CRAL Seminar @Observatory by Philippe Priolet
2026-04-24 11:00 - 12:00 (Europe/Paris) | Observatoire
Title: The puzzling nature of hot exozodiacal dust: the case of Beta Pictoris
Abstract: Hot exozodiacal clouds are populations of dust grains residing in the inner regions of main-sequence stars at temperatures exceeding 1000K. It is a puzzling phenomena in exoplanetary science. On theoretical grounds, such dust should rapidly sublimate or be expelled by radiation pressure, yet interferometric observations continue to reveal its presence around a growing number of stars. The lack of a satisfying physical model, combined with the intrinsic difficulty of resolving emission just tens of milliarcseconds from the host star, makes every new high-quality dataset particularly valuable.
In this talk, I will begin with a general introduction to exozodiacal dust: its origin, physical properties, and the interferometric techniques used to detect it. I will then present new VLTI/MATISSE observations of Beta Pictoris, one of the most iconic debris disk systems and a prime target for studying the inner regions of a young planetary system. A central challenge in the analysis of interferometric data is the proper handling of correlated noise, and I will describe our approach to estimating correlation matrices for MATISSE data, which is critical for obtaining robust constraints on the dust properties. I will close with an outlook on the future of this field, discussing the prospects offered by nulling interferometry with VLTI/NOTT, and the broader implications of exozodiacal dust for the direct imaging of Earth-like planets with next-generation facilities such as the Habitable Worlds Observatory and the Extremely Large Telescope.

CRAL Seminar @ENS - Francisco Rodrigues Montero (Chicago University)
2026-05-26 11:00 - 12:00 | ENS
Title: CALIMA: Opening the window to the imprint of formation and evolution of H2, CO, dust and PAHs on the ISM
Abstract: The thermodynamical state of the interstellar medium (ISM) in the local Universe is now understood to arise from a tightly coupled network of processes. Much of this progress, however, has been driven by theoretical frameworks that remain incomplete in their ability to self-consistently predict the co-evolution of all these components. Modern galaxy formation simulations have reached a remarkable level of sophistication, yet they typically rely on simplified treatments of radiative processes and of the microphysical mechanisms governing ISM heating and cooling. Conversely, photo-chemical models such as CLOUDY provide a detailed description of interactions between radiation, ions, molecules, and dust, but lack the ability to capture the dynamical, multi-scale nature of the ISM. Understanding the processes regulating the formation and evolution of molecules, dust, and polycyclic aromatic hydrocarbons (PAHs) is therefore crucial for galaxy evolution across cosmic time. These mechanisms remain poorly constrained under the low-metallicity, high star formation rate conditions characteristic of the high-redshift Universe. To address this gap, I will present the first fully self-consistent model of dust, CO, and H₂ implemented within the RAMSES code. This framework is coupled to radiative transfer, non-equilibrium thermochemistry, and a realistic multi-phase ISM description, and explicitly tracks carbonaceous and silicate grains together with PAHs. I will highlight applications ranging from high-resolution simulations of isolated galaxies probing the link between dust and PAH properties and local ISM conditions, to cosmological simulations exploring the origin and evolution of dust in the first galaxies.
Where? ENS Monod, Amphi C

CRAL Seminar @Obs – Vincent Chambouleyron (LAM)
2026-05-28 11:00 - 12:00 | Observatoire
Title: PAPYRUS: transforming a legacy telescope at Observatoire de Haute-Provence into an ELT innovation platform

Abstract:

Modern observatories rely on wavefront sensing and control to achieve their ultimate angular resolution. Adaptive optics (AO) has become a cornerstone of large telescope instrumentation, and all ELT instruments will operate behind an AO system. While AO technologies are now highly mature, several challenges still require further development and on-sky validation, particularly for high-contrast imaging and the direct detection of exoplanets — the main focus of this talk. Progress in this field depends on extensive on-sky experimentation, yet access to large telescopes for instrumentation R&D remains limited. PAPYRUS was created to address this gap by transforming a small legacy telescope at Observatoire de Haute-Provence into a dedicated adaptive optics platform for on-sky technology maturation. Operating from June 2022 to April 2026, PAPYRUS has enabled the testing of innovative wavefront sensing and control concepts under real observing conditions while fostering collaborations across the community. In this presentation, I will review four years of activities on the platform, highlight key technical and scientific results, and discuss the lessons learned from operating a flexible on-sky testbed designed to prepare future AO strategies for the ELT era.

CRAL Seminar @Obs – Olivier Ilbert (LAM)
2026-06-05 11:00 - 12:00 | Observatoire
Stellar mass assembly of massive galaxies in the first five billion years of the Universe

Over the past two decades, extensive multi-wavelength observations of the COSMOS field have provided an exceptional view of galaxy evolution across cosmic time. With the recent addition of JWST/NIRCam imaging, our understanding of the distant Universe has advanced dramatically. We can now investigate the physical properties and morphologies of massive galaxies at cosmic noon with unprecedented detail and extend these studies back to the primordial Universe.

After introducing the broader context of galaxy formation and evolution, I will present the confirmation for a population of unexpectedly bright galaxies already in place at z>10, i.e. less than 500 million years of cosmic time. These sources challenge standard models of early galaxy formation. While several explanations have been already suggested, our clustering measurements support a scenario in which star-formation efficiency was significantly elevated in the young Universe.

In the second part of the talk, I will present new results connecting star‑formation histories, morphology, and environment for galaxies at cosmic noon 1 < z < 3. These findings establish solid links between these key aspects of galaxy evolution, and shed new light on the emergence of the massive and quenched elliptical galaxies.

CRAL Seminar @Obs - Corentin Cudennec
2026-06-12 11:00 - 12:00 | Observatoire
Title: TBD

Abstract:

TBD

CRAL Seminar @ENS – Freeke van de Voort
2026-06-26 11:00 - 12:00 | ENS
Gas flows in the simulated circumgalactic medium —
Feedback-driven outflows are vital for creating realistic galaxies, but feedback models implemented in cosmological simulations vary wildly. The circumgalactic medium (CGM) may be able to break degeneracies and constrain these models. However, there are other differences between simulation efforts, such as which physical processes are included and which numerical method is used. Without understanding their impact on the CGM, we will not be able to confidently constrain galaxy formation models. Using zoom-in cosmological simulations, I will discuss some of the physical and observable properties of the galactic ecosystem. The presence of magnetic fields and feedback from relativistic cosmic rays changes the flow of gas in the CGM, affecting the efficiency of outflows driven by stars or supermassive black holes as well as the turbulence-driven mixing in the CGM. This also affects our simulations’ predictions for neutral hydrogen and metal ions. I will show how these effects of magnetic fields and cosmic rays vary across a wide range in halo mass, from dwarf galaxies to galaxy groups. Finally, I will show preliminary results from our work on thermal conduction in groups and clusters.
