The galaxies were initially found by the absorption
of background quasar light passing through the galaxies.
Not exact matches
Image
of the gravitational lens RX J1131 - 1231 galaxy with the lens galaxy at the center and four lensed
background quasars.
The ideal
background «lights» for such a study are
quasars, which are very distant bright cores
of active galaxies powered by black holes.
Jackson and colleagues used the Karl G. Jansky Very Large Array, in New Mexico, US, to study four examples
of gravitational lens systems where the
background quasar appears in a ring
of four, distorted images.
«We had expected we would see faint emissions right on top
of the
quasar, and instead we saw strong bright carbon emission from the galaxies at large separations from their
background quasars,» said J. Xavier Prochaska, professor
of astronomy and astrophysics at UC Santa Cruz and coauthor
of the paper.
From our perspective on Earth, there will be rare cases where a distant
background quasar and a stream
of primordial gas near a foreground galaxy are exactly aligned on the night sky.
The plane to the far right shows the
background galaxy and overlaid in the center
of the galaxy is a bright white light representing a
quasar.
Artists impression
of the power
of background galaxies to measure the size
of gas clouds as compared to the conventional method
of using
quasars.
«The polarization
of the waves coming from the
background quasar, combined with the fact that the waves producing the two lensed images traveled through different parts
of the intervening galaxy, allowed us to learn some important facts about the galaxy's magnetic field,» said Sui Ann Mao, Minerva Research Group Leader for the Max Planck Institute for Radio Astronomy in Bonn, Germany.
These include observations
of the microwave
background radiation — the relic radiation
of the early universe — and surveys
of astronomical objects — galaxies,
quasars, supernovae, gamma - ray bursters,... — over large fractions
of the sky out to large fractions
of the radius
of the observable universe.