http://xxx.lanl.gov/PS_cache/arxiv/p...704.3441v1.pdf

Ingolfur Agustsson, Tereasa G. Brainerd

One possibility, is that 'red' satellites are part of the same system as 'red' galaxies, while blue galaxies are random interlopers - some how missplaced.

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jwj

It's ok not to know. We should try harder to find out.

Not according to the paper

Like most journal-stuff, its as precise as a laser beam and clear as mud, but I read it as saying only that "red" galaxies (seen as they were long ago?) have a non-uniform distribution of satellites, while "blue" galaxies (seen as they are more recently?) have a more uniform distribution.

This "smoothing" of the distribution seems like a natural course of events, so I'm not sure what the significance of this paper is, other than confirming that which is to be expected?

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PW -- Plant Whisperer

The colors of the galaxies are NOT produced by a different redshift: both samples of galaxies are at comparable distances, and all of them are at reasonably small redshift. The colors are produced by different populations of stars in the two sets of galaxies.

The paper provides some evidence that the manner in which galaxies-now-full-of-red-stars formed may differ from the manner in which galaxies-now-full-of-blue-stars formed. The mechanism of galaxy formation or growth could be different, in other words.

Thanks, StupendousMan.

Let's see if I got this right: The "working paradigm" has been that a galaxy full of red stars is old, and one full of blue stars is young, and these observations throw a monkey wrench into that assumption? Because the distribution of satellites in blue galaxies "looks old" (high entropy/randomized)?

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PW -- Plant Whisperer

No, that's not quite it. There are plenty of ways one can try to explain the difference; without additional information, any could be correct. One of the possibilities is that red galaxies -- which are often elliptical and found in regions of higher density -- might have formed via mergers, whereas blue galaxies -- which are often spiral -- may not have suffered major mergers. If that story is true, it might explain why the distribution of satellite galaxies is different: in one case, we see all the satellites, in the other, we see only the survivors.

Again, that's not the only explanation, or even the best one. But I think it gives a flavor for the sort of explanations that one might see in the literature over the next few months and years.

Interesting thought...only the most 'in family' relatives survive collisions. Do galaxies look after their own?

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jwj

It's ok not to know. We should try harder to find out.

When I read the OP and saw references to anisotropy I got interested because somehow I got the idea in my head that the slight anisotropy of the CMBR was the origin of galactic formation. Only after reading the link did I realize we were talking about anisotropy of the distribution of baby galaxies around hosts.

Was I imaging the connection between the slight anisotropy of the CMBR and the origin of galactic formation. I know we don't know, but do you recall seeing that proposed somewhere like I do?

I'm not aware of any studies that directly link CMB anisotrophy with star formation regions. There are papers that discuss large scale structure effects:

http://xxx.lanl.gov/PS_cache/astro-p.../0609188v2.pdf

And there is this one, connecting large ionized clouds with potential contamination:

http://www.physorg.com/news96301312.html


Quote:
Originally Posted by PhysOrg.com
According to Kronberg, "One of the most exciting aspects of the discovery is the new questions it poses. For example, what kind of mechanism could create a cloud of such enormous dimensions that does not coincide with any single galaxy, or galaxy cluster? ...And separately, could the newly discovered fluctuating radio glow be related to unwanted foregrounds of the Cosmic Microwave Background (CMB) radiation?"

So it would follow gaseous star forming regions could cause similar distortions.

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jwj

It's ok not to know. We should try harder to find out.

This is actually a pretty good explantion with a few caveats.

First, it assumes the 'galaxy merger' scenario, for galaxies merging from 'proto-galaxies'. OR that Ellipticals are the merges of 2 large spirals, which was pretty well thwarted in the Arp Thread by Hamilcar.

[in one case, we see all the satellites, in the other, we see only the survivors]

This is actually pretty tricky to describe easily, BUT, that would mean this statement in the brackets, is essentially right in that the Elipticals are much older and so have had more time to actually 'pull in' many more of their dwarfs, than the much younger "Blue spirals'.

So Spiral galaxies do 'grow' by Dwarfs merging, and the longer the spirals are around, the bigger their bulges and the more dwarfs that merge with them the closer and closer they get to being Elliptical Galaxies.

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RussT
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Everything is, as it should be, otherwise, it wouldn't be!