Barred galaxies mass distribution

Some spiral galaxies, such as*Andromeda and Milky Way, are barred. So what
is the matter*distribution of such barred galaxies towards the hub,
especially with*respect to dark matter, and what is the common explanation
for this phenomenon? In addition, is there a certain type of galaxies that
tend to be barred, like with respect to size or age?

--
Hans Aberg

On Feb 10, 5:43 am, (Hans Aberg) wrote:
Some spiral galaxies, such as Andromeda and Milky Way, are barred. So what
is the matter distribution of such barred galaxies towards the hub,
especially with respect to dark matter, and what is the common explanation
for this phenomenon? In addition, is there a certain type of galaxies that
tend to be barred, like with respect to size or age?


There are no simple short answers to your questions. The answers
require dedicated study using books and journal literature. For all
the hype about the density wave theory, I am not sure that we really
know that much about spiral galaxies in general, and especially barred
spiral galaxies. Our understanding seems to me to be more descriptive
and heuristic than fundamental.

In 1983 I demonstrated something that I thought was quite interesting:

"A New Model For Barred Spiral Galaxies", Astrophysics and Space
Science, 92(2), 429-432, 1983.

The basic idea is: we know that the disks of spiral galaxies are often
warped. What I showed was that if you observe a warped disk from
certain angles you get quite realistic looking projection effect
"bars", i.e., there is no real bar, just an *apparent* bar. I also
demonstrated that you can get bar-within-ring projection effects in
this way. I thought this was a delightful idea that applied at least
in the case of distant, poorly-resovled galaxies. However the idea was
received with distain by the cognoscenti and silence from everyone
else. So I gave up trying to interest people in it. The computer
modelling I used was extremely primitive by today's standards. It
would be an interesting project to use advanced graphic techniques to
explore the full capability of this idea to reproduce the observed
properties of barred spiral galaxies.

Robert L. Oldershaw

In article ,
" wrote:

In 1983 I demonstrated something that I thought was quite interesting:

"A New Model For Barred Spiral Galaxies", Astrophysics and Space
Science, 92(2), 429-432, 1983.

The basic idea is: we know that the disks of spiral galaxies are often
warped. What I showed was that if you observe a warped disk from
certain angles you get quite realistic looking projection effect
"bars", i.e., there is no real bar, just an *apparent* bar.
......
The computer
modelling I used was extremely primitive by today's standards.

I would surmise that such a theory could easily be decided by todays
standards in observations and computing power. It is an interesting
observation though, that barred galaxies are warped.

The Wikipedia says that the Andromeda and Milky Way galaxies have been
found (more recently) to be barred galaxies. So this seems to go the
opposite way:*galaxies that formerly was thought to be purely spiral, are
now reclassified as barred.

So I assumed this being the case. Since these are among the*largest and
oldest galaxies known, I thought perhaps being barred was somehow related
to those properties. So are there a lot of small, young barred galaxies
out there?

--
Hans Aberg

On Feb 10, 6:03 pm, (Hans Aberg) wrote:

I would surmise that such a theory could easily be decided by todays
standards in observations and computing power. It is an interesting
observation though, that barred galaxies are warped.

The Wikipedia says that the Andromeda and Milky Way galaxies have been
found (more recently) to be barred galaxies. So this seems to go the
opposite way: galaxies that formerly was thought to be purely spiral, are
now reclassified as barred.

So I assumed this being the case. Since these are among the largest and
oldest galaxies known, I thought perhaps being barred was somehow related
to those properties. So are there a lot of small, young barred galaxies
out there?


The MWG and M31 are both warped. M31 is quite disturbed, with an inner
ring at a large angle wrt the general disk plane. Neither galaxy
appears to be strongly barred in the classical sense, but that is
still being worked out.

Galaxies that are overtly barred run the gamut: big, small, old,
young, near, far.

The one thing that correlates with "barredness" is interaction with
other galaxies, and a similar correlation is found for warping.

Robert L. Oldershaw

Thus spake Hans Aberg
Some spiral galaxies, such as
Andromeda and Milky Way, are barred. So what
is the matter=A0distribution of such barred galaxies towards the hub,
especially with=A0respect to dark matter, and what is the common explana=
tion
for this phenomenon? In addition, is there a certain type of galaxies th=
at
tend to be barred, like with respect to size or age?

