Black hole mass-sigma correlation

In article , Ulf Torkelsson
wrote:

My worry is that Newtonian 1/r forces are very special mathematically,
making formulas line up very nicely, making angular momentum around
different points independent. GR has some compensations thrown in, so it
could be that one has to take the interactions of the different components
into account in order to get better GR correction.

The order of magnitude estimate that I was using is based on GR.

Sure, that was clear from your posts.

There
are no gravitational waves in Newtonian gravity theory.

And this is, of course the reason one wants to put in GR corrections.

Apart from
that the differences between GR and Newtonian physics is small as long
as GM/(c^2 r) is small.

What might make a difference in the magnitude of this smallness is that it
may behave differently when just considering say two point masses, or a
large distribution of mass where individual components may emit
gravitational waves by mutual GR interaction (not just against the center
mass). In picture, this difference might be like the difference between
planets and a gas, with GR influences replacing gas hydrodynamic forces.

If the paper you quoted with the rough GR estimate does not do that latter
thing, integrating over the GR corrections, then that might be one thing
to look up before writing off GR influences as wholly negligible. --
Especially, if there is someone out there doing observations that might
suggest that the Milky Way black hole feeding rate is in fact higher than
explainable by the suggested the black hole mass-sigma correlation model,
the latter which only derives from Newtonian physics.

The most important thing, though, would be to pin down the feeding rate of
the Milky Way black hole. But if it eventually turns out to be higher than
earlier research suggested, and you are positively sure that there is an
estimate that once and for all rules out all GR effects, what should cause
it? -- The alternative explanation (to that of GR waves) would be that
there is some gas that for some reason is loosing its angular momentum.

Hans Aberg

Hans Aberg wrote:



If the paper you quoted with the rough GR estimate does not do that latter
thing, integrating over the GR corrections, then that might be one thing
to look up before writing off GR influences as wholly negligible. --


Hardly, it is my experience that if an effect does not work out at
the level of order-of-magnitude estimates, then there is no way that
it can work. On the other hand an effect that does work based on an
order-of-magnitude estimate may turn out to not work after a more
careful analysis because there may be terms that are cancelling each
other.

Especially, if there is someone out there doing observations that might
suggest that the Milky Way black hole feeding rate is in fact higher than
explainable by the suggested the black hole mass-sigma correlation model,
the latter which only derives from Newtonian physics.


The correlation between the black hole mass and the velocity spread
in elliptical galaxies and the bulges of disc galaxies does not say
anything about the present accretion rate onto the black hole. Based
on other sets of observational data we do expect the accretion to be
episodic and overall the accretion rates are expected to be larger
when the galaxies are young. The reason for this is that with a high
accretion rate the black hole is luminous and the galaxy will appear
as an active galaxy or even a quasar. The observations clearly show
that quasars were much more common at a redshift of 2 to 3 than they
are today, which has been interpreted as that the galaxies went
through an early phase of rapid accretion, and then settled down in
more quiet lifes.


The most important thing, though, would be to pin down the feeding rate of
the Milky Way black hole. But if it eventually turns out to be higher than
earlier research suggested, and you are positively sure that there is an
estimate that once and for all rules out all GR effects, what should cause
it? -- The alternative explanation (to that of GR waves) would be that
there is some gas that for some reason is loosing its angular momentum.


There is definitely gas in the center of the galaxy. We also do see
that there is plenty of star formation close to the galactic center.
Some of this gas may lose sufficient angular momentum through
magnetohydrodynamic processes to accrete onto the black hole, and in
that process the center will become more luminous for a while.

Ulf Torkelsson

[Mod. note: reformatted -- mjh.]

Hans Aberg wrote:



If the paper you quoted with the rough GR estimate does not do that latter
thing, integrating over the GR corrections, then that might be one thing
to look up before writing off GR influences as wholly negligible. --


Hardly, it is my experience that if an effect does not work out at
the level of order-of-magnitude estimates, then there is no way that
it can work. On the other hand an effect that does work based on an
order-of-magnitude estimate may turn out to not work after a more
careful analysis because there may be terms that are cancelling each
other.

Especially, if there is someone out there doing observations that might
suggest that the Milky Way black hole feeding rate is in fact higher than
explainable by the suggested the black hole mass-sigma correlation model,
the latter which only derives from Newtonian physics.


