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Cosmography of the local Universe



 
 
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  #1  
Old December 16th 13, 09:21 AM posted to sci.astro.research
Nicolaas Vroom
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Posts: 216
Default Cosmography of the local Universe

The video "Cosmography of the local Universe" gives a very impressive
view of the positions and peculiar velocities in the neighborhood
of the Milky way.
See http://vimeo.com/64868713# and http://arxiv.org/abs/1306.0091
In this last document there is the sentence:
"Detailed maps of motions are inputs to the translation
from redshift space to physical space and constrain the
underlying distribution of (mostly dark) matter. "
How do they know that most of the matter in our local
Universe is dark matter?

If someone explain to me the following sentence:
"We measure crude three-dimensional (3D) locations from their
systematic velocities and sky positions
(distorted from true positions by peculiar velocities)"
this would be helpful.
Next is written:
" and we can estimate their baryonic masses from their luminosities.
Unfortunately this information degrades with distance and can be
lacking in regions of heavy obscuration. In the case of redshift
surveys, low luminosity galaxies are mostly lost etc"
What this means is that lots of ordinary matter is not observed.
Which is true but again does not indicate that there is dark
matter involved.

Nicolaas Vroom
http://users.pandora.be/nicvroom/
  #2  
Old December 17th 13, 09:21 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default Cosmography of the local Universe

In article , Nicolaas Vroom
writes:

"Detailed maps of motions are inputs to the translation
from redshift space to physical space and constrain the
underlying distribution of (mostly dark) matter. "
How do they know that most of the matter in our local
Universe is dark matter?


Probably from the several hundred, if not several thousand, papers on
dark matter in the last 40 years or so.

If someone explain to me the following sentence:
"We measure crude three-dimensional (3D) locations from their
systematic velocities and sky positions
(distorted from true positions by peculiar velocities)"
this would be helpful.


Measuring the position on the sky is easy. Measuring a distance is
difficult. One can measure the redshift, but that corresponds to a
distance only if one knows the cosmological model and if the
cosmological redshift is much greater than that due to the peculiar
velocity. In the local universe, this is not the case. Lookup "
redshift-space distortions".

Next is written:
" and we can estimate their baryonic masses from their luminosities.
Unfortunately this information degrades with distance and can be
lacking in regions of heavy obscuration. In the case of redshift
surveys, low luminosity galaxies are mostly lost etc"
What this means is that lots of ordinary matter is not observed.
Which is true but again does not indicate that there is dark
matter involved.


Again, there are many, many, many papers on dark matter in the local
universe.
  #3  
Old December 17th 13, 10:50 PM posted to sci.astro.research
Nicolaas Vroom
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Posts: 216
Default Cosmography of the local Universe

Op dinsdag 17 december 2013 09:21:26 UTC+1 schreef Phillip Helbig:
In article , Nicolaas Vroom

writes:

How do they know that most of the matter in our local
Universe is dark matter?


Probably from the several hundred, if not several thousand, papers on
dark matter in the last 40 years or so.


I agree. But they should demonstrate dark matter based on observations.
The issues involved becomes clear by studying the next sentence:

The simple question can be asked if the distribution of observed
galaxies and the distribution of matter inferred from galaxy
motions agree. They should, if galaxies are reasonable tracers
of the ensemble of matter, and if our procedures are valid for
the interpretation of motions in terms of the matter distribution.

The matter inferred from galaxy motions should include both
vissible and darkmatter. If there is agreement then there is no
dark matter involved.

Measuring the position on the sky is easy. Measuring a distance is
difficult. One can measure the redshift, but that corresponds to a
distance only if one knows the cosmological model and if the
cosmological redshift is much greater than that due to the peculiar
velocity. In the local universe, this is not the case. Lookup "
redshift-space distortions".


See: http://astro.berkeley.edu/~mwhite/te...ni_red_mjw.pdf

Part of my misunderstanding comes from using the words measuring
and calculating.
If a certain physical law uses the equation a * b = c
than a and b are measured and c is calculated.
(of course a could also be calculated)
As such I would say: Calculating a distance is difficult.


