How do we test galaxy rotation

[BrankoRBabic]

Hi,
I wonder if there is a way to confirm that this forming ring galaxy has 3 degrees of rotation. For example, it seems that in this example, we have a ring galaxy in formation and one where the outer ring is in the processes of formation. But, it seems that the jets are emitting mass which is condensing an outer ring that is rotating clockwise. The ring also seems to be forming in two directions ie clockwise and also away from the central line. The inner mass seems to be rotating anticlockwise. That would make 3 degrees of rotation.
Any scientific tests available that would confirm 3 directions of rotation? Anyone got any ideas how to test and confirm direction of rotation in this galaxy?

 

[MeteorWayne]

What galaxy is it? Where does the annotated image come from? You need to give us some clues here

 

[BrankoRBabic]

Thanks Meteor.
This is the URL for this unbelievably beautiful galaxy. This must be one of the most beautiful sights I have come across and ought to be included in the best selection:

http://lh3.ggpht.com/_BDqap12Vdd0/SYZdQ ... -large.jpg

The example is full of interesting mechanistic steps. It seems to me that this example demonstrates 3 degrees of movement and could explain the wobble characteristic seen in this and other spiral formations:

http://s3.amazonaws.com/zoo2/123172.jpg

How would we scientifically, confirm that the galaxy is undergoing 3 degrees of movement?

 

[Saiph]

That appears to be a pair of colliding galaxies that hasn't settled out yet.

We test for rotation by taking a spectrum of the entire galaxy (or sections of it) and measuring the dopler shift across the disk.

 

[BrankoRBabic]

Thanks Saiph,

I thought this might be an early stage ring galaxy formation. The bilateral “Relativistic Jets” that are seen either end (ie 10 and 4 o’clock) appear to be spewing out mass. If this is mass being ejected from the “accretion disc”, then a mechanism for the formation of the outer ring of the ring galaxy might be in evidence:

http://lh3.ggpht.com/_BDqap12Vdd0/SYZdQ ... -large.jpg

The second example is a similar construct but at a much later stage where the outer ring of the galaxy is complete ie the central core has rotated 360 degrees to complete the outer ring:

http://casjobs.sdss.org/ImgCutoutDR6/ge ... height=512

Do you have the know-how to determine if these galaxies are spinning in the proposed way?

 

[Saiph]

I probably have the know-how, but I don't have the data. And as I don't have the experience/training required to utilize the data...any results would take a while

You can't tell much from a simple picture. For your idea you'd need the spectra of the galaxies, ideally chopped up into various sections so you can see what's going on in each section.

 

[BrankoRBabic]

Thanks Saiph,

could you have a try?

I do not have any other information on these galaxies but it would be a very useful exercise and not only because if a black hole at the centre of these galaxies is the entity that rotates in 3 dimensions, dragging all mass with it, then we have made a contribution by providing an insight into the behaviour of black holes!

 

[Saiph]

I think you're giving the BH to much credit. Their sphere of influence isn't that large, and is incapable of affecting the galaxy as a whole.

As for the analysis: I'll tell you what I can right now: In a colliding system you'll get sections going in all sorts of directions...but I'm unsure as to what you're looking for, or how it matters. I.e. I don't understand your question or hypothesis.

I also have very little idea of where to get that data, as I haven't been in that loop since I left college.

As for the jet creating the out ring, the jet has quite a bit of mass, sure, but not THAT much! The main reason we see it is because of it's high temperature, not because there's a lot of stuff there. Once that gas cools it'll disappear completely. In order to have a large, sustained structure to a galaxy it has to be a site of star formation, and that jet doesn't cut it.

 

[SpaceTas]

Yes the basic method is to take spectra and look at the radial velocity of the main stellar lines. For spiral galaxies (any galaxy with cold gas) you can use the H II line in the radio. The optical spectra are either a long slit placed along the axis of symmetry, then you get a 1 D slice of the galaxy. Less commonly (takes longer to do or need specialized instrument) spot spectra are taken and a map of velocity is made. I have added a spectrum of a starburst galaxy. It has emission lines, see how they curve that curve is caused by the different velocities of the glowing gas along the slit. From Cornell.

The link is http://coursewiki.astro.cornell.edu/foswiki/pub/Astro4410/HboInstruments/starburstspectrum.gif

A similar thing is done to measure the mass of black holes in the center of galaxies. But the effect of the black hole is only measurable, near the center. Here is a link to the classic HST example:
http://hubblesite.org/gallery/album/exotic/pr1997012a/

What is the name of the originally posted galaxy and origin of the image. I recognize it, but can't remember its name. Also it looks a bit like a multiwavelength composite; the perpendicular parts being x-rays from jets. I believe the radial velocity study of this galaxy has already been done.

 

[SpaceTas]

Ah!
I just recognized the galaxy.
It's Cen A (=NGC5128) and the image is a composite.
Link to image.
http://chandra.harvard.edu/photo/2009/cena/
I even took a spectrum of it years ago.

