Unusually Dusty Galaxy May Be Home To A Quasar
Quasars (quasi-stellar object) are extremely powerful objects. Powered by the emissions of powerful radiation from a central super-massive black hole, the light can often appear to astronomers on Earth as a jet-like feature. Additionally, if the beam of light emitted from the central black hole points directly at Earth, the accretion disk of material around the black hole, and the resulting “jet” can appear as a quasar, which typically outshine its host galaxy by over a hundred times. The team speculates that the black hole is devouring the equivalent mass of a few suns per year. It may have been eating at a more voracious rate earlier to bulk up to an estimated mass of three billion solar masses in just a few hundred million years.
“If you want to hide the stars with dust, you need to make lots of short-lived massive stars earlier on that lose their mass at the end of their lifetime. You need to do this very quickly, so supernovae and other stellar mass-loss channels can fill the environment with dust very quickly,” said Rogier Windhorst of Arizona State University (ASU), Tempe, Ariz. “You also have to be forming them throughout the galaxy to spread the dust throughout the galaxy,” added Matt Mechtley, also of ASU.
By using a nearby “reference” star, the team was able to carefully subtract light from the quasar image. Once the quasar was removed, the team was unable to detect any significant starlight in the region of the quasar. Had there not been any dust obscuring the stars, the stars would have been easily detected.
“It is remarkable that Hubble didn’t find any of the underlying galaxy,” said Windhorst. “The underlying galaxy is everywhere much fainter than expected, and therefore must be in a very dusty environment throughout. It’s one of the most rip-roaring forest fires in the universe. It’s creating so much smoke that you’re not seeing any starlight, anywhere. The forest fire is complete, not a tree is spared.”
“Because we don’t see the stars, we can rule out that the galaxy that hosts this quasar is a normal galaxy,” said Mechtley. “It’s among the dustiest galaxies in the universe, and the dust is so widely distributed that not even a single clump of stars is peeking through. We’re very close to a plausible detection, in the sense that if we had gone a factor of two deeper we might have detected some light from its young stars, even in such a dusty galaxy.”
The team’s results were published in the Sept 10th issue of the Astrophysical Journal Letters in a paper by M. Mechtley, R. Windhorst, and an international team of collaborators.
There are plans to observe this object with the upcoming James Webb Space Telescope. “The Webb telescope is designed to make a definitive detection of this,” said Windhorst. We will get solid detections of the stars with Webb’s better sensitivity to longer wavelengths of light, which will better probe the dusty regions in these young galaxies.
If you’d like to read the team’s full research paper, visit: http://arxiv.org/abs/1207.3283