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Dust inhibits shock wave in iconic group of galaxies

22 November 2024

The shock wave triggered by one of the five galaxies making up the iconic Stephan’s Quintet appears to be less disruptive than previously thought, with the shock likely being cushioned by dust particles in the surrounding gas. This finding is presented by a team of more than 60 astronomers, led by Marina Arnaudova (University of Hertfordshire, UK), who present their findings in the Monthly Notices of the Royal Astronomical Society, and results from the analysis of the first scientific observations of WEAVE, a state-of-the-art instrument co-developed in the Netherlands for a telescope on the Spanish island of La Palma. 

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WEAVE data overlaid on a James Webb Space Telescope image of Stephan's Quintet, with green contours showing radio data from LOFAR. The orange and blue colours follow the brightness of Hydrogen-alpha obtained with the WEAVE LIFU, which trace where the intergalactic gas is ionised. The hexagon denotes the approximate coverage of the new WEAVE observations of the system, which is 36 kpc wide (similar in size to our own galaxy, the Milky Way). Credit: Arnaudova et al.

3 million kilometres per hour

The researchers analyzed the characteristics of the moving gas in Stephan’s Quintet, a group of five galaxies 300 million light years away that was discovered in 1877 by Edouard Stephan. One of the five galaxies, NGC 7318b, is speeding through the region at 3 million kilometres per hour, causing a shock wave that in turn leads to chaotic movements in the gas.

Dual nature

The researchers discovered that the shock wave has a dual nature. When the shock rips through pockets of cold gas at hypersonic speeds, electrons are torn away from atoms, leaving a glowing trail of charged gas, as seen with WEAVE. The shock weakens, however, when it passes through hot gas instead of cold gas. The researchers suspect that the hot gas contains dust particles that absorb the shock wave.

First science results

“We came up with the concept of WEAVE 15 years ago. An excellent team of engineers and scientists made this instrument a reality, and Martina’s exciting results show how powerful WEAVE will be”, says Scott Trager (Kapteyn Astronomical Institute, University of Groningen), lead scientist of WEAVE.

WEAVE and its Large Integral Field Unit

WEAVE stands for William Herschel Telescope Enhanced Area Velocity Explorer. The instrument allows astronomers to measure the velocities of thousands of stars and galaxies simultaneously, along with other possible measurements. The core of WEAVE consists of nearly a thousand movable glass fibres that makes it somewhat like a weaving loom.

WEAVE was developed and built by the Netherlands, Spain and the UK, with contributions from France and Italy. The scientific results published today are based on the first science observations that were taken using WEAVE’s Large Integral Field Unit, a system developed and built by the Netherlands Research School for Astronomy (NOVA) and its Optical & Infrared Instrumentation Group.

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The core of WEAVE with movable glass fibers that are somewhat like a loom. The yellow ring is about 60 centimeters in diameter. (c) Gavin Dalton/Oxford University/STFC

Large Integral Field Unit

These so-called first light observations were carried out with the Large Integral Field Unit. This system was developed and built by the Optical/Infrared group of the Netherlands Research School for Astronomy (NOVA).

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The Large Integrated Field Unit with which the first observations were made. The black hexagon in the middle is the heart of the instrument. The system was developed and built by the Optical/Infrared Group of the Netherlands Research School for Astronomy. (c) NOVA

Scientific articles

WEAVE first light observations: Origin and dynamics of the shock front in Stephan's Quintet. Door: M.I. Arnaudova et al. In: Monthly Notices of the Royal Astronomical Society, 22 november 2024. [original (open access) | preprint (pdf)]

The wide-field, multiplexed, spectroscopic facility WEAVE: Survey design, overview, and simulated implementation. Door: S. Jin et al. In: Monthly Notices of the Royal Astronomical Society, Volume 530, Issue 3, May 2024 [original (open access)]

Last modified:22 November 2024 10.06 a.m.
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