By Pranjal Malewar 24 Sep, 2024
Collected at: https://www.techexplorist.com/early-universe-quasars-formed-cluttered-environments/90148/
Quasars, the most glowing objects in the Universe, are fueled by the accretion of material falling onto supermassive black holes. Several studies have suggested that early-universe quasars have massive black holes that must have been swallowing gas at very high rates.
Based on this, astronomers believe these quasars formed in some of the densest environments in the Universe. However, past measurements trying to confirm this have shown mixed results. A new study using the Dark Energy Camera (DECam) offers an explanation for these different findings and provides a way to link observations with theory.
Observations using the Dark Energy Camera (DECam) confirm astronomers’ expectation that early-Universe quasars formed in regions of space densely populated with companion galaxies.
The study was led by Trystan Lambert, who did this work as a PhD student at Diego Portales University in Chile and is now a postdoc at the University of Western Australia with ICRAR. Using DECam’s wide view, the team searched the largest area in the sky around an early-universe quasar to measure the number of nearby companion galaxies.
The team needed a quasar with a known distance to carry out their investigation. Fortunately, quasar VIK 2348-3054 had this information from earlier observations using the Atacama Large Millimeter/submillimeter Array (ALMA). DECam’s three-square-degree view allowed them to see a large area around it. Additionally, DECam has a unique filter that is ideal for spotting its companion galaxies.
Lambert said, “This quasar study was the perfect storm. We had a quasar with a well-known distance, and DECam on the Blanco telescope offered the massive field of view and exact filter that we needed.”
Thanks to DECam’s specialized filter, the team counted several companion galaxies around the quasar by detecting a very specific type of light they emit, known as Lyman-alpha radiation.
Lyman-alpha emitters are usually younger, smaller galaxies, and their Lyman-alpha emission helps measure their distances accurately. Researchers can create a 3D map of the area around a quasar by measuring the distances of several Lyman-alpha emitters.
After mapping the area around quasar VIK J2348-3054, Lambert and his team discovered 38 companion galaxies within 60 million light-years, which fits what is expected for quasars in crowded regions. However, they were surprised to find no companion galaxies within 15 million light-years of the quasar.
This finding sheds light on earlier studies that tried to classify early-universe quasar environments and offers a possible reason for their conflicting results. Since no other survey has covered such a large area as DECam, smaller surveys make a quasar’s environment seem emptier than it is.
Lambert said, “DECam’s extremely wide view is necessary for studying quasar neighborhoods thoroughly. You have to open up to a larger area. This suggests a reasonable explanation as to why previous observations are in conflict with one another.”
The team also proposes an explanation for the absence of companion galaxies near the quasar. The strong radiation from the quasar might be so intense that it affects or even halts star formation in these galaxies, making them hard to detect.
“Some quasars are not quiet neighbors. Stars in galaxies form from gas that is cold enough to collapse under its own gravity. Luminous quasars can be so bright as to illuminate this gas in nearby galaxies and heat it up, preventing this collapse.”
Chris Davis, NSF program director for NSF NOIRLab, said, “These findings show the value of the National Science Foundation’s productive partnership with the Department of Energy. We expect that productivity will be amplified enormously with the upcoming NSF-DOE Vera C. Rubin Observatory, a next-generation facility that will reveal even more about the early Universe and these remarkable objects.”
Journal Reference:
- Trystan S. Lambert, R.J. Assef, C. Mazzucchelli, E. Bañados, M. Aravena, F. Barrientos, J. González-López, W. Hu, L. Infante, S. Malhotra, C. Moya-Sierralta, J. Rhoads, F. Valdes, J. Wang, I.G.B. Wold, Z. Zheng. A lack of Lyman alpha emitters within 5Mpc of a luminous quasar in an overdensity at z=6.9: Potential evidence of negative quasar feedback at protocluster scales. Astronomy & Astrophysics, 2024; DOI: 10.1051/0004-6361/202449566
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