Free Astronomy Magazine July-August 2023 ARABIC VERSION

27 ICM in a protocluster from the early stages of the Universe. Galaxy clusters are so massive that they can bring together gas that heats up as it falls towards the clus- ter. “Cosmological simulations have predicted the presence of hot gas in protoclusters for over a decade, but observational confirmations has been missing,” explains Elena Rasia, researcher at the Italian National Institute for Astrophysics (INAF) in Trieste, Italy, and co-author of the study. “Pursuing such key observa- tional confirmation led us to care- fully select one of the most promis- ing candidate protoclusters.” That was the Spiderweb protoclus- ter, located at an epoch when the Universe was only 3 billion years old. Despite being the most inten- sively studied protocluster, the pres- ence of the ICM has remained elu- sive. Finding a large reservoir of hot gas in the Spiderweb protocluster would indicate that the system is on its way to becoming a proper, long- lasting galaxy cluster rather than dispersing. Di Mascolo’s team detected the ICM of the Spiderweb protocluster through what’s known as the ther- mal Sunyaev-Zeldovich (SZ) effect. This effect happens when light from the cosmic microwave back- ground — the relic radiation from the Big Bang — passes through the ICM. When this light interacts with the fast-moving electrons in the hot gas it gains a bit of energy and its colour, or