Massive black hole spotted without galaxy

Adding to the mystery is the detection of a deeply distorted galaxy located 50,000 light years away from the quasar. This so-called “companion” galaxy appears to be an extremely active stellar nursery, birthing new stars at a rapid rate, and it is also brighter in the infra-red spectrum than most galaxies.

The combination of these three factors — distorted shape, high rate of star production and ultra infra-red luminosity — suggests to the researchers that the companion galaxy suffered a cosmic collision about 100 million years ago, possibly with the galaxy-less quasar.

Such a collision would have stirred up dust and gas and enhanced the formation of stars, said Gèraldine Letawe, a member of the research team also from University of Liege in Belgium. Heat from the seething young stars, combined with dust and gas warmed up by the collision might be responsible for the galaxy’s intense infra-red glow.

To explain the strange cosmic setup they’ve discovered, the researchers have come up with various hypotheses, all of them equally strange:

• It’s possible that the quasar does have an encircling galaxy, but that it is too small and too faint to be detected. If a host galaxy does exist, then it would have be to either six times fainter than typical host galaxies or have a radius smaller than 300 light years. Most quasar host galaxies range between 6,000 and 50,000 light years across.
• The quasar may not have always been galaxy-less, but the collision with the companion galaxy may have somehow caused the quasar’s galaxy to disappear completely. The researchers note, however, that it is “hard to imagine how the complete disruption of a galaxy could happen.”
• The blob could be gas stolen by a slow-moving black hole as it traveled through the disc of a spiral galaxy.
• Perhaps the most intriguing theory is that the quasar is encircled by a galaxy made up almost entirely of dark matter, a theoretical substance which is thought to make up 25 percent of the matter in the universe but which cannot be directly detected using current technologies.

Computer simulations of galaxy collisions might be able to determine if the first two options are plausible, Letawe told SPACE.com in an email interview.

It may be possible to verify whether the galaxy is made up of dark matter by scanning the space around the quasar for evidence of gravity lensing, a phenomenon whereby a massive celestial object warps the fabric of space-time so much that light from distant objects is bent around it.

Another way to test for the presence of a dark matter energy may be to look for gases that appear to be moving as if drawn by the gravity of some unseen object, Letawe said.

The discovery is documented in the September 15 issue of the journal Nature.

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