Ecogia Science Meetings 2025-2026
Schedule
Meetings are at 14 in the Pavillon meeting room at Ecogia and on Zoom
2025-09-22 Riccardo Seppi ** Unveiling AGN Feedback with Galaxy Groups: end-to-end simulations and comparison to hydrodynamical models
Feedback from supernovae and active galactic nuclei strongly impacts the processes related to galaxy formation and the distribution of matter in the Universe. Galaxy groups, lying at the sweet spot where the gravitational binding energy is comparable to the one injected by the central AGN, provide key insights into feedback processes. Understanding these systems requires careful treatment of observational systematics and selection effects. In the first part of this talk, I will summarise the key results of the end-to-end simulations we built to robustly quantify the selection of X-GAP, a collection of 49 groups with high-quality XMM observations. In the second part, I will present our current strategy to compare X-GAP to hydro-dynamical simulations with various baryonic implementations, such as FLAMINGO, in order to put constraints on feedback models in simulations using real data. Finally, I will provide an outlook on what our work can teach us about the strength of gas expulsion from sub-Mpc scales, where currently no consensus exists.
2025-09-29 Elia Cenci ** MELIORA: Modelling of direct-collapse black hole seeds in large-scale cosmological simulations
The formation and growth of massive black holes (MBHs) at high redshift remain a key challenge in modern astrophysics. Observations of quasars at z > 6 indicate the presence of MBHs with masses exceeding 10^9 Msun, yet the processes responsible for their early assembly are highly debated. Direct-collapse black holes (DCBHs) are among the most promising candidates to seed the high-redshift over-massive black holes that were recently discovered with the James Webb Space Telescope (JWST). We introduce a novel framework that models DCBH seed formation and growth within evolving galactic environments in the MELIORA large-scale cosmological simulations. A self-consistent treatment of local Lyman-Werner flux from nearby star-forming halos is employed, alongside criteria for gas density, metallicity, and inflow rates, ensuring realistic conditions for seed formation. We will explore how variations in environmental and astrophysical conditions affect the initial mass function and spatial distribution of DCBH seeds, and compare to available data from JWST. Furthermore, we explore the implications of a scenario where the formation of DCBHs powers the emission from Little Red Dots. We will also discuss our results in the context of gravitational wave detection from high-redshift black holes with the upcoming Laser Interferometer Space Antenna (LISA).
2025-10-06 TBD
2025-10-13 Marco Tucci ** Euclid Quick Data Release (Q1): results and validation of the photo-z processing function
The ESA Euclid mission will measure the photometric redshifts of billions of galaxies in order to provide an accurate 3D view of the Universe at optical and near-infrared wavelengths. Photometric redshifts are determined by the PHoto-Z (PHZ) processing function on the basis of the multi-wavelength photometry of Euclid and ground-based observations. In this talk, I describe the PHZ pipeline used for the first quick (Q1) Euclid data release, the output products, and their validation with respect to the Euclid requirements. The PHZ pipeline is responsible for the following main tasks: i) source classification into star, galaxy, and quasar (or QSO) classes based on photometric colours; ii) determination of photometric redshifts for the core science; iii) determination of physical properties of galaxies for non-cosmological science. Areas for improvement for future Euclid data releases are also discussed in the talk.
2025-10-20 Dominique Eckert ** Testing AGN feedback models with galaxy group scaling relations
AGN feedback is a necessary ingredient of modern galaxy evolution models to produce realistic populations of galaxies, in particular to reproduce the shape of the galaxy stellar mass function. However, cosmological simulations lack the resolution to accurately implement accretion onto supermassive black holes and AGN-driven outflows. For this reason, AGN feedback is usually implemented using a sub-grid model, which is governed by a set of parameters that can be tuned to reproduce a set of observables. The hot atmospheres of galaxy groups are highly sensitive to the implementation of feedback, as the energy released by AGN over cosmic time rivals the binding energy of gas particles. As such, AGN feedback leads to ejection of gas from group-scale halos, in a way that strongly depends on the adopted feedback model. I will show how the scaling relations of galaxy groups can be used to discriminate between feedback models, with a focus on the relation between X-ray luminosity and gas temperature. I will then compare the observational scaling relations with the predictions of the FLAMINGO simulation suite, which implements several models with varying feedback strengths. I will then briefly discuss the implications of these results for large-scale structure cosmology.
2025-10-27 William Hurtley ** Euclid Q1: Counting Galaxies Correctly
Have you ever wondered how many galaxies there are in the Universe? The Galaxy Stellar Mass Function is this most basic and fundamental statistical measurement of the galaxy population, and perhaps the most fundamental that we can make. It encodes the enitre history of the process of galaxy formation and evolution and supplies a stringent constraint that any theoretical or phenomenological model of galaxy evolution must match. The Euclid Quick 1 data release in March 2025 was made from less than one week's worth of Euclid observing and was processed with an in-development pipeline, but already represents a large step in the data that we have available to answer our question. I'll describe the progress we've made so far in making a GSMF measurement with Q1, while attempting to dance around the data's slight idiosyncracies.