wavelength, changes slightly. “At the right wavelengths, the SZ effect thus appears as a shadowing effect of a galaxy clus- ter on the cosmic microwave back- ground,” explains Di Mascolo. By measuring these shadows on the cosmic microwave background, as- tronomers can therefore infer the existence of the hot gas, estimate its mass and map its shape. “Thanks to its unparalleled resolution and sensitivity, ALMA is the only facility currently capable of performing such a measurement for the distant progenitors of massive clusters,” says Di Mascolo. They determined that the Spider- web protocluster contains a vast reservoir of hot gas at a tempera- ture of a few tens of millions of de- grees Celsius. Previously, cold gas had been detected in this protoclus- ter, but the mass of the hot gas found in this new study outweighs it by thousands of times. This find- ing shows that the Spiderweb pro- tocluster is indeed expected to turn into a massive galaxy cluster in around 10 billion years, growing its mass by at least a factor of ten. Tony Mroczkowski, co-author of the paper and researcher at ESO, ex- plains that “this system exhibits huge contrasts. The hot thermal component will destroy much of the cold component as the system evolves, and we are witnessing a delicate transition.” He concludes that “it provides ob- servational confirmation of long- standing theoretical predictions about the formation of the largest gravitationally bound objects in the Universe.” These results help to set the ground- work for synergies between ALMA and ESO’s upcoming Extremely Large Telescope (ELT), which “will revolutionise the study of structures like the Spiderweb,” says Mario Nonino, a co-author of the study and researcher at the Astronomical Observatory of Trieste. The ELT and its state-of-the-art instruments, such as HARMONI and MICADO, will be able to peer into protoclus- ters and tell us about the galaxies in them in great detail. Together with ALMA’s capabilities to trace the forming ICM, this will provide a crucial glimpse into the assembly of some of the largest structures in the early Universe.     JULY-AUGUST 2023 ﻣﺠﻠﺔ FreeAstronomy ﺎﻟﻌﺮ ﺔ 27 ﺗُﻈﻬـــــﺮ ﻫـــــﺬﻩ اﻟﺼـــــﻮرة ﻋﻨﻘـــــﻮد ﻣﺠـــــﺮات أوﻟـــــﻲ ﺣـــــﻮل ﻣﺠـــــﺮة ﺷـــــ ﻜﺔ اﻟﻌﻨﻜﺒـــــﻮت اﻟﻤﻌﺮوﻓــﺔ ﺎﺳـﻢ MRC 1138-262 ــــﺎن ﻋﻤــــﺮ ﺷــــﻮﻫﺪت ﻓــــﻲوﻗــــﺖ واﻟـــ ـــﻮن اﻟ 3 ـــﺎراتﺳـــﻨﺔ ﻓﻘـــﻂ ﻣﻠ . ﻻ ﺗﻮﺟـــﺪ ﻣﻌﻈـــﻢ اﻟﻜﺘﻠـــﺔ ﻓـــﻲ اﻟﻌﻨﻘـــﻮد اﻷوﻟـــﻲ ﻤﻜــﻦ رؤ ﺘﻬـــﺎ ﻓـــﻲ ﻓــﻲ اﻟﻤﺠـــﺮات اﻟـــ ﻣﺮﻛــــــــــﺰ اﻟﺼــــــــــﻮرة وﻟﻜــــــــــﻦ ﻓــــــــــﻲ اﻟﻐــــــــــﺎز اﻟﻤﻌـــــــــــــــﺮوف ﺎﺳـــــــــــــــﻢ اﻟﻮﺳـــــــــــــــﻂ ﺑــــــــــــــــ اﻟﻌﻨﻘــــــــــــ . ﻮد ﻈﻬـــــــــــــﺮاﻟﻐـــــــــــــﺎزاﻟﺴـــــــــــــﺎﺧﻦ ﻛﺴﺤﺎ ﺔ زرﻗﺎء . [ESO / DiMascolo et al. ؛ HST: H. Ford] إن ﻋﻨﺎﻗﻴـﺪ ا ﺠـﺮات ﺿـﺨﻤﺔ ﺟـﺪاً ﺑﺤﻴ ـﺚ ﻳﻤﻜﻨﻬﺎ ﺗﺠﻤﻴﻊ اﻟﻐﺎز اﻟـﺬي ﻳﺴـﺨﻦ ﻋﻨـﺪﻣﺎ ﻳﺴﻘﻂ ﺑﺎﺗ ﺠﺎه اﻟﻌﻨﻘﻮد . ﺗﻮﺿﺢ إﻳﻠﻴﻨﺎ راﺳـﻴﺎ اﻟﺒﺎﺣﺜﺔ ﰲ ا ﻌﻬﺪ اﻟﻮﻃﻨﻲ اﻹﻳﻄـﺎﱄ ﻟﻠﻔﻴﺰﻳـﺎء اﻟﻔﻠﻜﻴــﺔ ﰲ ﺗﺮﻳﺴــﺘﺎ ﺑﺈﻳﻄﺎﻟﻴــﺎ وا ﺆﻟﻔــﺔ ا ﺸﺎرﻛﺔ ﺔ ﻟﻜﺘﺎﺑ اﻟﺪراﺳﺔ أدى . " اﻟﺴﻌﻲ وراء ﺗﺄﻛﻴﺪ اﻟ ﺮﺻﺪ اﻟﺮﺋﻴﴘ ﻫﺬا إﱃ اﺧﺘﻴﺎر ﺑﻌﻨﺎﻳـﺔ واﺣﺪة ﻣﻦ أﻛﺜﺮ اﻟﻌﻨﺎﻗﻴـﺪ اﻷوﻟﻴـﺔ ا ﺮﺷـﺤﺔ اﻟﻮاﻋـﺪة ". ﻛـﺎن ﻫـﺬا ﻫـﻮ ﻋﻨﻘـﻮ د ﺷـﺒﻜﺔ اﻟﻌﻨﻜﺒﻮت اﻷوﱄ اﻟﺬي ﻛﺎن ﻳﻮﺟﺪ ﰲ ﺣﻘﺒﺔ ﻛﺎن ﻋﻤﺮ اﻟﻜﻮن ﻓﻴﻬﺎ 3 ﻣﻠﻴﺎرات ﺳﻨﺔ ﻓﻘﻂ . ﺑ ﺎﻟﺮﻏﻢ ﻣﻦ ﻛﻮﻧﻪ ﻣﻦ أﻛﺜﺮ اﻟﻌﻨـﺎﴏ اﻷ ﻟﻴـﺔ و اﻟﺘﻲ ﺗﻤﺖ دراﺳﺘﻬﺎ ﺑﺸﻜﻞ ﻣﻜﺜﻒ إﻻ أن وﺟﻮد " اﻟﻮﺳﻂ ﺑ اﻟﻌﻨﻘﻮد " ﻇﻞ ﺑﻌﻴـﺪ ا ﻨـﺎل إن . اﻟﻌﺜﻮر ﻋﲆ ﺧﺰان ﻛﺒ ﻣﻦ اﻟﻐﺎز اﻟﺴـﺎﺧﻦ ﰲ اﻟﻌﻨﻘﻮد اﻷوﱄ ﻟﺸﺒﻜﺔ اﻟﻌﻨﻜﺒﻮت ﻣﻦ ﺷﺄﻧﻪ أن ﻳﺸ إﱃ أن اﻟﻨﻈﺎم ﰲ ﻃﺮﻳﻘﻪ ﻟ ﻴﺼﺒﺢ ﻋﻨﻘﻮد ﻣﺠـﺮات ﻃﻮﻳـﻞ اﻷﻣـﺪ ﺑـﺪﻻً ﻣـﻦ اﻟﺘﺸـﺘﺖ . اﻛﺘﺸﻒ ﻓﺮﻳـﻖ دي ﻣﺎﺳـ ﻜﻮﻟﻮ اﻟﻮﺳـﻂ ﺑـ ﻟ ﻠﻌﻨﻘﻮد ﺷﺒﻜﺔ اﻟﻌﻨﻜﺒﻮت اﻷوﱄ ﻣﻦ ﺧﻼل ﻣﺎ ﻳُﻌﺮف ﺘﺄﺛ ﺑ ﺑﺎﺳﻢ - ﺳﻮﻧﻴﺎﻳﻒ زﻳﻠـﺪوﻓﻴﺘﺶ اﻟﺤﺮاري . ﻳﺤﺪث ﻫﺬا اﻟﺘﺄﺛ ﻋﻨـﺪﻣﺎ ﻳﻤـﺮ اﻟﻀـﻮء ﻣـﻦ اﻟﺨﻠﻔﻴﺔ اﻟﻜﻮﻧﻴﺔ ا ﻴﻜﺮوﻳﺔ - اﻹﺷﻌﺎع ا ﺘﺒﻘﻲ ﻣﻦ اﻻﻧﻔﺠﺎر اﻟﻌﻈﻴﻢ " ﻋـﱪ – اﻟﻮﺳـﻂ ﺑـ اﻟﻌﻨﻘﻮد " ﻋﻨﺪﻣﺎ ﻳﺘﻔﺎﻋـﻞ ﻫـﺬا اﻟﻀـﻮء ﻣـﻊ ا ﻹﻟﻜﱰوﻧﺎت ﴎﻳﻌﺔ اﻟﺤﺮﻛﺔ ﰲ اﻟﻐﺎز اﻟﺴﺎﺧﻦ ﻓﺈﻧﻪ ﻳﻜﺘﺴﺐ اﻟﻘﻠﻴﻞ ﻣﻦ اﻟﻄﺎﻗﺔ وﻳﺘﻐ ﻟﻮﻧﻪ أو ﻃﻮﻟﻪ ا ﻮﺟﻲ ﻗﻠﻴﻼً . ﻳﻮﺿﺢ دي ﻣﺎﺳﻜﻮﻟﻮ : " ﻋﻨﺪ اﻷﻃﻮال ا ﻮﺟﻴـﺔ اﻟﺼـﺤﻴﺤﺔ ، ﻳﻈﻬـﺮ ﺗﺄﺛ ﺳﻮﻧﻴﺎﻳﻒ - زﻳﻠﺪوﻓﻴﺘﺶ اﻟﺤﺮاري ﻛﺘﺄﺛ ﻇﻞ ﻟﻌﻨﻘﻮد ﻣﺠـﺮات ﻋـﲆ ﺷـﻌﺎع اﻟﺨﻠﻔﻴـﺔ اﻟﻜﻮﻧﻴﺔ ا ﻴﻜﺮوي ." ﻳﻤﻜﻦ ﻟﻌﻠ ﻤﺎء اﻟﻔﻠﻚ ﻣـﻦ ﺧـﻼل ﻗﻴـﺎس ﻫـﺬه اﻟﻈـﻼل ﻋـﲆ اﻟﺨﻠﻔﻴـﺔ اﻟﻜﻮﻧﻴﺔ ا ﻴﻜﺮوﻳﺔ ، اﺳـﺘﻨﺘﺎج وﺟـﻮد اﻟﻐـﺎز اﻟﺴـﺎﺧﻦ وﺗﻘـﺪﻳﺮ ﻛﺘﻠﺘـﻪ ورﺳـﻢ ﺧﺮﻳﻄـﺔ ﻟﺸﻜﻠﻪ . ﻳﻘﻮل دي ﻣﺎﺳﻜﻮﻟﻮ " : ﺑﻔﻀﻞ اﻟﺪﻗـﺔ واﻟﺤﺴﺎﺳﻴﺔ اﻟﺘﻲ ﻻ ﻣﺜﻴﻞ ﻟﻬﺎ ، ﻓﺈن ﻣﺼﻔﻮﻓﺔ ( ا ﺎ ) ﻣﺮﺻﺪ ﻫﻲ ا ﻨﺸﺄة اﻟﻮﺣﻴـﺪة اﻟﻘـﺎدرة ــــــــ ﺣﺎﻟﻴًﺎ ﻋﲆ إﺟﺮاء ﻣﺜﻞ ﻫﺬا اﻟﻘﻴﺎس ﻟ ﻸﺳـﻼف