Why are we so sure that there is a need for dark matter?

[Dandav]

Let's summarize the key functionality of the Bar.

1. The Bar had been formed by tidal gravity force of the ring/spiral arms on the Bulge.

2. Due to that tidal force matter and stars from the Bulge had been pushed outwards into the two symmetrical arms that formed the bar. We can clearly see the direction of the tidal forces on the spherical bulge:

3. All the matter/stars in the Bar had been ejected outwards from the Bulge. It would never come back as long as the tidal force continue to work.

4. Therefore the Bar acts as an output funnel that transfer matter and stars from the bulge into the Ring and Spiral arms. Hence, The Bar is a key element in the transformation from a spherical bulge shape into a disc ring & spiral arms. 

5. We should consider the Bulge + Bar as one object that should be called Bar shape Bulge.

 

Edited December 16, 2022 by Dandav

[Dandav]

With regards to the Bar funneling of gas and stars.

In the following article our scientists understand that the Bar act as a funnel, but they wish to believe that it funnel matter from the spiral arm into the Bulge:

https://cosmoquest.org/x/2021/05/galactic-bars-may-funnel-material-and-trigger-star-formation/

"In a new study appearing in Astronomy & Astrophysics, researchers led by Eduardo González-Alfonso have switched to using infrared light. What we’re learning now is that a bar can act as a highway to funnel gas and dust from the outer parts of the galaxy into the core, where it can trigger star formation and feed the central supermassive black hole."

But that understanding is just based on a wish.

The tidal gravity force, won't let even one star to move inwards and I have proved it.

Therefore, the Bar can only funnel gas and stars from the Bulge into the Ring / Spiral arms!

Edited December 16, 2022 by Dandav

[Dandav]

This is the image of the milky way:

https://skyandtelescope.org/astronomy-news/the-milky-ways-new-arm/

 

 

"The Milky Way's basic structure involves two large spiral arms believed to originate at either end of an elongated central bar. "

"A few years ago, Benjamin and others used NASA's Spitzer Space Telescope to deduce that our galaxy really has just two main spiral arms, not four as had been thought. Called the Scutum-Centaurus and Perseus arms, these appear to connect up nicely with the ends of the galaxy's central bar."

So how it works?

The Bar is gravitational arm which acts as a highway to funnel gas, dust and stars from the Bulge into the two main spiral arms.

Any star there sets gravitational interaction with the nearby stars and follow with the outwards stream from the bulge to the spiral arms.

It works as a Cake Icing Piping Cream Pastry Bag

However, instead of delivering cream it delivers Stars, gas and dust from the Bulge into the spiral arms. The thickness of the spiral arm is dictated by the thickness of the edge of the Bar.

In the milky way this thickness/diameter is 3000LY.

Therefore, the bar adds new layer of stars as it revolves and increase the length of the spiral arms from inside.

Hence, the stars in the spiral arms do not need to follow the orbital motion of the bar.

The stars just need to hold each other in the arm by gravity and go with it wherever is goes.

As the gravitational spiral arm is constantly drifting outwards, then at any radius from the center the average velocity of stars is about 220Km/sec.

Therefore, there is no need for dark matter

The gravitational spiral arm is good enough!

 

Edited December 16, 2022 by Dandav

[Dandav]

I would like to add some more information about the real meaning of gravitational arm:

Our scientists have measured the density of G stars around the Sun.

They have measured 64 G stars at 50LY radius.

Based on that density we can calculate that the estimated G stars per 100LY should be 64 * 2^3 = 512 stars.

Surprisingly, when our scientists have measured the G stars in 100LY around us the have found exactly 512 stars.

That PROVES that the density of stars in our location is exactly 512 per 100LY.

I wonder why our scientists didn't continue and measured the number of stars in 200LY, 500LY and 1000LY in the Orion arm. Please be aware that the thickness of the Orion arm in our location is about 1000LY (and the Sun is located at about 200LY from the side of this arm)

In any case, based on the measured density, we can easily calculate the G stars in the 1000LY sphere (This is the diameter of the Orion arm/pipe):

512 * 10^3 = 512,000 stars.

