Thesis

Birds of a feather: seeking the earliest high-energy events in the Universe at the high- and low-energy ends of the spectrum

• Call:

  PT-CERN Call 2021/1

• Academic Year:

  2021

• Domain:

  Astroparticle Physics

• Supervisor:

  José Afonso

• Co-Supervisor:

• Institution:

  Universidade de Lisboa

• Host Institution:

  IA - Instituto de Astrofísica e Ciências do Espaço

• Abstract:

  The existence of powerful Active Galactic Nuclei (AGN) has now been established well within the first Gyr of the Universe, through observations of optically selected Quasi Stellar Objects (QSOs) up to the currently highest redshift of z ∼ 8. To understand the origins of the supermassive black holes (SMBH) that power QSOs, and how relevant they are to early galaxy and structure formation, it is fundamental to detect AGN activity well within the Epoch of Reionisation. Surprisingly, the sensitivity already exists to find such sources at both extremes of the electromagnetic spectrum, X-rays and radio wavelengths, but all efforts to detect them have so far been unsuccessful. This is presumably due to their expected rareness, but also due to the lack of understanding of the high-energy physical processes present in these youngest extreme sources in the Universe. While surveys to be performed with future telescopes such as Athena (x-rays) and SKA (radio) will overcome the former limitation, the latter suggests correct identification of such ”rosetta stone” sources will remain challenging, as we are still unable to optimise our observations and detection strategies to these sources. Taking advantage of the strong Portuguese participation in these two observatories, this PhD project will explore the synergies allowed by the combination of the unique capabilities of Athena and SKA for the exploitation of the earliest AGN activity. Following-up on our recent work, the student will explore state-of-the-art galaxy and SMBH formation and evolution models, analyse the assumed physical processes and implement new recipes for X-ray and radio emission - taking into account the most recent advances in our understanding of black hole accretion physics. This will improve methodologies for the selection of very high redshift AGN, to be tested in current surveys and used to optimise Athena and SKA observing strategies for the detection of the earliest examples of AGN activity.