Neither the bar nor the spiral arms are indicative of a greatly excess
mass distribution. These are the places in a galaxy where gas gathers
and new star formation takes place. The density distribution of older
stars being much more even. In other words the bar and the arms are
brighter, but not much more massive.

In the spiral arm there are younger stars, and therefore also larger and
more luminous stars which burn out and go supernova more quickly. Gas
blown off the supernovas will disperse outside the spiral arm, because
of convex curvature. Inside the spiral arm the gas becomes more
concentrated heading toward the centre of curvature of the arm. This
creates the conditions for the formation of a shock wave, which is
required for the gas to reach sufficient density to instigate a new wave
of star formation. Thus each spiral arm generates new stars inside of
itself.

As the galaxy ages the angle of the arms becomes increasing acute. In
the centre of the galaxy the positions for the formation of new stars is
not determined from a single arm. This is where the gas from the two
arms meets, naturally forming a symmetrical bar.


Regards

--=20
Charles Francis
substitute charles for NotI to email

On Feb 12, 5:11 am, Oh No wrote:

As the galaxy ages the angle of the arms becomes increasing acute. In
the centre of the galaxy the positions for the formation of new stars is
not determined from a single arm. This is where the gas from the two
arms meets, naturally forming a symmetrical bar.


I have a couple of questions relating to the standard model of spiral
arms, which you reviewed.

1. What is the fundamental origin of the two (usually 2) density waves
that are the basis for the whole model? What physical mechanism
excites the classical two-armed spirals that have such appealing
symmetry?

2. If symmetrical bars naturally form in the galaxy center where
incoming gas from the two arms intersect, how can we understand the
observed fact that strong bars often extend far away from the central
region, extending across nearly the whole optical disk?

3. Does the standard density wave model provide an understanding of
the remarkable bar-within-ring morphology that is well-documented and
not uncommon.

4. Does the standard density wave model provide an explanation for the
observed fact that barred galaxies are sometimes double-barred, i.e.,
a smaller bar is found interior to the main bar (with angles between
the two bars distributed in a reasonably random manner, including
nearly perpendicular examples)?

Do we really understand spiral galaxies all that well, or is it mostly
arm-waving, so-to-speak?

Robert L. Oldershaw

Thus spake "
Do we really understand spiral galaxies all that well, or is it mostly
arm-waving, so-to-speak?


I don't know all the answers to your questions. Galaxies are modelled
using supercomputers and I don't have any such access, nor am I expert
in the literature. I do know, because I have been studying data, that
the distribution of orbital velocities of stars is sufficiently broad
that older stars will spread out to cover the disc, not just the arms,
and that the arms are the places where gas collects and new stars form.
We also know, because it is well modelled, that shock waves in the gas
are necessary to achieve sufficient gas density for star formation.
Also we know that on galactic timescales collisions between galaxies are
common, and that this has a huge impact in creating the variety of
galaxy types - in particular I read not long ago that the bar within
ring formation you mention has been modelled as a result of galaxy
collisions.

As far as galaxy evolution models are concerned, we know that CDM models
don't work at all well in creating observed galaxy profiles, and we know
that we have a problem understanding the rate of galaxy formation from
the big bang. Both of those problems are addressed by the
teleconnection, which gives much more time for this to happen, and which
does not require CDM. I fear that further answers on the state of play
there await the demise of the CDM model so that the supercomputers are
turned to studying galaxies without it.


Regards

--
Charles Francis
substitute charles for NotI to email

On Feb 13, 2:37 am, Oh No wrote:
Thus spake "

Do we really understand spiral galaxies all that well, or is it mostly
arm-waving, so-to-speak?

I don't know all the answers to your questions. Galaxies are modelled
using supercomputers and I don't have any such access, nor am I expert
in the literature. I do know, because I have been studying data, that
the distribution of orbital velocities of stars is sufficiently broad
that older stars will spread out to cover the disc, not just the arms,
and that the arms are the places where gas collects and new stars form.
We also know, because it is well modelled, that shock waves in the gas
are necessary to achieve sufficient gas density for star formation.
Also we know that on galactic timescales collisions between galaxies are
common, and that this has a huge impact in creating the variety of
galaxy types - in particular I read not long ago that the bar within
ring formation you mention has been modelled as a result of galaxy
collisions.

