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New A&A Paper On Astrophysical Dark Matter



 
 
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  #1  
Old March 7th 15, 09:48 AM posted to sci.astro.research
Robert L. Oldershaw
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Default New A&A Paper On Astrophysical Dark Matter

Title: A new look at microlensing limits on dark matter in the Galactic halo

Author: M.R.S. Hawkins

Journal: Astronomy and Astrophysics, vol. 575, pg. 107, 2015

ArXiv.org: so far not posted

Relevant quotation from abstract: "The main result of this paper is
that it is easy to find low mass halo models consistent with the
observed Galactic rotation curve, which also imply an optical depth to
microlensing similar to that found by the MACHO collaboration. This
means that all-MACHO halos cannot be ruled out on the basis of their
observations... Limits placed on the MACHO content of the Galactic
halo from microlensing surveys in the Magellenic Clouds are
inconsistent and model dependent, and do not provide a secure basis
for rejecting an all-MACHO halo.

[Mod. note: reformatted -- mjh]
  #2  
Old March 8th 15, 09:35 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Posts: 273
Default New A&A Paper On Astrophysical Dark Matter

In article , "Robert L.
Oldershaw" writes:

Title: A new look at microlensing limits on dark matter in the Galactic halo

Author: M.R.S. Hawkins

Journal: Astronomy and Astrophysics, vol. 575, pg. 107, 2015

ArXiv.org: so far not posted

Relevant quotation from abstract: "The main result of this paper is
that it is easy to find low mass halo models consistent with the
observed Galactic rotation curve, which also imply an optical depth to
microlensing similar to that found by the MACHO collaboration. This
means that all-MACHO halos cannot be ruled out on the basis of their
observations... Limits placed on the MACHO content of the Galactic
halo from microlensing surveys in the Magellenic Clouds are
inconsistent and model dependent, and do not provide a secure basis
for rejecting an all-MACHO halo.


Suppose some person has a random-number generator, generates 1000
numbers, and show that they are compatible with a uniform-probability
distribution. If that's what he needs for his work, fine. However,
someone else needs the numbers one at a time, and notices that
sequential numbers (uniform probability between 0 and 1) are never more
than 0.2 apart, and thus for his purpose not random at all. Then the
first person says: I did the K-S test, and have proved that the numbers
are random, so they are.

Hawkins is like the first person. He made a claim which made some
testable predictions and they were confirmed. Then others pointed out
that his theory makes OTHER predictions which HAVE BEEN falsified. His
problem is that he ignores these. He doesn't even disagree with them,
he ignores them. Every few years, he trots out the same arguments and
doesn't seem to know, or care, that even ONE falsified prediction dooms
the theory (whether this prediction was noticed by himself or someone
else is irrelevant), as his "proof" are his old, confirmed predictions.
He cherry-picks data (emphasizing new data if it makes his ideas look
good, ignoring it if it doesn't), pushes the error bars to the limit to
make something agree with him, and, again, ignores criticism in the
literature. Even if he doesn't agree with it, common courtesy and good
science demand that one at least address it.

I think it is fair to say that practically no-one believes Hawkins's
claim that such compact objects make up a substantial fraction of dark
matter. At one time, it was a viable idea, like massive neutrinos. But
not anymore.
  #3  
Old March 9th 15, 01:47 PM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default New A&A Paper On Astrophysical Dark Matter

On Sunday, March 8, 2015 at 4:35:22 AM UTC-4, Phillip Helbig (undress to reply) wrote:
I think it is fair to say that practically no-one believes Hawkins's
claim that such compact objects make up a substantial fraction of dark
matter. At one time, it was a viable idea, like massive neutrinos. But
not anymore.


Apparently the referee(s) for this paper and the editor(s) at
Astronomy and Astrophysics see things quite differently. They must
have determined that Hawkins has a valid scientific argument.

[Mod. note: reformatted -- mjh]
  #4  
Old March 10th 15, 10:03 AM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default New A&A Paper On Astrophysical Dark Matter

On Monday, March 9, 2015 at 8:48:02 AM UTC-4, Robert L. Oldershaw wrote:

Apparently the referee(s) for this paper and the editor(s) at
Astronomy and Astrophysics see things quite differently. They must
have determined that Hawkins has a valid scientific argument.


Hawkins' paper is now posted to arXiv.org
http://arxiv.org/abs/1503.01935

The paper is well-written and has plenty of empirical support for its
arguments.

It is not strident, nor does it insist that the MACHO answer to the
dark matter puzzle is the only possible answer.

It presents the case for MACHO dark matter, and asks why there is so
much resistance to a potential answer that has more empirical support
than any other dark matter candidate.

