[evan_au]

3. Bulge (0 - 1KPC) - Why in the bulge each star orbits at different direction and orbital plane?
Why the Dark matter can't force the stars in the bulge to orbit in a disc?
4. Bar (1KPC to 3KPC) - How the dark matter could form the unique structure of the Bar?

Today I heard some projections on what might happen when the Milky Way Galaxy merges with Andromeda to form "Milkomeda".

They suggested that the result will be an elliptical galaxy, with stars taking many random paths.
- ie a bulge larger than our current galaxy
- and no bar
- I am sure that the university/supercomputer-level simulations would have taken into account some hypothetical distribution of Dark Matter in the original galaxies and the merged galaxy

Maybe it is time to go down to the bar and have a glass of dark matter.

[Dave Lev (OP)]

Today I heard some projections on what might happen when the Milky Way Galaxy merges with Andromeda to form "Milkomeda".
They suggested that the result will be an elliptical galaxy, with stars taking many random paths.
- ie a bulge larger than our current galaxy
- and no bar
- I am sure that the university/supercomputer-level simulations would have taken into account some hypothetical distribution of Dark Matter in the original galaxies and the merged galaxy

Sorry, the chance to get back a nice spiral galaxy after a collision is neglected.
Therefore, it is very clear that the spiral galaxy is not due to collision.

Maybe it is time to go down to the bar and have a glass of dark matter.

I hope that you do understand that the Dark matter (or even the Glass of dark matter) can't set all the elements in the spiral galaxy structure

However, there is already a confirmation in the following article that spiral galaxy can supports itself when the hydrogen originated from inside of the galactic center to outside.

http://pubs.sciepub.com/ijp/7/3/2/index.html#Figure4
"New Formulas and Mechanism for the Spiral Arm Formation of Galaxies"
It is stated:
"This model is the first attempt to think the spiral arm formation with the hydrogen originated from inside of the galactic center to outside. The proposed mechanism of the hydrogen production seems highly speculative, but the result of the simulations is very satisfactory,

It is stated that: "the result of the simulations is very satisfactory"
So why we can't accept the message from those scientists that tell us that the simulations of spiral galaxy while hydrogen originated from inside of the galactic center to outside is very satisfactory?
Why do we continue to hold the dark matter imagination?
Why can't we accept the simple observation and the mathematical simulation validation that the Bar is used as a funnel to drift stars from the Bulge directly to the spiral arms?
What's wrong with that understandings?
Why do we insist to believe in something that we can't see feel or smell?

I'm a chemist.
Why do you imagine I know or care how galaxies work?

Chemist is perfectly OK
 However, as you don't care how galaxy works, then why do you waste our time?

[Kryptid]

It is stated that: "the result of the simulations is very satisfactory"

So if you think that simulation is evidence, then that means a simulation of dark matter could constitute evidence too, right?

Why do we continue to hold the dark matter imagination?

The galactic rotation curve anomaly.

Why can't we accept the simple observation and the mathematical simulation validation that the Bar is used as a funnel to drift stars from the Bulge directly to the spiral arms?

Because the simulation being correct wouldn't eliminate the need for dark matter. The anomalous galactic rotation curve still needs to be explained.

Why do we insist to believe in something that we can't see feel or smell?

You can't see, feel or smell the radio waves that are flitting through the air either. Do you disbelieve in those?

[Bored chemist]

then why do you waste our time?

Pointing out your mistakes isn't wasting time.

On the other hand, you posting nonsense is a waste of everyone's time.Why do you do it?

[Dave Lev (OP)]

Because the simulation being correct wouldn't eliminate the need for dark matter. The anomalous galactic rotation curve still needs to be explained.

There is no need for dark matter to explain the anomalous galactic rotation curve.
Please look again at the rotation curve:
https://www.astronomy.ohio-state.edu/thompson.1847/1101/RotCurve2.gif
1. Bar - Below 3KPC
I have already explained how this segment works.
There is no need for dark matter as gravity that funnels the stars from the Bulge into the inwards side of the spiral arms is good enough:

http://pubs.sciepub.com/ijp/7/3/2/figure/4
The yellow line represents stars as they migrate outwards from the Bulge directly into the spiral arms.
We see that the Bar looks as a propeller of an airplane.
Let's assume that a star in a radius of 1KPC (R1) orbits at velocity V1 and try to verify the velocity of a star at different radius at this Bar (propeller)
It is clear that:
V = V1 (R / R1).
If R = R2 = 2KPC
V2 (at 2KPC) = 2 V1 (at 1KPC)
V3 (at 3KPC) = 3 V1
That linear increase in the calculated orbital velocity is fully correlated with the orbital velocity observations at the Bar section (Below 3KPC):
https://www.astronomy.ohio-state.edu/thompson.1847/1101/RotCurve2.gif
If you agree with that we can move on to the spiral arms.