So the stuff perpendicular to the dust lane (blue x-ray, light orange submillimeter radio) is from the jet starting at the central black hole, so not really part of the general galaxy and its rotation.

 

[SpaceTas]

The second galaxy image posted by BankoR... is of NGC 660 etc. The images is from Sloan Digital Survey.
http://cosmo.nyu.edu/hogg/rc3/NGC_660_UGC_1201_IRAS_01403+1323_irg.jpg

Just did a quick search to see if the rotation curves have been measured.
not much joy

 

[BrankoRBabic]

Thanks Saiph,

Given the said extreme gravitational properties of black holes, I do not believe that its gravitational effect is as limited as people say. In particular, one questions the nature of gravity and how such a weak force exerts so much effect throughout the universe.

Gravitational effects, universe wide, become easier to grasp if we consider how gravity exerts its effect. I believe that gravity is a weak, short range force that propagates from one gravity producing entity to another, in continuum. What I am trying to put across here is that gravity exerts its effect locally, to influence the next in line gravity point, which exerts its effect on the next in line gravitational entity and so on throughout the universe. Gravity therefore as I see it, propagates across the universe exercising gravitational effect on near by gravitational entities. The problem is to find a means by which one could test such a statement.

Is it conceivable that gravity is a property of precessing mass units?

 

[MeteorWayne]

Well that would go against the most sucessful theory that has made precise predictions that we verify every day: General Relativity.

You better flesh out your theory a bit more before challenging Einstein and decades of observations.

And BTW, a black hole has no more gravitational effect than any other object of the same mass that isn't compressed into such a small space. If it was a hundred thousand stars over the space of a light year, once you are more than a few light years a way, it acts just the same. There's nothing special about a black hole's gravity, other than the mass is condensed in a very small area. Unless you are very close, it makes no difference.

 

[Mee_n_Mac]

Thanks Saiph,

Given the said extreme gravitational properties of black holes, I do not believe that its gravitational effect is as limited as people say. In particular, one questions the nature of gravity and how such a weak force exerts so much effect throughout the universe.

Gravitational effects, universe wide, become easier to grasp if we consider how gravity exerts its effect. I believe that gravity is a weak, short range force that propagates from one gravity producing entity to another, in continuum. What I am trying to put across here is that gravity exerts its effect locally, to influence the next in line gravity point, which exerts its effect on the next in line gravitational entity and so on throughout the universe. Gravity therefore as I see it, propagates across the universe exercising gravitational effect on near by gravitational entities. The problem is to find a means by which one could test such a statement.

Is it conceivable that gravity is a property of precessing mass units?

When you say "short range" and "local" how "short" do you propose ? Within our solar system the orbits are determined mostly by the Sun's gravity but perterbations due to other planets are noticable. So it can be proven that, at solar distances, gravity is "additive" and is not progressive from one planet to the next. Given it works that way locally, why would you propose it works differently at larger distances ?

 

[BrankoRBabic]

What a helpful reply Space Tas, thank you very much.

As electrons are emitted and flow at about half the speed of light through the centre of the jets, presumably they interact with plasma particles to produce atoms. At that speed, electrons colliding with inner atomic electrons would provide a means whereby x-ray generation could be ongoing.

The really interesting possibility is that, as electrons form atoms interact with plasma particles emitted from the accretion volume, would electron interaction with black matter plasma also lead to elemental formation. If so, then the dust trail at the tip of the jets would presumably, in time, aggregate into mass that could eventually lead to planets and stars. Is the outer ring of the below ring galaxy dust or larger mass aggregations:

http://casjobs.sdss.org/ImgCutoutDR6/ge ... height=512

Ask the astronomer said this facility so Meteor Wayne, if precession of say sub atomic particles does not generate gravity what does. Any ideas?

 

[MeteorWayne]

I'd suggest you read what Einstein had to say, and do a little research on the current understanding of gravity before you create a new theory that has no basis in observed physics.

 

[BrankoRBabic]

I'd suggest you read what Einstein had to say, and do a little research on the current understanding of gravity before you create a new theory that has no basis in observed physics.

Thanks Meteor Wayne but what in YOUR opinion, generates gravity?

 

[BrankoRBabic]

Thanks Mee-n-Mac but when talking of gravitational effects in galactic terms, I have no idea of what the active distances would be but for example, the black hole (BH) exercises a gravitational effects that must extend to beyond the diameter of the accretion volume.

The very local effect of gravity the BH is said to exercise seems very under estimated. What would the accretion diameter be if the BH gravity did not exercise a distinctive effect on the accretion volume contents?

 

[DrRocket]

I'd suggest you read what Einstein had to say, and do a little research on the current understanding of gravity before you create a new theory that has no basis in observed physics.

Thanks Meteor Wayne but what in YOUR opinion, generates gravity?