The correlation between the black hole mass and the velocity spread
in elliptical galaxies and the bulges of disc galaxies does not say
anything about the present accretion rate onto the black hole. Based
on other sets of observational data we do expect the accretion to be
episodic and overall the accretion rates are expected to be larger
when the galaxies are young. The reason for this is that with a high
accretion rate the black hole is luminous and the galaxy will appear
as an active galaxy or even a quasar. The observations clearly show
that quasars were much more common at a redshift of 2 to 3 than they
are today, which has been interpreted as that the galaxies went
through an early phase of rapid accretion, and then settled down in
more quiet lifes.


The most important thing, though, would be to pin down the feeding rate of
the Milky Way black hole. But if it eventually turns out to be higher than
earlier research suggested, and you are positively sure that there is an
estimate that once and for all rules out all GR effects, what should cause
it? -- The alternative explanation (to that of GR waves) would be that
there is some gas that for some reason is loosing its angular momentum.


There is definitely gas in the center of the galaxy. We also do see
that there is plenty of star formation close to the galactic center.
Some of this gas may lose sufficient angular momentum through
magnetohydrodynamic processes to accrete onto the black hole, and in
that process the center will become more luminous for a while.

Ulf Torkelsson

[Mod. note: reformatted -- mjh.]

In article , Ulf Torkelsson
wrote:

If the paper you quoted with the rough GR estimate does not do that latter
thing, integrating over the GR corrections, then that might be one thing
to look up before writing off GR influences as wholly negligible. --

Hardly, it is my experience that if an effect does not work out at
the level of order-of-magnitude estimates, then there is no way that
it can work. On the other hand an effect that does work based on an
order-of-magnitude estimate may turn out to not work after a more
careful analysis because there may be terms that are cancelling each
other.

So suppose, in a thought-experiment setup, you have a galaxy consisting
entirely of binary stars with a black hole at the center.

Then you say that the GR gravitational waves that these binary stars emit
do not at all affect the angular momentum they have around the black hole?
But rather, these gravitational waves may cancel, making their loss of
angular momentum around the center become larger than the
order-of-magnitude level?

Especially, if there is someone out there doing observations that might
suggest that the Milky Way black hole feeding rate is in fact higher than
explainable by the suggested the black hole mass-sigma correlation model,
the latter which only derives from Newtonian physics.

The correlation between the black hole mass and the velocity spread
in elliptical galaxies and the bulges of disc galaxies does not say
anything about the present accretion rate onto the black hole.

According to the suggested model, I gather.

Based
on other sets of observational data we do expect the accretion to be
episodic and overall the accretion rates are expected to be larger
when the galaxies are young. The reason for this is that with a high
accretion rate the black hole is luminous and the galaxy will appear
as an active galaxy or even a quasar. The observations clearly show
that quasars were much more common at a redshift of 2 to 3 than they
are today, which has been interpreted as that the galaxies went
through an early phase of rapid accretion, and then settled down in
more quiet lifes.

This suggested explanation of what quasars are and black hole evolution
was also mentioned in the BBC program, though with less explanatory
detail.

There is definitely gas in the center of the galaxy. We also do see
that there is plenty of star formation close to the galactic center.
Some of this gas may lose sufficient angular momentum through
magnetohydrodynamic processes to accrete onto the black hole, and in
that process the center will become more luminous for a while.

Where would this galaxy center gas come from, if the suggested black hole
mass-sigma correlation model predicts that most of the center gas would be
eaten by the center black hole in the early stages of the galaxy
formation, and GR effects are excluded as explanation of getting more gas
into the center? That is, under the assumption that this observed amount
of gas and black hole feeding rate exceed the amount of the black hole
mass-sigma correlation model predictions.

Hans Aberg

In article , Ulf Torkelsson
wrote:

If the paper you quoted with the rough GR estimate does not do that latter
thing, integrating over the GR corrections, then that might be one thing
to look up before writing off GR influences as wholly negligible. --

Hardly, it is my experience that if an effect does not work out at
the level of order-of-magnitude estimates, then there is no way that
it can work. On the other hand an effect that does work based on an
order-of-magnitude estimate may turn out to not work after a more
careful analysis because there may be terms that are cancelling each
other.

