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#11
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
I should mention, regarding the rain idea I'm studying, that if matter is s=
hot out of a galaxy along the axis of rotation by BH jet activity, and it s= ubsequenty "rain's" back down onto the galaxy, the NET angular momentum of= the "rain" would also be zero. It would also be orthogonal to (have angul= ar momentum vector orthogonal to) the angular momentum of the galaxy. Thus, rain if it exists, will reduce net angular momentum of a galaxy, shut= ting down rotation and evolving the galaxy from spiral forms toward EO. This is possible if the individual particles, stars, gas, dust, rain back d= own along highly elliptical geometries with long axis coincident with galac= tic rotation vector, AND, the rain is random with regards to which side of = the central black hole it falls on. This way, the momentum vectors for eac= h "particle" are roughly within the disk of the galaxy's rotation, ~normal = to it's angular rotation vector. But the vector for each particle is diffe= rent so that there is no net rotation axis. In a sense, the rain would probably be a bit like a faint bar of stuff that= thermalization would randomize......the rain would become random like orbi= ts in a GC, and, the matter of the galaxy with which the interaction took p= lace would also become more random, more like an elliptical. So, BH jets, are observed to eject matter. **IF** that matter rains back d= own, then it should act to evolve the galaxy toward elliptical by some degr= ee. More rain, more evolution. Question is, can any observation detect such a rain IF it exists? We see f= aint extensions. But finding their velocity is harder still and I don't kn= ow of any observation for the velocity of the faint extended material along= BH jet axis'. This mechanism is why the EO to Bar evolution path makes no sense to me. T= here are only old stars in ellipticals. Barred spirals have newborn stars.= And most galaxies observed are ellipticals, and they have only old stars.= EO ought to be the end game it seems to me. Is it the general expectation that all elliptical galaxies will evolve to b= arred spirals eventually? rt |
#12
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
On 26/02/2017 04:43, wrote:
On Thursday, February 23, 2017 at 7:47:09 AM UTC-8, Martin Brown The general theory is that as galaxies age they mature towards having a barred spiral structure through perturbations of the stellar orbits in the galactic gravitational potential. See for example: https://www.nasa.gov/mission_pages/h..._galaxies.html http://hubblesite.org/hubble_discove..._evolution.pdf The same happens in numerical simulations of stars in galaxies. Nice images, some of my favorite galaxies. The sequence for bar evolution seems backwards to me (counter to entropy which wants to randomize things....globular clusters and ellipticals seem to me to be the end stage of evolution). Entropy doesn't mean what you think it means. When a galaxy is formed the original conditions determine how much total angular momentum it inherits from the gas cloud that it formed from. The ratio of mass to angular momentum influences what it looks like and at a certain amount of angular momentum spontaneous symmetry breaking occurs and the whole thing looks much more complicated. Q Is it known at what ratio of mass to angular momentum a forming galaxy necessarily becomes a spiral rather than elliptical? Here is one paper I found which tries to address the problem semianalytically. I found another but lost the link. Perhaps someone can suggest a better review of the morphology and secular of galaxies in relation to their instrinsic angular momentum. https://arxiv.org/pdf/1605.00647.pdf The formation of a bar also seems counter to Rubin observation that the circular velocity is constant with radius.......the larger circular orbit would inevitably sweep the arms into a spiral. ISTR that in the early days of large scale galactic simulations they had to work very hard to prevent bars from falling. I suspect bars and ellipticals represent a galactic manifestation of Ovenden's conjecture that stellar systems evolve towards configurations where the stars keep their distance from each other as far is possible. This is more the sequence that I'm studying / seeking evidence for: 1) Mice https://en.wikipedia.org/wiki/Mice_G...Telescope).jpg 2) Fornax https://en.wikipedia.org/wiki/Barred...a-99-hires.jpg 3) ngc1097 https://en.wikipedia.org/wiki/NGC_1097 4) ngc1232 https://en.wikipedia.org/wiki/NGC_12...e:NGC1232B.jpg This is about opposite the sequence at the Hubblesite link you sent. Basics: The net angular momentum of a globular cluster of stars is zero, right? Certainly small angular momentum. And slowly getting smaller by expelling the odd star to infinity and the remainder becoming ever more tightly gravitationally bound. Same for an elliptical (generally and ignoring the possible small rotation component some have). In contrast, spirals have large angular momentum in their outer disk stars, vs (much? near zero) smaller angular momentum in their central bulges of stars. That is because angular momentum scales as Mr^2 As suggested, To merge a counter rotating galaxy is a way to zero out the angular momentum. That's not what I'm suggesting. But that is the only thing that will work (or a galaxy with same spin whose orbit is retrograde to the first and with goldilocks conditions to null out the total angular momentum). Angular momentum is a *vector* quantity you have to add an equal and opposite amount to null it out. If you instead add angular momentum that is orthogonal, then you randomize the stellar orbits. This is what we see in ellipticals and globulars. Nonsense. If you added an orthogonal amount of angular momentum to original galaxy one with W1 = (I, 0, 0) and add W2 = (0, I, 0) You get a new merged galaxy with WTot = (I, I, 0) In other words sqrt(2).I and at 45 degrees to the original spin axis. The angular momentum of matter raining down along an approximately axial line (ie, in a highly elliptical orbital geometry, with the long axis of the ellipse being the rotation axis of the galaxy. Then, the axis of rotation for the galaxy is orthogonal to the axis of rotation for the ellipse of in falling material. You really do not understand the basics of Newtonian dynamics. As this "rain" component becomes "thermalized" by interacting with the mass of the galaxy, some of the disk stars orbits are transformed into elliptical orbits. In this way, a spiral galaxy could evolve to become an elliptical galaxy. Angular moment is one of the key invariants that is conserved in an isolated system - and that remains true even in the full GR treatment. And it all began from the BH that ejected matter along the axis of too much angular momentum. Each episode of activity, increasing the size of the bulge, until eventually the galaxy is an elliptical and the stars can age from there............