The Correlated Variations of Absorption Lines and Quasar Continuum

Abstract

Using the quasar spectra from the Sloan Digital Sky Survey and with variable C iv absorption line systems, we measure the Si iv and N v absorption line systems. We obtain 50 variable Si iv absorption line systems and 39 variable N v absorption line systems. We find that the variations in most of the C iv , Si iv , and N v absorption lines are correlated with the changes in quasar continuum. In addition, a significant portion of the variable absorption lines are the consistent variations of multiple systems with large velocity separations. Therefore, the variations of the C iv , Si iv , and N v absorption lines could be mainly driven by the changes in quasar radiations, which cause changes in ionization states or column densities of absorbing gas. We also find that the variable C iv , Si iv , and N v absorption line systems can be divided into low-ionization systems and high-ionization systems. The former positively responds to the changes in the quasar’s brightness, and the later is the oppositive case.