A trio of world-leading observatories joined forces to observe colliding galaxy clusters and map their components, including dark matter and intracluster gas which can’t be seen with visible light. They found that the violence of the collision heats the intracluster gas to 400 million degrees centigrade. This is an important result for understanding the evolution of structure in the Universe.
Space is a cold, lonely place so things like to
group together. Stars group together into galaxies; galaxies gather
together in clusters; and even galaxy clusters collide and merge into
larger clusters. But the stars we can see only tell part of the story.
Clusters also contain hot intracluster gas and dark matter. The various
components behave differently during a collision, so to understand the
complete picture we need to observe all of them.
The Subaru
Telescope, the XMM-Newton X-ray Survey (XXL), and the Green Bank
Telescope (GBT) teamed up to observe HSC J023336-053022 (XLSSC 105), a
pair of colliding galaxy clusters. The Subaru Telescope captured the
light from the stars in the cluster; XXL observed hot, thin gas; and the
MUSTANG-2 receiver installed on the GBT observed high-pressure gas. The
technological innovation of the GBT and MUSTANG-2 enabled observations
of such a high-pressure gas with high resolution. Astronomers could
infer the distribution of the invisible dark matter by using General
Relativity to analyze the distortion of the shapes of background
galaxies in the Subaru Telescope image. The data for these four
components were combined to create a complete picture. The results show
that the intracluster gas was originally 40 million degrees and the
energy released in the collision raised the temperature by ten times in
places. For reference, 400 million degrees centigrade is approximately
720 million degrees Fahrenheit, or about 27 times hotter than the core
of the Sun. This agrees with predictions, suggesting that the numerical
simulations of cluster collisions are accurate.
Lead researcher
Nobuhiro Okabe comments, "None of the observatories alone could have
achieved this collaborative result. The ongoing Subaru Telescope HSC-SSP
Survey observing the wide and deep Universe provides us with a rare
opportunity to discover many clusters undergoing collisions. We hope to
carry out follow-up observations of such clusters in X-ray and radio
bands in order to understand the details of structure formation of the
Universe."
This research was published in Monthly Notices of
the Royal Astronomical Society on September 9, 2020 as Okabe, Dicker,
Eckert et al. "Active
gas features in three HSC-SSP CAMIRA clusters revealed by high angular
resolution analysis of MUSTANG-2 SZE and XXL X-ray observations".
The Subaru Telescope Hyper Suprime-Cam (HSC) collaboration includes the astronomical communities of Japan and Taiwan, and Princeton University. The XXL is an international project based around an XMM-Newton Very Large Programme surveying two 25 deg2 extragalactic fields. The Green Bank Observatory is a facility of the National Science Foundation operated by Associated Universities, Inc., under a cooperative agreement with the National Science Foundation.
Relevant Links
Source: Subaru Telescope
