Lone, starless cloud may be a 'dark' galaxy
Astronomers using China's FAST radio telescope have discovered a compact cloud of hydrogen with no visible stars or galaxy around it. This could be one of the strongest candidates yet for an isolated "dark galaxy," containing nearly 500,000 times the sun's mass in neutral hydrogen. The discovery paper was posted to the arXiv preprint server on Sept. 24.
Astronomers have identified a compact cloud of hydrogen, found using China's FAST radio telescope, that may be the first dark galaxy ever discovered. This isolated cloud, J1351+0039, contains nearly half a million times the mass of our Sun in neutral hydrogen, with most of its mass likely being dark matter. The cloud has no visible stars or companion galaxies, making it a strong candidate for a dark galaxy, also known as a reionization-limited H I cloud (RELHIC).
The team studied J1351+0039 over three weeks, observing it for high-quality data. They found no signs of tidal disruption or nearby companions, suggesting it is truly isolated. The cloud's dynamics indicate it has a total mass of about 130 million solar masses, with its neutral hydrogen gas forming a round shape and rotating at only 4.2 km/s, supporting the idea that it may be a pressure-supported, starless dark galaxy.
While previous examples of dark galaxies were found near massive galaxies, the complete isolation of J1351+0039 makes it the most compelling candidate identified so far, according to the study led by Jin-Long Xu from the National Astronomical Observatories in China.
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