Shedding light on the mutual alignment of radio sources

The following blogpost is from Omar Contigiani about the Radio Galaxy Zoo paper that he published recently on the cosmic alignment of radio sources.

In the Radio Galaxy Zoo an incredible variety of creatures can be found — as our citizen scientists might know by now, radio sources in the sky can have all sorts of shape and sizes. The most powerful among them are plasma-filled jets emitted by the some of the largest elliptical galaxies in existence. Because of their precise structure, anyone can associate orientations to these sources by simply looking at the directions the jets point at.

Figure 1: Illustration of jet orientations distributed in the sky.  Note that this figure only depicts a small fraction of the total area covered by the observations upon which RGZ is based.  Credit: NASA, ESA, S. Baum & C. O’Dea (RIT), R. Perley & W. Cotton (NRAO/AUI/NSF).

Recently, our scientists have been looking at the directional properties of these fascinating beasts.  If a particular source points in a direction, is it possible that its neighbours also tend to do the same? Because the distances between adjacent objects are (quite literally) astronomical, it seems intuitive to assume that the relative orientations should be random. However, nature always finds subtle ways to mess with our intuition and it turns out that this is currently an open question in astronomy.  Thanks to Radio Galaxy Zoo’s numerous (almost two million) image classifications, the team was able to report the most precise measurement of this effect to date.  The results are available in a scientific article published in Monthly Notices of the Royal Astronomical Society this November.

The analysis performed in the study suggests that relative alignment of radio sources is present on distances which are dubbed as cosmological.  This is because only phenomena related to the history of the Universe as a whole are known to be connected to such large scales.

While this is an exciting step towards an answer, formulating any conclusive statement about this alignment and the reasons behind it appears to be difficult. What drives this effect? Is it related to a shared history or environment? More science needs to be done and more galvanising discoveries are waiting for us just around the corner.

Once again, without the contributions made by our volunteers all over the world, we would not have been so successful in our endeavours.  A big thank you to all our Radio Galaxy Zooites!

However, we have only reached 74% of our classification target. Head to Radio Galaxy Zoo to become involved and you will be contributing to real science being done today and may be co-authoring another great discovery with us!