So suppose, in a thought-experiment setup, you have a galaxy consisting
entirely of binary stars with a black hole at the center.

Then you say that the GR gravitational waves that these binary stars emit
do not at all affect the angular momentum they have around the black hole?
But rather, these gravitational waves may cancel, making their loss of
angular momentum around the center become larger than the
order-of-magnitude level?

Especially, if there is someone out there doing observations that might
suggest that the Milky Way black hole feeding rate is in fact higher than
explainable by the suggested the black hole mass-sigma correlation model,
the latter which only derives from Newtonian physics.

The correlation between the black hole mass and the velocity spread
in elliptical galaxies and the bulges of disc galaxies does not say
anything about the present accretion rate onto the black hole.

According to the suggested model, I gather.

Based
on other sets of observational data we do expect the accretion to be
episodic and overall the accretion rates are expected to be larger
when the galaxies are young. The reason for this is that with a high
accretion rate the black hole is luminous and the galaxy will appear
as an active galaxy or even a quasar. The observations clearly show
that quasars were much more common at a redshift of 2 to 3 than they
are today, which has been interpreted as that the galaxies went
through an early phase of rapid accretion, and then settled down in
more quiet lifes.

This suggested explanation of what quasars are and black hole evolution
was also mentioned in the BBC program, though with less explanatory
detail.

There is definitely gas in the center of the galaxy. We also do see
that there is plenty of star formation close to the galactic center.
Some of this gas may lose sufficient angular momentum through
magnetohydrodynamic processes to accrete onto the black hole, and in
that process the center will become more luminous for a while.

Where would this galaxy center gas come from, if the suggested black hole
mass-sigma correlation model predicts that most of the center gas would be
eaten by the center black hole in the early stages of the galaxy
formation, and GR effects are excluded as explanation of getting more gas
into the center? That is, under the assumption that this observed amount
of gas and black hole feeding rate exceed the amount of the black hole
mass-sigma correlation model predictions.

Hans Aberg

Hans Aberg wrote:

In article , Ulf Torkelsson
wrote:


So suppose, in a thought-experiment setup, you have a galaxy consisting
entirely of binary stars with a black hole at the center.

Then you say that the GR gravitational waves that these binary stars emit
do not at all affect the angular momentum they have around the black hole?


Not to a significant extent. On the other hand if we are speaking
about close binaries, which some of them will be, then the emission of
the gravitational waves will affect the angular momentum the two stars
have relative to their common center of mass.

But rather, these gravitational waves may cancel, making their loss of
angular momentum around the center become larger than the
order-of-magnitude level?


Quite frankly, I do not at all understand the above sentence.
Firstly the individual binaries should be completely uncorrelated to
each other, so you have to set up the systems in a *very* special way
to get the effect you suggest. Secondly the emission of gravitational
waves is much more important for the evolution of the individual
binaries, that is the shrinkage of the distance between the two stars,
than it is for the evolution of the orbits of the binaries around the
galaxy. Thirdly, if the gravitational waves cancel that should mean
less loss of angular momentum.

Now, there is another effect, which is important in the evolution of
globular clusters, and that is that near encounters between stars, in
particular encounters between binaries and single stars can lead to a
re-distribution of the angular momentum in the cluster, such that the
heavy stars will gather at the center of the cluster, and lighter
stars may even be completely thrown out of the system. This, though,
follows from nothing more than Newtonian mechanics, and thus not work
for ordinary galaxies, since the distances inbetween the stars are too
large then.



The correlation between the black hole mass and the velocity spread
in elliptical galaxies and the bulges of disc galaxies does not say
anything about the present accretion rate onto the black hole.



According to the suggested model, I gather.


No, because all the observations say is that there is a correlation
between the velocity spread and the black hole mass. To the best of my
knowledge no significant difference has been found between active and
non-active galaxies.




Based
on other sets of observational data we do expect the accretion to be
episodic and overall the accretion rates are expected to be larger
when the galaxies are young. The reason for this is that with a high
accretion rate the black hole is luminous and the galaxy will appear
as an active galaxy or even a quasar. The observations clearly show
that quasars were much more common at a redshift of 2 to 3 than they
are today, which has been interpreted as that the galaxies went
through an early phase of rapid accretion, and then settled down in
more quiet lifes.



