CRA SEMINAR | Dr. Misha Rashkovetskyi | Ohio State University | Host: Prof. John Wise

Speaker: Dr. Misha Rashkovetskyi 

Host: Prof. John Wise

Title: Spectral survey instrument reveals notes of discord with cosmic sound waves: DESI overview, BAO measurements and their cosmological implications

Abstract:

We have known that the Universe is vast and expands with acceleration for many years, yet the physical origin of this acceleration remains an open question. While the concordance cosmological model, ΛCDM, has been remarkably successful, recent cutting-edge observational results suggest that dark energy may evolve with time or that the standard model might not keep up with all the highest-quality data.

In this talk, I will introduce baryon acoustic oscillations (BAO), relic sound waves from the early Universe whose imprint in the large-scale distribution of galaxies provides a robust standard ruler for measuring the cosmic expansion history. I will then present an overview of the Dark Energy Spectroscopic Instrument (DESI), a 5000-object fiber spectrograph with robotic positioning highly optimized for conducting a spectroscopic galaxy survey at a record-breaking speed and scale.

One of DESI's main objectives is to measure BAO across cosmic time. I will discuss the methodology and results of the recent BAO analysis from DESI Data Release 2, based on the first three years of observations. Combining these measurements with cosmic microwave background and Type Ia supernova data yields intriguing indications of departures from the standard ΛCDM model, including possible evidence for evolving dark energy.

I will conclude with an outlook on upcoming DESI cosmological analyses, including full-shape clustering measurements from Data Release 2 and BAO results from the 5-year Data Release 3.