Now let's think about a 1000LY star cluster with 512,000 that stay somewhere in the open space.

Do we agree that it should have enough gravity force to bond all its stars without any need for central massive object?

I have found the following computer animation, derived from a type of computer code called an N-body simulation, shows 100 identical stars in a time-lapse movie where hundreds of years pass in one second.

http://www.astronet.ru/db/xware/msg/1178657

It is stated:

"The orbits of stars around the cluster are typically not as circular as the orbits of planets in our solar system. Cluster stars frequently fall more directly toward the center and many times trace out unusual and complex loops. The vast space inside a cluster result in stars colliding only rarely. "

If 100 Stars could hold themselves together by gravity then 512,000 stars can also do it.

However, it is important to notice that the orbital motion of the stars in the cluster isn't circular but unusual complex loops.

That can explain the orbital Bobbling motion of the stars near the Sun.

Each star is moving in a different direction but all of them are bonded by gravity force.

Therefore, we can claim that each star in the spiral arm holds itself to the arm by gravity force (while it orbits in a complex loop) and goes with the arm wherever the arm goes.

Hence, do you agree that there is no need for any sort of dark matter to bond the star to its spiral arm?

Edited December 17, 2022 by Dandav

[Dandav]

How the spiral arms really work?

In the following article it is stated:

https://www.astronomynotes.com/ismnotes/s8.htm

"Galaxies are billions of years old so the spiral pattern must be a long-lasting feature. What maintains the spiral pattern?"

So the key feature of spiral galaxy is that their spiral arms MUST be long-lasting.

Therefore, they can't be something that is created randomly by some sort of random activity as density wave and then break down.

Long lasting means - real structure that holds itself for millions over billions years!!!

Unfortunately, our scientists couldn't solve the enigma of the spiral arms as they have assumed that stars in the spiral arms should maintain their distance from the center  of the galaxy.

That is their ultimate mistake.

Stars in the spiral arms do not care about their distance from the center of the galaxy!

They only need to maintain themselves in the arm by gravity force.

However, as the arm spins, any star that is located farther away from the base of the arm, it facing stronger ejected forces.

It is similar to the Carousell momentum:

 

Therefore, the stars in the spiral arms do not maintain their distance from the center of the galaxy but only maintain their location in the arm.

Let's set the current available data:

1. At our location (8KPC from the center of the galaxy), the thickness of the arm is 1000LY and the G star density is 512 stars per 100LY sphere.

2. At the base (3KPC from the center), the spiral arm is connected to the ring and its thickness is 3000LY. I would assume that the G star density there should be much higher than this 512 per 100LY (however, I couldn't find any data on that.)

3. At the far edge of the spiral arm (12 -15 KPC from the center), the thickness of the arm is just 400LY. I assume that the G star density there must be much lower than 512 per 100LY. 

Based on that data let's verify how spiral arms really works:

We should consider the spiral arm as some sort of elastic cable that is made out of star clusters that are bonded to each other in a long line by gravity force.

Each star cluster holds itself to the one that is closer to the base.

The star cluster at the edge of the arm are facing the strongest ejecting force.

It would be stretched to its maximal gravity bonding force and therefore the thickness of the arm at this far end location is so low (only 400LY) and the density of stars should also be very low.

At some point, the orbital ejecting force would be stronger than the gravity bonding force and that last star cluster would be ejected from the spiral arm.

As it is ejected from the arm it would also be ejected from the galactic disc.

Therefore, any cluster that isn't located directly on the galactic disc couldn't be considered as part of the spiral arm.

At the same time new layer of stars would be added to the base of the spiral arm by the bar as it rotates and increase the arm from inside.

Hence, any star that had started its jury at the base of the spiral arm, would constantly drift outwards and at the end it would be ejected from the edge of the spiral arm.

In this process, the orbital motion of each star would be at kept at about 220 Km/sec while the spiral structure would be a long-lasting feature.

Hence, the life time of stars in the spiral arms is quite limited, while the life time of the spiral arms is unlimited.

