Cosmology with spectroscopic surveys

演讲人: Cheng Zhao EPFL
时间: 2022-11-17 14:00-2022-11-17 15:00
地点:S727 + Zoom Meeting (ID:940 4231 0038, password: 202211)

Modern cosmology is an observational driven science. Two dark components, dark matter and dark energy, are introduced to explain the invisible mass inferred from various astrophysical observations and the accelerated expansion of the Universe. They represent around 95% of the total mass-energy budget of the Universe today. However, little is known about their nature.
As a result of the competition between gravity and cosmic expansion, large-scale structures (LSS) provide a unique way to tackle the mysteries of the dark Universe. Massive spectroscopic surveys are thus carried out to trace the LSS with the 3D positions of galaxies and quasars, as well as the radial distributions of neutral Hydrogen clouds. Recent spectroscopic surveys has collected millions of spectra of galaxies and quasars, and revealed an uninterrupted view of the cosmos over the last 11 billion years. This large dataset permits percent-level measurements of many standard cosmological parameters, such as the Hubble constant, matter fluctuation amplitude, and dark energy density.
In this talk, the speaker will introduce the design and strategy of the state-of-art spectroscopic surveys, and review the process of obtaining cosmological constraints from the raw data, with the focus on robust estimates of statistical and systematic errors. The speaker will also discuss the prospects of cosmological studies with future surveys, and present forecasts based on the Fisher information matrix.


Cheng Zhao (赵成) received his BSc (2012) and PhD in astrophysics (2018) from Tsinghua University. Then he spent 4 years in Switzerland as a postdoctoral fellow at EPFL, before his joining in NAOC recently as a faculty member.
His research interests focus on revealing the nature of dark matter and dark energy through a multi-probe and multi-tracer manner. His research experience include data processing, simulation, theoretical modelling, and cosmological analyses with the large-scale distributions of galaxies, quasars, and voids.  
Since 2014, he has been participating in or leading key projects of the state-of-art large-scale spectroscopic surveys, including the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), SDSS-IV Extended BOSS (eBOSS), and the ongoing Dark Energy Spectroscopic Instrument (DESI). In particular, he constructed the thousands of mock catalogues that are used in almost all BOSS and eBOSS cosmological studies for the estimation of covariances.