VISTA helps astronomers pinpoint when the first massive galaxies were born
Astronomers have used the EuropeanSouthern Observatory's VISTA telescope to discover hundreds ofpreviously undetected massive galaxies. The findings are localized toa small patch of sky, and their discovery provides clues as to whensuch objects first emerged in the early Universe.
While any given patch of sky plays hostto countless galaxies, they become much more difficult to detect themore distant they are, appearing fainter and often obscured byforeground objects. Massive galaxies – which are a minimum of 50billion times the mass of the Sun – are some of the brightest suchobjects (and therefore some of the easiest to spot when they're closeto home), they become far less common the deeper you peer into theearly Universe.
The new research picks out hundreds ofpreviously unidentified distant galaxies by analyzing VISTA telescopenear-infrared wavelength imagery. Making observations in thiswavelength allows astronomers to see through obscuring clouds of dustthat hide distant objects from view in visible light observations.
All 574 galaxies are located in asingle patch of sky that appears around four times the size of a fullMoon – a region VISTA has been focused on for some six years. Thoseimages were combined with data recorded by NASA's Spitzer Space Telescope, which works with mid-infrared wavelengths.
The discoveries represent the largestever sample of massive galaxies in the early Universe. Studying them is helping scientists pinpoint when the first ever massive galaxiesappeared.
The findings reveal a huge growth in the number of theseobjects in a short period of time, with a large number of the massivegalaxies having already formed as little as three billion years afterthe Big Bang, a full 11 billion years ago. Furthermore, no evidencewas found of such galaxies existing earlier than one billion yearsafter the Big Bang.
More broadly, the study found thatthere are more massive galaxies out there than we thought, with previously hidden objects making up as much as half of massive galaxies present whenthe 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 galaxiescould be dustier than theories suggest, which is something that wouldmake them impossible to detect with VISTA. Future observations usingthe Atacama Large Millimeter/submillimeter Array (ALMA) will look tothe stars once more to search for signs of such objects in the earlyUniverse.
If such ancient, dusty and massivegalaxies are found, then their existence could lead to significantrethink of early Universe galaxy formation theories. They'd alsobecome a prime candidate for study by ESO's upcoming European Extremely Large Telescope (E-ELT), which will allow us to get a lookat some of the first ever galaxies to form.