Is it clear?

Edited December 17, 2022 by Dandav

[Halc]

On 12/12/2022 at 4:34 PM, JeffreysTubes8 said:

What math does Dandav do?

Almost none, which is why perhaps he actually believes the claptrap spewed in the above posts which violates mathematics at every step.

He did manage to notice that 64/50³ yields the same value as 512/100³. Hence the 'almost' in my above statement.

 

"It is mathematics which reveals every genuine truth, for it knows every hidden secret… Whoever then has the effrontery to study physics while neglecting mathematics should know from the start that he will never make his way through the portals of wisdom."

--- Roger Bacon (13th century)

[Dandav]

Dear Halc

Welcome back.

You were missing.

There is no need for complex mathematics to validate my explanation as it is so simple explanation and there is no need for dark matter.

However, as you insist for the math.

Please look at the orbital rotation curve:

Let's start with the bar: 

As I have already explained the velocity of the stars in Bar gravitational arm is based on their local velocity + the velocity of the arm.

The local orbital velocity of the stars = The orbital motion that is needed for the gravity interaction or bonding between the arm to the star and it is quite neglected.

Therefore, the main velocity impact in the bar is due to the orbital motion of the Bar.

Please remember:

P = 2 * 3.14 * R

Hence, as the bar is a linear object than a star at 2R should cross twice the distance as a star at R.

P1 = 2 * 3.14 * R

P2 = 2 * 3.14 * 2R

P2/P1 = 2

Therefore, a star at 2R should move twice faster than a star at R.

Please look at the rotation velocity for the bar.

Do you confirm that the math fully meets the Bar velocity observation?

Once you agree with that, we will move on to the math calculation of the spiral arm.

Edited December 17, 2022 by Dandav

[Dandav]

12 hours ago, Halc said:

"It is mathematics which reveals every genuine truth, for it knows every hidden secret…

I would like to remind you that with all the complex math that our scientists have used in their mega computation system, they have totally neglected the Bar segment.

Do you confirm that our scientists have just focused on the spiral arms and have no clue why the orbital motion in the bar is increasing linearly?

Edited December 18, 2022 by Dandav

[Dandav]

Dear Halc

Let me say it clearly.

The Bar is the most important feature in the spiral arm.

In the article It is stated:

NASA - Barred Spiral Galaxies Are Latecomers to the Universe

Bars form when stellar orbits in a spiral galaxy become unstable and deviate from a circular path. "The tiny elongations in the stars' orbits grow and they get locked into place, making a bar," explained team member Bruce Elmegreen of IBM's research Division in Yorktown Heights, N.Y. "The bar becomes even stronger as it locks more and more of these elongated orbits into place. Eventually a high fraction of the stars in the galaxy's inner region join the bar."

Therefore, I have few questions:

1. How could it be that those scientists from Nasa with deep knowledge in science could understand the real meaning of the bar and the real impact of tidal force? 

2. Do you agree that this "tiny elongations in the stars' orbits grow and they get locked into place" is a random process? If so, how could it be that this random process could set a Bar at a size of 3KPC which means triple times the size of the Bulge (1KPC)?

3. Why that random process always sets two symmetrical arms? Why never ever one arm, three or more?

4. Technically, the Bulge itself is the big brother of a globular star cluster. There are millions over billions globular star clusters in the universe. If that kind of process was real, then why we have never ever observed even a bar in any globular cluster in the entire universe?

5. How can you explain the following contradiction:

In one hand it is stated that stars are locked in the Bar: "The bar becomes even stronger as it locks more and more of these elongated orbits into place."

While on the other hand it is stated that the bar transfer gas towards the center: Bars are perhaps one of the most important catalysts for changing a galaxy. They force a large amount of gas towards the galactic center, fueling new star formation, building central bulges of stars, and feeding massive black holes.

So, how stars and gas could be locked in the bar and in the same time the same Bar can transfer the same gas and stars inwards?

6. How they couldn't understand that the Bar is a direct outcome of tidal force due to the ring + spiral arms that are located around the Bar?

