Nicknamed "green bean galaxies" because of their unusual appearance, these galaxies glow in the intense light emitted from the surroundings of monster black holes and are amongst the rarest objects in the Universe.
Read the full Research Paper Here
Many galaxies have a giant black hole at their centre that causes the gas around it to glow. However, in the case of green bean galaxies, the entire galaxy is glowing, not just the centre.
These new observations reveal the largest and brightest glowing regions ever found, thought to be powered by central black holes that were formerly very active but are now switching off.
Astronomer Mischa Schirmer of the Gemini Observatory had looked at many images of the distant Universe, searching for clusters of galaxies, but when he came across one object in an image from the Canada-France-Hawaii Telescope he was stunned -- it looked like a galaxy, but it was bright green.
It was unlike any galaxy he had ever seen before, something totally unexpected. He quickly applied to use ESO's Very Large Telescope to find out what was creating the unusual green glow.
"ESO granted me special observing time at very short notice and just a few days after I submitted my proposal, this bizarre object was observed using the VLT," says Schirmer.
"Ten minutes after the data were taken in Chile, I had them on my computer in Germany. I soon refocused my research activities entirely as it became apparent that I had come across something really new."
The new object, J2240, lies in the constellation of Aquarius (The Water Bearer) and its light has taken about 3.7 billion years to reach Earth.
After the discovery, Schirmer's team searched through a list of nearly a billion other galaxies and found 16 more with similar properties, which were confirmed by observations made at the Gemini South telescope.
General Background
In many galaxies the material around the supermassive black hole at the centre gives off intense radiation and ionises the surrounding gas so that it glows strongly.
These glowing regions in typical active galaxies are usually small, up to 10% of the diameter of the galaxy. However, the team's observations showed that in the case of J2240, and other green beans spotted since, it is truly huge, spanning the entire object.
J2240 displays one of the biggest and brightest such regions ever found. Ionised oxygen glows bright green, which explains the strange colour that originally caught Schirmer's attention.
"These glowing regions are fantastic probes to try to understand the physics of galaxies -- it's like sticking a medical thermometer into a galaxy far, far away," says Schirmer.
"Usually, these regions are neither very large nor very bright, and can only be seen well in nearby galaxies.
However, in these newly discovered galaxies they are so huge and bright that they can be observed in great detail, despite their large distances."
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