Progress in the Study of Velocity Shifts in Quasar Absorption Lines

Abstract

Outflow is a crucial form of quasar feedback and plays a significant role in understanding the co-evolution process of quasars and their host galaxies. This paper collects relevant literatures on the velocity shifts of outflow absorption lines, organizes the case data therein, conducts a comparative analysis of the identification methods, identification difficulties, and formation mechanisms of absorption line velocity shifts, and discusses the future research directions in this field. Although the current number of observational cases of absorption line velocity shifts is limited and their physical mechanisms remain unclear, with the growth of quasar survey data and the advancement of data processing technologies, breakthroughs in related research are expected. The study of absorption line velocity shifts can not only deepen the understanding of quasar outflow phenomena but also provide a new perspective for research on galaxy evolution.