2. Spiral arm segment 3KPC to 15 KPC
We already know that as the bar spines faster than the spiral arm, it adds new stars to the most inwards side of the arm and therefore it increases the spiral arm size (from inside).
In order to keep the spiral shape of the arm while new stars are added from inside, the stars that are already there must drift backwards and keep on with their current fixed velocity.
So, please look at the following image and focus on the connection point between the Bar and the spiral arm.
http://pubs.sciepub.com/ijp/7/3/2/figure/4
Let's assume that in this point there is a star (Let's call it Star A) which had just been delivered by the bar and is connected now to the spiral arm.
So, technically, star A is currently the most inwards star in the spiral arm and its orbital velocity might represent the maximal velocity of the spiral arm.
However, as the spin velocity of the bar is faster than the spin velocity of the spiral arm, than let's assume that after a given time frame (T) the Bar would move upwards and new star (let's call it star B) would be delivered from the bar to the arm.
Now star B is located at the most inwards side of the arm, while star A is second one in the yellow line.
As the Bar keeps its motion, new stars are coming and are connected to the most inwards side of the spiral arm.
After 100 new stars, Star A is already located 100 stars away from the most inwards point of the spiral arm.
Therefore, star A could keep its orbital velocity while new stars are added from inwards by the bar.
The key idea is that the spiral arm isn't a solid object where a star in the top would stay there forever.
It is a temporary structure of stars that constantly drift backwards while maintaining their fixed orbital velocity.
However, as new stars are constantly added from inside, the spiral arm shape is maintained over time.
So, if a star moves backwards at distance of D at a given time T then after 100T star A had already drifted backwards is the arm by a distance of 100D.
Hence, while new stars are added constantly at the most inwards side of the arm, all the millions or billions stars in this arm can maintain a fixed orbital velocity of about 220 Km/s without breaking the spiral arm shape.
However, that means that stars can't hold themselves in the arm for indefinitely.
Sooner or later a star which had been delivered by the bar at the most inwards side of the arm would be eventually ejected from the most outwards side of the arm.
In this way the orbital velocity of all the stars in the arm would be fixed and the temporary structure of the spiral arm would be stable.
Is it clear?

[Kryptid]

Is it clear?

Clearly wrong. Orbital velocity is determined by gravity.

[Dave Lev (OP)]

Orbital velocity is determined by gravity.

Yes, that is correct.
But the velocity of stars in the spiral arm is determined by movement of the arm.
As the arm is drifted constantly backwards (while new stars is coming from inside), all the stars in the arm can maintain their fixed orbital velocity.
Our scientists assume that a star keeps its orbital radius.
This is a sever mistake.
Any star in the spiral arm must only keep its location in the spiral arm...
As the spiral arm drifts backwards, the star is increasing the radius without increasing its velocity.
Actually, we can think on the spiral arm as some sort of elastic cable.
At the most inwards side of the arm it is connected to the ring. At this point its size is 3,000 LY which is almost 1KPC - exactly the same size as the Bulge although it is located 3KPC from the center.
At the most outwards side of the arm (15Kpc), its thickness is just 400LY.
So, the furthest star which is located in that elastic cable/arm, sets sever forces on the arm and therefore it stretches the arm backwards and the arm become thinner.
Sooner or later, the arm wouldn't maintain the last star in the arm and it would be ejected outwards from the arm and from the galactic disc.
So, any star that is not located directly at the galactic disc (at the given thickness of the arm) tells us that it had already been ejected from the spiral arms.