Next is written:
" and we can estimate their baryonic masses from their luminosities.
Unfortunately this information degrades with distance and can be
lacking in regions of heavy obscuration. In the case of redshift
surveys, low luminosity galaxies are mostly lost etc"
What this means is that lots of ordinary matter is not observed.
Which is true but again does not indicate that there is dark
matter involved.


Again, there are many, many, many papers on dark matter in the local
universe.


I agree, but in this whole paper the concept of darkmatter is not
discussed.
The starting sentence of the document reads:
"The large scale structure of the universe is a complex web of
clusters, filaments, and voids. "
This should be:
"etc of clusters, filaments, voids and darkmatter."
IMO if 85% of matter in the the universe is darkmatter than this should
be mentioned or are the authors of this document of the opinion that
this amount is much lower?

A different opinion is that darkmatter is closely linked within
the galaxies and that there is no darkmatter outside the galaxies
specific not in the voids. This is just a guess.

Nicolaas Vroom
http://users.pandora.be/nicvroom/
  #4  
Old December 19th 13, 09:57 AM posted to sci.astro.research
Steve Willner
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Posts: 1,172
Default Cosmography of the local Universe

In article ,
Nicolaas Vroom writes:
But they should demonstrate dark matter based on observations.


The video
http://vimeo.com/64868713# described at http://arxiv.org/abs/1306.0091
is an _illustration_ of current knowledge of galaxy positions,
masses, and motions. It isn't meant to demonstrate dark matter,
though as far as I can tell, the results are consistent with the
standard dark matter picture. In particular, galaxies exist
preferentially where dark matter is densest.

The matter inferred from galaxy motions should include both
vissible and darkmatter. If there is agreement then there is no
dark matter involved.


That second sentence seems to have an extra "no" in it, but the first
sentence is a misunderstanding. The video shows the _observed_
motions based on observations and with statistical corrections for
galaxies that cannot be observed because they are too faint or are in
the zone of avoidance. I didn't see a direct comparison with the
expected motions based on dark matter models, but there seems to be
at least qualitative agreement. Observed flows towards the Great
Attractor, for example, are larger than can be accounted for by
visible matter in that direction. (That statement doesn't come from
the video but rather from previous work.)

Part of my misunderstanding comes from using the words measuring
and calculating.


There's no real difference in practice. Be aware that the video
makes use of velocity-independent distances in order to measure (or
calculate, if you like) the peculiar velocities.

The starting sentence of the document reads:
"The large scale structure of the universe is a complex web of
clusters, filaments, and voids. "
This should be:
"etc of clusters, filaments, voids and darkmatter."


Or perhaps "...observed large scale structure...."

--
Help keep our newsgroup healthy; please don't feed the trolls.
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
  #5  
Old December 19th 13, 09:58 AM posted to sci.astro.research
Phillip Helbig---undress to reply
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Posts: 629
Default Cosmography of the local Universe

In article , Nicolaas Vroom
writes:

Op dinsdag 17 december 2013 09:21:26 UTC+1 schreef Phillip Helbig:
In article , Nicolaas Vroom

writes:

How do they know that most of the matter in our local
Universe is dark matter?


Probably from the several hundred, if not several thousand, papers on
dark matter in the last 40 years or so.


I agree. But they should demonstrate dark matter based on observations.
The issues involved becomes clear by studying the next sentence:

The simple question can be asked if the distribution of observed
galaxies and the distribution of matter inferred from galaxy
motions agree. They should, if galaxies are reasonable tracers
of the ensemble of matter, and if our procedures are valid for
the interpretation of motions in terms of the matter distribution.

The matter inferred from galaxy motions should include both
vissible and darkmatter. If there is agreement then there is no
dark matter involved.


Yes. But I don't see any contradiction. By definition, dark matter is
not "observed" and historically it was the fact that the observation of
the motions of (parts of) galaxies don't correspond to the matter which
can be directly inferred from the luminous stuff observed which led to
the dark-matter idea.