2025-11-03 Andrea Tramacere ** On the statistical characterization of the synchrotron multi-zone polarization of blazars
Polarimetric observations across multiple wavelengths show that blazars exhibit complex, energy-dependent polarization: the polarization fraction systematically decreases from X-rays to millimeter bands, while the electric vector position angle (EVPA) varies strongly. This behavior contradicts simple single-zone synchrotron models, indicating a turbulent jet with multiple emission regions. I present a statistical framework to interpret these patterns, emphasizing X-ray data from IXPE and optical results from RoboPol. Using a Monte Carlo approach with the JetSeT code, I simulate synchrotron emission from a turbulent, multi-cell region testing different distributions for the relevant physical parameters. The results show that the observed polarization trends are fully explained by a purely turbulent, multi-zone model, without requiring correlations between cell size and electron energy distribution (EED) parameters. The polarization degree mainly depends on the effective number of flux-weighted emitting cells, controlled by the dispersion of EED propertiesespecially the high-energy cutoff and low-energy spectral index. Assuming 90 % dispersion in the EED cutoff energy and ~ 0.51.5 dispersion in the spectral index, the model reproduces both the IXPE millimeter-to-X-ray polarization energy-dependent patterns and the optical polarization envelope revealed by RoboPol.
2025-11-10 Stèphane Paltani ** Towards RefleX 4
I will present the new developments in RefleX, which will lead to RefleX 4. A new propagator has been implemented, which can offer huge performance increase in some cases, especially for the creation of images. New physics has been included, in particular related to the gas dynamics. But more importantly, RefleX 4 will offer a complete paradigm shift. While RefleX 3 is mature, such kind of tools only expands the gap between more and more complex simulations and data. RefleX 4 will indeed allow parameter inferences of complex models, with the goal of largely alleviating the usual limitations faced in this process.
2025-11-17 TBD
2025-11-24 Angela Bongiorno ** Getting ready for LSST
The Vera Rubin Observatory's Legacy Survey of Space and Time (LSST) is becoming a reality, with its first survey observations planned for early next year. To be ready for this and fully exploit its potential, we have developed AGILE (AGN In the LSST Era), as part of an INAF in-kind contribution. AGILE is an end-to-end simulation pipeline capable of modelling the anticipated AGN population in LSST. It generates a "truth" catalog of galaxies and AGN, propagates it through LSST-like observing conditions and survey strategy, and produces mock images and catalogs that can be processed with the Rubin Science Pipelines. A key ingredient of AGILE is the specific accretion-rate distribution function p(lambda), which describes the black-hole accretion history over cosmic time. I will briefly describe how we are working to improve current estimates of p(lambda) using Euclid DR1 data
2025-12-01 Akke Viitanen ** AGILE: simulated LSST images and photometric catalogs of AGN, galaxies, and stars
The Vera Rubin Observatory's Legacy Survey of Space and Time (LSST) and Euclid present an unprecedented discovery potential for studying active galactic nuclei (AGN). However, accurate identification and characterization of AGN from optical/NIR photometry and variability data alone remains a challenge that can be met with end-to-end simulations. I will talk about our end-to-end simulation pipeline AGILE (AGN In the LSST Era; Viitanen, Bongiorno+, in prep.), and focus on generating simulated LSST images and data products. I will discuss our first look results in terms of recovering the fluxes of AGN, galaxies, and stars, and classifying type1 AGN within an LSST-like survey. Finally, I will outline tying our work to both existing and upcoming LSST survey data.
2025-12-08 Claudio Ricci ** Millimeter continuum emission as a probe of accretion in AGN
Recent studies suggest that the nuclear millimeter continuum emission observed in nearby AGN could originate from the same population of electrons responsible for the X-ray emission that is ubiquitously observed in accreting black holes. In my talk, I will present the results of several dedicated high-spatial resolution (~60-100 milliarcsecond) 100 GHz ALMA campaigns on a volume-limited, hard X-ray selected, sample of radio-quiet AGN. I will discuss the spectral, variability and polarimetric properties of this component, and show that nuclear mm emission is ubiquitous in non-jetted AGN. Our high-resolution observations reveal a tight correlation between the nuclear 100\,GHz and the intrinsic X-ray emission, which highlights the potential of ALMA continuum observations to detect heavily obscured AGN (up to an optical depth of one at 100GHz, i.e. ~1e27 cm^-2). Moreover, I will discuss how the spectral properties of the mm continuum emission can provide constraints on fundamental properties of the nuclear plasma and the accretion flow, such as the magnetic field strength and the fraction of non-thermal electrons in the X-ray corona.
