Galaxies without dark matter halos?

"TS" == Thomas Smid writes:

TS Joseph Lazio wrote in message
TS ...

You're mixing up two different measurements. Within the optical
disk, I think gas and stars usually co-rotate. (....) Outside the
optical disk, no stars are detected so one has to rely on the gas
to trace the gravitational potential.

TS The fact remains that in most publications gas rotation curves are
TS used to support the hypothesis that stars are bound by dark
TS matter. Why ? Presumably because star rotation curves wouldn't be
TS as conclusive.

Oh, come on. That's a fairly serious charge, deliberate suppression
of data. Surely you provide some illustrative examples?


TS Anyway, I wonder how one can be so sure about the exact amount and
TS distribution of the 'visible mass' in a galaxy and therefore the
TS need for dark matter in the first place: [...]

So work out the numbers in more detail; I'd actually be curious to
see this. Take a couple of example late-type spirals for which
good rotation curves exist. Assume that all of the dark matter is
in the form of 0.1 solar mass stars. How many stars would be
required and would the integrated light from them still be
undetectable?

TS Of course, outside the optical disk you would be hard pressed to
TS explain the rotation curves by low mass stars, but here, as you
TS admitted above, the curves do only represent the gas motion which
TS could be affected by a rotating magnetic field even in its neutral
TS form (...)

O.k., I've taken a look at your Web site, and don't understand one
crucial point. You spend a lot of time working out the force from a
magnetic field on ionized gas. Yet most (all?) of the gas
measurements in the outer parts of galaxies are of neutral gas. The
Lorentz force is F = q (v x B), so the Lorentz force on a neutral
hydrogen atom (q = 0) is F = 0. (I'll also conveniently ignore that
Vega-Beltran's work focused on *ionized* gas and he found general
agreement with stellar motions.)


TS However, even if observations of stars and globular clusters seem
TS to indicate the presence of dark matter, this is in my opinion not
TS a foregone conclusion [...]

O.k., so what's going on? You seem to admit that low-luminosity stars
can't help explain rotation curves, your Web pages indicate that the
expected magnetic force on the neutral gas from which rotation curves
are derived is 0. What's left?


I wouldn't call the existence of dark matter a foregone conclusion
either. There are a number of astronomers quite uncomfortable with
the entire dark matter and dark energy paradigm that's developed over
the past 5 years or so. Unfortunately, genuflections in the direction
of unknown magnetic fields aren't enough. Either some huge systematic
mistake(s) has been made or the Universe really does work like this.

--
Lt. Lazio, HTML police | e-mail:
No means no, stop rape. | http://patriot.net/%7Ejlazio/

Joseph Lazio wrote in message
...
"TS" == Thomas Smid writes:

TS Joseph Lazio wrote in message
TS ...

You're mixing up two different measurements. Within the optical
disk, I think gas and stars usually co-rotate. (....) Outside the
optical disk, no stars are detected so one has to rely on the gas
to trace the gravitational potential.

TS The fact remains that in most publications gas rotation curves are
TS used to support the hypothesis that stars are bound by dark
TS matter. Why ? Presumably because star rotation curves wouldn't be
TS as conclusive.

Oh, come on. That's a fairly serious charge, deliberate suppression
of data. Surely you provide some illustrative examples?

LOL! It's not a 'serious charge' of any kind! It's not 'suppression of
data'! It's a simple assumption that is historically used because gas
motions are so much easier to measure than stellar motions. Now it's
'carved in stone.' It's simply that there never was a theoretical or
observational justification for the assumption.

TS Anyway, I wonder how one can be so sure about the exact amount and
TS distribution of the 'visible mass' in a galaxy and therefore the
TS need for dark matter in the first place: [...]

So work out the numbers in more detail; I'd actually be curious to
see this. Take a couple of example late-type spirals for which
good rotation curves exist. Assume that all of the dark matter is
in the form of 0.1 solar mass stars. How many stars would be
required and would the integrated light from them still be
undetectable?

TS Of course, outside the optical disk you would be hard pressed to
TS explain the rotation curves by low mass stars, but here, as you
TS admitted above, the curves do only represent the gas motion which
TS could be affected by a rotating magnetic field even in its neutral
TS form (...)

O.k., I've taken a look at your Web site, and don't understand one
crucial point. You spend a lot of time working out the force from a
magnetic field on ionized gas. Yet most (all?) of the gas
measurements in the outer parts of galaxies are of neutral gas. The
Lorentz force is F = q (v x B), so the Lorentz force on a neutral
hydrogen atom (q = 0) is F = 0.

