New Evidence For Stellar-Mass Dark Matter Objects?

A interesting new development, or potential development, on the dark
matter front comes from a new paper by Mike Hawkins, which is in press
at MNRAS.

Hawkins' paper can be read at: http://arxiv.org/PS_cache/arxiv/pdf/...004.1824v1.pdf

SYNOPSIS: If quasar variability is intrinsic to the quasars, then one
would expect to see time dilation effects in distant versus nearby
quasars.

Supernovas manifest this time dilation. Therefore the quasars should
to - that is IF the variations in brightness occur at the quasar.

BUT HAWKINS REPORTS NO TIME DILATION IS SEEN IN NEARLY 900 QUASARS!

This is another enigma that may be resolved by stellar-mass dark
matter, as explained by Hawkins. If quasar variations are caused by
microlensing due to stellar-mass dark matter objects along the sight
lines between us and the quasars, then no time dilation would be
expected, since the microlensing-induced variations are relatively
"local". Hawkins comments that stellar-mass black holes are the most
likely candidate for the putative microlensing of quasars.

If this turns out to be the cause of quasar variability, it requires
that all of the dark matter is in the form of a huge population of
stellar-mass black holes. Think ARCADE-2 results, etc. Possible
conflict with MACHO results may mean the actual distribution of the
dark matter does not conform to our initial assumptions.

Hmmm, time for a new cosmological paradigm?

Stay tuned and keep an open mind.

RLO
www.amherst.edu/~rloldershaw

In article , "Robert L.
Oldershaw" writes:

A interesting new development, or potential development, on the dark
matter front comes from a new paper by Mike Hawkins, which is in press
at MNRAS.

Thanks for the hint.

Hawkins' paper can be read at: http://arxiv.org/PS_cache/arxiv/pdf/...004.1824v1.pdf

More comments after I have read it.

SYNOPSIS: If quasar variability is intrinsic to the quasars, then one
would expect to see time dilation effects in distant versus nearby
quasars.

Supernovas manifest this time dilation. Therefore the quasars should
to - that is IF the variations in brightness occur at the quasar.

BUT HAWKINS REPORTS NO TIME DILATION IS SEEN IN NEARLY 900 QUASARS!

The two cases are not comparable. There is reason to believe---and MUCH
work has gone into it---that supernovae nearby are pretty much the same
as distant supernovae. This is definitely not the case for quasars.
They are much more numerous at high redshift and thus obviously the
population evolves. Also, with a supernova one has a well defined time
scale for the event. This is not as straightforward, to say the least,
with quasars.

This is another enigma that may be resolved by stellar-mass dark
matter, as explained by Hawkins.

Except that it is ruled out for other reasons, as has been noted here
many times.

If quasar variations are caused by
microlensing due to stellar-mass dark matter objects along the sight
lines between us and the quasars, then no time dilation would be
expected, since the microlensing-induced variations are relatively
"local".

The extent to which this is true depends on the cosmological model. In
the currently favoured cosmological model, there is some dependence on
the redshift of the quasar.

Hawkins comments that stellar-mass black holes are the most
likely candidate for the putative microlensing of quasars.

Again, they are ruled out on other grounds.

On Tue, 20 Apr 10, "Robert L. Oldershaw" wrote:
IF the variations in brightness occur at the quasar.
BUT HAWKINS REPORTS NO TIME DILATION IS SEEN IN NEARLY 900 QUASARS!

A leading candidate for quasar variability is that we see them
"twinkle". That is, their angular size on our sky is smaller than the
"scatter size" of the Galactic ISM and possibly IGM, so that their
flight paths scintillate. Such scatter should be wavelength-dependent,
so can be researched accordingly. If confirmed as the mechanism, then
quasar twinkling would be unrelated to any quasar time dilation.

Eric

On 2010/04/20 08:53, Robert L. Oldershaw wrote:
... Hawkins comments that stellar-mass black holes are the most
likely candidate for the putative microlensing of quasars.

