What Does XMM-Newton Reveal About Dark Energy in the X-ray Universe?

[Vast]

Originally posted by marcus
the trigger is the thinning out of the average density of matter in the universe

This seems to say that once conventional matter becomes sparse, accelerated expansion takes over. How then can anything trigger a deceleration and contraction after such thinning out has taken effect?

This would eliminate a contraction phase, which Turok and Steinhardt predict in their model of a Cyclic Universe. (Correct me if I’m wrong) After reading their latest paper it seems they compare a prior contraction, (preceding the BB) to the eventual re-collapse of this Universe, which so far shows no sign of ever doing so.

Beyond Inflation: A Cyclic Universe Scenario

 

[wolram]

VAST, i hope MARCUS will not mind me quoting his post i dont
want to inflate his ego to much but his explanations are
clear and understandable
-------------------------------------------------------------------
.

Now we assume a cosmological constant of 0.6 joule per cubic km. That is what they estimate the dark energy density to be. So that is some energy that is intrinsic to space itself, not attached to any substance floating around in space. It has an expansive effect.

But back in the time of z = 10 (when Pello's galaxy emitted the light) the acceleration effect of the Lamdda 0.6 joules was overshadowed by the deceleration effect of the matter 2.2 or 2.4 joules.
So there was net deceleration.

Since that time space has expanded 11-fold
so the density of matter has gotten less by 11-fold
and is now down to 0.2 (or more precisely 0.22) joules

But while the matter density is being thinned out by expansion, the Lamda stays constant and is forever and always 0.6.

So now the Lamda dominates the matter and its acceleration effect prevails.

So the trigger is that the average density of matter masks the dark energy until the matter has thinned out enough.

 

[Vast]

Thanks wolram. I have to thank both you and marcus because this thread has been really insightful!

If I understand this correctly, the trigger is also referred to as a cosmic coincidence, associated with a certain phase of the Universe.
If theory and observational measurements confirm accelerated expansion, it seems the acceleration is just going to continue getting faster and faster.

So far what this suggests for the long run is an alternative to an eventual re-collapse. If a cosmological constant is to remain at 0.6 joule, then acceleration should always prevail

 

[wolram]

by VAST.

Thanks wolram. I have to thank both you and marcus because this thread has been really insightful!
--------------------------------------------------------------------
VAST you can't imagine how happy i am that you asked a question
on this thread, i would also like to thank MARCUS.

 

[ranyart]

Originally posted by Vast
This seems to say that once conventional matter becomes sparse, accelerated expansion takes over. How then can anything trigger a deceleration and contraction after such thinning out has taken effect?

This would eliminate a contraction phase, which Turok and Steinhardt predict in their model of a Cyclic Universe. (Correct me if I’m wrong) After reading their latest paper it seems they compare a prior contraction, (preceding the BB) to the eventual re-collapse of this Universe, which so far shows no sign of ever doing so.

Beyond Inflation: A Cyclic Universe Scenario

Actually this scenario was predicted sometime ago, but contary to your thoughts here:This would eliminate a contraction phase,which Turok and Steinhardt predict in their model of a Cyclic Universe.

 

[wolram]

ranyart.

yes i have read the cyclic universe theories, the most
prominent feature is the avoidance of the singularity
and a new way of accounting for the apparent over abundance
of energy.

 

[wolram]

http://www.nature.com/nsu/030609/030609-7.html
Alternative proposed to dark energy's cosmic doomsday.
---------------------------------------------------------------

The destruction begins, say Robert Caldwell of Dartmouth College in New Hampshire, USA, and his coworkers2, about a billion years before it ultimately ends in a Big Rip. First, gravity loses its grip at cosmic scales, allowing clusters of galaxies to drift apart.

Sixty million years before doomsday, our own galaxy, the Milky Way, fractures as stars slip from each other's grasp. A few months before the end, planetary systems like the solar system will be dismembered, and 30 minutes before the Big Rip, the planets and stars themselves disintegrate.

In the split-second before the end, atoms and molecules are torn apart, then the particles that constitute them. Finally, space itself flies open.

All of this is driven, the argument goes, by something known as phantom energy, which fills all of space. The density of phantom energy increases with time, like a bomb that grows ever bigger.

 

[marcus]

Originally posted by wolram
http://www.nature.com/nsu/030609/030609-7.html
...All of this is driven, the argument goes, by something known as phantom energy, which fills all of space. The density of phantom energy increases with time, like a bomb that grows ever bigger.

this is different from the usual picture
what people ordinarily assume for dark energy is
a constant energy density
(often called "cosmological constant" or Lambda)

it does not increase with time
and it does not eventually rip things apart that are gravitationally bound entities (like galaxy or solar system or planet)

nobody knows that the Lambda is actually constant----the evidence has been mounting that it is constant, some reported here at PF, but
nothing conclusive

since no one can say that it is constant, people are free to imagine other scenarios like "phantom energy" which increases over time and has dramatic effects.

