Radio relic discovered in a low-mass merging galaxy cluster

August 16, 2017 by Tomasz Nowakowski, report
(a) – The spectral index map of the radio relic in PLCK G200.9−28.2 between 235 and 610 MHz. (b) – The corresponding noise map. The resolution of the maps shown in upper left corner of each panel is 16.4′′ × 16.4′′. Credit: Kale et al., 2017.

Astronomers have detected a new single radio relic in a low-mass merging galaxy cluster known as PLCK G200.9−28.2. The finding, presented Aug. 5 in a paper published on the arXiv pre-print server, could offer some hints about merging processes in galaxy clusters.

PLCK G200.9−28.2 is a at a redshift of 0.22 with mass of about 270 trillion solar masses and an average temperature of 4.5 keV. Observations in X-rays show that this cluster has a disturbed morphology, which indicates an ongoing .

Radio relics are diffuse, elongated radio sources of synchrotron origin. Galaxy clusters undergoing mergers such as PLCK G200.9−28.2 are excellent places to search for these sources as they originate in acceleration and re-acceleration at merger-shocks. Radio relics occur in the form of spectacular single or double symmetric arcs at the peripheries of galaxy clusters.

Given that the number of known radio relics associated with merger shocks is still small, astronomers are interested in finding new examples of these sources. New detections are needed to create a large sample of relics, which could illuminate the connection between mergers and the generation of relics.

One candidate radio relic was spotted in PLCK G200.9−28.2 during previous observations and now a team of researchers led by Ruta Kale of the National Centre for Radio Astrophysics in Pune, India has re-investigated this extended radio source, performing follow-up studies. They used the Giant Metrewave Radio Telescope (GMRT), located near Pune, India and the Karl G. Jansky Very Large array (VLA) in New Mexico, to conduct radio observations of PLCK G200.9−28.2, which resulted in confirmation that the candidate source is, indeed, a radio relic.

"We report the discovery of a single radio relic in the galaxy cluster PLCK G200.9−28.2 using the Giant Metrewave Radio Telescope at 235 and 610 MHz and the Karl G. Jansky Very Large Array at 1500 MHz," the researchers wrote in the paper.

The study reveals that this extended radio source is a single radio relic with an arc-like morphology. The relic has dimensions of about 3.26 by 0.91 million light years, and is located approximately 2.9 million light years from the X-ray brightness peak in the . According to the paper, the relic has an integrated spectral index of 1.21 and the 235-610 MHz spectral index map shows steepening from the outer to inner edge of the relic. The authors noted that these findings are consistent with expectations for a relic generated by an underlying merger shock.

"The spectral index map of the relic shows flatter spectrum emission towards the outer edge and gradual steepening towards the inner side, strongly indicating an underlying merger shock," the paper reads.

The research shows that the new radio relic is the smallest in size in the sample of single relics with radio power above one septillion W Hz−1. Notably, it turns out that PLCK G200.9−28.2 has the lowest mass among the clusters known to host single arc-like radio relics.

Explore further: Radio halo discovered in a massive merging galaxy cluster

More information: Discovery of a radio relic in the low mass, merging galaxy cluster PLCK G200.9-28.2, arXiv:1708.01718 [astro-ph.CO]

Related Stories

Radio halo discovered in a massive merging galaxy cluster

February 25, 2016

(—Radio halos are enormous regions of diffuse radio emission, usually found at the centers of galaxy clusters. Recently, an international team of astronomers has discovered such a large area of diffuse emission, ...

Birth of a radio phoenix

April 28, 2015

Abell 1033 is a cluster of over 350 galaxies located about 1.7 billion light-years away. Collisions between galaxies in clusters are common events, and each merger heats and shocks the nearby gas. The rapidly moving, ionized ...

Giant magnetic fields in the universe

March 22, 2017

Astronomers from Bonn and Tautenburg in Thuringia (Germany) used the 100-m radio telescope at Effelsberg to observe several galaxy clusters. At the edges of these large accumulations of dark matter, stellar systems (galaxies), ...

ALMA's ability to see a 'cosmic hole' confirmed

March 17, 2017

Researchers using the Atacama Large Millimeter/submillimeter Array (ALMA) successfully imaged a radio "hole" around a galaxy cluster 4.8 billion light-years away. This is the highest resolution image ever taken of such a ...

Mysterious phenomena in a gigantic galaxy-cluster collision

March 10, 2015

Researchers using the Karl G. Jansky Very Large Array (VLA) have produced the most detailed image yet of a fascinating region where clusters of hundreds of galaxies are colliding, creating a rich variety of mysterious phenomena ...

Recommended for you

APEX takes a glimpse into the heart of darkness

May 25, 2018

The 12 m radio telescope APEX in Chile has been outfitted with special equipment including broad bandwidth recorders and a stable hydrogen maser clock for performing joint interferometric observations with other telescopes ...

Ancient meteorite tells tales of Mars topography

May 24, 2018

By looking at an ancient Martian meteorite that landed in the Sahara Desert, Lawrence Livermore National Laboratory (LLNL) scientists and collaborators have determined how and when the red planet's crustal topographic and ...


Adjust slider to filter visible comments by rank

Display comments: newest first

1.8 / 5 (5) Aug 16, 2017
@Captain Stumpy,
@Da Schneib,

Will you NOW APOLOGIZE to cantdrive85, HannesAlfven, Chris_Reeve and the Plasma Universe 'crowd' for your insulting/unsupported 'rebuttals' that DENIED SYNCHROTRON radiation occurred all over the place in our universe at all scales?

You lot ignorantly argued that if 'electric currents' occurred in space then we'd observe the synchrotron radiation from these.

Well, I/others have been pointing out for you for years now, that there ARE currents and associated synchrotron radiation sources/processes across space; which were either being misinterpreted, ignored, or too faint for instruments used previously.

Will you NOW ADMIT synchrotron radiations at many wavelengths can and do arise as cantdrive85, others (including myself) have been trying to point out; due to streams, processes and 'currents' of all kinds?

Can you UPDATE your knowledge base and counter arguments? :)
Da Schneib
5 / 5 (4) Aug 16, 2017
Nice. We need more of these; they will show merger morphology so we can search on these mergers and find out how common they are.
1 / 5 (1) Aug 18, 2017
@Captain Stumpy,
@Da Schneib,

Can you UPDATE your knowledge base and counter arguments? :)

That will never happen because they already know what they don't know.
Saw a few papers on age and the inability to accept new truth. Does not matter that the facts could be in front of their faces

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.