If a certain physical law uses the equation a * b = c
than a and b are measured and c is calculated.
(of course a could also be calculated)
As such I would say: Calculating a distance is difficult.


Well, in some sense, all one really measures are counts from a CCD as a
function of position. Everything else is calculation.

The starting sentence of the document reads:
"The large scale structure of the universe is a complex web of
clusters, filaments, and voids. "
This should be:
"etc of clusters, filaments, voids and darkmatter."


Dark matter is presumably included in the clusters and filaments.
  #6  
Old December 20th 13, 08:29 PM posted to sci.astro.research
Nicolaas Vroom
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Posts: 216
Default Cosmography of the local Universe

Op donderdag 19 december 2013 09:58:11 UTC+1 schreef Phillip Helbig:
In article , Nicolaas Vroom

writes:


The matter inferred from galaxy motions should include both
vissible and darkmatter. If there is agreement then there is no
dark matter involved.


This last sentence should be:
If there is agreement between the distribution of observed galaxies and
the distribution of matter inferred from galaxy motions then there is
no dark matter involved.

Yes. But I don't see any contradiction. By definition, dark matter is
not "observed"

directly but could be inferred indirectly via observed motions.

and historically it was the fact that the observation of
the motions of (parts of) galaxies don't correspond to the matter which
can be directly inferred from the luminous stuff observed which led to
the dark-matter idea.

Corect. But you have to be carefull to first include all low intensity
luminous matter and all invisible baryonic matter.
It is even possible inpriciple that there is enough baryonic matter
in galaxies to explain flat galaxy rotation curve and that no darkmatter
is required.

85% of all matter in the Universe is darkmatter.
I expect that the amount of darkmatter in galaxies is lower.
If that is the case than the amount of darkmatter outside
galaxies is even higher than 85%
This huge amount should be discussed because it influences
the galaxy motions and galaxy clusters.
  #7  
Old December 20th 13, 08:37 PM posted to sci.astro.research
Nicolaas Vroom
external usenet poster
 
Posts: 216
Default Cosmography of the local Universe

Op donderdag 19 december 2013 09:57:12 UTC+1 schreef Steve Willner:
In article ,

Nicolaas Vroom writes:
But they should demonstrate dark matter based on observations.


The video etc isn't meant to demonstrate dark matter,

They should include a discussion about darkmatter because 85%
of all matter is darkmatter

The matter inferred from galaxy motions should include both
vissible and darkmatter. If there is agreement then there is no
dark matter involved.


The last sentence should be:
If there is agreement between the distribution of observed galaxies
and the distribution of matter inferred from galaxy motions,
then there is no dark matter involved.

The issue is that both visible matter and darkmatter influence the
motion of galaxies. If visible matter agrees with the motions than
there is no darkmatter in the universe. This result should be
discussed in the document, because it is remarkable.

In fact you can go two paths:
1 Based on the observed_motions you can calculate the mass responsible for
these motions and compare this calculated mass with the observed_mass
2 Based on the observed_matter in the universe you can calculate the motions
and compare them with the observed_motions.
This is a very difficult exercise. I tried to do discuss this in
the newsgroup sci.physics.research.
(#1 is also not easy because the distribution of this mass has to be
calculated.
Ofcourse you can assume that the distribution of all mass is identical
as the distribution of visible matter, but that solution is too simple)

That second sentence seems to have an extra "no" in it, but the first
sentence is a misunderstanding. The video shows the _observed_
motions based on observations and with statistical corrections for
galaxies that cannot be observed because they are too faint or are in
the zone of avoidance.

That is correct but I think what you mean are calculated motions.
And IMO these calulations should include darkmatter.

Observed flows towards the Great
Attractor, for example, are larger than can be accounted for by
visible matter in that direction.

