Unveiling a Universe of Black Holes: The next Generation of AGN Surveys

10 March - 04 April 2025

Andrea Merloni, Roberto Assef, Benjamin Oppenheimer, Debora Sijacki, Celine Peroux

Black holes are not just exotic mathematical constructs, but key components of the observable Universe. Over the last two decades, thanks to detailed observational studies and state-of-the-art numerical simulations, the importance of black holes for a deeper understanding of structure formation has been established. Many questions, however, remain unanswered, in large part due the fact that active phases of black hole growth are very rare (thus requiring large datasets to be revealed) and the associated energy release operates on scales difficult to resolve in simulations and observations alike. Fortunately, the 2020s’ can be seen as a ‘golden era’ of large astronomical surveys, with ground-breaking observatories and experiments coming online in this decade.

The main objective of this MIAPbP program is to capitalize on the plethora of new and upcoming wide-area and deep surveys of the sky at different wavelengths (from radio to X-rays) to discuss and critically examine how they will contribute to change our understanding of black hole astrophysics and of the role of black holes in the broader picture of galaxy formation and evolution. In periods of rapid expansion, when new probes and datasets appear at an increasing rate, it is important to think of ‘refocusing’ exercises, when communities are brought together to learn from each other how to navigate the emerging scientific landscapes.

This ‘refocusing’ is the goal of our proposed workshop for the field of black holes astrophysics.

We invite both observers, who design and exploit astrophysical survey experiments with cutting edge new instruments, and theorists, experts in the physical processes governing the growth of black holes and the formation and evolution of galaxies in a cosmological context. We propose a program centered around four major science topics and explicitly devised to overcome communications and jargon barriers between different communities of astrophysicists.



Tentative Programme:

Week1: SMBH growth and relation to galaxy formation and evolution:
- What are the channels that feed the growth of SMBH? How do they depend on the properties
   of the host galaxies? How do they evolve with time?
- Which black hole-galaxy scaling relation is more fundamental? How do they extend (or not) to the low mass
- Is black holes’ growth self regulated, and if yes, on which physical scale(s)?
- How do we constrain observationally models for AGN feedback and galaxy/SMBH self-regulation?
- What evidence do we need not only to understand the effects of AGN feedback on the galaxy population,
  but also to discriminate between the many types of feedback proposed in the literature?
- What is the role of relativistic jets in shaping the immediate environment of SMBH?

Week 2: The physics of accretion onto black holes
- Do supermassive black holes accrete in a set of different modes?
- What is the balance of energy output in the different modes/phases of BH accretion?
- How do we constrain the physics and energetics of AGN outflows?
- What do TDE, QPE and the exotic nuclear transients reveal about the dynamics of accretion flows?
- What is the relative weight of TDE for the growth of BH at different epochs and in different systems?

Week 3: AGN as probes of the cosmos
- What is the mass of the different phases of the CGM and does it close the baryon budget?
- How are the metals distributed in the CGM and how far does it extend?
- What is the effect of AGN on the different phases of the galactic baryons? And how do they
  impede/modify cosmic gas inflows onto galaxies?
- How do different modes of AGN energy release couple with the multi-phase CGM and ISM?
- How can we use the new large QSO sample to learn about the CGM and the physics of AGN feedback itself?

Week 4: Early Universe and first black holes
- How do AGN populate galaxies across cosmic time?
- When and where did the first black holes form?
- What was the contribution of the first black holes to reionization?
- What is the mass distribution of seed black holes in the early phases of galaxy formation?
- How can we understand the early phases of rapid black hole growth?