More than Meets the Eye: Complete Imaging of Cluster Collision

Image credit: PI Nobuhiro Okabe; Subaru Telescope, National Astronomical Observatory of Japan/HSC-SSP collaboration; National Science Foundation/Green Bank Observatory/Green Bank Telescope; European Space Agency/XMM-Newton/XXL survey consortium.

An international team of astronomers using the National Science Foundation’s Green Bank Telescope (GBT) in Green Bank, West Virginia, has captured a snapshot of a giant cosmic collision. This composite image was created using radio, X-ray, and optical data collected with the MUSTANG-2 receiver on the GBT, the European Science Agency’s (ESA) XMM-Newton Satellite, and the National Astronomical Observatory of Japan’s (NAOJ) Subaru Telescope in Hawaii.

​​Galaxy cluster HSC J023336-053022 (XLSSC 105) – located about four billion light years away from Earth – is jam packed with hot intracluster gas and hundreds (or possibly thousands) of galaxies embedded in clumps of invisible matter, so-called dark matter. This cluster was independently discovered through surveys conducted by the Subaru Telescope (HSC-SSP)[1] and the XMM-Newton X-ray (XXL)[2].

The dazzling colors of the composite image reveal the contributions of each instrument. The Subaru Telescope optical image shows the galaxies, many of which have an orange hue, while the distribution of dark matter appears as a blue halo, reconstructed using the gravitational lensing effect predicted by Einstein’s theory of gravitation. This blue glow shows that the cluster is composed of two subclusters ­ –  and that these subclusters are undergoing a massive collision associated with the structure formation of the Universe.

The XMM-Newton Satellite, using the X-ray band, detected hot, dense gases, shown as green in the image. The Green Bank Telescope revealed the red region in the radio spectrum, representing hot, thin, high-pressure gas (difficult to see in the X-ray band) using the MUSTANG-2 receiver. MUSTANG-2 is a 223-feedhorn bolometer camera, with the current fastest mapping speed for continuum observations at 90 GHz with resolution of 10″ or less.

When the research team combined the complementary datasets of XMM-Newton and MUSTANG-2 they imaged the collision between the two subclusters; the collision is evidenced by a dramatic temperature increase resulting from the collision-induced shock – a rise from 40-million°C in the overall body of the cluster, to a whopping 400-million°C.

Observing a cluster merger such as this, and the extremely hot gas produced, is very difficult to do when observing in one band only. The international collaboration of the scientists, instruments, and datasets has captured this new and exciting aspect of structure formation.   

Want to learn more about the science behind this image? See the original article published in the Monthly Notices of the Royal Astronomical Society here.

To learn more about Green Bank Observatory Observatory science and to see research opportunities visit our website.

The Green Bank Observatory is a facility of the National Science Foundation and is operated by Associated Universities, Inc.



Jill Malusky, Green Bank Observatory Public Relations,

Charles Romero, Green Bank Observatory Post Doc

[1] The Hyper Suprime-Cam (HSC) collaboration includes the astronomical communities of Japan and Taiwan, and Princeton University.

[2] The XXL is an international project based around an XMM-Newton Very Large Programme surveying two 25 deg^2 extragalactic fields.

See this release in the news:

CNET: This ‘shock heated’ galaxy cluster is 25 times hotter than our sun’s core Cosmic furnace seen by X-ray observatory