Study claims Milky Way dark matter half what scientists thought

http://www.astronomy.com/news/videos...ntists-thought

"The current idea of galaxy formation and evolution, called the lambda cold dark matter theory, predicts that there should be a handful of big satellite galaxies around the Milky Way that are visible with the naked eye, but we don't see that," Kafle said. "When you use our measurement of the mass of the dark matter, the theory predicts that there should only be three satellite galaxies out there, which is exactly what we see: the Large Magellanic Cloud, the Small Magellanic Cloud, and the Sagittarius Dwarf Galaxy."

University of Sydney astrophysicist Professor Geraint Lewis, who was also involved in the research, said the missing satellite problem had been "a thorn in the cosmological side for almost 15 years."

It may solve the satellite galaxy problem, which was already fitting the
MOND model perfectly, but it still doesn't solve the problem of what
Dark Matter could be.

Also it may bring up another problem. If the Milky Way has half the Dark
Matter previously thought, that would also mean Andromeda does too, and
so does every other galaxy in the universe. So the amount of Dark Matter
has just dropped by half, even though the CMB curve data supposedly says
we have the perfect amount of Dark Matter right now. So how are they
going to explain away that discrepancy between the amount seen in
galaxies vs. the amount supposedly calculated from the CMB data?

Now it's possible this only applies to the Milky Way, it may have
unusually low amount of Dark Matter. But they've been seeing the same
satellite galaxy problem throughout most of the near universe. Are all
of these galaxies in the near universe unusual too? What is it about our
part of the universe that makes us so unusual? Etc.

Yousuf Khan

In article ,
Yousuf Khan writes:
http://www.astronomy.com/news/videos...ntists-thought

This appears to refer to an article by Kafle et al. (2014 ApJ 794,
59) in which they present a detailed analysis of stellar motions in
the outer galaxy. I've looked at only the abstract, which doesn't
mention the satellite galaxies. Net result is a halo mass of 8E11,
disk mass of 1E11, and bulge mass of 0.9E11 solar masses. The halo
mass is described as "small," but the "universal" ratio of dark to
baryonic matter would predict about 10E11 solar masses if I have the
numbers right. What this seems to be saying is that baryonic matter
is somewhat more concentrated in galaxies than dark matter is. I
don't understand why that's surprising, but this is not my field.

If the Milky Way has half the Dark Matter previously thought,

4/5, or am I doing something wrong?

So the amount of Dark Matter has just dropped

amount of dark matter _in galaxy haloes_ has dropped

An interesting wrinkle is that the bulge mass predicts a central
black hole mass of about 45 million solar masses, but the actual mass
is 4 million. This relates to an earlier thread in this newsgroup
about the difference between M31 and MW black holes. If the new
bulge mass is right, the MW black hole is much smaller than it ought
to be.

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Help keep our newsgroup healthy; please don't feed the trolls.
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On 15/10/2014 3:16 PM, Steve Willner wrote:
In article ,
Yousuf Khan writes:
http://www.astronomy.com/news/videos...ntists-thought

This appears to refer to an article by Kafle et al. (2014 ApJ 794,
59) in which they present a detailed analysis of stellar motions in
the outer galaxy. I've looked at only the abstract, which doesn't
mention the satellite galaxies. Net result is a halo mass of 8E11,
disk mass of 1E11, and bulge mass of 0.9E11 solar masses. The halo
mass is described as "small," but the "universal" ratio of dark to
baryonic matter would predict about 10E11 solar masses if I have the
numbers right. What this seems to be saying is that baryonic matter
is somewhat more concentrated in galaxies than dark matter is. I
don't understand why that's surprising, but this is not my field.

If the Milky Way has half the Dark Matter previously thought,

4/5, or am I doing something wrong?

The article says half. So if this study says the dark matter mass is
8E11, then it must mean they were working on the assumption of 16E11
dark matter mass before, rather than 10E11.

So the amount of Dark Matter has just dropped

amount of dark matter _in galaxy haloes_ has dropped

Then the question is how does Dark Matter distribute itself so selectively?

An interesting wrinkle is that the bulge mass predicts a central
black hole mass of about 45 million solar masses, but the actual mass
is 4 million. This relates to an earlier thread in this newsgroup
about the difference between M31 and MW black holes. If the new
bulge mass is right, the MW black hole is much smaller than it ought
to be.

I've always thought that the MW SMB was a little puny compared to other
galaxies of its size. They even found a dwarf galaxy with an SMB
recently which was 2.5 times bigger than the MW's.

