Aitana Vargas

An international team of astronomers led by Emanuele Daddi of the Commissariat a l’Energie Atomique in France has unveiled hundreds of one of the most mysterious objects present in the Universe: black holes.

The discovery was made possible using NASA’s Spitzer and Chandra X-ray telescopes, which were set out to probe 1,000 dusty galaxies lying 9 to 11 billion light-years away – the early Universe.

The finding accounts for a large number of the missing population of active massive black holes – also referred to as quasars or Active Galactic Nucleus (AGN) - that has eluded astronomers for decades. Quasars are high-energy objects surrounded by a doughnut-like cloud of dust and gas and powered by the rapid growth of a supermassive black hole at the galaxy’s core. Such an obscured environment makes them very hard to detect.

At first glance, astronomers uncovered very active star birth activity in the galaxies being studied, but there was no reason to believe that the galaxies hosted quasars. Nevertheless, a closer look revealed that hundreds of galaxies were giving off infrared-light and hiding active quasars.

The discovery represents the first direct evidence that most far-away massive galaxies spend their adolescence growing quasars at their centers. Although astronomers were aware that there should be more of these black holes in the young universe, they did not think that the new observations would raise the number to hundreds of millions, twice as much as it was known up-to-date.

The work digs deeper into the evolution of massive galaxies. Now astronomers believe that simultaneous star and black hole formation takes place until galaxies grow too large and their black holes prevent star formation.

The discovery is not fully consistent with theoretical work, which had suggested until now that collisions and mergers between galaxies were key to triggering quasar activity. The new observations suggest that active quasars may be present in undisturbed galaxies as well.

The results will be published in the November 10 issue of the Astrophysical Journal.

Picture/Illustration Credit (s):
NASA/JPL-Caltech/T.Pyle (SSC); X-ray: NASA/CXC/Durham/D.Alexander et al.; Infrared: NASA/JPL-Caltech/CEA/E.Daddi

Original Source (s):
Durham University Press Release
Harvard Press Release