Fireworks marked growth of galaxies in early universe
Washington: Growth of galaxies in the early universe was often accompanied by fireworks in the form of energy bursts caused by the massive central black hole accretion, astronomers said.
Galaxies in the early universe grew fast by rapidly making new stars.
Such prodigious star formation episodes are also characterised by the intense radiation of the newborn stars, the team led by Peter Barthel of the Kapteyn Institute of the University of Groningen in the Netherlands found.
The Milky Way is an extremely quiet galaxy; its central black hole is inactive, with only weak energy outbursts due to the occasional capture of a passing star or gas cloud.
This is in marked contrast to the 'active' galaxies of which there are various types and which were abundant in the early universe.
Quasars and radio galaxies are prime examples: owing to their bright, exotic radiation, these objects can be observed as far as the edge of the observable universe.
The light of the normal stars in their galaxies is extremely faint at such distances, but active galaxies can be easily detected through their luminous radio, ultraviolet or X-ray radiation, which results from steady accretion onto their massive central black holes.
Until recently these distant active galaxies were only interesting in their own right as peculiar exotic objects.
Little was known about the composition of their galaxies, or their relationship to the normal galaxy population.
However, in 2009 ESA's Herschel space telescope was enabled to detect heat radiation generated by the processes involved in the formation of stars and planets at a small scale, and of complete galaxies at a large scale.
Initial inspection of the observations has revealed that many emit bright far-infrared radiation.
The fact that these three objects, as well as many others from the observational sample, emit strong far-infrared radiation indicates that vigorous star formation is taking place in their galaxies, creating hundreds of stars per year during one or more episodes lasting millions of years.
"It is becoming clear that active galaxies are not only among the largest, most distant, most powerful and most spectacular objects in the universe, but also among the most important objects; many if not all massive normal galaxies must also have gone through similar phases of simultaneous black hole-driven activity and star formation," said Barthel.