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 Post subject: Huge-LQG
PostPosted: Sat, 16-02-13, 19:30 GMT 
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Just last month a structure even huger than the Great Wall (which may actually be several small structures...) was discovered in the SDSS data.
Aptly named Huge-LQG (Large Quasar Group), this structure is ~ 1240 Mpc across.
By comparison, the Sloan Great Wall is "only" a total of 450 Mpc in length.

Here is the full paper (which I'm sure Fridger has already memorized ;-)
http://mnras.oxfordjournals.org/content ... ts497.full

Some interesting conclusions:
- Universe can no longer be considered homogeneous even at Gpc scales
- We may be living within a "dark flow" (not to be confused with dark matter) that causes expansion to appear accelerated within the flow.
This explanation seems to have been motivated by older findings of a similar (controversial) flow in the WMAP data: http://www.sciencedaily.com/releases/20 ... 162829.htm

One thing is certain: we are discovering more about the structure of the universe by analyzing data not just in 2 or 3 dimensions, but also in the fourth: time!


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PostPosted: Sat, 16-02-13, 20:25 GMT 
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Yes that is a very intriquing observation threatening the basic homogeneity assumption of standard cosmology ... Further threads, perhaps not unrelated include the gigantic Black Hole at the core of NGC 1277 (Nov 28 2012). Remco van den Bosch and colleagues identified a black hole with a mass that's about 59 percent of the mass of the galaxie's central bulge or 14% of the galaxie's total mass! Here is a SDSS image of the region

Image

Credit David W. Hogg/Michael Blanton/SDSS Collaboration

And here is how NGC 1277 and its environment looks in celestia.Sci (using the SDSS color profile):

Image

Fridger


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PostPosted: Sun, 17-02-13, 4:24 GMT 
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So now we are beginning to discover more and more peculiarities in our dark matter models of the universe, which themselves might be peculiarities outside the Standard Model. As usual nature is more surprising than our wildest imaginations. :)

Just curious Fridger, how come you have less galaxies than in the SDSS screenshot (e.g., the one below NGC 1278)?
Also there are some black speckles in your galaxies. "Dark matter" perhaps? ;-)


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PostPosted: Sun, 17-02-13, 10:14 GMT 
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dirkpitt wrote:
...
Just curious Fridger, how come you have less galaxies than in the SDSS screenshot (e.g., the one below NGC 1278)?


That's easy to answer: The galaxy catalog in celestia.Sci is still based on my original NGC/IC catalog with "only" 10000+ galaxies, just with additional entries per galaxy that allow the new colorful rendering. Soon or later the NGC/IC catalog will of course be substituted by or merged with the much larger one from SDSS. The magnitudes of the missing galaxies above are all beyond ~16m! One drawback as to SDSS is that distances of these weak galaxies are only known via a measurement of the redshift z (Hubble's law). Notably for the members of galaxy clusters that subtend substantial NON-radial forces among each other, the Hubble law is largely inaccurate...

Anyway the OGL rendering code of all galaxies is entirely new compared to Celestia-SVN.

Quote:
Also there are some black speckles in your galaxies. "Dark matter" perhaps? ;-)


As to the mysterious "black dots": These are of course not related to dark matter but are a result of some quick, imperfect "cheating" ;-), since the real code is still in the making.

In my above illustration of NGC 1277, I just blended a faint random starfield with the elliptical galaxy image from celestia.Sci (with GIMP). As is familiar, foreground stars look incorrectly dark in normal blending mode. Apparently I have overlooked some and hence didn't erase them...

I think galaxies with weak background and foreground stars look MUCH better than entirely starless displays. As an example, here is celestia.Sci's splash image showing the E2 elliptical galaxy NGC 3226 and the SBa spiral NGC 3227:
Image

Unfortunately the real stars are long "exhausted" in these small FOV views of dim galaxies. So I decided to generate dim (nameless) star samples statistically with proper Hertzsprung-Russell color-magnitudes, luminosity- and spacial distributions. These samples are being blended in dynamically via my automag mechanism. The idea of using faint statistical star samples is just analogous to the statistical generation of my new high-quality shader stars for globular clusters(with proper catalog parameters), like in these examples:

http://forum.celestialmatters.org/viewt ... 0&start=20
http://forum.celestialmatters.org/viewt ... 0&start=26

But actually my elliptical galaxies show a weak mottled structure upon closer approach that is to simulate statistically the well-known halo of globular clusters.

See here, the close-up of NGC 1277

[Bigger size by clicking on image]
Image

Cheers,
Fridger


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 Post subject:
PostPosted: Sun, 17-02-13, 15:23 GMT 
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I must say it is amazing what can be done with what limited amount of data we have available to us.
Just by knowing the macroscopic characteristics of galaxy and star clusters (e.g., red shifts, luminosity distributions, etc) celestia.Sci can generate very convincing images that can be compared with reference images from telescopes.

This would be very useful if we were to first compute a dark matter or dark flow simulation on a supercomputer, then be able to plug the result into celestia.Sci and compare visually with photographic or spectrographic references. While the simulation may end up with galaxies in complete different locations randomly, macroscopic features like large structures and flows would be recognizable.


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