[Dandav]

If we would verify the DNA of the stars in the MW galaxy, do you agree that we should find that all the Billions stars there without exception - carry the same DNA?

What can we learn from that?

[Halc]

On 12/17/2022 at 2:17 PM, Dandav said:

I would like to remind you that with all the complex math that our scientists have used in their mega computation system, they have totally neglected the Bar segment.

  ... as evidenced by all the pictures and links to descriptions of the bar by those very neglectful scientists, and none by you.

On 12/17/2022 at 12:45 PM, Dandav said:

You were missing.

I was not bothering with nonsense that is over the top self contradictory.

On 12/17/2022 at 12:45 PM, Dandav said:

Please remember:

P1 = 2 * 3.14 * R

P2 = 2 * 3.14 * 2R

P2/P1 = 2

OK, this is a formula for the circumference of a circle of radius R. You have cleverly figured out that a circle that is twice as big has twice the circumference. You've managed to discover that 2*constant is twice 1*same-constant. I was hoping for some actual numbers.

On 12/17/2022 at 12:45 PM, Dandav said:

Therefore, a star at 2R should move twice faster than a star at R.

This doesn't follow. I can accept something like it with several conditions.  The pattern rotates without distortion, the stars move with the pattern, and the motion referenced above refers only to the tangential velocity.  From this, plus your little graph, how long does it take for the bar to go around once? That requires numbers. Can you do that? You've done no velocity math, only something concerning the circumference of a circle, and it is known that bar stars don't have circular orbits.

4 hours ago, Dandav said:

The Bar is the most important feature in the spiral arm.

The bar isn't a feature of a spiral arm. It's considered separate usually.

4 hours ago, Dandav said:

1. How could it be that those scientists from Nasa with deep knowledge in science could understand the real meaning of the bar and the real impact of tidal force? 

Maybe by having that "deep knowledge"

The bit about tidal force is tosh. The thing you quoted makes no mention of tides.

4 hours ago, Dandav said:

2. Do you agree that this "tiny elongations in the stars' orbits grow and they get locked into place" is a random process?

If it happens to one star, it might be a random process. If it happens to the majority of them, it's not random.

4 hours ago, Dandav said:

3. Why that [...] process always sets two symmetrical arms? Why never ever one arm, three or more?

Two is stable. Three is not.

4 hours ago, Dandav said:

why we have never ever observed even a bar in any globular cluster in the entire universe?

We do. They're called barred galaxies. Most globular clusters don't have very much angular momentum. Things with bars do.

4 hours ago, Dandav said:

5. How can you explain the following contradiction:

In one hand it is stated that stars are locked in the Bar: "The bar becomes even stronger as it locks more and more of these elongated orbits into place."

While on the other hand it is stated that the bar transfer gas towards the center: Bars are perhaps one of the most important catalysts for changing a galaxy. They force a large amount of gas towards the galactic center, fueling new star formation, building central bulges of stars, and feeding massive black holes.

Stars are not so easily deviated from their orbits. Gas clouds are quickly slowed by friction and can migrate closer to the center. This generates energy. The bar does leak material into the ring region, more stars than gas. The galaxy does lose energy overall and that must result in an overall falling of material towards the center.

4 hours ago, Dandav said:

6. How they couldn't understand that the Bar is a direct outcome of tidal force due to the ring + spiral arms that are located around the Bar?

Because that would be an understanding of nonsense. There's nothing supplying a tidal imbalance. Your picture completely contradicts how gravity works.

4 hours ago, Dandav said:

If we would verify the DNA of the stars in the MW galaxy, do you agree that we should find that all the Billions stars there without exception - carry the same DNA?

Any DNA molecule that approached an active star would be destroyed long before reaching it. Why kind of nonsense question is this? Are you now suggesting that stars are Earth animals?

[Dandav]

13 hours ago, Halc said:

18 hours ago, Dandav said:

why we have never ever observed even a bar in any globular cluster in the entire universe?

We do. They're called barred galaxies. Most globular clusters don't have very much angular momentum. Things with bars do.

You have just confirmed my message about the tidal impact!

