New papers investigate Galactic Rings in Galaxy Zoo

Hello Galaxy Zoo volunteers!

The fact that galaxies can host a multitude of different structures is no news to the volunteers: recent publications have looked at the spiral arms and bars in galaxies. There has now been some more recent work into a different, altogether rarer phenomenon that are called galactic rings. Galactic rings are objects that are commonly observed in the most strongly barred galaxies — it is theorised that these ring structures grow with the bars in galaxies. However, there are multiple theories that can explain these rare but significant features in galaxies, and the theories that claim to explain them remain purely theoretical.

To get an idea of exactly what is going on in ring galaxies requires a sample of galaxies which have galactic rings. Previous studies have relied on a handful of galaxies to study. However, Galaxy Zoo has proven to be the dataset of choice for any astronomer looking for the rarest of morphological phenomena, and Galaxy Zoo has once again provided the dataset for finding galactic rings in galaxies. Galaxy Zoo has always prided itself on not being just from the public but also for the public and for anyone the field of astronomy: all of the Galaxy Zoo data is available online for any astronomer to use. It is exactly the dataset that has allowed for the publication of two papers on galactic rings, by astronomer and long time friend of Galaxy Zoo, Ronald Buta, a Professor of Astrophysics at the University of Alabama. The first paper (here) used the public Galaxy Zoo 2 classifications to successfully define a sample of 3,962 ringed galaxies in Galaxy Zoo, and some examples are given in Fig.1.

Figure 1: Examples of various ring morphologies identified with the help of Galaxy Zoo 2.

A direct follow-up paper investigating fifty of these ringed galaxies in more detail was then published, again by Ronald Buta. In the second paper of this Galactic Rings revisited series, the main aim was to check how the rings in galaxies are related to the dynamics of the disc: theory suggests that rings are the result of resonances between the motions of the various rotating materials in galaxy discs. A resonance is an amplification caused when two oscillations match at just the right frequency: think of pushing someone on a swing. If you give a push at the top of the swing, then the amplitude (how high up the swing goes) will increase. The work described in this paper shows that galactic rings are likely to be exactly that: resonances between the bar+spiral pattern and rotating stars, and that various ring morphologies can be caused by different resonances in the outer discs of galaxies.

This work really showcases one of the key strengths of Galaxy Zoo: finding rare classes of objects in samples impossible to be classified by professional astronomers. So once again we’d like to say thank you, on behalf of astronomers around the world in the Galaxy Zoo team and those who have gone on to use the data from your hard work in other ways.