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Exploring How Galaxies are Transformed

22 Oct 2015, 21:22 UTC
Exploring How Galaxies are Transformed
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Fig 1: Spiral galaxy M74. ImageCredit: NASAWhen we look at galaxies out in the universe, we find that they come in many different types. Some galaxies have beautiful spiral structure (see Figure 1), while others look like irregular blobs of stars and gas. Still others look like featureless spheres of light (see Figure 2). These galaxies aren't only different in appearance, however. We find that we can separate galaxies into broad classes based not only on their shape (or morphology), but also on their stellar mass and how quickly they are forming stars (their star formation rate, or SFR). We find that galaxies with disky morphologies, such as the spiral galaxies mentioned above, tend to be relatively star-forming compared to galaxies with more elliptical morphologies, which appear smooth, round, and featureless and are often no longer forming stars.Fig 2: Elliptical galaxy ESO 325-G004. Image Credit: NASASince morphology and star formation rate often appear to be correlated in this way, it has been suggested by many that perhaps the processes responsible for shutting off star formation in galaxies are also associated with the formation of an elliptical component, called a "bulge." One such process for shutting off star formation is AGN feedback, which ...

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