Doppler Tests on Local Stars

In article ,
Oh No wrote:
Thus spake Joseph Lazio
"ON" == Oh No writes:

ON Thus spake Joseph Lazio
"ON" == Oh No writes:

ON Thus spake Steve Willner

Quasar positions measured by VLBI agree with those measured by
classical astrometry.

ON Yes, but in quantum theory when you do a classical measurement the
ON wave function collapses. There is a discontinuity in the
ON description of motion at the time of measurement. I am also
ON expecting a discontinuity in VLBI measurements when carried out
ON over a sufficient time that classical astronometry becomes
ON possible. Whether the apparent discontinuity in motion of IM
ON Pegasi is an instance of that, I would not like to say.

You'll have to define your terms quantitatively. Brisken et
al. (2003, AJ, 126, 3090) report observations of pulsars over a
minimum time baseline of 7 years. At least one pulsar (B1237+25)
has a proper motion in excess of 0.1 arcsec/year; over the course
of their observations it moved a distance of about 0.8 arcseconds.

Does 7 years and 0.8 arcseconds qualify as sufficient for
"classical" astrometry? If not, what does?

ON Of course it does, but this is another change of subject. Pulsars
ON are a high velocity star population and of little value or
ON relevance in measurements the orbital motion of the galaxy.

I'll restate my question: You'll have to define your terms
quantitatively. Astrometry at radio wavelengths using interferometers
has been done over the angular and time scales of "classical"
astrometry.

That is not a question, and I cannot see what it is intended to imply,
or why you think it relevant to anything I have said. The proper motion
of pulsars does not have a bearing on the rotation rate of the galaxy.

Perhaps you should re-read the thread, which is all conveniently
preserved in quoted text above. Joseph's final sentence is the key
one. You have asserted that there should be a difference between the
results of positional measurements using interferometry and those
using classical techniques `when carried out over a sufficient time
that classical astronometry becomes possible'. Such experiments have
in fact been done, so you now need to make a quantitative prediction
of what discrepancy you expect to see between the results, so that we
can test it against observation.

Martin
--
Martin Hardcastle
School of Physics, Astronomy and Mathematics, University of Hertfordshire, UK
Please replace the xxx.xxx.xxx in the header with herts.ac.uk to mail me

Oh No wrote:
Thus spake Kent Paul Dolan

Oh No wrote:

Thus spake Joseph Lazio

Does 7 years and 0.8 arcseconds qualify as
sufficient for "classical" astrometry? If not,
what does?

Of course it does, but this is another change of
subject. Pulsars are a high velocity star
population and of little value or relevance in
measurements the orbital motion of the galaxy.

Huh? Many pulsars are still part of the binary
partner stars with which they began their existence.

There is no reason to believe that such stars would
have motions different in kind from the rest of
stars in the the galaxy with which they rotate.


I am not suggesting that they do, excepting in so far as that they are a
high velocity population. We do not determine the orbital motion of the
galaxy from such stars. We do determine it from globular clusters, from
open clusters, and now from VLBI measurements on SgrA*, with,
incidentally, inconsistent results.


As a matter of fact people have found plenty of millisecond pulsars in
globular clusters.

Ulf Torkelsson

Thus spake Kent Paul Dolan
Oh No wrote:

excepting in so far as that [pulsars] are a
high velocity population.

Once again you are talking rot.

Who is? Once again you have made your
unsubstantiated dismissive claim that pulsars are a
"high velocity population", which makes exactly zero
sense.

Once again you are writing in complete ignorance. If you refer to first
paragraph of the paper under discussion, Brisken et al. (2003, AJ, 126,
3090) you will read the first sentence

"Radio pulsars are a high-velocity stellar population, with
typical speeds of hundreds of kilometers per second,"

Or do you know so much more than those who have studied them?


When you dismiss such obvious tools for checking
your theories because you find the facts about them
inconvenient (say, denying your theories), you are
playing fast and loose with intellectual dishonesty.

When you make such claims you are being quite dishonest yourself. Given
errors in distance meausurements of pulsars in the order of 40%, they
are not a population which could lead to any useful results.