This demonstrates my point.
To explain this you need more baryonic or nonbaryonic matter (or both)

Nicolaas Vroom
http://users.pandora.be/nicvroom/
  #8  
Old February 2nd 14, 08:49 AM posted to sci.astro.research
Nicolaas Vroom
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Posts: 216
Default Cosmography of the local Universe

Op vrijdag 20 december 2013 20:37:41 UTC+1 schreef Nicolaas Vroom:
Op donderdag 19 december 2013 09:57:12 UTC+1 schreef Steve Willner:

Observed flows towards the Great
Attractor, for example, are larger than can be accounted for by
visible matter in that direction.

This demonstrates my point.
To explain this you need more baryonic or nonbaryonic matter (or both)


In order to investigate what other authors had to say specific about
nonbaryonic in our local universe I read the following documents:

1) Formation and rotation of disc galaxies with halos (1980)
http://articles.adsabs.harvard.edu/f...NRAS.193..189F
2) a revised model for the formation of disk galaxies:
Low spin and dark halo expansion. (2007)
http://iopscience.iop.org/0004-637X/...X_654_1_27.pdf
3) The Extragalactic Distance Database: all digital Hi profile catalog
http://iopscience.iop.org/1538-3881/...138_6_1938.pdf
4) Cosmic Flows surveys and CLUES simulations
http://arxiv.org/pdf/1205.4627.pdf
5) The mid-infrared Tully-Fisher Relation: calibration of the
SNIa scale and H0 http://arxiv.org/pdf/1208.3311.pdf
6) Anatomy of Ursa Majoris http://arxiv.org/pdf/1211.5975.pdf
7) http://arxiv.org/abs/1303.5328 by Igor Karachentsev,
8) http://arxiv.org/abs/1306.0091 Cosmography of the Local Universe

For a detailed evalution see the following document:
http://users.telenet.be/nicvroom/fri...20age.htm#Ref1

My conclusion is that the scientists who study the local universe and the
evolution of galaxies dark matter in the form of nonbaryonic matter
is not mentioned. Specific nowhere you can read that 85% of the matter
in any galaxy should be nonbaryonic. That does not mean that the issue
of dark matter related towards the evolution of galaxies is not discussed,
but this dark matter is always considered invisible baryonic matter in
the form of gas,

A different situation arises if you study WMAP date. Only in these studies
related to CMB radiation the concept of non-baryonic matter is considered.
Their conclusion is that 85% of all matter in the universe should be
nonbaryonic. This number is very high specific if you want to explain
flat galaxy rotation curves.

Nicolaas Vroom
  #9  
Old March 3rd 14, 10:33 PM posted to sci.astro.research
Nicolaas Vroom
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Posts: 216
Default Cosmography of the local Universe

Op zondag 2 februari 2014 08:49:41 UTC+1 schreef Nicolaas Vroom:
Op vrijdag 20 december 2013 20:37:41 UTC+1 schreef Nicolaas Vroom:
Op donderdag 19 december 2013 09:57:12 UTC+1 schreef Steve Willner:

Observed flows towards the Great
Attractor, for example, are larger than can be accounted for by
visible matter in that direction.

This demonstrates my point.
To explain this you need more baryonic or nonbaryonic matter (or both)


In order to investigate what other authors had to say specific about
nonbaryonic in our local universe I read the following documents:


8) http://arxiv.org/abs/1306.0091 Cosmography of the Local Universe

For a detailed evalution see the following document:
http://users.telenet.be/nicvroom/fri...20age.htm#Ref1


In Scientific American of March 2014 there is an article about the same
subject.
For a review select:
http://users.telenet.be/nicvroom/Sci...rch%202014.htm
Two more documents are interesting:
1) http://arxiv.org/abs/1307.6210 23 July 2013
2) http://arxiv.org/abs/1309.1159 4 Sept 2013

Specific the second one is interesting which claims that it is very
difficult to simulate the dwarf galaxies of the Milky way in the way
they actual are (aligned in a plane)
What makes such a simulation difficult is non-baryonic dark matter
in the halo of the Milky way galaxy.
Such a halo is required to solve the missing matter problem or better:
the flat galaxy rotation curve issue.
IMO this leaves only one solution possible:
to allow for more invisible baryonic matter in the disc.

Nicolaas Vroom.
 




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