LUX - Observatoire de Paris - PSL - Centre de recherche en astronomie et astrophysique

The SVOM collaboration receives the 3AF Award for scientific excellence

Casoli Fabienne — 2026-10-08T13:02:24Z

The SVOM (Space-based Variable Objects Monitor) space mission, dedicated to the detection and study of gamma-ray bursts, was honored by the French Aeronautics and Astronautics Association (3AF) with the 2026 Award for Scientific Excellence on October 1, at CNES headquarters.

SVOM, launched on June 22, 2024, is dedicated to the detection and study of high-energy events—gamma-ray bursts—that originate from supernova explosions or the mergers of compact stars. It is a collaboration between two national space agencies, the China National Space Administration (CNSA) and the French National Center for Space Studies (CNES), with contributions from the CEA and the CNRS on behalf of France.

Hundreds of gamma-ray bursts

Since its launch, SVOM has detected 358 gamma-ray bursts and has enabled the measurement of the distance to more than 60 of them. The first scientific report on two years of operation showed that SVOM was largely living up to its promises, both in terms of detecting gamma-ray bursts—the core of the project—and in terms of the open Observatory-type program.

Susanna Vergani of LUX is delighted that this award has been given to The SVOM collaboration:

“I am very pleased that the SVOM team has received this prestigious award, which recognizes the scientific excellence of the results obtained thanks to the dedication of the French and Chinese teams of researchers and engineers, and which positions France as a leader in the study of high-energy phenomena in the Universe. At LUX, we make fundamental contributions to these results, notably by determining the distance to the most distant gamma-ray burst detected by SVOM, GRB 250314A, obtained by the Stargate collaboration at ESO's VLT using the X-shooter spectrograph. This triggered observations with the James Webb Space Telescope, which led to the discovery of the supernova associated with this gamma-ray burst—the most distant ever detected."

The Role of LUX

LUX is responsible for the analysis pipeline module of the visible telescope VT, which identifies the optical counterpart of the burst. The team is also heavily involved in the follow-up of SVOM bursts with large ground-based telescopes such as ESO's Very Large Telescope (a LUX researcher serves as Mission Scientist for this ground-based follow-up), and in studying synergies between SVOM and other major facilities such as the Vera Rubin Telescope, the LIGO and Virgo gravitational-wave detectors, and, in the future, CTAO and SKAO.

Contact at LUX

Susanna Vergani

More informations : www.svom.eu

Susanna Vergani (LUX), Bertrand Cordier (CEA, french PI of SVOM) and Andrea Saccardi, who prepared its PhD at LUX, celebrate the award.

S. Vergani

View online : SVOM honored with the 2026 scientific excellence award!

PhD defence of Théo Gayoux on 20 octobre 2026, 14h30

Casoli Fabienne — 2026-09-21T15:50:36Z

The PhD defence of Théo Gayoux will take place on 20 octobre 2026 at 14h30, in the conference room of château de Meudon, Meudon campus of Observatoire de Paris-PSL.

Thesis title

Galaxy Clusters as Cosmological Probes: Halo Mass Function Systematics, Extreme Value Statistics, and Impact of Clustering Dark Energy

Composition of the jury

David ELBAZ, Université Paris Cité, examiner
Jochen WELLER, referee
Etienne POINTECOUTEAU, Université de Toulouse, referee
Sunayana BHARGAVA, Université de la Côte d'Azur, examiner
Jenny SORCE, Université de Lille, examiner
Linda BLOT, Université de Tokyo, invited member
Pier-Stefano CORASANITI, Observatoire de Paris, thesis supervisor

Summary

Galaxy clusters constitute a powerful probe for testing and constraining theoretical cosmological models. They result from the cosmological evolution of the highest matter-density peaks in the primordial density field.

Given the complexity of the physical and cosmological processes involved in their formation and evolution, galaxy clusters are subject to numerous systematic biases, both observational and theoretical. Within the framework of the Euclid space mission, we conducted an in-depth study of a theoretical bias related to the modelling of their dark matter distribution and its impact on cosmological parameter constraints. Using high-resolution numerical simulations, we showed that assuming a deterministic mass profile can introduce a bias in cosmological inference based on cluster number counts. Indeed, observed mass distributions can systematically deviate from a prescribed parametric form and, consequently, adopting a non-parametric and stochastic approach can help mitigate this type of bias.