[Mod. note: that's enough accusations of dishonesty, on both sides,
please -- mjh]

Regards

--
Charles Francis
moderator sci.physics.foundations.
substitute charles for NotI to email

Thus spake Ulf Torkelsson
Oh No wrote:


As a matter of fact people have found plenty of millisecond pulsars in
globular clusters.


I have started to gather data on globular clusters, but at the moment I
have not found a test which could differentiate between the models.


Regards

--
Charles Francis
moderator sci.physics.foundations.
substitute charles for NotI to email

Thus spake Martin Hardcastle
In article ,
Oh No wrote:

The point is here that we have an entirely different way of measuring
v/r. It agrees far better with the standard model than it does with
your model. You need to explain that agreement if you want your model
to be taken seriously. To do that you will need to understand the way
the observations are made.

This is true. I accept that my understanding of VLBI has been incorrect
and appreciate your help. Having done quite a few searches I had found
only material which gives far too much detail of the engineering or
fails to explain the principle behind what is going on. I would
appreciate any pointers which would help. If my understanding is now
correct, then it would appear that the centre of the galaxy must be
rather nearer than current estimates. I know there is some uncertainty
in this distance, but it appears then that my attention should be on
quantifying that. Again, any pointers in the right direction would be
appreciated. I think there is a reference in the Reid paper you
mentioned, but I will probably need more than one.



Regards

--
Charles Francis
moderator sci.physics.foundations.
substitute charles for NotI to email

Thus spake Martin Hardcastle
Perhaps you should re-read the thread, which is all conveniently
preserved in quoted text above. Joseph's final sentence is the key one.
You have asserted that there should be a difference between the results
of positional measurements using interferometry and those using
classical techniques `when carried out over a sufficient time that
classical astronometry becomes possible'. Such experiments have in fact
been done, so you now need to make a quantitative prediction of what
discrepancy you expect to see between the results, so that we can test
it against observation.


I perceive that there was an ambiguity in what I had said. I had meant
to express the opposite. When classical measurement is possible I expect
the quantum wave function to collapse and for the classical result to be
restored.

Regards

--
Charles Francis
moderator sci.physics.foundations.
substitute charles for NotI to email

Thus spake Oh No
Thus spake Martin Hardcastle
In article ,
Oh No wrote:

The point is here that we have an entirely different way of measuring
v/r. It agrees far better with the standard model than it does with
your model. You need to explain that agreement if you want your model
to be taken seriously. To do that you will need to understand the way
the observations are made.

This is true. I accept that my understanding of VLBI has been incorrect
and appreciate your help. Having done quite a few searches I had found
only material which gives far too much detail of the engineering or
fails to explain the principle behind what is going on. I would
appreciate any pointers which would help. If my understanding is now
correct, then it would appear that the centre of the galaxy must be
rather nearer than current estimates. I know there is some uncertainty
in this distance, but it appears then that my attention should be on
quantifying that. Again, any pointers in the right direction would be
appreciated. I think there is a reference in the Reid paper you
mentioned, but I will probably need more than one.


The 1993 paper by Reid is interesting. He outline the gamut of methods
of determining distance of Sgr A*. Armando Caussade gives a more recent
web based report citing this paper at

http://www.armandocaussade.com/astro...ic_center.html

RRLyrae, and magnitude methods: There are various methods based on
magnitude, the most important probably being RR Lyrae. While various
estimates in the region of 8kpc have been made, they appear to be based
on controversial assumptions about the magnitude of RR Lyrae. In fact it
is stated that an importance of a measurement of the distance to SgrA*
as that it would enable use to better calibrate the RR Lyrae scale, not
the other way about.

Masers: This method is considered one of the best available, but it is
dependant on knowledge of the radial velocity of the maser sources in
order to calibrate the transverse velocity, from which distance may be
calculated from an accurate measurement of proper motion. As a result,
if the radial velocity measured from Doppler is overstated, then the
distance will also be overstated by the same proportion.

