How can that be?

As I mentioned in another thread, the disk of the satellite galaxies of
Andromeda is extremely thin:


http://arxiv.org/abs/1301.0446
A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda
Galaxy

From the abstract:
"The structure is vast: at least 400 kpc in diameter, but also extremely
thin, with a perpendicular scatter 14.1 kpc (99% confidence)."

Well, that is a factor of around 30... At only 150Kpc the rotation
period is 5 billion years.

Since the supposed "age of the Universe" this disk can at most have done
2.74 revolutions.

But Andromeda did not exist right after the supposed big bang so it must
be quite less than that.

How can it be so flat?

Isn't it that flat disks flatten themselves by rotating? This is clearly
not the case he there isn't enough time to do a lot of rotations.

Or I am miscalculating something?

This huge structure must be more ancient than 2.75 rotations. Much more.
Maybe 20, 30 rotations to flatten itself, at least!

On Monday, August 18, 2014 8:18:34 AM UTC-4, jacob navia wrote:
Or I am miscalculating something?
This huge structure must be more ancient than 2.75 rotations. Much more.
Maybe 20, 30 rotations to flatten itself, at least!

One thing you are obviously missing
is the possibility that the planar
morphology is NOT due to rotational
flattening.

Perhaps other models like the
capture/breakup model are needed?

[Mod. note: reformatted -- mjh]

In article , jacob navia
writes:

Well, that is a factor of around 30... At only 150Kpc the rotation
period is 5 billion years.

Since the supposed "age of the Universe" this disk can at most have done
2.74 revolutions.

But Andromeda did not exist right after the supposed big bang so it must
be quite less than that.

Leave out "supposed" and people will take you more seriously.

How can it be so flat?

Isn't it that flat disks flatten themselves by rotating? This is clearly
not the case he there isn't enough time to do a lot of rotations.

Probably. In which case your time-scale argument is irrelevant.

Or I am miscalculating something?

This huge structure must be more ancient than 2.75 rotations. Much more.
Maybe 20, 30 rotations to flatten itself, at least!

So why are you invoking the time-scale argument again?

There was some discussion recently that it was unbelievable that voids
could exist because it would take galaxies too long to clear out of
them. But that is not how voids form. Rather, galaxies themselves
formed elsewhere. Probably something similar applies here.

Jacob said:

"Isn't it that flat disks flatten themselves by rotating? This is
clearly not the case he there isn't enough time to do a lot of
rotations. thin, with a perpendicular scatter 14.1 kpc (99%
confidence)."

Well, that is a factor of around 30... At only 150Kpc the rotation
period is 5 billion years.

Since the supposed "age of the Universe" this disk can at most have done
2.74 revolutions.

But Andromeda did not exist right after the supposed big bang so it must
be quite less than that.

How can it be so flat? "

Brad said:
Isn't it that flat disks flatten themselves by rotating? This is clearly
not the case he there isn't enough time to do a lot of rotations

Prog. Theor. Phys. (1983) 70 (5): 1276-1282. doi: 10.1143/PTP.70.1276
Try this as a partial explanation for your question. In addition
review other articles written by H Sato

[Mod. note: please try to quote previous articles using the standard
quoting character , and restrict lines to 80 characters. I have
fixed the second of these but not the first in this posting -- mjh]

As I mentioned in another thread, the disk of the satellite galaxies of
Andromeda is extremely thin:

http://arxiv.org/abs/1301.0446
A Vast Thin Plane of Co-rotating Dwarf Galaxies Orbiting the Andromeda
Galaxy

From the abstract:
"The structure is vast: at least 400 kpc in diameter, but also extremely
thin, with a perpendicular scatter 14.1 kpc (99% confidence)."

Well, that is a factor of around 30... At only 150Kpc the rotation
period is 5 billion years.

Since the supposed "age of the Universe" this disk can at most have done
2.74 revolutions.

But Andromeda did not exist right after the supposed big bang so it must
be quite less than that.

How can it be so flat?

Isn't it that flat disks flatten themselves by rotating? This is clearly
not the case he there isn't enough time to do a lot of rotations.

Or I am miscalculating something?

This huge structure must be more ancient than 2.75 rotations. Much more.
Maybe 20, 30 rotations to flatten itself, at least!

Galaxy formation theories are still incomplete. IMO the problem is the
Dark Matter paradigm. But, here are alternatives. Humitaka Sato
coauthored several papers expanding on earlier work by Israel and
generalizing the ideas of metric junctions between Schwatrzschild,
deSitter spaces in matter dominated universe to explain the newly
discovered Voids.

