Astronomers use ALMA to pinpoint huge star-forming galaxies in the early Universe
A team of Japanese astronomers has usedthe European Southern Observatory's (ESO) Atacama Large Millimeter/submillimeter Array (ALMA) to spot a group of huge,youthful galaxies in the distant Universe. The discovery helps us tounderstand the formation of such galaxies, and how they evolve intothe elliptical galaxies we see today.
In comparison to earlier periods in itshistory, the modern Universe is a pretty tranquil place. Turn theclock back ten billion years and you'd find galaxies of monstrousproportions, with star formation rates hundreds or thousands oftimes that seen in the modern Milky Way. There aren't any of thesehuge galaxies left in the modern era, but they didn't simplydisappear. Instead, scientists believe that they evolved into the giant elliptical galaxies we observe today.
In order to fully understand theevolution of these monstrous star forming galaxies, its essentialthat we get a good look at them – something that's possible bypeering into the distant reaches of the Universe, from where thelight emitted 10 billion years ago is just now arriving at Earth.
Current theories suggest that such hugestar forming galaxies formed in locations where dark matter isparticularly concentrated, but up until now we've been unable toconfirm this, with the objects routinely obscured by clouds of dust.
The research team, which includedtwo University of Tokyo professors, set out to locate the ancient galaxies,searching a group of objects known as SSA22 with the NationalAstronomical Observatory of Japan's (NAOJ) Atacama Submillimeter Telescope Experiment (ASTE) telescope. The sensitivity of the instrument wasn't enough to confirmthe presence of the huge, highly active galaxies, but it did providean indication that they might be present.
To delve deeper, the researchers thenturned to ALMA, which is 10 times more sensitive and boasts 60 timesthe resolution of ASTE. With those capabilities, the team was able to confirm andpinpoint the location of nine galaxies.
They then compared the readings to visible light observations made by the NAOJ's Subaru Telescope, withthat data indicating that a web of dark matter is present at thelocation – a filament structure that's thought to be a progenitorof the largest structures in the Universe. The cluster sits right onan intersection of of the dark matter filaments – an area where theinvisible matter is particularly dense.
Overall, the findings sit in accordancewith theories stating where such huge star-forming galaxies should be found, and the research helps us to better understand how dark matterinforms the structure of the Universe. The team behind the discovery isn't done, but will continue its search for the monstrous ancient galaxies in the hope of uncovering more of the secrets of the early Universe.
The researchers posted their findingsin the Astrophysical Journal Letters.