Letters of Intent received in 2015

LoI 2017-281
Quasars at all cosmic epochs

Date: 2 April 2017 to 7 April 2017
Category: Non-GA Symposium
Location: Padova or Venezia, Italy
Contact: Mauro D'Onofrio (mauro.donofrio@unipd.it)
Coordinating division: Division J Galaxies and Cosmology
Other divisions:
Co-Chairs of SOC: Ascensión del Olmo (Instituto de Astrofisica de Andalucia CSIC)
Paola Marziani (INAF Osservatorio Astronomico di Padova)
Mauro D'Onofrio (Department of Physics and Astronomy, University of Padova)
Co-Chairs of LOC: Paola Marziani (INAF Osservatorio Astronomico di Padova)
Mauro D'Onofrio (Department of Physics and Astronomy, University of Padova)

 

Topics

1. observational properties of active galactic nuclei

2. accretion processes on supermassive black holes

3. connection between theory and observation for the emitting region of quasar

4. quasar evolution over cosmic time and quasars as cosmological tools

5. feedback and environment of active galaxies and quasars

 

Rationale

The last 50 years have seen a tremendous progress in the research on quasars. From a time when quasars were unforeseen oddities, we have come to a view that considers nuclear activity a coming of age experienced by most or all galaxies in their evolution. We have passed from a few tens of known quasars of the early 1970s to the almost 200,000 known today.

Not surprisingly, accretion processes on the central black holes in the nuclei of galaxies — the key concept in our understanding of quasars - have gained an outstanding status in present-day astrophysics. Accretion produces a rich spectrum of phenomena in all bands of the electromagnetic spectrum. The power output of highly-accreting quasars has impressive effects on their host galaxies.

All the improvement in telescope light gathering and in computing power notwithstanding, we still miss a clear connection between observational properties and theory for quasars, as provided, for example, by the H-R diagram for stars. We do not yet have a complete self-consistent view of nuclear activity with predictive power, as we do for main-sequence stellar sources.

At the same time quasars offer many “windows open onto the unknown.” On small scales, quasar properties depend on phenomena very close to the black hole event horizon. On large scales, quasars’ potential to map the matter density of the Universe and help reconstruct the Universe’s space time geometry is still largely unexploited.

The times are ripe for a critical assessment of our present knowledge of quasars as accreting systems and of their evolution across the cosmic time. The aim of this meeting is to review the main observational scenario following an empirical approach, to present and discuss theories, and then to analyze how a closer connection between theory and observation can be achieved, identifying those aspects of our understanding that are still on a shaky terrain and are therefore uncertain knowledge.

With this approach we also intend to celebrate the 70th birthsday of Jack Sulentic. Considering the healthy skepticism and disdain for preconceived ideas that have informed his scientific activity, we plan one-two talks to the main paradigm shifts that occurred in quasars’ research and to allott 30 minutes for a free discussion at the end of each day.

The meeting will cover topics ranging from the nearest environment of the black hole, to the environment of the host galaxies of AGNs and the quasars as marker of the large scale structure and of the geometry of spacetime of the Universe. This includes the accretion disk, the emission and absorption regions, the presence of a circumnuclear starburst, the host galaxy and its interaction with other galaxies. Special attention will be devoted to some problems that remain outstanding and clearly not solved: the existence of two quasar classes, radio quiet and radio loud, the properties of the central black hole, the dynamics of the accretion flow in the inner parsecs and the origin of the accretion matter, the quasars’ small and large scale environment, the feedback processes produced by the black hole into the host galaxy, the quasar “strange” evolutionary pattern, and the use of quasars as cosmological standard candles.

The scheme planned includes review talks (45 min), invited (35 min) and contributed (20 min) oral presentations, and posters. A discussion session of 30 min at the end of each day is also planned.