Detecting dark matter

In article , greywolf42 wrote:

Actually, it is not motion of galaxies relative to each other that requires
the "additional" dark matter, it is the the fact that cosmologists "need"
about 100 times more matter than is observed to "make" omega = 1. (Omega is
the ratio of matter in the universe to that needed to "close" the universe.)

I don't think that's right -- a lot of dark matter is detected in
galaxy clusters by the need to keep galaxies bound to the cluster,
given their motions relative to the cluster. So Ed is right.
X-ray-emitting gas in galaxy clusters also allows measuring
the cluster's total mass, and again shows lots more dark than visible matter.

This is sometimes confusing, because the internal rotation of spiral
galaxies needs about 9 parts in 10 dark matter to "normal" matter to make
pure gravitation work. So the omega "flatness" problem needs ANOTHER factor
of 10 (above the dark matter "needed" for internal spiral galaxy modelling).

Observations of motion in
galaxies have been done by measuring the motion
of gas halos with spectrometers as individual stars
cannot be resolved.

This is also true inside spiral galaxies. We measure ONLY the motions of
gas*, not the motions of stars. Then we ASSUME that the stars move the same
as gas -- because we ASSUME that ONLY gravity is at work.

This is quite false too. Of course we can and do measure the
bulk orbital motions of stars in *disk* galaxies, in visible light,
even without detecting the stars individually. Motions of gas clouds
(HI and CO) are also measured, in radio frequencies. I haven't heard
any reason to think they're inconsistent.

A new scope, the Planetary
Nebula Spectrograph, can measure the motion
of individual novas in elliptical galaxies that do
not contain gas. The unexpectedly close mass to
light ratio needed to explain the motion within these
galaxies shows that they do not contain a lot of
invisible matter.

Translation: No dark matter is needed in galaxies if we focus on stellar
motions.

I don't know about ellipticals, but that's certainly not true
for most disk galaxies. They sure do show evidence of dark matter
(or something like MOND, though I'm told that's hard to support now).

Even minimal fact-checking would have prevented your posting these errors!

Stuart Levy

Stuart Levy wrote in message
...
In article , greywolf42 wrote:

Actually, it is not motion of galaxies relative to each other that
requires
the "additional" dark matter, it is the the fact that cosmologists "need"
about 100 times more matter than is observed to "make" omega = 1. (Omega
is
the ratio of matter in the universe to that needed to "close" the
universe.)

I don't think that's right -- a lot of dark matter is detected in
galaxy clusters by the need to keep galaxies bound to the cluster,
given their motions relative to the cluster. So Ed is right.
X-ray-emitting gas in galaxy clusters also allows measuring
the cluster's total mass, and again shows lots more dark than visible
matter.

The only reason we "need" dark matter "to keep galaxies bound in the
cluster, given their motions relative to the cluster" is to "save" the Big
Bang. This is a third evolution of dark matter. Anytime an actual
observation disproves the BB, we add another epicycle. There are about a
dozen MAJOR ad hoc epicycles so far.

This is sometimes confusing, because the internal rotation of spiral
galaxies needs about 9 parts in 10 dark matter to "normal" matter to make
pure gravitation work. So the omega "flatness" problem needs ANOTHER
factor
of 10 (above the dark matter "needed" for internal spiral galaxy
modelling).

Observations of motion in
galaxies have been done by measuring the motion
of gas halos with spectrometers as individual stars
cannot be resolved.

This is also true inside spiral galaxies. We measure ONLY the motions of
gas*, not the motions of stars. Then we ASSUME that the stars move the
same
as gas -- because we ASSUME that ONLY gravity is at work.

This is quite false too. Of course we can and do measure the
bulk orbital motions of stars in *disk* galaxies, in visible light,
even without detecting the stars individually.

Another bull**** evidence-snipper. See below.

Got a contrary reference?

Motions of gas clouds
(HI and CO) are also measured, in radio frequencies. I haven't heard
any reason to think they're inconsistent.

???? Hello? Perhaps if you left the evidence in, instead of snipping it
you might be able to apply that thing between your ears for more than simple
storage.

Does your background allow you to detect any difference between a molecule
of free gas and a star? Do you think that magnetic fields might affect one
more than the other?

