Exploring a Galaxy Zoo Result

by Muhammad Alfian Rasyidin

Welcome back citizen scientists! Have you visited Galaxy Zoo Site and classified any new pictures today? Your help is really significant, especially for astronomers. Let me tell you how astronomers use the information that you collected through Galaxy Zoo. Astronomers have used some of those classifications to analyze whether there are some specific types of galaxies found in more dense environments or less dense environments. Amazingly, they found impressive results, that no astronomers had ever realized before. Elliptical galaxies tend to be found in the more dense environments, and spiral galaxies are found in less dense environments.

Let’s take a deeper look at an article I read by Dr. Ramin Skibba and the Galaxy Zoo Team. This research mainly compares how clustered galaxies are; based on their morphology, which simply means the shape of the galaxy itself. Astronomers have already known that the galaxies are more clustered than just random clustering. What scientists mean by clustering is how many galaxies are within certain distances of each other. Clustering also relates to how dense an environment looks. For instance, a dense environment has more clustered galaxies at small distances, which also means that there is a larger number of galaxies within a given area.

skibbaetal09_fig2

Let’s take a look at the graph on the top, which is from the article I read. In the upper panel, with the black squares, y-axis indicates how likely galaxies are to be clustered at certain distances between galaxies as shown by the x-axis. So as you see for the black squares when x-value is smaller the y-value is greater, meaning that galaxies are more likely associated with other galaxies if they are near each other. As galaxies get farther apart, they look a bit more random. In the bottom panel, red squares represent elliptical galaxies and blue squares represent spiral galaxies. This information, about the shape of the galaxy, is taken from Galaxy Zoo Data where citizen scientists classified how a galaxy looked. The y-axis is set so values >1 mean they are more likely to be clustered, also values <1 mean they are less likely to be clustered. While x-axis is still representing the distance within between galaxies. Based on the graph, it shows us that elliptical galaxies are more likely to be found within small distances of each other, meaning they live in the more dense environment than spiral galaxies.

Well, this article highlights only one of hundreds of results that astronomers have discovered by using Galaxy Zoo data. Astronomers need these large data sets to make their findings more reliable. For instance, pretend that you are collecting the survey about how a galaxy image looks. Here, you can’t just rely on one person to determine whether a specific galaxy image is elliptical or spiral. There is more chance for that person to make a mistake. But, if you have thousands of people vote, and more than ninety percents of them say the same answer, do you think you will have more confidence to make a conclusion whether it is elliptical or spiral? Which method is more reliable and accurate? For those reasons, a citizen scientist’s help matters!

Sources:

http://blog.galaxyzoo.org/2014/06/27/explaining-clustering-statistics-we-use-to-study-the-distribution-of-galaxy-zoo-galaxies/http://mnras.oxfordjournals.org/content/399/2/966.full.pdf

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