More than five years after the Arecibo Observatory radio telescope collapsed, archived data collected at the northern Puerto Rico facility has contributed to identifying what could be one of the most compelling dark galaxy candidates yet discovered. Researchers led by scientists at Australia’s Swinburne University of Technology reported in the journal Monthly Notices of the Royal Astronomical Society that they combined archived observations from the Arecibo Legacy Fast Arecibo L-band Feed Array Survey (ALFALFA) with newer measurements from China’s 500-meter Aperture Spherical Radio Telescope (FAST) to study an unusual object about 310 million light-years from Earth.
The object, designated AGC 322753, appears to hold a massive concentration of hydrogen gas while showing no detectable signs of stars, making it a strong dark galaxy candidate, a hypothetical type of galaxy that lacks the starlight normally used to identify such structures. Independent detections by the two telescopes rule out radio frequency interference or other false positives that may have affected previous studies, the team said.
Researcher Marco Monaci said AGC 322753 ranks among the most promising dark galaxy candidates uncovered through the ALFALFA and FASHI surveys. Arecibo’s 305-meter dish operated from 1963 until its instrument platform collapsed on December 1, 2020, and the study shows its archive remains a valuable scientific resource.