Washington: A new study has revealed that dead galaxies made stars on outskirts, but no longer in their interiors even 3 billion years after the Big Bang.
The NASA/ESA Hubble Space Telescope and ESO's Very Large Telescope (VLT) for the first time analyzed how star formation in dead galaxies sputtered out billions of years ago.
Astronomers refer to these big galaxies as red and dead as they exhibit an ample abundance of ancient red stars, but lack young blue stars and show no evidence of new star formation.
The estimated ages of the red stars suggest that their host galaxies ceased to make new stars about ten billion years ago. This shutdown began right at the peak of star formation in the Universe, when many galaxies were still giving birth to stars at a pace about twenty times faster than nowadays.
The researchers also used the SINFONI instrument on ESO's Very Large Telescope to collect light from the galaxies, showing precisely where they were churning out new stars. SINFONI could make these detailed measurements of distant galaxies thanks to its adaptive optics system, which largely cancels out the blurring effects of Earth's atmosphere.
According to the new data, the most massive galaxies in the sample kept up a steady production of new stars in their peripheries. In their bulging, densely packed centres, however, star formation had already stopped.
A leading theory was that star-making materials are scattered by torrents of energy released by a galaxy's central supermassive black hole as it sloppily devours matter. Another idea was that fresh gas stops flowing into a galaxy, starving it of fuel for new stars and transforming it into a red and dead spheroid.
The study is published in the journal Science.
