Galaxies in the early universe grew fast by rapidly making new stars. Such prodigious star formation episodes, characterized by the intense radiation of the newborn stars, were often accompanied by fireworks in the form of energy bursts caused by the massive central black hole accretion in these galaxies. This discovery was made by a group of astronomers led by astronomer Peter Barthel of the Kapteyn Institute of the University of Groningen in the Netherlands.
In marked contrast to the 'active' galaxies of which there are various types and which were abundant in the early universe, our Milky Way galaxy forms stars at a slow, steady pace: on average one new star a year is born. Since the Milky Way contains about a hundred billion stars, the actual changes are very slight. 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.
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. Peculiar exotic objects Until recently these distant active galaxies were only interesting in their own right as peculiar exotic objects.
'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,' says Peter Barthel.
More information: Peter Barthel, Martin Haas, Christian Leipski, and Belinda Wilkes. "Extreme Host Galaxy Growth in Powerful Early-epoch Radio Galaxies". * The Astrophysical Journal Letters, Volume 757, Number 2. doi:10.1088/2041-8205/757/2/L26 Journal reference: Astrophysical Journal Letters
Source: The Daily Galaxy via University of Groningen
Image credit: ESA/NASA/RUG/MarcelZinger