With the simple mind of a mathematician, I almost ran away from the lab when I started coding my SED fitter and encountered the "beautiful mess" of: magnitudes, photometric systems and filters (exact same name for two filters with remarkably different transmission curves), photon vs energy counting, etc. And even when finally the fluxes were in physical units... here comes the debate on what is the suitable lambda to use (for plotting!! :-)) and the strong opinions regarding fluxes and
density fluxes... Little did I understand at that point that it is not that astrophysicist like to complicate their lives (don't we?), but that there is a fascinating combination of historical and technical reasons that prevent having a "clean" and homogeneous way to go from what is observable to SI traceable flux measurements. In this ID I will go
briefly on how we calibrate now, why it is not enough for some cases and interesting initiatives in this context like the Landolt Satellite Project.

The shaping of planetary nebulae on their evolution from asymptotic giant branch (AGB) circumstellar envelopes (CSE)

to their final, most often axisymmetrical, form is still a process with many unknown details. For this, the study of the transition

objects, pre-planetary nebulae (pPNe), is key to understand the whole shaping process. After creating a detailed 3-D

morpho-kinematical model of M1–92, a pPN with one of the richest chemistry, we obtain a full description of the nebula’s

physical and chemical properties, finding robust discrepancies in the 12C/13C isotopic ratio across structures depending on

their age and linking it to its ongoing shaping process.

The number of applications to graduate programs is growing extremely fast without a significant increase in the number of available positions, making it harder to run an admissions process that is fair and efficient. Last week, the AAS Graduate Admissions Task Force (GATF) released a summary of their final report, which includes recommendations aimed at improving the current state of graduate admissions in astronomy. One of the topics they addressed is the use of recommendation letters, which were also the focus of a recent open letter from early-career researchers to the GATF. In this ID, I’ll summarise the key points from both documents, focusing on the role of recommendation letters, with the aim to discuss together whether, in their current form, they are truly effective tools for evaluating students fairly and equitably.

The Epoch of Reionization (EoR) marks a critical phase in the evolution of the universe, yet remains poorly understood. While star-forming galaxies are acknowledged as key contributors to ionized bubble formation, the extent of contribution from alternative sources such as shock-heated ISM or emission from X-ray binaries remains unclear. In this study, we employ cosmological radiative transfer simulations to explore the impact of diverse sources on intergalactic medium (IGM) properties. Our focus is not merely data fitting, but rather understanding whether the interpretation of Lyman-ɑ forest observations is changed by using theoretical models incorporating non-stellar sources.

Moving beyond the EoR, the study explores the Epoch of Helium Reionization (HeEoR), when HeII transitions to HeIII (𝑧 ≲ 4), predominantly driven by quasar-produced ionizing photons. Using the parametrization of the quasar luminosity function (QLF) proposed by Shen et al. (2020), we examine its implications for recent observations suggesting an extended HeEoR.

Finally, the study delves into the origin of UV luminosity function (UVLF) variability, potentially explaining the unexpectedly high abundance of UV-bright galaxies at extreme redshifts observed by JWST. By exploring the stochasticity of star formation and dust attenuation driven by different implementations of supernova feedback, we provide insights into the UVLF's evolution and its link to early galaxy morphologies. This presentation will highlight these findings and their broader implications for our understanding of cosmic reionization.

Type Ia and other peculiar supernovae (SNe) are thought to originate from the thermonuclear explosions of white dwarfs (WDs). Some of the proposed channels involve the ejection of a partly exploded WD (e.g. Iax SN remnant) or the companion of an exploding WD at extremely high velocities (>400 km s^-1). Characterization of such hyper-runaway/hypervelocity (HVS) WDs might therefore shed light on the physics and origins of SNe. Here we analyse the Gaia DR3 data to search for HVS WDs candidates and peculiar sub-main-sequence (sub-MS) objects. We retrieve the previously identified HVSs and find 46 new HVS candidates. Among these we identify two new unbound WDs and two new unbound sub-MS candidates. The remaining stars are hyper-runaway WDs and hyper-runaway sub-MS stars. The numbers and properties of the HVS WD and sub-MS candidates suggest that extreme velocity ejections (>1000 km s^-1) can accompany at most a small fraction of type Ia SNe, disfavouring a significant contribution of the D6-scenario to the origin of Ia SNe. The rate of HVS ejections following the hybrid WD reverse-detonation channel could be consistent with the identified HVSs. The numbers of lower-velocity HVS WDs could be consistent with type Iax SNe origin and/or contribution from dynamical encounters. We also searched for HVS WDs related to known SN remnants but identified only one such candidate ( https://ui.adsabs.harvard.edu/abs/2023MNRAS.518.6223I/abstract).

I will describe an extended, ongoing observational effort aimed at discovering and studying the properties of a large sample of dual and strongly lensed QSOs at sub-arcsec separations. With these data, we will be able to address numerous scientific questions, including testing several previously untested predictions of galaxy/SMBH evolution models, developing more accurate predictions of massive BH merger rates and LISA GW event rates, and studying dark matter distribution in the central kpc of lensing galaxies. We select candidates using Gaia and Euclid data and follow up on targets with various space- and ground-based telescopes, including an ESO large program with VLT/MUSE, to obtain spatially resolved spectroscopy. This has produced, for the first time, a substantial sample of confirmed dual AGN beyond the local universe, and the most compact quadruply lensed QSO ever discovered.

The Gaia mission has recently completed its last scientific observations. This is a good time to reflect on why this is a great mission, with one of the worst data access policy. I will provide a biased view on some of the revolutionary results it led to and provide a brief overview of what is still planned for the young and patient people in the audience.

Galaxies don’t just form stars—they continuously exchange gas with their surroundings. This circumgalactic medium (CGM) is a turbulent, magnetized mix of gas shaping how galaxies evolve. Observations reveal a multiphase CGM, but capturing this complexity in simulations is a major challenge due to small lengthscales involved. 

In this talk, I will explore:

- Why small-small effects in multiphase astrophysical gas are important?

- How turbulence & magnetic field shape CGM structure?

- How a new subgrid model can bring these small-scale effects to large-scale cosmological simulations?

By improving how we model the CGM, we can better interpret observational data and refine our understanding of galaxy evolution. Let's talk about how we can make that happen.

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The Informal Discussion is in-person only, and held in the ESO library.

At around 10:30, we will continue in the discussion at science coffee.

Fellowship selection processes in academia are designed to reward scientific excellence, yet research suggests that bias—especially unconscious bias—can subtly influence evaluation outcomes, often disadvantaging underrepresented groups. In this informal discussion, we will first explore the impact of bias on selection processes, with a particular focus on hidden, unconscious biases that shape decision-making without evaluators even realizing it We will then examine how prestigious fellowship programs, including Marie Skłodowska-Curie Actions (MSCA), the European Research Council (ERC), and other major astronomy and astrophysics fellowships, attempt to mitigate these biases. Using insights from peer-reviewed studies and official funding reports, we will analyze how different selection panels confront issues such as Halo bias, linguistic bias, and cognitive bias.

I will summarize 3 recent papers about galaxies at z>=10, and the Ho tension. I will then discuss, without offering solutions, whether such results place the standard Cosmological model en course towards the rocky shores of a funtamental(s) crisis.