{snip replaced}
============================
Ed Keane:
Observations of motion in galaxies have been done by measuring the motion of
gas halos with spectrometers as individual stars cannot be resolved.

greywolf42:
This is also true inside spiral galaxies. We measure ONLY the motions of
gas*, not the motions of stars. Then we ASSUME that the stars move the same
as gas -- because we ASSUME that ONLY gravity is at work.

*In a few cases, we can get a few O and B stars. These stars are highly
luminescent, highly massive -- and very short-lived (a few million to 10
million years lifetimes). Since orbital times are around 100 My, these O
and B stars have no time to deviate significantly from the motion of the gas
that births them.
============================

A new scope, the Planetary
Nebula Spectrograph, can measure the motion
of individual novas in elliptical galaxies that do
not contain gas. The unexpectedly close mass to
light ratio needed to explain the motion within these
galaxies shows that they do not contain a lot of
invisible matter.

Translation: No dark matter is needed in galaxies if we focus on stellar
motions.

I don't know about ellipticals, but that's certainly not true
for most disk galaxies. They sure do show evidence of dark matter
(or something like MOND, though I'm told that's hard to support now).

Even minimal fact-checking would have prevented your posting these errors!

Current popular theories are not "facts". Now goodbye in this thread. I
don't feel like wasting my time with someone that snips the evidence and
then claims it never existed.

greywolf42
ubi dubium ibi libertas

In article , greywolf42 wrote:

[...]

The only reason we "need" dark matter "to keep galaxies bound in the
cluster, given their motions relative to the cluster" is to "save" the Big
Bang.

No, that's not right. We need an explanation of why galaxies
manage to to stay bound to their clusters regardless of how they
(galaxies or cluster) got to be there.

The only Big Bang connection that I see here is the assumption
that the "dark" extra matter must be non-baryonic stuff,
to be compatible with elemental abundances that came from
Big Bang theories. I.e. if not for some variety of big bang
theory, there'd still need to be lots of mysteriously invisible
matter, but it could be ordinary matter in some invisible form.

Observations of motion in
galaxies have been done by measuring the motion
of gas halos with spectrometers as individual stars
cannot be resolved.

This is also true inside spiral galaxies. We measure ONLY the motions of
gas*, not the motions of stars. Then we ASSUME that the stars move the
same
as gas -- because we ASSUME that ONLY gravity is at work.

This is quite false too. Of course we can and do measure the
bulk orbital motions of stars in *disk* galaxies, in visible light,
even without detecting the stars individually.

Another bull**** evidence-snipper. See below.

Got a contrary reference?

You didn't read what I wrote. I said *disk* galaxies.
Your quote about the new measures of galaxy dynamics
measured via planetary nebulae, though interesting, doesn't apply to
those -- they were looking at ellipticals, whose motion
seems to be a lot less ordered than in the disks of disk galaxies.

For a review mentioning that it is indeed normal to make
both optical and radio measures of disk galaxy rotation curves,
see e.g. Binney & Merrifield, Galactic Astronomy, pp 506-509 or so.

In other words, your

Translation: No dark matter is needed in galaxies if we focus on stellar
motions.

is not a correct interpretation of what they found --
even though what they found surely is interesting!

Stuart

"greywolf42" == greywolf42 writes:

greywolf42 Stuart Levy wrote in message
greywolf42 ...
In article , greywolf42 wrote:

Actually, it is not motion of galaxies relative to each other that
requires the "additional" dark matter, it is the the fact that
cosmologists "need" about 100 times more matter than is observed
to "make" omega = 1. (...)

I don't think that's right -- a lot of dark matter is detected in
galaxy clusters by the need to keep galaxies bound to the cluster,
given their motions relative to the cluster. So Ed is right.
X-ray-emitting gas in galaxy clusters also allows measuring the
cluster's total mass, and again shows lots more dark than visible
matter.

greywolf42 The only reason we "need" dark matter "to keep galaxies
greywolf42 bound in the cluster, given their motions relative to the
greywolf42 cluster" is to "save" the Big Bang.

Levy was correct. Zwicky was postulating "unseen" matter in the Coma
cluster of galaxies in the 1930s, about 30 years before the Big Bang
had achieved its current prominence. Ignore the Big Bang if you'd
like, but if you think that Newton was even close to correct in his
description of gravity, the motions of galaxies in clusters require
more matter than is seen.