What rules out the black holes being larger? - Even small galaxies are
hard to observe.

Hans

On Wed, 21 Apr 10 07:09:46 GMT, Hans Aberg wrote:
On 2010/04/20 08:53, Robert L. Oldershaw wrote:
... Hawkins comments that stellar-mass black holes are the most
likely candidate for the putative microlensing of quasars.

What rules out the black holes being larger? - Even small galaxies are
hard to observe.

Presumably Hawkins means that the stellar-mass black holes are in the
quasars' host galaxies. For quasars to be microlensed by galaxy-mass
black holes along the line of sight, would require an impossible
population of such galaxy-mass black holes.

Eric Flesch

In article , "Robert L.
Oldershaw" writes:

A interesting new development, or potential development, on the dark
matter front comes from a new paper by Mike Hawkins, which is in press
at MNRAS.

Based on the references and so on, it seems to be a new paper; strange
that just above the abstract it looks like it comes from 1988. Maybe
some relativistic time dilation? :-)

SYNOPSIS: If quasar variability is intrinsic to the quasars, then one
would expect to see time dilation effects in distant versus nearby
quasars.

BUT HAWKINS REPORTS NO TIME DILATION IS SEEN IN NEARLY 900 QUASARS!

This is another enigma that may be resolved by stellar-mass dark
matter, as explained by Hawkins. If quasar variations are caused by
microlensing due to stellar-mass dark matter objects along the sight
lines between us and the quasars, then no time dilation would be
expected, since the microlensing-induced variations are relatively
"local".

Let me quote from the paper (section 5.2):

...there are two main difficulties with this approach [i.e. that the
variability is due to microlensing]. Firstly, although the observed
variations agree well with model predictions from microlensing
simulations, it is difficult to rule out the possibility of intrinsic
variations. Secondly, it appears that the rate of detection of
compact bodies in the Galactic halo by the MACHO project (Alcock et
al. 1997) is incompatible with the population required to produce the
observed variation in the quasar light curves.

In other words, if there were enough of these objects around to
explain the quasar variability, the MACHO project would have seen
them. It seems that even Hawkins is not too enthusiastic about this
possibility. This is good; he is an observer, not a theoretician.
Observers should publish their observations. (Also, as I have
pointed out here, no microlensing scenario can reproduce the observed
distribution of amplifications.)

Hawkins comments that stellar-mass black holes are the most
likely candidate for the putative microlensing of quasars.

Actually (quoting from the same section) he says "stellar mass
bodies".

As a side note, Hawkins also says that the most probable redshift for
the lenses in a microlensing scenario is 0.5. First, this is confusing:
what he means is that the lenses at that redshift have the biggest
effect (i.e. there is no concentration of lenses at that redshift, which
incidentally would imply an inhomogeneous universe or strong evolution
in the population). This is explained in the reference he cites.
However, this result (and the fact that this "most effective redshift"
depends very weakly on the redshift of the source) is true in the
Einstein-de Sitter universe. In the currently favoured cosmological
model, the "most effective redshift" is somewhat larger and depends
somewhat more strongly on the source redshift. (See Fig. 2 in the
Turner, Ostriker and Gott paper cited by Hawkins, where one sees the
difference between Omega=1 and Omega=0 for 0 cosmological constant.
With a cosmological constant, the effect is more pronounced. See Figs.
5 and 6 of Fukugita, Futamase, Kasai and Turner (Apj 393, 1, 3--21 (1
July 1992).)

Hmmm, time for a new cosmological paradigm?

Note that paradigm shifts in the manner of Thomas Kuhn rarely happen
in real science. Even the "Copernican revolution" was not one;
Ptolemy's ideas were the favoured ones only because the church burned
people who thought otherwise. Max Born did much investigation of how
progress is actually made in science, and concludes that the paradigm
shift happens rarely, if at all.

