Rubin LSST-France, LAPP Annecy, 18-20/05/2026

Session

Science talks

19 mai 2026, 09:30

17. LSSTCam filter throughput measurements with the CBP

Nathan AMOUROUX

19/05/2026 09:30

The Vera C. Rubin Observatory’s LSST requires accurate photometric calibration to meet its science goals, particularly for cosmological measurements using Type Ia supernovae. The Collimated Beam Projector (CBP) has been developed to support this effort. By projecting an array of collimated beams onto the telescope pupil, the CBP enables direct measurements of the telescope’s photometric...

20. First interesting results from the StarDICE experiment

Marc Betoule (LPNHE)

19/05/2026 09:50

StarDICE is a metrology experiment with the goal of establishing
precise flux references for the Vera Rubin Observatory. The success of
this enterprise is expected to boost the constraining power of the
supernovae survey (as measured by the DETF FoM) by a factor 2. To this
effect, a 16 inches robotic telescope installed at the Observatoire de
Haute Provence is conducting a long duration...

4. Controlling and monitoring the Simonyi Telescope optical system

Dominique Boutigny (LAPP)

19/05/2026 10:10

The Simonyi telescope is a complex optical system that uses a sophisticated real time control system to deliver optimal quality images.
I will explain how the mirrors, rotator, hexapods, etc. are controlled and how the telemetry data are used to monitor and improve the performances of the telescope.
I will not enter into the details of the Active Optics system but will rather focus on the...

13. Impact of atmospheric transmission on SNe Ia cosmology in Deep Rolling LSST survey

Philippe Gris (LPCA)

19/05/2026 14:00

The results of a study related to the impact of atmospheric transmission (parameters: airmass, aerosol, ozone, precipitable water vapor) on SNe Ia cosmology using recent LSST simulations of Deep Rolling scenarios will be presented.

21. skysurvey: towards realistic SNe Ia simulations for the LSST era

Luna Dellazzeri (IP2I)

19/05/2026 14:20

Type Ia Supernovae (SNe Ia) are at the center of current tensions on H₀ and w, the parameters characterising the expansion of the Universe. Controlling survey cross-calibration, selection functions, and SNe Ia variability is essential to avoid systematic biases in cosmological inference. Realistic simulations are key to addressing these systematics, but existing tools remain limited in their...

16. Simulation-Based Inference (SBI) for cosmology with type Ia Supernovae (SNe Ia).

Adam Trigui (IP2I)

19/05/2026 14:40

Systematic uncertainties associated to calibration, selection functions and astrophysical effects are dominating the error budget of SNe Ia cosmology. Correction methods applied to account for these systematics, and especially for the complex combination of selection functions and astrophysical variability, are questionable, particularly given the current H0 and Λ tensions for which SNe Ia...

19. Cosmology and stellar physics with strongly lensed supernovae from Rubin-LSST

Raoul Canameras (LAM)

19/05/2026 15:00

Strongly lensed supernovae (SNe) enable independent measurements of the Hubble constant (H₀) through time-delay cosmography, offering a critical test of the current H₀ tension. Their rapid follow-up also enables unique diagnostics of early explosion physics and progenitor properties. In this talk, I will present forecasts for (a) measurements of the Hubble constant and (b) constraints on SN...

14. Gravitational lensing beyond approximations: relativistic lightcones for modern cosmological surveys

M. Laurent MAGRI-STELLA (LAPP)

20/05/2026 09:00

Are the standard approximations used in gravitational lensing still adequate in the era of precision cosmology? If not, how can we move beyond them?

As cosmological tensions sharpen, a new generation of surveys such as Euclid and LSST is set to deliver an unprecedented volume of data, with billions of galaxies analyzed through increasingly sophisticated pipelines, including machine-learning...

12. Optimization of Weak Lensing Lightcone Simulations for Higher-Order Statistics in the LSST era

Juan Mena-Fernández (CPPM)

20/05/2026 09:20

We present a framework for generating lightcone simulations optimized for Stage-IV cosmic shear analyses using Higher-Order Statistics (HOS). We revisit and improve key design choices from previous simulation campaigns, assessing their impact under survey conditions representative of 10 years of LSST observations. We show that uniform spacing in scale factor provides better accuracy than...

1. Breaking Through Blending : A Multi-Survey Approach to Dark Energy with LSST, Euclid, and Roman

Samuel Mesquita (IN2P3/LPSC)

20/05/2026 09:40

Surveys like the Vera C. Rubin Observatory's LSST, ESA's Euclid, and NASA's Roman Space Telescope aim to explore dark energy through measurements of weak gravitational lensing and large-scale structure. However, blending, where faint overlapping galaxy sources are misidentified, introduces substantial errors in galaxy shape and flux measurements, especially for deep, ground-based surveys like...

24. Unbinned Weak Lensing Mass Estimation from Raw Ellipticities

Caio Lima de Oliveira (Universidade Estadual de Londrina)

20/05/2026 10:00

We present a per-galaxy weak lensing likelihood built directly on raw ellipticities and photometric P(z), modeling the unlensed ellipticity distribution while jointly fitting cluster mass and center via tangential and cross shear, with results from HSC and LSST Data Preview 1.

22. Various things about data quality in Fink

Dr Sylvie Dagoret (IJCLab)

20/05/2026 11:00

In the alerts received by the Fink broker, we identified a number of diaObjects associated with stable Gaia stars that nevertheless triggered multiple detections in the Rubin alert pipeline within the Deep Drilling Fields.

After cross-matching these objects with the Gaia catalog of stable stars with magnitude G < 20.5 mag, we investigate a sample of eight such stars using Fink cutouts and...

18. From Optical–Gamma-Ray Correlations to Real-Time Blazar Alerts in Fink

Julian Hamo (IJCLab)

20/05/2026 11:20

Blazars are among the most violent non-thermal sources in the Universe, exhibiting dramatic variability across the electromagnetic spectrum. Yet, a key question remains: how tightly coupled are their optical and $\gamma$-ray emissions, and what does this reveal about the physical processes powering relativistic jets?

In this work, we present a multi-year study of optical–$\gamma$-ray...

3. Probing dark matter with stellar-stream density fluctuations in the LSST era

Matthieu Pelissier (LPSC/UGA)

20/05/2026 11:40

Dark matter subhalos with masses from 10⁶ to 10⁹ solar masses are mostly invisible, but could impact the structure of stellar streams observed by Rubin-LSST. We present a quantitative study of how LSST systematics affect density-fluctuation measurements used to constrain dark matter. Our results show that systematics increase the minimum detectable subhalo mass by a factor of ~2. This project...

23. A Scientific exploration only possible with Rubin-LSST: Search for hidden baryons through interstellar scintillation

marc moniez (LAL-IN2P3)

20/05/2026 12:00

Cool molecular hydrogen H2 may be the ultimate possible constituent to the Milky-Way baryonic hidden matter. I will describe a new way to search for such transparent matter in the Galactic discs and halo, through its diffractive and refractive effects on the light of background stars.
I will show that a mini-survey of a few hours with the telescope of the Vera Rubin Observatory, consisting in...