Joeseph, you've made this claim before. And it's been answered before.
Neutral gas always has a magnetic moment. Magnetic fields accelerate
neutral gas via it's paramagnetic or diamagnetic properties. It won't
accelerate neutral gas as fast as ionized gas, but the final motions should
be the same.

In other words, the force is not zero. It is significantly smaller than for
ionized gas. So it may take a year or a decade to accelerate to the same
speeds it took only seconds to accelerate the ionized gas.

(I'll also conveniently ignore that
Vega-Beltran's work focused on *ionized* gas and he found general
agreement with stellar motions.)

And you also made this claim in a prior post. But Vega-Beltran's work
contradicted this claim.

TS However, even if observations of stars and globular clusters seem
TS to indicate the presence of dark matter, this is in my opinion not
TS a foregone conclusion [...]

O.k., so what's going on? You seem to admit that low-luminosity stars
can't help explain rotation curves, your Web pages indicate that the
expected magnetic force on the neutral gas from which rotation curves
are derived is 0. What's left?

I provided you what's going on, just above. And this is a repeat of a prior
post.

I wouldn't call the existence of dark matter a foregone conclusion
either. There are a number of astronomers quite uncomfortable with
the entire dark matter and dark energy paradigm that's developed over
the past 5 years or so. Unfortunately, genuflections in the direction
of unknown magnetic fields aren't enough. Either some huge systematic
mistake(s) has been made or the Universe really does work like this.

I'd say clearly the former. The assumption that gas and stars move alike
was the primary huge systematic mistake.

greywolf42
ubi dubium ibi libertas

Joseph Lazio wrote in message
...
"TS" == Thomas Smid writes:

TS Joseph Lazio wrote in message
TS ...

You're mixing up two different measurements. Within the optical
disk, I think gas and stars usually co-rotate. (....) Outside the
optical disk, no stars are detected so one has to rely on the gas
to trace the gravitational potential.

TS The fact remains that in most publications gas rotation curves are
TS used to support the hypothesis that stars are bound by dark
TS matter. Why ? Presumably because star rotation curves wouldn't be
TS as conclusive.

Oh, come on. That's a fairly serious charge, deliberate suppression
of data. Surely you provide some illustrative examples?

LOL! It's not a 'serious charge' of any kind! It's not 'suppression of
data'! It's a simple assumption that is historically used because gas
motions are so much easier to measure than stellar motions. Now it's
'carved in stone.' It's simply that there never was a theoretical or
observational justification for the assumption.

TS Anyway, I wonder how one can be so sure about the exact amount and
TS distribution of the 'visible mass' in a galaxy and therefore the
TS need for dark matter in the first place: [...]

So work out the numbers in more detail; I'd actually be curious to
see this. Take a couple of example late-type spirals for which
good rotation curves exist. Assume that all of the dark matter is
in the form of 0.1 solar mass stars. How many stars would be
required and would the integrated light from them still be
undetectable?

TS Of course, outside the optical disk you would be hard pressed to
TS explain the rotation curves by low mass stars, but here, as you
TS admitted above, the curves do only represent the gas motion which
TS could be affected by a rotating magnetic field even in its neutral
TS form (...)

O.k., I've taken a look at your Web site, and don't understand one
crucial point. You spend a lot of time working out the force from a
magnetic field on ionized gas. Yet most (all?) of the gas
measurements in the outer parts of galaxies are of neutral gas. The
Lorentz force is F = q (v x B), so the Lorentz force on a neutral
hydrogen atom (q = 0) is F = 0.

Joeseph, you've made this claim before. And it's been answered before.
Neutral gas always has a magnetic moment. Magnetic fields accelerate
neutral gas via it's paramagnetic or diamagnetic properties. It won't
accelerate neutral gas as fast as ionized gas, but the final motions should
be the same.

In other words, the force is not zero. It is significantly smaller than for
ionized gas. So it may take a year or a decade to accelerate to the same
speeds it took only seconds to accelerate the ionized gas.

(I'll also conveniently ignore that
Vega-Beltran's work focused on *ionized* gas and he found general
agreement with stellar motions.)

And you also made this claim in a prior post. But Vega-Beltran's work
contradicted this claim.

