Scientists at the University of Massachusetts Amherst are claiming to have observed the most luminous galaxies every seen in the universe, and they have decided to call them "outrageously luminous." In fact, they're so bright that so-called "hyper-luminous" and ultra-luminous" galaxies don't even come close.
The researchers used the 50-meter diameter Large Millimeter Telescope (LMT) in the study. This is the world's largest and most sensitive single-aperture instrument for studying star formation.
When categorizing luminous sources, infrared galaxies are seen as "ultra-luminous" when they have a rating of 1 trillion solar luminosities. They are seen as "hyper-luminous" when at 10 trillion solar luminosities. Now, though, researchers have discovered galaxies at 100 trillion solar luminosities. There was no name for such objects, until now.
"The galaxies we found were not predicted by theory to exist; they're too big and too bright, so no one really looked for them before," said Min Yun, one of the researchers involved in the study. "Knowing that they really do exist and how much they have grown in the first 4 billion years since the Big Bang helps us estimate how much material was there for them to work with. Their existence teaches us about the process of collecting matter of galaxy formation. They suggest that this process is more complex than many people thought."
The new galaxies aren't nearly as large as they appear. Their extreme brightness is instead suggested to be due to gravitational lensing, which magnifies light passing near massive objects. Because of this, the galaxies look about 10 times brighter than they really are. With that said, the galaxies are still extremely bright, and this brightness is probably due to amazingly high rates of star formation.
"The Milky Way produces a few solar masses of stars per year, and these objects look like they are forming one star every hour," said Yun.
The research team is currently not sure how many tens to hundreds of solar masses of gas can be converted into stars so efficiently in these objects. However, further study of the objects may help shed light on the matter.
The findings reveal a bit more about these bright galaxies and show that "outrageously luminous" galaxies may exist in the universe.
The study was published in the March 15 issue of the journal Monthly Notices of the Royal Astronomical Society.