We then focused on the cosmological properties of the most massive galaxy clusters by adapting a statistical framework emerging from extreme value theory to their study. We investigated the statistical relationships between their masses ranked in ascending order. This analysis revealed a connection between the halo mass function and the universal probability distribution of extreme values, as well as a new statistical approach based on the magnitude between two mass ranks. This framework enables us to test the consistency of a given cosmological model while accounting for and mitigating systematic errors in observed masses. Using this formalism, we were able to assess the accuracy of cluster mass measurements from the Planck satellite and their consistency with the LCDM model.

Finally, we contributed to the development and scientific exploitation of the first numerical simulation of inhomogeneous dark energy modelled as a fluid, using the newly developed Nefertiti code. This simulation enabled us to investigate the impact of dark energy non-linearities across different scales and on different probes. We showed that inhomogeneous dark energy models have a significant influence on the nonlinear regime of structure formation and leave a detectable signature on the scale of massive clusters, for example, in their density profiles and masses.

PhD defence of Romane Cologni on 22 september 2026, 2pm

Casoli Fabienne — 2026-09-19T15:50:00Z

The PhD defence of Romane Cologni will take place on Tuesday, September 22nd, at 14h, in the amphitheater of the Institut d'Astrophysique de Paris.
It can be watched live on https://youtube.com/live/qkJ1n-JUwkU?feature=share.

Thesis title

Tracing molecular gas and star formation in super spiral galaxies — A case study of failed quenching

Composition of the jury

Benoit Semelin (LUX), président
Samuel Boissier (LAM), referee
Miguel Querejeta (Madrid Observatory), referee
Laure Ciesla (LAM), examiner
David Elbaz (CEA), examiner
Annie Hughes (IRAP), examiner
Philippe Salomé (LUX), co-supervisor
Damien Le Borgne (IAP), co-supervisor

Abstract

Super-spiral galaxies are among the most massive and extended star-forming disk galaxies in the local Universe. Their existence raises an important question: at such high masses, galaxy-evolution models typically predict that star formation should gradually decline—or already have ceased. This is the so-called quenching. Yet, these galaxies are still forming stars. This PhD thesis aims at investigating how they sustain their star-forming activity and what such sources can reveal about the evolution of massive galaxies.

Based on the first spatially resolved study of molecular gas in 19 super-spiral galaxies, observed with the IRAM NOEMA interferometer and combined with multi-wavelength data, this work shows that these objects are analogous to giant spiral galaxies rather than a distinct galaxy population. They contain abundant reservoirs of molecular gas that fuel ongoing star formation, which are distributed in very large rotation-dominated disks whose extent scales with that of the stellar disk. The local star-formation efficiency remains comparable to that of more typical lower-mass spiral galaxies. Their continued star formation therefore seem to not result from unusually efficient star formation, but rather from the persistence of a vast and stable cold gas reservoir. These findings suggest that the absence of quenching in these galaxies is linked to insufficient feedback, thus unable to disperse or heat their molecular gas across the full extent of the disk.

Crédit : Ugo Fleury

In radio astronomy, meeting the challenge of Square Kilometer Array data: Launch of the ASTRA project

Mancini Marco — 2026-06-22T15:50:23Z

In radio astronomy, meeting the data challenge of the Square Kilometre Array: launch of the ASTRA project

Data volumes so large that they can no longer be processed and analysed on local machines, established processing methods that are difficult to adapt to distributed architectures, and the challenge of making these resources accessible to astronomers who are not specialists in radio astronomy: these are some of the challenges faced by the scientific community with the arrival of instruments such as the Square Kilometre Array Observatory (SKAO).

France recently became the 14th member country of the SKAO, marking an important step in its involvement in this new era of radio astronomy.

[fr]Les membres de la collaboration ASTRA réunis à l'Observatoire de Paris-PSL lors de la réunion de lancement du projet. [en]The ASTRA collaboration meets at the Observatoire de Paris ' />

The ASTRA collaboration meets at the Observatoire de Paris

The ASTRA project

The ANR-NumPEx ASTRA (Alliance for Scalable Techniques in Radio Astronomy) project, whose kick-off meeting took place from 15 to 17 June at the Observatoire de Paris-PSL, aims to address these challenges in preparation for the implementation of the French node of the European SKA Regional Center (SRC).