 

A Bulge, Globular cluster or star cluster without the ring and the spiral arms around it would never ever set any sort of a bar shape.

Only a structure with spiral arms and ring can set the Bar.

If you would take out the Ring and the spiral arms from that barred galaxy, then the left-over bulge would lose Its Bar shape.

So, please can you offer ONE real image of Bulge or globular cluster (without ring & spiral arms) that could form a bar shape?

13 hours ago, Halc said:

18 hours ago, Dandav said:

3. Why that [...] process always sets two symmetrical arms? Why never ever one arm, three or more?

Two is stable. Three is not.

Two symmetrical arms are stable due to tidal gravity impact.

Three isn't stable as the tidal impact works on both symmetrical sides of the object.

There are no stable bar arms without tidal force!!!!

13 hours ago, Halc said:

18 hours ago, Dandav said:

6. How they couldn't understand that the Bar is a direct outcome of tidal force due to the ring + spiral arms that are located around the Bar?

Because that would be an understanding of nonsense. There's nothing supplying a tidal imbalance. Your picture completely contradicts how gravity works.

As you insist to ignore the ultimate impact of the Tidal, let's discuss it deeply.

Please look at the following image:

 

Do you confirm that tidal gravity force due to that satellite squeeze the central objects from upwards and downwards, while it would push matter from the central object at the direction of the satellite and also symmetrically from the other side?

Now, let's use a pure spherical cluster (at a radius R) and set one million satellites in a ring around it.

What would be the outcome?

Don't you agree that the combined tidal forces of those million satellites would squeeze the central object from upwards and downwards one million times stronger?

However, as for any direction around the cluster there is a satellite, then do you agree that the spherical cluster would change it shape to a nice symmetrical pita bread without any bar structure?

 

 

 

We actually see this structure.

It is called ring galaxy:

 

Please look carefully at this galaxy.

It has no bar and no two main spiral arms, only bulge and ring.

You don't know that yet, but this ring galaxy would be transformed in the future into full barred spiral galaxy with bar and two main spiral arms.

However, in the meantime, when you look at this image, do you think that the central Bulge has a pure sphere shape as a Mondial Ball?

If so, you have a severe mistake.

The central bulge already got a pita bread shape.

Therefore, if its diameter in this top view image is S, I can promise you that its diameter from the side view is significantly lower. It might be even lower than 1/2 S.

 

13 hours ago, Halc said:

The bar isn't a feature of a spiral arm. It's considered separate usually.

The Bar is a key feature of barred spiral galaxy.

If you take out the ring and spiral arms from the barred galaxy, there will be no bar.

Please also be aware the Bar is an integrated part of the Bulge.

Therefore, as the Bar rotates, the whole Bulge with its stars and gas clouds is also rotates.

It might be difficult for us to detect the rotation of the bulge, but it is there.

Conclusion:

Sorry, you can't ignore the great impact of tidal force.

Take out the tidal force from barred galaxy, and you have no bar.

Take out the bar and you have no twin spiral arms.

How long can you hold the dark matter imagination and reject real tidal gravity force?

Why do you insist to reject the impact of tidal force as it can explain the clear operation of the spiral galaxy without using even one gram of dark matter???

Edited December 19, 2022 by Dandav

[Halc]

14 hours ago, Dandav said:

However, as for any direction around the cluster there is a satellite, then do you agree that the spherical cluster would change it shape to a nice symmetrical pita bread without any bar structure?

You seem to change your mind. Before you said a ring would distort a spherical mass into a bar:

On 12/13/2022 at 12:08 PM, Dandav said:

As the cluster is not solid, the tidal force due to the ring would change the spherical shape of the cluster to symmetrical Bar structure.

The pita is closer, but the effect is pretty trivial. Earth is definitely pita shaped, but the tides only contribute a meter or two of variance, and that's the most significant tide in the solar system. Meanwhile, Earth is 44 km thicker around the equator than from top to bottom, and that's due to the same thing that creates the bar: angular momentum.

