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Pierre-Alain Duc (Observatoire astronomique de Strasbourg)16/05/2022 16:25
The LSST consortium is made of several science collaborations, including DESC for which the French community is particularly active. However a number of French researchers especially from INSU also have an important contribution in the Galaxies Science Collaboration. I will review these activities, with an emphasis on the LSB science, and sky background subtraction which is crucial to...
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Roya Mohayaee (Institut d'Astrophysique de Paris/Sorbonne université)16/05/2022 16:55
The standard model of cosmology is founded on the cosmological principle which
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is the hypothesis of large-scale homogeneity and isotropy of the Universe.This hypothesis imposes that the rest frame of distant galaxies coincides with the rest frame of CMB. I will present some of the results we have obtained using the latest catalogues of radio galaxies and quasars which show that the... -
Jean-Charles Cuillandre (CEA Saclay)16/05/2022 17:30
The Rubin LSST and the Euclid survey will each deliver groundbreaking astronomical datasets over this decade in the optical and near-infrared. Both surveys will map thousands of square degrees of sky from the ground and space respectively, with
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an overlap area of approximately 9000 square degrees at high galactic latitudes. The combination of Euclid’s high spatial resolution imaging in the... -
Dr Julien Peloton (CNRS-IJCLab)17/05/2022 09:30
We will review the status of Fink, the latest scientific results, and the plans for the Rubin commissioning (and beyond).
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Dr Emille Ishida (CNRS/LPC-Clermont)17/05/2022 09:55
The recent increase in volume and complexity of available astronomical data has led to a wide use of supervised machine learning techniques. Active learning strategies have been proposed as an alternative to optimize the distribution of scarce labeling resources. However, due to the specific conditions in which labels can be acquired, fundamental assumptions, such as sample representativeness...
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Marina Masson (UGA - LPSC)17/05/2022 10:15
Gamma-Ray Bursts (GRB) are among the most energetic phenomena in the Universe. The interaction of their blast wave with the Interstellar Medium produces an afterglow that can be observed from a larger angle, in a wide range of the electromagnetic spectrum and during more time than the prompt emission. Viewed off-axis, this emission has a negligible gamma-ray flux and is hence called ”GRB...
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Benjamin Racine (CPPM/IN2P3/CNRS)17/05/2022 11:00
I will present an overview of the new ZTF calibration pipeline developped at in2p3, giving an update on different steps: bias corrections, flatfielding, star-flats, photometric calibration (ubercal), and scene modeling photometry.
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Madeleine Ginolin (IP2I)17/05/2022 11:20
Je présenterais des résultats préliminaires de l'échantillon "volume limited" de SNeIa de ZTF : distributions en stretch, couleur,... ainsi que les dépendances des magnitudes des SNe à ces mêmes paramètres.
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Guy Augarde (LPNHE)17/05/2022 11:40
One main approach to constrain the dark energy equation of state is to construct a Hubble diagram, the evolution of luminosity distance with respect to the redshift using Type Ia Supernovae (SN Ia) used as luminosity distance indicators.
Measuring distances to SNe Ia requires a model of the SN spectrophotometric evolution, taking into account the intrinsic diversity of SNe Ia.The model...
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Estelle Robert (IP2I)17/05/2022 12:00
On développe un code de forward modelling dans le but d'extraire une valeur du taux de croissance des structures fsigma8. Je vais présenter le Direct Acyclic Graph (DAG) de ce code.
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Bastien Carreres (CPPM)17/05/2022 12:15
Type Ia supernova are known to be standard candles, that means that we can infer their distance from their flux measurement and build their Hubble Diagram. Peculiar velocities can be retrieved from the HD residuals, but until now the statistic of SN Ia was too low to use these velocities as cosmological probe. With the next generation of surveys (LSST, ZTF) the statistics of supernovae will...
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Simona Mei18/05/2022 09:30
We explore machine learning networks to detect galaxy clusters in optical images. We present first result on the SDSS. Our networks are very efficient to reproduce the redmapper cluster catalog.
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thibault guillemin (LAPP)18/05/2022 09:55
I will present a comparison of the performance of the redMaPPer, WaZP and AMICO cluster algorithms on cosmoDC2 data, focusing on the estimated completeness and purity as a function of the mass and the redshift of the simulated dark matter halos. Some first studies on the properties of clusters found specifically by one algorithm will also be presented, highlighting the complementarity of the...
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Dr Michel Aguena (LAPP)18/05/2022 10:15
The abundance of galaxy clusters is a powerful probe for cosmology, especially on large optical surveys where hundreds of thousands can be detected. It does require, however, an appropriate characterization of the observational effects on the detection of clusters and on their properties. In this work we evaluate the impact of photometric redshifts using the Wavelet Z Photometric (WaZP)...
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Calum Murray (LPSC)18/05/2022 11:05
Weak lensing is a powerful tool to estimate the matter distribution around massive galaxy clusters. In this work we consider weak lensing magnification. In general such effects are measured by counting the number of galaxies in circular annuli from the lens centre. In this work we present a new method which improves on the standard approach by using the full galaxy magnitude distribution,...
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Constantin Payerne (LPSC (IN2P3))18/05/2022 11:25
A standard choice for cosmological cluster analyses is a Poissonian likelihood; however such a likelihood neglects the effects of sample variance from density fluctuations across the survey volume. To date this assumption has been justified but to make the most of the future data such as that of the Rubin Observatory and the Euclid satellite, improvements to the cluster likelihood must be...
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Manon Ramel (LPSC / IN2P3)18/05/2022 11:45
Due to the greater depth of the survey and blurring by the atmosphere, over a half of the galaxies observed by the LSST will appear to overlap on the line of sight. This effect, called blending, perturbs detections and measurements of shapes and fluxes of galaxies, and is expected be even stronger in high-density regions such as galaxy clusters. In this talk, I will present recent work based...
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Biswajit Biswas (APC)18/05/2022 12:00
As the Large Survey of Space and Time (LSST) will detect fainter objects, the increased object density will lead to more overlapping sources. For LSST, we expect around 60% of galaxies to be blended. In order to better constrain Dark Energy parameters, mapping the matter content of our Universe with weak gravitational lensing is one of the main probes for the upcoming large cosmological...
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Joseph Chevalier (IJCLab)18/05/2022 14:00
We compare the performances of a PhotoZ estimator Delight, a hybrid method of template fitting (based here on SED CWW templates) and machine learning.
In a first step, we compare the performance of Delight's z-phot vs z-spec regression on DC2 simulations with that of LePhare's "state of the art" template fitting method and a machine learning method, the ramdom forest trees.
In a second...
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Jean-Eric Campagne (LAL-IN2P3-CNRS and Univ. Paris 11)18/05/2022 14:15
The DESC Bayesian analysis pipeline project recently created aims to coordinate and promote the development of a standardized open source Bayesian Pipeline which ultimately could connect pixels to cosmology. Two subprojects has emerged: one concerning "Pixels to shear" starting from simulated/DC2 images to infer posterior weak lensing shear and convergence fields on the sky (eg. BLISS,...),...
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Kirill Grishin (Universite de Paris)
The distribution of galaxy clusters, the largest gravitationally bound structures in the Universe, helps us to estimate fundamental constants and constrain different cosmological models. With the expected development and commissioning of astronomical instruments, such as LSST, in the next decade, the depth of imaging data for a significant area of the sky will allow us to select nearly...
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