TS However, even if observations of stars and globular clusters seem
TS to indicate the presence of dark matter, this is in my opinion not
TS a foregone conclusion [...]

O.k., so what's going on? You seem to admit that low-luminosity stars
can't help explain rotation curves, your Web pages indicate that the
expected magnetic force on the neutral gas from which rotation curves
are derived is 0. What's left?

I provided you what's going on, just above. And this is a repeat of a prior
post.

I wouldn't call the existence of dark matter a foregone conclusion
either. There are a number of astronomers quite uncomfortable with
the entire dark matter and dark energy paradigm that's developed over
the past 5 years or so. Unfortunately, genuflections in the direction
of unknown magnetic fields aren't enough. Either some huge systematic
mistake(s) has been made or the Universe really does work like this.

I'd say clearly the former. The assumption that gas and stars move alike
was the primary huge systematic mistake.

greywolf42
ubi dubium ibi libertas

greywolf42 ) writes:
[...]
Joeseph, you've made this claim before. And it's been answered before.
Neutral gas always has a magnetic moment. Magnetic fields accelerate
neutral gas via it's paramagnetic or diamagnetic properties. It won't
accelerate neutral gas as fast as ionized gas, but the final motions should
be the same.

This seems to require that mu.grad(B) is (a) significantly bigger than
nonmagnetic, dissipative forces and (b) proportional to vxB. (mu is the
magnetic moment of a gas molecule, v the velocity of the molecule and B
the magnetic field; all are vectors.) Neither condition seems
to be self-evidently satisfied.

--John Park

greywolf42 ) writes:
[...]
Joeseph, you've made this claim before. And it's been answered before.
Neutral gas always has a magnetic moment. Magnetic fields accelerate
neutral gas via it's paramagnetic or diamagnetic properties. It won't
accelerate neutral gas as fast as ionized gas, but the final motions should
be the same.

This seems to require that mu.grad(B) is (a) significantly bigger than
nonmagnetic, dissipative forces and (b) proportional to vxB. (mu is the
magnetic moment of a gas molecule, v the velocity of the molecule and B
the magnetic field; all are vectors.) Neither condition seems
to be self-evidently satisfied.

--John Park

In article ,
greywolf42 writes:

TS The fact remains that in most publications gas rotation curves are
TS used to support the hypothesis that stars are bound by dark
TS matter.
....
It's a simple assumption that is historically used because gas
motions are so much easier to measure than stellar motions. Now it's
'carved in stone.' It's simply that there never was a theoretical or
observational justification for the assumption.

I think you will find that the original work on disk rotation
velocities used visible observations of stars. Nowadays, it's more
common to use H I because the gas can be used beyond the observed
disk. It was a huge surprise when these observations were first
done, and flat rotation curves continued beyond the radius of visible
starlight.

Can you cite any _observations_ where the gas and stellar velocities
disagree? How about locally in the Milky Way? Any disagreement
between gas (CO, H I) and stellar velocities?

Neutral gas always has a magnetic moment. Magnetic fields accelerate
neutral gas via it's paramagnetic or diamagnetic properties. It won't
accelerate neutral gas as fast as ionized gas, but the final motions should
be the same.

If this is the explanation, what magnetic field pattern do you
require? Is it consistent with observed polarization?

In other words, the force is not zero. It is significantly smaller than for
ionized gas. So it may take a year or a decade to accelerate to the same
speeds it took only seconds to accelerate the ionized gas.

And what magnetic field strength? Is that consistent with Zeeman
splitting, Faraday rotation, and synchrotron emission?

--
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.)

In article ,
greywolf42 writes:

TS The fact remains that in most publications gas rotation curves are
TS used to support the hypothesis that stars are bound by dark
TS matter.
....
It's a simple assumption that is historically used because gas
motions are so much easier to measure than stellar motions. Now it's
'carved in stone.' It's simply that there never was a theoretical or
observational justification for the assumption.

I think you will find that the original work on disk rotation
velocities used visible observations of stars. Nowadays, it's more
common to use H I because the gas can be used beyond the observed
disk. It was a huge surprise when these observations were first
done, and flat rotation curves continued beyond the radius of visible
starlight.

Can you cite any _observations_ where the gas and stellar velocities
disagree? How about locally in the Milky Way? Any disagreement
between gas (CO, H I) and stellar velocities?

