More from Chris's talk – red spirals

Chris told me in the pub yesterday that “it’s nice to give a Galaxy Zoo talk where people are already familiar with the story; it means that people already know the story.” That’s a testament to the success of your classifications — from what I’ve seen at this meeting, it seems that in just a year and a half, Galaxy Zoo has gone through evolved from a cool new strategy for doing science to a source of exciting research results. The results Chris presented about red spirals were particularly interesting. Karen Masters has blogged about these red spirals before. Spiral galaxies usually contain lots of young, blue stars, but these “red spirals” contain old, red stars. What this means is that the formation of new stars in these galaxies has been shut off. Galaxy Zoo’s contribution — your contribution — has been to show that red spirals most often live at the edge of galaxy clusters. They are clusters that have just begun to move toward the centers of clusters due to the clusters’ gravitational attraction. The attraction of the galaxy clusters has led to new star formation being shut off, but not to the shape of the galaxy changing — a process that Chris called “gentle strangulation.” The gravitational attraction is just right — enough to shut off star formation, but not enough to deform the galaxy.