That sounds suspiciously like the debating technique of someone with an axe to grind and likely someone with a wacko theory to advocate. Your idea of the propagation of gravity along sequentially arranged bodies qualifies handily.

MeteorWayne's opnion is irrelevant, even though his opinion is well supported. As he told you, the best available theory of gravitation is general relativity. In that theory what we call gravity is an effect of the curvature of the space-time manifold. That curvature is described by a tensor and, up to a constant multiple, the curvature tensor is the stress-energy tensor, also called the momentum tensor. The stress-energy tensor is determined by the distribution of mass and energy in the universe.

General relativity is well supported by experimental evidence and has proved to be quite accurate. It has withstood the challenges of all competing theories, save one, that are refuted by the same data that supports general relativity. The sole exceptin is Einstein-Cartan theory, which is experimentally indistinguishable from GR with current measurement technology. Einsten-Cartan theory does not support your incorrect notion of gravity either.

 

[BrankoRBabic]

Thank you Dr Rocket.

Clearly no room for a creative discussion there.

 

[Saiph]

I'm sure some here would be game for creative discussion, as long as you present it as such. If you ask how things would look or behave if we had such a way to propagate gravity you'll get a different response than insisting that's how it really is.

For instance if it propagates via connections between bodies, there is no change in the simple 2 body system. However, should you implement a 3 body problem you have some sever complications. The gravity from the core body, requiring the transmission via an intermediary to the outlying 3rd body has it's gravity highly variable to that last body, depending entirely upon the position of the middleman. It's quite possible that the middleman be far enough away, or out of position for transmission, means the gravity of the core object isn't transmitted at all to the 3rd body....which drifts off into space.


The big problem with this idea is why can gravity be directly transmitted to one close body, but not a further body? Why the intermediary? What's different? Does the gravity seem to still come from the primary? or the intermediary?

 

[SpaceTas]

Hello all,

there has been a digression of topic in 2 directions. One is on the link between galaxy rotation and central black holes and from there into the nature of gravity ....

It is only within a few black hole radii that the effects of general relativity dominate orbits i.e. the innermost stable orbit. Beyond that normal Newtonian mechanics is good enough for a general idea. So now consider what a star feels far (many many radii) from a black hole at the center of the Milky Way. (I'll use our galaxy because I can remember the numbers). The central black hole is about a million solar masses, and acts as a point mass, around that is the central bulge of the galaxy with about 30 million solar masses. For a distant star this too would act like a point mass, and would produce 30 times the gravity force (Force gravity goes as Mass) from the black hole.

Generally once you are away from an object or collection of objects, the gravity rules act as if the object is a point mass and you have Keplerian orbits with the orbital velocities decreasing as 1/r (r=radius from center). So at some point once you are outside most of the mass of the galaxy you would expect the velocities to decrease as 1/r. In fact the velocities don't, throughout most of the galaxy the velocities are roughly constant. This holds at long distances from the center. Explaining this is easy; you are still within the body of galaxy; inside the mass distribution. However, the visible stars, dust gas etc is not enough to explain the flat rotation curve especially way at the edges of the visible galaxy. Hence dark matter or a modified version of gravity at long distances (eg MOND).

Every measurement so far has the mass of the central black hole as a small fraction of the mass of the galaxy; hence for the most part it can be ignored.

Close up ignoring a black hole is "nuts".
Not all black holes create extreme tidal effects near them. These are described as turning astronauts into spaghetti etc.

For stellar mass black holes, the tides are extreme. Near the Swartzchild radius the "difference in gravity force" (= tide) between the feet and head of a human ("standing up") is like trying to do chin-ups with the weight of 10 million people hanging onto your feet. Sorry couldn't resist the analogy.

But near a 10 million solar mass black hole the tides (differences in gravity) are much less and our "astronut" would easily remain intact and be able to do chin-ups all the way to the event horizon. The reason is tides go as 1/(r*r*r) and the radius of a black hole goes up as its mass. So a 10 million mass black hole is million times the radius of a 10 solar mass black hole but produces 1/(millionxmillionxmillion)th less tidal stress on our "astronut". Continuing the analogy, our "astronut" experiences only 1/(million x million)th of the weight of the average human rather than 10 million times the weight. ......... No sweat, if you can do normal chin-ups.

So 2 sorts of gravitational extreme effects (GR and tides) are limited to close to the black hole and don't affect the galaxy as a whole.

 

[MeteorWayne]

Very well said, and welcome to Space.com!!

 

[DrRocket]

Very well said, and welcome to Space.com!!

I'll second that !!!

Factual, clear, informative, and consistent with physics. Couldn''t ask for more.

 

[BrankoRBabic]

In this remarkable image of jets emitted from the central region of the Centaurus A we see jets which are said to be rich in electron content. Are these bilateral jets equal in the quantity of material emitted. For example are the jets bipolar i.e. is one jet rich in electrons and the other rich in positrons?

http://chandra.harvard.edu/photo/2003/c ... et_420.jpg