Neutral gas always has a magnetic moment. Magnetic fields accelerate
neutral gas via it's paramagnetic or diamagnetic properties. It won't
accelerate neutral gas as fast as ionized gas, but the final motions should
be the same.

If this is the explanation, what magnetic field pattern do you
require? Is it consistent with observed polarization?

In other words, the force is not zero. It is significantly smaller than for
ionized gas. So it may take a year or a decade to accelerate to the same
speeds it took only seconds to accelerate the ionized gas.

And what magnetic field strength? Is that consistent with Zeeman
splitting, Faraday rotation, and synchrotron emission?

--
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.)

John Park wrote in message
...
greywolf42 ) writes:
[...]
Joeseph, you've made this claim before. And it's been answered before.
Neutral gas always has a magnetic moment. Magnetic fields accelerate
neutral gas via it's paramagnetic or diamagnetic properties. It won't
accelerate neutral gas as fast as ionized gas, but the final motions
should
be the same.

This seems to require that mu.grad(B) is (a) significantly bigger than
nonmagnetic, dissipative forces and (b) proportional to vxB. (mu is the
magnetic moment of a gas molecule, v the velocity of the molecule and B
the magnetic field; all are vectors.) Neither condition seems
to be self-evidently satisfied.

The theoretical conditions you've listed are not necessary. A magnetic
field accelerates ALL gas in the region. Ionized gas will acclerate (far)
more quickly than neutral gas. Everything is being accelerated.
'Dissipative' terms such as collisions will not affect the overall
paramagnetic or diamagnetic accelerations of the region. Such interactions
will tend to unify the gas motions.

It is also observed that gas does not move in the same manner as stellar
bodies in the same galactic region. (One of the few that actually maps
stars, for example, Bottema, R.; van der Kruit, P. C.; Valentijn, E. A.;
'The stellar velocity dispersion of the edge-on spiral galaxy NGC 891'):
http://groups.google.com/groups?hl=e...kfupis9a%40cor
p.supernews.com

greywolf42
ubi dubium ibi libertas

John Park wrote in message
...
greywolf42 ) writes:
[...]
Joeseph, you've made this claim before. And it's been answered before.
Neutral gas always has a magnetic moment. Magnetic fields accelerate
neutral gas via it's paramagnetic or diamagnetic properties. It won't
accelerate neutral gas as fast as ionized gas, but the final motions
should
be the same.

This seems to require that mu.grad(B) is (a) significantly bigger than
nonmagnetic, dissipative forces and (b) proportional to vxB. (mu is the
magnetic moment of a gas molecule, v the velocity of the molecule and B
the magnetic field; all are vectors.) Neither condition seems
to be self-evidently satisfied.

The theoretical conditions you've listed are not necessary. A magnetic
field accelerates ALL gas in the region. Ionized gas will acclerate (far)
more quickly than neutral gas. Everything is being accelerated.
'Dissipative' terms such as collisions will not affect the overall
paramagnetic or diamagnetic accelerations of the region. Such interactions
will tend to unify the gas motions.

It is also observed that gas does not move in the same manner as stellar
bodies in the same galactic region. (One of the few that actually maps
stars, for example, Bottema, R.; van der Kruit, P. C.; Valentijn, E. A.;
'The stellar velocity dispersion of the edge-on spiral galaxy NGC 891'):
http://groups.google.com/groups?hl=e...kfupis9a%40cor
p.supernews.com

greywolf42
ubi dubium ibi libertas

greywolf42 ) writes:
John Park wrote in message
This seems to require that mu.grad(B) is (a) significantly bigger than
nonmagnetic, dissipative forces and (b) proportional to vxB. (mu is the
magnetic moment of a gas molecule, v the velocity of the molecule and B
the magnetic field; all are vectors.) Neither condition seems
to be self-evidently satisfied.

The theoretical conditions you've listed are not necessary. A magnetic
field accelerates ALL gas in the region.

But why should a mu.grad(B) force have the same direction as a vxB force?

Ionized gas will acclerate (far)
more quickly than neutral gas.

"Far more" sounds right. If the magnetic field gradient is as high as 10
microGauss per kiloparsec, I estimate that, acting on the magnetic moment of a
(neutral) hydrogen atom, over the lifetime of the galaxy, it would produce a
velocity change of the order of 0.1 micrometers per second. This would
correspond to a change in position of the order of 100 light seconds over
the lifetime of the galaxy. Hence my comment about dissipative, nonmagnetic
forces.

--John Park