AT A GLANCE Project Information
Project Title: PAGN: The physics of active galactic nuclei
Project Objective: Supermassive black holes residing in active galactic nuclei (AGNs) sometimes produce relativistic jets of enormous power. Objects with jets pointed towards us are called blazars. Using blazars as a tool, we aim to make a breakthrough in our understanding of the AGN physics. We will investigate the formation of gamma-ray radiation, try to resolve a longstanding question on the location of the gamma-ray emitting region, learn how the jets are accelerated, and understand the structure and physics of the broad- line region.
Project Duration and Timing: 5 years, 2013 to 2017
Project Funding: Academy of Finland 500.000€
Project Partners: • Institute for Nuclear Research, Moscow, Russia
• ISDC, Univ. of Geneva, Switzerland
Spectral energy distribution of a few blazars in the gamma-ray region. One sees strong breaks at energies of about a few gigaelectron-volt, presumably related to annihilation of photons by UV line photons.
The team inferred that if gamma radiation
were being produced in regions heavy with UV photons, then this would explain the breaks
in the gamma spectrum, as the
interaction between gamma photons with UV photons of the right level would effectively lead to the gamma photons disappearing through a well known process called photon-photon annihilation. This realisation helped the team to deduce that gamma radiation must be produced within a certain region of the blazar, a region with a high density of UV photons. Travel too far from the blazar and the UV field is too weak, with no gamma-UV photon-photon annihilation being observed, and hence no breaks in the gamma spectrum, but travel too close to the black hole and all gamma photons will be annihilated, and no gamma- ray photons will be observed. Previous similar projects had given
estimates on the position of gamma-ray emitting region of between one thousand and one million times the event horizon
www.projectsmagazine.eu.com
size. Significantly, the work of Poutanen and his team has reduced the uncertainty factor in this positional estimate from one thousand to ten.
Presenting the theories The
team have effectively recorded a
triumvirate of discoveries in the field of black hole analysis, but despite their belief in the significance and importance of their observations, Poutanen is being careful not to get too excited. “These are big discoveries that will help to develop scientific understanding of black holes and how they operate, but we know that in Astronomy it can take several years before people are convinced,” muses the Professor. The team are now looking forward to
presenting their findings to their contemporaries, and beginning the series of papers and conferences that will lead to their work being seen as not just exciting new theories, but solid scientific facts that form the basis of current comprehension.
★ 33 MAIN CONTACT
Prof. Juri Poutanen Graduated from the Leningrad State University in 1987. PhD in Astronomy at the University of Helsinki in 1994. Postdoc at Stockholm Observatory in 1994-1996, research associate at Uppsala (1996-1997) and Stockholm Universities (1997-2001). Full professor of astronomy at University of Oulu, Finland from 2001. From 2014 – professor of astronomy and Director of Tuorla observatory, University of Turku.
Contact: Tel: +358 2 3338943 Email:
juri.poutanen@utu.fi Web:
http://astrophysics.fi
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