See: Prog. Theor. Phys. (1983) 70 (5): 1276-1282. doi: 10.1143/PTP.70.1276
See: Prog. Theor. Phys. (1984) 71 (5): 938-945. doi: 10.1143/PTP.71.938
See: Prog. Theor. Phys. (1986) 76 (6): 1250-1259. doi: 10.1143/PTP.76.1250


He found that the growth of voids resulted in first a thin matter
shell that denied ' crossover' of matter that kept voids comparatively
devoid of matter that resulted in a "snowplow" effect that
concentrated matter. It seems reasonable to add this process to the
formation of matter structures so that he Flatness would be a result
of constraints brought about by this division of the Universe into 2
distinct spacetime regimes.

Brad

[Mod. note: reformatted -- mjh]

On 8/18/14, 7:18 AM, jacob navia wrote:

This huge structure must be more ancient than 2.75 rotations. Much more.
Maybe 20, 30 rotations to flatten itself, at least!

At several hundred z's,
Galactic formation dimensions were much smaller
with faster rotation
imprinting the present visual display at z=0.

Le 20/08/2014 15:43, brad a écrit :
Prog. Theor. Phys. (1983) 70 (5): 1276-1282. doi: 10.1143/PTP.70.1276
Try this as a partial explanation for your question. In addition
review other articles written by H Sato

No, that doesn't apply. That theory is speaking about the huge voids
that happen to appear in the "foam" that seems to be the universe at
larger scales.

Thos voids are made of galaxies since *their absence* characterizes them.

Galaxies group in filaments (or "rivers") of galaxies and are obviously
much smaller than the filaments they build, that are made of several
clusters of galaxies at their intersections. This web is like a
condensation of matter in a foam.

Galaxies are very small at this scales. Galactic structures can't be
affected by forces acting at intra-cluster of bigger objects. And the
scientist you cite is describing VOIDS as a consequence of some
equations about the universe as a whole, nothing less.

Not Andromeda's disk.

With all due respect, I have the feeling that applying those very
general equations to galactic scales is a mistake of several orders of
magnitude.

The temperature-constant expansion the scientist is speaking about tries
to explain how this foam came to look like it looks today, not how the
same expansion would yield a flat disk, a completely different outcome,
at much smaller scales.

But anyway it was a completely strange idea, this kind of "pressure"
that would make the galaxies concentrate at the borders.

A condensation process is, for instance, rain.

When it rains, the condensation is directed and carried into rivers,
i.e. *paths in the gravitational field*, that carry the product of the
condensation away.

It rains galaxies out there. And voids (like mountains) are avoided by
the condensation product that is directed into rivers, that flow into
clusters of galaxies.

This was a powerful idea. Will those ponds of galaxies eventually
overflow and fill some of the voids?

After some unimaginable time?

It was a nice article, thanks for your answer.

In article ,
jacob navia writes:
Isn't it that flat disks flatten themselves by rotating?

If you are imagining mass that is originally in the center and then
spreads out by centrifugal force, I don't know a single astronomical
example of that. (I won't swear I'm not missing something.) More
common is initially spherical collapse, where the collapse along one
axis proceeds fairly rapidly and collapse in the perpendicular plane
is greatly slowed by angular momentum or a magnetic field or both.
Magnetic fields are likely to be important for star formation but
probably not for galaxy formation, but I don't think either one is
certain.

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

Le 22/08/2014 19:01, Steve Willner a écrit :
More
common is initially spherical collapse, where the collapse along one
axis proceeds fairly rapidly and collapse in the perpendicular plane
is greatly slowed by angular momentum or a magnetic field or both.
Magnetic fields are likely to be important for star formation but
probably not for galaxy formation, but I don't think either one is
certain.

That sounds very plausible. The collapse along one axis proceeds fairly
rapidly and kinetic energy is gained by the collapsing material in the
direction of the collapsing axis.

Obviously it will overshoot the central plane and at the other side, the
same forces will make it stop and then reverse and fall in the other
direction, where it will overshoot again (but less) the central disk.

This will take a HUGE amount of time!

We are speaking here about GALAXIES, and even for dwarf galaxies their
movements are VERY slow. One revolution of that disk is 5GY. How much
time a single damped oscillation will take is anyone guess, but several
oscillations are SURELY required in my humble opinion.

Relember: the galaxies are aligned with a form factor of around 30.

400 kpc diameter, 14 kpc thin.

This structure is incredibly OLD, at least 50 GY or more. You have to
align precisely all this galaxies in this rotating disk.

And that takes an incredibly amount of time!

On 8/26/2014 7:13 AM, jacob navia wrote:
We are speaking here about GALAXIES, and even for dwarf galaxies their
movements are VERY slow. One revolution of that disk is 5GY. How much
time a single damped oscillation will take is anyone guess, but several
oscillations are SURELY required in my humble opinion.

Relember: the galaxies are aligned with a form factor of around 30.

400 kpc diameter, 14 kpc thin.

This structure is incredibly OLD, at least 50 GY or more. You have to
align precisely all this galaxies in this rotating disk.

And that takes an incredibly amount of time!

So you're ignoring the possibility that they were closer together
before the universe expanded this much, and therefore such a collapse
would happen faster?

[Mod. note: quoted text trimmed -- mjh]