I think it's fair to say there is LESS reason to take phantom energy seriously than there is reason to assume the ordinary constant dark energy but that's not to say people should be discouraged from constructing these alternative scenarios

 

[Vast]

Originally posted by ranyart
Any later developing lifeforms would be looking back at this moment as the dawn of Universe, no contraction needed, its a perceptional 'Bounce'!

The usual cosmic model is that of a universe beginning in a cosmic singularity, therefore it seems reasonable to assume a multi universe scenario each beginning in the same manner.

But I think this is off topic to dark energy.

 

[wolram]

NEREID, mentioned the SNOWMASS BOOK, this is new to me its at
http://supernova.lbl.gov/~evlinder/sci.html.
i think its interesting and informative.
thanks NEREID.

 

[hellfire]

some questions

May be I am asking a little bit too late here, but here are some basic questions for my understanding of the observations done by A. Blanchard:

1. I read that this is an X-ray observation of the intergalactic medium in far clusters. In the press release it is written that in old clusters ‘there are more X-rays than today’. What does this mean? Does this mean that old clusters ‘in past’ were more distributed throughout space than today and that they went a gravitational collapse since then (so that some of them grouped into a single cluster and therefore the X-ray emission is received from a narrower region)?

2. It is also argued in the press release, that, if dark energy were existent, it would impede the gravitational collapse of clusters leaving them unchanged from ‘the past’ up to now. But, what is meant with ‘past’? Usually, it is postulated that clusters formed due to gravitational collapse (bottom-up model). Therefore the dark energy (if existent) must be dominating or influencing this process in a later point of time after the actual collapse (otherwise they would not be formed). When is this epoch to be located in time?

3. What is the relation between X-ray intensity and mass? I remember have read somewhere that additionally to mass estimations done according to observations of dynamics and application of the virial theorem, there is the possibiltiy of mass estimations of clusters according to X-ray observations.

Thanks. Regards.

 

[meteor]

I can't opine about this paper because I haven't read it still
"A model of holografic dark energy"
http://arxiv.org/abs/hep-th/0403127
But it seemed to me that the denomination "holographic dark energy" is at least curious, no?

 

[wolram]

http://arxiv.org/PS_cache/astro-ph/pdf/0204/0204500.pdf


by HELLFIRE.
1. I read that this is an X-ray observation of the intergalactic medium in far clusters. In the press release it is written that in old clusters ‘there are more X-rays than today’. What does this mean? Does this mean that old clusters ‘in past’ were more distributed throughout space than today and that they went a gravitational collapse since then (so that some of them grouped into a single cluster and therefore the X-ray emission is received from a narrower region)?
---------------------------------------------------------------------
the above url is over 170 pages long and is comprehensive.
i haven't been able to confirm that old clusters are more
x ray active, maybe NEREID or other PF members can answer
your questions, in the meantime i will read the posted article.

 

[wolram]

the subject of X ray emissions from early-type galaxies seems
to be very wide, from the posted url----------
studies of large sample of early type galaxies are suggestive that
the X-ray structure of these systems is mostly determined by
the gravitational potential well produced by large amounts of
dark matter rather than by thermal mechanisms.
---------------------------------------------------------------------
cD galaxies are galaxies with a nucleus of a very luminous
elliptical embedded in an extended amorphous halo of low surface
brightness, "this galaxy type may have been formed by collision".
---------------------------------------------------------------------
some early type galaxies that have hot (1KeV) interstellar
medium trapped by the galaxy potential well whose emission is
due to thermal processes.
---------------------------------------------------------------------
i haven't read all the article yet but i think you will find it
very infomative.

 

[wolram]

posted by METEOR.

But it seemed to me that the denomination "holographic dark energy" is at least curious, no?
----------------------------------------------------------------
yes it is, if it wasn't for the Hubble scale problem this theory
might be better than others.

 

[hellfire]

Thanks wolram, it looks a bit intimidating... but I will try to take a look. Anyway, it would be great if someone could answer shortly my questions.

 

[marcus]

Originally posted by hellfire
Thanks wolram, it looks a bit intimidating... but I will try to take a look. Anyway, it would be great if someone could answer shortly my questions.

hello hellfire, I remember enjoying your discussions before and I would like to try later today to answer, if no one gets to it earlier. I may not be able to because am supposed to be away for part of the day.

I think we already found the relevant technical paper by Blanchard
and posted, discussing this business of more dark matter and less (or zero) dark energy. IIRC he needs to assume a lower Hubble parameter to make all the numbers add up.

It will take me a while to reconstruct his argument. Maybe you already have and can explain it.

