Homeless Quasar Poses Intergalactic Mystery
Washington (United States):
European astronomers have discovered a true space oddity: a quasar without a detectable home galaxy. The discovery has led to speculation that the host galaxy could be made up entirely of dark matter, or that a normal galaxy collided with another object that happened to contain a quasar.The research team studied 20 relatively close quasars (a mere five billion light years away) drawing on data from both the Hubble Space Telescope and the ESO Very Large Telescope (VLT). In 19 of the 20 cases, they found that the quasar was, as expected, sited at the centre of a massive galaxy.The researchers note that observing the host galaxy of a quasar is often challenging work because the quasar completely outshines the host, masking the galaxy’s underlying structure.By combining observation data from Hubble and the ESO VLT, and making observations of a reference star at the same time, the astronomers were able to disentangle the quasar light from any possible light from an underlying galaxy.But in the case of quasar HE0450-2958, no host galaxy could be found. This means the galaxy must be six times fainter than normal, or as much as 170 times smaller than normal. A quasar's host galaxy's radius is typically between 6,000 and 50,000 light-years, but this one can be no bigger than 300 light-years from end to end.
"The absence of a massive host galaxy, combined with the existence of the blob and the star-forming galaxy, lead us to believe that we have uncovered a really exotic quasar", says Frédéric Courbin from the Ecole Polytechnique Federale de Lausanne, Switzerland.
Lucy Sherriff
15th September 2005
http://www.theregister.co.uk/2005/09/15/homeless_quasar_mystery/
Washington (United States):
European astronomers have discovered a true space oddity: a quasar without a detectable home galaxy. The discovery has led to speculation that the host galaxy could be made up entirely of dark matter, or that a normal galaxy collided with another object that happened to contain a quasar.The research team studied 20 relatively close quasars (a mere five billion light years away) drawing on data from both the Hubble Space Telescope and the ESO Very Large Telescope (VLT). In 19 of the 20 cases, they found that the quasar was, as expected, sited at the centre of a massive galaxy.The researchers note that observing the host galaxy of a quasar is often challenging work because the quasar completely outshines the host, masking the galaxy’s underlying structure.By combining observation data from Hubble and the ESO VLT, and making observations of a reference star at the same time, the astronomers were able to disentangle the quasar light from any possible light from an underlying galaxy.But in the case of quasar HE0450-2958, no host galaxy could be found. This means the galaxy must be six times fainter than normal, or as much as 170 times smaller than normal. A quasar's host galaxy's radius is typically between 6,000 and 50,000 light-years, but this one can be no bigger than 300 light-years from end to end.
"The absence of a massive host galaxy, combined with the existence of the blob and the star-forming galaxy, lead us to believe that we have uncovered a really exotic quasar", says Frédéric Courbin from the Ecole Polytechnique Federale de Lausanne, Switzerland.
Lucy Sherriff
15th September 2005
http://www.theregister.co.uk/2005/09/15/homeless_quasar_mystery/