(Also note that if Kuhn's statement is not scientific, then it probably
doesn't apply to science. On the other hand, if it is scientific, then,
by his own criteria, it is merely a current paradigm, and will be
replaced by a new paradigm, so again it probably doesn't apply to
science.)

Robert L. Oldershaw wrote:

[...]

Hawkins' paper can be read at:

http://arxiv.org/PS_cache/arxiv/pdf/...004.1824v1.pdf

[...]

BUT HAWKINS REPORTS NO TIME DILATION IS SEEN IN
NEARLY 900 QUASARS!

If you have to scream to be heard, quite possibly
what you are saying is incomprehensible at any
volume.

That also oversimplifies the matter. A group of 810
quasars with a 37 year long set of observations were
analyzed against a group of 68 quasars with an 8
year long set of observations taken at more frequent
intervals, using Fourier analysis.

Hawkins comments that stellar-mass black holes are
the most likely candidate for the putative
microlensing of quasars.

What I found him to say was this:

If the variations are due to microlensing then
the conclusions of the MACHO project would have
to be modified, presumably by a reassessment of
the shape of the Galactic halo, and the expected
dark matter content.

If the effects of time dilation are offset by an
increase of timescale of variation with
cosmological time, then a mechanism must be
found which does not alter the shape of the SED,
or involve a correlation of black hole mass with
luminosity.

That doesn't seem to match what you say he wrote.
Did I miss it somewhere?

If this turns out to be the cause of quasar
variability, it requires that all of the dark
matter is in the form of a huge population of
stellar-mass black holes.

How sad for you that every time you are told that
this possibility has been robustly eliminated by
observations, you come back to it like a moth
fatally attracted to a flame.

You perhaps missed the cited paper's section 5.2,
where this possibility is excluded by existing
observations.

Hmmm, time for a new cosmological paradigm?

I've noticed a few things about cosmology, as an
amateur observer.

- Many researchers spend their entire professional
lives moving the field forward, some inchwise,
somein huge steps, and yet fail to come to closure
on their personal goals. Famous examples are
Einstein, Hoyle, Hubble, and (so far) Hawkings.

- Paradigm shifts in cosmology seem to occur at
intervals perhaps longer than the professional
career of an average researcher, that is, at
intervals of several tens of years.

I've noticed a couple of things about your postings,
versus your citations, too.

- Every week to month, you latch onto some one new
finding by some one researcher, notice that it has
changed cosmology in some way [as any new finding
in any field of science must necessarily change
that science, if in no other way, then by adding
to its base of observations], and declare that it
is "time for a new cosmological paradigm".

This would be, in particular, one presumes,
entirely by coincidence, the one previously and
for years espoused by you, but already thoroughly
debunked by [lack of necessarily corresponding]
observations.

- Yet none of those same researchers, apparently
experts in your estimation, since you cite them in
your support, find themselves screaming in the
article abstract "TIME FOR A NEW COSMOLOGICAL
PARADIGM".

Instead, as scientists do, they present their
conclusions calmly, tentatively, as possibly
incomplete or missing some unobvious alternative
explanation, as subject to review and correction
by others, and as modifying, rather than toppling,
the field of science in which they work.

That is the case in the present citation, where
the author demonstrates that cosmology needs a
changed brushstroke somewhere, not demolition and
reconstruction from the rubble.

[At the end of his article, he's accomplished
confirming that expansion must be true, since
it is so robustly supported by supernovae
analysis, and yet that the time dilation this
expansion would seem to imply for QUASARS seems
not to be observed. Mostly, this seems to me to
mean that we don't understand QUASARS very
well, something unsurprising since it has been
true all my adult life, not that we don't have
a robust working cosmological science
framework.]

Could you explain to the group if you detect any
discrepency here, between cosmology paradigm shifts
occurring on a time scale of several tens of years,
and you calling for them on a time scale of a few
tens of days, and if so, where the cause might lie?

xanthian.

On Apr 30, 5:12*am, Kent Paul Dolan wrote:

That doesn't seem to match what you say he wrote.
Did I miss it somewhere?