Globular Clusters: One attempts to measure the distances to globular
clusters (itself not hugely accurate) and assumes that globular clusters
have a uniform mass distribution about the centre of the galaxy. A broad
distribution of distance estimates has been produced, from 6.2 +-0.9 to
10.1+-0.7. As I understand the inherent error in distance measurements
of globular clusters is 25%, and the favoured figure of R0~7 is almost
as close the figure I need, of just under 6kpc as it is to the more
accepted result, R0=8. This method is then indecisive.

Trigonometric parallax.
Although Caussade says that Reid has measured this, no parallax error is
stated and Reid makes no reference to it in his paper. Nor can I find
any other paper referring to such a measurement.

Keplerian orbits: Unfortunately to determine the Keplerian orbit we need
to know both the radial and the transverse velocities. The method would
have to be completely reworked if there is a systematic error in radial
velocity, and will give a different result.


In conclusion it seems that the best method we have for determining the
distance to SgrA* is from H20 masers, and that this method is dependant
on the effect which I have found in local stars. If the overstatement of
radial velocity is correct, then SgrA* is indeed correspondingly much
closer than we have thought.

Regards

--
Charles Francis
moderator sci.physics.foundations.
substitute charles for NotI to email

In conclusion it seems that the best method we have for determining the
distance to SgrA* is from H20 masers, and that this method is dependant
on the effect which I have found in local stars. If the overstatement of
radial velocity is correct, then SgrA* is indeed correspondingly much
closer than we have thought.

I suggest that you read some of the recent papers
describing the center of the Milky Way. A good place
to start would be the proceedings of a conference called

GALACTIC CENTER WORKSHOP 2006-FROM THE CENTER OF THE MILKY WAY TO
NEARBY LOW-LUMINOSITY GALACTIC NUCLEI
18-22 April 2006, Bad Honnef, Germany

Many (all?) of the papers are freely available on-line,
either directly

http://www.iop.org/EJ/toc/1742-6596/54/1

or indirectly, via astro-ph.

Have fun.

Thus spake Stupendous_Man
In conclusion it seems that the best method we have for determining the
distance to SgrA* is from H20 masers, and that this method is dependant
on the effect which I have found in local stars. If the overstatement of
radial velocity is correct, then SgrA* is indeed correspondingly much
closer than we have thought.

I suggest that you read some of the recent papers
describing the center of the Milky Way. A good place
to start would be the proceedings of a conference called

GALACTIC CENTER WORKSHOP 2006-FROM THE CENTER OF THE MILKY WAY TO
NEARBY LOW-LUMINOSITY GALACTIC NUCLEI
18-22 April 2006, Bad Honnef, Germany

Many (all?) of the papers are freely available on-line,
either directly

http://www.iop.org/EJ/toc/1742-6596/54/1

or indirectly, via astro-ph.

Have fun.


Thanks, will do.

Regards

--
Charles Francis
moderator sci.physics.foundations.
substitute charles for NotI to email

"KPD" == Kent Paul Dolan writes:

KPD Oh No wrote:
Thus spake Joseph Lazio

Does 7 years and 0.8 arcseconds qualify as sufficient for
"classical" astrometry? If not, what does?

Of course it does, but this is another change of subject. Pulsars
are a high velocity star population and of little value or
relevance in measurements the orbital motion of the galaxy.

KPD Huh? Many pulsars are still part of the binary partner stars with
KPD which they began their existence.

Uhh, no. There is a subset, millisecond or recycled pulsars, that
tend to be binary. As a whole, though, the population consists of
isolated objects.

KPD There is no reason to believe that such stars would have motions
KPD different in kind from the rest of stars in the the galaxy with
KPD which they rotate.

Yes, there is. The average velocity of pulsars is something like 450
km/s. (Ref: D. Lorimer has done a lot of work on this topic.) That
means that most of them have velocities well in excess of the typical
star, and a good fraction of pulsars are not bound to the Galaxy.

Having said that, one can still use pulsars to probe the structure of
the Galaxy.

KPD Moreover, pulsars are excellent tools for exactly the kind of
KPD measurements you're attempting to evaluate: [...]

No disagreement on the rest of the post.

--
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