A bridge made of hot gas joining together two galaxy clusters over 10 million light-years of space has been discovered by researchers working with the ESA’s Planck space telescope. The discovery is the first of its kind.
“Large-scale structure of the cosmos
Galaxy formation and evolution
Planck’s primary task is to capture the most ancient light of the cosmos, the Cosmic Microwave Background, or CMB. As this faint light traverses the Universe, it encounters different types of structure including galaxies and galaxy clusters — assemblies of hundreds to thousands of galaxies bound together by gravity.”
“If the CMB light interacts with the hot gas permeating these huge cosmic structures, its energy distribution is modified in a characteristic way, a phenomenon known as the Sunyaev-Zel’dovich (SZ) effect, after the scientists who discovered it.”
Planck has already utilized this effect in order to find galaxy clusters themselves, but it also works as a way to detect very faint filaments of gas connecting different galaxy clusters together.
“In the early Universe, filaments of gaseous matter pervaded the cosmos in a giant web, with clusters eventually forming in the densest nodes.”
“Much of this tenuous, filamentary gas remains undetected, but astronomers expect that it could most likely be found between interacting galaxy clusters, where the filaments are compressed and heated up, making them easier to spot.”
“Planck’s discovery of a bridge of hot gas connecting the clusters Abell 399 and Abell 401, each containing hundreds of galaxies, represents one such opportunity.”
“The presence of hot gas between the billion-light-year-distant clusters was first hinted at in X-ray data from ESA’s XMM-Newton, and the new Planck data confirm the observation.”
This is also the first time that Planck has detected inter-cluster gas by utilizing the SZ effect technique.
“By combining the Planck data with archival X-ray observations from the German satellite Rosat, the temperature of the gas in the bridge is found to be similar to the temperature of the gas in the two clusters — on the order of 80 million degrees Celsius.”
“Early analysis suggests the gas could be mixture of the elusive filaments of the cosmic web mixed with gas originating from the clusters.”
“A more detailed analysis and the possible detection of gas bridges connecting other clusters will help to provide a more conclusive answer.”
Source: European Space Agency
Image Credits: Sunyaev–Zel’dovich effect: ESA Planck Collaboration; optical image: STScI Digitized Sky Survey