 

The ring galaxy you picture is Hoag's object, and it is known to have an unusually spherical central mass, which nicely contradicts your promise. Physics doesn't work by promises. It works by observation and mathematics.

Concerning mathematics, I gave you an absolutely trivial exercise to see if you had any arithmetic capability at all. You only showed that a circle that is twice as large has twice the circumference.

I asked how long it takes for the bar to go around once, and you ran away to hide. You apparently can't do it despite the existence of a nice graph giving you the answer. Not looking for lots of digits of precision. 1 digit will do.

 

[Dandav]

Dear Halc

Our scientists don't know why spiral arms in the base (3KPC) are so thick (3000LY) while at the far edge (15KPC) they are so narrow (only 400LY)

They don't even dare to ask themselves this question as they have totally got lost.

That by itself proves that they don't have a basic clue how spiral galaxy really works.

In the following article they fully admit that: "A spiral galaxy is at once a beautiful sight and a physical puzzle"

http://www.physics.smu.edu/jcotton/ph1311/ch14b.htm

"A spiral galaxy is at once a beautiful sight and a physical puzzle. The problem is understanding how the arms remain as stable long-term features."

Therefore, even today with all the imagination of dark matter, Density wave, Bar structure, "unstable regions"... our scientists still have a major problem of  "how the arms remain as stable long-term features".

In the following article it is stated:

https://academic.oup.com/mnras/article/478/1/932/4993268

"Spiral arms form due to unstable regions where self-gravity dominates, or from initially leading density waves, but are eventually broken up by the disc shear."

"Spiral arms can be transient in nature, but a long-lived swing amplified mode can exist in galaxy discs over several rotations"

 "spiral arms can be broken and re-made"

So, they clearly know that the idea of the "unstable regions" will help to set only several rotations of the spiral arms before they would break down.

But they hope that somehow, "spiral arms can be broken and re-made"

In this article it is stated clearly that there is no consistent theory and there is no single mechanism:

"a consistent theory to describe all galaxy spiral structure is elusive, and a single mechanism may not be responsible for all types of observed spiral structure."

Sorry, spiral arm isn't a physical puzzle.

I offer you a single mechanism that is based on real science and is called Tidal.

This Tidal can explain the full structure of all the complex galaxies in the Universe, how they had been evolved and why they wouldn't break down and remain as stable long-term features

But you prefer to reject real science and stay at the darkness while holding the dark matter that we would never ever see as it just proves that our scientists don't know how spiral galaxy really works.

 

Edited December 20, 2022 by Dandav

[Halc]

You still haven't done a single bit of arithmetic. All just standing on a box and spouting noise.

How long does it take this bar to go around once? There's no point in listening to somebody who cannot multiply two simple numbers together.

[OceanBreeze]

17 hours ago, Dandav said:

But you prefer to reject real science and stay at the darkness while holding the dark matter that we would never ever see as it just proves that our scientists don't know how spiral galaxy really works.

 

You have not proven anything regarding your tidal theory and it is you who that is staying in the darkness while rejecting the work of mainstream scientists. Mainstream scientists have done a great deal of research on Spiral structure in barred galaxies.

If you follow the link, you will find just one of many fine papers on the subject.

Here is just a brief abstract and even this shows a deep understanding about the spiral structure and the role the bar plays in the dynamical evolution of these galaxies:

Abstract

A method, which we have developed for determining corotation radii, has allowed us to map in detail the radial resonant structures of barred spiral galaxies. Here, we have combined this information with new determinations of the bar strength and the pitch angle of the innermost segment of the spiral arms to find relationships between these parameters of relevance to the dynamical evolution of the galaxies. We show how (1) the bar mass fraction, (2) the scaled bar angular momentum, (3) the pitch angle, and (4) the shear parameter vary along the Hubble sequence, and we also plot along the Hubble sequence (5) the scaled bar length, (6) the ratio of bar corotation radius to bar length, (7) the scaled bar pattern speed, and (8) the bar strength. It is of interest to note that the parameters (2), (5), (6), (7), and (8) all show breaks in their behaviour at type Scd. We find that bars with high shear have only small pitch angles, while bars with large pitch angles must have low shear; we also find a generally inverse trend of the pitch angle with bar strength. An inference that at first seems counter-intuitive is that the most massive bars rotate most slowly but have the largest angular momenta. Among a further set of detailed results, we pick out here the 2:1 ratio between the number of spiral arms and the number of corotations outside the bar. These results give a guideline to theories of disc–bar evolution.