To achieve this goal, ASTRA will develop generic, unified and extensible platforms specifically designed to meet the challenges of modern radio astronomy.

The project will deploy four radio astronomy processing pipelines already used with SKA precursor instruments such as NenuFAR, ASKAP and LOFAR, on a distributed computing architecture involving major French high-performance computing centres.

These four pipelines correspond to four major scientific programmes of the SKA:

pulsar observations;
the epoch of reionisation of the Universe;
wide-field radio imaging;
mapping of neutral hydrogen in the Magellanic Clouds.

[fr]Légende : Les quatre thématiques scientifiques étudiées dans le cadre du projet ASTRA. En haut à gauche : représentation de la technique de Pulsar Timing Array (EPTA). En haut à droite : le Petit Nuage de Magellan observé à 21 cm (Pingel et al., 2022). En bas à gauche : la source radio B3 0157+405A issue du relevé LoTSS (crédit Maya Horton et l'équipe *surveys* de LOFAR). En bas à droite : simulation de l'époque de la réionisation (Alvarez et al., 2009). [en]Illustration of the four science cases of ASTRA. Top-left: Pulsar Timing Array representation from EPTA (https://www.epta.eu.org/news/ipta-dr2-news.html). Top-right: The Small Magellanic Cloud at 21 cm (Pingel et al. 2022). Bottom-left: The radio source B3 0157+405A from the LoTSS wide-area survey (credit Maya Horton and the LOFAR surveys team). Bottom-right: Simulation of the Epoch of Reionisation (Alvarez et al. 2009). ' />

Illustration of the four science cases of ASTRA.
Top-left: Pulsar Timing Array representation from EPTA (https://www.epta.eu.org/news/ipta-dr2-news.html).
Top-right: The Small Magellanic Cloud at 21 cm (Pingel et al. 2022).
Bottom-left: The radio source B3 0157+405A from the LoTSS wide-area survey (credit Maya Horton and the LOFAR surveys team).
Bottom-right: Simulation of the Epoch of Reionisation (Alvarez et al. 2009).

An alliance of skills

The ASTRA consortium, led by Marc-Antoine Miville-Deschênes (LPENS), brings together a wide range of complementary expertise in astrophysics, data processing and high-performance computing.

The project builds on developments carried out within the joint laboratories (LabCom) ECLAT and AERIAL, as well as within the European projects EXTRACT and SPECTRUM, and the NumPEx Exsa-AToW project.

The ASTRA collaboration brings together LPENS (ENS-PSL), IRISA (University of Rennes), CEA/IRFU, LUX and LIRA at the Observatoire de Paris-PSL, as well as APC, LPC2E, LAB and Lagrange.

As a true alliance between the French actors involved in radio astronomy data processing, ASTRA will strengthen the links between the astronomical community and the high-performance computing community. The project will run for four years.

Contact

LUX: Florent Mertens
florent.mertens at obspm.fr

LUX is investigating a new generation of submillimeter receivers for ALMA

Mancini Marco — 2026-05-05T08:30:14Z

ALMA2030: a new step in exploring the cold Universe

Since scientific observations began in 2011, the ALMA interferometer has continued to revolutionize millimeter and submillimeter wavelength astronomy and the observation of the cold Universe. Combining high spatial and spectral resolution with ultra-sensitive, low-noise observations, it has led to a better understanding of our cosmic origins: the formation of planets and protoplanetary disks, the evolution of galaxies and merger events such as the Antennae system, which trigger episodes of intense star formation, and interstellar gas clouds where ALMA has revealed filamentary structures and regions of fragmentation with unprecedented precision.

ALMA's radio telescopes on the Chajnantor Plateau in Chile's Atacama Desert.

ESO/S. Guisard

ALMA has proven essential for studying the early Universe as well as bodies in the Solar System. It has also enabled major advances in prebiotic chemistry, including the discovery of complex organic molecules in young stellar systems. In 2019, it also played a key role in the Event Horizon Telescope (EHT) collaboration, contributing to the very first image of a black hole.