[Dave Lev (OP)]

Our scientists don't really understand why the Bar is so important for the activity of spiral galaxy, therefore, they just ignore it.
So, I have asked myself what would happen to a spiral galaxy if it loses its bar?
The answer is simple - You would get a ring galaxy:
Hoag's Object, an unusual ring galaxy - Hubble Space Telescope
https://www.astrobin.com/full/nvye4e/0/
The Hoag's ring galaxy is a perfect example.
There is no Bar that can funnel the stars from the Bulge into the main spiral arms.
If you look carefully on the ring, you would see that its made of unlimited number of thin spiral arms.
The direction of those tinny spiral arms tells us the spinning direction of the ring.
So how it really works?
Each star that is ejected from the central bulge must find its way by itself as there is no Bar that can collect them all and funnel them into the main spiral arms.
Therefore, as a star is ejected outwards from the central bulge it is attracted by the ring gravity force.
Statistically it can get to anyone of those tiny spiral arms.
As an example - we can use a Rolette.
Each ball/star is ejected from the center and fall statistically in a different slot/spiral tinny arm.
Once the star is there, it is connected to the inwards side of that tinny spiral arms.
Over time, new stars would fall exactly at the same slot/tinny spiral arm and all the stars in that tinny arm would be shifted backwards.
Sooner or latter, each star would be ejected from the outwards side of the ring.
If at some point the Bugle would stop to eject new stars, the ring would continue to eject stars from its outwards side, without getting new from the inwards side.
Eventually, the ring would disappear.

One more example:
https://www.facebook.com/edgeoftheunivers/photos/a.660437801012218/903938739995455
It is stated:
"LEDA 1000714 is a ring galaxy in the constellation Crater. LEDA 1000714 is one of a very rare group of galaxies called Hoag-type galaxies, named after the prototype, Hoag's Object. it is estimated that roughly 0.1% of all galaxies are this type. It's a rare galaxy that is challenging our understanding of the universe. This galaxy is approximately 300 million light years away. It was discovered by Burçin Mutlu-Pakdil, an astrophysicist at the University of Arizona."
Our scientists claim: " It's a rare galaxy that is challenging our understanding of the universe"
My answer for those scientists is as follow: If you would eliminate the dark matter imagination you would understand that gravity force of the ordinary matter is good enough for the proper activity in any type of galaxy.
Each galaxy works on the very basic laws of gravity forces.
That's all

[Dave Lev (OP)]

We already know that the Bar forces any star to orbit at its maximal velocity once it get to the most outwards side of the Bar. Therefore, without the bar, it is expected that the orbital velocity of stars in that ring would be relatively low.
Therefore, this is one more evidence why there is no need for dark matter in any type of galaxy.

[Kryptid]

The bar isn't some kind of magical propulsion system that lets stars violate Kepler's third law.

[Dave Lev (OP)]

The bar isn't some kind of magical propulsion system that lets stars violate Kepler's third law.

There is no violation of any physical law by the Bar (including the Kepler's third law).
In the article it is stated:

https://scitechdaily.com/galactic-bar-paradox-a-mysterious-and-long-standing-cosmic-conundrum-resolved-in-cosmic-dance/
It is stated:
"The bar pulsations result from its regular encounters with the Galactic spiral arms, in what can be described as a “cosmic dance”. As the bar and spiral arm approach each other, their mutual attraction due to gravity makes the bar slow down and the spiral speed up.Once connected, the two structures move as one and the bar appears much longer and slower than it actually is. As the dancers split apart, the bar speeds up while the spiral slows back down."
It is specifically stated: "their mutual attraction due to gravity makes the bar slow down and the spiral speed up."
It is also stated: "Once connected, the two structures move as one"

Hence the same gravity force that holds the stars in the bar arm and in the spiral arm as one connected temporary structure, also keeps each arm as a temporary structure.

[Kryptid]

There is no violation of any physical law by the Bar (including the Kepler's third law).

If it's orbiting faster than Kepler's third law allows, then it is.

It is specifically stated: "their mutual attraction due to gravity makes the bar slow down and the spiral speed up."

The bar contains stars too. If the bar is slowing down, then the stars in the bar are also slowing down. So you have some stars speeding up and others slowing down. So overall, there is no average gain in velocity. If there is no average gain in velocity, then the anomalous galactic rotation curve remains unresolved.

Even if it was true that they somehow sped up and retained that increased orbital speed indefinitely, then they should no longer be able to maintain an orbit around the Milky Way galaxy because they are going too quickly to be retained by the Milky Way's gravity. That was the whole problem from the beginning. The stars in the outer regions of the galaxy are orbiting too fast for the amount of gravity that the Milky Way should be producing if there was only normal matter present. The fact that the galaxy has kept these super-fast stars demonstrates the need for extra gravity that is caused by something we can't see: i.e. dark matter.

Hence the same gravity force that holds the stars in the bar arm and in the spiral arm as one connected temporary structure, also keeps each arm as a temporary structure.

