THE DARK SIDE OF THE ACCRETION HISTORY OF THE UNIVERSE

Abstract: 

The study of Active Galactic Nuclei (AGN) is currently at the forefront of astrophysical research. Observations over the last decade have shown that these objects are not only important for constraining the accretion history of the Universe but they may also hold the key for understanding how galaxies evolve. Unknown parameter and a major limitation in those studies is the fraction of AGN that are hidden behind clouds of dust and gas. Those obscured sources are challenging to observe directly and as a result current constraints on their demographics suffer large uncertainties.

Limitations in the data analysis methods are at the heart of the problem. Systematic and random errors have a profound impact on the interpretation of the observations and are primarily responsible for the current confused picture. We therefore propose key improvements in methodology to exploit the vast volume of available data. All the prime extragalactic X-ray and infrared surveys will be combined to minimise Poisson errors by providing AGN samples over 1 dex larger than any previous study.

Bayesian inference and Monte Carlo Markov Chain methods will be developed to propagate all sources of error into the analysis and determine the space density of moderately obscured (N_H<1e24cm^2) AGN detected at X-rays. A Bayesian approach will be used to identify the distinct spectral signature in the infrared of heavily absorbed AGN (N_H>1e24cm^?ˆ’2), which are missing from X-rays as a result of their extreme obscuration. Maximal constraints on the fraction of obscured AGN in the Universe will be placed by reconstructing the X-ray background spectrum using a new set of high energy AGN model spectra, which will inlcude all the key physics at play.

The proposed project will therefore provide the most accurate estimate of the AGN space density as a function of obscuration, luminosity and redshift afforded by current data.

Project info

Acronym:
DARK
Coordinating Institution:
National Observatory of Athens
Scientific Coordinator:
Georgakakis Antonis
Research Team 2 Leader:
Georgantopoulos Ioannis
Research Team 3 Leader:
Mastichiadis Apostolos
Research Team 4 Leader:
Charmandaris Vassilios
Research Team 5 Leader:
Meligkotsidou Loukia

Stats

I.D.:
106
Mis:
383549
Duration (months):
36
Budget:
600 000.00
Diavgeia:
ΑΔΑ: Β43Β9-ΙΝ9

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