barred spiral has massive molecular inflow to core

[notFritzArgelander]

There's a HST image of NGC 1300 but ESO320-G030 was studied.

https://phys.org/news/2021-05-barred-ga ... nflow.html

[Michael131313]

That is a quite spectacular image. Thanks nFA

[Graeme1858]

Who would have thought there would be water vapour at a galaxy starburst region!

Interesting article.

I put NGC1300 into Stellarium, a great AP target for next winter!

Regards

Graeme

[helicon]

I'm really surprised by the water vapor finding.

[turboscrew]

What causes some galaxies to have the bars?

[notFritzArgelander]

What causes some galaxies to have the bars?

Most galaxies that have spiral arms also have bars these days (~65%) it's a sign of maturity. In the early universe bars among spirals were only about 20%.

Bars and spiral arms coming off central bars were explained in the mid 1960s as density waves by Lin and Shu. Some external gravitation perturbation such as a close encounter with another galaxy sets up a resonant response in the galaxy disk. The full details are described in https://en.wikipedia.org/wiki/Density_w ... piral_arms

With regard to the specifics of bar formation see https://en.wikipedia.org/wiki/Barred_spiral_galaxy.

The creation of the bar is generally thought to be the result of a density wave radiating from the center of the galaxy whose effects reshape the orbits of the inner stars. This effect builds over time to stars orbiting further out, which creates a self-perpetuating bar structure.

The Lindblad resonance is another important idea, historically. https://en.wikipedia.org/wiki/Lindblad_resonance It was an intuitive leap that the Lin and Shu theory did the maths to explain.

[turboscrew]

Ah. Didn't really understand yet, but got the idea. Thanks!

[notFritzArgelander]

Ah. Didn't really understand yet, but got the idea. Thanks!

It’s actually the same problem as calculating the modes of a vibrating membrane. Except that instead of displacement from equilibrium you have patterns of density.

[turboscrew]

Ah. Didn't really understand yet, but got the idea. Thanks!

It’s actually the same problem as calculating the modes of a vibrating membrane. Except that instead of displacement from equilibrium you have patterns of density.

And I guess the "beats" are gravitation field changes due to bigger lumps of matter rotating around the nucleus?

[notFritzArgelander]

Ah. Didn't really understand yet, but got the idea. Thanks!

It’s actually the same problem as calculating the modes of a vibrating membrane. Except that instead of displacement from equilibrium you have patterns of density.

And I guess the "beats" are gravitation field changes due to bigger lumps of matter rotating around the nucleus?

Yes. The complication is that there's a nonlinear feedback mechanism through the density dependence of the gravitational potential.

[turboscrew]

It’s actually the same problem as calculating the modes of a vibrating membrane. Except that instead of displacement from equilibrium you have patterns of density.

And I guess the "beats" are gravitation field changes due to bigger lumps of matter rotating around the nucleus?

Yes. The complication is that there's a nonlinear feedback mechanism through the density dependence of the gravitational potential.

You mean, a little bit like Lotka-Volterra?

[notFritzArgelander]

And I guess the "beats" are gravitation field changes due to bigger lumps of matter rotating around the nucleus?

Yes. The complication is that there's a nonlinear feedback mechanism through the density dependence of the gravitational potential.

You mean, a little bit like Lotka-Volterra?

Yes, a bit. The peaks in the predator prey populations are more like the 2 dimensional spiral shaped density peaks than one might guess at first.

[notFritzArgelander]

Yes. The complication is that there's a nonlinear feedback mechanism through the density dependence of the gravitational potential.

You mean, a little bit like Lotka-Volterra?

Yes, a bit. The peaks in the predator prey populations are more like the 2 dimensional spiral shaped density peaks than one might guess at first.

You know, the more I think about it, the more exact the analogy between spiral arms of gas and stars and predator-prey populations becomes!

In the analogy, the bunnies are necessary for more wolves to be supported. So the bunny population peaks before the lynx population does. Similarly at a given radius, the gas density peaks before the stars do. There is an offset between the spiral pattern of the gas and the spiral pattern of the stars as I recall. Here is a reference that exhibits that offset for the galaxy M51.

https://academic.oup.com/mnras/article/ ... 60/2417434

Stars are like the predator, feeding on the gas. The physical mechanisms underlying the rotational motion around the galaxy are quite different though. The gas hangs together due to viscosity effects while the stars don't.

So the predator-prey relationship over time is A LOT like the spiral density wave pattern in space.

This kept me entertained very nicely and I had new thoughts. Thanks!