Article by: Andacs Robert Eugen, on 09 July 2023, at 10:32 am PDT

Lado Samushia, an associate professor of physics at Kansas State University, is actively involved in a collaborative research endeavor focused on unraveling the mysterious force behind the universe's accelerating expansion, commonly referred to as dark energy (Samushia, 2022).

To aid in this ambitious investigation, the team is utilizing the cutting-edge Dark Energy Spectroscopic Instrument (DESI), housed at the renowned Kitt Peak National Observatory in Tucson, Arizona. DESI, overseen by the U.S. Department of Energy's Lawrence Berkeley National Laboratory, empowers scientists to meticulously map and analyze a vast array of celestial objects, including galaxies, quasars, and stars (Samushia, 2022).

The collaboration recently released an initial dataset comprising nearly two million objects, providing researchers with a wealth of information to analyze and interpret. As part of this data release, several papers have been published, addressing various aspects of the early data findings. These papers encompass investigations into galaxy clustering, the study of rare objects, and detailed descriptions of the DESI instrument and survey operations (Samushia, 2022).

Within this collaborative effort, Hanyu Zhang, a doctoral student in physics at Kansas State University supervised by Samushia, assumes a lead authorship role in a paper titled "The DESI One-Percent Survey: Exploring the Halo Occupation Distribution of Luminous Red Galaxies and Quasi-Stellar Objects with AbacusSummit." The paper is accessible on the pre-print server arXiv (Zhang et al., 2022).

The research team's analysis focuses on two specific types of galaxies: luminous red galaxies and galaxies hosting quasi-stellar objects in their centers. The findings indicate a clear trend: luminous red galaxies tend to gain mass over time while acquiring fewer satellite galaxies. These insights provide valuable insights into the physics underlying the evolution of massive galaxies (Zhang et al., 2022).

DESI employs a sophisticated system consisting of 5,000 robotic positioners, which accurately maneuver optical fibers to capture light from objects located millions or even billions of light-years away. Functioning as the world's most powerful multi-object survey spectrograph, DESI can collect light from over 100,000 galaxies in a single night. By analyzing the captured light, researchers can determine the distance to each object, ultimately constructing a comprehensive three-dimensional map of the cosmos (Samushia, 2022).

The expansion of the universe causes a stretch in the wavelength of light, resulting in a phenomenon known as redshift. DESI specializes in measuring redshifts, providing crucial data that contributes to solving some of the most fundamental puzzles in astrophysics, including the nature of dark energy and its evolution throughout the history of the universe (Samushia, 2022).

In summary, the ongoing research efforts led by Lado Samushia and the collaborative team utilizing the DESI instrument offer significant advancements in understanding the mysteries of dark energy and its role in shaping the universe's expansion (Samushia, 2022; Zhang et al., 2022).

The research has been published at Kansas State University.