I also used a NewScientist interview as a source. In this interview,
Mike Hawkins could afford to be a bit more relaxed, less on the
defensive from barking dogs, and speak his mind more freely. Spare me
your comments on the scientific fastidiousness of NewScientist; I
already have considered ALL aspects of this issue.

* If this turns out to be the cause of quasar
* variability, it requires that all of the dark
* matter is in the form of a huge population of
* stellar-mass black holes.

How sad for you that every time you are told that
this possibility has been robustly eliminated by
observations, you come back to it like a moth
fatally attracted to a flame.

I do not know how many times we are going to have to go round this
circle. Many times in the history of science something has been
"robustly eliminated" and then found to be correct because the
falsification involved flawed assumptions.

I think there is credible evidence for stellar mass black holes and so
do other scientists. You ignore this positive evidence because it
conflicts with your faith in the "falsification" and the existing
paradigm.

I think we should let nature show us what the dark matter is, and not
try to tell nature what the dark matter can be and what it cannot be.

Let's agree to differ. When new evidence appears to support your
beliefs, feel free to call attention to it. Please afford me the same
right of free speech.


I've noticed a few things about cosmology, as an
amateur observer.


From 1905 until 1919 and from about 1925 until the present Einstein
was regarded as a brilliant genius or an embarrassment to "sound
science". It all depended on who you talked to. Academic scholars of
his time treated Faraday as an amateur and a "crackpot".

Do you get the picture? If you try to advocate for a change of
paradigms, many people are going to go out of their way to try to
silence you.

[Mod. note: I think once we start comparing ourselves to Einstein --
or even Bozo the Clown -- we are out of the remit of this newsgroup.
Further posts in this thread will be rejected unless they have clear
astrophysical content -- mjh]



Could you explain to the group if you detect any
discrepency here, between cosmology paradigm shifts
occurring on a time scale of several tens of years,
and you calling for them on a time scale of a few
tens of days, and if so, where the cause might lie?

The paradigm shift I am talking about: from the standard models of
cosmology and particle physics to Discrete Scale Relativity is a once
in 100-400 years type of paradigm shift. Not once a month, not once a
year, not once a decade. Once every 100-400 years, on average. Sorry
if that offends your sensibilities or beliefs.


Hope this helps,
RLO
www.amherst.edu/~rloldershaw

In article , "Robert L.
Oldershaw" writes:

I also used a NewScientist interview as a source. In this interview,
Mike Hawkins could afford to be a bit more relaxed, less on the
defensive from barking dogs, and speak his mind more freely. Spare me
your comments on the scientific fastidiousness of NewScientist; I
already have considered ALL aspects of this issue.

Consider that while no-one doubts Hawkins's abilities as an observer,
his wider-reaching theoretical speculations have mostly been debunked.

I do not know how many times we are going to have to go round this
circle. Many times in the history of science something has been
"robustly eliminated" and then found to be correct because the
falsification involved flawed assumptions.

Perhaps, but that doesn't imply that it must also be the case for your
hypothesis.

I think there is credible evidence for stellar mass black holes and so
do other scientists.

It is generally accepted that a population of stellar-mass black holes
large enough to make up a significant fraction of the dark matter is
ruled out by observations.

In article , "Robert L.
Oldershaw" writes:

Is keeping one's mind open to new or unexpected hypotheses such a bad
thing?

No.

If you look carefully at the history of science, and
especially astrophysics, I think you will find strong motivation for
us to be a little less sure of ourselves, and much less inclined to
rush to judgement.

However, I do not consider a geocentric theory of the solar system to be
valid, though there are people who still believe it. Neither do I think
that we live on the INSIDE of a sphere, a hollow Earth, although there
are people who believe it (including a descendant of Kepler). There is
a middle ground between dogma on the one side and "anything goes" on the
other.

In the debates you mentioned, EVIDENCE provided the answer. In neither
case did some grand theory predict one or the other outcome.