On 20/02/2017 19:50, wrote:
On Wednesday, February 8, 2017 at 7:45:27 AM UTC-8, Martin Brown wrote:
On 06/02/2017 05:56, wrote:
On Tuesday, January 24, 2017 at 9:06:13 AM UTC-8, Martin Brown wrote:
On 23/01/2017 22:45, wrote:
On Friday, January 20, 2017 at 8:44:02 AM UTC-8, Martin Brown wrote:

Thanks for the links and comments.

Question: Is there evidence that material (gas and or stars) is
"raining" back down onto galaxies where the radio jets appear to
be old and fading?

Not really. You are guessing and still haven't provided us with some
idea of where to pitch explanations.


See Malin image at end of this post...........that's the stuff above the
galaxy that's observed for many galaxies. I'm looking for evidence that
stuff falls back inward and reduces the angular momentum of the material
and stars around the central BH system.

I forget the references (could look them up, but....), but I recall that
active galaxies with jets have excess angular momentum compared to
average.

The reason that a black hole spins up is that it is very compact just
like a ballet dancer spins up when they bring their arms in. The stars
and other infalling matter in the accretion disk brings in ever more
angular momentum with it and that has to be conserved.

It would be as well to study the standard explanation of how Centaurus A
looks like it does before concocting a new explanation.

http://chandra.harvard.edu/photo/2002/0157/

Fairly serious shockwave through it around 10My ago is the favourite.

So what I'm exploring and asking about, is the idea that a pair of
galaxies merge, the angular momentum of the stars is over time
communicated to the center. The massive black holes meanwhile move and
themselves merge....my idea I'm exploring is that this creates a bar of
stars, then the black holes slide down the bars and merge........see
wiki: https://en.wikipedia.org/wiki/Barred_spiral_galaxy

A dust lane is easy to see in many barred galaxies, and the dust lanes
are not aligned. They are offset and near center, curve into a circular
geometry. Imagine that's the ~path taken by the black holes which began
at the ends of the bar and created the bar, then after losing some
angular momentum, slid down the bar into the center and merged (or will
merge in cases where there still exists a pair of BH's observed)

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.

(is there any observation where there is a bar in a galaxy, AND, there
are a pair of bright knots mid way to the center? ie, is there any
galaxy where there are perhaps two partial bars that don't connect on
center?)

That then creates excess angular momentum in the core after the BH's
have merged, and that then creates the jets. At least that's the idea
I'm exploring.

If true, then the only galaxies that should have jets are those where
there is excess angular momentum near the central black holes. The
question the n is, do the radio jets carry matter and or stars with
them?

The jets will surely entrain a small cylinder of material with them but
they won't do much to a star or gas cloud beyond a quick bright flash
(and slowing it down for a while) - especially since the motion of a
star would not leave it in the jet for very long. Scheuer's denist's
drill model of jets still fits the observations pretty well.

http://mnras.oxfordjournals.org/cont.../1513.full.pdf

Easy answer, no, but, see:

David Malin ultra deep image of Centaurus A showing faint stellar
extension s aligned with galactic radio jets (google search images,
"david malin, deep image, centaurus A" if link doesn't work:

https://www.google.com/url?sa=i&rct=...urce=images&cd
=&cad=rja&uact=8&ved
hUKEwie4q-Ro5_SAhUCyWMKHRfuClkQjRwIBw&url=
http%3A%2F%2Fwww.pbase.com%2Fimage%2F110608746&psi gQjCNHhArY_rn55WQOZp
Sdxzgu6_6ah0g&ust=1487700691719675

There is something that is out along the line of the jets (gas, stars,
both?). And IF matter were to rain back down onto a system with
increased angular momentum, the "rain" would be perpendicular to the
angular momentum of the initial system, thus reducing the angular
momentum............transforming a spiral into an elliptical (or
increasing the size of a central bulge).

You clearly don't understand angular momentum so this is going nowhere.

You would have to drop serious amounts of matter in a retrograde orbit
into a black hole to appreciably alter its huge angular momentum. Whilst
I am inclined to never say never I am pretty sure that it would require
incredibly exceptional circumstances for this to happen in a real galaxy
system.

A retrograde orbit BH merger would be about the only thing that might.

--
Regards,
Martin Brown