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View Full Version : Where baryons are...dark matter ain't?



trinitree88
2011-Jul-12, 01:29 PM
There might be a rationale for an asymmetry in baryonic matter density if there's a compensating dark matter asymmetry so that the total density remains constant....SEE:Grin, Dore', Kamionkowski http://arxiv.org/PS_cache/arxiv/pdf/1107/1107.1716v1.pdf

kzb
2011-Jul-14, 11:41 AM
I've only skimmed the first page. However have I got this right:
First, DM was required in clumps in the early universe, in order to collect the baryonic matter into proto-galaxies.
But now, DM is required to do precisely the opposite, that is, be where the baryonic matter is not, in order to even out the mass ??
I need a lie down.

trinitree88
2011-Jul-14, 01:02 PM
kzb. Yep. Lots of people need to lie down.

kzb
2011-Jul-15, 11:49 AM
OK idea coming up for which I apologise to the Mods before I've even written it.

Reference your other thread about the OOPS with the 2MASS galactic luminosity underestimates.

Let's imagine someone was to come along and use this corrected 2MASS data alone to study and rationalise galactic rotation curves. Bear in mind the data is truncated at four disk scale-lengths. I wonder if that someone, using this corrected data, would feel any need to invoke DM (or, come to that, MOND) to rationalise the rotation curves? My suspicion is no, they would not. There'd be no systematic "missing mass" in large spiral galaxies out to these radii.

However now we have this paper, where it is stated that DM was always excluded from the inner regions of large galaxies. That's convenient isn't it?

(I do appreciate BTW, there is still the extended gas disk rotation curve to explain, which this 2MASS correction does not affect (since it is measured by radio).)