Unveiling the Mystery: Investigating Velocity Shifts of Broad Absorption Lines in Quasar Outflows

Supermassive black holes have a significant impact on the gas in galaxies through the release of energy in the form of radiation and kinetic energy, which influences the evolution of the galaxy. This phenomenon is referred to as AGN feedback, and various studies have demonstrated its crucial role in the formation and evolution of host galaxies. One important form of feedback for quasars is the outflows they generate, which can produce blueshifted broad absorption line features (BALs) on the spectrum of background sources. By studying the velocity shifts of BALs, researchers can gain insight into the lifetimes, locations, and geometries of quasar winds. However, the physical mechanism that causes the velocity shift of BALs is still controversial, and research on this topic is limited due to the scarcity of observation cases.

In recent years, several cases of BALs with velocity shifts have been reported, which suggest that the outflows in these sources are influenced by radiation from the central source. However, the scarcity of measured cases of BAL velocity shifts still limits further research. To gain a deeper understanding of outflowing absorption line velocity shifts, it is essential to search for more observed cases. This study aims to comprehensively search for BAL velocity shifts from quasars with multi-epoch observations by the Sloan Digital Sky Survey (SDSS) and perform some statistical analysis based on the obtained sample.

Overall, this research highlights the importance of studying quasar outflows and their impact on the evolution of galaxies. It also emphasizes the need for more observational data to improve our understanding of the physical mechanisms behind the velocity shifts of BALs.