Galaxies lurking in distant glowing dust

Clearing the air on what lies behind hot dust visible in the distant universe, a team of researchers has revealed that the bright dusty galaxies are hiding some secret companions.

The University of Sussex researchers found that the glow of heated dust reaching our planet is frequently due to three or four galaxies instead of a single one, as scientists had previously assumed.

The study applied a statistical method to data from the Herschel Space Observatory to solve one of astrophysics' great conundrums.

Lead author Dr Jillian Scudder said: "This is a really interesting result because when we assumed that one galaxy had to be responsible for all of the dust emission, it implied that the galaxy must be forming a tremendous number of new stars."

Scudder added, "Forming that number of stars in a galaxy so early in the Universe is quite hard to explain. By finding that each galaxy is actually two or three galaxies, we've dropped the number of stars these galaxies have to be producing by a third."

Far-infrared observations are relatively low resolution, and so each object detected by Herschel is blurred over an area about 26 times as large as the entire Milky Way. But if you look at the same patch of sky with better resolution, a number of galaxies appear, not just one.

The study looked at a sample of 360 objects detected at 250 micron by Herschel within the COSMOS field and revealed that the sample is almost entirely made up of at least two dust-bright galaxies hiding within the low-resolution images from Herschel.

The study is published in Monthly Notices of the Royal Astronomical Society.