 

[marcus]

hellfire, it turns out there was some discussion in this very thread!
what I was remembering was on the first page of this thread. this link may be the one to the technical article that corresponds to the
wide-audience account you mentioned.

Originally posted by marcus
Alain Blanchard must be the most important dissident to the
"concordance" cosmology picture. the leader of the opposition.

his most recent preprint in arxiv is
http://arxiv.org/astro-ph/0402297

I'm not sure but I think
the article you pointed to in Astronomy magazine
by Amanda Jefter (dated 23 December 2003) refers
to earlier articles of Blanchard

mainly this one
http://arxiv.org/astro-ph/0304237

but also this 3-pager
http://arxiv.org/astro-ph/0311626

Nereid may have responded to the gist of what
is in these articles in another thread. I forget which.
Or I may have. I don't think Blanchard's case is strong
enough yet to start bringing more people over to his side
but he certainly bears watching. If he continues to
assemble evidence of much more dark matter then
he could start a shift of opinion.

I think the argument here is between dark matter and dark energy.

the concordance model says that familiar types of matter total around 4 or 5 percent of the average density in space

but that leaves 96 percent to account for

the "concordance" estimate is that it is split 73 d.energy plus
23 d.matter

Blanchard's main message, if I understand it, is to give much more importance to dark matter and less to dark energy.

he may also favor a lower value than 71 for the Hubble parameter
and consequently a lower overall density (so that the observed amount of ordinary matter would play a larger role)
...

I looked back at an earlier thread and found another blanchard link
http://arxiv.org/abs/astro-ph/0311381

 

[marcus]

hello again,
I'm copying your post so we have your questions in front of us. If we are lucky we will be able to put your questions together with the links to Blanchard's papers and recall how his arguments go, and respond to your questions. Or you will beat me to it and figure out
Blanchard's reasoning yourself.

Originally posted by hellfire
May be I am asking a little bit too late here, but here are some basic questions for my understanding of the observations done by A. Blanchard:

1. I read that this is an X-ray observation of the intergalactic medium in far clusters. In the press release it is written that in old clusters ‘there are more X-rays than today’. What does this mean? Does this mean that old clusters ‘in past’ were more distributed throughout space than today and that they went a gravitational collapse since then (so that some of them grouped into a single cluster and therefore the X-ray emission is received from a narrower region)?

2. It is also argued in the press release, that, if dark energy were existent, it would impede the gravitational collapse of clusters leaving them unchanged from ‘the past’ up to now. But, what is meant with ‘past’? Usually, it is postulated that clusters formed due to gravitational collapse (bottom-up model). Therefore the dark energy (if existent) must be dominating or influencing this process in a later point of time after the actual collapse (otherwise they would not be formed). When is this epoch to be located in time?

3. What is the relation between X-ray intensity and mass? I remember have read somewhere that additionally to mass estimations done according to observations of dynamics and application of the virial theorem, there is the possibiltiy of mass estimations of clusters according to X-ray observations.

Thanks. Regards.

 

[wolram]

http://www.astro.ucla.edu/~wright/cosmolog.htm

2 Feb 2004 - A group led by Prof. Tom Shanks of the University of Durham, UK, has suggested that the Sunyaev-Zeldovich effect may have significantly affected the WMAP results on the anisotropy of the cosmic microwave background. However, the S-Z effect goes through zero at 220 GHz and the ARCHEOPS balloon-borne CMB experiment which observes at 143 and 217 GHz sees the same map and angular power spectrum as WMAP. The fact that ARCHEOPS agrees with WMAP within -4.4+/-2.8% in the amplitude of the first acoustic peak means that the S-Z effect has very little influence on the WMAP results. So this was another scientific theory that, like the dodecahedral Universe, was already disproven by the time the authors sent out their press release.
-----------------------------------------------------------------------
the S-Z effect has been used in many arguments in cosmology
NWs view is that it is immaterial regarding WMAP data.
but others are taking advantage of this effect to define
the parameters of galaxies.

 

[wolram]

http://www.sciencedaily.com/releases/2002/04/020422073037.htm



By comparing the X-ray emission and the Sunyaev-Zeldovich effect, Mohr can study even faint, high-redshift galaxy clusters that are currently inaccessible by other means. Such measurements, correlating galaxy cluster redshift distribution, structure and spatial distribution, should determine the equation of state of dark energy and, therefore, help define the essence of dark energy.