The discussion and conclusions sections are thought-provoking.
  #5  
Old March 10th 15, 10:05 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Posts: 273
Default New A&A Paper On Astrophysical Dark Matter

In article , "Robert L.
Oldershaw" writes:

On Sunday, March 8, 2015 at 4:35:22 AM UTC-4, Phillip Helbig (undress to reply) wrote:
I think it is fair to say that practically no-one believes Hawkins's
claim that such compact objects make up a substantial fraction of dark
matter. At one time, it was a viable idea, like massive neutrinos. But
not anymore.


Apparently the referee(s) for this paper and the editor(s) at
Astronomy and Astrophysics see things quite differently. They must
have determined that Hawkins has a valid scientific argument.

[Mod. note: reformatted -- mjh]


Scientific literature is discussion. Editors and referees are there to
guarantee a minimum of quality, but not to decide what is correct and
what is not (except in the case of obviously crackpot papers, and
sometimes not even then). Sort of like a moderated newsgroup, but a bit
more strict. :-) Discussion can exist only if there are different
points of view. Go back a few years and you will find many papers
claiming that the Hubble constant was 50 or less. That doesn't mean
that the editor and referees believed that this must be completely
correct.

Otherwise, you don't abide by the scheme "refereed journal paper is
proof that the argument is correct". Anyone interested in this needs to
take ALL work in this field into account, not just touting those papers
which support a preconceived idea and ignoring those which don't.

Certainly no-one can claim that Hawkins has not had the opportunity to
plead his case. Also, even if it turns out that his claims about the
Milky-Way halo are correct, there are still arguments against his claim
that most of the dark matter in the universe is in the form of compact
objects with Jupiter-to-solar masses.
  #6  
Old March 10th 15, 07:08 PM posted to sci.astro.research
Robert L. Oldershaw
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Posts: 617
Default New A&A Paper On Astrophysical Dark Matter

On Tuesday, March 10, 2015 at 5:05:35 AM UTC-4, Phillip Helbig (undress to reply) wrote:

Certainly no-one can claim that Hawkins has not had the opportunity to
plead his case. Also, even if it turns out that his claims about the
Milky-Way halo are correct, there are still arguments against his claim
that most of the dark matter in the universe is in the form of compact
objects with Jupiter-to-solar masses.


You forgot to mention that there are also other arguments FOR "his
claim that most of the dark matter in the universe is in the form of
compact objects with Jupiter-to-solar masses".

What we need to get a definitive answer to the dark matter problem are
not beliefs based on prior assumptions and tentative empirical
findings. What we need are new observations that are more diagnostic
and less easily hand-waved away than past observations. Given the
promise of forthcoming technical advances like SKA and future
microlensing efforts, there is hope that strong empirical guidance
will not be too long in coming.

Until then it would behoove us not to marry any hypothetical class of
dark matter candidates, nor to spurn others simply because they
conflict with our expectations. It's ok to root for favorites, but
let's have a level playing field. Hawkins' paper eloquently makes the
case that this this scientific balance and objectivity has been
missing in dark matter research for quite awhile.

[Mod. note: reformatted -- mjh]
  #7  
Old March 11th 15, 08:56 AM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Posts: 273
Default New A&A Paper On Astrophysical Dark Matter

In article , "Robert L.
Oldershaw" writes:

Certainly no-one can claim that Hawkins has not had the opportunity to
plead his case. Also, even if it turns out that his claims about the
Milky-Way halo are correct, there are still arguments against his claim
that most of the dark matter in the universe is in the form of compact
objects with Jupiter-to-solar masses.


You forgot to mention that there are also other arguments FOR "his
claim that most of the dark matter in the universe is in the form of
compact objects with Jupiter-to-solar masses".


Yes, of course there are, but science is asymmetric: even very many
arguments in favour of a theory can't prove it, but just one argument
against it, in the sense of a failed prediction, can disprove it.

It's like the uniform-deviate--random-number generator: If the K-S test
says the numbers are compatible with a uniform distribution, that is an
argument for it. If someone notices that there is a maximum distance
(less than 1) between successive numbers, then it has been proven not to
be a good random-number generator. You can't say "It's 50-50; one
argument for, one against".

Until then it would behoove us not to marry any hypothetical class of
dark matter candidates, nor to spurn others simply because they
conflict with our expectations. It's ok to root for favorites, but
let's have a level playing field. Hawkins' paper eloquently makes the
case that this this scientific balance and objectivity has been
missing in dark matter research for quite awhile.


The reason most people think that dark matter is some sort of
non-baryonic (and non-neutrino) elementary particle is because there are
good arguments against other candidates, including Hawkins's. Even if
some people root for particle dark matter, you can't criticize their
experiments for looking for it any more than you can criticize Hawkins
for not looking for it.
  #8  
Old March 12th 15, 09:44 AM posted to sci.astro.research
Gary Harnagel
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Posts: 659
Default New A&A Paper On Astrophysical Dark Matter

If you look at a chart of star types versus fraction of stars in that
category, the less massive the star, the larger the fraction. About
three-quarters of the stars in our galaxy are M-type stars and account
for about 15% of the mass of all stars. Each star type larger than M
accounts for a smaller fraction of mass.

