HEAPOW: Collision of Clusters (2021 Aug 16)

[bystander]

HEAPOW: Collision of Clusters (2021 Aug 16)

Clusters of galaxies, groups of hundreds to thousands of individual galaxies bound by their mutual gravitational attraction, are the largest bound structures in the Universe. Understanding how the material Universe grows and evolves is largely a problem of understanding the processes by which clusters of galaxies evolve. Galaxy clusters are really just enormous collections of Dark Matter; the stars in the member galaxies constitute only a tiny bit of the total mass of the cluster. Stars don't even constitute most of the normal matter from the cluster; most of this normal matter, protons, electrons, neutrons and stuff, is found in the hot gas between the member galaxies, and this gas is so hot it only emits in the X-ray band. Galaxy clusters can even form gravitational bonds with other clusters (or even many such clusters), forming so-called "superclusters". Sometimes, one cluster can collide with another, producing cosmic fireworks (on scales large in space and long in time). The image above is an X-ray image from the Chandra X-ray Observatory of a cluster called Abell 1775. Abell 1775, nearly a billion lightyears from earth, is actually composed of a small subcluster smashing into a larger one - or at least that's what happened about a billion years before this image was taken. The image shows X-rays (colored blue) from the hot intracluster gas that is stirred up and shaken by this titanic collision. Of particular note is the peculiar X-ray "tail" curving to the left near the center of the image. The sharp edge near the upper left of the X-ray image marks a "cold front" where density and temperature abruptly drop. These features are important evidence about how clusters merge and how they might help drive growth of supermassive black holes, but there's still some debate about whether these features are evidence of the small cluster sloshing within the larger cluster, or slingshotting through it.

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Author: Dr. Michael F. Corcoran

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Abell 1775: Chandra Catches Slingshot During Collision
NASA | MSFC | SAO | Chandra X-ray Observatory | 2021 Jul 15

Click to view full size image 1 or image 2

X-ray: NASA/CXC/Leiden Univ./A. Botteon et al.;
Radio: LOFAR/ASTRON; Optical/IR:PanSTARRS

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When the titans of space — galaxy clusters — collide, extraordinary things can happen. A new study using NASA's Chandra X-ray Observatory examines the repercussions after two galaxy clusters clashed.

Galaxy clusters are the largest structures in the Universe held together by gravity, containing hundreds or even thousands of individual galaxies immersed in giant oceans of superheated gas. In galaxy clusters, the normal matter — like the atoms that make up the stars, planets, and everything on Earth — is primarily in the form of hot gas and stars. The mass of the hot gas between the galaxies is far greater than the mass of the stars in all of the galaxies. This normal matter is bound in the cluster by the gravity of an even greater mass of dark matter.

Because of the huge masses and speeds involved, collisions and mergers between galaxy clusters are among the most energetic events in the Universe. ...

A new image of Abell 1775 contains X-rays from Chandra (blue), optical data from the Pan-STARRS telescope in Hawaii (blue, yellow, and white), and radio data from the LOw Frequency ARray (LOFAR) in the Netherlands (red). The tail is labeled in this image along with a region of gas with a curved edge, called a "cold front," that is denser and cooler than the gas it is plowing into. The tail and the cold front all curve in the same direction, creating a spiral appearance. A separate labeled image shows the field of view of the Chandra data. ...

Nonthermal Phenomena in the Center of Abell 1775: An 800 kpc
Head-Tail, Revived Fossil Plasma and Slingshot Radio Halo ~ A. Botteon et al

• Astronomy & Astrophysics 649:A37 (May 2021) DOI: 10.1051/0004-6361/202040083
• arXiv.org > astro-ph > arXiv:2103.01989 > 02 Mar 2021 (v1), 11 May 2021 (v2)

The Merger Dynamics of the Galaxy Cluster Abell 1775: New Insights from Chandra
and XMM-Newton for a Cluster Simultaneously Hosting a WAT and a NAT Radio Sources ~ Dan Hu et al

• arXiv.org > astro-ph > arXiv:2103.03382 > 04 Mar 2021 (v1), 19 Mar 2021 (v2)