Chinese scientists rely on galaxy cruises to obtain the strongest evidence of dark energy observations to date.

the eBOSS International Cooperation Group has released the latest batch of research results to the world. These include two scientific papers on dark energy research by Zhao Gongbo, a researcher at the National Observatory, and an associate researcher of Wang Wei, respectively, the first author. Based on the largest galaxy-watching eBOSS project in the world, Zhao’s team developed new theories and data analysis methods, using the cross-association of samples of the two galaxies, in the space-time range of 700 million to 1.8 billion light-years ago (this range has never been explored before), and successfully measured the growth rate of cosmic background expansion and structure (see Figure 1).

Chinese scientists rely on galaxy cruises to obtain the strongest evidence of dark energy observations to date.

A diagram of cosmic exploration since sdSS Galaxy Cruise snares nearly 20 years (1998-2019). Source: eBOSS International Cooperation Group.

“This work confirms the presence of dark energy at 11 standard deviation levels, and is the strongest evidence of dark energy observations to date based on galaxy patrols (Figure 2),” Zhao explained. The study found that eBOSS observations support the dark energy dynamics behavior we have previously discovered. “

Chinese scientists rely on galaxy cruises to obtain the strongest evidence of dark energy observations to date.

The limit of dark energy components based on the latest eBOSS observations. Source: Zhao Gongbo, eBOSS Co-op, 2020.

The difficulty of galaxy-patrol cosmology lies in data processing, especially the analysis of observational statistical errors and systematic errors. eBOSS is the first multi-objective day to be conducted in the world over a wide space-time scale, creating the conditions for cross-association analysis (see Figure 3). “Cross-association not only reduces statistical errors, but more importantly, effectivecontrol control system errors to obtain more accurate and reliable results.” Wang said.

Dark energy is the main component of the universe at present, revealing its essence is of great scientific significance. The eBOSS International Cooperation Group consists of more than 30 world-class astronomical research units, including the National Observatory. Since its operation in 2014, the eBOSS project has lasted six years, obtaining nearly 1 million galaxy spectra between 0.6 and 2.2 redshifts, and achieving a series of important scientific results and successfully completing scientific missions.

Chinese scientists rely on galaxy cruises to obtain the strongest evidence of dark energy observations to date.

Two-point correlation functions of two types of galaxies based on eBOSS sky-watching data. Source: Wang Wei et al., (eBOSS Cooperative Group), 2020.

As the director of the scientific working group of eBOSS International Cooperation Group, Zhao Hassitu has been involved in leading the eBOSS project since 2015 in the research of cutting-edge cosmological applications such as sky observation, data processing and dark energy. This study provides a solid foundation for the follow-up study on the nature of dark energy based on china’s space station telescopes, DESI, PFS and other larger-scale galaxy patrols.