Séminaire Doctorants / Seminar PhD students |
| « M2 internship / master's thesis work » |
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Marie Lecroq, Emma Ayçoberry et Axel Lapel |
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"The James Webb Space Telescope will be the largest and most powerful space telescope ever built. One of its main goals will be to study the birth of the first stars and galaxies of our Universe. Preparing for the exploitation of JWST data requires an improvement of the models currently used to interpret the light emitted by primeval galaxies. To reproduce the emission from such galaxies more realistically than possible today, it is necessary to examine the contribution from massive binary stars, which some recent studies suggest could play a signifiant role in the production of high-energy radiation in these young star-forming regions. Achieving this requires an extensive exploration of the spectral signatures of these stars and their dependence on galaxy physical parameters. While waiting for JWST observational data, the models can be tested and optimized using ultraviolet and optical spectra of nearby analogs of primeval galaxies. Full fits to such observations, which have never been achieved so far, will confirm the reliability of the models, which could then be used to carry out a statistical study of the distribution of physical parameters of primeval galaxies."
"Gravitational lensing is a probe of the distribution of matter in the Universe and thus, allow us to determine cosmological parameters. Using the CFIS-UNIONS data, we can try to extract cosmological parameters using peak counts statistic. The first step to do so is to characterize the impact of each systematics on the parameters in order to know which one has to be better modeled. On this work I thus study the impact of the metacalibration shear bias, baryonic feedback, redshift estimate, intrinsic alignment and boost factor." "The growing amount of observational evidence for the recent acceleration of the expansion of the Universe suggests that canonical theories of cosmology and particle physics are incomplete or incorrect. If the standard picture admits an effective dark energy component in the form of a cosmological constant, nothing prevents questioning this paradigm in favor of dynamical dark energy or modified gravity models that could help cope with fine-tuning requirements and alleviate possible tensions between cosmological datasets. In the light of forthcoming next-generation facilities, tackling the dark energy enigma will require optimizing current cosmological probes and developing new tests to characterize the dynamics and geometry of the Universe at higher redshifts. In this presentation, I will introduce the not-so-known "Redshift-Drift" experiment as a model-independent probe of the real-time expansion of the Universe. I will provide a brief overview of its potential to discriminate different cosmological models at the background level and present encouraging forecasts on the constraints over the dark energy equation of state with a combination of the E-ELT and SKA telescopes." |
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vendredi 17 décembre 2021 - 16:00 Salle du Conseil, Institut d'Astrophysique |
| Page web du Séminaire / Seminar's webpage |