A galaxy thought to have gone astray may simply be hiding from view, suggests a new study.
In September, an international team of scientists led by Pierre Magain at the Universite of Liege, Belgium, reported finding a peculiar quasar, dubbed HE0450-2958, that seemed to have no host galaxy.
Quasars are extremely bright light emissions, thought to be powered by matter falling into a supermassive black hole lurking at the centre of a galaxy. As matter falls into the black hole, it is heated to extreme temperatures, creating the bright emissions.
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But so far no quasar has been found without a companion galaxy and the discovery opened questions about what could be feeding Magain鈥檚 discovery. He speculated that the black hole could was being fed by surrounding dark matter 鈥� invisible to Earthly instruments.
But new research from David Merritt, an astrophysicist at the Rochester Institute of Technology, New York, US, suggests the quasar may have an accompanying galaxy after all, which is simply too faint to see.
Faint chance
Merritt and colleagues believe the quasar may be outshining its galactic host, making it extremely difficult to detect. This could be the case if the quasar were generated by a small, but particularly voracious, black hole within a diminutive galaxy. This category of quasar is known as a 鈥渘arrow-line Seyfert 1鈥�.
Magain鈥檚 team originally calculated that, if there were a host galaxy, it would need to be six times fainter than would be expected for such a bright quasar, leading them to suspect there was none there.
But Merritt and colleagues determined that that if the quasar was a narrow-line Seyfert 1, then the black hole and surrounding galaxy could actually be 10 times smaller than for a normal quasar. 鈥淭hey didn鈥檛 detect a galaxy,鈥� Merritt told New 杏吧原创. 鈥淚t鈥檚 clear in retrospect that they shouldn鈥檛 have expected to.鈥�
Radiation physics
Hubble images also show a blob of gas floating close to the quasar. Merritt鈥檚 team says that it is possible this could be part of a spiral arm of the host galaxy. Their work has been submitted to the Monthly Notices of the Royal Astronomical Society.
鈥淭he interpretation as a Seyfert fits in better with our understanding of galaxy evolution, and indeed of basic black hole and radiation physics,鈥� says David Floyd of the Space Telescope Science Institute, who was not involved in either study
Floyd does not discount Magain鈥檚 conclusion, but thinks Merritt鈥檚 idea fits best. 鈥淚t would be a remarkable discovery indeed if a quasar were found in such a low mass galaxy,鈥� he says. 鈥淏ut it seems unlikely.鈥�
Space Telescope Science Institute