This suggested explanation of what quasars are and black hole evolution
was also mentioned in the BBC program, though with less explanatory
detail.


With all due respect to BBC, I would not use them as a substitute
for the professional scientific literature. May I suggest that you do
a search in ADS using a few simple words such as "quasar", "evolution"
and "black hole" for instance.




There is definitely gas in the center of the galaxy. We also do see
that there is plenty of star formation close to the galactic center.
Some of this gas may lose sufficient angular momentum through
magnetohydrodynamic processes to accrete onto the black hole, and in
that process the center will become more luminous for a while.



Where would this galaxy center gas come from, if the suggested black hole
mass-sigma correlation model predicts that most of the center gas would be
eaten by the center black hole in the early stages of the galaxy
formation, and GR effects are excluded as explanation of getting more gas
into the center?


I think we discussed this a couple of weeks ago already. The answer
is that there is a continuous inflow of gas through the galactic disc
to the central region because processes in the disc, such as the
spiral arms, are constantly transporting angular momentum outwards,
and as a result of this matter must stream inwards. There is no need
for gravitational waves or any other GR effect (which anyway is to
weak by many-orders-of-magnitude), but it is rather a question of
hydrodynamic, or possibly magnetohydrodynamic, processes.

Ulf Torkelsson

Hans Aberg wrote:

In article , Ulf Torkelsson
wrote:


So suppose, in a thought-experiment setup, you have a galaxy consisting
entirely of binary stars with a black hole at the center.

Then you say that the GR gravitational waves that these binary stars emit
do not at all affect the angular momentum they have around the black hole?


Not to a significant extent. On the other hand if we are speaking
about close binaries, which some of them will be, then the emission of
the gravitational waves will affect the angular momentum the two stars
have relative to their common center of mass.

But rather, these gravitational waves may cancel, making their loss of
angular momentum around the center become larger than the
order-of-magnitude level?


Quite frankly, I do not at all understand the above sentence.
Firstly the individual binaries should be completely uncorrelated to
each other, so you have to set up the systems in a *very* special way
to get the effect you suggest. Secondly the emission of gravitational
waves is much more important for the evolution of the individual
binaries, that is the shrinkage of the distance between the two stars,
than it is for the evolution of the orbits of the binaries around the
galaxy. Thirdly, if the gravitational waves cancel that should mean
less loss of angular momentum.

Now, there is another effect, which is important in the evolution of
globular clusters, and that is that near encounters between stars, in
particular encounters between binaries and single stars can lead to a
re-distribution of the angular momentum in the cluster, such that the
heavy stars will gather at the center of the cluster, and lighter
stars may even be completely thrown out of the system. This, though,
follows from nothing more than Newtonian mechanics, and thus not work
for ordinary galaxies, since the distances inbetween the stars are too
large then.



The correlation between the black hole mass and the velocity spread
in elliptical galaxies and the bulges of disc galaxies does not say
anything about the present accretion rate onto the black hole.



According to the suggested model, I gather.


No, because all the observations say is that there is a correlation
between the velocity spread and the black hole mass. To the best of my
knowledge no significant difference has been found between active and
non-active galaxies.




Based
on other sets of observational data we do expect the accretion to be
episodic and overall the accretion rates are expected to be larger
when the galaxies are young. The reason for this is that with a high
accretion rate the black hole is luminous and the galaxy will appear
as an active galaxy or even a quasar. The observations clearly show
that quasars were much more common at a redshift of 2 to 3 than they
are today, which has been interpreted as that the galaxies went
through an early phase of rapid accretion, and then settled down in
more quiet lifes.



This suggested explanation of what quasars are and black hole evolution
was also mentioned in the BBC program, though with less explanatory
detail.


With all due respect to BBC, I would not use them as a substitute
for the professional scientific literature. May I suggest that you do
a search in ADS using a few simple words such as "quasar", "evolution"
and "black hole" for instance.




There is definitely gas in the center of the galaxy. We also do see
that there is plenty of star formation close to the galactic center.
Some of this gas may lose sufficient angular momentum through
magnetohydrodynamic processes to accrete onto the black hole, and in
that process the center will become more luminous for a while.



Where would this galaxy center gas come from, if the suggested black hole
mass-sigma correlation model predicts that most of the center gas would be
eaten by the center black hole in the early stages of the galaxy
formation, and GR effects are excluded as explanation of getting more gas
into the center?