"Temporary" being the key word here. What do you think happens when they are no longer one structure?

[Dave Lev (OP)]

The bar contains stars too. If the bar is slowing down, then the stars in the bar are also slowing down. So you have some stars speeding up and others slowing down. So overall, there is no average gain in velocity. If there is no average gain in velocity, then the anomalous galactic rotation curve remains unresolved.

Don't you agree that the dark matter idea can't offer a solution for the galactic rotation curve in the Bar segment?
If you think that the gravity is not good enough for the Bar, then how the bar really works based on your understanding?

[Dave Lev (OP)]

Quote from: Dave Lev on Today at 09:09:17
Hence the same gravity force that holds the stars in the bar arm and in the spiral arm as one connected temporary structure, also keeps each arm as a temporary structure.

"Temporary" being the key word here. What do you think happens when they are no longer one structure?

If you try to break down the temporary structure of the spiral arm in the galactic disc, then all the stars in that arm would be kicked out from the galactic disc.
Nothing would help. Not even the dark matter imagination.

[Dave Lev (OP)]

Even if it was true that they somehow sped up and retained that increased orbital speed indefinitely, then they should no longer be able to maintain an orbit around the Milky Way galaxy because they are going too quickly to be retained by the Milky Way's gravity.

Again, do you mean that there is a problem in the bar or in the galactic disc?

That was the whole problem from the beginning.

But so far you have no real solution for the Bar rotation curve problem?

The stars in the outer regions of the galaxy are orbiting too fast for the amount of gravity that the Milky Way should be producing if there was only normal matter present.

As the stars are connected to the spiral arm, then their orbital velocity is dictated by the orbital velocity of the arm itself.

The fact that the galaxy has kept these super-fast stars demonstrates the need for extra gravity that is caused by something we can't see: i.e. dark matter.

Actually, it is very difficult even for the spiral arms to keep those stars that are located at the most outwards locations in the spiral arms.
We clearly see that those stars at the far end of the spiral galaxy stretch the arm to its maximal.
Therefore, the thickness there is just 400 LY (at 15KPC) instead of 3000Ly at the base on the arm (at 3KPC).
The dark matter idea CAN'T explain this phenomenon!!!
Therefore, I call it the dark matter imagination.
Why do we prefer the dark matter idea that can only solve 25% of the problems while the gravity of the spiral arms can solve 100% of the problems?
Please be aware that at some point those far end stars in the spiral arms must be disconnected from the arm.
The dark matter idea can't also give an answer for that
Therefore, the only way for a star to keep itself in the galactic disc is by holding the spiral arm.

[Kryptid]

Don't you agree that the dark matter idea can't offer a solution for the galactic rotation curve in the Bar segment?

No, I don't agree.

If you think that the gravity is not good enough for the Bar, then how the bar really works based on your understanding?

Gravity is good enough if you are including the gravity from dark matter.

If you try to break down the temporary structure of the spiral arm in the galactic disc, then all the stars in that arm would be kicked out from the galactic disc.

The fact that the structure is temporary means that it does, eventually, break down. Yet those stars aren't kicked out from the galactic disk.

Nothing would help. Not even the dark matter imagination.

The extra gravity contributed by dark matter absolutely would help. It's that extra gravity that keeps those fast-moving stars from getting away from the galaxy.

Again, do you mean that there is a problem in the bar or in the galactic disc?

Neither. It's your misunderstanding that is the problem.

But so far you have no real solution for the Bar rotation curve problem?

What "bar rotation curve problem"? I think you are mixing up two different issues.

As the stars are connected to the spiral arm, then their orbital velocity is dictated by the orbital velocity of the arm itself.

Which, in turn, is dictated by gravity (hence why I mentioned Kepler's third law).

The dark matter idea CAN'T explain this phenomenon!!!

Because...?

Why do we prefer the dark matter idea that can only solve 25% of the problems while the gravity of the spiral arms can solve 100% of the problems?

Where did you get those numbers from?

Please be aware that at some point those far end stars in the spiral arms must be disconnected from the arm.
The dark matter idea can't also give an answer for that

It was never supposed to.

Therefore, the only way for a star to keep itself in the galactic disc is by holding the spiral arm.

And that holding is done by gravity. The gravity produced by normal matter isn't enough. Hence why we need dark matter.

[Dave Lev (OP)]

Quote from: Dave Lev on Yesterday at 18:55:01
Why do we prefer the dark matter idea that can only solve 25% of the problems while the gravity of the spiral arms can solve 100% of the problems?