ALMA's partners — Europe, North America, and East Asia — together with the host country Chile, are now embarking on a new ambitious phase as part of the ALMA2030 plan. The goal is to significantly increase wideband sensitivity (WSU: Wideband Sensitivity Upgrade)
Learn more
of the heterodyne receivers that form the core of its telescopes and that use ultra-sensitive detector elements known as “SIS” (Superconductor–Insulator–Superconductor).

This modernization represents a major technological leap that will allow ALMA to observe the Universe with unprecedented precision and efficiency. By expanding the scope and sensitivity of its observations, ALMA will open entirely new perspectives for understanding the cosmos.

In their cryostat, 10 receivers from one of ALMA's telescopes.

S. Otarola - ALMA (ESO/NAOJ/NRAO)

The Instrumental Research and Development group at LUX (See the team)
has recognized expertise in SIS detectors for the submillimeter range, with a key contribution to channel 1 of the HIFI instrument on ESA's Herschel space mission. As part of the WSU program, the group has been awarded an ESO research contract to contribute to the development of the next generation of SIS detectors for Band 9: one of ALMA's submillimeter windows, centered at a wavelength of 0.45 mm.

The kick-off meeting, held on April 20 at the Paris Observatory, brought together the ESO team and the three study partners: the Superconducting Detectors and Instrumentation team at LUX, the Department of Astrophysics at the University of Oxford (United Kingdom), and the University of Groningen / NOVA (Netherlands). These three partners have highly complementary roles, with the University of Oxford in charge of the design of the SIS junctions, the LUX team defining the fabrication process and producing the SIS devices, and NOVA responsible for their characterization.

This study is expected to lead to a choice between two technical options, with an ambitious sensitivity goal. One important aspect will be to demonstrate the feasibility of producing series of several dozen receivers, as ALMA consists of no fewer than 66 telescopes. See you in three years for the final results!

SVOM space mission: scientific assessment of the first year of operations

Mancini Marco — 2026-04-29T09:02:55Z

SVOM space mission: scientific assessment of the first year of operations

After a year of scientific operations for the French-Chinese space mission SVOM (Space-based multi-band astronomical Variable Objects Monitor), the French teams presented on April 23 an initial assessment showing that SVOM is fully fulfilling its promises — and even exceeding them.

Vue d'artiste du satellite SVOM.

CNES

SVOM, launched on 22 June 2024, is dedicated to the detection and study of high-energy events known as gamma-ray bursts, which originate from supernova explosions or mergers of compact stars. It is a collaboration between two national space agencies, the China National Space Administration (CNSA) and the Centre National d'Études Spatiales (CNES), with contributions from the CEA and the CNRS for France.

A very promising first assessment

First quantitative assessment: SVOM has detected no fewer than 285 bursts, a quarter of which had not been detected by other space systems (Swift, Einstein Probe or Fermi). This is an important statistic that also makes it possible to detect events that do not fit into one of the two well-known populations of gamma-ray bursts: long bursts thought to be due to supernovae, and short bursts linked to the coalescence of two neutron stars.

For example, SVOM detected a burst that repeated several times in a single day, a completely new phenomenon that is not yet well understood.

Most bursts detected by the ECLAIRS instrument have been followed up with multi-wavelength observations: their afterglow emission is detected in X-rays in 77% of cases and in visible or near-infrared wavelengths in 66% of cases. This is essential for determining key information such as their distance and environment.

Thanks to the efficient system for locating bursts, broadcasting alerts in near real time, and mobilizing ground-based telescopes, nearly half of the GRBs detected by SVOM have a measured redshift and therefore a known distance.

Exploring the distant Universe

SVOM has also demonstrated its ability to detect very distant bursts, particularly thanks to the sensitivity of the ECLAIRS instrument in hard X-rays. One of the mission's main goals is to trace star formation in the most distant galaxies, since gamma-ray bursts mark the end of massive stars' evolution.

The event GRB 250314A was identified as the signal from a supernova in a galaxy at a redshift of 7.3 — only 730,000 years after the Big Bang, during the so-called reionization era of the Universe. This is by far the most distant supernova ever detected, yet its characteristics are remarkably similar to those of supernovae in the nearby Universe.

This important result required the mobilization of several ground-based telescopes (ESO's VLT, Grantecan in the Canary Islands) as well as the James Webb Space Telescope. Multi-wavelength astronomy requires strong coordination between observatories and teams.

