Séminaire Univers / |
| « Can we really ignore galaxy astrophysics in cosmology? » |
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Romain Paviot |
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As cosmological surveys reach unprecedented statistical precision, the question of whether galaxy astrophysics can be treated as a nuisance — or must be modeled carefully — becomes increasingly important. In this talk, I will speak about two key ingredients that are more physically complex than standard assumptions suggest, with potentially significant consequences for cosmological parameter inference. The first concerns intrinsic alignments (IA) of galaxies. Rather than a simple tidal response, IA appears to depend strongly on galaxy type, colour, and stellar mass, with distinct alignment signals between early and late-type galaxies. The amplitude and even the sign of these alignments likely reflect the formation history of galaxies — when and how they assembled — making IA a multi-dimensional astrophysical process. I will discuss how current models may be insufficient to capture this complexity, and what need to be done to further constraints IA for stage IV surveys analyses. The second concerns the Halo Occupation Distribution (HOD) framework, widely used to populate dark matter halos with galaxies for clustering and lensing analyses. Standard HOD assumptions — including assembly-bias-free prescriptions and simple satellite profiles — are a convenient but potentially inadequate description of reality. I will discuss how extensions motivated by galaxy formation physics can alter predicted two-point statistics at a level relevant to current and forthcoming surveys. Together, these two threads point to a broader message: galaxy astrophysics is not simply a foreground to be marginalized over, but carries physical information that, if ignored, may bias our cosmological conclusions. |
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mardi 31 mars 2026 - 11:00 Salle des séminaires Évry Schatzman Institut d'Astrophysique de Paris |
| Pages web du séminaire / Seminar's webpage |