It's also worth pointing out that we need dark matter to exist because
we've detected some. Both neutrinos and black holes are dark matter.
Neither exist in a sufficient quantity to explain all of the dark
matter required, but both exist. If we have two examples of dark
matter, it is not unreasonable to suggest that there might be a third
example of dark matter.

This is also true inside spiral galaxies. We measure ONLY the
motions of gas*, not the motions of stars. Then we ASSUME that
the stars move the same
as gas -- because we ASSUME that ONLY gravity is at work.

This is quite false too. Of course we can and do measure the bulk
orbital motions of stars in *disk* galaxies, in visible light, even
without detecting the stars individually.

greywolf42 Another bull**** evidence-snipper. See below.

greywolf42 Got a contrary reference?

How about NGC 4650A, for which a stellar rotation curve has been
measured? URL:
http://adsabs.harvard.edu/cgi-bin/np...pJ...587L..23S .

Motions of gas clouds (HI and CO) are also measured, in radio
frequencies. I haven't heard any reason to think they're
inconsistent.

[...]
greywolf42 Does your background allow you to detect any difference
greywolf42 between a molecule of free gas and a star? Do you think
greywolf42 that magnetic fields might affect one more than the other?

I notice that you provide no evidence to suggest that gas and stellar
motions differ. (I've posted pointers of rotation curves derived from
gas motions, check Google.) It's not obvious to me that magnetic
fields should be important. First, the gas motions are measured for
*neutral* gas. How do the magnetic fields and neutral atoms couple?
Second, the kinetic energy in the rotation is of orders of magnitude
larger than the magnetic energy density. How can the magnetic field
be comparable in influence to the rotation?

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/
sci.astro FAQ at http://sciastro.astronomy.net/sci.astro.html

Joseph Lazio wrote in message
...
"greywolf42" == greywolf42 writes:

greywolf42 Stuart Levy wrote in message
greywolf42 ...
In article , greywolf42 wrote:

Actually, it is not motion of galaxies relative to each other that
requires the "additional" dark matter, it is the the fact that
cosmologists "need" about 100 times more matter than is observed
to "make" omega = 1. (...)

I don't think that's right -- a lot of dark matter is detected in
galaxy clusters by the need to keep galaxies bound to the cluster,
given their motions relative to the cluster. So Ed is right.
X-ray-emitting gas in galaxy clusters also allows measuring the
cluster's total mass, and again shows lots more dark than visible
matter.

greywolf42 The only reason we "need" dark matter "to keep galaxies
greywolf42 bound in the cluster, given their motions relative to the
greywolf42 cluster" is to "save" the Big Bang.

Levy was correct. Zwicky was postulating "unseen" matter in the Coma
cluster of galaxies in the 1930s, about 30 years before the Big Bang
had achieved its current prominence.

LOL! Zwicky was producing a steady-state theory expressly to counter the
early big-bang. "Prominence" has nothing to do with it. However, Zwicky's
"unseen" matter is not the "dark matter" that we discuss today. Unseen
simply means we haven't yet observed it. "Dark" matter -- by definition --
cannot interact by EM, and cannot be directly observed by us.

Ignore the Big Bang if you'd
like, but if you think that Newton was even close to correct in his
description of gravity, the motions of galaxies in clusters require
more matter than is seen.

Your two separate assertions in the statement above are both unsupported and
incorrect.

1) Newton has nothing to do with it. As gravity is not the only force in
the universe.

2) Even if we required gravity as the be-all and end-all of cosmology, we
don't have any problems at all with cluster motions outside of the big bang.
It is the fact that the observations of apparent motion (filtered through
the theory of the BB) explicitly contradict the big bang that gives the
problem.

It's also worth pointing out that we need dark matter to exist because
we've detected some. Both neutrinos and black holes are dark matter.
Neither exist in a sufficient quantity to explain all of the dark
matter required, but both exist. If we have two examples of dark
matter, it is not unreasonable to suggest that there might be a third
example of dark matter.

Neither neutrinos nor black holes are dark matter. Dark matter is not
merely matter that cannot be seen. Dark matter is -- by definition and
theoretical requirement -- unable to interact with matter EXCEPT by gravity.
Hence neutrinos are not matter. Black holes don't exist. They are a
theoretical phantom, disproved by observational evidence (quasiperiodic
variations). But the serve an important purpose in cosmology. Whenever a
cosmologist finds something that cannot be explained he postulates a black
hole to power things.