I think we discussed this a couple of weeks ago already. The answer
is that there is a continuous inflow of gas through the galactic disc
to the central region because processes in the disc, such as the
spiral arms, are constantly transporting angular momentum outwards,
and as a result of this matter must stream inwards. There is no need
for gravitational waves or any other GR effect (which anyway is to
weak by many-orders-of-magnitude), but it is rather a question of
hydrodynamic, or possibly magnetohydrodynamic, processes.

Ulf Torkelsson

In article , Ulf Torkelsson
wrote:

But rather, these gravitational waves may cancel, making their loss of
angular momentum around the center become larger than the
order-of-magnitude level?

Quite frankly, I do not at all understand the above sentence.

It was asking for clarification of your second sentence:

Hardly, it is my experience that if an effect does not work out at
the level of order-of-magnitude estimates, then there is no way that
it can work. On the other hand an effect that does work based on an
order-of-magnitude estimate may turn out to not work after a more
careful analysis because there may be terms that are cancelling each
other.

This second sentence suggests that order-of-magnitude estimates will give
a faster loss of angular momentum than a more careful analysis will, due
to cancellations of terms rather than them adding up.

Now, there is another effect, which is important in the evolution of
globular clusters, and that is that near encounters between stars, in
particular encounters between binaries and single stars can lead to a
re-distribution of the angular momentum in the cluster, such that the
heavy stars will gather at the center of the cluster, and lighter
stars may even be completely thrown out of the system. This, though,
follows from nothing more than Newtonian mechanics, and thus not work
for ordinary galaxies, since the distances inbetween the stars are too
large then.

How disappointing that GR effects are so supposedly weak in term of galaxy
evolution. :-)

This suggested explanation of what quasars are and black hole evolution
was also mentioned in the BBC program, though with less explanatory
detail.


With all due respect to BBC, I would not use them as a substitute
for the professional scientific literature. May I suggest that you do
a search in ADS

Sorry, I do not know what ADS is.

using a few simple words such as "quasar", "evolution"
and "black hole" for instance.

The program itself consisted of the researchers involved in the work
explaining it themselves, which I guess ought to have some credibility.

The next step might be to inquire in mailing lists and newsgroups, like
this one, where those professionals that so wish can reply.

The next step to that might be to sit down with the professional
scientific literature in the field, especially if one aims at writing
papers within the field oneself. However, I do not have any such ambitions
in the field of astronomy, but merely want to have some general intuitions
communicated to me.

I was once, a decade ago, briefly interested in the GRQM question, as it
is mathematically intriguing to combine GR and QM, and in the process
perhaps also give GR a unified matter model. If one should have any chance
to fairly directly verify any such model, that seems be to correlate it
directly with what is going on at the black hole event horizon. My vague
memory of the Hawking black hole radiation paper is that suggestion does
not actually try to combine GR and QM to a single unified theory and
extract the result from that, but merely assumes a sharp classical GR
event horizon and extracts the effects from particle pairs inside and
outside that sharp event horizon boundary.

It is not so difficult to create candidates for a GRQM theory aiming at a
GR Schrodinger equation. For example, take the Lorentzian cotangent bundle
as a one particle model, and generate from that a Fock space for the
n-particle model, with QM states (= statistical waves) the cotangent
fields of that 4(n+1) dimensional manifold. Impose conditions creating a
timespace-energymomentum connection. Extract QM field equations and the
generalization of Einstein's GR equation from suitable metric and other
variations of a suitably cooked up Lagrangian.

Sounds so easy in theory, but is pretty hard in practise.

Where would this galaxy center gas come from, if the suggested black hole
mass-sigma correlation model predicts that most of the center gas would be
eaten by the center black hole in the early stages of the galaxy
formation, and GR effects are excluded as explanation of getting more gas
into the center?

I think we discussed this a couple of weeks ago already.

Nope. Related topics maybe.

The answer
is that there is a continuous inflow of gas through the galactic disc
to the central region because processes in the disc, such as the
spiral arms, are constantly transporting angular momentum outwards,
and as a result of this matter must stream inwards. There is no need
for gravitational waves or any other GR effect (which anyway is to
weak by many-orders-of-magnitude), but it is rather a question of
hydrodynamic, or possibly magnetohydrodynamic, processes.