Where did you get those numbers from?

Well, there are too many open questions about the dark matter, please answer the following:

1. It is much less than 25%. I hope that we all agree that our scientists don't have a clue what is it and how it had been created and why it is there exactly at the density that they wish. However, please specify the dark matter density formula that is invented for the Milky way.

2. Galactic Disc -
A. How this dark matter formula can set the disc only at the spiral arms (3KPC to 15KPC)?
B. Why in the Bulge there is no Disc at all?
C. Why the disc does not continue after 15KPC? Actually, do you confirm that when arm is ended, the stars after that point are ejected from the disc?
D. Why the thickeners of the arm at the base is 3000LY while at the end it is 400LY? How Kepler law can explain this phenomenon

3. Bar -
Can you please explain how the same dark matter that aim to keep the orbital velocity of the stars in the galactic disc at a fixed velocity can suddenly increase so dramatically the orbital velocity of stars in this section? How the dark matter formula can justify that dramatic increase

4. Ring
A. How the dark matter formula can justify the creation of the Ring?
B. Why the ring is always created between the end of the bar to the base of the spiral arms?
C. Why do you think that Kepler law works better with dark matter for this section?

[Origin]

It is much less than 25%.

Why do you enjoy making up stuff?

I hope that we all agree that our scientists don't have a clue what is it and how it had been created and why it is there exactly at the density that they wish.

Classic Dave BS.  You imply the Astrophysicists lie and make up a number for 'a density they wish', instead of the truth which is they describe the density that the evidence suggests.  This is probably to subtle for Dave to get.

However, please specify the dark matter density formula that is invented for the Milky way.

Again Dave throws astrophysics under the bus, implying the research is just made up.

2. Galactic Disc -
A. How this dark matter formula can set the disc only at the spiral arms (3KPC to 15KPC)?
B. Why in the Bulge there is no Disc at all?
C. Why the disc does not continue after 15KPC? Actually, do you confirm that when arm is ended, the stars after that point are ejected from the disc?
D. Why the thickeners of the arm at the base is 3000LY while at the end it is 400LY? How Kepler law can explain this phenomenon

3. Bar -
Can you please explain how the same dark matter that aim to keep the orbital velocity of the stars in the galactic disc at a fixed velocity can suddenly increase so dramatically the orbital velocity of stars in this section? How the dark matter formula can justify that dramatic increase

4. Ring
A. How the dark matter formula can justify the creation of the Ring?
B. Why the ring is always created between the end of the bar to the base of the spiral arms?
C. Why do you think that Kepler law works better with dark matter for this section?

So basically, you don't know much about astrophysics, so you make up absurd WAGs to answer questions that come from your ignorance.  Nice...

[Kryptid]

What dark matter formula are you talking about? Scientists do indeed have ideas about what dark matter could be: axions, sterile neutrinos, WIMPS, and primordial black holes for example.

[Dave Lev (OP)]

What dark matter formula are you talking about? Scientists do indeed have ideas about what dark matter could be: axions, sterile neutrinos, WIMPS, and primordial black holes for example.

Well, if it is too difficult to offer the dark matter density formula for the milky way then let's move on.
Please look at the following rotation cure.
Do you confirm that the dark matter can ONLY explain at its best case the orbital velocity at the galactic disc and no more than that?
https://www.astronomy.ohio-state.edu/thompson.1847/1101/RotCurve2.gif

Hence, there are still too many open questions.
So please - would you kindly answer the following questions:

2. Galactic Disc -
A. How this dark matter formula can set the disc only at the spiral arms (3KPC to 15KPC)?
B. Why in the Bulge there is no Disc at all?
C. Why the disc does not continue after 15KPC? Actually, do you confirm that when arm is ended, the stars after that point are ejected from the disc?
D. Why the thickeners of the arm at the base is 3000LY while at the end it is 400LY? How Kepler law can explain this phenomenon

3. Bar -
Can you please explain how the same dark matter that aim to keep the orbital velocity of the stars in the galactic disc at a fixed velocity can suddenly increase so dramatically the orbital velocity of stars in this section? How the dark matter formula can justify that dramatic increase

4. Ring
A. How the dark matter formula can justify the creation of the Ring?
B. Why the ring is always created between the end of the bar to the base of the spiral arms?
C. Why do you think that Kepler law works better with dark matter for this section?

If you can't do so, then how can we believe in the dark matter invention/imagination?