ESO VLT: Galaxies have evolved from earliest forms

Quasars are among the brightest objects in the universe and can be used as lighthouses to study the universe between the quasars and Earth. 

Here researchers have discovered a galaxy that lies in front of a quasar and by studying the absorption lines in the light from the quasar, they have measured the elemental composition in the galaxy in great detail, despite the fact that we are looking approx. 11 billion years back in time. 

Credit: Graphic: Chano Birkelind, Niels Bohr Institute

The early galaxies of the universe were very different from today's galaxies. Using new detailed studies carried out with the ESO Very Large Telescope and the Hubble Space Telescope, researchers, including members from the Niels Bohr Institute, have studied an early galaxy in unprecedented detail and determined a number of important properties such as size, mass, content of elements and have determined how quickly the galaxy forms new stars.

The results are published in the scientific journal, Monthly Notices of the Royal Astronomical Society.

"Galaxies are deeply fascinating objects. The seeds of galaxies are quantum fluctuations in the very early universe and thus, understanding of galaxies links the largest scales in the universe with the smallest.

It is only within galaxies that gas can become cold and dense enough to form stars and galaxies are therefore the cradles of starsbirths", explains Johan Fynbo, professor at the Dark Cosmology Centre at the Niels Bohr Institute at the University of Copenhagen.

Early in the universe, galaxies were formed from large clouds of gas and dark matter.

Gas is the universe's raw material for the formation of stars. Inside galaxies the gas can cool down from the many thousands of degrees it has outside galaxies.

When gas is cooled it becomes very dense. Finally, the gas is so compact that it collapses into a ball of gas where the gravitational compresion heats up the matter, creating a glowing ball of gas – a star is born.

"By combining the observations from both methods – absorption and emission – we have discovered that the stars have an oxygen content equivalent to approx. 1/3 of the Sun's oxygen content.

This means that earlier generations of stars in the galaxy had already built up elements that made it possible to form planets like Earth 11 billion years ago," conclude Johan Fynbo and Jens-Kristian Krogager.

More information: dx.doi.org/10.1093/mnras/stt955