Self-gravitating gas flows at the dawn of galaxy formation: the thread between ultra-compact star clusters, massive black holes and Little Red Dots

by Prof. Lucio Mayer (Institute of Computational Science, University of Zurich)

Thursday 12 Mar 2026, 11:30 → 12:30 Europe/Rome

Sala Jappelli (Osservatorio Astronomico di Padova)

Observations carried out with the James Webb Telescope (JWST) have 
led to several exciting and unexpected discoveries
in the first billion year of cosmic history. Among them, the early
emergence of disk galaxies, the existence of sizable massive black holes 
as early as z=10, the presence of massive ultra-compact star clusters revealed by
gravitational lensing at similarly early epochs, and the puzzling Little Red Dots 
(LRDs). Likewise, various evidence suggests that star formation in  
early galaxies was comparatively much more efficient than at later epochs,
pointing to a diminishing effect of feedback processes. I will show
how self-gravitating gas flows inside and around early disk galaxies, in 
absence of effective self-regulation by feedback, can trigger 
gravitational collapse at various scales, providing a natural route
to form ultra-compact star clusters as well as supermassive stars (SMS) in
dense galactic nuclei. In particular, I will present results 
of high-resolution cosmological zoom-in simulations
with sub-pc scale resolution that can produce star clusters matching the
properties of extreme systems such as Cosmic Gems. The central densities
of these clusters are so high that the formation of intermediate
mass black holes (IMBHs) at their centers is unavoidable. Multiple 
IMBHs can then arise in primordial galactic disks and grow quickly via
mutual mergers and  accretion, potentially explaining the earliest massive black holes.
In galactic nuclei, SMSs form surrounded by self-gravitating 
supermassive gas disks (SMDs). The properties of the SMS+SMD systems
surprisingly match the properties of LRDs, and can reproduce their
V-shaped spectra and line broadening while at the same time explaining
the puzzling lack of X-rays. In this scenario LRDs emerge in the stage
prior to the formation of a massive black hole from the collapse of the 
SMS, and are preferentially triggered by galaxy mergers, as perhaps
suggested by the very recent discovery of dual LRDs.

 

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https://unipd.zoom.us/j/82482883288?pwd=MVvmMWSGaiVrGMyAFOdyQG61OAcI7D.1

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