This is also true inside spiral galaxies. We measure ONLY the
motions of gas*, not the motions of stars. Then we ASSUME that
the stars move the same
as gas -- because we ASSUME that ONLY gravity is at work.

This is quite false too. Of course we can and do measure the bulk
orbital motions of stars in *disk* galaxies, in visible light, even
without detecting the stars individually.

greywolf42 Another bull**** evidence-snipper. See below.

greywolf42 Got a contrary reference?

How about NGC 4650A, for which a stellar rotation curve has been
measured? URL:

http://adsabs.harvard.edu/cgi-bin/np...pJ...587L..23S

April 2003. Maybe something new, for a change. Sorry, the reference is not
available to non-members of the APJ. Got one I can download? Otherwise
will have to wait for the library.

Motions of gas clouds (HI and CO) are also measured, in radio
frequencies. I haven't heard any reason to think they're
inconsistent.

[...]

greywolf42 Does your background allow you to detect any difference
greywolf42 between a molecule of free gas and a star? Do you think
greywolf42 that magnetic fields might affect one more than the other?

I notice that you provide no evidence to suggest that gas and stellar
motions differ.

Another pathetic evidence snipper. Gad, what cowards science has come to.

(I've posted pointers of rotation curves derived from
gas motions, check Google.)

And your point would be what?

It's not obvious to me that magnetic
fields should be important. First, the gas motions are measured for
*neutral* gas. How do the magnetic fields and neutral atoms couple?

Neutral molecules have charges, though the total charge is zero. They are
accelerated by their paramagnetic and diamagnetic properties.

Second, the kinetic energy in the rotation is of orders of magnitude
larger than the magnetic energy density. How can the magnetic field
be comparable in influence to the rotation?

Non sequiteur. The EM FORCE is stronger on gas molecules than the
gravitational FORCE. Rotation is the result, not a competing effect.

{evidence replaced for second time}
============================
Ed Keane:
Observations of motion in galaxies have been done by measuring the motion of
gas halos with spectrometers as individual stars cannot be resolved.

greywolf42:
This is also true inside spiral galaxies. We measure ONLY the motions of
gas*, not the motions of stars. Then we ASSUME that the stars move the same
as gas -- because we ASSUME that ONLY gravity is at work.

*In a few cases, we can get a few O and B stars. These stars are highly
luminescent, highly massive -- and very short-lived (a few million to 10
million years lifetimes). Since orbital times are around 100 My, these O
and B stars have no time to deviate significantly from the motion of the gas
that births them.

Ed Keane:
A new scope, the Planetary Nebula Spectrograph, can measure the motion of
individual novas in elliptical galaxies that do not contain gas. The
unexpectedly close mass to light ratio needed to explain the motion within
these galaxies shows that they do not contain a lot of invisible matter.

greywolf42:
Translation: No dark matter is needed in galaxies if we focus on stellar
motions.
============================

See? No dark matter needed in ellipticals (which do not have the
disk-shaped magnetic fields which give rise to the magnetically-driven gas).

Bye in this thread, oh cowardly evidence snipper.

greywolf42
ubi dubium ibi libertas

Stuart Levy wrote in message
...
In article , greywolf42 wrote:

[...]

The only reason we "need" dark matter "to keep galaxies bound in the
cluster, given their motions relative to the cluster" is to "save" the
Big
Bang.

No, that's not right. We need an explanation of why galaxies
manage to to stay bound to their clusters regardless of how they
(galaxies or cluster) got to be there.

The only Big Bang connection that I see here is the assumption
that the "dark" extra matter must be non-baryonic stuff,
to be compatible with elemental abundances that came from
Big Bang theories. I.e. if not for some variety of big bang
theory, there'd still need to be lots of mysteriously invisible
matter, but it could be ordinary matter in some invisible form.

Observations of motion in
galaxies have been done by measuring the motion
of gas halos with spectrometers as individual stars
cannot be resolved.

This is also true inside spiral galaxies. We measure ONLY the motions
of
gas*, not the motions of stars. Then we ASSUME that the stars move
the
same
as gas -- because we ASSUME that ONLY gravity is at work.

This is quite false too. Of course we can and do measure the
bulk orbital motions of stars in *disk* galaxies, in visible light,
even without detecting the stars individually.

Another bull**** evidence-snipper. See below.

Got a contrary reference?

