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Experimental Particle and Astro-Particle Physics Seminar
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Europe/Zurich
Description
Abstract:
Baryon acoustic oscillation (BAO) measurements from the Dark Energy Spectroscopic Instrument (DESI) have revealed hints that dark energy may depart from a cosmological constant, with a preference for an evolving equation of state at the $2.8$--$4.2\sigma$ level when combined with other datasets. I will present the perspective on this question offered by the completed Dark Energy Survey (DES), whose final six-year dataset covers $\sim\!5000\,\mathrm{deg}^{2}$ and enables an independent test combining both geometric and growth probes from within a single experiment.
I will first discuss the DES Y6 analysis of weak gravitational lensing and galaxy clustering ($3\times2$pt), built from 140 million source galaxy shapes and 9 million lens galaxy positions. I will outline the developments to the analysis framework and present the constraints on the $\Lambda$CDM parameters this combination measures best, the abundance of matter $\Omega_{\mathrm{m}}$ and the clustering amplitude $S_{8}$, placing them in context with early-Universe measurements from the CMB.
I will then turn to the DES dynamical dark energy constraints, obtained by combining $3\times2$pt with DES type Ia supernovae and DES BAO. By bringing growth and geometry together within a single experiment, these legacy results realize the multi-probe program envisioned at the inception of DES: lensing, clustering, supernovae and BAO measured, calibrated and combined by one collaboration on one telescope. DES alone is consistent with a cosmological constant at the $2.2\sigma$ level, and this level of agreement is robust to removing any individual probe. I will close on the complementarity between the DES and DESI results, and on how the multi-probe program pioneered by DES will be carried forward by Rubin and the next generation of surveys.