Astronomers have used the European
Southern Observatory's VISTA telescope to discover hundreds of
previously undetected massive galaxies. The findings are localized to
a small patch of sky, and their discovery provides clues as to when
such objects first emerged in the early Universe.
While any given patch of sky plays host to countless galaxies, they become much more difficult to detect the more distant they are, appearing fainter and often obscured by foreground objects. Massive galaxies – which are a minimum of 50 billion times the mass of the Sun – are some of the brightest such objects (and therefore some of the easiest to spot when they're close to home), they become far less common the deeper you peer into the early Universe.
The new research picks out hundreds of previously unidentified distant galaxies by analyzing VISTA telescope near-infrared wavelength imagery. Making observations in this wavelength allows astronomers to see through obscuring clouds of dust that hide distant objects from view in visible light observations.
All 574 galaxies are located in a single patch of sky that appears around four times the size of a full Moon – a region VISTA has been focused on for some six years. Those images were combined with data recorded by NASA's Spitzer Space Telescope, which works with mid-infrared wavelengths.
The discoveries represent the largest ever sample of massive galaxies in the early Universe. Studying them is helping scientists pinpoint when the first ever massive galaxies appeared.
The findings reveal a huge growth in the number of these objects in a short period of time, with a large number of the massive galaxies having already formed as little as three billion years after the Big Bang, a full 11 billion years ago. Furthermore, no evidence was found of such galaxies existing earlier than one billion years after the Big Bang.
More broadly, the study found that there are more massive galaxies out there than we thought, with previously hidden objects making up as much as half of massive galaxies present when the Universe was between 1.1 and 1.5 billion years old.
The results, though groundbreaking, aren't the end of the story. It's possible that some massive galaxies could be dustier than theories suggest, which is something that would make them impossible to detect with VISTA. Future observations using the Atacama Large Millimeter/submillimeter Array (ALMA) will look to the stars once more to search for signs of such objects in the early Universe.
If such ancient, dusty and massive galaxies are found, then their existence could lead to significant rethink of early Universe galaxy formation theories. They'd also become a prime candidate for study by ESO's upcoming European Extremely Large Telescope (E-ELT), which will allow us to get a look at some of the first ever galaxies to form.
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