OK. But if there is not sufficiently strong GR effects, your explanations
seem to suggest that by Newtonian physics, if some matter flows inwards
towards the black hole, other matter must on the expense of that flow
outwards, picking up the angular momentum of the matter flowing into the
black hole. It would mean that a general galaxy evolutionary model where
all matter in the galaxy in succession falls into the black hole is
impossible. Unless the galaxy sucks up matter from the environment without
it. But then galaxies should always grow with age, and never diminish in
size.

Thank you for your inputs.

Hans Aberg

In article , Ulf Torkelsson
wrote:

But rather, these gravitational waves may cancel, making their loss of
angular momentum around the center become larger than the
order-of-magnitude level?

Quite frankly, I do not at all understand the above sentence.

It was asking for clarification of your second sentence:

Hardly, it is my experience that if an effect does not work out at
the level of order-of-magnitude estimates, then there is no way that
it can work. On the other hand an effect that does work based on an
order-of-magnitude estimate may turn out to not work after a more
careful analysis because there may be terms that are cancelling each
other.

This second sentence suggests that order-of-magnitude estimates will give
a faster loss of angular momentum than a more careful analysis will, due
to cancellations of terms rather than them adding up.

Now, there is another effect, which is important in the evolution of
globular clusters, and that is that near encounters between stars, in
particular encounters between binaries and single stars can lead to a
re-distribution of the angular momentum in the cluster, such that the
heavy stars will gather at the center of the cluster, and lighter
stars may even be completely thrown out of the system. This, though,
follows from nothing more than Newtonian mechanics, and thus not work
for ordinary galaxies, since the distances inbetween the stars are too
large then.

How disappointing that GR effects are so supposedly weak in term of galaxy
evolution. :-)

This suggested explanation of what quasars are and black hole evolution
was also mentioned in the BBC program, though with less explanatory
detail.


With all due respect to BBC, I would not use them as a substitute
for the professional scientific literature. May I suggest that you do
a search in ADS

Sorry, I do not know what ADS is.

using a few simple words such as "quasar", "evolution"
and "black hole" for instance.

The program itself consisted of the researchers involved in the work
explaining it themselves, which I guess ought to have some credibility.

The next step might be to inquire in mailing lists and newsgroups, like
this one, where those professionals that so wish can reply.

The next step to that might be to sit down with the professional
scientific literature in the field, especially if one aims at writing
papers within the field oneself. However, I do not have any such ambitions
in the field of astronomy, but merely want to have some general intuitions
communicated to me.

I was once, a decade ago, briefly interested in the GRQM question, as it
is mathematically intriguing to combine GR and QM, and in the process
perhaps also give GR a unified matter model. If one should have any chance
to fairly directly verify any such model, that seems be to correlate it
directly with what is going on at the black hole event horizon. My vague
memory of the Hawking black hole radiation paper is that suggestion does
not actually try to combine GR and QM to a single unified theory and
extract the result from that, but merely assumes a sharp classical GR
event horizon and extracts the effects from particle pairs inside and
outside that sharp event horizon boundary.

It is not so difficult to create candidates for a GRQM theory aiming at a
GR Schrodinger equation. For example, take the Lorentzian cotangent bundle
as a one particle model, and generate from that a Fock space for the
n-particle model, with QM states (= statistical waves) the cotangent
fields of that 4(n+1) dimensional manifold. Impose conditions creating a
timespace-energymomentum connection. Extract QM field equations and the
generalization of Einstein's GR equation from suitable metric and other
variations of a suitably cooked up Lagrangian.

Sounds so easy in theory, but is pretty hard in practise.

Where would this galaxy center gas come from, if the suggested black hole
mass-sigma correlation model predicts that most of the center gas would be
eaten by the center black hole in the early stages of the galaxy
formation, and GR effects are excluded as explanation of getting more gas
into the center?

I think we discussed this a couple of weeks ago already.

Nope. Related topics maybe.

The answer
is that there is a continuous inflow of gas through the galactic disc
to the central region because processes in the disc, such as the
spiral arms, are constantly transporting angular momentum outwards,
and as a result of this matter must stream inwards. There is no need
for gravitational waves or any other GR effect (which anyway is to
weak by many-orders-of-magnitude), but it is rather a question of
hydrodynamic, or possibly magnetohydrodynamic, processes.