(ellipticals have older stars) It doesn't work like that. You would have to drop serious amounts of matter in a retrograde orbit Serious amounts of matter............yes But the angular momentum would remain the *same* the galaxy might spin more slowly as it became more massive since the same angular momentum would be shared by a larger total mass retrograde orbit.............no. It needs to cancel out or randomize, the existing angular momentum. See above. Sorry but you do not have a clue. -- Regards, Martin Brown |
#13
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
In article ,
writes: Is it the general expectation that all elliptical galaxies will evolve to barred spirals eventually? No. Most, maybe all, galaxies evolve to ellipticals. There is great debate about the mechanism and the timing of this evolution, but observations show greater fractions of ellipticals at later cosmic times. One paper I happen to be familiar with is at http://adsabs.harvard.edu/abs/2015ApJ...803...26P I especially like Figs 12 and 13 (and had nothing at all to do with making them other than helping provide some of the data). -- Help keep our newsgroup healthy; please don't feed the trolls. Steve Willner Phone 617-495-7123 Cambridge, MA 02138 USA |
#14
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
On Wednesday, March 1, 2017 at 1:43:29 PM UTC-8, Martin Brown wrote:
On 26/02/2017 04:43, ross wrote: On Thursday, February 23, 2017 at 7:47:09 AM UTC-8, Martin Brown If you instead add angular momentum that is orthogonal, then you randomize the stellar orbits. This is what we see in ellipticals and globulars. Nonsense. If you added an orthogonal amount of angular momentum to=20 original galaxy one with W1 = (I, 0, 0) and add W2 = (0, I, 0) You get a new merged galaxy with WTot = (I, I, 0) In other words sqrt(2).I and at 45 degrees to the original spin axis. Regards, Martin Brown OK, fine, yes I understand and see that result. But you are considering just one infalling object and it's single interaction with a single entity of the original galaxy. Suppose I have a spiral galaxy, disk with central bulge. We can find the net angular momentum. Now, thought experiment, I take a bunch of mass, call it a bunch of stars and I place them far above the spiral galaxy, say 100,000 to 200,000 light years from the black hole, in a clump along the axis of rotation of the spiral galaxy. Then, I allow all of these stars to rain down onto the spiral galaxy. They fall on random sides of the black hole, and have random elliptical motions with a very large eccentricity..........long axis parallel to the spiral axis of rotation. Suppose the total mass of this infalling material is significant in comparison to, but smaller than, the mass of the spiral galaxy. For each in falling thought experiment star, that interacts with a star of the spiral, the net angular momentum will become as you say, at a 45 degree angle. =20 HOWEVER, some of the in falling stars have a 45 degree angle one way, and others have a 45 degree angle in another orientation. And, as the falling stars manage to fall all around the black hole like rain drops, the net angular momentum for each of these infalling stars is in a different direction. Further, some are falling from North pole down onto the galaxy, others are falling from the South pole up into the galaxy, further increasing the random nature of the resultant stellar motions. Take those, and then secondary and tertiary further interactions with the spiral galaxy stars, and the total motions become randomized and the galactic net angular momentum will be reduced..........right? Now I don't know that it is known what the faint extensions of active galaxies are (gas, dust, stars, ????.........e.g. David Malin's unsharp masking method for bringing out faint details for these objects, showing extensions coincident with radio jet directions for several active galaxies.... So I don't know that the extensions are stars (does anyone?) But no matter what, if the total mass is significant and if that mass rains back down, it still seems to me that it should reduce the net angular momentum of the spiral. rt |
#15
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
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#16
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Single vs Double hot spots for BH Jets? (e.g. Pictor A)
OK, decades since I've crunched some of these equations, so thanks for
the refresher. How about this example: at (0,0,0) I have a SMBH at the center of a galaxy. The galaxy is purely a disk of stars in the XY plane, with rotation about the Z axis. Right hand rule, thumb North, fingers show stellar rotation direction. Disk is thin, call it 1pc compared to 50kpc radius for the disk. Now, I drop a bunch of stars from N and S of the SMBH. They fall onto different sides of the SMBH, AND, they thermalize with the disk stars. Seems to me I will form a central bulge where initially none existed. From your comments (which make sense), the net angular momentum of the system will not change. But where I'm still confused, is how the sum of angular momentum of the in falling material, adds to the disk rotation angular momentum. for the disk material, the angular momentum vector is in the north Z direction. For the infalling material, the angular momentum vector for each in falling star is in the XY plane, orthogonal to the disk material. As the infalling material "thermalizes" with the disk stars, a central bulge will form with random motions..........but I am not sure how the Net becomes changed or if it does. If the infalling material falls in equally on all sides of the central SMBH, then, it must have zero angular momentum. Therefore by your comments, (which make sense) the resultant bulge must have a net angular momentum that's still along the Z axis north. right? rt |
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