You didn't read what I wrote. I said *disk* galaxies.
Your quote about the new measures of galaxy dynamics
measured via planetary nebulae, though interesting, doesn't apply to
those -- they were looking at ellipticals, whose motion
seems to be a lot less ordered than in the disks of disk galaxies.

My quote was explicitly on disk galaxies.

I know I already said, "bye". However, I still reserve the right to point
out new, outright lies.

{snip}

greywolf42
ubi dubium ibi libertas

In article ,
Joseph Lazio writes:
It's also worth pointing out that we need dark matter to exist because
we've detected some. Both neutrinos and black holes are dark matter.
Neither exist in a sufficient quantity to explain all of the dark
matter required, but both exist. If we have two examples of dark
matter, it is not unreasonable to suggest that there might be a third
example of dark matter.

It's perhaps worth pointing out that planets, white dwarfs, brown
dwarfs, neutron stars, and even low mass stars "count" as dark matter
in the context of galaxy rotation curves and cluster velocity
dispersions. (Not to mention asteroids and cannon balls, and it
wouldn't surprise me if there are others I've omitted.) All that is
required to be "dark matter" is that the ratio of mass to luminosity,
measured in solar units, be much greater than one.

--
Steve Willner Phone 617-495-7123
Cambridge, MA 02138 USA
(Please email your reply if you want to be sure I see it; include a
valid Reply-To address to receive an acknowledgement. Commercial
email may be sent to your ISP.)

greywolf42 wrote in message
...

Joseph Lazio wrote in message
...

{snip to the reference section}

This is also true inside spiral galaxies. We measure ONLY the
motions of gas*, not the motions of stars. Then we ASSUME that
the stars move the same
as gas -- because we ASSUME that ONLY gravity is at work.

This is quite false too. Of course we can and do measure the bulk
orbital motions of stars in *disk* galaxies, in visible light, even
without detecting the stars individually.

{snip by Joseph}

greywolf42 Got a contrary reference?

How about NGC 4650A, for which a stellar rotation curve has been
measured? URL:

http://adsabs.harvard.edu/cgi-bin/np...pJ...587L..23S

April 2003. Maybe something new, for a change. Sorry, the reference is
not
available to non-members of the APJ. Got one I can download? Otherwise
will have to wait for the library.

{snip}

The abstract reads:

"We present the first measurement of the stellar kinematics in the polar
ring of NGC 4650A. There is well-defined rotation, with the stars and gas
rotating in the same direction, and with similar amplitude. The gaseous and
stellar kinematics suggest an approximately flat rotation curve, providing
further support for the hypothesis that the polar material resides in a disk
rather than in a ring. The kinematics of the emission-line gas at and near
the center of the S0 galaxy suggest that the polar disk lacks a central
hole. We have not detected evidence of two equal-mass, counterrotating
stellar polar streams, as is predicted in the resonance levitation model
proposed by Tremaine & Yu. A merger seems the most likely explanation for
the structure and kinematics of NGC 4650A."

There are several conclusions here that can be translated:

1)
Statement: "the S0 galaxy"

Translation: There are no discernable spiral arms on this galaxy. (Oddly,
the authors have not identified whether this is an S0a, S0b or S0c galaxy.)

2)
Statement: "The kinematics of the emission-line gas at and near the center
of the S0 galaxy suggest that the polar disk lacks a central hole"

Translation: There is no discrepancy between observed mass and theoretical
rotation by pure gravitation.

3)
Statement: "There is well-defined rotation, with the stars and gas rotating
in the same direction, and with similar amplitude"

Translation: Although the stars and gas orbit in the same direction, they
don't always move at the same speed. Though their speeds are within a
factor of 10 of each other.

4)
Statement: "The gaseous and stellar kinematics suggest an approximately flat
rotation curve."

Translation: ??? Supposedly they were measuring the rotation curve. I
don't understand how this got inverted in the abstract to a "suggest."
Unless the error bars are on the order of the measured values.


What do these items tell us in general about this galaxy?

Item 1) tells us that there is no significant magnetic field in this disk
galaxy. Magnetic fields give rise to spiral arms -- at least they do in the
lab and in theory. Hence, the lack of spiral arms indicates the lack of a
well-established galactic magnetic field.

Item 2) seconds the understanding of item 1). Without a well-established
magnetic field, there will be no central magnetic vortex filaments. It is
these latter that cause cosmologists to postulate massive central black
holes in spiral galaxies.