Does this relationship continue for smaller masses (to Jupiter-size
and below)? Could it not be that interstellar space is full of this
junk?

Gary
  #9  
Old March 12th 15, 09:45 AM posted to sci.astro.research
Robert L. Oldershaw
external usenet poster
 
Posts: 617
Default New A&A Paper On Astrophysical Dark Matter

On Wednesday, March 11, 2015 at 3:56:47 AM UTC-4, Phillip Helbig (undress to reply) wrote:

The reason most people think that dark matter is some sort of
non-baryonic (and non-neutrino) elementary particle is because there are
good arguments against other candidates, including Hawkins's. Even if
some people root for particle dark matter, you can't criticize their
experiments for looking for it any more than you can criticize Hawkins
for not looking for it.


Some interesting logic here, but I hope you can grasp the fact that I
am most certainly not criticizing anyone for doing any
experiments/observations. I do criticize 40 years of insisting that
particle dark matter is the best candidate and ignoring the writing on
the wall in hopes that the mythical particles are just around the next
corner.

In today's New York Times there is an article about reports of
gamma-rays emitted from one dwarf galaxy and the possibility of a
breakthrough in the particle dark matter search. The hype is laid on
thick and the go-to band leader Neil Weiner leads the parade.

Eventually the article gets around to mentioning the fact that another
group failed to see gamma-rays coming from the same dwarf galaxy
(Reticulum-2). Nowhere to be seen is mention of the fact that the
FERMI-LAT and DES groups posted papers to arXiv.org reporting that no
gamma-ray radiation was detected for larger samples of dwarf galaxies.

What do you think the chances are that the paper of M.R.S. Hawkins
would get proper coverage in the media? I'd say pretty darn low. Yet
his reanalysis of the microlensing results is at least as newsworthy
as the latest "hint" of wimps, if not considerably more.

This is not solely the attitude/fault of the media, as Weiner's
comments amply demonstrate. The particle physics community is driving
it, and driving it hard.

[Mod. note: reformatted -- mjh]
  #10  
Old March 12th 15, 09:11 PM posted to sci.astro.research
Phillip Helbig (undress to reply)[_2_]
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Posts: 273
Default New A&A Paper On Astrophysical Dark Matter

In article , "Robert L.
Oldershaw" writes:

The reason most people think that dark matter is some sort of
non-baryonic (and non-neutrino) elementary particle is because there are
good arguments against other candidates, including Hawkins's. Even if
some people root for particle dark matter, you can't criticize their
experiments for looking for it any more than you can criticize Hawkins
for not looking for it.


Some interesting logic here, but I hope you can grasp the fact that I
am most certainly not criticizing anyone for doing any
experiments/observations.


The entire tone of the rest of your post indicates that you are.

I do criticize 40 years of insisting that
particle dark matter is the best candidate


40 years ago, it wasn't the leading candidate. By a process of
elimination, it is left standing while essentially all other candidates
have been ruled out.

and ignoring the writing on
the wall in hopes that the mythical particles are just around the next
corner.


Who ignores what? People have read Hawkins's papers, they have pointed
out errors, and Hawkins ignores such work. Even if he doesn't agree, he
should address criticism.

Hopes? Wishes? Dreams? People do experiments and report what they
see.

In today's New York Times there is an article about reports of
gamma-rays emitted from one dwarf galaxy and the possibility of a
breakthrough in the particle dark matter search. The hype is laid on
thick and the go-to band leader Neil Weiner leads the parade.


Please distinguish scientific discussion from media hype. By the way, I
recall some recent media hype about rogue planets. Please refrain from
cherry picking.

What do you think the chances are that the paper of M.R.S. Hawkins
would get proper coverage in the media?


I once invited Mike to give a talk in Hamburg, and he came and gave it.
I saw several newspaper clippings. He has also written a popular book.
Considering that I came across it by chance at a stall selling used
books at a folk festival in Oxfordshire, my guess is that a fair number
were published. His case has been heard. But anyway, why is MEDIA
coverage important at all? On the one hand, you criticize media hype.
On the other hand, you seem sad because Hawkins and you don't get
enough.

I'd say pretty darn low. Yet
his reanalysis of the microlensing results is at least as newsworthy
as the latest "hint" of wimps, if not considerably more.


Maybe science writers notice that he repeats the same argument and
ignores criticism and have better things to write about.

This is not solely the attitude/fault of the media, as Weiner's
comments amply demonstrate. The particle physics community is driving
it, and driving it hard.


Looking for things which are not ruled out is what experimentalists do.
No-one is "driving anything hard".
 




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