2025-12-15 Skipped (ap Lab) ** nan
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2025-12-22 Holidays
2025-12-29 Holidays
2026-01-05 Holidays
2026-01-12 Carlo Ferrigno ** How to try to infer geometry in accreting pulsars
After a brief introduction on the subject of high-mass X-ray pulsars, I will discuss some of the methods appeared in literature that are potentially useful to infer the geometrical properties of pulsars: i.e., the location of magnetic poles and the rotation axis inclination with respect to the line of sight. This analysis will reveal also properties of the radiation beaming and ultimately of the processes originating radiation.
2026-01-19 Vitalii Sliusar ** Light coherence in astrophysics
The Hanbury Brown-Twiss (HBT) effect, discovered in the 1950s and further developed in the 1960s, was originally used to estimate stellar angular diameters through intensity correlations measured by spatially separated detectors. When the two detectors in an HBT experiment are co-located, typically implemented using a beam splitter, a zero-baseline intensity correlation is obtained, which after deconvolution of the detector response function, yields the temporal component of the second-order coherence function. Unlike spatial coherence, this function is independent of the source brightness distribution, or its size, depending only on the spectral band and the properties of the source's emission process itself - photon statistics. Along with photometric and spectral information, the second order coherence function can be used to constrain the emission mechanisms and discriminate between thermal, synchrotron, bremsstrahlung and stimulated emission processes. In this talk I will describe the practical implementation of the instrument used for second-order coherence function measurements and will focus on its application to characterize emission processes in typical astrophysical sources. I will also discuss application of second-order coherence function's variability for lensed sources to constrain cosmological parameters.
2026-01-26 Maksat Satybaldiev ** Gamma-ray orbital modulation in spider pulsars
Compact binary millisecond pulsars (spiders) are short-period binary systems consisting of a millisecond pulsar and a low-mass companion. These systems emit across the entire electromagnetic spectrum and are particularly bright in gamma-rays. Pulsed gamma-ray emission has been observed in many of these systems and is believed to originate from the neutron star's current sheet. Some spiders also exhibit orbital modulation in X-rays and gamma-rays. The X-ray modulation can be explained by an intrabinary shock emission model, where pulsar wind particles are re-accelerated and Doppler boosted along the shock tangent, producing orbitally modulated photons via synchrotron radiation. This shock typically wraps around the pulsar, causing modulation to peak at the pulsar's inferior conjunction. If similar processes were responsible for the gamma-ray modulation, its peak should align with X-ray modulation. However, in three previously studied systems, the X-ray and gamma-ray modulation peaks occur at opposite orbital phases, suggesting different underlying mechanisms, such as inverse Compton scattering of companion star photons by pulsar wind particles or synchrotron emission from wind particles interacting with the companion's magnetosphere. Using data from the recently published Third Fermi Large Area Telescope Catalog of Gamma-Ray Pulsars (3PC), we searched for gamma-ray orbital modulation in 43 redback and black widow pulsars. We detected significant modulation in seven systems, including three newly identified ones. In my talk I will introduce spider pulsars, discuss our findings, focusing on the measured modulated fractions and their relation to system properties such as gamma-ray flux, luminosity, binary inclination and X-ray light curves.
2026-02-02 Skipped
2026-02-09 Ezequiel Treister ** Following Hard X-ray Selected AGN Through Galaxy Mergers: Insights from multi-wavelength follow-up of BASS sources
Hard X-ray selection with Swift-BAT provides one of the most complete and least biased census of local AGN, making BASS an ideal sample to study supermassive black hole growth across different environments. In this talk, Ill discuss what weve learned about SMBH accretion in galaxy mergers by combining the power of hard X-ray selection with extensive multiwavelength follow-upparticularly with ALMA. Ill show results from three recent studies: (1) multiwavelength SED fitting revealing how AGN luminosity, star formation, and obscuration evolve through the merger sequence, with late-stage mergers showing dramatically elevated nuclear obscuration; (2) high-resolution ALMA observations of molecular gas in mergers hosting dual and single AGN, which surprisingly show that dual AGN occurrence may be more about variability and obscuration than gas supply; and (3) extending the newly-established mm-X-ray correlation technique to known dual AGN systems, we demonstrate that this method can unveil heavily obscured dual AGN (NH > 10 cm) at very small nuclear separations that would otherwise remain hidden. Together, these results highlight why starting with hard X-ray selection and following up at multiple wavelengthsespecially in the millimeteris essential for reaching a full picture of SMBH growth in mergers.
2026-02-16 Hancheng Li ** nan
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2026-02-23 Enrico Bozzo ** nan
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2026-03-02 Manon Regamey ** nan
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2026-03-09 TBD
2026-03-16 TBD
2026-03-23 TBD
2026-03-30 TBD
2026-04-06 TBD
2026-04-13 TBD
2026-04-20 TBD
2026-04-27 TBD
2026-05-04 TBD
2026-05-11 TBD
2026-05-18 TBD
2026-05-25 TBD
2026-06-01 TBD
2026-06-08 TBD
2026-06-15 TBD
2026-06-22 TBD
2026-06-29 TBD