OK. But if there is not sufficiently strong GR effects, your explanations
seem to suggest that by Newtonian physics, if some matter flows inwards
towards the black hole, other matter must on the expense of that flow
outwards, picking up the angular momentum of the matter flowing into the
black hole. It would mean that a general galaxy evolutionary model where
all matter in the galaxy in succession falls into the black hole is
impossible. Unless the galaxy sucks up matter from the environment without
it. But then galaxies should always grow with age, and never diminish in
size.

Thank you for your inputs.

Hans Aberg

Hans Aberg wrote:

In article , Ulf Torkelsson
wrote:
It was asking for clarification of your second sentence:

Hardly, it is my experience that if an effect does not work out at
the level of order-of-magnitude estimates, then there is no way that
it can work. On the other hand an effect that does work based on an
order-of-magnitude estimate may turn out to not work after a more
careful analysis because there may be terms that are cancelling each
other.



This second sentence suggests that order-of-magnitude estimates will give
a faster loss of angular momentum than a more careful analysis will, due
to cancellations of terms rather than them adding up.


Yes, what I was trying to say is that a detailed analysis will not
give you as a result a significantly higher rate of loss of angular
momentum than you get from the simple order-of-magnitude estimate, but
there is a chance that a careful analysis may reveal a reason why the
loss of angular momentum must be much lower than the
order-of-magnitude estimate suggests.




Now, there is another effect, which is important in the evolution of
globular clusters, and that is that near encounters between stars, in
particular encounters between binaries and single stars can lead to a
re-distribution of the angular momentum in the cluster, such that the
heavy stars will gather at the center of the cluster, and lighter
stars may even be completely thrown out of the system. This, though,
follows from nothing more than Newtonian mechanics, and thus not work
for ordinary galaxies, since the distances inbetween the stars are too
large then.



How disappointing that GR effects are so supposedly weak in term of galaxy
evolution. :-)


One may also take the point of view that it is amazing how rich and
complicated results one can get from classical physics.

Another point of view is that since the parameter GM/(c^2 r) is a
good indicator of when general relativity becomes important, we see
that there are two regimes in which general relativity can be studied
without resorting to extremely high precision measurements. The one
regime is the physics of compact objects, such as neutron stars and
black holes, in which r is small, and the other regime is cosmology,
where r is large, but M grows as r^3 and therefore the ratio will not
be small. Galaxies as well as the world we live on exist right in
between where the distances are large enough and the masses small
enough that Newtonian physics is good enough.

This suggested explanation of what quasars are and black hole evolution
was also mentioned in the BBC program, though with less explanatory
detail.

With all due respect to BBC, I would not use them as a substitute
for the professional scientific literature. May I suggest that you do
a search in ADS



Sorry, I do not know what ADS is.

http://adswww.harvard.edu/

or

http://cdsads.u-strasbg.fr/

for Europeans is a data base containing abstract, and often also
complete articles from almost all of the astronomical literature. If
you want to find first-hand references on anything astronomical this
is the place to look.

The answer
is that there is a continuous inflow of gas through the galactic disc
to the central region because processes in the disc, such as the
spiral arms, are constantly transporting angular momentum outwards,
and as a result of this matter must stream inwards. There is no need
for gravitational waves or any other GR effect (which anyway is to
weak by many-orders-of-magnitude), but it is rather a question of
hydrodynamic, or possibly magnetohydrodynamic, processes.



OK. But if there is not sufficiently strong GR effects, your explanations
seem to suggest that by Newtonian physics, if some matter flows inwards
towards the black hole, other matter must on the expense of that flow
outwards, picking up the angular momentum of the matter flowing into the
black hole. It would mean that a general galaxy evolutionary model where
all matter in the galaxy in succession falls into the black hole is
impossible. Unless the galaxy sucks up matter from the environment without
it. But then galaxies should always grow with age, and never diminish in
size.



Well, this is right, apart from that you only need a small amount of
mass far from the center of mass to absorb all of the angular momentum
that is lost from the inflowing gas. Anyway the gas which is reaching
the galactic center is a small fraction of all of the matter of the
galaxy.

Ulf Torkelsson