As far as galaxy evolution models are concerned, we know that CDM models
don't work at all well in creating observed galaxy profiles, and we know
that we have a problem understanding the rate of galaxy formation from
the big bang. Both of those problems are addressed by the
teleconnection, which gives much more time for this to happen, and which
does not require CDM. I fear that further answers on the state of play
there await the demise of the CDM model so that the supercomputers are
turned to studying galaxies without it.
Regards
Charles Francis

To Dr. Francis and all.
Some years ago, Philip Plait, (Bad-Astronomy Blog)
and I discussed galaxy types, IMHO he's an expert,
and I gathered from our conversations this analysis.
(Philip is a rather modest type, and may deny his
input, but I'll acknowledge he as my source.)

We should think in terms of galactic construction
as part of a galactic superstructral formation.

The large heavy spherical galaxies occupy
the center of gravity's of the galactic clusters.

The "barring" of the galaxies revolving about that
center of mass are subject to tidal forces, with
those "tidal forces" themselves creating the bar
structure, much like tidal forces operate on Earth,
because of the moon and sun.

In "celestrial mechanics" that effect is equivalent
to the Roche Limit induction mechanism.

Regards
Ken

On Feb 15, 4:02 am, "Ken S. Tucker" wrote:
On Feb 13, 2:37 am, Oh No wrote:



Thus spake "

Do we really understand spiral galaxies all that well, or is it mostly
arm-waving, so-to-speak?

I don't know all the answers to your questions. Galaxies are modelled
using supercomputers and I don't have any such access, nor am I expert
in the literature. I do know, because I have been studying data, that
the distribution of orbital velocities of stars is sufficiently broad
that older stars will spread out to cover the disc, not just the arms,
and that the arms are the places where gas collects and new stars form.
We also know, because it is well modelled, that shock waves in the gas
are necessary to achieve sufficient gas density for star formation.
Also we know that on galactic timescales collisions between galaxies are
common, and that this has a huge impact in creating the variety of
galaxy types - in particular I read not long ago that the bar within
ring formation you mention has been modelled as a result of galaxy
collisions.

As far as galaxy evolution models are concerned, we know that CDM models
don't work at all well in creating observed galaxy profiles, and we know
that we have a problem understanding the rate of galaxy formation from
the big bang. Both of those problems are addressed by the
teleconnection, which gives much more time for this to happen, and which
does not require CDM. I fear that further answers on the state of play
there await the demise of the CDM model so that the supercomputers are
turned to studying galaxies without it.
Regards
Charles Francis

To Dr. Francis and all.
Some years ago, Philip Plait, (Bad-Astronomy Blog)
and I discussed galaxy types, IMHO he's an expert,
and I gathered from our conversations this analysis.
(Philip is a rather modest type, and may deny his
input, but I'll acknowledge he as my source.)

We should think in terms of galactic construction
as part of a galactic superstructral formation.

The large heavy spherical galaxies occupy
the center of gravity's of the galactic clusters.

The "barring" of the galaxies revolving about that
center of mass are subject to tidal forces, with
those "tidal forces" themselves creating the bar
structure, much like tidal forces operate on Earth,
because of the moon and sun.

In "celestrial mechanics" that effect is equivalent
to the Roche Limit induction mechanism.

Regards
Ken

The "hypothesis" that the baring of galaxies
due to tidal effects is somewhat subjective,
however, an examination of the "Coma Cluster",

http://antwrp.gsfc.nasa.gov/apod/ap020203.html

appears to support that hypothesis, because
the "spiral" galaxy's form in a region where the
gravitational potential changes, when that potential
is calculated from the galactic cluster.

The gradient of potential in the mid part of the cluster
is fairly flat, because it is near the Center of Gravity,
however as the observations from the ref above notes,
spirals increase in prominence as one tends beyond
the C of G.

Tidal effects in GR are descibed by Weinbergs'
"Grav & Cosmo" eq.(6.10.1), though I think the
Newtonian Roche Limit induction is adequate.
Regards
Ken

"Ken S. Tucker" wrote:

though I think the
Newtonian Roche Limit induction is adequate.

???

Why would there be a Roche Limit involved? If
I understand correctly, that's the point at
which solid bodies orbiting larger bodies are
torn to pieces by tidal forces.

But at the scales involved, galaxies aren't
solid bodies at all, they are swarms of
particles. The galaxy may well be torn apart
by tides, but surely the math is different
than "Roche Limit" math?

xanthian.