 

[wolram]

. What is the relation between X-ray intensity and mass? I remember have read somewhere that additionally to mass estimations done according to observations of dynamics and application of the virial theorem, there is the possibiltiy of mass estimations of clusters according to X-ray observations.
---------------------------------------------------------------------
http://www.astro.su.se/~ostlin/ColMag/Source/colMag_clusters.html

The image here shows a view of the core of the Virgo cluster in the X-ray waveband and illustrates the structure of the hot, gravitationally-bound gas in the cluster's potential well. This potential well is sufficiently deep that the gas between the galaxies within the cluster is compressed and heated to high enough temperature that emits radiation at X-ray wavelengths. Images of this X-ray radiation illustrate the very extended potential well of the cluster, which contains two major peaks, associated with sub-groups of galaxies within the cluster. Nevertheless, the X-ray image still appears much smoother than the distribution of the individual galaxies. Moreover, the temperature and the distribution of the X-ray gas can be used to estimate the mass of the cluster (assuming that the hot X-ray gas behaves as an ideal gas) and in all cases this has been found to significantly exceed the mass contained within the galaxies. These observations are one of the strongest pieces of evidence for dark matter on large scales in the Universe. Observing at X-ray wavelengths requires the use satellites to get above the absorption from the Earth's atmosphere, which is opaque in the X-ray band.

 

[wolram]

2. It is also argued in the press release, that, if dark energy were existent, it would impede the gravitational collapse of clusters leaving them unchanged from ‘the past’ up to now. But, what is meant with ‘past’? Usually, it is postulated that clusters formed due to gravitational collapse (bottom-up model). Therefore the dark energy (if existent) must be dominating or influencing this process in a later point of time after the actual collapse (otherwise they would not be formed). When is this epoch to be located in time?
--------------------------------------------------------------------
according to first paper on this thread, 5 billion YRS ago.

 

[wolram]

after reading all these papers the main stream view seems
to hold true, we used to have a nice quiet universe until
AE came along and spoilt it, now we have a suicidal one full
of DARK ENERGY that is pushing us to oblivion, it seems that
everything in nature gets recycled except nature itself,
life after the BIG RIP seems implausible without some kind of
divine intervention, so on a cosmological time scale its
BIG BANG count to---------------- its all over by by.
it maybe philosophical but i canot think that our universe
is a use once and throw away item, I'm sure that main stream
science will be found incorrect, and that universes dont
die they just get recycled.

 

[hellfire]

Excellent, thanks again wolram for the references and also marcus for your efforts. After reading again the article (I think I misinterpreted something) and the references I consider all my questions answered:

Regarding the epoch of start of domination of the cosmological constant (5 billion years ago), I have to apologize since I did not read the article referred in the first post of this thread.

The third question (x-ray / mass relation) seams to be clear with:

This potential well is sufficiently deep that the gas between the galaxies within the cluster is compressed and heated to high enough temperature that emits radiation at X-ray wavelengths.

And this fits with the claim of Blanchard, that they found fewer x-rays than today: potential wells are postulated to be deeper today, which is an argument against the cosmological constant.

Regards.

 

[hellfire]

in the press release in the second link of the thread:

http://www.esa.int/sci_mediacentre/...html?release=54

it is in fact written that

They seem to give out more X-rays than today.

According to the quote in the previous post, this would imply that potential wells were more deep in the past, which fits with the cosmological constant hypothesis and contradicts Blanchards own thesis.

Any help?

Regards.

 

[wolram]

HELLFIRE.

may i refer you to NED Wrights website ref (Hubble parameter)
http://www.bright.net/~mrf/App9.html
blanchard is arguing that more DARK MATTER exists in the
universe than others theories, which could require an
adjustment to the H-P=71, as the H-P has been refined over
the years it now seems almost unshakable, the BIG problem
with cosmology seems to be that numbers can be manipulated
to fit a pet theory, i guess we will have to wait for the
data from new satellite missions to see what amount of
dark matter, dark energy is out there.
i was hopping that MARCUS or NEREID would jump in as they
are easier to understand and much better qualified than me.

 

[wolram]

HELLFIRE.
i have found this link in ref to to your question, have a
look ,i have not read it all yet so maybe you can tell me
if it helps.
http://www-xray.ast.cam.ac.uk/~jss/research/mnr_5510.pdf

 

[marcus]

Originally posted by wolram
... would jump in as they
are easier to understand and much better qualified than me.

the more explaining you do on PF the easier to understand
you get

6 months ago you only asked one-line questions
and the more questions you asked the better they got
now you elucidate and the more you
practice the better it gets
(hellfire and Nereid may have noticed, why should I jump in?)

today is Greg B's 21 birthday
what shall we say to him on this occasion
except that we see that the PF he has built
seems now and then to be good for something
beyond simple recreation

 

[wolram]

well to start i think GREG Bs built a world leading science
forum that everyone should be proud of, but MARCUS i value
your contributions as you know i am a minnow in this sea
of whales, i am stuck on the variance of x-ray luminosity
in clusters over time, intuitively i would say that it would
decrease, but the clusters may be evolving gravitationally
or could be acquiring mass, the last post in this thread is
the closest i have come to finding an answer.