I want to know if there is actually observation of the creation of new galaxies or if everything is already set -up in that matter ?
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I want to know if there is actually observation of the creation of new galaxies or if everything is already set -up in that matter ?
Administrator
I suppose it depends on what you mean by "new galaxies".Originally Posted by Don J
- There are dwarf galaxies forming as debris from the collision of larger galaxies.
- There are low surface brightness galaxies which may have been around for a very long time, but have been very slow about getting local densities high enough for star formation.
- There are new galaxies being created from the collision of old ones.
- There are very distant (z>6) galaxies which are clearly seen as new.
I suspect that you are asking about local galaxies forming from pristine primordial gas clouds that have thus far escaped condensing into galaxies... I don't know of any examples, or remember any papers discussing examples of this.
Forming opinions as we speak
Established Member
Thanks ! So it is safe to consider that the Universe is actually in a steady state codition even if it is expandind ?
Administrator
I don't know what you mean by "steady state condition". If galaxies are continuing to age, and star-forming is continuing to drop off after a peak five to eight billion years ago... what is steady?
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Established Member
What is Minkowski Object becoming?
Established Member
Steady state in the sense that there is only an evolution of already existing objects.
Administrator
You must be aware that the term "Steady State Universe" has some pretty well established meanings that are far outside of your usage here... right? The Hubble Ultra Deep Field, and other deep surveys have pretty much completely invalidated the Steady-State idea, but there are still people who don't like the Big Bang, and are looking for ways to re-assert SSU as an alternative. You, as a supporter of non-mainstream ideas should be careful about using or misusing such terms.
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Established Member
We see galactic mergers in progress, and the aftermath of them. So no, it is not steady state at all. Just that things don't happen quickly out there.
Established Member
I am not saying that nothing is happening with the actual existing stuff.
Just that everything seem to be already set-up in term of creation of new galaxies forming from pristine primordial gas clouds.
Let me rephrase my previous assertion (post 3)
Is it safe or (conceivable) to assume that there is a finite number of Galaxies in an infinite Universe ?
Administrator
It's doubtful that the universe is infinite. It's likely that the mass of all the matter in the universe is roughly constant. The location of the mass seems to be changing as the voids slowly get less concentrated.
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Administrator
I would say it is not even safe to say there is a fixed number of galaxies, as galaxies may merge.
Established Member
Does that mean that the ultimate "destiny"of galaxies inside a cluster will be to merge together and ends up with only one big galaxy ?
Established Member
Nothing would be that certain. Galaxies in a typical cluster would moving at a fair speed (which is what led Fritz Zwicky to first postulate Dark Matter), and as per Chaos theory, it would be impossible to forecast precisely the future interactions. eg. I imagine a galaxy could get expelled just like stars get expelled from star clusters.
Established Member
Unless cosmic expansion accelerates even more dramatically then the cosmological constant interpretation suggests, yes. N-ody systems aren't actually stable, just very long-lived. The long-term state of an isolated cluster of galaxies would be one large central galaxy surrounded by a very extended halo of individual stars and clusters, stripped from the original galaxies during close encounters. In today's clusters, as much as 10-25% of the starlight already comes from these loose stars - it's tricky to pick out their unresolved light from galaxy stellar halos, requiring very careful baffling of the telescope against stray light (although Hubble can see red giants in Virgo, and big ground-based telescopes can find planetary nebulae between its galaxies) . Chris Mihos has done some especially nice work on the Virgo Cluster in picking out the intracluster light and finding trails indicating individual encounters in the "recent" past.
Fred Adams has speculated carefully about the really long-term future of the Universe, including a book. If you wait long enough, a galaxy would be a central black hole surrounded by degenerate stelar remnants and stellar-mass back holes. If protons decay, there's another whole epoch to consider.
Established Member
Because they have had time to collapse - this is rather like being amazed that there are no babies being born in a retirement home.Just that everything seem to be already set-up in term of creation of new galaxies forming from pristine primordial gas clouds.
Established Member
At the difference than we can still observe the Universe back in time when it was in the "baby state" .
Astronomers find clouds of primordial gas from the early universe
http://news.ucsc.edu/2011/11/pristine-gas.html
It seem from the sentence I have bolded that the theoretical models for the formation of Galaxies is(are) still very hypothetical ?The spectrographic analysis of the pristine gas clouds places them in time at about 2 billion years after the Big Bang, or nearly 12 billion years ago. At that time, theoretical models predict that galaxies were growing by pulling in vast streams of cold gas, but these "cold flows" have never been seen. According to Fumagalli, the pristine gas clouds are potential candidates for these elusive cold flows. Further studies are needed, however, to see if the newly discovered gas clouds are associated with galaxies.
Established Member
But not all of them have. Many have missed collapse so far. There are plenty of high velocity clouds around Milky Way, such as Smith´s Cloud, which is right now beginning a collision with Milky Way disc.
When a high velocity cloud hits galaxy disc, it creates a feature like Gould Belt. But what happens when two high velocity clouds hit each other away from any existing galaxy?
Established Member
Look again how they found the gas - by looking at absorption features in quasar spectra. We cannot see these clouds in anything like enough detail to spot things like cold flows. We'd only be able to see them if they were happening very close to us - close enough for a direct detection of an extended source and its mapping.At the difference than we can still observe the Universe back in time when it was in the "baby state" .
To extend the analogy - it does not matter if there is a maternity unit half a mile away and you sometimes hear babies crying, they are too far away to see in the level of detail required to find out if they wear cloth or plastic nappies.
The current model has a few weaknesses but it makes testable predictions and so far it best matches observations. Otherwise it would not be the current model.
