those in the modern Universe.


I'm betting that this is the real answer. There are plenty of spirals, they just don't look like them because the structures are too dim to detect, except in the very brightest galaxies. Unfortunately it's going to be many years before this hypothesis can be proven right or wrong. The JWST should settle the issue.

I might add that the OPs are also selective among the possibilities proposed, choosing those that they favor.

Tensor
2012-Jul-20, 06:21 PM
Well, I've just got to mine my favorite quote from the abstract:


Alternatively, current instrumentation may simply not be sensitive enough to detect spiral structures comparable to those in the modern Universe.

But somehow it's sensitive enough to detect this one, but not other brighter ones? Good point.


I'm betting that this is the real answer. There are plenty of spirals, they just don't look like them because the structures are too dim to detect, except in the very brightest galaxies.

There are brighter galaxies at that z, than the one under discussion, but our instruments are only sensitive enough to detect the spiral structure in this one, not the brighter ones? Another good point.


Unfortunately it's going to be many years before this hypothesis can be proven right or wrong.

No it's not. At least not at this z. Unless you have a good explanation for why other, brighter galaxies, at this z, don't exhibit spiral structures, when the model in this paper explains it and is consistent with observations.


The JWST should settle the issue.

It may at greater z.


I might add that the OPs are also selective among the possibilities proposed, choosing those that they favor.

Actually, it's not that we favor them so much, as we're trying to provide the possibilities the others ignore or don't even know about because they don't read the actual papers.

TooMany
2012-Jul-21, 12:35 AM
The author's of the paper said:


Alternatively, current instrumentation may simply not be sensitive enough to detect spiral structures comparable to those in the modern Universe.

I said:


[I'm betting] there are plenty of spirals, they just don't look like them because the structures are too dim to detect, except in the very brightest galaxies.


But somehow it's sensitive enough to detect this one, but not other brighter ones? Good point.
There are brighter galaxies at that z, than the one under discussion, but our instruments are only sensitive enough to detect the spiral structure in this one, not the brighter ones? Another good point.


You need to deliberately misinterpret what I said (in an illogical way) to make some point? And add some sarcasm to boot?



Actually, it's not that we favor them so much, as we're trying to provide the possibilities the others ignore or don't even know about because they don't read the actual papers.

What you pointed out, about the satellite galaxy possibly shaping the arms of this spiral, is stated in the news story sited by Gigabyte and in the paper's abstract. The possibility that I quoted above is not in the news story, but it is in the paper's abstract.

Gigabyte
2012-Jul-21, 12:51 AM
Sarcasm is against the rules. I just found this out recently.

Nereid
2012-Jul-27, 06:40 AM
Of some relevance, this, hot off the arXiv press: A new scaling relation for HII regions in spiral galaxies: unveiling the true nature of the mass-metallicity relation (F. F. Rosales-Ortega et al. (http://arxiv.org/abs/1207.6216)):


We demonstrate the existence of a -local- relation between galaxy surface mass density, gas metallicity, and star-formation rate density using spatially-resolved optical spectroscopy of HII regions in the local Universe. One of the projections of this distribution, -the local mass-metallicity relation- extends over three orders of magnitude in galaxy mass density and a factor of eight in gas metallicity. We explain the new relation as the combined effect of the differential radial distributions of mass and metallicity in the discs of galaxies, and a selective star-formation efficiency. We use this local relation to reproduce -with remarkable agreement- the total mass-metallicity relation seen in galaxies, and conclude that the latter is a scale-up integrated effect of a local relation, supporting the inside-out growth and downsizing scenarios of galaxy evolution.(my bold)