Item 3) shows us that -- even without any significant magnetic field -- gas
and stars do not move in lockstep. Of course the motions are "similar!"
Stars form from gas. Hence, they are born with the motions of gas. Then
they can diverge with time. I'll predict that the link between gas and
stellar motions is strongest with O and B stars -- since they are
necessarily young.

Item 4) shows us how strongly theoretical considerations are affecting this
supposedly observational paper.


In summary, this abstract supports (slightly) what I was saying about gas
and stars moving differently in spiral galaxies. It certainly provides no
evidence against anything I was saying, because this is apparently not a
galaxy with a significant magnetic field -- since it's not a spiral galaxy.

However, I'll still try to get to the library to look at the details.

greywolf42
ubi dubium ibi libertas

In article , greywolf42 wrote:
[...]
Observations of motion in
galaxies have been done by measuring the motion
of gas halos with spectrometers as individual stars
cannot be resolved.

This is also true inside spiral galaxies.
We measure ONLY the motions of gas*, not the
motions of stars. Then we ASSUME that the stars move
the same as gas -- because we ASSUME that ONLY gravity is at work.

and Stuart Levy replied:
This is quite false too. Of course we can and do measure the
bulk orbital motions of stars in *disk* galaxies, in visible light,
even without detecting the stars individually.

Another bull**** evidence-snipper. See below.

Got a contrary reference?

You didn't read what I wrote. I said *disk* galaxies.
Your quote about the new measures of galaxy dynamics
measured via planetary nebulae, though interesting, doesn't apply to
those -- they were looking at ellipticals, whose motion
seems to be a lot less ordered than in the disks of disk galaxies.

My quote was explicitly on disk galaxies.

Which quote was that? The only quote (of other people's material)
that I saw you (greywolf42) make was this one, which does refer to
elliptical and not disk galaxies:

A new scope, the Planetary
Nebula Spectrograph, can measure the motion
of individual novas in elliptical galaxies that do
not contain gas. The unexpectedly close mass to
light ratio needed to explain the motion within these
galaxies shows that they do not contain a lot of
invisible matter.

The other things you've said were assertions, not quotes,
and mostly baseless assertions, e.g.:
- that there'd be no need to invoke dark matter if
not to support Big Bang theories
(false as Joseph Lazio and I have explained), or that

- astronomers have measured galactic dynamics by tracing gas motions
rather than stellar motions (false at least for disk galaxies),
with the apparent implication that
- gas motions (affected by nongravitational forces somehow)
weren't representative of stellar motions,
and so the estimated gravitational mass from
gas motions was a wild overestimate of the true mass.

But again as Lazio and I have pointed out, astronomers
do indeed measure both stellar and gas-cloud motions
and find them comparable. So this chain of argument doesn't help you
if you are trying to find a way around the need for dark matter.

If you argue with a fool... Ah well. At least anyone who's
followed the thread this far should have some idea of where
to look if they're still puzzled.

I don't like the idea of dark matter either -- to think that
the bulk of the universe is something that's not only invisible
but exotic and perhaps even (in some theories) completely
undetectable by anything except its gravity. Ugh.

But then, I thought a cosmological constant was an ugly idea
too, and now it seems there's even more of that. I can only
hope that our descendents will figure out what could possibly
be going on with dark matter and dark energy. Meanwhile,
like so many situations in science as in life, I'll have to
live with the ambiguity of partial, and partially-wrong,
understanding.

Cheers

Stuart Levy

Steve Willner wrote in message
...
In article ,
Joseph Lazio writes:
It's also worth pointing out that we need dark matter to exist because
we've detected some. Both neutrinos and black holes are dark matter.
Neither exist in a sufficient quantity to explain all of the dark
matter required, but both exist. If we have two examples of dark
matter, it is not unreasonable to suggest that there might be a third
example of dark matter.

It's perhaps worth pointing out that planets, white dwarfs, brown
dwarfs, neutron stars, and even low mass stars "count" as dark matter
in the context of galaxy rotation curves and cluster velocity
dispersions. (Not to mention asteroids and cannon balls, and it
wouldn't surprise me if there are others I've omitted.) All that is
required to be "dark matter" is that the ratio of mass to luminosity,
measured in solar units, be much greater than one.

No, they don't "count" as dark matter, because their presence has already
been "counted" in the big bang cosmology as normal matter.

greywolf42
ubi dubium ibi libertas