Administrator
You are asking here about an area that is pretty new in terms of our ability to explore observationally. Since Hubble and LeMaitre first described the expanding universe, we've been slowly increasing our ability to observe closer to the beginning. You've probably read about some of the observing boundaries, such as the epoch of reionization (which we now think was about z=8, give or take 2). This is something that makes it hard to see things optically or in the infrared before that period, and the initial galaxies had to have formed before that, because it is the light of their first stars that did the reionizing. The JWST should let us observe back to that boundary.
Very recently work has started anticipating the building of the SKA, which should enable us (among other things) to observe highly redshifted Hyperfine Hydrogen radiation (21cm) from time before that, and map how early the concentrations of gas and cold flows happened. So, yes, they haven't been observed directly yet. They have appeared in simulations, so they are expected. The age of the universe when they do get observed will supply some additional tuning parameters to our models of the universe, and let us predict and model other things in more reliable detail.
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Order of Kilopi
Origin and evolution of the structure in the universe (galaxies, large-scale structures) is a central problem in cosmology. Here is a good lecture on the subject (9 MB pdf).
Everyone is entitled to his own opinion, but not his own facts.
Suspended
How did the Hubble UDF completely invalidate the Steady-State idea?
Administrator
In short, it observed numerous small star-forming galaxies at an early epoch. These were so different from the universe today that the state of the universe is observationally confirmed as not steady. The fact that lots of small star forming galaxies at z~6 is consistent with LCDM is nice for us who are working on the assumption that LCDM is close to right, but the point is that the steady state universe was eliminated as a possibility by HUDF and other such studies of the early universe.
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Suspended
Those numerous small, massively star-forming galaxies are only small and fantastically star-forming when you apply the theoretical assumptions of an expanding universe to interpret their distance, size and luminosity. That is a completely circular argument for LCDM.
Administrator
Really? Show me how they could exist as the norm in a steady state explanation of the universe. Show some numbers.
Forming opinions as we speak
Order of Kilopi
What about the morphology of those galaxies? That doesn't depend on anybody's theoretical assumptions.
The HUDF shows that ... the early universe was filled with dwarf galaxies, but no fully formed galaxies like our Milky Way. -- source
If the universe was in a "steady state," as you inexplicably seem to desire, some of those most distant galaxies would be fully formed. Well, sorry, but they're not. There are no fully formed galaxies like the Milky Way back then.
By the way, the faintest objects in the HUDF are less than one four-billionth the brightness of stars that can be seen with the naked eye. This would tend to indicate that they are, you know, kinda far away. Or is the fact that things generally appear less luminous when they're farther away too much of a "theoretical assumption" for you?
Everyone is entitled to his own opinion, but not his own facts.
Established Member
Is there any datas comparing the surface brightness of galaxies at high and low redshift made from the HUDF survey ?If so what are the results about that comparaison?
Eta
A quick search on the internet returned this ...
http://proceedings.aip.org/resource/...sAuthorized=no
Eta2
I just find the freely available paper on arxiv.
http://search.arxiv.org:8081/details...o-ph/0509611v2
Is it possible to have the full datas about the surface brightness of galaxies at high and low redshift from the HUDF survey to verify ?
Last edited by Don J; 2012-May-12 at 06:25 AM.
Established Member
The distance ladder is vulnerable to errors on every step, and to accumulation of errors over several steps - like the notorious mixing of several cepheid types.
How far out is the Hubble constant reliably checked by independent distance measurements?
Established Member
Hmm It seem rather that the HUDF datas are showing some unexpected surprise...in favor of the steady state universe.
Evidence for a Non-Expanding Universe: Surface Brightness Data From HUDF
http://search.arxiv.org:8081/details...o-ph/0509611v2
from the abstrac
Surface brightness data can distinguish between a Friedman-Robertson-Walker expanding universe and a non-expanding universe. For surface brightness measured in AB magnitudes per angular area, all FRW models, regardless of cosmological parameters, predict that surface brightness declines with redshift as (z+1)^-3, while any non-expanding model predicts that surface brightness is constant with distance and thus with z. High-z UV surface brightness data for galaxies from the Hubble Ultra Deep Field and low-z data from GALEX are used to test the predictions of these two models up to z=6. A preliminary analysis presented here of samples observed at the same at-galaxy wavelengths in the UV shows that surface brightness is constant, mu=kz^0.026+-0.15, consistent with the non-expanding model. This relationship holds if distance is linearly proportional to z at all redshifts, but seems insensitive to the particular choice of d-z relationship. Attempts to reconcile the data with FRW predictions by assuming that high-z galaxies have intrinsically higher surface brightness than low-z galaxies appear to face insurmountable problems. The intrinsic FUV surface brightness required by the FRW models for high-z galaxies exceeds the maximum FUV surface brightness of any low-z galaxy by as much as a factor of 40. Dust absorption appears to make such extremely high intrinsic FUV surface brightness physically impossible. If confirmed by further analysis, the impossibility of such high-surface-brightness galaxies would rule out all FRW expanding universe (big bang) models.
Moderator
How did you determine that this is a credible paper? Just by it being on arxiv? It doesn't seem to be published, there is no hint of peer-review, and it was apparently presented at something called "the First Crisis in Cosmology Conference".
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Suspended
You're citing some pretty old news here (2004). I think those conclusions have long since been dropped. I'd have to do some digging, but originally it appeared that the galaxies were irregular suggesting not fully formed but with the newer cameras they look more like local galaxies although they are interpreted to be much smaller, massive and as having star formation rates around 100X the local rate. Of course these conclusions are dependent upon the angular size and brightness expectations based on the expansion model.
Could you cite a more recent paper (not a news blurb) that makes that claim, particular for some other morphology (not size)?
Oh boy. You put words in my mouth and then make fun of them? Of course they are very far away where did you get the idea that I'm arguing that they are not?
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