Shockwaves generated by a collision between the galaxies of Stephen’s Quintet and an intruding galaxy are driving strange processes in the intergalactic medium, the tenuous cloud of hotter-than-hot hydrogen plasma that exists in the space between galaxies.
new observations made with james webb space telescope (WEBB or JWST) and the Atacama Large Millimeter/submillimeter Array (alma) provides astronomers with good information about the intruder Galaxy NGC 7318b as it winds its way into this cluster of galaxies at a relative speed of about 1.8 million miles per hour (about 800 kilometers per second). fast enough to travel from earth until Moon And come back in only 15 minutes.
Violent attack by Stephen’s quintet is triggering an even bigger shockwave Galaxy Which is rippling through the interstellar plasma and kickstarting “recycling plants” for hot and cold molecular hydrogen gas between the five galaxies. In addition, astronomers found a giant cloud of gas breaking up to form a less dense “fog” of hot gas; The JWST/ALMA observations show collisions between the two clouds and even a tail of hot gas forming from the formation of a new galaxy.
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Discovering these phenomena could help scientists understand how turbulence affects the intergalactic medium and how collisions affect galaxy formation. Stars and the evolution of galaxies in general.
“As this intruder crashes into the cluster, it is colliding with an old gas streamer, which was likely caused by a previous interaction between the two other galaxies, and is creating a huge shockwave,” the project’s lead astronomer Philip Appleton and senior scientist at Caltech’s Infrared Processing and Analysis Center (IPAC) said in a Statement, (opens in new tab)
“As the shockwave passes through this strange streamer, it is creating a highly turbulent, or unstable, cooling layer, and it is in regions affected by this violent activity that we are seeing unexpected structures and recycling of molecular hydrogen gas,” Appleton said. Told. “This is important because molecular hydrogen forms the raw material that can eventually form stars, so understanding its fate will tell us more about the evolution of Stefan’s quintet and galaxies in general.”
Located approximately 270 million light-years from Earth in the constellation Pegasus, the Stephens Quintet consists of the galaxies NGC 7317, NGC 7318a, NGC 7318b, NGC 7319, and NGC 7320. The Five Galaxies have proven to be ideal laboratories for studying galactic interactions. , including violent confrontations, and how these interactions affect their environments.
But Stephan’s Quintet is different from other sites of galactic collisions because these mergers usually trigger bouts of rapid star formation, which these five galaxies do not. Instead, the turbulence of these galactic collisions in Stephan’s quintet is being felt in the intergalactic medium, where there is not enough raw material to trigger star birth.
This means the collision-triggered disturbance is not being masked by star formation, meaning astronomers get a fuzzy view of NGC 7318b as it rapidly breaks up into Stephan’s quintet.
Taking advantage of this opportunity, Appleton and team zoomed in on three key regions in Stephen’s Quintet using ALMA, an astronomical interferometer of 66 radio telescopes in the Atacama Desert region of northern Chile. The observations allowed astronomers to build up a clear picture for the first time of how hydrogen gas continually moves and takes shape.
“The power of ALMA is evident in these observations, providing astronomers with new insights and a better understanding of these previously unknown processes,” Joe Pesce, ALMA program officer for the US National Science Foundation, said in the same statement.
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Examining the Three Areas of Disturbance
At the center of the main shockwave, a region designated Field 6, a giant cloud of cold molecules is being broken up and turned into a tail of hot molecular hydrogen. As the same process continues, the hydrogen is recycled through the same temperature steps over and over again.
“What we’re seeing is the disintegration of a giant cloud of cold molecules into the super-hot gas, and interestingly, the gas doesn’t survive the shock, it just cycles through hot and cold phases,” Appleton said. Told. “We do not yet fully understand these cycles, but we do know that the gas is being recycled because the length of the tail exceeds the time it takes for the clouds to dissipate.”
This hydrogen “recycling plant” isn’t the only strange phenomenon these shockwaves are triggering. In an area called Field 5, the team observed two cold clouds of gas connected by a stream of hot molecular hydrogen gas. One of the clouds has a bullet-like shape and is punching through this filament, creating a ring-like structure.
“A molecular cloud-piercing through the gaseous gas, and leaving havoc in its wake, can be rare and not yet fully understood,” said Björn Imonts, an astronomer at the National Radio Astronomy Observatory (NRAO) and project co-investigator. May go.” same statement. ,
But our data show that we have taken the next step in understanding the puzzling behavior and turbulent life cycle of molecular gas clouds in Stephen’s Quintet.”
Of the regions examined by the team, Field 4 appears to be the most “normal” and calm, hosting a less turbulent environment that has seen the collapse of hydrogen gas to trigger the formation of the disk of stars. The team believes this marks the beginning of a small dwarf galaxy forming in Field 4.
Pierre Guillard, a researcher at the Institut d’Astrophysique de Paris, said, “In Field 4, it is likely that a pre-existing large cloud of dense gas became unstable due to the shock, and collapsed to form new stars. ” in France and a project co-investigator, said in the same statement. “The shock wave in the intergalactic medium of Stephen’s quintet has created molecular gas as cool as that in our own Milky Way, and yet, it forms stars much more slowly than expected.”
Gillard believes that these new observations have important implications for theoretical models of the effects of turbulence in the universe. He added, however, that additional work will be needed to understand the effects of high levels of turbulence and the mixing of hot and cold gas.
The JWST images of Stefan’s quintet combined with ALMA’s observations yielded a wealth of information about the relationship between the cold, hot molecular and ionized hydrogen gases in the wake of the giant shockwave, prompting the team to turn to spectroscopic data to reach more Will happen. Complete understanding of the field.
“These new observations have given us some answers, but have ultimately shown us just how much we don’t know yet,” Appleton said. “While we now have a better understanding of gas structures and the role of turbulence in creating and maintaining them, future spectroscopic observations will detect gas motion through the Doppler effect, telling us how fast the hot gas is moving, allow us to measure the temperature of the hot gas, and see how the gas is being cooled or heated by the shockwaves. Essentially, we’ve got one side of the story. Now it’s time to get to the other .
The team’s findings were presented Monday (Jan. 9) at the 241st meeting of the American Astronomical Society.
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