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]

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.

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]

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.

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.

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]

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.

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

In article ,
Gary Harnagel writes:
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.

Down to some mass perhaps 1/3 or 1/4 of the Sun's. Below that, the
fraction decreases. See review by Chabrier (2003 PASP, 115, 763:
http://www.jstor.org/stable/10.1086/376392 , especially Fig 2) for an
example. I suppose there's more recent work.

Does this relationship continue for smaller masses (to Jupiter-size
and below)?

It's hard to know, but there are limits based on gravitational
lensing observations.

Could it not be that interstellar space is full of this junk?

Depends on the quantitative definition of "full of." There are quite
likely many objects, but their overall contribution to the mass
budget is probably negligible.

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