A versatile observatory

Finally, more than 60% of SVOM's observation time is devoted to an open observatory-type program that takes advantage of its capabilities in X-ray, visible, and gamma-ray observations. Several dozen transient sources have already been observed, for example a thermonuclear X-ray burst from a neutron star (SVOM observes a thermonuclear explosion on a neutron star).

Les sources transitoires X et gamma détectées par SVOM en mars 2026.

CNES/CEA/CNRS

This already represents a very fruitful harvest for the Franco-Chinese SVOM mission, which is expected to continue observations for at least two more years. Given the excellent condition of all instruments, SVOM could potentially operate for a decade or more.

Practical information

Contact at LUX: Susanna Vergani
More information: www.svom.eu
CNES page: SVOM project

Instruments on board SVOM

SVOM is equipped with two gamma-ray instruments (ECLAIRs and GRM) to detect the prompt emission of gamma-ray bursts, as well as an X-ray telescope (MXT) and an optical telescope (VT). The latter is reoriented within minutes after a GRB detection to identify the optical counterpart of the afterglow.

Information on the burst position in the sky is also transmitted to the ground in less than a minute, allowing large telescopes to rapidly point toward the event and observe it.

This synergy between space- and ground-based observations, combined with multi-wavelength capabilities, is a key scientific strength of the SVOM mission.

The role of LUX in the SVOM collaboration

LUX is responsible for the VT analysis pipeline module that identifies the optical counterpart of GRBs. The team is also strongly involved in follow-up observations with major ground-based telescopes such as ESO's Very Large Telescope (a LUX researcher serves as Mission Scientist for this ground-based program).

In addition, LUX contributes to studies of synergies between SVOM and other major facilities such as the Vera Rubin Observatory, gravitational wave detectors LIGO and Virgo, and future observatories like CTAO and SKAO.

ALMA 2040

Mancini Marco — 2026-03-31T14:19:32Z

LUX participates in the national and European ALMA 2040 reflection

What will be the next major observatory at millimetre and submillimetre wavelengths by 2040? What successor to ALMA, the "Atacama Large Millimeter/submillimeter Array", the large radio telescope co-financed by Europe via the European Southern Observatory (ESO) alongside North America, Asia and Chile, and which has revolutionized our understanding of the cold Universe? As part of a call for ideas called Expanding Horizons, Transforming Astronomy in the 2040s, ESO is currently consulting the European astrophysical community and collecting proposals for the next major European astronomy infrastructure, following the Extremely Large Telescope that is being built in Chile.

Under the banner ALMA2040, the European millimetre and submillimetre community is therefore organising itself to identify the key scientific questions by 2040 and to propose an ambitious concept. About thirty "white papers" on the science of a next-generation mm/submm observatory were submitted to ESO in December 2025

On the French side, reflection is also underway. A ALMA2040 workshopwas held on 26 and 27 March 2026 at the IAP, co-organised by LUX researchers, and financially supported by the Astrophysics of the Cold Universe and Galaxies and Large Structures APIs of the Paris Observatory. The LUX teams have a number of intensive users of ALMA, with around twenty publications per year using ALMA data; they actively participate in the national millimetre and submillimetre radio astronomyobservation service and have contributed to ALMA2040's working groups and white papers.

ALMA's antennas at night on the Chajnantor Plateau, with the Milky Way superimposed (artist's impression)
source

Alex Pérez

For two days, the participants debated the science they would like to do with this future telescope, its technical specifications, synergies with large telescopes on the ground and in space such as the ELT, the SKA, Euclid, Webb. The discussions and conclusions of this workshop will strengthen the French involvement in the project in response to ESO's "Expanding Horizons" call for projects, which should be published in the3rd quarter of 2026. The next stop will be from 13 to 17 July at ESO (Garching), with the workshop "Expanding Horizons: What are the astronomical challenges of the 2040s ?", with the main objective of debating the major scientific challenges for tomorrow's astrophysics and the infrastructures that will be needed to meet them.

