For some in-depth movies of what happens when two galaxies collide, click here. As a result, the well-ordered disk we saw before never has as much chance to survive and grow before it is destroyed by these encounters. Unlike the previous system, this has many mergers - violent collisions - with other galaxies, over a wide range of times. These movies are of a galaxy with similar mass, but one which experienced a more violent history. The different movies in the series show different observable quantities: what the galaxy would look like to the Hubble Space Telescope, or in X-rays, or if you could see different observational tracers of star formation and gas in the galaxy. This series of movies shows the galaxy at present day, and “flies through” from the outskirts to the center and back again, so you can see all the structure. For a movie of the gas on large scales, click here. This links to a movie of the gas, on the same scale as the image and stellar movies above. If you’re curious, here’s a picture of the gas in this galaxy, with the same style as above (magenta for cold/neutral gas, green for warm ionized gas, and red for hot gas). The images above link to full movies of the simulations, or you can download them here and here. Then you really see how thin the disk forming the young stars in the central few kiloparsecs of the galaxy can be. But we also show an image where we don’t allow dust to attenuate the stars. To make it easier to read, we show the full mock images of the stars (same style as the previous figure set), including the extinction by dust. Thin disks are possible, and compatible with strong feedback! It has been a challenge for decades to produce galaxies with thin disks, and some people have argued it may be incompatible with strong feedback - but the parameters in these simulations are all identical, and the mass here agrees well with observations. We see a remarkably thin disk of young stars - this is despite the violence of the outflows from the galaxy. These images show the disk of the present-day galaxy, in stars and gas, formed in our simulation with an “intermediate” history (at Milky-Way masses). Gas and the Formation of Disks from the Cosmic Web: Face-on and Edge-onīelow, you can see movies of a simulation starting from slightly different initial conditions, with a different color scheme designed to highlight the cosmic web feeding the galaxies. Here you can see much more of the structure of the surrounding inter-galactic medium - the “cosmic web” and how it is impacted by galactic winds. This shows the gas from the same simulation, but on a larger scale (200 kpc, instead of 50). Magenta is cold molecular/atomic gas (T10^6 K), making up the galaxy halo. Red regions are obscured by large amounts of dust. Blue regions are young star clusters which have blown away the gas and dust out of which they formed. This shows a mock three-color image (u/g/r bands) of what this galaxy would look like in visible light wavelengths. At later times, things “calm down” and a more relaxed disk starts to form. Massive outflows driven by feedback from stars are plainly evident, and especially at early times have a dramatic impact on the surrounding inter-galactic medium. The scale is fixed at 50 physical kiloparsecs on a side (so at early times, the galaxies occupy only a small fraction of this). These movies show the formation of a galaxy, similar in mass to the Milky Way, from early times (redshift z=100) to the present. These are from the FIRE project: for more information, go to our project website here:Ī Milky-Way Mass Galaxy in Formation (m12q) Those stars then ‘light up’ the medium around them: they alter it with both their radiation heating up and pushing on the medium, as well as supernova explosions. They follow the region that will become a single galaxy by the present time, tracing the evolution of dark matter and gas, which eventually turns into stars. These movies show simulations of individual galaxies forming, starting at a time when the Universe was just a a few million years old (redshift of 100). Movies from the FIRE (Feedback In Realistic Environments) Project
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