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View Full Version : Any "barred" spiral galaxy computer simulations please?



Questing1
2017-Feb-01, 05:07 AM
I'm trying to understand the theory behind the formation of, and stable persistence of galaxy "bars", if anybody can help please? Are there any computer simulations, and are these simulations well founded? are there any remaining questions and or disagreements concerning theories?

What I find interesting, is bars imply that stars are orbiting at increasing rotational velocities at increasing galaxy radius. I've been reading about the proposed solution to this, the theorized elliptical orbits of stars within the bar, but I cannot visualize important aspects of this. Like why would the bars then marry up with the sweeping galaxy arms that lay beyond the bar? I think I need a computer sim for this.

Thank you

DaCaptain
2017-Feb-01, 08:21 AM
A quick google search on "barred galaxy simulations" brings up a bunch of info and animations. Most of it looks pretty legit but others on this forum would be able to tell you what's accurate.

Reality Check
2017-Feb-01, 10:00 PM
Barred spiral galaxy (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.[6]
The citation is to Gas accretion on spiral galaxies: bar formation and renewal (2002) (https://arxiv.org/abs/astro-ph/0206273)

The effects of gas accretion on spiral disk dynamics and stability are studied through N-body simulations, including star formation and gas/stars mass exchange. The detailed processes of bar formation, bar destruction and bar re-formation are followed, while in the same time the disk to bulge ratio is varying. The accreted gas might be first prevented to flow inwards to the center by the bar gravity torques, which maintains it to the outer Lindblad resonance. While the first bar is weakening, the accreted gas replenishes the disk, increasing the disk-to-bulge ratio, and the disk self-gravity. A second bar is then unstable, with a higher pattern speed, due both to the increased mass, and shorter bar length. Three or four bar episodes have been followed over a Hubble time. Their strength is decreasing with time, while their pattern speed is increasing. Detailed balance of the angular momentum transfer and evolution can account for these processes. The gas recycled through star formation, and rejected through stellar mass loss plays also a role in the disk dynamics. Implications on the spiral galaxy dynamics and evolution along the Hubble sequence, and as a function of redshift are discussed.

SAO/NASA Astrophysics Data System (ADS) (http://www.adsabs.harvard.edu/) has plenty of results (960) for 'simulation barred spiral galaxy'. However these probably need more computing power than an individual has available.

Questing1
2017-Feb-07, 12:36 PM
Thank you guys. I'm finding some contradictory opinions. Unstable temporary bars? Stable sustaining bars? But I havent had the time I really delve into this subject yet. When I do, I'll share what I turn up