Measuring the fine-structure constant on quasar spectra: High spectral resolution gains more than large size of moderate spectral resolution spectra

Abstract

By analyzing the data from the Sloan Digital Sky Survey (SDSS) Data Release 16, which the spectra of the Quasars are major samples, we focus on the investigation of the possible variations of the fine structure constant on the cosmological temporal scales over the universe. We analyzed 14495 quasar samples (red shift z<1) constrained in the literature by using emission-line method on [OIII] doublet and obtained Δα/α=0.70±1.6×10-5. We investigated the precision limit for the measurement of fine-structure constant by SDSS spectrum analysis by designing the simulation about three main sources of systematics: Noise, Outflow of gas, and Skyline. In addition, we exerted cross-correlation analysis on a high-resolution spectrum from MagE (MagE Observations at the Magellan II Clay telescope) named “J131651.29+055646.9” and got the result Δα/α=-9.16±11.38×10-7. Better constraints (Skyline subtraction algorithm) may improve the precision slightly by using SDSS. The more possible and efficient method may be to constrain Δα/α with the spectra of high-resolution spectroscopy and large active galaxy/QSO surveys.