James Webb Space Telescope spies Milky Way mimics that could challenge theories of galaxy evolution

JWST seems to show objects that are causing some viewers, headaches :) I note from the paper published for this report.

ref - First Look at z > 1 Bars in the Rest-Frame Near-Infrared with JWST Early CEERS Imaging, https://arxiv.org/abs/2210.08658, 12-Dec-2022.

"Stellar bars are key drivers of secular evolution in galaxies and can be effectively studied using rest-frame near-infrared (NIR) images, which trace the underlying stellar mass and are less impacted by dust and star formation than rest-frame UV or optical images. We leverage the power of JWST CEERS NIRCam images to present the first quantitative identification and characterization of stellar bars at z>1 based on rest-frame NIR F444W images of high resolution (~1.3 kpc at z ~ 1-3). We identify stellar bars in these images using quantitative criteria based on ellipse fits. For this pilot study, we present six examples of robustly identified bars at z>1 with spectroscopic redshifts, including the two highest redshift bars at ~2.136 and 2.312 quantitatively identified and characterized to date. The stellar bars at z ~ 1.1-2.3 presented in our study have projected semi-major axes of ~2.9-4.3 kpc and projected ellipticities of ~0.41-0.53 in the rest-frame NIR. The barred host galaxies have stellar masses ~ 1×10^10 to 2×10^11 M⊙, star formation rates of ~ 21-295 M⊙ yr^−1, and several have potential nearby companions. Our finding of bars at z ~1.1-2.3 demonstrates the early onset of such instabilities and supports simulations where bars form early in massive dynamically cold disks. It also suggests that if these bars at lookback times of 8-10 Gyr survive out to present epochs, bar-driven secular processes may operate over a long time and have a significant impact on some galaxies by z ~ 0."

My observation. The March issue of Sky & Telescope has a report on spiral galaxies. "14 Where Do Spirals Come From? Spiral galaxies are ubiquitous in the nearby universe, yet we still don’t know how their patterns arise." "By Monica Young" It seems the need for recycling spiral arms over billions of years is acute and density waves must recreate spiral arms regularly, but they will look different too at different ages. However, spiral galaxies as seen by JWST out to 11 billion light years, is well beyond *nearby*. Using cosmology calculators, z=3.0 is about 11.5 Gly distance. Trouble here in BB cosmology? I note another report from concerning JWST spiral galaxies seen too.

Reading about spiral galaxies I was surprised to find that the arms are not groups of stars that travel together. They are density waves, like traffic slowdowns. At some particular radius, called the "corotation radius" the stars and the arms rotate at the same angular velocity. Outside that radius the arms travel faster than the stars, inside that radius the stars travel faster than the arms.
I hazard a guess the formation of arms is the result of two competing forces, just as traffic slowdowns are. In traffic, people are far quicker to slow down when they start closing the gap with the car in front of them than they are to speed up once the gap opens.
I can't hazard a guess how that occurs in galaxies though.