Quasars are extremely bright celestial objects powered by supermassive black holes, often located in dense cosmic environments. It was widely believed that these early-Universe quasars thrived in such dense regions, but attempts to confirm this with observations have been inconclusive-until now. DECam, installed on the U.S. National Science Foundation's Victor M. Blanco 4-meter Telescope at Cerro Tololo Inter-American Observatory in Chile, provided the clarity needed.
Leading the study was Trystan Lambert, who conducted this research during his PhD at Diego Portales University in Chile and now holds a postdoctoral position at the University of Western Australia. Using DECam's expansive field of view, Lambert's team undertook the largest survey ever around an early-Universe quasar to assess the density of its surrounding galaxies.
The quasar under study, VIK 2348-3054, has a well-documented distance, previously established by the Atacama Large Millimeter/submillimeter Array (ALMA). This, coupled with DECam's narrowband filter, made it possible to identify surrounding galaxies by detecting Lyman-alpha radiation-a specific light emitted by hydrogen during star formation.
"Everything aligned perfectly for this study," Lambert said. "We had the right quasar and the perfect tool in DECam to examine its environment."
The research team mapped the quasar's cosmic neighborhood and identified 38 companion galaxies within 60 million light-years. However, they found none within a 15 million light-year radius, providing a potential explanation for previous conflicting studies: earlier surveys focused on smaller areas, leading to misleading results.
"DECam's wide view is essential for these types of observations," Lambert explained. "Smaller-scale studies may have missed key details, contributing to inconsistent conclusions."
The researchers also offered a theory to explain the absence of galaxies near the quasar. They suggest that the quasar's intense radiation could inhibit star formation in nearby galaxies by heating the gas needed for star formation.
"Quasars can be disruptive neighbors," Lambert added. "Their brightness could be halting star formation in nearby galaxies."
Further observations are planned to confirm this theory and expand the sample size by studying additional quasars.
"These results showcase the powerful collaboration between the National Science Foundation and the Department of Energy," noted Chris Davis, NSF program director for NSF NOIRLab. "With the upcoming NSF-DOE Vera C. Rubin Observatory, we will gain even deeper insights into the early Universe."
Related Links
DECam
Understanding Time and Space
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