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Beginner Is the Moon moving away from the Earth? Note that this agrees with the results reported in this Astrobite for low redshifts! Figure 3. Color-mass diagrams for bulge galaxies. The galaxies are colored by specific star formation rate, which is just star formation rate divided by mass.
But the authors note that there are still some unclear results. For instance, they also compare the color-mass trends of active galactic nuclei AGNs; the purple points in Figure 2 with the trends of inactive galaxies. The authors find that AGNs might have some effect on quenching, particularly in mergers, but more data is needed to be certain. Email Address. Suggest a Paper Topic! Powell, C. The main reason the late-type galaxies spirals and irregulars are blue is that the brightness contribution of the hotter stars Main sequence O, B, and such surpasses the contribution of colder, less massive stars even though, there are more low mass stars than high mass stars.
Read more about it here and here. In early-type galaxies elliptical and lenticular , we have an older population of stars, no dust, no star-formation. The luminosity contribution of massive young stars does not exist here. If you look at the spectrum of an elliptical galaxy, you'll notice that is similar to the spectrum of a KIII star that's a red gigant, a very much evolved sun-type star , this tells us that the main contribution of light comes from this kind of stars.
We don't have blue elliptical galaxies because there are no young stars, star formation, or dust to make stars, that can give us a significant blue light contribution. There aren't yellow spiral ones, because the massive stars will shine brighter than the less-massive stars. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group.
Create a free Team What is Teams? Learn more. Why aren't there blue elliptical galaxies or yellow spiral galaxies? Ask Question. Asked 1 year, 8 months ago. Active 7 months ago. Viewed times.
She and her collaborators were able to identify a large population of galactic oases in the huge map provided by the Sloan Digital Sky Survey. The researchers found that these galaxies tend to form near the edges, as opposed to the centers, of the voids - like hermits that want to remain within earshot of civilization. But the most remarkable finding is how blue the void galaxies appear. No, this is not because they are lonely.
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