January 25, 2012
Astronomers Find Link To Early Universe And Today’s Massive Galaxies
Astronomers have found the strongest link ever between the most powerful bursts of star formation in the Universe, and the most massive galaxies found today.
The astronomers also found that the emergence of supermassive black holes played a role in causing the sudden end to the starburst.
Astronomers used the LABOCA camera on the ESO-operated Atacama Pathfinder Experiment (APEX) telescope, along with measurements made with ESO's Very Large Telescope and NASA's Spitzer Space Telescope, to look at the way distant galaxies are gathered together in groups or clusters.
They determined that the more closely the galaxies are clustered, the more massive are their halos of dark matter.
By measuring the masses of the dark matter halos around the galaxies, astronomers found that these distant starburst galaxies from the early cosmos eventually become giant elliptical galaxies, which are the most massive galaxies in today's Universe.
“This is the first time that we've been able to show this clear link between the most energetic starbursting galaxies in the early Universe, and the most massive galaxies in the present day," Ryan Hickox (Dartmouth College, USA and Durham University, UK), the lead scientist of the team, said in a statement.
The new observations also indicate that the bright starbursts in these galaxies last for 100 million years, which is a short time in cosmological terms. However, during this time, the galaxies are able to double the quantity of stars in the galaxies.
“We know that massive elliptical galaxies stopped producing stars rather suddenly a long time ago, and are now passive. And scientists are wondering what could possibly be powerful enough to shut down an entire galaxy´s starburst,” Julie Wardlow, from University of California at Irvine and member of the team, said in a statement.
The astronomers say that at that stage in the history of the cosmos, the starburst galaxies are clustered in a very similar way to quasars, which indicates they are found in the same dark matter halos.
Mounting evidence suggest the intense starburst powers the quasar by feeding large quantities of material into the black hole.
The quasar then emits powerful bursts of energy that are believed to blow away the galaxy's remaining gas, which effectively shuts down the star formation phase.
“In short, the galaxies´ glory days of intense star formation also doom them by feeding the giant black hole at their centre, which then rapidly blows away or destroys the star-forming clouds,” David Alexander, from Durham University, UK and a member of the team, said in a statement.
The team's findings appear in a paper (http://www.eso.org/public/archives/releases/sciencepapers/eso1206/eso1206.pdf) published in the journal Monthly Notices of the Royal Astronomical Society.
Image 1: The LABOCA camera on the ESO-operated 12-meter Atacama Pathfinder Experiment (APEX) telescope reveals distant galaxies undergoing the most intense type of star formation activity known, called a starburst. This image shows these distant galaxies, found in a region of sky known as the Extended Chandra Deep Field South, in the constellation of Fornax (The Furnace). The galaxies seen by LABOCA are shown in red, overlaid on an infrared view of the region as seen by the IRAC camera on the Spitzer Space Telescope. By studying how some of these distant starburst galaxies are clustered together, astronomers have found that they eventually become so-called giant elliptical galaxies – the most massive galaxies in today´s Universe. The galaxies are so distant that their light has taken around ten billion years to reach us, so we see them as they were about ten billion years ago. Because of this extreme distance, the infrared light from dust grains heated by starlight is redshifted into longer wavelengths, and the dusty galaxies are therefore best observed in submillimeter wavelengths of light. The galaxies are thus known as submillimeter galaxies. Credit: ESO, APEX (MPIfR/ESO/OSO), A. Weiss et al., NASA Spitzer Science Center
Image 2: This red circle on this chart shows the position of the Extended Chandra Deep Field South, in the southern constellation of Fornax (The Furnace). Credit: ESO, IAU and Sky & Telescope
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