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Beyond IDCS J1426.5+3508



 
 
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  #51  
Old October 4th 12, 08:09 PM posted to sci.astro.research
Nicolaas Vroom
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Posts: 216
Default Beyond IDCS J1426.5+3508

On Wednesday, October 3, 2012 9:58:43 AM UTC+2, Phillip Helbig
wrote:
Why do you expect the density to be as you described it?

I expect that a galaxy cluster more or less is the same as a
dwarf eliptical galaxy like: NGC 147
See: http://en.wikipedia.org/wiki/NGC147
That means the highest density is in the center and slowly decreases.
Those distributions are the same I have used to study the Virial Theorem
This description is identical for the bulge of our Milky Way.

The following link is "interesting":
http://en.wikipedia.org/wiki/Virial_...#Virial_radius
They use the equation rho c = 3*H^2/8*pi*G to study the behaviour
of a single galaxy cluster while at the same type that same equation
is used to study the whole Universe.

Nicolaas Vroom
http://users.telenet.be/nicvroom
  #52  
Old October 4th 12, 08:14 PM posted to sci.astro.research
Richard D. Saam
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Posts: 240
Default Beyond IDCS J1426.5+3508

On 10/1/12 2:17 AM, Phillip Helbig---undress to reply wrote:

H^2 = \frac{8\pi G\rho}{3}

Thus the critical density is, by definition, 3H^2/(8\pi G) since the
value of the density is always the critical density in the Einstein-de
Sitter universe. So H(z) is proportional to the square root of the
density. (If lamnda and/or k are not zero, then the expression for H(z)
is of course more complicated.)

In a purely mathematical sense
critical density rho_c is proportional to H^2/G
and
critical density rho_c is proportional to H^2
if G is a constant.
but alternatively
critical density rho_c is proportional to H
if H/G is a constant.

As previously posted by Jonathan Thornburg,
lunar ranging in our local bound system indicates
(d^2G/dt^2)/G = (4 ± 5) * 10^{-15}/year^2
but this does not negate
a delta G in galactic cluster systems
in near equilibrium with expanding critical density rho_c.

http://arxiv.org/abs/1106.4052
states the traditional physics:

critical density rho_c is proportional to H^2
with G constant

but no attempt is made
in using this relationship
to dimensionally explain the Table C1 data
represented by the slope 1.91 ~ 2
graphed in Figure C1

that can be dimensionally explained by:

critical density rho_c is proportional to H
with H/G constant.
  #53  
Old October 4th 12, 08:14 PM posted to sci.astro.research
Richard D. Saam
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Posts: 240
Default Beyond IDCS J1426.5+3508

On 10/2/12 3:16 PM, Nicolaas Vroom wrote:
On Thursday, September 20, 2012 8:30:10 AM UTC+2, Richard D. Saam wrote:

A more appropriate study may be: Implicit Priors in Galaxy Cluster
Mass and Scaling Relation Determinations
http://arxiv.org/abs/1106.4052
Adam Mantz (NASA/GSFC), Steven W. Allen (KIPAC, Stanford/SLAC)


Table C1 page 11 shows 4 lines with of galaxy cluster data
with almost identical kT values.
De values for z, E(z), M2500 and kT are shown:
16) 0.295 1.163 2.67 8.03
22) 0.352 1.201 4.02 8.05
23) 0.355 1.203 6.02 8.08
37) 0.686 1.462 3.07 8.08

The lines 22 and 23 are almost identical but the M2500
values are rather different.
What is the explanation ?

The explanation is not readily apparent.
Also:
The kT values in the the keV range
represent the inter galactic gas temperature
as related to gravitational energy.
A graphical plot of kT vs z indicates no correlation
Also
A graphical plot of M2500 vs z indicates no correlation
but
A graphical plot of M2500 vs kT indicates the slope 1.9 correlation.
and
A graphical plot of E(z)*M2500 vs kT indicates the slope 1.9 correlation.
What is the explanation ?

We need a better idea of the galactic distribution with time
to be provided in part by
http://www.darkenergysurvey.org/
"an extremely sensitive 570-Megapixel digital camera, DECam,
mounted on the Blanco 4-meter telescope at Cerro Tololo Inter-American
Observatory high in the Chilean Andes"
for detecting redshifted long-wavelength red and infrared light
and coupled with X-ray gamma-ray surveys.
  #54  
Old October 5th 12, 08:17 PM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default Beyond IDCS J1426.5+3508

In article , Nicolaas Vroom
writes:

On Wednesday, October 3, 2012 9:58:43 AM UTC+2, Phillip Helbig
wrote:
Why do you expect the density to be as you described it?

I expect that a galaxy cluster more or less is the same as a
dwarf eliptical galaxy like: NGC 147


Why? Also, for comparison one needs the mass, which is usually less
precisely known than the light.

That means the highest density is in the center and slowly decreases.


OK, the NFW drops off more quickly.

They use the equation rho c = 3*H^2/8*pi*G to study the behaviour
of a single galaxy cluster while at the same type that same equation
is used to study the whole Universe.


The critical density, of course, is important for the entire universe.
However, in order for something to collapse and form structure, then, at
least to first order, it has to locally exceed the critical density, so
it is not surprising to see this crop up in the context of smaller
structures as well.
  #55  
Old October 5th 12, 08:20 PM posted to sci.astro.research
Phillip Helbig---undress to reply
external usenet poster
 
Posts: 629
Default Beyond IDCS J1426.5+3508

In article , "Richard D. Saam"
writes:

Thus the critical density is, by definition, 3H^2/(8\pi G) since the
value of the density is always the critical density in the Einstein-de
Sitter universe. So H(z) is proportional to the square root of the
density. (If lamnda and/or k are not zero, then the expression for H(z)
is of course more complicated.)

In a purely mathematical sense
critical density rho_c is proportional to H^2/G
and
critical density rho_c is proportional to H^2
if G is a constant.
but alternatively
critical density rho_c is proportional to H
if H/G is a constant.

As previously posted by Jonathan Thornburg,
lunar ranging in our local bound system indicates
(d^2G/dt^2)/G = (4 ± 5) * 10^{-15}/year^2
but this does not negate
a delta G in galactic cluster systems
in near equilibrium with expanding critical density rho_c.


There are also constraints on the variability of G over cosmological
distances. Not as strict as the local constraints, but strict enough to
rule out it being important for explaining something---at best, one
could hope to marginally DETECT a variation.
  #56  
Old October 6th 12, 10:43 AM posted to sci.astro.research
Nicolaas Vroom
external usenet poster
 
Posts: 216
Default Beyond IDCS J1426.5+3508

On Friday, October 5, 2012 9:17:32 PM UTC+2, Phillip Helbig---undress to reply wrote:
The critical density, of course, is important for the entire universe.
However, in order for something to collapse and form structure,
then, at least to first order, it has to locally exceed the
critical density, so it is not surprising to see this crop up
in the context of smaller structures as well.

The problem is that the density of the Universe is smaller
than the density of a galaxy cluster which inturn
is smaller than the density of a single large galaxy.
For the critical density I expect the same relation.
If that is true it means that you can not compare one
with the other.

This picture is even more complex if you assume that 80%
of all the matter in the Universe is non-baryonic.
Table 4 in
http://iopscience.iop.org/0004-637X/...1038/fulltext/
shows the amount of gas in a galaxy cluster is roughly
10% (20%) of the total mass.
Is my assumption understanding correct that the total
mass of a galaxy cluster including all baryonic and non
baryonic mass is a factor 5 higher than the total mass ?

Nicolaas Vroom
 




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