Yousuf Khan

In article ,
Yousuf Khan writes:
The article says half.

How was that calculated? All I did was multiply the combined mass of
the bulge and disk by the ratio of dark to baryonic matter in the
concordance cosmology.

Then the question is how does Dark Matter distribute itself so selectively?

I don't understand the question. Baryonic matter forms stars and
galaxies. This occurs primarily where dark matter is densest, but in
general one expects baryonic matter to have relatively bigger density
peaks. (This is goes by the name of "biasing," which I admit is not
very descriptive.) The fundamental reason is that baryonic matter
interacts by forces other than gravitation.

A web search on "dark matter biasing" turns up lots of references.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
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On 17/10/2014 2:31 PM, Steve Willner wrote:
In article ,
Yousuf Khan writes:
The article says half.

How was that calculated? All I did was multiply the combined mass of
the bulge and disk by the ratio of dark to baryonic matter in the
concordance cosmology.

Don't know, just going by what the article says.

Then the question is how does Dark Matter distribute itself so selectively?

I don't understand the question. Baryonic matter forms stars and
galaxies. This occurs primarily where dark matter is densest, but in
general one expects baryonic matter to have relatively bigger density
peaks. (This is goes by the name of "biasing," which I admit is not
very descriptive.) The fundamental reason is that baryonic matter
interacts by forces other than gravitation.

A web search on "dark matter biasing" turns up lots of references.

You can easily see why baryonic matter would have biasing (literally
see, as it's related to the electromagnetic force), but Dark Matter
shouldn't have any other forces that it interacts with. Being left with
only gravity, it should have just very coarse biasing.

Yet, Dark Matter seems to have as rich of a biasing capability as the
baryonic matter around it. It's like as if it is following the baryonic
matter around it. Apparently it has higher concentrations near the
galactic bulges, while having less in the outskirts, it has another set
of concentrations with galactic clusters and superclusters, it's like as
if it's a mirror of the baryonic structures themselves.

What I'm getting at here (obtusely) is that Dark Matter doesn't exist,
and it's an illusory effect being created by the baryonic structures
themselves. That's why we can't find it in our particle accelerators
because it's nothing more than an illusion. It's gravity itself working
differently than we thought.

This would extend out to Dark Energy as well at the larger scales. Dark
Energy would be an illusory effect of gravity working in a different way
that originally thought. My feeling is that it's all being caused by the
effects of the quantum vacuum energy amplifying or diminishing gravity
as the shapes of the structures around it change.

Yousuf Khan

In article ,
Yousuf Khan writes:
You can easily see why baryonic matter would have biasing (literally
see, as it's related to the electromagnetic force),

Good.

but Dark Matter
shouldn't have any other forces that it interacts with. Being left with
only gravity, it should have just very coarse biasing.

"Biasing" means the overdensity of baryonic matter _relative to_ dark
matter, so by definition dark matter has no biasing.

Yet, Dark Matter seems to have as rich of a biasing capability as the
baryonic matter around it. It's like as if it is following the baryonic
matter around it.

From a theoretical viewpoint, it's the other way around: baryons tend
to concentrate in regions where the dark-matter density is high.
That's partly gravity but with bias because of the electromagnetic
forces.

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA

On 30/10/2014 5:38 PM, Steve Willner wrote:
In article ,
Yousuf Khan writes:
but Dark Matter
shouldn't have any other forces that it interacts with. Being left with
only gravity, it should have just very coarse biasing.

"Biasing" means the overdensity of baryonic matter _relative to_ dark
matter, so by definition dark matter has no biasing.

From here, it seems like a chicken and egg situation. What is biasing
what? Is the DM getting concentrated because of the concentration of
baryonic matter, or is the baryonic matter getting concentrated by the DM?

From the point of view of apparent mass, it would seem that DM would be
controlling the BM. But from the point of view of braking and frictional
forces, BM would have much more opportunities to get concentrated first,
with the DM following along with it.

Yet, Dark Matter seems to have as rich of a biasing capability as the
baryonic matter around it. It's like as if it is following the baryonic
matter around it.

From a theoretical viewpoint, it's the other way around: baryons tend
to concentrate in regions where the dark-matter density is high.
That's partly gravity but with bias because of the electromagnetic
forces.

I think people aren't thinking far enough outside the box with Dark
Matter. They've convinced themselves that it must be some sort of
massive particles, but what if it's really nothing more than an illusion
caused by a type of Casimir Effect? Differences in vacuum energies
between galactic regions of space and void regions.

Yousuf Khan