اﻟﺒﻌﻴﺪة ﻟﻠﻌﻨﺎﻗﻴﺪ اﻟﻀﺨﻤﺔ . ﻟﻘﺪ ﺗﻮﺻﻠﻮا إﱃ أن ﻋﻨﻘﻮد ﺷﺒﻜﺔ اﻟﻌﻨﻜﺒﻮت اﻷوﱄ ﻳﺤﺘـﻮي ﻋـﲆ ﺧﺰان ﺿﺨﻢ ﻣﻦ اﻟﻐﺎز اﻟﺴﺎﺧﻦ ﻋﻨـﺪ درﺟـﺔ ﺣﺮارة ﺑﻀﻊ ﻋﴩات ا ﻼﻳ ﻣـﻦ اﻟـﺪرﺟﺎت ا ﺌﻮﻳﺔ . ﰲ اﻟﺴﺎﺑﻖ ، ﺗﻢ اﻛﺘﺸﺎف ﻏﺎز ﺑـﺎرد ﰲ ﻫﺬا اﻟﻌﻨﻘﻮد اﻷوﱄ ﻟﻜﻦ ﻛﺘﻠﺔ اﻟﻐﺎز اﻟﺴـﺎﺧﻦ ا ﻮﺟﻮدة ﰲ ﻫﺬه اﻟﺪراﺳـﺔ اﻟﺠﺪﻳـﺪة ﺗﻔﻮﻗـﻪ ﺑﺂﻻف ا ﺮات . ﻳُﻈﻬﺮ ﻫﺬا اﻻﻛﺘﺸﺎف أﻧـﻪ ﻣـﻦ ا ﺘﻮﻗ ﻊ ﺑﺎﻟﻔﻌـﻞ أن ﻳﺘﺤـﻮل ﻋﻨﻘـﻮد ﺷـﺒﻜﺔ اﻟﻌﻨﻜﺒﻮت اﻷوﱄ إﱃ ﻋﻨﻘـﻮد ﻣﺠـﺮات ﺿـﺨﻢ ﺧﻼل ﺣﻮاﱄ 10 ﻣﻠﻴﺎرات ﺳﻨﺔ ﻣﻤﺎ ﻳﺰﻳﺪ ﻛﺘﻠﺘﻪ ـﺑـ ﻌﴩ ﻣـﺮات ﻋـﲆ اﻷﻗـﻞ . ﻳﻮﺿـﺢ ﺗـﻮﻧﻲ ﻣﺮوزﻛﻮﻓﺴ ـﻜﻲ ا ﺆﻟ ـﻒ ا ﺸ ـﺎرك ﻟﻠﻮرﻗ ـﺔ اﻟﺒﺤﺜﻴــﺔ واﻟﺒﺎﺣــﺚ ﰲ ا ﺮﺻــﺪ اﻷوروﺑــﻲ اﻟﺠﻨﻮﺑﻲ ": أن ﻫﺬا اﻟﻨﻈـﺎم ﻳُﻈﻬـﺮ ﺗﺒﺎﻳﻨـﺎت ، ﻫﺎﺋﻠﺔ ﺳﻮف ﻳﺪﻣﺮ ا ﻜﻮن اﻟﺤﺮاري اﻟﺴﺎﺧﻦ اﻟﻜﺜ ﻣﻦ ا ﻜﻮﻧﺎت ا ﻟﺒﺎردة ﻣﻊ ﺗﻄﻮر اﻟﻨﻈﺎم وﻧﺤﻦ ﻧﺸﻬﺪ ﺗﺤﻮﻻً دﻗﻴﻘًﺎ وﻳﺨﻠﺺ إﱃ أن ذﻟﻚ ﻳﻮﻓﺮ ﺗﺄﻛﻴﺪًا ﻟﻠﺘﻨﺒﺆات اﻟﻨﻈﺮﻳﺔ ﻃﻮﻳﻠـﺔ اﻷﻣـﺪ ﺣﻮل ﺗﻜﻮﻳﻦ أﻛﱪ اﻷﺟﺮام ا ﺮﺗﺒﻄﺔ ﺑﺎﻟﺠﺎذﺑﻴﺔ . ﰲ اﻟﻜﻮن ﺗﺴـﺎﻋﺪ ﻫـﺬه اﻟﻨﺘـﺎﺋﺞ ﰲ ﺗﻤﻬﻴ ـﺪ اﻟﻄﺮﻳـﻖ ﻟﺘﻀـﺎﻓﺮ اﻟﺠﻬـﻮد ﻟﻠﻌ ﻤـﻞ ﻋـﲆ اﻻرض ﺑـ ﻣﺼﻔﻮﻓﺔ ﻣﺮﺻﺪ أ ﺎ) ( و اﻟﺘﻠﺴـﻜﻮب اﻟﻜ ﺒـ ﻟﻠﻐﺎﻳﺔ ) اي ال ﺗﻲ ( ا ﺴﺘﻘﺒﲇ واﻟﺬي ﺳﻴﺤﺪث ﺛﻮرة ﰲ دراﺳﺔ اﻟﻬﻴﺎﻛﻞ ﻣﺜﻞ ﻋﻨﻘـﻮد ﺷـﺒﻜﺔ اﻟﻌﻨ " ﻜﺒﻮت ﻛﻤﺎ ﻳﻘﻮل ﻣﺎرﻳﻮ ﻧﻮﻧﻴﻨﻮ ا ﺆﻟـﻒ ا ﺸﺎرك ﻟﻠﺪراﺳﺔ واﻟﺒﺎﺣﺚ ﰲ ا ﺮﺻﺪ اﻟﻔﻠﻜﻲ ﰲ ﺗﺮﻳﺴﺘﻲ ﺑﺈﻳﻄﺎﻟﻴﺎ . إن اﻟﺘﻠﺴـــﻜﻮب اﻟﻜﺒـــ ﻟﻠﻐﺎ ال اي) ﻳـــﺔ (ﺗﻲ ا ﺴﺘﻘﺒﲇ ﺳﻴﻜﻮن ﺑﻔﻀﻞ أﺣﺪث أﺟﻬﺰﺗﻪ ﻣﺜﻞ ﻣﻄﻴﺎف ﻫﺎ رﻣﻮﻧﻲ و وﻛﺎﻣ ا اﻟﺘﺼـﻮﻳﺮ ﻣﻴﻜﺎدو ، ﻗﺎدرًا ﻋﲆ اﻟﻨﻈﺮ إﱃ اﻟﻌﻨﺎﻗﻴﺪ اﻷوﻟﻴﺔ وإﺧﺒﺎرﻧﺎ ﻋﻦ ا ﺠﺮات ا ﻮﺟﻮدة ﻓﻴﻬﺎ ﺑﺘﻔﺼﻴﻞ ﻛﺒ ﺟﻨﺒًﺎ إﱃ ﺟﻨـﺐ ﻣـﻊ ﻗـﺪرات ﻣﺼـﻔﻮﻓﺔ (ـﺎ أ) ﻣﺮﺻﺪ ﻟﺘﺘﺒـﻊ ﺗﺸـﻜﻴﻞ اﻟﻮﺳـﻂ ﺑـ اﻟﻌﻨﻘﻮد وﻫﺬا ﺳﻴﻮﻓﺮ ﺤﺔ ﻣﻬﻤﺔ ﻋﻦ ﺗﺠﻤﻴﻊ ﺑﻌﺾ ﻣﻦ أﻛﱪ اﻟﻬﻴﺎﻛﻞ ﰲ اﻟﻜﻮن ا ﺒﻜﺮ . ﻳﻮﻟﻴﻮ - ﺃﻏﺴﻄﺲ 2 0 2 3