Contacts:

Maryvonne Gerin équipe Milieu interstellaire et plasmas, maryvonne.gerin at observatoiredeparis.psl.eu
Philippe Salomé équipe Galaxie et cosmologie, philippe.salome at observatoiredeparis.psl.eu

MOONS: The largest astronomical instrument begins its journey to Chile An 11,000 km journey to the stars

Mancini Marco — 2025-12-11T13:10:40Z

MOONS, a state-of-the-art spectrograph built by a consortium of six countries (the United Kingdom, Italy, France, Portugal, Switzerland, and Chile) as well as ESO, will set sail to unlock the secrets of the Universe. This month, after more than a decade of innovation and collaboration, MOONS (Multi-Object Optical and Near-Infrared Spectrograph) left the UK Astronomy Technology Center (UK ATC) in Edinburgh, where the entire instrument was assembled and tested. This marks the start of an 11,000 km journey to the European Southern Observatory's (ESO) Paranal site in Chile.
MOONS was built by an international consortium led by the UK Astronomy Technology Centre (UK ATC) at the Royal Observatory Edinburgh, involving collaboration across six countries. Th`is project marks a significant milestone for French science and engineering, particularly through the development of new expertise in using fibers in cryogenic environments—a responsibility led by France.
Its journey to Chile marks the final stage before its integration into ESO's Very Large Telescope (VLT) and its first use in 2026.

Chargement du spectrographe

UK ATC

UK ATC has led the project, which has been supported from the outset by CNRS-INSU and the Paris Observatory-PSL. Within the consortium, France has been responsible for the fiber link, the slit environment, the shutter, and the data reduction pipeline.
Its unique capabilities will enable astronomers to study millions of stars and galaxies, providing unprecedented data on the formation and evolution of galaxies and the structure of our Milky Way. This will help answer some of the biggest questions in astronomy.

Contacts:

Hector FLORES Co-PI Français du projet, LUX, Observatoire de Paris-PSL, CNRS, hector.flores@obspm.fr

Isabelle GUINOUARD Chef de Projet Français, UNIDIA, Observatoire de Paris-PSL, CNRS, isabelle.guinouard@obspm.fr

Frédéric ROYER Responsable DRS, LIRA, Observatoire de Paris-PSL, CNRS, frederic.royer@obspm.fr

The ENGRAVE collaboration wins the Into Change Award

Mancini Marco — 2025-12-04T09:27:12Z

The Danish Ministry of Higher Education and Science has awarded one million euros to the international collaboration ENGRAVE (Electromagnetic counterparts of gravitational wave sources at the Very Large Telescope), of which Susanna Vergani, researcher at LUX, is member of the Executive Committee. The Into Change award recognizes European research groups that have conducted exceptional and innovative studies at the highest international level, while embodying fundamental scientific values such as curiosity, collaboration, and openness. The first edition of the award was given to ENGRAVE in recognition of its groundbreaking discoveries at the intersection of physics, cosmology, and astrophysics, particularly the discovery of the origin of heavy elements in neutron star mergers.

Fundamental questions about the formation of the elements in the periodic table are still open. A major breakthrough happened in 2017 when the collision of two neutron stars was observed for the first time through the emission of gravitational waves and then through the detailed study of the kilonova produced by the explosion. The characteristics of that event demonstrated that neutron star mergers are a source of heavy elements in the Universe.
Aware that they were at the beginning of a new era in astrophysics, in early 2018 the main European groups involved in this area of research joined forces to create the ENGRAVE project, with the goal of coordinating the massive observational resources necessary to capture the rare explosions that trigger the formation of heavy elements, especially using the European Southern Observatory telescopes, but also the Hubble and James Webb telescopes from space.
Promoting interdisciplinary exchange across thirteen European countries (including France) among physicists and astrophysicists, ENGRAVE now operates at the forefront of multi-messenger astrophysics: a rapidly developing field that combines observations of gravitational waves and electromagnetic radiation to understand the most extreme events in the universe and the chemical enrichment of the universe.

Two new recruitments at LUX

Mancini Marco — 2025-10-24T08:02:12Z

This morning, our director was very pleased to announce that the CPJ (Junior Professor Chair) campaign for this autumn has been favorable to LUX, with two new arrivals at the laboratory:

For the CPJ-CNRS project:
France in the SKA Observatory Era: Towards the Beginning of Operations of the Largest Radio Observatory (SKA-FORCE)
The selected candidate is Florent Mertens .

For the CPJ-PSL project:
Study of Galaxies and the Interstellar Medium in the Era of Large Radio Telescopes
The selected candidate is Andrea Bracco.