 

I suggest you read the entire paper It certainly contradicts your claim that our scientists "don't have a basic clue how spiral galaxy really works".

It seems to me you are the one without a basic clue, but you are pushing your own basically crackpot theory as fact, without sufficient scientific support to back it up. If you continue to claim your own theory as fact while at the same time rejecting established mainstream theories, I may have to move this thread out of Astronomy and Space and into Alternate theory section of this forum.

[Dandav]

On 12/21/2022 at 1:05 AM, OceanBreeze said:

Mainstream scientists have done a great deal of research on Spiral structure in barred galaxies.

If you follow the link, you will find just one of many fine papers on the subject.

Here is just a brief abstract and even this shows a deep understanding about the spiral structure and the role the bar plays in the dynamical evolution of these galaxies:

Thanks for this article.

It offers deep data on Bars activities in wide kinds of spiral galaxies.

"We have measured here several parameters characterizing the bar, such as its length, the pattern speed, the angular momentum, and the bar strength. We have also determined some relevant properties of the arms of the galaxies: the pattern speed of the spiral structure and the pitch angle of the spiral arms. We study the influence of the bar on the spiral structure by interpreting the relationship between these two sets of parameters."

They hope that this data would help us to understand how spiral galaxy really works:

"These results give a guideline to theories of disc–bar evolution."

"In a more general way, the pitch angle can be used in tests of theories that show how the spiral arms are themselves formed."

 

They also offer recommendations:

"In general, the Lagrangian points L1,L2, L4, and L5, which define the corotation, are not aligned in a single circle (see fig. 3.14 of Binney & Tremaine 2008), this means that we should use the term corotation region rather than corotation radius, and this explains why we obtain peaks in the histogram of the phase-reversals"

 

They see a correlation between the spiral arms shape to the Bar:

"It is interesting to note that if the bar has either a very low value of the relative angular momentum or has a rather large value, then the spiral arms are tightly wound."

"This means that given a pitch angle of the spiral arms, those galaxies for which the disc mass fraction is minimum also host a bar with maximal relative angular momentum, and vice versa"

"The pitch angle varies uniformly with the radius, this means that the (θ, ln r) points of the spiral arm are better fitted by a polynomial than by a linear fit."

"the crossing point between the two envelope lines is at λ_bar ≃ 10⁻², which means that the most wide open spiral arms are found in galaxies that have a bar with a relative angular momentum of 10^−2"

"this shows that spiral galaxies with a stronger bar can only have a spiral structure with tightly wound arms, and also that an open spiral is found only in galaxies with a weaker bar. As shown in this figure, we do not find a galaxy in our sample that has a strong bar with open arms. This result does not favour the bar-driven spiral invariant manifold theory, which predicts that stronger bars should have less tightly wound arms (i.e. larger values of the pitch angle) than weaker bars"

As they see so deep correlation between the Bar to the Spiral arms, why they didn't ask themselves what kind of force can set a correlation?

Is it the dark matter or dark glue?

Why they didn't even consider the idea of tidal force?

 

However, they have noticed that the bars of the spiral galaxies are losing angular momentum, and therefore slowing down.

"we obtain that λ˙bar<0λ˙bar<0⁠, which means that the bar loses relative angular momentum while is evolving."

"In consequence, it means that the bars of the spiral galaxies are losing angular momentum, and therefore slowing down while growing in size and mass."

For me, this is the most important message.

If the bar is slowing down, then why it doesn't stop? Why we have never ever observed any bar as it stops? how come that all the bars in every millions over billions spiral galaxy keep their rotation/motion while they are losing angular momentum?

Do they have an answer for that?

Edited December 22, 2022 by Dandav